JP2534248B2 - Reversible thermosensitive recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reversible thermosensitive recording material for performing image formation and erasing by utilizing reversible transparency change of a thermosensitive layer with temperature.

RELATED ART JP-A-54-119377 and JP-A-55-154198 disclose a reversible thermosensitive recording material having a thermosensitive layer in which an organic low molecular substance such as a higher fatty acid is dispersed in a resin matrix such as a vinyl chloride resin. Is proposed. Image formation and erasure with this type of recording material utilize reversible transparency change of the heat-sensitive layer depending on temperature, but in the case of conventional reversible heat-sensitive recording material, when an image is formed with a minute energy of a thermal head or the like. Although it is possible to form a cloudy image with the heat-sensitive layer being transparent, it is difficult to form a transparent image with the heat-sensitive layer being cloudy.

OBJECT The object of the present invention is to provide a reversible thermosensitive recording material capable of forming an image, particularly a transparent image on a white background, even with a small amount of energy such as that of a thermal head, and therefore always obtaining a high contrast image.

Structure The reversible thermosensitive recording material of the present invention comprises a resin base material and an organic low molecular weight substance dispersed in the resin base material as main components, and has a reversible thermosensitive layer whose transparency reversibly changes depending on temperature. In thermosensitive recording materials, the boiling point is 200 ℃ in the thermosensitive layer.
It is characterized by containing at least one kind of the above high boiling point solvent and at least one kind of the following additive group.

Additive group: polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide, lower olefin oxide addition of oil or polypropylene glycol Acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; higher fatty acid, aromatic carboxylic acid, higher aliphatic sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester or phosphoric acid mono- or di-ester Ca, Ba, or Mg; low-sulfated oil; poly-long-chain alkyl acrylate; acrylic oligomer; poly-long-chain alkyl methacrylate; long-chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer Olef In-maleic anhydride copolymer.

The present inventor, in the conventional reversible thermosensitive recording material, when the thermosensitive layer contains a high boiling point solvent having a boiling point of 200 ° C. or higher and the above-mentioned additive, the crystal size of the organic low molecular weight substance is reduced by a small energy. However, they have found that the desired object can be achieved by controlling the temperature, and have reached the present invention.

The recording (and erasing) principle of the recording material of the present invention utilizes a change in transparency of the heat-sensitive layer (or sheet) depending on the temperature.
This will be described with reference to the drawings. In FIG. 1, and the resin base material, the heat-sensitive layer mainly composed of a resin matrix organic low-molecular material dispersed in is in the cloudy opaque state at room temperature, for example T ₀ or less. When this is heated to a temperature between T _{1 and} T ₂ , it becomes transparent, and in this state, it remains transparent even when it is returned to room temperature of T ₀ or lower. Further heating to a temperature of T ₃ or higher results in a semi-transparent state intermediate between maximum transparency and maximum opacity. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. In addition, this opaque state
After being heated to a temperature between T _{0 and} T ₁ , when cooled to room temperature, that is, a temperature of T ₀ or less, a state between transparent and opaque can be obtained. Also, the one that became transparent at room temperature again
When it is heated to a temperature of T ₃ or higher and returned to room temperature, it becomes cloudy and opaque again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be obtained.

Thus after heating the entire heat-sensitive layer to a temperature between T ₁ through T ₂ by heat roll or the like, and transparent to cool to room temperature T ₀ or less, then it is heated to T ₃ or more image-wise to a thermal head or the like If that part is made opaque, a white image is formed in this layer. If a colored sheet is arranged under the heat-sensitive layer having such a white image, this image can be recognized as a white image with the color of the colored sheet as a background. On the other hand, after heating the entire partially opaque heat-sensitive layer to a temperature of T ₃ or higher, the temperature is returned to room temperature of T ₀ or lower to make the whole cloudy and opaque, and then a thermal head or the like is used to image-form T ₁ to T. If you heat it to a temperature between ₂ and make that part transparent, a transparent image is formed against a white background. If a colored sheet is arranged under the 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 recording and erasing operations on the heat sensitive layer as described above can be repeated 10 ⁴ times or more.

In order to prepare the heat-sensitive recording material of the present invention, generally, (1) a solution in which four components of a resin base material, an organic low molecular weight substance, a high boiling point solvent and the additive are dissolved, or a solution of a resin base material (the solvent is an organic low A low-molecular-weight organic substance is dispersed in a fine particle form, and a high-boiling solvent and additives are dissolved in the dispersion liquid to prepare paper, plastic film, glass plate, metal plate, etc. Or heat-sensitive layer is formed by coating (or impregnating) on the support of (2) above.
It is prepared by kneading the components in the presence or absence of a solvent, while heating them if necessary, and shaping the mixture into a sheet to prepare a heat-sensitive sheet. Examples of the solvent include tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like. The organic low-molecular substance is precipitated as fine particles in the heat-sensitive layer or heat-sensitive sheet obtained not only when a dispersion is used but also when a solution or kneaded material 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 has an effect on the transparency at maximum transparency. For this reason, the base material is preferably a resin having good transparency, mechanical stability, and good film forming properties. Examples of such resin include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer. Vinyl chloride-based copolymers such as; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylates Methacrylate copolymers, silicone resins, etc. may be mentioned. These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular substance may be appropriately selected in accordance with the selection of the temperatures T _{0 to} T ₃ in FIG.
C., especially about 50 to 150.degree. C. are preferred. Such organic low-molecular substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; saturated or Unsaturated mono- or dicarboxylic acids or their esters, amides, or ammonium salts; Saturated or unsaturated halogen fatty acids or their esters, amides, or ammonium salts; Allylcarboxylic acids or their esters, amides, or ammonium salts; Acids or their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts Carboxylic acid esters of thio alcohol. These may be used alone or in admixture of two or more. The carbon number of these compounds is preferably 10 to 60, preferably 10 to 38, and particularly preferably 10 to 30. The alcohol group in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance is at least one kind of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH,-.
_{COOR, -NH, -NH 2, -S} -, - S-S -, - O-, is preferably a compound containing a halogen and 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, docosyl behenate; C ₁₆ H ₃₃ —O
−C ₁₆ H ₃₃ , C ₁₆ H ₃₃ −S−C ₁₆ H ₃₃ , C ₁₈ H ₃₇ −S−C ₁₈ H ₃₇ , C ₁₂
H ₂₅ -S-C ₁₂ H ₂₅ , C ₁₉ H ₃₉ -S-C ₁₉ H ₃₉ , C ₁₂ H ₂₅ -SS
−C ₁₂ H ₂₅ , Etc., such as ether or thioether. Of these, 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 in the present invention, and higher fatty acids having 16 to 24 carbon atoms are more preferred.

Next, a high-boiling point solvent having a boiling point of 200 ° C. or higher is a material that contributes to the formation of a transparent image in cooperation with the above-mentioned additives when heated by a small amount of energy, usually in a heat-sensitive layer or a heat-sensitive sheet,
It exists in a compatible state with the organic low molecular weight substance or the resin base material. Specific examples of such high boiling point solvents include tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate and phthalic acid. Diheptyl, di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzene phthalate, dibutyl adipate, di-n-hexyl adipate, adipic acid Di-2-ethylhexyl, alkyl adipate 610, di-2-ethylhexyl azelate, dibutyl sebacate, di-2 sebacate
-Ethylhexyl, diethylene glycol dibenzoate, triethylene glycol di-2-ethylbutyrate, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate, tributyl acetylcitrate and the like and mixtures thereof.

Further, the additives as described above are usually present in the heat-sensitive layer or the heat-sensitive sheet in a compatible state with the organic low-molecular weight substance or the resin base material, like the high boiling point solvent. Specific examples of these additives are as follows. In addition, EO represents ethylene oxide, PO represents propylene oxide, EG represents ethylene glycol, PEG represents polyethylene glycol, and the numerical values in parentheses after EO and PO respectively represent the number of moles added.

Specific examples of additives: glyceryl monocaprylate, glyceryl monomyristate, glyceryl monostearate, glyceryl monooleate, glyceryl distearate, glyceryl dioleate, decaglyceryl monolaurate, decaglyceryl monomyristate, decaglyceryl Monostearate, decaglyceryl monooleate, decaglyceryl monolinoleate, decaglyceryl monoisostearate, decaglyceryl distearate, decaglyceryl dioleate, decaglyceryl diisostearate, decaglyceryl tristearate, decaglyceryl Trioleate, decaglyceryl triisostearate, decaglyceryl pentastearate, decaglyceryl pentaoleate, decaglyceryl pentaisostearate, decag Lyceryl heptastearate, decaglyceryl heptaoleate, decaglyceryl heptaisostearate, decaglyceryl decastarate, decaglyceryl decaoleate, decaglyceryl decaisostearate, diglyceryl monostearate, diglyceryl monooleate, Diglyceryl dioleate, diglyceryl monoisostearate, tetraglyceryl monostearate, tetraglyceryl monooleate, tetraglyceryl tristearate, tetraglyceryl pentastearate, tetraglyceryl pentaoleate, hexaglyceryl monolaurate, hexa Glyceryl monomyristate, hexaglyceryl monostearate, hexaglyceryl monooleate, hexaglyceryl tristearate, hexaglyceryl Printer stearate, hexa glyceryl pentaoleate, hexaglyceryl Lupo Lili ricinoleate, propylene glycol monostearate,
Pentaerythritol monostearate, pentaerythritol monopalmitate, pentaerythritol tallow fatty acid ester, sorbitan monocaprylate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan sesquistearate,
Sorbitan tristearate, sorbitan monooleate, sorbitan sesquioleate, sorbitan trioleate, sorbitan monoisostearate, sorbitan sesquiisostearate, sorbitan monotol oil fatty acid ester, sorbitan sesquitol oil fatty acid ester, sorbitan triol oil fatty acid ester , EG monostearate, EG distearate, PEG monolaurate, P
EG monostearate, PEG monooleate, PEG dilaurate, PEG distearate, PEG dioleate, glyceryl monooleate EO (5), glyceryl monooleate
EO (15), glyceryl monostearate EO (5), glyceryl monostearate EO (15), glycerin vegetable oil fatty acid ester EO (5), glycerin vegetable oil fatty acid ester EO (15), sorbitan monolaurate EO (20), Sorbitan monopalmitate EO (20), sorbitan monostearate EO (20), sorbitan tristearate EO (2
0), sorbitan monostearate EO (6), sorbitan monooleate EO (20), sorbitan trioleate
EO (20), sorbitan monooleate EO (6), sorbitan monoisostearate EO (20), lauryl ether
EO (2), lauryl ether EO (4,2), lauryl ether EO (9), lauryl ether EO (21), lauryl ether EO (25), cetyl ether EO (2), cetyl ether EO (5,5) , Cetyl ether EO (7), cetyl ether EO (10), cetyl ether EO (15), cetyl ether EO (20), cetyl ether EO (23), cetyl ether
EO (25), cetyl ether EO (30), cetyl ether EO
(40), stearyl ether EO (2), stearyl ether EO (4), stearyl ether EO (20), oleyl ether EO (7), oleyl ether EO (10), oleyl ether EO (15), oleyl ether EO ( 20), oleyl ether EO (50), behenyl ether EO (5), behenyl ether EO (10), behenyl ether EO (20),
Behenyl ether EO (30), nonylphenol EO
(4), nonylphenol EO (6), nonylphenol
EO (7), nonylphenol EO (10), nonylphenol EO (12), nonylphenol EO (14), nonylphenol EO (16), nonylphenol EO (20), nonylphenol EO (40), sorbit hexastearate EO
(6), sorbit tetrastearate EO (60), sorbit tetraoleate EO (6), sorbit tetraoleate EO (30), sorbit tetraoleate EO (4
0), sorbit tetraoleate EO (60), sorbit monolaurate EO (6), monolaurate EO (10),
Monostearate EO (1), Monostearate EO
(2), monostearate EO (4), monostearate
EO (10), Monostearate EO (25), Monostearate EO (40), Monostearate EO (45), Monostearate EO (55), Monooleate EO (2), Monooleate EO (6), Monooleate EO (10), stearylamine EO (5), stearylamine EO (10), stearylamine EO (15), oleylamine EO (5), oleylamine EO (10), oleylamine EO (15), stearylpropylenediamine EO (8) ), Stearamide EO
(4), stearamide EO (15), oleic amide EO (5), oleic amide EO (10), oleic amide EO (15), lanolin EO (1), lanolin alcohol
EO (5), Lanolin Alcohol EO (10), Lanolin Alcohol EO (20), Lanolin Alcohol EO (40), Solbit Beeswax EO (6), Solbit Beeswax EO (20),
Cetyl ether EO (1) PO (4), cetyl ether EO
(10) PO (4), cetyl ether EO (20) PO (4), cetyl ether EO (1) PO (8), cetyl ether EO (2
0) PO (8), decyl tetradecyl ether EO (12) PO
(6), decyl tetradecyl ether EO (20) PO
(6), decyl tetradecyl ether EO (30) PO
(6), dodecylbenzenesulfonic acid Ba, dodecylbenzenesulfonic acid Mg, stearylbenzenesulfonic acid Ca,
Stearylbenzenesulfonic acid Ba, stearylbenzenesulfonic acid Mg, eicosylbenzenesulfonic acid Ca, eicosylbenzenesulfonic acid Ba, eicosylbenzenesulfonic acid Mg, eicosylbenzenesulfonic acid Na, funnel oil of the following structural formula (low-grade sulfuric acid Castor oil) Low-sulfated olive oil with the following structural formula Olefin-maleic anhydride copolymer having the following structural formula (However, R ₁ , R ₂ , R ₃ , and R ₄ are hydrogen or an alkyl group having 1 to 20 carbon atoms, and n is an integer of 10 to 200.) Styrene-maleic anhydride copolymer having the following structural formula (However, R ₁ and R ₂ are hydrogen or an alkyl group having 1 to 20 carbon atoms, n
Is an integer from 10 to 200) Acrylic oligomer of the following structural formula [However, R ₁ and R ₃ are hydrogen or an alkyl group having 1 to 20 carbon atoms, R ₂
Is CH _{2 m} (m = 1 to 20), n is an integer of 5 to 30] 2,4,7,9-tetramethyl-5-decyne-in the following structural formula
4,7-diol.

The weight 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, more preferably 2: 1 to 1: 5. If the ratio of the base material is less than this, it becomes difficult to form a film in which the organic low molecular weight substance is held in the base material,
On the other hand, when the amount is more than this, the amount of the organic low molecular weight substance is small, and thus it becomes difficult to make the opaque.

On the other hand, the amount of the high boiling point solvent having a boiling point of 200 ° C. or higher is 0.01 to 1 part by weight, preferably 0.05 to 0 part by weight per 1 part by weight of the resin base material.
5 parts by weight is suitable. If the amount used is less than 0.01, it is difficult to form a transparent image with reduced energy, and if it exceeds 1 part, the mechanical strength of the film is lost.

The amount of additives used is 0.005 per 1 part by weight of resin base material.
-1 part by weight, preferably 0.01-0.3 part by weight. If the amount used is less than 0.005 part, it is difficult to form a transparent image with a small amount of energy as in the case of a high boiling solvent, and if it exceeds 1 part, it is difficult to form a film.

Hereinafter, the present invention will be described in more detail with reference to Examples. All parts are parts by weight.

Example 1 Behenic acid on a 75 μm thick polyester film 10 parts Vinyl chloride-vinyl acetate copolymer (VYHH manufactured by UCC) 25 parts Di-2-ethylhexyl adipate 6 parts Glyceryl monostearate 2 parts Tetrahydrofuran 157 parts Apply the solution with a wire bar, heat dry 15
A white opaque reversible thermosensitive recording material was prepared by providing a thermosensitive layer having a thickness of μm.

Example 2 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that glyceryl monostearate was changed to an olefin-maleic anhydride copolymer (Homogenol M-8 manufactured by Kao Corporation).

Example 3 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that glyceryl monostearate was changed to sorbitan monooleate.

Example 4 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that glyceryl monostearate was replaced with an acrylic oligomer (KD-140 manufactured by Kyoeisha Yushiki Kagaku Kogyo KK).

Example 5 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that glyceryl monostearate was changed to EO (40) monostearate.

Example 6 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that glyceryl monostearate was changed to EO (40) lanolin alcohol.

Example 7 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that di-2-ethylhexyl adipate was changed to dibutyl phthalate.

Example 8 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that di-2-ethylhexyl adipate was replaced with tricresyl phosphate.

Comparative Example 1 Example 1 except that glyceryl monostearate was omitted.
A white opaque reversible thermosensitive recording material was prepared in the same manner as described in 1.

Comparative Example 2 A white opaque reversible thermosensitive recording material was prepared in the same manner as in Example 1 except that di-2-ethylhexyl adipate was omitted.

Next, a 0.7 mJ / dot energy was applied to each recording material by a thermal head (a thin film line head of 8 dots / mm) to form a transparent image. This was placed on black drawing paper, and the reflection density was measured with a Macbeth densitometer RD514.

 The results are shown in the table below.

Effect Since the reversible thermosensitive recording material of the present invention contains a high boiling point solvent and the additives as described above, it is possible to control the growth of crystals of an organic low molecular weight substance, and a clear transparent image on a white background can be obtained even with minute energy such as a thermal head. It has the advantage that it can be formed.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of image formation and erasing in the heat-sensitive layer of the reversible heat-sensitive recording material of the present invention.

Claims (2)

(57) [Claims] 1. A reversible thermosensitive recording material comprising, as a main component, a resin matrix and an organic low molecular weight substance dispersed in the resin matrix and having a thermosensitive layer whose transparency reversibly changes depending on temperature. A reversible heat-sensitive recording material, characterized in that the heat-sensitive layer further contains at least one high boiling point solvent having a boiling point of 200 ° C. or higher and at least one of the following additives. Additive group: polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide, lower olefin oxide addition of oil or polypropylene glycol Acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; higher fatty acid, aromatic carboxylic acid, higher aliphatic sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester or phosphoric acid mono- or di-ester Ca, Ba, or Mg; low-sulfated oil; poly-long-chain alkyl acrylate; acrylic oligomer; poly-long-chain alkyl methacrylate; long-chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer Olef In-maleic anhydride copolymer. 2. The high boiling point solvent is tributyl phosphate, 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, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, Di-n-hexyl adipate, di-2-ethylhexyl adipate, alkyl 610 adipate, di-2-ethylhexyl azelate,
Dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate and tributyl acetylcitrate The reversible thermosensitive recording material according to claim 1, which is selected from the group.