JPH0281672A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To increase adhesiveness with a heating device such as a thermal head and also thermal sensitivity to form a sharp image by providing a sticking prevention layer consisting of specific tri(polyoxyethylenealkyl ether)ester phosphate on a thermal recording layer. CONSTITUTION:On a support, a thermosensitive layer is provided which consists mainly of resin, a basic material, and an organic low-molecular substance dispersed in the resin and has transparency which changes reversibly depending on temperature. In addition, on the thermosensitive layer, a sticking prevention layer is provided which consists of tri(polyoxyethylenealkyl ether)ester phosphate expressed by the formula. A sheet for overhead projector can be prepared easily by using this reversible laminated thermosensitive member. Furthermore, an overcoat layer has superior slipperiness with a thermal head and also high compatibility with water or oily marker ink in terms of wettability. That is, the sticking prevention layer consists mainly of tri(polyoxyethylenealkyl ether) ester phosphate. In the formula, R is either an alkyl group or an alkylaryl group.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a reversible thermosensitive recording material that performs recording and erasing by utilizing a reversible change in transparency of a thermosensitive member depending on temperature.

[Prior art]

As a thermosensitive recording material that can be reversibly recorded and erased,
It is known that a heat-sensitive layer is provided on a support by dispersing an organic low-molecular substance such as a higher alcohol or a higher fatty acid in a resin such as polyester or polyamide (Japanese Unexamined Patent Application Publication No. 1983-1982).
119377, Japanese Unexamined Patent Publication No. 55-154198), recording using such recording materials, that is, image formation and erasing, utilizes changes in transparency due to temperature of the heat-sensitive layer.

However, in conventional reversible thermosensitive recording materials, when forming an image by heating the surface with a thermal head, etc., the friction with the heating means is large, so sufficient adhesion cannot be achieved, resulting in a decrease in thermal sensitivity. As a result of unevenness on the surface,
It was difficult to form clear images. Furthermore, in severe cases, the reversible thermosensitive recording material may be fused to the heat generating portion, causing the thermal head to stop running.

In order to avoid such inconvenience, the applicant first
(a) forming an overcoat layer mainly composed of silicone rubber or silicone resin on the heat-sensitive layer (Japanese Patent Application No. 62-55650); or (b) forming an overcoat layer mainly composed of polysiloxane graft polymer. A reversible thermosensitive recording material was proposed in which the friction on one surface was reduced by forming layers (Japanese Patent Application No. 152,550/1982).

However, as a result of such a conventional overcoat layer having too good releasability, (a) ink is completely repelled with a water-based marker, resulting in poor addition.

(b) Even with oil-based markers, the ink tends to be repelled,
Even if additions can be made, the ink is not applied uniformly, which is a disadvantage when viewed as an overhead projector (○HP).

〔the purpose〕

The present invention is a reversible thermosensitive recording material that can form a clear image by improving thermal sensitivity by improving adhesion with the heating means when forming an image by heating with a thermal head, etc. The object of the present invention is to provide a reversible heat-sensitive recording material that has improved writeability with both water-based and oil-based markers, taking into account its use as a paper marker.

〔composition〕

As a result of intensive research to achieve the above object, the present inventor has discovered that the main component is a resin base material on a support and an organic low-molecular substance dispersed in this resin base material, and the transparency is reversible depending on the temperature. A heat-sensitive layer that changes to is provided, and further thereon, the following general formula is provided.

(R = alkyl group or alkylaryl group, n = integer of 1 or more) It has been found that the above object can be achieved by providing a recording material.

That is, the tri(
The overcoat layer made of polyoxyethylene alkyl ether (phosphoric acid ester) not only has smoothness against heating means such as a thermal head, but also has improved wettability against water-based and oil-based marker inks.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The recording principle of the recording material of the present invention utilizes the change in transparency due to temperature of the heat-sensitive layer, and is well known in itself, but will be described again as we proceed with the explanation of the present invention. Since this seems more convenient, I will explain this recording principle using a drawing (Fig. 1).

In the drawings, the heat-sensitive layer is, for example, in a cloudy, opaque state at room temperature of T0 or higher. When it is heated to a temperature between 10 and 72 degrees, it becomes transparent, and even if it is returned to room temperature below T, it remains transparent.

Further heating to a temperature of T1 or higher results in a translucent state intermediate between maximum transparency and maximum opacity.

Next, when this temperature is lowered, the liquid returns to its initial cloudy and opaque state without becoming transparent again.

In addition, when this opaque state is heated to a temperature of 10 to 11 and then cooled to room temperature, that is, a temperature of T0 or higher, it can assume a state between transparent and opaque. Moreover, if the material that becomes transparent at room temperature is heated again to a temperature of 13 or higher and returned to room temperature, it will return to a cloudy, opaque state.

That is, it can take both opaque and transparent forms, as well as an intermediate state between them, at room temperature.

Therefore, for example, the entire layered heat-sensitive member (a heat-sensitive layer provided on a support or a heat-sensitive sheet) having a heat-sensitive layer with such properties is heated to a temperature of 10 to 72°C, and then cooled to room temperature of T0 or higher. A white image is formed by partially heating this to a temperature of T1 or higher using a thermal head or the like to make that part opaque. If a layered colored member is placed on the back side of the layered heat-sensitive member having the white image, this image can be recognized as a white image against the background of the color of the colored member.

On the other hand, after heating the entire layered heat-sensitive member to a temperature above T1, returning it to room temperature below TIl and making it cloudy and opaque, partially heated to a temperature between 11 and 72 with a thermal head etc. to make the part transparent. A transparent image is then formed on the white surface.

If a colored member is placed on the back side of a layered heat-sensitive member having such a transparent image, this image can be recognized as an image of the color of the colored member against a white background.

Recording and erasing on the layered heat-sensitive member as described above can be repeated at least 104 times.

If the image obtained in this way is projected onto a screen using an overhead projector (○HP), for example,
The transparent part transmits light, but the cloudy part scatters light and is opaque, so that a positive or negative projected image can be formed on the screen. In other words, by using a reversible layered heat-sensitive member, it is possible to
You can add OH to N mail without creating P sheets or OHP sheets using a word processor or thermal transfer ribbon.
P sheets can be created.

By the way, as mentioned earlier, when the heat-sensitive layer (reversible heat-sensitive recording layer) comes into direct contact with the thermal head and is heated, the heat-sensitive layer will melt and stick to the thermal head, and in severe cases, the running of the thermal head will be interrupted. This causes defects and sometimes causes the thermal head to stop running. Therefore, an overcoat layer is generally formed on the heat-sensitive layer to prevent such problems. As mentioned above, various defects have been found in conventional overcoat layers.

In the recording material of the present invention, as this overcoat layer,
One that has both slipperiness against thermal heads and improved wettability for water-based and oil-based marker inks, that is, a stick-preventing layer containing tri(polyoxyethylene alkyl ether) phosphate as the main component. There is.

The thus obtained reversible thermosensitive recording material can have a significantly reduced coefficient of friction on its surface. By the way, when heating and forming an image using a line head among thermal heads, the recording material is sandwiched between the head and a platen roller, and is pressed by the head and moves in accordance with the movement of the platen roller. The position of the head is moved to selectively heat each line and form an image.5 At that time, the reversible thermosensitive recording material of the present invention
As mentioned above, the friction coefficient of the surface is very small, so it is very smooth even when it moves while being pressed by the head, so there is little room for air to enter between it and the head, which means that it has good adhesion with the head. As a result, the heat transfer from the thermal head to the recording material, that is, the thermal sensitivity is improved.

In order to produce the reversible thermosensitive recording material of the present invention, - Generally, a thermosensitive layer (reversible thermosensitive recording layer) is formed on a support by the following method.
After forming, a method of forming a stick prevention layer is adopted, but in step (1), a self-supporting heat-sensitive sheet may be formed from the heat-sensitive layer material by a normal film-forming method without using a particular support. .

(1) An organic low-molecular substance is dispersed in the form of fine particles in a solution in which a resin base material and an organic low-molecular substance are dissolved, or in a solution of the resin base material (use a solvent that does not dissolve the organic low-molecular substance). The dispersion is made into plastic films and glass plates.

Forms a heat-sensitive layer by coating and drying on a support such as a metal plate.
Next.

(2) A solution in which tri(polyoxyethylene alkyl ether) phosphate is dissolved or dispersed is applied thereon and dried to form a stick prevention layer.

As the solvent for forming the heat-sensitive layer, various solvents can be used depending on the type of organic low-molecular substance and resin base material. For example, tetrahydrofuran, methyl ethyl ketone,
Methyl isobutyl ketone, chloroform, carbon tetrachloride,
Examples include organic solvents such as ethanol, toluene, xylene, and benzene.

In the heat-sensitive layer thus formed, the organic low-molecular substance exists in a dispersed state as fine particles in the resin base material.

The resin base material used for the heat-sensitive layer is a material that forms a film or sheet in which a low-molecular-weight organic substance is uniformly dispersed and holds, and also influences the transparency at maximum transparency. For this reason, the resin base material is preferably a resin with good transparency, mechanical stability, and good film-forming properties. Examples of such resins include polyvinyl chloride; vinyl chloride-vinyl acetate copolymer, and vinyl chloride-vinyl acetate copolymer. Vinyl chloride copolymers such as vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride acrylate copolymer; vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile Vinylidene chloride copolymers such as 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 T and ~T shown in FIG.
Examples of such organic low-molecular substances, which are preferably about 00°C, especially about 50 to 150°C, include alkanols; alkanediols; halogen alkanols or halogen alkanediols; alkylamines; alkanes; alkenes;
Alkyne; halogen alkane; halogen alkene.

Halogenalkyne; cycloalkane; cycloalkene;
Cycloalkynes; Saturated or unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; Saturated or unsaturated halogenated fatty acids or their esters, amides or ammonium salts; Allylcarboxylic acids or their esters, amides or ammonium salts; Halogen allylcarboxylic acids or their esters,
Examples include amide or ammonium salt; thioalcohol; thiocarboxylic acid or ester thereof, amine or ammonium salt; carboxylic acid ester of thioalcohol. These may be used alone or in a mixture of two or more. The carbon number of these compounds is 10-60°, preferably 10-38, particularly preferably 10-30. The alcohol group moiety in the ester may be saturated or unsaturated, or may be halogen-substituted. In any case, organic low-molecular substances contain oxygen, nitrogen,
At least one of sulfur and halogen, e.g. -OH, -
C0OH, -CONH, -COOR (R is 10nH, n
+1; n=1 to 20), -NH-, -NH,, -
Preferably, it is a compound containing 8--SS--, halogen, or the like.

More specifically, these compounds include lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid,
Stearic acid, behenic acid, nonadecanoic acid, arachidic acid,
Higher fatty acids such as oleic acid; esters of higher fatty acids such as methyl stearate, tetradecyl stearate, octadecyl stearate, octadecyl laurate, tetradecyl palmitate, dodecyl behenate; C1j133-0-Cxsth3. Ctsllii-5
-Ctc)Ixi.

C,,H,7-5-C□H□? , cxzszs-s-c
m2H25+C15)I, 5-3-CtsHis, c
1211ts-s-s-clJis.

CH3 CH, ・C)l, ・0COC1, H2sCH, ・C8
,・cocol. H37 CH,・CH,・coo(cur)1s・C)I-CH
,・CHlSteCH,・CH,・cco (CHz)1s・CH−C
)I,・CH1CH.

There are ethers and thioethers such as

The ratio of the organic low molecular weight substance to the resin base material in the heat-sensitive layer is preferably about 1:0.5 to 1:1s by weight, and if the ratio of the resin base material is less than this.

It becomes difficult to form a film in which the organic low-molecular substance is held in the resin base material, and on the other hand, if the amount exceeds this, it becomes difficult to make it opaque because the amount of the organic low-molecular substance is small.

The anti-stick layer used in the present invention is made of the above-mentioned tri(polyoxyethylene alkyl ether) phosphate (hereinafter abbreviated as "phosphate triester").This phosphate triester is a known substance. and
In the phosphoric acid triester represented by the above general formula used in the present invention, which is a viscous and non-volatile liquid at room temperature, R representing an alkyl group or an alkylphenyl group usually has 8 to 24 carbon atoms. Further, n, which indicates the number of moles of ethylene oxide added, is an integer of 1 or more, and those in the range of 1 to 20 are usually high in solubility and easy to use.

The phosphoric acid triester used in the present invention exhibits a high stick prevention effect even with a very small amount of adhesion, and the amount of adhesion is 0.01 to 0.5 g/m'', preferably 0.01 to 0.5 g/m'' to the recording layer. 05 to 0.3 g/m" is sufficient. The phosphoric acid triester layer can be formed on the recording layer by dissolving the phosphoric acid triester in an appropriate solvent, such as an organic solvent such as ethanol, methanol, ethyl acetate, or methyl ethyl ketone, and applying the solution on the recording layer and drying it. It can be carried out. In this case, the concentration of phosphoric acid triester in the solvent is about 0.1 to 5% by weight, preferably about 0.5 to 3% by weight, and the drying conditions are 70 to 100°C and lO
~30 seconds is sufficient.

Unlike ordinary anti-stick agents, the phosphoric acid triester used in the present invention is liquid at room temperature, so even if it adheres to the thermal head, it will not deteriorate the recording performance of the thermal head.

That is, since cleaning of the thermal head is almost unnecessary, running performance is extremely good.

In addition, the phosphoric acid triester of the present invention has an antistatic effect, so it prevents dust and dust from adhering to the product surface due to static electricity, and also avoids adhesion between products due to static electricity. Further, the phosphoric acid triester of the present invention can be applied by conventional coating and drying operations. Furthermore, since there is no need to use it together with a binder resin, a decrease in the heat sensitivity of the product is prevented, and the stick residue of the binder resin itself does not adhere to the thermal head.

Representative examples of the phosphoric acid triester represented by the above general formula used in the present invention are listed below.

(1) Tri(polyoxyethylene) lauryl ether phosphate (n = 2) Ct-H
-s O(CHzCHtO)z\ Cz-Hzs o-(cH, cH, ○), -p=.

/ cl, H,, -〇-(CH, CH, O).

(2) Tri(polyoxyethylene) lauryl ether phosphate (n=4) ChxH*
s 0-(CHzCHzO)4\ C,, H,, -0-(CH, CH, O), -P=0/ clxHtx 0-(cH, CH, O).

(3) Tri(polyoxyethylene) lauryl ether phosphate (n=8) Cx s
Hz −-0-(CH* CHz O)s\ (4) Tri(polyoxyethylene) stearyl ether phosphate (n: 15) C1°H3,-0-(CH2CH,O),.

＼ (5) Tri(polyoxyethylene) nonylphenyl ether phosphate ester (n:10)C
, Hl, -■-〇-(CH, CH, ○),.

\Next, "part" and "part" here indicate examples and comparative examples.
%" are based on weight.

Example 1 Behenic acid was applied onto a 75 μm thick polyester film.
4 parts stearyl stearate
1 part tetrahydrofuran
A solution consisting of 82 parts was applied with a wire bar and dried by heating to form a heat-sensitive recording layer having a thickness of about 15 μm.

On this heat-sensitive recording layer, a stick-prevention layer liquid consisting of 995 parts of ethanol was applied in an adhesion amount of 0.01 g/l112 to provide a stick-preventing layer, thereby producing a reversible heat-sensitive recording material.

Example 2 Except that a stick prevention layer was formed by applying a stick prevention layer liquid consisting of 995 parts of ethanol so that the adhesion amount was 0.02 g/ff+2,
A reversible thermosensitive recording material was prepared in exactly the same manner as in Example 1.

Example 3 Except that a stick prevention layer was formed by applying a stick prevention layer solution consisting of 995 parts of ethanol to a coating amount of 0.01 g/l112.
A reversible thermosensitive recording material was prepared in exactly the same manner as in Example 1.

Example 4 Except that a stick prevention layer was formed by applying a stick prevention layer solution consisting of 995 parts of ethanol to a coating amount of 0.02 g/l112.
A reversible thermosensitive recording material was prepared in exactly the same manner as in Example 1.

Example 5 A reversible thermosensitive recording material was prepared in exactly the same manner as in Example 1, except that a stick prevention layer was formed by applying a stick prevention layer liquid consisting of 995 parts of ethanol to a coating amount of 0.02 g/m2. It was created.

Comparative Example 1 After uniformly dissolving a composition consisting of a catalyst (5RX212 manufactured by Toshi Silicone Co., Ltd.) 0.1 part and 89.9 parts of toluene, it was coated with a wire bar and dried.
A reversible thermosensitive recording material was prepared in exactly the same manner as in Example 1, except that a stick prevention layer made of silicone rubber with a thickness of 0.5 μm was provided.

Comparative Example 2 A composition consisting of a catalyst (PL-8 manufactured by Shin-Etsu Silicone Co., Ltd.) 0.1 part and 89.9 parts of toluene was applied and dried, and a stick prevention layer made of silicone rubber with a thickness of 0.1 μm was provided. A reversible thermosensitive recording material was prepared in exactly the same manner as in Example 1.

The seven types of samples prepared as described above were examined for addition properties with water-based and oil-based inks, staking resistance, etc. The results are shown below.

(Left below) ○00. Good Δ00. Possible ×60. Impossible test method: 1) Addition property: Use OHP marker sold by Ricoh Educational Equipment Co., Ltd. 2) Stick resistance: Use Ricoh Co., Ltd. thermal head (Ricoh Co., Ltd. CUVAX MC50) to evaluate iterability [Efficacy] Silicone-based mold release agents such as those in the comparative example have good stick resistance (stick prevention effect) because they have good slipperiness against the line head, but the surface energy level is too low, making it difficult to write with OHP markers. On the other hand, the material of the present invention not only has good stick resistance but also has good retouchability with water-based and oil-based pens.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the recording and erasing principle of the reversible thermosensitive recording material of the present invention. Patent applicant Rico Co., Ltd. −

Claims (1)

[Scope of Claims] 1. A thermosensitive recording layer is provided on a support, the main component being a resin base material and an organic low-molecular substance dispersed in the resin base material, and the transparency of which changes reversibly depending on the temperature. Furthermore, there are the following general formulas, ▲mathematical formulas, chemical formulas, tables, etc.▼ (R=alkyl group or alkylaryl group, n=an integer of 1 or more) A reversible thermosensitive recording material characterized by being provided with an anti-stick layer made of phosphoric acid ester.