JPS63178081A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To enhance printing density, to improve printing quality and to perform printing many times, by incorporating an ethylenic copolymer in a heat- meltable ink layer. CONSTITUTION:In a thermal transfer recording medium wherein a heat-meltable ink layer is provided on a film base material, an ethylenic copolymer is contained in the heat-meltable ink layer. As the ethylenic copolymer, one having number average mol.wt. of 1X10<3>-1X10<4> is pref. The ethylenic copolymer means a copolymer of ethylene and other vinyl monomer. As the other vinyl monomer, a vinyl monomer having a polar group having strong compatibility with respect to a base material film composed of polyester polyimide is pref. from the aspect of the adhesiveness between the base material film and the ink layer. As the vinyl monomer, vinyl acetate, acrylic acid or the like are designated. The compounding amount of the ethylenic copolymer is desirably 10-20wt.% of the total amount of the solid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel thermal transfer recording medium that can be used many times and is used in thermal transfer recording type printers and facsimile machines.

[Conventional technology]

Conventionally, as a thermal transfer recording medium intended for multiple uses, Japanese Patent Application Laid-Open No. 54-68253-1 and Japanese Patent Application Laid-Open No. 55-1
0557 '9, JP 57-185191, JP 57-185192, JP 57-1
No. 85193, JP-A-57-185194,
JP-A-57-185195 discloses a microporous polymer structure impregnated with heat-melting ink, and JP-A-56-8984 and JP-A-57-160 disclose
No. 691 and Japanese Unexamined Patent Publication No. 58-18329T disclose inorganic fine particle matrices impregnated with heat-melting ink. However, in these thermal transfer recording media, since the resin or fine particles forming the matrix are non-transferable, the amount of ink transferred per unit volume is small, resulting in insufficient print density.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal transfer recording medium that can be printed many times and that can produce prints with relatively high density.

[Means for solving problems]

As a result of extensive studies, the inventors of the present invention found that ink components include low melting point resins, colorants, and additives such as softeners, petroleum resins, surfactants, and lubricants that are added as necessary. discovered a new fact that a thermal transfer recording medium made by adding a relatively low molecular weight ethylene copolymer can be printed many times and can obtain high-density prints, and has developed the present invention. It was completed.

That is, the present invention provides a heat-sensitive transfer recording medium comprising a heat-melt ink layer provided on a film substrate, wherein the heat-melt ink layer contains an ethylene copolymer. It is.

Since the thermal transfer recording medium of the present invention contains a relatively low molecular weight ethylene copolymer in the ink layer, the ink has good affinity with the paper to be transferred, and the ink layer easily causes cohesive failure, resulting in a large number of Since multiple printing is possible and the amount of transfer per one printing is relatively large, high-density printing is possible. Further, in the present invention, by using an ethylene-based copolymer having a polar group that has a strong affinity with the base film, a heat-sensitive transfer recording medium with strong adhesive force between the ink layer and the base film can be obtained.

The present invention will be explained in detail below.

The ethylene copolymer used in the present invention is
It refers to a copolymer obtained by a copolymerization reaction of ethylene and other vinyl monomers. Other vinyl monomers include
From the viewpoint of adhesiveness between the base film and the ink layer, a vinyl monomer having a polar group having a strong affinity for the base film made of polyester polyimide or the like is preferred. Specific examples of such vinyl monomers include vinyl formate, vinyl acetate, vinyl butyrate, acrylic acid, vinyl acrylate, methyl acrylate, ethyl acrylate, methacrylic acid, vinyl methacrylate, methyl methacrylate, and methacrylate. Ethyl acid, acrylonitrile, acrylamide, methyl vinyl ketone, 2-oxyvinylacetic acid, vinyl ethyl ether, vinyl acetic acid, vinyl glycolic acid, N-vinylmethylamine, N-vinylethylamine,
Examples include, but are not limited to, 3-vinyl acrylic acid and vinyl isocyanate.

Further, when using an ethylene copolymer using a vinyl ester as a vinyl monomer, a copolymer in which all or a portion of the ester groups are saponified may be used.

The copolymer composition ratio of the ethylene copolymer is not particularly limited, but preferably contains 5% by weight or more of one unit of a vinyl monomer having a polar group, more preferably 10% by weight or more.
It is desirable that the content be at least % by weight.

The number average molecular weight of this ethylene-based copolymer is not particularly limited, but it is preferable that the average molecular weight is in the range of lXl0'' to 1x103.Multiple printability is related to the ink melt viscosity, and high melt viscosity The number of prints tends to increase as the number average molecular weight of the ethylene copolymer is less than 1 x 103, the viscosity of the ink is low and sufficient multi-printability may not be obtained; On the other hand, if the melt viscosity is too high, even if printing is possible multiple times, the non-transferability of the copolymer may increase and the printing density may decrease, as seen in the prior art.

Furthermore, the above-mentioned ethylene copolymers can be used not only alone, but also in combination with a plurality of types.

Components other than the ethylene copolymer used in the ink component of the heat-melting ink layer used in the present invention include a low melting point resin, a colorant, and a softener, petroleum resin, surfactant, There are additives such as lubricants.

The low melting point resin used in the present invention is not particularly limited as long as it is commonly used, such as paraffin wax, carnauba wax, ceresin wax, oxidized wax, microcrystalline wax, montan wax, polyethylene wax, and oxidized polyethylene wax. , castor wax, ester wax, synthetic wax, etc.

The colorant used in the present invention is not particularly limited as long as it is a commonly used organic pigment, inorganic pigment, dye, or other substance capable of coloring and recording, such as carbon black, basic base dye, neozapon dye, etc. , Zapon dye, lake red, alkali blue navy blue, crystal violet lactone, magnetic iron oxide, etc.

The additives to be added as necessary are not particularly limited as long as they are commonly used, and for example, suitable ones can be selected and used from the following. In other words, softeners include organic acid esters such as phthalate esters and adipic esters, phosphate esters, epoxies, other plasticizers, oily substances such as mineral oil, vegetable oil, animal oil, and castor oil. Liquid rubber and petrolatum, as well as other materials that are liquid or semi-solid at room temperature, are used. As the petroleum resin, aliphatic or aromatic homopolymers or copolymers are used. The surfactant is appropriately selected from anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. As the lubricant, polyhydric alcohol, higher fatty acid, fluorocarbon, fatty acid amide lubricant, ester lubricant, etc. are used.

The composition ratio of the ink layer of the present invention varies depending on other factors such as the characteristics of the thermal recording printer head to which the thermal transfer recording medium is applied and the recording speed, and is not particularly limited.
In the total solid content of the ink layer, it is desirable to contain the low melting point resin in an amount of 10 to 80% by weight, preferably 20 to 50% by weight, and the colorant in an amount of 5 to 30% by weight, preferably 10 to 20% by weight.

In addition, softeners, petroleum resins, surfactants, and lubricants to be blended as necessary are based on 100 parts by weight of the total solid content.
It is desirable to use 0 to 10 parts by weight, preferably 0 to 5 parts by weight, respectively. In addition, the amount of the ethylene copolymer is not particularly limited, but is 5 to 50% of the total solid content.
It is desirable that the weight be %, preferably 10 to 20% by weight. If the amount of ethylene copolymer is less than 5% by weight,
Multiple transfers may become impossible, while 50% by weight
If it exceeds 100%, inconveniences such as a decrease in ink coating properties and a decrease in print density may occur.

The base film used in the present invention is not particularly limited as long as it has heat resistance and high affinity with the ethylene copolymer contained in the ink layer. For example, specifically, resin films such as polyester and polyimide are preferably used.

The thickness of the base film can be generally applied in the range of 3 to 20 μm, preferably in the range of 4 to 10 μm. Thin ones less than 3 μm are easy to tear, and
If it exceeds μm, excessive applied energy is required, which is not practical. The structure of the back surface of the base film is arbitrary, and an anti-sticking layer or the like may be provided.

Methods for coating the ink of the present invention on a base film to form a heat-melt ink layer include true melt coating, or solvent coating in which each ink component is appropriately dissolved or dispersed in a solvent. Any method may be used, such as gravure coating method, roll coating method,
Known techniques such as the wire barcode method can be applied.

Although the thickness of the ink layer is not limited, it is preferably 3 to 30 μm, more preferably 5 to 15 μm. If it is less than 3 μm, the print density will decrease from the second time onwards,
If it exceeds 30 μm, excessive applied energy will be required.

[Effect]

The thermal transfer recording medium according to the present invention contains a resin component with high adhesiveness to the base film in the ink component, and since the number average molecular weight of the resin component is relatively low, it has low affinity with the transfer paper. good. Therefore, during ink transfer,
It is presumed that the ink layer easily causes cohesive failure, making it possible to print at high density and multiple times.

〔Example〕

The present invention will be explained below with reference to examples, but the scope of the present invention is not limited in any way by these examples.

Example 1 Low melting point resin Paraffin wax 40 parts by weight Ester wax 30 parts by weight Carnauba wax 15 parts by weight Pigment Carbon black 15 parts by weight A mixture of the above components was dispersed for 4 hours using a sand grinder while heating to 120°C, and then ethylene was added. - Vinyl acetate copolymer (number average molecular weight: 3°000, vinyl acetate content: 1
4% by weight) was added to 85 parts by weight of the above mixture, and the mixture was again dispersed for 1 hour. The ink thus obtained was applied onto a polyester film having a thickness of 6 μm to form an ink layer having a thickness of 10 μm. This thermal transfer recording medium was printed on a serial type thermal printer with a 0.
Solid black printing was performed with an applied energy of 4 mJ/dat. The transfer paper used was high quality paper with a Beck smoothness of 250s. As a result, a high-density, high-quality printed body was obtained with no decrease in print density up to 5 times. Figure 1 shows the results graphically. Print density refers to the ratio of incident light (Io) to reflected light (1), and is -1og I/I. It is expressed as

Example 2 Low melting point resin Paraffin wax 33 parts by weight Ester wax 30 parts by weight Carnauba wax 20 parts by weight Softener Vaseline 2 parts by weight Pigment
Carbon black 15 parts by weight The mixture consisting of the above components was dispersed in a sand grinder for 4 hours while being heated to 120°C, and then ethylene-acrylic acid copolymer (number average molecular weight = 3.500, acid value: 120 (acrylic acid 1 part of 15 fflff was added to 85 parts by weight of the above mixture, and the mixture was again dispersed for 1 hour. The ink thus obtained was applied onto a polyester film having a thickness of 6 μm to form an ink layer having a thickness of 10 μm. This thermal transfer recording medium was subjected to a printing test in the same manner as in Example 1. As a result, a high-density, high-quality printed body with no decrease in print density was obtained up to 5 times. Figure 1 shows the results.

Example 3 In Example 1, an ethylene-vinyl acetate copolymer having a different molecular weight (number average molecular weight: 30°000, vinyl acetate content: 14% by weight) was used instead of the ethylene-vinyl acetate copolymer of the ink component. A heat-sensitive transfer recording medium that was completely the same except for the addition of the above was prepared, and the same printing test as in Example 1 was conducted. As a result, although the print density was generally somewhat low up to the fifth time, there was no decrease in print density. Figure 1 shows the results.

Example 4 In Example 2, instead of the ethylene-acrylic acid copolymer of the ink component, an ethylene-acrylic acid copolymer having a different molecular weight (number average molecular t: 32°000, acid value: 120(
A completely similar thermal transfer recording medium was prepared except that acrylic acid content (weight %) was added, and the same printing test as in Example 1 was conducted. As a result, although the print density was generally somewhat low up to the fifth time, there was no decrease in print density. No. -1
The results are shown in the figure.

Example 5 In Example 1, an ethylene-vinyl acetate copolymer having a different molecular weight (number average molecular t 15°000, vinyl acetate content: 28% by weight) was added instead of the ethylene-vinyl acetate copolymer as an ink component. Otherwise, a completely similar thermal transfer recording medium was prepared, and the same printing test as in Example 1 was conducted.

As a result, although the print density was generally somewhat low up to the fifth time, there was no decrease in print density. Figure 1 shows the results.

Comparative Example 1 In Example 1, polyethylene (number average molecule it's
, 000) was prepared, and the same printing test as in Example 1 was conducted. As a result, although the density at the first printing was high, the density from the second printing onwards was low, making it impossible to print multiple times. Figure 1 shows the results.

〔Effect of the invention〕

According to the present invention, print density is high and print quality is good.
A thermal transfer recording medium that can be printed multiple times is obtained, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the number of times of printing and print density when printing was performed using the thermal transfer recording media obtained in Examples 1 to 5 and Comparative Example 1. (h) Agent: Patent Attorney Akira Hirose 7'-・7.

Claims (1)

[Scope of Claims] 1. A heat-sensitive transfer recording medium comprising a heat-melt ink layer provided on a film base material, wherein the heat-melt ink layer contains an ethylene copolymer. 2. Ethylene copolymer is 1 x 10^3 to 1 x 10^
The thermal transfer recording medium according to claim 1, which has a number average molecular weight of 4. 3. The thermal transfer recording medium according to claim 1 or 2, wherein the ethylene copolymer is a copolymer of ethylene and a monomer having a polar group that has strong affinity with the base film.