JPH04290796A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material which has high color development sensitivity without color shading or decoloring and also without discharge attributed to the contact between the material and a plasticizer or oil. CONSTITUTION:This thermal recording material consists of a color development layer containing a color development substance which is normally colorless or pale and a developer which develops the color of said color development material. In addition, the thermal recording material contains organic phosphate, its metal salt or basic salt expressed by formula 1 as a developer.

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 containing a specific organic phosphate, a metal salt thereof, or a basic salt thereof as a color developer.

0002

[Prior Art and Problems to be Solved by the Invention] A heat-sensitive recording medium uses a color-forming substance that is usually colorless or light-colored and a color developer that develops color from the color-forming substance when exposed to heat, in a separated state. It is produced by coating the surface of a support such as paper, synthetic paper, plastic film or sheet together with a sensitizer, binder and other additives. Then, in the recording apparatus, when a heat generating element such as a thermal head or a hot pen comes into contact with this recording medium, the color-forming substance and the color developer react to form a color such as black and are recorded. Compared to other recording media, such recording media do not require complicated processing such as development and fixing, can be recorded using relatively simple equipment in a short time, and generate less noise. Because of its advantages such as small size, low environmental pollution, and low cost, it is used not only for copying books and documents, but also for recording paper for various measurements, computers, facsimiles, telex machines, ticket vending machines, and prepaid machines. Widely used as recording material for cards, labels, etc.

Conventionally, various acidic substances have been proposed as color developers for thermally coloring color-forming substances, and in particular, phenolic compounds such as bisphenol-A, p-
-Hydroxybenzoic acid benzyl ester, 4,4'-cyclohexylidene diphenol, 1,1,3-tris(
(3'-tert-butyl-4'-hydroxy-6'-methylphenyl) butane, or organic carboxylic acid derivatives are used alone or in combination of several types. However, when these acidic substances are used, the color development sensitivity is not yet sufficient, and there are drawbacks such as color unevenness, color reversion, or discoloration during storage.

[0004] Therefore, attempts have been made to achieve higher sensitivity by using a sensitizer, which is a third substance, as a color-forming substance or developer. For example, it has been proposed to use 4-benzyloxybiphenyl, dimethyl phthalate, stearamide, phenyl benzoate, etc. in combination, and although this improves color development sensitivity to some extent, it is still not sufficient and may cause uneven coloring and discoloration. , and further improvements were desired.

[0005] Furthermore, if these heat-sensitive recording materials are stored in a vinyl chloride bag, come into contact with a desk mat made of vinyl chloride, or touch the heat-sensitive recording materials with your hands, the vinyl chloride may leak. There has been a problem that the plasticizer may migrate or the coloring area may fade due to oil from hands and fingers.

It has also been proposed to form a film on the surface of the heat-sensitive recording material that does not allow penetration of plasticizers and oil, but this method has the drawbacks of increasing costs and making it difficult to print on the overcoat layer. , it could hardly be called a practical method.

For this reason, Japanese Patent Application Laid-Open No. 59-14989 discloses hydroxyphenylphosphine derivatives, and Japanese Patent Application Laid-Open No. 62-90284 discloses the use of specific phosphonate derivatives in combination with other color developers. However, when these color developers are used, the color fades significantly when stored at high temperatures, and water resistance is insufficient, resulting in fogging in non-printed areas. It has the disadvantage of being large, and improvements in these areas have been desired.

[0008] Furthermore, in JP-A-2-310084, storage stability was improved by adding a specific organic phosphate derivative, but it is essential to use a phenol compound or the like as a color developer. , it was necessary to aim for even higher preservability.

[0009]

[Means for Solving the Problems] In view of the above-mentioned current situation, the present inventors have developed a product that not only has excellent color development sensitivity, but also has no color unevenness or color fading, and also disappears even when it comes in contact with plasticizers and oils. As a result of extensive research in order to obtain a unique heat-sensitive recording material, we have found that by using a specific organic phosphate, its metal salt, or its basic salt as a color developer, it has excellent printing speed and extremely high color development sensitivity. Furthermore, the inventors have discovered that the solvent resistance and storage stability are also significantly improved, and have arrived at the present invention.

That is, the present invention provides a heat-sensitive recording material provided with a color-forming layer containing a normally colorless or light-colored color-forming substance and a color developer that causes the color-forming substance to develop color when heated. The present invention provides a heat-sensitive recording material characterized by containing a specific organic phosphate represented by the general formula 2, a metal salt thereof, or a basic salt thereof.

[0011]

[Case 2]

The heat-sensitive recording material of the present invention will be explained in more detail below.

The above general formula 2 (chemical formula 1) used in the present invention
Among the organic phosphates, metal salts thereof, or basic salts thereof represented by (same as ), examples of the halogen atoms represented by X, Y, and Z include fluorine, chlorine, and bromine atoms.

Examples of the alkyl group include methyl, ethyl, butyl, octyl, decyl, dodecyl, tertiary dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, triacontyl, etc., and the aryl group includes: Examples include phenyl, tolyl, xylyl, ethylphenyl, butylphenyl, tert-butylphenyl, tert-amylphenyl, chlorophenyl, hydroxyphenyl, and the like.

Therefore, representative examples of the organic phosphate represented by the above general formula 2, its metal salt or its basic salt used in the present invention include the compounds shown in the following formulas 3 to 19.

[0016]

[C3]

[0017]

[C4]

[0018]

[C5]

[0019]

[C6]

[0020]

[C7]

[0021]

[Chemical formula 8]

[0022]

[Chemical formula 9]

[0023]

[Chemical formula 10]

[0024]

[Chemical formula 11]

[0025]

[Chemical formula 12]

[0026]

[Chemical formula 13]

[0027]

[Chemical formula 14]

[0028]

[Chemical formula 15]

[0029]

[Chemical formula 16]

[0030]

[Chemical formula 17]

[0031]

[Chemical formula 18]

[0032]

[Chemical formula 19]

[0033] The method of synthesizing the organic phosphate represented by the above formula 2, its metal salt or its basic salt used in the present invention is not particularly limited, but for example, it may be synthesized by a method according to the synthesis example shown below. be able to.

Synthesis Example 1 4-(p-methylphenylsulfonylphenyl)-1,
2-phosphate zinc salt (No. 14 compound, chemical formula 16
) synthesis of

52.9 g of 3,4-dihydroxyphenyl-4-methylphenylsulfone, 31 phosphorus oxychloride
．． 3 g was dissolved in 100 ml of dioxane. 42.4 g of triethylamine while preventing contact with moisture from 30 to 4
It was slowly added dropwise at 0°C. After further stirring at 30° C. for 3 hours, the by-produced triethylamine hydrochloride was removed by filtration. The viscous liquid obtained by removing the solvent from the filtrate is gradually added to distilled water 3
00ml to obtain white crystals. 10% on this
Add 80g of sodium hydroxide aqueous solution and further adjust the pH to 8~
An alkaline aqueous solution was added until the concentration reached 9. After stirring for 1 hour,
4-(p-methylphenylsulfonylphenyl)-1,
53.4 g of white crystals of 2-phosphate sodium salt were obtained (yield 76.6%).

Using 10 g of this sodium salt, distilled water -
Dissolve in 100 ml of isopropanol (1:1), add 1.9 g of zinc chloride and react to obtain the desired white crystal 9.
．． 8g was obtained.

The zinc and phosphorus contents of the obtained target product were measured. The results are shown below. Zn content 9.11% (theoretical amount 9.13%) P content
8.67% (theoretical amount 8.65%)

By the same operation, magnesium chloride and nickel chloride were used to prepare magnesium salts (No. 15 compound, Chemical compound 17).
) and a nickel salt (Compound No. 13, Chemical Formula 15) were obtained.

The metal and phosphorus contents of the obtained target product were measured. The results are shown below. Mg salt: Mg content 3.57% (theoretical amount 3.60
%) P content 9.19% (theoretical amount 9.17%) Ni salt Ni content 8.26% (theoretical amount 8.27%)
P content 8.73% (theoretical amount 8.73%)

0040
] Synthesis Example 2 Synthesis of 4-(ethoxycarboxyphenyl)-1,2-phosphate zinc salt (NO.7, Chemical formula 9)

18.2 g of protocatechuic acid ethyl ester and 10.73 g of phosphorus oxychloride were dissolved in 100 ml of dioxane. 14.9g of triethylamine while preventing contact with moisture
was slowly added dropwise at 30 to 40°C. After further stirring at 30° C. for 3 hours, the by-produced triethylamine hydrochloride was removed by filtration. The viscous liquid obtained by removing the solvent from the filtrate was poured little by little into 100 ml of distilled water to obtain white crystals. To this was added 30 g of a 10% aqueous sodium hydroxide solution, and further an aqueous alkaline solution was added until the pH reached 8-9. 1
Stir for 4-(ethoxycarboxyphenyl)-1
, white crystals of the sodium salt of 2-phosphate 13.4
g (yield: 76.5%).

Using 10 g of this sodium salt, distilled water -
Dissolved in 100 ml of isopropanol (1:1) and added 2.8 g of zinc chloride to give 8.5 g of white crystals of the desired product.
I got g.

As a result of infrared spectroscopic analysis, the obtained reaction product had the following characteristic absorption, and was confirmed to be the desired product.

[0044]2980cm-1, 1710cm-1, 1
610cm-1, 1500cm-1, 1300cm-1
, 1100cm-1, 1090cm-1, 1010cm
-1, 980cm-1, 760cm-1

[0045] Metal (Zn) and phosphorus contents were also measured. The results are shown below. Zn content 11.81% (theoretical amount 11.85%) P content 11.24% (theoretical amount 11.23%)

0046
] Various sensitizers can be used in combination to increase the color development sensitivity of the heat-sensitive recording material of the present invention. Examples of these sensitizers include zinc acetate, zinc octylate, zinc laurate, zinc stearate, zinc oleate, zinc behenate, zinc benzoate, zinc salicylate dodecyl ester salt, calcium stearate, magnesium stearate, Metal organic acid salts such as aluminum stearate, amide compounds such as stearamide, stearic acid methylolamide, stearoyl urea, acetanilide, acetoacetanilide, benzoic acid stearylamide, ethylene bisstearic acid amide, hexamethylene bisoctylic acid amide, 1,2-bis(3,4-dimethylphenyl)ethane, m-terphenyl, 1,2-bis(3-methylphenoxy)ethane, p-benzylbiphenyl, p-benzyloxybiphenyl, diphenyl carbonate, bis(
4-methylphenyl) carbonate, dibenzyl oxalate, phenyl 1-hydroxy-2-naphthalenecarboxylate, benzyl 1-hydroxy-2-naphthalenecarboxylate, phenyl 3-hydroxy-2-naphthalenecarboxylate, 3-hydroxy- 2-naphthalenecarboxylic acid anilide, methylene dibenzoate, 1,4-bis(2-
(vinyloxyethoxy)benzene, 2-benzyloxynaphthalene, benzyl 4-benzyloxybenzoate, dibenzyl terephthalate, dibenzoylmethane, 4-methylphenoxy-p-biphenyl, etc., especially amide compounds and/or metal organic acids. Salt is preferred because of its great effect.

Furthermore, a conventionally known color developer can be used in combination with the organic phosphate, its metal salt, or its basic salt used as a color developer in the present invention. The organic phosphate, its metal salt or its basic salt of the present invention is also excellent in the effect of improving storage stability.
Even when used in combination with other color developers, it has the effect of not causing problems such as color reversion or discoloration.

Examples of these conventionally known color developers include p-octylphenol, p-tert-butylphenol, p-phenylphenol, p-hydroxyacetophenone, α-naphthol, β-naphthol, and p-tert-octylcatechol. , 2,2'-dihydroxybiphenyl, bisphenol-A, 1,1-bis(p-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)heptane, 2,2-bis-(3-methyl- 4-hydroxyphenyl)propane, 2,2-bis(3,5-
dimethyl-4-hydroxyphenyl)propane, 2,2
-bis(4-hydroxy-3,5-dichlorophenyl)
Propane, bis(4-hydroxyphenyl)sulfone,
Bis(4-hydroxy-3-allylphenyl)sulfone, bis(3,4-dihydroxyphenyl)sulfone, 1
, 1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)ether, 1,1,
3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, bis[2-(4 -hydroxyphenylthio)ethoxy]methane, 4-(4-isopropoxybenzenesulfonyl)phenol, 4-hydroxyphthalic acid dimethyl ester, bis(4-hydroxyphenyl)acetic acid butyl ester, p-hydroxybenzoic acid benzyl, 3,5 −
Examples include phenols such as di-tert-butylsalicylic acid and organic carboxylic acids.

Various dyes are well known as the usually colorless or light-colored color-forming substance used in the present invention, and there are no particular limitations as long as they are used in general heat-sensitive recording paper.

Specific examples of these dyes (color-forming substances) include: (1) triarylmethane compounds; for example, 3,
3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone)
, 3-(p-dimethylaminophenyl)3-(2-phenyl-3-indolyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethyl-3-indolyl)phthalide, 3, 3-bis(9-ethyl-3-carbazolyl)-5-dimethylaminophthalide, 3,3-
Diphenylmethane compounds such as bis(2-phenyl-3-indolyl)-5-dimethylaminophthalide; For example, 4,4-bis(dimethylamino)benzhydrin benzyl ether, N-2,4,5-tri N-halophenyl leuco auramine such as chlorophenyl leuco auramine, xanthene compounds; for example, rhodamine-β-anilinolactam, 3-diethylamino-7-
Octylaminofluorane, 3-diethylamino-7-
(2-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-(β-ethoxyethylamino)fluoran, 3-piperidino-6-methyl-7 -anilinofluorane, 3-ethyltolylamino-6-methyl-7-anilinofluorane, 3-cyclohexylmethylanilino-6-methyl-7-anilinofluorane, 3
-diethylamino-6-chloro-7-γ-chloropropylaminofluorane, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane, 3
-dibutylamino-7-(2-chlorophenyl)aminofluorane, etc., ■thiazine compounds; for example, benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue, etc.; ■spiro compounds; for example, 3
-Methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-
Examples include methylnaphtho-(3-methoxybenzo)spiropyran, and several types of these dyes may be used in combination.

The organic phosphate, its metal salt or its basic salt, and the above-mentioned color-forming colorless dye used in the present invention are usually atomized by a grinder such as a ball mill, attrizer, or sand grinder, or by a suitable emulsifying device, and then Depending on the situation, various additive materials are added to make the coating liquid.

[0052] This coating solution usually contains polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose,
Polyacrylamide polymers, starches, binders such as styrene-maleic anhydride copolymers, vinyl acetate-maleic anhydride copolymers, styrene-butadiene copolymers, kaolin, silica, diatomaceous earth, talc, titanium dioxide, carbonic acid Fillers such as calcium, magnesium carbonate, and aluminum hydroxide are blended, but in addition to these, metal soaps such as calcium stearate, waxes, light stabilizers, waterproofing agents, dispersants, antifoaming agents, fillers, etc. can be used as needed.

The desired heat-sensitive recording material can be obtained by applying this coating liquid to paper or film.

[0054] The amount of the organic phosphate, its metal salt or its basic salt used in the present invention varies depending on the required performance and recording suitability, as well as the type and amount of other additives used in combination. Although not particularly limited, it is usually 0.1 to 10% per part of color-forming dye.
use the section.

[0055]

EXAMPLES The present invention will be explained in more detail with reference to Examples below. However, the present invention is not limited by the following examples.

Example 1 20 g of 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluorane and 100 g of a 10% polyvinyl alcohol aqueous solution were thoroughly ground to prepare a dye dispersion (liquid A). ) was obtained.

Sample compound (see Table 1) 20g and 10%
100 g of a polyvinyl alcohol aqueous solution was sufficiently ground to obtain a color developer dispersion (liquid B).

20 g of 1,2-bis(3,4-dimethylphenyl)ethane and 100 g of a 10% polyvinyl alcohol aqueous solution were thoroughly ground to obtain a sensitizer dispersion (liquid C).

Liquids A, B, C and finely powdered silica were mixed in a weight ratio of 1:2:2:0.5 and sufficiently dispersed to obtain a coating liquid.

This coating liquid was applied to a thickness of 32 μm on a base paper of 50 g/m 2 and dried to obtain a heat-sensitive recording material.

Using the obtained thermal paper, a thermal printing device (T
H-PMD: manufactured by Okura Electric Co., Ltd.) with a pulse width of 0.
．． The color density of the recorded image printed at 7 msec was measured using a Macbeth densitometer (model RD-933, manufactured by Macbeth).

[0062] The colored thermal paper was also stored at 60°C for 5 hours under dry conditions and at 40°C and 90% relative humidity for 24 hours, and changes in density of the background and colored areas were measured. Storage stability was measured.

Furthermore, after stamping dioctyl phthalate on the colored area, the sample was stored at 60° C. for 4 hours under dry conditions, and the change in concentration was measured to evaluate plasticizer resistance.

As Comparative Example 1, heat-sensitive recording materials were obtained by using Similar Compound 1 of Chemical Formula 20, Similar Compound 2 of Chemical Formula 21, and Bisphenol-A instead of the sample compound of Example 1. These heat-sensitive recording materials were also measured in the same manner as in Example 1, and the results are shown in Table 1.

[0065]

[Table 1]

[0066]

[C20]

[0067]

[C21]

Example 2 20 g of 3-dibutylamino-7-(2-chlorophenyl)aminofluorane and 100 g of a 10% polyvinyl alcohol aqueous solution were sufficiently ground to obtain a dye dispersion (liquid A).

20 g of bisphenol A and 100 g of a 10% polyvinyl alcohol aqueous solution were sufficiently ground to obtain a color developer dispersion (liquid B).

20 g of stearamide was ground in a ball mill with 100 g of a 10% polyvinyl alcohol aqueous solution to obtain a sensitizer dispersion (liquid C).

20 g of the sample compound (Table 2) was ground in a ball mill together with 100 g of a 10% aqueous polybutyl alcohol solution to obtain a color developer dispersion (liquid D).

[0072] Mix A liquid, B liquid, C liquid, D liquid and finely powdered silica at a weight ratio of 1:2:2:0.4:0.5, and add 50 g of calcium carbonate to 200 g of the mixed liquid. and dispersed to obtain a coating liquid. Using this coating liquid, thermosensitive recording paper was prepared in the same manner as in Example 1, and the same tests were conducted.

As Comparative Example 2, heat-sensitive recording materials were obtained by using Comparative Compound 3 of Chemical Formula 22, Comparative Compound 4 of Compound 23, and Comparative Compound 5 of Compound 24 in place of the sample compound of Example 2. . These heat-sensitive recording materials were also measured in the same manner as in Example 2, and the results are shown in Table 2.

[0074]

[Table 2]

[0075]

[C22]

[0076]

[C23]

[0077]

[C24]

From the results in Tables 1 and 2, it can be seen that the heat-sensitive recording material using the specific organic phosphate, its metal salt, or its basic salt of the present invention not only has excellent color development sensitivity but also has excellent storage stability and plasticization resistance. It also has excellent drug properties.

On the other hand, even with organic phosphate compounds, conventional derivatives other than those of the present invention do not exhibit sufficient effects as color developers, and also have very little effect on improving storage stability. Certain organic phosphates of the invention,
It is clear that the effect of using the metal salt or basic salt is extremely specific.

[0080]

[Effects of the Invention] The heat-sensitive recording material of the present invention not only has excellent color development sensitivity, but also has no color unevenness or color fading, and does not fade even if it comes into contact with plasticizers or oils.

Claims (1)

[Claims] Claim 1: A color-forming substance that is usually colorless or light-colored;
In a heat-sensitive recording material provided with a color-forming layer containing a color developer that causes the color-forming substance to develop color when heated, the color developer is an organic phosphate represented by the following general formula 1, a metal salt thereof, or a basic salt thereof. A heat-sensitive recording material characterized by containing salt. [Chemical formula 1]