JPH0880676A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE: To obtain a thermal transfer recording medium having film fastness and high in transfer sensitivity enabling low energy printing by providing a hot-melt ink layer containing an epoxy resin specified in its softening temp. and an isocyanate adduct of higher fatty acid/polyhydric alcohol ester. CONSTITUTION: The m.p. of an isocyanate adduct of higher fatty acid/polyhydric alcohol ester is planned low in order to perform low energy printing. In place of a conventional method adding a small amt. of a thermoplastic resin with a high m.p. in order to prevent the background staining accompanied by this planning, one or more kind of an epoxy resin with a softening temp. of 50--180 deg.C is added. By this constitution, an ink compsn. having film fastness and high in transfer sensitivity enabling low energy printing not generating background staining is obtained. The epoxy resin to be used is a compd. having two or more α-epoxy groups rich in reactivity in one molecule thereof and imparts useful cured matter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording medium, and more particularly to an ink composition for forming a color material layer (ink layer) thereof. More specifically, the present invention relates to a thermal transfer recording medium having a coating film fastness and excellent transferability that enables low energy printing without background stain.

[0002]

2. Description of the Related Art A thermal transfer recording medium is one in which at least one color material layer is coated on a sheet-shaped support such as paper or plastic film, and a solid ink is melted by heat. The recording is performed by transferring the ink onto the recording paper by using the recording medium. As a method of thermal transfer,
Generally, a method of heating with a heating element from the side opposite to the coated surface or the coated surface side via a recording paper, or a method of electrically heating the recording medium provided with a resistance layer is used. The color material layer is composed of a heat-fusible substance containing a pigment and a dye as a colorant. Carnauba wax, paraffin wax, or the like is used as the heat-meltable substance. As the support, polyethylene terephthalate (PET) film, polycarbonate film, synthetic paper, condenser paper and the like, which are excellent in surface smoothness and dimensional stability, are generally used.

When recording a transfer image on plain paper or the like using such a thermal transfer recording medium, a thermal transfer printer equipped with, for example, a thermal head is generally used. In this case, it is desirable to keep the thermal energy required for printing as low as possible. The reason for this is that by keeping the heat energy required for printing lower than before, the heating and cooling cycle time of the head can be shortened, heat deterioration of the head can be prevented, and the line printer can be made smaller in size. Is. Further, it is also possible to compensate for the lack of heat resistance of the base film. However, if the melting point of the ink composition is designed to be low in order to increase the transfer sensitivity of the thermal transfer recording medium, the background stain is generated due to the low melting point component of the wax when printing on plain paper, and the fixability and robustness of the printing are also improved. In addition to the decrease, there has been a problem that a so-called blocking phenomenon occurs when the environmental temperature rises during storage.

In order to solve these problems, conventionally, a resin component is introduced into a binder (Japanese Patent Laid-Open No. 87-234234).
No. 54-163044, No. 56-98269,
No. 62-130887) or coating a resin-based overcoat layer on a wax ink (JP-A-61-2242).
No. 893) and the like have been dealt with, but none of them satisfying the combined requirements in a balanced manner has been obtained. Therefore, an object of the present invention is to provide a thermal transfer recording medium having a coating film fastness and capable of low-energy printing without background stain and high transfer sensitivity.

[0005]

In order to solve the above problems, the inventors of the present invention have conducted earnest research and as a result, designed a low melting point of an isocyanate adduct of a higher fatty acid polyhydric alcohol ester for low energy printing. , A coating film by adding one or more epoxy resins having a softening temperature of 50 to 180 ° C. instead of the conventional method in which a small amount of a high melting point thermoplastic resin is added in order to prevent the background stain. It has been found that an ink composition having fastness and high transfer sensitivity that enables low energy printing without background stain can be obtained.

The present invention has been made based on the above findings, and in a thermal transfer recording medium having at least one heat-meltable ink layer provided on a substrate, the heat-meltable ink layer has a softening temperature of 50 to 180. The above object is achieved by providing a thermal transfer recording medium characterized by containing an epoxy resin at ℃ and an isocyanate adduct of a higher fatty acid polyhydric alcohol ester.

The components of the heat-meltable ink constituting the heat-meltable ink layer of the heat transfer recording medium of the present invention will be described below.

The epoxy resin used in the present invention is
It is a compound having two or more highly reactive α-epoxy groups in one molecule and provides a useful cured product.

As the epoxy resin, for example, an epoxy resin obtained by reacting an active hydrogen compound with epichlorohydrin can be used. An active hydrogen compound is a phenolic --OH or a carboxylic acid --COO.
It is a compound having hydrogen such as H and -NH _{2 of} amine.

The most common epoxy resin is 4,4'-
It is obtained by reacting dioxydiphenylpropane (bisphenol A) with epichlorohydrin in the presence of an alkali such as an alkali hydroxide, and is represented by the following general formula.

Embedded image The magnitude of n is related to the molar ratio of bisphenol A to epichlorohydrin.

Another general epoxy resin is an acid reaction product of phenol and formalin (novolak resin), and is represented by the following general formula.

Embedded image The value of n is 0 to 5, and the simplest one is bisphenol F (n = 0).

Other epoxy resins used in the present invention include diglycidyl ether of dihydric phenol such as resorcinol, epoxidized chlorinated hydroquinone, epoxidized via disodium salt of substituted hydroquinone, 3,3 ', Glycidyl ethers of polyphenols such as 3 ", 3"'-tetraxytetraphenylethane, glycidyl ethers of aliphatic and other dialcohols and trialcohols, glycidyl ethers of organic acids and epichlorohydrin, glycidyl ethers of amines or amides, etc. Can be mentioned.

The softening temperature of the epoxy resin is 50-18.
It is necessary to be 0 ° C., and particularly preferably 60 to 110 ° C. When the softening temperature is lower than this, transfer may occur only by pressing the thermal head, which is a cause of scumming and is not preferable.

The epoxy resin can be produced by any conventionally known method other than the reaction between the active hydrogen compound and epichlorohydrin. For example, the reaction of inserting an epoxy group in the molecule is as follows. It is possible to use 1) a liquid phase oxidation reaction of a double bond compound with hydrogen peroxide or a peracid (mostly a peracid), 2) an air oxidation reaction of a double bond compound, 3) a reaction using an ylide, etc. it can. In the present invention, this epoxy resin may be used as it is, or may be used after adding an appropriate curing agent such as amine.

The epoxy resin used in the present invention may be a commercially available product, for example, Epicoat 1001 (Epoxy resin obtained from bisphenol skeleton, softening temperature 64-74 ° C.) manufactured by Shell Chemical Co., Ltd. Ink Chemical Industry Co., Ltd. Epicron 9055 (epoxy resin obtained from bisphenol skeleton, softening temperature 140 to 1
55 ° C.) and the like can be used.

The isocyanate adduct of higher fatty acid polyhydric alcohol ester used in the present invention is obtained by addition reaction of an isocyanate compound with an esterified product of higher fatty acid and polyhydric alcohol. The isocyanate adduct may be present alone or in combination of two or more in the hot-melt ink layer.

As the higher fatty acid for obtaining the higher fatty acid polyhydric alcohol ester, saturated fatty acid, unsaturated fatty acid, alicyclic fatty acid, oxygen-containing fatty acid, hydroxy fatty acid and the like can be used. The number is
It is 2 to 60, preferably 5 to 50, and particularly preferably 10 to 40. In the present invention, a fatty acid having a melting point of 20 ° C. or higher and a carbon number of 10 to 40 can be preferably used, and examples thereof include capric acid, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, and heptadecyl acid. Saturated fatty acids such as, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melissic acid, and raceric acid; acrylic acid, crotonic acid, isocrotonic acid, caproic acid, undecylenic acid, Unsaturated fatty acids such as oleic acid, elaidic acid, cetoleic acid, erucic acid, brassic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, sardonic acid, nisinic acid, propiolic acid, stearolic acid; isovaleric acid and the like. Branched fatty acids, malvalic acid, stercri Alicyclic fatty acids such as acids, hydronocarbic acid, scholme-gulonic acid, and golulinic acid; oxygen-containing fatty acids such as sabinic acid, iprolic acid, yarapinolic acid, uniperic acid, ricinoleic acid, and cerebronic acid; and hydroxy such as 12-hydroxystearic acid. Fatty acids; can be used. Above all, it is most effective to use lanolin fatty acid obtained by saponifying lanolin secreted from sebaceous glands of sheep. These fatty acids can be used alone or in combination of two or more kinds.

As the polyhydric alcohol for obtaining the higher fatty acid polyhydric alcohol ester, saturated aliphatic polyol, unsaturated aliphatic polyol, alicyclic polyol, oxygen-containing aliphatic polyol and the like can be used. The number of carbon atoms in the polyol is 1 to 50, preferably 1 to 20, and particularly preferably 1 to 10. In the present invention, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, trimethylene glycol, butanediol, pentanediol, hexylenediol, octylenediol, Glycerin, trimethylolpropane, pentaerythritol, dipentaerythritol, 1,3-butylene glycol, glycerin monoallyl, [4- (hydroxyethoxy) phenol] propane, sorbitol, sorbit, neopentyl glycol, trishydroxyethyl isocyanurate, bisphenol , Hydrogenated bisphenol, bisphenol glycol ether,
Various epoxy group-containing compounds (for example, triglycidyl isocyanurate) and the like are used. These polyhydric alcohols may be used alone or in combination of two or more.

As the isocyanate compound to be added to the higher fatty acid polyhydric alcohol ester, monoisocyanate, diisocyanate, triisocyanate and the like can be used. For example, methyl isocyanate, ethyl isocyanate, n-propyl isocyanate, n-isocyanate.
Butyl isocyanate, octadecyl isocyanate,
Monoisocyanates such as polymethylene polyphenyl isocyanate; 2,4-tolylene diisocyanate, 4,
4'-diphenylmethane diisocyanate, dianisidine diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, trans vinylene diisocyanate, N, N '(4,4'-dimethyl-3,3'-diphenyl diisocyanate) uresion, 2, Diisocyanates such as 6-diisocyanate methylcaproate; triphenylmethane triisocyanate, tris (4-phenylisocyanate thiophosphate) 4,4 ′, 4 ″ -trimethyl-3,3 ′, 3 ″
-Triisocyanates such as triisocyanate-2,4,6-triphenylcyanurate; Particularly, diisocyanate and triisocyanate are preferable, and aromatic type is more preferable.
These isocyanate compounds may be used alone or in combination of two or more.

The esterification reaction between the higher fatty acid and the polyhydric alcohol can be carried out by any conventionally known method. The degree of esterification is not particularly limited. The addition reaction of the higher fatty acid polyhydric alcohol ester prepared according to the above method and the isocyanate compound can be carried out according to a conventionally known method. The number of moles of the isocyanate compound added is not particularly limited, but is preferably about 0.1 to 5 moles per 1 mole of the higher fatty acid polyhydric alcohol ester. The isocyanate adduct of higher fatty acid polyhydric alcohol ester according to the present invention may be a commercially available product, for example, Ranox FR-1410N manufactured by Yoshikawa Oil Co., Ltd. may be used.

In addition to the epoxy resin and isocyanate adduct of higher fatty acid polyhydric alcohol ester which are the constitutional conditions of the present invention, a binder material may be added to the hot-melt ink layer, if necessary. As the binder material to be added, styrene such as styrene, vinyltoluene, α-methylstyrene, chlorostyrene, vinylbenzoic acid, sodium vinylbenzenesulfonate, and aminostyrene, homopolymers and copolymers of derivatives and substitution products thereof are used. Can be used. Further, methacrylic acid esters and methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate and hydroxymethacrylate; acrylic acid esters and acrylic acid such as methyl acrylate and 2-ethylhexyl acrylate; dienes such as butadiene and isoprene; acrylonitrile,
Vinyl ethers, maleic acid and maleic acid esters, maleic anhydride, cinnamic acid, and vinyl monomers such as vinyl chloride; homopolymers or copolymers with other monomers can also be used. Of course, in the case of the vinyl-based polymer, a polyfunctional monomer such as divinylbenzene may be used as a cross-linked polymer. Furthermore, polycarbonate, polyester, silicone resin, fluorine resin, phenol resin, tempene 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 copolymers, the copolymers include random copolymers, alternating copolymers, block copolymers and interpenetrating copolymers, depending on the required application. A copolymerization mode such as the above can be appropriately selected and used. When two or more kinds of polymers or oligomers are mixed and used, in addition to mechanical mixing such as melt mixing, solution mixing and emulsion mixing, they are mixed by coexisting polymerization or multi-stage polymerization method when polymerizing the polymer or oligomer components. You may.

Particularly in the present invention, it is preferable to use ethylene / vinyl acetate resin as the binder material, and any commercially available ethylene / vinyl acetate resin can be used, but the vinyl acetate content is 15 to 45. It is preferable that the melt flow rate is about 50% by weight and the melt flow rate is about 50 to 800. For example, EVAFLEX-40Y manufactured by Mitsui DuPont Polychemical Co., Ltd. (vinyl acetate content:
40% by weight) or the like can be used.

Further, it is necessary to add a colorant to the hot melt ink layer. As the colorant, carbon black,
Black dyes and pigments such as oil black and graphite; C.I. I. Pigment Yellow 1, 3, 3, 74, 97, 98 and the like, acetoacetic acid arylamide monoazo yellow pigments (fast yellow); C.I. I. Pigment Yellow 12, 13 and 14 and the like, acetoacetic acid arylamide-based bisazo yellow; C.I. I. Solvent Yellow 19, 77, 79, C.I. I. Yellow dyes such as Disperse Yellow 164; C.I. I. Pigment Red 8, 49: 1, 5
3: 1, 57: 1, 81: 122, 5 and the like red pigments; C.I. I. Solvent Red 52, 58, 8 and other red dyes; C.I. I. Pigment Blue 15: 3 and other copper phthalocyanines and their derivatives, modified dyes and the like can be used, and also colored or colorless sublimable dyes, conventional printing inks, and other dyes and pigments well known for coloring purposes 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 pigment or a white pigment. Furthermore, in order to improve the dispersibility in the binder material component, the surface of the colorant is treated with a surfactant, a coupling agent such as a silane coupling agent, a polymer material, a polymer dye or a polymer graft pigment. You may use.

Further, organic or inorganic fine particles may be added to the heat-meltable ink layer for the purpose of improving heat resistance stability.

Further, olefin homopolymers or copolymers of ethylene, propylene, etc., organic acid graft olefin copolymers, chlorinated paraffins, low molecular weight urethane compounds, plasticizers solid at room temperature, surfactants, etc. Antistatic agent and / or inhibitor, conductive agent, antioxidant, thermal conductivity improver, magnetic substance, strong derivative, preservative, perfume, antiblocking agent, reinforcing filler, release agent, foaming agent, sublimability A substance, an infrared absorbing agent and the like may be added to the heat fusible ink layer or other layers.

There are no particular restrictions on the amount of each of the above components of the heat-meltable ink used in the present invention, but the general range is 5-80% by weight of the epoxy resin and the higher fatty acid polyhydric alcohol ester. The isocyanate adduct is 5 to 80% by weight, the colorant is 10 to 60% by weight, and the optional component is 0 to 50% by weight. More preferably, the epoxy resin is 10 to 60% by weight, the isocyanate adduct of higher fatty acid polyhydric alcohol ester is 10 to 60% by weight, and the colorant is 15 to 45% by weight.
And the optional ingredient is 0.1 to 50% by weight.

The thermal transfer recording medium of the present invention is a hot melt obtained by mixing the epoxy resin, the isocyanate adduct of the higher fatty acid polyhydric alcohol ester, the colorant and, if necessary, the above-mentioned hot melt substance, various additives and the like. It is manufactured by applying a functional ink on a substrate and forming at least one hot-melt ink layer. The thickness of the heat-meltable ink layer is not particularly limited, but is preferably about 0.1 to 10 μm.

In the thermal transfer recording medium of the present invention, a release layer may be provided between the substrate and the heat-meltable ink layer. By providing the release layer, a highly sensitive thermal transfer recording medium can be obtained. The wax used in the release layer is preferably one or more selected from the group consisting of natural wax, synthetic wax and compounded wax. In addition to waxes, resins such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, polyethylene and petroleum resin may be added in order to improve coating strength and flexibility.

In the thermal transfer recording medium of the present invention, a release layer made of the above waxes is formed on a base material, and a heat-meltable ink layer is formed on the release layer by the heat-meltable ink. . The release layer is formed by a usual method for manufacturing a thermal transfer recording medium, for example, a method of applying wax or a heat-meltable ink with a wire coater. There is no particular limitation on the thickness of the release layer.

The base material used for the thermal transfer recording medium of the present invention is preferably a base material having heat resistance strength and high dimensional stability and surface smoothness. More specifically, it has been conventionally used mainly as a base film of a thermal transfer recording medium. Capacitor paper,
In addition to papers such as glassine paper and synthetic paper and polyethylene terephthalate, thin film sheets and films of resin films such as polycarbonate, polyethylene, polystyrene, polypropylene, polyimide and polyamide are used. The thickness of the base material is not particularly limited, but is about 1.5 to 20.
The range of μm is preferred. Further, when recording is performed using a thermal head or the like, in order to improve heat resistance and runnability on the side of the base material in contact with the head, a silicone-based or fluorine-based compound, a resin layer, a crosslinked polymer layer, a metal layer, etc. May be provided.

The thermal transfer recording medium of the present invention comprises at least one heat-fusible ink layer provided in contact with the base material or the coating layer on the base material. Etc. may be included.

The meltable ink for forming the heat-meltable ink layer is produced by preparing a solution or dispersion emulsion in a solvent or a dispersion medium capable of dissolving or stably dispersing the heat-meltable substance, and using a ball mill, a sand mill or an attritor. , A dyno mill, a three-roll mill or the like. Further, after the colorant is dispersed by the above method, fine particles may be added and stirred and mixed by a homomixer, a disper, a dissolver or the like. Further, without using a solvent or the like, they may be melt-mixed with a heating type three-roll, a heating type kneader, a heating type sand mill, a heating type attritor or the like.

The hot-melt ink prepared in this manner is applied to the base material or the coating layer on the base material by a solution or melt coating method using a gravure coater, a wire bar or the like.
Printed. Alternatively, the heat-meltable ink may be pulverized by a spray dry method and then powder-coated on a substrate by an electrostatic coating method or the like. In this case, after the powder coating, if necessary, heating, pressurizing, solvent treatment, etc. may be performed to fix the heat-meltable ink on the base material before use.

[0034]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. In the following examples, parts represent parts by weight unless otherwise specified.

[Example 1] -Isocyanate adduct of higher fatty acid polyhydric alcohol ester [Ranox FP-1410N (Yoshikawa Oil Co., Ltd.)
40 parts Epoxy resin [Epicoat 1001 (manufactured by Shell Chemical Co., Ltd.)]; 40 parts Estergum HS (manufactured by Arakawa Chemical Co., Ltd.); 5 parts Carbon black; 15 parts Mix with 200 parts and ball mill 1
The mixture was kneaded for 2 hours to obtain a uniform coating liquid. This coating solution was applied onto a polyethylene terephthalate film (Lumirror (registered trademark) manufactured by Toray) having a thickness of 3.5 μm using a wire bar so that the thickness of the coating film after drying was 3 μm, and the heat was applied. A fusible ink layer was provided to prepare a thermal transfer recording medium. The thermal transfer recording medium thus produced was printed on plain paper (BEKK 160 seconds) by a line type thermal transfer printer (NIP5234, NEC 9.4 dots / mm), and the density of the transferred image was measured. In order to investigate the relationship between the printing energy and the transferred image density, the density adjustment lever is operated to change the pulse width of the applied voltage between 0.65 and 0.85 seconds, and the transferred density is measured by the Macbeth densitometer (RD514
Type). As a result, the pulse width of the applied voltage required to obtain a transferred image having a density of 1.2 was 0.66 seconds. No background stain was observed during printing. In order to examine the blocking resistance, five sheets of the thermal transfer recording medium obtained in this example were stacked and a load of 500 g / cm ² was applied and stored at room temperature and 65% RH for one week. When the presence or absence was observed, blocking was not observed at all.

[Example 2] -Triresin isocyanate adduct of pentaerythritol behenate (additional mole number 0.5); 40 parts-Epoxy resin [Epiclon 9055 (manufactured by Dainippon Ink and Chemicals, Inc.)]; 40 Parts-Ester gum HS (manufactured by Arakawa Chemical Co., Ltd.); 5 parts-Carbon black; 15 parts A thermal transfer recording medium was prepared from the above components in the same manner as in Example 1 and printing was tried. As a result of measuring the density after transfer with a Macbeth densitometer (RD514 type), the pulse width of the applied voltage required to obtain a transferred image with a density of 1.2 was 0.66 seconds. Further, when the presence or absence of blocking was observed by the same method as in Example 1, no blocking was observed at all.

Comparative Example 1-Isocyanate adduct of higher fatty acid polyhydric alcohol ester [Ranox FP-1410N (Yoshikawa Oil Co., Ltd.)
80 parts) -Ester gum HS (manufactured by Arakawa Kagaku Co., Ltd.); 5 parts-Carbon black; 15 parts
A uniform coating solution was obtained. This coating solution was hot-melt coated on the same polyethylene terephthalate film as in Example 1 to a film thickness of 3 μm, and a heat-meltable ink layer was provided to prepare a thermal transfer recording medium. When printing was performed on this thermal transfer recording medium in the same manner as in Example 1, when the pulse width of the applied voltage was 0.65 seconds, the density was 0.20.
No transfer image was obtained. The pulse width of the applied voltage required to obtain a transferred image having a density of 1.2 was 0.85 seconds. Further, when the presence or absence of blocking was observed by the same method as in Example 1, blocking was recognized.

Comparative Example 2 Epoxy resin [Epiclon 9055 (manufactured by Dainippon Ink and Chemicals, Incorporated)]: 80 parts Ester gum HS (Arakawa Chemical): 5 parts Carbon black: 15 parts From the above components A thermal transfer recording medium was produced in the same manner as in Example 1 and printing was tried. As a result of measuring the density after transfer with a Macbeth densitometer (RD514 type), the pulse width of the applied voltage required to obtain a transferred image with a density of 1.2 is 0.75 seconds,
When the pulse width of the applied voltage is 0.65 seconds, the density is 0.6
Only 0 transfer image was obtained. Further, when the presence or absence of blocking was observed by the same method as in Example 1, blocking was recognized.

[0039]

As described in detail above, according to the thermal transfer recording medium of the present invention, since the heat-fusible ink layer contains the epoxy resin and the isocyanate adduct of higher fatty acid polyhydric alcohol ester, High sensitivity, low energy printing is possible and suitable for high speed printing. Also,
There is no transfer unevenness, the robustness of printing does not deteriorate, and there is no concern about blocking. Further, by further providing a peeling layer, it is possible to improve the transfer peeling property and the resolution of the heat-meltable ink layer, in addition to the above effects.

Claims (2)

[Claims] 1. A thermal transfer recording medium comprising at least one heat-meltable ink layer provided on a substrate, wherein the heat-meltable ink layer comprises an epoxy resin having a softening temperature of 50 to 180 ° C. and a higher fatty acid polyhydric alcohol ester. A thermal transfer recording medium containing an isocyanate adduct. 2. A release layer is further provided between the substrate and the hot-melt ink layer, and the wax component of the release layer is one or two selected from the group consisting of natural wax, synthetic wax and compounded wax. The above is the thermal transfer recording medium according to claim 1.