JPS5942998A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To provide a heat sensitive recording material excellent in heat responsiveness, imparting a high density sharp image even in high speed and high density recording and excellent in color developability and image stability in high speed recording, characterized in that specific phenolic substance is used as a color coupler. CONSTITUTION:Phenolic compound shown by the formula (wherein X is a lower alkyl or halogen and n is 0-3) (e.g., benzyl m-hydroxybenzoate) is used as a color coupler and contained along with a leuco dye [e.g., 3-(N-cyclohexyl-N- methylamino)-6-methyl-7-anilinofluorane] to obtain an objective heat sensitive recording material. EFFECT:Troubles such as scum adhesion or sticking to a thermal head are not generated and recording characteristics are excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that has excellent color development and image stability during high-speed recording.

In general, heat-sensitive recording sheets are formed by providing a heat-sensitive color-forming layer containing a color-forming colorless dye and a color developer such as a phenolic substance on a support such as paper or film, and instantaneously forming the film by heating with a thermal head or the like. Color recording is obtained through a chemical reaction.

Compared to other recording materials, this heat-sensitive recording sheet can produce records in a relatively short time without undergoing complicated processes such as phenomenon and fixing, does not generate noise, and is relatively inexpensive. Due to certain advantages, it is widely used not only for copying books, documents, etc., but also as a recording material for various information and measuring instruments such as electronic computers, facsimiles, telex machines, and medical measuring instruments.

However, in recent years, with the development of society, there has been a strong demand for faster recording, and therefore there is a strong desire for faster recording apparatuses themselves and for the development of recording systems that can meet this demand.

Conventionally, such heat-sensitive recording channels for high-speed recording are disclosed in Japanese Patent Application Laid-open No. 53-39139 and Japanese Patent Application Laid-open No. 53-26139.
No. 1, JP-A-53-5636, JP-A-53-1
As disclosed in Japanese Patent No. 1036, etc., low melting point heat-melting substances such as various waxes, fatty acid amylomono-alkylated biphenyls, substituted biphenyl alkalis, coumarin compounds, and diphenylamines are used as sensitizers or melting point depressants. Additions to thermosensitive coloring layers have been proposed.

In this method of adding a sensitizer, it is necessary to melt the sensitizer immediately before the color reaction occurs, so in high-speed recording, sufficient thermal response to minute amounts of heat cannot be obtained in a short period of time. In addition, because the fusible substances in the color forming layer melt, problems such as adhesion of residue on the thermal head, smearing, trailing, and ghosting are likely to occur. Even under storage conditions, background coloration (capri) occurred over time, and the contrast of recorded images often deteriorated.

Therefore, it is desirable to have a heat-sensitive recording sheet for high-speed recording without the addition of such an increaser or melting point depressant.
Color-forming colorless dyes with structures such as lactones, lactams, and spiropyrans used in heat-sensitive recording sheets usually have a high melting point of 160 to 240°C, so they are suitable for high-speed recording without adding sensitizers or melting point depressants. In order to obtain heat-sensitive recording sheets, phenolic substances have been used as color developers, which have a low melting point and have a high ability to color colorless dyes.

Regarding color developers for phenols, Japanese Patent Publication No. 45-140
A large number of substances have been described in various documents including Publication No.
6 to 158°C) is frequently used from the viewpoint of quality stability, price, and ease of acquisition.

However, this bisphenol A has the drawback of a high thermal coloring temperature.

In contrast, phenolic substances with low melting points, such as 4-
Tertiary-butylphenol (melting point 94-99°C),
When monophenols such as α-naphthol (melting point 95-96°C) and β-naphthol (melting point 119-122°C) are used, the storage stability and stability of the heat-sensitive recording sheet are poor, and the background color gradually changes even at room temperature. Not only does it develop color, but it also has a strong so-called phenol odor, making it impractical.

Further, in Japanese Patent Publication No. 54-12819, 2,2-bis(4''-Hyl'roquinphenyl) normal hexa/(melting point 99-103°C) is disclosed in Japanese Patent Publication No. 55-27253 fi 1,1-bis It is described that (4'-Poxyphenyl) alkanes (alkanes have 3 to 13 carbon atoms) can be used to produce heat-sensitive recording sheets with low melting points and good stability and color development. is difficult to synthesize and has problems in availability.

Furthermore, JP-A-56-144193 describes that lower alkyl esters or benzyl esters of p-hydroxybenzoic acid are easy to synthesize and can produce highly sensitive heat-sensitive recording sheets. This method has the disadvantage that the coloring part undergoes rapid natural discoloration, and crystals of the phenolic substance precipitate in the coloring part (so-called white powder phenomenon).

As mentioned above, among the color developers that can be used practically and industrially, there are currently few that have been found that produce clear and high-density colored images during high-speed recording, and that produce stable colored images. be.

The inventors of the present invention have conducted various studies to improve these many drawbacks, and as a result, by using a phenolic substance represented by the following formula (+) as a color developer, they have achieved extremely excellent practical results. It has been discovered that a heat-sensitive recording sheet for high-speed recording can be obtained which has the following characteristics, and the present invention has been completed.

That is, according to the present invention, a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and its color developer is characterized in that a phenolic substance represented by the general formula is used as the color developer. A thermosensitive recording material is provided.

In the general formula (1), X represents a lower alkyl group and/or a halogen atom, I is 0 to 3, and when a plurality of substituents X are bonded to benzene, the substituents X are the same or May be different. The lower alkyl group is usually preferably one having 1 to 4 carbon atoms, and the halogen atom includes chlorine, fluorine and the like.

In the heat-sensitive recording material of the present invention, the leuco dye and the color developer may be supported on the same support, or may be supported on separate supports.

When the leuco dye and the color developer are supported on separate supports, the supports are placed one on top of the other so that the leuco dye side and the color developer side are in contact with each other, and a thermal coloring reaction is caused. After the color reaction, by separating each,
A colored image can be obtained.

According to the present invention, a heat-sensitive recording material exhibiting the excellent properties listed below can be obtained by using the phenolic substance of the general formula (+).

(1) Highly sensitive heat-sensitive recording sheets can be produced without the need for sensitizers or melting point depressants. In particular, because it has excellent thermal responsiveness, high-density, clear images can be obtained even in high-speed, high-density recording.

(2) There are no problems such as adhesion of debris or sticking to the thermal head, and the recording aptitude is excellent.

(3) By coating thin base paper or film, it is possible to obtain excellent copying paper for infrared ray and Strozefratsunyu type thermal copying machines.

(4) It is possible to reduce the amount of coating and improve production efficiency.

(5) It is easy to synthesize, can be obtained in high yield and purity, and can be produced at relatively low cost.

Next, the leuco dyes used in the present invention include triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes, which are generally known as colorless to light-colored colorless dyes, and are not particularly limited. For example, crystal violet lactone 3-diethylamino-6-methyl-7-anilinofluoran 3-(N-ethyl-1)-)luidino)-6-methyl-
7-anilinofluorane 3-diethylamino-6-methyl-7-(ortho,)ξ
large methylanilino) fluorane 3-pyrrolidino-6
-Methyl-7-anilinofluorane 3-piperidino-6-methyl-7-anilino1 fluorane 3-(N-chlorohequine-N-7+thylamino)-6
-Methyl-7-anilinofluoran 3-diethylamine-7-(orthochloroanilino)fluoran 3-,)ethylamino-7-(meta-trifluoromethylanilino)fluoran 3-diethylamino-6-methyl-7 -Chlorofluoran 3-diethylamino-6-methylfluoran 3-cyclohexylamino-6-chloro o77t, Oran Kasa.

Further, the compound of formula (1) used in the present invention is preferably used in an amount of 1 to 6 times the amount of the leuco dye.

Specific examples of the phenolic substance represented by the general formula (1) include those shown below.

0 Cl-13 HO 113 In the heat-sensitive recording material of the present invention, various commonly used binders may be used as appropriate for bonding and supporting on a support, such as polyvinyl alcohol, methoxy cellulose, hydrogel, etc. Water-soluble materials such as ethyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolide, polyacrylamide, polyacrylic acid, starch, gelatin, etc., or polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl meccrylate, etc. Aqueous emulsions can be used as binders.

Furthermore, in the heat-sensitive recording material of the present invention, if necessary,
Further, conventional auxiliary additives such as fine powders of calcium carbonate, phosphoric acid, alumina, magnesia, talc, titania, sulfuric acid, aluminum stearate, etc. can be added to improve the clarity of the colored image.

The heat-sensitive recording material of the present invention is produced 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 used in various fields, especially as a heat-sensitive recording material for high-speed recording.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A mixture consisting of the following compositions was separately pulverized and dispersed for two days using a magnetic Zeel mill to obtain [A] solution, CB) solution,
[0′) solution was prepared.

(A) Liquid 3-(N-cyclohequine-N-methylamine)-6-
Methyl-7-anilino 20 parts by weight Fluorane 10% hydroxyethyl cellulose aqueous solution 20' Water 60
〃CB) Liquid 10% Hydroxy7ethyl Cellulose Aqueous Solution 201F Water
60
・(C) Liquid calcium carbonate 20 parts by weight 5% methylcellulose aqueous solution 20 Using the solutions [A) to (0) obtained as above, a heat-sensitive coloring layer solution having the following composition was prepared, and the standard basis weight was 50 f. //m'' commercially available high-quality paper with a dry coating amount of 4 to 17 m2, select Wire No. The heat-sensitive recording sheet of the present invention is calendered so that
I made (a).

Thermosensitive coloring layer liquid [A] liquid 10 parts by weight [B] liquid 30 # [CD liquid 30] Example 2 Same as Example 1 except that the following CDE liquid was used in place of liquid [B] in Example. A thermosensitive recording sheet (b) was prepared.

[D] Liquid 10% hydroxyethyl cellulose aqueous solution 2
0 Water
60 Example 3 Thermal recording sheet (c) was prepared in the same manner as in Example 1 except that the following [one] solution was used instead of the CH3 solution in Example 60
I made it.

[E] Solution 10 Aqueous solution of ethyl cellulose 2
0# water
60 [Comparative Example 1] A thermosensitive recording sheet (
d) was made.

CF) Liquid bisphenol A 20 parts by weight 10
Thihydroxyethylcellulose aqueous solution 20
〃water
60 [Comparative Example 2] A thermosensitive recording sheet (C
)made.

[G] Liquid p-hydroxybenzoic acid benzyl ester 2
0 parts by weight 10% hydroxyethyl cellulose aqueous solution 20
tr water
6°.

Thermal recording sheets (a) to (e) obtained as above
) WoG I [High-speed printing with facsimile machine (manufactured by Ricoh) (printing speed: 0.94m5ec, applied voltage: 16V
.

18V, 20V)L, its color density is Macbeth RD -
Measured at 514. The results are shown in Table-1.

Table 1 As is clear from Table 1, the heat-sensitive recording sheet of the present invention has excellent color development during high-speed recording, produces less white powder,
It can be seen that it is extremely useful as a heat-sensitive recording sheet.

Patent applicant Ricoh Co., Ltd. Agent Patent Attorney Toshiaki Ikeura 45

Claims (1)

[Claims] (1) Color-forming reaction between leuco dye and its color developer In the heat-sensitive recording material used for tea cutting, as the color developer, the general formula (wherein X represents a lower alkyl group and/or a halogen atom) is used. , n is 0 to 3, and when multiple substituents X are bonded to the benzene nucleus, these substituents X may be the same or different). Heat-sensitive recording material.