JPS6395989A - Thermal transfer recording material - Google Patents

Abstract

PURPOSE:To improve transparency while maintaining printing characteristics, by providing on a transparent base a thermal transfer ink-receiving layer comprising an organic high molecular weight material and a powder which have a substantially equal refractive index. CONSTITUTION:An organic high molecular weight material and a powder having a substantially equal refractive index are dissolved or dispersed in a solvent such as toluene and trichloroethylene to prepare a coating liquid. The coating liquid is applied to a transparent film of polyethylene terephthalate, a polycarbonate or the like to provide a thermal transfer ink-receiving layer, thereby producing a thermal transfer recording material. The difference between the refractive index of the organic high molecular weight material and that of the powder must be within + or -0.15, preferably, + or -0.05. The organic high molecular weight material may be an alkyd resin, an acrylic resin, an epoxy resin or the like, and the powder may be silica, a clay, lime, light calcium carbonate or the like.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a new recording material for thermal transfer.
The present invention relates to a recording material that has particularly excellent transparency and is suitable for use in overhead projectors (hereinafter referred to as OHP).

(Prior art) The heat melt transfer method, which is one of the heat transfer recording methods, involves superimposing a recording material such as an ink ribbon having a heat melt ink layer onto a recording material, and heating patterns such as letters and figures from above the ink ribbon. This is a method of heating a pattern and transferring heat-melting ink from an ink ribbon onto a recording material.

On the other hand, in an OHP in which light is transmitted through the sheet and characters, figures, etc. on the sheet are projected onto a screen, the heat-melt ink transfer method described above is used to create the sheet.

In this case, the conventional recording materials used as sheets for OHP have been transparent films coated with rubber-based adhesive layers or acrylic-based adhesive layers, or coated layers containing solid waxes that are highly compatible with hot-melt ink (especially 60-154096) etc. have been used and proposed.

(Problem to be solved by the invention) However, as thermal transfer printers capable of high-speed printing have been developed in recent years, the sharpness of print quality that accompanies high-speed printing has also improved on recording materials. demands or are not adequately meeting these demands.

In particular, in OHP sheets, when the ink-receiving layer is composed only of organic polymer materials as in the prior art, when using recent high-speed printing models, it is difficult to accurately transfer figures and characters from the ribbon. However, if the film is stored under load for a long period of time, blocking may occur.

On the other hand, when an ink-receiving layer is formed by dispersing powders such as silica, clay, quartz, etc. in an organic polymer material, thermal transfer ink can be accurately accepted, chipping is reduced, and blocking is prevented. Less likely to occur.

Here, the ink-receiving layer of the 0f (P sheet is required to have excellent translucency in the film state, but the transparency of the ink-receiving layer can be improved by dispersing powder in the ink-receiving layer. may be damaged.

That is, if the particle size of the powder dispersed in the ink-receiving layer is too large, the transparency will generally be poor and chipping will likely occur.

Furthermore, even if the particle size is fine, powder that forms a coating surface that reflects light extremely diffusely on the surface will also result in poor surface gloss and reduced translucency.

(Means to Solve the Problem) In response, the inventors of the present invention have attempted to improve the transparency of a recording material having an ink-receiving layer containing dispersed powder.
As a result of intensive research on the combination of powder and organic polymer material that make up the ink-receiving layer, we found that if the powder is mixed with a powder whose refractive index is close to that of the organic polymer material, the film transparency of the ink-receiving layer will be impaired. They discovered that there was no such thing, and completed this invention.

That is, in the recording material of the present invention, the thermal transfer ink-receiving layer formed on the transparent layer is composed of an organic polymer material and powder having substantially the same refractive index of light. This paper proposes a recording material suitable for thermal transfer OHP sheets.

In this invention, as the transparent base material, any transparent film such as polyethylene terephthalate, polycarbonate, polyacetal, etc. may be used, but in general, biaxially stretched polyethylene terephthalate with a film thickness of 25 to 1
For those in the range of 0.00 p and m, the film thickness may be determined as appropriate depending on the characteristics of the printer. In this embodiment, a film having a thickness of about 50 pm is used, but this is for the purpose of applying it to low-speed and high-speed printing and to various types of machines.

In this invention, organic polymer materials include alkyd resins, acrylic resins, ethylene-vinyl acetate copolymers, styrene-acrylic copolymers, styrene-maleic acid copolymers, saturated polyester resins, epoxy resins, phenolic resins, and polyurethane resins. resin, melamine resin, polyolefin, coumaron resin, xylene resin, ketone resin, etc.

Furthermore, resins obtained by adding other polymers as side chains to these resins can also be used. Furthermore, the above resins can be used alone or in combination of two or more. Also,
Among the resins listed in 1-, those having reactivity can be used in combination with known curing agents.

On the other hand, in this invention, powder means silica, clay, quartz, light calcium carbonate, colloidal calcium carbonate,
Inorganic powders such as precipitated barium sulfate, mica, talc, aluminum hydroxide, magnesium carbonate, colloidal hydrated aluminum silicate, diatomaceous earth, asbestos, glass peas, and hydrophobically treated products.

Further, benzoguanamine, phenolic resin, styrene resin, acrylic resin, polyolefin, vinylidene chloride-acrylonitrile, and organic transparent pigments which are crosslinked products thereof can also be used in this invention.

Silica has a light refractive index similar to that of the above-mentioned organic polymer material and is therefore effective in this invention, but the one that was particularly effective was silica obtained by a dry process and treated with hydrophobicity. there were. Hydrophobic treatment generally involves treating the parent wood groups on the silica surface to make them hydrophobic using a treatment agent such as dimethylcyclosilane or trimethylchlorosilane, but in this invention, silane monomers other than these are used as the treatment agent. ,
Powder surface-treated with a silane coupling agent, polysiloxanes, modified polysiloxanes, or organic polymer materials can also be used.

In this invention, organic polymer materials and powders having substantially the same light refractive index are selected from the group of organic polymer materials and powders listed in "2", and a mixture thereof is used for thermal transfer. This forms an ink-receiving layer.

In addition, in this invention, the refractive index is substantially equal.
The difference between the respective refractive indexes is within ±0.15, preferably ±
It means a range of 0.05.

According to the research of the present inventors, the various organic polymers mentioned above are selected from one or more of saturated polyester resins, styrene-acrylic copolymers, and epoxy resins, and the powders are hydrophobic silica, One or more of colloidal calcium carbonate and pentuguanamine, the refractive index of which is substantially equal in the range of 1.5 to 1.7, or the most suitable for achieving the object of the present invention. This has been shown to be favorable.

For example, the refractive index of polyester resin is 1.53 to 1.5.
7, anhydrous silica is 1.55, hydrated silica is 1.45 ~
(2), 50, and the optical refractive index of silica hydrophobized with a high substitution rate with trichlorosilane is considered to be close to that of anhydrous silica. When these silicas are blended into a polyester resin, it can be seen that the hydrophobic silica whose refractive index is most similar exhibits high transparency.

In addition, transparency is required for OHP sheets,
If the amount of powder increases in the ratio of organic polymer material to powder, the film strength will decrease and the transparency will become insufficient, so the appropriate blending ratio of powder to 100 parts by weight of organic polymer material is 800 parts by weight. parts, for example 0.5 to 800 parts by weight, preferably 1 to 300 parts by weight.

A paint-like composition is prepared by dissolving or dispersing the above organic polymeric material in a powdered solvent, and the coating composition is applied onto the transparent base material described in ``2'' and dried to form an ink-receiving layer.
Create a website sheet.

Here, the solvent may be any solvent that can be uniformly dissolved or dispersed in powder form with the organic polymer material, such as petroleum solvents such as toluene and xylene, polar solvents such as MEK and DMF, etc. ,],],,)-]] It is possible to use a chlorinated solvent such as dichloroethane, dichlorethylene, perchlorethylene, or the like.

Furthermore, when applying the above-mentioned paint-like composition to a transparent substrate, the concentration of the solid content consisting of organic polymer and powder is adjusted depending on the coating method so that an appropriate viscosity is obtained, for example, by using a reverse roll coater. If 0.1~]OWt! , 1 to 5 wt% for a bar coater (0'), and 10 to 00 wt% for a hot melt coater. The coating layer coated on the transparent substrate in this way forms a dry and stable ink-receiving layer, and the thickness of the ink-receiving layer formed in this case is 0.01 to 10 gm, preferably 0.5 to 5 ILm.
As long as it is within the range.

(Effects of the Invention) In summary, the recording material for thermal transfer according to the present invention has a composition in which an organic polymer material having substantially the same refractive index of light and powder are coated with a solvent on a transparent base material surface. Since the ink-receiving layer is formed by coating a material, it is possible to obtain a layer with extremely high transparency without adversely affecting printing characteristics, and therefore it is suitable for OHP sheets and is of practical use. It becomes a highly valuable recording material.

(Example) Examples of this invention will be shown below.

Example 1 Coating agents having the following various compounding side compositions were applied to a 50 lm thick film of polyethylene terephthalate (manufactured by Toshi Co., Ltd., Remirror T) as a base material using a bar coater #5, and dried at 130°C for 30 seconds. A thermal transfer OHP sheet was prepared, and its printing performance, haze, powder removal, and film strength were evaluated.

The evaluation criteria are as follows, and the evaluation results are shown in Table 1.

Evaluation criteria (1) Printing performance: NEC's thermal transfer Printan PC-PR
◎
, ○ indicates that both models are fairly clear and good, △ indicates that only one model is good, and × indicates that both models are defective.

(2) Haze (transparency): Judging on OHP, comparing the transparency with that of the same base material without coating, those showing the same transparency as ○, those with inferior transparency was marked as ×.

(3) Powder removal: When the coated surface was rubbed with a finger, those that did not peel off were rated as O1, those that peeled off slightly were rated as △, those that peeled off severely, and those that peeled off endlessly with continued rubbing were rated as ×.

(4) Film strength: When the coated surface was rubbed with a fingernail, the coated surface did not peel off as ○, the coated surface slightly peeled off as Δ, and the coated surface that peeled off easily as X.

Blend example (1) Epoxy resin (refractive index 1.57: Epicote 1
007 manufactured by Yuka Shell Epoxy Co., Ltd.) 100 parts by weight of phthalic anhydride 2o Tsunobenzoguanamine (refractive index 1.5: Eposter MS manufactured by Nippon Shokubai Kagaku Co., Ltd.) Concentration 2. Let it be a solution of Oz.

(2) Epoxy resin (refractive index 1.57, Epicoat 10
07 (manufactured by Yuka Shell Epoxy Co., Ltd.) 10 parts by weight Hydrophobic silica (refractive index 1.55 + HDK 200 manufactured by WACHER Co., Ltd.) 15 Horns Add MEK/toluene mixed solution to the above composition to obtain a solid content concentration of 2. Let it be a solution of Oz.

(3) Polyester resin (refractive index 1.53-1.57
10 parts by weight of hydrophobic silica (refractive index 1.55: HDK n-zo).

9iACHER) 27
Add MEK/toluene mixed solution to the above composition to make the solid content concentration 2. Let it be a solution of Oz.

(4) Epoxy resin (refractive index 1.57: Epikote 1
007 manufactured by Yuka Shell Epoxy Co., Ltd.) 100 parts by weight of colloidal calcium carbonate (Refractive index 1.65-1.68: Newlite F manufactured by Nitto Funka Co., Ltd.) 1.5r ME to the above composition
Add the K/toluene mixed solution to make the solid concentration 2. Let it be a solution of Oz.

Comparative blending example (1) Polyester resin (refractive index 1.53-1.57:
Byron 20 manufactured by Toyobo Co., Ltd.) 10 parts by weight titanium oxide (
Refractive index 2.3-2.6) 1 J ME to the above composition
K/)-toluene mixed solution is added to make a solution with a solid content concentration of 2.5z.

(2) Polyester resin (refractive index 1.53-1.57:
1089 manufactured by Toshisha Co., Ltd.) 10 parts by weight Hydrophobic silica (Refractive index 1.55: HDK H2O00WA
(manufactured by CHER)
75 Horn Add MEK/toluene mixed solution to the above composition to make a solution with a solid content concentration of 2.5z.

(3) BLANK Substrates that are not coated as is Table 1

Claims (2)

[Claims] (1) A recording material for thermal transfer, characterized in that a thermal transfer ink-receiving layer made of powder and an organic polymer material having substantially the same light refractive index is formed on a transparent base material. (2) The recording material for thermal transfer according to claim 1, wherein the blending ratio of the powder to the organic polymeric material is 8 times or less.