JP2000141924A - Thermal transfer recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal transfer recording medium in which a static electricity is suppressed even without using an antistatic agent without conveying fault caused by the electricity, by specifying a surface resistance value, and coating at least entirety or part of one layer of a recording layer side with a coating liquid using water. SOLUTION: At least one layer of a thermal transfer recording layer side is provided by an aqueous coating process. A volume intrinsic resistance is controlled by improving its water content by the process. A solution is regulated by the process by suitably selecting from a process for dropping a hot water containing an emulsifier on a hot melted heat meltable material, and a process for previously incorporating the emulsifier in the hot melted material, and dropping hot water on the material to form an emulsion. In this case, thicknesses of the respective layers are set so that the transfer recording layer is 0.5 to 4.0 μm, an intermediate layer is 0.05 to 2.0 μm and a surface layer is 0.1 to 2.0 μm, thereby setting a surface resistance value when measured from a surface of the recording layer side to 2×1010 to 9×1010 Ω.

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 a thermal transfer recording medium capable of obtaining a high quality printed image on a receiving paper even when used in a printer equipped with a thermal head having a line edge type.

[0002]

2. Description of the Related Art In general, a thermal transfer recording medium is provided with a thermal transfer recording layer mainly composed of a heat-fusible substance, a resin and a colorant on the surface of a support directly or via an intermediate layer. Stick prevention layer (back layer) on the back of the support
Is provided. Recently, the thermal transfer recording medium and a recording material (such as receiving paper) have been used to perform recording with a line-edge type thermal head.

[0003] In this end face line type thermal head, the pressure is increased because the area of the contact portion between the thermal transfer recording medium and the thermal head is generally small, and the thermal transfer recording medium is slid at a high pressure. The static electricity is more likely to be generated on the thermal transfer recording medium than in the case of recording by the method. Then, there is a problem that the heat generating resistance portion or the resistance portion protection film of the thermal head is easily damaged by the static electricity. There is also a problem that a circuit element near the heating resistor is destroyed. Furthermore, although not limited to the end face line type thermal head, there has also been a problem that winding and unsatisfactory conveyance may occur during winding and unwinding of the thermal transfer recording medium. In the conventional thermal head, the generation of static electricity was not so large as to be a problem.

[0004] For these reasons, many thermal transfer recording media have been proposed to prevent the generation of static electricity. For example, (1) a conductive colorant or a filler is contained in the thermal transfer recording layer (Japanese Patent Publication No. 5-82317, JP-A-2-63791).
), (2) providing an antistatic layer on one or both sides of the support (JP-A-2-3377, JP-A-2-1824901)
No.). In addition, there has been proposed (3) a thermal transfer recording medium in which the moisture content of the thermal transfer recording layer (including the release layer) is 0.3 to 4.0% by weight to improve the transferability (Japanese Patent Laid-Open No. 5-32062). issue).

However, the conductive colorant or filler of the above (1) is expensive and, in addition, the conductive colorant or the like (powder) must be dispersed in a large amount in the binder of the thermal transfer recording layer to record. Easy to lose characteristics. When the antistatic layer to which the surfactant or the like of the above (2) is added is provided on the back surface of the support, the thermal head becomes contaminated during recording, and
When an antistatic layer is provided between the support and the thermal transfer recording layer, there are disadvantages that the support and the thermal transfer recording layer are corroded and the storage stability of the recording medium is deteriorated. In addition, according to the use of the thermal transfer recording medium (3) in which the moisture content of the thermal transfer recording layer is specified, an image excellent in transferability without dropping on either rough paper or synthetic paper can be obtained. However, although rare, a transport failure may occur.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal transfer recording medium which does not cause a conveyance failure or the like due to static electricity even when a printer equipped with an end line type thermal head is used. Another object of the present invention is to provide a thermal transfer recording medium capable of suppressing generation of static electricity without using an antistatic agent. Still another object of the present invention is to provide a thermal transfer recording medium capable of obtaining a high quality printed image on a recording material.

[0007]

Means for Solving the Problems The present inventors have found a desired range for controlling the volume resistivity by improving the water content by water-based coating and preventing the occurrence of electrostatic breakdown. The present invention has been made based on this.

According to the present invention, first, in a thermal transfer recording medium provided with at least a thermal transfer recording layer on a support,
The surface resistance of this recording medium measured from the surface on the thermal transfer recording layer side is in the range of 2 × 10 ^{10 to} 9 × 10 ¹³ Ω, and at least one layer on the thermal transfer recording layer side contains all or all of the solvent. A thermal transfer recording medium characterized by being formed by applying a coating liquid partially using water is provided.

Second, the first thermal transfer recording medium is provided, wherein an intermediate layer is provided between the thermal transfer recording layer and the support.

Thirdly, there is provided the above-mentioned first or second thermal transfer recording medium, wherein a back prevention layer is provided on the side of the support opposite to the thermal transfer recording layer.

Fourth, the thermal transfer recording medium according to any one of the first to third aspects, wherein the moisture content of the entire thermal transfer recording medium is 0.5 to 4% by weight.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The “surface resistance” can be determined as follows. That is, from FIG. 1, the surface resistivity can be defined as the resistance per unit area, and like the volume resistivity, the surface resistivity is the resistance per 1 u of the material. The surface resistivity is obtained by the following equation (1).

(Equation 1) Where ρ _s surface resistivity [Ω] c Perimeter [mm] d Gap [mm] R _s Measured surface resistance [Ω] HP 16008B Taking into account the resistance cell, equation (1) becomes equation (2) below.

(Equation 2) The inner diameter of D ₁ electrode [mm] outer diameter of D ₂ electrode [mm]

In the thermal transfer recording medium of the present invention, a thermal transfer recording layer is provided on a support directly or via an intermediate layer, and between the support and the intermediate layer or between the support and the thermal transfer recording layer as necessary. An under layer having a primer function or a heat insulating function is provided on the heat transfer recording layer, and if necessary, a surface layer is provided on the thermal transfer recording layer to improve the adhesiveness to the recording material. Is provided with a heat-resistant lubricating layer (back layer). Therefore, in the present invention, the layer on the thermal transfer recording layer side means a thermal transfer recording layer, an intermediate layer, an under layer, and a surface layer.

The intermediate layer contains a wax and a resin as main components to improve the adhesiveness of the ink to the support of the thermal transfer recording layer, that is, the adhesiveness is high at normal temperature and narrow under heat printing. The material is melted at a temperature range so as to easily adhere to the recording material, and a conventionally known material can be used as it is for the formation.

That is, the waxes include carnauba wax, candelilla wax, rice wax, montan wax, shellac, beeswax, wood wax, ozokerite, and other natural waxes, paraffin, oxidized paraffin, and the like.
Synthetic waxes such as microcrystalline, polyethylene, polyethylene oxide, ceresin, and kazole; higher fatty acids such as palmitic acid, stearic acid, behenic acid, montanic acid, and lanolinic acid; and monohydric alcohols, alcohol esters, and amides thereof. .

The resin includes acrylic resin, polyester, polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, urethane, cellulose, vinyl chloride-vinyl acetate copolymer, petroleum resin, rosin resin and derivatives thereof. , Polyamide and the like. One or more of these may be appropriately selected, but the melting point or softening point thereof is preferably in the range of 50 to 120 ° C.

In order to improve the adhesion between the intermediate layer and the support or to provide the intermediate layer with elasticity, the intermediate layer may be made of an isoprene rubber, a styrene-butadiene rubber, a butadiene rubber, a nitrile rubber, or the like. Preferably, a vulcanized rubber is added.

The thermal transfer recording layer is formed mainly of a colorant, waxes and resin. As the coloring agent, all those known in the art, such as carbon black, organic or inorganic pigments, and various dyes, can be used.
The materials mentioned for the intermediate layer can be used as they are for waxes and resins.

As the support, a known film or paper may be used, and a polyester film such as polyethylene terephthalate or a plastic film such as polycarbonate, triacetylcellulose, polyimide or polyamide is also used.

The back layer protects the base material (support) from high temperature when heat is applied by the end face line type thermal head and ensures transportability. Silicone oil, silicone rubber, silicone resin, polyimide, epoxy resin,
A resin such as a phenol resin, a melamine resin, or cellulose may be applied in a thin film form.

The under layer and the surface area provided as needed in the present invention can be provided by a method known in this category. In the present invention, each layer except the back layer, that is, at least one layer on the side of the thermal transfer recording layer needs to be provided by an aqueous coating method. The formation of the layer not based on the aqueous coating method can be performed by a known method such as a hot melt coating method or a solvent coating method.

In the aqueous coating method of the present invention, it is necessary to prepare a solution for coating. To this end, (1) hot water containing an emulsifier is added dropwise to a hot-melt material that has been heated and melted. Alternatively, an emulsifier is previously contained in a heat-meltable heat-fusible material, and hot water is dropped into the emulsifier to form an emulsion, or (2) emulsion polymerization of a monomer (monomer of the heat-meltable material) in water, For example, turbid polymerization is performed, or (3) the heat-fusible material is modified with a hydrophilic functional group and solubilized or dispersed in water. These methods may be appropriately selected according to the material.

The thickness of each layer of the thermal transfer recording medium is 0.5 to 4.0 μm for the thermal transfer recording layer, 0.2 to 3.0 μm for the intermediate layer,
The under layer is preferably 0.05 to 2.0 μm, and the surface layer is preferably 0.1 to 2.0 μm.
μm is appropriate.

The water drying of the water-coated layer is usually carried out by hot air, which is carried out when the total water content of the thermal transfer recording medium is 0.5 to 4.0% by weight, more preferably 1.0 to 3.0% by weight.
Drying is preferably performed so as to be in the range of weight%. 0.
At less than 5% by weight, the antistatic effect is small, and conversely 4.0% by weight
In the above case, electrostatic destruction occurs, and blocking (sticking of the surface due to fusion) when the thermal transfer recording medium is wound into a roll is unpreferable.

The moisture content of the thermal transfer recording medium can be measured by a Karl Fischer potential titration method, an infrared moisture meter, a heat loss measurement method, or the like.

[0026]

Next, the present invention will be described in detail with reference to examples. Here, both parts and% are based on weight.

Examples 1 to 3 and Comparative Examples 1 to 4 A polyethylene terephthalate film (PET film) having a thickness of 4.5 μm was prepared as a support, and silicone rubber (Toray Dow) was provided on the side opposite to the side on which the thermal transfer recording layer was coated. Corning Co., Ltd., SD7226) with a dry adhesion of 0.05 g
/ M ² to provide a heat-resistant lubricating layer.

(Preparation of Intermediate Layer Coating Solution) Intermediate Layer A: Carnauba wax 8 parts Candelilla wax 5 parts Polyethylene resin (manufactured by Toyobo Co., Byron 650) 2 parts Methyl ethyl ketone 60 parts Toluene 25 parts The above materials are used in a solvent. The mixture was heated, melted and cooled, and dispersed by a ball mill for 12 hours to obtain an intermediate layer coating liquid A.

Intermediate layer B: Carnauba wax emulsion (solid content 30%, average particle size 0.3 μm) 27 parts Candelilla wax emulsion (solid content 30%, average particle size 0.4 μm) 16 parts Polyester resin aqueous dispersion Liquid (30% solid content, manufactured by Toyobo Co., Ltd., Vironal MD1330) 7 parts Water 40 parts Methanol 10 parts The above materials were mixed to obtain an intermediate layer coating liquid B.

(Preparation of Coating Solution for Thermal Transfer Recording Layer) Ink Layer A: Carbon Black 3 parts Candelilla wax 6 parts Ethylene-vinyl acetate copolymer (melt index 10, vinyl acetate content 28%) 6 parts Toluene 85 parts or more The material was heated and melted in a solvent, precipitated by cooling, and dispersed by a ball mill for 12 hours to obtain a thermal transfer recording layer coating liquid A.

(Preparation of Coating Solution for Thermal Transfer Recording Layer) Ink Layer B: Carbon black aqueous dispersion (solid content: 20%, carbon black 19 parts and polyacrylic acid 1 part water 80 parts dispersed by ball mill) 15 Part Candelilla wax emulsion (solid content 30%, average particle size 0.4 μm) 20 parts Ethylene-vinyl acetate copolymer (emulsion polymerized product, solid content 40%, vinyl acetate content 60%) 15 parts Methanol 10 parts Water 40 Parts The above materials were mixed to obtain a thermal transfer recording layer coating liquid B.

(Preparation of Thermal Transfer Recording Medium) Using the above coating liquids, changing the combination and drying time, coating the intermediate layer and the thermal transfer recording layer in this order on the previously prepared support. Was prepared. The coating liquid after drying of each layer intermediate layer 1.5 g / m ^2, were unified in the thermal transfer recording layer 1.2 g / m ^2. Drying was performed using a hot air circulation type dryer, and the wind speed was 5 m /
Seconds.

Printing is performed on these thermal transfer recording media,
In addition, static electricity measurement and moisture measurement were performed. The results are shown in Table 1. Table 1 also shows the printing and measurement conditions.

(1) Printing conditions: Thermal head: End-face thin film line type thermal head (manufactured by ROHM, 8 dots / m
m) Platen pressure: 200 g / cm Transfer receiving body: Cast coat label Printing speed: 10 inches / sec

(2) Static electricity measurement condition: 2c in which the probe type surface voltmeter is brought into contact with the thermal head and the thermal transfer recording medium
m Installed in two places, the ribbon winding section before and after printing,
A grounded metal member was brought into contact with the back surface, and measurement was performed at a position facing the metal member.

(3) Moisture measurement conditions: Measurement ribbon is 10c
Cut to 50m width x 50cm length and oven at 120 ℃
Heating for minutes, and the weight loss before and after heating was determined (n
= 3).

(4) Measurement of surface resistance: High resistance meter 4329A manufactured by Hewlett-Packard Japan
And resistance cell 16008A, applied voltage 10
At 0 V, the measurement was performed on the entire recording medium from the thermal transfer recording layer side.
(Conversion method is surface resistance = 18.8Rs (Rs; reading).
At that time, the guard electrode facing the main electrode was set to GND (0 V). )

[0038]

[Table 1]

As a result of the suppression of the static electricity to 1.0 kV or less, the heating resistance of the end face line type thermal head does not break down, and the transportability of the thermal transfer recording medium in the printer is good. Further, in Examples 1 to 3 in which the water content and the surface resistance were within the range of the present invention, the amount of static electricity was suppressed low. On the other hand, in Comparative Examples 1 to 3, static electricity was high, and winding occurred at the winding portion of the ribbon. Some destruction of the heating resistor was also observed.
In addition, there was a sense at the time of unwinding. In Comparative Example 4, although the static electricity was low, the moisture content was too high, and blocking due to sticking occurred. Then, it was found that a thermal transfer recording medium having a desired water content of 0.5 to 4.0% by weight can be obtained by applying one of the layers with an aqueous coating and optimizing the drying time.

[0040]

According to the first aspect of the present invention, it is possible to form a transfer image of good quality without causing transport failure due to electrostatic breakdown, discharge, or static electricity. According to the invention of claim 2, a clearer transfer image can be obtained. According to the third aspect, the movement of the thermal transfer recording medium with respect to the thermal head is smooth.
According to the fourth aspect of the present invention, the winding and winding of the thermal transfer recording medium are performed favorably.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for a method for determining surface resistance or surface resistivity.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuyoshi Inamura 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2C068 AA06 BB08 BB18 BB22 BC01 BC12 BC30 BC33 2H111 AA01 BA07 BA08 BA61 BA65 BA68 DA02

Claims (4)

[Claims] 1. A thermal transfer recording medium having at least a thermal transfer recording layer provided on a support, wherein the recording medium has a surface resistance of 2 × 10 2 when measured from the surface on the thermal transfer recording layer side.
It is in the range of ^{10 to} 9 × 10 ¹³ Ω, and at least one layer on the side of the thermal transfer recording layer is formed by applying a coating liquid using water for all or a part of the solvent. Thermal transfer recording medium. 2. The thermal transfer recording medium according to claim 1, wherein an intermediate layer is provided between the thermal transfer recording layer and the support. 3. The thermal transfer recording medium according to claim 1, wherein a back layer is provided on a side of the support opposite to the thermal transfer recording layer. 4. The thermal transfer recording medium has a water content of 0.5 to 0.5.
4. The thermal transfer recording medium according to claim 1, wherein the content is 4% by weight.