JPH03230993A - Thermal reversible recording material - Google Patents

Abstract

PURPOSE:To set thermal recording characteristics to a high temp. region and to also control a transparentizing recording temp. range to a practically suffi cient range by using keton having a higher alkyl group or semicarbazone de rived therefrom as an org. low-molecular substance. CONSTITUTION:Ketone or semicarbazone derived therefrom as an org. low- molecular substance is advantageously employed in the expansion of transparentizing temp. width as compared with conventional fatty acid and one with a high m.p. can be obtained. By using two or more kinds of ketone or semicarbazone derived therefrom in combination, the rising or expansion of the transparentizing temp. width can be controlled and a material controlled in the temp. dependent transparency turbidity reversible phenomenon correspond ing to a use can be provided. Ketone contains a ketone group and a higher alkyl group as essential constituent groups and can also contain a non- substituted or substituted aromatic or heterocyclic ring.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a thermosensitive reversible recording material.

[Prior Art] Conventionally, heat-sensitive reversible recording media are known in which a recording layer is formed by coating a recording material made of a resin base material mixed with an organic low-molecular substance on a support.

This method performs recording by utilizing the phenomenon that the recording material becomes transparent or cloudy depending on the temperature.

As for the organic low-molecular substances in such recording materials,
Hitherto, higher fatty acids and their esters, derivatives such as acid amides, alkanols, alkanes, etc. have been proposed, but the main materials have actually been limited to fatty acids.

In JP-A-54-119377 and JP-A-55-154198, the temperature at which the opaque material becomes transparent after death is generally low, and even when considering the type of fatty acid, it is about 65 to 72°C, and the temperature range for transparency is 2 to 72°C. 4 degrees Celsius, which is virtually unusable in the specific summer environment in Japan, and it is also possible to make at least a partially opaque recording part transparent, or to form a transparent image on a recording material that is entirely opaque. There were difficulties in controlling the temperature during the process, and there were problems in terms of reliability and practicality.

JP-A No. 63-39378, B3-13031110
No., JP-A No. 1-23788, etc., proposals take these points into consideration, but fatty acid esters, ethers,
By incorporating specific organic low-molecular substances such as thioethers or plasticizers, the temperature at which it becomes transparent is expanded,
We are making improvements in practicality. However, the improvement in the clearing temperature was not yet sufficient, and it was observed that the recorded image sometimes changed and disappeared in an environment of 60 to 65 degrees Celsius. Further improved materials such as these are required.

[Problems to be Solved by the Invention] An object of the present invention is to provide a heat-sensitive reversible recording material that eliminates the above-mentioned inconveniences and drawbacks, has excellent environmental storage resistance, and has a margin for recording control by heating. The purpose is to

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors found that ketones having higher alkyl groups and semicarbazones derived therefrom are used as low molecular substances in the recording materials. It was discovered that it is effective to select the following, leading to the present invention.

That is, the present invention is a heat-sensitive reversible recording material comprising a recording material containing a ketone having a higher alkyl group or a semicarbazone derived therefrom as a low molecular substance and a resin.

The ketone of the present invention or the semicarbazone derived therefrom as an organic low-molecular substance is generally advantageous in extending the clearing temperature l] compared with conventional fatty acids, and can also be obtained with a high melting point.

In addition, in the present invention, by using a combination of two or more types of ketones or semicarbazones derived therefrom, it is possible to adjust the increase or expansion of the clearing temperature 1],
It becomes possible to provide materials that control the reversible phenomenon of temperature-dependent transparency and cloudiness depending on the application.

The ketone used in the present invention includes a ketone group and a higher alkyl group as essential constituent groups, and may also include an aromatic ring or a heterocycle that is unsubstituted or has a substituent.

The total number of carbon atoms in the ketone is 16 or more, preferably 21 or more.

Further, the semicarbazone used in the present invention is derived from the above ketone.

Examples of the ketones and semicarbazones used in the present invention include the following.

Name 2-hexadecanone 9-heptadecanone 3-octadecanone 2-nonadecanone 7-icosanone 2-henicosanone 11-henicosanone 12-tricosanone 9-pentacosanone 9-hexacosanone 14-hebutacosanone Chemical Formula % Formula % Thermosensitive reversible of the present invention To prepare the recording material, (1) a solution containing a resin base material and at least one of the organic low-molecular substances of the present invention, such as ketone or its semicarbazone derivative; A dispersion liquid in which a molecular substance is dispersed in the form of fine particles, (3) a melted liquid of a resin base material and the above-mentioned organic low-molecular substance, or any of the above is applied and dried on a support such as a plastic film, paper, glass plate, metal plate, etc. to form a heat-sensitive layer. Various solvents for forming the heat-sensitive layer can be selected depending on the type of base material and organic low-molecular substance, and examples thereof include tetrahydrofuran, tetrahydropyran, dioxane, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene, etc. Can be mentioned.

Incidentally, in the heat-sensitive layer obtained not only when a dispersion is used but also when a solution or a melt is used, the organic low-molecular substance precipitates as fine particles and exists in a dispersed state.

The resin base material used for the heat-sensitive layer forms a layer in which a low-molecular-weight organic substance is uniformly dispersed, and is a material that influences the transparency at maximum transparency.

Therefore, the resin base material is preferably a resin that has good transparency, is mechanically stable, and has good film-forming properties. Such resins include polyvinyl chloride; vinyl chloride-vinyl acetate copolymer;
vinyl chloride-vinyl acetate-vinyl alcohol copolymer,
Vinyl chloride copolymers such as vinyl chloride-vinyl acetate-maleic acid copolymers, vinyl chloride acrylate copolymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers, etc. Examples include vinylidene chloride copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylate-methacrylate copolymers; silicone resins, and the like. These may be used alone or in combination of two or more.

On the other hand, the organic low-molecular substance may be appropriately selected depending on the temperature To to T3 shown in FIG. As such organic low-molecular substances, at least one of the ketones or derivatives thereof of the present invention may be used, or a mixture of two or more thereof may be used.

Further, the ratio of the organic low molecular weight substance to the resin base material in the heat-sensitive layer is preferably about 2=1 to 1:16 in terms of weight ratio, and 1:1 to 1:
3 is more preferred. If the ratio of the base material is less than this, it will be difficult to form a layer that retains the organic low molecular weight substance in the base material, and if it is higher than this, it will be difficult to make it opaque because the amount of the organic low molecular weight substance is small. . Alternatively, by using a mixture of two or more types, the temperature T O% T in FIG.
The ratio of the mixture may be appropriately selected depending on the desired control temperature shown in 3.

The thickness of the heat-sensitive layer is generally 1 to 30 μm. If it is thicker than this, the heat sensitivity will decrease, and if it is less than this, the contrast will decrease.

In addition to the above-mentioned components, the heat-sensitive layer may contain the following additives in order to maintain the transparent temperature during repeated heating.

Tributyl phosphate, commonly used as a plasticizer,
Tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate , diisononyl phthalate, 0 dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-2-ethylhexyl azelate, dibutyl sebacate, Examples include di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol-2-ethylbutylade, methyl acetyl ricinoleate, butyl acetyl ricinoleate, butylphthalyl butyl glycolate, tributyl acetyl citrate, and the like.

The weight ratio of the organic low-molecular substance to these additives is preferably about 1:0.01 to about 140.8.

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

Note that parts here are based on weight.

Example 1 1 3 parts of vinyl chloride-vinyl acetate copolymer and 1 part of 2henicosanone were dissolved in 15 parts of tetrahydrofuran by heating, this solution was applied onto a 75 μm thick polyester film using a wire bar, and dried at 135 to 140°C. A recording sheet was obtained by providing a recording layer with a thickness of 15 μm. This sheet is obtained in a cloudy and opaque state. Heat this sheet to a temperature of 95~
After being kept in an oven at 102°C for 30 seconds, it was taken out and allowed to cool, yielding a sheet that turned transparent. Then, when the surface of the recording layer portion was brought into contact with a heated head controlled at 135° C., a pattern was obtained in which the contact portion became cloudy and opaque. Measurement of reflection density using Macbeth densitometer RD514,
The density in the transparent area was 1.73, and the density in the cloudy area was 0.43.

When this sheet was projected on an OHP, the cloudy parts were projected black and could be seen as a sufficiently projected image. Even when this sheet was left in an oven controlled at 60 to 70°C, no change in the cloudy pattern was observed.

Further, this sheet was held again in a second bath at a temperature of 95 to 102 DEG C. for 30 seconds, and then taken out and allowed to cool, the cloudy pattern disappeared and a completely transparent sheet was obtained.

The above operation was repeated five times and the same phenomenon could be stably observed.

Example 2 A solution prepared by heating and dissolving 3 parts of saturated polyester resin, 0.98 parts of 22-tritetracontanone, and 0.1 part of di-n-heptyl phthalate in 17 parts of tetrahydrofuran was prepared according to Example 1 until it became cloudy and opaque. A record sheet was created. This sheet was kept in an oven controlled at 95° C.±3° C. for 30 seconds, then taken out and allowed to cool, yielding a transparent sheet.

Cut this sheet into two pieces and heat one of them to 135±3℃.
The recording sheet was kept in an oven controlled for 30 seconds and then allowed to cool to obtain a cloudy, opaque recording sheet.

The reflection density of the two sheets was measured using a Macbeth densitometer RD514, and the transparent sheet showed 1,75, and the cloudy opaque sheet showed 0.47.

3 Example 3 A cloudy, opaque resin was prepared according to Example 1 using 3 parts of vinyl chloride-vinyl acetate copolymer resin, 0.95 parts of 18pentatriacontanone, 0.05 parts of 2-docosanoylnaphthalene, and 15 parts of tetrahydrofuran. A film sheet was obtained.

This sheet was contact-heated from 65°C to 95°C in 5°C increments using a temperature gradient tester, and then allowed to cool, and the heated portion was measured using a Macbeth densitometer. At this time, the temperature when the reflection density exceeds 1.0 was determined as the transparency temperature, and the range was determined from 65 to
The temperature reached 75°C, and the maximum clear density was 1.73 and the maximum cloudy density was 0.44.

Example 4 3 parts of vinyl chloride-vinyl acetate copolymer, 0.8 part of 2-henicosanone, and 0.2 part of 2-henicosanone semicarbazone were mixed in 1:1 vol of tetrahydrofuran/methyl ethyl ketone.
A cloudy, opaque film sheet was obtained according to Example 1 using a mixed solvent. This sheet was held in an oven at 85 to 100°C for 30 seconds and then allowed to cool, yielding Sheet 4 which turned transparent.

Next, a thermal head heated to 135° C. or higher is brought into contact with the surface of the transparent sheet to make the contact area cloudy and opaque, and the reflection density of the transparent area and the cloudy and opaque area is measured using a Magbeth densitometer RD514. 83, 0.3 in opaque areas
8 and high contrast was obtained.

[Effects of the Invention] As explained above, by discovering a ketone having a higher alkyl group or a semicarbazone derived therefrom as an organic low-molecular substance, the heat-sensitive recording properties of a reversible recording material can be made into a high temperature range, and transparent recording can be achieved. The temperature range can also be controlled within a practically sufficient range, the effect of improving the environmental stability of the recording material is brought about, and a new versatile reversible recording material can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the phenomenon of transparency and cloudiness depending on the temperature of a thermosensitive reversible recording material. 5 Figure 1 T. 1 ■2 3 degrees

Claims (2)

[Claims] (1) A heat-sensitive reversible recording material composed of a recording material containing a resin and a ketone having a higher alkyl group as a low molecular substance. (2) The heat-sensitive reversible recording material according to claim 1, wherein the low molecular weight substance is a semicarbazone derived from the ketone.