JP2895140B2 - Heat-sensitive reversible recording material - Google Patents

Description

The present invention relates to a reversible thermosensitive recording material.

[Related Art] Conventionally, there has been known a thermosensitive reversible recording medium in which a recording material in which an organic low-molecular substance is mixed with a resin base material is applied on a support to form a recording layer.

In this method, recording is performed using a phenomenon that a recording material becomes transparent and opaque depending on temperature. As organic low-molecular substances in such recording materials, higher fatty acids and derivatives thereof such as esters and acid amides, alkanols, alkanes, and the like have been conventionally proposed. However, in practice, stearic acid and behenic acid are mainly used as main materials. Since the concentration of the organic low-molecular substance in the resin base material is small, the concentration of the opaque part (white turbid part) is low, and when the amount is large, the concentration of the opaque part is high, but the transparent part is transparent. The part is small,
As a result, the contrast at the time of image formation was insufficient.
Further, since the temperature range in which the opaque portion becomes transparent is as narrow as about 2 to 4 ° C., when at least a part of the entire opaque recording material is made transparent, or when a transparent image is formed on the entire opaque recording material, Temperature control was difficult and there was a problem in terms of practicality and reliability.

JP-A-63-39378 and 63-1 filed by the present applicant
No. 30380 is a proposal that considers these points, but proposes to improve the practicability by expanding the clearing temperature range by including specific organic low molecular substances such as ether, thioether or plasticizer. I have.

[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 which improves the above-mentioned disadvantages.

[Means for Solving the Problems] The present inventors have conducted intensive studies to solve the above problems, and as a result, as a low molecular substance in the recording material,
The present inventors have found that the use of a specific phosphoric acid ester is particularly effective for improving the contrast and can increase the transparency temperature range and improve the image stability, as compared with the case where a conventional fatty acid is used.

That is, the present invention relates to at least one of phosphoric esters represented by the following general formulas (1) and / or (2):
It is a thermosensitive reversible recording material characterized by containing a polymer resin.

(RO) _n P (O) (OH) _3-n (1) (wherein, R represents a straight-chain alkyl group having 8 to 28 carbon atoms, and n represents 1 or 2) (RO) ₃ P ( 2) (wherein, R represents a linear alkyl group having 8 to 28 carbon atoms) Examples of the phosphate ester used in the present invention include CH ₃ (CH ₂ ) ₁₁ OPO (OH) ₂ (lauryl acid Phosphate), CH ₃ (CH ₂ ) ₁₃ OPO (OH) ₂ (myristyl acid phosphate), CH ₃ (CH ₂ ) ₁₅ OPO (OH) ₂ (stearyl acid phosphate), [CH ₃ (CH ₂ ) ₉ O] ₂ P (O) OH (didecanoyl phosphate), [CH ₃ (CH ₂ ) ₁₁ O] ₂ P (O) OH (dilauryl phosphate), [CH ₃ (CH ₂ ) ₁₃ O] ₂ P (O) OH (Dimyristyl phosphate), [CH ₃ (CH ₂ ) ₁₅ O] ₂ P (O) OH (dipalmityl phosphate), [CH ₃ (CH ₂ ) ₁₇ O] ₂ P (O) OH (distearyl phosphate) , [CH ₃ (CH ₂ ) ₂₁ O] ₂ P (O) OH (divehenyl phosphate), [CH ₃ (CH ₂ ) ₂₃ O] ₂ P (O) OH (Dilignoceryl phosphate), [CH ₃ (CH ₂ ) ₁₇ O] ₃ P (tristearyl phosphite), [CH ₃ (CH ₂ ) ₂₁ O] ₃ P (tribehenyl phosphite), and the like. it can.

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

For example, as a method for synthesizing alkyl phosphates with high purity using a high-molecular-weight long-chain alcohol, in the case of a monoester, it is preferable to use a reaction from pyrophosphoric acid and a long-chain alcohol to obtain RSOC, Cooper, etc. JAOCS 40 , 642 (1963 According to the method of the above), a method of obtaining a long-chain alkylphosphoryl dichloride from the reaction of a long-chain alcohol and phosphorus oxychloride and hydrolyzing it is preferred.

In the case of a diester, a dialkylphosphonic acid is obtained by a reaction between a long-chain alcohol and phosphorus trichloride, purified by vacuum distillation, and then treated with chlorine gas to obtain a dialkylphosphonochloridate. The decomposition method is good.

When the phosphates of the present invention are used, the reason why they are effective in improving the contrast as compared with conventional higher fatty acids such as stearic acid and behenic acid is unknown, but they are effective in expanding the temperature range for clearing. It is presumed that this is due to the fact that the melting and crystallization temperatures have a range of several degrees.

To prepare the heat-sensitive reversible recording material of the present invention, (1) a solution in which a resin base material and at least one kind of the above-mentioned phosphate ester are dissolved, (2) fine particles of the above-mentioned phosphate ester in a solution of the resin base material (3) a melt of a resin base material and the above-mentioned phosphate ester, or any of the above (1) to (3) on a support such as a plastic film, paper, a glass plate, or a metal plate. It is made by coating and drying to form a thermosensitive layer. The solvent for forming the heat-sensitive layer can be variously selected depending on the type of the base material and the organic low molecular weight substance. For example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform,
Examples include carbon tetrachloride, ethanol, toluene, benzene and the like. It should be noted that, of course, when a dispersion or a solution is used, the organic low-molecular substance is precipitated as fine particles in the heat-sensitive layer obtained when a solution or a solution is used, 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 an organic low-molecular substance is uniformly dispersed and held, and that gives transparency at the time of maximum transparency. For this reason, the resin base material is preferably a resin having good transparency, mechanical stability, and good film formability. Examples of such a resin include polyvinyl chloride; vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. Polyvinylidene chloride, vinylidene chloride, vinylidene chloride-vinyl copolymer, vinylidene chloride-acrylonitrile copolymer, etc .; polyester; polyamide; polyacrylate or polymethacrylate or acrylate; Methacrylate copolymer; silicone resin and the like. These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular-weight material may be suitably selected according to selected temperature T ₀ through T ₃ of FIG. 1. As such an organic low-molecular substance, at least one of the phosphoric esters of the present invention is used, but a mixture of two or more may be used.

The ratio of the organic low-molecular substance to the resin in the heat-sensitive layer is preferably about 2: 1 to 1:16 by weight, more preferably 1: 1 to 1: 3. If the ratio of the base material is less than this, it becomes difficult to form a film holding the organic low-molecular substance in the resin, and if it is more than that, it becomes difficult to make the film opaque because the amount of the organic low-molecular substance is small. Alternatively, by using two or more kinds of mixtures, the ratio of the mixtures may be appropriately selected according to the desired control temperatures shown as temperatures T _{0 to} T ₃ in FIG.

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

In addition to the above-mentioned components, the following additives can be added to the heat-sensitive layer in order to maintain and expand the transparent temperature range when repeatedly heated and performed.

Tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, phthalate, which are generally used as plasticizers Di-n-octyl acid, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyl decyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-2 adipate -Ethylhexyl, azelaic acid-2-ethylhexyl, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol-2-ethyl butyrate, methyl acetyl ricinoleate, acetyl ricinoleic acid Chill, butyl phthalate butyl glycolate, and the like acetyl tributyl citrate is.

The ratio between the organic low-molecular substance and these additives is preferably about 1: 0.01 to 1: 0.8 by weight.

[Examples] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The parts here are based on weight.

Example 1 1 part of dipalmityl phosphate, 3.0 parts of a vinyl chloride-vinyl acetate copolymer (UIHH manufactured by UCC; vinyl chloride 86 / vinyl acetate 14), and dissolved in 50 parts of tetrahydrofuran by heating, and then 30 parts of tetrahydrofuran is recovered by distillation. Concentrate this concentrated solution to 7.5 μm
Apply on a thick polyester film with a wire bar,
A recording sheet was prepared by drying in an oven at 135 to 140 ° C. and providing a heat-sensitive recording layer having a thickness of about 15 μm.

Example 2 1 part of distearyl phosphate, 3.0 parts of a vinyl chloride-vinyl acetate copolymer (same as in Example 1), and heated and dissolved in 80 parts of tetrahydrofuran, and then 60 parts of tetrahydrofuran was recovered by distillation. A recording sheet was prepared in the same manner as in Example 1.

Example 3 1 part of stearyl acid phosphate, vinyl chloride
A recording sheet was prepared in the same manner as in Example 1 except that a solution containing 3.0 parts of a vinyl acetate copolymer (same as in Example 1) and 20 parts of tetrahydrofuran was used.

Example 4 A recording sheet was prepared in the same manner as in Example 2 using 0.5 parts of dibephenyl phosphate, 0.5 part of tristearyl phosphite, and 3.0 parts of a vinyl chloride-vinyl acetate copolymer (the same as in Example 1).

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.

Example 5 A recording sheet was prepared in the same manner as in Example 3, except that 0.5 parts of behenic acid and 0.5 of dipalmityl phosphate were used.

The recording sheets obtained as described above (Examples 1 to 5,
Comparative Examples 1 and 2) All were obtained as opaque and opaque sheets.

These recording sheets were heated from 50 ° C. to 120 ° C. in steps of 5 ° C. for 30 seconds in an open state, cooled to room temperature, and the reflection density was measured with a Magbeth densitometer RD514. At this time, the temperature at which the reflection density exceeded 1.0 was defined as the transparency temperature, and the range and width were shown. Table 1 shows the results of the maximum transparent density and the maximum cloudiness density.

[Effects of the Invention] As described above, the discovery of long-chain alkyl phosphates as an organic low-molecular substance improves the recording contrast of a recording material and also makes the transparent recording temperature range practically sufficient. This makes it possible to provide a general-purpose novel heat-sensitive reversible recording material.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for explaining a transparent turbidity phenomenon depending on the temperature of a thermosensitive reversible recording material.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-178079 (JP, A) JP-A-63-179789 (JP, A) JP-A-1-103486 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. A heat-sensitive reversible recording material comprising at least one phosphoric ester represented by the following general formulas (1) and / or (2) and a polymer resin. (RO) _n P (O) (OH) _3-n (1) (wherein, R represents a straight-chain alkyl group having 8 to 28 carbon atoms, and n represents 1 or 2) (RO) ₃ P ( 2) (wherein R represents a straight-chain alkyl group having 8 to 28 carbon atoms)