JPS59178292A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance stability of a developed color image, by a method wherein a phenol having a specified melting point and a specified solubility in water is incorporated into a color forming layer, in a thermal recording material provided with a color forming layer comprising N,N'-diphenylthiourea. CONSTITUTION:At least one selected from the group consisting of monophenol, bisphenol and triphenol having a melting point of not lower than 90 deg.C and a solubility in water of not higher than 0.1g/100g is incorporated into the color forming layer comprising a known colorless or light-colored basic dye and N,N'- diphenylthiourea. An example of such phenol is 4,4'-butylidene-bis(3-methyl-6-t- butylphenol). Per 1pt. of the dye, N,N'-diphenylthiourea is used in a quantity of 1-5pts., the phenol is used in a quantity of 0.5-5pts., and in addition, other recording characteristic adjusting agent is used in a quantity of 1-5pts. and a pigment is used in a quantity of 1-40pts. Further, a binder is used in a quantity of 10-30wt% of the total weight of solids.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording medium, in particular, which improves the stability of striped colored images and uncolored areas against water, and prevents uncolored areas (background) from being exposed even when exposed to alcohol, ammonia gas, etc. A thermal recording material that does not fog and has improved fading of colored images (
(Regarding.

It has been known for a long time that colors are produced by reacting color-forming substances such as crystalline (iolet lactone) with acidic substances (S), and it is also known, for example, in the US patents, to thermally develop colors using these materials. No. 1353.9375. However, when the recorded colored image comes into contact with water, the image density decreases in a heat-sensitive recording material composed of a color-forming substance and a known acidic substance such as a phenolic substance or an organic acid. There were problems such as a significant decrease in color density, and a significant decrease in color density even if the uncolored area that had come in contact with water was heated again.Furthermore, there were problems such as alcohol, wet two-component diazocopy developer, and dry diazocopy developer. There was also the problem that uncolored areas would become foggy when exposed to the ammonia gas agent.

In recent years, thermal recording materials have been increasingly used as recording media, and when these thermal recording materials are used as tickets for station management systems or price tags at supermarkets, etc., the colored images may fade when exposed to water, or Serious problems have arisen such as lack of reliability, such as the coloring density being extremely low even if uncolored areas that have been touched by water are heated again, and uncolored areas that come in contact with alcohol such as sake, will become colored.

In addition, thermal paper has become popular as a recording medium for facsimile, and in offices and the like, another serious problem has arisen in that thermal paper develops color when overlaid with a diazo copy.

In order to solve the above problems, many methods have been proposed, such as providing a single barrier layer on the heat-sensitive layer or above and below the heat-sensitive layer, and adding various additives into the heat-sensitive layer, but these methods have not been sufficiently effective. However, it has the drawback of increasing manufacturing costs, and there is currently no satisfactory solution.

The inventors of the present invention previously conducted a patent on a heat-sensitive recording material containing a normally colorless to light-colored color-forming colorless dye and N,N'-diphenylthiourea.

This heat-sensitive recording material is capable of retaining a colored image in water for a long period of time (for example, 24 hours).
It has the great feature that the image density does not decrease at all even when exposed to water for a long period of time, and that the original color density is maintained even if uncolored areas that have been exposed to water for a long time are heated again. We also use alcohol and ammonia gaff, which is a developer for wet two-component diazocopy and a developer for dry diazocopy.
It also has the great feature of hardly coloring even when it comes into contact with ammonia water.

However, this thermosensitive recording material could not necessarily be said to have sufficient image stability (discoloration) when left for a long time in a normal room.

The purpose of the present invention is to provide a heat-sensitive recording medium using N,N'-diphenylthiourea without impairing the excellent features described above.
The purpose is to improve the stability of colored images.

As a result of intensive research, the present inventors have found that the purpose of the present invention is to incorporate specific phenols into the coloring layer containing N,N'-diphenylthiourea, which is truly more effective than 1tca.
I found out that it can be done.

In the present invention, the phenols used as antifading agents in combination with N,N'-diphenylthiourea are monophenols, bisphenols, and triphenols having a melting point of 90° C. or higher and a solubility in water of 0.19/1002 or lower. Phenols with a melting point of less than 90°C generally not only have unstable sublimation properties and other physical properties, but also reduce production efficiency because the dryer temperature is limited to less than 90°C in the drying process after coating. Therefore it is not suitable for use. Furthermore, the solubility in water is 0. Those with an I P/100 F or more have the disadvantage of being colored at the coating stage.

It has the above melting point and solubility in water, and N
, 4,4-butyrythene-bis(3-methyl-
6-t-butylphenol) (melting point 208°C, the same applies hereinafter), 2,2'-methylene-bis(4-methyl-6-t
-butylphenol) (1,20℃), 2,2'-methylenebis(4-ethyl-6-t-butylphenol)
(119°C), 2,5-di-t-butyl-hydroquinone (202°C), 2,5-di-t-amylhydroginone (172°C), bis(3-methyl-4-human 5-tert-butyl-benzyl) sulfide (115°C),
2,2'-methylene-bis(4-methyl-6-cyclohexyl-phenol) (118°C), bis-(3,3
'-bis-(4'-hydroxy-3-1-butylphenol)-ml] chestnut, coal ester (165°C)
, 4,4'-methylene-bis(2,6-di-t-butylphenol) (154°C), 4,4'-thiobis-(6
-t-butyl-0-cresol), 2,6-bis(27
-Hytrooxy-3-t-butyl-5-methylbenzyl)-4-methylphenol (171°C), 2,2'-iso-butyritene-bis=(4,6-di-methylphenol) (160°C), 4 , 4'-thiobis-(2-methyl-6-t-butylphenol) (127°C), bisC2
-('2-hydroxy-5-methfk-3-t-7'thyl-benzyl)~4-methyl-6-t-butyrunenyl]terephthalate) (2,40°C), 2-hydroxy-4
-Methoxy-4-chlorobencineenone ('312℃)
, 2-hydroxy-4-methoxy-2'-carboxybenzophenone (166°C), Tris (3,s-sheet t
-7'-1-4-hydroxy-phenyl) incyanate (221°C), Tris[β-(3°5-di-t-
7” thyl-4-hydroxyphenyl)propionyl-
Oxyethyl] incyane) (126°C), i, 3.
5) Limethyl-2,4゜6-tris(3,5-
di-t-butyl-4-hydroxy-benzyl)benzene (244°C), N,N'-hexamenalene bis(3,
5-di-t-butyl-4-hydroxy-hydrocinnamide) (156°C), 1,1.3-)lis(2-methyl-
4-hydroxy-5-t-butylphenyl)butane (1
85°C), 2,2-dihydroxy-3,3-di(α-methyl-cyclohexyl)-5,5′-dimethyl-diphenylmethane (130°C), and the like.

When these phenols are used in combination with N,N'-diphenylthiourea, they do not cause fogging on ammonia and alcohols.

Various dyes are well known as the normally colorless to light-colored basic colorless dye used in the present invention, and examples thereof include, but are not limited to, the following.

Crystal violet lactone (blue), 3-diethylamino-6-methyl-7-anilinofluorane (black), 3-(N-:r-fk-P-tolubuino)-6
-Methyl-7-anilinofluorane (black), 3-diethylamine-6-methyl-7-(ortho,/zo large methylanilino)fluoran (black), 3-pyrrolidino6-methyl-7-anilinoflu Oran (black), 3-
piperidino-6-methyl-7-anilinofluorane (
Black L3-(N-cyclohexyl-N-methylamine)
-6-methyl-7-anilinofluorane (black), 3-
Diethylamino-7-(ortho-chloroanilino)fluoran (black), 3-diethylamino-7-(meta-trifluoromethylanilino)fluoran (black), 3-
Diethylamine-6-methyl-chlorofluorane (red), 3-diethylamino-6-methyl-fluorane (red), 3-cyclohexylamino-6-chlorofluorane (orange), 3- (+N-inamyl-N-ethyl Amino)-6-methyl-7-anilinofluorane (black)
0 The color developer, basic colorless dye, and the phenol of the present invention are agitated using a ball mill, attritor, sand grinder, etc., or made into fine particles using a pulverizer, and usually a binder and other additives are added to prepare the coating liquid. be done.

Binders used in the present invention include, for example, polyvinyl alcohol, casein, starch and modified starch, carboxymethyl cellulose, hydroxyethyl cellulose,
Polyvinylpyrrolidone, styrene-maleic anhydride copolymers and their alkaline solutions, polyacrylamide, styrene-butadiene copolymers, polyvinyl acetate, latexes of polyacrylic esters, gelatin, shellac, etc. are available. Not limited.

The heat-sensitive recording material of the present invention may optionally contain other additives in the heat-sensitive layer, such as inorganic or organic pigments such as clay, calcium carbonate, aluminum hydroxide, talc, titanium oxide, and zinc oxide, waxes, fatty acid amides, etc. It is also possible to add recording property adjusting agents such as, various fatty acid metal salts to prevent sticking, water resistance agents to improve water resistance, phenolic resins, surfactants, etc.

The substrate used in the present invention is generally paper such as wood-free paper, medium-quality paper, or coated paper, but other materials such as galanic fiber sheets, plastic sheets, and film-laminated papers can also be used as substrates. I can do it.

The type of phenol used in the present invention, the amount of the phenol and N,N'-diphenylthiourea, and the amount of other various components are determined according to the required performance and recording suitability, and are not particularly limited, but usually 1 to 5 parts of N,N'-diphenylthiourea per 1 part of basic colorless dye;
Use 0.5 to 5 parts of phenols to prevent fading, 1 to 5 parts of a recording property modifier, and 1 to 40 parts of an inorganic or organic pigment, and the binder should preferably be in an amount of 0 to 30 parts by weight based on the total solid content. be.

The effects of the present invention will be explained in more detail below using Examples.

Example 1 a) Production of heat-sensitive recording material Liquids A and B having the following compositions were separately dispersed in a paint shaker (Toyo Seiki FF) f1011.

Solution A: 3-(N-inamyl-N-ethylamino)-6-methyl-7-anilite fluorane 51 Light calcium carbonate 232 Stearamide 5? zinc stearate
57 points IJ vinyl alcohol 12 liquid 352 water
52? Liquid B: N-diphenylthiourea 15-aluminum hydroxide 1524.4-butylidene-bis(3-methyl-6-t-butylphenol)
52 Zinc stearate 3gorivinyl alcohol 12% solution 35r water
52 f Next, add 1257 parts of A liquid, 125 parts of B liquid and 1 part of polyvinyl alcohol.
Add 2% solution 502 and 4Qr of water, mix, stir and adjust to make a coating liquid, then apply this coating liquid to 502/rr? A heat-sensitive recording material was obtained by coating and drying the coating on the surface of high-quality paper using a Meyer bar so that the coating amount after drying was 82 mm.

The following quality evaluation tests were conducted on the obtained thermosensitive recording material.

b) Characteristic Test (2) Decrease in Colored Image Density After Water Immersion (Water Immersion Discoloration) A 140° C. hot plate was brought into contact with the thermosensitive recording material for 5 seconds at a pressure of 2 kg/ca to obtain a colored image. Next, this colored image was soaked in water and left for J days. Thereafter, the optical densities of the colored portions before and after the test were measured using a Macbeth reflection densitometer (RI) Model 514 (using a visual filter), and the results shown in the table were obtained.

(2) Recoloration of uncolored areas after immersion in water (water immersion recoloring ability) The uncolored heat-sensitive recording material was immersed in water and left for one day.

Thereafter, the heat-sensitive recording material was taken out, air-dried, and brought into contact with a 140° C. hot plate at a pressure of 2 ky/crtl for 5 seconds to obtain a colored image. The optical density of the colored portion after the test was measured using a Machess reflection densitometer model RJ)-514 (using a visual filter), and the results shown in the table were obtained.

In the test of ■■, it can be said that the higher the optical density after the test, the better the characteristics.

■ Background fogging test using various chemicals Methyl alcohol, wet two-component diazocopy developer (
Copy developer SD manufactured by Ricoh Co., Ltd.) and aqueous ammonia (28% solution), which is a developer for dry diazo copying, are added to gauze, and after touching the thermal paper, the color density of the contact area is measured using a Macbeth reflection densitometer RD-514. The results are shown in the table below.

In this test, it can be said that the lower the optical density, the better the characteristics. (2) Color fading test A hot plate at 140° C. was brought into contact with the thermosensitive recording material for 5 seconds at a pressure of 2 kqAa to obtain a colored image. Next, this colored image was heated at 20°C.
After 10 days in a room with an illuminance of 500 lux, the 65th team measured the concentration again and obtained the results shown in the table.

In this test, it can be said that the higher the concentration, the better the characteristics.

Example 2 The basic colorless dye in Solution A in Example 1 was replaced with 3-(N-ynamyl-N-ethylamino)-6-methyl-7-anilitufluorane, and 3-(N-cyclo-xyl-
The test was conducted in exactly the same manner as in Example 1, except that N-methylamine)-6-methyl-7-anilite fluorane was used.

The results are shown in the table.

Examples 3 to 6 In Example 3, 1° L3-1 lith (2- Methyl-4-hydroxy-5-t-butylphenyl)butane, -cyclohexyl) in Example 4, -5,5-dimethyl-diphenylmethane, 2,2-methylene- in Example 5
bis(4-methyl-6-t-butylphenol), 2,2-methylene-bis(4-ethyl-6-t-butylphenol) in Example 6
The test was conducted in the same manner as in Example 1, except that the sample was changed to (-butylphenol). The results are shown in the table.

Comparative Example] The test was carried out in the same manner as in Example 1, except that water was used instead of 4,4-butylidene-bis (3-methyl-6-butylphenol), which is the phenol in liquid B in Example 1. went. The results are shown in the table.

Reference Example 1 A test was conducted in exactly the same manner as in Example 1, except that bisphenol A was used instead of N,N'-diphenylthiourea, the color developer in Solution B in Example 1.

The results are shown in the table.

As is clear from the table, the heat-sensitive recording materials according to the embodiments of the present invention containing phenols have no loss in water immersion discoloration, water immersion recoloring ability, and background fogging properties due to various chemicals compared to the comparative example [K] which does not contain phenols. It was possible to significantly improve the fading resistance without causing any problems.

Patent Applicant Honshu Seikai Co., Ltd. Procedural Amendment Document 1982 Monthly! 3rd Japan Patent Office Commissioner Kazuo Wakasugi 2, Name of the invention Thermosensitive recording medium 3, Relationship with the case of the person making the amendment Patent applicant 4, Date of the amendment order 6, Internal medicine of the amendment (1) Specification, page 5, line 20 r(118℃), ] to r(
161℃),” is corrected.

(2) r4 on page 6, lines 4-5. , i'-thiobis-(
6-t-butyl-O-cresol)," is deleted.

(3) “4.4′-thiobis=(
2-methyl-6-t-butylphenol) (127℃
), ” to be deleted.

528-

Claims (1)

[Claims] A thermosensitive material with a coloring layer containing a basic colorless dye and N,N'-diphenylthiourea has a melting point of 9 at °C.
Above 0°C, solubility in water is O, 19/. 100f[T] A heat-sensitive self-report material containing one or more selected from monophenols, bisphenols, and triphenols.