JPS63236683A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material wherein a part other than a developed color image becomes transparent after development treatment, by providing a thermal color forming layer consisting of a colorless color forming substance, a coupler forming a color at the time of heating, a dispersant therefor and a colorless binder to one surface of a transparent support. CONSTITUTION:As a colorless color forming substance, a xanthene type compound, a triarylmethane type compound, a thiazine type compound or the like are used and, as a colorless coupler, a phenolic compound, an aromatic carboxylic acid derivative and a multivalent metal salt thereof are designated. Further, as a colorless binder, a water-soluble compound such as methyl cellulose, an alkali salt of an iso(diiso)butylene/maleic anhydride copolymer or the like or a water-insoluble emulsion of a styrene/butadiene/acrylic acid copolymer is designated. As a transparent support, papers, a plastic sheet and a composite material thereof are used and the thickness thereof is pref. 10-100mum in usual.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to heat-sensitive recording materials. More specifically, the present invention relates to a heat-sensitive recording material in which a colored image formed on a transparent support can be read using transmitted light.

The conventional technology is g.A heat-sensitive recording material using a colorless color-forming substance and a color-developing substance that can cause the color-forming substance to develop color when heated is disclosed in Japanese Patent Publication No. 43-4.
No. 160, Special Publication No. 14039/1973, etc., and this has recently been published in the field of facsimile, combiator, etc.
It is widely used in the fields of printers such as calculators, recorders for medical measurement, automatic ticket vending machines, thermal recording labels, etc.

In order to make images easier to read, these heat-sensitive recording materials are coated with a colorless color-forming substance on a support such as opaque paper, synthetic paper, or film, and a color-developing property that allows the color-forming substance to develop color when heated. The substance is the main component, and additives such as sensitizers, binders, and lubricants are added to form a coating liquid, which is then applied. A thermal printer with a built-in thermal head or the like is used to color the heat-sensitive recording material.

Further, other uses of heat-sensitive recording materials include those described on pages 223 to 225 of ``Printing Engineering ■, Signal Conversion and Transmission Theory'' (Kyoritsu Publishing Co., Ltd.). That is, first of all,
The main ingredients are a colorless color-forming substance and a color-developing substance capable of coloring the color-forming substance when heated, and further additives such as a sensitizer, binder, and lubricant are added to form a coating liquid. A heat-sensitive recording sheet is prepared by coating substantially transparent paper, plastic film, etc., and then the coated surface of this sheet is brought into close contact with the printed surface of the document, and the surface opposite to the coated surface of the heat-sensitive recording sheet ( There is a method of irradiating infrared rays from the back side) to form a colored image on the coated surface. In this case, the printed area of the document absorbs more infrared rays than the non-printed area and becomes high temperature, and this high temperature printed area heats the coated surface of the thermal recording sheet that is in close contact with the printed area, causing the printed area to heat up. On the other hand, it forms an image that is a mirror image, and the resulting colored image can be seen from the other side of the transparent support.

The support used in such a method must be substantially transparent and have a sufficiently smooth surface to ensure faithful heat conduction from the document surface and Compared to thermal paper, it has sufficient color development sensitivity and color density, and has less density unevenness, and in particular, it is possible to obtain images with intermediate density and gradation. Furthermore, since the colored image is viewed from the side of the transparent support, it is rich in gloss and appears to be of high quality, and it also has excellent water resistance, heat and humidity resistance, plasticizer resistance, etc.

By the way, the above-mentioned heat-sensitive recording materials can be used even if the support is opaque, such as opaque paper, synthetic paper, or film, or transparent, such as transparent paper or transparent plastic film. The heat-sensitive coloring layer formed is an opaque layer due to the sensitizer and lubricant that are usually added to it.

Problems to be Solved by the Invention As a new use of copy sheets, for example, an OHP (overhead projector) is used to enlarge and project a copy using transmitted light. The parts other than the image must be substantially transparent, and currently, copy sheets for enlarged projection are obtained by copying onto transparent glass sheets or the like using an electronic copying machine. If the heat-sensitive recording material is transparent after the color development process except for the color image, the color development material can be used as it is as a copying sheet for enlarged projection using transmitted light by OHP or the like. Therefore, there is a need for a heat-sensitive recording material whose portions other than the colored image are substantially transparent after coloring treatment.

Means for Solving the Problems The present inventors have achieved the present invention as a result of extensive research to solve the above-mentioned problems. Namely, the present invention is based on a substantially transparent support. A heat-sensitive coloring layer consisting only of a color-forming substance that is substantially colorless, a color-developing substance that can develop color when heated, a dispersant that can disperse these, and a binder that is substantially colorless is provided on one side. Provided is a heat-sensitive recording material characterized by:

The heat-sensitive recording material of the present invention will be explained in detail.

In the present invention, xanthine-based compounds, triarylmethane-based compounds, spiropyran-based compounds, diphenylmethane-based compounds, thiazine-based compounds, etc. are used as the substantially colorless color-forming substances, and specific examples thereof include 2- Anilino-3-methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-
6-(methylunclo\quinruamino)-fluorane,
2-anilino-3-methyl-6-(ethylimpentylamino)-fluoran, 2-anilino-3-methyl-6
-butylaminofluorane, 2-(p-chloroanil)
/ ) -3-Methyl-6-dinithylaminofluorane, 2- (o-fluoroanilino)-6-dinithylaminofluorane, 2- (o-fluoroanilino)-6
-sibutylaminofluorane, 2-anilino-3-methyl-6-piperidinofluorane, 2-ethoxyethylamino-3-chloro-6-ethylaminofluorane, 2
-3,3'-bis-(p-dimethylaminophenyl) as a triarylmethane compound such as -chloro-3-methyl-6-dinithylaminofluorane, -6-dimethylaminophthalide, 3-(p- dimethylaminophenyl)
-3-(1,2-dimethylamineindol-3-yl)phthalide, 3-methyl-3-spiro-dinaphthopyran as a subiropyran compound, 1.3.3-)rifthyl-6'-nitro8' -7 toxic biro (indoline-2,2'-benzobilane), diphenylmethane compounds such as 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucoauramine, etc., thiazine compounds such as nopenzoyl leuco Examples include methylene blue and p-nitrobenzylleucomethylene blue. These color-forming substances may be used alone or in combination. Further, specific examples of substantially colorless color developing substances include p-octylphenol, 1,1
-bis-(p-hydroxyphenyl]propane, 2.2
-bis(p-hydroxyphenyl)-propane, 1,1
-bis(p-hydroxyphenyl)-cyclohexyl,
4. Phenolic compounds such as 4-sulfonyldiphenol, bis-(3-allyl-4-hydroxyphenyl)sulfone, hephthal p-hydroxybenzoate, ethyl p-hydroxybenzoate, dimethyl 4-hydroxyphthalate, Examples include aromatic carboxylic acid derivatives such as 3,5-di-tert-butylsalicylic acid, and examples of carboxylic acids include their polyvalent metal salts.

Furthermore, specific examples of colorless binders include methyl cellulose,
Methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch and its derivatives, casein, gelatin, alkali salts of styrene-maleic anhydride copolymers, iso( or diiso)
Water-soluble products such as alkali salts of styrene-maleic anhydride copolymer, polyacetate vinyl chloride/vinyl acetate copolymer, polystyrene, polyacrylic acid ester, polyurethane, styrene/butadiene/acrylic acid copolymer, etc. Examples include water-insoluble emulsions.

Substantially transparent supports used in the present invention include papers such as glassine paper and tracing paper; cellophane;
Polyester, polyvinyl chloride, polypropylene, cellulose acid, polyethylene,
Plastic sheets such as polystyrene and polycarbonate, and composites of these materials are used. Furthermore, these supports may be subjected to corona discharge treatment or provided with an underlayer of gelatin, nitrocellulose, terpene phenol resin, etc. in order to improve adhesion to the coating solution. The thickness of the support is usually 10-100μ, more preferably 30-50μ.

The heat-sensitive recording material of the present invention is produced by separately grinding the substantially colorless color-forming substance and the color-developing substance as described above in an aqueous medium using a colorless dispersant such as polyvinyl alcohol or sodium polyarylate. Micronization treatment is performed using a ball mill or the like to form particles of 01 to 5μ, preferably 1 to 3μ.
μ and then mixed with the above-mentioned substantially colorless binder to form a coating solution, which is applied onto the above-mentioned support with a dry weight of 5 to 20 g/d, preferably 7 to 12 g/d. It is obtained by coating and then drying.

In the heat-sensitive recording material of the present invention, a protective film made of a colorless, transparent resin film or the like may be provided on the heat-sensitive coloring layer.

When copying using the heat-sensitive recording material obtained in the present invention, the light source used is an incandescent tungsten bulb, a xenon lamp, a high-pressure mercury lamp, an iodine lamp, an infrared semiconductor laser, an infrared light emitting diode, etc., preferably 7
A light source having an emission wavelength showing a peak in the infrared region of 00 to 15 QQ nm is used.

Since the heat-sensitive recording material of the present invention is substantially transparent, it can be used, for example, for an overhead projector after copying an original, or for a display panel.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

In the examples, "parts" represent "parts by weight."

Example 1 Solutions [A] and [B] were prepared by separately dispersing mixtures having the following compositions using a sand grinder so that the average particle size was 1 to 3 μm.

[:AE solution (color former) [B] solution (color developer) [C] solution (binder) A 50% SBR latex bottom solution was prepared, and the solid content when dried was deposited on a polyester film with a thickness of about 50μ. It was coated to give a weight of 10 g β and dried to obtain a heat-sensitive recording material of the present invention.

Example 2 A thermosensitive recording material (thermal recording sheet) was prepared in the same manner as in Example 1.
After that, a compound mainly composed of colloidal hydrated aluminum silicate and a copolymer of ammonium methacrylate-ethyl acrylate-methyl methacrylate were added to the heat-sensitive coloring layer of this heat-sensitive recording sheet in a solid weight ratio of 1:5. A protective coat was applied to the mixed coating liquid so that the dry thickness was 2 μm, and the mixture was dried to obtain a heat-sensitive recording material with a protective coat.

Example 3 In Example 1, a 25% PVA aqueous solution was used instead of the 50% SBR latex of cc'3a, and (A) liquid: [
A heat-sensitive recording material was prepared in the same manner as in Example 1 except that liquid B: liquid [C] was mixed in a ratio of 8:46:46, and then the same as in Example 2 was applied onto the heat-sensitive coloring layer of this heat-sensitive recording material. By providing a protective layer, a heat-sensitive recording sheet with a protective coat was obtained.

Examples 4 to 8 Heat-sensitive recording materials of the present invention were obtained in the same manner as in Example 1, but using binders and supports shown in Table 1.

Comparative Example 1 A thermosensitive recording sheet was obtained in the same manner as in Example 1, except that 6% of calcium carbonate was added as a filler to the thermosensitive coloring layer forming liquid.

Comparative Example 2 A thermosensitive recording sheet was obtained in the same manner as in Example 1 except that opaque high-quality paper was used instead of the polyester film.

A coloring test and a transparency test were carried out using the present invention and the heat-sensitive recording sheet for prints obtained as described above. The results are shown in Table 2.

Table 2 [Color density] Xenon lamp (lighting voltage 250V, charging voltage 37V)
Using a Macbeth reflection densitometer (rLI)-914, measure the color density when printing with a light source (xenon lamp) applied to the other side of the heat-sensitive recording sheet, with the printed surface of the original facing the coated surface of the heat-sensitive recording sheet using 11 has been confirmed.

〔transparency〕

Transparency is expressed by the following formula, and the larger the value, the better the transparency.

A: Reflection density (
Macbeth value) Application Example The thermosensitive recording material of the present invention obtained in Example 1 (Made) The thermosensitive coloring layer surface of the recording sheet 9 was brought into close contact with the original, and the Cannon was applied from the opposite side of the thermosensitive recording sheet to the surface on which the thermosensitive coloring layer was provided. Irradiate light with a lamp.

A copy of the original was created as a colored image on the thermosensitive coloring layer. When this colored heat-sensitive recording sheet was used for enlarged projection using an overhang, a clear enlarged colored image was projected on the screen.

Effects of the Invention A substantially colorless and transparent heat-sensitive recording sheet has been changed, and after coloring (recording) treatment, coloring (recording) 1-7
By applying transmitted light to the colored (recorded) sheet, the 9 images could be read easily. It was also possible to perform enlarged projection by irradiating this colored (recorded) sheet with transmitted light.

Claims (1)

[Claims] 1. A substantially colorless color-forming substance, a color-developing substance capable of developing color when heated, a dispersing agent capable of dispersing these, and a substantially colorless binder on one side of a substantially transparent support. A heat-sensitive recording material characterized by being provided with a heat-sensitive coloring layer consisting of