JPH029684A - Thermal recording sheet - Google Patents

Abstract

PURPOSE:To perform writing having sharp hue using a felt pen of oily ink by incorporating not only a compound represented by a specific formula as an org. coupler but also p-benzyl biphenyl in a thermal color forming layer. CONSTITUTION:A compound represented by formula I (wherein R is a 1-3C alkyl group) is used as an org. coupler. As a basic leuco dye to be used, there is no special limit but a triphenylmethane compound, a fluorane compound, an azaphthalide compound and a fluorene compound are pref. and, other than the coupler and the dye, p-benzyl biphenyl is used as a sensitizer. The use amounts of the org. coupler, the sensitizer and a filler being other component per one pts. of the basis leuco dye are respectively 1-8pts., 3-10pts. and 1-20pts. in usual and a binder is properly used in an amount of 10-25% by wt. of the total solid.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a highly sensitive heat-sensitive recording sheet with improved writing properties using oil-based ink.

(Prior art) In general, heat-sensitive recording sheets are produced by grinding and dispersing a colorless or light-colored basic colorless dye and an organic color developer such as a phenolic substance into fine particles, and then mixing them together, filling them with a binder, etc. agent, sensitivity enhancer.

A coating liquid obtained by adding lubricants and other auxiliary agents.It is coated on a support such as synthetic paper, film, or plastic. Color recording is obtained through a chemical reaction.

These thermal recording sheets are used as measurement recorders, computer terminal printers, and facsimiles.

It is applied to a wide range of fields such as automatic ticket vending machines and barcode labels, but these recording devices are diversifying.

As performance increases, the quality required for heat-sensitive recording sheets also becomes more sophisticated.For example, as recording speeds increase, it becomes possible to obtain clear colored images with high density even with minute thermal energy. On the other hand, there is a demand for heat-sensitive recording sheets that have excellent storage properties such as light resistance, weather resistance, and oil resistance.

On the other hand, in JP-A-59-79793, JP-A-60-127190, JP-A-61-22987, and JP-A-1+2-273885,
Heat-sensitive recording materials using bis(hydroxyphenyl)acetic acids and having excellent heat response, weather resistance, smoothness, water resistance, oil resistance, plasticizer resistance, etc. have been proposed.

(To be solved by the invention!!B) However, the thermal responsiveness of these thermosensitive recording materials is still not satisfactory.

Furthermore, as thermal recording paper has recently become popular, there are many opportunities to add notes using oil-based ink, Feltben, after thermal recording. However, since oil-based inks contain various organic solvents, for example, when writing on black color-forming thermal recording paper using oil-based red ink, the coloring caused by the solvent, which is the original color of the thermal recording paper, occurs. A problem arises in that pure red writing cannot be obtained because the black color and the red color of the red ink are mixed. This applies not only to red but also to other colors.

An object of the present invention is to solve these problems and provide a highly sensitive heat-sensitive recording sheet on which writing can be done in clear colors using an oil-based felt ink of any color.

(Means for Solving the Problems) The present invention provides the following formula (
By using the compound represented by I) and containing p-benzylbiphenyl, the above problems are solved at once.

ooR [In the formula, R represents an alkyl group having 1 to 3 carbon atoms] Specific examples of the compound represented by formula (I) include the following.

Methyl bis(4-hydroxyphenyl)acetate
Hydroxyphenyl) ethyl acetate bis(4-hydroxyphenyl) n-propyl acetate bis(4-hydroxyphenyl) isopropyl acetate The basic colorless dyes used in the present invention are not particularly limited, but include triphenylmethane, fluoran, etc. Preferred are azaphthalide-based, azaphthalide-based, fluorene-based, etc., and specific examples of these are shown below.

Triphenylmethane leuco dye 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalitonofluorane 3-(N-ethyl-P-tolubuino)-6-methyl-
7-anilinofluoran 3-(N-ethyl-N-ynamylamino)-6-methyl-7-ayutsunofluoran 3-diethylamitsu 6-methyl-7-(o,p-dimethylanilino) Fluoran 3-pyrrolidino-6-methyl-7-anilinofluoran 3-piperidino-6-methyl-7-anilinofluoran 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-anilinofluoran 3-diethylamino-7-(m-trifluoromethylanilino)fluoran 3-N-n-dibutylamino-6-methyl-7-anilinofluoran 3-N-n-dibutyl Amino-7-(0-chloroanilino)fluoran 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran 3-dibutylamino-6-methyl-7-(o, p -dimethylanilino)fluoran 3-(N-methyl-N-protoruamino)-6-methyl-7-ayurifluoran 3-diethylamino-6-chloro-7-anilinofluoran 3-dibutylamino-7 -(o-Chloranilino)fluoran 3-diethylamino-7-(0-chloroanilino)fluoran 3-diethylamino-6-methyl-chlorofluoran 3-diethylamino-6-methyl-fluoran 3-cyclohexylamino-6-chlorofluoran 3-diethylamino-benzo[al-fluorane azaphthalide-based leucochemical 3-(4-diethylamino-2-ethoxyphenyl)-
3-(1-ethyl-2-methylindol-3-yl)
-4-Azaphthalide 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-7-azaphthalide 3-(4-diethylamino-2-ethoxyphenyl)- 3-(1-octyl-2-methylindol-3-yl)-4-azaphthalide 3- (4-N-cyclohexyl-N-methylamino-
2-methoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalidefluorene-based leuco material 3.6,6°-tris(dimethylamino)spiro[fluorene-9, 3°-phthalide] 3.6,6°-tris(diethylamino)spiro[fluorene-9,3°-phthalide] These dyes can be used alone or in combination of two or more.

In the present invention, p-benzylbiphenyl is used in addition to the above color developer and dye. Although these have a function as a sensitizer, they are extremely effective for the first objective of the present invention.

In the present invention, as an image stabilizer.

4.4'-butylidene (6-t-butyl-3-methylphenol) 2.2'-di-t-butyl-5,5'-dimethyl-4,
4'-Sulfonyldiphenol 1.1.3-)-lith(2-methyl-4-hydroxy-
5-cyclohexylphenyl)butane t,t,3-)
-Lis(2-methyl-4-hydroxy-5-t-butylphenyl)butane or the like may also be added.

The binder used in the present invention has a degree of polymerization of 200.
~1900 fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, Styrene-maleic anhydride copolymers, styrene-butadiene copolymers and cellulose derivatives such as ethylcellulose and acetylcellulose, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral polystyrene and their copolymers. Examples include polymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumaron resins.

The amount of organic color developer and basic colorless dye used in the present invention,
The types and amounts of other various components are determined according to the required subject matter and recording suitability, and are not particularly limited. Usually, 1 part of the basic colorless dye is mixed with 1 to 8 parts of the organic color developer. part, 3 to IO parts of sensitizer, and 1 to 20 parts of filler are used, and the binder is suitably 10 to 25% of the total solid content.

A desired heat-sensitive recording sheet can be obtained by applying a coating liquid having the above composition to any support such as Paper 1 synthetic paper, film, or plastic.

The above-mentioned Ia color developer, basic colorless dye, sensitizer, and materials to be added as necessary are atomized to a particle size of several microns or less using a grinder such as an attritor sand grinder or a suitable emulsifier. A coating liquid is prepared by adding a binder and various additive materials depending on the purpose.

This coating liquid contains fillers, mold release agents to prevent sticking such as fatty acid metal salts, lubricants to prevent pressure coloring such as fatty acid amide, ethylene bisamide, montan wax, and polyethylene wax, sodium dioctyl sulfosuccinate, Sodium dodecylbenzenesulfonate, lauryl alcohol sulfate ester, sodium salt.

Dispersants such as alginates, benzophenone-based or triazole-based ultraviolet absorbers, other antifoaming agents, optical brighteners, waterproofing agents, etc. can be added.

As fillers used in the present invention, all inorganic and organic fillers commonly used in the field of paper processing can be used, such as clay, talc, silica, magnesium carbonate, alumina tetrahydroxide, aluminum hydroxide, etc. Examples include fine particles of magnesium, barium sulfate, kaolin, titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, urea, formalin resin, polystyrene, phenol resin, and the like.

Further, for the purpose of increasing color development sensitivity, an undercoat such as a polymer material containing filler may be provided under the heat-sensitive layer.

(Function) The reason why the heat-sensitive recording sheet of the present invention does not change color even when written with oil-based ink is considered to be as follows. Generally, when writing is performed on a heat-sensitive recording sheet with an oil-based felt ink, the color developer, leuco dye, and sensitizer in the heat-sensitive coloring layer are dissolved in the organic solvent contained in the ink.

Then, as the solvent evaporates, a coloring composition in which these color developer, leuco dye, and sensitizer are integrated is formed on the writing area. Therefore, for example, if red ink is used, the red color and the developed color of the heat-sensitive recording sheet will mix, resulting in a dull written image.

On the other hand, the heat-sensitive recording sheet of the present invention uses a specific color developer bis(
It consists of 4-hydroxyphenyl)acetate, a leuco dye, and a specific sensitizer. Furthermore, the solubility of these materials in solvents is extremely low, and almost no color-forming composition is formed even when the solvent evaporates, so it is thought that discoloration due to oil-based ink does not occur.

Furthermore, in the present invention, the melting/dissolving diffusion rate and saturation solubility of the color developer with respect to the sensitizer used are extremely high, and the melting/dissolving diffusion rate and saturation solubility of the dye are also high. When a coloring agent, a sensitizer, and a leuco dye cause a physicochemical reaction, a coloring composition is quickly formed, and a colored image with high density can be obtained.

Furthermore, the sensitizer used in the present invention has a property that crystallization is extremely difficult to occur even when dissolved in the organic solvent contained in the oil-based marker and the organic solvent is subsequently vaporized. Sometimes no white powder is produced.

(Example) The present invention will be explained below by way of examples. still.

In the description, parts indicate parts by weight.

[Example (Test No. 1)] Solution A (Developer molecule I1. solution) Solution B (Dye dispersion 11 and C1 night (sensitizer dispersion?&) 8 solutions of the above composition were averaged with a sand grinder. The powder was ground to a particle size of 1 micron, and then a dispersion liquid was mixed at the following ratio to prepare a coating liquid.

Each of the above compositions was ground with a sand grinder to an average particle size of 1 micron. Next, the dispersion liquid was mixed in the following proportions to prepare a coating liquid.

Each of the above coating liquids was applied in an amount of 6.5 g/m on one side of a base paper of 50 g/m''.
The sheet was coated and dried to a concentration of 0 g/m' and then treated with a supercalender to a smoothness of 200 to 600 seconds to prepare a heat-sensitive recording sheet.

[Comparative Example 1 (Tests N002 to 5)] Liquid E (Developer Dispersion) A thermosensitive recording sheet was prepared in the same manner as in Example 1.

[Comparative Example 2 Test No. 66-11)] Solution A (Developer molecule IL solution) B? & (Dye dispersion W,) Solution B (dye dispersion) F fatigue (sensitizer dispersion) Each of the above compositions was ground with a sand grinder to an average particle size of 1 micron, and then dispersed in the following proportions. The liquids were mixed to form a coating liquid.

From then on, a thermosensitive recording sheet was prepared in the same manner as in Example 1.

Table 1 summarizes the results of quality tests performed on the thermal recording papers obtained in the above Examples and Comparative Examples.

Note (1) Sho (2) Sho (3) Sho (4) Static color density: 10g/CI on a hot plate heated to 105℃
Press it for 5 seconds at a pressure of I+2 and measure the color development using a Macbeth densitometer (RD-914, using an amber filter, the same applies hereinafter).

Dynamic color density; manufactured by Matsushita Densen - Thermal facsimile 0F-I
Using QOO, applied energy Q, 58mj/Dot
, the image density recorded with a pulse width of 0.97 milliseconds was measured using a Macbeth densitometer.

Discoloration due to oil-based ink: Teranishi Kagaku oil-based red marker ink No. 500 was used to write on a thermal paper sample, and the degree of discoloration relative to the original red color was visually measured.

○: Almost no discoloration Δ: Slight discoloration ×: Significant discoloration White powder generated by oil-based ink; written on a thermal paper sample using Teranishi Chemical oil-based red magic ink No. 5QQ, After 15 minutes, the degree of white powder generation was visually measured.

○・・・White powder does not occur ×...white powder will occur (Effect of the invention) The following points can be mentioned as effects of the present invention.

(1) Since the oil-based felt ink does not cause discoloration or white powder when writing, it has become possible to freely write on thermosensitive recording sheets using these writing instruments.

(2) Excellent thermal response.

Method of writing procedural amendment) Voluntary writing of procedural amendment) August 4, 1988 Commissioner of the Patent Office Yoshi 1) Mr. Bun Yi August-5, 1988 Sent 1, Indication of case Patent Application No. 1618 of 1988
72 No. 2, Name of the invention Thermal recording material 3, Relationship with the case of the person making the amendment Patent applicant address name: 1-4-1 Oji, Kita-ku, Tokyo 114 Jujo Paper Co., Ltd. 4, agent: 114 δ911- 5106

Claims (1)

[Claims] (1) In a heat-sensitive recording sheet in which a heat-sensitive color-forming layer containing a colorless or light-colored basic colorless dye and an organic color developer as main components is provided on a support, the heat-sensitive color-forming layer has the following organic color developer: 1. A heat-sensitive recording sheet which prevents discoloration caused by an oil-based marker and is characterized by containing a compound represented by the general formula (I) and p-benzylbiphenyl. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) [In the formula, R represents an alkyl group having 1 to 3 carbon atoms. ]