JPH0483681A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve a head matching by making a pigment have a specific oil absorption and an average particle diameter thereof nearly the same as an average particle diameter of leuco dyestuff and a developer or larger than that wherein the average particle thereof is within a specific range. CONSTITUTION:A pigment has an oil absorption of 80-300ml/100g (under JIS k 5101) and an average particle diameter within a range of 1-6mum and includes ones having nearly the same average particle diameter as a leuco dyestuff and a developer or larger than that wherein the average particle diameter thereof is 0.5-2.5mum. The oil absorbing pigment is used without being dispersed physically, so that a primary oil absorbing property will be displayed. Since the average particle diameter is larger than that of the leuco dyestuff and the developer, it is very effective for preventing a sticking at printing. As for a size of the pigment, 1-6mum as a particle diameter is appropriate. However, 1.5-3mum is preferable to obtain a higher sensibility.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a heat-sensitive recording material, and more specifically to a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye that is colorless or light-colored at room temperature and a color developer for the leuco dye. Concerning improvements in recording materials.

[Conventional technology]

Recently, various recording materials have been researched and developed and put into practical use in the information recording field, in response to social demands such as diversification and increase in information, resource conservation, and pollution-free technology.Among them, thermal recording materials are (1) A colored image is recorded simply by heating, eliminating the need for a complicated developing process. (2) It can be manufactured using relatively simple and compact equipment, and the resulting recording material can be easily handled. (3) paper is often used as the support;
In this case, the support cost is not only inexpensive, but also has the advantage that the feel of the resulting recorded material is similar to that of plain paper.
It is widely used in the fields of computer output, printers such as calculators, recorders for medical measurement, low and high speed facsimiles, automatic ticket vending machines, thermal copying, etc.

The above-mentioned heat-sensitive recording material is produced by applying and drying a coating liquid for forming a heat-sensitive coloring layer containing a coloring component that can cause a coloring reaction when heated, onto a support such as ordinary paper, synthetic paper, or a synthetic resin film. A colored image is recorded on the heat-sensitive recording material thus obtained by heating it with a thermal pen or a thermal head. A difficulty in putting this method into practice is that the surfaces of the thermal head and the heat-sensitive recording material become sticky or sticky when heat is applied. This so-called "sticking" prevents the smooth feeding of the recording medium, which not only causes the line spacing to become short during recording and causes blurred recorded images, but also makes continuous recording impossible and may even damage the thermal head. be.

In order to improve the above-mentioned drawbacks, methods such as adding general clay, talc, calcium carbonate, titanium oxide, etc. to the heat-sensitive coloring layer, increasing the amount of adhesive in the heat-sensitive coloring layer, waxes, etc. A method of adding a mold release agent, starch powder, valve powder, etc. (JP-A-47-2793, JP-A-4
No. 8-33832, JP-A No. 4990142, JP-A No. 5
4) have been proposed. Also, special public service No. 5847999
The publication proposes the use of coarse particles having an average particle size of 6 to 20 particles.

[Problem to be solved by the invention]

However, although such heat-sensitive recording materials are effective in preventing sticking, they have low sensitivity and
Or the surface is rough and white.

It has the disadvantage of causing a deterioration in image quality, which is called white spots, and so far no satisfactory product has been obtained.

Accordingly, one object of the present invention is to provide a heat-sensitive recording material that has improved the above-mentioned conventional drawbacks, that is, to provide a heat-sensitive recording material that is excellent in head matching properties such as sticking and has high image quality.

[Means to solve the problem]

As a result of intensive studies, the present inventors have determined that an oil-absorbing pigment having a specific oil absorption amount and average particle size is contained, and that the average particle size of the leuco dye and color developer is equal to or smaller than the above-mentioned pigment. The present inventors have found that the above object can be achieved by doing so, and have completed the present invention.

That is, according to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, the average particle size of the leuco dye and the color developer is 0.5 to 0.5.
2.5pm, and the oil absorption amount is 80 to 30 as a pigment.
0d/100g (according to JIS K 5101), and the average particle size is in the range of 1 to 6, and is approximately the same as or larger than the average particle size of the leuco dye and color developer. Provided are a heat-sensitive recording material characterized by containing a material having the following properties, and a method for producing the same.

In the heat-sensitive recording material of the present invention, the oil-absorbing pigment used in combination with the leuco dye and the color developer has an oil absorption amount of 80 to 300 ml/100 g based on JIS K 5]01 and an average particle size of 1 to 6 μm. be. Note that the average particle size referred to here means the 50% particle size measured by a coal tar counter.

Specific examples (commercially available) of the oil-absorbing pigment used in the present invention include those shown in Table 1, but of course the oil-absorbing pigment is not limited thereto.

Table 1 Oil absorption and average particle size can be changed by physical or chemical treatment, but what is important in the present invention is that
The purpose is to make the average particle size of the oil-absorbing pigment larger than the average particle size of the dispersion of leuco dye and color developer. In other words, in recent years, as a trend toward higher sensitivity, it has become common to increase dispersion efficiency and dispersion time, and to increase the dispersion efficiency for leuco dyes to less than 1 s and for color developers to 2 μs or less. At the same time, oil-absorbing pigments have also been dispersed together with color developers, and have followed the trend of becoming finer particles.

Amid this trend toward higher sensitivity, oil-absorbing pigments have been physically destroyed by being dispersed with a sand grinder or the like, and oil-absorbing properties have been reduced due to dispersion, which has hindered matching quality.

By utilizing this oil-absorbing pigment without physical dispersion, it exhibits its original oil-absorbing properties, and since the average particle size is larger than that of leuco dyes and color developers, it prevents sticking during printing. It is extremely effective. As for the size of the pigment, a particle size of 1 to 6 .mu.m is suitable, but a particle size of 1.5 to 3 .mu.m is preferable for higher sensitivity. If this particle size is less than 1.5 μm, it will be the same as the particle size of the color developer, and the effect on sticking will be weakened.

Further, if the particle size exceeds 6 μm, the smoothness decreases due to surface roughness, resulting in insufficient sensitivity, and larger particles cause foreign matter such as white spots and white spots that do not develop color on the image.

The addition ratio of the oil-absorbing pigment used in the present invention is sufficient as long as it absorbs the melted components of the leuco dye and color developer, but it is also possible to use it in combination with other pigments.
The dry weight amount in the heat-sensitive coloring layer is 10 to 70% by weight, preferably 20 to 60% by weight.

The leuco dyes used in the present invention may be applied singly or in a mixture of two or more types. As such leuco dyes, those applied to this type of heat-sensitive material can be arbitrarily applied. For example, triphenyl Methane type, fluorane type, phenothiazine type.

Leuco compounds of dyes such as auramine, spiropyran, and indolinophthalide are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p- dimethylaminophenyl)-6-dibutylaminophenyl, 3.3-bis(P-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6- Chlorfluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-N-Methyl-N-isobutyl-6-methyl-7-anilinofluorane.

3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane.

3-diethylamino-7-lylorofluorane.

3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-(N-P-tolyl-N-ethylamino) -6-Methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-trifluoromethylphenyl)amino)-6-dinithylaminofluoran Oran52- (3,
6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(+n-trichloromethylanilino)fluoran.

3-diethylamino-7-(O-chloroanilino)fluoran, 3-dibutylamino-7-(O-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl -7-(2', 4'-
dimethylanilino)fluoran, 3-(N,N-diethylamino)-5-methyl-7-(
N,N-dibenzylamino)fluoran, benzoylleucomethylene blue 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3- (2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide,3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide,3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide,3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5
7-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane.

3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro- 7-(α-phenylethylamino)fluoran, 3-(N-ethyl-P-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(0-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluorane, 3-(N-methyl-N-isopropylamino)-6-methyl7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3.6-bis( dimethylamino) fluorene spiro(9
゜3')-6'-dimethylaminophthalide, 3-(N
-benzyl-N-cyclohexylamino)-5,6-penzo 7-α-naphthylamino-4'bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N -(2-ethoxypropyl)amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-
6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino 4', 5'-benzofluorane, and the like.

In addition, the color developer used in the present invention includes various electron-accepting compounds that cause the leuco dye to undergo catalytic color development, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids, and metal salts thereof. It is preferably applied, and specific examples include those shown below.

4.4'-isopropylidene bisphenol, 4.4
′ -isopropylidene bis(0-methylphenol)
, 4.4'-Secondary-butylidene bisphenol 4.4'-Isopropylidene bis(2-tert-
butylphenol), 4.4'-cyclohexylidene diphenol, 4.4
′ -isopropylidene bis(2-chlorophenol)
, 2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4.4'-butylidenebis(6-tert-butyl- 2-methylphenol), 1.1.3-tris(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane, 1.1.3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4.4'-thiobis(6-tert-butyl-2-
methylphenol), 4,4'-diphenolsulfone.

4-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4.4'-diphenolsulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, Stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis(4-hydroxyphenylthio)-3,5
-Dioxahebutane.

1.5-bis(4-hydroxyphenylthio)-3=oxapentane, 1.3-bis(4-hydroxyphenylthio)-propane.

1.3-bis(4-hydroxyphenylthio)-2-hydroxypropane, N,N'-diphenylthiourea, N,N'-di(m-chlorophenyl)thiourea, salicylanilide, 5-chloro-salicylanilide , salicyl-0-chloroanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-def-1-dioic acid, metals such as zinc, aluminum, and calcium in hydroxynaphthoic acid Salt, bis-(4-hydroxyphenyl)acetic acid methyl ester, bis=(4-hydroxyphenyl)acetic acid benzyl ester, 1.3-bis(4-hydroxycumyl)benzene, 1.
4-bis(4-hydroxycumyl)benzene, 2.4'
-diphenolsulfone, 3,3'-diallyl-4,4'-diphenolsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, α,α-bis(4-hydroxyphenyl)-α-methyltoluene , antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, etc.

In order to produce the heat-sensitive recording material of the present invention, leuco dye,
When the color developer and the oil-absorbing pigment are bonded and supported on a support, various commonly used binders can be used as appropriate, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic acid In addition to water-soluble polymers such as terpolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, Emulsions such as polyurethane, polyacrylic acid, polyacrylic ester, polymethacrylic ester, vinyl chloride/vinyl acetate copolymer, ethylene/vinyl acetate copolymer, styrene/butadiene copolymer, styrene/butadiene/acrylic copolymer, etc. Latex such as polymers, etc.

Further, in the present invention, it is also possible to use common pigments commonly used in this type of recording material, such as calcium carbonate, silica, zinc oxide,
In addition to inorganic fine powders such as titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated calcium and silica, urea-formalin resin,
Examples include organic fine powders such as styrene/methacrylic acid copolymer and polystyrene resin.

Furthermore, in the present invention, sensitizers, lubricants, waxes, surfactants, auxiliaries, etc. commonly used in heat-sensitive coloring layers can also be used as necessary.

The heat-sensitive recording material of the present invention can be produced, for example, by applying a coating liquid for forming a heat-sensitive coloring layer containing each of the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, drying it, and subjecting it to calender treatment. It is obtained by In this case, an undercoat layer may be provided below the thermosensitive coloring layer, and an overcoat layer may be provided above. In addition, leuco dye, color developer,
The amount of oil-absorbing pigment used is 5 to 40% by weight and 20% by weight, respectively.
-60% by weight, 20-60% by weight is suitable.

〔Effect of the invention〕

The heat-sensitive recording material of the present invention has excellent head matching properties such as sticking, has high sensitivity, and is extremely practical.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples. Note that all parts and percentages shown below are based on weight.

Preparation of [Liquid A] 10% polyvinyl alcohol aqueous solution 20 parts water
60 parts of the mixture having the above composition was mixed with 5 parts using a sand mill.
Milled for ~10 hours to an average particle size of 1 μm.

Preparation of [Liquid B] 10% polyvinyl alcohol aqueous solution 25 parts water
75 parts The mixture having the above composition was ground using a sand mill for 2 to 5 hours to give an average particle size of 1.5 threshold.

Example 1 Using [liquid A] and [liquid B] obtained as described above, a coating liquid for forming a heat-sensitive coloring layer having the following composition was prepared.

[Coating liquid]

[Liquid A] 10 parts [Liquid B] 50 parts Water 5
0 parts The above coating liquid has a basis weight of 47g#r? The heat-sensitive recording paper of the present invention was obtained by applying and drying the mixture to a high-quality paper with a dry coating amount of 3.0 g/rr, followed by calendering.

Example 2 In Example 1, except that Mizukasil P-832 (average particle size 2.7 μs) was used instead of Callite KT,
A thermosensitive recording paper of the present invention was obtained in the same manner as in Example 1.

Example 3 A thermosensitive recording paper of the present invention was obtained in the same manner as in Example 1, except that the average particle size of [Liquid B] was changed to 2 μm.

Comparative Example 1 Preparation of [Liquid C] As [Liquid C], Callite KT was added in advance to the composition of [Liquid B], and the mixture was ground and dispersed in a sand mill for 2 to 5 hours to give an average particle size of 1.5 μm. In addition, Callite KT
The oil absorption amount after dispersing it alone (average particle size 1.5 particles) is 6.
It had decreased to 0+nQ/100g.

Callite KT 25 parts 10% polyvinyl alcohol aqueous solution 25 parts water
75 parts Next, a coating liquid for forming a heat-sensitive coloring layer was prepared by mixing and stirring a ratio of [liquid A]:[liquid C] = 1:10, and thereafter, a heat-sensitive recording layer for comparison was prepared in the same manner as in Example 1. Got paper.

Comparative Example 2 In Example 1, instead of Callite KT, Tunex E (manufactured by Shiraishi Calcium Co., Ltd.; oil absorption 42 ml/10
A thermal recording paper for comparison was obtained in the same manner as in Example 1, except that 0 g; average particle size: 4.4 mm) was used.

Comparative Example 3 In Example 1, Br11 was used instead of Callite KT.
1iant-15 (manufactured by Shiraishi Calcium Co., Ltd.; oil absorption 4
3.5mfl/100g; average particle size 0.55μff1)
A comparative thermosensitive recording paper was obtained in the same manner as in Example 1 except that .

Comparative Example 4 A comparative thermal recording paper was obtained in the same manner as in Example 1, except that the average particle size of the CB liquid was changed to 3N.

Using the thermal recording paper of the present invention and the comparative thermal recording paper obtained as described above, the following quality evaluation was carried out. The results are shown in Table-2.

(1) Dynamic color development A thermal printing actual frame device with a thin film head manufactured by Matsushita Electronics Components, head power 0.45W/dot, 1 line recording time 20m5ec/1ine, scanning line density 8 x 3
．． Under the condition of 85 dots/mm, the pulse width was set to 0.2.0.
6 and 1.0 m5ec, and the print density was measured using a Macbeth densitometer RD-914.

(2) Sticking test Fuji Xerox Co., Ltd. il! Facsimile Telecopier 7
At 005, the Institute of Image Electronics Engineers of Japan Na3 chart was received, and the occurrence of sticking was visually observed. In addition, adhesion of head residue was also visually observed.

From the results in Table 2, it can be seen that the heat-sensitive recording material of the present invention is superior to the comparative heat-sensitive recording materials in terms of sticking, residue adhesion, etc., and is extremely useful.

Patent applicant Rico Co., Ltd.

Claims (3)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, the average particle size of the leuco dye and the color developer is 0.5 to 2.5 μm. In addition, as a pigment, the oil absorption amount is 80 to 300ml/100g (J
ISK5101) and has an average particle size in the range of 1 to 6 μm, and has an average particle size that is approximately the same as or larger than the above-mentioned leuco dye and color developer. A heat-sensitive recording material characterized by: (2) The heat-sensitive recording material according to claim 1, wherein the pigment has an average particle size of 1.5 to 3 μm. (3) In a method for producing a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer as main components is provided on a support,
Leuco dye and color developer with an average particle size of 0.5 to 2.5 μm
Dispersion treatment is carried out so that
Oil absorption measured by JISK5101 is 80-300m
After adding a pigment having an average particle size of 1 to 6 μm and approximately the same as or larger than the average particle size of the leuco dye and color developer. , a method for producing a heat-sensitive recording material, which comprises coating the same on a support.