JP3073857B2 - Image recording method for reversible thermosensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method which makes it possible to use a reversible thermosensitive recording material which causes a reversible change in transparency or color tone with temperature for a long time and repeatedly.

[0002]

2. Description of the Related Art In recent years, a reversible thermosensitive recording material which can form a temporary image and erase the image when it becomes unnecessary has been attracting attention. As a typical example, a reversible thermosensitive recording material in which a low-molecular organic material such as a higher fatty acid is dispersed in a resin base material such as a vinyl chloride-vinyl acetate copolymer is known (Japanese Patent Application Laid-Open No. Sho 54/1979). -11
9377, JP-A-55-154198 and the like).

If such a reversible thermosensitive recording material is used repeatedly, the heat and pressure of the thermal head cause scum, dust and the like to adhere to the surface of the reversible thermosensitive recording material, making accurate recording and erasing impossible. Can be seen.
Several countermeasures against this have been proposed. For example, (i) a method of cleaning by providing a cleaning box in which a card surface is attached to and detached from the apparatus main body at a specific position (JP-A-3-296981, JP-A-3-296981) 3-2969
No. 82, etc.) and (ii) Although a direct cleaning effect is not expected, a method of erasing an image by immersing a reversible thermosensitive recording material in hot water and heating it in a liquid bath (particularly, No. 57-89992) and the like. In addition to this, there is a method (iii) for cleaning a reversible thermosensitive recording material proposed by the present applicant (described in Japanese Patent Application No. 4-345422).

[0004]

However, according to the methods (i) and (ii), the reversible thermosensitive recording material cannot always be efficiently and repeatedly repeated over a long period of time. In the method (iii), there is still room for improvement.

It is an object of the present invention to clean dirt in a usual place so that a reversible thermosensitive recording material whose transparency or color tone changes reversibly depending on temperature can be used many times. Stubborn oil, grease, etc., especially when used in a factory, oil such as cutting oil, lubricating oil, rust preventive agent, etc. An object of the present invention is to provide a method for cleaning a reversible thermosensitive recording material (an image recording method as a whole).

[0006]

The first aspect of the present invention is a reversible thermosensitive recording material whose transparency or color tone changes reversibly depending on temperature, and whose surface layer has a surface energy (surface tension). In an image recording method using a reversible thermosensitive recording material having a density of 30 dyn / cm or less and repeating image formation and image erasing, the reversible thermosensitive recording material is washed. Here, the reversible thermosensitive recording material
The surface layer is advantageously selected from fluorine-based materials.
You. As a means for washing here, washing by dipping the reversible thermosensitive recording material in a liquid bath (preferably hot water),
Washing with a wet cleaning roller, a sponge roller, a cloth brush, or the like, or washing with a wet cleaning cloth may be used. Note that these washings may be repeatedly performed two to three times.

Hereinafter, the present invention will be described in more detail. In the present invention, “a reversible thermosensitive recording material (in which the transparency or color tone is reversibly changed depending on temperature)” is a material (recording medium) that causes a visible change due to a temperature change.
It is. The visible change can be divided into a change in color state and a change in shape, and the present invention mainly uses a material that causes a change in color state. Changes in the color state include changes in transmittance, reflectance, absorption wavelength, scattering degree, and the like, and an actual reversible thermosensitive recording material performs display by a combination of these changes. More specifically, at present, the materials can be classified into two types: materials in which the transparent state and the cloudy state are reversibly changed, and materials in which the color such as dyes is chemically changed.

As a typical example, there is exemplified a material in which a heat-sensitive layer in which a low-molecular organic substance such as a higher alcohol or a higher fatty acid is dispersed in a resin base material such as a polyester is provided on a support. As a typical example, a leuco-based thermosensitive recording material having enhanced reversibility is given.

The heat-sensitive layer of the type which causes a change in the transparency has a resin base material and an organic low-molecular substance dispersed in the resin base material as main components. As described later, the reversible thermosensitive recording material has a temperature range in which the material becomes transparent. Further, the reversible thermosensitive recording material here uses the change in transparency (transparent state, cloudy opaque state) as described above, and the difference between this transparent state and cloudy opaque state is presumed as follows. That is, in the case of (I) transparent, the particles of the organic low-molecular substance dispersed in the resin base material are composed of large particles of the organic low-molecular substance, and the light incident from one side is not scattered and is opposite. (II) In the case of white turbidity, the particles of the organic low molecular weight substance are composed of polycrystals in which fine crystals of the organic low molecular weight substance are aggregated, and the crystal axis of each crystal Is oriented in various directions, so that light incident from one side is refracted many times at the interface between the crystals of the organic low-molecular substance particles, and is scattered, so that it appears white.

In FIG. 1 (representing a change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material has a temperature of, for example, T ₀ or less. At room temperature, it is cloudy and opaque. This became clear when heated to a temperature T _2, which remains also clear again returned to the normal temperature of T ₀ or less in this state. This may be because the crystalline low-molecular organic material before reaching the T ₀ or less from the temperature T ₂ is between the single crystal from a polycrystalline via a semi-molten state grows. Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. This after low-molecular organic material is melted at a temperature T ₃ or more,
It is considered that polycrystals are precipitated by cooling. When this opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature equal to or lower than T ₀ , an intermediate state between transparent and opaque can be obtained.
Also, by returning to room temperature After heating to be again T ₃ or more temperature which became clear at the normal temperature, the flow returns to cloudy opaque state again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be taken.

Therefore, the heat-sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent ground and a transparent image on a cloudy ground, and the change can be repeated many times. It is possible. If a colored sheet is arranged on the back of such a heat-sensitive layer, a color image of the colored sheet on a white background or a white image on a colored background of the colored sheet can be formed. Further, when projected by an OHP (overhead projector) or the like, the cloudy portion becomes a dark portion, the transparent portion transmits light, and becomes a bright portion on the screen. Further, when an image of the reversible thermosensitive recording material is used as a reflection image, providing a layer that reflects light on the back surface of the recording layer can increase the contrast even if the thickness of the recording layer is reduced. Specifically, Al, Ni, Sn or the like is deposited.

In order to prepare the reversible thermosensitive recording material according to this type of the present invention, generally, (1) a solution in which two components of a resin base material and an organic low-molecular substance are dissolved, or (2) a solution of the resin base material (solvent) A dispersion liquid in which at least one of the organic low-molecular substances is not dissolved) is applied to a support such as a plastic film, a glass plate, or a metal plate and dried. Then, a heat-sensitive layer may be formed.

The solvent for forming the heat-sensitive layer or the heat-sensitive recording material can be variously selected depending on the type of the resin base material and the organic low-molecular substance. For example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, Benzene and the like can be mentioned. In addition, of course, when a dispersion is used,
Even when a solution is used, in the heat-sensitive layer obtained, the organic low-molecular substance is precipitated 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 organic low-molecular substances are uniformly dispersed and held, and that affects the 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. Such resins include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-based copolymer such as vinyl chloride-acrylate copolymer; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, Vinylidene chloride-based copolymers such as vinylidene chloride-acrylonitrile copolymer; polyester; polyamide; polyacrylate or polymethacrylate or acrylate-methacrylate copolymer; and silicone resin. These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular substance may be any substance that changes from polycrystal to single crystal by heat in the recording layer, and generally has a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. . Such organic low molecular weight substances include alkanol; alkane diol; halogen alkanol or halogen alkane diol; alkylamine; alkane; alkene; alkyne; halogen alkane; halogen alkene; halogen alkyne; cycloalkane; cycloalkene; cycloalkyne; 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; aryl carboxylic acids or their esters, amides or ammonium salts; Their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; thioalcohols Carboxylic acid esters, and the like. These may be used alone or in combination of two or more. The carbon number of these compounds is 10 to 60, preferably 10 to 38, 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 contains at least one kind of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH-, -COO
_{R, -NH -, - NH 2} , -S -, - SS -, - O-, is preferably a compound containing a halogen and the like.

More specifically, these compounds include la
Uric acid, dodecanoic acid, myristic acid, pentadecane
Acid, palmitic acid, stearic acid, behenic acid, nonadeca
Higher fatty acids such as acid, araginic and oleic acid; stearic acid
Methyl phosphate, tetradecyl stearate, stearin
Octadecyl acid, octadecyl laurate, palmitin
Of higher fatty acids such as tetradecyl acrylate and dodecyl behenate
Stele; C₁₆H₃₃-O-C₁₆H₃₃ , C₁₆H₃₃-S-C₁₆H₃₃ , C₁₈H₃₇-S-C₁₈
H₃₇ , C₁₂H_{twenty five}-S-C₁₂H_{twenty five} , C₁₉H₃₉-S-C₁₉H₃₉ , C₁₂H
_{twenty five}-S-S-C₁₂H_{twenty five} , And ether or thioether. In particular, the present invention
Higher fatty acids, especially palmitic acid, stearic acid,
Higher fatty acids having 16 or more carbon atoms such as henic acid and lignoceric acid
Are preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.
No.

In order to widen the range of temperatures at which transparency can be achieved, the organic low-molecular substance described in this specification may be appropriately combined, or such an organic low-molecular substance may be combined with another material having a different melting point. . These are disclosed, for example, in JP-A-63-3
No. 9378, JP-A-63-130380 and Japanese Patent Application No. 63-14
No. 754, Japanese Patent Application No. 1-140109, and the like, but are not limited thereto. The ratio between the organic low-molecular substance and the resin base material in the heat-sensitive layer was 2: 2 by weight.
About 1 to 1:16 is preferable, and 1: 1 to 1: 3 is more preferable. When 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 when the ratio is higher, the amount of the organic low-molecular substance is small, so that the opacity is increased. Becomes difficult.

In addition to the above components, additives such as a surfactant and a high-boiling solvent can be added to the heat-sensitive layer in order to facilitate formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling solvents: tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, diphthalic phthalate -n-octyl, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-adipate
2-ethylhexyl, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate, methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl Phthalyl butyl glycolate, tributyl acetyl citrate.

Examples of surfactants and other additives: polyhydric alcohol higher fatty acid ester; polyhydric alcohol higher alkyl ether; polyhydric alcohol higher fatty acid ester, higher alcohol, higher alkyl phenol, higher fatty acid higher alkyl amine, higher fatty acid amide Lower olefin oxide adducts of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salts of higher alkylbenzene sulfonic acids; higher fatty acids, aromatic carboxylic acids, higher fatty acid sulfonic acids, aromatic sulfonic acids, sulfuric acid monoesters Or phosphoric acid mono- or di-ester Ca, Ba or Mg salts; low sulfated oil; poly long chain alkyl acrylate; acrylic oligomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate-amine-containing monomer copolymer ; Stille - maleic anhydride copolymer; olefin - maleic anhydride copolymer.

A protective layer may be provided on the heat-sensitive layer to protect the heat-sensitive layer. Protective layer (thickness 0.1-5μ
Examples of the material of m) include silicone rubbers, silicone resins (described in JP-A-63-221087), polysiloxane graft polymers (described in Japanese Patent Application No. 62-152550), ultraviolet curable resins, and electron beams. And cured resins (described in the specification of Japanese Patent Application No. 63-310600). In any case, a solvent is used at the time of coating, and it is preferable that the solvent does not easily dissolve the resin of the thermosensitive layer and the organic low-molecular substance. As a solvent that is difficult to dissolve the resin and organic low molecular weight substance of the heat sensitive layer
Examples thereof include n-hexane, methyl alcohol, ethyl alcohol, and isopropyl alcohol, and alcohol-based solvents are particularly desirable from the viewpoint of cost.

Further, an intermediate layer may be provided between the protective layer and the heat-sensitive layer in order to protect the heat-sensitive layer from a solvent, a monomer component and the like of the protective layer forming liquid. As the material of the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the resin base material in the thermosensitive layer.
That is, polyethylene, polypropylene, polystyrene,
Examples include polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like. The thickness of the intermediate layer is preferably about 0.1 to 2 μm.

Next, the heat-sensitive layer formed by a reversible thermochromic composition utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound will be described. A thermochromic composition utilizing a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound, when the electron-donating color-forming compound and the electron-accepting compound are melted by heating. Generating an amorphous color former, while heating the amorphous color former at a temperature lower than the melting temperature, causing the electron accepting compound to crystallize and discolor the color former. The phenomenon of the above is used.

The thermochromic composition instantaneously develops a color upon heating, and its coloring state is stably present at room temperature, while the composition in the coloring state is instantly heated by heating below the coloring temperature. The color is erased, and the erased state is stably present even at room temperature, and such a reversible peculiar coloring / erasing behavior is a novel and surprising phenomenon that has not been seen before.

FIG. 2 shows the principle of color development and decoloration when this composition is used as a heat-sensitive recording medium, that is, the principle of image formation and image erasure.
This will be described with reference to the graph shown in FIG. The vertical axis of the graph represents the color density, the horizontal axis represents the temperature, the solid line shows the image forming process by heating, and the broken line shows the image erasing process by heating. A is the concentration in a fully erased state, B is the concentration in the complete colored state when heated to T ₅ temperature above, C is the concentration in the T ₄ below the temperature of complete colored state, D is T ₄ shows the concentration when heated and erased with a temperature between through T _5.

The composition according to the invention is in a colorless state (A) at temperatures below T ₄ . To perform recording (image formation) forms a recorded image by color (B) by heating to T ₅ temperature above the thermal head or the like. The recorded image be returned to T ₄ temperature below according solid 51, is not lost memory of the recording holds the intact (C).

Next, in order to erase the recorded image, the formed recorded image is heated to a temperature between T _{4 and} T ₅ lower than the color development temperature to be in a colorless state (D). This state be returned to T ₄ below temperatures, it is held as colorless state (A). That is, the process of forming the recorded image reaches C along the path indicated by the solid line ABC, and the recording is held. Next, in the erasing process of the recorded image, the erasing state is reached to A by the route of the broken line CDA. The behavior characteristics of forming and erasing the recorded image are reversible and can be repeated many times.

The reversible thermochromic composition contains a color former and a developer as essential components. A color-forming state is formed by heating and melting the color-forming agent and the color developer, while the color-forming state is erased by heating at a temperature lower than the color-forming temperature, and the color-forming state and the decoloring state are stably present at room temperature. It is. As described above, such a mechanism of color development and decolorization in the composition is such that when a color former and a developer are heated and melted and mixed at a color development temperature, the composition undergoes amorphization to change the color development state. On the other hand, when heated at a temperature lower than the color development temperature, the color developer is crystallized to form a color developing composition to form an erased state of color development. However, by heat-sensitive layer the process of decolorizing is heated to T ₅ or more temperature is taken also in this case, the particles of color former and the developer is returned to the original, to form a new colored state Is advantageous.

A composition comprising an ordinary color former and a developer, for example, a leuco compound having a lactone ring, which is a dye precursor widely used in conventional thermal recording paper, and a phenolic compound exhibiting a color developing effect. When this is melted and mixed by heating, a color development state based on ring opening of the lactone ring of the leuco compound is obtained. This coloring state is an amorphous state in which both are compatible. Although this colored amorphous state exists stably at room temperature, it does not crystallize even when heated again, and there is no separation of the phenolic compound from the leuco compound, so there is no ring closure of the lactone ring and decolorization. Do not.

On the other hand, when the composition of the color former and the color developer according to the present invention is melted and mixed by heating, it becomes a colored state, exhibits an amorphous state as in the conventional case, and is stable at room temperature. Exists. However, in the case of the present invention, when the color-formed amorphous composition is heated at a temperature lower than the color-forming temperature, that is, at a temperature that does not reach the molten state, crystallization of the color developer occurs, and the composition becomes compatible with the color-forming agent. The bond due to the state cannot be maintained, and the color developer is separated from the color former. It is considered that due to the separation of the color developing agent from the color forming agent due to crystallization, the color developing agent cannot accept electrons from the color forming agent, and the color forming agent loses its color.

The above-mentioned specific coloring / decoloring behavior observed in the thermochromic composition includes the mutual solubility of the coloring agent and the color developing agent by heating and melting, the strength of action of both in the color forming state, and the color developing agent. Is related to the solubility of the color former, the crystallinity of the developer, etc.
In principle, it becomes amorphous by heating and melting, while
Any color former / color developer system that causes crystallization by heating at a temperature lower than the color development temperature can be used as a composition component in the present invention. Further, those having such characteristics show endothermic changes due to melting and exothermic changes due to crystallization in thermal analysis. Therefore, the color former / developer system applicable to the present invention can be easily analyzed by thermal analysis. You can check. In addition, the reversible thermochromic composition system according to the present invention may include a third substance, for example, the reversible decoloring behavior is maintained even when a polymer substance is present. Was confirmed. In the thermochromic composition of the present invention, the decoloration is caused by separation from the color former due to crystallization of the color developer. is important.

Next, examples of the developer preferably used in the present invention are as follows. As described above, the developer applicable to the present invention can be easily found by thermal analysis. However, the present invention is not limited to this. (1) An organic phosphoric acid compound represented by the following general formula (1): R ₁ -PO (OH) ₂ (1) (where R ₁ is a linear or branched alkyl group or alkenyl having 8 to 30 carbon atoms) Specific examples of the organic phosphoric acid compound include the following. Octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid.

(2) An organic acid having a hydroxyl group at the α-position carbon represented by the following general formula (2): R ₂ —CH (OH) COOH (2) (where R ₂ is a straight chain having 6 to 28 carbon atoms) Specific examples of the organic acid having a hydroxyl group at the carbon at the α-position include the following. α-hydroxyoctanoic acid,
α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic Acid, α-hydroxydocosanoic acid and the like.

The color former used in the present invention is a compound having an electron-accepting property, and is itself a colorless or light-colored dye precursor, and is not particularly limited, and may be a conventionally known one such as triphenylmethanephthalide. There are a compound, a fluoran compound, a phenothiazine compound, a leuco auramine compound, a rhodamine lactam compound, a spiropyran compound, an indolinophthalide compound and the like, and specific examples include the following. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-
Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethylaminophenyl)-
6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-
Bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7- Methylfluoran, 3-diethylamino-7,8
-Benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-
Ethylamino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylamino Fluoran, 2-
{3,6-bis (diethylamino) -6- (o-chloroanilino) xanthyl lactam lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- ( o-
Chloranilino) fluoran, 3-dibutylamino-7
-(O-chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6
-Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N,
N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluoran, benzoleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-2'- Methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'methoxy-5'-chlorophenyl) phthalide, 3- (2'hydroxy-4'-dimethyl Aminophenyl) -3-
(2'-methoxy-5'-nitrophenyl) phthalide,
3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methoxyphenyl) phthalide, 3-morpholino-7- (N-propyl- Trifluoromethylaniline)
Fluoran, 3-diethylamino-5-chloro-7-
(N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5
-Chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-p-toluidino) -7- (α-
Phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α
-Phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3-
(N-methoxytoluidino) -7- (pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran,
3-dibutylamino-6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-dimethylaminophthalide, 3-
(N-benzyl-N-cyclohexylamino) -5,6
-Benzo-7-α-naphthylamino-4'-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6 Methyl-7-anilinofluoran, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5' −
Benzofluoran, 3-N-methyl-N-isobutyl-
6-methyl-7-anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7- (2 ',
4'-dimethylanilino) fluoran and the like.

Particularly preferred color formers used in the present invention are those containing halogen as a substituent. Examples of such a device include the following. 3,3-bis (p-dimethylaminophenyl) -6
-Chlorophthalide, 3-cyclohexylamino-6-chlorofluorane, 3-cyclohexylamino-6-bromofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluoran, 3
-Dipropylamino-7-chlorofluoran, 3-diethylamino-6-chloro-7-phenylamino-fluoran, 3-pyrrolidino-6-chloro-7-phenylamino-fluoran, 3-diethylamino-6-chloro-7
-(M-trifluoromethylphenyl) amino-fluoran, 3-cyclohexylamino-6-chloro-7- (o
-Chlorophenyl) amino-fluoran, 3-diethylamino-6-chloro-7- (2 ', 3'-dichlorophenyl) amino-fluoran, 3-diethylamino-6-
Methyl-7-chlorofluoran, 3-dibutylamino-
6-chloro-7-ethoxyethylamino-fluoran,
3-diethylamino-7- (o-chlorophenyl) amino-fluoran, 3-diethylamino-7- (o-bromophenyl) amino-fluoran, 3-diethylamino-7- (o-chlorophenyl) amino-fluoran, 3
-Dibutylamino-7- (o-fluorophenyl) amino-fluoran, 6'-bromo-3'-methoxybenzoindolino-pyrrospirane, 3- (2'-methoxy-
4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2 '-Methoxy-5'-chlorophenyl) phthalide, 2- {3,6-bis (diethylamino)}-9- (o-chlorophenyl) amino-xanthyl benzoate lactam and the like.

A preferred color former when used in the present invention is a compound represented by the following general formula (3).

Embedded image (Provided that R ₃ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom or an amino group which may be substituted, X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group. , M is an integer of 1 or 2, Y is a carbon number of 1-4.
An alkyl group or an alkoxy group having 1 to 2 carbon atoms, n is 1
Or an integer of 2. )

Specific examples of the compound represented by the general formula (3) include the following. 3-
(N-methyl-N-phenylamino) -7-amino-fluoran, 3- (N-ethyl-N-phenylamino)-
7-amino-fluoran, 3- (N-propyl-N-phenylamino) -7-amino-fluoran, 3- {N-
Methyl-N- (p-methylphenyl) amino} -7-amino-fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-amino-fluoran, 3-
{N-propyl-N- (p-methylphenyl) amino}
-7-amino-fluoran, 3- {N-methyl-N-
(P-ethylphenyl) amino} -7-amino-fluoran, 3- {N-ethyl-N- (p-ethylphenyl)
Amino} -7-amino-fluorane, 3- {N-propyl-N- (p-ethylphenyl) amino} -7-amino-fluoran, 3- {N-methyl-N- (2 ′, 4′-dimethyl) Phenyl) amino} -7-amino-fluoran,
3- {N-ethyl-N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluoran, 3- {N-propyl-N- (2', 4'-dimethylphenyl) amino}
-7-amino-fluoran, 3- {N-methyl-N-
(P-chlorophenyl) amino} -7-amino-fluoran, 3- {N-ethyl-N- (p-chlorophenyl)
Amino} -7-amino-fluoran, 3- {N-propyl-N- (p-chlorophenyl) amino} -7-amino-fluoran, 3- (N-methyl-N-phenylamino) -7-methylamino -Fluoran, 3- (N-ethyl-N-phenylamino) -7-methylamino-fluoran, 3- (N-propyl-N-phenylamino) -7-
Methylamino-fluoran, 3- {N-methyl-N-
(P-methylphenyl) amino} -7-ethylamino-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-benzylamino-fluoran, 3
-{N-methyl-N- (2 ', 4'-dimethylphenyl)
Amino} -7-methylamino-fluoran, 3- {N-
Ethyl-N- (2 ′, 4′-dimethylphenyl) amino
-7-ethylamino-fluoran, 3- {N-methyl-
N- (2 ', 4'-dimethylphenyl) amino} -7-benzylamino-fluoran, 3- {N-ethyl-N-
(2 ′, 4′-dimethylphenyl) amino} -7-benzylamino-fluoran, 3- (N-methyl-N-phenylamino) -7-dimethylamino-fluoran, 3- (N
-Ethyl-N-phenylamino) -7-dimethylamino-fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -7-diethylamino-fluoran,
3- {N-ethyl-N- (p-methylphenyl) amino} -7-diethylamino-fluoran, 3- (N-methyl-N-phenylamino) -7-dipropylaminofluoran, 3- (N- Ethyl-N-phenylamino) -7
-Dipropylaminofluoran, 3- {N-methyl-N
-(P-methylphenyl) amino} -7-dibenzylamino-fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-dibenzylamino-fluoran, 3- {N-ethyl -N- (p-methylphenyl)
Amino} -7-di (p-methylbenzyl) amino-fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -7-acetylamino-fluoran, 3-
{N-ethyl-N- (p-methylphenyl) amino}-
7-benzoylamino-fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -7- (o-methoxybenzoyl) amino-fluoran, 3- {N-ethyl-N- (p-methyl Phenyl) amino} -6-methyl-7-phenylamino-fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -6-methyl-7-phenylamino-fluoran, 3- {N- Methyl-N- (p-methylphenyl) amino} -6-tert
-Butyl-7- (p-methylphenyl) amino-fluoran, 3- (N-ethyl-N-phenylamino) -6
Methyl-7- (N-ethyl-N- (p-methylphenyl) amino-fluoran, 3- {N-propyl-N-
(P-methylphenyl) amino} -6-methyl-7-
{N-methyl-N- (p-methylphenyl) amino}-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -5-methyl-7-benzylamino-fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -5 -Chloro-7-dibenzylamino-fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -5-methoxy-7-dibenzylamino-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -6-methyl-fluoran, 3- {N-
Ethyl-N- (p-methylphenyl) amino} -5-methoxy-fluoran and the like.

The developers are used alone or in combination of two or more. Similarly, the color former can be applied alone or in combination of two or more. The thermochromic composition can be formed as a thermosensitive layer on a support and used as a reversible thermosensitive recording material. In this case, the reversible thermosensitive recording material is obtained by uniformly dispersing or dissolving a color former and a developer together with a binder in water or an organic solvent according to a conventionally known method, and applying the resultant to a substrate. .

As the binder, various conventional binders can be appropriately used. For example, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxy cellulose, carboxymethyl cellulose, methyl cellulose, cellulose acetate, gelatin, casein, starch, polyacrylic acid Soda, polyvinylpyrrolidone, polyacrylamide, maleic acid copolymer, acrylic acid copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylic esters, polymethacrylic esters, vinyl chloride-vinyl acetate copolymer Coalesce, styrene copolymer, polyester,
There are polyurethane and the like.

In the present invention, various additives used in ordinary thermosensitive recording paper, for example, a dispersant, a surfactant, a filler,
A color image stabilizer, an antioxidant, a light stabilizer, a lubricant and the like can be added. Further, as described above, a protective layer and an intermediate layer may be provided as necessary.

The reversible thermosensitive recording material used in the present invention has a surface layer (when the heat-sensitive layer is a surface layer, the heat-sensitive layer,
In the case where a protective layer is provided on the heat-sensitive layer, it is necessary that the protective layer has a surface energy (surface tension) of 30 dyn / cm or less. This is for the following reason. Incidentally, the conventional heat-sensitive layer of the, for providing the low-energy surface layer on such protective layer is advantageous on creation of the reversible thermosensitive recording material.

As pointed out above, stubborn oils are generally composed of cutting oils, lubricating oils, rolling oils and rust-preventive oils. ) Is obtained (from Maruzen's "Oil Chemistry Handbook").

[Table 1]

Therefore, if the surface of the reversible thermosensitive recording medium to which dirt adheres has a value lower than the surface tension of the oil, the reversible thermosensitive recording medium is less likely to get wet, and is easily removed even if dirt such as oil adheres.

As described above, examples of the polymer used in the surface layer of the reversible thermosensitive recording material used in the present invention include the following. Polytetrafluoroethylene 18.5 dyn / cm Polydimethylsiloxane 24 dyn / cm Polyvinylidene fluoride 25 dyn / cm Poly 1,2-butadiene 25 dyn / cm Poly 2-methylpropane 27 dyn / cm Polyvinyl fluoride 28 dyn / cm Polyvinyl methyl ester 29 dyn / Cm Polypropylene 29 dyn / cm As a material, a fluorine-based polymer having a particularly low surface tension (typically, ethylene tetrafluoride) is good, and as a surface layer, a conventional protective layer is chemically coated or Further, it may be mixed as an additive in the protective layer. Also,
In addition to the surface, the surface can be fluorinated by plasma polymerization or glow discharge.

The support (substrate) in the reversible thermosensitive recording material used in the present invention may be paper, synthetic paper, plastic film, or a composite thereof, depending on the purpose of use. Not done. Further, the reversible thermosensitive recording material used in the present invention may be a long one or an endless one.

Assuming that the reversible thermosensitive recording material in the present invention is often used in the form of a card, the temperature of the liquid bath used for actual washing is changed to the change temperature of the reversible thermosensitive recording material ( It is desirable to wash at a temperature equal to or approximately equal to the temperature at which the transparency or color tone changes reversibly). In this case, as shown in FIG. 3, the cleaning liquid 1 is heated by a heater or the like so that the liquid temperature becomes a temperature suitable for erasing an image, and the liquid is circulated so as to be preferably in a certain range. In FIG. 3, 2 is a heat pump, 3 is air blowing,
Reference numeral 4 denotes a card-like reversible thermosensitive recording material. FIG.
FIG. 5 shows a state in which the surface of the card-like reversible thermosensitive recording material is cleaned while moving. FIG. 4 shows an example in which the heat-sensitive layer is on the back surface of the card, and FIG. 5 shows an example in which the heat-sensitive layer is on the front surface of the card. In the figure, 5 is a fiber cloth, 6 is a heater,
Reference numeral 7 denotes a sponge roll, 8 denotes a transport belt, 9 denotes a paper feed roll, 10 denotes a pump, and 11 denotes a scraping roll.

For washing, a volatile solvent (particularly, alcohol or the like (a hydrogen atom of a chain or alicyclic hydrocarbon is converted to a hydroxyl group (OH
Preference is given to volatile solvents of the hydroxy compound) substituted with a group). It is preferable that a surfactant and / or organic or inorganic fine particles are added to the cleaning liquid. The presence of the surfactant can further improve the cleaning effect on the surface of the reversible thermosensitive recording material, and it has good adhesion to the reversible thermosensitive recording material with organic or inorganic fine particles (approximately 50 μm in particle diameter). The presence of a substance (typically, iron powder, Al powder, etc.) without the presence of the fine particles can further improve the cleaning effect by hitting the surface of the reversible thermosensitive recording material.

The liquid (washing liquid) used in the washing in the present invention may be any liquid having a boiling point equal to or higher than the clearing temperature of the reversible thermosensitive recording material and equal to or higher than the temperature at which the material becomes cloudy or decolorized. Liquids having a medium boiling point (boiling point of 100 to 150 ° C.) include the following liquids. Hot water, normal butyl alcohol, isobutyl alcohol, secondary butyl alcohol,
Normal amyl alcohol, secondary amyl alcohol, methyl amyl alcohol, tetrahydrofurfuryl alcohol,
Dipropyl ketone, methyl propyl ketone, methyl orthobutyl ketone, methyl orthoamyl ketone, cyclohexanone, methylcyclohexanone, orthobutyl acetate, isobutyl acetate, sec-butyl acetate, 3-methoxybutyl acetate, ortho-amyl acetate, sec-amyl acetate, propionic acid Positive butyl,
Isopropyl lactate, diethyl carbonate, cellosolve, methyl cellosolve, diethyl cellosolve, isopropyl cellosolve, cellosolve acetate, methyl cellosolve acetate, furfural, mesityl oxide, monochlorobenzene, high flash point naphtha, M. & P. Naphtha, toluene, xylene, Solvesso No. 1, No. 2.

The surfactants usable in the present invention include (1) anionic surfactants. Fatty acid salts RCOONa 2. 2. Higher alcohol sulfates ROSO ₃ Na Liquid fatty acid sulfates R (OSO ₃ Na)
COOR'4. 4. Sulfates of aliphatic amines and aliphatic amides RCONHR'CH ₂ CH ₂ OSO ₃ Na Fatty alcohol phosphate salts ROP (ON
a) ₂ 7. Fatty acid amide sulfonates RCONR'CH ₂
CH ₂ SO ₃ Na 8. Alkyl allyl sulfonates

Embedded image

Embedded image

Embedded image 9. 9. Naphthalene sulfonates of formalin condensation Other anionic activators (2) Cationic activators Aliphatic amine salts

Embedded image 2. Quaternary ammonium salts

Embedded image 3. Alkyl pyridium salt

Embedded image 4. Other cationic activators (3) Nonionic activators Polyoxyethylene alkyl ethers RO (C
₂ H ₄ O) nH _2. Polyoxyethylene alkyl phenol ethers

Embedded image 3. Polyoxyethylene alkyl esters RCOO
_{(C 2 H 4 O) nH} 4. Sorbitan alkyl ester

Embedded image 5. Polyoxyethylene sorbitan alkyl esters

Embedded image 6. Other nonionic surfactants (4) Amphoteric surfactants (5) Surfactant mixture 1. Anionic mixed type 2. Cationic mixed type Nonionic mixed type 4. 4. Anion and nonionic mixed type 5. Cationic and nonionic mixed type Other mixed types

[0049]

Next, the present invention will be described more specifically with reference to examples. All parts here are by weight.

[0050] Example 1 4 parts to about 100 [mu] m 6 parts behenic acid on a polyester film having a thickness eicosanoic diacid phthalate A drill 2 parts of vinyl chloride - vinyl acetate - phosphate ester copolymer 20 parts (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha (Denka Vinyl # 1000MT) A solution consisting of 150 parts of tetrahydrofuran was applied and dried by heating to form a reversible thermosensitive recording layer having a thickness of about 10 μm. On this, the following liquid was further applied, dried, and cured by UV to form a low energy surface layer having a thickness of about 3 μm (surface tension: 19.6 dyn / c).
m). UV curable fluorine resin liquid (UV 98%) (DEFENSA 239-1, manufactured by Dainippon Ink and Chemicals, Inc.) Appropriately diluted with solvent MIBK. 24
Printing was performed with a VEPDO voltage of 0.7 msec pulse width. Prepare these four sheets and put on them cutting oil (cottonseed oil), lubricating oil (glycerin), rolling oil (rapeseed oil),
Two or three drops of rust preventive oil (oleic acid) were applied to the surface, respectively, and stored at room temperature for one day to prepare an oil stain sample. Then, one cleaning step is sufficient (A) to 〜 without using the heater 6 in the cleaning device shown in FIG.
(D) Oil stains were blown off, and then the print was erased with a hot roller at 85 ° C., and printing was performed again under the above conditions. As a result, a good printed image was obtained as before. Even if this was repeated 50 times, a good image was obtained with almost no change.

Example 2 Same as Example 1 until the reversible thermosensitive recording layer was provided. The low-energy surface layer was spray-coated with a commercially available fluorine spray (3M Scotchguard), dried, and dried to a thickness of about 1 μm. A layer (surface tension 20.5 dyn / cm) was formed. Printing was carried out under the same conditions as in Example 1, and an oil stain sample was prepared in the same manner. This time was performed without using the heater 6 of the cleaning device shown in FIG. 5, and the same good results as in Example 1 were obtained. Was.

Comparative Example 1 The same printing and oil stain were performed on the recording material having no low-energy surface layer of Example 1 and a single cleaning step was performed with the cleaning device shown in FIG. 4 or FIG. Oil stain lines remained, and some of the prints were insufficiently erased by the heat roller. When printing was performed again, there were several places where printing was not possible.

Example 3 The same procedure as in Example 1 was carried out until a printed image was formed and an oil stain sample was prepared. Then, hot water was heated to 85 ° C. using a heater 4 with the cleaning device shown in FIG. 4 or FIG. After cleaning, (A)
The oil stains of (D) to (D) were sufficiently blown off, and the print was erased. When printing was performed again under the above conditions, a good printed image was obtained as in the above. Even if this was repeated 50 times, it hardly changed.

[0054]

According to the present invention, since the surface of the reversible thermosensitive recording material is maintained in a good condition by washing, a good image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining characteristics of a reversible thermosensitive recording material used in the method of the present invention.

FIG. 2 is a diagram for explaining characteristics of another reversible thermosensitive recording material used in the method of the present invention.

FIG. 3 is a schematic view of an example of an apparatus used for carrying out the method of the present invention.

FIG. 4 is a schematic view of an example of another apparatus used for carrying out the method of the present invention.

FIG. 5 is a schematic view of an example of still another apparatus used for carrying out the method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 liquid bath (cleaning liquid) 2 heat pump 3 air blowing 4 reversible thermosensitive recording material 5 fiber cloth 6 heater 7 sponge roll 8 transport belt 9 paper feed roll 10 pump 11 scraping roll

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-133781 (JP, A) JP-A-5-96853 (JP, A) JP-A-57-89992 (JP, A) JP-A-6-96 210957 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/26

Claims (4)

(57) [Claims] 1. Reversibility of transparency or color tone depending on temperature
Reversible thermosensitive recording material that changes to
When the surface energy (surface tension) is 30 dyn / cm or less
Using a certain reversible thermosensitive recording material,
When repeating image erasing, washing the reversible thermosensitive recording material
An image recording method characterized by performing purification. 2. The method according to claim 1 , wherein the surface layer of the reversible thermosensitive recording material is
2. The image recording method according to claim 1, wherein the image recording method comprises a fluorine-based material. 3. The cleaning means for washing the reversible thermosensitive recording material by immersing the reversible thermosensitive material in a liquid bath.
Cleaning roller, a cleaning or cleaning with the cleaning cloth by a sponge roller or cloth brush according to claim 1
Or the image recording method according to 2 . Wherein the temperature of the liquid used for cleaning of said substantially equal to the change in temperature of the reversible thermosensitive recording material, cleaning and reversible thermosensitive recording material of the transparency or allowed to change the color tone according to claim 1 or 2, wherein at the same time Image recording method.