JPS61152485A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material which is excellent in storability of recording performance before printing, record stability after printing, and fastness to light of color-forming substances by using a specific compound as a precursor in the thermal recording material. CONSTITUTION:Micro capsules containing a basic dye precursor and an organic solvent and an electron acceptor compound capable of producing chromogenic reactions with the dye precursor are provided on the same side of a supporter. The wall of the micro capsule has impermeable property in general but when heated becomes previous to the dye precursor and the electron acceptor compound, forming pictures. When using micro capsules containing the dye precursor of the compound of the formula, the occurrence of fogging is relieved since the contact with the electron acceptor compound is reduced. Also, using the compound whose sixth amine residue group has a C4 or more group, the occurrence of spontaneous coloration of the precursor is reduced, and the fastness of the color-forming substances is raised. The micro capsules are formed by forming the polymer wall around the oil droplets of a core substance by emulsification.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a heat-sensitive recording material, and in particular to a heat-sensitive recording material that has excellent storage performance before printing and stability of recording after printing. Regarding. Furthermore, the present invention relates to a heat-sensitive recording material that exhibits little natural coloring due to its basic dye precursor.

``Prior art'' Heat-recording materials using basic dye precursors and electron-accepting compounds are manufactured by Tokuko Akihiro J-IIfiOJf and Tokuko Shoμ3-
It is disclosed in ≠ito issue etc.

The minimum performance that a heat-sensitive recording material should have is (1) sufficient color density and color development sensitivity, (2) fogging (
(Color development during storage before and after use) f: Does not occur, (
3) The coloring material should have sufficient solidity after coloring, but currently no material has been obtained that completely satisfies these requirements.

In particular, from the viewpoint of long-term storage of the recording insects, there is a strong demand for improvement in the capri of the non-image area after use and the fastness of the coloring body.

Tokukai Akira! Tar f/u JI4+ contains microcapsules containing a photopolymerizable vinyl compound, a photopolymerization initiator, and one component that causes a color-forming reaction, and the other component that reacts with the components to form a color, on the same support. A light and heat sensitive recording material has been invented. When this recording material is heated, other fractions mainly outside the capsule that undergo a color reaction pass through the capsule wall and enter the capsule. After printing, the capsule maintains substantially the same capsule form as before printing.

Therefore, the heated part can be colored by heating,
Furthermore, the entire surface is exposed to light to polymerize the vinyl compound contained in the core, thereby preventing the transmission of the color-forming component and preventing the development of color in the uncolored areas (also referred to as "fixing"). Also, another method is Tokukaisho! 17-/
No. 23014, Japanese Unexamined Patent Publication No. 23014, Showa zt-t2. ! After thermal recording, light irradiation is performed using a light- and heat-sensitive recording material comprising a diazo compound, a coupling component, and an alkali generator or a coloring aid as disclosed in No. 09, etc., to decompose the unreacted diazo compound. , a method of stopping color development is known. However, this recording material gradually undergoes pre-coupling during storage, which may cause undesirable coloring (fogging).
It has been invented to contain at least one of a coupling component and a coloring aid in the core of the microcapsule.

The photo-fixable heat-sensitive recording material using the MyFre capsule described above has a simple recording device, and the recording material has good storage stability.
The stability of the image and background area after recording is excellent.

Furthermore, Tokukai Akira! In the embodiment of Tata/44!1, the composition of the core material when using a sun base coloring component is required to be photopolymerized and hardened, but the core material composition does not have a photopolymerization function, i.e. Even in the case of a core material composition that does not contain a vinyl compound and a photopolymerization initiator at the same time, the pre-printing and post-printing reaction fractions are separated by the capsule wall, resulting in excellent storage and stability.

By isolating the color-forming components in this way, the coloring was greatly improved, but when exposed to light for a long time, fogging, which is typical of this system using capsules, sometimes occurred.

"Problems to be Solved by the Invention" Therefore, the first object of the present invention is to provide a heat-sensitive recording material that has excellent storage performance of recording performance before printing and stability of recording after printing.

A second object of the present invention is to provide a heat-sensitive recording material that has excellent light fastness, especially in the background area and color formers.

"Means for Solving the Problems" As a result of intensive research, the present inventors have developed a microcapsule containing a basic dye precursor and an organic solvent in the core, and an electron acceptor that causes a coloring reaction with the dye precursor. The microcapsule walls that form the microcapsules are impermeable, but can be permeable to the precursor and/or the electron-accepting compound by heating. This is achieved by a heat-sensitive recording material for forming an image, in which the precursor is a compound represented by the following general formula.

In the above formula, R1 is an alkyl group having 1 to t carbon atoms, and R2 is
is an alkyl group or alkoxyalkyl group having 11 carbon atoms, or a tetrahydrofurfuryl group, R
3 is a hydrogen atom, from the number of carbon atoms /! The alkyl group th
e represents a halogen atom, and R4 represents a substituted or unsubstituted atom group having t to 20 carbon atoms.

In the above formula, among the substituents represented by R□, an alkyl group having 7 to 7 carbon atoms is preferable, and in particular, an alkyl group having 2 to 7 carbon atoms is preferable.
The alkyl group is preferred. Among the substituents represented by R2, alkyl groups or alkoxyalkyl groups having carbon atoms from μ to t and tetrahydrofurfuryl groups are preferred, and alkyl groups or alkoxyalkyl groups having from μ to O carbon atoms and tetrahydrofurfuryl groups are particularly preferred. . Among the substituents represented by R3, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluorine atom, and a chlorine atom are preferred, and a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, and a chlorine atom are particularly preferred.

Among the substituents represented by R4, an aryl group having 6 to 1 carbon atoms is preferable, and when the aryl group is substituted, a halogen, an alkyl group, or an alkoxy group is preferable as the substituent. In particular, an aryl group having 6 to 10 carbon atoms is preferable, and when the aryl group is substituted, a halogen group, an alkyl group, or an alkoxy group is preferable as the substituent.

In the present invention, the basic dye precursor is microencapsulated to reduce contact with electron-accepting compounds and reduce capri.Although the effect and reason are not clear, the carbon atom is added to the amine residue at the 4-position of the fluoran compound. By introducing a group with a size of several microns or more, this effect was achieved by reducing the natural color development of the dye precursor and improving the fastness of the color former.

The heat-sensitive recording material using the basic dye precursor according to the present invention has good stability in the non-image area before and after use, and is extremely stable in color development, even when exposed to light or heated for a long time.
It is particularly advantageous in terms of long-term preservation of records, as it hardly causes discoloration or fading even when humidified.

In addition, the basic dye precursor according to the present invention has the advantage of being extremely easily soluble in oil used as a solvent when microencapsulated, making it easy to make high-concentration capsules.

Specific examples of the basic dye precursor according to the present invention are 1) co-anilino J-methyl-+-N-ethyl-N-
Butylaminofluorane 2)-monoanilino-3-lytetra-a-N-ethyl-N-
Butylaminofluoranyl 2-Q-chloroanilino-a-N-ethyl-N-butylaminofluoranli co〇-chloroanilino-6-cyptylaminofluoranyl λ-anilino 3-methyl-4-N-ethyl-N -isobutylaminofluorane 6) Coanilino 3-methyl-4-N-ethyl-N-
Isoamyl fluorine 7) Co-P-) Cyidino-3-methyl-+-N-ethyl-N-isoamyl fluorine 1) 2-anilino-3-chloro-4-N-ethyl-N-isoamyl fluorine 2
co-anilino-3-ethyl-4-N-ethyl-N-
in-amyl-2-nofluorane/ 0) co-0-chloroanilino-4-N-ethyl-N-isoamyl-2-nofluorane/ /) co-7-chloroanilino-3-methyl-4-diisoamylaminofluoran-2) co-anilino-3-methyl-j-N -Ethyl-
N-hemocylaminofluorane / j) co-anilino 3-methyl-4-N-ethyl-N-r-ethoxypropylaminofluorane / 4C) co-anilino 3-methyl-4-N-ethyl-N-r-ethoxy Propylaminofluorane/j) Co-anilino J-chloro-4-N-ethyl-Nr-ethoxypropylaminofluorane/4)
J-Q-Rishin 4-anilinoj-N-ethyl-Nr-ethoxycubyl aminofluorane 17) 2-anilino-
3-Methyl-4-N-ethyl-N-tetrafurfurylaminofluorine/I) J-anilino-3-chloro-4-N-ethyl-N
-tetrahydrofurfurylaminofluoranl)2-0-chloroanilino-4-N-tetrahydrofurfurylaminofluorano)x-p-methoxyanilino-3-methyl-4-N
-ethyl-N-isoamylaminofluorane and the like.

Although the basic dye precursor according to the present invention may be used in combination with other basic dye precursors, it is preferable that the usage ratio of the basic dye precursor according to the present invention is 70% by weight or more.

Examples of the electron-accepting compound according to the present invention include acid clay, activated clay, phenolic resin, alkyl- or aralkyl-substituted salicylic acid, and metal salts thereof. Further, when used in thermal recording paper, preferable examples of compounds among phenol derivatives include compounds having at least one phenolic hydroxyl group, and more preferably compounds having at least one phenolic hydroxyl group, and more preferably 7 Enol nine, for example bis-(
Hiro-hydroxyphenyl)alkane derivative, bis-(3
-chloro-q-hydroxyphenyl)alkane derivative,
Bis-(≠-hydroxyphenyl) sulfone, (≠-hydroxyphenyl)-(μ′-alkoxyphenyl) sulfone derivative, P-hydroxybenzoic acid ester derivative, resorcinol monoester derivative, orceric acid ester derivative, gallic acid ester derivative, These include salicylic acid, its alkyl or aralkyl substituted products, or its zinc salt.

The following compounds are typical examples of phenol derivatives.

(1) co,2-bis(4A-hydroxyphenyl)
Propane C2)/l/-bis(-hydroxyphenyl)hexane ('') 't'-bis(3-di-hydroxyphenyl)cyclohexane -Hydroxyphenyl)-coethylbutane (5) P-human ■benzyl xybenzoate (6) j, j-
Zinc di-α-methylbenzylsalicylate (') "t"-dihydro-4xy-3'-isopropyldiphenylsulfone (')'s'-bis(4cm hydroxyphenyl)cyclohexane (9) Resorcinic acid cinnaelectric ester (10 )
β-7enethyl orselinate (11) Cinnamyl orselinate (U) β-〇-chlorophenoxy orselinate (
1g) β-phenoxyethyl resorcinate (14
) Resorcinic acid-0-methylbenzyl ester (1g) Resorcin W! -dimethylphenoxyethyl ester (1g) β,β'-Hydroxyphenylthioethyl ether) Resorcinic acid β-phenoxyethyl ester (Ig) β,β'-His-Hydroxyphenylthioethyloxy Methane Among these, phenol compounds such as alkylene bisphenol and cycloalkylene bisphenol, and phenol compounds having an electron-withdrawing group are particularly excellent.

The microcapsules of the present invention are destroyed by heat or pressure, as used in conventional recording materials, and color is developed by bringing the reactive substance contained in the core of the microcapsule into contact with the reactive substance outside the microcapsule. It does not cause a reaction, but rather permeates through the microcapsule wall and causes a reaction by heating the reactive substance present in the core and outside of the microcapsule. Until now, it has been known that when microcapsule walls are formed by polymerization, they do not become completely impermeable, but are permeable. This permeability of the microcapsule wall was known to be a phenomenon in which low-molecular substances gradually permeate over a long period of time, but the phenomenon in which they permeate instantaneously due to heating as in the present invention is unknown. It wasn't.

Therefore, the microcapsule wall of the present invention does not necessarily melt when heated! ! In fact, the results show that the higher the melting point of the wall, the better the shelf life. Even when the core material of the Insect Trap Microcapsule liquid was removed and heated using the method of the present invention, the surface of the wall was not polished at all. Will not melt or soften.

The heat-sensitive recording material of the present invention can record heat even if any of the components that cause a color reaction is placed in the core of the microcapsule, and has excellent storage stability and stability. However, it was found that thermal coloring properties were higher when a basic dye precursor, which is a coloring component, was included in the core. Furthermore, it should be noted that dissolving the color-forming component in a broadly defined organic solvent is advantageous in terms of both thermal color development and storage stability. The point is t, 71
1C-CO000CIC,S is required. More preferably, the range is Fi70'C-/10°C. The capsule wall changes from a glass state to a rubber state due to instantaneous heating by the thermal head, and the water passes through the capsule wall as described above.
Diffusion contact of the color-forming components is followed by a reaction. According to microscopic observation, the reactivity outside the capsule penetrates into the capsule and reacts, causing the inside of the capsule to be colored. The glass transition point of the capsule of the present invention is either the glass transition point itself inherent to the capsule wall, or the glass transition point "as a system" including the effects of various substances outside the capsule. In particular, when the glass transition point controlling agent outside the capsule is heated and melted during thermal printing and comes into close contact with the capsule wall, a drastic drop in the glass transition point is observed.

The microcapsules of the heat-sensitive recording material of the present invention are made by emulsifying a core material and then forming a wall of a polymeric material around the oil droplets. The actant forming the polymeric material is added to the interior of the oil droplet and/or to the exterior of the oil droplet. Specific examples of the polymeric substance include polyurethane, polyurea, boria, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, and the like.

The microcapsule wall of the present invention is particularly effective when using a four-mic encapsulation method by polymerizing a glue actant from inside an oil droplet. That is, it is possible to obtain capsules having a uniform particle size, long shelf life, and suitable as a tear ratio recording material within a short period of time.

This method and specific examples of compounds are described in U.S. Pat.
, 7J, No. 1, J, No. 794, 46.

For example, when polyurea polyurethane is used as a capsule wall material, a polyvalent incyanate and a second substance that reacts with it to form the capsule wall (e.g., polyol, Boriaone) are mixed into the aqueous phase or the oily liquid to be encapsulated, and then submerged in water. By emulsifying and dispersing and then increasing the temperature, a polymer formation reaction occurs at the oil droplet interface, forming microcapsule walls.

At this time, it is possible to use an auxiliary solvent with a low boiling point and strong dissolving power in the oily liquid. Polyurea is produced even without the second additive mentioned above.

In the above cases, regarding the polyisocyanate to be used and the polyol and polyamine to be reacted with it, US Pat.
No. 326, special public show ur-μ03g No. 7, same μ turco μ
l! No. 2, JP-A-Sho μt-10/9/No., same at-ruo
tt issue, and they can also be used.

Furthermore, a tin salt or the like can also be used in combination to promote the urethanization reaction.

Furthermore, the glass transition point of the wall can be greatly changed by appropriately selecting the polyvalent incyanate, which is the first wall film-forming substance, and the polyol or boriaone, which is the second wall film-forming substance.

Basic dye precursors are dissolved in a solvent alone or in combination and contained in microcapsules. As a solvent, natural or synthetic oils can be used alone or in combination. Examples of solvents include cottonseed oil, kerosene, aliphatic ketones, aliphatic esters, norahin, naphthenic oil, alkylated biphenyls,
Alkylated terphenylene, talaphin, alkylated naphthalene, l-phenyl-l-xylylethane,
l-phenyl-/-p-ethylphenylethane, l-1
Diarylethanes such as 1-ditolylethane and the like can be mentioned. As an auxiliary solvent, a water-insoluble organic solvent such as ethyl acetate, toluene, methylene chloride, etc. can be used.

Various other additives such as antioxidants and ultraviolet absorbers can be contained in the microcapsules.

The basic dye precursor is 0.1 to 50wt in the capsule.
% is used.

When making microcapsules, water-soluble polymers can be used.Water-soluble polymers include water-soluble anionic polymers, nonionic polymers, and amphoteric polymers. Both natural ones and synthetic ones can be used, and examples include those having a -C00-1-S O-a group. Specific anionic natural polymers include gum arabic and alginic acid, while semi-synthetic products include carboxylic dimethylcellulose, phthalated gelatin, sulfated starch, sulfated cellulose, and lignin sulfonic acid.

Synthetic products include maleic anhydride-based (including hydrolyzed T-based) copolymers, acrylic acid-based (including methacrylic acid-based) polymers and copolymers, vinylbenzene sulfonate, phosphoric acid-based polymers, and copolymers. Examples include polymers and carboxy-modified polyvinyl alcohol.

Examples of nonionic polymers include polyvinyl alcohol, hydroxyethyl cellulose, and methyl cellulose.

Examples of amphoteric compounds include gelatin.

These water-soluble polymers are used as an aqueous solution containing 0 wt % o, at-i.

The particle size of the capsules is adjusted to 20μ or less. Generally, if the particle size exceeds 20 μm, the print quality tends to be poor.

In particular, when heating with a thermal head is performed from the coated layer side, the thickness is preferably tμ or less to avoid pressure fog.

When making microcapsules, they can be made from an emulsion containing at least 0.0% by weight of the component to be converted into microcapsules.

On the other hand, electron-accepting compounds have a solid concentration in a water-soluble polymer aqueous solution! ~gawt% (injected and dispersed. Dispersion is performed by means such as a ball mill, sand mill, attritor, colloid mill, etc., and atomized.

The particle size is preferably 10μ or less, preferably 2μ or less.

When making microcapsules, the water-soluble polymer in the dispersion is 1! [Water-soluble polymers can be used. At this time, the concentration V of the water-soluble polymer is 2 to 30 wt.
%, and the microcapsule liquid and the electron-accepting compound dispersed liquid are coated on a support separately or as a mixture.

The amount of coloring component is 0 as the solid content of the basic dye precursor.
．． 01~/, Ill/m'', preferably ao.

O! ~O6μI! /fn2, the solid content of the electron-accepting compound is o, r ~z, og7m'', preferably O0!
Coat so that the ratio is ~1Ali/pyH.

The thermosensitive recording paper of the present invention has sufficient resistance to various chemicals and oils because the color former and unreacted basic dye precursor are in the capsule, but a water-soluble polymer coating layer is provided on the thermosensitive color layer. It is possible to further strengthen the resistance and improve running performance in the thermal head section.

The heat-sensitive recording material of the present invention contains silica, barium sulfate, titanium oxide, aluminum hydroxide, zinc oxide, etc. for the purpose of preventing sticking to a thermal head and improving writing properties.
Pigments such as calcium carbonate, fine powders such as styrene beads, urea-melamine resin, etc. can be used.

Similarly, metal soaps can also be used to prevent sticking. The amount of these used is O,
2 to 797 m.

The paper used for the support is sized with a neutral sizing agent such as an alkylcutene dimer and subjected to specific heat extraction.
It is advantageous in terms of storage stability over time to use neutral paper of 4 to 10% (as described in %Kaisho 1!-/lcof/).

In order to prevent the coating liquid from penetrating into the second paper and to improve the contact between the recording heat head and the heat-sensitive recording layer, Japanese Patent Application Laid-Open No. Wf97-/
The paper described in No./61ar7 and having a Bekk smoothness of 0 seconds or more is advantageous.

Furthermore, the optical surface roughness described in JP-A-5R-73TA Taco No. is less than jμ and the thickness is 4co~7! μ paper, density 0° fl/at+ as described in JP-A-5R-Tori No. 1
Paper with an optical contact ratio of /j% or more, JP-A-Sho sr.
-Canadian Standard Freeness (JIS) as described in Two No. 27
The pulp is beaten to a pulp of 00cc or more, and then made into paper to prevent the coating liquid from penetrating.
JP-A-52-3Ir!, which uses the glossy side of a base paper made by a Yankee machine as the coating surface to improve the color density and folding strength, as described in JP-A-52-3Ir! The paper described in the above-mentioned No. 1, in which the base paper is subjected to several electric discharge treatments to improve its coating suitability, can also be used in the present invention and gives good results.

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

Binders include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, human tetraxypropylcellulose, gum arabic, gelatin, polyvinylbitetraridone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic acid. Various emulsions of esters and ethylene-vinyl acetate copolymers can be used. The amount used is 0.5 to 5 g/m2 of solid content.

The heat-sensitive recording material of the present invention contains microcapsules containing a basic dye precursor, a main component of an electron-accepting compound, and other additives to prepare a coating solution, and then coated on a support such as paper or a synthetic resin film. Apply on top using coating methods such as par coating, blade coating, air knife coating, gravure coating, roll coating, spray coating, dip coating, curtain coating, etc., and dry to remove the solid content. -koj77/fn”
A heat-sensitive recording layer is provided.

The thermal recording material of the present invention is useful as recording paper for thermal printers and thermal facsimile devices.

"Example" Examples 1I are shown below, but the present invention is not limited thereto.

Example l Basic dye precursor 2-anilino-3-methyl-j
-N-ethyl-N-yamylaminofluorane o, p
g% l-phenyl-7-xylylethane sti, tolylene diinocyanate and trimethylolpronone (j:
/) 0.7 g of adduct and propylene oxide (l:φ) adduct O and coI of ethylene cyapone were added and dissolved.

In this way, the obtained solution was dissolved in water, rlif/C polyvinyl alcohol O, and Colo I, and in the solution, Coo (1 (
After emulsification, water iog was added and heated for 2 hours at j0@C to 700 CVC to obtain a capsule dispersion (A).

On the other hand, the mixture was dispersed in a sand mill overnight with 3,J'-di-alpha-methylbenzylsalicylic acid coOII''4t7% polyvinyl alcohol aqueous solution IOOG, which is an electron-accepting compound, to obtain a dispersion (B) having an average particle size of μ.

Dispersion liquid (A) and dispersion liquid (B) are mixed at a weight ratio of 1:2 to prepare a coating liquid.

This was coated on neutral paper having a basis weight of uJli/ln so that the solid content was 7jl/m' and dried at sz''c for 30 minutes to obtain thermal recording paper.

The obtained thermosensitive recording paper was stored for one week in an atmosphere with a relative humidity of 10% to"c to test its storage stability.
Measuring the degree of Capri generation from its visual density;
In addition, in order to confirm the fastness to light, we
The concentration after irradiation with 0 lux fluorescent lamp light for io hours was measured in the same manner. The smaller these values are, the more preferable they are.

In order to check the fastness of the colored body, a stamp heated to Vc/JO"C was applied for 1 second under a pressure of z o 017 cm'.
After developing a color and storing it in an atmosphere of IO"c relative humidity Hto% for one week, the concentration was measured to determine the residual rate of the coloring material. Also, after irradiating with 32,000 lux fluorescent lamp light for 10 hours, the same procedure was carried out. The density was measured and the residual rate of the colored material was determined.These values were
It can be said that the larger the value, the better. The results are shown in Table 1.

Examples Co-anilino-3-medellus J as a co-basic dye precursor
A thermal recording paper was obtained in the same manner as in Example 1 using -N-ethyl-N-γ-ethoxypropylaminofluorane and the nine-electron-accepting compound Toshiteco and Corbis(4cm hydroacyphenyl)pro/cene. . Tests similar to those in Example 1 were conducted, and the results are shown in Table 1.

Example 3 2-anilino-3-methyl-6 as basic dye precursor
A thermosensitive recording paper was obtained in the same manner as in Example I using -N-ethyl-N-tetrahydrofurfurylaminofluorane and 29 μm dihydroxybenzoic acid benzyl ester as the electron-accepting compound. Tests similar to those in Example 1 were conducted, and the results are shown in Table 1.

Example 4 2-O-chloroanilino 6- as a basic dye precursor
Using N-ethyl-N-isoamylaminofluorane,
As an electron-accepting compound.

A thermosensitive recording paper was obtained in the same manner as in Example 1 using Corbis-(hydroxyphenyl)furopane. The same test as in Example 1 was conducted and the results are shown in Table 1.

Comparative Example 1 2-anilino-3-methyl-6 as basic dye precursor
- using dinithylaminofluorane and 2,2-bis-(young-hydroxyphenyl) as an electron-accepting compound.
A thermosensitive recording paper was obtained in the same manner as in Example 1 using Pronowall.

Tests similar to those in Example I were conducted and the results are shown in Table 1.

Comparative Example 2 Basic dye precursor 2-anilino-3-methyl-1
-Diethylua 5-nofluorane! I in 5% polyvinyl alcohol (polymerization degree 1ooo) aqueous solution! O
Disperse it with I in a ball mill for a day and night. On the other hand, similarly, the electron-accepting compound Co, Corbisu(-hydroxyphenyl)poA://01'f: 1
%-livinyl alcohol aqueous solution/Dull in a ball mill for a day and night. After mixing these one type of dispersion, kaolin (Jossia kaolin) 209 was added and well dispersed, and then 10% of Norahin wax emulsion was added. Dispersion liquid (Middle East oil and fat Cellosol #44 t)! 77
Add this to make a coating solution.

The coating liquid was applied to neutral paper having a basis weight of top/m2 so that the solid content coating amount was H1/m2, and toca
The coated paper was obtained by drying at c for 1 minute.

Tests similar to those in Example 1 were conducted, and the results are shown in Table 1.

(1) Uncolored thermal recording paper ro oc'B, Hto%
Store inside for 1 week. Next, measure the coloring density.

(2) JJ, 000 on the recording surface of uncolored thermal recording paper
10 hours of lux fluorescent light irradiation. Color density was measured.

(3) Store the chromophore in IO'cRHrO% for 1 week.

The concentration before and after was measured and the residual rate was determined.

(4) The colored body was irradiated with Jj, 000 lux fluorescent lamp light for 70 hours. The concentration before and after was measured and the residual rate was determined.

Table 1 shows that the thermal recording paper of the present invention had a low color density and was excellent even when exposed to high temperature, high humidity, or high intensity light before color development.

However, since Comparative Example 1 uses capsules, it is excellent under high temperature and high humidity conditions, but under high-intensity light, the coloring density is high and the ratio is low. On the other hand, in the comparative example that does not use capsules, the temperature is high.
Both under high humidity and high-intensity light, the coloring density is high and storage is poor.

9. The color former of the present invention has excellent temperature/humidity resistance and light resistance.

Claims (1)

[Scope of Claims] A microcapsule containing a basic dye precursor and an organic solvent as a core, and an electron-accepting compound that causes a color-forming reaction with the precursor on the same side of a support; In a heat-sensitive recording material in which the formed microcapsules are impermeable but pass through the precursor and/or the electron-accepting compound to form an image when heated, the precursor is represented by the following general formula: A heat-sensitive recording material characterized by being a compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the above formula, R_1 represents an alkyl group having 1 to 8 carbon atoms,
R_2 is an alkyl group or alkoxyalkyl group having 4 to 18 carbon atoms, or a tetrahydrofurfuryl group, R_3 is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or a halogen atom; R_4 is substituted or unsubstituted; , and represents an aryl group having 6 to 20 carbon atoms.