KR102183015B1 - Image display device - Google Patents

Abstract

An object of the present invention is to provide an image display device with improved visibility.
In order to solve the above problems, the image display device 1 of the present invention comprises a white light source 2 having a continuous emission spectrum, an image display cell 4, and a polarizer disposed on the viewer side than the image display cell 4 (8) and the polarizer (8) have two oriented films having a retardation of 3,000 nm or more and 150,000 nm or less on the visual side, and the two oriented films are substantially parallel to or different from each other. It is characterized in that it has a data and the difference is 1,800 nm or more.

Description

Image display device {Image display device}

The present invention relates to an image display device.

Image display devices are widely used in mobile phones, tablet terminals, PCs, televisions, PDAs, electronic dictionaries, car navigation systems, music players, digital cameras, digital video cameras, and the like. With the progress of miniaturization and weight reduction of image display devices, their use is not already limited to offices or indoors, and their use is also expanding outdoors and while moving in cars or trams.

Among these, opportunities for visually recognizing an image display device through polarizing filters such as sunglasses are increasing. In this regard, Patent Document 1 reports that when a polymer film having a retardation of less than 3,000 nm is used on the viewing side than on the viewing side of the liquid crystal display device, a strong interference color appears when the screen is observed through the polarizing plate. Has been. In addition, as a means to solve the above problem, Patent Document 1 describes that the retardation of the polymer film used on the viewer side rather than the polarizing plate on the viewer side is 3,000 to 30,000 nm.

WO 2011/058774

The present inventors have repeatedly examined the practicality of the image display device by the above method, and as a result of using one oriented film whose retardation value is controlled to be more than a certain amount, color tone such as rainbow spots is disturbed. Even if silver did not occur, when two such oriented films were used, it was found that in some cases, remarkable disturbance in color tone such as rainbow unevenness occurs. Accordingly, an object of the present invention is to solve this problem and provide an image display device with improved visibility.

As a result of repeating day and night studies to solve the above problem, the inventors of the present invention showed that the above phenomenon is remarkable when the orientation principal axes of the two orientation films are not parallel to each other, and there is a difference in the retardation of the two orientation films. As a result, it was found that it is possible to suppress the disturbance of color tone such as rainbow spots even when the orientation principal axes of the two orientation films are not parallel. The inventors of the present invention have made further studies and improvements based on these findings to complete the present invention.

Representative invention is as follows.

Clause 1.

(1) a white light source with a continuous emission spectrum,

(2) an image display cell,

(3) a polarizer disposed on the viewer side than the image display cell, and

(4) having two oriented films having retardation of 3,000 nm or more and 150,000 nm or less on the visible side than the polarizer,

The two oriented films have a retardation that is substantially parallel to each other or different from each other, and the difference is 1,800 nm or more.

Image display device.

Item 2.

The image display device according to item 1, wherein the difference in retardation between the two oriented films is 3,500 nm or more.

Clause 3.

The image display device according to item 1 or 2, wherein the white light source having the continuous emission spectrum is a white light emitting diode.

According to the present invention, the visibility of an image display device is improved. In particular, deterioration of image quality due to disturbance in color tone typified by rainbow irregularities occurring when visual recognition is performed through a polarization filter is alleviated. In addition, in this specification, "rainbow unevenness" is a concept including "color unevenness", "color shift", and "interference color".

1 is a typical schematic diagram of an image display device with a touch panel.

An image display device typically has an image display cell and a polarizing plate. Liquid crystal cells or organic EL cells are typically used for image display cells. Fig. 1 shows a typical schematic diagram of an image display device using a liquid crystal cell as the image display cell.

The liquid crystal display device 1 has a light source 2, a liquid crystal cell 4, and a touch panel 6 as a functional layer. Here, in this specification, the side on which the image of the liquid crystal display device is displayed (the side where a person visually recognizes the image) is referred to as the ``viewer side'', and the side opposite to the viewer side (that is, a light source commonly referred to as a backlight light source in a liquid crystal display device) This setting side) is referred to as "the light source side". In addition, in Fig. 1, the right side is the viewer side, and the left side is the light source side.

Polarizing plates (light source-side polarizing plate 3 and viewing-side polarizing plate 5) are respectively provided on both the light source side and the viewer side of the liquid crystal cell 4. Each polarizing plate 3, 5 typically has a structure in which polarizer protective films 9a, 9b, 10a, 10b are laminated on both sides of a film called polarizers 7 and 8. In the image display device 1 of FIG. 1, a touch panel 6 is provided as a functional layer on the viewer side rather than the viewer side polarizing plate 5. The touch panel shown in Fig. 1 is a resistive touch panel. The touch panel 6 has a structure in which two transparent conductive films 11 and 12 are disposed via a spacer 13. The transparent conductive films 11 and 12 are obtained by stacking the base films 11a and 12a and the transparent conductive layers 11b and 12b. Further, on the light source side and the viewer side of the touch panel 6, transparent substrates, such as anti-scattering films 14 and 15, are provided via an adhesive layer.

In Fig. 1, although the touch panel 6 is described as a functional layer provided on the viewer side of the viewer side polarizing plate 5, it is not limited to the touch panel, and any layer may be used as long as it has a film. In addition, although a resistive touch panel has been described as the touch panel, it is also possible to use another type of touch panel such as a projection type capacitive type. The touch panel of FIG. 1 has a structure having two transparent conductive films, but the structure of the touch panel is not limited thereto, and for example, the number of transparent conductive films and/or anti-scattering films may be one. In the liquid crystal display device 1, the anti-scattering film does not necessarily have to be disposed on both sides of the touch panel 6, and may be a structure disposed on either side, or may be a structure in which a scattering prevention film is not disposed on both sides. The anti-scattering film may be disposed on the touch panel via the adhesive layer or on the touch panel without the adhesive layer.

<Position relationship of orientation film>

An orientation film may be used for various purposes in an image display device. In addition, in this specification, an orientation film means a polymer film which has birefringence. From the viewpoint of improving visibility, the image display device preferably has two oriented films having retardation of 3,000 nm or more and 150,000 nm or less, and the values of the retardation are different from each other. The difference in the retardation value of the two orientation films is not particularly limited, but is preferably 1,800 nm or more from the viewpoint of improving visibility. In addition, it is preferable that the two alignment films are arranged so that their alignment main axes are substantially parallel to each other. In the liquid crystal display device of Fig. 1, the alignment film is typically a film on the viewer side of the polarizer 8 (hereinafter referred to as ``viewer side polarizer''), that is, the viewer side polarizer ( The base film 11a of the transparent conductive film 11 located on the light source side than 8) the polarizer protective film 10b (hereinafter referred to as ``viewable side polarizer protective film'') more on the visible side (hereinafter) than the spacer 13 (hereinafter , Referred to as "light source side base film"), the base film 12a of the transparent conductive film 12 located on the viewing side than the spacer 13 (hereinafter referred to as "view side base film"), and the viewing side polarizer protective film The scattering prevention film 14 (hereinafter referred to as ``the light source side scattering prevention film'') between (10b) and the light source side base film 11a and a scattering prevention film located on the visible side than the visible side base film 12a ( 15) (hereinafter referred to as "visible side scattering prevention film") can be used.

The position at which the two orientation films are installed is not particularly limited and is arbitrary as long as it is on the viewing side than the viewing side polarizer 8. For example, in the case of the liquid crystal display device of FIG. 1, an arrangement illustrated in Table 1 below can be taken.

As described above, the positions of the two oriented films are not particularly limited as long as they exist on the viewing side rather than the viewing side polarizer. That is, the orientation film with higher retardation may be arranged on the visual side than the other orientation film, and the orientation film with higher retardation may be arranged on the light source side than on the other orientation film. Therefore, in the examples of patterns 1 to 10 shown in Table 1 above, when an orientation film with higher retardation is disposed on the viewer side than on the other orientation film, and an orientation film with higher retardation is on the light source side than on the other orientation film. This includes the case of being placed in. Further, the patterns 1 to 10 shown in Table 1 are merely examples and may be other combinations. For example, in the above, the anti-scattering film may be any other functional film that can be installed on an image display device.

In the present specification, when a plurality of orientation films (film groups) are used for a single member, they are regarded as one film. Here, the member means that it is judged as a separate member from the viewpoint of functional and/or purpose such as, for example, a polarizer protective film, a light source side scatter prevention film, a light source side base film, a viewer side base film, and a viewer side scatter prevention film. do.

The difference in retardation between the two oriented films is preferably 1,800 nm or more, preferably 2,500 nm or more, preferably from the viewpoint of suppressing the disturbance of color tone such as rainbow spots in the image displayed by the image display device. It is 3,200 nm or more, preferably 3,500 nm or more, preferably 4,000 nm or more, preferably 5,000 nm or more.

From the viewpoint of suppressing disturbance of color tone such as rainbow spots in an image displayed by an image display device, the two oriented films are preferably arranged so that their orientation main axes are substantially parallel to each other. Therefore, the angle formed by the orientation main axis of the two orientation films is preferably 0°±20° or less, preferably 0°±15° or less, preferably 0°±10° or less, preferably 0°C. It is less than ±5 degrees, preferably less than 0 degrees ±3 degrees, preferably less than 0 degrees ±2 degrees, preferably less than 0 degrees ±1 degrees, preferably less than 0 degrees. In addition, in this specification, the term "below" means that it takes only the next numerical value of "±". Therefore, the "0 degrees ± 20 degrees or less" means allowing the fluctuation in the range of 20 degrees up and down around 0 degrees.

As described above, it is preferable that the two oriented films have mutual orientation main axes in parallel, but the greater the retardation difference between the two films, the greater the allowable range of the angle. If the retardation difference between the two films is 3,500 nm or more, preferably 4,000 nm or more, rainbow stains can be suppressed regardless of the angle.

From the viewpoint of suppressing rainbow irregularities, it is preferable that at least one of the two alignment films has an angle formed by its orientation main axis and the polarization axis of the visible side polarizer of approximately 45 degrees. Specifically, the angle is 45 degrees ± 30 degrees or less, 45 degrees ± 20 degrees or less, preferably 45 degrees ± 15 degrees or less, preferably 45 degrees ± 10 degrees or less, preferably 45 degrees ± 7 degrees or less. , Preferably 45 degrees ± 5 degrees or less, preferably 45 degrees ± 3 degrees or less, preferably 45 degrees. It is preferable to satisfy the said positional relationship with respect to the orientation film which has a higher retardation among the two orientation films.

Arranging the cyclic oriented film to satisfy the above conditions is, for example, a method of disposing the cut cyclic oriented film so that its orientation main axis is at a specific angle with the polarization axis of the polarizer, or cyclic oriented orientation. It can be performed by the method of extending|stretching a film diagonally and arrange|positioning so that it may become a polarization axis and a specific angle of a polarizer.

<Retardation of orientation film>

It is preferable that the retardation of the two oriented films is 3,000 nm or more and 150,000 nm or less from the viewpoint of reducing rainbow irregularities. The lower limit of the retardation of the alignment film is preferably 4,500 nm or more, preferably 6,000 nm or more, preferably 8,000 nm or more, preferably 10,000 nm or more. On the other hand, the upper limit of the retardation of the orientation film is that even if a polyester film having a retardation higher than that is used, the effect of improving additional visibility is not substantially obtained, and the thickness of the orientation film also increases depending on the height of the retardation. Since there is a tendency to do this, it is set to 150,000 nm from the viewpoint that it may be contrary to the request of a thinner furnace, but it is also possible to set a higher value.

In the present specification, one oriented film having a retardation of 3,000 nm or more and 150,000 nm or less may be constituted by combining two or more adjacent oriented films as long as the oriented main axes are substantially parallel. For example, when the orientation main axes of the orientation film having a retardation of 2,000 nm and the orientation film of 1,000 nm are in a parallel state, they can be regarded as one orientation film having a retardation of 3,000 nm. Here, substantially parallel means that the angle formed by the two oriented main axes is 0°±20° or less, preferably 0°±15° or less, preferably 0°±10° or less, preferably 0°±5° or less. , Preferably it is within 0°±3°, preferably 0°±2° or less, preferably 0°±1° or less, and preferably 0°. In this relationship, a plurality of films can be regarded as a single film as a "film group". Here, "adjacent" includes both the case where the adjacent oriented film is pasted and the case where it is not pasted.

The liquid crystal display device may be provided with an alignment film having a retardation of less than 3,000 nm at an arbitrary position. The retardation of such an oriented film is, for example, 50 nm or more, 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more. Further, the upper limit of the retardation of such an oriented film is, for example, less than 3,000 nm, less than 2,500 nm, or less than 2,300 nm.

The oriented film having retardation of less than 3,000 nm may be a uniaxially stretched oriented film or a biaxially stretched oriented film, but it is preferably a biaxially stretched oriented film from the viewpoint of reducing the ease of tearing of the film.

The retardation of the orientation film can be measured according to a known method. Specifically, it can be obtained by measuring the refractive index and thickness in the biaxial direction. It is also possible to obtain using a commercially available automatic birefringence measuring device (for example, KOBRA-21ADH: manufactured by Oji Measuring Instruments Co., Ltd.).

From the viewpoint of more effective suppression of rainbow spots, the oriented film has a ratio (Re/Rth) of its retardation (Re) and thickness direction retardation (Rth) is preferably 0.2 or more, preferably 0.5 or more, preferably It is more than 0.6. The thickness direction retardation means the average value of retardation obtained by multiplying two birefringences ΔNxz and ΔNyz as viewed from the cross section in the film thickness direction by the film thickness d, respectively. As Re/Rth increases, the action of birefringence increases isotropy, and the occurrence of rainbow spots on the screen can be more effectively suppressed. In addition, in this specification, the case where it describes simply as "retardation" means in-plane retardation.

The maximum value of Re/Rth is 2.0 (i.e., a fully uniaxially symmetric film), and as it approaches a fully uniaxially symmetric film, the mechanical strength in a direction orthogonal to the orientation direction tends to decrease. Therefore, the upper limit of Re/Rth of the polyester film is preferably 1.2 or less, and preferably 1.0 or less. Even if the ratio is 1.0 or less, it is possible to satisfy the viewing angle characteristics (about 180 degrees left and right, and about 120 degrees up and down) required for the image display device.

The orientation film can be produced by appropriately selecting a known method. For example, orientation films include polyester resins, polycarbonate resins, polystyrene resins, syndiotactic polystyrene resins, polyetheretherketone resins, polyphenylene sulfide resins, cycloolefin resins, liquid crystal polymer resins and cellulose resins. It can be prepared by using at least one selected from the group consisting of resin to which is added. Therefore, the orientation film is a polyester film, a polycarbonate film, a polystyrene film, a syndiotactic polystyrene film, a polyetheretherketone film, a polyphenylene sulfide film, a cycloolefin film, a liquid crystal film, and a liquid crystal compound added to a cellulose resin. It can be a film.

Preferred raw resins for the orientation film are polycarbonate and/or polyester, and syndiotactic polystyrene. These resins have excellent transparency and excellent thermal and mechanical properties, so that retardation can be easily controlled by stretching. Polyesters typified by polyethylene terephthalate and polyethylene naphthalate are preferred because their inherent birefringence is large and large retardation can be obtained relatively easily even if the film thickness is thin. In particular, polyethylene naphthalate is suitable for a case in which retardation is particularly high because of a high intrinsic birefringence among polyesters, or in a case in which a film thickness is to be made thin while maintaining a high retardation. As a representative example of a polyester resin, a more specific method for producing an oriented film will be described later.

<Manufacturing method of orientation film>

Hereinafter, a method of manufacturing an orientation film will be described using a polyester film as an example. The polyester film can be obtained by condensing an arbitrary dicarboxylic acid and a diol. As dicarboxylic acid, for example, terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5 -Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonecarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3- Cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2, 2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecadicarboxylic acid, and the like.

As a diol, for example, ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1 ,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and the like.

The dicarboxylic acid component and the diol component constituting the polyester film may be used individually or in combination of two or more. Specific polyester resins constituting the polyester film include, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like, preferably polyethylene terephthalate and polyethylene naphthalate. , Preferably polyethylene terephthalate. The polyester resin may contain other copolymerization components, and from the viewpoint of mechanical strength, the proportion of the copolymerization component is preferably 3 mol% or less, preferably 2 mol% or less, and more preferably 1.5 mol% or less. These resins have excellent transparency and excellent thermal and mechanical properties. In addition, these resins can easily control retardation by stretching.

The polyester film can be obtained according to a general manufacturing method. Specifically, the non-oriented polyester formed by melting the polyester resin and extruding into a sheet shape is stretched in the longitudinal direction using the difference in speed of the roll at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction by a tenter. By performing heat treatment, an oriented polyester film can be obtained. The polyester film may be a uniaxially stretched film or a biaxially stretched film. The cyclic oriented oriented film may be stretched at an angle of 45 degrees.

Production conditions for obtaining a polyester film can be suitably set according to a known technique. For example, the longitudinal stretching temperature and the transverse stretching temperature are usually 80 to 130°C, and preferably 90 to 120°C. The longitudinal draw ratio is usually 1.0 to 3.5 times, and preferably 1.0 to 3.0 times. In addition, the transverse draw ratio is usually 2.5 to 6.0 times, preferably 3.0 to 5.5 times.

Controlling the retardation in a specific range can be performed by appropriately setting the draw ratio, the draw temperature, and the thickness of the film. For example, the higher the difference in draw ratio between longitudinal and transverse stretching, the lower the stretching temperature, and the thicker the film, the easier it is to obtain a higher retardation. Conversely, the lower the difference in the draw ratio between the longitudinal stretching and the transverse stretching, the higher the stretching temperature, and the thinner the film thickness, the easier it is to obtain a lower retardation. Further, the higher the stretching temperature and the lower the total draw ratio, the easier it is to obtain a film having a lower ratio of retardation and retardation in the thickness direction (Re/Rth). Conversely, as the stretching temperature is lower and the total draw ratio is higher, a film having a higher ratio of retardation and retardation in the thickness direction (Re/Rth) is obtained. Further, the heat treatment temperature is usually preferably 140 to 240°C, and preferably 180 to 240°C.

In order to suppress the variation of retardation in the polyester film, it is preferable that the thickness variation of the film is small. In order to provide a retardation difference, if the longitudinal draw ratio is decreased, the value of the vertical thickness deviation may increase. Since there is a region where the value of the vertical thickness deviation is very high in a certain range of the draw ratio, it is preferable to set the film forming conditions so as to deviate from that range.

The thickness variation of the oriented polyester film is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less. The thickness variation of the film can be measured by any means. For example, take a continuous tape-shaped sample (3 m in length) in the flow direction of the film, and use a commercially available measuring device (e.g., Seiko EM Co., Ltd. Electronic Micrometer Millitron 1240) at a 1 cm pitch. By measuring the thickness of 100 points, the maximum value (dmax), the minimum value (dmin), and the average value (d) of the thickness are obtained, and the thickness deviation (%) can be calculated by the following equation.

<Image display cell and light source>

An image display device can typically have a liquid crystal cell or an organic EL cell as an image display cell. In addition, it is preferable that the image display device has a white light source having a continuous and wide emission spectrum from the viewpoint of suppressing rainbow irregularities. When the image display device includes a liquid crystal cell, it is preferable that the image display device includes such a light source as a light source independent from the image display cell. On the other hand, in the case of an organic EL cell, since it itself has a function of a light source, it is preferable that the organic EL cell itself emits light having a continuous and wide emission spectrum. The method and structure of the light source having a continuous and wide emission spectrum is not particularly limited, and may be, for example, an edge light type or a direct type type. The "continuous and broad emission spectrum" means an emission spectrum in which a wavelength region of at least 450 to 650 nm, preferably a wavelength region in which the intensity of light becomes zero in the visible region, does not exist. The visible light region is, for example, a wavelength region of 400 to 760 nm, and may be 360 to 760 nm, 400 to 830 nm, or 360 to 830 nm.

As a white light source having a continuous and wide emission spectrum, a white light-emitting diode (white LED) can be mentioned, for example. White LEDs include phosphor type (i.e., a blue light using a compound semiconductor, or an element that emits white by combining a light emitting diode and a phosphor that emits ultraviolet light) and organic light-emitting diodes (OLEDs). have. From the viewpoint of having a continuous and wide emission spectrum and excellent luminous efficiency, a white light-emitting diode comprising a blue light-emitting diode using a compound semiconductor and a light-emitting element in which a yttrium-aluminum-garnet-based yellow phosphor is combined is preferable.

The liquid crystal cell can be used by appropriately selecting any liquid crystal cell that can be used in a liquid crystal display device, and the method or structure is not particularly limited. For example, a liquid crystal cell such as VA mode, IPS mode, TN mode, STN mode or band alignment (π type) can be appropriately selected and used. Therefore, the liquid crystal cell can be used by appropriately selecting a liquid crystal made of a known liquid crystal material and a liquid crystal material that may be developed in the future. In one embodiment, a preferred liquid crystal cell is a transmissive liquid crystal cell.

As the organic EL cell, an organic EL cell known in the art can be appropriately selected and used. The organic EL cell is a light-emitting body (organic electroluminescent light-emitting body), and typically has a structure in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially stacked on a transparent substrate. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative, a light emitting layer made of a fluorescent organic solid such as anthracene, and an electron injection layer made of such a light emitting layer and a perylene derivative. Laminates, etc. are mentioned. In this way, since the organic EL cell has both the function as an image display cell and a function as a light source, an independent light source is unnecessary when the image display device includes the organic EL cell. That is, the light source and the image display device in the image display device may be independent of each other or may be integral forms as long as their functions are exhibited.

When an organic EL cell is used as an image display cell, a polarizing plate in an image display device is not essential. However, since the thickness of the organic light emitting layer is very thin, about 10 nm, external light is reflected from the metal electrode and is again emitted to the viewing side, and the display surface of the organic EL display device may look like a mirror when viewed from the outside. In order to shield the mirror reflection of such external light, it is preferable to provide a polarizing plate and a quarter wave plate on the visual side of the organic EL cell. Therefore, when the image display device has an organic EL cell and a polarizing plate, considering the liquid crystal cell 4 in FIG. 1 as an organic EL cell, and considering the viewing side polarizing plate 5 as a polarizing plate, the liquid crystal display device 1 The positional relationship of the orientation film in can be applied as it is.

<Polarizing plate and polarizer protective film>

The polarizing plate has a structure in which both sides of a film-shaped polarizer are sandwiched between two protective films (sometimes referred to as "polarizer protective film"). As for the polarizer, arbitrary polarizer (or polarizing film) used in the technical field can be appropriately selected and used. As a typical polarizer, a polyvinyl alcohol (PVA) film or the like may be mentioned in which a dichroic material such as iodine is dyed, but the polarizer is not limited thereto, and known and may be developed in the future may be appropriately selected and used.

Commercially available PVA films can be used. For example, "Kuraray Vinylon (manufactured by Kuraray Co., Ltd.)", "Tosero Vinylon (manufactured by Tosero Corporation)], and "Nichigo Vinylon (Nippon Synthetic Chemical Co., Ltd.) ) Manufacturing)] can be used. As a dichroic material, iodine, a diazo compound, a polymethine dye, etc. are mentioned.

The polarizer can be obtained by any method, for example, by uniaxially stretching a PVA film dyed with a dichroic material in an aqueous boric acid solution, and washing and drying while maintaining the stretched state. The draw ratio of uniaxial stretching is usually about 4 to 8 times, but is not particularly limited. Other manufacturing conditions and the like can be appropriately set according to a known method.

The protective film on the viewing side of the viewing side polarizer (the viewing side polarizer protective film) may be an orientation film or any film conventionally used as a polarizer protective film, but is not limited thereto.

The kind of the light source side protective film of the visibility side polarizer and the protective film of the light source side polarizer can be arbitrarily selected and used suitably a film conventionally used as a protective film. From the viewpoint of handling property and ease of availability, for example, a triacetylcellulose (TAC) film, an acrylic film, and a cyclic olefin film (for example, a norbornene film), a polypropylene film, and a polyolefin film (for example, TPX ) It is preferable to use a film that does not have at least one birefringence selected from the group consisting of.

In one embodiment, it is preferable that the light source side protective film of a visibility side polarizer, and the visibility side protective film of a light source side polarizer are an optical compensation film which has an optical compensation function. Such an optical compensation film can be appropriately selected according to each method of liquid crystal, for example, a resin obtained by dispersing a liquid crystal compound (e.g., a discotic liquid crystal compound and/or a birefringent compound) in triacetyl cellulose, a cyclic olefin resin (e.g. For example, from one or more selected from the group consisting of norbornene resin), propionyl acetate resin, polycarbonate film resin, acrylic resin, styrene acrylonitrile copolymer resin, lactone ring-containing resin and imide group-containing polyolefin resin, etc. What is obtained is mentioned.

Since optical compensation films are commercially available, it is also possible to appropriately select and use them. For example, "Wide View-EA" and "Wide View-T" for TN method (manufactured by Fujifilm), "Wide View-B" for VA method (manufactured by Fujifilm), VA-TAC (manufactured by Konica Minolta Corporation) ), ``Zeonoa Film'' (manufactured by Xeon Corporation), ``Aton'' (manufactured by JSR), ``X-plate'' (manufactured by Nitto Denko), and ``Z-TAC'' for IPS method (manufactured by Fujifilm), and `` CIG" (manufactured by Nitto Denko Corporation), "P-TAC" (manufactured by Okura Industrial Corporation), and the like.

The polarizer protective film may be laminated directly on the polarizer or through an adhesive layer. From the viewpoint of improving adhesion, it is preferable to laminate through an adhesive. It does not specifically limit as an adhesive agent, Any thing can be used. From the viewpoint of thinning the adhesive layer, water-based (that is, an adhesive component dissolved in water or dispersed in water) is preferable. For example, in the case of using a polyester film as a polarizer protective film, polyvinyl alcohol-based resins, urethane resins, etc. are used as main components, and isocyanate-based compounds, epoxy compounds, etc. are blended as necessary to improve adhesion. The composition can be used as an adhesive. The thickness of the adhesive layer is preferably 10 µm or less, more preferably 5 µm or less, and even more preferably 3 µm or less.

When a TAC film is used as a polarizer protective film, it can be pasted using a polyvinyl alcohol-based adhesive. When using a film having low moisture permeability, such as an acrylic film, a cyclic olefin film, a polypropylene film, or TPX as a polarizer protective film, it is preferable to use a photocurable adhesive as an adhesive agent. As a photocurable resin, a mixture of a photocurable epoxy resin and a photocationic polymerization initiator, etc. is mentioned, for example.

The thickness of the polarizer protective film can be arbitrarily set, for example, in the range of 15 to 300 µm, preferably in the range of 30 to 200 µm.

<Touch panel, transparent conductive film, base film, scattering prevention film>

The image display device may include a touch panel. The type and method of the touch panel are not particularly limited, and examples thereof include a resistive touch panel and a capacitive touch panel. Regardless of the method, the touch panel usually has one or two or more transparent conductive films. The transparent conductive film has a structure in which a transparent conductive layer is laminated on a base film. As described above, for the base film, an orientation film or another film conventionally used as a base film, or a rigid plate such as a glass plate can be used.

Other films conventionally used as the base film include various resin films having transparency. For example, polyester resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, (meth)acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, A film obtained from at least one resin selected from the group consisting of a polyvinyl alcohol resin, a polyarylate resin, and a polyphenylene sulfide resin may be used. Among these, polyester resins, polycarbonate resins, and polyolefin resins are preferred, and polyester resins are preferred.

Although the thickness of the base film is arbitrary, the range of 15 to 500 µm is preferable.

The base film may be subjected to an etching treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation, etc., or undercoat treatment on the surface in advance. Thereby, the adhesiveness with the transparent conductive layer etc. provided on the base film can be improved. Further, before providing the transparent conductive layer or the like, the surface of the base film may be subjected to vibration damping and cleaning by solvent cleaning or ultrasonic cleaning, if necessary.

The transparent conductive layer may be directly laminated on the base film, but may be laminated through an easily adhesive layer and/or various other layers. As another layer, a hard coat layer, an index matching (IM) layer, a low refractive index layer, etc. are mentioned, for example. As a typical lamination structure of a transparent conductive film, the following 6 patterns are mentioned, but are not limited to these.

(1) Base film/Easy adhesive layer/Transparent conductive layer

(2) Base film/Easy adhesive layer/Hard coat layer/Transparent conductive layer

(3) Base film/Easy adhesive layer/IM (index matching) layer/transparent conductive layer

(4) Base film/Easy adhesive layer/Hard coat layer/IM (index matching) layer/Transparent conductive layer

(5) Base film/Easy adhesive layer/Hard coat layer (also serves as IM with high refractive index)/Transparent conductive layer

(6) Base film/Easy adhesive layer/Hard coat layer (high refractive index)/Low refractive index layer/Transparent conductive thin film

Since the IM layer itself is a lamination configuration of a high refractive index layer/low refractive index layer (the transparent conductive thin film side is a low refractive index layer), it can be made difficult to see the ITO pattern when viewing the liquid crystal display screen by using this layer. As in the above (6), it is also possible to integrate the high refractive index layer of the IM layer and the hard coat layer, which is preferable from the viewpoint of thickness reduction.

The configurations (3) to (6) are particularly suitable for use in a capacitive touch panel. In addition, the configurations (2) to (6) are preferable from the viewpoint of preventing oligomers from depositing on the surface of the base film, and it is preferable to provide a hard coat layer on the other side of the base film.

The transparent conductive layer on the base film is formed of a conductive metal oxide. The conductive metal oxide constituting the transparent conductive layer is not particularly limited, and is selected from the group consisting of indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, and tungsten. Conductive metal oxides of one or more metals are used. The metal oxide may further contain metal atoms shown in the above group as necessary. Preferred transparent conductive layers are, for example, a tin-doped indium oxide (ITO) layer and an antimony-doped tin oxide (ATO) layer, and preferably an ITO layer. Further, the transparent conductive layer may be an Ag nanowire, an Ag ink, a self-organizing conductive film of Ag ink, a network electrode, a CNT ink, or a conductive polymer.

The thickness of the transparent conductive layer is not particularly limited, but is preferably 10 nm or more, more preferably 15 to 40 nm, and even more preferably 20 to 30 nm. When the thickness of the transparent conductive layer is 15 nm or more, it is easy to obtain a good continuous film having a surface resistance of, for example, 1×10 ³ Ω/□ or less. In addition, if the thickness of the transparent conductive layer is 40 nm or less, a layer with higher transparency can be obtained.

The transparent conductive layer can be formed according to a known procedure. For example, a vacuum evaporation method, a sputtering method, and an ion plating method can be illustrated. The transparent conductive layer may be amorphous or may be crystalline. As a method of forming the crystalline transparent conductive layer, it is preferable to form an amorphous film once on a substrate, and then heat and crystallize the amorphous film together with a flexible transparent substrate.

The transparent conductive film of the present invention may be patterned by removing a part of the inside of the transparent conductive layer. The transparent conductive film in which the transparent conductive layer is patterned has a pattern forming portion in which a transparent conductive layer is formed on a base film, and a pattern opening on the base film that does not have a transparent conductive layer. As for the shape of the pattern formation part, in addition to a stripe shape, a square shape etc. are mentioned, for example.

It is preferable that the touch panel has one or two or more anti-scattering films as the transparent substrate. As the anti-scattering film, it is also possible to use an orientation film or various films conventionally used as an anti-scattering film (for example, a transparent resin film described for the base film). When two or more anti-scattering films are provided, they may be formed of the same material or may be different.

The polarizer protective film, the base film, and the anti-scattering film can contain various additives within a range that does not interfere with the effect of the present invention. For example, ultraviolet absorbers, inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light resistance agents, flame retardants, heat stabilizers, antioxidants, antigelling agents, surfactants, and the like. Further, in order to exhibit high transparency, it is also preferable that the polyester film contains substantially no particles. "Substantially not containing particles" means that, for example, in the case of inorganic particles, when the inorganic element is quantified by fluorescence X-ray analysis, it is detected by weight of 50 ppm or less, preferably 10 ppm or less, particularly preferably. It means the content which falls below the limit.

The orientation film may have various functional layers. Examples of such functional layers include a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a low reflection antiglare layer, an antireflection antiglare layer, an antistatic layer, a silicone layer, an adhesive layer, an antifouling layer, a water repellent layer and a blue cut layer, etc. One or more selected from the group consisting of may be used. By providing an anti-glare layer, an anti-reflection layer, a low-reflection layer, a low-reflection anti-glare layer, and an anti-reflection anti-glare layer, the effect of improving color unevenness when observed from the oblique direction can also be expected.

When providing various functional layers, it is preferable to have an easily adhesive layer on the surface of the orientation film. At this time, it is preferable to adjust the refractive index of the easily bonding layer to be near the geometric average of the refractive index of the functional layer and the refractive index of the alignment film from the viewpoint of suppressing interference caused by reflected light. The adjustment of the refractive index of the easily adhesive layer can be performed by a known method, and can be easily adjusted by, for example, containing titanium, zirconium, or other metal species in the binder resin.

(Hard coat layer)

The hard coat layer may be a layer having hardness and transparency, and is usually formed as a cured resin layer of various curable resins such as an ionizing radiation curable resin cured by ultraviolet rays or electron beams, and a thermosetting resin cured by heat. In order to appropriately add flexibility and other physical properties to these curable resins, a thermoplastic resin or the like may be appropriately added. Among the curable resins, ionizing radiation curable resins are preferred from the viewpoint of obtaining a representative and excellent hard coating film.

As the ionizing radiation curable resin, a conventionally known resin may be appropriately employed. In addition, as the ionizing radiation curable resin, a radically polymerizable compound having an ethylenic double bond, a cationic polymerizable compound such as an epoxy compound, etc. are typically used, and these compounds are monomers, oligomers, prepolymers, etc., which may be used alone or in combination of two or more. Can be used in combination. Representative compounds are various (meth)acrylate-based compounds that are radically polymerizable compounds. Among the (meth)acrylate-based compounds, examples of compounds used with a relatively low molecular weight include polyester (meth)acrylate, polyether (meth)acrylate, acrylic (meth)acrylate, epoxy (meth)acrylate, Urethane (meth)acrylate, etc. are mentioned.

Examples of the monomer include monofunctional monomers such as ethyl (meth)acrylate, ethylhexyl (meth)acrylate, styrene, methylstyrene, and N-vinylpyrrolidone; or, for example, trimethylolpropane tri(meth) Acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di( Polyfunctional monomers, such as meth)acrylate and neopentyl glycol di(meth)acrylate, etc. are also used suitably. The (meth)acrylate means an acrylate or a methacrylate.

In the case of curing the ionizing radiation curable resin with an electron beam, a photoinitiator is unnecessary, but in the case of curing with ultraviolet rays, a known photoinitiator is used. For example, in the case of a radical polymerization system, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. can be used alone or in combination as a photoinitiator. In the case of a cationic polymerization system, an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonic acid ester, etc. can be used alone or in combination as a photoinitiator.

The thickness of the hard coat layer may be an appropriate thickness, for example, 0.1 to 100 µm, but usually 1 to 30 µm. Further, the hard coat layer can be formed by appropriately employing various known coating methods.

A thermoplastic resin or a thermosetting resin may be appropriately added to the ionizing radiation curable resin in order to adjust properties appropriately. As a thermoplastic resin or a thermosetting resin, acrylic resin, urethane resin, polyester resin, etc. are mentioned, respectively, for example.

In order to impart light resistance to the hard coat layer to prevent discoloration, deterioration in intensity, cracking, etc. due to ultraviolet rays contained in sunlight or the like, it is also preferable to add an ultraviolet absorber to the ionizing radiation curable resin. In the case of adding an ultraviolet absorber, in order to reliably prevent curing of the hard coat layer from being inhibited by the ultraviolet absorber, the ionizing radiation curable resin is preferably cured with an electron beam. The ultraviolet absorber may be selected from known substances such as organic ultraviolet absorbers such as benzotriazole compounds and benzophenone compounds, or inorganic ultraviolet absorbers such as zinc oxide, titanium oxide and cerium oxide in fine particles having a particle diameter of 0.2 μm or less. The amount of the ultraviolet absorber added is about 0.01 to 5% by mass in the ionizing radiation curable resin composition. In order to further improve light resistance, it is preferable to add a radical scavenger such as a hindered amine radical scavenger in combination with an ultraviolet absorber. In addition, the electron beam irradiation has an acceleration voltage of 70 kV to 1 MV and an irradiation dose of 5 to 100 kGy (0.5 to 10 Mrad).

(Glare layer)

As the antiglare layer, a conventionally known one may be appropriately adopted, and is generally formed as a layer in which an antiglare agent is dispersed in a resin. As the anti-glare agent, inorganic or organic fine particles are used. The shape of these fine particles is a spherical shape, an ellipse shape, and the like. The fine particles are preferably transparent. Examples of such fine particles include silica beads as inorganic fine particles and resin beads as organic fine particles. Examples of the resin beads include styrene beads, melamine beads, acrylic beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, benzoguanamine-formaldehyde beads, and the like. The fine particles can be usually added in an amount of 2 to 30 parts by mass, preferably about 10 to 25 parts by mass per 100 parts by mass of the resin powder.

It is preferable that the resin for dispersing and maintaining the anti-glare agent has a higher hardness as possible as in the hard coat layer. Therefore, as the resin, for example, a curable resin such as an ionizing radiation curable resin or a thermosetting resin described in the hard coat layer can be used.

The thickness of the anti-glare layer may be a suitable thickness, usually about 1 to 20 µm. The antiglare layer can be formed by appropriately employing various known coating methods. In addition, in the coating liquid for forming the anti-glare layer, it is preferable to appropriately add a known anti-settling agent such as silica in order to prevent precipitation of the anti-glare agent.

(Anti-reflection layer)

As the antireflection layer, a conventionally known one may be appropriately employed. In general, the antireflection layer is composed of at least a low refractive index layer, and also consists of a multi-layered layer with a low refractive index layer and a high refractive index layer (which has a higher refractive index than the low refractive index layer) alternately stacked adjacent to each other, and the surface side as a low refractive index layer. . Each thickness of the low-refractive-index layer and the high-refractive-index layer may be a suitable thickness according to the application, and is preferably about 0.1 µm when stacked adjacent to each other, and about 0.1 to 1 µm when the low-refractive-index layer alone.

As the low refractive index layer, a layer containing a low refractive index material such as silica and magnesium fluoride in a resin, a layer of a low refractive index resin such as a fluorine-based resin, a layer containing a low refractive index material in a low refractive index resin, a low refractive index such as silica and magnesium fluoride A thin film formed by forming a layer of a material by a thin film formation method (for example, a physical or chemical vapor phase growth method such as vapor deposition, sputtering, CVD, etc.), a film formed by a sol-gel method to form a silicon oxide gel film from a sol solution of silicon oxide, or Examples of the refractive index material include a layer in which pore-containing fine particles are contained in a resin.

The pore-containing fine particles refer to fine particles containing gas inside, fine particles having a porous structure containing gas, and the like, and the refractive index of the entire fine particles is reduced in appearance due to the voids caused by the gas relative to the original refractive index of the solid part of the fine particles. Means fine particles. Examples of such pore-containing fine particles include silica fine particles disclosed in Japanese Patent Application Laid-Open No. 2001-233611. As the pore-containing fine particles, in addition to inorganic substances such as silica, hollow polymer fine particles disclosed in Japanese Unexamined Patent Application Publication No. 2002-805031 and the like can be mentioned. The particle diameter of the pore-containing fine particles is, for example, about 5 to 300 nm.

As a high refractive index layer, a layer containing a high refractive index material such as titanium oxide, zirconium oxide, and zinc oxide in a resin, a layer of a high refractive index resin such as a fluorine-free resin, a layer containing a high refractive index material in a high refractive index resin, and titanium oxide , A thin film formed by forming a layer made of a high refractive index material such as zirconium oxide or zinc oxide by a thin film formation method (for example, a physical or chemical vapor phase growth method such as vapor deposition, sputtering, or CVD).

(Antistatic layer)

As the antistatic layer, a conventionally known one may be appropriately employed, and is generally formed as a layer containing an antistatic layer in a resin. As the antistatic layer, an organic or inorganic compound is used. For example, as an antistatic layer of an organic compound, a cationic antistatic agent, an anionic antistatic agent, an amphoteric antistatic agent, a nonionic antistatic agent, an organometallic antistatic agent, etc. can be mentioned, and these antistatic agents are only used as low molecular weight compounds. It is also used as a polymer compound. In addition, conductive polymers such as polythiophene and polyaniline are also used as the antistatic agent. Further, as the antistatic agent, conductive fine particles made of, for example, metal oxides are also used. The particle diameter of the conductive fine particles is, for example, about 0.1 nm to 0.1 μm in average particle diameter from the viewpoint of transparency. In addition, as the metal oxide, for example, ZnO, CeO ₂ , Sb ₂ O ₂ , SnO ₂ , ITO (indium doped tin oxide), In ₂ O ₃ , Al ₂ O ₃ , ATO (antimony doped tin oxide), AZO ( Aluminum-doped zinc oxide) and the like.

As the resin containing the antistatic layer, for example, a curable resin such as an ionizing radiation curable resin or a thermosetting resin as described in the hard coat layer is used, as well as the surface of the antistatic layer itself by forming an antistatic layer as an intermediate layer. When strength is unnecessary, a thermoplastic resin or the like is also used. The thickness of the antistatic layer may be a suitable thickness, usually about 0.01 to 5 µm. The antistatic layer can be formed by appropriately employing various known coating methods.

(Antifouling floor)

As the antifouling layer, a conventionally known one may be appropriately adopted, and in general, a paint containing an antifouling agent such as wax is used in the resin, including silicon compounds such as silicone oil and silicone resin; fluorine compounds such as fluorine surfactants and fluorine resins; Thus, it can be formed by a known coating method. The thickness of the antifouling layer may be set to an appropriate thickness, usually about 1 to 10 µm.

Example

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited by the following examples, but it is also possible to carry out appropriate changes within a range suitable for the purpose of the present invention, and they are all It is included in the technical scope of the present invention.

An image display device including a touch panel having the configuration shown in the following "Configuration of an image display device" was produced, and a white image was displayed by disposing a polarizing film on the viewer side surface so as to be parallel to the viewer side surface. While maintaining the parallel state, while rotating the polarization axis of the polarizing film by 360 degrees, the white image was viewed from the front through the polarizing film to check the presence and extent of occurrence of rainbow spots, and evaluated according to the following criteria.

<Evaluation criteria>

◎: When observed from the front, no rainbow stains are observed.

○: When observed from the front, a rainbow stain is slightly observed.

X: When observed from the front, a rainbow stain is strongly observed.

<Configuration of image display device>

(1) Backlight light source: White LED or cold cathode tube

(2) Image display cell: Liquid crystal cell

(3) Polarizing plate on the viewing side: A polarizing plate in which a TAC film is adhered to both sides of a polarizer made of PVA and iodine

(4) Light source side scattering prevention film: The following orientation films A to C were used alone or in combination (refer to Table 4 below). When two oriented films were used, they were bonded together so that the mutually oriented main axes were parallel.

Orientation film A

PET resin pellets having an intrinsic viscosity of 0.62 dl/g were dried under reduced pressure (1 Torr) at 135°C for 6 hours, and then fed to an extruder and dissolved at 285°C. This polymer was filtered through a filter medium of a stainless steel sintered body (with a nominal filtration accuracy of 10 µm, 95% of particles cut), extruded from the crest into a sheet shape, and then wrapped around a casting drum with a surface temperature of 30°C using an electrostatic casting method to cool and solidify. An unstretched film was made.

The unstretched film was introduced into a tenter stretching machine, the end of the film was held with a clip, and guided to a hot air zone at a temperature of 125°C, and stretched 4.0 times in the width direction. Next, while maintaining the width stretched in the width direction, the treatment was carried out at a temperature of 225°C for 30 seconds, and further 3% relaxation treatment was performed in the width direction, and the uniaxial orientation film A having a film thickness of about 100 μm Got it. The retardation value was 10,200 nm. Rth was 13,233 nm, and Re/Rth ratio was 0.771.

Orientation film B

By changing the thickness of the unstretched film, the uniaxial orientation film B was obtained in the same manner as the orientation film A except that the thickness of the film was set to about 80 µm. The retardation value was 8,300 nm.

Orientation film C

By changing the thickness of the unstretched film, the uniaxial orientation film C was obtained in the same manner as the orientation film A except that the thickness of the film was set to about 50 µm. The retardation value was 5,200 nm. Rth was 6,600 nm, and Re/Rth ratio was 0.788.

(5) Touch panel: Resistive touch panel manufactured using ITO glass with a transparent conductive layer made of ITO on a glass substrate.

(6) Visual side scattering prevention film: The following orientation films 1-5 were used in combination of 1 sheet or 2 sheets (refer to following Table 4). When two oriented films were used, they were bonded together so that the mutually oriented main axes were parallel.

Orientation film 1

It carried out similarly to the orientation film A, and obtained the orientation film 1 whose retardation value is 10,200 nm. Rth was 13,233 nm, and Re/Rth ratio was 0.771.

Orientation film 2

It carried out similarly to the orientation film B, and obtained the orientation film 2 whose retardation value is 8,300 nm.

Orientation film 3

By changing the thickness of the unstretched film, the uniaxial orientation film 3 was obtained in the same manner as the orientation film A except that the thickness of the film was set to about 65 µm. The retardation value was 6,600 nm.

Orientation film 4

It carried out similarly to the orientation film C, and obtained the orientation film 4 whose retardation value is 5,200 nm. Rth was 6,600 nm, and Re/Rth ratio was 0.788.

Orientation film 5

The unstretched film was heated to 105°C using a heated roll group and an infrared heater, and then stretched 2.0 times in the running direction with a roll group having a difference in circumferential speed, and then stretched 4.0 times in the width direction in the same manner as the orientation film A. In the same manner as the orientation film A, biaxially oriented orientation film 5 having a film thickness of about 50 μm was obtained. The retardation value was 3,200 nm. The Rth was 7,340 nm, and the Re/Rth ratio was 0.436.

The light source side scattering prevention film and the visibility side scattering prevention film were arranged so that the angle formed by the orientation main axis of the orientation film on the side with higher retardation and the polarization axis of the viewing side polarizer was 45 degrees. In addition, the orientation film with the lower retardation value was arranged so that the angle formed by the orientation principal axis and the orientation principal axis of the orientation film with the higher retardation was 30 degrees, and the above rainbow stain evaluation (◎, ○, ×) was performed. I did. In addition, the two orientation films used as the light source side scattering prevention film in Test No. 13 were arranged so that the angle formed by their orientation main axis might be 7 degrees. In addition, aside from the above-described rainbow spot evaluation, the rainbow spot was evaluated while rotating without fixing the orientation film on the viewer side.

The retardation (Re) was measured as follows. That is, the orientation principal axis direction of a film was calculated|required using two polarizing plates, and the 4cm*2cm rectangle was cut out so that the orientation principal axis direction might be orthogonal, and it was set as the sample for measurement. Refractive indexes (Nx, Ny) of the two axes orthogonal to this sample and the refractive index (Nz) of the thickness direction were obtained using an Abbe refractometer (manufactured by Atago, NAR-4T), and the absolute value of the difference in refractive index of the two axes (|Nx -Ny|) was calculated|required as the anisotropy (ΔNxy) of the refractive index. The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by FineLuf), and the unit was converted to nm. The retardation (Re) was obtained from the product of the refractive index anisotropy (ΔNxy) and the film thickness d (nm) (ΔNxy×d). In addition, Nx, Ny, Nz and film thickness d (nm) were calculated by the same method as for the measurement of retardation, and the average value of (△Nxz×d) and (△Nyz×d) was calculated to determine the thickness direction retardation (Rth). Obtained.

The evaluation results are shown in Table 2 below.

As shown in Table 2, when two orientation films having a retardation of 3,000 nm or more are installed on the viewer side than on the viewer side polarizer, and the retardation of each orientation film is the same, a clear rainbow stain occurs and the visibility is significantly lowered. It was confirmed to be. On the other hand, it was confirmed that the occurrence of rainbow spots was suppressed by making a difference of 1,800 nm or more in the retardation values of the two oriented films, and the effect became remarkable by increasing the retardation difference. In addition, if the retardation difference between the two oriented films is about 3,500 nm or more, particularly 4,000 nm or more, even if the angle formed by the orientation main axis of the two oriented films is 45 degrees, the rainbow stain is not conspicuous, and the orientation angle of the film is increased. It was confirmed that the rainbow stain was not conspicuous. When the retardation difference between the two oriented films was 1,700 nm or less, it was confirmed that a rainbow stain was not conspicuous when the angle of the orientation main axis of both films was 20 degrees or less, and less noticeable at 15 degrees or less.

When the angle formed by the orientation main axis of the two orientation films is 20 degrees to 45 degrees, it is shown that the rainbow unevenness is inconspicuous if the equation of "corresponding angle (degrees) ≤ 0.00667 x retardation difference + 13" is satisfied, Preferably, it was shown that the rainbow irregularity can be suppressed more effectively by satisfying the "corresponding angle (degrees) ≤ 0.00667 × retardation difference +23".

1 liquid crystal display
2 light source
3 Light source side polarizer
4 liquid crystal cell
5 viewer side polarizer
6 touch panel
7 light source side polarizer
8 viewer side polarizer
9a polarizer protective film
9b polarizer protective film
10a polarizer protective film
10b viewer side polarizer protective film
11 Light source side transparent conductive film
11a light source side base film
11b transparent conductive layer
12 viewer side transparent conductive film
12a viewer side base film
12b transparent conductive layer
13 spacer
14 Light source side shatterproof film
15 viewer side shatterproof film

Claims (3)

(1) a white light source with a continuous emission spectrum,
(2) an image display cell,
(3) a polarizer disposed on the viewer side than the image display cell, and
(4) having two oriented films having retardation of 3,000 nm or more and 150,000 nm or less on the visible side than the polarizer,
The two oriented films have a retardation ratio (Re/Rth) of 0.2 or more and 2.0 or less,
The two oriented films have different retardations, and the difference is 1,800 nm or more,
Image display device. The method of claim 1,
An image display device in which a difference in retardation between the two alignment films is 3,500 nm or more. The method according to claim 1 or 2,
The white light source having the continuous emission spectrum is a white light emitting diode.

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