JPS59165681A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material free from discoloration of a recorded image, blushing or the like and high in heat response characteristic, by a method wherein a combination of a specified p-hydroxybenzoic acid ester and a specified naphthol dervative is incorporated in a thermal color forming layer as a color developer together with a leuco dye. CONSTITUTION:In a thermal recording material provided on a base with a thermal color forming layer comprising a leuco dye, e.g., 3-cyclohexylamino-6- methyl-7-anilinofluoran, and a color developer as main constituents, a combination of a p-hydroxybenzoic acid ester of formula I , wherein R1 is H or 1-3C alkyl, and a naphthol derivative of formula II or III, wherein R2 is 10-21C alkyl or formula IV (wherein X is halogen; R3 is 1-3C alkyl or alkoxy; each of n and m is 0-3), e.g., a compound of formula V, in a ratio of preferably 2:1-5:1 is used as the color developer.

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 particularly, it is a method of producing a color by combining a usually colorless or slightly pale leuco compound and a color developer which is released by reacting with the leuco compound under heat. 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 coated 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 the diversification and increase of information, resource conservation, and non-pollution. (1) A colored image is recorded simply by heating, eliminating the need for a complicated developing process. (2) It can be manufactured using relatively simple and compact equipment, and the resulting recording material is easy to handle. (3) Paper is often used for special holidays, and in this case, not only is the support cost low, but the feel of the resulting memory material is similar to that of regular paper. Because of these advantages, it is widely used in the field of computer output, printers such as calculators, recorders for medical measurement, low and high speed facsimile fields, automatic ticket vending machines, thermal copying fields, etc.

The above-mentioned heat-sensitive recording material is produced by coating and drying a heat-sensitive coloring layer solution containing a coloring component that can cause a coloring reaction when heated, on a support such as ordinary paper, synthetic paper, or synthetic fat 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 material disclosed in Japanese Patent Publication No. 43-4160, but such conventional heat-sensitive recording materials have low thermal responsiveness and are difficult to use during high-speed recording. Sufficient color density could not be obtained.

As a method to improve such drawbacks, for example, Japanese Patent Application Laid-open No. 49
JP-A-34842 describes nitrogen-containing compounds such as acetamide, stearamide, m-nitroaniline, and dinitrile phthalate; JP-A-52-10674.6 describes acetoacetanilide; JP-A-53-11036 describes The publication describes the use of N,N-diphenylamine derivatives, benzamide derivatives, or carbazole derivatives in JP-A-53-39.
Publication No. 139 contains alkylated biphenyls and biphenylalkanes, and Publication No. 144193/1983 contains p
- A method of increasing sensitivity by incorporating a hydroxybenzoic acid ester derivative into a heat-sensitive coloring layer has been disclosed, and among them, a method using a p-hydroxybenzoic acid ester derivative as a color developer is the most effective method. be.

However, these color developers have the disadvantage that the recorded image naturally fades or becomes white (white powder is produced on the surface of the image area).

〔the purpose〕

An object of the present invention is to provide a heat-sensitive recording material that has improved the above-mentioned drawbacks, that is, a heat-sensitive recording material that exhibits less fading, whitening, etc. of recorded images and has poor thermal responsiveness.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer as main components is provided on a support,
As the color developer, p-hydroxybenzoic acid ester represented by the following general formula (I) and the following general formula (n) or @)
There is provided a heat-sensitive recording material characterized in that it uses a combination of naphthol derivatives represented by:

(In the formula, R□ represents hydrogen or an alkyl group having 1 to 3 carbon atoms.) (In the formula, R2 is an alkyl group having 10 to 21 carbon atoms. m is O to 3
(represents an integer of ) p represented by the general formula (1), which is one component of the color developer used in the present invention.
-Hydroxybenzoic acid ester has a melting point of 100-15
0"C and has high color developing ability, it has higher thermal responsiveness than conventional color developing substances such as 4.4'-isopropylidenediphenol and 4.4'-butylidenediphenol, and Provides a colored image with excellent uniformity.Also, the general formula (1
The color developer of the naphthol derivative of general formula (It) or @) used in combination with the color developer of ) has a melting point of 80
At ~250°C, the color developing ability is low when used alone, but when used in combination with the component of formula (I), it becomes eutectic and fades to prevent recrystallization of the component of formula (I) in the image area. It is thought that the phenomenon of whitening can be prevented.

Examples of the p-hydroxybenzoic acid ester represented by the general formula (1) include the following.

Further, naphthol induction represented by the formula Cn) [■] can be exemplified, but the present invention is not limited thereto.

In the present invention, the color developer consisting of the above-mentioned combination is generally 1 to 10 parts by weight, preferably 1 part by weight, per 1 part by weight of the leuco dye described below.
It is used in a range of 2 to 6 parts by weight. Also, general formula [
The weight ratio of the color developing substance of [I] and the color developing substance of [■] or CI [1E type] is preferably 1:1 to 1O:1, preferably 2:1 to 5:1. Good range. Further, if necessary, p-hydroxybenzoic acid of formula (I) and (n)
Alternatively, each of the naphthol derivatives of the formula @) may be used alone or as a mixture of more than one. Furthermore, if necessary, a conventionally used 7-enol acidic substance can be added.

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:
Any dye that has been applied to this type of heat-sensitive material may be used, and for example, leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3,3-his(p-dimethylaminophenyl)-6-
Dimethylaminophthalide (also known as crystal violet lactone, 3.3-bis(p-dimethylaminophenyl)-6-dibutylaminophenyl, 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-chlorofluoran, 3-diethylamino- 7-Methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-10-fluorane, 3-(N-p-)lyl-N-ethylamino]-6-methyl- 7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-)!jchloromethylphenyl)
amine)-6-dinithylaminofluorane, 2-(3,
6-bis(diethylamino)-9-(O-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(0-chloroanilino) ) fluoran, 3-dibutylamino-7-(0-chloroanilino)fluoran, 3-N-methyl-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, pensoylleucomethylene 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'-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-morpholino-7-(N-propyl- trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilinofluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, /-7-(C-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-)luidino)-7- (α-phenylethylamino)fluoran, 3-diethylamine-
7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-( N-methyltoluidino)-7-(p
-n-butylanilino)fluoran, 3-(N-benzyl-cyclohexylamino)-5,6-penzo 7-α
-Naphthylamino-47-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc. These can be used alone or in combination of two or more vertebrae.

In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyl, etc. Cellulose-derived L such as ethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, etc. Sodium polyacrylate, polyvinylpyrrolidone, Acrylic acid amide/acrylic acid ester copolymer, Acrylic acid amide/Acrylic acid ester/Methacrylic acid ternary copolymer, Styrene/maleic anhydride copolymer alkali salt, inbutylene/maleic anhydride copolymer alkali salt In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, and styrene/butadiene Polymers, polyacrylic acids, polyacrylic esters, vinyl chloride/vinyl acetate copolymers, polybutyl methacrylate, ethylene/vinyl acetate copolymers, styrene/butadiene/acrylic copolymers, and other latexes can be used.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, thermofusible substances ( or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium carbonate and silica. Others, urea-
Organic fine powders such as formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned, and examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts, as well as various Waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, other thermofusible organic compounds, etc. Examples include those having a melting point of about 50 to 200°C.

The heat-sensitive recording material of the present invention can be produced by, for example, applying a coating liquid for forming a heat-sensitive layer containing the above-mentioned components onto an appropriate support such as paper, synthetic paper, or plastic film, and drying it. It is used in the field of recording, especially as a heat-sensitive recording material for high-speed recording that requires high image stability.

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 has 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 heat-sensitive recording material in which a leuco dye is supported as a transfer layer. It can be used as a thermal transfer type heat-sensitive recording material consisting of a transfer sheet supported on a body and a receptor sheet supported on a support using a color developer as a receptor layer.

In the case of thermal transfer type thermal recording materials, the transfer sheet is
A desired colored image can be formed on the receiving layer surface of the receiving sheet by overlapping the receiving sheets so that the receiving layer is in contact with the transfer layer of the transfer sheet and thermally printing from the front or back surface of the polymerized sheet.

〔effect〕

According to the present invention, in other words, as a color developer, the general formula (1
) By using a combination of p-hydroxybenzoic acid ester represented by the formula (n) or the naphthol derivative represented by the general formula (@), it is possible to obtain a heat-sensitive recording material exhibiting the excellent properties listed below.

(1) High thermal responsiveness (high sensitivity).

(21) There is very little fading or whitening of recorded images.

〔Example〕

The present invention will be explained in detail below using Examples and Comparative Examples.

Examples 1 to 5 The following compositions were ground in a magnetic ball mill for one day [A].
A CH3 solution was prepared.

[A] Solution 10 Polyvinyl alcohol aqueous solution 300
/1 water
400 p (BE solution p-benzyl hydroxybenzoate 150 parts by weight Calcium carbonate 1oo 10% aqueous hollyvinyl alcohol solution 200 tt water
500 [C:], CDI in the same manner except that the naphthol derivative of the following formula was used in place of the naphthol derivative in the CB) solution.
, [E) and CFE solution were prepared.

Next, add liquids [A] to [F] to [A] and [B], respectively.
, [A] and [C:] , CADI and CDI , (A]
In combination with [E] and [A] and [F], CA:
]:[:B:] = CA]IC]=[A:]:[:D
]= CA:]:[:E) = CA):(F:] =
A heat-sensitive coloring layer solution was prepared by mixing and stirring at a weight ratio of 1:8, and the mixture was coated with a wire spar and dried on 527 fake commercially available high-quality paper so that the dry coating amount was about 51.

This was calendered to have a Bekk smoothness of 700 to 1200 seconds to produce a heat-sensitive recording sheet of the present invention (Examples 1, 2, 3, 4., and 5, respectively).

Comparative Examples 1, 2.3 In addition, as a comparative example, benzyl p-hydroxybenzoate (Comparative Example 1) and 2,2'-methylenebis(3-methyl -6-
Comparative heat-sensitive recording sheets were produced in the same manner except that t-butylphenol (Comparative Example 1) was used (Comparative Examples 1 and 2, respectively).

In addition, the following composition was dispersed in a magnetic ball mill for one day,
[G] Solution was prepared.

[G] Liquid bisphenol Al 50 Parts by weight Stearic acid amide 75 Calcium carbonate 100 10 Polyvinyl alcohol aqueous solution 200 Water
475 Next (A):
[G) = 1°8 (weight ratio) to prepare a thermosensitive coloring layer solution, and then a comparative thermosensitive recording sheet (Comparative Example 3) was produced in the same manner as in the example.

Next, tests for dynamic color density and fading and whitening of recorded images were conducted on these heat-sensitive recording sheets as follows.

(1) Dynamic coloring sensitivity: Using a thermal printing experimental device with a thin film head made of under-desk electronic components, the head power was 0.45 W/dot, the recording time per line was 20 m5/L, and the scanning line density was 8.
X 3.85 dots) Under the condition of 7mm, pulse width is 1.0
, 1.2 , 1.4 , 1.6 , 1.8°2.0
It prints at m sec, and the print density is Macbeth Densitometer R.
Measured with D-514 (filter W-106).

(2) Image fading resistance...For the samples whose dynamic coloring sensitivity was measured in (1), those with print density of 1.0 to 1.2 were left at room temperature for 15 days. The density was measured and this was designated as D), and the density reduction rate was determined according to the following formula.

(3) Image whitening: The same test as in (2) was conducted, and the results were visually determined as shown below.

○ Almost no white powder generation △ White powder is generated, but it is not a practical problem death × Impractical due to large amount of white powder generation The test results are shown in Table-1.

As can be seen from Table 1, the thermal recording sheet of the present invention has higher dynamic coloring sensitivity than the conventional one using bisphenol A/stearamide system (Comparative Example 3), and Comparative Example 1 in which no naphthol derivative is used in combination. .Fade of image compared to 2,
It was confirmed that the whitening was improved.

Patent applicant: Ricoh Co., Ltd. Agent Patent Attorney Toshiaki Ikeura (23) 435-

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, p-hydroxybenzoic acid represented by the following general formula (1) is used as the color developer. A heat-sensitive recording material characterized by using a combination of an ester and a naphthol derivative represented by the following general formula (II) or @). (In the formula, R1 represents hydrogen or an alkyl group having 1 to 3 carbon atoms.) (In the formula, R2 is an alkyl group having 10 to 21 carbon atoms, an alkyl group having 1 to 3 prime numbers, or an alkoxy group, and n and m are O ~
represents the integer of 3)]