JPH02178087A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain the title recording material having a thermal recording layer excellent in transparency and light fastness before use by using a specific fluorane compound as a color former. CONSTITUTION:A fluorane compound represented by formula (wherein R1 and R2 are an alkyl group which may have a substituent, R3 is a hydrogen atom, an alkyl group which may have a substituent or an alkoxy group and a ring A is an aromatic ring) is included in a microcapsule as a color former and the use amount of this color former is set to 0.05-5.0g/m<2> and polyurethane is used in the wall material of the microcapsule. As a coupler to a leuco dye, a phenol compound is used and dissolved in a hardly water-soluble or water- insoluble org. solvent such as ethyl acetate to be emulsified and dispersed. A coating solution containing the microcapsule having the color former included therein, a dispersion containing a partial saponification product of polyvinyl alcohol having the coupler emulsified and dispersed therein and a binder is prepared and applied to a support such as paper or a synthetic resin film to be dried.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a heat-sensitive recording material having a heat-sensitive layer provided on a support. More specifically, the present invention relates to a heat-sensitive recording material having a heat-sensitive layer having excellent transparency and light resistance before use.

(Prior art) The thermal recording method does not require full development, (2) when the support is paper, the paper quality is similar to ordinary paper, (3) it is easy to handle, and (4) the color density is high. , (5) the recording device is simple and inexpensive, and (6) there is no noise during recording, so it has rapidly become popular in the field of facsimiles and printers in recent years, and the use of thermal recording is also expanding. There is.

Against this background, in recent years, in order to apply multicolor or overhead projector (
It has become desirable to develop a transparent heat-sensitive recording material that can be directly recorded with a thermal recorder for use in OHP (abbreviated as OHP). However, conventional transparent heat-sensitive recording materials cannot This is a so-called transparent thermosensitive film that is used in facsimiles, etc., by placing it in close contact with a document and irradiating it with light to cause the image area of the original to absorb infrared rays and raise the temperature of the image area, thereby causing the thermosensitive recording film to develop color. It does not have the thermal sensitivity that can be achieved directly with a thermal head.

Furthermore, the heat-sensitive layer of a heat-sensitive recording material that can be thermally recorded with a thermal head is devitrified, and it has not been possible to achieve the desired transparency even if the material is simply coated on a transparent support.

The present inventors have developed a heat-sensitive recording material capable of overcoming these conventional drawbacks by employing a combination of a colorless or light-colored basic dye precursor and a color developer as a coloring system, and incorporating the former into microcapsules. disclosed a new transparent heat-sensitive material that can be obtained by dissolving the latter in an organic solvent that is sparingly soluble or insoluble in water, emulsifying and dispersing the latter, mixing the two, and coating this on a support (patent application). Showa 62-8819
No. 7).

(Problems to be Solved by the Invention) However, it has been found that the transparency and light resistance before use of the above heat-sensitive recording material are significantly affected by the stability of the coloring agent in the microcapsules of the heat-sensitive layer. Bisindolyl phthalide compounds, fluoran compounds, and the like are known as compounds that develop colors from red to magenta.

However, for example, 3,3-bis(1-n-octyl-2
-Methylindol-3-yl) phthalide has excellent oil solubility and develops quickly, exhibiting a deep magenta color, but recording materials using this compound have poor light resistance before use, and the background yellows due to photodecomposition products. Furthermore, although 3-diethylamino-7,8-henzofluorane has excellent light resistance before use, it has the disadvantage of poor oil solubility.

The present inventors have investigated the oil solubility, water solubility, partition coefficient, pKa, polarity of substituents, position of substituents, and changes in crystallinity and solubility when used in combination with respect to color formers and color developers. We have pursued the development of good recording material materials and recording materials, focusing on the following characteristics.

(Object of the Invention) Therefore, an object of the present invention is to provide a heat-sensitive recording material having a heat-sensitive layer having excellent transparency and light resistance before use.

(Structure of the Invention) The object of the present invention was achieved by developing a recording material using a fluoran compound represented by the following general formula as a coloring agent.

In the above formula, R,, Rff represents an alkyl group that may have a substituent, R1 represents a hydrogen atom, an alkyl group or an alkoxy group that may have a substituent, and the original represents an aromatic ring. , preferably at least one of R1 and Rs is represented by a substituent having a total number of carbon atoms of 10 or more.

R1 and Rt in the above formula each independently represent a saturated or unsaturated alkyl group, a cycloalkyl group, and these represent an aryl group, an alkoxy group, an aryloxy group, an acyloxy group, a halogen atom, an acylamino group, an aminocarbonyl group, or A substituent such as a cyano group may be present.

Among the substituents represented by R+ and R1, alkyl groups or alkoxyalkyl groups having 1 to 21 carbon atoms, aryl groups having 6 to 12 carbon atoms, and 1 to 1 carbon atoms;
The acyl group of No. 8 is preferred, and these may be substituted with a halogen atom, an alkoxy group, an aryl group, an aryloxy group, an alkyl group, an acyl group, a cyano group, a hydroxy group, a furfuryl group, or the like.

R,, R, are bonded to each other to form a 5- to 8-membered ring, such as piperidine, morpholine, loridine, piperazine,
A ring such as hexamethyleneimine, caprolactam, or indole may be formed.

R1 and Rt are more preferably an alkyl group or an alkoxyalkyl group having a total of 1 to 21 carbon atoms.

R1, R1 are methyl group, ethyl group, n-propyl group, n-butyl group, 1so-butyl group, n-amyl group, 1so-amyl group, n-hexyl group, n-heptyl group, n -Octyl group, 2-ethylhexyl group, n-dodecyl group, n-octadecyl group, ethoxyethyl group, ethoxypropyl group, 2-ethylhexyloxyethyl group, 2
-ethylhexyloxypropyl group and the like.

R1 in the above formula is a saturated hydrogen atom, an unsaturated alkyl group,
Alternatively, it represents an alkoxy group or a cycloalkyl group, which may have a substituent such as an alkoxy group, an acyloxy group, a halogen atom, or a cyano group.

Among the substituents represented by Rs, hydrogen atom, carbon atom number 1
An alkyl group or alkoxy group of 21 and a fluorine atom are preferred.

R1 is a hydrogen atom, methyl group, ethyl group, n-butyl group, 1so-butyl group, n-amyl group, 1so-amyl group, n-hexyl group, n-heptyl group, n-octyl group, 2- Ethylhexyl group, n-dodecyl group, n-octadecyl group, ethoxyethyl group, ethoxypropyl group, 2-ethylhexyloxyethyl group, 2-ethylhexyloxypropyl group, n-butyloxy group, 1so-
butyloxy group, n-amyloxy group, 1so-amyloxy group, n-hexyloxy group, n-hebutyloxy group, n-octyloxy group, 2-ethylhexyloxy group, n-dodecyloxy group, n-octadecyloxy group,
Examples include a cyclohexyl group and a fluorine atom.

Ring A is (A) is preferred, R4 being selected from the groups indicated by R1.

n represents an integer from 1 to 6, R2 represents -0-15-NR,-, and R6 represents a hydrogen atom, an alkyl group, an alkyl group, or an acyl group.

Furthermore, within ring A is preferable from the viewpoint of synthetic handling and color development.

Next, specific examples of the color former of the present invention will be shown, but the present invention is not limited thereto.

(D) (E) Comparative test 800 Akebono each of fine powders of compounds (A), (D), and (F) ground using a milk wasp were added to 3 g of MMC-210 (a solvent for pressure-sensitive copying paper made by Kureha Chemical Co., Ltd.). and shaking at 25°C for 6 hours. Furthermore, after removing insoluble matter from these solutions, the dissolved concentrations were measured by high performance liquid chromatography.

The results are shown in Table 1.

Table 1 Among the above compounds, (A), (D) and the known compound 3-diethylamino-7,8-benzofluorane (F
) shows the results of a comparative test of solubility with

As described above, it is clear that the fluoran compound used in the present invention has much better oil solubility than known compounds.

In the present invention, by encapsulating the above-mentioned color forming agent in microcapsules, it is possible to prevent fogging during the production of the heat-sensitive material, and at the same time, to improve the shelf life and recordability of the heat-sensitive material. In this case, by selecting the wall material and manufacturing method of the microcapsules, it is possible to increase the image density during recording. The amount of color former used is preferably 0.05 to 5.0 g/rd.

Examples of the wall material of the microcapsule include polyurethane, polyurea, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone, polyvinyl alcohol, etc. 0 In the present invention, two or more of these polymeric substances can also be used in combination.

In the present invention, among the above-mentioned polymeric substances, polyurethane, polyurea, polyamide, polyester, polycarbonate, etc. are preferable, and polyurethane and polyurea are particularly preferable.

The microcapsules used in the present invention are preferably microencapsulated by emulsifying a core material containing a reactive substance such as a coloring agent, and then forming a wall of a polymer material around the oil droplets. In this case, a reactant forming a polymeric substance is added to the interior of the oil droplet and/or to the exterior of the oil droplet. Details of microcapsules that can be preferably used in the present invention, such as a preferred method for producing microcapsules, are described in, for example, JP-A-59-222716.

Here, the organic solvent for forming oil droplets can be appropriately selected from those commonly used as pressure-sensitive oils. Among these, preferred oils include compounds represented by the following general formulas (1) to (I[I), triallylmethane (e.g. tritolylmethane, tolyldiphenylmethane), terphenyl compounds (e.g. terphenyl), Examples include alkylated diphenyl ethers (eg, propyl diphenyl ether, hydrogenated terphenyl (eg, hexahydroterphenyl), diphenyl ether, chlorinated paraffin, etc.).

When n-1, the total number of alkyl groups is 6 or less.

(I[I) where R1 is hydrogen or an alkyl group having 1 to 18 carbon atoms,
R1 represents an alkyl group having 1 to 18 carbon atoms @p'
% Q' represents an integer of 1 to 4, and the total number of alkyl groups is 4 or less.

In addition, the alkyl group of R1 and R1 is preferably an alkyl group having 1 to 8 carbon atoms.

(■) In the formula, R3 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, R4 represents an alkyl group having 1 to 12 carbon atoms, and n represents 1 or 2.

pX, q dew represents an integer from 1 to 4; in the case of n-1, the total number of alkyl groups is 4 or less; in the formula,
RS and RS represent a hydrogen atom or the same or different alkyl group having 1 to 18 carbon atoms.

m represents an integer of 1 to 13, R3 and ql represent integers of 1 to 3, and the total number of alkyl groups is 3 or less.

In addition, the alkyl group of R8 and Rh is particularly preferably an alkyl group having 2 to 4 carbon atoms.

Examples of the compound represented by formula (1) include dimethylnaphthalene, diethylnaphthalene, and diisopropylnaphthalene.

Examples of the compound represented by formula (n) include dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, and diisobutylbiphenyl.

Examples of compounds represented by formula (+11) include 1-methyl-1-dimethylphenyl-1-phenylmethane, -
ethyl-1-dimethylphenyl-1-phenylmethane,
1-Propyl-1-dimethylphenyl-1-phenylmethane is mentioned.

It is also possible to use the above oils together or with other oils.

In the present invention, the size of the microcapsules is preferably 4 microns or less, as measured by the volume average particle size measured, for example, by the measurement method described in JP-A No. 60-214990.

Preferred microcapsules produced as described above are not ruptured by heat or pressure as is used in conventional recording materials (reactive substances contained in the core and outside of the microcapsules are It can penetrate through the capsule wall and react.

In the present invention, the wall material of the microcapsule is selected,
If necessary, a glass transition point adjusting agent (for example, Japanese patent application 1986-
119862) to prepare microcapsules consisting of walls with different glass transition points, and by selecting combinations of basic colorless dye precursors with different hues and their color developers. It is possible to achieve intermediate colors. Therefore, the present invention is not limited to monochromatic thermal paper, but can also be applied to two-color or multicolor thermal paper and thermal paper suitable for recording images with gradation.

Further, if necessary, a photofading inhibitor described in, for example, Japanese Patent Application No. 60-125470, Japanese Patent Application No. 60-125471, and Japanese Patent Application No. 60-125472 can be appropriately added.

In addition to the above-mentioned compounds, any known color developer that causes a color-forming reaction when heated with the basic colorless dye used in the present invention can be used as appropriate. For example,
Color developers for leuco dyes include phenolic compounds, triphenylmethane compounds, triphenylmethane compounds, sulfur-containing phenol compounds, carboxylic acid compounds, sulfone compounds, urea or thiourea compounds, etc. , the details of which are described in, for example, Gi Pulp Technology Times (1985, pages 49-54 and 65-70).
℃ is preferable, and among them, phenols and organic acids which are poorly soluble in water at 60 to 200℃ are preferable.When two or more types of color developers are used in combination, solubility increases, so it is preferable.

Among the color developers used in the present invention, particularly preferred ones are represented by the following general formulas (rV) to (■).

methyl group, ethyl group and butyl group are particularly preferred.

(Vl) 0ORt R2 is an alkyl group, especially a butyl group, a pentyl group,
Heptyl and octyl groups are preferred.

Cll0. □１ m=o~2, n=2~11 R1 is an alkyl group or an aralkyl group.

In the present invention, a color developer is dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then mixed with an aqueous phase containing a surfactant and having a water-soluble polymer as a protective colloid to emulsify and disperse it. Use in the form of a dispersion.

R1 is an alkyl group, an aryl group, or an aralkyl organic solvent for dissolving the color developer can be appropriately selected from organic solvents that are 11 soluble or insoluble in water, but in particular those with a boiling point of 150
It is preferable to use an organic solvent having a temperature of 0.degree. C. or lower because of its good thermal sensitivity. Examples of these organic solvents include ethyl acetate, isopropyl acetate, butyl acetate, and methylene chloride.

In the present invention, these organic solvents can be mixed with high-boiling esters or the pressure-sensitive oil as appropriate, but esters are particularly preferred from the viewpoint of stability of the developer emulsion dispersion. It is preferable.

Examples of high-boiling esters include phosphoric esters (e.g., triphenyl phosphate, tricresyl phosphate, butyl phosphate,
Octyl phosphate, talesyl diphenyl phosphate), phthalate esters (diptyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, octyl phthalate, butylbenzyl phthalate), dioctyl tetrahydrophthalate, benzoate esters (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate), abietate ester (ethyl abietate, benzyl abietate), dioctyl adipate, isodecyl succinate, dioctyl azelaate, oxalate ester (dibutyl oxalate, Dipentyl oxalate), diethyl malonate, maleate ester (dimethyl maleate, diethyl maleate, diptyl maleate), tributyl citrate, sorbate ester (methyl sorbate, ethyl sorbate, methyl sorbate), sebacate ester (diptyl sebacate, dioctyl sebacate), ethylene glycol esters W4 (formic acid monoesters and diesters, butyric acid monoesters and diesters, lauric acid monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters, oleic acid monoesters and diesters), triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, boric acid esters (
tributyl borate, tripentyl borate), etc.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase to be mixed with the oil phase in which the color developer is dissolved can be appropriately selected from known anionic polymers, nonionic polymers, and amphoteric polymers. However, polyvinyl alcohol, gelatin, cellulose derivatives, etc. are preferable, especially partially saponified polyvinyl alcohol, especially saponification degree of 75 to 90%.
Preferably.

(Function) In particular, when a partially saponified polyvinyl alcohol is used as a protective colloid, for reasons that are not clear, it stabilizes the color developer emulsion dispersion, resulting in a heat-sensitive recording material phase when used as a heat-sensitive recording material. The transparency can be made extremely good. In order to make the effect of this partially saponified polyvinyl alcohol most effective, it is preferable to use it during emulsification, but it is also possible to add the partially saponified polyvinyl alcohol after emulsifying with another protective colloid.

Further, as the surfactant to be contained in the aqueous phase, one can be appropriately selected from anionic or nonionic surfactants that do not cause precipitation or aggregation by interacting with the above-mentioned protective colloid. .

Preferred surfactants include sodium alkylbenzenesulfonate (for example, sodium dodecylbenzenesulfonate), sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene gelicol (for example, polyoxyethylene nonylphenyl ether), and the like. can.

The emulsified dispersion containing partially saponified polyvinyl alcohol of a color developer in the present invention is produced by mixing an oil phase containing a color developer and an aqueous phase containing a protective colloid and a surfactant at high speed.
It can be easily obtained by mixing and dispersing using a means commonly used for fine particle emulsification, such as ultrasonic dispersion.

A melting point depressant for a color developer may be added to this emulsified dispersion as appropriate. Some of these melting point depressants are
It also functions as a glass transition point regulator for the capsule wall. Examples of such compounds include hydroxy compounds, carbamate ester compounds, sulfonamide compounds, aromatic methoxy compounds, etc. For details, see
For example, it is described in Japanese Patent Application No. 59-244190.

These melting point depressants can be used in an amount of 0.1 to 2 parts by weight, preferably 0.5 to 1 part by weight, per 1 part by weight of the color developer that lowers the melting point. It is preferable that the color developer and the like whose melting point is lowered by this are used at the same location.If they are added to different locations, it is preferable to add them in an amount 1 to 3 times the above-mentioned amount.

The heat-sensitive recording material of the present invention can be coated using a suitable binder.

As a binder, polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxypropylcellulose, gum arabic, gelatin, polyvinylpyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic acid ester-ethylene-vinyl acetate, etc. Various emulsions such as polymers can be used. The amount used is 0.5 to 5 g/n (solid content).

The heat-sensitive recording material of the present invention is produced by preparing a coating liquid containing a partially saponified polyvinyl alcohol dispersion in which microcapsules containing a color former and at least a color developer are emulsified and dispersed, and other additives such as a binder. It is produced by coating and drying a heat-sensitive layer having a solid content of 2.5 to 25 g/rd on a support such as paper or a synthetic resin film by a coating method as described below. The heat-sensitive layer of the heat-sensitive material produced in this manner surprisingly has good transparency, although the reason is not clear.

Transparency here refers to Integrating Sphere Method HT manufactured by Nippon Seimitsu Kogyo ■.
It can be expressed as haze (%) measured with an R meter. However, the transparency of an actual heat-sensitive layer test sample is based on the fine irregularities on the surface of the heat-sensitive layer (light scattering has a large influence. When measuring the internal transparency of a layer using a haze meter, a simple method is to attach a receding adhesive tape onto the heat-sensitive layer, and then evaluate the measured value with almost all surface scattering removed.

The heat-sensitive recording material of the present invention contains silica, barium sulfate, titanium oxide, aluminum hydroxide, zinc oxide,
Pigments such as calcium carbonate, fine powders such as styrene pieces, urea-melamine resin, etc. can be added, but in order to maintain the transparency of the heat-sensitive layer, additives are added on top of the heat-sensitive layer mainly to improve storage stability and stability. For details on the protective layer, which is preferably added to the protective layer provided by a known method, see, for example, Paper and Pulp Technology Times J.
(September issue, 1985), pages 2-4.

Similarly, metal soaps can also be added to prevent sticking. The amount used is 0.2-7g/
It is nr.

The paper used for the support is heat extracted pH 6 sized with a neutral sizing agent such as an alkyl ketene dimer.
~9 Neutral paper (described in JP-A-55-14281)
The use of is advantageous in terms of storage stability over time.

Thermal recording head and heat-sensitive layer prevent the coating liquid from soaking into the paper! j1
1! In order to improve contact with
The paper described in No. 687 having a (meter basis weight) 2 and a Bekk smoothness of 90 seconds or more is advantageous.

In addition, the optical surface roughness described in JP-A-58-136492 is 8μ or less and the thickness is 40 to 75μ, JP-A-58-136492.
Paper with a density of 0°9 g/cm3 or less and an optical contact ratio of 15% or more, described in JP-A No. 8-69097, JP-A-58-690
Canadian standard freeness described in No. 97 (JIS P812
Paper made from pulp beaten to 400 cc or more in 1) to prevent penetration of coating liquid, JP-A-58-65
695, the glossy side of base paper made by a Yankee machine is used as the coated surface to improve the color density and resolution, and the method described in JP-A-59-35985, in which the base paper is subjected to corona discharge treatment. Papers with improved coating suitability may also be used in the present invention with good results. In addition to these, any support commonly used in the field of heat-sensitive recording paper can be used as the support of the present invention.

Furthermore, when a transparent support is used as a support, the heat-sensitive material of the present invention can be seen as a transmitted image or a reflected image from one side of the transparent support, but especially in the latter case, the background part can be seen as a transmitted image or a reflected image. If the back side is visible, the image will not be clear, so to make it look white, a white pigment may be added to the heat-sensitive layer, or a liquor containing a white pigment may be additionally applied.

In either case, it is effective to perform this on the outermost layer on the opposite side from the side where the recorded image is viewed. Examples of preferred white pigments include talc, calcium carbonate, calcium sulfate, magnesium carbonate, magnesium hydroxide, alumina, synthetic silica, titanium oxide, barium sulfate, kaolin, calcium silicate, urea resin, and the like.

The dispersed particle size is preferably 10 microns or less.

The transparent supports mentioned here include polyester films such as polyethylene terephthalate and polybutylene terephthalate, films of cellulose derivatives such as cellulose triacetate films, polystyrene films, polypropylene films, polyolefin films such as polyethylene, etc. They can be used alone or in combination.

The thickness of the transparent support used is 20 to 200 .mu.m, particularly preferably 50 to 100 .mu.m.

In the present invention, an undercoat layer can be provided between the transparent support and the heat-sensitive layer in order to enhance adhesion between the two layers. Gelatin, synthetic polymer latex, nitrocellulose, etc. are used as the material for the undercoat layer. Lower V! The amount of layer applied is O
,1g/-~2. It is preferably in the range of 0 g/rr (, particularly preferably in the range of 0.2 g/rr to 1.0 g/rr).

If it is less than 0.1 g/rr+, the adhesion between the support and the heat-sensitive layer will not be sufficient; Og/n (even if it is increased above this, the adhesive force between the support and the heat-sensitive layer has reached saturation, which is disadvantageous in terms of cost).

The undercoat layer is coated with a hardening agent because the image quality of the heat-sensitive layer may deteriorate if the undercoat layer swells due to the water contained in the heat-sensitive layer when the heat-sensitive layer is coated on top of it. It is desirable to cure it.

As hardeners that can be used in the present invention, the following can be mentioned.

■Divinylsulfone-N,N'-ethylenebis(vinylsulfonylacetamide), l,3-bis(vinylsulfonyl)-2-propatol, methylenebismaleimide,
5-acetyl-1,3-diacryloyl-hexahydro-g-)riazine, 1.3.5-triacryloyl-hexahydro-S-triazine, 1.3.5-trivinylsulfonyl-hexahydro-5-) Active vinyl compounds such as riazine.

■2,4-dichloro-6-hydroxy-3-triazine sodium salt, 2,4-dichloro-6methoxyS-
Triazine, 2,4-dichloro6-(4-sulfoanilino)-s-t-riazine sodium salt, 2,4-dichloro-6-(2-sulfoethylamino)-s-triazine, N-N'-bis Active halogen compounds such as (2-chloroethylcarbamyl)piperazine.

■Bis(2,3-epoxypropyl)methylpropylammonium p-toluenesulfonate, 1.4-bis(2',3'-epoxypropyloxy)butane, 1.
3.5-) Epoxy compounds such as diglycidyl isocyanurate and 1,3-diglycidyl-5-(T-acetoxy-β-oxypropyl)isocyanurate.

■2.4.6-doriethylene-s-) riazine, 1,
Ethyleneimino compounds such as 6-hexamethylene-N,N'-bisethyleneurea and bis-β-ethyleneiminoethylthioether.

■1.2-di(methanesulfonoxy)ethane, 1.4
- Methanesulfonic acid ester compounds such as di(methanesulfonoxy)butane and 1°5-di(methanesulfonoxy)pentane.

■Dicyclohexylcarbodiimide, 1-cyclohexyl-3-(3-)dimethylaminopropyl)carbodiimide-p-)rienesulfonate, l-ethyl-3-(
3-dimethylaminopropyl) carbodiimide hydrochloride.

■2.5-dimethylisoxazole perchlorate, 2
-Isoxazole compounds such as ethyl-5-phenylisoxazole-3'-sulfonate and 5,5'-(paraphenylene)bisisoxazole.

■Inorganic compounds such as chromium alum, chromium acetate, boric acid, and zirconium salts.

■N-carboethoxy 2-isopropoxy 1,2-dihydroquinoline, N-(1-morpholinocarboxy)-
Dehydrated condensation type peptide reagents such as 4-methylpyridinium chloride, active ester compounds such as N,N'-aziboyldioxydisuccinimide, and N,N'terephthaloyldioxydisuccinimide.

[Phase] Toluene-2,4-diisocyanate, ■.

Isocyanates such as 6-hexamethylene diisocyanate.

Among these, dialdehydes such as glutaraldehyde and 2°3-dihydroxy-1,4-dioxane, and boric acid are particularly preferred.

The amount of these hardeners added is based on the weight of the base coat material.
An appropriate addition amount can be selected in the range of 0.20% by weight to 3.0% by weight depending on the coating method and desired degree of curing.

If the amount added is less than 0.20% by weight, the degree of curing will be insufficient no matter how long it is allowed to last, and the undercoat layer will swell when applying the heat-sensitive layer, and conversely, if it is more than 3.0% by weight. The problem is that the degree of curing progresses too much, the adhesion between the undercoat layer and the support worsens, and the undercoat layer becomes film-like and peels off from the support.

Depending on the curing agent used, if necessary, caustic soda may be added to adjust the p)I of the liquid to an alkaline earth metal, or the pH of the liquid may be made acidic using citric acid or the like.

It is also possible to add an antifoaming agent to eliminate foam generated during coating, or to add an activator to improve liquid leveling and prevent coating streaks. .

Moreover, it is also possible to add an antistatic agent if necessary.

Furthermore, before applying the undercoat layer, it is desirable to activate the surface of the support by a known method.

Activation treatment methods include acid etching treatment,
Flame treatment using a gas burner, corona treatment, glow discharge treatment, etc. are used, but from the point of view of cost or simplicity, U.S. Pat.
No. 846.727, No. 3,549,406, No. 3
．． 590. The corona discharge treatment described in No. 107 and the like is most preferably used.

The heat-sensitive recording material of the present invention can, of course, be designed for OHP use, and can also be coated directly on the support with heat-sensitive layers capable of forming different colors, or via the above-mentioned protective layer or undercoat layer. Furthermore, one layer selected from a known photosensitive layer, a heat-sensitive layer, and a light-sensitive heat-sensitive layer is provided on the support, and furthermore, as described in this specification, the layer can be colored in a color different from that of the eyebrows. Various embodiments are possible depending on the use and purpose, such as the possibility of providing a substantially transparent heat-sensitive layer.

The coating liquid according to the present invention can be applied by a generally well-known coating method,
For example, dip coating method, air knife coating method, curtain coating method, roller coating method, doctor coating method,
Coating can be performed by a wire bar code method, a slide coating method, a gravure coating method, or an extrusion coating method using Holapara described in US Pat. No. 2,681,294. U.S. Pat. No. 2.761.791 and U.S. Pat. No. 3,508,947, as appropriate.
No. 2.941.898, and No. 3526.5.
Specification No. 28, Yuji Harasaki, “Coating Engineering” 253
It is also possible to apply the coating simultaneously in two or more layers using the method described in ``P. (Published by Asakura Shoten, 1973)'', and an appropriate method can be selected depending on the amount of coating, coating speed, etc.

Pigment dispersants, thickeners, flow modifiers, antifoaming agents, foam inhibitors, mold release agents, and colorants may be appropriately added to the coating liquid used in the present invention as long as they do not impair the properties. There is nothing wrong with that.

The coloring agent according to the present invention can be produced by a known method (for example, JP-A-49-40553, JP-A-49-119718, etc.).
Manufactured by. For example, the corresponding 2-hydroxy-
It can be easily obtained by reacting 4-dialkylaminobenzoylbenzoic acid with a β-naphthol derivative in the presence of a condensing agent such as acetic anhydride, sulfuric acid, or phosphorus oxychloride.

Synthesis Example-1 0.1 mol of 2-(2hydroxy-4-diethylaminobenzoyl)benzoic acid and 0 mol of 2-methoxy-6-n-octadecylnaphthalene in a three-way flask equipped with a stirrer.
．． Weigh out 50cc of 1 mol, 80% sulfuric acid and heat to 100°C.
The reaction mixture stirred for 10 hours was poured into water and diluted with sodium hydroxide solution. It was made alkaline with 8 liquids. When this reaction mixture was separated using a hexane-ethyl acetate mixed solvent using silica gel as a carrier, the compound of Example (A) was obtained with a melting point of 79-80.
Obtained as white crystals at °C.

Synthesis Examples 2 and 3 Specific example (
Compound B) was obtained (Synthesis Example-2), and 2 of Synthesis Example-1 was obtained.
-(2-hydroxy-4-diethylaminobenzoyl)
2-(2-hydroxy-4-ethyl-(2ethylhexyloxypropyl)aminobenzoyl)benzoic acid was used instead of benzoic acid, and β-naphthol was used instead of 2-methoxy-6-n-octadecylnaphthalene. The compound of Specific Example (D) was obtained in the same manner as Synthesis Example 1 except that each compound was used (Synthesis Example 3).

Compound of Specific Example (B) Melting point: 85-6°C Specific Example (D)
Compound of melting point 93-4°C (Example) The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto.

(Examples 1 to 3) [Preparation of capsule liquid] 14 g of the coloring agent shown below, 60 g of Takenate D-11ON (capsule wall material manufactured by Narita Pharmaceutical ■), and Sumithorp 200
(Ultraviolet absorber manufactured by Sumitomo Chemical ■) 2g 1-phenyl-1
-55g of xylylethane and 55g of methylene chloride
was added to a mixed solvent and dissolved. This leuco dye solution was mixed with 100 g of 8% polyvinyl alcohol aqueous solution and 4 ml of water.
0g and 2% sodium salt of dioctyl sulfosuccinate (dispersing agent) 1.4g was mixed with an aqueous solution of 1.4g, and emulsified with an Ace homogenizer manufactured by Nippon Seiki ■ at 000γpm for 5 minutes, and further 150g of water was added, After reacting at ℃ for 3 hours, the capsule size was reduced to 0. A 7μ capsule solution was produced.

[Preparation of developer emulsion dispersion]

Color developer represented by the following structural formula (a) 7g, (b) 7g
, (c), 7 g of tricresyl phosphate, and 3 g of diethyl maleate were dissolved in 38 g of ethyl acetate. The obtained developer solution was mixed with an 8% polyvinyl alcohol (Kuraray fiPVA205: saponification degree 87-89%) aqueous solution 1
00 g of water, 150 g of water, and 0.5 g of sodium dodecylbenzenesulfonate were mixed and emulsified for 5 minutes at room temperature using an Ace homogenizer manufactured by Nippon Seiki ■ to obtain an emulsified dispersion with a particle size of 0.5 μm. I got it.

Zinc salt Color developer (b) Color developer (C) [Preparation of heat-sensitive material] 5.0 g of the above capsule liquid, 10.0 g of color developer emulsion dispersion
, and 5.0 g of water were mixed with stirring to prepare a coating solution.Then, this coating solution was allowed to stand for one hour and the state of the coating solution was observed, and the stability of the coating solution was confirmed. As mentioned above, after standing for 1 hour, the coating liquid was applied to a transparent polyethylene terephthalate (PET) film with a thickness of 70 μm, and the solid content was 15 glr.
After coating and drying, the transparency of this film was measured using an integrating sphere HTR meter manufactured by Nippon Seimitsu Kogyo, and the haze was less than 8% in all cases, indicating extremely good transparency. It has been demonstrated that Furthermore, when this film was colored by facsimile, it exhibited a vivid magenta color. Also, 32000 lu was added to this film before use.
Even after 16 hours of irradiation with x fluorescent lamp, no yellowing of the skin was observed. Furthermore, the light fastness of the obtained image was excellent.

The coloring agent used is as follows.

Example 1 Compound Example 2 of Specific Example (A) Compound Example 3 of Specific Example (B) Comparative Example-1 of Compound of Specific Example (D) Using 3-diethylamino-7,8-benzofluorane as a coloring agent The test was conducted in the same manner as in Example 1 except for the following. As a result, some crystals precipitated in the capsules, and even when applied to a transparent film, the film became opaque during the drying process.

Comparative Example-2 All the samples were
The test was conducted in the same manner as in Example 1.

1 under a 320001ux fluorescent light on this film before use.
After 6 hours of irradiation, significant yellowing of the skin was observed.

Claims (1)

[Scope of Claims] A heat-sensitive recording material in which microcapsules having a color former and a heat-sensitive layer having a color developer are provided on a support, in which a fluoran compound represented by the following general formula is used as the color former. Features of heat-sensitive recording material. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the above formula, R_1 and R_2 are alkyl groups that may have a substituent, and R_3 is a hydrogen atom, an alkyl group or an alkoxy group that may have a substituent. , ring A represents an aromatic ring.