JPH0952449A - Heat transfer sheet for forming raised image and image forming method used thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer sheet for forming a raised image, which can be easily read by touch with fingers, form a raised letter image for the blind excellent in durability for finger reading and, at the same time, by which a letter image with India ink can also be formed simultaneously with the raised letter image through one printing action with the same heat transfer sheet. SOLUTION: In the heat transfer sheet for forming raised image, an expansile ink layer 3 containing a foaming agent and a resin binder is formed on one side of a base material sheet 1. A hot melt coloring layer 5 containing a colorable substance and a hot melt binder is formed on the expansile ink layer 3.

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, particularly Braille for blind people, and more specifically for Braille images for blind people and sighted persons (those who have normal visual ability). The above-mentioned thermal transfer sheet for forming a raised image capable of forming all of the ink characters (characters written for reading with braille read by fingers) 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.

It is considered that the reading of the Braille printed matter by the ink characters can provide the character information to the healthy person and the visually impaired person at the same time, and the utility value is very high. . However, in order to implement it, it is necessary to print the ink characters on a sheet for recording the Braille characters by a conventionally known ink character recording method in advance, and then take steps to record the Braille characters by the embossing method after alignment. A great deal of time and labor was required for printing one sheet.

In order to solve such a problem, there is a technique of simultaneously forming a Braille image and an ink character by an electrophotographic method using a foaming toner and an ordinary toner, as disclosed in Japanese Patent Laid-Open No. 56-1671.
No. 56 discloses this.

[0005]

However, based on the invention proposed in this publication, the combination of the expandable toner and the ordinary toner makes it possible to read the ink characters in Braille for the blind by the Japanese Braille notation method or the like. If you create a document that
The ink-printed part can be read well, but the braille part is chipped due to friction with the finger, the height of the convex part is easily reduced (crushed), or part or all of the point pixel is dropped from the transfer target. As a result, there was a problem in durability against reading.

[0006] Further, since the feeling is greatly different from that of ordinary braille formed thickly by embossing, there is a problem that the tactile readability is poor.

The present invention has been made in view of the above circumstances, and an object thereof is to form a Braille image for a blind person, which is easily read by a finger and has excellent durability by the touch. Another object of the present invention is to provide a heat transfer sheet for forming a raised image, which can form an ink character image by one printing operation using the same heat transfer sheet.

[0008]

In order to achieve such an object, the thermal transfer sheet for forming a raised image of the present invention is an expansive ink layer containing a foaming agent and a resin binder on one surface of a base sheet. And a heat-meltable coloring layer containing a coloring substance and a heat-melting binder on the expandable ink layer.

In a preferred embodiment of the present invention, the heat-fusible binder contained in the heat-fusible colored layer has a number average molecular weight of 1,000 or less.

In a preferred embodiment of the present invention, the heat-melting colored layer is further provided with a heat-melting layer containing a heat-melting substance having a number average molecular weight of 1,000 or less as a main component on the surface side.

In a preferred embodiment of the present invention, the heat-fusible binder contained in the expansive ink layer has a number average molecular weight of 1,000 or more and 30,000 or less.

In a preferred embodiment of the present invention, the foaming agent contained in the expansive ink layer is a thermally expansive microcapsule containing a readily volatile hydrocarbon.

In a preferred embodiment of the present invention, a peelability adjusting layer is formed between the expansive ink layer and the base sheet.

In a preferred embodiment of the present invention, a heat-sensitive adhesive layer is formed between the expansive ink layer and the heat-fusible coloring layer.

In a preferred embodiment of the present invention, the melting point of the hot-melt binder contained in the expansive ink layer is m.
p1, mp1> mp2 when the melting point of the heat-meltable binder contained in the heat-meltable colored layer is mp2.

As a preferred embodiment of the present invention, the melting point of the resin binder contained in the expansive ink layer is m.
p1, where the melting point of the heat-meltable binder contained in the heat-meltable colored layer is mp2, the difference between mp1 and mp2 is 30 ° C. or more and 100 ° C. or less.

Further, the present invention has an expansive ink layer containing a foaming agent and a resin binder on one surface of the base sheet, and the coloring substance and the heat-fusible binder are provided on the expansive ink layer. A method for forming a raised image using a heat transfer sheet for forming a raised image having a heat-fusible colored layer containing the method, wherein the method comprises stacking the thermal transfer sheet and a transfer target, and heat-melting from the back surface side of the substrate sheet. The first heating is performed to melt only the colored layer so that it can be transferred in an image form to form ink characters, and the second heating is used to soften the expansive ink layer from the back side of the base sheet to enable transfer. Imagewise transfer the expansive ink layer to the image,
By applying heat to the transferred expansive ink layer, the transferred expansive ink layer is expanded to form a three-dimensional raised image.

Further, as a preferred embodiment of the present invention, the means for applying heat to the transferred expansive ink layer is configured to be performed by light irradiation.

Further, as a preferred embodiment of the present invention, the maximum energy wavelength of the irradiated light is 1.0 to 4.0 μm.
Is configured to be

The heat-transfer sheet for forming a raised image of the present invention has an expansive ink layer containing a foaming agent and a resin binder on one surface of a substrate sheet, and a coloring substance and a coloring substance on the expansive ink layer. In order to obtain a constitution having a heat-meltable colored layer containing a heat-meltable binder, a constant energy E is applied by a thermal head, for example, at the time of heat transfer.
When 1 is added, only the heat-meltable colored layer coated on the surface is transferred. On the other hand, when a constant energy E2, which is stronger than E1, is applied, the expansive ink layer is softened and the expansible ink layer is transferred onto the thermally fusible coloring layer.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a thermal transfer sheet for forming a raised image (hereinafter, simply referred to as "thermal transfer sheet 30") of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a thermal transfer sheet 30 of the present invention has an expansive ink layer 3 containing a foaming agent and a resin binder on one surface of a substrate sheet 1. 3 has a heat-meltable coloring layer 5 containing a coloring substance and a heat-melting binder. As the base material sheet 1, the same base material 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.
Examples of preferable base sheet include polyester,
Polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer saponification, fluororesin, chlorinated rubber, stretched such as ionomer, or unstretched film, Capacitor paper, paraffin paper, etc.

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

In the present embodiment, the expansive ink layer 3 contains the foaming agent and the resin binder as described above.

Examples of the foaming agent used in the present invention include azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, N, N'dinitroso-N, N'dimethylterephthalamide and P-toluenesulfonyl. Organic foaming agents such as hydrazide, hydrazolcarbonamide, P-toluenesulfonyl azide, acetone-P-sulfonylhydrazone; inorganic foaming agents such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate; solvents that volatilize at low temperatures internally Examples include heat-expandable microcapsules containing In the present invention, it is preferable to use the heat-expandable microcapsules among these. When the heat-expandable microcapsules are contained, the resulting image-formed product exhibits high elasticity, and exhibits extremely excellent durability.

The heat-expandable microcapsules have a capsule structure in which a hydrocarbon that volatilizes at a low temperature is contained inside a wall material made of a thermoplastic resin, and in the present invention, by irradiation with light (heating), 10-15 in unfoamed state
The volume expands by 0 times.

Hydrocarbons to be encapsulated in the heat-expandable microcapsules are methyl chloride, methyl bromide, trichloroethane, dichloroethane, n-butane, n-heptane, n-.
Propane, n-hexane, n-pentane, isobutane,
Aliphatic hydrocarbons having a fluorine atom such as 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 if necessary, a crosslinking agent can be used.

The particle size of the heat-expandable microcapsules is preferably 0.1 to 50 μm, and more preferably 0.1 to 50 μm.
It is preferably ˜30 μm.

Commercially available products of such heat-expandable microcapsules are, for example, F-20 and F- of the "Matsumoto Microsphere" series manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.
30, F-40, F-50, F80S, F82, F80
Examples thereof include VS and F100, and “Expansel” series manufactured by Nippon Ferrite Co., Ltd.

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.

The material forming the resin binder of the expansive ink layer 3 is, for example, a phenoxy resin, a vinyl-based resin such as polyvinyl acetate, polyacrylic acid ester, polymethacrylic acid ester, polyethylene terephthalate, polybutylene terephthalate, or the like. Examples thereof include polyester, 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,
Examples thereof include acrylonitrile, vinyl chloride-vinylidene chloride copolymer, and rubber resins.

The number average molecular weight of the resin used for such a resin binder is preferably 1,000 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, a better braille image can be obtained 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 due to 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. 25,000 or less, particularly preferably 1
It is 0000 or more and 25000 or less.

Further, in order for the heat-melting type transfer layer to arbitrarily break (foil break) under a constant heat transfer sheet peeling condition, the binder resin preferably has an appropriate tensile breaking strength. That is, the tensile elongation at break defined by JIS-K-7127 is preferably 50% or more and 2000% or less, and more preferably 100% or more and 1000% or less.

When the tensile elongation at break is less than 50%, the strength required as a binder resin is insufficient, the durability against damage due to the tactile reading of Braille images is poor, and further on the transfer sheet before thermal transfer is performed. There is a problem that the expansive ink layer 3 is easily cracked. On the other hand, when this value exceeds 2000%, the expansive ink layer 3 is less likely to be broken at a portion corresponding to the contour of the braille image, and the uncut foil is attached to the braille image to reduce the tactile readability. This causes a problem that a part of the image is missing.

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

The colorant can be arbitrarily added in an amount that 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.

The expandable 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 when heat energy during heat transfer or energy such as heat for foaming described later is applied, or it is applied to the transfer target in advance. It may be a color that develops when it comes into contact with an existing object, or it 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 expandable ink layer 3 is the base material 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.

On such an expansive ink layer 3, a heat-meltable coloring layer 5 containing a coloring substance and a heat-melting binder is formed.

Wax is preferably used as the heat-melting binder contained in the heat-melting colored layer 5, and more specifically, microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax and various low-melting waxes. Examples thereof include molecular weight polyethylene, wooden wax, beeswax, spermaceti wax, ivowa wax, wool wax, shellac wax, candelilla wax, petrolactam, partially modified wax, fatty acid ester, and fatty acid amide.

The number average molecular weight of the wax as the heat-meltable binder is 200 to 1000, preferably 400 to 1000.

The melting point of the heat-melting binder contained in the heat-melting colored layer 5 is mp2, and the melting point of the heat-melting binder contained in the expandable ink layer 3 is mp1.
, The relationship between them is mp1> mp2,
Further, the difference between mp1 and mp2 is preferably 30 ° C. or higher, more preferably 30 to 100 ° C. If such a relationship is not satisfied, only the heat-melting colored layer 5 on the surface layer is transferred with low printing energy to form a so-called black character portion, and the heat-melting colored layer 5 and the expansive ink layer are printed with high printing energy. 3 cannot be transferred to form a so-called braille source portion.

As the coloring substance contained in the heat-fusible coloring layer 5, carbon black, a water-dispersible pigment or the like is used. Examples of water-dispersible pigments include “FUJI SP RED 5126” manufactured by Fuji Dye Co., Ltd. and “FUJI SP BLUE
6002 ”and the like.

Such a coloring substance is usually contained in an amount of about 1 to 10 parts by weight as a solid content per 100 parts by weight of the heat-melting binder of the heat-melting colored layer 5. The thickness of such a heat-fusible colored layer 5 is set to about 0.5 to 5.0 μm.

A small amount of resin used in the expansive ink layer 3, for example, 1 to 3 is added to the heat-fusible coloring layer 5.
By containing 0 wt%, more preferably 5 to 20 wt%, the adhesiveness of the expansive ink layer 3 to the transferred material 10 containing the components of the heat-fusible coloring layer 5 can be improved. If the added amount is too small, the effect of improving the adhesiveness is small, and if the added amount is too large, the transferability when transferring only the ink characters is adversely affected.

In such a thermal transfer sheet 30, it is a preferred embodiment to provide the peelability adjusting layer 2 between the expansive ink layer 3 and the base sheet 1 as shown in FIG. Further, as shown in FIG. 3, a heat-sensitive adhesive layer 4 may be provided between the expansive ink layer 3 and the heat-meltable coloring layer 5, and the heat-melting layer 6 may be provided on the surface of the heat-melting colored layer 5. This is the preferred embodiment.

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. 4, the peelability adjusting layer 2 is separated from the expansive ink layer 3 of the base sheet 1 and is transferred together with the transferred heat-fusible coloring layer 5a and expansive ink layer 3a. A peeling layer 2a that peels and transfers to the body 10 side; remains after the transfer as shown in FIG. 5 on the base material sheet 1 side, and the expansive ink layer 3 is easily peeled off and transferred to the transferred body 10. Heat-fusible coloring layer 5a and expansive ink layer 3
As shown in FIG. 6 and the release layer 2b constituting a, the peelability adjusting layer is melted by the heat at the time of transfer and the cohesive force is reduced, and the layer is separated and the expansive ink layer 3 is peeled off. The heat-fusible coloring layer 5a and the expansive ink layer 3 transferred to the transfer body 10.
There are three types of layer separation layers 2c constituting a.

Further, the release layer 2a and the release layer 2b can be used together.

When the peelability adjusting layer is the peeling layer 2a or the layer separating layer 2c, the transferred expansive ink layer 3a.
Since the peeling layer or the layer separating layer is also transferred to the outermost surface of the ink, the resin forming the peelability adjusting layer may be selected so as not to impair the expansivity of the expansive ink layer 3a. is necessary. Further, the peeling layer 2a has an effect as a protective layer for the raised image, but should not impair the feel of the finger when reading by touch.

The resin forming the release layer 2b has a releasing property itself 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. A crosslinked silicone resin, or an acrylic resin or polyester containing a release agent crosslinked with polyisocyanate is preferable. And the application is performed by a normal method such as gravure coating and roll coating,
The coating thickness is preferably 0.05 to 5.00 μm, and is 0.1
More preferably, it is 0 to 2.00 μm.

The resin forming the peeling layer 2a 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, the above-mentioned foaming agent, especially
By including the thermally expandable microcapsules, it is possible to expand (foam) together with the transferred image to facilitate 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 separation layer 2c is a resin that is melted by heat when transferring the expansive ink layer 3 from the thermal transfer sheet and reduces 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 to the heat diffusing dye, a heat diffusing dye of any color can be added to the peeling adjusting layer.

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.

Further, as described above, as shown in FIG. 3, a heat-sensitive adhesive layer 4 is provided between the expansive ink layer 3 and the heat-fusible coloring layer 5, or on the heat-fusible coloring layer 5. Providing the heat melting layer 6 is a preferred embodiment. 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, the heat-expandable microcapsules may expand in plane directions other than the height, resulting in insufficient durability against tactile reading such as Braille images. Because there is.
The heat-melting layer 6 is formed to prevent so-called character stains that may occur when the heat-melting colored layer 5 is transferred. The heat-melting layer 6 contains a heat-melting substance having a number average molecular weight of 1,000 or less as a main component, and specifically, microcrystalline wax, carnauba wax, paraffin wax or the like is used. The thickness of the heat melting layer 6 is 0.
It is about 1 to 2.0 μm.

Materials usable for the heat-sensitive adhesive layer 4 are
Microcrystalline wax, carnauba wax,
Wax such as paraffin wax; acrylic rubber, styrene-butadiene rubber, ethylene-propylene rubber,
Synthetic rubber such as isoprene rubber, butadiene rubber, nitrile rubber and chlorinated butyl rubber; unvulcanized rubber such as natural rubber; vinyl resin such as polyvinyl acetate and polyvinyl chloride; polyester resin such as polyethylene terephthalate and polybutylene terephthalate A thermoplastic resin such as ethylene-vinyl acetate copolymer or polyamide alone;
Alternatively, they are appropriately mixed. Further, by mixing the heat-expandable microcapsules in the heat-sensitive adhesive layer 4, it is possible to foam the heat-sensitive adhesive layer 4 and make it easier to read the raised image such as Braille.

When a thermal head is used as the heating means for transferring the raised image to the transfer object 10 by using the thermal transfer sheet 30, the base sheet 1 is heated from the side where the expansive ink layer 3 is not formed. Done. 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.

An image forming method using the thermal transfer sheet 30 for forming a raised image as described above will be described. In particular, in the present invention, a single thermal transfer sheet 30 is used to form a Braille image for the blind and an ink character for a sighted person (a person who has normal visual ability) (a character written for reading with a finger to a Braille character read by a finger). It is characterized in that both can be formed together by one printing operation, but in the case of forming ink characters and in the case of forming braille images in order to facilitate understanding of the respective formation states. I will explain separately.

In the case of forming ink characters, the thermal transfer sheet 30 and the transferred material 10 are superposed, and the first heating is performed in the image shape at the temperature at which the heat-meltable coloring layer 5 of the thermal transfer sheet 30 can be melt-transferred. Crimp on.
After that, the heat-fusible colored layer 5 formed in an image form is peeled from the heat transfer sheet 30 and transferred to the transfer target 10 side.
In this case, the expansive ink layer 3 is not melt-transferred by the first heating. That is, the first heating is heating at a temperature at which only the heat-melting colored layer 5 can be melt-transferred, and heating at a temperature at which the expansive ink layer 3 is not melt-transferred. Incidentally, mp1> mp2 is as described above.

In the case of forming a Braille image, the thermal transfer sheet 30 and the transferred material 10 are superposed, and the second heating is performed at the temperature at which not only the heat-fusible coloring layer 5 of the thermal transfer sheet 30 but also the expansive ink layer 3 can be transferred. Then, the transfer target 10 is pressure-bonded. Then, the heat-fusible colored layer 5 and the expansive ink layer 3 formed in an image form are peeled off from the heat transfer sheet 30 and transferred to the transfer target 10 side. In this case, the heat-fusible coloring layer 5 is impregnated in the transferred material 10, and the expansive ink layer 3 is softened and transferred.
That is, the second heating is heating at a temperature at which the heat-meltable colored layer 5 and the expansive ink layer 3 can be transferred. Thereafter, thermal energy for foaming the image transferred to the transfer target 10 is applied to the transfer image, and the transferred expansive ink layer 3 expands (foams) to give a three-dimensional raised image such as Braille. Becomes Various means for applying heat energy can be used, for example, heating with an oven, hot air heating with an electric heating wire, infrared irradiation heating, laser beam irradiation heating, heating methods such as electromagnetic heating, and a transfer target. Examples include a heating method of contacting with a heating roll.
Among these, the method using light irradiation is particularly preferable. The maximum energy wavelength of the irradiated light is 1.0 to
It is preferably 4.0 μm.

The heat-fusible coloring layer 5 is used as the transferred material 1.
Since it exists in a state of being impregnated with 0, it has a kind of sealing effect.

Transferred object 10 used when performing thermal transfer
There are various forms such as a sheet state, a small roll 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,
Any of those obtained by using carbon fiber, chitin fiber, chitosan fiber, etc. 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, waste paper, glassine paper, newsprint, condenser. Examples include paper. Furthermore, without going through the steps of making polyethylene terephthalate film, polyvinyl chloride film, polyethylene naphthalate film and polyimide film, which are plastic films manufactured by using various thermoplastic resins as raw materials, and also thermoplastic resins. Synthetic papers processed into a paper shape (for example, Yupo FPG-150 manufactured by Oji Yuka) can also be used.

The transferred material 10 must have a surface shape capable of sufficiently absorbing the melted heat-melting colored layer 5. This is because the heat-melting colored layer 5 that has been transferred in advance is melted by the heat for foaming, and the transferred raised image peels off during the foaming operation. From this viewpoint, it is particularly preferable to use natural paper such as copy paper.

From the thermal transfer sheet 30 described above, the transfer target 10 is transferred.
The heating means used for transferring the image to the image, that is, the means for applying the thermal energy, can control the heating amount according to the image information from the computer (the first heating and the second heating can be formed into a predetermined pattern. Any of various conventionally known methods 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. Further, when an electric heating layer is provided on the back side of the thermal transfer sheet, it is possible to use an electric heating type energizing head for a melt transfer system.

As described above, by using the thermal transfer sheet of the present invention, it is possible to easily output a printed matter in which ink characters and Braille characters are written together by one printing operation. That is, the visually impaired person and the healthy person can obtain the same information from a single output product.

Also, unlike the Braille printed by the conventional embossing method, a concave recess is not formed on the back surface on which the Braille image is formed, and an opposite surface such as a paper printed with ink characters for the sighted person. Braille can be printed without damaging the ink character 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, the 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).

[0082]

EXAMPLES The present invention will be described in more detail with reference to specific examples of the present invention.

[Example 1] As the base material sheet 1, a thickness 6 in which the back surface of the surface on which the expansive ink layer is formed is heat-treated
A polyethylene terephthalate film having a thickness of μm was prepared. On the surface of this film, a coating solution 1 for the expansive ink layer having the following composition, which was stirred so as to be able to be applied uniformly, was formed to a thickness of 30.
It was applied by reverse roll coating so as to have a thickness of μm and dried to form an expansive ink layer 3.

(Expandable Ink Layer Coating Liquid 1) Polyester Water Dispersion (Toyobo Co., Ltd., Vylonal MD-1930, Solid Content Concentration 30%, Number Average Molecular Weight of Resin 25,000) 40 parts by Weight Thermal Expansion Microcapsule (Matsumoto Yushi-Seiyaku Co., Ltd., Matsumoto Microsphere F-20VS) 15 parts by weight Water 20 parts by weight Then, on the expandable ink layer 3, a heat-meltable coloring having the following composition is formed. The layer coating solution 1 was applied and dried by direct gravure coating so that the coating thickness was 2.0 μm to form the heat-meltable colored layer 5.

(Heat-meltable colored layer coating liquid 1) -Carnauba wax aqueous solution (WE-95 manufactured by Konishi Co., Ltd., solid content concentration 30%) ... 100 parts by weight-Red pigment aqueous dispersion (Fuji dye (stock) ), FUJI SP RED 5126) 10 parts by weight water 50 parts by weight Then, on the heat-meltable colored layer 5, a heat-melting layer coating solution 1 having the following composition is applied to a coating thickness of 1.0 μm. Was applied and dried by a direct gravure coat to form a hot melt layer 6.

(Hot Melt Layer Coating Liquid 1) Carnauba Wax Aqueous Solution (Konishi Co., Ltd., WE-95, solid content concentration 30%) 100 parts by weight Water 50 parts by weight The thermal transfer sheet thus prepared Of the heat-melting layer 6, the heat-melting colored layer 5 and the expansive ink layer 3 having a thickness of 150 μm
The thermal ink (KMT-85-6MPD2-HTV) was used to transfer a group of ink characters of a predetermined image and a group of braille characters (planned) of a predetermined pattern from the back surface of the thermal transfer sheet by using a thermal head (KMT-85-6MPD2-HTV).

In this case, the printing energy was adjusted by adjusting the pulse width for applying a voltage to the thermal head in a pulsed manner, and the group of ink characters and the group of braille characters (planned) were simultaneously transferred in one printing operation.

That is, the head applied voltage is 12.0 V and the printing speed is 33.3 m at the transfer position of the ink character group of the thermal transfer sheet.
By partially heating the thermal head under printing conditions of s / line and applied pulse width of 6.0 ms / line, only the heat-meltable coloring layer 5 (including the heat-melting layer 6) is transferred to a predetermined ink character. Group (letter) is filled in, while head applied voltage of 12.0V,
Printing speed 33.3 ms / line, applied pulse width 16.
By partially heating the thermal head under a printing condition of 0 ms / line, the heat-meltable coloring layer 5 (heat-melting layer 6
And the expansive ink layer 3 were transferred, and dot pixels having a diameter of about 1 mm constituting a Braille document were transferred.

Next, after peeling the transfer sheet from the transfer paper, an infrared heater having a maximum energy wavelength of 1.2 μm (short wavelength infrared radiator: Z made by Heraeus Co., Ltd .: Z
KB600 / 80G) and the infrared ray was irradiated on the transfer paper for 20 seconds at a distance of 5 cm. As a result, the transferred expansive ink layer 3 was expanded to form a braille group, and a sample of Example 1 in which this braille group and the above-mentioned ink character group were mixed was prepared.

Braille group (partial) for this pixel sample
For, the "braille height" and the "foam strength" were evaluated. As a result, the “Braille height” was 200 μm or more, and it was confirmed that the Braille document could be read satisfactorily. Regarding "foam strength", the thermally expanded point pixels were hardly crushed or torn even by touching with a finger, and no change was observed in tactile readability even after repeated tactile reading.

Also, the ink character group (part) of this pixel sample
For, it was confirmed that the printing was performed extremely clearly. That is, it was confirmed that the ink-character pixels were transferred without excess and deficiency, and the ink-character pattern corresponding to the image pattern to which energy was applied was transferred well.

Example 2 In the above Example 1, the expansive ink layer coating liquid 1 was replaced with the expansive ink layer coating liquid 2 shown below, and a thermal transfer sheet was prepared according to the procedure shown in the above Example 1. It was made.

(Expandable ink layer coating liquid 2) Polyester resin (manufactured by Daicel Chemical Industries, Ltd., PLACCEL H1P resin number average molecular weight 10000) 20 parts by weight Thermally expandable microcapsules (Matsumoto Yushi-Seiyaku Co., Ltd.) Manufactured by Matsumoto Microsphere F-30VS) 25 parts by weight Toluene 200 parts by weight Using the thermal transfer sheet prepared as described above, Example 1
A transfer experiment was performed in the same manner as in the case of, and the pixel sample of Example 2 in which the braille group and the ink character group were mixed was prepared.

Regarding this pixel sample, Braille group (partial)
For, the "braille height" and the "foam strength" were evaluated. As a result, the “Braille height” was 200 μm or more, and it was confirmed that the Braille document could be read satisfactorily. Regarding "foam strength", the thermally expanded point pixels were hardly crushed or torn even by touching with a finger, and no change was observed in tactile readability even after repeated tactile reading.

Also, the ink character group (part) of this pixel sample
For, it was confirmed that the printing was performed extremely clearly. That is, it was confirmed that the ink-character pixels were transferred without excess and deficiency, and the ink-character pattern corresponding to the image pattern to which energy was applied was transferred well.

Example 3 In the above-mentioned Example 1, the expansive ink layer coating liquid 1 was replaced with the expansive ink layer coating liquid 3 shown below, and a thermal transfer sheet was prepared according to the procedure shown in the above-mentioned Example 1. It was made.

(Expandable ink layer coating liquid 3) Aqueous polyester 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 Using the thermal transfer sheet prepared in this manner, Example 1
A transfer experiment was performed in the same manner as in the case of, and a pixel sample of Example 3 in which a braille group and an ink character group were mixed was prepared.

Braille group (partial) for this pixel sample
For, the "braille height" and the "foam strength" were evaluated. As a result, the “Braille height” was 200 μm or more, and it was confirmed that the Braille document could be read satisfactorily. Regarding "foam strength", the thermally expanded point pixels were hardly crushed or torn even by touching with a finger, and no change was observed in tactile readability even after repeated tactile reading.

Also, the ink character group (part) of this pixel sample
For, it was confirmed that the printing was performed extremely clearly. That is, it was confirmed that the ink-character pixels were transferred without excess and deficiency, and the ink-character pattern corresponding to the image pattern to which energy was applied was transferred well.

[Example 4] In Example 1, the following releasability adjusting layer coating liquid was applied between the base sheet 1 and the expansive ink layer 3 by gravure printing and dried to remove the releasability adjusting layer. 2 (dry thickness 1.0 μm) is provided, and the expansive ink layer 3
The following heat-sensitive adhesive layer coating solution was applied between the heat-meltable colored layer 5 and the heat-meltable colored layer 5 by gravure printing and dried to provide the heat-sensitive adhesive layer 4 (dry thickness 2.0 μm) to prepare a thermal transfer sheet.

(Releasability adjusting layer coating liquid) Polymethacrylic acid ester resin (Dianal BR-85 manufactured by Mitsubishi Rayon Co., Ltd.) 10 parts by weight Methyl ethyl ketone 50 parts by weight Toluene 50 parts by weight (heat-sensitive adhesion Layer coating liquid) Polyester aqueous dispersion (manufactured by Toyobo Co., Ltd., Vylonal MD-1930, solid content concentration 30%, number average molecular weight of resin 25,000) 20 parts by weight Water 10 parts by weight Thermal transfer prepared in this manner Example 1 using a sheet
A transfer experiment was performed in the same manner as in the above case, and a pixel sample of Example 4 in which a braille group and an ink character group were mixed was prepared.

Braille group (partial) for this pixel sample
For, the "braille height" and the "foam strength" were evaluated. As a result, the “Braille height” was 200 μm or more, and it was confirmed that the Braille document could be read satisfactorily. Regarding the “foam strength”, the thermally expanded point pixels were hardly crushed or torn even when touched with a finger, and no change in tactileness was observed even after repeated tactile reading.

Also, the ink character group (part) of this pixel sample
For, it was confirmed that the printing was performed extremely clearly. That is, it was confirmed that the ink-character pixels were transferred without excess and deficiency, and the ink-character pattern corresponding to the image pattern to which energy was applied was transferred well.

[0104]

As described above in detail, the thermal transfer sheet for forming a raised image of the present invention has an expansive ink layer containing a foaming agent and a resin binder on one surface of the base sheet, and the expansive Since a structure having a heat-fusible coloring layer containing a coloring substance and a heat-fusible binder is adopted on the ink layer, it is possible to use one and the same thermal transfer sheet to make a Braille image and an ink-character image in one printing operation. Can be formed simultaneously. Further, the Braille image formed by transfer is easy to read by a finger and exhibits an excellent effect on durability by the touch.

[Brief description of drawings]

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

FIG. 2 is a schematic sectional view showing another preferred embodiment of the thermal transfer sheet for forming a raised image.

FIG. 3 is a schematic sectional view showing another preferred embodiment of the thermal image transfer sheet for forming a raised image.

FIG. 4 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. 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate sheet 2 ... Releasability adjusting layer 3 ... Expandable ink layer 4 ... Heat-sensitive adhesive layer 5 ... Heat-fusible coloring layer 6 ...

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location 7416-2H B41M 5/26 E 7416-2H A

Claims (12)

[Claims] 1. A base sheet having an expandable ink layer containing a foaming agent and a resin binder on one surface thereof, and a heat-melting composition containing a coloring substance and a heat-meltable binder on the expandable ink layer. A heat-transfer sheet for forming a raised image, which has a colored layer. 2. The heat-transfer sheet for forming a raised image according to claim 1, wherein the heat-meltable binder contained in the heat-meltable colored layer has a number average molecular weight of 1,000 or less. 3. The raised image according to claim 2, further comprising a heat-melting layer containing a heat-melting substance having a number average molecular weight of 1,000 or less as a main component on the surface side of the heat-melting colored layer. Thermal transfer sheet for forming. 4. The resin binder contained in the expandable ink layer has a number average molecular weight of 1,000 or more and 3,000.
The thermal transfer sheet for forming a raised image according to any one of claims 1 to 3, which is 0 or less. 5. The foaming agent contained in the expandable ink layer is a thermally expandable microcapsule containing easily volatile hydrocarbons therein. Heat transfer sheet for image formation. 6. The thermal transfer sheet for forming a raised image according to claim 1, wherein a peelability adjusting layer is formed between the expansive ink layer and the base sheet. . 7. The heat transfer for forming a raised image according to claim 1, wherein a heat-sensitive adhesive layer is formed between the expansive ink layer and the heat-meltable colored layer. Sheet. 8. When the melting point of the resin binder contained in the expandable ink layer is mp1 and the melting point of the heat-meltable binder contained in the heat-meltable colored layer is mp2, m
The thermal transfer sheet for forming a raised image according to any one of claims 1 to 7, wherein p1> mp2. 9. When the melting point of the resin binder contained in the expandable ink layer is mp1 and the melting point of the heat-meltable binder contained in the heat-meltable colored layer is mp2, m
The thermal transfer sheet for forming a raised image according to any one of claims 1 to 8, wherein a difference between p1 and mp2 is 30 ° C or more and 100 ° C or less. 10. A base sheet having an expandable ink layer containing a foaming agent and a resin binder on one surface thereof, and a heat-melting composition containing a coloring substance and a heat-meltable binder on the expandable ink layer. Image forming method using a heat transfer sheet for image formation having a heat-sensitive coloring layer, wherein the heat transfer sheet and the transfer target are superposed, and only the heat-melting coloring layer is applied from the back side of the base material sheet. The first heating that can be melted and transferred to the image form is performed to form ink characters, and the second heating that softens the expansive ink layer from the back side of the base sheet to enable the transfer is imaged. Transferring the expansive ink layer in an image form and applying heat to the transferred expansive ink layer to expand the transferred expansive ink layer to form a raised image having a three-dimensional effect. The image forming method raised features. 11. The raised image forming method according to claim 10, wherein the means for applying heat to the transferred expansive ink layer is performed by light irradiation. 12. The method for forming a raised image according to claim 11, wherein the maximum energy wavelength of the irradiated light is 1.0 to 4.0 μm.