JPH08475B2 - Reversible thermosensitive recording material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming thermosensitive recording material, and more particularly to a reversible thermosensitive recording material capable of forming and erasing an image by a difference in heat energy.

[0002]

2. Description of the Related Art Reversible thermosensitive recording materials have hitherto been disclosed in JP-A-58-191190, JP-A-60-193691, JP-A-3666,525 and JP-A-54-119377. , JP-A-63-39377, JP-A-63-41186, U.S. Pat.No. 4,028,118, JP-A-50-81157, JP-A-50-105555, International Publication WO 90/11898 It is disclosed in Japanese Patent Publication No.

However, among the above publications, US Pat.
028,118, JP-A-50-81157 and JP-A-50-1055
According to the contents disclosed in Japanese Patent Laid-Open No. 55-55, the image formed varies depending on the temperature, and the image formation was insufficient. In addition, JP-A-58-191190 and JP-A-60-19
Those described in 3691 and U.S. Pat.No. 3,666,525 are provided with a recording layer composed of a leuco dye, a developer and a binder, and if necessary, a low vapor pressure solvent or a heat melting substance is used. The color is developed by using thermal energy, and the color is erased by water, water vapor or some organic solvent. Since this method uses water vapor or an organic solvent for erasing, the mechanism becomes extremely complicated when an erasing mechanism is to be incorporated in a device such as a printer. In addition, there is a drawback that unintended decoloring occurs due to moisture in the air.

Recording and erasing can be carried out as intended by only controlling the heat energy for coloring and erasing. Such techniques are disclosed in JP-A-54-119377 and JP-A-63-63.
As described in JP-A-39377 and JP-A-63-41186, it has a heat-sensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the base material, and has a thermal energy To reversibly change the light diffusivity of the heat-sensitive layer for image formation and erasure, and molecules having both color-developing and decolorizing functions as described in WO 90/11898. Some have a heat-sensitive layer containing a complex salt as a coloring / decoloring agent together with a leuco dye, and perform coloring and decoloring by a reversible reaction of the leuco dye.

However, since the former forms an image by changing the diffusion state of light, the visual contrast of the image is extremely low, and a color image cannot be obtained. Also,
The latter forms an image with a dye, but since the same substance needs to have both a color developing function and a color erasing function, the color developing function is not sufficient and the color density is low. Also, it is extremely difficult to design the erasing temperature for each device in which it is used.

[0006]

As described above, until now, there has been no technique capable of recording and erasing a high-contrast image only by thermal energy and further freely designing the temperature of recording and erasing. .

The object of the present invention is to solve the problems of the above-mentioned prior art, and to chemically develop and decolorize only by controlling the heat energy to obtain a high coloring density and a high contrast, and to decolorize. It is to provide a reversible thermosensitive recording material whose temperature can be freely set.

[0008]

The above object is a recording material in which a recording layer containing a leuco dye, a developer, a decoloring agent and a binder as a main component is provided on a support, and the decoloring agent is This can be achieved by using a reversible heat-sensitive recording material characterized by being a complex salt of an organic acid and an amine compound.

A feature of the present invention is that a complex salt of an organic acid and an amine compound is used as a decoloring agent as described above.
Among them, the organic acid is a benzene ring in which a phenolic hydroxyl group, a carboxyl group or a sulfone group is independently or plurally substituted and a derivative thereof, and examples thereof include benzoic acid, gallic acid, phloroglucinol, phthalic acid, salicylic acid, and parahydroxybenzoic acid. Acids, sulfosalicylic acids and their derivatives can be used. Among these, especially, paramethylbenzoic acid, parapropylbenzoic acid, paramethoxybenzoic acid, metamethylbenzoic acid, orthomethylbenzoic acid, 3,4,5-trimethylbenzoic acid, parachlorobenzoic acid, metachlorobenzoic acid, orthochlorobenzoic acid, etc. Benzoic acid derivatives and terephthalic acid such as monomethyl terephthalate, monoethyl terephthalate and monobutyl terephthalate
An excellent decoloring property can be obtained when using a talic acid monoester .

The amine compound is a compound having one or a plurality of amino groups in the molecule and is a compound which forms a complex salt with the above organic acid.
Excellent erasing properties can be obtained when the following are used.

(A) A linear or branched alkylamine having an alkyl group having 8 or more carbon atoms, such as octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, 4,4- Dipropyloctylamine, 5-ethyldodecylamine, 2,6-diethyldecylamine, 2,4,6-tributyloctylamine, etc.

(B) an ether-containing alkylamine having a linear or branched alkyl group containing an ether bond,
For example, methoxypropylamine, ethoxypropylamine, 2-ethylhexaoxypropylamine, dodecyloxypropylamine, etc., such as C _n H _{2n + 1} -X- (CH ₂ )
_m -NH ₂ (wherein, X represents an oxygen atom, n = 1~18, m = 1~
An amine compound represented by 5).

(C) Thioether-containing alkylamines having a linear or branched alkyl group containing a thioether bond, such as metathioxypropylamine, ethioxypropylamine, 2-ethylhexathioxypropylamine and dodecyltiamine. Oxypropylamine and other compounds of the general formula C _n H _{2n + 1} -X- (CH ₂ ) _m -NH ₂ (where X is a sulfur atom, n
= 1 to 18 and m = 1 to 5).

(D) Secondary or tertiary amines, for example,
Dioctylamine, N-ethyldecylamine, N, N-methylhexadecylamine, tributylamine, etc.

The leuco dye and the color developer may be those conventionally used in conventional thermal papers such as crystal violet lactone and 3-indolino-3-p.
-Dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 2- (2
-Fluorophenylamine) -6-diethylaminofluorane, 2- (2-fluorophenylamino) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5- Methyl-7-t-butylfluorane, 3-diethylamino-6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino-3-methyl-6- ( N-ethyl-p-toluidino) -fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-N-methylcyclohexylamino-6-methyl-7 Leuco dyes such as -anilinofluorane and 3-N-ethylbenzylamino-6-methyl-7-anilinofluorane, bisphenol A, esters of benzoic acid, derivatives of salicylic acid, p-hydroxybenzoic acid and its esters Use a color developer such as gallic acid and its ester.

As the binder, any water-soluble resin such as polyvinyl alcohol, gelatin and casein, and acrylic resin, polyester resin, cellulose derivative, vinyl resin, styrene resin and the like can be used as long as they are film-forming resins. can do.

Further, various additives are added as needed.

[0018]

When the recording operation is performed on the reversible thermosensitive recording material of the present invention using a thermal printer or the like, only the portion to be printed is heated for an extremely short time, and at that time, the leuco dye and the color developer chemically react with each other. An image is formed by the generation of a dye that absorbs visible light.

Then, when this is heated for several seconds on a hot plate or the like, the dye forming the image chemically reacts with the decoloring agent and returns to the leuco dye again. That is, the leuco dye reacts with the color developer to become a dye (coloring reaction), and the dye reacts with the decoloring agent to form a leuco dye (decoloring reaction).

The color reaction takes place extremely quickly at relatively high temperatures. On the other hand, the decolorization reaction occurs even at a relatively low temperature,
The reaction speed is slow. Therefore, if the heating is performed for an extremely short time, only the coloring reaction occurs, and the decoloring reaction does not occur.

In order for the image to be stable after printing, it is necessary to prevent the decoloring reaction from occurring at room temperature.
Therefore, in the present invention, a complex salt of an amine compound and an organic acid is used as a decoloring agent. The complex salt dissociates into an organic acid and an amine compound at a constant temperature, and the amine compound contributes to the decoloring reaction. Therefore, the decolorization reaction does not occur below this dissociation temperature. This dissociation temperature is determined by the combination of an amine compound used as a complex salt and an organic acid.

Further, since the speed of the decoloring reaction by this decoloring agent is extremely slow as compared with the speed of the color developing reaction, it does not compete with the color developing reaction carried out by heating for a short time, and therefore a high color developing density can be obtained. A color former (developing agent) and a decolorizer capable of obtaining an arbitrary decoloring temperature can be independently selected.

In this regard, international publication WO 90/11898
In the case of, the color developing agent and the decoloring agent use the same molecule or complex salt as the color developing agent and the decoloring agent, so that the coloring reaction and the decoloring reaction cannot be controlled independently, and the coloring density becomes insufficient. ,
There is a drawback that the design of the erasing temperature is limited.

[0024]

EXAMPLES The reversible thermosensitive recording material of the present invention will be specifically described below with reference to examples.

[0025]

Example 1 Liquid A 2- (2-chlorophenylamino) -6-diethylaminofluorane 10 parts Methacrylic resin (Dianal BR-106 manufactured by Mitsubishi Rayon) 5 parts Toluene 40 parts Liquid B p-hydroxybenzoate 5 parts 5 parts Decoloring agent of the present invention (complex salt of benzoic acid and octadecylamine) 5 parts Methacrylic resin (Dianal BR-106 manufactured by Mitsubishi Rayon) 7.5 parts Toluene 40 parts Solution A and solution B having the above compositions are respectively prepared using a ball mill. After crushing and dispersing for 20 hours, 1 part of solution A to 4 parts of solution B
A recording layer coating solution was prepared by thoroughly mixing the components in a ratio of 1 part. A wire bar was used to apply this coating solution onto a white-processed polyester film having a thickness of 50 μm so that the dry weight was 8 g / m ^2, and the coating was dried and the reversible heat-sensitive recording sheet (Table 1) was prepared.

Further, in the preparation of the above-mentioned heat-sensitive recording sheet 1, the heat-sensitive recording sheet was similarly prepared except that the decoloring agent of the present invention in the liquid B was replaced by complex salts 2 to 12 composed of the organic acid and amine shown in Table 1. (2 to 12 in Table 1) were prepared.

Thermosensitive recording sheet prepared as described above
About 1 to 12 Seiko Epson Thermal Printer AP
Printing was performed using -850, and the reflection optical density of the printed portion was measured with a reflection optical densitometer manufactured by Macbeth. Next, the surface temperature of the hot plate was raised by 10 ° C. per minute, and the surface temperature when the thermosensitive recording sheet brought into contact with the surface of the hot plate was decolored was taken as the decoloring temperature. Table 1 also shows the reflection optical density and the decoloring temperature of the printed portion of each thermosensitive recording sheet. The thermosensitive recording sheets 1 to 12 were completely decolored at the decoloring temperatures shown in Table 1. Further, when the same printing and erasing were repeated, it was confirmed that the material has reproducibility and is extremely excellent as a reversible thermosensitive recording material.

It was also confirmed that the erasing temperature can be freely set in a wide range by selecting the organic acid and amine compound constituting the complex salt.

[0029]

[Table 1]

[0030]

Example 2 Solution A 2- (2-chlorophenylamino) -6-diethylaminofluorane 10 parts Polyvinyl alcohol 2 parts Distilled water 40 parts Solution B benzyl p-hydroxybenzoate 5 parts Decolorizer of the present invention (terephthalic acid Monomethyl and octadecylamine complex salt) 5 parts Fine powder silica (Nipsil E743 made by Nippon Silica) 10 parts Polyvinyl alcohol 10 parts Distilled water 10 parts Liquid A and liquid B having the above composition are pulverized and dispersed by a ball mill for 20 minutes respectively. It was Then, these dispersions were thoroughly mixed at a ratio of 2 parts of solution A to 5 parts of solution B to prepare a recording layer coating solution. Using a wire bar, this coating solution was applied onto a white processed polyester film having a thickness of 50 μm so that the dry weight was 8 g / m ^2, and dried to prepare a reversible thermosensitive recording sheet 13 without the background covering. did.

Further, in the preparation of the heat-sensitive recording sheet 13, the heat-sensitive recording sheet (14 to 17 in Table 2) was similarly used except that the developer of the present invention in the liquid B was changed to that shown in Table 2.
Was produced. The heat-sensitive recording sheet 18 was produced without using a color developer.

Thermosensitive recording sheet prepared as described above
Table 2 shows the results of measuring the reflection optical density and the erasing temperature of the printed portion for each of 13 to 18 in the same manner as in Example 1.
It was shown to. The thermal recording sheets 14 to 17 of this example also show excellent printability and erasability as in the case of Example 1, and
The reproducibility was also good. Further, since the thermosensitive recording sheet 18 did not show any printing at all, it is understood that the decolorizing agent of the present invention is essentially different from the decoloring agent of the above-mentioned WO 90/11898.

Further, it was confirmed by this example that the decolorizing agent of the present invention can be used in combination with various developers.

[0034]

[Table 2]

[0035]

As described above, by using the reversible thermosensitive recording material as the material of the constitution of the present invention, the problems of the prior art can be solved, and the chemical reaction can be achieved chemically only by controlling the thermal energy. It has been possible to provide a reversible thermosensitive recording material which is capable of coloring and erasing, obtaining a high color density and a high contrast, and freely setting the erasing temperature. Therefore, the materials of the present invention can be used in a wide range of devices.

In recent years, a large amount of paper is consumed by OA equipments from the standpoint of the rapid increase of municipal waste and the protection of the global environment. However, the spread of the material of the present invention reduces the amount of paper used. It can be expected that it can be reduced significantly.

Claims (6)

[Claims] 1. A recording material comprising a support and a recording layer comprising a leuco dye, a color developer, a decoloring agent and a binder as main components, wherein the decoloring agent is a complex salt of an organic acid and an amine compound. And a reversible thermosensitive recording material. 2. The reversible thermosensitive recording material according to claim 1, wherein the organic acid constituting the complex salt as the decoloring agent is benzoic acid or its derivative. 3. The reversible thermosensitive recording material according to claim 1, wherein the organic acid forming the complex salt which is the decoloring agent is a terephthalic acid monoester . 4. The reversible heat-sensitive material according to claim 1, wherein the amine compound constituting the complex salt which is the decoloring agent is an alkylamine having a linear or branched alkyl group having 8 or more carbon atoms. Recording material. 5. The amine compound constituting the complex salt, which is the decoloring agent, is an ether-containing alkylamine or thioetheralkylamine containing a linear or branched alkyl group containing an ether bond or a thioether bond, and has the general formula C _n H _{2n + 1} -X- (CH ₂ ) _m -NH ₂ (where X is an oxygen atom or a sulfur atom, n = 1 to 18, m = 1 to 5) The reversible thermosensitive recording material according to claim 1. 6. The reversible thermosensitive recording material according to claim 1, wherein the amine compound constituting the complex salt which is the decoloring agent is a secondary or tertiary amine.