JPH01237190A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having a high sensitivity and a transparent thermal recording layer which can be used for an overhead projector, by using a specified compound as part of a color developer. CONSTITUTION:A compound of general formula (I) is used as part of a color developer, in a thermal recording material in which a thermal recording layer comprising at least color former containing microcapsules and the color developer is provided on a support. In the formula, R is hydrogen, a halogen, ester group or substd. or unsubstd. alkyl. The compound of general formula (I) can be easily obtained by bringing the corresponding phenols and an allyl halide into reaction with each other in the presence of a base, taking out a phenol allyl ether compound thus formed, and heating the ether compound. The base may be sodium carbonate, potassium carbonate or the like, and the reaction solvent may be acetone, dimethylformamide, dimethylacetamide or the like. The reaction is carried out at a temperature ranging from room temperature to 150 deg.C for a period of time of 1-20hr.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a heat-sensitive recording material having a heat-sensitive layer provided on a support. Regarding materials.

<Prior art> The thermal recording method has the following advantages: (1) development is not required, (2) when the support is paper, the paper quality is similar to ordinary paper, (3) it is easy to handle, and (≠) the color density is high. (j) The recording device is simple and inexpensive; and (6) There is no noise during recording. Therefore, it has rapidly become popular in the fields of facsimiles and printers in recent years, and thermal recording applications are becoming increasingly popular. is also expanding.

Against this background, in recent years, in order to adapt to multicolor, overhead projectors (
It has become desirable to develop a transparent heat-sensitive recording material that can be directly recorded with a thermal head for use in OHP.

However, conventional transparent heat-sensitive recording materials are
#It is a so-called transparent thermosensitive film that absorbs infrared rays into the image area of the document by irradiating it with light, raising the temperature of the image area, which causes the thermosensitive recording film to develop color, and is used in facsimiles, etc. 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 simply coating it on a transparent support cannot achieve the desired transparency.

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 a solvent that is sparingly soluble or insoluble in water, emulsifying and dispersing the latter, mixing the two, and coating this on a support (Special Gansho 61-♂r/7
No. 7).

<Problems to be Solved by the Invention> However, it has been found that the transparency of the above heat-sensitive recording material is significantly affected by the emulsion stability of the color developer in the heat-sensitive layer. For example, when using λ,2-bis(≠-hydroxyphenyl)propane, which is known as a color developer in heat-sensitive recording materials, important drawbacks regarding transparency, such as easy crystallization and easy fogging, have been revealed.

<Object of the Invention> Accordingly, an object of the present invention is to provide a heat-sensitive recording material having a transparent heat-sensitive layer that has high sensitivity and can be used for OHP.

<Structure of the Invention> The object of the present invention was achieved by developing a recording material using a compound represented by general formula (I) as a part of a color developer.

In formula (I), R represents a hydrogen atom, a halogen atom, an ester group, or an alkyl group which may have a substituent.

Among the substituents represented by R in the above general formula, preferred ones are represented by the following general formula (II).

Here, R1 and R2 each independently represent a hydrogen atom or an alkyl group, and the alkyl group may be substituted, and R1
, R2 may be bonded to each other.

Preferred examples of -C- are shown below.

HHH In the above formula, R represents a hydrogen atom or an alkyl group.

Xl and X2 each independently represent a hydrogen atom, a halogen atom,
Various synthesis methods can be considered for the preferred compounds of the present invention, which represent a hydroxyl group, an aryl group, an allyl group, or an alkyl group that may have a substituent, but in the present invention, the corresponding phenols and/or % allyl chloride in the presence of a base to extract the allyl ether compound of phenol, which can be easily obtained by further heating.

Sodium carbonate, potassium carbonate, etc. are used as the base, and the reaction solvent consists of acetone, dimethylformamide, dimethylacetamide, etc.

The reaction temperature ranges from room temperature to 110°C, and the reaction time is /-20 hours.

Claisen rearrangement of allyl ether compound is /JO-2!
It is carried out in a temperature range of 0'C.

The allyl halide is used in a molar ratio of / to 70 mol relative to the phenol.

A synthesis example is shown below.

(Synthesis example) jOQ Mitsuro flask, λ-bis(Hiro-hydroxyphenyl)propane 3≠P, J [7! Add JR rot, potassium carbonate, and 200 g of dimethylformamide, and stir at 70°C for several hours. Next, the reaction product was poured into water, extracted with toluene, and the solvent was distilled off to give =, 2-bis(t
An allyl ether compound of A-hydroxyphenyl)propane was obtained.

Further, by heating this compound for 3 hours under a nitrogen atmosphere at CO/Q0C, a viscous oil of the desired λ and cocose (3-allyl-hydroxyphenyl)furopane was obtained. A basic dye precursor that gives a colored product upon contact with the above-mentioned color developer will now be described.

As the basic dye precursor used in the present invention, a colorless or light-colored one is appropriately selected from known compounds that develop color by donating electrons or accepting protons such as acids. Such compounds have partial skeletons such as lactones, lactams, sultones, spiropyrans, esters, and amides, and these partial skeletons are ring-opened or cleaved upon contact with a color developer. Preferred compounds include Examples include triarylmethane compounds, diphenylmethane compounds, xanthine compounds, thiazine compounds, and spiropyran compounds.

Particularly preferred compounds are those represented by the following general formula.

In the formula, R1 is an alkyl group having 1 to 8 carbon atoms, R1 is an alkyl group having 4 to 18 carbon atoms, an alkoxyalkyl tyrant, or a tetrahydrofurfuryl group, and R1 is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms. The group or halogen atom, R4, represents a 1L-substituted or 1WIA-free aryl group having 6 to 20 carbon atoms.

As the 1 to 4 substituents, an alhel group, an alkoxy group, a halogenated alkyl group, and a halogen atom having 1 to 5 carbon atoms are preferable.

In the present invention, C is capable of preventing fogging during the production of heat-sensitive materials, and at the same time, improving the raw storage and archival storage properties of the heat-sensitive materials by encapsulating the above-mentioned coloring agent in microcapsules. . In this case, the image density during recording can be increased by selecting the wall material and manufacturing method of the microcapsules.The amount of color former used is preferably 0.05 to 5.0 g/r. .

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, ζ can also be a combination of two or more of these polymeric substances.

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, for example, in JP-A-59-22271 (i).

Here, the organic solvent for forming the oil droplets can be appropriately selected from among those used as pressure-sensitive oils. Among these, preferable oils include compounds represented by the following general formulas (1) to (lft), triallylmethane (e.g., tolytylmethane, tolyldiphenylmethane), and terphenyl compounds (e.g.,
terphenyl), alkylated diphenyl ethers (e.g. propyl diphenyl ether, hydrogenated terphenyl (
Examples include tosahydroterphenyl), diphenyl ether, and chlorinated paraffin.

In the formula, R' is hydrogen or alkyl having 1-10 carbon atoms/14
', 1?2 represents an alkyl group having 1 to 18 carbon atoms
p l and q + are 1 to 4! ! represents a number, and the total number of alkyl groups is 4 or less.

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

(II) In the formula, IP represents a hydrogen atom or a) L having 1 to 12 carbon atoms, 174 represents an alkyl group having 1 to 12 carbon atoms, and n represents 1 or 2.

P"%Q" represents an integer from 1 to 4; when n=1, the total number of alkyl groups is 4 or less; when n=1, the total number of alkyl groups is 6 or less.

(III) (Rゝ)p3 (R')q3 In the formula, R',
R' represents a hydrogen atom or a same or different alkyl group having 1 to 18 carbon atoms.

III is 1-13! ! The number @P”-Q’ is 1
Represents an integer of ~3, and alkyl! The total sum of S is 3 or less.

Incidentally, R', alnyl W in I<' 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 (11) include dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, and diisobutylbiphenyl.

Examples of compounds represented by formula (ill) include 1-methyl-1-dimethylphenyl-1-phenylmethane, l-
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 can be prepared by heating and pressure as used in conventional recording materials.
(The reactive substance contained in the core and outside of the microcapsule can penetrate through the microcapsule wall and react.)

In the present invention, the wall material of the microcapsule is selected,
If necessary, glass transition point MA adjuster (for example, patent application 1986
-119862) to prepare microcapsules consisting of walls with different glass transition points, and select combinations of basic colorless dye nil precursors with different hues and their color developers. This makes it possible to realize multiple intermediate colors. Therefore, the present invention is not limited to thermal paper for parcels, but can also be applied to two-color or multi-color thermal paper and thermal paper suitable for recording images with gradation.

In addition, if necessary, for example, Japanese Patent Application No. 1973-/2j≠70, AO-/λ! The photofading inhibitor described in μ7/No. 60-12≠7λ can be added as appropriate.

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,
Examples of color developers for leuco dyes include phenolic compounds, triphenylmethane compounds, sulfur-containing phenol compounds, carboxylic acid compounds, sulfone compounds, urea or thiourea compounds, etc. , Paper and Pulp Technology Times (1913) ≠ Taryo Attendant and page 4j-70. Among these, especially the melting point is jO'C~λ! 0°C is preferable, and 1s00 (Nie 2000) is preferable, and water-soluble phenols and organic acids are preferable.If two or more color developers are used in combination, 7 is preferable because the solubility increases. .

Among the color developers used in the present invention, particularly preferred ones are represented by the following general formulas [1v] to (Vl).

m w O~2, n-2~11 (V) R1 is an alkyl group, an aryl group, or an aralkyl group, and a methyl group, an ethyl group, and a butyl group are particularly preferred.

71) 11) h is an alkyl group, especially a butyl group, a pentyl group,
Heptyl and octyl groups are preferred.

(Vl) R1 is an alkyl group or an aralkyl group.

In the present invention, "C" is obtained by dissolving a color developer in an organic solvent that is poorly soluble or insoluble in water, and then mixing this with an aqueous phase containing a surfactant and having a water-soluble polymer as a protective colloid,
It is used in the form of an emulsified and dispersed ink product.

The organic solvent for dissolving the color developer can be appropriately selected from organic solvents that are sparingly soluble or insoluble in water, but in particular, when an organic solvent with a boiling point of 150°C or lower is used, it has good thermal sensitivity. These preferred 4!1 solvents include:
Examples 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 emulsified bone material as a color developer. It is preferable to use

Examples of high-boiling esters include phosphoric esters (e.g., triphenyl phosphate, tricresyl phosphate, butyl phosphate,
Octyl phosphate, talesyl diphenyl phosphate), ethyl phthalate (dibutyl phthalate, 2-ethylhexyl phthalate, ethyl phthalate, octyl phthalate, butylbenzyl phthalate), dioctyl tetrahydrophthalate, benzoate ester (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate), abietate ester (ethyl abietate, benzyl abietate), dioctyl adipate, isodecyl succinate, dioctyl azelate, oxalate ester dibutyl acid, dipentyl oxalate), diethyl malonate, maleate ester (dimenal maleate, diethyl maleate, dibutyl maleate), tributyl citrate, sorbate ester (methyl sorbate, ethyl sorbate, bunal sorbate), Sebacate esters (dibutyl sebacate, dioctyl sebacate), ethylene glycol esters 1 (formate monoesters and diesters, butyrate 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) and the like.

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) Particularly, when a partially saponified polyvinyl alcohol is used as a protective colloid, the reason is not clear, but as a result of stabilizing the material in the developer emulsifying valve 11, the thermal sensitivity of the thermal recording material F+ increases. The transparency of the recording material phase can be made very 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.

In addition, as the surfactant to be included for hydration, select one from anionic or nonionic surfactants that does not interact with colloids and cause precipitation or aggregation. You can use it.

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 be mentioned.

In the present invention, the emulsion component 11 containing partially saponified polyvinyl alcohol of the color developer is obtained by mixing an oil phase containing the color developer and an aqueous phase containing a protective colloid and a surfactant with high speed stirring and ultrasonication. etc., can be easily obtained by using the means used for ordinary fine particle emulsification and increasing the temperature of the mixture at °C + lk.

Add a melting point depressant of a color developer to this emulsion component 11 as appropriate.
You can also add 3. Some of these melting point depressants also have the function of controlling the glass transition point of the capsule wall. Examples of such compounds include human mixi compounds, carbamate ester compounds, sulbonamide compounds, and aromatic methoxy compounds, the details of which are described in, for example, 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 to use the depressant and the color developer, which lowers the melting point, at the same location.If they are added at different locations, it is recommended to add 1 to 3 times the amount of addition (1) above. preferable.

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

Binders include 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 solid content used is 0.5 to 58/mouth.

The heat-sensitive recording material of the present invention is a coating containing microcapsules encapsulating a color former and at least a color developer with an emulsion content of 11, a partially saponified polyvinyl alcohol with a content of 11, and other additives such as a binder. make a liquid,
It is coated on a support such as paper or a synthetic resin film by the coating method described below and dried to a solid content of 2.5 to 25 g.
/ nT heat-sensitive tubing.

The heat-sensitive layer of the heat-sensitive material produced in this manner surprisingly has extremely good transparency, although the reason is not clear.

Transparency here refers to Integrating Sphere Method I manufactured by Nippon Seimitsu Kogyo ■.
It can be expressed as haze (%) measured with an ITR meter. However, the transparency of the actual heat-sensitive layer test sample is greatly affected by the disturbance in the light 11 due to minute irregularities on the surface of the heat-sensitive layer. Therefore, when measuring the inherent transparency of the heat-sensitive layer, which is a problem in the present invention, that is, the transparency inside the heat-sensitive layer, using a haze meter, a transparent adhesive tape is pasted on the heat-sensitive layer as a convenient method. , the evaluation is based on 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,
Qn materials such as calcium carbonate, styrene beads, urea
Although it is possible to add powder such as melamine resin,
In order to maintain the transparency of the heat-sensitive layer, a protective layer for the purpose of preservation and stability is preferably provided on the heat-sensitive layer by a known method. For details, see [Paper and Pulp Technology Times J
(September issue, 1985), pages 2-4.

Similarly, metal soaps can also be added to prevent sticking. Use 1 of these is 0.2~7g
/■ is.

The paper used for the support is thermally extracted paper sized with a neutral sizing agent such as furkyl ketene dimer.
The use of neutral paper No. 116-9 (described in Japanese Patent Application Laid-Open No. 14281/1982) is advantageous in terms of storage stability over time.

In order to prevent the coating liquid from penetrating into the paper and improve the contact between the thermal recording head and the thermal recording layer, the
The paper described in No. 117 and having a Bekk smoothness of 90 seconds or more is advantageous.

Also, paper with an optical surface roughness of 8μ or less and a II roughness of 40 to 75μ as described in JP-A-58-136492, and a paper with a density of 0°9 g/cm3 or less and an optical surface roughness as described in JP-A-58-69097 Paper with a contact rate of 15% or more, JP-A-58-69
Canadian Standard Freeness (JIS P81) described in No. 097
Paper made from pulp beaten to 400 cc or more in 21) and prevented from soaking in the coating liquid, JP-A-58-[3]
5695, the glossy side of base paper made by a Yankee machine is used as the coating surface to improve the color density and resolution, and the method described in JP-A-59-35985.
Papers whose base paper has been subjected to a corona discharge treatment to improve the suitability of coating with C can also be used in the present invention and give 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.

In addition, when a transparent support is used as a support, the thermal 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 image can be seen as a transmitted image or a reflected image. If the back side of the part is visible, the image will not be clear, so to make it look white, a white pigment may be added to the jS heat layer, or a layer containing 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.

Preferably, the divided particle size is less than 10 microns.

The transparent supports mentioned here include polyester films such as polyethylene terephthalate and polybutylene lenticulate, films of cellulose derivatives such as cellulose triacetate films, polystyrene films, polypropylene films, polyolefin films such as polyethylene, etc. These can be used alone or by bonding together -U''C.

The j7 diameter of the transparent support is preferably 20 to 200μ, particularly preferably 50 to loOμ.

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. The coating layer of the undercoat layer is O,
Ig/+t-~2. It is preferably in the range of 0°2 g/m'' to 1.0 g/m''.
A range of 0g/nt" is preferred.

If it is less than 0.1 g/m", the adhesion between the support and the heat-sensitive layer will not be sufficient, and even if it is increased to more than 2.0 g/m", the adhesion between the support and the heat-sensitive layer will reach saturation. This is disadvantageous in terms of cost.

When the undercoat layer is coated on top of the heat-sensitive layer, 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. It is desirable to cure the material using

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-propatur, methylenebismaleimide, 5--7'cetyl-1 , 3-cyacryloyl-hexahydro-3-triazine, 1.3.5-triacryloyl-hexahydro-8-triazine, 1.3.5-)
ribinylsulfonyl-hexahydro-s-triazine,
Active vinyl compounds such as.

■2.4-dichloro-6-hydronitocys-I riazine sodium salt, 2.4-dichloro-6-nodoxy-S-triazine, 2.4-dichloro-[3-(4-sulfoanilino)-s-1 Riazine sodium salt, 2.
4-dichloro-6-(2-sulfoethylamino)-s
- Active halogen compounds such as 1-riazine and N-No-bis(2-chloroethylcarbamyl)piperazine.

■Bis(2,3-epoxypyl)methylpropylammonium P-1-luenesulfonate, 1,4-bis(2',3'-epoxypropyloxy)butane, 1,3,5-triglycidyl isocyanate Nurate, ■,
Epoxy compounds such as 3-diglycidyl-5-(γ-acetoxyβ-oxypropyl)isocyanurate.

■2,4. G-triethylene-5-1-riazine, 1.
Ethyleneimino compounds such as 6-hexamethylene-N,N''-bisethyleneurea and bis-β-ethyleneiminoethylthioether.

■1.2-di(methanesulf;1;oxy)ethane, 1
．． Methanesulfonic acid ester compounds such as 4-di(methanesulfonoxy)butane and 1°5-di(methanesulfonoxy)pentane.

■Dicyclohexylcarbodiimide, ■-Cyclohexyl-3-(3-)dimethylaminopropyl)carbodiimide-P-trienesulfonate, l-ethyl-3-(
3-dimethylaminopropyl) carbodiimide hydrochloride.

■2.5-dimethylisooquinazole perchlorate,
Isoxazole compounds such as 2-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 condensed peptide reagents such as -4-methylpyridinium chloride; active ester compounds such as N,N'-aziboyldioquine disuccinimide and N,N'-terephthaloyldioxydisuccinimide.

[Phase] Toluene-2.4-diisocyanate, 1°6-
Isocyanates such as 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 undercoat material.
0.2(1!i)% to 3. It is possible to select the appropriate addition amount within the range of U weight % depending on the application 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 the heat-sensitive layer is applied. When the amount is more than In%, the degree of curing progresses too much, the adhesion between the undercoat layer and the support deteriorates, and the undercoat layer becomes film-like and has the disadvantage of peeling off from the support.

Depending on the curing agent used, if necessary, caustic soda can be added to make the p 11 of the °C1 solution alkaline, or citric acid or the like can be used to make the p 11 of the solution acidic.

It is also possible to add an antifoaming agent to eliminate the foam that occurs during application, or to add an activator to improve liquid leveling (and prevent the formation of application streaks). be.

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

Furthermore, in step 1) of applying an undercoat layer, it is desirable to activate the surface of the support by a known method.

Activation treatment method C is etching treatment with acid;
Flame treatment using a gas burner, corona treatment, glow discharge treatment, etc. are used, but from the viewpoint of cost and convenience, US Pat. Nos. 2,715.075 and 2.
The corona discharge treatment described in No. 8,16.727, No. 3,549,406, No. 3.590.107, etc. is most preferably used.

The heat-sensitive recording material of the present invention can, of course, be designed for OIIP, and can also be formed by forming two or more heat-sensitive layers on a support directly, each of which can develop a different color, 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 one support, and furthermore, a layer described in this specification that can be colored in a different color from this layer is provided. Various embodiments of C1 are possible depending on the use and purpose, such as the provision of a substantially transparent heat-sensitive layer.

The coating liquid according to the present invention can be applied by well-known coating methods such as dip coating method, air knife coating method,
Curtain coating method, roller coating method, doctor coating method, wire barcoding method, slide coating method, gravure coating method, or extrusion coating method using a popper described in U.S. Patent No. 2,681,294, etc. Can be applied. as needed,
US Patent No. 2. '761.791, same number 3.508.
No. 947, No. 2.941,898, and No. 3.5
26.528, written by Yuji Harasaki, "Coating F, page 3253 (published by Asakura Shoten, 1973), etc., it is also possible to divide and coat 2F!1 or more at the same time. An appropriate method can be selected depending on the coating speed, etc.

Incorporating pigment components, thickeners, flow modifiers, antifoaming agents, foam inhibitors, mold release agents, and colorants into the coating liquid used in the present invention, as necessary, improves the properties. As long as it doesn't bend, there's nothing I can do about it.

(Effects of the Invention) According to the present invention, the total stability of the color developer emulsion dispersion can be significantly improved, so that a heat-sensitive recording material having a transparent heat-sensitive layer can be efficiently produced with good reproducibility. Not only this, but also the transparency of the thermal recording material obtained is extremely good.

(Example) The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

Example [Preparation of capsule liquid] 14 g of crystal bioleft lactone (leuco dye), 60 g of Tagenate D-11ON (capsule wall material made by Sotoen Yakuhin (Ito)), and 2 g of Sumisorb 200 (ultraviolet absorber made by Sumitomo Chemical 9η) were added to 1 It was added to and dissolved in a mixed solvent of 55 g of phenyl-1-xylylethane and 55 g of methylene chloride.This leuco dye solution was mixed with 8% polyvinyl alcohol aqueous solution IUOg and water 40 g (H and
Mix 1.4 g of sodium salt of dioctyl sulfosuccinate (11.0%) in an aqueous solution, emulsify for a minute at 10.00 Orpm with an Ace homogenizer manufactured by Kuchiki fi'jfi Wholesale, and further add water/jOf. , 4LOOC for 3 hours to prepare a capsule liquid with a capsule size of 0.7μ.

[Preparation of developer emulsion dispersion]

Color developer (a)7 represented by the following structural formula? , (b)7
? and 2,λ-bis(3-allyl-≠
-Hydroxyphenyl) propane 3, P and tricresyl m acid 7? , diethyl maleate 3? and ethyl acetate 31
Dissolved in rf. The obtained developer solution was mixed with an aqueous solution of polyvinyl alcohol (PVA manufactured by Kuraray Co., Ltd.: saponification degree t7~r?%)/00? and water/jO? , and an aqueous solution of dodecylbenzenesulfonic acid Nd-O, SY, and emulsified it for a minute at 10°000 rpm at room temperature using Nippon Seiki's Ace Homogenizer to obtain a particle size of 0°! Obtain an emulsified dispersion of μ.

Color developer (a) Color developer (b) [Preparation of heat-sensitive material] The above capsule liquid 5.0? , developer emulsion dispersion IQ, 0?
, water, and or were stirred and mixed to prepare a coating liquid. Next, this coating G was left for one hour and the state of the coating liquid was observed, and the stability of the coating liquid was confirmed. As described above, the coating solution after covering the lid for several hours was transferred to a transparent polyethylene terephthalate (PET) film with a thickness of 70 μm so that the solid content was /jf/
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 r%, indicating that it had extremely good transparency. Proven. When the color of this film was reproduced by facsimile, it showed a clear deep true color.

Comparative Example When preparing the color developer emulsion dispersion in Example, 2.2-bis(4t-hydroxy) was used instead of 2.2-bis(3-allyl-Hydroxyphenyl)propane. phenyl) flonone Th use.

Other than that, the test was conducted in the same manner as in the example. the result,
When stirred and mixed with capsule liquid, some color develops, and even when applied to a transparent film, some of the color developer crystallizes during the drying process and the film becomes opaque.

Claims (1)

[Scope of Claims] 1) A heat-sensitive recording material in which microcapsules containing at least a color former and a heat-sensitive layer having a color developer are provided on a support, as part of the color developer represented by the general formula (I). A heat-sensitive recording material characterized by using a compound represented by: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) In formula (I), R represents a hydrogen atom, a halogen atom, an ester group, or an alkyl group that may have a substituent.