JPH029952B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention improves the recording suitability of a thermal recording paper that utilizes a color-forming reaction under heat between a normally colorless or light-colored basic colorless dye and an organic color developer. In the thermal recording method, recording is generally performed by pressing a thermal head or pen with a certain pressure on the thermal recording paper and making contact with it, so the surface of the head or pen has a high hardness and is resistant to abrasion. This is required. For this reason, thermal heads are usually
On top of heating resistors such as Ta ₂ N, Ta-Si, Ta-Al, SnO ₂ , Ni-Cr, silicon, RnO ₂ , Pt-Ag, etc.
Although it is equipped with a wear-resistant layer or a resistor protection layer made of hard materials such as SiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , SiC, and glass, the head As the pressing pressure and sliding speed of thermal recording paper tend to increase, there is an increasing need to make the head of thermal recording paper less likely to wear out. In addition, when recording, as the thermal head is heated and cooled, the heat-sensitive material contained in the coloring layer of the heat-sensitive recording paper is melted and then solidified. It has been pointed out that there is a phenomenon of scum adhering to the surface, and a phenomenon of color development when the edge of the head substrate or the like rubs the surface of the thermal recording paper when the thermal head slides. Conventionally, it has been known to use organic fillers for abrasion resistance, such as urea-formalin resin (Japanese Patent Application Laid-open No. 54-25845), phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, urea resin. , melamine resin, polyurethane resin, etc. (Japanese Patent Application Laid-Open No. 1983-25845) have been proposed, but
When these organic fillers are used, they have very poor dispersibility compared to inorganic fillers, making it impossible to obtain a desirable coating, or adding these organic fillers may cause scum adhesion and staining. There were many causes of this, and there was a general tendency to worsen the background color. The present invention incorporates fine granular guanamine, whose basic structural unit is the following general formula, into the color-forming layer of thermal recording paper.
It is characterized by containing formaldehyde resin. general formula (However, R is H, CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ,
It represents NH ₂ , NO ₂ , acetyl group, C ₆ H ₁₁ , C ₆ H ₅ , benzyl group or methylphenyl group. ) The present invention will be explained in detail below. The guanamine formaldehyde resin used in the present invention has the above-mentioned general formula as a basic structural unit,
Specific examples thereof include benzoguanamine formaldehyde resin, acetylguanamine formaldehyde resin, acetoguanamine formaldehyde resin, benzylguanamine formaldehyde resin, methylbenzoguanamine formaldehyde resin, and nitrobenzoguanamine formaldehyde resin, especially benzoguanamine formaldehyde resin. Acetoguanamine formaldehyde resin is preferred. These resins are required to be in the form of fine particles and have an average particle size of 5 μm or less, preferably about 0.1 to 1 μm. If the average particle size exceeds 5μ, the resin itself becomes scum and adheres to the thermal head, sometimes causing printing to become impossible. The organic color developer used in the present invention is not particularly limited, and any type of color developer may be used; Monophenolic 4-
The effects of the present invention are most pronounced when a hydroxyphenyl compound or a phthalic acid monoester is used as a color developer. Monophenolic 4-hydroxyphenyl compounds include ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, isobenzyl 4-hydroxybenzoate, and 4-hydroxybenzoate. Benzyl hydroxybenzoate, methylbenzyl 4-hydroxybenzoate,
4-hydroxybenzoic acid esters such as 4'-t-butylbenzyl 4-hydroxybenzoate, 4-
4-hydroxyphthalic acid diesters such as dimethyl hydroxyphthalate, diisopropyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate, dihexyl 4-hydroxyphthalate, 4-hydroxyacetophenone, P-phthalate, etc. Enylphenol, benzyl-4-hydroxyphenyl acetate, P-benzylphenol, and 4-hydroxyphenyl-4'-n-butyloxyphenyl sulfone, 4-hydroxyphenyl-4'-n-hexyloxyphenyl Enylsulfone, 4
-Hydroxyphenyl-4'-n-octyloxyphenyl sulfone, 4-hydroxyphenyl-
4'-n-decyloxyphenyl sulfone, 4-hydroxyphenyl-4'-n-dodecyloxyphenyl sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 4-hydroxyphenyl-4 '-p-isopropylbenzyloxyphenyl sulfone, 4-hydroxyphenyl-
4'-β-phenethyloxyphenylsulfone, 4
-Hydroxyphenyl-4'-β-ethoxyethyloxyphenyl sulfone, 4-hydroxyphenyl-4'-β-butoxyethyloxyphenyl sulfone, 4-hydroxyphenyl-4'-β-phenoxyethyl Oxyphenyl sulfone, 4-hydroxyphenyl-4'-o-chlorobenzoyloxyphenyl sulfone, 4-hydroxyphenyl-
4'-β-t-butylbenzoyloxyphenyl sulfone, 4-hydroxyphenyl-4'-β-octylbenzoyloxyphenyl sulfone, 4-hydroxyphenyl-4'-lauriloyloxyphenyl sulfone, 4- Hydroxyphenyl-4'-decanoyloxyphenyl sulfone, 4-hydroxyphenyl-4'-myristoyloxyphenyl sulfone, 4-hydroxyphenyl-4'-stearyloxyphenyl sulfone, 4-hydroxyphenyl- 4'-β-phenoxypropionyloxyphenyl sulfone, 4-hydroxyphenyl-4'-
Hexadecylsulfonyloxyphenylsulfone, 4-hydroxyphenyl-4'-decylsulfonyloxyphenylsulfone, 4-hydroxyphenyl-4'-p-toluenesulfonyloxyphenylsulfone, 4-hydroxyphenyl-4' -p
-isopropylbenzenesulfonyloxyphenyl sulfone, 4-hydroxyphenyl-4'-(4
-pt-butylphenoxybutyloxy)phenylsulfone, 4-hydroxyphenyl-4'-
(4-pt-amylphenoxybutyloxy)
phenyl sulfone, 4-hydroxyphenyl-
Examples include 4'-(5-pt-butylphenoxyamyloxy) phenylsulfone, 4-hydroxyphenyl-4'-(6-pt-butylphenoxyhexyloxy) phenylsulfone, etc. can do. On the other hand, phthalic acid monoesters include phthalic acid monophenyl ester, phthalic acid monobenzyl ester, phthalic acid monocyclohexyl ester, phthalic acid monomethyl phenyl ester, phthalic acid monoethyl phenyl ester, phthalic acid monoalkyl benzyl ester, and phthalic acid monoester. Examples include acid monohalogen benzyl esters and phthalic acid monoalkoxybenzyl esters. Compared to bisphenol compounds, these color developers have
Excellent color development sensitivity and background color quality. Especially,
Benzyl 4-hydroxybenzoate is preferred. In addition, as a bisphenol compound, 4,4'-
Isopropylidene diphenol (bisphenol A), 4,4'-(1-methyl-n-hexylidene) diphenol, 4,4'-cyclohexylidene diphenol, 4,4'-thiobis(4-tert-butyl- 3-methylphenol) and the like. On the other hand, various dyes are well known as basic colorless dyes that are usually colorless or light-colored, and are not particularly limited. For example, examples of fluoran-based colorless dyes include the following. 3-diethylamino-6-methyl-7-anilylfluorane (black), 3-(N-ethyl-P-toluideino)-
6-methyl-7-anilinofluorane (black),
3-diethylamino-6-methyl-7-(ortho,
para-dimethylanilino)fluorane (black),
3-pyrrolidino-6-methyl-7-anilinofluorane (black), 3-piperidino-6-methyl-7-anilylfluorane (black), 3-N-
cyclohexyl-N-methylamino)-6-methyl-7-anilylfluorane (black), 3-diethylamino-7-(meta-trifluoromethylanilino)fluorane (black), 3-dibutylamino-7-( ortho-chloroanilino)fluoran (black), 3-diethylamino-6-methyl-chlorofluoran (red), 3-diethylamino-6
-Methylfluorane (red), 3-cyclohexylamino-6-chlorofluorane (orange). In addition, among fluoran-based black coloring dyes, 3-diethylamino-6-methyl-(para-chloroanilino)fluoran, 3-diethylamino-7-
(ortho-chloroanilino)fluorane, 3-(N
-ethyl-P-toluideino)-6-methyl-7
-anilinofluorane, 3-dibutylamino-6
-Methyl-(ortho-chloroanilino)fluorane, 3-(N-ethyl-isoamyl)amino-6
- Methyl-7-anilinofluorane is considered to be a dye with rather low coloring properties, and the density of the colored image is slightly insufficient, but metal salt derivatives of nitrobenzoic acid and phthalic acid monoester are used in the coloring layer. By adding , image density can be improved. Furthermore, basic colorless dyes other than fluoran-based dyes include crystal violet lactone, methyl violet lactone, and 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-
ethyl-2-methylindol-3-yl)4-
azaphthalide, 3-(4-diethylamino-2-
An example thereof is ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-7-azaphthalide. The organic color developer and basic colorless dye mentioned above are atomized to a particle size of several microns or less using a grinder such as a ball mill, an attritor, or a sand glider, or a suitable emulsifying device, and then finely divided into guanamine. A coating liquid is prepared by adding formaldehyde resin and various additive materials depending on the purpose. This coating liquid usually contains polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, starches, styrene, etc.
Binders such as maleic anhydride copolymer, vinyl acetate maleic anhydride copolymer, and styrene-butadiene copolymer are used, and in addition, mold release agents such as fatty acid metal salts, lubricants such as waxes, and benzophenone-based or triazole-based ultraviolet absorbers, water-resistant agents such as glyoxal, dispersants, antifoaming agents, etc. are used as appropriate. Inorganic or organic fillers may also be added. By applying this coating liquid to paper and various films, the desired thermosensitive recording paper can be obtained. The amounts of various components used in the present invention are determined according to the performance and recording suitability required depending on the performance of the thermal recording device, and are not particularly limited, but usually per part of the basic colorless dye. Color developer 3~
10 parts, guanamine formaldehyde resin 1-25
The binder is used in an amount of about 10 to 20% by weight based on the total solid content. The amount of guanamine formaldehyde resin used is about 1 to 60% by weight based on the total solid content of the coloring layer. If the amount used is less than this, the effect of preventing lees adhesion will be reduced, and if it exceeds 60% by weight, the recording density will likely be insufficient. Since the present invention is constructed as described above, it is possible to obtain a thermosensitive recording paper that has almost no lees adhesion or staking, has little head abrasion, and is also effective against color development by rubbing. Next, typical examples will be described to specifically explain the present invention. Example 1 Liquid A (dye dispersion) 3-diethylamino-6-methyl-7-anilinofluorane 2.0 parts 10% polyvinyl alcohol aqueous solution 4.6 parts Water 2.5 parts Liquid B (developer dispersion) 4-hydroxybenzoic acid Benzyl 6.0 parts Zinc stearate 0.5 parts 10% polyvinyl alcohol aqueous solution 16.3 parts Water 9.7 parts Each solution A and B was separately ground and dispersed in an attritor for 3 hours, then both solutions were mixed to form benzoguanamine with an average particle size of 0.3μ. 10 parts formaldehyde resin, and 10
% polyvinyl alcohol aqueous solution was added to prepare a heat-reducing paint. In addition, as a comparative example, 10 parts of aluminum hydroxide, kaolin clay, or calcium carbonate was mixed in place of the benzoguanamine formaldehyde resin, and the same procedure as above was made. The amount of these paints applied to base paper with a basis weight of 50g/ ^m2 was
It was coated to a density of 6.0 g/m ² and dried, and calendered to obtain a black thermosensitive recording paper with a smoothness of 200 to 500 seconds. The results of quality and performance tests are shown in Table 1.

【table】

[Table] As shown in the results in Table 1, the thermal recording paper of the present invention has higher whiteness and smoothness than comparative examples using conventionally used inorganic fillers such as aluminum hydroxide, kaolin clay, or calcium carbonate. It was observed that the color strength and color density were high, there was no problem of color development due to rubbing, and there was very little wear on the thermal pen. Example 2 Liquid A (dye dispersion) 3-(N-cyclohexyl-N-methylamino)-
6-Methyl-7-anilinofluorane 1.5 parts 10% polyvinyl alcohol aqueous solution 3.4 parts Water 1.9 parts Solution B (developer dispersion) Benzyl 4-hydroxybenzoate 6 parts Zinc stearate 1.5 parts 10% polyvinyl alcohol aqueous solution 18.8 Part water 11.2 parts Both A and B separately with an attritor 3
After pulverization and dispersion, both liquids were mixed and the average particle size was 0.3μ.
Alternatively, 10 parts of 3μ benzoguanamine formaldehyde resin was added to make a heat-sensitive paint. For comparison, a product containing 10 parts of 6μ benzoguanamine formaldehyde resin was also prepared. Similarly, thermal paints were also created using acetoguanamine formaldehyde resin with various particle sizes. A thermosensitive recording paper was obtained in the same manner as in Example 1 using these paints. The quality and performance test results are shown in Table 2.

【table】

[Table] As shown in Table 2, the examples of the present invention are good in terms of scum adhesion, rubbing color development, and thermal pen abrasion, so the recorded images are good even when printed continuously for a long time. Example 3 Solution A (dye dispersion) 3-diethylamino-6-methyl-(para-chloroanilino)fluoran 1.5 parts 10% polyvinyl alcohol aqueous solution 3.4 parts Water 1.9 parts Solution B (color developer dispersion) Each developer in Table 3 Colorant 6 parts Zinc stearate 1.5 parts 10% polyvinyl alcohol aqueous solution 18.8 parts Water 11.2 parts Solution C (stabilizer dispersion) Each stabilizer in Table 3 1.0 parts 10% polyvinyl alcohol aqueous solution 2.5 parts Water 1.5 parts A, B, C After grinding and dispersing each liquid separately for 1 hour using a test sand grinder, 6.8 parts of liquid A,
A paint was prepared by mixing 37.5 parts of liquid B, 5 parts of liquid C, and 30 parts of a 30% dispersion of benzoguanamine formaldehyde resin. Each of the above coating liquids was applied in an amount of 6.0g/on a 50g/ ^m2 base paper.
The sheet was coated and dried to a thickness of 2 m ² , and the sheet was treated with a supercalender to a smoothness of 200 to 500 seconds. Table 3 shows the results of a quality performance test performed on the obtained black-colored thermal recording paper.

[Table] As shown in Table 3, the examples of the present invention have extremely excellent dynamic coloring properties because a metal salt of nitrobenzoic acid or phthalic acid monoester was added as a stabilizer.

Claims (1)

[Scope of Claims] 1. A thermosensitive recording paper provided with a coloring layer containing a basic colorless dye and an organic color developer, wherein the coloring layer contains particles having an average particle size of 5 μm or less and having the following general formula as a basic constituent unit. A thermal recording paper characterized by containing guanamine formaldehyde resin. general formula (However, R is H, CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ,
It represents NH ₂ , NO ₂ , acetyl group, C ₆ H ₁₁ , C ₆ H ₅ , benzyl group or methylphenyl group. 2. The heat-sensitive recording paper according to claim 1, wherein the guanamine-formaldehyde resin is contained in an amount of 1 to 60% by weight based on the total solid content of the coloring layer. 3. The thermal recording paper according to claim 1, wherein the organic color developer is benzyl 4-hydroxybenzoate.