JPH07290849A - Thermal transfer sheet for printing many times, and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a thermal transfer sheet for printing many times which is capable of performing printing without print irregularities and also is free from a sudden deterioration of print density in accordance with printing frequency as well as a method for manufacturing the sheet. CONSTITUTION:A thermal transfer sheet for printing in many times consists of a heat-melting ink layer 2 and a transfer control layer 3 laminated in that order on a substrate 1. The transfer control layer 3 does not contain a colorant, but is composed of a porous molding resin component, a resin component and a non-miscible wax component. The porous molding resin component and the heat-melting wax component are phase-separated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet having a heat-fusible ink layer which can be used many times and which is mainly used in printers for printing character information.

[0002]

2. Description of the Related Art Conventionally, as a thermal transfer recording medium used in a thermal printer, a facsimile or the like, a thermal transfer sheet having a heat-fusible ink layer provided on one surface of a base film has been used. A conventional thermal transfer sheet uses a base material film such as capacitor paper or paraffin paper having a thickness of about 10 to 20 μm or a plastic film such as polyester or cellophane having a thickness of about 3 to 20 μm. A heat-meltable ink layer is formed by applying a heat-meltable ink in which wax is mixed with a coloring agent such as a pigment or a dye. Then, a predetermined portion is heated and pressed from the back side of the substrate film by a thermal head, and the heat-melting ink layer in the portion corresponding to the printing portion of the heat-melting ink layer is transferred to the printing paper to perform printing. . However, in such a conventional thermal transfer sheet, the heat-meltable ink layer heated and pressed by the thermal head is transferred to the printing paper in one use,
There is a problem in that printing can be performed only once at the same location, the thermal transfer sheet is consumed in large amounts, running costs are high, and it is not economical.

Therefore, various thermal transfer sheets that can be used many times have been developed. For example, (1) JP-A-54-68253 and JP-A-55-105
On a base film such as disclosed in No. 579,
A microporous layer and a heat-meltable ink are simultaneously formed by coating and drying a coating liquid in which a resin component for forming a porosity and a heat-meltable ink component are mixed, or heat-melted on the microporous layer. (2) JP-A-3-15595 in which the heat-meltable ink is gradually exuded by submerging the heat-meltable ink into the fine porous layer by applying the heat-resistant ink and drying it. By providing a heat-meltable ink layer on a base film as disclosed in, and by providing a fine porous layer containing a heat-meltable ink having a poor affinity with a resin on the substrate film, the ink outflow amount can be reduced. Controlled (3) Mixing a porous resin component as disclosed in JP-A-5-246156 and heat-melting particles having a releasing action on the resin component to form particles of heat-melting particles. The pore size of the porous material is determined by the diameter Method, and the like. Further, (4) Japanese Patent Application Laid-Open No. 2-127083 describes a method of forming a fine porous layer by melting a porous-forming resin component and a heat-meltable ink component in a common solvent.

[0004]

However, when the thermal transfer sheet as in (1) is used, the heat-meltable ink is fused to the fine porous eyes with repeated printing, and the ink outflow amount is reduced. However, there is a drawback in that the print density is reduced accordingly. Further, the thermal transfer sheet as in (2) is a fine porous material containing a colorant by applying and drying a coating liquid obtained by mixing a porous-forming resin component and a heat-meltable ink component having poor affinity with the resin. When a layer is formed, carbon or the like is mixed in the resin for forming the porosity, and the mechanical strength of the fine porous layer decreases, so that the pore size of the porous layer cannot be increased or the fine porous layer peels off during printing. Occurs,
There is a problem that the entire ink layer is transferred. Further, in the method of mixing the porosity-forming resin component and the heat-melting particles having a releasing action with respect to the resin component as in (3), and determining the pore size of the porous material by the particle diameter of the heat-melting particles,
It is difficult to control the pore size of the porous material because it is difficult to control the particle diameter of the heat-meltable particles and because the heat-meltable particles aggregate.
As a result, the amount of transferred ink becomes uneven, and printing unevenness appears especially when printing solid areas. In addition, the surface of the heat-meltable particles is covered with the resin for forming the porosity, and the formation of the porosity is unstable in many cases where the holes do not penetrate.
In the initial printing, since the porous pores are not fully opened,
Problems such as low initial print density occur. This tendency is particularly remarkable when a releasing resin or the like is mixed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above drawbacks, to enable printing without printing unevenness a number of times, and to reduce or increase the printing density drastically with the number of printings. It is an object of the present invention to provide a thermal transfer sheet for multi-use printing excellent in practicality and a method for producing the same.

[0006]

In order to achieve the above object, the thermal transfer sheet of the present invention comprises a base film, a heat-fusible ink layer and a transfer control layer which are laminated in this order for multi-time printing. In the thermal transfer sheet, the transfer control layer is composed of a resin component for forming a porosity and a heat-melting wax component incompatible with the resin component, which does not contain a coloring agent, and the resin component for forming a porosity and the heat-melting wax. A thermal transfer sheet for multi-use printing is characterized in that the components are phase-separated. Further, the thermal transfer sheet for multi-time printing contains a release agent. In addition, in a method for producing a thermal transfer sheet for multi-use printing, in which a heat-meltable ink layer and a transfer control layer are laminated in this order on a substrate film, the transfer control layer does not contain a colorant and is porous. Resin component and a heat-melting wax component that is incompatible with the resin component, the resin component for forming a pore and the heat-melting wax component are dissolved in a solvent that is a poor solvent of the other and a parent solvent of each other, After the mixed coating liquid is applied onto the heat-meltable ink layer and then dried, a transfer control layer utilizing phase separation of the resin component for forming a pore and the heat-meltable wax component is formed. The method for producing a thermal transfer sheet for multi-use printing is characterized.

[0007]

The function of the transfer control layer in the thermal transfer sheet of the present invention is
A coating solution for forming a transfer control layer, which does not contain a colorant, and is made by dissolving a resin component for forming a porosity and a heat-fusible wax component in a solvent that is a poor solvent for each other and is a hydrophilic solvent for each other, and is then dried. By doing so, the resin component and the heat-meltable wax component are formed in a phase-separated state. That is, when the transfer control layer forming coating liquid is applied, the resin component and the heat-meltable wax component can be stably applied in a compatible state. After coating, the solvent is evaporated during drying and the thermal transfer sheet is formed in a state where the resin component and the heat-meltable wax component are phase-separated. Further, the heat-melting wax component is melted by heating during printing, and pores for controlling the outflow amount of the heat-melting ink are formed. Here, the size of the pores can be controlled by adjusting the mixing ratio of the porosity forming resin component and the wax component. Therefore, by carrying out this adjustment, it is possible to stably form the transfer control layer having the optimum strength and pore size for printing many times. Furthermore, when a transfer control layer is formed, by adding a release agent, it is possible to prevent the heat-meltable ink from fusing to the porous resin and causing clogging, resulting in a decrease in print density with the number of prints. To do. At the time of peeling, the adhesion between the porous resin and the heat-meltable ink is kept low to prevent the entire transfer of the ink layer. Further, according to the manufacturing method of the present invention, since the through hole can be easily formed,
Since the initial print density does not decrease and the pore size is uniform,
No printing unevenness. Furthermore, according to the manufacturing method of the present invention,
Since the resin component for forming a porosity and the heat-melting wax component are phase-dissolved in a completely dissolved state, the resin component for forming a porosity or the release agent does not cover the surface of the pores, and the mold release It is difficult for the pores to be blocked even if an agent is added.

[0008]

Preferred Embodiments Next, preferred embodiments will be described with reference to the drawings. FIG. 1 is a sectional view showing a thermal transfer sheet of the present invention. As shown in FIG. 1, the thermal transfer sheet of the present invention comprises a substrate film 1, a heat-fusible ink layer 2 formed on one surface of the substrate film 1, and a transfer control layer 3 provided thereon. Is. FIG. 2 is an application example of the thermal transfer sheet of the present invention. The thermal transfer sheet of the present invention optionally contains a primer layer 4 for providing adhesiveness between the base film 1 and the heat-fusible ink layer 2, It is also possible to provide the back surface layer 5 on the other surface of the base film 1.

As the base material film used in the thermal transfer sheet of the present invention, the same base material film as used in the conventional thermal transfer sheet can be used as it is, and other materials can also be used. There is no particular limitation. Specific examples of preferable substrate film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin,
There are plastics such as chlorinated rubber and ionomer, papers such as condenser paper and paraffin paper, non-woven fabrics and the like, and a substrate film obtained by combining these may be used. The thickness of this substrate film can be appropriately changed depending on the material so that its strength and thermal conductivity are appropriate, but its thickness is preferably 2 to 25 μm, for example. or,
A slip layer may be provided on the back surface of the base film to prevent the thermal head from sticking and to improve the slipperiness. As the slip layer, a resin layer to which a slip agent, a surfactant, inorganic particles, organic particles, a pigment or the like is added can be preferably used.

In the thermal transfer sheet of the present invention, the thickness of the heat-meltable ink layer 2 provided on one surface of the base film is 4 to 30 μm, and particularly preferably 5 to 15 μm. 5 μm
If it is less than the following, sufficient printing density may not be obtained, and
If it is more than μm, the printing sensitivity may decrease. Further, when the adhesiveness between the base film and the heat-meltable ink layer is insufficient, the heat-meltable ink layer may be formed via a primer layer as an adhesive layer. The adhesive may be formed of acrylic resin, nylon resin, vinyl chloride / vinyl acetate copolymer, polyester resin, urethane resin, or the like, and the thickness is preferably about 0.1 to 0.2 μm.

The heat-fusible ink layer comprises a conventionally known colorant and a binder, and if necessary, mineral oil, vegetable oil,
Higher fatty acids such as stearic acid, plasticizers, thermoplastic resins,
What added various additives, such as a filler, is used. Examples of the wax component used as the binder include microcrystalline wax, carnauba wax, and paraffin wax. Furthermore, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, spermaceti wax, ivowa wax, wool wax, shellac wax, candelilla wax, petrolactam,
Various waxes such as polyester wax, partially modified wax, fatty acid ester and fatty acid amide are used.
Among these, those having a melting point of 50 to 85 ° C. are particularly preferable. If the temperature is 50 ° C or lower, there will be a problem with storage stability and
If the temperature is 5 ° C or higher, the sensitivity is insufficient. The melt viscosity is 100
A wax having a melt viscosity in the range of 10 to 15,000 mPas at 0 ° C. is preferable. If it is 10 mPas or less, bleeding or the like occurs in printing, and if it is 15000 mPas or more,
Transfer failure will occur.

Examples of the resin component used as the binder include ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer, polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer. Polymers, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethyl cellulose or polyacetal, and the like. Those having a relatively low softening point conventionally used as a hot-melt adhesive, for example, a softening point of 50 to 80 ° C. are preferable.

The colorant can be appropriately selected from known organic or inorganic pigments or dyes,
For example, it has a sufficient coloring density and discolors due to light, heat, etc.
Those that do not fade are preferred. Further, it may be a substance that develops a color by heating or a substance that develops a color by coming into contact with a component applied to the surface of the transfer target. Furthermore, the color of the colorant is not limited to cyan, magenta, yellow and black, and colorants of various colors can be used.

Further, in order to provide the heat-meltable ink layer with good heat conductivity and heat-melt transferability, a heat-conductive substance may be added as a binder filler. Examples of such fillers include carbonaceous materials such as carbon black, metals such as aluminum, copper, tin oxide, molybdenum disulfide, and metal compounds.

The hot-melt ink layer is formed by mixing and adjusting the colorant component and the binder component as described above, and if necessary, a solvent component such as water and an organic solvent. The working liquid is applied by a conventionally known method such as hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, and roll coating. Also,
There is also a method of forming using an aqueous or non-aqueous emulsion coating liquid. The thickness of the heat-meltable ink layer varies depending on the number of times printing is set, but is preferably about 4 to 30 μm. If it is less than 4 μm, the print density after the second printing will decrease,
If it exceeds 30 μm, a large amount of printing energy is required, which is not preferable.

The transfer control layer formed on the heat-meltable ink layer does not contain a colorant, and the porosity-forming resin component and the heat-meltable wax component are used as a solvent which is a hydrophilic solvent for each other and a poor solvent for the other. After the melted coating liquid for forming the transfer control layer is applied and then dried, the resin component and the heat-meltable wax component are phase-separated. Thereafter, the heat-melting wax component is melted by heating during printing, and pores through which the heat-melting ink flows out are formed. Here, the porosity-forming resin component is insoluble in the heat-meltable ink, and has heat resistance and physical strength to the extent that structural loss does not occur at the temperature at which the heat-meltable ink flows out and is transferred. It is retained on the thermal transfer sheet side without being transferred to the surface. As a result of such a transfer control layer being formed on the surface of the thermal transfer sheet, the thermal meltable ink layer is suppressed from being transferred in all layers in the thickness direction, and is gradually consumed for each printing. It is possible to print many times with little change in density. Further, by containing the release agent, it is possible to prevent the heat-meltable ink from being fused to the porous forming resin to cause clogging and to reduce the print density with the number of prints. Further, at the time of peeling, the adhesiveness between the porous resin and the heat-meltable ink is kept low to prevent the entire transfer of the ink layer.

Examples of the porosity forming resin used in the transfer control layer include cellulose esters such as cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose butyrate, benzyl cellulose, ethyl cellulose, carboxymethyl cellulose and the like. Cellulose ethers, cellulose derivatives such as nitrocellulose in which the hydroxyl groups of cellulose have been substituted with different groups at various degrees of substitution, or vinyl acetate-based materials such as polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, etc. Resin, polymethylmethacrylate, ethylene-ethyl acrylate copolymer, acrylic resin such as silicon modified acrylic resin, vinyl chloride resin, chlorine resin such as vinylidene chloride resin, polyvinyl formal, Polyvinyl acetacetal, polyacetal resin to polyvinyl butyral, polystyrene, one or a mixture of two or more resins having heat resistance such as polycarbonate is used. Among these, the cellulose derivative and the vinyl chloride-vinyl acetate copolymer give good results.

The heat-meltable wax component incompatible with the resin component used in the transfer control layer has a low solubility in the solvent of the resin component, and is added to the wax component used in the heat-meltable ink layer. It is also possible to use a resin having a melting point of up to about 80 ° C., for example, a urethane type or a polyester type. In particular, neopentyl type polyol short chain long chain saturated dibasic acid long chain linear saturated fatty acid ester,
It has high solubility in toluene and is preferably used.

As a method for forming the transfer control layer, a solvent that dissolves only the above-mentioned resin component for forming a porosity and a solvent that does not dissolve the resin component for forming a porosity but only the above-mentioned hot-melt wax component are mixed. A coating liquid prepared by dissolving a porous forming resin and a heat-meltable wax component in a solvent is applied onto the heat-meltable ink layer to form a transfer control layer having a thickness of 0.2 μm to 4 μm. Further, if necessary, it may be heated at a temperature higher than the melting point of the hot-melt wax after coating. When the thickness of the transfer control layer is thinner than 0.2 μm, the physical strength of the transfer control layer is lowered, and when the thickness is thicker than 4 μm, a large amount of printing energy is required and the printing density is lowered. The solvent used is selected depending on the combination of the porosity-forming resin and the hot-melt wax component, but when cellulose acetate butyrate is used as the resin and candelilla wax is used as the hot-melt wax, MEK (porosity-forming) is used. A mixed solvent of a solvent that dissolves only the resin) and toluene (a solvent that dissolves only the hot-melt wax component) is used. At this time, the transfer control layer is formed by mixing 50 parts by weight to 600 parts by weight of the heat-melting wax component with 100 parts by weight of the resin for forming porosity in the solvent. The heat-melting wax component is 5
If it is less than 0 parts by weight, the pore size becomes small and the printing density decreases, which is not preferable. On the other hand, if it is more than 600 parts by weight, the pore diameter becomes large, and the strength of the porous membrane decreases, which is not preferable. According to the above method, 0.5 μm to 1
A porous membrane having a pore size of 0 μm, more preferably 1 μm to 5 μm is formed. The compounding ratio of the porous resin and the heat-melting wax, the thickness of the transfer control layer, etc. are appropriately determined depending on the printing conditions such as printing energy and printing pressure.

Further, when the transfer control layer is formed, by adding a releasing agent, the porous forming resin and the heat-fusible ink can have a releasing effect on the other. As a result, the heat-meltable ink is prevented from being fused with the porous resin to cause clogging, and the printing density is prevented from decreasing with the number of printings. Further, at the time of peeling, the adhesiveness between the porous resin and the heat-meltable ink is kept low to prevent the entire transfer of the ink layer. Suitable release agents include silicone-modified acrylic resin, silicone resin, fluororesin, and fluoro-modified acrylic resin, and these are used as a mixture with a porous-forming resin. The amount of the release agent added is preferably 20 parts by weight to 100 parts by weight with respect to 100 parts by weight of the porous-forming resin. If the amount of the releasing agent is less than 20 parts by weight, a good releasing action cannot be obtained. When it is more than 100 parts by weight, the strength of the transfer control layer is lowered.

Needless to say, the multi-print thermal transfer sheet of the present invention can be applied to color printing, and the thermal transfer printer for printing the multi-print thermal transfer sheet of the present invention is not particularly limited to a line type or a serial type.

[0022]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified. Example 1 As a base film, a thickness of 4.5 μm heat-treated
On one side of the polyethylene terephthalate film of
A coating solution for the heat-meltable ink layer having the following composition is applied and dried to form a heat-meltable ink layer having a thickness of 7 μm, and a coating solution for the transfer control layer having the following composition is applied on the layer and dried. Then, a transfer control layer having a thickness of 0.3 μm was formed to obtain a thermal transfer sheet for multiple printing of the present invention. Coating liquid carbon black for hot melt ink layer (Diamond Black manufactured by Mitsubishi Kasei) 15 parts Candelilla wax 25 parts Paraffin wax 50 parts Ethylene-vinyl acetate copolymer 10 parts Transfer control layer coating liquid Cellulose acetate butyrate 10 parts Can Delilax wax 20 parts Toluene 100 parts MEK 200 parts

Example 2 A thermal transfer sheet for multiple-printing of the present invention was obtained in the same manner as in Example 1 except that the coating liquid for the heat-meltable ink layer and the coating liquid for the transfer control layer had the following compositions. Coating liquid carbon black for hot-melt ink layer (Diamond Black manufactured by Mitsubishi Kasei) 15 parts Carnauba wax 10 parts Paraffin wax 65 parts Ethylene-vinyl acetate copolymer 10 parts Transfer control layer coating liquid Cellulose acetate butyrate 10 parts Candelilla Wax 20 parts Silicon modified acrylic resin (20% toluene solution) 25 parts Toluene 100 parts MEK 240 parts

Example 3 A thermal transfer sheet for multi-printing of the present invention was obtained in the same manner as in Example 2 except that the transfer control layer coating liquid had the following composition and the thickness of the transfer control layer was 2 μm. Transfer Control Layer Coating Liquid Cellulose Acetate Butyrate 10 parts Neopentyl type polyol long chain linear saturated dibasic acid long chain linear saturated fatty acid ester (Nisshin Fine Chemical Co., Ltd. TMA573) 20 parts Toluene 100 parts MEK 200 parts

Comparative Example 1 A thermal transfer sheet for multi-printing of the present invention was obtained in the same manner as in Example 1 except that the composition for the transfer control layer coating was as follows. Transfer control layer coating liquid Cellulose acetate butyrate 10 parts Particulate carnauba wax having an average particle size of 2.2 μm (25% MEK dispersion) 80 parts Toluene 100 parts MEK 140 parts

Comparative Example 2 A thermal transfer sheet for multi-printing of the present invention was obtained in the same manner as in Example 1 except that the coating liquid for the transfer control layer had the following composition. Transfer control layer coating liquid Cellulose acetate butyrate 10 parts Particulate carnauba wax with an average particle size of 2.2 μm (25% MEK dispersion) 20 parts Silicon modified acrylic resin (20% toluene solution) 25 parts Toluene 100 parts MEK 180 parts

Using the thermal transfer sheets of the above-mentioned Examples and Comparative Examples, printing was carried out under the following conditions, the print density was measured, and the results shown in Table 1 were obtained. Printing conditions Used equipment: Line thin film head type Printing energy: 23 mj / mm Image receiving paper; Fine paper (Beck smoothness 400 seconds)

[0028]

[Table 1]

[0029]

As described above, according to the present invention, when the transfer control layer forming coating liquid is applied, the resin component and the wax component can be stably applied in a compatible state. After coating, the solvent evaporates during drying and the thermal transfer sheet is formed with the resin component and the wax component phase-separated. Furthermore, the heating during printing melts the wax component and forms pores that control the outflow amount of the hot-melt ink. Here, the size of the pores can be controlled by adjusting the mixing ratio of the porosity forming resin component and the wax component. Therefore,
By carrying out this adjustment, it is possible to stably form a transfer control layer having the optimum strength and pore size for printing many times. Further, according to the manufacturing method of the present invention, since the through holes can be easily formed, the initial print density does not decrease, and the pore size is uniform, so that there is no print unevenness.

[0030]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a thermal transfer sheet of the present invention.

FIG. 2 is a cross-sectional view showing an application example of the thermal transfer sheet of the present invention.

[Explanation of symbols]

 1. Base film 2. Heat-meltable ink layer 3. Transfer control layer 4. Primer layer 5. Back layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41M 5/30

Claims (3)

[Claims] 1. A multi-print thermal transfer sheet comprising a base film, a heat-meltable ink layer and a transfer control layer laminated in this order, wherein the transfer control layer contains no colorant and is porous. A thermal transfer sheet for multi-use printing, comprising a resin component for heat-use and a heat-meltable wax component which is incompatible with the resin component, and the resin component for forming porosity and the heat-meltable wax component are phase-separated. 2. The thermal transfer sheet for multiple printing according to claim 1, wherein a release agent is contained in the transfer control layer. 3. A method for producing a thermal transfer sheet for multi-printing, comprising a base film, a heat-meltable ink layer, and a transfer control layer laminated in this order, wherein the transfer control layer does not contain a colorant. A solvent composed of a resin component for forming a porosity and a heat-melting wax component incompatible with the resin component, wherein the resin component for forming a porosity and the heat-melting wax component are respective parent solvents and become poor solvents of the other. To form a transfer control layer utilizing the phase separation of the resin component for forming a pore and the heat-melting wax component by coating the heat-melting ink layer with the coating liquid dissolved and mixed in the solution and drying it. A method for producing a thermal transfer sheet for multi-use printing, which comprises: