JPH082131A - Thermal transfer image receiving material and white coating composition therefor - Google Patents

Abstract

PURPOSE:To provide a white coating compsn. for a thermal transfer image receiving material reduced in the degree of discoloration at a high temp. and excellent in chemical resistance. CONSTITUTION:A white coating compsn. contains white pigment and an org. binder as essential components and used in the formation of the image receiving layer of a thermal transfer image receiving material. The org. binder is composed of a phenoxy resin or the phenoxy resin and a saturated polyester resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white coating composition used for forming an image receiving layer of a thermal transfer image receptor and a thermal transfer image receptor using the same.

[0002]

2. Description of the Related Art In recent years, management of parts and products in manufacturing processes in manufacturing plants,
For printing barcodes used for product management in the distribution field, product management in the field of use, etc.
Bar code printers and label printers that use thermal transfer recording materials have come into use.

Some articles to which such a bar code is attached are exposed to a high temperature after attaching the bar code. For example, heat treatment is performed at about 180 ° C. in the printed wiring board manufacturing process and at about 250 ° C. in the semiconductor inspection process.

As an image receiving body for forming an image on a bar code printer or a label printer using a thermal transfer recording material, there is known one having a white image receiving layer comprising a white pigment and an organic binder formed on a film substrate. Has been.

However, when a label having an image such as a bar code formed on such an image receptor is used for an article exposed to a high temperature as described above, the white image receiving layer is discolored by the high temperature heating and the reflectance is increased. However, there is a problem that the printed image cannot be read because the image quality is greatly reduced. Further, when the label is used in a factory or the like, there are problems that chemicals such as acid and alkali are applied, the image receiving layer is corroded, the color is discolored, and the printed image comes off.

In view of the above points, the present invention is a thermal transfer image receptor which is excellent in heat resistance and gives an image receiving layer excellent in chemical resistance and less in the degree of discoloration when heated at a high temperature of 150 to 280 ° C., for example. An object of the present invention is to provide a white coating composition for use and a thermal transfer image receptor using the same.

[0007]

The present invention is a white coating composition comprising a white pigment and an organic binder as essential components, which is used for forming an image receiving layer of a thermal transfer image receptor, wherein the organic binder is a phenoxy resin, or The present invention relates to a white coating composition (first invention) for a thermal transfer image receptor, which comprises a phenoxy resin and a saturated polyester resin.

The present invention further relates to the first invention, wherein the weight ratio of the phenoxy resin to the saturated polyester resin is 100:
It relates to a white coating composition for a thermal transfer image receptor, which is characterized in that it is 0 to 5:95.

The present invention further relates to the white coating composition for a thermal transfer image receptor according to the first invention, which further comprises a titanate coupling agent.

The present invention further comprises an image-receiving layer containing a white pigment and an organic binder as essential components on one side of the substrate,
A thermal transfer image receptor having an adhesive layer on the other surface, wherein the organic binder comprises a phenoxy resin, or a phenoxy resin and a saturated polyester resin (second invention).

[0011]

Functions and Examples The white coating composition for a thermal transfer image receptor of the present invention is characterized by using a phenoxy resin or a mixture of a phenoxy resin and a saturated polyester resin as its organic binder.

By using such a specific resin as the organic binder, the image receiving layer obtained is from 150 to 2
Even when heated at a high temperature of about 80 ° C, the degree of discoloration is small,
Since the reflectance does not decrease so much, the reading of the printed image is not hindered. Also, it has excellent chemical resistance to acids and alkalis and is hardly attacked by these chemicals.

When a material other than the resin of the present invention is used as the organic binder, for example, a polyamide resin is used,
When it is heated to about 250 ° C., the white image-receiving layer becomes brown and the reflectance is significantly lowered, so that it cannot be used.

When the white image-receiving layer containing various organic binders is heat-treated at 250 ° C. for 1 hour, the decrease rate of the reflectance after the heat treatment with respect to the reflectance before the heat treatment is as follows.

Organic Binder Reflectance Reduction Rate (%) Polyamide Resin 70.8 Phenoxy Resin 19.7 Phenoxy Resin / Saturated Polyester Resin 13.3 (6.3 / 93.7 Weight Ratio) Saturated Polyester Resin 6.8 Saturated Although the polyester resin has excellent heat resistance as described above, it is inferior in chemical resistance. Therefore, when a saturated polyester resin is used, it is used in combination with a phenoxy resin. In the present invention, the saturated polyester resin may be mixed with a small amount of a phenoxy resin to obtain, for example, saturated polyester resin /
It has been found that even a mixture of phenoxy resin = 95/5 weight ratio improves the chemical resistance.

The phenoxy resin used in the present invention has the following formula (I):

[0017]

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It is a resin composed of repeating units represented by:

The saturated polyester resin used in the present invention is produced by polycondensation of a dibasic acid and a dihydric alcohol (including a compound having a phenolic hydroxyl group). Dibasic acids include phthalic acid, phthalic anhydride, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, aromatic dicarboxylic acids such as benzenediacetic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid. And one or more of aliphatic dicarboxylic acids such as suberic acid, azelaic acid and sebacic acid. Examples of the dihydric alcohol include aliphatic diols such as ethylene glycol, propylene glycol, 1,4-butanediol, hexanediol, decanediol, dodecanediol, hexadecanediol, diethylene glycol, triethylene glycol and polyethylene glycol, and benzenedimethanol. One or more of aromatic diols such as and dihydric phenols such as hydroquinone. Among these polyester resins, those in which the dibasic acid has a mixture of terephthalic acid and isophthalic acid as a main component and the dihydric alcohol has ethylene glycol as a main component are particularly preferable.

In the present invention, the weight ratio of the phenoxy resin to the saturated polyester resin is preferably 100: 0 to 5:95. If the proportion of the saturated polyester resin is higher than the above range, the chemical resistance becomes poor, which is not preferable.

A mixture of a phenoxy resin and a saturated polyester resin is preferable, and a mixture of a phenoxy resin and a saturated polyester resin in a weight ratio of 95: 5 to 5:95 is particularly preferable in terms of excellent heat resistance and chemical resistance. preferable.

The white pigment used in the present invention may be one or more of titanium oxide, calcium carbonate, talc and the like.

In the white coating composition of the present invention, the organic binder content is preferably 30 to 70% by weight and the white pigment content is 30 to 70% by weight based on the total solid content. When the ratio of the organic binder is higher than the above range,
That is, if the proportion of the white pigment is less than the above range, the hiding property of the receiving layer image is deteriorated, and as a result, the reflectance tends to be lowered, while if the proportion of the organic binder is less than the above range, that is, the white pigment When the ratio is more than the above range, the coating property tends to deteriorate and the fixing property of the printed image tends to deteriorate.

In the white coating composition of the present invention, it is preferable to add a titanate coupling agent in addition to the organic binder and the white pigment.

By incorporating the titanate coupling agent, the adhesion between the white pigment and the organic binder is improved, and the heat resistance and chemical resistance are further improved. The reason is not necessarily clear, but the titanate coupling agent chemically bonds with the OH group on the surface of the white pigment, while it binds with the organic binder by molecular entanglement, and the white pigment and the organic binder It is presumed that the material behaves as a uniform composite material, which improves heat resistance and chemical resistance.

The titanate coupling agent is represented by the following formula (II):

[0027]

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Pyrophosphate type compounds such as bis (dioctylpyrophosphate) oxyacetate titanate and isopropylbis (dioctylpyrophosphate) titanate represented by are preferred. In addition, carboxy type such as isopropyl triisostearoyl titanate, isopropyl trioctanoyl titanate,
Tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl phosphite)
A phosphite type such as titanate can also be used.

The titanate coupling agent is 0.2 to 5% by weight, especially 0.2 to 1% by weight, based on the white pigment.
It is preferred to add. If the amount of the titanate coupling agent used is less than the above range, the heat resistance and chemical resistance improving effects are not sufficiently exerted, while if it is more than the above range, the amount of unreacted titanate coupling agent increases, and The effect of improving the properties and chemical resistance tends to decrease. The white pigment may be previously treated with a titanate coupling agent, or may be added at the time of preparing the coating composition.

The white coating composition of the present invention can be prepared by dissolving and dispersing the above components in an appropriate organic solvent. Examples of the organic solvent include aromatic solvents such as toluene, benzene and xylene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, cellosolve solvents such as methyl cellosolve and ethyl cellosolve, and alcoholic solvents such as isopropyl alcohol. Or they can be mixed and used.

An image receptor for thermal transfer can be obtained by coating the above white coating composition on an appropriate substrate and drying it to form an image receiving layer.

The coating amount of the image-receiving layer (coating amount after drying, the same applies hereinafter) is suitably about 10 to 50 g / m ² .

The above-mentioned substrate is preferably one which can withstand heating at 150 to 280 ° C. As such a substrate, a polyimide film, an aramid film, a polyarylate film, a polyethersulfone film, a polysulfone film, a polyphenylene sulfide film, a polyphenylene sulfide film, Examples thereof include ether ether ketone film and polyetherimide film. The thickness of the substrate is 25-100μ
m is suitable.

The image receptor may be used as it is, but it is preferable to form an adhesive layer on the surface opposite to the image receptor layer to simplify the laminating operation. As the pressure-sensitive adhesive used for forming such a pressure-sensitive adhesive layer, one having good heat resistance is preferable, and for example, ones such as silicone resin type and acrylic resin type can be used. The suitable amount of the adhesive layer applied is about ²⁰ to 50 g / m ² .

The image receptor is usually used in a state in which a release sheet material is laminated on the adhesive layer side and is wound in a roll shape.

The image-receiving body of the present invention is usually made of a thermal transfer recording material and is used as labels by forming an image on the image-receiving layer with a thermal transfer printer such as a bar code printer or a label printer equipped with a thermal head. This is used by being attached to a transfer target.

As the thermal transfer recording material, a material capable of forming a heat resistant image is suitably used. For example, those disclosed in Japanese Patent Application No. 6-76169 previously filed by the present applicant can be preferably used. This is a thermal transfer recording material comprising a base material and a heat-meltable ink layer comprising a vehicle and a colorant, wherein the vehicle is a heat-meltable material and a polyphenylene sulfide resin, a polyether sulfone resin, a polysulfone resin. , Wholly aromatic polyimide resin, polyamideimide resin, polyetherimide resin,
At least one selected from the group consisting of polyarylate resin, polyetheretherketone resin and fluororesin
It is a thermal transfer recording material comprising a heat-resistant resin of one kind.

As the thermal printing means, a thermal transfer printer using a laser beam, a thermal pen, a thermal stamp, etc. can be used in addition to the above.

Next, the present invention will be described with reference to examples.

Examples 1 to 4 and Comparative Example 1 A polyimide film having a thickness of 76 μm was coated with an adhesive layer of 27 g / m ² of a silicone resin adhesive on one side, and Table 1 was formed on the opposite side. The white coating composition shown in (3) was applied and dried to form an image receiving layer having a coating amount of 28 g / m ² to obtain a thermal transfer image receptor.

The heat resistance and chemical resistance of each of the obtained thermal transfer image receivers were examined as follows. The results are shown in Table 1.

(1) Heat resistance Each thermal transfer image receptor was placed in a heat oven and heat-treated at 250 ° C. for 1 hour, and the reflectance before and after the heat treatment was measured by a reflection density measuring device (Macbeth RD914). Further, the rate of decrease of the reflectance after the heat treatment with respect to the reflectance before the heat treatment was obtained.

(2) Chemical resistance Each thermal transfer image receptor was immersed in diluted hydrochloric acid (concentration 10% by weight) or diluted sodium hydroxide solution (concentration 10% by weight) at 25 ° C. for 24 hours.
After soaking for a time, the surface was visually observed and the chemical resistance was evaluated according to the following criteria. 4 ... Not invaded at all. 3 ... Slightly invaded. 2 ... Slightly invaded. 1 ... Remarkably invaded.

[0044]

[Table 1]

Further, about 27 mg (in terms of solid content) of the white coating composition used in Examples 1 and 4 was weighed in an aluminum pan with an electronic balance, heat-treated in a hot oven at 250 ° C. for 12 hours, and then weighed. Is measured
The residual ratio (% by weight) shown by the following formula was determined. The larger the value of the residual ratio, the less the decomposition by heat and the better the heat resistance.

Residual ratio = (weight after heat treatment / weight before heat treatment) × 100 The results are shown in Table 2.

[0047]

[Table 2]

[0048]

The thermal transfer image receptor having an image receiving layer formed from the white coating composition of the present invention is, for example, 15
A label used for a transfer target that is exposed to the high temperature as described above and has a low degree of discoloration even when heated at a high temperature of about 0 to 280 ° C and has excellent chemical resistance. Useful for creating classes.

Claims (4)

[Claims] 1. A method for forming an image receiving layer of a thermal transfer image receptor,
A white coating composition comprising a white pigment and an organic binder as essential components, wherein the organic binder comprises a phenoxy resin, or a phenoxy resin and a saturated polyester resin, a white coating composition for a thermal transfer image receptor. 2. The white coating composition for a thermal transfer image receptor according to claim 1, wherein the weight ratio of the phenoxy resin to the saturated polyester resin is 100: 0 to 5:95. 3. The white coating composition for a thermal transfer image receptor according to claim 1, further comprising a titanate coupling agent. 4. A thermal transfer image receptor in which a white pigment and an image receiving layer containing an organic binder as essential components are provided on one side of the substrate, and an adhesive layer is provided on the other side, wherein the organic binder is a phenoxy resin. Alternatively, a thermal transfer image receptor comprising a phenoxy resin and a saturated polyester resin.