JPH09127885A - Display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to lessen the reflection of the light from outside entering from the exit surface of an element within the element and to improve the contrast of a displayed image, etc., by providing the light exit surface with a circularly polarizing means. SOLUTION: Only the linearly polarized light component in the longitudinal direction aligned to the axis 11a of the polarized light of a linear polarizing plate 11 among the external light rays L having the random polarization components made incident on the linearly polarized light 11 from outside is made incident by passing the polarizing plate 11. The incident linearly polarized light 14 in the longitudinal direction changes to a right (or left) circularly polarized light 15 at the time of passing a quarter-wave plate 23 having a double refractive main axis 23a inclined 45 deg.. This right (or left) circularly polarized light 15 is reflected on the inside surface of the electrode 1 of an org. electric field light emitting (org. E1) element 40 and is reflected as the left (or right) circularly polarized light 16. This light is changed again into the linearly polarized light 17 in the transverse direction at the time of passing the quarter-wave plate 23 and the emission thereof to the outside is shut off by the polarizing plate 11. As a result, the degradation in the contrast at the time of light emission as the display element does not arise and the sufficient light emissive luminance is maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device,
For example, a self-luminous flat display, in particular
The present invention relates to a display device suitable for an organic electroluminescent display using an organic thin film for an electroluminescent layer.

[0002]

2. Description of the Related Art An organic electroluminescent device (hereinafter sometimes referred to as an organic EL device) has a film thickness of 1 μm or less,
It has ideal characteristics as a self-luminous display device, such as converting electric energy into light energy by injecting a current and emitting light in a planar manner.

FIG. 22 shows an example of a conventional organic EL element 10. This organic EL element 10 includes an ITO (Indium tin oxide) transparent electrode 5, a transparent substrate (for example, a glass substrate) 6,
The hole transport layer 4, the light emitting layer 3, the electron transport layer 2, and the cathode (for example, an aluminum electrode) 1 are sequentially formed by, for example, a vacuum vapor deposition method.

By selectively applying a DC voltage 7 between the transparent electrode 5 which is an anode and the cathode 1, the holes injected from the transparent electrode 5 pass through the hole transport layer 4 and from the cathode 1. The injected electrons reach the light emitting layer 3 via the electron transport layer 2 and electron-hole recombination occurs, and light emission 8 of a predetermined wavelength is generated from this, and the transparent substrate 6
It can be observed from the side.

The light emitting layer 3 may contain, for example, a zinc complex, but may be a layer consisting essentially of a zinc complex (provided that a plurality of zinc complexes can be used in combination), or zinc. It may be a layer in which a fluorescent substance is added to the complex. In addition, zinc complex and other luminescent substances such as anthracene, naphthalene, phenanthrene, pyrene, chrysene,
Perylene, butadiene, coumarin, acridine, stilbene and the like may be used in combination. A mixture with such a zinc complex or a fluorescent substance can be contained in the electron transport layer 2.

FIG. 23 shows another conventional example. In this example, the light emitting layer 3 is omitted, and the electron transporting layer 2 is made to contain a mixture with the above zinc complex or a fluorescent substance. Light emission of a predetermined wavelength from the interface between the transport layer 2 and the hole transport layer 4
18 shows an organic EL element 20 configured so that 18 occurs.

FIG. 24 shows a specific example of the above organic EL element. That is, a laminated body of each organic layer (hole transport layer 4, light emitting layer 3 or electron transport layer 2) is disposed between the cathode 1 and the anode 5, and these electrodes are crossed in a matrix to form a stripe shape. A signal voltage is applied in time series by the luminance signal circuit 30 and the control circuit 31 with a built-in shift register, and light is emitted at each of a large number of intersection positions (pixels).

Therefore, with such a structure, it can be used not only as a display but also as an image reproducing apparatus. The above stripe pattern can be arranged for each color of red (R), green (G), and blue (B) to be configured for full color or multi-color.

In a display device including a plurality of pixels using such an organic EL element, the organic thin film layers 2, 3 and 4 which emit light are generally sandwiched between the transparent electrode 5 and the metal electrode 1 and are transparent. Light is emitted to the electrode 5 side.

However, in the organic EL element, Mg and MgA are used as the metal electrode 1 in order to improve the emission brightness.
It is often the case that a metal having a high light reflectance, such as g, MgIn, Al, LiAl, etc., is used to reflect the emitted light to increase the emission amount (emission luminance). Therefore, in such an element structure, when it is not electroluminescent, it is a mirror with strong light reflectivity, and there is reflection or reflection of the outside scene.
Further, even when the light is emitted, the contrast is lowered and black cannot be expressed, which may cause a fatal problem for use as a display.

As described above, in the conventional organic EL element, the reflection of the incident external light inside the element is likely to adversely affect the pixel display. However, in the conventional organic EL device, no effective countermeasure has been taken against the problem of reflection of external light.

[0012]

SUMMARY OF THE INVENTION The object of the present invention was made in view of the above-mentioned circumstances, in which light reflection by a highly reflective reflecting surface such as a metal electrode incorporated in an element is prevented. It is an object of the present invention to provide a display element which can be effectively prevented and which does not cause a decrease in contrast during light emission as a display element and can secure sufficient emission brightness.

[0013]

The present inventor has conducted extensive studies in order to solve the above-mentioned object, and as a result, the reflection of external light can be greatly reduced without impairing the performance as a light emitting device. The inventors have found a prevention mechanism and arrived at the present invention.

That is, the present invention relates to a display element in which the circularly polarizing means is provided on the light emitting surface side.

The present inventor significantly reduces the reflection of the light from the outside incident from the light emitting surface of the display element inside the element, and significantly improves the contrast of the display image and the like.
It has been found that it is extremely effective to provide a circular polarization means on the light emitting surface.

The above "display element" means an organic EL.
The concept includes not only elements such as elements but also devices such as displays incorporating the elements (the same applies hereinafter).

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The display device according to the present invention may have a structure in which a light reflecting layer is formed on the side of the light emitting layer opposite to the light emitting surface.

Further, the circularly polarizing means is particularly a linear polarizing plate and a linear polarizing plate.
It is desirable to be composed of a quarter wave plate.

In this case, the quarter-wave plate is composed of a plurality of birefringent plates so that a phase difference of approximately one-quarter wavelength can be obtained in a wide wavelength range. It is desirable to be configured by a plurality of birefringent plates having different refraction characteristics (for example, different birefringent plates are bonded together).

Further, it is desirable that the quarter-wave plate has a polarization axis that is 45 degrees with respect to the polarization axis of the linear polarizing plate or that has an inclination equivalent thereto.

In the display element of the present invention, specifically, the circularly polarizing means is provided on the light emitting side of the element, and the incident light from the outside is transmitted, but the incident light is reflected light reflected inside the element. It is designed so that it will not be exposed to the outside.

Further, a first electrode, a light emitting layer, and a second electrode having a high light reflectance are laminated on an optically transparent substrate, and on the opposite substrate on which these are laminated. Circular polarization means is provided and can be configured as an electroluminescent device.

A first electrode, a light emitting layer, and a second electrode having a high light reflectance are laminated on an optically transparent substrate, and circularly polarized light is provided between these laminates and the substrate. Means are provided and can be configured as an electroluminescent device. In this case, at least a part of the transparent substrate may also serve as the circular polarization means.

In these electroluminescent devices, at least one stripe-shaped plurality of organic layers including a light-emitting layer are provided on a plurality of stripe-shaped first electrodes (for example, ITO transparent electrodes), and the first electrodes are provided. A plurality of crossed stripe-shaped second electrodes (for example, a metal electrode such as Al having strong light reflectivity)
Are preferably provided, and are suitable for an organic electroluminescence device (organic EL device) or a display. This is suitable for a passive matrix type (simple matrix type) display.

[0025]

EXAMPLES The present invention will be described in detail below with reference to examples.

1 to 17 show a first embodiment in which the present invention is applied to an organic EL device.

FIG. 1 shows that in the organic EL element 40 according to this embodiment, a quarter wavelength plate 23 is provided on the transparent substrate 6 side which is a light emitting surface.
FIG. 3 is a schematic diagram showing a state in which a linear polarizing plate 11 is sequentially arranged.

Then, the external light L is reflected by the linear polarization plates 11 and 1 /
Passing through the circular polarization means 49 constituted by the four-wave plate 23,
Although reflected by the inner surface of the metal electrode 1 of the organic EL element 40, this reflected light is blocked by the circular polarization means 49 and does not return to the external light incident side. In order to understand this, the contents examined by the present inventor in the course of reaching the present invention will be described with reference to FIG.

FIG. 21 shows an optical system for preventing the return of the laser light of the optical pickup, which is well known in the optical technical field.

That is, according to the optical system shown in FIG.
1/4 wavelength plate 12 and linear polarization plate 11 on the light incident side with respect to 13
Are sequentially arranged, and light L incident from the outside of the linear polarizing plate 11
Is reflected by the reflecting surface (reflecting plate) 13, and the reflected light returns in the direction opposite to that at the time of incidence. This will be described below.

First, since the linearly polarizing plate 11 has a vertical polarization axis 11a as shown in the drawing, the randomly polarized light L entering the linearly polarizing plate 11 is a linearly polarized light that matches the polarization axis 11a. Only the component passes and becomes linearly polarized light 14. And 1 /
The four-wave plate 12 has a birefringent main axis 12a inclined by 45 degrees with respect to the polarization axis 11a of the linear polarizing plate 11 described above.

Therefore, when the randomly polarized light L is incident on the linear polarizing plate 11, the polarized light 14 that has passed through the linear polarizing plate 11 and is vertically polarized is 1 /
Due to the birefringence characteristic of the four-wave plate 12, right (or left) circularly polarized light 15 is incident on the reflecting surface 13 as shown in the figure. That is, the linear polarization plate 11 and the quarter-wave plate 12 constitute a circular polarization means 19, and circular polarization is realized by combining both of them.

Then, the reflected light 16 reflected by the reflecting surface 13
Is returned to the left (or right) polarized light in the direction opposite to that at the time of incidence, and is incident on the quarter wavelength plate 12 again. This incident light 16 is
Due to the birefringence characteristics of the quarter-wave plate 12, this quarter-wave plate
After passing through 12, first, the reflected light 17 having a horizontal polarization as shown in the drawing that is orthogonal to the vertical polarization immediately after entering from the linear polarization plate 11
Changes to

Therefore, since this polarized light 17 has a polarization direction different from the polarization axis 11a of the linear polarizing plate 11, it is blocked by the linear polarizing plate 11 and cannot go out of the linear polarizing plate 11. .

However, although such an optical system for preventing reflection (return) is used for an optical pickup, it has been proved that it cannot be applied as it is to the above-mentioned organic EL element due to its peculiarity. did.

That is, instead of monochromatic light such as laser light,
In the wavelength range over the entire visible light range, since the conventional quarter-wave plate 12 as shown in FIG. 21 is used as a single plate, it is specified in the same manner as the results shown by the curves 26 and 27 in FIG. The phase difference of ¼ wavelength can be obtained only at the wavelength (in other words, other than the specific wavelength).

Therefore, the return light cannot be blocked over the entire visible light range, and the desired antireflection effect cannot be obtained. Therefore, as shown by the curve a in FIG. 4, reflection can be prevented only for light having a wavelength in the vicinity of 550 nm, which is substantially the center of visible light.

However, the present inventor has noticed that a special birefringent plate capable of obtaining a phase difference of ¼ wavelength in almost the entire visible light range has been developed, and this has been cleverly applied to an organic EL element. The present invention has devised a structure capable of effectively and sufficiently shielding the return light due to the reflection of the above-mentioned incident light inside the element.

That is, as shown in FIG. 1, external light L having a random polarization component which is incident on the linear polarizing plate 11 from the outside.
Of these, only the vertical linearly polarized light component that matches the polarization axis 11a of the linearly polarizing plate 11 passes through the linearly polarizing plate 11 and is incident, and the incident vertical linearly polarized light 14 is the birefringence with an inclination of 45 degrees. When passing through the quarter-wave plate 23 having the principal axis 23a, it changes to right (or left) circularly polarized light 15, and this right (or left) circularly polarized light 15 is reflected on the inner surface of the electrode 1 of the organic EL element 40, The light is reflected as left (or right) circularly polarized light 16 and again changes to lateral linearly polarized light 17 when passing through the quarter-wave plate 23, and is blocked from being emitted to the outside by the linearly polarizing plate 11.

The mechanism for preventing such reflection (return) is similar to that described in FIG. 21, but the quarter wave plate 23 used in this embodiment has a different birefringence characteristic as shown in FIG. It is characterized in that it is constituted by laminating a single birefringent plate 21 and a birefringent plate 22. With this, a phase difference of ¼ wavelength can be obtained in almost the entire visible light region.

FIG. 2 is an enlarged cross-sectional view showing a main part of a concrete example of the organic EL element 40 schematically shown in FIG. 1. On one surface of the transparent substrate 6, the ITO transparent electrode 5 and the holes are formed. The transport layer 4, the light emitting layer 3, the electron transport layer 2 and the metal electrode 1 are laminated, and the birefringent plate 21 and the birefringent plate 22 are attached to the light emitting side of the transparent substrate 6.

Here, the birefringence plates 21 and 22 have different plate thicknesses and different birefringence dispersions. And
If they are attached so that the phase difference is canceled, the amount of phase difference can be set to an arbitrary value at two wavelengths. If there are three pieces, since the color changes depending on the frequency, as in the case of three wavelengths, the phase difference can be adjusted in the same way as the method of correcting chromatic aberration by combining lenses in the optical system. Spaces may exist between the birefringent plate 21 and the birefringent plate 22 and between the birefringent plate 22 and the linear polarizing plate 11.

Here, the phase difference Δ of the phase difference plate (birefringence plate)
The following relationship generally holds between nd and the birefringence (n _e , n _o ). Δnd = (n _e −n _o ) × d (where Δn is birefringence, n _e is the refractive index of extraordinary light, n _o is the refractive index of ordinary light, and d is the plate thickness).

The birefringence (Δn) of the retardation plate is
Generally, it depends on the wavelength (λ) as expressed by the following equation. Δn (λ) = A + B / (λ ² −λ _O ² ) (where A and B are constants and λ _O is an absorption edge).

As described above, generally, the wavelength dependence of the phase difference of the birefringence is almost equal to the refractive index dispersion, and exhibits a change like the curve of FIG. 3 showing the wavelength dependence of the birefringence phase difference. That is, the wavelength dependence of the phase difference of the birefringence is large in both the birefringence dispersion curve 26 of the birefringence plate 21 and the birefringence dispersion curve 27 of the birefringence plate 22 in the blue region on the short wavelength side, and the long wavelength side. Is smaller in the red area.

In this case, the ideal birefringence index dispersion characteristic of the 1/4 wavelength plate is that the birefringence phase difference corresponding to 1/4 of each wavelength (that is, 100 nm at a wavelength of 400 nm and 700 nm at a wavelength of 400 nm, for example).
175 nm), the phase difference of 1/4 wavelength can be obtained by the refractive index dispersion of the birefringent plate 21 and the birefringent plate 22 shown by the curves 26 and 27 in FIG. The wavelength range becomes narrow.

That is, when the quarter-wave plate is, for example, only the birefringent plate 21 in FIGS. 1 and 2, the refractive index dispersion curve 26 in FIG. The phase difference of ¼ wavelength can be obtained only near the wavelength range of about 500 nm where Similarly, the quarter-wave plate is the birefringent plate 22.
If it is only 1/4, it is only around the wavelength range of about 460 nm.
The phase difference of wavelength cannot be obtained. Therefore, as it is, 1
The wavelength range in which the phase difference of / 4 wavelength is obtained is extremely limited, and the antireflection (return prevention) effect shown in FIG. 1 cannot be obtained in a wide wavelength range.

Thus, with only one birefringent plate,
The wavelength range in which the phase difference of / 4 wavelength is obtained becomes considerably narrow.
Therefore, the phase difference of ¼ wavelength can be obtained only at a specific wavelength, and when the light having a wavelength other than that wavelength is incident, the above-mentioned change in the polarization direction cannot be obtained. Therefore, as shown in FIG. When the number of the refraction plates is one, the reflectance greatly increases on the short wavelength side and the long wavelength side as shown by the curve a.

On the other hand, when the birefringent plate 21 and the birefringent plate 22 are bonded together as shown in FIGS. 1 and 2, a peculiar birefringence dispersion characteristic is obtained as shown by a curve 24 in FIG. be able to. That is, the thickness of each birefringent plate is changed to cancel the phase difference, and a change curve very close to the quarter-wave retardation line (refractive index dispersion line) 25 can be obtained. Although such a superposition effect itself is publicly known, the present inventor first applied the effect to an organic EL device and realized a very useful result.

That is, as shown in FIG. 3, a quarter-wave phase difference is almost obtained over almost the entire wavelength range (particularly in the range of 460 nm to 660 nm), and the change of the polarization direction shown in FIG. 1 is ensured. Therefore, the reflected light 17 is sufficiently shielded without passing through the polarizing plate 11. Therefore, a sufficient antireflection effect is obtained, the reflectance is almost zero in a wide wavelength range as shown by the curve b in FIG. 4, and the reflectance is extremely small on the short wavelength side and the long wavelength side.

FIG. 4 is a graph showing the change in reflectance with wavelength due to the birefringence phase difference. A birefringence plate having a phase difference of 1/4 wavelength set to 550 nm which is the center wavelength of visible light is shown in FIG.
It is a calculation result when it is mounted on a mirror having 100% reflectance. In this case, the reflection is strong in the blue and red wavelength range,
The display surface of the organic EL element looks like a so-called lavender color. And the average reflectance in the visible light range is 5 to 10
%.

On the other hand, when two birefringent plates are stuck together as in the present embodiment, it is possible to match the phase difference of 1/4 wavelength between the two wavelengths, and the 1/4 wavelength around it. Since it does not deviate much from (see FIG. 3), it becomes possible to prevent reflection in almost the entire visible light region. Then, in the calculation similar to the above, the average reflectance is about 1 to 2%, and it looks almost black visually.

From this, as shown in FIGS. 1 and 2, the circular polarization means 49 using the birefringent plates 21 and 22 capable of adjusting the phase difference of ¼ wavelength in a wide wavelength range of visible light is used as the organic EL. Element 40
If it is adhered to the light emitting surface of, it is possible to prevent the return of light in almost all visible light. The return prevention effect is controlled by controlling the thickness d of each of the birefringent plates 21 and 22.
Sufficient reproduction is ensured by reproducing the phase difference of / 4 wavelength.

In the organic EL element, it is necessary for each layer to be formed as a flat film for high performance, and as a result, the metal electrode 1 finally formed is extremely flat like a mirror and causes irregular reflection. The amount of light reflected there is sufficient. However, when such a mirror surface is present, external light is likely to be reflected, and the adverse effect on the display due to the reflection (such as deterioration of contrast) is conspicuous.
However, on the other hand, since such a mirror surface exists, the above-mentioned geometrical optical analysis result is well established, and the antireflection effect of the circularly polarizing plate 49 is surely obtained, which is extremely effective for the organic EL element.

Next, the organic EL element 40 according to this embodiment will be described in more detail. FIG. 5 is a schematic plan view of the organic EL element 40 configured as above. On the upper surface of the transparent substrate 6, ITO transparent electrodes 5 are formed in the same pattern in a stripe shape, and on the transparent electrodes 5, a SiO ₂ insulating film 9 is formed in the same pattern in a matrix orthogonal to these electrodes in a stripe shape. It is formed into a shape. Then, the insulating film 9-
Between 9, the hole transport layer 4, the light emitting layer 3, the electron transport layer 2,
The metal electrodes 1 are laminated in this order in substantially the same pattern, and this laminated body is formed in the same pattern as the insulating film 9 in the same pattern in a stripe shape.

As shown in FIG. 6, on the surface of the transparent substrate 6 in which the respective layers are laminated in a matrix in this way, as shown in FIG. 6, a quarter-wave plate in which the birefringent plate 21 and the birefringent plate 22 are bonded together. 2
A circular polarization means 39 composed of 3 and a linear polarization plate 11 is attached. FIG. 6 showing the state is an enlarged view of the portion a in the cross section taken along the line AA of FIG. The intersection of the upper and lower electrodes is an individual pixel PX. Then, FIG. 7 shows an enlarged cross-sectional view taken along line BB of the portion a as a cross-sectional view.

Next, the manufacturing steps shown in FIGS. 8 to 16 for the organic EL device according to this embodiment shown in FIGS. 5 to 7 will be described in more detail.

FIG. 8 is an enlarged cross-sectional view of the main part showing the manufacturing process. As shown in FIG. 8, the transparent substrate 6 (thickness T = 1.1 m
ITO (Indium Tin Oxi) on one side of the float glass of m
de) by the sputtering method, and then, as shown in FIG.
As shown in the sectional view of line IX), the transparent electrode 5
Is formed into a stripe pattern with a width w ₁ = 2 mm and a pitch w ₂ = 2.54 mm in units of 8 pieces. Each of these transparent electrodes 5 has a resistance of about 300Ω at both ends.

Next, as shown in FIG. 10, the SiO ₂ insulating film 9 is used as a mask to insulate the organic laminated body described later.
For example, 10 stripes are formed by etching after vapor deposition of iO ₂ . Its width w ₃ is 1 mm and its pitch w ₄ is 2.
The thickness is 54 mm and the film thickness t is 100 nm.

The vapor deposition of SiO ₂ uses a vacuum vapor deposition apparatus 32 as shown in FIG. A pair of supporting means 34 fixed below the arm 33 is provided inside the device, and the transparent substrate 6 is faced downward between the fixing means 34, 34, and masks 37, 38 described later are provided. Alternatively, a stage mechanism (not shown) capable of setting 39 is provided. Then, a predetermined number (five) of various vapor deposition sources 35 are arranged below the transparent substrate and the mask. The vapor deposition source 35 is heated by a resistance heating method or an electron beam heating method by a power source 36.

Transparent substrate 6 on which SiO ₂ insulating film 9 is formed
After cleaning the surface thoroughly with an organic solvent and ultraviolet (UV) ozone treatment, the vacuum vapor deposition device 32 adjoins the stripes that emit three colors of red (R), green (G), and blue (B). The organic layer and the metal electrode for each color were formed by the following procedure using the same vapor deposition mask.

First, the transparent substrate 6 and the red (R) color mask 37 are set in the vacuum deposition apparatus 32. FIG. 12 is a partial enlarged cross-sectional view showing the positional relationship between the transparent substrate 6 and the mask 37. As shown in the figure, the vapor deposition aligns (masks) the slit-shaped opening 37a of the mask 37 in the region between the insulating films 9-9. The openings 37a of the mask 37 are formed at intervals of every three holes with respect to the region between the insulating films 9-9. Therefore, this masking shields the region other than the red (R) light emitter region.

As described above, after the red (R) color mask 37 was applied, the vacuum deposition apparatus was maintained at a vacuum degree of 3 × 10 ^-6 Torr, and the triphenyldiamine derivative TPD of the following structural formula was used.
(N, N'-bis (3-methylphenyl) 1,1'-biphenyl-4,4'-diamine) deposition rate 0.3 nm / s
To a thickness of 50 nm to form a hole transport layer 4R.

Then, using the same mask 37 as it is,
Alq ₃ (tris- (8-hydroxyquinoline) aluminum) of the following structural formula and laser dye DCM (4-dicyanomethylene-6- (p-dimethylaminostyryl) -2
-Methyl-4H-pyran) at 0.3 nm / s and 0.03, respectively.
The light emitting layer 3R is vapor-deposited at a vapor deposition rate of nm / s to a thickness of 20 nm, and the light emitting layer 3R is laminated on the hole transport layer 4R in substantially the same pattern.

Then, using the same mask 37 as it is,
Alq ₃ (tris- (8-hydroxyquinoline) aluminum) having the following structural formula was vapor deposited at a vapor deposition rate of 0.3 nm / s to a thickness of 40 nm, and the electron transport layer 2R was laminated on the light emitting layer 3R in substantially the same pattern, Finally, magnesium and silver are vapor-deposited to a thickness of 200 nm by co-evaporation at a vapor deposition rate of 2 nm / s, and the electrode 1 is laminated on the electron transport layer 2R in substantially the same pattern.

[0066]

Embedded image

[0067]

Embedded image

[0068]

Embedded image

Next, as shown in FIG. 13, the mask is changed to the mask 38 for green (G) color. As shown in the drawing, the mask 38 is aligned so that the slit-shaped opening 38a is aligned with the region between the insulating films 9-9 adjacent to the laminated region formed by the red (R) color mask 37. To be done. The mask 38 is formed in the same pattern as the mask 37 for the red (R) color described above, and shields the light emitting regions other than the green (G).

After the mask 38 for the green (G) color was applied in this manner, the vacuum deposition apparatus was maintained at a vacuum degree of 3 × 10 ^-6 Torr, and first, the triphenyldiamine derivative TP described above was used.
D is vapor deposited at a vapor deposition rate of 0.3 nm / s to a thickness of 50 nm to form a hole transport layer 4G.

Then, using the same mask 38 as it is,
The above Alq ₃ is vapor-deposited at a vapor deposition rate of 0.3 nm / s to a thickness of 50 nm, and the light emitting layer 3G is laminated on the hole transport layer 4G in substantially the same pattern. This light emitting layer also serves as the electron transport layer 2G.

Further, magnesium and silver were vapor-deposited on this by co-evaporation at a vapor deposition rate of 2 nm / s to a thickness of 200 nm,
The electrode 1 is laminated in substantially the same pattern as the light emitting layer 3G (and the electron transport layer 2G).

Next, as shown in FIG. 14, the mask 39 is changed to the blue (B) color mask 39. As shown in the drawing, the mask 39 is aligned so that the slit-shaped opening 39a is aligned with the region between the insulating films 9-9 adjacent to the laminated region formed by the mask 38 for the green (G) color. To be done. The mask 39 is formed in the same pattern as the masks for red (R) color and green (G) color, and shields the light emitting regions other than blue (B).

After the mask 39 for the blue (B) color is applied in this manner, the above-mentioned triphenyldiamine derivative TPD is first maintained while the vacuum deposition apparatus is kept at a vacuum degree of 3 × 10 ^-6 Torr.
To a thickness of 50 nm at a deposition rate of 0.3 nm / s to form a hole transport layer 4B.

Then, using the same mask 39 as it is,
Zn (oxz) ₂ (zinc complex of 2- (o-hydroxyphenyl) -benzoxazole) having the following structural formula was vapor-deposited at a vapor deposition rate of 0.3 nm / s to a thickness of 50 nm to form a hole transport layer 4B.
The light emitting layer 3B is laminated on the top in substantially the same pattern. This light emitting layer also serves as the electron transport layer 2B.

Finally, the deposition rate of magnesium and silver is 2
It is vapor-deposited to a thickness of 300 nm by co-evaporation of nm / s, and the electrode 1 is laminated on the light emitting layer 3B (and the electron transport layer 2B) in substantially the same pattern.

[0077]

Embedded image

FIG. 15 shows an organic EL device obtained by stacking organic layers to electrodes (cathodes) by vapor deposition using the same mask for each color in the above manufacturing process. On the back surface of the substrate 6 of the organic EL device thus obtained, the birefringent plates 21 and 22 and the linear polarizing plate 11 were sequentially laminated as shown in FIG. 16 to integrally form a circular polarizing plate 49.

What was used as the circularly polarizing plate 49 is one in which a two-layer laminated broadband quarter-wave plate 23 (manufactured by Nitto Denko Corporation) consisting of birefringent plates 21 and 22 and a linear polarizing plate 11 are bonded together. . These materials are optical crystal thin plates such as calcite and mica.

In the above manufacturing process, the mask was changed under the vacuum condition in the vacuum or in the condition that the vacuum film was broken and the vapor deposition film was exposed to the atmosphere. There was no.

Next, with respect to the organic EL element 40 obtained above, the reflectance of external light was measured.

That is, when the He-Ne laser and the Ar ion laser were irradiated from the light emitting surface side of the transparent substrate of the organic EL element, the reflectance was 75% or more when the above circular polarization means 49 was not used. However, it was confirmed that the reflectance of the present example manufactured by laminating the circular polarization means 49 as described above decreased to 2% or less.

Further, the non-light emitting states of these organic EL devices were measured and compared. As a measuring method, four 40 W fluorescent lamps were lit on the ceiling, the organic EL element was directed almost directly upward 2 m below, and the light emitting surface (panel) was looked into to look into it.

As a result, in the non-light emitting state, the circular polarization means 49
In the case of not using, the metallic luster of the metal electrode was seen and the image of the ceiling was seen, but in the case of this example, the metal electrode was observed to be almost black.

Then, when the organic EL element is made to emit light, in the case of this embodiment, the color purity of the emitted colors of red, green and blue is good, and the non-emissive portion around the light emitting portion looks black, and the light is emitted. The contrast between the part and the non-light emitting part was clearly observed, and the contrast was very good. On the other hand, in the case where the circularly polarizing means 49 is not used, the emission brightness is twice or more as compared with that of the present embodiment, but the color is not clear and the image of the outside world is projected, which is very difficult to see. Met.

As described above, according to this embodiment, the birefringent plate
A circular polarization means 49 composed of a quarter-wave plate 23 in which 21 and a birefringent plate 22 are bonded together and a linear polarization plate 11 is provided on the surface of the organic EL element opposite to the light emitting surface of the transparent substrate. Therefore, the reflection of the incident external light inside the organic EL element is significantly reduced, and the reflection can be prevented in almost the entire visible light region. Therefore, even in the light emitting state of the element, the light emitting portion and the non-light emitting portion can be clearly distinguished, the contrast is very good, and the color purity of the emitted color is good.

The organic EL element 25 according to the present embodiment described above was lit by the so-called dynamic drive method by the drive circuit shown in FIG. 17 having the current control circuit section.

This drive circuit uses an operational amplifier OPA to operate a device current flowing through a column (current flowing through a pixel PX).
i is configured to be controlled by a luminance signal from the outside.

That is, the stripe-shaped column electrodes (the above-mentioned electrodes 1) and the stripe-shaped line electrodes (the above-mentioned transparent electrodes 5) vertically intersect each other in a matrix, and each pixel (pixel) is located at this intersection. The PX is formed in a passive matrix type structure. Each pixel PX can be regarded equivalently as a diode D connected in the forward direction. Then, one column electrode 1 is connected to each current control circuit portion 41, and the other line electrode 5 is connected to the driving power supply V _C, and is driven by the control signal CS. This drive circuit and its operation will be described in more detail.

The current control circuit section 41 includes a large number of pixels PX.
A reference resistor R _ref capable of monitoring the current i flowing in each of the pixels as a voltage V _m ; and a FET (F as a current control element connected between the reference resistor R _ref and the pixel PX).
and an external PROM (Progr) for the monitored voltage V _m and current control circuit section 41.
an operational amplifier element (operational amplifier) OPA for comparing a luminance signal voltage V _S supplied from an ammable read only memory) and outputting a control voltage V _CS for the FET.

In the PROM, image information to be displayed on the organic EL element 40 is programmed and stored in advance.
This is P by the instruction from the micro processing unit MPU operated by the personal computer PC.
The video information is input to the ROM, the video information is sampled, and a predetermined luminance signal voltage V _S is output from the PROM. This luminance signal voltage is adjusted to a desired voltage value by the resistor r,
This adjusted voltage V _SA is input to the + terminal of the operational amplifier OPA.

On the other hand, in order to turn on the pixel PX,
A drive transistor (here, an NPN bipolar transistor) Tr is connected between the power supply V _C and the pixel PX, a control voltage CS for switching is selectively applied to the base of this transistor, and each line electrode 5 is sequentially switched. . Therefore, at the timing when the transistor Tr is turned on by the control voltage CS, the power supply voltage V _C is applied to the line electrode 5, whereby the current i flows between the line electrode 5 and the column electrode 1 and the pixel PX is turned on.

Such a lighting operation is continued while the power supply voltage V _C is applied to the line electrode 5 and at the same time as the ON state of the FET due to the above-mentioned luminance signal voltage continues (that is, during the period in which the current i flows). Since such an operation is performed for each line corresponding to the luminance signal, a target display image can be obtained from the EL element 40.

In this case, the current i flowing through the pixel PX is made to flow corresponding to the emission brightness required there, but this can be realized by the current control circuit section 41. This will be described below.

The positive terminal of the operational amplifier OPA has the above-mentioned structure.
Luminance signal voltage V_SAIs input and its − terminal
Is the reference resistance R_refThe current i flows through the
Resistance R _refPotential difference across both ends of the
Detection voltage V_m) Is entered.

Under the condition of V _SA > V _m , the output V _{CS of the} operational amplifier OPA rises and the gate potential V FET is
_G rises and V _m −V _G becomes smaller, lowering the source-drain resistance of the FET and increasing the current i. In this way, when i increases and i · R _ref = V _m reaches V _SA , V _CS does not rise any more and the resistance value of the FET stabilizes, and i becomes a constant value V _m / R _ref . Stabilize.

Therefore, while the brightness signal voltage from the PROM is being applied, the brightness signal voltage V _SA and the detection voltage V _SA are applied.
_The current i flows through the FET as the variable resistance until _m matches, and the current flows through the pixel PX until the target current amount is reached, so that a desired light emission brightness is always obtained.

The switching operation of the line electrode 5 on the power supply V _C side will be described below.
The oscillation pulse from LK is input to the counter CT ₁ and, in combination with the counter CT ₂ having the same number of bits, the switching line selector LS for each predetermined count number.
Is operated, and a TTL level voltage is output to a predetermined selection line. This output is inverted by the inverter INV, and the inverted output is applied to the base of the transistor Tr as the control signal CS. The power supply voltage V _C is applied to the line electrode 5 via the transistor Tr turned on by this application. Is supplied to.

As described above, since the amount of current flowing through the pixel PX is controlled by the drive circuit of FIG. 17, it is possible to accurately control the brightness of each pixel and always realize clear light emission (image display). .

The drive circuit shown in FIG. 17 is an example, and the current control circuit section 41 is provided with a voltage hold circuit, the constituent elements are appropriately changed, or the like so that the current control is performed more accurately. be able to. Further, the circuit for supplying the luminance signal voltage from the outside may be variously modified, and the PROM may be operated in conjunction with the line sensor LS. In the PROM, the video signal may be sampled and held, or may be A / D converted after sampling. Further, it is also possible to perform the brightness control by controlling the applied voltage which is conventionally performed without providing the drive circuit of FIG. 17 including these changes.

With the above driving circuit, each pixel has a voltage of 15 to 20 volts for a pixel, and red and blue pixels have a voltage of 20 to 30 volts.
It was confirmed that the voltage of the volt can be sequentially pulsed at intervals of 60 μs to several seconds.

18 and 19 are enlarged cross-sectional views of the essential parts showing the second and third embodiments of the present invention applied to an organic EL device, respectively.

In the case of these embodiments, while the circular polarization means 49 is provided on the side opposite to the light emitting surface of the substrate 6 in the above-mentioned first embodiment, as shown in the figure, the circular polarization means 49 is transparent. Board 6
The substrate 6 also serves as the circularly polarizing plate 49 (or the circularly polarizing plate 49 also serves as the substrate 6) provided between the inner surface of the substrate and the organic layer.
In this way, the organic EL element 51 is configured.

That is, in the example of FIG. 18, between the transparent substrate 6 and the laminated body composed of the organic layer (ITO transparent electrode, hole transport layer 4, light emitting layer 3, electron transport layer 2) and electrode layer 1, A circular polarization plate 49 is provided. The circularly polarizing plate 49 is, as in the case of the above-described first embodiment, seen from the side of the electrode 1 which is the reflecting surface,
The birefringent plate 21, the birefringent plate 22, and the linearly polarizing plate 11 are laminated in this order.

In the case of the organic EL element 52 of FIG. 19, the electron transport layer 2 of the organic layers also serves as the light emitting layer (this may be applied to the embodiment of FIG. 2 as well). .), The present invention can be applied to the circular polarization means.
The arrangement of 49 is the same as in the case of FIG.

In the manufacturing process of the organic EL device, the transparent substrate 6 is heated to the highest temperature in the process of depositing the ITO transparent electrode 5 on the substrate 6 by vapor deposition. However, the ITO transparent electrode 5 can be formed by an ion assisted vapor deposition method or a sputtering method with a considerably low resistance value without forcibly heating the transparent substrate 6.

Therefore, in the production of the organic EL device shown in FIG. 18 or FIG. 19, after the film-shaped circularly polarizing plate 49 was attached on the substrate 6, the temperature was set to 80 ° C. or lower at 150 nm by the above method.
Since it is possible to form an ITO transparent electrode having a thickness of 40 Ω / cm ² , the film heat resistance of the circularly polarizing plate 49 is sufficient under these temperature conditions, and the circularly polarizing plate 49 can be formed in the element without deteriorating. Will be retained.

Therefore, the circularly polarizing plate 49 is provided on the transparent substrate 6,
It is possible to directly form an organic EL element on this. Actually, in this example, the ITO transparent electrode 5 was formed on the surface of the transparent substrate 6 on which the two-layer laminated broadband birefringent plate 23 (manufactured by Nitto Denko Corporation) and the linear polarizing plate 11 were formed by the sputtering method. It is formed to a thickness of 150 nm, and SiO ₂ 9 is added to 1
It was formed to a thickness of 50 nm, and a pattern similar to that of the above-described first embodiment was produced. Then, red (R), green (G), and blue (B) are formed on top of this by the same manufacturing process as in the first embodiment.
The striped laminate of each color was formed by vapor deposition to produce the organic EL device 52 of FIG.

When the organic EL element 52 thus produced was irradiated with light and viewed from the light emitting surface side of the substrate 6, there was no reflection of light and it looked almost black. Further, as in the first embodiment, the organic EL element 52 was lit by a drive circuit (FIG. 17) having a current control circuit section in a dynamic drive system. As a result, light was emitted with good contrast, almost similarly to the first embodiment. These results were the same for the device of FIG.

Therefore, according to these embodiments, the same effect as that of the first embodiment described above can be obtained, and the circularly polarizing plate 49 is provided on the substrate 6 in advance, and the element is formed on this. Further, the circularly polarizing plate 49 can be stably held between the transparent substrate 6 and the laminated body such as the organic layer.

FIG. 20 shows a fourth embodiment of the present invention, in which the present invention is applied to a light transmission type liquid crystal display.

That is, a transparent electrode layer 43a such as ITO (indium tin oxide: a conductive oxide obtained by doping indium with tin) and a liquid crystal alignment film with a high contrast are provided on the inner surface of a transparent substrate 42a such as glass. A laminated body 1 in which, for example, SiO oblique vapor deposition layers 44a are sequentially laminated to realize a domain.
A; similarly to this, a transparent electrode layer is formed on the inner surface of the substrate 42b.
43b, for example, a laminated body 1B in which an SiO oblique vapor deposition layer 44b is sequentially laminated;
A liquid crystal cell is formed by arranging 44a and 44b so as to face each other and sandwiching a granular spacer 45 for realizing a predetermined cell gap d, and a ferroelectric liquid crystal 46 is injected into the cell gap to surround the liquid crystal cell. Has a structure in which is sealed with an adhesive.

Then, as shown in the figure, a quarter-wave plate 23 composed of a birefringent plate 21 and a birefringent plate 22 and a circular polarizing plate 49 composed of a linear polarizing plate 11 are attached to the surface on the transparent substrate 42b side. It is a thing.

The light transmissive liquid crystal is used in, for example, a personal computer, etc., and the liquid crystal 46 switches according to an electric signal by an applied voltage to transmit or block the backlight BL to display a character or an image. It has a function.

By providing the circularly polarizing means 49, the circularly polarized light component of the transmitted light BL is emitted as linearly polarized light 47 (corresponding to the linearly polarized light 17 in FIG. 1) as shown in the drawing. On the other hand, the incident light 48 from the outside receives the circular polarization means 49.
Even if the light is reflected at the surface of the substrate 42b that forms the boundary with or at each interface inside the cell 50, the polarization axis of the reflected light 46 (corresponding to the circularly polarized light 16 in FIG. 1) is different from that of the polarizing plate 11 by the circular polarization means 49. It becomes different linearly polarized light 47 and does not pass through the polarizing plate 11.

Therefore, also in this example, the same effects as those of the above-described first embodiment can be obtained, such as antireflection inside the element and good contrast.

Although the embodiments of the present invention have been described above, the above-described embodiments can be variously modified based on the technical idea of the present invention.

For example, the linearly polarizing plate used for the circularly polarizing means may have a horizontal polarization axis, and the birefringent plate is a laminate of two or more birefringent plates having a thickness different from those of the above-mentioned embodiments. However, what is necessary is just to obtain a phase difference of ¼ wavelength.

The thickness of each of the electrodes, the hole transport layer, the light emitting layer, and the electron transport layer is determined in consideration of the operating voltage of the device, and is not limited to the above-mentioned embodiments. The composition and arrangement of each of these layers, the pattern and layout of pixels, and the like can be variously changed. As the electrode material having a high reflectance, well-known materials such as Al and Al alloys can be used in addition to MgAg.

Further, as the method for producing each layer of the device, the usual vacuum vapor deposition method, Langmuir-Blodgett (LB) vapor deposition method, dip coating method, spin coating method,
Vacuum gas deposition method, organic molecular beam epitaxy method (OMBE)
Can be adopted. Note that the hole transport layer or the electron transport layer may contain a fluorescent substance.

Further, the optical element of the present invention can be applied not only to a passive matrix (simple matrix) type but also to an active matrix type element. Also, it may be applied as a mono-color image pickup device, and
In addition to the display described above, it can be used as a light source such as a dial, and in this case, it is not necessary to form a matrix, and the light emitting region may be divided. Further, it may be applied to a self-luminous element other than the above-mentioned EL.

[0122]

According to the present invention, since the circularly polarizing means is provided on the light emitting surface, it is possible to greatly reduce the reflection inside the element of the light incident from the emitting surface of the element from the outside. It is possible to remarkably improve the contrast of a display image or the like.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an organic EL device according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the organic EL device.

FIG. 3 is a graph showing wavelength dependence of birefringence retardation.

FIG. 4 is a graph showing changes in reflectance with wavelength due to the same birefringence phase difference.

FIG. 5 is a schematic plan view of the organic EL device.

6 is an enlarged cross-sectional view of a portion taken along line AA of FIG.

FIG. 7 is an enlarged cross-sectional view of a portion taken along the line BB.

FIG. 8 is an enlarged cross-sectional view of a main part showing a manufacturing process of the same organic EL element.

9 is an enlarged cross-sectional view showing another manufacturing process (IX- in FIG. 8).
It is a sectional view taken along line IX).

FIG. 10 is an enlarged cross-sectional view showing another manufacturing process.

FIG. 11 is a schematic view of a vacuum vapor deposition device that can be used in the manufacturing process.

FIG. 12 is an enlarged cross-sectional view showing another manufacturing process.

FIG. 13 is an enlarged cross-sectional view showing the other manufacturing process.

FIG. 14 is an enlarged sectional view showing another manufacturing process.

FIG. 15 is an enlarged sectional view showing another manufacturing process.

FIG. 16 is an enlarged cross-sectional view showing another manufacturing process.

FIG. 17 is a drive circuit diagram of the same organic EL element.

FIG. 18 is an enlarged cross-sectional view of a main part of the organic EL element according to the second embodiment of the present invention.

FIG. 19 is an enlarged cross-sectional view of a main part of an organic EL device according to a third embodiment of the present invention.

FIG. 20 is an enlarged cross-sectional view of a main part of a liquid crystal display element according to a fourth embodiment of the present invention.

FIG. 21 is a perspective view schematically showing antireflection means.

FIG. 22 is a schematic cross-sectional view of an organic EL element according to a conventional example.

FIG. 23 is a schematic cross-sectional view of another organic EL element of the same.

FIG. 24 is a schematic cross-sectional view showing a specific example of the same organic EL element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode (cathode) 2 ... Electron transport layer 3 ... Emitting layer 4 ... Hole transport layer 5 ... Transparent electrode (anode) 6 ... Transparent substrate 11 ... Linear polarizing plate 11a ... longitudinal polarization axis 12,23 ... quarter wave plate 12a, 23a ... 45 degree tilted polarization axis 13 ... reflecting surface 14 ... vertical polarization 15 ... right circular polarization 16 ... Left circularly polarized light 17 ... Horizontally polarized light 21, 22 ... Birefringent plate 23 ... Quarter wave plate 24 ... Birefringence when the birefringent plates 21 and 22 are bonded Dispersion curve 25: Birefringence dispersion line capable of obtaining a phase difference of ¼ wavelength 26: Birefringence dispersion curve of birefringence plate 21 27: Birefringence dispersion curve of birefringence plate 22 40 50, 51 ... Organic EL element 49 ... Circular polarizing means (circular polarizing plate) L, BL ... Light a ... Reflectance curve in the case of a single-layer birefringent plate b ... Birefringence Reflection curve when multiple plates are attached PX ... Pixel

Claims (11)

[Claims] 1. A light emitting device having a circular polarization means on the light exit surface side. 2. The display element according to claim 1, wherein a light reflecting layer is formed on the side of the light emitting layer opposite to the light emitting surface. 3. The display element according to claim 1, wherein the circularly polarizing means comprises a linearly polarizing plate and a quarter-wave plate. 4. A quarter-wave plate is approximately one-quarter in a wide wavelength range.
The display device according to claim 3, wherein the display device is configured by a plurality of birefringent plates so as to obtain a phase difference of 4 wavelengths. 5. The display element according to claim 4, wherein the quarter-wave plate is composed of a plurality of birefringent plates having different birefringence characteristics. 6. The display element according to claim 3, wherein the quarter-wave plate has a polarization axis of 45 degrees with respect to the polarization axis of the linear polarizing plate or an inclination equivalent to the polarization axis. 7. A circularly polarizing means is provided on the light emitting side of the element to allow the incident light from the outside to pass through, but to shield the reflected light reflected inside the element from the outside so as not to the outside. The display element according to claim 1, wherein the display element is 8. A first electrode, a light emitting layer, and a second electrode having a high light reflectance are laminated on an optically transparent substrate, and on the opposite substrate on which these are laminated. The display device according to claim 1, wherein the display device is provided with a circular polarization means and is configured as an electroluminescence device. 9. A first electrode, a light emitting layer, and a second electrode having a high light reflectance are laminated on an optically transparent substrate, and circularly polarized light is provided between these laminates and the substrate. The display device according to claim 1, wherein the display device is provided with means and is configured as an electroluminescent device. 10. The plurality of stripe-shaped first electrodes,
10. The display element according to claim 8, wherein at least one stripe-shaped plurality of organic layers including a light emitting layer and a plurality of stripe-shaped second electrodes intersecting with the first electrode are provided. . 11. The display device according to claim 10, which is an organic electroluminescent device or a display.