JPS63179795A - Reversible thermal recording material - Google Patents

Abstract

PURPOSE:To uniformize the surface of a thermal recording layer and make it possible to form a clear image with high contrast, by incorporating a silicone oil into the thermal recording layer. CONSTITUTION:A silicone oil is incorporated in a thermal recording layer of a reversible thermal recording material, which layer comprises a resin matrix and an organic low molecular weight substance dispersed in the resin matrix as main constituents and the transparency of which can be reversibly varied depending on temperature. The resin matrix is preferably constituted of a resin having favorable transparency, being mechanically stable and having a favorable film-forming property, such as polyvinyl chloride. The organic low molecular weight substance is preferably an alkane diol or the like which has a melting point of 30-200 deg.C, particularly, 50-150 deg.C. The silicone oil, such as an amino- modified polysiloxane, is effective for forming a uniform coated film of the thermal recording layer upon evaporation of a solvent when the layer is provided. The amount of the silicone oil used is preferably about 0.001-1pt.wt. per 100pts.wt. of the organic low molecular weight substance.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a reversible thermosensitive recording material for recording and erasing by utilizing the reversible change in transparency of a thermosensitive layer depending on temperature. ' A heat-sensitive recording material capable of reversible recording and erasing is provided on a support with a heat-sensitive layer in which an organic low-molecular substance such as a higher fatty acid is dispersed in a resin such as polyester or polyamide, as disclosed in, for example, JP-A No. No. 54-119377, No. 55-1514
It is known as No. 198.

Recording with this type of recording material, that is, image formation and erasing, utilizes the change in transparency of the heat-sensitive layer depending on the temperature.

When such a reversible heat-sensitive recording material is made by a coating method, that is, by coating a heat-sensitive layer forming liquid on a support and drying it to form a heat-sensitive layer, unevenness generally called yuzu skin occurs on the surface of the heat-sensitive layer. Transparency of transparent parts tends to decrease, and therefore, when a recorded material with image or non-image areas with such low transparency is projected with an overhead projector as a projection original, the non-image area becomes an image with reduced brightness. Moreover, when a colored sheet is disposed on the back side of a recorded matter and viewed as a reflective image, there is a drawback that the contrast of the recorded image is reduced.

Another object of the present invention is to provide a reversible thermosensitive recording material that can form a clear image with high contrast by making the surface of the thermosensitive layer uniform.

J-11 The reversible thermosensitive recording material of the present invention mainly consists of a resin matrix and an organic low-molecular substance dispersed in the resin matrix, and its transparency changes reversibly depending on the temperature. A reversible heat-sensitive recording material having a heat-sensitive layer is characterized in that the heat-sensitive layer further contains silicone oil.

The recording (and erasing) principle of the recording material of the present invention utilizes the change in transparency of the heat-sensitive M (or sheet) depending on the temperature, and this will be explained with reference to the drawings.

In FIG. 1, the heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material is, for example, T
It is cloudy and opaque at room temperature above 0. This is T□〜T
When heated to a temperature between 2 and 3, it becomes transparent, and in this state T
. It remains transparent even after returning to room temperature below. 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 18 degrees and then cooled to room temperature, that is, a temperature of T0 or higher, it can assume a state between transparent and opaque.

Also, the above-mentioned material that became transparent at room temperature is T again.

If it is heated to a temperature above and returned to room temperature, it will return to a cloudy, opaque state. That is, it can take both opaque and transparent forms and an intermediate state between them at room temperature.

Therefore, the entire heat-sensitive layer is heated to a temperature between T2 and T2 using a hot roll, then cooled to room temperature above T0 to make it transparent, and then heated imagewise to a temperature above T1 using a thermal head etc. to remove that part. Once opaque, a white image is formed in this layer. Note that if a colored sheet is placed under the heat-sensitive layer having such a white image, this image can be recognized as a white image against the background of the color of the colored sheet. On the other hand, after heating the entire partially opaque heat-sensitive layer to a temperature of 13 or higher, T0
After the whole is returned to room temperature and made cloudy and opaque, it is heated in an imagewise manner to a temperature of 11 to 12 using a thermal head or the like to make that part transparent, thereby forming a transparent image with a white background. Note that if a colored sheet is placed under a heat-sensitive layer having such a transparent image, this image can be recognized as an image of the color of the colored sheet against a white background.

The above-described recording and erasing operations on the heat-sensitive layer can be repeated 104 times or more.

In order to make the heat-sensitive recording material of the present invention, generally (1) a solution containing the three components of a resin base material, an organic low-molecular substance, and a silicone oil, or a solution of the resin base material (the solvent does not dissolve the organic low-molecular substance); A dispersion liquid obtained by dispersing an organic low-molecular substance in the form of fine particles and dissolving or dispersing silicone oil in this is applied onto a support such as paper, plastic film, glass plate, metal plate, etc. (or impregnation) to form a heat-sensitive layer; or (2) knead the above three components in the presence of a solvent, heating if necessary, form this into a sheet, and form the heat-sensitive layer itself into a heat-sensitive sheet. It is created by Tetrahydrofuran is used as a solvent.

Examples include methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, and benzene. Incidentally, not only when a dispersion is used, but also when a solution or a mixed material is used, the organic low-molecular substance is precipitated as fine particles in the resulting heat-sensitive layer or heat-sensitive sheet.

Exist in a dispersed state.

The resin base material used in the heat-sensitive layer forms a layer in which organic low-molecular substances are uniformly dispersed.

It is a material that affects transparency at maximum transparency.

Therefore, the base material has good transparency and is mechanically stable.

In addition, a resin with good film-forming properties is preferable. Such resins 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. Vinyl chloride copolymers such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer; polyester; polyamide; polyacrylate or polymethacrylate or acrylate. Examples include tol methacrylate copolymer and silicone resin. These may be used alone or in combination of two or more.

On the other hand, the organic low-molecular substance is at a temperature of T0 to T as shown in FIG.

It may be selected appropriately depending on the melting point 3.
Examples of such organic low-molecular substances, which are preferably about 0 to 200°C, particularly about 50 to 150°C, include alkanols;
Alkanediol; halogenalkanol or halogenalkanediol; alkylamine; alkane; alkene; alkyne; halogenalkane; Amide.

or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides, or ammonium salts; allyl carboxylic acids or their esters, amides, or ammonium salts = halogen allyl carboxylic acids or their esters, amides, or ammonium salts;
Thioalcohols; thiocarboxylic acids or their esters, amines, or ammonium salts; carboxylic acid esters of thioalcohols, and the like. These may be used alone or in a mixture of two or more. The carbon number of these compounds is 10 to 60, preferably 10 to 38. Especially 10-3
0 is preferred. The alcohol group moiety in the ester may be saturated or unsaturated, and may be substituted with halogen. In any case, the organic low-molecular substance contains at least one of oxygen, nitrogen, sulfur, and halogen in the molecule, for example, -011,-COOHl-CONI+.

-COOR, -NH, -NH2, -5-1-S -5-
A compound containing 1-0-, halogen, etc. is preferable.

More specifically, these compounds include higher fatty acids such as lauric acid, dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, arachidic acid, and oleic acid; methyl stearate, and tetradecyl stearate. , octadecyl stearate, octadecyl laurate, tetradecyl palmitate.

Ester of higher fatty acids such as tocosyl behenate; C-GH
,3-0-C,GH,3,C1,H,,-5-C1,H
l.

C,,H3,-5-CIIIH3,,C1□H25-3
-C1□H2,.

C1,H,,-5-C1,H3,,C1□H2,-5-
5-C□, H, .

CH2・CH2・0COC11H,,,CH,・CH2
・○COC□7H.

CH3 CH2・CH2・C00(CH2)□,・CH-CH2
・CH.

○CH2・CH2・COO(CH-)1S・CH-CH,
・CHCH.

CH2・CH2・COOC1□H2,, CH2・CH2
・C00C1, Hl.

CH.

"CH2・CH2・COO(CH2)zs・CH-CH2
・CH.

CH2・CH2・COO(CL)zs・CH-CH2・
CH3CH.

CH2・CH2・C00C,,H,,.

CH.

There are ethers and thioethers such as Among these, in the present invention, higher fatty acids, particularly higher fatty acids having 16 or more carbon atoms such as palmitic acid, stearic acid, behenic acid, and lignoceric acid are preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.

Next, the silicone oil used for the heat-sensitive layer is effective in forming a uniform coating film of the heat-sensitive layer after the solvent evaporates when the heat-sensitive layer is formed by the method described above.As the silicone oil, dimethylpolysiloxane, Methylphenylpolysiloxane, methylhydrodiene polysiloxane, alkyl-modified polysiloxane, amino-modified polysiloxane,
Examples include carboxyl-modified polysiloxane and alcohol-modified polysiloxane.

The ratio of the organic low-molecular substance to the resin base material in the heat-sensitive layer is preferably about 1:0.5 to 1:16 by weight. If the ratio of the resin base material is less than this, the organic low-molecular substance is On the other hand, if the amount exceeds this, it becomes difficult to form a film retained in the base material.

Since the amount of organic low molecular weight substance is small, it is difficult to make it opaque.

On the other hand, the amount of silicone oil used is 10% of the organic low molecular weight substance.
If the amount used is less than 0.001 part by weight, it will be difficult to maintain a uniform surface of the heat-sensitive layer, whereas if it exceeds this amount, the mechanical strength of the heat-sensitive layer will deteriorate. Below, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages are based on weight.

Example 1 Behenic acid on a 75 μm thick polyester film
A white opaque reversible heat-sensitive recording material was prepared by applying a solution consisting of 10 parts and 150 parts of tetrahydrofuran using a wire bar and drying to form a heat-sensitive layer with a thickness of 15 μm.

Example 2 A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that methyl silicone oil (Shin-Etsu Silicone Co., Ltd. IKF-69) was used instead of methyl phenyl silicone oil.

Example 3 Methylphenyl silicone oil was replaced with alcohol-modified silicone oil (SF8428 manufactured by Tou Silicone Co., Ltd.)
) A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that

Example 4 A reversible thermosensitive recording material was prepared in the same manner as in Example 1, except that amino-modified silicone oil (SF8417, manufactured by Tomu Silicone Co., Ltd.) was used as the methylphenyl silicone oil.

Comparative Example A reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that the methylphenyl silicone oil was omitted.

Next, each recording material was heated at 70° C. and 90° C. for 1 minute, then allowed to cool to room temperature, placed on black drawing paper, and the reflection density was measured using a Macbeth densitometer RD514. Further, the recording material heated at 70° C. to make it transparent was applied to an overhead projector, and the uniformity was visually judged based on the brightness. The results are shown in the table below.

Effects Since the reversible heat-sensitive recording material of the present invention contains silicone oil, there is no unevenness in the heat-sensitive layer, such as orange skin, and therefore clearer images with higher contrast than before can be formed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the recording and erasing principle in the heat-sensitive layer of the reversible heat-sensitive recording material of the present invention. Patent applicant Ricoh Co., Ltd. Agent Patent attorney Sa 1) Morio; (Ji, i:, -

Claims (1)

[Claims] 1. In a reversible thermosensitive recording material that has a thermosensitive layer whose main components are a resin matrix and an organic low-molecular substance dispersed in the resin matrix and whose transparency changes reversibly depending on the temperature,
A reversible heat-sensitive recording material characterized in that the heat-sensitive layer further contains silicone oil.