JPH0270480A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain excellent thermal response, preservation stability and to prevent skin fog by incorporating one or more of compounds selected from fluorene derivatives having specific temperature of melting point in a thermal coloring layer. CONSTITUTION:One or more of compounds selected from fluorene derivatives are added into a thermal coloring layer which contains leuco dye and organic acidic substance. The derivatives include melting point lower than those of both or one of the leuco dye and the organic acidic substance, and solubility in the leuco dye and/or the organic acidic substance to dissolve one or both of them to perform the operation of accelerating the reaction of both, i.e., as a coloring accelerator. Thus, it is necessary that its melting point ranges at 50-200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent heat sensitivity and storage stability.

[Industrial Application Fields] In recent years, with the diversification of information, the number of information sites has increased, and in the field of information recording to record this information,
Various recording methods and recording materials have been researched and put into practical use. Among them, the thermal recording method is: 1. A recorded image can be obtained by simply heating the thermal recording material, and no complicated development process is required. 2. The manufacturing and storage management of the thermal recording material is similar to that of other recording materials. It is easier and cheaper than
In many cases, inexpensive paper is used as a support for heat-sensitive recording materials, but this has the advantage that the resulting recording material has a feel similar to that of plain paper. It is used in many fields such as output, stomach printers, recorders for various measuring instruments, facsimile machines, automatic ticket issuing machines, and thermal copying machines.

Heat-sensitive recording materials used for these purposes have conventionally contained leuco dyes that are colorless or light-colored at room temperature and organic acidic substances such as phenolic compounds that react with the leuco dyes to develop color when heated. It is known that a heat-sensitive coloring layer is provided on a support such as paper, synthetic paper, synthetic resin film, etc.
0 and Special Publication No. 45-14,039). However, these conventional heat-sensitive recording materials have a problem in that their thermal responsiveness is insufficient and sufficient color density cannot be obtained when used for high-speed recording. In the field of information recording as well, the time required to heat the thermal head is shortened, and sufficient density can be produced with a low voltage, thereby increasing the recording speed and making it compatible with high-speed recording. This is requested.

Therefore, in an attempt to solve these problems with conventional heat-sensitive recording materials, it has been proposed to add a thermofusible substance to the heat-sensitive coloring layer to improve thermal responsiveness. (Japanese Unexamined Patent Publications No. 51-27.599 and 48-49.231). However, even with this technology, as the demand for high-speed recording has become even higher in recent years, satisfactory results regarding the thermal response have not yet been obtained. If the sensitivity of a heat-sensitive recording material is increased, for example, when used for facsimile, etc., there is a problem that so-called background fogging (self-coloring due to heat during storage) is likely to occur.

[Problems to be Solved by the Invention] The present invention was devised in view of the above points, and its purpose is to have excellent thermal responsiveness, and at the same time, to reduce storage stability and prevent skin fogging. It is necessary to provide a heat-sensitive recording material that is unlikely to cause this.

[Means for Solving the Problems] That is, the present invention provides a heat-sensitive coloring layer containing a leuco dye that is colorless or light-colored at room temperature and an organic acidic substance that reacts with the leuco dye and develops a color when heated, on a support. In the heat-sensitive recording material, the heat-sensitive coloring layer contains one or more compounds selected from fluorene derivatives having a melting point of 50 to 200°C.

In the present invention, the leuco dye used as a coloring agent is colorless or light-colored at room temperature, and is a substance that develops color by reacting with an acidic substance under heating. Triallylmethane dyes such as 6-dimethylaminophthalide, diphenylmethane dyes such as 4,4'-bisdimethylaminobenzhydride pencyl ether, thiazine dyes such as benzoylleucomethylene blue, and 3-dimethylaminobenzhydride pencyl ether. Examples include spiro-based dyes such as methylspirodinaphthopyran, and other dyes such as fluoran-based, leuco-olamine-based, indoline-based, and indigo-based dyes.

The organic acidic substance used together with the leuco dye is a substance that becomes a color developer when it comes into contact with the leuco dye when heated, and includes various phenolic compounds and organic acids. Organic acidic substances used for this purpose include:
Preferably, it is solid at room temperature and liquefies or vaporizes at 50° C. or higher.

Specific examples of such substances include phthalic anhydride, gallic acid, salicylic acid, 4,4'-isopropylidene (2-chlorophenol), 4,4'-isopropylidene (2-1-butylphenol), 4,4'-isopropylidene (2-1-butylphenol), .4'-5e
c-Butylidenephenol, 4,4°-(1-methyl-
〇-hexylidene) diphenol, 4-phenylphenol-4-hydroxydiphenoxide methyl-4-hydroxybenzoate, 4-hydroxyacetophenone salicylic acid anilide, 4,4-cyclohexylidene diphenol, 4,4゛-cyclohexylidene his (2-methylphenol), 4,4°-benzylidenephenol,
Examples include 4,4°-thiobis(6-1-butyl-3-methylphenol), novolac type phenol resin, halogenated novolac type resin, α-naphthol, β-naphthol and the like.

One or more compounds selected from fluorene derivatives having a melting point of 50 to 200° C. are added to the thermosensitive coloring layer containing the leuco dye and organic acidic substance. This fluorene derivative has a melting point lower than both the leuco dye and/or the organic acidic substance, has solubility in the leuco dye and/or the organic acidic substance, and dissolves one or both of them. In order to exhibit the function of promoting the reaction between the two, that is, the function of a color development accelerator, it is necessary that the melting point is within the range of 50 to 200'C.

Such fluorene derivatives are preferably represented by the following general formula. Examples of the substituent R include an alkyl group, an alkoxy group, a substituted alkyl group, an unsaturated or cycloalkyl group, an aryl group, an aryloxy group, an acyl group, a substituted acyl group, an aralkyl group, and the like.

As a specific example of a fluorene derivative having such a substituent R, for example, 2-benzylfluorene (mp: 1
06°C), 3-benzylfluorene (mp: 103°C)
), 4-benzylfluorene (mp: 77°C), 1-
Benzoylfluorene (mp: 91°C), 3-benzoylfluorene (mp: 124°C), 4-benzoylfluorene (mp: 83°C), 3-(2-methylbenzyl>fluorene (mp: 85°C), 3- (3-
methylbenzyl) fluorene (mo: 67°C), 3
-(4-methylbenzyl)fluorene (ml): 120
°C), 3-(4-phenylbenzyl)fluorene (m
p: 167°C), 3-(2-methoxybenzyl)fluorene (mp: 73°C), 3-(3-methoxybenzyl)fluorene (mp: 118°C), 3-(4°-
methoxybenzyl) fluorene (+np: 117℃)
, 3-(α-methylbenzyl)fluorene (mp:
83℃), 3-phenethylfluorene (mp: 144℃)
), 3-(2°-methylbenzoyl)fluorene (m
p: 137°C), 3-(3°-methylbenzoyl)fluorene (np: 106°C), 3-(4-methylbenzoyl)fluorene (fflp: 117°C), 3-(2
-methoxybenzoyl)fluorene (mp: 107°C)
, 3-(3-methoxybenzoyl)fluorene (mp:
104°C), 3-(4°-methoxybenzoyl)fluorene (mp: 156°C), 3-(α-phenylacetyl)fluorene (mp: 153°C), and the like.

These fluorene derivatives may be used alone, or two or more thereof may be used in combination.

The amount of this fluorene derivative used varies depending on the type of leuco dye and organic acidic substance used, but it is usually 0.5 to 3 parts by weight per 1 part by weight of leuco dye.
0 parts by weight, preferably 1 to 10 parts by weight.

Furthermore, various additives can be added to the heat-sensitive recording material of the present invention depending on its use.

Examples of such additives include, for example, polyvinyl alcohol (PVA), methylcellulose polyacrylic acid, casein, gelatin, starch, which isolates and fixes the leuco dye dispersed in fine particles and the organic acidic substance from each other. Binder such as derivative, whiteness of thermosensitive coloring layer,
There are white pigments and aliphatic metal salts such as calcium carbonate, kaolin, clay, talc, and titanium oxide that are added to improve the slipperiness and stickiness of writing instruments. These additives are mixed or applied separately to a support such as a paper film to form a thermosensitive coloring layer.

[Function 1] In the heat-sensitive recording material of the present invention, the fluorene derivative contained in the heat-sensitive coloring layer has a melting point lower than both the leuco dye and/or the organic acid substance constituting the heat-sensitive coloring layer. Alternatively, it is considered that it has a sublimation point and has solubility in leuco dyes and/or organic acidic substances, and acts as a color development accelerator that dissolves one or both of them and promotes the reaction between them.

[Examples] The present invention will be specifically described below based on Examples and Comparative Examples.

Example 1 (1) Preparation of liquid A 3-(N-cyclohexyl-N-methylamine)-6-
15 parts of methyl-7-ayurifluorane, 50 parts by weight of 3-benzylfluorene, and 500 parts by weight of a 10 wt% PVA aqueous solution were pulverized and mixed in a ball mill for 24 hours,
Solution A was prepared.

(2) Preparation of liquid B 75 parts by weight of bisphenol A and 1 swt%-PVA
500 parts by weight of an aqueous solution was pulverized and mixed in a ball mill for 24 hours to prepare Solution B.

(3) Preparation of thermal recording paper Prepare a coating solution by mixing 100 parts by weight of Part A and 100 parts by weight of Part B. Apply this coating onto the base paper and dry. After drying, the coating amount is 5 g. /Trt thermal recording paper was obtained.

The heat-sensitive recording paper thus obtained was colored in a stamp-type color tester at a temperature range of 60 to 120°C, and the color density was measured using a reflection S-shaped needle (Sakura Digital Reflection Densitometer PDA-
45> was conducted. Results first
Shown in the table.

In addition, a heat resistance test was conducted in which the obtained uncolored thermosensitive recording paper was left in a constant temperature bath at 60° C. for 24 hours, and the heat resistance (fogging) of the thermosensitive coloring layer was investigated by measuring the color density after being left. . The results are shown in Table 1.

Example 2 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 above, except that 3-benzoylfluorene was used instead of 3-benzylfluorene in preparing Liquid A. A color development test and a heat resistance test were conducted in the same manner as above.

The results are shown in Table 1.

Comparative Example A thermosensitive recording paper was prepared in exactly the same manner as in the above Example, except that stearic acid amide was used in place of the above 3-benzylfluorene in preparing Liquid A, and the same procedure as in Example 1 was carried out. , a color development test and a heat resistance test were conducted. The results are shown in Table 1.

Table 1 [Effects of the Invention] The heat-sensitive recording material of the present invention has excellent thermal responsiveness, excellent storage stability, and is resistant to background fogging.

Patent applicant: Nippon Steel Chemical Co., Ltd.

Claims (1)

[Claims] (1) In a heat-sensitive recording material provided on a support, a heat-sensitive color-forming layer containing a leuco dye that is colorless or light-colored at room temperature and an organic acidic substance that reacts with the leuco dye to develop color when heated, the heat-sensitive color-forming layer , the melting point is 50-200℃
A heat-sensitive recording material characterized by containing one or more compounds selected from fluorene derivatives.