JPS6195981A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material having high sensitivity and excellent head matching property as well as lesser ground fogging by adding a silicic acid-calcium carbonate complex as a white pigment to a thermal color- forming layer. CONSTITUTION:A silicic acid-calcium carbonate complex, or a silice acid-calcium carbonate coprecipitate formed by blowing CO2 gas into an aqueous solution of sodium silicate and calcium chloride or calcium hydroxide, is added as a white pigment to a thermal color-forming layer to obtain a thermal color- forming layer having the feature of silicic acid such that oil absorption is high and the feature of calcium carbonate such that ground fogging is small. The preferred amount of the white pigment to add is 0.5-5 pts.wt., more preferably 1-3 pts.wt. on the basis of a pt.wt. leuco dye.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a heat-sensitive recording material, and more specifically, the present invention relates to a heat-sensitive recording material, and more specifically, a leuco dye that is colorless or slightly light-colored at room temperature and an acidic substance that reacts with the leuco dye when heated to develop a color. The present invention relates to an improvement in a heat-sensitive recording material in which a heat-sensitive coloring layer containing as a component is provided on a support.

[Prior art]

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 development process. (2) It can be produced using a relatively simple and compact device, and the resulting recording material is easy to handle. (3) paper is often used as the support;
In this case, not only the cost of the support is low, but also the feel of the obtained recording 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 heat-sensitive coloring layer liquid containing a coloring component capable of causing a coloring reaction when heated on 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.

Conventional examples of such heat-sensitive recording materials include, for example, the heat-sensitive recording materials disclosed in Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-14039; Responsiveness was low, and sufficient color density could not be obtained during high-speed recording. And as a way to improve these shortcomings.

For example, JP-A-49-38424 discloses acetamide.

Nitrogen-containing compounds such as stearamide, halo-nitroaniline, dinitrile phthalate, etc., acetoacetanilide in JP-A-52-106748, and JP-A-53-1103.
No. 6 discloses N,N-diphenylamine derivatives, benzamide derivatives, and carbazole derivatives in JP-A-53-3.
No. 9139 discloses alkylated biphenyls and biphenylalkanes, and JP-A-56-144193 discloses ρ.
A method for increasing speed and sensitivity by incorporating ρ-oxybenzoic acid ester derivatives has been disclosed, and among them, the most effective method is to use a ρ-oxybenzoic acid ester derivative as a color developer. It was known.

However, recently, in the facsimile field, demands for faster recording, higher density in low-temperature environments, and smaller equipment have been increasing, and this has led to a demand for even higher sensitivity of thermal recording paper. Ru. In response to these demands, it is difficult to achieve the desired high sensitivity using only the color developer and sensitizer mentioned above, and rather, it is necessary to reduce the content of white pigments and binders, which are not the basic color forming materials, as much as possible. Improving the color development speed of materials is being considered. However, in the case of conventionally known white pigments such as calcium carbonate, clay, and talc, when the content is reduced, there arises a drawback that head matching properties such as sticking and adhesion of head dregs deteriorate.

In addition, as another method for increasing the sensitivity of the heat-sensitive coloring layer, an attempt was made to add silicic acid, which has a high oil absorption, to the heat-sensitive coloring layer alone, but this also improved the head matching property, but caused background fog. However, none of the methods has yielded satisfactory results yet.

〔the purpose〕

The purpose of the present invention is to achieve higher sensitivity than previously known (
An object of the present invention is to provide a heat-sensitive recording material which has high dynamic color development sensitivity), has little background fog, and has excellent head matching properties such as sticking and head residue adhesion.

〔composition〕

According to the present invention, there is provided a heat-sensitive recording material in which a heat-sensitive coloring layer is provided on a support, the heat-sensitive color-forming layer mainly comprising a normally colorless or slightly pale-colored leuco dye and a color developer capable of coloring the leuco dye when heated. A heat-sensitive recording material is provided, characterized in that a heat-sensitive coloring layer contains a composite of silicic acid and calcium carbonate as a white pigment.

The silicic acid/calcium carbonate composite referred to in the present invention is not a simple mixture of silicic acid and calcium carbonate, but is prepared by blowing carbon dioxide gas into an aqueous solution of sodium silicate and calcium chloride or calcium hydroxide to co-precipitate it. The white pigment is a silicic acid/calcium carbonate coprecipitate, and it is thought that silicic acid and calcium carbonate are mixed in a molecular state or a form close to it to form particles. The present inventors have discovered that when this silicic acid/calcium carbonate coprecipitate is contained as a white pigment in a heat-sensitive coloring layer, it has the advantage of combining the characteristics of silicic acid, which has a high oil absorption, and the characteristics of calcium carbonate, which has low background fog. It has been discovered that a thermosensitive recording material can be obtained.

The white pigment of the present invention is added to the heat-sensitive coloring layer in the same manner as ordinary pigments, but the amount added is 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, per 1 part by weight of the leuco dye. used at a rate of

The heat-sensitive recording material of the present invention can have various structures, including all conventionally known structures that utilize a color-forming reaction between a leuco dye and a color developer. For example, the heat-sensitive recording material of the present invention includes a heat-sensitive recording material having a structure in which a leuco dye and a color developer are supported on a support as the same coating layer or separate coating layers, or a leuco dye layer and a color developer. It includes a heat-sensitive recording material having a structure in which an intermediate layer is interposed between two layers, and a heat-sensitive recording material having a structure in which a protective layer is provided on the surface or back surface of a heat-sensitive coloring layer.

The leuco dyes used in the present invention can be applied singly or in combination of two or more types, but such leuco dyes include:
For example, leuco compounds of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specific examples of 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-diethylaminophenyl, 3.3-bis (P-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(P-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran .

3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane.

3-diethylamino-7,8-benzfluorane, 3-
Diethylamino-6-methyl-7-chlorofluorane, 3-(N-ρ-toly-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane Oran, 2- (N-(3'-trifluoromethylphenyl)
amino)-6-dinithylaminofluorane.

2-(3,6-bis(diethylamino)-9-(o-
chloranilino)xantylbenzoic acid lactam), 3-
Diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-ralaniυ))fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3 -N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl- to -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-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'-me1-xy5'-ditrophenyl)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-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-( N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-P-fluorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran.

3-(N-Ethyl-p-toluidino)-7-(α-)enylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7- (α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(ρ-ropethylanilino)fluoran, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

Further, as the color developer used in the present invention, various electron-accepting substances that react with the leuco dye and develop color when heated are used, and specific examples thereof include phenol as shown below. sexual substance.

Examples include organic or inorganic acidic substances, esters and salts thereof, and the like.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di t,e
rt-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis (2,6
-dibromophenol), 4,4'-isopropylidene bis(2,6-dichlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'
-isopropylidene bis(2,6-dimethylphenol), 4,4'-isopropylidene bis(2-terj-
butylphenol), 4.4'-5ec-butylidene diphenol, 4.4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis(2-
methylphenol), 4-t, ert, -butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5
-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phloroglycine, phloroglycin Carboxylic acid, 4 tert-octylcatechollenbis(4-chlorophenol), 2,2'-methylenebis(4-methyl-6-cert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl ρ-hydroxybenzoate, Propyl p-hydroxybenzoate, butyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, ρ-hydroxybenzoate-ρ-florbenzyl, ρ-chlorobenzyl hydroxybenzoate, ρ-methylbenzyl P-hydroxybenzoate, P-
n-octyl hydroxybenzoate, benzoic acid, zinc salicylate, ■-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4 '-chlorodiphenyl sulfone, bis(hydroxyphenyl) sulfide, 2-hydroxy-p-
Toluic acid, 3,5-di-t. Zinc ert-butylsalicylate, tin 3,5-jerj-butylsalicylate,
Tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid,
Stearic acid, 4-hydroxyethylic acid, boric acid, etc.

In the present invention, in order to bind and support the leuco dye, color developer, and white pigment on a support, various conventional binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxy Cellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose and other cellulose derivatives, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer , styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate,
In addition to water-soluble polymers such as gelatin and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer,
Polyacrylic acid, polyacrylic ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/
A latex such as an acrylic copolymer can be used6.Furthermore, in the present invention, in addition to the leuco dye, color developer and white pigment, if necessary, a material commonly used in this type of heat-sensitive recording material may be used. Auxiliary additive ingredients, e.g. surfactants,
A thermofusible substance (or lubricant), etc. can be used in combination.

In this case, white pigments other than those of the present invention include, 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 also be used, and thermofusible Examples of the sexual substances include higher fatty acids or their esters, amides, or metal salts, as well as various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, and 3,4-epoxy. -50% of dialkyl hexahydrophthalate, higher ketones, other thermofusible organic compounds, etc.
Those having a melting point of about ~200°C are used.

The heat-sensitive recording material of the present invention can be produced, for example, by applying a heat-sensitive layer forming coating solution containing the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying it. It is applied to various recording fields.

〔effect〕

The heat-sensitive recording material of the present invention uses a composite of silicic acid and calcium carbonate as a white pigment, so the amount added to the heat-sensitive coloring layer can be reduced, and it has high sensitivity, good head matching properties, and This has the effect of reducing fog.

〔Example〕

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 1 Solution A> 40% polystyrene dispersion 750 parts lO
% polyvinyl alcohol aqueous solution 200//water
501
1 Disperse the above mixture in a sand grinder for 30 minutes to prepare an undercoat coating liquid, and after drying, the coating amount after drying is 4 g/rr? An undercoated paper was created by applying it with a wire bar adjusted to give the following properties.

<Liquid B> 3-(N-methyl-N-cyclohexyl)amino-6-
Methyl-7-anirite fluorane 300 parts 10% polyvinyl alcohol aqueous solution 300 water
400〃〈
Solution C> Benzyl P-hydroxybenzoate 120 parts Tetrabromobisphenol A 3011 Silicic acid/calcium carbonate composite 100 (Molar ratio of silicic acid component to calcium carbonate = 1:1) Zinc stearate 25 10% polyvinyl alcohol aqueous solution 200 parts water
525//Mixtures having the above compositions were ground in a sand grinder for 2 times.
Liquids B and C were prepared by pulverization and dispersion for ~4 hours.

Next, liquid B and liquid C were mixed and stirred so that the weight ratio B:C was 1:6 to prepare a heat-sensitive coating liquid, and then the coated amount of leuco dye after drying was 0.25% on the undercoated paper. 5g/m
It was applied with a wire bar adjusted so that This coated paper was calendered to a smoothness of 700 to 1500 seconds to prepare a heat-sensitive recording material of the present invention.

[Comparative example]

In addition, for comparison with Example 1, silicic acid (Tokuyama Manufacturer Y.
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that Fine Seal E-70) manufactured by Tatsu ■ was used alone.

Comparative Example 2 A heat-sensitive recording material was produced in the same manner as in Example 1, except that calcium carbonate (Tunekusu E manufactured by Shiraishi Kogyo@) was used alone instead of the silicic acid/calcium carbonate composite in [Liquid C] in Example 1. was created.

Comparative Example 3 Instead of the silicic acid/calcium carbonate composite in [Liquid C] in Example 1, the weight ratio of silicic acid and calcium carbonate was 2=1.
A heat-sensitive recording material was prepared in the same manner as in Example 1, except that a simple mixture of silicic acid/calculum carbonate was used.

Dynamic color development sensitivity for the above heat-sensitive recording materials.

Tests were conducted according to the following test methods for head matching properties (sticking, head residue adhesion) and background density. 6 (1) Dynamic coloring sensitivity: Using a thermal printing experimental device with a thin film head manufactured by Matsushita Electronics Iol. Head power 0.4
5w/dot, line recording time 20m5/Q, scanning line density 8 x 3.85 dots/ms, pulse width 0.4.0.6.0.8.1.0°1.2.1 .4.
80 lines were printed at 1,6*8eC each, and the print density was 81 with Macbeth Densitometer lID-514 (Filter Lee 106)! I decided.

(2) Head matching property When measuring the dynamic color development sensitivity shown in (1), sticking was observed on the printed sample, and head scum was observed by I11 of the thermal head after printing was completed, and the following evaluations were performed.

■Sticking Print line skipping due to O-nistic Obtains uniform solid coloring power with no blurring at all. It was done.

∆: Printing error due to slight stick There is a jump in the color, and the solid coloring power is 1 level. It wasn't the only one.

×; The printing line is skipped by the stick. There is a lot of The character length was also short 6- ■Head debris adhesion O: There is a slight amount of debris adhering to the thermal head. No way.

Δ: There is debris attached, but after the resistor flows.

×: There is a lot of residue attached, and there may be some dirt on the resistor. accumulate.

(3) Skin density... Macbeth densitometer RD-514 (filter -wrat, ten-106) The test results are shown in Table-1 6 As can be seen from the results shown in Table-1, 1 The thermal record of the present invention The material has less background fogging than when silicic acid is used alone as a white pigment in the heat-sensitive coloring layer as in the past, and has better head matching properties than when calcium carbonate is used alone. It can be confirmed that this method is still superior to the case where a similar mixture is used in terms of both background fog and head matching properties.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color-forming layer is provided on a support, the heat-sensitive color-forming layer is composed mainly of a normally colorless or slightly light-colored leuco dye and a color developer capable of coloring the leuco dye when heated. A heat-sensitive recording material characterized by containing a composite of silicic acid and calcium carbonate as a white pigment.