JP2000301835A - Multicolor heat sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow formation of an accurate pattern and a high color developing density to be compatible by providing at least two types or more of dye layers made of leuco dyes having different color developing hues and developer layers each containing a developer formed on one or both surfaces of upper and lower layers adjacent to the dye layers on a support. SOLUTION: In the heat sensitive recording medium 1 utilizing a color developing reaction of a leuco dye with a developer, a developer layer 3 is provided on a support 2, and dye layers made of 4Y, 4M and 4C are provided thereon. In this case, three types of the layers 4Y, 4M and 4C are arranged repeatedly in a stripe state in a width direction. The layer 3 contains the developer and a binder, and contains various type additives as needed. The layers 4 and the layer 3 are preferably provided so as to be covered with a microcapsule to be broken by a heat or a pressure when heated or provided with a fog preventing layer containing a heat fusible substance between the layer 4 and the layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium capable of multicolor display.

[0002]

2. Description of the Related Art Conventionally, heat-sensitive recording media utilizing a color-forming reaction between a leuco dye and a color developer have been widely known and used in a wide range of fields such as automatic ticket vending machines, labels, facsimile machines, and various industrial recorders. . Further, since the color hue can be selected depending on the molecular structure of the leuco dye, application to multicolor thermal recording is expected, and some proposals have already been made.

Conventionally, a multicolor thermal recording method utilizing a color-forming reaction between a leuco dye and a color developer includes the following: (1) a high-temperature and low-temperature coloring layer which forms a different hue with different coloring heat energy on a support. And (2) a method in which a plurality of color-forming layers for forming different hues are divided and formed in the medium plane direction to selectively control the heating position.

[0004]

The method of laminating the multicolor coloring layers of the above item (1) and utilizing the difference in heating temperature is proposed in JP-A-9-267557 and JP-A-7-304260. Although it is possible to obtain a desired color at an arbitrary place, it is necessary to control the temperature reaching each of a plurality of stacked layers. It is.

The method of forming a plurality of color-forming layers in the above-mentioned item (2) in the medium plane direction and controlling the heating position to form a multi-color color is disclosed in Japanese Patent Application Laid-Open Nos. 60-989 and 60-89. 208283.

In Japanese Patent Application Laid-Open No. 60-989, a medium having couplers arranged in a mosaic, stripe, or island shape is interposed via a ribbon containing an oxidized developer.
A method of obtaining a multicolor image by selectively heating only the pixels to be colored is described, but the apparatus becomes complicated, a ribbon needs to be prepared, or the used ribbon must be discarded. Must.

In Japanese Patent Application Laid-Open No. 60-208283, two or more types of color-forming layers that develop colors having different hues are partially provided on a support, and these are selectively heated only to pixels to be colored. Thus, a method for obtaining a multicolor image has been proposed.

When this method is used, a medium in which a coloring layer formed by mixing a leuco dye and a developer is partially provided, such as a so-called conventional thermosensitive recording medium, can be considered. For example, yellow, magenta, and cyan (hereinafter, Y,
M and C), three types of color forming layers formed by mixing a leuco dye and a color developing agent are partially provided on a support, and these are selectively heated only to pixels to be colored. Thus, a multi-color image or a full-color image can be obtained. However,
With this method, it is difficult to satisfy all of the color density, image resolution, and color separation. Because, if an attempt is made to form a high-precision pattern by printing, the forming method is limited to offset printing or the like, and the thickness of the color-forming layer is reduced,
There is a problem that the color density is reduced. Further, in order to obtain a high color-forming density, it is necessary to increase the amount of the color-forming composition and increase the film thickness. However, an increase in the amount of the color-forming composition causes a decrease in the strength of the coating film. When the film thickness is increased, a general printing technique cannot form a high-definition pattern, resulting in reduced image resolution, adjacent color-forming layers of different colors intermingled, and poor color separation of pixels. There's a problem.

An object of the present invention is to provide a multi-color heat-sensitive recording medium which has a high resolution and a high color density by solving the above-mentioned problems in a heat-sensitive recording medium utilizing a color-forming reaction between a leuco dye and a color developer. That is.

[0010]

The heat-sensitive recording medium according to the present invention comprises at least two types of leuco dyes having different coloring hues formed side by side on a support without overlapping each other. And a developer layer containing a developer formed as one or both of upper and lower layers adjacent to the dye layer.

According to one embodiment of the present invention, each dye layer has a stripe shape and is repeatedly arranged in a certain order such that different layers are adjacent to each other.

According to another embodiment of the present invention, at least one index mark for detecting the position of each dye layer is provided on the support for each repeating unit of the dye layer. .

According to one embodiment of the present invention, the index mark is provided on the support with infrared absorbing ink.

According to another embodiment of the present invention, the index mark is provided by coloring a part of the dye layer.

According to yet another embodiment of the present invention,
Each dye layer has a predetermined area for each different layer, and is arranged apart from each other.

According to another embodiment of the present invention, at least one of the dye layer and the developer layer is a dye layer or a developer in which a leuco dye or a developer is dispersed in a binder in a molecular state. It is formed of a colorant layer ink.

According to one embodiment of the present invention, at least one of the dye layer and the developer layer is formed in a system that does not attack the previously formed layer.

According to another embodiment of the present invention, the dye layer and the developer layer are covered with microcapsules which are destroyed by heat or pressure when heated.

According to another embodiment of the present invention, an antifogging layer is provided between the dye layer and the color developer layer.

As a result of repeated studies by the present inventors to solve the above-mentioned problems, a multicolor heat-sensitive recording medium having a high color density can be obtained by adopting the structure of the heat-sensitive recording medium having the above-described structure. I found that.

That is, in the conventional method, since a color-forming layer formed by mixing a leuco dye and a color developer is used, a sufficient color density cannot be obtained when the thickness of the color-forming layer to be provided partially is small. However, in this method, the dye layer and the developer layer are separated, and only the dye layer is patterned with high definition, so that the amount of dye can be increased even in a thin film. Therefore, a high color density can be obtained.

According to the present invention, for example, a multicolor image or a full-color image can be formed by partially providing a dye layer for coloring yellow, magenta, and cyan, and selectively heating pixels to be colored. is there. Here, the resolution of an image can be improved as the area of the dye layer or the heated portion is reduced.

In the present invention, there is only required a technique of partially providing only a dye layer with a relatively small film thickness, and it can be easily produced by printing or the like.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in more detail with reference to the accompanying drawings according to embodiments and examples of the present invention.

FIGS. 1A and 1B are a schematic sectional view and a plan view showing the structure of a thermosensitive recording medium as one embodiment of the present invention. In these figures, reference numeral 4
Y, 4M, and 4C denote dye layers that develop yellow, magenta, and cyan, respectively. As is well shown in the sectional view of FIG. 1A, in the thermosensitive recording medium 1 of the present embodiment,
A developer layer 3 is provided on a support 2, and then 4Y, 4Y,
It has a form in which a dye layer 4 made of M, 4C is provided. As is well shown in the plan view of FIG. 1B, in the thermal recording medium 1 of the present embodiment, three types of dye layers 4Y, 4Y,
M and 4C are repeatedly arranged in a stripe shape in the width direction.

FIG. 1 (c) is a schematic sectional view similar to FIG. 1 (a) showing the structure of a thermal recording medium as another embodiment of the present invention. On the support 2, a dye layer 4 is provided, and then a developer layer 3 is provided. FIG. 1D shows the structure of a heat-sensitive recording medium according to still another embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view similar to FIG. 1. In this embodiment, a configuration in which the dye layer 4 is sandwiched between the color developer layers 3, that is,
Two developer layers 3 are provided as upper and lower layers of the dye layer 4. These configurations are advantageous for forming a full-color image, and the resolution of the image is improved as the width of the dye layer is reduced.

FIG. 2A is a plan view showing the structure of a thermosensitive recording medium according to still another embodiment of the present invention. In the heat-sensitive recording medium 1 of this embodiment, dye layers 4K, 4B, and 4R that emit black, blue, and red, respectively, are formed in a relatively large area above or below the developer layer. By selectively heating pixels to be colored using the thermal recording medium shown in FIG. 2A, for example, as shown in FIG. And images 4Kp, 4Bp, and 4Rp. In the present invention, since the dye layer can be formed by printing pressure, the shape of the dye layer can be freely set.

As the support 2 used in the present invention, paper,
Examples of the sheet include a plastic sheet and a thin metal sheet. Paper and a plastic sheet are particularly preferable.

The color developer layer 3 basically comprises a color developer and a binder, and may contain various additives as required. As the color developer, those generally used for pressure-sensitive recording paper, heat-sensitive recording paper and the like are typified, and one type or a mixture of two or more types can be used, and specific examples thereof are described below. However, the present invention is not limited to this, and there is no particular limitation.

Inorganic acidic substances such as activated clay, attapulgite, colloidal silica and aluminum silicate. 2,2-
Bis (4 ^, -hydroxyphenyl) propane, 4,4 ^, -
Phenolic compounds such as dihydroxydiphenylsulfone, bis (4-hydroxyphenyl) ether, 4-cyclohexylphenol, and 4-n-dodecylphenol. Aromatic carboxylic acids such as 4-phenylbenzoic acid and phthalic acid mono-n-butyl ester, and polyvalent metals such as zinc, magnesium, calcium, manganese, tin, nickel, iron and copper of the aromatic carboxylic acids and the like. Salts and other organic acidic substances can be used.

Specifically, the developer layer 3 is prepared by dispersing or dissolving the developer in a suitable solvent together with a binder and additives using a paint shaker or a kneader or the like. After preparing the ink for use, it can be formed by a bar coater, printing, or the like. At this time, it is preferable that the color developer in the color developer layer is small particles, and it is more preferable that the color developer is dispersed in a molecular state, since color density and color sensitivity are improved. For this reason, the developer is dissolved in an organic solvent, or the developer is melted and mixed in a binder by heating, etc., so that the developer is uniformly dispersed in a binder in a molecular state for a developer layer. A more desirable method is to prepare an ink and form a color developer layer using the ink. However, if the dye layer that is not resistant to the organic solvent is formed before the color developer layer, use of a color developer layer ink that uses an organic solvent will cause the leuco to form simultaneously with the formation of the color developer layer. Since there is a problem that the dye and the developer are mixed with each other to cause color development, it is necessary to form the developer layer in a system that does not attack the dye layer. The thickness can be set appropriately, but if it is too thin, the color density is low, and if it is too thick, the color sensitivity decreases. Of course, the types and amounts of the binder and the additive can be appropriately selected.

The dye layer 4 basically comprises a colorless or light-colored leuco dye and a binder, and may contain various additives as necessary. Leuco dyes are typically used for pressure-sensitive recording paper, heat-sensitive recording paper, etc., but materials are selected for each dye layer according to the hue to be colored, and one or more types are mixed. It is possible to use it. Specific examples include the following, but the present invention is not limited thereto, and there is no particular limitation.

As a yellow coloring material, 3-cyclohexylamino-6-chlorofluoran, 3,6-dimethoxyfluoran, 3,6-dibutoxyfluoran and the like.

As magenta coloring materials, 3-diethylamino-7,8-benzofluoran and 3,3-bis (1-n-butyl-2-methylindol-3-yl)
Phthalide, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3- (N-ethyl-N-
Isopentyl) amino-7,8-benzofluoran, 3
-Diethylamino-7-chlorofluoran and the like.

As cyan-based coloring materials, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (CVL), 3- (4-diethylamino-2-)
Ethoxyphenyl) -3- (1-ethyl-2-methluindol-3-yl) -4-azaphthalide, 3- (4-
Diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide and the like.

Examples of black coloring materials include 3-diethylamino-6-methyl-7-anilinofluoran,
Dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-dipentylamino-6-methyl-7-
Anilinofluoran, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluoran and the like.

Examples of green coloring materials include 3-diethylamino-7-chloroanilinofluoran and 3-diethyl-7-dibenzylaminofluoran.

Further, other than the above, fluoranmethane compounds, triarylmethane compounds, spiro compounds, diphenyl compounds, thiazine compounds, lactam compounds, fluorene compounds and the like can be used.

For the production of the dye layer 4, specifically,
Disperse or dissolve the leuco dye in a suitable solvent together with a binder and additives using a paint shaker or kneader, etc., to prepare a dye layer ink, and then form a pattern by screen printing, gravure printing, offset printing, etc. It is possible to form. At this time, the leuco dye in the dye layer is preferably small particles, and is more preferably dispersed in a molecular state, since color density and color sensitivity are improved. For this reason, by dissolving the leuco dye with an organic solvent, or by melting and mixing the leuco dye in the binder by heating, to prepare a dye layer ink in which the leuco dye is uniformly dispersed in the binder in a molecular state, A method of forming a dye layer using this ink is more desirable. However, if the color developer layer that is not resistant to the organic solvent is formed before the dye layer, use of a dye layer ink that uses an organic solvent will cause the leuco dye to develop simultaneously with the formation of the dye layer. The dye layer needs to be formed in a system that does not attack the color developer layer, since the agents are mixed and there is a problem that color formation occurs. The thickness can be set appropriately, but if it is too thin, the color density is low, and if it is too thick, the color sensitivity decreases. The area can be set appropriately, but if the area per color is large, images of different colors can be obtained depending on the location of the medium, and if the area per color is reduced, high-definition full-color An image is obtained. Of course, the types and amounts of the binder and the additive can be appropriately selected.

The multicolor heat-sensitive recording medium of the present invention may be produced by any method as long as it can prevent the leuco dye and the developer from reacting and coloring before heating. Specifically, the following method can be used, but the present invention is not limited to this.

When a dye layer and a color developer layer are provided adjacent to each other, a layer to be formed later does not contain a solvent or is formed using a solvent which does not easily dissolve the leuco dye and the color developer.

The leuco dye and the developer are coated with microcapsules which are destroyed by heat or pressure during heating.

An antifogging layer containing a thermofusible substance such as a thermoplastic resin or wax is provided between the dye layer and the developer layer.

The binder resin used for the dye layer and the developer layer in the present invention can be used alone or in combination of two or more. Specific examples include the following. Any material can be used as long as it can bind the leuco dye and the developer, as long as the content of the present invention is not hindered, and there is no particular limitation.

Hydroxyethyl cellulose, methyl cellulose, cellulose acetate, gelatin, starch, polyvinylpyrrolidone, polyacrylamide, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polystyrene, styrene copolymer, phenoxy resin, Polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylate, polymethacrylate, acrylic acid copolymer, maleic acid copolymer, polyvinyl alcohol, chlorinated vinyl chloride resin, polyamide, phenolic resin, epoxy resin , Guamin resin, vinyl ester resin, polyimide,
Urethane resin, maleic acid resin, melamine resin, urea resin, etc., and a combination of these resins and a curing agent.

(Poly) ester acrylate, (poly)
A combination of a photopolymerizable monomer or oligomer such as urethane acrylate, epoxy acrylate, polybutadiene acrylate, silicone acrylate, melamine acrylate, and optionally a photopolymerization initiator.

In the present invention, it is necessary to selectively heat only the pixel to be colored. For example, an index mark is appropriately provided in a recording medium, and the mark is always detected by an appropriate means such as a sensor. The problem can be solved by heating with a thermal head while performing tracking based on this detection signal.

As one embodiment, as shown in FIG. 3, three dye layers 4Y, 4M, 4
Medium 1 in which C is repeatedly arranged in a stripe shape in the width direction.
In this example, an index mark 5 is formed by infrared absorbing ink at the position of the layer 4Y that develops each yellow color on the support 2 and moves in the direction of the arrow with respect to the line thermal head 6. The first yellow position is read by the infrared sensor 7 provided in the printing machine or the line thermal head, the thermal head heating element is tracked at this position, and the heating element of the line thermal head to be colored yellow is heated, An image of the first line is formed. Further, the card is advanced in the direction of the arrow, the position of each yellow is read, the position of the line thermal head heating element is tracked in the same manner as the first line, and heating corresponding to the image to be colored yellow is sequentially performed. And a yellow image can be obtained. Similarly to the formation of a yellow image, after reading the position of each yellow in the direction of the arrow by the infrared sensor 7, the line thermal head heating element is shifted to the position opposite to the arrow by the width direction length x of the dye layer 4Y. Tracking and heating corresponding to the image to be colored magenta,
A magenta image can be obtained. Similarly, after the position of each yellow in the direction of the arrow is read by the infrared sensor 7, the total length of the dye layers 4Y and 4M in the width direction is x + y in the direction opposite to the arrow, or in the direction opposite to the arrow.
By tracking the line thermal head heating element at a position shifted in the same direction as the arrow by the width direction length x and heating corresponding to the image to be colored cyan, a cyan image can be obtained. A full-color image can be obtained by combining these Y, M, and C images.

As another embodiment, as shown in FIG. 4, sensors 7a, 7b,
7c, line thermal heads 6a, 6
b, 6c are arranged in series in the direction of the arrow, and the medium 1 in which three types of dye layers 4Y, 4M, and 4C for coloring in Y, M, and C are repeatedly arranged in a stripe shape in the width direction is moved in the direction of the arrow. Shall be. The end of the medium 1 is heated and colored to obtain index marks 4Yi, 4Mi, and 4Ci of the respective colors, and the mark Yi is detected by the sensor 7a. The yellow image can be obtained by heating the heating element to be heated in a short time. Similarly, the mark 4Mi is detected by the sensor 7b, the magenta image is detected by tracking the heating element position of the line thermal head 6b and the heating element to be heated to magenta is detected, and the mark 4Ci is detected by the sensor 7c. Thermal head 6c
A cyan image can be obtained by tracking the heating element position and heating the heating element to be heated to cyan.
A full-color image can be obtained by combining these Y, M, and C images. In this case, if the mark is formed before the image formation by a separate process or a mark formation heating unit provided in the printing machine, the image formation can be completed in one pass.

Of course, the type of the sensor, the position of the mark, and the material can be appropriately selected, and may be provided on a surface different from the image formation.

Further, in the present invention, sticking,
Protective layer, intermediate layer, undercoat layer, etc., as necessary to prevent scratches, print marks, scum adherence to the head, background fog, stabilize paint, improve adhesion, adjust sensitivity during heating, etc.
Although layers such as various functional layers can be provided, any material may be used as long as the content of the present invention is not impaired.

In any part of the medium composition, if necessary, a light stabilizer, a light absorber, a fluorescent agent, an antioxidant, a conductive agent, a crosslinking agent, a lubricant, a plasticizer, a polymerization initiator, a surfactant, a filler Various additives may be added as long as the content of the invention is not impaired.

[0053]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Unless otherwise specified, “parts” and “%” in the examples indicate “parts by weight” and “% by weight”, respectively. Example 1 (Formation of a leuco dye layer) A mixture having the following composition was crushed using a paint shaker so that the particle size became 1 μm or less.
The dispersion [A] was prepared by dispersion.

[A] solution: TG31 (manufactured by Nippon Kayaku) 2 parts BR115 (manufactured by Mitsubishi Rayon) 1 part cyclohexane 12 parts [A] solution is applied on a 200 μm-thick polyester film, dried and dried to a film thickness of about 1 μm Was formed.

(Formation of Developer Layer) A mixture of the following composition was pulverized and dispersed using a paint shaker so that the particle size became 1 μm or less, to prepare a liquid [B].

Solution [B]: D8 (manufactured by Nippon Soda) 2 parts BR115 (manufactured by Mitsubishi Rayon) 1 part Cyclohexane 12 parts [B] Solution is applied on the leuco dye layer, dried and dried to a film thickness of about 5 μm. A developer layer was formed to obtain a thermosensitive recording medium. Example 2 Example 1 was formed on a polyester film having a thickness of 200 μm.
A developer layer was formed in the same manner as in Example 1 so as to have a thickness of 5 μm, and a dye layer in the same manner as in Example 1 was formed so as to have a thickness of 1 μm to obtain a thermosensitive recording medium. Comparative Example 1 Solution [A] and solution [B] of Example 1 were mixed at a ratio of 1: 2, applied on a polyester film having a thickness of 200 μm, and dried to form a recording layer having a thickness of about 1 μm. Thus, a heat-sensitive recording medium was obtained.

The heat-sensitive recording medium obtained as described above was colored using a thermal head, and the reflection density was measured with a Macbeth reflection densitometer. Table 1 shows the results.

[0058] As is clear from the table, the thermosensitive recording medium constituted by the constitution of the present invention has a higher color density than the medium having the conventional constitution.

[0059]

According to the present invention, a high-precision pattern can be obtained in a thermosensitive recording medium capable of obtaining a multicolor image by controlling a heating position by utilizing a color development reaction between a leuco dye and a color developer. It has been found that a multicolor heat-sensitive recording medium which can easily achieve both high color density and high color density can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a thermosensitive recording medium according to various embodiments of the present invention.

FIG. 2 is an explanatory diagram showing a configuration and a usage example of a thermosensitive recording medium as still another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing one embodiment of an image forming method when using the thermosensitive recording medium of the present invention.

FIG. 4 is an explanatory diagram showing another embodiment of the image forming system different from FIG. 3 when the thermosensitive recording medium of the present invention is used.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Multicolor heat-sensitive recording medium 2 Support 3 Developer layer 4 Dye layer 4Y Dye layer that develops yellow 4M Dye layer that develops magenta 4C Dye layer that develops cyan 4K Dye layer that develops black 4B Blue Dye layer 4R Dye layer 4Yi 4Y is heated by heating 4Yi 4Y and is used as an index mark 4Mi 4M is heated and magenta is used as an index mark 4Ci 4C is heated and cyan is used as an index mark 4Kp 4K 4Bp 4Bp 4B is heated to heat red or colored characters or images 4Rp 4R is heated to red or heated characters or images 5 Index marks with infrared absorbing ink 6 Line thermal head 6a Line thermal head for 4Y coloring 6b Line thermal head for 4M coloring 6c Line thermal head for 4C color development 7 Infrared sensor 7a 4Yi sensor 7b 4Mi sensor 7c 4Ci sensor X 4Y width direction Y 4M width direction length Z 4C width direction length

Claims (10)

[Claims] 1. A support, at least two or more dye layers formed of leuco dyes having different coloring hues formed side by side on the support without overlapping each other, and an upper layer adjacent to the dye layer. A thermosensitive recording medium comprising: a developer layer containing a color developer, formed as one or both of the lower layers. 2. The heat-sensitive recording medium according to claim 1, wherein each of the dye layers has a stripe shape, and is repeatedly arranged in a predetermined order such that different layers are adjacent to each other. 3. An index mark for detecting the position of each dye layer is provided for each repeating unit of the dye layer.
3. The thermosensitive recording medium according to claim 2, wherein at least two pieces are provided on the support. 4. The heat-sensitive recording medium according to claim 3, wherein the index mark is provided on the support with an infrared absorbing ink. 5. The thermosensitive recording medium according to claim 3, wherein the index mark is provided by coloring a part of the dye layer. 6. The thermosensitive recording medium according to claim 1, wherein each dye layer has a predetermined area for each different kind of layer, and is arranged apart from each other. 7. At least one of the dye layer and the developer layer is formed of a dye layer or a developer layer ink in which a leuco dye or a developer is dispersed in a binder in a molecular state. Item 7. The thermal recording medium according to any one of Items 1 to 6. 8. The heat-sensitive device according to claim 1, wherein at least one of the dye layer and the developer layer is formed in a system that does not attack the previously formed layer. recoding media. 9. The heat-sensitive recording medium according to claim 1, wherein the dye layer and the developer layer are covered with microcapsules that are destroyed by heat or pressure when heated. 10. The heat-sensitive recording medium according to claim 1, wherein an antifogging layer is provided between the dye layer and the developer layer.