JPH06199041A - Recording method - Google Patents

Abstract

PURPOSE:To improve repetition durability by a method wherein incombustible liquid is provided between a heat generating body and a recording material during formation and erasing of an image, in a device to form and erase an image through contact of the heat generating body with a reversible heat- sensitive recording material and relative movement thereof. CONSTITUTION:In a recording method wherein an image is formed and erased by utilization of a change in transparency owing to the temperature of a heat- sensitive layer 3 through relative movement of a reversible heat-sensitive recording material 3 and a heat generating body 1 in a state to bring the two members into contact with each other, volatile or non-volatile and incombustible or flame retardant liquid 2 is located between the heat generating substance 3 and the reversible heat-sensitive recording material 1. Silicone oil and fluorocarbon oil are used for the liquid 2, having a thickness of 1-20mum, temperature of 25 deg.C, and viscosity of 0.5-1000cp. Rollers 5 are arranged on both sides of the recording material 3 with the heat generating body 1 nipped therebetween, when occasion demand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method using a reversible thermosensitive recording material capable of repeatedly writing and erasing information by heating.

[0002]

2. Description of the Related Art In recent years, rewritable materials have been demanded as thermal recording materials in order to save paper resources. As the most effective material, one having a heat-sensitive layer in which an organic low molecular weight substance such as higher alcohol or higher fatty acid is dispersed in a resin such as polyester on a support is disclosed in, for example, JP-A-54-
No. 119377 and JP-A No. 55-154198 are known. Recording with this type of reversible heat-sensitive recording material, that is, image formation and its erasing is based on the change in transparency depending on the temperature of the heat-sensitive layer. It can be formed and erased.

On the other hand, the most general method for heating a heat-sensitive recording material for recording is heating with a thermal head, and repetitive rewriting with a thermal head is usually performed even when recording a reversible heat-sensitive recording material.

[0004]

However, in the rewriting by the thermal head, the reversible thermosensitive recording material is liable to deteriorate in comparison with the heating method such as the hot stamp. In addition, when the reversible thermosensitive recording material is repeatedly rewritten by a heating element such as a thermal head, scratches as shown in FIG. 8 occur on the surface of the thermosensitive layer or the protective layer, resulting in a uniform image. It cannot be formed or erased. It should be noted that erasing the image is more effective by means such as a heat roller or hot stamp than the thermal head. Further, if dust, dust, dust or the like adheres to a heating element such as a thermal head, heat from the thermal head is hard to be transferred to the reversible thermosensitive recording material, so that image formation and erasing cannot be performed. The present invention solves the above-mentioned drawbacks, and even when image formation and erasure are repeatedly performed on a reversible thermosensitive recording material a number of times, the reversible thermosensitive recording material is unlikely to be deteriorated or scratched, and dust and dirt are not generated. The present invention provides an image recording and / or erasing method which eliminates defects in image formation and its erasing due to heat transfer isolation due to dust and the like, and which improves repetitive durability.

[0005]

SUMMARY OF THE INVENTION The present invention provides a recording method for forming / erasing an image (information) by contacting a reversible thermosensitive recording material with a heating element and moving them relative to each other. Alternatively, at the time of erasing, a volatile or non-volatile, non-combustible or flame-retardant liquid is allowed to exist between the heating element and the reversible thermosensitive recording material.

The present inventors have variously studied the recording method (printing method and erasing method) using the reversible thermosensitive recording material. At the moment,
The causes of deterioration of the heat-sensitive layer of the reversible heat-sensitive recording material include
When the reversible thermosensitive recording material is heated and softened, it is deformed due to the pressure from the thermal head. In some cases, the reversible thermosensitive recording material has a temperature range higher than the required temperature. It is known that the heat-sensitive layer loses reversibility due to these causes because it is heated up to the point of causing so-called thermal destruction. Further, like the heat-sensitive layer, the protective layer is also deformed by heat and pressure, which is shown in FIG.
It is also known that the scratches shown in will be visible. In addition, with the deterioration of the reversible thermosensitive recording material, dust and dust mainly generated from the deteriorated reversible thermosensitive recording material itself adhere to the surface of the reversible thermosensitive recording material and the thermal head to transfer heat. It is also known that it causes image defects due to alienation. However, in order to reduce the friction, the friction coefficient between the reversible thermosensitive recording material and the heating element may be reduced or the pressure may be reduced. The method of reducing the friction coefficient has long been a protective layer of the reversible thermosensitive recording material. Attempts have been made by using a highly slippery material such as silicone resin, and some results have been achieved, but it is still insufficient. Although it is better to lower the pressure as much as possible, the thermal sensitivity gradually decreases as the pressure is reduced, and unevenness in image density tends to occur, so there is a limit to lowering the pressure.

In consideration of the above phenomenon and the like, the inventors of the present invention, regarding the above, where the thermal destruction occurs is in the center of each dot, as shown by the shaded area in FIG. Of the heat sensitive layers, the side closest to the surface directly below the heating element has the highest temperature, so this place is easily destroyed, and for the above, it is reversible heat sensitivity that the thermal sensitivity decreases when the pressure is reduced. This is because the air layer existing between the recording material and the heating element blocks heat, and therefore it is necessary to prevent the presence of a liquid between the heating element and the reversible thermosensitive recording material to form an air layer. For example, even if the pressure is reduced, the heat of the heating element is efficiently transferred to the reversible thermosensitive recording material, and the liquid layer is also effective for lowering the friction coefficient between the heating element and the reversible thermosensitive recording material. , Etc. The present invention is based on these.

The present invention will be described in more detail below.
As described above, the deterioration of the reversible thermosensitive recording material is roughly divided into two phenomena, deformation and thermal destruction. It is not clear at present what causes the thermal destruction, but, for example, the resin and the organic low-molecular substance are compatible with each other at a temperature higher than the clouding temperature and above a certain temperature, so that they are melted together to form a dispersed structure. Causes such as disappearance are considered. On the other hand, in order to prevent thermal destruction, it is effective to heat the reversible thermosensitive recording material so that the temperature does not vary depending on the place. That is, the temperature should be as high as possible from the top to the bottom of the heat-sensitive layer and from one end to the other end in the direction along the surface without making the high temperature region as shown in FIG. Deterioration can be prevented by heating to a suitable temperature. on the other hand,
In order to prevent the deformation, it is possible to prevent the deterioration by reducing the force applied by the heating element to the reversible thermosensitive recording material, especially the shear stress. As described above, mainly these two phenomena occur individually or in combination to cause scratches on the surface of the reversible thermosensitive recording material, and to collect dust and dirt.

The following (1) and (2) can be considered as such a heating method. (1) By widening the distance between the reversible thermosensitive recording material and the heating element, (1-1) applying no force that causes deformation or scratch of the reversible thermosensitive recording material, (1-2) temperature The gradient is gentle and uniform heating is performed, or (1-3) both are performed once. (2) Do not record at a low temperature and heat it uniformly to create a place where the temperature is too high. For this purpose, (2-1) take a long heating time, or (2-2) preheat to make the temperature of the reversible thermosensitive recording material higher than room temperature (however, lower than the recording temperature). One of the following is adopted. The method of the present invention advantageously employs means for realizing the method (1) among these (1) and (2).

The conditions for satisfying the above (1) are as follows. In the configuration shown in FIG. 1, a heat-resistant protective layer (described as “TC protective layer” in the figure) and an air layer exist between the heat-sensitive layer and the heating element, but Increasing the distance increases the thickness of either (or both) of the two layers. Certainly, if the thickness of the heat-resistant protective layer or the air layer is increased, deterioration of the heat-sensitive layer can be avoided. However, when the heat-resistant protective layer is thickened, the surface of the protective layer is more likely to be destroyed, that is, scratches are more likely to occur as the amount of heat required for recording is increased. Also, when the air layer is thickened, the surface of the protective layer will not be destroyed, but since the effect of heat insulation of the air is very high, heat will not reach the heat sensitive layer even if it is slightly separated, and the distance will be very large. Fine control is required.

The conditions satisfying the above (2) are as follows. The force that deforms the reversible thermosensitive recording material is mainly a shearing force generated by friction between the heating element and the reversible thermosensitive recording material, and other factors include static load between the heating element and the reversible thermosensitive recording material. is there. In the present invention, a layer of liquid is present between the heating element and the reversible thermosensitive recording material to separate the heating element from the reversible thermosensitive recording material,
The shearing force due to friction between the heating element and the reversible thermosensitive recording material is reduced. Further, the static load can be reduced for the same reason that the condition (1) is satisfied.

Therefore, when a liquid layer such as a water layer is used instead of the air layer, the thermal conductivity of both is 3.17 of that of air.
Water is 0.673 (unit: W / mk, measured at 80 ° C) compared to × 10 ^-2 (unit: W / mK, measured at 100 ° C), which is 10 times higher than that of the air layer. Changes in the amount of heat conduction are smaller than in the case of the air layer. Therefore, the decrease in heat conduction due to the increase in thickness is smaller than that in the case of the air layer, and it becomes possible to easily widen the distance between the reversible thermosensitive recording material and the heating element. Further, it goes without saying that the protective layer can be prevented from being destroyed as in the case where the air layer is thickened. Furthermore, since the thermal head and the reversible thermosensitive recording material are not brought into direct contact with the liquid, it is possible to prevent the reversible thermosensitive recording material from being scratched during transportation.

Next, a means for increasing the distance between the heat sensitive layer and the heating element will be considered. In the method of pressing the reversible thermosensitive recording material against the heating element using the conventional platen roller, it was possible to soften the degree of contact between the heat-sensitive layer and the heating element by lowering the pressing pressure, but the pressure If it is low, it becomes difficult to make the degree of adhesion uniform, and so-called uneven contact tends to occur. Therefore, instead of pressing with a platen roller, the surface tension of the liquid is used, and at the time of recording / erasing, the reversible thermosensitive recording material and the heating element are brought into close proximity to or in contact with each other in the presence of the liquid, so that the pressure is still low. It was confirmed that uniform contact was obtained.

Specifically, as shown in FIG. 2, the liquid 2
The reversible thermosensitive recording material 3 and the heating element 1 are brought into contact with each other to hold the reversible thermosensitive recording material 3 on the surface of the heating element. Further, as shown in FIG. 3, when the member 4 having a smooth surface is provided before and / or after the heating element 1, the supply amount of the liquid 2 is further stabilized. As a method other than using the surface tension of the liquid, as shown in FIG. 4, rollers 5 are arranged in front of and behind the heating element 1 to hold the reversible thermosensitive recording material 3 and move it.
It is also effective to hold the reversible thermosensitive recording material on the surface of the heating element by applying tension to the reversible thermosensitive recording material 3.

In the present invention, both a non-volatile liquid and a volatile liquid can be used, but their main uses and required qualities are different.

When a non-volatile liquid is used, it is difficult to remove the liquid once it is attached, and therefore it is not suitable for recording the display of a card. Among them, the endless belt-shaped reversible heat-sensitive recording material 3 is suitable for circulation. For this, for example, a device of the form shown in FIG. In such a usage, the liquid 2 is repeatedly exposed to the heat of the heating element 1, so that the deterioration due to the heat is generally a problem. The temperature of the heating element is 200 ℃ on the hot plate and 300 ℃ on the thermal head.
Since it reaches close to the liquid, a liquid that does not deteriorate at each temperature is required. In the example shown in FIG. 5, it is necessary to know the display status from the outside. In the figure, 6 is a container having a display unit. Therefore, in carrying out the method of FIG. 5, there are silicone oils, fluorocarbon oils, fatty acids, phenols, alcohols, ketones, esters and the like, which have volatility equal to or lower than that of water at room temperature. .

On the other hand, in the case of a volatile liquid, air bubbles are generated around the heating element, so it is not desirable to use the liquid so that the liquid always remains around the heating element. Immediately before the reversible thermosensitive recording material comes into contact with the heating element. A suitable method is to apply a liquid to a reversible thermosensitive recording material and evaporate and remove it after recording. An example of such usage is recording on the display portion of a card (as a particularly suitable example although it can be used for a display or the like). The required quality must be a liquid that does not ignite the vapor, that is, a non-combustible or flame-retardant vapor, since the vapor of a volatile liquid diffuses around. Specific examples thereof include silicone oils and fluorocarbon oils that exhibit volatility equal to or higher than that of water at room temperature.

Of the above liquids, silicone oil and fluorine-based oil, both volatile and non-volatile, are particularly preferable.

The thickness between the heating element and the reversible thermosensitive recording material is preferably 20 μm or less, more preferably 1 μm or more. In order to obtain this thickness, the viscosity of the liquid at 25 ° C. is 0.5 cp (centipoise) or more and 1000 c or more.
It is preferably p or less. Above this range, heat will not be transferred to the reversible thermosensitive recording material, and below this range, the thickness between the thermosensitive layer and the heating element will be thin, and the temperature distribution in the reversible thermosensitive recording material will be rapidly completed, resulting in a reversible thermosensitive recording material. The thermal material is likely to deteriorate. Further, at a low viscosity of 0.5 cp or less, it is difficult to maintain the thickness of the liquid, and at a high viscosity of 1000 cp or more, it is difficult to relatively convey the reversible thermosensitive recording material.

The heating element in the present invention means, regardless of the heat source, all the parts which are in contact with the reversible thermosensitive recording material and have a temperature higher than the recording temperature as viewed from the reversible thermosensitive recording material ( Strictly speaking, only the surfaces that are in contact). For example, in the case of a thermal head, the surface of the protective layer of the resistance heating element, which is heated to a high temperature by the heat generated by the resistance heating element, is regarded as the heating element.

The reversible thermosensitive recording material in the present invention means
It is a material that reversibly causes visible changes due to temperature changes. The visible change can be divided into a change in color tone and a change in shape, but in the present invention, a material that causes a change in color tone is mainly used. Changes in color tone include changes in transmittance, reflectance, absorption wavelength, scattering degree, and the like, and an actual reversible thermosensitive recording material displays with a combination of these changes. More specifically, (a) a material in which the transparent state and the cloudy state reversibly change. (B) A material such as a dye whose color changes reversibly. Currently, it can be classified into two types of systems. As a typical example of (a), as described in the prior art, a resin base material such as polyester having a heat-sensitive layer in which organic low molecular weight compounds such as higher alcohols and higher fatty acids are dispersed is provided, and ( Examples of (b) include those obtained by enhancing the reversibility of conventional leuco-type heat-sensitive recording materials (eg, described in JP-A-188293 and JP-A-188294).

The transparent state in the above-mentioned (a) "a material composed of a resin base material and an organic low-molecular substance dispersed in the resin base material and reversibly changing the transparent and cloudy states by heating" The difference from the cloudy and opaque state is presumed as follows. That is, (i) in the case of being 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. It looks transparent because it penetrates to the side,
Further, in the case of (ii) 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 axes of the individual crystals are oriented in various directions. The light incident from is refracted many times at the crystal interface of the organic low-molecular substance particles and is scattered, so it looks white,
And so on.

In FIG. 6 (representing the change in transparency due to heat), a thermosensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material is, for example, T
It is cloudy and opaque at room temperature below ₀ . When this is heated, it begins to become transparent from the temperature T ₁ and the temperature T ₂ ~
When it is heated to T ₃ , it becomes transparent, and in this state, it remains transparent even if it is returned to room temperature below T ₀ again. This is because as the resin begins to soften near the temperature T ₁ and the softening progresses, the resin shrinks and reduces the interface between the resin and the organic low-molecular substance particles or the voids in the particles, so that the transparency gradually increases and the temperature T ₂ increases. ~
At T ₃ , the organic low molecular weight substance is in a semi-molten state and becomes transparent by filling the remaining voids with the melted organic low molecular weight substance, and the seed crystal is cooled while remaining, and crystallized at a relatively high temperature. When the resin is still soft,
It is considered that the resin follows the volume change of the particles due to crystallization, voids are not formed, and the transparent state is maintained. Further heating to a temperature of T ₄ or higher results in a semitransparent state between the maximum transparency and the maximum opacity. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. This is because after the organic low molecular weight substance has completely melted at a temperature of T ₄ or higher, it becomes a supercooled state and crystallizes at a temperature slightly higher than T ₀ , and at that time, the resin cannot follow the volume change accompanying the crystallization and the void Is likely to occur. However, the temperature-transparency change curve shown in FIG. 6 merely shows a typical example, and the transparency and the like in each state may change depending on the material by changing the material.

Therefore, the heat-sensitive layer can be selectively heated by selectively applying heat to form a cloudy image on a transparent background and a transparent image on a cloudy background, and the change can be repeated many times. It is possible. By arranging a coloring sheet on the back surface of such a heat-sensitive layer, it is possible to form an image of the color of the coloring sheet on a white background or a white image on the background of the color of the coloring sheet. 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.

Using such a reversible thermosensitive recording material,
To perform image formation and erasure (image erasure), a method using a thermal head for image formation, and a member dedicated to the image erasing, for example, a heating member such as a heat block, a heat roller, or a thermal head are used. Alternatively, a method of changing the applied energy condition in image formation and image deletion using a single thermal head may be considered, but the method is not limited to these.

As a method of allowing a volatile silicone oil to exist between an energy applying member such as a thermal head and the reversible thermosensitive recording material at the time of image recording, a felt, a sponge roller or the like may be placed on the reversible thermosensitive recording material immediately before recording. A method of applying volatile silicone oil may be considered. In addition, as a method for allowing the volatile silicone oil to exist between the energy applying member such as a thermal head and the reversible thermosensitive recording material at the time of erasing an image, the volatile silicone oil is volatile on the reversible thermosensitive recording medium in the same manner as during recording. A method of applying silicone oil, a method of applying a volatile silicone oil with a felt or the like directly to a heat roller that slides immediately before erasing in the case of a heat roller or the like can be considered.

In order to prepare the reversible thermosensitive recording material of (a) used in the present invention, generally, (1) a solution in which two components of a resin base material and an organic low molecular weight substance are dissolved or (2) a solution of the resin base material. A dispersion liquid in which an organic low molecular weight substance is dispersed in fine particles is used (as a solvent, one that does not dissolve at least one of the organic low molecular weight substances is used) is applied on a support such as a plastic film, a glass plate or a metal plate. It may be dried to form a laminated heat-sensitive layer. 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 weight substance, for example, tetrahydrofuran,
Methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, benzene and the like can be mentioned. The organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state in the heat-sensitive layer obtained not only when the dispersion liquid is used but also when the solution is used.

The resin base material used for the heat-sensitive layer is a material that forms a layer in which an organic low molecular weight substance is uniformly dispersed and held, and has an effect on the transparency at maximum transparency. Therefore, the resin base material is preferably a resin having good transparency, mechanical stability, and good film-forming property. Such resins include polyvinyl chloride; vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl acetate-maleic acid copolymers, vinyl chloride-acrylate copolymers, etc. Vinyl chloride-based copolymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-acrylonitrile copolymers and other vinylidene chloride copolymers; polyesters; polyamides; polyacrylates or polymethacrylates or acrylate-methacrylates Copolymer; Silicone resin and the like can be mentioned. Needless to say, these resins may be used alone or in combination of two or more.

On the other hand, as the organic low molecular weight substance, any substance that changes from polycrystal to single crystal due to heat in the recording layer (changes within the temperature range of T _{1 to} T ₃ shown in FIG. 6) may be used.
Generally, those having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. are used. Such organic low molecular weight substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkyl amines; alkanes; ankenes; 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; halogenallylcarboxylic acids or Of their esters, amides or ammonium salts; thioalcohols; thiocarboxylic acids or their esters, amines or ammonium salts; of thioalcohols Carboxylic acid esters, and the like. These may be used alone or in admixture of two or more. The carbon number of these compounds is 10
60, preferably 10-38, particularly 10-30 are preferred. The alcohol group moiety 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 of oxygen, nitrogen, sulfur and halogen in the molecule, for example, -OH, -COOH, -CONH, -COOR, -N.
_{H, -NH 2, -S -,} - S-S -, - O-, is preferably a compound containing a halogen and the like.

More specifically, as these compounds,
Uric acid, dodecanoic acid, myristic acid, pentadecane
Acid, palmitic acid, stearic acid, behenic acid, nonadeca
Higher fatty acids such as acid, araginic acid and oleic acid;
Methyl acid salt, tetradecyl stearate, stearic acid
Octadecyl, octadecyl laurate, palmitic acid
Tetradecyl, dodecyl behenate; Etc., such as ether or thioether. Above all, the present invention
Higher fatty acids, especially palmitic acid, stearic acid,
Higher fats with 16 or more carbon atoms such as henic acid and lignoceric acid
Acids are preferable, and higher fatty acids having 16 to 24 carbon atoms are preferable.
Furthermore, higher fatty acids having 16 to 24 carbon atoms are more preferable.

Further, in order to expand the temperature range in which the material can be made transparent, an appropriate combination of the organic low molecular weight substances described in this specification or a combination of such an organic low molecular weight substance with another material having a different melting point can be used. Good. These are disclosed, for example, in JP-A-63-39378 and JP-A-63-130380.
Gazettes, such as Japanese Patent Application No. Sho 63-14754, Japanese Patent Application No. 1
However, the present invention is not limited thereto.

The thickness of the heat sensitive layer is preferably 1 to 30 μm,
2 to 20 μm is more preferable. If the heat-sensitive layer is too thick, heat distribution will occur in the layer and it will be difficult to achieve uniform transparency. On the other hand, if the heat-sensitive layer is too thin, the white turbidity is lowered and the contrast is lowered. Further, the white turbidity can be increased by increasing the amount of the organic low molecular weight substance in the heat sensitive layer. 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 1: 1 to 1: 3. If the ratio of the resin base material is below this range, it will be difficult to form a film in which the organic low molecular weight material is retained in the resin base material. Becomes difficult.

In addition to the above components, additives such as a surface active agent and a high boiling point solvent can be added to the heat-sensitive layer in order to prepare a transparent image. Specific examples of these additives are as follows. Tributyl phosphate, tri-phosphate
2-ethylhexyl, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate, phthalate Acid diisononyl, dioctyldecyl phthalate, diisodecyl phthalate, butylbenzyl phthalate, dibutyl adipate, di-n-hexyl adipate, di-2-hexylhexyl 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, acetylcitric acid Ribuchiru.

Examples of surfactants and other additives; polyhydric alcohol higher fatty acid esters; polyhydric alcohol higher alkyl ethers; polyhydric alcohol higher fatty acid esters, higher alcohols, higher alkylphenols, higher alcohols, higher alkylamines, higher fatty acids Amides, oils and fats or polypropylene glycols, lower olefin oxides;
Acetylene glycol; Na, Ca, Ba or Mg salt of higher alkylbenzene sulfonic acid; Higher fatty acid, aromatic carboxylic acid, higher fatty acid sulfonic acid, aromatic sulfonic acid, sulfuric acid monoester or phosphoric acid mono- or di-ester Ca, Ba Or Mg salt; low-sulfated oil; poly long-chain alkyl acrylate; acrylic orgomer; poly long-chain alkyl methacrylate, long-chain alkyl methacrylate-amine-containing monomer copolymer; styrene-maleic anhydride copolymer; olefin-anhydrous Maleic acid copolymer.

When the image of this reversible thermosensitive recording material is used as a reflection image, a contrast can be enhanced by providing a light reflecting layer on the back surface of the thermosensitive layer even if the thickness of the thermosensitive layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned (described in JP-A No. 64-14079).

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 the solvent, monomer components and the like of the protective layer-forming liquid (JP-A-1-13378).
1). As the material for 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 heat sensitive layer. That is, specifically, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like can be mentioned. Although the thickness of the intermediate layer varies depending on the use, it is preferably about 0.1 to 2 μm. Below this,
The protective effect decreases, and if it exceeds this, the thermal sensitivity decreases.

EXAMPLES The present invention will be described more specifically by way of examples, but the present invention is not limited thereto. All parts and% herein are by weight.

Example 1 (Preparation of reversible thermosensitive recording material) P having a thickness of about 100 μm
Aluminum was vacuum-deposited on the ET film so as to have a thickness of about 400 liters to form a light reflecting layer, and a liquid having the following composition was applied and dried thereon to form a heat sensitive layer. Stearic acid 5 parts Behenic acid 5 parts Diisodecyl phthalate 3 parts Vinyl chloride-vinyl acetate copolymer resin 39 parts (Denka vinyl # 1000MT manufactured by Denki Kagaku Kogyo Co., Ltd.) Tetrahydrofuran 100 parts Toluene 65 parts Next, on the heat-sensitive layer: Approximately 3μ made of UV curable resin by coating / drying the composition liquid and UV irradiation.
A protective layer of m is provided, and it becomes a cloudy state at a second specific temperature of about 100 ° C. or higher, and a region of the first specific temperature is about 70 ° C.
A reversible thermosensitive recording film having a characteristic of becoming transparent at a temperature of 100 ° C. or higher was prepared. 75% butyl acetate solution of urethane acrylate UV-curable resin (Dainippon Ink and Chemicals, Unidick C7-157) 10 parts Toluene 10 parts

Experiment 1 Silicone oil (KF54 manufactured by Shin-Etsu Silicone Co. Ltd., boiling point is unknown but non-volatile) was attached to a part of the surface of the reversible thermosensitive recording material in a transparent state, and solid printing was attempted by a thermal head. The pressing pressure of the thermal head at this time was 100 g / cm ² , and the applied energy was dropped to 0.15 mj / dot, which is half the normal applied energy.

Experiment 2 Silicone oil (KF54 manufactured by Shin-Etsu Silicone Co., Ltd.) was attached to a part of the surface of the reversible thermosensitive recording material in a transparent state, and solid printing was attempted by a thermal head. The applied energy at this time was 0.3 mj / dot, which was equal to the normal applied energy. Further, the pressing pressure of the thermal head was set to 20 g / cm ^{2 which} was 1/5 of the usual pressure. As a result, it was cloudy as a whole as a whole, but was uniformly cloudy only at the place where the silicone oil was attached.

Experiment 3 (Example 1) Silicone oil (KF54 manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to the entire surface of the reversible thermosensitive recording material in a transparent state, and solid printing with a thermal head and erasing with a hot plate were repeated. It was The pressing pressure of the thermal head is 25g /
in the cm ^2, set to the lowest energy in the energy range the applied energy of the thermal head when the first examines the thermosensitive degree to create a graph such as shown in FIG. 7, the concentration of the clouding is stable (The position of the ↑ mark in the figure, 0.
25 mj / dot). The hot plate was set so that the surface temperature was 80 ° C. and pressed against the reversible thermosensitive recording material at a pressure of 100 g / cm ² for 1 second. Table 1 shows the image densities on the reversible thermosensitive recording material at the beginning of the repetition, the 100th time and the 200th time.

Experiment 4 (Example 2) The kind of silicone oil used was KF9 manufactured by Shin-Etsu Silicone Co., Ltd.
An experiment similar to that of Experiment 3 was carried out by changing to 6L-0.65 (volatile, boiling point 100 ° C.). The results are summarized in Table 1.

Experiment 5 (Comparative Example 1) Printing and erasing were repeated in the same manner as in Experiment 3 without applying silicone oil. The pressing pressure of the thermal head was 100 g / cm ² , and the printing energy was determined to be 0.3 mj / dot by examining the thermal sensitivity (Δ in FIG. 7).
mark). The results are summarized in Table 1.

Experiment 6 Silicone oil (KF54 manufactured by Shin-Etsu Silicone Co., Ltd.) was attached to a part of the surface of the reversible thermosensitive recording material in a transparent state, and solid printing was attempted by a thermal head. The applied energy at this time was 0.15 mj / dot, which was half the normal applied energy. As a result, only the place where the silicone oil adhered became cloudy.

Experiment 7 Silicone oil (KF54 manufactured by Shin-Etsu Silicone Co., Ltd., boiling point is unknown but non-volatile) was attached to a part of the surface of the reversible thermosensitive recording material in a transparent state, and solid printing was attempted by a thermal head. The applied energy at this time is 0.3 mj
/ Dot was made equal to the normal applied energy. Also,
The pressing pressure of the thermal head is 1/5 of the normal pressure, 20 g / c
It was in m ^2. As a result, it was cloudy as a whole as a whole, but was uniformly cloudy only at the place where the silicone oil was attached.

Experiment 8 Silicone oil (KF54 manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to the entire surface of the transparent reversible thermosensitive recording material to repeat solid printing with a thermal head and erasing with a hot plate. The applied energy of the thermal head at this time was first examined by examining the thermal sensitivity and a graph as shown in FIG. 7 was created, and the position relationship between this graph and the applied energy was set to be the same as in the normal case (see FIG. The position of ↑ mark in the inside, 0.18 mj for 0.30 mj / dot for normal
/ Dot). The hot plate was set so that the surface temperature was 80 ° C. and pressed against the reversible thermosensitive recording material at a pressure of 100 g / cm ² for 1 second. Table 1 summarizes the results of visual determination of scratches and head shavings on the recording medium and the image density at the beginning of the repetition and at the 100th repetition.

Experiment 9 The kind of silicone oil used was KF9 manufactured by Shin-Etsu Silicone Co., Ltd.
An experiment similar to that of Experiment 8 was carried out by changing to 6L-0.65 (volatile, boiling point 100 ° C). The results are summarized in Table 1.

Experiment 10 (Comparative Example 2) An experiment similar to Experiment 3 was conducted without applying silicone oil and setting the thermal head applied energy to the usual 0.30 mj / dot. The results are summarized in Table 1.

[0048]

[Table 1] ○: Almost none ×: Yes

[0049]

As is clear from the description of the examples, the reversible thermosensitive recording material was prepared by allowing a liquid to exist between the reversible thermosensitive recording material and the energy applying member during recording and / or erasing. A liquid layer is formed on the top of the reversible thermosensitive recording material to prevent scratches and thermal head debris from being generated. In addition, the temperature gradient is gentle and uniform heating can be performed. Since heat transfer margins such as dust, dust, and dust are also absorbed, a printed image with high image density can be obtained even after repeated recording.

[Brief description of drawings]

FIG. 1 is a diagram showing a temperature distribution at the moment when heat is applied to a reversible thermosensitive recording material by a thermal head.

FIG. 2 is a diagram for explaining the method of the present invention.

FIG. 3 is a diagram for explaining the method of the present invention.

FIG. 4 is a diagram for explaining the method of the present invention.

FIG. 5 is a diagram for explaining the method of the present invention.

FIG. 6 is a diagram showing a change in transparency of a reversible thermosensitive recording material due to heat.

FIG. 7 is a graph showing the thermal sensitivity of the reversible thermosensitive recording materials in Experiments 3, 5 and 8.

FIG. 8 is a diagram showing an example of a typical pattern of scratches appearing on the surface of a heat-sensitive layer or a protective layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating element 2 Liquid 3 Reversible thermosensitive recording material 4 Member having a smooth surface 5 Roller 6 Container

Front Page Continuation (72) Inventor Kunichika Moroboshi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Yoshihiko Hotta 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. Within

Claims (6)

[Claims] 1. A recording method for forming / erasing an image by contacting a reversible thermosensitive recording material with a heating element and moving them relative to each other, wherein the heating element and the reversible feeling are formed when the image is formed or erased. A recording method characterized in that a volatile or non-volatile, non-combustible or flame-retardant liquid is allowed to exist between the recording material and the thermal recording material. 2. A liquid having a smooth surface in front of and / or behind the heating element in the moving direction of the reversible thermosensitive recording material is provided, and a liquid to be present between the reversible thermosensitive recording material and the heating element is provided. The recording method according to claim 1, wherein an appropriate amount is used. 3. The recording method according to claim 1, wherein rollers are arranged on both sides of the reversible thermosensitive recording material so as to sandwich the heating element and to apply tension to the reversible thermosensitive recording material. 4. The recording method according to claim 1, wherein the thickness of the liquid between the heating element and the reversible thermosensitive recording material is 1 μm or more and 20 μm or less. 5. The recording according to claim 1, wherein the heating element and the reversible thermosensitive recording material are embedded in a liquid, and the reversible thermosensitive recording material is always in the liquid for image formation / erasing. Method. 6. The viscosity of the liquid is 0.5 c at a temperature of 25 ° C.
The recording method according to claim 1, wherein the recording method is p (centipoise) or more and 1000 cp or less.