JPH04270688A - Image-receiving sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To obtain an improved image-receiving sheet for thermal transfer recording which is esp. suitable for a thermal recording using a thermally sublimable dye and stable for a relative humidity change in environment and has no possibility of a trouble in passing through a printer caused by the occurrence of a curl. CONSTITUTION:An image-receiving sheet for thermal transfer recording is obtained by providing an image-receiving layer accepting an image from a colorant transfer sheet on the surface of a paper substrate. To accomplish the above purpose, a back surface layer containing a binder mainly composed of a plate pigment with a glass transition point of 30-60 deg.C is provided on the rear of the paper substrate.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to the improvement of an image-receiving sheet for thermal transfer recording, and in particular, an image-receiving sheet that is suitable for thermal transfer recording using heat-sublimable dye, is stable against changes in relative humidity in the environment, and is curlable. The present invention relates to an image-receiving sheet for thermal transfer recording that eliminates paper feeding troubles caused by occurrence of .

0002

[Prior Art] The thermal recording method, which allows a recorded image to be obtained at the same time as an input signal, is used in a wide range of applications such as facsimiles, computer terminal printers, and measuring instrument printers because the equipment is relatively simple, inexpensive, and produces low noise. has been done. The most commonly used recording medium for these thermal recording methods is so-called color-forming type thermal recording paper, which is provided with a recording layer that develops color by causing physical or chemical changes when heated. However, color-forming thermal recording paper tends to develop unnecessary color during the manufacturing process and during storage, and the storage stability of recorded images is also poor, causing discoloration when it comes into contact with organic solvents, chemicals, etc. There are drawbacks.

[0003] Therefore, as a recording medium to replace the color-forming type thermal recording paper, a recording method using colored coloring materials itself has been proposed. Paper is a solid coloring material.
The colorant is applied onto a support such as a polymer film, the coloring material on the support is brought into contact with the image-receiving sheet, and the coloring material on the support is heated by a thermal recording head and selectively transferred to the image-receiving sheet. A method for obtaining a recorded image has been proposed.

In this recording method, the coloring material on the support is melted, evaporated, or sublimated by heat and transferred to the image-receiving sheet, and a recorded image is obtained by adhesion, adsorption, or dyeing. It has the characteristic that paper can be used. In particular, recording methods using sublimable dyes as coloring materials produce images with excellent gradation, and attempts are being made to apply them to full-color recording applications.

However, when plain paper is used as the image-receiving sheet, dyeing is particularly difficult to occur, and not only the color density of the recorded image is low, but also the color fades significantly over time. For this reason, Japanese Patent Application Laid-Open No. 57-107885, U.S. Patent No. 3,601,484, etc. disclose a method of improving recording sensitivity and storage stability by using an image receiving sheet with an image receiving layer mainly composed of a thermoplastic resin. is proposed.

[0006] Also, Japanese Patent Application Laid-Open No. 62-238791,
JP-A No. 61-277493 and other publications propose a method of crosslinking thermoplastic resins in order to further improve their physical properties, and JP-A No. 60-212374 proposes a method of crosslinking thermoplastic resins during printing. In order to prevent the surface of the coloring material layer of the sheet from fusing with the surface of the image-receiving layer of the image-receiving sheet, a method of incorporating a releasable substance into the image-receiving layer is also disclosed in JP-A No. 62-222895. A method has been proposed in which a modified resin is used in the image-receiving layer.

[0007]

[Problems to be Solved by the Invention] However, in the image receiving sheet in which a resin layer is formed on the surface of the support, in particular,
When paper is used as a support, there will be a difference in the equilibrium moisture content between the front and back sides, and the amount of volume change due to moisture change will also differ. That is, the resin layer on the front surface has a lower equilibrium moisture content than the cellulose fibers on the back surface, and the amount of volume change due to moisture change is also smaller than that on the back surface. Therefore, an image-receiving sheet that is flat in an environment with relatively low relative humidity will curl with the surface resin layer inside when the relative humidity increases, and an image-receiving sheet that is flat in an environment with relatively high relative humidity will curl. When the relative humidity is low, the paper curls with the back side inward.

Since it is difficult to feed a curled image-receiving sheet to a printer, the relative humidity of the environment in which the printer is placed has to be adjusted appropriately, but this is not practical due to the narrow tolerance range of relative humidity. There is a strong desire to improve this serious deficiency. A method has also been proposed in which a resin layer is also formed on the back side of the support to equalize the equilibrium moisture content and the amount of volume change due to moisture changes on the front and back sides, but generally the resin constituting the image receiving layer is made of expensive resin such as polyester. Because it is resin,
Forming such a resin layer merely to prevent curling is economically disadvantageous.

[0009]

[Means for Solving the Problems] In view of the current situation, the present inventors have conducted intensive research on a method for preventing the occurrence of curling caused by changes in relative humidity in image-receiving sheets for thermal transfer recording. The inventors discovered that the formation of curls can be extremely effectively suppressed by providing a back layer containing a binder having a specific glass transition point and a plate-like pigment as a main component, and have completed the present invention. .

The present invention provides an image-receiving sheet for thermal transfer recording comprising an image-receiving layer for receiving a transferred image from a color material transfer sheet on the surface of a paper support. This is an image-receiving sheet for thermal transfer recording, characterized in that it has a back layer containing a binder having a glass transition point of 30 to 60° C. as a main component.

[0011]

[Function] Paper supports constituting the image receiving sheet of the present invention include coated papers such as art paper, coated paper, lightweight coated paper, lightly coated paper, cast coated paper, etc., gloss type, dull type, matte type, etc. Furthermore, uncoated paper such as high-quality paper, medium-quality paper, super-calendered paper, single-gloss base paper, etc. are preferably used.

The image-receiving layer formed on such a paper support functions to receive the dye transferred from the color material transfer sheet, and is made of, for example, a polyester resin having an ester bond, a polyacrylic acid ester resin, or a polycarbonate resin. It is formed mainly from synthetic resins such as resins, polyvinyl acetate resins, styrene acrylate resins, vinyl toluene acrylate resins, polyurethane resins having urethane bonds, polyamide resins having amide bonds, and urea resins having urea bonds.

The image-receiving layer forming coating solution generally contains one or more of the above-mentioned resins, and optionally an antistatic agent.
It is prepared by adding ultraviolet absorbers, anti-fusing agents, antioxidants, dyes, antifoaming agents, surfactants, pigments such as colloidal silica, crosslinking agents, and other auxiliary agents, but the resulting coating The liquid can be coated using, for example, a blade coater, air knife coater, bar coater, rod blade coater, roll coater,
It is coated onto a paper support using a gravure coater, curtain coater, etc. and dried. The coating amount is 1g/m2 in terms of dry weight.
Above, it is preferably adjusted within a range of about 2 to 10 g/m2.

As described above, the image-receiving sheet for thermal transfer recording of the present invention has an image-receiving layer on the surface of a paper support and a specific back layer on the back side. A barrier layer may be formed between the back layer and the back layer, if necessary. This barrier layer is formed, for example, by a method of applying and drying one or more types of an inorganic pigment and an aqueous liquid of a water-soluble resin or a synthetic resin using a coating device similar to the above. The coating amount is adjusted to be 3 g/m 2 or more, preferably 8 to 30 g/m 2 in terms of dry weight.

[0015] When a barrier layer is provided between the paper support and the image-receiving layer, the surface smoothness and cushioning properties of the paper support are improved, and the adhesion between the color material transfer sheet and the image-receiving sheet is improved. Penetration of the layer coating liquid into the paper support is suppressed, and the diffusion of heat applied from the thermal head into the support is also suppressed, improving thermal efficiency during recording, resulting in improved recording sensitivity and image quality. improves. Furthermore, when a barrier layer is provided between the paper support and the back layer, the permeation of the back layer forming coating liquid into the paper support is suppressed, so that the curl prevention effect, which is the desired effect of the present invention, is suppressed. achieved more efficiently. However, the barrier layer is provided as appropriate depending on the characteristics of the paper support, the quality of the intended image-receiving sheet, etc., and is not necessarily an essential component. It is also possible to have a multilayer structure of two or more layers.

[0016] Preferable inorganic pigments constituting the barrier layer include, for example, calcium carbonate, kaolin, titanium oxide, aluminum hydroxide, barium sulfate, etc., and examples of water-soluble resins include polyacrylamide, carboxyl groups, and hydroxyl groups. Various resins contained, such as carboxyl group-containing polyethylene, polyvinyl alcohol,
Examples include cellulose resin. Furthermore, examples of aqueous synthetic resins include alkali-soluble types such as polyacrylic esters, polymethacrylic esters, polyolefins, polybutadiene, polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyurethane, and polyesters; Examples include emulsions and suspensions of polymers and copolymers of swelling type, alkali non-swelling type, and modified type. Furthermore, in the barrier layer forming coating liquid, if necessary, for example, starch, modified starch, binders such as protein adhesives, antioxidants, dyes, antifoaming agents, surfactants, and other auxiliary agents may be added. etc. may be added.

[0017] In the image-receiving sheet of the present invention, the plate-like pigment is formed on the back side of the paper support as a main component, and 3
Certain back layers containing binders with a glass transition temperature of 0 to 60° C. are generally prepared by applying a coating solution containing these substances to, for example, a blade coater, an air knife coater,
It is formed by coating and drying on a paper support using a bar coater, rod blade coater, roll coater, gravure coater, curtain coater, etc.

The reason why the formation of such a specific back layer suppresses the occurrence of curling due to changes in relative humidity is not necessarily clear, but it is presumed as follows. That is, since the binder used in the back layer of the present invention has a considerably higher glass transition point than binders for general paper coating, it is formed by combining this with a flat pigment. It is presumed that the back layer exhibits strong resistance to bending, that is, curling, and effectively suppresses the occurrence of curling in the resulting image-receiving sheet. Incidentally, even if an amorphous pigment is used instead of a tabular pigment, the desired effect of the present invention cannot be obtained, and even if a binder having a glass transition point outside the above-mentioned specific glass transition point is used, the present invention is still not achieved. The desired effect of the invention cannot be obtained.

[0019] It is preferable that the proportion of the plate-shaped pigment used is 50% by weight or more of the total pigments constituting the back layer.
In particular, when the content is 70% by weight or more, an excellent curl improving effect is achieved. In addition, in general, in order to provide strong surface strength to the coating layer, a binder with a low glass transition point is preferable.
For example, in ordinary coated papers for printing such as art paper and coated paper, binders having a glass transition point of 0° C. or lower are preferably used. However, in the image receiving sheet of the present invention,
If the glass transition point of the binder is lower than 30° C., the desired improvement effect of the present invention of suppressing curling cannot be obtained. This is presumed to be because when the glass transition point is lower than 30° C., even if the bonding force to the pigment is sufficiently exerted, the strength against bending of the coating layer is insufficient. However, if the glass transition point of the binder constituting the back layer is higher than 60°C, the bonding force for the pigment will be insufficient and the surface strength of the back layer will not only become too weak, but also the strength of the back layer will succumb to the movement of the paper. As a result, the desired effect of the present invention cannot be obtained. Therefore, in the back layer of the present invention, a binder having a glass transition point of 30 to 60°C, preferably 40 to 55°C is selectively used.

[0020] Furthermore, it is desirable that the proportion of the binder having a specific glass transition point used is 5% by weight or more of the total solids constituting the back layer, particularly in the range of about 5 to 55% by weight. It is more preferable to adjust. In addition, if the coating amount of the back layer is less than 5 g/m2 in terms of dry weight,
The bending resistance strength of the sheet expected of the back layer cannot be obtained sufficiently, making it difficult to obtain the desired effects of the present invention. However, even if it is applied in a large amount exceeding 25 g/m2, there is no big difference in the effect obtained and it is economically useless, so the amount of coating of the back layer should be 5 g/m2 or more in terms of dry weight, preferably It is adjusted within a range of about 8 to 25 g/m2. In addition, antioxidants, dyes, antifoaming agents, surfactants, antistatic agents, lubricants, and other auxiliary agents may be added to the back layer coating liquid as necessary. It is also possible to form further coating layers on the back layer.

[0021]

[Examples] Examples will be described below to more specifically explain the present invention, but the present invention is of course not limited to these. In addition, unless otherwise specified, "parts" and "%" in the text represent "parts by weight" and "% by weight," respectively, converted to solid content.

Example 1 A barrier layer coating liquid having the following composition was coated with a wire bar on the surface of a high-quality paper having a basis weight of 101 g/m2 by dry weight.
A barrier layer was formed by coating and drying at 0 g/m2. [Barrier layer coating liquid] Modified styrene/butadiene/methyl methacrylate copolymer latex [Product name: JSR-
0530, manufactured by Japan Synthetic Rubber Co., Ltd.] 90 parts and light calcium carbonate [Product name: Brilliant S-15, manufactured by Shiraishi Kogyo (
Co., Ltd.] was stirred in a mixer, water was added to make the solid content concentration 50%, and then 3 parts of oxidized starch and calcium stearate [trade name: Nopcoat C-104, San Nopco (
Co., Ltd.] and then add water to make the solid content concentration 4.
A 7% barrier layer coating solution was prepared.

Next, apply 7 g/dry weight of an image-receiving layer coating liquid having the following composition to the barrier layer surface using a wire bar.
m2 was applied and dried to form an image-receiving layer. [Image-receiving layer coating liquid] Polyester resin [Product name: Vylon
200, manufactured by Toyobo Co., Ltd.] 100 parts, amino-modified silicone [Product name: KF-393, manufactured by Shin-Etsu Chemical Co., Ltd.]
0.5 part, epoxy modified silicone [Product name: X-22
-343, manufactured by Shin-Etsu Chemical Co., Ltd.] was added and dissolved in methyl ethyl ketone/toluene (weight ratio 1:1) while stirring with a mixer to prepare an image-receiving layer coating liquid with a solid content concentration of 15%. did.

[0024] Thereafter, a back layer coating liquid having the following composition was applied to the back side of the high-quality paper using a wire bar at a dry weight of 15 g/
m2 was applied and dried to form a back layer. [Back layer coating liquid] Kaolin, a flat pigment [Product name: Ultra White-90, E. M. C. [Product name: BF-1] 90 parts and amorphous pigment heavy calcium carbonate [Product name: BF-1]
00, manufactured by Bihoku Funka Co., Ltd.] was dispersed in water to prepare a pigment slurry with a solid content concentration of 50%, and an acrylic emulsion with a glass transition point of 45°C was added to this as a binder.
20 parts of Aron A-104 (trade name, manufactured by Toagosei Co., Ltd.) were added thereto, and water was further added to obtain a back layer coating liquid with a solid content concentration of 35%.

The image-receiving sheet thus obtained was subjected to supercalender treatment under the following conditions to obtain an image-receiving sheet for thermal transfer recording of the present invention. [Super calendar conditions] Linear pressure: 90 kg/cm, surface temperature of chrome-plated metal roll: 70°C, paper passing speed:
5 m/min, number of paper passes: 2 The following quality tests were conducted on the thus obtained image receiving sheet for thermal transfer recording, and the results are listed in Table 1. [Evaluation test for curl occurrence] An image-receiving sheet for thermal transfer recording cut into 100 mm x 130 mm so that the paper-making direction of the paper support is the longitudinal direction was subjected to high humidity atmospheric conditions of 40° C. and 90% relative humidity at 20° C. The samples were left for one day and one night under the standard atmospheric conditions of 65% relative humidity and the low humidity atmospheric conditions of 30° C. and 10% relative humidity, and the occurrence of curl was visually evaluated.

Example 2 A barrier layer coating solution having the following composition was applied to the same high-quality paper as in Example 1 using a wire bar at a dry weight of 15 g/m2.
The coating was applied and dried, and then supercalendered under the following conditions to form a barrier layer. [Barrier layer coating liquid] 10 parts of titanium oxide [product name: FA-55W, manufactured by Furukawa Mining Co., Ltd.] was dispersed using a Coles dispersion machine, and a polyolefin resin pigment [product name: Chemipearl A-100, Mitsui Petrochemicals Co., Ltd.] was dispersed into this. Co., Ltd.] 30 parts, polystyrene resin pigment [trade name: Lowpeik OP-84J, manufactured by Nippon Acrylic Co., Ltd.] 45 parts, polyvinyl alcohol [trade name: PVA-205, manufactured by Kuraray Co., Ltd.] 5 parts, polystyrene - 10 parts of acrylic copolymer latex [trade name: Cevian A-4720, manufactured by Daicel Corporation] was added and stirred to prepare a coating liquid with a solid content concentration of 35%. [Super calendar conditions] Linear pressure: 60 kg/cm, surface temperature of chrome-plated metal roll: 25°C, paper passing speed:
5 m/min, number of paper passes: 2 Next, an image-receiving layer coating liquid having the following composition was coated on the barrier layer surface with a dry weight of 7 g/m 2 using a wire bar and dried to form an image-receiving layer. [Image-receiving layer coating liquid] 10 parts of alcohol-modified silicone oil [trade name: Toray Silicone SF-8427, manufactured by Toray Silicone Co., Ltd.] and 15 parts of colloidal silica (trade name: Adelite AT-30A, manufactured by Asahi Denka Co., Ltd.) , water-based modified urethane resin [trade name: Hydran AP-40, manufactured by Dainippon Ink and Chemicals Co., Ltd.] 100 parts, epoxy-modified silicone oil [trade name: Poron MF-11, manufactured by Shin-Etsu Chemical Co., Ltd.] 3 parts, Crosslinking catalyst [Product name: Catalyst P
A-20, manufactured by Dainippon Ink & Chemicals Co., Ltd.] was added and stirred to prepare an image-receiving layer coating solution.

Hereinafter, the image receiving sheet for thermal transfer recording of the present invention obtained by forming a back layer in exactly the same manner as in Example 1 and then supercalendering was evaluated in the same manner as in Example 1, and the results are shown below. 1.

Example 3 A barrier layer coating solution having the following composition was coated on both sides of the same high-quality paper as in Example 1 using a wire bar at a dry weight of 20 g/m 2 per side and dried to form a barrier layer. [Barrier layer coating liquid] Heavy calcium carbonate [Product name: Softon 1800, manufactured by Bihoku Funka Co., Ltd.] using a Coles disperser.
60 parts, light calcium carbonate [Product name: Brilliant S
-15, manufactured by Shiraishi Kogyo Co., Ltd.] 40 parts, 0.2 parts of sodium polyacrylate were dispersed in water to obtain a pigment slurry with a solid content concentration of 55%, and 3 parts of oxidized starch and modified styrene-butadiene copolymer Combined latex (product name: JSR-0696,
(manufactured by Japan Synthetic Rubber Co., Ltd.) was added thereto, and water was further added to prepare a barrier layer coating liquid having a solid content concentration of 50%.

Hereinafter, an image receiving sheet for thermal transfer recording of the present invention obtained by forming an image receiving layer and a back layer in exactly the same manner as in Example 2 and then supercalendering was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Image receptor for thermal transfer recording obtained in exactly the same manner as in Example 3, except that the glass transition point of the binder constituting the back layer was changed as appropriate from -5°C to 65°C. The sheet was evaluated in the same manner as in Example 1, and the results are shown in FIG.

Example 5 In Example 3, the dry coating amount of the back layer was 0 g/m2.
An image-receiving sheet for thermal transfer recording obtained in exactly the same manner as in Example 3 except that the weight was changed as appropriate from 30 g/m2 to 30 g/m2 was evaluated in the same manner as in Example 1, and the results are shown in FIG.

Example 6 In Example 3, the blending ratio of the flat pigment and the amorphous pigment constituting the back layer was 0:100 to 100 by dry weight.
An image-receiving sheet for thermal transfer recording obtained in exactly the same manner as in Example 3 except that the value was changed appropriately to 0 was evaluated in the same manner as in Example 1, and the results are shown in FIG.

Example 7 A product was obtained in exactly the same manner as in Example 3, except that the blending ratio of the pigment and binder constituting the back layer was changed as appropriate from 95:5 to 0:100 on a dry weight basis. The image-receiving sheet for thermal transfer recording obtained above was evaluated in the same manner as in Example 1, and the results are shown in FIG.

Example 8 In Example 3, the back layer coating liquid was changed to a coating liquid having the following composition, and the coating amount was 10 g/m2 in terms of dry weight.
An image-receiving sheet for thermal transfer recording obtained in exactly the same manner as in Example 3 except for the change was evaluated in the same manner as in Example 1, and the results are listed in Table 1. [Back layer coating liquid] Kaolin, a flat pigment [Product name: Ultra White-90, E. M. C. [Product name: BF-1] 90 parts and amorphous pigment heavy calcium carbonate [Product name: BF-1]
00, manufactured by Bihoku Funka Co., Ltd.] was dispersed in water to prepare a pigment slurry with a solid content concentration of 50%, and an acrylic emulsion with a glass transition point of 45°C was added to this as a binder.
20 parts of Aron A-104 (trade name, manufactured by Toagosei Co., Ltd.), 15 parts of oxidized starch, and further water were added to obtain a back layer coating liquid with a solid content concentration of 30%.

Comparative Example 1 An image receiving sheet for thermal transfer recording was obtained in exactly the same manner as in Example 1 except that the back layer was not provided.
Evaluations were made in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 An image-receiving sheet for thermal transfer recording was obtained in exactly the same manner as in Example 2 except that the back layer was not provided.
Evaluations were made in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 An image-receiving sheet for thermal transfer recording was obtained in exactly the same manner as in Example 3 except that the back layer was not provided.
Evaluations were made in the same manner as in Example 1, and the results are shown in Table 1.

[0038]

[Table 1]

[0039]

Effects of the Invention As is clear from the results shown in Table 1 and FIGS. 1 to 4, the occurrence of curling was effectively suppressed in all of the image-receiving sheets for thermal transfer recording of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the glass transition point of the binder constituting the back layer and the occurrence of curl in the image receiving sheet.

FIG. 2 is a graph showing the dry coating amount of the back layer and the occurrence of curl on the image-receiving sheet.

FIG. 3 is a graph showing the blending ratio of the flat pigment and the amorphous pigment constituting the back layer and the occurrence of curl in the image-receiving sheet.

FIG. 4 is a graph showing the blending ratio of the pigment and binder constituting the back layer and the occurrence of curl in the image-receiving sheet.

Claims (4)

[Claims] 1. An image receiving sheet for thermal transfer recording comprising an image receiving layer for receiving a transferred image from a color material transfer sheet on the surface of a paper support, wherein a plate-like pigment is mainly provided on the back surface of the paper support. 1. An image-receiving sheet for thermal transfer recording, comprising a back layer containing a binder having a glass transition point of 30 to 60°C. Claim 2: The coating amount of the back layer is 5 to 25 g in dry weight.
2. The image-receiving sheet for thermal transfer recording according to claim 1, wherein the image-receiving sheet is: 3. The image-receiving sheet for thermal transfer recording according to claim 1, wherein the proportion of the flat pigment constituting the back layer is 50% by weight or more of the total pigments in the back layer. 4. The ratio of the binder having a glass transition point of 30 to 60°C constituting the back layer is 5% of the total solids of the back layer.
The image-receiving sheet for thermal transfer recording according to claim 1, wherein the amount is 50% by weight.