JP2934975B2 - Thermal transfer recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thermal transfer recording medium used in a thermal transfer recording apparatus such as a printer, a facsimile, etc.
The present invention relates to a thermal transfer recording medium capable of performing high-quality transfer recording without being affected by the surface of a receiving paper.

[Conventional technology]

The thermal transfer recording method uses a thermal transfer recording medium obtained by applying at least one layer of a thermal fusible ink on a sheet-like substrate, and superimposes the thermal transfer recording medium such that the thermal fusible ink layer is in contact with the transfer target paper. In addition, this is a recording method in which the ink layer is heated and melted by a heating head from the substrate side of the thermal transfer recording medium to obtain a transfer image on the transfer receiving paper. According to this method, the apparatus to be used has been widely used in recent years because the apparatus to be used is low noise, has excellent operability and maintainability, and can use plain paper as a transfer paper.

[Problems to be solved by the invention]

However, in the conventional hot-melt ink as described above, the binder material is mainly composed of wax, and the hot-melt ink is transferred to the surface of the receiving paper by softening of the wax. However, there is a problem that the surface of the receiving paper is easily affected. That is,
The wax has a large decrease in viscosity due to heat, and has a very low melt viscosity.
When the contact area of the ink with the concave portion during the melting is small, for example, when the Bekk smoothness of the surface of the transfer receiving paper becomes 30 to 40 seconds or less, the ink ride becomes uneven and this causes a deterioration in image quality.

If the thickness of the ink is increased so that a large amount of ink is transferred to one point, the ink surely covers the surface of the paper to be transferred, so that there is no problem of a decrease in recording density or blur due to poor transfer of the ink. However, on the other hand, the bleeding becomes large, the size of one dot becomes large, and the resolution becomes poor, which causes deterioration in image quality.

Further, as those using a resin as a binder material of the hot-melt ink, JP-A-54-87234 and JP-A-54-16304
No. 4, No. 56-98269, No. 62-130887, etc. are known, but it is hard to say that performance is sufficient.

In Japanese Patent Publication No. 60-59159, the softening temperature is 60-110 ° C.
Epoxy resin is used as a binder material for hot-melt ink, but if there is no release layer, the melt viscosity of the resin is high, so the surface of the receiving paper is affected, and the printing performance is poor. In this case, since the softening temperature of the epoxy resin is low, thermal stability of the ink sheet is lacking, and blocking occurs in a storage test at 60 ° C., which is not practical.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal transfer recording medium which is less affected by the surface of a sheet to be transferred and can perform high-quality transfer. Another object of the present invention is to provide a thermal transfer recording medium having good resolution.

[Means for solving the problem]

The present inventors have conducted intensive studies and found that a release layer was provided between the base material and the heat-meltable ink layer, and the binder material of the heat-meltable ink was a softening temperature of 115 from a conventional wax-based material. It has been confirmed that the above object can be achieved by changing to an epoxy resin at a temperature of from 160C to 160C, and the present invention has been completed.

That is, the present invention relates to a thermal transfer recording medium obtained by applying a hot-melt ink onto a base material, having a release layer between the base material and the hot-melt ink layer, and having the hot-melt ink having a softening temperature of 115 ° C. An object of the present invention is to provide a thermal transfer recording medium characterized by containing an epoxy resin at a temperature of from 160 ° C. to 160 ° C. and a coloring agent as main components.

Conventionally, waxes used as binder materials for hot-melt inks include paraffin wax, carnauba wax, montan wax, beeswax, wood wax, candelilla wax, low molecular weight polyethylene, α-olefin oligomers and modified products thereof. If necessary, mineral oils such as spindle oil and linseed oil, vegetable oils such as tung oil, plasticizers such as dioctyl phthalate and dibutyl phthalate, higher fatty acids such as oleic acid and stearic acid, metal salts thereof, amide and other Derivatives are mixed and dispersed together with dyes and pigments and applied to a thin plastic film or condenser paper to form a thermal transfer recording medium.

Such conventional waxes as binder materials have a relatively clear melting point in a temperature range of about 50 ° C. to about 150 ° C. because of their crystalline nature, and when heated above the melting point, the solid phase rapidly changes from a solid phase to a liquid phase. Changes to At a temperature about 30 ° C. higher than the melting point, the liquid becomes a low-viscosity liquid having a viscosity of about 10 ^{−2 to} 10 poise.

On the other hand, many resins have essentially no melting point, and gradually change from a solid phase to a liquid phase at the glass transition point (Tg). The change in viscosity during this period usually decreases to at most about 10 ³ to 10 ⁵ poise even at a temperature about 50 ° C. higher than Tg. In the case of thermal transfer recording, the transfer and fixing sensitivity is basically governed by the melt viscosity and melt viscoelasticity of the binder material. Disadvantageous. However, the present inventors have a release layer between the base and the hot-melt ink, and use an epoxy resin having a softening temperature of 115 ° C to 160 ° C as a binder material of the hot-melt ink, at the expense of sensitivity. It has been found that high-quality transfer recording can be performed without high resolution and without being affected by the surface of the paper to be transferred. Hereinafter, the details of the thermal transfer recording medium of the present invention will be described.

As the base material of the thermal transfer recording medium of the present invention, condenser paper, papers such as glassine paper, polyester, polyimide,
Thin film sheets and films of plastics such as polycarbonate, polyamide, polyethylene and polypropylene are used. The thickness of the substrate is preferably in the range of about 2 to 20 μm. When recording is performed using a thermal head or the like, a silicon-based or fluorine-based compound, a resin layer or a crosslinked polymer layer, a metal A layer or the like may be provided.

For the release layer, silicone resins, higher fatty acids, higher fatty acid metal salts, fatty acid derivatives, higher alcohols, waxes and the like are used. Particularly preferably, waxes are used, for example, paraffin wax,
Montan wax, carnauba wax, beeswax, wood wax, candelilla wax and low molecular weight polyethylene, α
-Known waxes conventionally used as binder materials for hot-melt inks such as olefin oligomers and modified products thereof. The above waxes may be used alone or in combination of two or more. In addition to waxes, ethylene-
Acrylic acid copolymer, ethylene-vinyl acetate copolymer,
Resins such as polyethylene and petroleum resin may be added.

The epoxy resin used as the binder material of the present invention has a softening temperature of 115 ° C to 160 ° C. An epoxy resin having a softening temperature of less than 115 ° C. is liable to cause blocking of the hot-melt ink and lacks stability during storage and use, which is not preferable. Further, when the softening temperature exceeds 160 ° C., the thermal stability is good, but the sensitivity is lowered, so that the use may be limited.

The purpose of the binder material of the present invention can be sufficiently achieved even if the binder material is composed of only one or more epoxy resins. However, if necessary, other polymers and additives may be added and mixed.

For example, styrene and vinyl toluene, α-methylstyrene, 2-methylstyrene, chlorostyrene, vinylbenzoic acid, sodium vinylbenzenesulfonate, styrene such as aminostyrene and derivatives thereof, homopolymers and copolymers of substituted products, Methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid esters such as hydroxyethyl methacrylate and methacrylic acid,
Acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, and acrylic acids, butenes such as butadiene and isoprene, acrylonitrile, vinyl ethers,
Maleic acid and maleic acid esters, maleic anhydride, cinnamic acid, vinyl chloride and other vinyl monomers alone or copolymers with other monomers can be used.
Needless to say, the vinyl resin may be used as a crosslinked polymer using a polyfunctional monomer such as divinylbenzene. Furthermore, polycarbonate, polyamide, polyester, polyurethane resin, silicone resin, fluorine resin, phenol resin, terpene resin, petroleum resin, hydrogenated petroleum resin, alkyd resin, ketone resin, cellulose derivative and the like may be used. When these polymers or oligomers are used in the form of a copolymer, the copolymer may be a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, A copolymerization mode such as a penetration copolymer can be appropriately selected and used. When two or more kinds of polymers and oligomers are mixed and used, in addition to mechanical mixing such as melt mixing, solution mixing, and emulsion mixing, polymer and oligomer components are mixed by coexistence polymerization, multistage polymerization, or the like. You may.

Further, if necessary, waxes, oils, and liquid plasticizers as used in conventional hot-melt inks may be added and mixed. However, it is preferable in terms of image quality that the epoxy resin component accounts for generally 30% or more, preferably 70% or more in volume concentration of all the binder material components.

Colorants include carbon black, oil black,
Black dyes such as graphite; CI Pigment Yellow 1, 3 and 7
Acetyl acetate aryl amide monoazo yellow pigments (fast yellow) such as 4, 97 and 98; CI Pigment Yellow 12, 12
Acetoacetic acid arylamide-based bisazo yellow pigments such as 13, 13 and 14; CISolvent Yellow 19, 77, 79, CI Disperse Ye
yellow dyes such as llow164; CI Pigment Red 48, 49: 1, 53: 1,
57: 1, 81, 122, 5 and other red or red pigments; CISol
red dyes such as vent Red 52, 58, and 8; CI Pigment Blue 1
Copper phthalocyanine and its derivatives such as 5: 3 and the like, blue dyes and pigments such as modified products can be used, and colored or colorless sublimable dyes and the like, conventional printing inks, dyes and pigments known in other coloring applications can be used. .

These dyes and pigments may be used alone or in combination of two or more. Of course, the color tone may be adjusted by mixing with an extender or a white pigment. Furthermore, the surface of the colorant is treated with a surfactant, a coupling agent such as a silane coupling agent, a polymer material, or a polymer dye or a polymer graft pigment to improve the dispersibility of the binder component. May be used.

The thermal transfer recording medium of the present invention has a release layer between the substrate and the heat-meltable ink, and an epoxy resin and a colorant having a softening temperature of 115 ° C to 160 ° C, and further, if necessary, the various additives described above. Is formed by disposing a hot-melt ink in which is mixed on a base material.

Production of the hot melt ink of the present invention, in a solvent or dispersion medium capable of dissolving or stably dispersing the binder material,
It can be prepared as a solution or a dispersion emulsion by using a mixing and dispersing machine such as a ball mill, a sand mill, an attritor, a basket mill, and a three-roll mill. In addition, the solvent may be melt-mixed with a heated three-roll, heated kneader, heated sand mill, heated attritor, or the like without particular use of a solvent or the like. Furthermore, an epoxy resin as a main binder material may be prepared by synthesis in the presence of a coloring agent, an additive, and the like, to obtain a hot-melt ink.

The hot-melt ink thus prepared is applied and printed on a substrate by a solution or a melt coating method using a gravure coater, a wire bar or the like.

Alternatively, the heat-meltable ink may be pulverized by a spray drying method, a pulverizing method, or the like, and then powder-coated on the substrate by an electrostatic coating method or the like. In this case, after the powder coating, if necessary, heating, pressurizing, solvent treatment, or the like may be performed to fix the hot-melt ink on the base material before use.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

In the following examples, parts are by weight unless otherwise specified.

Example 1 The following layers were formed on a 6 μm-thick polyester film to form an ink sheet as a thermal transfer recording medium.

Release layer 100 microcrystalline wax (melting point = 75 ° C)
The coating was applied to a thickness of 1.5 μm with a wire bar in a constant temperature bath at 0 ° C. to provide a release layer.

Hot-melt ink layer A hot-melt ink having the following composition was kneaded in a ball mill at room temperature for 24 hours to prepare a hot-melt ink.

The heat-meltable ink liquid obtained above is applied on the release layer by a wire bar so that the heat-meltable ink layer has a thickness of 3 μm, and dried at 60 ° C. to form an ink sheet as a thermal transfer recording medium. Was formed.

Example 2 The following layers were formed on a polyimide film having a thickness of 4 μm to form an ink sheet as a thermal transfer recording medium.

Release Layer Carnauba wax (melting point = 82 ° C.) was applied with a wire bar to a thickness of 1.5 μm in a thermostat at 100 ° C. to form a release layer.

Hot-melt ink layer A hot-melt ink having the following composition was kneaded in a ball mill at room temperature for 24 hours to prepare a hot-melt ink.

The heat-meltable ink liquid obtained above is applied on the release layer by a wire bar so that the heat-meltable ink layer has a thickness of 3 μm, and dried at 60 ° C. to form an ink sheet as a thermal transfer recording medium. Was formed.

Example 3 The following layers were formed on a polyester film having a thickness of 4 μm to form an ink sheet as a thermal transfer recording medium.

Release Layer An oxidized paraffin wax (melting point = 85 ° C.) was applied to a thickness of 1.5 μm with a wire bar in a constant temperature layer at 100 ° C. to provide a release layer.

Hot-melt ink layer A hot-melt ink having the following composition was kneaded in a ball mill at room temperature for 24 hours to prepare a hot-melt ink.

The heat-meltable ink liquid obtained above is applied on the release layer by a wire bar so that the heat-meltable ink layer has a thickness of 3 μm, and dried at 60 ° C. to form an ink sheet as a thermal transfer recording medium. Was formed.

Comparative Example 1 A hot-melt ink having the following composition was melt-mixed at 100 ° C. and kneaded with a three-roll mill to prepare a hot-melt ink.

・ 50 parts of paraffin wax (melting point = 72 ° C.) ・ 20 parts of carnauba wax ・ 10 parts of ethylene-vinyl acetate copolymer ・ 20 parts of carbon black The hot-melt ink obtained above was heated on a hot plate heated to 110 ° C. It was applied on a 4 μm thick polyester film with a wire bar so that the thickness of the hot-melt ink layer was 3 μm to obtain a thermal transfer ink sheet.

Comparative Example 2 A hot-melt ink having the following composition was kneaded in a ball mill at room temperature for 24 hours to prepare a hot-melt ink.

The hot-melt ink liquid obtained above was applied on a 4 μm-thick polyimide film with a wire bar,
To provide a hot-melt ink layer having a thickness of 2.5 μm.

Comparative Example 3 The following layers were formed on a 6 μm-thick polyester film to form an ink sheet as a thermal transfer recording medium.

Release layer 100 microcrystalline wax (melting point = 75 ° C)
The coating was applied to a thickness of 1.5 μm with a wire bar in a constant temperature bath at 0 ° C. to provide a release layer.

Hot-melt ink layer ・ Paraffin wax (melting point = 72 ° C) 12 parts ・ Carnauba wax 2 parts ・ Ethylene-vinyl acetate copolymer 2 parts ・ Carbon black 4 parts ・ Toluene 40 parts ・ Methyl ethyl ketone 40 parts The above composition is used in a ball mill. The heat-meltable ink liquid obtained by kneading at 40 ° C. for 24 hours is coated on the release layer with a wire bar so that the heat-meltable ink layer has a thickness of 3 μm. And

Comparative Example 4 The following layers were formed on a 4 μm-thick polyester film to form an ink sheet as a thermal transfer recording medium.

Release Layer Carnauba wax (melting point = 82 ° C.) was applied with a wire bar to a thickness of 1.5 μm in a thermostat at 100 ° C. to form a release layer.

Hot-melt ink layer The hot-melt ink liquid of Comparative Example 2 was applied on the release layer with a wire bar so that the hot-melt ink layer had a thickness of 3 μm, to obtain a thermal transfer ink sheet.

A serial printer PC manufactured by NEC Corporation using the ink sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 4.
Printing was performed using -PR150V, and the print density, recording sensitivity, and resolution of the transferred image were tested.

 Table 1 shows the results.

The evaluation method of the recording characteristics shown in Table 1 above is as follows.

Printing density: Continuous printing was measured with a Macbeth reflection densitometer.

Thermal transfer paper has a Beck smoothness of 200
Seconds, bond paper is 15 seconds.

Recording sensitivity: Thermal head heating element size (1 / 12mm = 83
μm) on a thermal transfer paper with a print density of 1.
The evaluation was made based on the thermal head applied energy (E) required for recording in 2.

Evaluation criteria ○; E <0.08mJ / dot △; 0.08mJ / dot ≦ E ≦ 0.11mJ / dot ×; 0.11mJ / dot <E or print density less than 1.2 Resolution: legibility of kanji (especially with many strokes) ).

Evaluation criteria ；: Good readable.

Δ: Normal ×: Difficult to read Thermal stability of the ink sheet: After storage at a temperature of 60 ° C. for 10 hours, blocking evaluation and print evaluation were performed and compared with those before the environmental test.

The evaluation results of each hot-melt ink shown in Table 1 will be supplementarily described below.

Comparative Example 1 using wax as a binder material shows relatively good printing results on thermal transfer paper, but has low print density on bond paper having irregularities on the surface of the receiving paper, and character crushing on kanji with many strokes. And may be difficult to read.

Comparative Example 2 using an epoxy resin having a low softening temperature as a binder material has performance close to that of the thermal transfer recording medium of the present invention, but lacks thermal stability of an ink sheet because an epoxy resin having a low softening temperature is used. At 60 ° C, blocking occurs and cannot be used.

Comparative Example 3 showed the effect of providing a release layer containing wax as a main component between the base material and the hot-melt ink layer. In this case, the print quality is improved as compared with Comparative Examples 1 and 2, but is inferior to the Examples.

In Examples 1 to 3, a release layer containing wax as a main component was provided between the base material and the hot-melt ink layer, and the softening temperature was 115 ° C.
Examples in which an epoxy resin having a temperature in the range of -160 ° C was used as a binder material were shown, and they showed very good printing results, and showed high printing density even on bond paper. Further, the thermal stability of the ink sheet was good, and the blocking as in Comparative Example 2 did not occur.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a high-quality transfer image, which is less affected by the unevenness of the surface of the transfer receiving paper, and has good thermal stability and good fixability. A thermal transfer recording medium is obtained.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. A thermal transfer recording medium comprising a base material coated with a heat-fusible ink, a release layer between the base material and the heat-fusible ink layer, wherein the heat-fusible ink has a softening temperature. 115 ° C
A thermal transfer recording medium comprising an epoxy resin at a temperature of up to 160 ° C. and a coloring agent as main components.