JPH03193489A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain thermal recording paper improved in pencil writing properties, reduced in the blur to aqueous ink and similar to general office paper in hand by together using silica and light calcium carbonate both of which have specific mean particle sizes as the pigment added to a protective layer. CONSTITUTION:A coating solution containing microcapsules which are contain a diazo compound or the like, a coupling component, a basic substance and other additives is prepared to be applied to a support and the coated support is dried to form a thermal recording layer while a protective layer consisting of a water-soluble polymer and pigment is provided on the thermal recording layer. At this time, as the pigment, silica having a mean particle size of 2.0 - 5.0mum and light calcium carbonate having a mean particle size of 0.5 - 2.0mum are together used. Further, starch particles are contained in the protective layer in an amount of 5.0 - 50.0% by wt. of the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and particularly to a fixable diazo-based heat-sensitive recording material. In more detail,
It can be photofixed after thermal recording, has excellent writability with pencils or mechanical pencils (hereinafter simply referred to as pencil writability), has performance comparable to that of general office paper, with little bleeding of water-based rubber stamps, and is soft to the touch. , relates to a direct heat-sensitive recording material whose surface gloss etc. are close to the texture of paper.

(Prior Art) The thermal recording method has the advantage that the recording device is compact, easy to maintain, and inexpensive, and is used in a wide range of fields such as facsimiles, printers, plotters, and word processors. In recent years, with the increase in the amount of information, especially in the field of facsimile, and the spread of information network services using dedicated optical fiber communication networks, there has been a demand for faster information transmission. Materials with excellent responsiveness are being provided one after another. However, the leuco color-forming heat-sensitive recording material, which is the recording material normally used in the heat-sensitive recording method, has the disadvantage that color develops in unexpected places due to harsh handling or heating after recording, or when solvents adhere to it, staining the recorded image. have. In recent years, research on diazo-based heat-sensitive recording materials has been actively conducted as a heat-sensitive recording material that does not have such drawbacks. For example, JP-A-57-123086, Journal of the Institute of Image Electronics Engineers, 1
1.290 (1982), etc., thermal recording is performed on a recording material using a diazo compound, a coupling component, and a basic component (including substances that become basic when heated), and then light irradiation is performed. This process decomposes unreacted diazo compounds and stops color development. In addition, various studies are being conducted to improve the shelf life of this recording material.
One such method is to contain at least one of the substances involved in color reaction in microcapsules, such as JP-A No. 60-201986, JP-A No. 60-214990, JP-A No. 60-214992, JP-A No. 60-214992, Showa 60-2404
No. 91, JP-A No. 60-244594, etc. for details.

However, in order to improve thermal responsiveness, such thermal paper has a recording layer that efficiently transfers heat from the head to the recording paper as a means of efficiently utilizing the thermal energy provided by the thermal head. Many materials have extremely smooth surfaces, making them glossy and smooth to the touch compared to general office paper. The unique textures of this thermal paper, such as the unpleasant feeling of being sticky or sticking to your hands, and the high gloss that makes it feel unnatural like it's shiny or shiny,
As thermal paper has become more widespread, its problems have come into focus.

In addition to its texture, regular thermal paper also has drawbacks such as poor writing quality with a pencil and severe smearing of seals and stamps using water-based ink, so further quality improvements are desired as office recording media. It is rare.

One of the ways to solve these problems is laser facsimile, which uses a toner heat fixing method that uses plain paper as a recording medium, but because of this recording method, the equipment is large, expensive, and requires a high-output power supply. It also has the major disadvantage of requiring regular maintenance and inspection.

For this reason, recording media that use conventional heat-sensitive recording methods do not cause unnecessary color reaction after printing, and have the characteristics of good performance as general office paper, that is, good pencil writeability and little bleeding of water-based inks. There is a strong demand for thermal paper that has a low surface gloss and a feel similar to that of ordinary paper.

In response to such demands, for example, special calender treatments using a leuco coloring layer as disclosed in JP-A-1-196388 and JP-A-1-188388, and JP-A 1-255588
No., JP-A No. 1-221279, JP-A No. 1-22127
Various improvements have been reported over the overcoat layer of No. 7, etc., but none of them are sufficient in terms of color development after printing, texture of plain paper, writing feel with pencil, bleeding of water-based ink, etc.

(Objective of the Invention) Therefore, the object of the present invention is to provide a paper that does not cause unnecessary color reaction after printing, has good pencil writing properties, is less likely to bleed with water-based ink, and has a good texture such as texture and surface gloss for general office work. An object of the present invention is to provide thermal recording paper that is similar to paper.

(Structure of the Invention) The purpose of the present invention is to (1) prepare a diazo compound on a support;
A heat-sensitive recording material comprising a heat-sensitive recording layer containing a coupling component and a basic substance or a substance that becomes basic by heat, and further provided with a protective layer made of a water-soluble polymer and a pigment on the heat-sensitive recording layer. A heat-sensitive recording material characterized in that silica having an average particle diameter of 2.0 to 5.0 μm and light calcium carbonate having an average particle diameter of 0.5 to 2.0 μm are used together as pigments added to the protective layer.

(2) The heat-sensitive recording material according to claim (1), wherein the protective layer contains starch particles in an amount of 5.0% to 50.0% by weight based on the total weight of the protective layer.

(3) the diazo compound in the recording layer, a coupling component,
This has been achieved by the heat-sensitive recording material according to claim (1) or (2), in which either a basic substance or a substance that becomes basic by heat is encapsulated in microcapsules.

The thermal paper obtained by the present invention does not cause unnecessary color reaction due to light fixation after printing, and has excellent pencil writing quality.
It has become a new material that breaks the conventional concept of thermal paper, with a good feel to the touch and less bleeding of water-based inks.

Various known diazo-based heat-sensitive recording materials can be used in the heat-sensitive recording layer of the present invention, but to explain this, the diazo compound and the coupling component contained in the recording layer are brought into contact with each other by heating. The diazo compound used is a photodegradable compound that decomposes when exposed to light of a specific wavelength before the coloring reaction.

The photodegradable diazo compound here mainly refers to aromatic diazo compounds, and more specifically refers to aromatic diazonium salts, diazosulfonate compounds, and diazoamino compounds. It is generally said that the photodecomposition wavelength of a diazo compound is its maximum absorption wavelength. Also, the maximum absorption wavelength of diazo compounds varies from about 200 nm to 700 nm, depending on their chemical structure.
It is known that it changes up to about nm. (Photolysis and chemical structure of r-photosensitive diazonium salts, Takahiro Tsunoda, Ao Yamaoka, Journal of the Photographic Society of Japan 29 (4) pp. 197-205 (1)
965) ) That is, when a diazo compound is used as a photodegradable compound, it is decomposed by light of a specific wavelength depending on its chemical structure. Furthermore, by changing the chemical structure of the diazo compound, the hue of the dye after the reaction can be changed even when the same coupling component is used for the coupling reaction.

A diazo compound is a compound represented by the general formula ArN,X. (In the formula, Ar represents a substituted or unsubstituted aromatic ring, and N
2 represents a diazonium group, and X represents an acid anion.

) Specific examples of the diazo compound used in the present invention include the following examples.

4-Diazo-1-dimethyl7minobenzene, 4-diazo-2-butoxy-5-chloro-1-dimethylaminobenzene, 4-diazo-1-methylbenzylaminobenzene, 4-diazo-1-ethylhydroxyethylaminebenzene, 4 -diazo-1-diethyl 7minor 3-methoxybenzene, 4-diazo-1-morpholinobenzene, 4-
Diazo-1-morpholino-2,5-dibutoxybenzene.

4-Diazo-1-tolylmercapto-2,5-jethoxybenzene, 4-diazo-1-piperazino-2-methoxy-5-rubenzene, 4-diazo-1-(N,,
N-dioctyl 7-minocarbonyl) hembin. 4-Diazo-1(4-tart-octylphenoxy)benzene, 4-diazo-1-(2-ethylhexanoylpiperidino)-25-dibutoxybenzene, 4-diazo-1-(
25-di-tart-7milphenoxyα-butameylpiperidino)benzene, 4-diazo-1-(4-methoxy)phenylthio-2,5-jethoxybenzene, 4
-Diazo-1-(4-methoxy)benz7 mido2.5
- Jetoxybenzene.

4-Diazo-1-pyrrolidino-2-methoxybenzene Specific examples of the acid that forms a diazonium salt with the above diazo compound include the following examples.

Cn F tna-+ COOH (n is an integer of 1 to 9), C8F 2m+l S 02 H (m is an integer of 1 to 9), boron tetrafluoride, tetraphenylboron, hexafluorophosphoric acid, aromatic carboxylic acid, Aromatic sulfonic acid.

Metal halides (zinc chloride, cadmium chloride, tin chloride)
etc.) etc.

The coupling component used in the present invention is one that forms a dye by coupling with a diazo compound in a basic atmosphere, and includes so-called active methylene compounds having a methylene group next to a carbonyl group, phenol derivatives, naphthol derivatives, etc. , Specific examples include the following.

Resorcin, phloroglucin, sodium 2,3-dihydroxynaphthalene-6-sulfonate, 1-hydroxy-2-naphthoic acid morpholinopropyl 7mide, 1,5-
Dihydroxynaphthalene, 2.3-dihydroxynaphthalene, 2.3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide, 2-hydroxy-3-naphthoic acid octyl 7mide, 2-human Oxy 3-naphthoic acid anilide, pencylacetonilide, 1-phenyl-3-methyl-5
-Pyrazolone, 1-(2,4,6-drichlorophenyl)-3-7nilino-5-pyrazolone, 2-(3-a-
(2,5-di-tart-amylphenoxy)-butane-7midobenzamido)phenol, 2,4-bis-(benzoylacetamino)toluene, 1,3-bis-(pivaloylaceto-7minomethyl)benzene, and the like.

These coupling components can be used alone or in combination of two or more, and any hue can be obtained as required.

As one of the color development aids of the present invention, it is preferable to add a basic substance as necessary for the purpose of making the system basic during heating and promoting the coupling reaction.

As these basic substances, used are sparingly water-soluble or water-insoluble basic substances, and substances that generate alkali upon heating.

Basic substances include inorganic and organic ammonium salts,
organic amines, amides, urea and thiourea and their derivatives,
Nitrogen-containing compounds include thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidacillines, triazoles, morpholines, piperidines, 7midines, formamidines, and pyridines. It will be done. Two or more of these basic substances can be used in combination.

In addition, the color development aid of the present invention contains phenol derivatives, naphthol derivatives, alkoxy-substituted benzenes, alkoxy-substituted naphthalenes, hydroxy compounds, amide compounds, sulfonamide compounds can be added. These compounds are thought to lower the melting point of the coupling component or the basic substance, or to improve the thermal permeability of the microcapsule wall, resulting in a high color density.

The coloring aids of the present invention also include thermofusible substances.

The heat-melting substance is a substance having a melting point of 506°C to 150°C that is solid at room temperature and melts by heating, and is a substance that dissolves a diazo compound, a coupling component, or a basic substance. Specific examples of these compounds include fatty acids 7
Examples include mido, N-substituted fatty acid amides, ketone compounds, urea compounds, and esters.

Microcapsules containing the diazo compound of the present invention can be prepared, for example, by the method described in JP-A-59-190888. The polyurea and polyurethane that form the walls of the microcapsules can be obtained by polymerizing the corresponding monomers by the method described above, but the amount of monomer used is such that the average particle size of the microcapsules is 0.3μ to 12μ.
, the wall thickness is determined to be 0.01 to 0.3. Moreover, it is preferable to apply the diazo compound at 0.05 to 5.09/m2.

Microcapsules containing the diazo compound of the present invention are prepared by dissolving a diazonium salt and the same or different compounds that react with each other to produce a polymeric substance in a non-aqueous solvent with a boiling point of 40°C or more and 95°C or less at normal pressure. After dispersing and emulsifying the solution in a hydrophilic protective colloid solution, the system was heated while reducing the pressure in the reaction vessel to distill off the non-aqueous solvent and move the wall-forming substance to the oil droplet surface. Substantially solvent-free microcapsules produced by forming a wall film by proceeding with a polymer production reaction by polyaddition and polycondensation are particularly preferred in terms of achieving a good shelf life.

In the present invention, the coupling component is 0.1 to 30 parts by weight and the basic substance is 0.1 to 30 parts by weight per 1 part by weight of the diazo compound.
．． It is preferable to use it in a proportion of 1 to 30 parts by weight.

The coupling component, basic substance, and other coloring aids used in the present invention are preferably used as a solid fraction together with the water-soluble polymer using a sand mill or the like. Preferred water-soluble polymers include water-soluble polymers used when preparing microcapsules (for example, Japanese Patent Application Laid-Open No. 1986-1999).
190886). In this case, the diazo compound, coupling component, and coloring aid are each added in an amount of 5 to 40% by weight based on the water-soluble polymer solution.

Preferably, the dispersed particle size is 10 microns or less.

A free radical generator (a compound that generates free radicals when irradiated with light) used in photopolymerizable compositions and the like can be added to the heat-sensitive recording material of the present invention for the purpose of reducing the monotony of yellow in the background. Examples of free radical generators include aromatic ketones, quinones, benzoin, benzoin ethers, azo compounds,
Examples include organic disulfides and acyloxime esters. The amount of the free radical generator to be added is preferably 0.01 to 5 parts by weight per 1 part by weight of the diazo compound.

Similarly, for the purpose of reducing yellowing, a polymerizable compound having an ethylenically unsaturated bond (hereinafter referred to as a vinyl monomer) can be used.

Vinyl monomers have at least one ethylenically unsaturated bond (vinyl group, vinylidene group, etc.) in their chemical structure.
It is a compound that has the chemical form of a monomer or a prepolymer. Examples thereof include unsaturated carboxylic acids and their salts, esters of unsaturated carboxylic acids and aliphatic polyhydric alcohols, and 7-mides of unsaturated carboxylic acids and aliphatic polyhydric amine compounds. The vinyl monomer is used in an amount of 0.2 to 20 parts by weight per 1 part by weight of the diazo compound.

It is preferable that the free radical generator and the vinyl monomer are contained in microcapsules together with the diazo compound.

In the present invention, in addition to the above materials, citric acid is used as an acid stable side.
Tartaric acid, oxalic acid, boric acid, phosphoric acid, birophosphoric acid, etc. can be added.

The heat-sensitive recording material of the present invention is prepared by preparing a coating solution containing microcapsules containing a diazo compound, a coupling component, a basic substance, and other additives, and applying the coating solution to a support such as paper or a synthetic resin film. A heat-sensitive recording layer having a solid content of 2.5 to 309/m<2> is provided by coating and drying by a coating method such as bar coating, blade coating, F-knife coating, gravure coating, roll coating, spray coating, or dip coating. Further, it may be applied sequentially with the protective layer described below, or may be applied in multiple layers at the same time.

In the heat-sensitive recording material of the present invention, microcapsules,
A coupling component, a base, etc. may be contained in the same layer as described in the above method, or a laminated structure in which they are contained in separate layers can also be adopted. It is also possible to provide an intermediate layer on the support as described in Japanese Patent Application No. 177,669/1980, and then coat the heat-sensitive recording layer.

As the support of the present invention, any paper support used for ordinary pressure-sensitive paper, thermal paper, dry or wet diazo copying paper, etc. can be used, as well as neutral size paper supports such as flukyl ketene dimer. Neutral paper with a pH of 6 to 9 (described in Japanese Patent Application No. 55-14281), which has been sized with a pH 6 to 9 neutral paper (described in Japanese Patent Application No. 55-14281), which satisfies the relationship between Steckigt sizing degree and metric basis weight described in Japanese Patent Application Laid-Open No. 57-116687, and Paper with a smoothness of 90 seconds or more, paper with an optical surface roughness of 8μ or less and a thickness of 30 to 150μ as described in JP-A-58-136492, a density of 0.99 as described in JP-A-58-69091 /cm
' Paper with an optical contact rate of 15% or more, Canadian standard freeness (JIS
P8121) Paper made from pulp beaten to 4 (locc or more) to prevent the coating solution from seeping in. The glossy side of the base paper made by the Yankee machine described in JP-A No. 58-65695 is the coated surface, and the color density is In addition, it is also possible to use paper that improves resolving power, such as paper that has been subjected to a corona discharge treatment on the base paper described in JP-A No. 59-35985 to improve its coating suitability.

Furthermore, the thermal paper of the present invention is characterized in that a protective layer capable of imparting a paper texture is formed on the thus formed thermal recording layer. That is, a protective layer consisting of a water-soluble polymer and a pigment is provided on the heat-sensitive recording layer, and as the pigment, silica with an average particle diameter of 2.0 to 5.0 μm and silica with an average particle diameter of 0 μm are used.
．． Light calcium carbonate with a thickness of 5 to 2.0 μm is used in combination, more preferably 5.0% by weight to the total weight of the protective layer.
By containing 50.0% by weight of starch particles, it became possible to impart paper feel, pencil writing properties, and characteristics of less bleeding by water-based ink.

As the water-soluble polymer, it is preferable to use a binder that has high resistance to abrasion, oil, etc., has good film-forming properties, and has strong coating film strength, especially from the point of view of pencil writability.

Specific examples of such binders include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, styrene-maleic anhydride copolymer hydrolyzate, carboxy-modified polyvinyl alcohol, alkyl-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, and polyacrylic. 7 mid,
Examples include starch, saponified products of vinyl acetate-polyacrylic acid copolymers, and the like.

Further, as a result of extensive studies regarding the pigments to be added, it was not possible to obtain a completely satisfactory result by adding a single pigment. As a result of further various studies, we have discovered a system that uses the present invention, silica with an average particle size of 2.0 to 5.0 μm, and light calcium carbonate with an average particle size of 0.5 to 2.0 μm. Ta. The average particle diameter of silica is the actual value measured from the SEM photograph, and the average particle diameter of light calcium carbonate is the average particle diameter of light calcium carbonate.
ICROTRAC PARTICLE-512E ANA
This is the average particle diameter measured by LYZ, ER). The silica having an average particle diameter of 2.0 to 5.0 μm may be colloidal silica or amorphous silica, but is not particularly limited, but amorphous silica having an average particle diameter of 3.0 to 4.5 μm is most preferable. There are no particular restrictions on the mixing ratio of these pigments, but a weight ratio of silica to light calcium carbonate of 1 = 1 to 1: 0.1 is recommended from the viewpoint of lead IIi writing performance and reducing bleeding of water-based ink. It is preferable. The total amount of pigment is also not particularly limited, but 5% of the total weight of the protective layer is
If it exceeds 0%, color density tends to decrease due to its hiding power.

These materials are thoroughly mixed with a binder using a dispersing machine such as a homogenizer mixer or a mixer to prepare a coating liquid for the protective layer. In addition, various additives such as those used in the heat-sensitive recording layer, such as metal soap, wax, etc., may be added to the coating liquid as necessary.
Surfactants, antistatic agents, ultraviolet absorbers, antifoaming agents, conductive agents, fluorescent dyes, layer color dyes, and the like may be added. This protective layer coating solution is coated on the already prepared heat-sensitive recording layer to obtain the heat-sensitive paper of the present invention. At this time, the heat-sensitive recording liquid may be applied simultaneously in a multilayer manner, or may be applied sequentially. There is no particular limitation on the coating amount, but the dry coating amount is generally 0.5 to 8.
．． (It is desirable to set it to 1+/%.

The thermal paper thus obtained has a feel similar to that of general office paper in terms of feel, surface gloss, etc., excellent pencil writing properties, and little bleeding of water-based ink. Furthermore, in order to improve the feel and writability, the protective layer should contain 5.0% to 50% by weight based on the total weight of the protective layer.
．． It is preferable to include 0% by weight of starch particles, and most preferably from 10.0% to 30.0% by weight. The addition of starch particles improves the texture,
Pencil writing properties are further improved. If the amount added exceeds 50.0% by weight based on the total weight of the protective layer, the feeling of roughness increases rapidly, and if it is less than 5.0% by weight, no effect of the addition will be observed. Regarding the types of starches, in addition to starches such as potato starch, wheat starch, corn starch, tapioca starch, sago starch, and rice starch, there are also processed starches such as oxidized starch, esterified starch, etherified starch, pregelatinized starch, and roasted starch. There are modified starches such as calcined dextrin, enzyme-modified dextrin, enzymatically decomposed dextrin, cross-linked starch, and grafted starch, and the present invention is not particularly limited to these starch types, but wheat starch is most preferably used. .

In addition, after coating and drying, post-processing is possible using known techniques, such as calendar processing to improve sensitivity and image quality Uρ, and a thin layer of resin on the opposite side of the recording layer formation surface to prevent static electricity. Providing layers, etc. may be implemented as necessary.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited only to the following Examples.

(Example-1) ■ Formation of heat-sensitive recording layer 1-morpholino-2,5-dibutoxybenzene-4-diazonium hexafluorophosphate 3.45 parts, xylylene diisocyanate and trimethylolpropane (3.45 parts)
: 1) 18 parts of the adduct were added to a mixed solvent of 6 parts of tricresyl phosphate and 5 parts of ethyl acetate, and dissolved by heating. This diazo compound solution was mixed with an aqueous solution containing 5.2 parts of polyvinyl alcohol dissolved in 58 parts of water, and emulsified and dispersed at 20°C to obtain an emulsion having an average particle size of 2.5 μm. 100 parts of water was added to the obtained emulsion and heated to 60°C while stirring, and after 2 hours, a capsule liquid containing the diazo compound in the core substance was obtained.

Next, 10 parts of 2-human 0xy-3-naphthoic acid 7nylide and 10 parts of triphenylguanidine were added to 200 parts of a 5% polyvinyl alcohol aqueous solution and dispersed in a sand mill for about 24 hours to obtain a dispersion with an average particle size of 3μ. Ta.

To 50 parts of the capsule solution of the diazo compound obtained as described above, 50 parts of a dispersion of a coupling component and triphenylguanidine and 10 parts of a 40% calcium carbonate dispersion were added to prepare a coating liquid. Spread this coating solution on smooth high-quality paper (7
59/m2) using a coating bar to dry weight 10
9/m2 and dried at 50°C for 1 minute to prepare thermal recording paper.

■ Formation of protective layer 7.4% polyvinyl alcohol (Kuraray Pv^-117
) Aqueous solution 409.69. Add water 1009 to 30% zinc stearate emulsion 13.39 and mix well to obtain a protective layer stock solution. In addition, amorphous silica (Japan Silica Nip Seal E-+50ha average particle diameter 4 μm) 27c+
and 0.279° of sodium hexametaphosphate were dispersed with 739° of water using a homogenizer to obtain a silica pigment dispersion. Similarly, light calcium carbonate (manufactured by Shiraishi Kogyo Co., Ltd., light calcium carbonate PC1279, sodium hexametaphosphate 0.2
79 and water 639 were dispersed with a homogenizer, and further atomized in a ball mill overnight until the average particle size became 1.4 μm to obtain a light calcium carbonate dispersion.

These dispersions were combined into protective layer stock solution 4009, light calcium carbonate dispersion 6.459, and amorphous silica pigment dispersion 10.0.
A coating liquid for a protective layer was obtained by mixing 90% of each.

Get this first! The protective layer was coated on the coloring layer of the thermosensitive recording paper produced in the above manner so that the dry weight of the protective layer was 2.09/rrr to obtain the desired thermosensitive paper.

(Example-2) In Example-1, amorphous silica (Japan Silica Nip Seal E-1) was used instead of amorphous silica (Japan Silica Nip Seal E-+50J, average particle size 4 μm).
A thermal paper was obtained in the same manner as in Example 1, except that a sample of 50K and an average particle diameter of 4.5 μm was used.

(Example-3) In Example-1, amorphous silica (Nip Seal E-+50J, manufactured by Nippon Silica, average particle size 4 μm) was replaced with amorphous silica (Syroid 266, manufactured by Fuji Davidson, average particle size 3.0 μm). Thermal paper was obtained in the same manner as in Example 1 except that the paper was removed using the same method as in Example-1.

(Example-4) In Example-1, amorphous silica (Japan Silica Nip Seal ε-2) was used instead of amorphous silica (Japan Silica Nip Seal E-+50J, average particle size 4 μm).
A thermal paper was obtained in the same manner as in Example-1 except that 00, average particle diameter 2.5 μm) was used.

(Example-5) In Example-1, amorphous silica (Japan Silica Nip Seal E-2) was used instead of amorphous silica (Japan Silica Nip Seal E-+50J, average particle size 4 μm).
A thermal paper was obtained in the same manner as in Example-1 except that 00^, average particle diameter 2.0 μm) was used.

(Example-6) In Example-1, wheat starch 7 was added to the protective layer coating liquid.
．． A thermal paper was obtained in the same manner as in Example-1 except that 729 was added.

(Example-7) In Example-2, wheat starch 7 was added to the protective layer coating liquid.
．． A thermal paper was obtained in the same manner as in Example-2 except that 729 was added.

(Example-8) In Example-2, wheat starch 1 was added to the protective layer coating liquid.
A thermal paper was obtained in the same manner as in Example-2 except that 6.629 was added.

(Example-9) In Example-2, wheat starch 2 was added to the protective layer coating liquid.
．． 32! A thermal paper was obtained in the same manner as in Example-2 except that ;1 was added.

(Example-10) In Example-1, wheat starch 4 was added to the protective layer coating liquid.
6. A thermal paper was obtained in the same manner as in Example 1-1 except that 31c+ was added.

(Example-11) In Example-2, 0 wheat starch was added to the protective layer coating liquid.
．． A thermal paper was obtained in the same manner as in Example-2 except that 959 was added.

(Example 12) A thermal paper was obtained in the same manner as in Example 1, except that in Example 1, a dispersion in which the minor calcium carbonate was atomized until the average particle diameter was 0.5 μm was used.

(Example 13) Thermal paper was prepared in the same manner as in Example 1, except that the dispersion liquid that had been atomized when the average particle size of the minor calcium carbonate reached 2.0 μm was used. Obtained.

(Comparative Example-1) In Example-1, amorphous silica (Japan Silica Nip Seal E-2) was replaced with amorphous silica (Japan Silica Nip Seal E-+50J, average particle size 4 μm).
A heat-sensitive recording material was obtained in the same manner as in Example-1 except that 2OA (average particle size: 1.0 μm) was used.

(Comparative Example-2) In Example-1, amorphous silica (Syroid 161 manufactured by Fuji Davidson Co., Ltd., average particle size 7.5 μm) was used instead of amorphous silica (Japan Silica Nip Seal E-+50J, average particle size 4 μm). A thermal paper was obtained in the same manner as in Example-1 except that .

(Comparative Example-3) A thermal paper was obtained in the same manner as in Example-1 except that the slight calcium carbonate dispersion was not added when preparing the protective layer coating solution in Example-1.

(Comparative Example 4) A thermal paper was obtained in the same manner as in Example 3, except that the slight calcium carbonate dispersion was not added when preparing the protective layer coating solution in Example 3.

(Comparative Example-5) A thermal paper was obtained in the same manner as in Example-3 except that the slight calcium carbonate dispersion was not added when preparing the protective layer coating solution in Example-3.

(Comparative Example-6) A thermal paper was obtained in the same manner as in Example-4, except that the slight calcium carbonate dispersion was not added when preparing the protective layer coating solution in Example-4.

(Comparative Example 7) A thermal paper was obtained in the same manner as in Example 5, except that the slight calcium carbonate dispersion was not added when preparing the protective layer coating solution in Example 5.

(Comparative Example-8) A thermal paper was obtained in the same manner as in Example-1 except that in Example-1, a dispersion liquid in which the fine calcium carbonate was atomized until the average particle diameter was 0.3 μm was used.

(Comparative Example-9) Thermal paper was produced in the same manner as in Example-1, except that the dispersion liquid that had been atomized when the average particle size of the minor calcium carbonate reached 2.3 μm in Example-1 was used. Obtained.

(Comparative Example-10) A thermal paper was obtained in the same manner as in Example-1, except that the silica-based pigment dispersion was not added during the preparation of the protective layer coating solution.

(Comparative Example-11) A thermal paper was obtained in the same manner as in Example-6 except that the silica-based pigment dispersion was not added during the preparation of the protective layer coating solution.

(Comparative Example-12) A thermal paper was obtained in the same manner as in Example-1 except that a protective layer was not provided on the thermal recording layer in Example-1.

(Comparative Example-13) 2-7 Nilino 3- as an electron-donating colorless dye precursor
Methyl-6-N ethyl-N iso7mil7minofluorane 109, bisphenol A20 as electron-accepting compound
9 and 1009, respectively, of 5% polyvinyl alcohol (
Clara PVA-105) was dispersed in a ball mill overnight with an aqueous solution to increase or decrease the average particle diameter by 1.5 μmm to obtain each dispersion.

Further, calcium carbonate 809 was dispersed with a 0.5% sodium hexametaphosphate solution 1609 using a homogenizer. These dispersions were mixed in a ratio of 59 parts of an electron-donating colorless dye precursor dispersion liquid, 109 parts of an electron-accepting compound dispersion liquid, and 159 parts of a calcium carbonate dispersion liquid, followed by 39 parts of a 21% zinc stearate emulsion and a paraffin having a melting point of 68°C. Wax dispersion (Hidrin D-337 manufactured by Middle East Yushi)
29 was added to obtain a coating liquid for heat-sensitive recording. This coating liquid for heat-sensitive recording was applied to smooth high-quality paper with a basis weight of 759 as in Example-1 using a coating bar so that the dry weight of the heat-sensitive coloring layer was 10q/rrt, and the coating liquid was coated at 50°C for 30 minutes. After drying for a minute, a thermosensitive recording paper was obtained. Furthermore, in Example-1,
A thermal paper was obtained in the same manner as in Example-1 except that a protective layer was provided on the thermal paper obtained as described above.

The thermal paper obtained as described above was treated with a calendar and then evaluated by the following method. The results are shown in Table 1.

[Color density]

G111 mode (Hifax 700, Hitachi ■
(manufactured by Ricoh), and then the entire surface was exposed and fixed using Ricopy Super Dry 100 (manufactured by Ricoh ■).

The printed portion of the obtained recorded image was measured using a Macbeth reflection density meter (Model RD-9+8 manufactured by Macbeth).

[Fog density]

The red printed area density (fog) was also measured in the same manner as the color density.

(Scratch fog) The white background of thermal paper after printing was thermally recorded and optically fixed in the same manner as for color density, and then scratched with a fingernail to see if color developed.

0: No color developed at all.

X; Colored black and dirty.

(Pencil writing properties) Writing was performed on the obtained thermal paper using a pencil and a mechanical pencil, and the writing quality, pencil stickiness, etc. were evaluated in terms of the density of He%B%H, and the results were evaluated in the following four grades.

◎; Can write very smoothly. Even at H density, the pencil sticks well and writes well.

○: Can write smoothly without applying pressure.

In addition, the density of the writing area where the pencil sticks well is also high.

△: Difficult to write without applying some pressure. Regarding the darkness of H, it is very difficult to write, and the tip of the writing instrument feels slippery, making it uncomfortable.

Also, the density in the writing area is a little low, but it is at a level that is not a problem for practical use.

×9 Even if I apply a lot of pressure, the writing instrument slips, and the pencil doesn't stick well, and even at the density of B, the density is weak, making it very difficult to write.

Exceeds the practical tolerance for general office use.

(Bleeding of water-based ink) A rubber stamp with water-based ink (Shachihata sol stamp pad JIS 7063) was applied to the obtained heat-sensitive recording material, and the appearance was observed and evaluated in the following three stages.

○: Just like when stamping on general office paper, the letters do not bleed and can be read without any problems.

It also dries quickly.

Δ: Slight blurring, but the text is readable and there is no problem in practical use.

×: The original shape is blurred to the point that it is almost impossible to discern, and the letters are completely unreadable. It also doesn't dry well and gets dirty when you touch it.

〔touch〕

We asked 10 people who are employed in general office work (those who have handled facsimile paper) to touch the samples, and compared and evaluated the texture. .

◎: 9 Å or more out of 10 people evaluated the feel as the same.

7 to 81 people evaluated the feel as being the same.

614 to 6 people rated it as having the same feel.

×: The same texture was evaluated as 3 Å or less.

As shown in Table 1, the present invention provides thermal paper that does not cause unnecessary color reaction after printing, has excellent pencil writing properties, has little bleeding from water-based ink, and has a feel and texture that is surprisingly similar to ordinary paper. It is clear that this was obtained.

Claims (3)

[Claims] (1) A heat-sensitive recording layer containing a diazo compound, a coupling component, and a basic substance or a substance that becomes basic with heat is provided on the support, and a protection layer made of a water-soluble polymer and a pigment is further provided on the heat-sensitive recording layer. In the heat-sensitive recording material provided with a layer, the pigments added to the protective layer include silica having an average particle diameter of 2.0 to 5.0 μm and silica having an average particle diameter of 0.5 to 2.0 μm.
A heat-sensitive recording material characterized by the combined use of 0 μm light calcium carbonate. (2) 5.0% by weight based on the total weight of the protective layer in the protective layer
The heat-sensitive recording material according to claim 1, characterized in that it contains ~50.0% by weight of starch particles. (3) the diazo compound in the recording layer, a coupling component,
The heat-sensitive recording material according to claim 1 or 2, wherein either a basic substance or a substance that becomes basic by heat is encapsulated in microcapsules.