JPH05155138A - Thermal transfer recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] In the conventional thermal transfer recording medium, the boundary between printing and non-printing can be clarified by granulating each material of the ink layer, and the transfer layer is easily cut during transfer, resulting in a high resolution. improves. However, on the other hand, the layers were not sufficiently bound to cause scumming, and the heat sensitivity and abrasion resistance were insufficient. The present invention eliminates such defects and provides a thermal transfer recording medium having both high sensitivity and abrasion resistance. According to the present invention, in a thermal transfer recording medium having a heat-fusible ink layer containing a heat-fusible substance and a colorant on a support, the thermal diffusivity of the ink layer is 0.019 cm ² / sec or less. It is characterized by that. The heat-meltable ink layer here may be a single layer or a laminated layer.

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,
More specifically, the present invention relates to a thermal transfer recording medium that has good thermal sensitivity and abrasion resistance, and that the obtained transferred image has excellent resolution.

[0002]

2. Description of the Related Art Thermal transfer ink ribbon (thermal transfer recording medium)
Researches for improving the abrasion resistance of images created by using are carried out everywhere, and many proposals have been made.
Some of them are as follows. 1) A colorant, resin particles having a melting point or a softening point of 60 to 140 ° C., wax having a melting point or a softening point of 70 to 130 ° C., and an ink containing a water-soluble resin as a main component are used (Japanese Patent Application Laid-Open No. 6-58242).
3-45091). 2) A resin, solid solution particles containing wax as a main component, a colorant, and a binder as main components (JP-A-63-84980). 3) A laminate ink layer having a first layer containing styrene resin particles and a wax as a main component and a second layer containing a colorant, tackifying resin particles and a wax as a main component (Japanese Patent Laid-Open No. Sho 63-63). No. 84981). 4) Particles composed of a colorant and a thermoplastic resin, wax particles and a water-soluble resin (Japanese Patent Laid-Open No. 63-89383).
Publication). 5) Those having first and second ink layers containing heat-meltable fine particles (JP-A-63-51180).

[0003]

In the thermal transfer recording medium described in 1) to 4), the boundary between printing and non-printing can be made clear by granulating each material, and the transfer layer is easily cut during transfer recording. Therefore, the resolution is improved. However, the binding of the layers was insufficient, causing scumming, and the heat sensitivity and abrasion resistance were insufficient. On the other hand, although the thermal transfer recording medium described in the above 5) has improved thermal sensitivity, it cannot be said to be sufficient, and in particular, it is insufficient in terms of high-speed printing compatibility and high-density recording compatibility. Furthermore, it was insufficient in terms of wear resistance. The present invention solves the above problems, and an object of the present invention is to provide a thermal transfer recording medium having both high sensitivity and abrasion resistance.

[0004]

The present invention relates to a thermal transfer recording medium comprising a support and a heat-meltable ink layer containing a heat-meltable substance and a colorant, and the thermal diffusivity of the heat-meltable ink layer. Is 0.019 cm ² / sec or less.

The inventors of the present invention have conducted studies on a good heat-meltable ink layer from various angles and found that the thermal diffusivity of the ink layer is 0.019 cm ² / sec or less. It was confirmed that the intended purpose could be achieved. The present invention has been made on the basis thereof.

Due to this low thermal diffusivity in the present invention, the heat applied from the thermal head is difficult to escape to the transfer paper and is efficiently consumed to melt the ink layer. Therefore, printing can be performed with a small printing energy, and the thermal sensitivity is improved.

As a method for obtaining a thermal transfer recording medium having an ink layer (thermal transfer recording layer) having such a low thermal diffusivity, for example, there is a method in which the ink layer contains heat-meltable fine particles. Although the content of the heat-meltable fine particles varies depending on the particle size, it is preferably about 40% or more of the entire ink layer, but if the particle size is large, the content may be further reduced. .. FIG. 1 is a schematic cross-sectional view of an example of a thermal transfer recording medium according to the present invention, in which 1 is a support, 2 is a first ink layer, 3 is a second ink layer, and 22 is a first ink layer.
Heat-meltable fine particles contained in the ink layer, 23 is a binder in the first ink, 31 and 32 are colorants contained in the second ink layer, heat-meltable fine particles, and 33 is a binder in the second ink layer. Represents a drug. In the thermal transfer recording medium of the present invention, the binders 23 and 33 are not always essential components.

The average particle diameter of the heat fusible particles 22, 32 is preferably in the range of 0.1 to 3.00 μm. When the ink layer is composed of two layers, the average particle diameter of the heat-meltable fine particles 22, 32 in the first ink layer 2 close to the support and the second ink layer 3 thereabove is as follows: .60 to 3.00 μm Second ink layer: It is suitable to be in the range of 0.15 to 0.35 μm.

The "average particle diameter" referred to here is obtained from the particle morphology observed from the cross section of the thermal transfer recording medium. The cross section can be easily measured by a transmission electron microscope (TEM) after forming a sample by a conventional method. The particle size in this TEM observation and the particle size of the coating liquid that forms the ink layer are roughly the same. Therefore, it can be appropriately set according to the average particle size in the coating liquid state. The particle size of the coating liquid is LA-70 manufactured by Horiba Ltd. by the laser diffusion method.
It can be easily measured with 0 or the like. Further, the thermal diffusivity can be easily measured by PIT-RI manufactured by Vacuum Riko.

An organic lubricant is used as the main component of the heat-meltable fine particles 22 and 32. The organic lubricant is added in order to improve the fusion property of the heat-meltable fine particles 22, 32 due to the heat during printing.
It is important that the melt viscosity is less than 60 cps at 100 ° C. When it is 60 cps or more, the fusion is insufficient, the boundary between the continuous layer portion of the first ink layer 2 and the non-printed portion becomes unclear, and the transferability deteriorates. Also, the second
The ink layer 3 has poor adhesion to the receiving paper. Therefore, the thermal sensitivity is lowered, and an image void occurs when printing at high speed or when printing on low smooth paper.

In addition to the above conditions, in order to improve the abrasion resistance of the transferred image, the penetration at 40 ° C. is 4.0.
The following is desirable. If the penetration is more than 4.0, sufficient mechanical strength cannot be obtained, and friction causes image distortion. The penetration degree at 40 ° C. is defined because frictional heat rises from room temperature when the image is rubbed.

As the organic lubricant used as the heat-meltable fine particles 22 and 32, natural waxes such as carnauba wax, candelilla wax, rice wax, castor wax and monta wax: 12-hydroxystearic acid derivative: modified polyethylene: α-Olefin: maleic anhydride derivative: lanolin wax derivative: amides such as aliphatic amide and aromatic amide. In particular, the use of carnauba wax is preferable in terms of hardness and endothermic properties.

In the present invention, the thermoplastic resin may be appropriately mixed and fused with the organic lubricant and used in a solid solution state. These thermoplastic resins have a melting point or softening point of 70.
Various resins at 140 ° C can be used. Specific examples of this include acrylic resin, methacrylic resin, styrene resin, vinyl acetate resin, vinyl chloride resin, vinylidene chloride resin, petroleum resin, terpene resin, olefin resin, polyester resin, polyacetal resin or copolymers thereof. I can give you. Melting point or softening point is 70
If the temperature is lower than ℃, the abrasion resistance of the transferred image in a high temperature environment (30 to 60 ℃) is deteriorated, and if it is higher than 140 ℃, high energy is required for thermal transfer recording, the recording speed becomes slow, and the life of the thermal head becomes long. Will be shortened and other problems will occur.

An unvulcanized rubber which can impart a high binding property and flexibility in a small amount can be added to the ink layer as a part or all of the binding agent used if necessary. As those unvulcanized rubbers, polyisoprene, polybutadiene,
Styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, butyl rubber, silicone rubber, fluorine rubber, urethane rubber and the like, preferably polyisoprene, polybutadiene, ethylene propylene rubber, butyl rubber and nitrile rubber are mentioned. Note that these preferable rubbers have a melting point of 60 ° C to 200 ° C. In addition, E
You may use thermoplastic resins, such as VA and EEA. Further, various oil agents can be used as a softening agent for the layer.

When the first ink layer 2 is composed of an unvulcanized rubber and a heat-meltable fine particle, the ratio of each is 3 to 3.
It is desirable that the range is 0/97 to 70, preferably 5 to 20/95 to 80. When the content of the organic lubricant is 3% or less, a sufficient binding function, that is, the low-temperature ink layer is dropped off and the abrasion resistance is deteriorated. On the other hand, if it exceeds 30%, the lubricity of the surface of the transferred image is deteriorated so that the effect of improving the wear resistance cannot be obtained, and the releasability thereof is deteriorated to lower the thermal sensitivity.

The thickness of the first ink layer 2 is usually 0.5 to 5 μm.
m, preferably 1.0 to 2.0 μm. 0.
If the thickness is less than 5 μm, the above effect cannot be obtained, and the transferability to low smooth paper deteriorates. On the other hand, when the thickness exceeds 5 μm, transfer failure occurs at low energy or high speed printing. In addition, a binder resin (low melting point resin) used in the second ink layer may be appropriately added to the first ink layer, and the preparation thereof may be carried out by using an ordinary organic solvent dispersion liquid, water dispersion liquid or emulsion liquid. Prepared by the coating used. More preferably, an emulsion having a stable particle size is used.

Next, the second ink layer will be described. This second ink layer 3 contains a colorant and a heat-fusible substance as main components as in the conventional case, and if necessary, a low melting point resin (binder resin).
It is composed of

The colorant is appropriately selected from conventionally known dyes and pigments. Specific examples of the organic lubricant are as described above. Low melting point resins include polyamide-based, polyester-based, polyurethane-based, vinyl chloride-based, cellulose-based, petroleum-based, styrene-based, butyral-based, phenol-based resins, ethylene-vinyl acetate copolymers and ethylene-acrylic resins. Resin, terpene resin, etc. are mentioned.

The ratio of each of these components is as follows: colorant / organic lubricant /
Resins = 5 to 50/30 to 90/5 to 50 (weight) are suitable. Similarly to the case of the first ink layer, the method of forming the heat-fusible ink layer also employs coating with an organic solvent solution, an aqueous dispersion, or an emulsion liquid. Therefore, it is preferable to use emulsified heat-meltable fine particles for the second ink layer as well as the first ink layer. The thickness of the ink layer is usually 0.8 to 5 μm, preferably 1 to 2.5 μm. If the thickness is less than 0.8 μm, the optical density is insufficient and voids are generated when transferred to paper with low smoothness, and if it exceeds 5.0 μm, transfer failure occurs at high energy printing at low energy.

Further, in the first and second ink layers, in addition to the above components, a plasticizer such as fatty acid ester, glycol ester, phosphoric acid ester, epoxidized linseed oil, and a softener such as mineral oil, animal oil, vegetable oil, A small amount (30% or less) of oily substances such as liquid paraffin and silicone oil can be added. In the case of the first ink layer 2, maximum 8%
Up to a colorant can be added.

As the support 1 for supporting the single-layer ink layer of the present invention or the first and second ink layers as shown in FIG. 1, polyester, polycarbonate, triacetyl cellulose, polyamide, polyimide or the like can be used. A heat-resistant plastic film, cellophane, sulfuric acid paper, condenser paper, etc. can be used, and if necessary, silicone resin, fluororesin, polyimide resin, epoxy resin, etc. can be used on one side (the side in contact with the thermal head) of these supports. You may provide a heat resistant layer, such as a phenol resin, a melamine resin, and a cellulosic resin. Further, an intermediate layer may be provided between the single ink layer or the first ink layer 2 and the support 1 to improve the adhesive force.

[0022]

EXAMPLES The present invention will be described below with reference to examples. All percentages and parts are by weight.

Example 1 Polyethylene terephthalate (PE having a thickness of about 4.5 μm)
T) A coating liquid of the following ink layer components was applied on the film using a wire bar so that the thickness after drying was about 3.0 μm, and dried with hot air at 60 ° C. to form an ink layer. (Ink layer component) Carnauba wax emulsion (solid content 30%) 250 parts (Carnauba wax 27 parts and nonionic emulsifier (HLB14) 3.0 parts were mixed and melted at 90 ° C., and hot water 70.0 parts was added thereto. The mixture was stirred and pre-emulsified with a disperser, then emulsified with a high-pressure homogenizer and rapidly cooled with water to obtain an emulsion with an average particle size of about 1.5 μm. Ethylene-vinyl acetate copolymer latex (solid) 30%) 33 parts (Sumikaflex 410, manufactured by Sumitomo Chemical Co., Ltd.) Carbon black aqueous dispersion (solid content 20%) 75 parts Surfactant (Reodol TW-S120) 1 part Water 61 parts Methanol 80 parts

Example 2 A polyethylene terephthalate film having a thickness of about 4.5 μm was coated with a coating liquid of the following first ink layer component by a wire bar so that the thickness after drying was about 1.5 μm,
The first ink layer was formed by drying with warm air at 60 ° C. (First ink layer component) Carnauba wax 7: candelilla wax = 7: 3 mixed wax emulsion (solid content 30%) (average particle size: about 1.95 µm) 155 parts Styrene-butadiene rubber latex (solid content) 50%) (JSR0561, manufactured by Japan Synthetic Rubber Co., Ltd.) 7 parts Water 88 parts Further, a wire bar is further applied thereon so that the thickness of the coating liquid containing the following second ink layer component is about 1.4 μm after drying. It was applied and dried at 70 ° C. to form a second ink layer. (Second Ink Layer Component) Carnauba Wax Emulsion (Solid Content 30%) 250 parts (Except that the anionic emulsifier (HLB13) was used instead of the emulsifier of Example 1, an average particle size of about 0 was obtained. .224 μm emulsion) Ethylene-vinyl acetate copolymer latex (solid content 30%) 33 parts (Sumikaflex410 Sumitomo Chemical Co., Ltd.) Carbon black aqueous dispersion (solid content 20%) 75 parts Surfactant (Reodol TW-S120) 1 part water 61 parts methanol 80 parts

Example 3 A thermal transfer recording medium was prepared in exactly the same manner as in Example 2 except that the first ink layer component of Example 2 was replaced with the following first ink layer component. (First Ink Layer Component) The same carnauba wax emulsion as used in Example 1 (solid content 30%) (average particle size: about 1.04 μm) 150 parts butadiene rubber latex (solid content 50%) (JSR # 0700) , Made by Japan Synthetic Rubber Co., Ltd.) 10 parts water 90 parts

Example 4 A thermal transfer recording medium was obtained in exactly the same manner as in Example 3 except that the second ink layer component of Example 3 was replaced with the following second ink layer component. (Second ink layer component) Carnauba wax emulsion (average particle size of about 0.29 μm) (solid content 30%) 183 parts Candelilla wax emulsion (average particle size of about 0.18 μm) (solid content 30%) 67 parts Ethylene -Vinyl acetate copolymer latex (solid content 30%) (Sumikaflex 401, manufactured by Sumitomo Chemical Co., Ltd.) 33 parts Carbon black aqueous dispersion (solid content 20%) 75 parts Surfactant (Reodol TW-S120) 1 part Water 61 parts 80 parts of methanol

Comparative Example 1 Drying was performed at 85 ° C. in the process of forming the first ink layer of Example 2.
A thermal transfer recording medium was prepared in exactly the same manner as in Example 1 except that hot air was used. The first ink layer became translucent due to the fusion of the particles.

Comparative Example 2 The following ink layer components were coated on the same support as in Example 1 by the hot melt coating method to a thickness of about 3.0 μm to obtain a thermal transfer recording medium. (Ink layer component) Carnauba wax 40 parts Paraffin wax 32 parts Carbon black 15 parts Mineral oil 3 parts Ethylene-vinyl acetate resin (Smitate KE10, Sumitomo Chemical Co., Ltd.) 10 parts

Regarding these six types of thermal transfer recording media, recycled paper having a Bekk smoothness of about 50 seconds [paper source (manufactured by Ricoh Co.)]
And a light-weight coated paper (New Age 70, manufactured by Kanzaki Paper Co., Ltd.) for about 400 seconds and a thermal transfer printer (Atec) for barcodes.
h company: SWEDOT196), 20 ° C 60%
Printing was performed under standard conditions of RH by applying standard energy. The results are shown in Table 1. In Comparative Examples 1 and 2, the occurrence of ink layer flaking was observed at 0 ° C.

[Table 1] Transferability: It was evaluated by whether or not the bar code part was clearly printed. ○: The barcode part is clearly printed and transferred. X: The bar code portion is unclearly printed, and some bar codes are not partially transferred. Bar code read rate: Laser check on the bar code part LC-2811 (Symbol Technology)
les. Inc. (Manufactured by the company), the laser was randomly scanned every 100 times, and the number of times the laser could be read was expressed as a percentage. That is, a reading rate of 100% is 10
This means that the laser could be scanned 0 times and read 100 times, indicating that the bar code was clear. Abrasion resistance (cardboard test): 4c on bar code
A m × 7 cm square cardboard plate was applied, and a load of 1 kgf was applied, and the same place was rubbed 50 times with a love tester for evaluation. 〇… The barcode part is almost clean and can be read with a barcode scanner without any problems. ×: The bar code part is very dirty and difficult to read with a bar code scanner.

[0030]

In the thermal transfer recording medium of the present invention, the thermal diffusivity of the ink layer is set to 0.019 cm ² / sec or less, whereby the thermal sensitivity and high-speed printing compatibility can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a thermal transfer recording medium according to the present invention.

[Explanation of symbols]

 1 Support 2 First Ink Layer 3 Second Ink Layer 22,32 Thermal Melting Fine Particles 23,33 Binder 31 Colorant

Claims (5)

[Claims] 1. A thermal transfer recording medium comprising a support and a heat-meltable ink layer containing a heat-meltable substance and a colorant, wherein the heat-meltable ink layer has a thermal diffusivity of 0.019 cm ^2.
/ Sec or less, a thermal transfer recording medium. 2. The thermal transfer recording medium according to claim 1, wherein the heat-fusible ink layer is composed of a multilayer including a layer containing a colorant and a layer not containing the colorant. 3. A colorless first ink layer in which the heat-meltable ink layer is on the support side and contains a heat-meltable substance as a main component, and the heat-meltable substance and coloring are on the first ink layer. The thermal transfer recording medium according to claim 1, wherein the thermal transfer recording medium comprises a laminate with a second ink layer containing an agent as a main component. 4. The thermal transfer recording medium according to claim 1, 2 or 3, wherein the heat fusible substance is in a fine particle state. 5. The heat fusible substance of the first ink layer is fine particles having an average particle size of 0.60 to 3.00 μm, and the heat fusible substance of the second ink layer is 0.15 to 0. .35μ
The thermal transfer recording medium according to claim 3 or 4, which is fine particles of m.