JP3198472B2 - Image recording method - Google Patents

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 repeating image recording by heating (repeat of writing and erasing of information).
The present invention relates to a good recording method for a reusable thermosensitive film or card using a reversible thermosensitive recording material.

[0002]

2. Description of the Related Art In recent years, rewritable materials have been demanded as heat-sensitive recording materials in order to save paper resources. As the most influential material, there is provided, on a support, a heat-sensitive layer in which organic low-molecular substances such as higher alcohols and higher fatty acids are dispersed in a resin such as polyester.
This is known from JP-A-119377, JP-A-55-154198, and the like. Recording (image formation) and erasing of this type of reversible thermosensitive recording material utilizes a change in transparency due to the temperature of the thermosensitive layer. Like a conventional irreversible thermosensitive recording material, a thermal head or a hot stamp is used. It has the feature that image formation and erasure are possible.

As a method of heating a heat-sensitive recording material for recording, heating by a thermal head is the most common, and repetitive rewriting (repeated recording) by a thermal head has also been studied for recording of a reversible thermosensitive recording material. ing. However, recently, it has been pointed out that repeated rewriting by a thermal head significantly accelerates deterioration of a reversible thermosensitive recording material, as compared with repeated rewriting by other heating methods such as hot stamping. I have.

[0004]

The present invention relates to an image recording method, and more particularly, to an image recording method in which reversible reversible thermosensitive recording materials are repeatedly rewritten by a thermal head so that the reversible thermosensitive recording materials do not deteriorate or hardly occur. It provides a method.

[0005]

SUMMARY OF THE INVENTION The present invention is as follows. A reversible thermosensitive recording material that is in a first color state at a first specific temperature higher than room temperature, and is heated to a second specific temperature higher than the first specific temperature and then cooled to a second color state. used, the image recording method for performing repeated rewriting a thermal head, the thermal head and availability of
When the relative thermal recording material is moved intermittently and relatively
In both cases, the reversible thermosensitive recording material is
While moving to the thermal head,
Period during which the pulse current of the heating element of the pad is flowing and the movement starts
Image that does not overlap with the time of
Recording method.

Further, the invention has the following features.
Are as follows: Compatible with the above thermal head
With the inverse thermosensitive recording material, it is relatively intermittently moved.
The reversible thermosensitive recording material moves relative to the thermal head
Of the thermal head during the
The image recording method described above, wherein the pulse current of the heating element falls.
Law.

Hereinafter, the method of the present invention will be described in more detail. The density of the reversible thermosensitive recording material used in the present invention does not change at room temperature, but the density can be changed by heating to a certain temperature range. The temperature region in which the concentration changes is roughly divided into two, and in the present invention, the “lower temperature” region is defined as the “first specific temperature”.
And the “higher temperature” region is referred to as a “second specific temperature” region. The reversible thermosensitive recording material used in the present invention changes its color state when heated to a first specific temperature,
When heated to a specific temperature and then cooled, it has the property of changing to another color.

As mentioned above, the reversible thermosensitive recording material deteriorates considerably depending on the frequency of use, particularly in image formation considered to be due to a thermal head. The reason for this deterioration is presumed as follows. The current reversible thermosensitive recording material is mainly composed of an organic low-molecular substance and a resin base material. The reversible thermosensitive recording material becomes very soft because it exceeds the softening point of the material. Therefore, even a slight stress due to friction with the thermal head is easily deformed, and the material structure changes. It is considered that the result of the accumulation of these changes appears as deterioration of the reversible thermosensitive recording material.

Here, the strain generated inside the reversible thermosensitive recording material is determined by the stress applied inside the reversible thermosensitive recording material and the hardness of the reversible thermosensitive recording material at that time. Further, the stress applied to the inside of the reversible thermosensitive recording material is determined by the load and the frictional force between the thermal head and the reversible thermosensitive recording material. In general, the frictional force becomes the largest at the moment when the reversible thermosensitive recording material starts to move, and at this moment, if the inside of the reversible thermosensitive recording material is in a soft state, the internal strain becomes conspicuous. become.

From these facts, to prevent the reversible thermosensitive recording material from deteriorating due to the thermal head, it is necessary to: The weight between the thermal head and the reversible thermosensitive recording material is reduced. 2. The coefficient of friction (particularly at high temperatures) between the thermal head and the reversible thermosensitive recording material is reduced. 3. While the reversible thermosensitive recording material is not cooled down but is softened, the reversible thermosensitive recording material does not start moving. Such conditions are required.

The third condition corresponds to the printing method described in the first aspect. By the way, when a pulse current is applied to the heating element of the thermal head, the transition curve of the temperature has a shape similar to that obtained by passing a rectangular wave through an analog integrating circuit. In other words, the temperature rises sharply at the rise of the pulse but gradually becomes gentle, and the temperature becomes the highest at the fall of the pulse. Therefore, it is considered that the temperature of the reversible thermosensitive recording material also reached the highest temperature near the time of the fall of the pulse and was in a softened state.
In the first aspect, the average temperature reached by heating by the thermal head indicates a value obtained by adding the temperatures at the time of rising and falling of the pulse and dividing by two.

From the above, the third condition can be rephrased as follows. 4. The movement of the reversible thermosensitive recording material does not start during and immediately after the pulse is flowing through the heating element. In particular, the movement of the reversible thermosensitive recording material does not start when the pulse falls. From these, two methods can be considered when the printing method is specifically considered. B) When the relative movement between the reversible thermosensitive recording material and the thermal head is performed by intermittent driving of a pulse motor or the like, by adjusting the relationship between the drive timing and the timing of the pulse current of the thermal head heating element,
The timing at which the movement starts intermittently and repeatedly and the timing at which the pulse current flows (particularly, the timing at which the pulse falls) are not overlapped. (B) The relative movement between the reversible thermosensitive recording material and the thermal head is performed by continuous driving of a DC motor or the like, and the pulse current of the thermal head heating element is applied after the driving is started and the speed of the relative movement is stabilized. Here, the former method is the printing method described in claim 3, and the latter method is the printing method described in claim 2.

In the above intermittent driving, the relative movement between the reversible thermosensitive recording material and the thermal head is schematically shown in FIG. In the present invention, a in FIG.
Is referred to as a moving period, period b is referred to as a recoil period, and period c is referred to as a stationary period. Even when driven by a pulse motor, there may be no period of b or c depending on the driving conditions, and if neither b nor c is present, it can be regarded as equivalent to continuous driving by a DC motor. In the case of continuous driving, once driving is started, it is always regarded as a moving period until driving is stopped. Referring to FIG. 1, the method (a) will be described. The pulse current rises in the period a, and the pulse current falls in the period a to the period c. Further, if the pulse current falls during the period from the period a to the period b in FIG. 1, the movement is slightly reversed in the period b.
Since the frictional force also acts in the opposite direction, even if the reversible thermosensitive recording material is not completely cooled at the moment of the start of movement and distortion occurs, it can be canceled. Therefore, in particular, the printing method of claim 4 has an effect of preventing deterioration even if the reversible thermosensitive recording material is not always cooled at the start of movement. In order to make the most of this effect, it is particularly preferable that the pulse rises in the latter half of the period a and falls in the first half of the period b. Also, b
When there is no period only, it is more preferable to make the pulse fall in the first half of the period c or in the second half of the period a.

Although the method of recording one recording dot with one pulse current has been described above, in the case where a plurality of pulse currents are applied to one recording dot, it is necessary to determine whether or not one pulse is applied during one period of movement. In the present invention, the period in which the temperature of the heating element rises due to the group of the pulse current
It is regarded as corresponding to the period during which two pulse currents are flowing.

In the present invention, the term "reversible thermosensitive recording material" means that the state of its color does not change at room temperature, but when it is heated to a certain temperature, it changes to the first color state. When the temperature is returned to the normal temperature after the temperature is raised, the material becomes a second color state, and the change in the color state can be repeated many times. Changes in the color state include changes in transmittance, reflectance, absorption wavelength, scattering degree, and the like, and an actual reversible thermosensitive recording material performs display by a combination of these changes. More specifically, a material that reversibly changes between a transparent state and a cloudy state. Materials whose color changes chemically, such as dyes. At present, they can be classified into two types.

As a conventional technique and as has been repeatedly described, a heat-sensitive layer in which an organic low-molecular substance such as a higher alcohol or a higher fatty acid is dispersed in a resin base material such as a polyester is provided on a support. What is provided is a typical example. As a typical example, a leuco-based thermosensitive recording material having enhanced reversibility is given.

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

In FIG. 2 (representing the change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and an organic low-molecular substance dispersed in the resin base material is, for example, T _0.
At the following room temperature, it is cloudy and opaque. This is called temperature T ₂
When the temperature is returned to room temperature below T ₀ , the film remains transparent. This is from temperature T ₂ to T ₀
It is considered that the crystal grows from a polycrystal to a single crystal through the semi-molten state of the organic low-molecular substance until the following.
Upon further heating to T ₃ or more temperature becomes translucent state intermediate between the maximum transparency and the maximum opacity. Next, when the temperature is lowered, the state returns to the original cloudy and opaque state without taking the transparent state again. This after low-molecular organic material is melted at a temperature T ₃ or more, presumably because the polycrystals precipitated by being cooled. When the opaque state is heated to a temperature between T _{1 and} T ₂ and then cooled to room temperature, that is, a temperature lower than T ₀ , an intermediate state between transparent and opaque can be obtained. Also, by returning to room temperature After heating to be again T ₃ or more temperature which became clear at the normal temperature, the flow returns to cloudy opaque state again. That is, both opaque and transparent forms at room temperature and intermediate states thereof can be taken.

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

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

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

The resin base material used for the heat-sensitive layer is a material that forms a layer in which organic low-molecular substances are uniformly dispersed and held, and that affects the transparency at the time of maximum transparency. For this reason, the resin base material is preferably a resin having good transparency, mechanical stability, and good film formability.

Examples of such a resin include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinyl chloride. Vinyl chloride copolymers such as acrylate copolymers; polyvinylidene chloride copolymers such as polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer; polyester; polyamide; polyacrylate or poly Methacrylate or acrylate-methacrylate copolymer; silicone resin and the like.
These may be used alone or as a mixture of two or more.

On the other hand, the organic low molecular weight substance may be any substance that changes from polycrystalline to single crystal by heat in the recording layer, and generally has a melting point of 30 to 200 ° C., preferably 50 to 150 ° C.
A temperature of about ° C is used. Such organic low molecular weight substances include alkanol; alkane diol; halogen alkanol or halogen alkane diol; alkylamine; alkane; alkene; alkyne; halogen alkane; halogen alkene; halogen alkyne; cycloalkane; cycloalkene; Unsaturated mono- or dicarboxylic acids or esters thereof,
Amides or ammonium salts; saturated or unsaturated halogen fatty acids or their esters, amides or ammonium salts; aryl carboxylic acids or their esters, amides or ammonium salts; halogen allyl carboxylic acids or their esters, amides or ammonium salts; thioalcohols Thiocarboxylic acids or their esters;
Amines or ammonium salts; carboxylic acid esters of thioalcohols and the like. These may be used alone or in combination of two or more. The carbon number of these compounds is 1
0-60, preferably 10-38, particularly preferably 10-30. The alcohol group in the ester may be saturated or unsaturated, and may be halogen-substituted. In any case, the organic low molecular weight substance contains at least one kind of oxygen, nitrogen, sulfur and halogen in the molecule, for example,-
OH, -COOH, -CONH-, -COOR, -NH
_{-, - NH 2, -S -} , - S-S -, - O-, it is preferably a compound containing a halogen and the like.

More specifically, these compounds include
Uric acid, dodecanoic acid, myristic acid, pentadecane
Acid, palmitic acid, stearic acid, behenic acid, nonadeca
Fatty acids such as acid, araginic and oleic acid; stearic acid
Methyl phosphate, tetradecyl stearate, stearin
Octadecyl acid, octadecyl laurate, palmitin
Of higher fatty acids such as tetradecyl acrylate and dodecyl behenate
Steal; C₁₆C₃₃-OC₁₆C₃₃, C₁₆C₃₃-SC₁₆C₃₃, C₁₈C₃₇-SC₁₈C₃₇, C₁₂C_{twenty five}-SC₁₂C_{twenty five}, C₁₉C₃₉-SC₁₉C₃₉, C₁₂C_{twenty five}-S-S-C₁₂C
_{twenty five}, And ether or thioether. In particular, 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 preferred, and higher fatty acids having 16 to 24 carbon atoms are more preferred.
Good.

In order to widen the range of temperatures at which transparency can be achieved, the organic low-molecular substances described in this specification may be appropriately combined, or such an organic low-molecular substance may be combined with another material having a different melting point. . These are disclosed, for example, in JP-A-63
JP-A-39378, JP-A-63-130380, and Japanese Patent Application Nos. 63-14754 and 1-14011.
No. 09, but not limited thereto. The ratio between the organic low-molecular substance and the resin base material in the heat-sensitive layer is preferably about 2: 1 to 1:16, more preferably 1: 1 to 1: 3 by weight. When the ratio of the resin base material is less than this, it becomes difficult to form a film in which the organic low-molecular substance is held in the resin base material, and when the ratio is higher, the amount of the organic low-molecular substance is small, so that the opacity is increased. Becomes difficult.

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

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 adducts of fats and oils or polypropylene glycol; acetylene glycol; Na, Ca, Ba or Mg salts of higher alkylbenzene sulfonic acids; higher fatty acids, aromatic carboxylic acids, higher fatty acid sulfonic acids, aromatic sulfonic acids, monoesters of sulfuric acid Or Ca, Ba or Mg salts of phosphoric acid mono- or di-esters; low sulfated oils; poly long chain alkyl acrylates; acrylic oligomers;
Poly long chain alkyl methacrylate; long chain alkyl methacrylate to amine-containing monomer copolymer; styrene-maleic anhydride copolymer; olefin-maleic anhydride copolymer.

A protective layer can be provided on the heat-sensitive layer to protect the heat-sensitive layer. Protective layer (thickness 0.1-5
Examples of the material of the formula (μm) include silicone rubber, silicone resin (described in JP-A-63-221087), and polysiloxane graft polymer (Japanese Patent Application No. 62-15255).
No. 0) and an ultraviolet curable resin or an electron beam curable resin (described in Japanese Patent Application No. 63-310600). In each case, a solvent is used during application,
It is desirable that the solvent does not easily dissolve the resin of the heat-sensitive layer and the organic low-molecular substance. Examples of the solvent that hardly dissolves the resin and the organic low-molecular substance in the heat-sensitive layer include n-hexane, methyl alcohol, ethyl alcohol, and isopropyl alcohol, and an alcohol-based solvent is particularly desirable in terms of cost.

Further, an intermediate layer can 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 solution. As the material of the intermediate layer, the following thermosetting resins and thermoplastic resins can be used in addition to those listed as the resin base material in the thermosensitive layer.
That is, polyethylene, polypropylene, polystyrene,
Examples include polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like. The thickness of the intermediate layer is preferably about 0.1 to 2 μm.

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

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

FIG. 3 shows the principle of color formation and decoloration when this composition is used as a thermosensitive recording medium, ie, image formation and image erasure.
This will be described with reference to the graph shown in FIG. The vertical axis of the graph represents the color density, the horizontal axis represents the temperature, the solid line shows the image forming process by heating, and the broken line shows the image erasing process by heating. A is the concentration in a fully erased state, B is the concentration in the complete colored state when heated to T ₅ temperature above, C is the concentration in the T ₄ below the temperature of complete colored state, D is T ₄ shows the concentration when heated and erased with a temperature between through T _5.

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

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

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

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

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

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

Next, examples of the developer preferably used in the present invention are as follows. As described above, the developer applicable to the present invention can be easily found by thermal analysis. However, the present invention is not limited to this. (1) An organic phosphoric acid compound represented by the following general formula (1): R ¹ -PO (OH) ₂ (1) (where R ¹ is a linear or branched alkyl group or alkenyl having 8 to 30 carbon atoms) Specific examples of 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) An organic acid having a hydroxyl group at the α-position carbon represented by the following general formula (2): R ² —CH (OH) COOH (2) (where R ² is a straight chain having 6 to 28 carbon atoms) Specific examples of the organic acid having a hydroxyl group at the carbon at the α-position include the following. α-hydroxyoctanoic acid, α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic Acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid and the like.

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

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

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

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

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

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

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

In the present invention, various additives, such as dispersants, surfactants, fillers, and the like, which are used in ordinary thermosensitive recording paper, for the purpose of improving the coating properties or recording properties as required.
A color image stabilizer, an antioxidant, a light stabilizer, a lubricant and the like can be added.

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

The support (substrate) in the present invention may be paper, synthetic paper, plastic film or a composite thereof, depending on the purpose of use, and is not particularly limited. Further, in the reversible thermosensitive recording medium of the present invention, it may be long or endless.

[0051]

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

(Preparation of Reversible Thermosensitive Recording Film) Behenic acid 7 parts Eicosane diacid 3 parts Diisodecyl phthalate 2 parts Vinyl chloride / vinyl acetate copolymer resin 40 parts on a polyester film (support) having a thickness of about 100 μm (VYHH manufactured by UCC) A liquid consisting of 150 parts of THF and 15 parts of toluene was applied and dried to form a heat-sensitive recording layer (about 7 μm thick) made of a reversible heat-sensitive recording material. Next, a liquid having the following composition is coated on the heat-sensitive recording layer, dried, and UV-coated.
Irradiation to protect layer (about 2μ)
m), and becomes cloudy when the second specific temperature is about 100 ° C. or higher, and the area of the first specific temperature is about 70 ° C. or higher and 1
A reversible thermosensitive recording film having the property of becoming transparent up to 00 ° C. was prepared. (Protective layer forming liquid composition) 10 parts of a 75% butyric acetate solution of a urethane acrylate-based UV-curable resin (manufactured by Dainippon Ink and Chemicals, Inc .: Unidic C7-157) 10 parts of toluene 10 parts (repeated image recording) Image recording was repeated on the film by the following four methods using a thermal head, and the change in recording density was measured. The results are summarized in Table 1.

Example 1 A cloudy image was formed on a thermosensitive recording film by a thermal head, and clarification was performed by a heat roller. This was repeated up to 500 times. The conditions for forming a cloudy image on the reversible thermosensitive recording material were as follows: the stepping motor was driven intermittently at one step / line, and recording was performed with a recording pulse width of 2 ms and a line cycle of 20 ms. Here, FIG.
Is about 2 ms, the period of (b) is about 1 ms, and the period of (c) is about 17 ms. The relationship between the moving cycle and the recording pulse is 2 ms after 1 ms from the beginning of FIG.
The recording pulse of s was started, and the temperature of the reversible thermosensitive recording material was set to be lowest at the head position of (a), that is, at the start of movement.

Example 2 The reversible thermosensitive recording material was moved by changing the gear ratio by 10
Driving is performed step by step / line, and the moving speed per line does not change, but continuous driving is performed without the periods (b) and (c). Otherwise, formation of a cloudy image and transparency were performed under the same conditions as in Example 1.
Repeated up to times.

Embodiment 3 In FIG. 1A, the period is approximately 3 ms, and the period in FIG.
In ms, the drive system was adjusted so that the recoil period of (b) did not occur. Other than that, cloudy image formation and transparency were repeated up to 500 times under the same conditions as in Example 1.

Example 4 A recording pulse having a pulse width of 2 ms was started at the end of the period of FIG. 1A, and the formation of a cloudy image and transparency were performed up to 500 times under the same conditions as in Example 1 except for this. Repeated.

Comparative Example 1 The reversible thermosensitive recording material was moved intermittently in the same manner as in Example 1, and the relationship between the moving cycle and the print pulse was such that the recording pulse was applied 15 ms after the beginning of FIG. It is set up so that the recording pulse falls just at the beginning of (a). Other than that, cloudy image formation and transparency were repeated up to 500 times under the same conditions as in Example 1.

Comparative Example 2 The reversible thermosensitive recording material was moved intermittently in the same manner as in Example 1. The relationship between the moving cycle and the printing pulse was such that the recording pulse was applied 16 ms after the beginning of FIG. After the start-up, it was set so that the timing at the beginning of (a) and the period of the recording pulse overlapped. Other than that, cloudy image formation and transparency were repeated up to 500 times under the same conditions as in Example 1.

[0059]

[Table 1]

[0060]

According to the method of the present invention, it is possible to prevent the reversible thermosensitive recording material from deteriorating due to repeated image formation by the thermal head.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the method of the present invention.

FIG. 2 is a diagram for explaining image formation / erasure in a reversible thermosensitive recording material according to the present invention.

FIG. 3 is a view for explaining image formation / erasure in another reversible thermosensitive recording material according to the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akihide Ito 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-1-304996 (JP, A) JP-A 3-87293 (JP, A) JP-A-4-301483 (JP, A) JP-A-5-278348 (JP, A) JP-A-5-8507 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/32

Claims (2)

(57) [Claims] 1. A state of a first color at a first specific temperature higher than normal temperature, and a second color state by cooling after heating at a second specific temperature higher than the first specific temperature. using a reversible thermosensitive recording material, an image recording method for performing repeated rewriting a thermal head, is moved between said thermal head and a reversible thermosensitive recording material relatively and intermittently, in one cycle of intermittent drive An image recording method characterized in that a period during which a pulse current of a heating element of a thermal head is flowing and a time when the reversible thermosensitive recording material moves with respect to the thermal head do not overlap with a time when the reversible thermosensitive recording material moves. . 2. The method according to claim 1, wherein the thermal head and the reversible thermosensitive recording material are relatively intermittently moved, and the reversible thermosensitive recording material is moved relative to the thermal head or during a period of recoil. the image recording method according to claim 1, wherein the pulse current of the heating element of the head falls.