JPH09156226A - Heat transfer sheet for forming raised image and image forming method using the same - Google Patents

Abstract

(57) [Abstract] [Problem] A raised image that can form a bulky raised image, is easy to read with a finger, and has durability due to the touch, and also has good foil breakability and excellent reliability. There is provided a thermal transfer sheet for forming a raised image capable of forming a sheet and an image forming method using the sheet. SOLUTION: In a thermal transfer sheet for image formation, comprising a transfer material having an expansive ink layer on a base sheet, the expansive ink layer contains a foaming agent and a resin binder, A crack is present on the surface of the transfer material having the expansive ink layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer sheet which is effective for producing raised images, especially Braille for the blind, and more specifically, it is easy to read with a finger, has durability against touching, and has a foil break. TECHNICAL FIELD The present invention relates to a thermal transfer sheet for forming a raised image, which is capable of forming a raised image having good reliability and excellent reliability, and an image forming method using the same.

[0002]

2. Description of the Related Art Conventionally, when printing a Braille document for a blind person according to Japanese Braille notation in accordance with output information from a computer, for example, a Braille printer "TP-32" manufactured by Toyo Hybrid Co., Ltd. Like printed matter by
Embossing is used to form tactile projections on paper.

In order to print Braille on paper by this method, it is necessary to use paper having a thickness that does not break the protruding Braille image portion formed by embossing. Therefore, the thickness is 100
It was not possible to print tactile Braille on paper of less than μm.

In addition, since the printing of Braille by embossing produces a concave depression on the paper surface opposite to the side to be touched, it is similar to the backside of a normal printed matter in which ink characters are recorded for the sighted person. If you try to print Braille that indicates the contents,
There is a problem that it becomes difficult to read because of the concave pattern of Braille on the opposite side. (Hereinafter, in the present specification, those with normal eyesight to the blind are sighted people,
Characters for sighted people are referred to as ink characters for braille for blind people. In order to solve such a problem, Japanese Patent Application Laid-Open No. 4-333858 discloses a technique for forming a printed image by melting and transferring an ink film by a heating means.

[0005]

However, in order to realize the tactile readability equivalent to that of the ordinary embossed braille printed matter, a braille height of 300 μm or more, which is equivalent to those, is required. Therefore, in order to transfer such a thick layer from a thermal transfer sheet with a thermal head, it is necessary to apply extremely high energy from the base film side of the thermal transfer sheet, and such high energy causes the base film to break. There was a problem that it would be done.

Moreover, it is very difficult to apply such high energy to the thermal head because of the performance of the thermal head.

In order to solve such a problem, the inventor of the present application has already proposed various proposals regarding a thermal transfer sheet for forming a raised image in which an expansive ink layer containing a foaming agent is formed on a base sheet. (Japanese Patent Application No. 7-
225886).

However, even in these proposals,
In order to produce an image with a raised height of 300 μm, such as a braille image, the thermal expansion ink layer is limited to 10 g / m ² due to the restriction of the thermal expansion ratio resulting from the performance of the foaming agent.
It is necessary to apply a large amount of about 50 g / m ^2, and transfer the thick thermally expansive ink layer applied in this way in a uniform and stable state (improving foil breakability). Is not always easy.

Therefore, in order to improve this point, when a material having a low tensile rupture strength is selected as a binder of the heat-expandable ink layer in order to cut a thick layer with a weak force, the durability of the produced image on rubbing etc. Occurs. In addition, if a foil or other solid material is added to improve the foil cutting property, the durability of the foil will be deteriorated.

The present invention was conceived in view of the above circumstances, and its object is, of course, that a bulky raised image can be formed, easy to read by a finger, and durable by a touch. In view of the above, it is an object of the present invention to provide a thermal transfer sheet for forming a raised image, which is capable of forming a raised image having good foil breakability and excellent reliability, and an image forming method using the same.

[0011]

In order to achieve such an object, the present invention provides a thermal transfer sheet for forming a raised image, which comprises a transfer material having an expansive ink layer on a base sheet. The expandable ink layer contains a foaming agent and a resin binder, and the surface of the transfer material having the expandable ink layer is configured to have cracks.

Further, the transfer material has an expansive ink layer on the surface layer, and the expansive ink layer has a crack on its surface.

The transfer material has an expansive ink layer and a heat-sensitive adhesive layer formed on the expansive ink layer, and cracks are present on the surface of the heat-sensitive adhesive layer. Is configured as follows.

The transfer member has an expansive ink layer and a heat-sensitive adhesive layer formed on the expansive ink layer. The surface of the heat-sensitive adhesive layer and the surface of the expansive ink layer (heat-sensitive adhesive layer) The surface on the side where the adhesive layer is laminated) is configured so that cracks exist respectively.

The width of the crack is 10 nm to 5 nm.
μm.

Further, the depth of the crack is formed larger than the width of the crack.

The ratio of the surface area occupied by the cracks to the surface of the transfer material is 0.5 to 20%.

Further, the expanding agent contained in the expandable ink layer is composed of heat-expandable microcapsules containing easily volatile hydrocarbons.

Further, the peelability adjusting layer is formed between the expansive ink layer and the base sheet.

The present invention is also a method for forming a raised image using any one of the above-mentioned thermal transfer sheets for forming a raised image, wherein the thermal transfer sheet and the material to be transferred are superposed, and an expansive ink layer is imaged. After heating and pressing in a circular pattern, the transfer material having the image-shaped expandable ink layer is peeled from the thermal transfer sheet and transferred to the transfer target side, and then heat is applied to the transferred expandable ink layer. The transferred expansive ink layer is expanded to form a three-dimensional raised image.

In the present invention, since the surface of the transfer material having the expansive ink layer is cracked, it is possible to cut the expansive ink layer with a weak force. Therefore, the image transferability from the thermal transfer sheet is improved.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. First, a preferred example of the thermal transfer sheet 30 for forming a raised image of the present invention (hereinafter, simply referred to as "thermal transfer sheet 30") will be described.

As shown in FIG. 1, the thermal transfer sheet 30.
Has an expansive ink layer 3 provided on one surface of the base sheet 1. In the embodiment shown in FIG. 1, the expansive ink layer 3 itself constitutes a transfer body to which the ink is transferred. Then, the surface 3 of the expansive ink layer 3
The surface a, that is, the surface of the transfer body is in a cracked state, and many cracks are present. 2 (a) and 2 (b) each show a situation in which the cracked surface is observed with a scanning electron microscope.
Is an observation magnification of 2000 times, and FIG. 2 (a) is an observation magnification of 5000 times.
It is double.

As shown in FIG. 2, many cracks 7 in the present invention have a width W (FIG. 2 (b)) of 10 nm.
˜5 μm, preferably 100 nm to 3 μm.
If this value exceeds 5 μm, the proportion of voids inside the planar image formed by transfer increases, resulting in a disadvantage that the strength of the expanded image is significantly reduced, and if this value is less than 10 nm. In that case, most of the cracks are closed while the thermal transfer sheet is stored in an unused state or due to heat applied at the time of transfer, so that there is an inconvenience that the effect due to the presence of the cracks cannot be obtained. Further, the depth of the crack 7 is larger than the width W of the crack 7. When the depth of the crack 7 is smaller than the width W of the crack 7, the crack 7 does not contribute to the improvement of foil breakage.

The ratio of the surface area occupied by the cracks 7 to the surface of the transfer material (in this case, the expansive ink layer 3) is preferably 0.5 to 20%, more preferably 2 to 10%. The occupancy ratio of the crack 7 is, for example, as shown in FIG.
Using the results of the photographic observation shown in (a), 50
In the surface layer area of μm × 50 μm, it may be determined by image processing how much surface area the cracked portion occupies. If this ratio exceeds 20%, the ratio of voids inside the planar image formed by transfer increases, which causes a disadvantage that the strength of the expanded image is significantly reduced. Is less than 0.5%, most of the cracks are closed while the thermal transfer sheet is stored in an unused state or due to heat applied during transfer, and the effect of the presence of the cracks cannot be obtained. The inconvenience occurs.

Such cracks 7 are prepared by preparing a coating liquid in which a resin used for the outermost layer of the transfer material (in this case, the expansive ink layer 3) is dispersed in water, and after coating this, drying. It is formed by In this case, it is particularly important to set the drying conditions when the coating film is dried, and it is necessary to adjust it according to the physical properties of the resin used. There is no particular limitation on the type of the coating liquid in which the resin is dispersed in water, as long as it can cause cracks by adjusting the drying conditions after the coating film. Among them, a particularly preferable coating liquid is a polyester aqueous dispersion prepared by the method for producing an aqueous dispersion described in JP-B-61-58092. This is an aromatic dicarboxylic acid whose polycarboxylic acid component does not contain a sulfonic acid metal base 40 to 9
9.5 mol%, aliphatic or alicyclic dicarboxylic acid 59.
5 to 0 mol% and 0.5 to 10 mol% of a metal sulfonate-containing aromatic dicarboxylic acid, wherein the polyol component is an aliphatic glycol having a prime number of 2 to 8 and / or a fat having a carbon number of 6 to 12. A polyester resin having a molecular weight of 2500 to 30000 and a softening point of 40 to 200 ° C and a water-soluble organic compound having a boiling point of 60 ° C to 200 ° C are mixed in advance and water is added thereto; or the above polyester resin And a water-soluble organic compound having a boiling point of 60 to 200 ° C. are added to water; or the above polyerter resin is added to a mixed solution of water and a water-soluble organic compound having a boiling point of 60 to 200 ° C. It
When a dry coating film is made using the polyester aqueous dispersion produced by this manufacturing method, the coating film shrinks easily during drying.Therefore, by setting the drying conditions optimally, a crack structure is generated on the surface. Can be made.

The ink layer 3 having a cracked structure contains a resin binder 31 and heat-expandable microcapsules 32 containing a readily volatile hydrocarbon as a suitable foaming agent.

As the base sheet 1, the same base sheet as that used in the conventional thermal transfer sheet can be used, and it is not particularly limited as long as it can withstand the heat at the time of thermal transfer. Preferred substrate sheets include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, saponified ethylene-vinyl acetate copolymer, fluororesin, and chlorinated rubber. , Stretched or unstretched films such as ionomers, condenser paper, and paraffin paper.

The thickness of the base material sheet 1 can be appropriately changed depending on the material so that the strength and thermal conductivity thereof are appropriate, but it is preferably 2 to 100 μm, more preferably 3 μm. Is about 25 μm.

In this embodiment, the expansive ink layer 3 contains the thermally expansive microcapsules 32 and the resin binder 31 containing easily volatile hydrocarbons which are suitable examples of the foaming agent as described above.

The heat-expandable microcapsule 32 has a capsule structure in which a hydrocarbon that volatilizes at a low temperature is contained inside a wall material made of a thermoplastic resin. The volume expands 10 to 150 times.

Hydrocarbons contained in the heat-expandable microcapsules 32 are methyl chloride, methyl bromide, trichloroethane, dichloroethane, n-butane, n-heptane, n.
An aliphatic hydrocarbon having a fluorine atom such as -propane, n-hexane, n-pentane, isobutane, isoheptane, neopentane, petroleum ether, and Freon, or a complex mixture of these hydrocarbons can be used.

The wall material of the heat-expandable microcapsule is made of vinylidene chloride, vinyl chloride, acrylonitrile, styrene, polycarbonate, methyl methacrylate, ethyl methacrylate, vinyl acetate polymer, or a copolymer or mixture of these resins. It can be used, and a crosslinking agent is used if necessary.

The particle size of the thermally expandable microcapsule 32 is
The diameter is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm.

Such heat-expandable microcapsules 32
Examples of commercially available products are F-20 and F-3 of "Matsumoto Microsphere" series manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.
0, F-40, F-50, F80S, F82, F80V
S, F100, etc., and "Expansel" series manufactured by Nippon Ferrite Co., Ltd. can be mentioned. When the heat-expandable microcapsules are contained, the resulting image-formed product exhibits high elasticity, and exhibits extremely excellent durability.

Such a heat-expandable microcapsule 32
Other examples of the foaming agent usable in the present invention include azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, N, N'dinitroso-N, N'dimethylterephthalamide, P-toluenesulfonylhydrazide. , Hydrazol carbonamide, P
-Toluenesulfonyl azide, acetone-P-sulfonylhydrazone, and other organic foaming agents; sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and other inorganic foaming agents; and the like.

The material constituting the resin binder 31 of the expansive ink layer 3 is, for example, vinyl-based resin such as polyvinyl acetate, polyacrylic acid ester, polymethacrylic acid ester, polyester such as polyethylene terephthalate or polybutylene terephthalate, Examples thereof include polystyrene, polyamide, polyurethane, acrylonitrile, vinyl chloride-vinylidene chloride copolymer, acrylonitrile-vinylidene chloride copolymer, and rubber-based resins such as vulcanized rubber and unvulcanized rubber. Examples of rubber resins include chloroprene rubber, fluororubber, silicone rubber, synthetic isoprene rubber, butyl rubber, urethane rubber, acrylic rubber, styrene-butadiene rubber, ethylene-propylene rubber, polyisoplane rubber, butadiene rubber, nitrile rubber, and chlorinated rubber. Examples include synthetic rubber such as butyl rubber, unvulcanized rubber such as natural rubber, and vulcanized rubber. Particularly preferred are polyester, acrylonitrile, vinyl chloride-vinylidene chloride copolymer, and rubber resin.

The number average molecular weight of the resin used for the resin binder 31 is preferably 1000 or more.

A natural wax such as carnauba wax, paraffin wax or beeswax having a number average molecular weight of less than 1000, or a synthetic wax such as polyethylene wax or stearic acid or Armor Wax having a number average molecular weight of less than 1000 is used as a resin binder. When it is used as the main component of, the formed braille image may be very fragile.

Further, such a low molecular weight binder is
When the image transferred from the thermal transfer sheet is expanded (foamed) to form a raised image, it is softened or melted, so that the viscosity is very likely to be lowered. For this reason,
The binder may soak into the transferred material (transferred substrate) or flow out around the braille image to be formed, and the thermally expandable microcapsules are retained on the transferred material (transferred substrate). There is an inconvenience that it becomes difficult.

When a fine raised image such as Braille is thermally transferred onto a transfer-receiving member, it is extremely important to transfer only a heated portion without excess or deficiency in order to form an accurate image. For this reason, the resin binder of the expansive ink layer 3 needs to be transferred by cutting the foil only at a desired portion during thermal transfer. For this purpose, the number average molecular weight of the resin binder is preferably 30,000 or less, and 2500
It is particularly preferably 0 or less.

Further, when durability against breakage due to tactile reading of a Braille image or the like is particularly required, it is possible to obtain a better Braille image when the molecular weight of the resin binder is larger. Number average molecular weight is 30
It is preferably 00 or more, and particularly preferably 10,000 or more.

That is, in consideration of the accuracy of forming a raised image such as a braille image and the durability against breakage by touch, the resin binder preferably has a number average molecular weight of 1,000 or more and 30,000 or less, more preferably 3,000 or more and 25,000 or less, particularly preferably 1
It is 0000 or more and 25000 or less.

A coloring agent may be added to the expansive ink layer 3 if necessary.

The colorant may be added in any amount so long as it does not hinder the coating and formation of the expansive ink layer 3 on the substrate sheet 1. That is, it is preferable to select a colorant that is uniformly dissolved or dispersed in the solvent or dispersion medium used for coating the expansive ink layer 3.

For example, when the expansive ink layer 3 is formed by coating an aqueous dispersion containing water as a dispersion medium, the colorant selected is selected from those which are uniformly dispersed or dissolved in water. It is preferable that an aqueous dispersion of carbon black be used for coloring gray or black, and a water-soluble or water-dispersible organic pigment corresponding to each color for coloring chromatic color. Alternatively, an inorganic pigment can be used.

Similarly, when the expansive ink layer 3 is dissolved in a mixed liquid of water and an organic solvent or an organic solvent,
The colorant is preferably selected from those that are uniformly dispersed or dissolved in such a solvent or dispersion medium, and in this case as well, it is said that arbitrary coloring is possible depending on the desired hue, saturation, and brightness. There is no end.

Further, the expansive ink layer 3 is formed on the thermal transfer sheet.
Although it is colorless at the time of forming, it may be one that develops color by the addition of heat energy during thermal transfer or optical energy for foaming described later, or one that has been previously applied to the transfer target. It may be a color that develops when it comes into contact with, or may be a color that develops or changes to another color by heat foaming or touching the raised image with a finger.

Further, in order to impart good thermal conductivity and melt transferability to the expansive ink layer 3, a substance having good thermal conductivity can be added to the expansive ink layer 3. As such a substance, powders or fine powders or whiskers of a metal or a metal oxide or a metal sulfide such as copper, aluminum, tin oxide or molybdenum disulfide, or a carbonaceous substance such as carbon black should be used. You can

The expansive ink layer 3 is the base sheet 1 described above.
On one side, a resin obtained by adding necessary additives such as a cross-linking agent and a cross-linking reaction accelerating catalyst to the resin as described above, a suitable organic solvent, a mixture of an organic solvent and water, or water. Is formed by applying and drying a solution or dispersion that is dissolved or dispersed in, by a conventional method such as gravure coating, coating with a screen plate, reverse roll coating method using a gravure plate, or air knife coating. .

The expansive ink layer 3 has a thickness of 10 μm to 1
00 μm is preferable, and 20 μm to 80 μm is preferable.

The content ratio of the thermally expandable microcapsules in the expandable ink layer 3 is preferably 30 parts by weight or more and 200 parts by weight or less, particularly 50 parts by weight or more and 150 parts by weight, relative to 100 parts by weight of the resin binder. It is preferably less than or equal to parts by weight. If less than 30 parts by weight,
If the expansive ink layer 3 does not expand sufficiently and exceeds 200 parts by weight, the durability against tactile reading such as Braille images tends to be insufficient.

It is also a preferred embodiment of the present invention to provide a heat-sensitive adhesive layer 4 on the surface of the expansive ink layer 3 as shown in FIG. In this case, the expansive ink layer 3 and the heat-sensitive adhesive layer 4 constitute a transfer body, and the surface of this transfer body, that is, the surface 4a of the heat-sensitive adhesive layer 4 has already been described above. There are cracks similar to. In this case, the crack depth of the heat-sensitive adhesive layer 4 is
It is preferable that the thickness is equivalent to the thickness of the heat-sensitive adhesive layer 4. Further, it is preferable that the surface of the expansive ink layer 3 located below the heat-sensitive adhesive layer 4 also has cracks similar to those described above. However, in this case, the cracks of the heat-sensitive adhesive layer 4 and the cracks of the expansive ink layer 3 do not have to be continuous and may be formed independently (normally, they are formed independently. ). The method of forming such a crack may be performed according to the method described above.

The heat-sensitive adhesive layer 4 is provided to transfer the expansive ink layer 3 at a relatively low temperature. When the transfer temperature is high and the expansion (foaming) temperature is reached,
This is because the heat-expandable microcapsule may expand in a plane direction other than the height, and the durability against tactile reading such as Braille images may be insufficient.

Materials usable for the heat-sensitive adhesive layer 4 include waxes such as microcrystalline wax, carnauba wax and paraffin wax; acrylic rubber, styrene-butadiene rubber, ethylene-propylene rubber, isoprene rubber, butadiene rubber, nitrile rubber, Synthetic rubber such as chlorinated butyl rubber; unvulcanized rubber such as natural rubber;
Vinyl-based resins such as polyvinyl acetate and polyvinyl chloride;
Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; thermoplastic resins such as ethylene-vinyl acetate copolymer and polyamide are used alone or in an appropriate mixture. In addition, the heat-sensitive adhesive layer 4
By mixing the heat-expandable microcapsules,
It can be foamed to make it easier to read a raised image such as Braille.

Further, in the thermal transfer sheet 30 of the present invention, a peelability adjusting layer 2 may be provided between the expansive ink layer 3 and the base sheet 1 as shown in FIG.

The peelability adjusting layer 2 is for peeling and adhering only the image forming portion of the expansive ink layer 3 to the transferred material when forming a raised image using the thermal transfer sheet 30, and The peelability of the 30 and the expansive ink layer 3 when heated is adjusted.

As shown in FIG. 5, the peelability adjusting layer 2 is separated from the expansive ink layer 3 of the base sheet 1 and is peeled off to the transfer target 10 side together with the transferred expansive ink layer 36 to be transferred. Release layer 21; remains on the substrate sheet 1 side even after being transferred as shown in FIG. 6, so that the expandable ink layer 3 is easily peeled off and the expandable ink layer 36 transferred to the transfer target 10 is transferred. As shown in FIG. 7, the release layer 22 constituting the release layer 22 is melted by the heat at the time of transfer to lower the cohesive force, so that the layer is separated and the expansive ink layer 3 is peeled off. 10
Layer separation layer 2 constituting the expansive ink layer 36 transferred to the surface
There are three types:

Further, the release layer 21 and the release layer 22 can be used together.

When the peelability adjusting layer is the peeling layer 21 or the layer separating layer 23, the transferred expansive ink layer 36.
Since the peeling layer or the layer separating layer is also transferred to the outermost surface of (3), the resin forming such a peelability adjusting layer does not hinder the expansivity of the expansive ink layer 36 (3). It is necessary to select one. Further, the peeling layer 21 is
It has the effect of a protective layer for the raised image, but it should not impair the feel of the finger when reading.

The resin forming the release layer 22 has a releasing property such as silicone resin, fluororesin, polymethylpentene, polypropylene, etc., acrylic resin, linear polyester, vinyl chloride-acetic acid. Varnishes such as vinyl copolymer, polyvinyl butyral, polyvinyl acetal, polyvinyl acetate, nitrocellulose, and cellulose acetate butyrate to which a release agent such as silicone resin, fluororesin, wax, and fatty acid amide is added, or the above resin What was crosslinked with various crosslinking agents can be used. For example, isophorone diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, polyisocyanates such as adduct bodies and biuret bodies and trimers obtained by adding diisocyanate to trimethylolpropane,
A cross-linking agent having an epoxy group, an aziridine group or an oxazoline group, a cross-linking agent such as melamine, and a chelating agent such as aluminum, zinc, titanium or zirconium can be used.

Preferably, a crosslinked silicone resin,
Alternatively, it is an acrylic resin or polyester containing a release agent crosslinked with polyisocyanate. Then, the coating is performed by a usual method such as gravure coating or roll coating, and the coating thickness is preferably 0.05 to 5.00 μm,
More preferably, it is 0.10 to 2.00 μm.

The resin forming the peeling layer 21 is selected from thermoplastic resins which do not impede the heating rate of the expansive ink layer 3 and which can form a coating film. In order to make it easy to read, inorganic substances such as silica, calcium carbonate, magnesium carbonate, and aluminum hydroxide, which are matting agents, and polycarbonate, polyethylene, and ethylene-
Fine particles of an organic substance such as a vinyl acetate copolymer can also be dispersed.

Further, by including the above-mentioned thermally expandable microcapsules in the peeling layer 21, it is possible to expand (foam) together with the transferred image to facilitate the tactile reading.

The thermoplastic resin used is acrylic resin, linear polyester, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, polyvinyl butyral, polyvinyl acetal, polyvinyl acetate,
There are solutions or dispersions of polyamide, urethane, acrylonitrile, polyisobutylene, neoprene, natural rubber and the like. Preferred are vinyl chloride-vinylidene chloride copolymer, acrylonitrile, and acrylic resin, which serve as a barrier layer for hydrocarbon that is a foaming agent of the expansive ink layer 3. Then, the coating is carried out by a usual method such as gravure coating, roll coating, air knife coating, and the coating thickness is preferably 0.05 to 5.00 μm,
More preferably, it is 0.10 to 2.00 μm.

The resin for forming the layer separating layer 23 is a resin that is melted by heat when transferring the expansive ink layer 3 from the thermal transfer sheet to lower the cohesive force. It can be selected from thermoplastic resins. For example, microcrystalline wax, carnauba wax, paraffin wax, Fischer Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ivota wax, wool wax, shellac wax, candelilla wax, petrolactam, partially modified wax, There are various waxes such as fatty acid ester, fatty acid amide, silicone wax, polyvinyl butyral, polyvinyl acetal, polyvinyl acetate, polyamide, polyester, acrylic resin, polyurethane, etc., alone or in a mixture. Mainly low molecular weight polyethylene. Then, the application is carried out by a usual method such as gravure coating, roll coating, air knife coating or the like in the state of being melted by heat, heat-melted in a solvent, made into a solution, or in a dispersion state. The coating thickness is preferably 0.05 to 5.00 μm, more preferably 0.10 to 2.00 μm.

In another embodiment, the expandable ink layer 3
When the resin used for the peelability adjusting layer 2 has a dyeing property with respect to the heat diffusing dye, a heat diffusing dye of any color can be added to the peeling adjusting layer 2.

By forming in this way, by the heat in the drying step when applying the expansive ink layer 3,
The expansive ink layer 3 can be colored arbitrarily by diffusing the heat-diffusible dye added to the peelability adjusting layer 2, and the heat-expandable microcapsules (or foaming agent) and the binder resin are dissolved in water. The expansive ink layer 3 formed by applying and drying a dispersed or dissolved liquid can be dyed with a heat-diffusible dye that is insoluble or difficult to disperse in water.

As the heat diffusible dye, any conventionally known dye can be used and is not particularly limited. For example, as a preferred dye, as a red dye, MS
Red G, Macrolex Red Violet R, Ceres Red 7B, Sama
ron Red HBSL, Resolin Red F3BS, etc.
As a yellow dye, Holon Brilliant Yellow 6GL,
PTY-52, Macrolex Yellow 6G, etc., and as the blue dye, Kayaset Blue 714, Waxolin Blue AP-FW, Holon Brilliant Blue SR, MS.
Blue 100 etc. can be mentioned. Further, not only one kind of these heat diffusible dyes but also two or more kinds may be arbitrarily mixed to obtain a desired color tone.

When a thermal head is used as a heating means for transferring a raised image to a transfer body using a thermal transfer sheet, heating is performed from the side of the base sheet 1 on which the expansive ink layer 3 is not formed. . It is preferable to provide a heat resistant slipping layer for imparting heat resistance, slip properties, or both physical properties to the heating surface. The heat resistant slipping layer contains a heat resistant resin and a substance acting as a thermal release agent or a lubricant as basic constituent components. Cross-linking various thermoplastic resins with a known cross-linking agent is an effective method for improving the heat resistance of the resin, for example, when there is a hydroxyl group on the side chain or molecular end of the thermoplastic resin, polyisocyanate, etc. The cross-linking agent can be used. When using a cross-linking agent, a catalyst is used if necessary.

A method for forming a raised image using the thermal transfer sheet 30 for forming a raised image as described above will be described below.

First, as shown in FIG. 8, the thermal transfer sheet 30 and the transferred material 10 are superposed on each other, and the thermal transfer sheet 3 is formed.
The intumescent ink layer 3 of 0 is image-wise heated to be transferred 10
After pressure bonding, the image-shaped expansive ink layer 3 (37) is peeled from the thermal transfer sheet 30 and transferred to the transfer target 10 side as shown in FIG. In this case, as the shape of the transferred body 10 used when performing the thermal transfer, there are various forms such as a sheet state, a small winding state and a card state.
And the material is not limited to natural fibers such as cellulose, synthetic fibers such as vinylon, nylon, polyester and acrylic, metal fibers such as stainless steel, inorganic fibers such as alumina and silicate, carbon fibers, chitin fibers and chitosan fibers. Any of the materials such as those obtained by using the can be used. Examples of papers using natural fibers include high-quality paper, medium-quality paper, copy paper, art paper, coated paper,
Kraft paper, Kent paper, paperboard, drawing paper, card paper,
Examples include sleached paper, glassine paper, newsprint, condenser paper, and the like.

Further, a plastic film produced by using various thermoplastic resins as raw materials, such as polyethylene terephthalate film, polyvinyl chloride film, polyethylene naphthalate film and polyimide film, and a step of making the same thermoplastic resin. Synthetic papers processed into paper without passing through (for example, Yupo FPG-1 manufactured by Oji Yuka)
50) and the like can also be used.

From the above-mentioned thermal transfer sheet 30 to the transferred body 10
As the heating means used when transferring the image to the image, that is, the means for applying the thermal energy, various conventionally known methods capable of controlling the heating amount according to the image information from the computer can be used. For example, a thermal head for a thermal melting transfer system used in a word processor, a thermal head for a sublimation transfer system used in a video printer, a laser head used in a laser printing system printer, or the like can be used. Furthermore, when an electric heating layer is provided on the back side of the thermal transfer sheet,
It is also possible to use an energizing head for an energizing heating type melt transfer system.

The image-like expansive ink layer 37 (3) thus transferred to the transferred body 10 side expands (foams) by being applied with thermal energy as shown in FIG. A three-dimensional raised image (expanded expansive ink layer 38 (3)) is formed. As the heat energy applying means, any of various conventionally known applying means can be used, for example, heating by an oven, hot air heating by a heating wire, infrared irradiation heating, laser beam heating, heating methods such as electromagnetic heating, and a non-transfer member. Examples include a heating method of contacting with a heating roll. I can do it.

Further, the raised image (image-formed product) such as Braille of the present invention does not cause a dent on the back surface on which the raised image is formed, unlike the one printed by the embossing method generally used conventionally. It is possible to print Braille on an opposite surface of a paperboard or the like on which ink characters are printed for a sighted person without damaging the ink characters information. So, for example, the back and front of a receipt that records payment details of money, the back and front of a business card on which normal text is printed, the front of a prepaid card with magnetic information recorded, or an airline ticket or ticket. It can also be printed on the front and back surfaces of, and has a very wide range of applications.

In the present specification, particularly, Braille in which the thermal transfer sheet of the present invention is effective has been described in detail as an example, but the raised image may be a picture, a symbol, or a character, not Braille. Absent. The raised image can also be used as a stamp (letterpress).

[0078]

EXAMPLES The present invention will be described in more detail with reference to specific examples of the present invention. In the text, parts or% are based on weight unless otherwise specified.

[Example 1] As the substrate sheet 1, a polyethylene terephthalate film having a thickness of 6.0 µm, which was heat-treated on the back side of the surface on which the expansive ink layer was formed, was used and stirred so as to be uniform. The intumescent ink layer coating liquid 1 having the following composition was applied by gravure reverse coating to a thickness of 30 μm. Then, this coating film was dried by blowing air at 50 ° C. for 30 seconds to obtain a continuous film-shaped thermal transfer sheet of the present invention.

(Expandable ink layer coating liquid 1) -Polyester aqueous dispersion (Toyobo Co., Ltd., Bayronal MD-1930, solid content concentration 30%, number average molecular weight of resin 25000) ... 40 parts by weight-Thermal expansion property Microcapsule (Matsumoto Yushi-Seiyaku Co., Ltd., Matsumoto Microsphere F-20VS) 15 parts by weight Water 20 parts by weight The expansive ink layer of this thermal transfer sheet was accelerated at an acceleration voltage of 10 k.
As a result of observing with a scanning electron microscope at V and an observation magnification of 5000 times, many cracks having a width of 0.1 to 1.2 μm were found. It was also confirmed that the depth of the crack was about 5 μm and the surface area ratio occupied by the crack was about 5%.

The expansive ink layer of the thermal transfer sheet thus produced was superposed on a quality paper having a thickness of 150 μm, and the thermal head (KMT-85-
6MPD2-HTV) and a head applied voltage of 12.
Approximately 170 μm, which is formed by heating from the thermal head, performing transfer under the printing conditions of 0 V, printing speed 33.3 ms / line, applied pulse width 16.0 ms / line
By controlling the image information so that the pixels on all four sides form a circle with a diameter of about 1 mm, the dot pixels of 1 mm forming the Braille document were transferred.

Next, after peeling the transfer sheet from the transfer paper, it was heated in an oven at 100 ° C. for 1 minute to expand the transferred expansive ink layer to prepare a point pixel sample of Example 1.

Example 2 In Example 1, the drying conditions after applying the expansible ink layer coating liquid 1 were changed.
That is, the coating film was dried by blowing air at 40 ° C. for 50 seconds to obtain a continuous film-like thermal transfer sheet of the present invention.
As a result of observing the expansive ink layer of this thermal transfer sheet with a scanning electron microscope in the same manner as in Example 1, the result was 0.0.
Many cracks having a width of 5 to 0.5 μm were generated. Also,
It was confirmed that the depth of the crack was about 3 μm, and the surface area ratio occupied by the crack was about 0.8%.

After that, a point pixel sample of Example 2 was prepared in accordance with the procedures of the transfer method and foaming method shown in Example 1 above.

Example 3 In Example 1, the drying conditions after applying the expansive ink layer coating liquid 1 were changed.
That is, the coating film was dried by blowing air at 70 ° C. for 30 seconds to obtain a continuous film-shaped thermal transfer sheet of the present invention.
As a result of observing the expansive ink layer of this thermal transfer sheet with a scanning electron microscope in the same manner as in Example 1, the result was 0.5.
Many cracks having a width of up to 2.0 μm were generated. It was also confirmed that the depth of the crack was about 5 μm and the surface area ratio occupied by the crack was about 18%.

After that, a point pixel sample of Example 3 was prepared in accordance with the procedures of the transfer method and the foaming method shown in Example 1 above.

[Example 4] Intumescent ink layer coating liquid 1 in Example 1 was replaced with intumescent ink layer coating liquid 2 shown below.
I changed it. Furthermore, after coating the expansive ink layer coating liquid 2, the coating film was dried by blowing air at 50 ° C. for 30 seconds to obtain a continuous film-like thermal transfer sheet of the present invention. The expansive ink layer of this thermal transfer sheet was observed with a scanning electron microscope in the same manner as in Example 1 above, and as a result,
Many cracks having a width of 1.2 μm were generated. It was also confirmed that the depth of the crack was about 5 μm and the surface area ratio occupied by the crack was about 5%.

After that, a point pixel sample of Example 4 was prepared in accordance with the procedures of the transfer method and foaming method shown in Example 1 above.

(Expandable ink layer coating liquid 2) Polyester water dispersion liquid (manufactured by Toyobo Co., Ltd., Vylonal MD-1930, solid content concentration 30%, number average molecular weight of resin 25000) ... 40 parts by weight-Pyrolysis type Foaming agent (sodium hydrogen carbonate) 15 parts by weight Water 20 parts by weight (Comparative Example 1) In the above-mentioned Example 1, the drying conditions after applying the expansive ink layer coating liquid 1 were changed. That is, the coating film was dried by blowing 120 ° C. air for 30 seconds to obtain a continuous film-like thermal transfer sheet of the present invention. As a result of observing the expansive ink layer of this thermal transfer sheet with a scanning electron microscope in the same manner as in Example 1, no cracks were present. Thereafter, a point pixel sample of Comparative Example 1 was prepared according to the procedures of the transfer method and the foaming method shown in Example 1 above.

(Example 5) After forming an expansive ink layer in the same manner as in Example 1 (the same as the state of generation of cracks), a thermosensitive adhesive layer having the following composition was formed on the expansible ink layer. The coating liquid for coating was applied by roll coating to a thickness of 2 μm and dried. When drying the coating film of the heat-sensitive adhesive layer, the coating film was dried by blowing air at 50 ° C. for 30 seconds to obtain a continuous film-shaped thermal transfer sheet of the present invention. As a result of observing the heat-sensitive adhesive layer of this heat transfer sheet with a scanning electron microscope in the same manner as in Example 1 above, many cracks having a width of 0.1 to 1.2 μm were found. It was also confirmed that the depth of the crack was about 3 μm, and the surface area ratio occupied by the crack was about 3%. The cracks of the expansive ink layer and the heat-sensitive adhesive layer were discontinuous in the film thickness direction.

After that, a point pixel sample of Example 5 was prepared in accordance with the procedures of the transfer method and the foaming method shown in Example 1 above.

(Specific Evaluation Method) "Foil breakability" of the prepared point pixel samples (Examples 1 to 5 and Comparative Example 1)
Was evaluated according to the following criteria.

After heating with a foil-breaking thermal head, the difference between the transfer sheet and the transfer paper is peeled off, and the thermal expansion layer adjacent to the heated location is
The degree of transfer from the transfer sheet without being cut was evaluated in three levels.

⊚: The thermal expansion layer did not have any uncut residue, and the tactile readability was very good.

The force required for peeling was extremely small, and peeling could be performed extremely easily.

O: Almost no uncut residue of the thermal expansion layer,
It did not hinder the reading. The force required for peeling was relatively weak and could be easily peeled.

X: Since the film remains uncut around the point pixels, it was difficult to read the point pixels with a finger. A large force was required for peeling, and it was not possible to peel easily.

The evaluation results are shown in Table 1 below. Although not shown in Table 1, the "Braille height" and the "strength of the foam" in the example samples of the present invention were extremely good.

[0099]

[Table 1]

[0100]

The effects of the present invention are clear from the above results. That is, in the present invention, since the surface of the transfer material having the expansive ink layer is configured to have cracks, it is possible to cut the expansive ink layer with a weak force. The image transferability from the sheet is improved, and highly reliable image transferability can be obtained. of course,
It can form a bulky raised image, is easy to read with a finger, and is durable by reading.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a thermal transfer sheet for forming a raised image.

2A and 2B are diagrams showing a cracked state of the surface of a transfer material having an expansive ink layer of a thermal transfer sheet for forming a raised image, respectively.

FIG. 3 is a schematic cross-sectional view of a thermal transfer sheet for forming a raised image, provided with a heat-sensitive adhesive layer.

FIG. 4 is a schematic cross-sectional view of a thermal transfer sheet for forming a raised image, which is provided with a peelability adjusting layer.

FIG. 5 is a schematic cross-sectional view showing a peeling state of a thermal transfer sheet for forming a raised image, which is provided with a peelability adjusting layer.

FIG. 6 is a schematic cross-sectional view showing a peeling state of a thermal transfer sheet for forming a raised image, which is provided with a peelability adjusting layer.

FIG. 7 is a schematic cross-sectional view showing a peeling state of a thermal transfer sheet for forming a raised image, which is provided with a peelability adjusting layer.

FIG. 8 is a schematic cross-sectional view in which a thermal transfer sheet and a transfer target sheet are superposed.

FIG. 9 is a schematic cross-sectional view showing a situation in which the expansive ink layer is transferred from the thermal transfer sheet to the transfer target.

FIG. 10 is a schematic cross-sectional view showing a state in which the expansive ink layer of the transferred material is irradiated with light to be expanded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate sheet 3 ... Intumescent ink layer 7 ... Crack 10 ... Transferred object 31 ... Resin binder 32 ... Thermally expandable microcapsule

Claims (10)

[Claims] 1. A thermal transfer sheet for image formation, comprising a transfer material having an expansive ink layer on a base sheet, wherein the expansive ink layer contains a foaming agent and a resin binder. A thermal transfer sheet for forming a raised image, characterized in that cracks are present on the surface of the transfer material having the expansive ink layer. 2. The thermal transfer sheet for forming a raised image according to claim 1, wherein the transfer member has an expansive ink layer as a surface layer, and cracks are present on the surface of the expansive ink layer. 3. The transfer material has an expansive ink layer and a heat-sensitive adhesive layer formed on the expansive ink layer, and cracks are present on the surface of the heat-sensitive adhesive layer. The thermal transfer sheet for forming a raised image according to claim 1. 4. The transfer material has an expansive ink layer and a heat-sensitive adhesive layer formed on the expansive ink layer, and the surface of the heat-sensitive adhesive layer and the surface of the expansive ink layer (heat-sensitive adhesive layer) The heat transfer sheet for forming a raised image according to claim 1, wherein cracks are present on each of the surfaces on which the adhesive layers are laminated). 5. The width of the crack is 10 nm to 5 μm.
The thermal transfer sheet for forming a raised image according to any one of claims 1 to 4. 6. The thermal transfer sheet for forming a raised image according to claim 1, wherein the depth of the crack is formed larger than the width of the crack. 7. The thermal transfer sheet for forming a raised image according to claim 1, wherein a ratio of the surface area occupied by the cracks to the surface of the transfer body is 0.5 to 20%. 8. The raised image forming agent according to claim 1, wherein the foaming agent contained in the expandable ink layer is a heat-expandable microcapsule containing easily volatile hydrocarbons. Thermal transfer sheet. 9. The peelability adjusting layer is formed between the expansive ink layer and the substrate sheet.
A heat transfer sheet for forming a raised image according to any one of 1. 10. A method for forming a raised image using the thermal transfer sheet for forming a raised image according to any one of claims 1 to 9, wherein the method comprises stacking the thermal transfer sheet and a transfer-receiving member to expand the image. After the ink layer is imagewise heated and pressure-bonded, the transfer material having the imageable expansive ink layer is peeled from the thermal transfer sheet and transferred to the transfer target side, and then the transferred expansive ink layer is heated. Is added to expand the transferred expansive ink layer to form a raised image having a three-dimensional effect.