JPH03224784A - Thermal reversible recording material - Google Patents

Abstract

PURPOSE:To improve contrast, to magnify a transparentizing temp. region and to stabilize an image by using specific phosphoric ester as the low-molecular substance in a recording material. CONSTITUTION:At least one kind of phosphoric ester represented by formula (RO)nP(O)(OH)3-n (wherein R is a 8-29C alkyl group and n is 1 or 2) and/or formula (RO)3P (wherein R is a 8-28C alkyl group) and a high-molecular resin are contained. As phosphoric ester, for example, CH3(CH2)11OPO(OH)2 and CH3(CH2)13OPO(OH)2 are designated. A thermal reversible recording material is prepared by applying either one of a solution having a resin base material and at least one kind of phosphoric ester dissolved therein, a dispersion prepared by dispersing phosphoric ester in a resin base material solution in a fine particulate state or a solution of the resin base material and phosphoric ester to a support such a plastic film and drying the coating layer to form a thermal layer. As the resin base material, a resin having good transparency, mechanical stability and good film forming properties is pref.

Description

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

Does this mean that the recording material is temperature dependent and transparent? Recording is performed using the phenomenon of clouding.

Organic low-molecular substances in such recording materials include:
Higher fatty acids and their esters, derivatives such as acid amides, alkanols, alkanes, etc. have been proposed in the past, but the main materials have actually been limited to higher fatty acids such as stearic acid and behenic acid, so it is difficult to use them for resin base materials. If the amount of organic low-molecular-weight substances is small, the density in the opaque areas (cloudy areas) will be low; conversely, if the amount of organic low-molecular substances is large, the density in the opaque areas will be high, but the transparent areas and transparent areas will be small, resulting in poor contrast during image creation. It was enough. In addition, since the temperature range at which the opaque portion becomes transparent is narrow, about 2 to 4 degrees Celsius, when at least a partially opaque recording material is made transparent, or when a transparent image is formed on a completely opaque recording material, Temperature control was difficult, and there were problems in terms of practicality and reliability.

JP-A-83-39378 and JP-A-83-110380 filed by the present applicant are proposals that take these points into consideration, but they do not include specific organic low-molecular substances such as ethers, thioethers, or plasticizers. By doing so, we are proposing improvements in practicality by expanding the transparent temperature range.

[Problems to be Solved by the Invention] An object of the present invention is to provide a different and novel heat-sensitive reversible recording material that improves the above-mentioned disadvantages.

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that by using a specific phosphoric acid ester as a low molecular substance in the recording material, the conventional method can be improved. The present invention was achieved based on the findings that this method is particularly effective in improving contrast, expands the transparent temperature range, and improves image stability, compared to the case where fatty acids are used.

That is, the present invention provides the following general formula (1) and/or (2
) and a polymer resin.

Examples of the phosphoric acid ester used in the present invention include CH:l (CH2) u OPO(OH) 2 (lauryl acid phosphate) CH3(CH2)
n 0PO(OH) 2 (myristyl acid phosphate), CH3(CH2) rSOPO(OH)
2 (stearyl acid phosphate), [CH3(
CH2) s O12P(0)OH (dilauryl phosphate), [CH3(CH2) n O12P(0)O
H (dilauryl phosphate), ECM3 (CH2) 0] 2P (0) OH (cimilistyl phosphate), [
CH3(CH2) +s 012 P(0)OH (cybalmityl phosphate), [CH3(CH2) rr
O12P(0)OH (distearyl phosphate), [
CH3(CH2) 210]2P(0)OH (dibehenyl phosphate), [CH3(CH2) 23012
P(0)OH (siligutuseryl phosphate), [CH
3(CH2) rr 013 P (tristearyl phosphite), [CH3(CH2) 21013P()
ribhenyl phosphite), etc.

These alkyl phosphate esters can be synthesized by a known method using a higher alcohol.

For example, as a method for synthesizing alkyl phosphate esters with high purity using a high-molecular-weight long-chain alcohol, in the case of monoester, R, S, Cooper et al. JAOC840, 842
(1963) in which a long-chain alkylphosphoryl dichloride is obtained from the reaction of a long-chain alcohol and phosphorus oxychloride and then hydrolyzed.

In the case of diesters, dialkylphosphonic acid is obtained by the reaction of long-chain alcohol and phosphorus trichloride, purified by vacuum distillation, treated with chlorine gas to obtain dialkylphosphonochloridate, and then hydrolyzed in hot water. A better method is to disassemble it.

The reason why the phosphoric acid esters of the present invention are more effective in improving contrast than conventional higher fatty acids such as stearic acid and behenic acid is unknown, but it is effective in expanding the transparency temperature range. This is presumably due to the fact that the melting and crystallization temperatures vary by several degrees.

In order to produce the thermosensitive reversible recording material of the present invention, (1) a solution in which a resin base material and at least one of the above phosphoric esters are dissolved; (2) the above phosphoric ester is added to the solution of the resin base material in the form of fine particles. (8) a melt of the resin base material and the above phosphoric ester, the above (
It is produced by coating any one of 1) to (3) on a support such as a plastic film, paper, glass plate, metal plate, etc. and drying it 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, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, and benzene. Note that 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 is a material that forms a layer in which a low-molecular-weight organic substance is uniformly dispersed and maintains 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 copolymers such as vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride acrylate copolymer; polyvinylidene chloride, Vinylidene chloride copolymers such as vinylidene chloride-vinyl chloride copolymers and vinylidene chloride-acrylonitrile 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, organic low-molecular substances have a temperature T as shown in FIG. -T3 may be selected as appropriate. At least one of the phosphoric acid esters of the present invention is used as such organic low-molecular substance, but a mixture of two or more types can also be used.

The weight ratio of the organic low-molecular substance to the resin in the heat-sensitive layer is preferably about 2:1 to 1:16, more preferably 1:1 to 1:3. If the ratio of the base material is less than this, it will be difficult to form a film that retains the organic low-molecular substance in the resin, and if it exceeds this, the amount of the organic low-molecular substance will be small.
It becomes difficult to make it opaque. Alternatively, by using a mixture of two or more types, the temperature T in FIG.

The ratio of the mixture may be appropriately selected depending on the desired control temperature shown in -T3.

The thickness of the heat-sensitive layer is generally 1 to 30 μm.

If it is thicker than this, the thermal sensitivity will be reduced, and if it is less than this, the contrast will be reduced.

In addition to the above-mentioned components, the heat-sensitive layer may contain the following additives in order to maintain and expand the transparency 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, dihebutyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyldecyl phthalate , diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate,
Di-n-hexyl adipate, di-2-ethylhexyl adipate, 2-ethylhexyl azelaate, dibutyl sebacate, di-2-ethylhexyl sebacate,
Diethylene glycol dibenzoate, triethylene glycol-2-ethyl butylade, methyl acetyl ricinoleate, butyl acetyl ricinoleate.

Examples include butylphthalyl butyl glycolate, tributyl acetyl citrate, and the like.

The weight ratio of the organic low-molecular substance to these additives is preferably about 1:01 inch to 1:0.8 (L).

[Example] The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to these examples. Note that parts here are based on weight.

Example 1 1 part of cival mityl phosphate, vinyl chloride-vinyl acetate copolymer (formerly HH manufactured by UCC, PVC 8B/vinegar and 14)
After heating and dissolving 3.0 parts of tetrahydrofuran in 50 parts of tetrahydrofuran, 30 parts of tetrahydrofuran was recovered and concentrated by distillation. This concentrated solution was applied onto a 7.5μ thick polyester film with a wire bar and heated in an oven at 135-140°C. A recording sheet was prepared by drying and providing a heat-sensitive recording layer with a thickness of about 15 μI.

Example 2 After heating and dissolving 1 part of distearyl phosphate, 3.0 parts of vinyl chloride-vinyl acetate copolymer (same as in Example 1), and 80 parts of tetrahydrofuran, 60 parts of tetrahydrofuran was recovered by distillation. A recording sheet was prepared in the same manner as in Example 1 using the solution.

Example 3 A recording sheet was prepared in the same manner as in Example 1 using a solution consisting of 1 part of stearyl anrad phosphate, 3.0 parts of vinyl chloride-vinyl acetate copolymer (same as in Example 1), and 20 parts of tetrahydrofuran. .

Example 4 The same procedure as in Example 2 was carried out using 0.5 parts of dibephenyl phosphate, 0.5 parts of tristearylphosphite, and 3.0 parts of vinyl chloride-vinyl acetate copolymer (same as in Example 1). A record sheet was created.

Comparative Example 1 A recording sheet was prepared in the same manner as in Example 3 except that 1 part of stearic acid was used.

Comparative Example 2 A recording sheet was prepared in the same manner as in Example 3 except that 1 part of behenic acid was used.

Comparative Example 3 A recording sheet was prepared in the same manner as in Example 3, except that 0.5 part of behenic acid and 0.5 part of civalmityl phosphate were used.

Recording sheets obtained as described above (Examples 1 to 4).
Comparative Examples 1 to 3) All were obtained as cloudy and opaque sheets.

These recording sheets were heated to 50"C in 5°C increments for 12
After heating in an oven for 30 seconds to 0°C, cool to room temperature,
The reflection density of this was measured using a Magbeth densitometer RD5L4. At this time, the temperature at which the reflection density exceeded 1.0 was defined as the transparency temperature, and its range and width were shown. Further, Table 1 shows the results of maximum clear density and maximum cloudy density.

Table [Effects of the Invention] As explained above, by discovering long-chain alkyl phosphate esters as organic low-molecular substances, the recording contrast of recording materials has been improved, and the transparent recording temperature range has been kept within a practically sufficient range. This makes it possible to provide a new general-purpose heat-sensitive reversible recording material.

Claims (1)

[Scope of Claims] A heat-sensitive reversible recording material characterized by containing at least one kind of phosphoric acid ester represented by the following general formula (1) and/or (2) and a polymer resin. (RO)_nP(O)(OH)_3_-_n...(1
) (In the formula, R represents an alkyl group having 8 to 28 carbon atoms, and n represents 1 or 2) (RO)_3P...(2) (In the formula, R represents an alkyl group having 8 to 28 carbon atoms)