JPH06199042A - Image recording method - Google Patents

Abstract

PURPOSE:To provide a sharply increased life for a recording material by a method wherein after transparency or a color tone is changed in one and the same recording region the predetermined number of time, it is changed in a different recording region, in an image recording method using a recording medium having a reversible heat- sensitive material. CONSTITUTION:In a recording medium 1 having a plurality of image recording surfaces (recording regions) 11 and 12, to provide an increased life, a recording method (1) wherein the recording surface is changed at intervals of some number of times, a recording method (2) wherein after recording is repeatedly made on one and the same surface, no recording is thereafter made on the recording surface but recording is made on a different recording surface are employed. Namely, in a case (1), recording is recorded alternately on the recording surfaces 11 and 12, namely, after recording is made on the first recording surface 11 by using a single thermal head, an image on the recording surface 12 is erased and consecutively an image on the recording surface 11 is erased, and an image is recorded on the recording surface 12. Further, in a case of (2), first, recording and erasing of an image are repeated on the recording surface 11, and secondly, after the above is repeated the specified number of times, recording and erasing are effected, in a similar manner described above, on the recording surface 12.

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 for repeatedly forming and erasing images on a reversible thermosensitive recording material.

[0002]

2. Description of the Related Art In recent years, temporary image formation (recording) can be performed and the image can be erased when it is no longer needed.
Moreover, reversible heat-sensitive recording materials that can be repeatedly recorded and erased have been receiving attention. As a typical one,
A reversible thermosensitive recording material in which an organic low molecular weight substance such as a higher fatty acid is dispersed in a resin base material such as a vinyl chloride resin is known (Japanese Patent Laid-Open No. 55-154198).

However, the surface of such a conventional reversible thermosensitive recording material (hereinafter sometimes simply referred to as "recording material") is heated when an image is repeatedly formed and erased by heating, particularly when a thermal head is used. While rubbing while scratching, scratches were generated on the surface, and when the scratches became severe, there was the inconvenience that a uniform image could not be formed.

The present inventors have proposed that a protective layer be provided on the surface of such a recording material to reduce scratches on the surface when a thermal head is used (JP-A-63-221087).
(Japanese Patent Laid-Open No. 63-317385 and Japanese Patent Laid-Open No. 2-566). However, it has been difficult to say that merely providing a protective layer on the surface of a conventional recording material is sufficient when the number of times recording / erasing is repeated is large.

Further, in the recording material of the type in which the organic low molecular weight substance is dispersed in the resin base material described above, if a heating method in which heat and pressure are applied simultaneously such as a thermal head is used, the organic low molecular weight substance increases as the number of recordings increases. There is a drawback that particles are aggregated and the contrast (white turbidity) is lowered.

[0006]

SUMMARY OF THE INVENTION The present invention is an image recording method capable of remarkably increasing the life of a recording material by supplementing the life of the above reversible thermosensitive recording material with a specific recording method. Is provided.

[0007]

According to the present invention, in an image forming method for recording and erasing an image using a recording material having a reversible thermosensitive material, transparency or color tone is changed a predetermined number of times in the same recording area. After that, it is characterized in that it is changed in another recording area.

The present invention will be described in more detail below. FIG. 1 shows an example in which the recording medium has a plurality of image recording surfaces and the recording area is the recording surfaces. Specifically, the image recording surfaces 11 and 12 are formed at two locations on the recording medium 1. Of course, the number of recording surfaces may be more than that.

When a plurality of image recording surfaces are provided, (a) a method of changing the recording surface at a certain number of times, and (b) repeatedly recording on the same recording surface and then recording on this recording surface. Instead, there are two methods: recording on another recording surface.

The "method of changing the recording surface every certain number of times" in (a) is the following means. That is, for example, recording is performed alternately on the recording surface 11 and the recording surface 12 of FIG. That is, using only one thermal head, the image recorded on the recording surface 12 is first erased after recording on the recording surface 11. Then, the image on the recording surface 11 is erased, and the image is recorded on the recording surface 12. By doing so, recording and erasing can be performed only by passing the card 1 partially provided with the recording material in one direction (including the reverse direction), and there is an advantage that the device configuration can be simplified. . In this case, the voltage is
The recording energy can be changed by changing the pulse width.

Further, the recording surface may not be changed every time, but may be changed every two or more times. This number may be a fixed number or not a fixed number but may be changed for each recording depending on the purpose of use. May be changed. Furthermore, the previous or previous record may be left without being deleted for each record. For example, when 5 recording surfaces are set, after sequentially recording on 5 recording surfaces and using all the recording surfaces, after the 6th recording, the first recorded one of the 5 recordings is erased. The sixth recording is performed. By doing so, the usage history can be appropriately left. In addition,
It goes without saying that the life of the card is doubled by using two recording surfaces. Further, by increasing the number of recording surfaces to three or more, the life can be tripled or more.

The above-mentioned (b) "method of repeatedly recording on the same recording surface and then not recording on this recording surface but recording on another recording surface" is the following means. That is, for example, recording and erasing of an image are repeated on the recording surface 11 of FIG.
After repeating this for a certain number of times, the storage and deletion of the image is repeated for a certain number of times on the recording surface 12.

The term "a certain number of times" common to the above (a) and (b) means that (i) the life of the recording material according to the present invention (more accurately, "the recording material" occupying the recording surface). In this case, the allowable number of times that recording / erasing can be performed is set in advance in the information storage unit and the recording surface is switched, and (ii) the recording surface is detected by detecting the degree of deterioration of the recording material. There are two switching methods of and. Even in these cases, the life of the card 1 is doubled by providing two recording surfaces, and the life is also tripled by providing three or more recording surfaces. This method has an advantage that the recording surface changes depending on the number of times of repeated recording, and the life of the card 1 itself easily changes.

FIG. 2 shows three examples of recording methods in which the size of the recording area is a pixel, and such methods prevent concentrated recording at one location, resulting in deterioration of the recording material. Is to prevent. The term "pixel" as used herein refers to a unit that constitutes an individual image. For example, when an image is formed by heat generated by the thermal head, it can be said that the size of the heating element of the thermal head is one pixel. , Also, if the image was created with the intention of being composed of a collection of sizes of the heating elements of the thermal head, the collection becomes a pixel,
That is.

FIG. 2A shows the overlap of the recording surfaces when the numbers 1, 2, and 3 are recorded.
It is a part commonly recorded with the number 3. That is, even if different numbers are used, a certain portion is always concentrated and used for recording, and it is felt that the entire recording material is deteriorated due to the deterioration of the portion. This is a common phenomenon not only for numbers, but also for kanji, hiragana, katakana, and the alphabet.

As shown in FIG. 2B, the life can be doubled by moving the recording surface beyond the overlapped recording portion of the diagonal line. Further, as shown in FIG. 2 (c), the life can be quadrupled by moving to four locations.

Compared with the above-mentioned method of changing the image recording position, this method of changing the pixel unit does not require the image recording surface to be larger than necessary, and the other portion (non-recording surface 13) of the recording material is printed. It can be effectively used for advertisements, etc. In this method, it is preferable to change the recording surface at regular intervals, preset the number of times in the information recording unit, and change the recording surface in pixel units.

There are two methods for setting the number of repetitions for changing the recording surface. One is to apply the information storage unit and the other is to detect deterioration of the recording material. The recording surface may be provided on only one side or both sides of the recording medium.

The information storage section is arranged in a portion which is not used for displaying the recording material, such as a magnetic storage section, an IC, an optical memory or the like. In the recording device, the number of times stored in the information storage unit is detected, and recording is performed on the recording surface of the recording material according to the number of times, and the number of times is recorded once in the information recording unit between the detection of the number of times and recording. Memorize the increased value.

Deterioration of the recording material varies depending on the recording material, but is usually represented by a decrease in the image density and an increase in the background density (the image becomes difficult to erase). Deterioration detection is achieved by measuring this concentration change. In a recording material in which an organic low molecular weight substance is dispersed in the resin base material, deterioration due to repeated appearance appears as a decrease in white turbidity. FIG. 3 shows how the recording material deteriorates. This recording material, which was initially recorded with a cloudy density (D ₁ ), can be recorded with a constant density up to a certain number of times (A ₁ ), but when the number of repetitions A ₁ is exceeded, the whiteness gradually begins to decrease. At this time, the use limit density (D ₂ ) is set in advance, and when D ₂ is reached (the number of repetitions: A ₂ ), it moves to the next recording position. This limit number of times varies depending on the recording conditions such as use environment, energy and pressure.

The detection of the density is performed by using a means for irradiating light and a means for detecting light. When the support is transparent, a means for irradiating light and a means for detecting light are usually arranged sandwiching the recording material to detect a change in transparency.

When the support is opaque, a reflecting means is arranged on the recording surface side of the recording material to detect a change in reflectance.
Even when the support is transparent, it is possible to detect a change in reflectance by disposing a reflecting plate and a light absorbing plate on one side.

The part to be detected is preferably a part recorded at a constant repeat interval, for example, a part recorded every time or 2 to
It is good to have a part that records once every four passes.
There is a demerit that the deterioration of the entire recording material is not visible at the part where irregular recording is performed. If there is no part to be recorded periodically, a fixed position may be periodically recorded and the position may be detected for deterioration detection.

By the way, the "reversible thermosensitive recording material" in the present invention is a material which reversibly causes a visible change due to a temperature change. The visible change can be divided into a change in color state and a change in shape, but 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, etc., and in actual reversible thermosensitive recording materials, display is performed by a combination of these changes. More specifically, anything that reversibly changes transparency and color tone by heat may be used. For example, a mixture of two or more kinds of polymers, which changes to transparent or cloudy depending on the difference in compatibility (special characteristics Kaisho 61-25
8853), which utilizes a phase change of a liquid crystal polymer (Japanese Patent Laid-Open No. 62-66990), which has a first color state at a first specific temperature higher than room temperature and is higher than the first specific temperature. The second color state can be obtained by heating at a high second specific temperature and then cooling.

In particular, the one whose color state changes at the first specific temperature and the second specific temperature is preferably used. As an example of these, a transparent state is obtained at a first specific temperature and a cloudy state is obtained at a second specific temperature (Japanese Patent Laid-Open No. 55-15419).
No. 8), a color that develops at a second specific temperature and a color that disappears at a first specific temperature (Japanese Patent Application No. 2-414438), a white turbid state at the first specific temperature, and a second specific temperature. Which becomes transparent (JP-A-3-169590), those which develop black, red, blue or the like at a first specific temperature and which are decolorized at a second specific temperature (JP-A-2-188293, JP-A-2
No. 188294). Among these, the following two materials are particularly representative. A material that reversibly changes between a transparent state and a cloudy state. A material whose color such as dye changes chemically.

As the conventional technique and as repeatedly described above, a heat-sensitive layer in which an organic low molecular weight substance such as a higher alcohol or a higher fatty acid is dispersed in a resin base material such as polyester is formed on a support. The one provided is a typical example. As a typical example, a leuco thermosensitive recording material having enhanced reversibility can be mentioned.

A heat-sensitive layer of the type that causes a change in the transparency (where the image recording surfaces 11 and 12 are formed).
Is mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material. The reversible thermosensitive recording material here has a temperature range in which it becomes transparent, as described later. The thermoreversible recording medium of the present invention utilizes the transparency change (transparent state, cloudy opaque state) as described above, and the difference between the transparent state and the cloudy opaque state is presumed as follows. That is, in the case of (i) transparent, the organic low-molecular-weight substance particles dispersed in the resin base material and the resin base material are in close contact with each other without a gap, and there is no void inside the particles, and the light enters from one side. The light appears to be transparent because it is transmitted to the opposite side without being scattered. (Ii) In the case of white turbidity, the particles of the organic low molecular weight substance are composed of fine particle crystals of the organic low molecular weight substance. This is because a void is formed at the interface or at the interface between the particles and the resin base material, and light incident from one side appears white because it is refracted, reflected and scattered at the interface between the void and the crystal and at the interface between the void and the resin.

In FIG. 4 (representing the change in transparency due to heat), a heat-sensitive 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 ~
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 it remains and is 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 is completely melted at a temperature of T ₄ or higher, it is supercooled and crystallized 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. 4 is only a representative example, and changing the material may change the transparency in each state depending on 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. Also, when projected with an OHP (overhead projector) or the like, the cloudy part becomes a dark part, and the transparent part transmits light and becomes a bright part on the screen. Further, when the image of the reversible thermosensitive recording material is used as a reflection image, if a layer that reflects light is provided on the back surface of the recording layer, the contrast can be increased even if the thickness of the recording layer is reduced. Specifically, vapor deposition of Al, Ni, Sn and the like can be mentioned.

To prepare a 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 weight substance are dissolved, or (2) a solution of a resin base material (solvent As the material used, a liquid in which at least one of the organic low molecular weight substances is not dissolved is used, and a dispersion liquid in which the organic low molecular weight substance is dispersed in the form of fine particles is applied to a support such as a plastic film, a glass plate, or a metal plate and dried. Then, the heat sensitive layer may be formed.

The solvent for preparing the heat-sensitive layer or the heat-sensitive recording material can be variously selected depending on the kind of the resin base material and the organic low molecular weight substance, and for example, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, Examples thereof include benzene. Of course, when using the dispersion,
Even when a solution is used, the organic low molecular weight substance is precipitated as fine particles and exists in a dispersed state in the obtained heat-sensitive layer.

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.

Examples of 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- Vinyl chloride-based copolymers such as acrylate copolymers; polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymers, vinylidene chloride-based copolymers such as vinylidene chloride-acrylonitrile copolymers; polyesters; polyamides; polyacrylates or polyacrylates Methacrylate or acrylate-methacrylate copolymer; silicone resin and the like can be mentioned. These may be used alone or in combination of two or more.

On the other hand, as the organic low molecular weight substance, any substance which changes from polycrystal to single crystal due to heat in the recording layer may be used, and those having a melting point of 30 to 200 ° C., preferably about 50 to 150 ° C. are generally used. . Such organic low-molecular substances include alkanols; alkane diols; halogen alkanols or halogen alkane diols; alkylamines; alkanes; alkenes; alkynes; halogen alkanes; halogen alkenes; halogen alkynes; cycloalkanes; cycloalkenes; cycloalkynes; saturated or Unsaturated mono- or dicarboxylic acids or their esters, amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; arylcarboxylic acids or their esters, amides or ammonium salts; halogenallylcarboxylic acids or Thioalcohols; esters, amides or ammonium salts thereof; 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 preferably 10 to 60, preferably 10 to 38, and particularly preferably 10 to 30. 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-, -COO.
_{R, -NH -, - NH 2} , -S -, - SS -, - 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; steer
Methyl phosphate, tetradecyl stearate, stearin
Acid octadecyl, octadecyl laurate, palmitin
Of higher fatty acids such as tetradecyl acid acid and dodecyl behenate
Steal; Etc., such as ether or thioether. Above all, 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
Is preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.
Yes.

In order to widen the range of temperatures at which the material can be made transparent, the organic low molecular weight substances described in this specification may be appropriately combined, or such organic low molecular weight substances may be combined with other materials having different melting points. . These are, for example, JP-A-63-3
9378, JP 63-130380 and other publications, and Japanese Patent Application 63-14
No. 754, Japanese Patent Application No. 1-140109 and the like are disclosed, but the invention is not limited thereto. The ratio of the organic low molecular weight substance and the resin base material in the heat sensitive layer is 2: 2 by weight.
It is preferably about 1 to 1:16, more preferably 1: 2 to 1: 8. 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 weight material is retained in the resin base material. Becomes difficult.

In addition to the above components, additives such as a surfactant and a high boiling point solvent may be added to the heat-sensitive layer in order to facilitate the formation of a transparent image. Specific examples of these additives are as follows. Examples of high boiling point solvents: tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, diphthalate. -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 acetylricinoleate, butyl acetylricinoleate, 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 alkylphenol, higher fatty acid higher alkylamine, higher fatty acid amide , Lower olefin oxide adduct of fats and oils or polypropylene glycol; 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 degree of sulfated oil; poly long chain alkyl acrylate; acrylic orgomer; poly long chain alkyl methacrylate; long chain alkyl methacrylate to amine-containing monomer copolymer; styrene-maleic anhydride copolymer;
Olefin-maleic anhydride copolymer.

The recording layer may be crosslinked by heat, UV, EB or the like. Thereby, it becomes possible to improve the repeating durability. Of these, crosslinking by EB is preferable.

A protective layer may be provided on the heat-sensitive layer to protect the heat-sensitive layer. Protective layer (thickness 0.1-5 μm)
The materials used are silicone rubber and silicone resin.
(Described in JP-A-63-221087), polysiloxane graft polymer (described in Japanese Patent Application No. 62-152550), ultraviolet curable resin or electron beam curable resin (described in Japanese Patent Application No. 63-310600). Description) and the like. In any case, a solvent is used at the time of coating, but it is desirable that the solvent is difficult to dissolve the resin of the heat sensitive layer and the organic low molecular weight substance. N- is a solvent that does not easily dissolve the resin and organic low-molecular substances in the heat-sensitive layer.
Hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like can be mentioned, and an alcohol solvent is particularly preferable in terms of cost.

Furthermore, 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 and the monomer component of the protective layer forming liquid. 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, polyethylene, polypropylene, polystyrene,
Examples thereof include polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate and polyamide. The thickness of the intermediate layer is preferably about 0.1 to 2 μm.

Subsequently, the thermosensitive layer (where the recording surface is constituted) is formed by a reversible thermochromic composition utilizing the color reaction between the electron-donating color-forming compound and the electron-accepting compound. Let's talk about things. A thermochromic composition utilizing a color-forming reaction between an electron-donating color-developing compound and an electron-accepting compound is prepared by heating and melting the electron-donating color-developing compound and the electron-accepting compound. Amorphous chromophores are formed, while when the amorphous chromophore is heated at a temperature lower than the melting temperature, the electron-accepting compound causes crystallization and the chromophore disappears. It utilizes the phenomenon of.

The heat-coloring composition instantly develops color upon heating, and the color-developed state thereof is stable even at room temperature. On the other hand, the composition in the color-developed state is instantly heated by heating at a temperature not higher than the color-developing temperature. The color is erased, and the erased state is stable even at room temperature, and such a reversible peculiar color developing and erasing behavior is a novel and surprising phenomenon that has never been seen before.

The principle of coloring and erasing, that is, image forming and image erasing when this composition is used as a thermal recording medium is shown in FIG.
This will be explained with reference to the graph shown in. The vertical axis of the graph represents the color density, the horizontal axis represents the temperature, the solid line represents the image forming process by heating, and the broken line represents the image erasing process by heating. A is the density in the completely erased state, B is the density in the completely colored state when heated to a temperature of T ₆ or higher, C is the density at a temperature of T ₅ or lower in the completely colored state, and D is T ₅ It shows the concentration when heat erasing is performed at a temperature between T _{6 and} T ₆ .

This composition is in a colorless state (A) at a temperature of T ₅ or lower. In order to perform recording (image formation), a color image is formed by heating (T) to a temperature of T ₆ or higher with a thermal head or the like to form a recorded image. Even if the recorded image is returned to the temperature of T ₅ or less according to the solid line, the state (C) is maintained as it is and the recording memory property is not lost.

Next, in order to erase the recorded image, the formed recorded image is heated to a temperature between T _{5 and} T _{6 which} is lower than the coloring temperature, so that a colorless state (D) is obtained. In this state, the colorless state (A) is maintained as it is even if the temperature is returned to T ₅ or lower. That is, the process of forming the recorded image reaches C by the path of the solid line ABC and the recording is held. Next, in the process of erasing the recorded image, the erased state is maintained by reaching A through the path of the broken line CDA. The behavior characteristics of formation and erasure of 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. Then, the coloring state is formed by heating and melting the color-developing agent and the color-developing agent, while the coloring state is erased by heating at a temperature lower than the coloring temperature, and the coloring state and the erasing state exist stably at room temperature. Is. As described above, the mechanism of coloring and decoloring in the composition is such that when the coloring agent and the color developer are heated and melt-mixed at the coloring temperature, the composition causes an amorphization and a coloring state. On the other hand, it is based on the property that, when heated at a temperature lower than the coloring temperature, the developer of the colored composition causes crystallization to form an erased state of coloring. However, even in this case, since the heat-sensitive layer is heated to a temperature of T ₆ or higher and then decolored, the particles of the color-developing agent and the color-developing agent are restored to form a new color-developing state. Is advantageous to.

A composition comprising an ordinary color-forming agent and a color-developing agent, 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 having a color-developing effect. When this is melt-mixed by heating, it becomes a coloring state based on the ring opening of the lactone ring of the leuco compound. This colored state is an amorphous state in which both are compatible. Although this colored amorphous state is stable at room temperature, it does not crystallize even when heated again, and because the phenolic compound is not separated from the leuco compound, the lactone ring is not closed and decolorized. I don't.

On the other hand, when the composition of the color former and the developer is also melted and mixed by heating, it becomes a colored state, exhibits an amorphous state as in the conventional case, and exists stably at room temperature. . However, in the case of the present invention, when the composition in the colored amorphous state is heated below the coloring temperature, that is, at a temperature at which the molten state is not reached, crystallization of the developer occurs and a compatibility state with the color developing agent occurs. The bond due to can not be retained, and the color developer separates from the color developer. It is considered that due to the crystallization of the color developer from the color developer, the color developer cannot accept electrons from the color developer and the color developer is decolorized.

The above-mentioned peculiar coloring and decoloring behavior observed in the thermochromic composition is the mutual solubility of the color former and the color developer by heating and melting, the strength of both actions in the color developing state, and the color developer. Is related to the solubility of the color developing agent, the crystallinity of the developer, etc.
In principle, it causes amorphization by heating and melting, while
Any color former / 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 change due to melting and exothermic change due to crystallization in thermal analysis, and therefore the color former / developer system applicable to the present invention can be easily confirmed by thermal analysis. can do. Further, the reversible thermochromic composition system according to the present invention may contain a third substance, for example, the reversible decoloring behavior thereof is retained even if a polymer substance is present. Was confirmed. In the thermochromic composition of the present invention, the decolorization is due to the separation from the color former due to the crystallization of the color developer. Therefore, in order to obtain an excellent decoloring effect, the color developer should be selected. is important.

Next, examples of the color developer preferably used in the present invention are as follows. As described above, the color developer applicable to the present invention can be easily found by thermal analysis. It is not limited to ones. (1) Organic phosphoric acid compound represented by the following general formula (1) R ₁ —PO (OH) ₂ (1) (wherein R ₁ is a linear or branched alkyl group or alkenyl having 8 to 30 carbon atoms) Representing a group) Specific examples of this 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) Organic acid having a hydroxyl group at the α-position carbon represented by the following general formula (2) R ₂ —CH (OH) COOH (2) (wherein R ₂ is a straight chain having 6 to 28 carbon atoms) Representing a linear or branched alkyl group or alkenyl group) Specific examples of the organic acid having a hydroxyl group at the α-position carbon 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 here is a compound exhibiting an electron-accepting property, and is a colorless or light-colored dye precursor itself, and is not particularly limited, and conventionally known ones, for example,
There are triphenylmethanephthalide-based compounds, fluoran-based compounds, phenothiazine-based compounds, leucoauramine-based compounds, rhodamine-lactam-based compounds, spiropyran-based compounds, indolinophtalide-based compounds, and the like. To be 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-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-
Diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np
-Tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino } -6-Diethylaminofluorane, 2- {3,6-bis (diethylamino) -6- (o
-Chloranilino) xanthyl benzoate lactam}, 3
-Diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7
-(O-chloranilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N
-Methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- Anilino Fluoran, 3
-(N, N-diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluorane, 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'-dimethylaminophenyl) -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) fluorane, 3-diethylamino-5-
Chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenyl Ethylamino) fluorane, 3- (N-ethyl-p-toluidino)
-7- (α-phenylethylamino) fluorane, 3-
Diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3
-Diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methoxytoluidino) -7- (pn
-Butylanilino) fluorane, 3- (N-methyl-N)
-Isopropylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene spiro (9,3 ')- 6'-Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4 '
-Bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N- (2
-Ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane, 3-N-methyl-N-
Isobutyl-6-methyl-7-anilinofluorane, 3
-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7
-(2 ', 4'-dimethylanilino) fluorane and the like.

Particularly preferred color formers are those containing halogen as a substituent. Something like this:
For example, the following may be mentioned. 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3-cyclohexylamino-6-chlorofluorane, 3-cyclohexylamino-6-bromofluorane, 3-diethylamino-7-chlorofluorane, 3 -Diethylamino-7-bromofluorane, 3-
Dipropylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-phenylamino-fluorane, 3-pyrrolidino-6-chloro-7-phenylamino-fluorane, 3-diethylamino-6-chloro-7-
(M-Trifluoromethylphenyl) amino-fluorane, 3-cyclohexylamino-6-chloro-7- (o
-Chlorophenyl) amino-fluorane, 3-diethylamino-6-chloro-7- (2 ', 3'-dichlorophenyl) amino-fluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-dibutylamino-
6-chloro-7-ethoxyethylamino-fluorane,
3-diethylamino-7- (o-chlorophenyl) amino-fluorane, 3-diethylamino-7- (o-bromophenyl) amino-fluorane, 3-diethylamino-7- (o-chlorophenyl) amino-fluorane, 3
-Dibutylamino-7- (o-fluorophenyl) amino-fluorane, 6'-bromo-3'-methoxybenzoindolino-pyrrolospirane, 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 lactam benzoate and the like.

A more preferable color former is represented by the following general formula (3).
Is a compound represented by.

[Chemical 1] (However, R ₃ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₄ is a hydrogen atom or an optionally substituted amino group, 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 to 4.
Alkyl group or alkoxy group having 1 to 2 carbon atoms, n is 1
Or represents an integer of 2. )

Specific examples of the compound represented by the general formula (3) include the followings. 3- (N-methyl-N-phenylamino) -7-amino-fluorane, 3- (N-ethyl-N-phenylamino) -7-amino-fluorane, 3- (N-propyl-)
N-phenylamino) -7-amino-fluorane, 3-
{N-methyl-N- (p-methylphenyl) amino}-
7-amino-fluorane, 3- {N-ethyl-N- (p
-Methylphenyl) amino} -7-amino-fluorane, 3- {N-propyl-N- (p-methylphenyl)
Amino} -7-amino-fluorane, 3- {N-methyl-N- (p-ethylphenyl) amino} -7-amino-
Fluorane, 3- {N-ethyl-N- (p-ethylphenyl) amino} -7-amino-fluorane, 3- {N-
Propyl-N- (p-ethylphenyl) amino} -7-
Amino-fluorane, 3- {N-methyl-N- (2 ',
4'-Dimethylphenyl) amino} -7-amino-fluorane, 3- {N-ethyl-N- (2 ', 4'-dimethylphenyl) amino} -7-amino-fluorane, 3-
{N-propyl-N- (2 ', 4'-dimethylphenyl)
Amino} -7-amino-fluorane, 3- {N-methyl-N- (p-chlorophenyl) amino} -7-amino-
Fluorane, 3- {N-ethyl-N- (p-chlorophenyl) amino} -7-amino-fluorane, 3- {N-
Propyl-N- (p-chlorophenyl) amino} -7-
Amino-fluorane, 3- (N-methyl-N-phenylamino) -7-methylamino-fluorane, 3- (N-
Ethyl-N-phenylamino) -7-methylamino-fluorane, 3- (N-propyl-N-phenylamino)-
7-methylamino-fluorane, 3- {N-methyl-N
-(P-methylphenyl) amino} -7-ethylamino-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-benzylamino-fluorane,
3- {N-methyl-N- (2 ', 4'-dimethylphenyl) amino} -7-methylamino-fluorane, 3-
{N-ethyl-N- (2 ', 4'-dimethylphenyl) amino} -7-ethylamino-fluorane, 3- {N-methyl-N- (2', 4'-dimethylphenyl) amino}-
7-benzylamino-fluorane, 3- {N-ethyl-
N- (2 ', 4'-dimethylphenyl) amino} -7-benzylamino-fluorane, 3- (N-methyl-N-phenylamino) -7-dimethylamino-fluorane, 3
-(N-ethyl-N-phenylamino) -7-dimethylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7-diethylamino-fluorane, 3- {N-ethyl- N- (p-methylphenyl) amino} -7-diethylamino-fluorane, 3- (N-
Methyl-N-phenylamino) -7-dipropylaminofluorane, 3- (N-ethyl-N-phenylamino)-
7-dipropylaminofluorane, 3- {N-methyl-
N- (p-methylphenyl) amino} -7-dibenzylamino-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -7-dibenzylamino-fluorane, 3- {N- Ethyl-N- (p-methylphenyl) amino} -7-di (p-methylbenzyl) amino-
Fluoran, 3- {N-methyl-N- (p-methylphenyl) amino} -7-acetylamino-fluorane, 3
-{N-ethyl-N- (p-methylphenyl) amino}
-7-benzoylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -7- (o-
Methoxybenzoyl) amino-fluorane, 3- {N-
Ethyl-N- (p-methylphenyl) amino} -6-methyl-7-phenylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -6-methyl-7-phenylamino -Fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -6-ter
t-Butyl-7- (p-methylphenyl) amino-fluorane, 3- (N-ethyl-N-phenylamino) -6
-Methyl-7- (N-ethyl-N- (p-methylphenyl) amino-fluorane, 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-fluorane, 3- {N-ethyl-N- (p-methylphenyl) amino} -5 -Chloro-7-dibenzylamino-fluorane, 3- {N-methyl-N- (p-methylphenyl) amino} -5-methoxy-7-dibenzylamino-
Fluoran, 3- {N-ethyl-N- (p-methylphenyl) amino} -6-methyl-fluorane, 3- {N-
Ethyl-N- (p-methylphenyl) amino} -5-methoxy-fluorane and the like.

The color developing agents are applied alone or in admixture of two or more. Similarly, the color-developing agent can be applied alone or in a mixture of two or more kinds. 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 heat-sensitive recording material can be 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 coating this on a substrate. .

As the binder, various conventional binders can be appropriately used, and examples thereof include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxy cellulose, carboxymethyl cellulose, methyl cellulose, cellulose acetate, gelatin, casein, starch and polyacrylic acid. Soda, polyvinylpyrrolidone, polyacrylamide, maleic acid copolymer, acrylic acid copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylic acid esters, polymethacrylic acid esters, vinyl chloride / vinyl acetate copolymer Coalesce, styrene copolymer, polyester,
There is polyurethane etc.

In the present invention, various additives such as a dispersant, a surfactant, a filler, and the like used in ordinary heat-sensitive recording paper are used for the purpose of improving coating properties or recording properties, if necessary.
It is also possible to add a color image stabilizer, an antioxidant, a light stabilizer, a lubricant and the like.

As described above, the protective layer and the intermediate layer may be provided if necessary.

The above-mentioned support (base) depends on the purpose of use.
It may be paper, synthetic paper, plastic film or a composite thereof, and is not particularly limited. Further, in the reversible thermosensitive recording medium used in the present invention, whether it is a card-shaped one or a long one, further,
It may be endless.

[0062]

EXAMPLES (Parts and percentages here are based on weight.) Γ-Fe ₂ O ₃ 10 parts Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 2 parts (UCC) on white PET with a thickness of about 188 μm Co., Ltd .: VAGH) Coronate L (10% toluene solution) 2 parts Methyl ethyl ketone 43 parts Toluene 43 parts A solution consisting of 43 parts is applied with a wire bar and dried by heating to about 1
A magnetic recording layer having a thickness of 0 μm was provided.

Next, 75% acetic acid 10 parts butyl solution of urethane acrylate UV curable resin (Dainippon Ink and Chemicals Co., Ltd .: Unidick C7-164) MEK 10 parts solution was applied with a wire bar, and after heating and drying. 80
A smoothing layer having a thickness of about 3 μm was provided by curing with a w / cm ultraviolet lamp, and Al was vacuum-deposited to a thickness of about 400 Å thereon.

Furthermore, behenic acid (NAF-22S manufactured by NOF CORPORATION) 6 parts Niicosane diacid (SL-20 manufactured by Okamura Oil Co., Ltd.) 4 parts Diisodecyl phthalate 3 parts Vinyl chloride-vinyl acetate-phosphoric acid Ester copolymer 35 parts (manufactured by Denki Kagaku Kogyo KK: # 1000p) THF 150 parts A solution consisting of 15 parts toluene was applied with a wire bar and dried by heating to provide a heat sensitive layer having a thickness of about 15 μm.

A solution of 10 parts of polyamide resin (manufactured by Toray Industries, Inc .: CM8000) and 90 parts of methanol was further applied on it with a wire bar and dried by heating to form an intermediate layer having a thickness of about 1 μm.

Furthermore, a solution containing 10 parts of 75% butyl acetate of urethane acrylate type UV-curable resin in butyl acetate (manufactured by Dainippon Ink and Chemicals: Unidick C7-157) and 10 parts of IPA was applied with a wire bar. 80 after heating and drying
A recording medium was prepared by curing with a w / cm ultraviolet lamp and providing an overcoat layer having a thickness of about 5 μm. This recording medium was heated to 80 ° C. to make the heat sensitive layer transparent.

Using this recording medium, UV ink (UVS PCDW manufactured by Morohoshi Ink Co., Ltd.
(Yellow, crimson, indigo, black), a pattern was printed by an offset printing method and then irradiated with ultraviolet rays to be cured. Subsequently, after forming a cloudy image (number) on the recording surface 11 with the thermal head, the image on the recording surface 11 was erased with the thermal head, and an image was formed on the recording surface 12. This was repeated 200 times with random numbers (recording surface 1
When the image was formed on any of Nos. 1 and 12, it was counted as once), and the image slightly started to deteriorate (decrease in white turbidity). On the other hand, when the image was formed and erased only on the recording surface 11, the deterioration of the image started about 100 times.

After repeatedly recording only on the recording surface 11 using the same recording material, the number of times is stored as magnetic information in the magnetic recording layer below the heat sensitive layer, and recording is performed on the recording surface 11 at a predetermined 90 times. When the recording was stopped and then recording was performed on the recording surface 12, no image deterioration was observed even after repeatedly recording 180 times (90 times on the recording surface 11 and 90 times on the recording surface 12).

Further, using the same recording material, as shown in FIG. 6, an image is formed at the recording position at the right corner (portion (M) in FIG. 6) every time, and the reflection density (reflectance) at that position is measured. Then, the degree of deterioration was detected. When image recording was repeated 95 times on the recording surface 11, image deterioration was detected.
When the image was recorded on, the image was not deteriorated even if it was recorded further 95 times, and it was possible to record up to 190 times in total.

Furthermore, only the recording surface 11 is used, and FIG.
As shown in (C), when the recording position was changed by the thickness of the number each time, the image was not deteriorated up to 370 times, and the deterioration of the image was observed after about 380 times.

[0071]

According to the present invention, since the recording area is changed according to the number of times of repetitive recording, the life of the recording material can be greatly extended.

[Brief description of drawings]

FIG. 1 is a diagram showing an example in which a recording surface is formed at two locations on a recording material.

FIG. 2A is a diagram showing an overlap of recording surfaces when numbers 1, 2, and 3 are recorded on a recording material. FIG. 6B is a diagram showing an example in which the recording surface is moved to a position above the overlapped recording portion with diagonal lines. (C) is a figure which shows an example when a recording surface is moved to four places.

FIG. 3 is a diagram showing how a recording material is deteriorated.

FIG. 4 is a diagram showing a change in transparency of a recording material due to heat.

FIG. 5 is a diagram showing a change in color development reaction of a recording material due to heat.

FIG. 6 is a diagram of an example in which a mark indicating the degree of deterioration of the recording material is provided on a part of the recording surface.

[Explanation of symbols]

 1 card (reversible thermosensitive recording material) 11,12 image recording surface 13 non-recording surface

Claims (7)

[Claims] 1. A method of recording an image using a recording medium having a reversible thermosensitive material, wherein the transparency or the color tone is changed a predetermined number of times in the same recording area and then changed in another recording area. Image recording method. 2. The image recording method according to claim 1, wherein the recording medium has a plurality of image recording surfaces made of a reversible thermosensitive material, and the recording area is the recording surface. 3. The size of the recording area is a pixel.
Image recording method described. 4. The image recording method according to claim 1, wherein the recording area is changed every fixed number of times. 5. The image recording method according to claim 2, wherein after repeatedly recording in the same recording area, recording is not performed in this recording area, but in another recording area. 6. The image recording method according to claim 1, wherein the recording medium has an information storage unit, and the number of times of repetition is recorded in the information storage unit. 7. The image recording method according to claim 5, wherein deterioration of the reversible thermosensitive material is detected and the area is changed.