JPH04220394A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material with high sensitivity and white texture by using hollow resin fine particles each with a nucleus contained in an air-gap as hollow resin fine particles of an undercoat layer. CONSTITUTION:Hollow resin fine particles each with a nucleus contained in an air-gap to be used in an undercoat layer are easy to scatter light in comparison with normal hollow resin fine particles containing no nucleus so as to enable lowering the texture concentration of a thermal recording material. Many normal hollow resin fine particles contain water in the air gap so that water evaporate to become hollow fine particles. Therefore, normal hollow resin fine particles are inferior to normal non-hollow resin fine particles in drying efficiency. In the hollow fine particles used in this invention, however, the nucleus is contained in the air-gap so as to be in the state of floating on the water. Therefore, the undercoat liquid using the hollow fine particles of this invention also has an advantage in being the same as the undercoat liquid using the non-hollow resin fine particles in the drying efficiency.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having improved properties by providing an undercoat layer between a support and a heat-sensitive coloring layer.

0002

[Prior Art] Recently, various recording materials have been researched and developed in the field of information recording and put into practical use in response to social demands such as diversification and increase in information, resource conservation, and pollution-free environment. Among them, heat-sensitive recording materials are characterized by (1) the ability to record a colored image simply by heating, eliminating the need for a complicated development process, and (2) the ability to be manufactured using relatively simple and compact equipment; (3) Paper is often used as a support, and in this case, not only is the support cost low, but the feel of the resulting recording material is also low. Because of its advantages such as being similar to plain paper, it can be used for computer output, printers such as calculators, recorders for medical measurement, low and high speed facsimiles, automatic ticket vending machines, thermal copying, labels for POS systems, etc. It is widely used in

[0003] The above heat-sensitive recording materials are usually produced by coating a support such as paper, synthetic paper, or synthetic resin film with a heat-sensitive coloring layer solution containing a coloring component that can cause a coloring reaction when heated and drying it. The heat-sensitive recording material thus obtained is heated with a thermal pen or a thermal head to record a colored image. As a conventional example of such a heat-sensitive recording material, for example, Japanese Patent Publication No. 43-4160
The heat-sensitive recording materials disclosed in Japanese Patent Application Publication No. 45-14039 can be mentioned, but such conventional heat-sensitive recording materials have, for example, low thermal responsiveness and cannot obtain sufficient color density during high-speed recording. . As a method for improving such drawbacks, for example, JP-A No. 49-38424 discloses that nitrogen-containing compounds such as acetamide, stearamide, m-nitroaniline, and dinitrile phthalate are used in JP-A No. 52-1.
No. 06746 discloses acetoacetic acid anilide in JP-A No. 5
3-11036 discloses N,N-diphenylamine derivatives, benzamide derivatives, and carbazole derivatives; JP-A-53-39139 discloses alkylated biphenyls and biphenylalkanes; JP-A-56-144193
The publication describes p-hydroxybenzoic acid ester derivatives,
Although methods have been disclosed for increasing speed and sensitivity by including each of them, at present, no fully satisfactory results have been obtained by any of the methods. Further, as another method, a method is disclosed in JP-A-56-164890, etc., in which a leuco dye with a high melting point is made amorphous, thereby lowering the melting point and increasing the sensitivity. However, since the amorphous dye has an activated surface and is highly reactive, there are problems in that it causes large liquid fog or background fog in a heat-sensitive coloring coating solution or heat-sensitive recording material, and is inferior in whiteness.

Therefore, in order to suppress background fog and increase dynamic coloring sensitivity, the thermal conductivity of the support was increased to 0.04 Kca.
1/mh°C or less (Japanese Patent Application Laid-open No. 55-164192), or by providing a layer mainly composed of micro hollow spherical particles on the support (Japanese Patent Application Laid-open Nos. 59-5093 and 59-225).
987), etc., and a method using non-expandable micro hollow particles of 5 μm or less made of thermoplastic resin in the intermediate layer (Japanese Patent Laid-Open No. 62-5886).
is proposed.

[0005]

[Problems to be Solved by the Invention] However, the heat-sensitive recording materials proposed in the above-mentioned JP-A-55-164192, JP-A-59-5093, etc. have insufficient foamability and are not flexible to wall materials. However, it is difficult to say that a fully satisfactory result has been obtained, as there may be cases where the heat-sensitive recording material is not strong enough, the heat-insulating property is insufficient, or the adhesion between the thermal head and the heat-sensitive recording material is insufficient. Furthermore, the heat-sensitive recording material proposed in the above-mentioned Japanese Patent Application Laid-Open No. 62-5886 does not give sufficiently satisfactory results.

[0006] Accordingly, an object of the present invention is to provide a heat-sensitive recording material with high sensitivity and a white background.

[0007]

[Means for Solving the Problems] According to the present invention, an undercoat layer containing resin hollow fine particles as a main component on a support, and a leuco dye and a color developer that causes the leuco dye to develop color when heated are provided as main components. There is provided a heat-sensitive recording material formed by sequentially laminating a heat-sensitive coloring layer and a heat-sensitive coloring layer, characterized in that the hollow resin particles are resin hollow particles having a nucleus in the void.

[0008] In the present invention, the hollow resin particles with nuclei in the voids used in the undercoat layer scatter light more easily than ordinary resin hollow particles without nuclei, and therefore are suitable for heat-sensitive recording materials. It is possible to lower the skin density of Of course, since the fine particles are hollow particles, an undercoat layer using them has high heat insulation properties, and therefore a highly sensitive heat-sensitive recording material can be provided.

[0009] Furthermore, many of the ordinary resin hollow particles contain water in their pores, and the water evaporates to become hollow particles. Therefore, the drying efficiency of ordinary resin hollow particles is lower than that of ordinary non-hollow resin particles. However, the hollow microparticles used in the present invention have nuclei in the voids and are floating in water. Therefore, the undercoat liquid using the hollow fine particles of the present invention also has the advantage that the drying efficiency is the same as that of the undercoat liquid using non-hollow resin fine particles.

The resin hollow fine particles used in the present invention have a thermoplastic polymer shell and contain a core and air or other gas inside, and are approximately spherical, with an average particle diameter of 0.5
~1.0 μm. The core and shell material are made of a polymer or copolymer of styrene, vinylidene chloride, acrylic acid, acrylic acid ester, acrylonitrile, etc., and the particle size of the core is 0.05 to 0.5 μm. Note that this resin hollow fine particle can be easily produced.

[0011] In order to provide the undercoat layer on the support, the resin hollow fine particles are dispersed in water together with a binder such as a known water-soluble polymer or aqueous polymer emulsion, and this is applied to the surface of the support. , obtained by drying. In this case, the coating amount of the resin hollow particles is at least 1 g, preferably 2 to 15 g per 1 m2 of the support.
The coating amount of the binder resin may be such as to strongly bond the undercoat layer to the support, and is usually 2 to 50% by weight based on the total amount of the resin hollow particles and the binder resin. be.

In the present invention, the binder used in forming the undercoat layer is appropriately selected from conventionally known water-soluble polymers and/or aqueous polymer emulsions. Specific examples include water-soluble polymers such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose,
Cellulose derivatives such as ethyl cellulose, polysodium acrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/ Maleic anhydride copolymer alkali salt, polyacrylamide,
Examples include sodium alginate, gelatin, and casein. In addition, aqueous polymer emulsions include latex such as styrene/butadiene copolymer, styrene/butadiene/acrylic copolymer, vinyl acetate resin, vinyl acetate/acrylic acid copolymer, and styrene/acrylic acid ester copolymer. Examples include emulsions of acrylic acid ester resins, polyurethane resins, and the like.

In addition, in the undercoat layer of the present invention, in addition to the resin hollow fine particles and the binder, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, thermofusible Substances, surfactants, etc. can be used in combination. In this case, specific examples of the filler and thermofusible substance include the various fillers shown below in connection with the components of the thermosensitive coloring layer. Further, in order to make the surface of the undercoat layer formed on the support as described above even smoother, the plane may be smoothed by calendering after the undercoat layer is formed.

[0014] The leuco dyes used in the heat-sensitive coloring layer of the present invention can be applied singly or in a mixture of two or more, and as such leuco dyes, those used in this type of heat-sensitive material can be arbitrarily applied. For example, leuco compounds of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes 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-diethylaminophthalide, 3
, 3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7- Dimethylfluorane, 3-diethylamino-7-chlorofluorane, 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-diethylaminofluorane, 2-{3,6-bis(diethylamino)-9
-(o-chloroanilino)xantylbenzoic acid lactam}, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-di-
n-Butylamino-7-(o-chloroanilino)fluorane, 3-N-methyl-N,n-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-
Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N-diethylamino)-5-
Methyl-7-(N,N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8
'-Methoxy-benzoindolino-spiropyran, 6'
-Bromo-3'-methoxy-benzoindolino-spiropyran, 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'-methylphenyl)phthalide, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N -(2-ethoxypropyl)amino-6-methyl-7-anilinofluorane, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane 3-morpholino-7-(N-propyl -trifluoromethylanilino)fluorane, 3-pyrrolidino-7
-m-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylamino Fluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-
p-Toluidino)-7-(α-phenylethylamino)
Fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluoran, 2 -chloro-3-(N-methyltoluidino)
-7-(p-n-butylanilino)fluoran, 3-(
N-methyl-N-isopropylamino)-6-methyl-
7-anilinofluorane, 3-di-n-butylamino-
6-Methyl-7-anilinofluorane, 3,6-bis(
dimethylamino)fluorenespiro(9,3')-6'
-dimethylaminophthalide, 3-(N-benzyl-N-
cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino -4', 5
'-benzofluorane, 3-N-methyl-N-isopropyl-6-methyl-7-anilinofluorane, 3-N-
Ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(2
',4'-dimethylanilino)fluorane, etc.

[0016] As the color developer used in the heat-sensitive coloring layer of the present invention, various electron-accepting compounds or oxidizing agents that cause the leuco dye to develop color upon contact are used. Such materials are conventionally known, and specific examples include those shown below.

4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(o-methylphenol), 4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis(2-tertiary butylphenol), zinc p-nitrobenzoate, 1,
3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanuric acid, 2
, 2-(3,4'-dihydroxydiphenyl)propane, bis(4-hydroxy-3-methylphenyl) sulfide, 4-{β-(p-methoxyphenoxy)ethoxy}salicylic acid, 1,7-bis(4- hydroxyphenylthio)-3,5-dioxaheptane, 1,5-bis(4
-Hydroxyphenylthio)-5-oxapentane, phthalic acid monobenzyl ester monocalcium salt, 4,4
'-Cyclohexylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 2,2'
-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl-2-methyl)phenol, 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-methyl)phenol, 4,4'-diphenolsulfone, 4-isopropoxy-4'-hydroxy Diphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate,
Stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis(4-hydroxyphenylthio)-
Propane, N,N'-diphenylthiourea, N,N'-
Di(m-chlorophenyl)thiourea, salicylanilide, methyl bis-(4-hydroxyphenyl)acetate, benzyl bis-(4-hydroxyphenyl)acetate, 1,3-
Bis(4-hydroxycumyl)benzene, 1,4-bis(4-hydroxycumyl)benzene, 2,4'-diphenolsulfone, 2,2'-diallyl-4,4'-diphenolsulfone, 3 ,4-dihydroxyphenyl-4
'-Methyldiphenylsulfone, 1-acetyloxy-
Zinc 2-naphthoate, zinc 2-acetyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate,
α,α-bis(4-hydroxyphenyl)-α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 4,4'-thiobis(2-methylphenol),
4,4'-thiobis(2-chlorophenol) and the like.

In the heat-sensitive coloring layer of the present invention, various conventional binders can be used as appropriate in order to coat the leuco dye and developer onto the undercoat layer, and specific examples thereof include: The same materials as those exemplified in the application of the undercoat layer may be mentioned.

In addition, in the thermosensitive color forming layer of the present invention, in addition to the leuco dye and color developer, if necessary, further:
Auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, thermofusible substances, surfactants, etc., can be used in combination. In this case, the filler may be, for example,
Calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as talc, surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned. Examples of the sexual substances include higher fatty acids or their esters, amides, or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4- 5 such as epoxy-dialkyl hexahydrophthalate, higher ketones, and other thermofusible organic compounds.
Examples include those having a melting point of about 0 to 200°C.

In the present invention, a layer containing a filler, a binder, a thermofusible substance, etc. may be provided as an intermediate layer between the undercoat layer and the heat-sensitive coloring layer, if necessary. In this case, specific examples of the filler, binder, and thermofusible substance include those exemplified in connection with the heat-sensitive coloring layer or undercoat layer.

Furthermore, in the heat-sensitive recording material of the present invention, a protective layer may be provided on the heat-sensitive coloring layer for the purpose of improving matching properties of thermal heads, etc., and further enhancing recorded image storage stability. In this case, the above-mentioned fillers, binders, surfactants, and thermofusible substances can also be used as components constituting the protective layer.

The heat-sensitive recording material of the present invention is produced by, for example, coating the above-mentioned layer-forming coating liquid on a suitable support such as paper, synthetic paper, or plastic film and drying it. Applied to the recording field.

[0023]

EXAMPLES Next, the present invention will be explained in more detail with reference to examples. Note that all parts and percentages shown below are based on weight.

Example [Liquid A] 3-(N-methyl-3-N-cyclohexyl)
Amino 20 parts -6-methyl-
7-anilinofluorane 10% polyvinyl alcohol aqueous solution
20 parts water

60 copies

0025
] [Liquid B] Benzyl p-hydroxybenzoate
10 copies
Polyvinyl alcohol 10% aqueous solution
25 parts calcium carbonate
15
Part water

50 copies

[0026] A mixture of the above compositions was dispersed using a sand mill so that the average particle size of each was 2 μm or less to prepare [Liquid A] and [Liquid B].

[Liquid C] Core-containing resin hollow particles (styrene acrylic)
40 parts (solid content 38%; muticle manufactured by Mitsui Toatsu Co., Ltd.) Styrene/butadiene copolymer latex (solid content 47%)
Part 10 Water

50 copies

[0028] The mixture consisting of the above formulation was stirred and dispersed using a disper to prepare an undercoat liquid, and this was coated on commercially available high-quality paper (basis weight 52 g).
/m2) to obtain an undercoated paper such that the weight after drying was 6 g/m2.

Next, the above [Liquid A] and [Liquid B] were mixed and stirred at a weight ratio of 1:8 to prepare a thermosensitive coloring layer forming liquid, and this was applied to the surface of the above-mentioned undercoated paper. A heat-sensitive coloring layer was provided by coating and drying so that the weight after drying was 7 g/m2, and then supercalender treatment was carried out so that the Beck smoothness was 500 to 600 seconds to obtain a heat-sensitive recording material of the present invention. .

Comparative Example 1 In [Liquid C] of Example, resin hollow fine particles (manufactured by Rohm and House Co., Ltd.; Lowpeque OP-84, solid content 38%) were used instead of the core-containing resin hollow fine particle muticle. A comparative heat-sensitive recording material was obtained in the same manner as in the examples.

Comparative Example 2 In [Liquid C] of Example, non-hollow resin fine particles (manufactured by Mitsui Toatsu Co., Ltd.: SPMM-HS, solid content 38%) were used instead of the core-containing resin hollow fine particle muticles. teeth,
A comparative heat-sensitive recording material was obtained in the same manner as in the examples.

Each of the heat-sensitive recording materials obtained as described above was tested for dynamic color development sensitivity and background density. The results are shown in Table 1. The test was conducted as follows.

Dynamic coloring property: In a thermal printing experimental device equipped with a thin film head manufactured by Matsushita Electronic Components Co., Ltd., the head power was 0.4.
Printing was performed with pulse widths of 0.3, 0.4, 0.5, and 0.6 msec under conditions of 5 w/dot, 1 line recording time of 20 msec/l, and scanning line density of 8 x 3.85 dots/mm.
The print density was measured using a Macbeth densitometer RD-914.

[0034]

[Table 1]

From the results in Table 1, it can be seen that the heat-sensitive recording material of the present invention has high sensitivity and a white background.

[Effect of the invention] The heat-sensitive recording material of the present invention has the following effects:
In a heat-sensitive recording material in which an undercoat layer containing resin hollow fine particles as a main component and a heat-sensitive color-forming layer containing a leuco dye and a color developer as a main component that cause the leuco dye to develop color when heated are sequentially laminated on a support. Since the resin hollow fine particles have a structure in which a core is contained in the void, the resin hollow particles have high sensitivity and a white background.

Claims (1)

[Claims] Claim 1: An undercoat layer containing resin hollow fine particles as a main component and a heat-sensitive coloring layer containing a leuco dye and a color developer that causes the leuco dye to develop color when heated are sequentially laminated on a support. 1. A heat-sensitive recording material characterized in that the hollow resin particles are resin hollow particles having a nucleus in a void.