JPH08267920A - Thermal recording method and apparatus - Google Patents

Abstract

PURPOSE: To obtain an image of high gradation and high accuracy by efficiently utilizing energy of laser beam for recording an image and sufficiently ensuring the dynamic range of the laser beam. CONSTITUTION: A thermal recording material S having a thermal layer consisting of microcapsules including a color former and a photothermal conversion agent and a coupler is preheated to temp. immediately before color development by a heating roll 22 and subsequently irradiated with laser beam L modulated corresponding to recording data to collectively heat the microcapsules to allow the thermal recording material S to develop a color in desired density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording method and apparatus for recording an image or the like with a light beam in a state where a thermal recording material is preheated.

[0002]

2. Description of the Related Art A thermal recording method is widely used in which heat energy is applied to a thermal recording material to record an image or the like. In particular, a laser has emerged which enables high-speed recording by using a laser as a heat source (Japanese Patent Laid-Open No. 50-23617).
JP-A-58-94494, JP-A-62-77983
No. JP-A-62-78964).

The applicant of the present invention has applied to such a thermal recording method as a heat-sensitive recording material capable of recording a good image with high quality, and a color former, a color developer and a light absorbing dye (on a support). A material having a photothermal conversion agent, which develops a color at a concentration according to the heat energy supplied by reacting the color developing agent with the color developing agent has been developed and applied for a patent (Japanese Patent Application No. 3-62684). No., Japanese Patent Application No. 3-187494).

FIG. 7 schematically shows the structure of the thermosensitive recording material. This thermosensitive recording material 2 comprises a support 4
The color developer 8 encapsulated in the microcapsules 6, the color developer 10, and the light-absorbing dye 12 are dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then the emulsion is dispersed. The heat-sensitive layer 14 is formed by applying a coating liquid.
The protective layer 16 is further formed on the top.

The heat-sensitive recording material 2 thus constructed is
When the laser beam modulated according to the recorded information is irradiated, the light absorbing dye 12 converts the light energy of the laser beam into heat energy, and the substance permeability of the microcapsules 6 increases according to the heat energy. On the other hand, color developer 10
Increases its fluidity and comes into contact with the color former 8. Then, the color developing agent 10 and the color developing agent 8 react with each other to realize color development with a predetermined density.

[0006]

By the way, the thermosensitive recording material 2 is constructed so as not to develop color with low heat energy in order to maintain a stable storage state. That is, the microcapsule 6 has a characteristic that it does not exhibit substance permeability until it reaches a predetermined temperature (glass transition temperature). Further, the heat-sensitive layer 14 containing the color developer 10 is also in a non-fluid state at room temperature. Therefore, in order to bring the thermosensitive recording material 2 into a color-developable state, it is necessary to bring the thermosensitive layer 14 into a fluid state and heat energy enough to heat the microcapsules 6 to the glass transition temperature or higher. As a result, the dynamic range of the laser is narrowed by the amount of heat energy required for color development, which makes it difficult to obtain an image with high gradation. In addition, the burden on the device side for color development becomes considerably large.

On the other hand, the fluidity of the heat-sensitive layer 14 containing the color-developing agent 10 exhibits "Arrhenius type" behavior in which the fluidity sharply increases (the viscosity decreases) as the temperature rises. FIG. 8 shows the measurement result of the temperature dependence of the viscosity of the color developer 10. In this case, the viscosity decreases by one digit or more with respect to the temperature rise of only 40 ° C. from 80 ° C. to 120 ° C. Also,
From the relationship shown in FIG. 8, heating from room temperature to 120 ° C. causes 2
It can be considered that the viscosity is reduced by more than an order of magnitude.

However, in the case of the thermosensitive recording material 2, since the light absorbing dye 12 for converting the light energy of the laser beam into the heat energy is uniformly dispersed in the heat sensitive layer 14, the heat energy is applied to the microcapsules 6. There is a problem that the heat energy is not efficiently used because the heat energy is dispersed more than necessary in other portions.

An object of the present invention is to efficiently use the energy of a light beam for recording an image and the like, and to secure a sufficient dynamic range of the light beam to obtain an image with high gradation and high accuracy. The object is to provide a heat recording method and apparatus which can be obtained.

[0010]

In order to achieve the above object, the present invention provides a photothermal conversion agent for converting supplied light energy into heat energy, a color developer, and an increase in the heat energy. In a thermal recording method for recording desired information on the heat-sensitive recording material, using a heat-sensitive recording material having a color-developing agent which is housed in a microcapsule with increased substance transmittance and reacts with the color-developing agent. The photothermal conversion agent is localized in the microcapsules, and the heat-sensitive recording material is supplied with heat energy less than the coloring heat energy of the heat-sensitive recording material to preheat the heat-sensitive recording material, and then the preheated heat-sensitive recording material. Is irradiated with a light beam modulated according to recording information, and the heat-sensitive recording material is colored to a predetermined density based on the heat energy obtained from the light beam.

Further, according to the present invention, a photothermal conversion agent for converting the supplied light energy into heat energy, a color developer, and a microcapsule in which the material transmittance increases with an increase in the heat energy are contained in the microcapsules. In a thermal recording device for recording desired information on the heat-sensitive recording material using a heat-sensitive recording material having a color-developing agent that reacts with a color-developing agent, the photothermal conversion agent is localized in the microcapsules. Preheating means for preheating the heat-sensitive recording material by supplying heat energy less than the coloring heat energy of the heat-sensitive recording material, and irradiating the preheated heat-sensitive recording material with a light beam modulated according to record information. A light beam irradiating means, and the heat-sensitive recording material is colored to a predetermined density based on heat energy obtained from the light beam.

[0012]

In the thermal recording method and apparatus of the present invention, the thermal recording material in which the photothermal conversion agent is localized inside or near the wall of the microcapsule encapsulating the color former is used.
By preheating the entire heat-sensitive recording material until just before color development, the fluidity of the developer is sufficiently increased, and the microcapsules are heated to a state immediately before the appearance of substance permeability. Then, the heat-sensitive recording material preheated as described above is irradiated with the light beam modulated according to the recorded information. In this case, the energy of the light beam is converted into heat energy by the photothermal conversion agent, and the photothermal conversion agent localized in the microcapsules effectively increases the material permeability of the microcapsules. As a result, the color developer penetrates into the microcapsules by a predetermined amount and reacts with the color developer, whereby desired information is recorded with the minimum required light energy.

[0013]

The thermal recording method and apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

The thermal recording apparatus 20 shown in FIG. 1 scans a thermal recording material S, which is sub-scanned and conveyed in the direction of arrow B, with a laser beam L in the direction of arrow A to record an image or the like, and serves as preheating means. The heat roll 22 and a laser scanning optical system 24 as a light beam irradiating means are basically constructed.

The heat roll 22 preheats the heat-sensitive recording material S to a predetermined temperature immediately before color development, and cooperates with the pair of nip rolls 26a and 26b to convey the heat-sensitive recording material S in the sub-scanning direction in the arrow B direction. Laser scanning optical system 24
Is a laser diode 28 that outputs a laser beam L.
A collimator lens 30 for collimating the laser beam L, a cylindrical lens 32, a reflecting mirror 34, and a polygon mirror 36 for deflecting the laser beam L.
, Fθ lens 38, and the cylindrical lens 32
And a cylindrical mirror 40 that cooperates with the polygon mirror 36 to correct the surface tilt of the polygon mirror 36. In this case, the laser beam L is irradiated onto the thermosensitive recording material S from between the nip rolls 26a and 26b. The control unit 42
Controls the preheating temperature of the heat sensitive recording material S by the heat roll 22 and controls the laser diode 28 via the driver 44.

Here, the heat-sensitive recording material S used in this embodiment, as shown in FIG. 2, has a heat-sensitive layer 48 on the support 46 which is colored to a predetermined density by heat energy obtained from the laser beam L. And a protective layer 50 is further formed on the heat sensitive layer 48.

The heat-sensitive layer 48 constituting the heat-sensitive recording material S.
Is a microcapsule 56 containing a color-developing agent 52 and a light-absorbing dye 54 (photothermal conversion agent) and a developer 58 dissolved in an organic solvent that is sparingly soluble or insoluble in water, and then emulsified and dispersed. The coating liquid contained is applied onto the support 46 (JP-A-4-331186, JP-A-4-3).
No. 07292).

The color-forming agent 52 is one which causes a color-forming reaction upon contact with a substance. Specifically, a combination of a photodegradable diazo compound and a coupler or a combination of an electron-donating dye precursor and an acidic substance is preferable. .

The photodecomposable diazo compound is a compound that reacts with a developer 58 called a coupling component described later to develop a desired hue, and decomposes when receiving light of a specific wavelength before the reaction. , A diazo compound that has no coloring ability even when the coupling component acts. The hue in this coloring system is mainly determined by the diazo dye produced by the reaction of the diazo compound and the coupling component. Therefore, as is well known, the coloring hue can be easily changed by changing the chemical structure of the diazo compound or the chemical structure of the coupling component, and almost any coloring hue can be obtained depending on the combination. it can.

The photodecomposable diazo compound in this embodiment mainly refers to an aromatic diazo compound, and more specifically, a compound such as an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound or the like. The diazonium salt is a compound represented by the general formula ArN ₂ ⁺ X ⁻ (wherein Ar represents a substituted or unsubstituted aromatic moiety, N ₂ ⁺ represents a diazonium group, and X ⁻ represents an acid). Represents an anion).

It is generally said that the photolysis wavelength of a diazonium salt is its absorption maximum wavelength. The absorption maximum wavelength of the diazonium salt is 200 n depending on its chemical structure.
It is known to change from m position to 700 nm position ("Photolysis and chemical structure of photosensitive diazonium salt" written by Takahiro Tsunoda and Ao Yamaoka, Journal of the Photographic Society of Japan 29 (4) 197-1.
05 (1965)). That is, when a diazonium salt is used as a photodecomposable compound, it is decomposed by light having a specific wavelength according to its chemical structure, and if the chemical structure of the diazonium salt is changed, it is possible to obtain a coupling reaction with the same coupling component. The hue of the dye also changes.

As the light source for photolysis, various light sources that emit light of a desired wavelength can be used. Examples thereof include various fluorescent lamps, xenon lamps, xenon flash lamps, mercury lamps of various pressures, photographic flashes, Various light sources such as a strobe can be used.

Many diazosulfonate compounds are known, and they can be obtained by treating each diazonium salt with sulfite. Moreover, a diazo amino compound can be mentioned as another diazo compound. The diazoamino compound is a compound obtained by coupling a diazo group with dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulphonic acid, monoethanolamine, diethanolamine, guanidine and the like.

A coupling component (developer 5) which forms a dye by coupling with a diazo compound (diazonium salt).
Examples of 8) include 2-hydroxy-3-naphthoic acid anilide and resorcin.

Further, by using two or more of these coupling components in combination, an image with any color tone can be obtained. Since the coupling reaction between these diazo compound and the coupling component easily occurs in a basic atmosphere,
A basic substance may be added in the layer.

As the basic substance, a hardly water-soluble or water-insoluble basic substance or a substance which generates an alkali upon heating is used. Examples thereof are inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines and triazoles. , Nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines and pyridines. Two or more basic substances may be used in combination.

The electron-donating dye precursor is not particularly limited, but it has the property of developing a color by donating electrons or accepting a proton such as an acid, and is generally colorless and lactone. A compound having a partial skeleton such as lactam, sultone, spiropyran, ester or amide, which is opened or cleaved by contact with the developer 58, is used. Specifically, there are crystal violet lactone, benzoyl leuco methylene blue, malachite green lactone, rhodamine B lactam, 1,3,3-trimethyl-6′-ethyl-8′-butoxyindolinobenzospiropyran and the like.

As the color developer 58 for these color formers, an acidic substance such as a phenol compound, an organic acid or a metal salt thereof, an oxybenzoic acid ester is used.

The light absorbing dye 54 is preferably a dye that absorbs light having a wavelength in the visible light region little but absorbs light having a wavelength in the infrared region particularly high. Examples of such dyes include cyanine dyes, phthalocyanine dyes, pyrylium or thiopyrylium dyes, azurenium dyes, squarylium dyes, metal complex salt dyes such as Ni and Cr, naphthoquinone dyes or anthraquinone dyes, indophenol dyes. Examples thereof include dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, aminium or diimmonium dyes, and nitroso compounds.

Among these, in the sense that the laser diode 28 that oscillates near-infrared light that has been put into practical use can be used, the absorption efficiency of light in the near-infrared region having a wavelength of 700 nm to 900 nm is particularly high. Those are preferable.

The microcapsules 56 increase the material permeability of their walls due to an increase in the supplied thermal energy, and can be manufactured, for example, as follows.

That is, in order to manufacture the microcapsules 56 used in this embodiment, any of the interfacial polymerization method, the internal polymerization method and the external polymerization method can be adopted. It is preferable to employ a method of emulsifying the core substance containing the absorption dye 54 in an aqueous solution in which a water-soluble polymer is dissolved, and then forming a wall of the polymer substance around the oil droplets.

The reactant forming the polymer substance is added inside the oil droplet and / or outside the oil droplet. Specific examples of the polymer substance include polyurethane, polyurea,
Polyamide, polyester, polycarbonate, urea-
Formaldehyde resin, melamine resin, polystyrene,
Examples thereof include styrene methacrylate copolymer and styrene-acrylate copolymer. Preferred polymeric substances are polyurethane, polyurea, polyamide, polyester,
Polycarbonate, particularly preferably polyurethane and polyurea. Two or more polymer substances can be used in combination.

Specific examples of the water-soluble polymer include gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like. For example, when polyurea is used as a capsule wall material, a polyisocyanate such as diisocyanate, triisocyanate, tetraisocyanate or polyisocyanate prepolymer and a polyamine such as diamine, triamine or tetraamine and an amino group are The microcapsule wall can be easily formed by reacting a prepolymer containing one or more of them, piperazine or a derivative thereof, a polyol, or the like with an interfacial polymerization method in an aqueous solvent.

Further, for example, for the composite wall made of polyurea and polyamide or the composite wall made of polyurethane and polyamide, for example, polyisocyanate and acid chloride or polyamine and polyol are used to adjust the pH of the emulsifying medium as the reaction liquid. It can be prepared by heating afterwards.

Further, the other heat-sensitive recording materials Sa, Sb, Sc used in this embodiment contain the light absorbing dye 54 inside the wall of the microcapsule 56 as shown in FIGS. Alternatively, the light absorbing dye 54 is attached to the outer surface or the inner surface of the wall of the microcapsule 56. In addition, when the absorption amount of energy of the laser beam L is increased to further enhance the sensitivity of the thermal recording materials Sa, Sb, Sc, at the same time, the light absorbing dye is also provided outside the microcapsule 56 and / or inside the wall of the microcapsule 56. 54 can be added.

When attached to the outside of the microcapsules 56 (FIG. 4), the light absorbing dye 54 has a high infrared absorption efficiency and a high light absorption in the visible light region from the viewpoint of preventing coloring of the heat-sensitive recording material Sb. It is particularly preferable to select and use a small amount appropriately. When contained in the wall of the microcapsule 56 (FIG. 3), it is particularly preferable to use a light-absorbing dye having an active group that reacts with the wall material of the microcapsule 56 when the microcapsule 56 is formed.

Specific examples of the above-mentioned active group include an isocyanate group, a hydroxy group, a mercapto group and an amino group, but an isocyanate group and a hydroxy group are particularly preferable. Further, a solid sensitizer can be added to swell the wall of the microcapsule 56 when heated by the laser beam L.

The solid sensitizer is selected from among the plasticizers for polymers used as the walls of the microcapsules 56.
Those having a melting point of 50 ° C. or higher, preferably 120 ° C. or lower and solid at room temperature can be selected and used. For example, when the wall material is made of polyurea or polyurethane, a hydroxy compound, a carbamic acid ester compound,
Aromatic alkoxy compounds, organic sulfonamide compounds,
Aliphatic amide compounds and aryl amide compounds are preferably used.

Next, the above-mentioned thermal recording materials S, Sa, S
The operation of the thermal recording device 20 using b and Sc and its action and effect will be described.

First, the control unit 42 controls the thermal recording material S (S
a to Sc) to the heat roll 22 and the nip roll 26
Preheating is carried out while being sub-scanned in the direction of arrow B while being sandwiched between a and 26b. That is, the heat roll 22 heated by the control unit 42 is heated by the thermal recording material S (Sa).
To Sc), the thermal recording material S (Sa
~ Sc) is preheated to a temperature just before color development.

The characteristic curve a of FIG. 6 is the thermal recording material S (S
It shows the relationship between the temperature of a to Sc) and the color density. In the case of the characteristic curve a in the figure, the thermal recording material S (Sa-
Sc) is preheated to the temperature T1. In this case, the temperature T1 is the same as that of the microcapsules 56 contained in the heat-sensitive layer 48.
Is set to a temperature lower than the glass transition temperature at which it exhibits substance permeability. In this state, the developer 58 contained in the heat-sensitive layer 48 rapidly exhibits fluidity due to the thermal energy supplied from the heat roll 22 based on the Arrhenius type behavior.

On the other hand, in the above state, the control unit 42
Drives the laser diode 28 via the driver 44. The laser diode 28 is made up of the thermal recording material S (Sa
To Sc), the laser beam L modulated according to the gradation of the image recorded is output. The laser beam L is collimated by the collimator lens 30 and then guided to the polygon mirror 36 via the cylindrical lens 32 and the reflection mirror 34. The polygon mirror 36 is rotating at a high speed, and the laser beam L reflected by its reflecting surface is guided to the thermosensitive recording material S (Sa to Sc) via the fθ lens 38 and the cylindrical mirror 40, and the direction of arrow B is shown. The thermal recording material S which is sub-scanned and conveyed to the
(Sa-Sc) is main-scanned in the direction of arrow A.

In this case, the light energy of the laser beam L is converted into heat energy by the light absorbing dye 54 localized inside the wall of the microcapsules 56 included in the heat sensitive layer 48 or in the vicinity thereof. Due to this heat energy, the temperature of the microcapsules 56 exceeds the glass transition temperature, and the substance permeability appears, and further, the temperature rises to increase the substance permeability.
The developer 58 to which the fluidity is imparted penetrates into the microcapsules 56 by a predetermined amount and comes into contact with the color former 52 to cause a color reaction, whereby a gradation image is formed. The thermal recording material S on which the gradation image is formed
For (Sa to Sc), the gradation image can be fixed by irradiating with light of a specific wavelength, if necessary.

Here, in the case of the heat-sensitive recording material S, the light absorption dye 54 for supplying heat energy to the microcapsules 56 is contained in the microcapsules 56,
In the case of the thermal recording material Sa, the microcapsules 56
Contained in the wall of the thermal recording material Sb,
In the case of Sc, since it is attached on the outer or inner surface of the wall of the microcapsule 56, only the microcapsule 56 can be efficiently heated without heating the developer 58 or the like more than necessary. . Therefore, the laser beam L
The light energy from the light is supplied to the microcapsules 56 extremely efficiently and contributes to color development.

Further, the heat-sensitive recording material S (Sa to Sc)
Is preheated to the temperature T1 shown in FIG. 5 by the heat energy supplied from the heat roll 22, so that the laser diode 28 is controlled in a wide range from the room temperature where the thermal recording device 20 is installed to the temperature T2. No need.
Therefore, the laser diode 28 has a temperature of T1 to T
The image is controlled in the range of 2 and a high-gradation image is accurately formed. Further, since the laser diode 28 is not required to have a high output, the entire structure of the thermal recording device 20 is simplified and the cost is low.

In the heat-sensitive recording material S (Sa to Sc), a plurality of coloring agents 52 that develop different colors and a plurality of light absorbing pigments 54 that absorb the laser beams L having different wavelengths.
It is also possible to localize each of these and the microcapsules 56 (see Japanese Patent Laid-Open No. 63-319183) and record a multicolor image or the like by using the laser beams L having different wavelengths. Further, by providing the heat-sensitive layer 48 for each color, it is possible to form a multi-layer and record a multicolor image or the like (see Japanese Patent Application No. 6-21266).

[0048]

According to the thermal recording method and apparatus of the present invention, the following effects can be obtained.

That is, by preheating the entire heat-sensitive recording material until just before color development, the fluidity of the color developer is sufficiently increased and preparation for color development is completed. Then, in this state, when the light beam modulated according to the recorded information is irradiated, the photothermal conversion agent localized in the microcapsules converts the light energy of the light beams into heat energy, and the substance of the microcapsules. Increase the transmittance. In this case, the photothermal conversion agent does not apply heat energy to unnecessary portions, so that the light beam causes an efficient color-forming reaction. Therefore, the output of the light beam required for color development can be minimized. Further, since the thermosensitive recording material is preheated in advance during recording with the light beam, it is possible to secure a sufficient dynamic range of the light beam and obtain an image with high gradation and high accuracy.

[Brief description of drawings]

FIG. 1 is a structural explanatory diagram of an embodiment of a thermal recording apparatus according to the present invention.

FIG. 2 is a structural explanatory view of a thermal recording material applied to the thermal recording apparatus according to the present invention.

FIG. 3 is a structural explanatory view of a thermal recording material applied to the thermal recording apparatus according to the present invention.

FIG. 4 is a structural explanatory view of a thermal recording material applied to the thermal recording apparatus according to the present invention.

FIG. 5 is a structural explanatory view of a thermal recording material applied to the thermal recording apparatus according to the present invention.

FIG. 6 is an explanatory diagram of color forming characteristics of a heat-sensitive recording material applied to the heat recording apparatus according to the present invention.

FIG. 7 is a structural explanatory view of a heat-sensitive recording material according to a conventional technique.

FIG. 8 is a characteristic diagram showing the relationship between the viscosity of a color developer and temperature.

[Explanation of symbols]

20 ... Thermal recording device 24 ... Laser scanning optical system 28 ... Laser diode 36 ... Polygon mirror 42 ... Control part S (Sa-Sc)
… Thermal recording material

Claims (5)

[Claims] 1. A photothermal conversion agent for converting supplied light energy into heat energy, a color developing agent, and the color developing agent housed in a microcapsule whose substance transmittance increases as the heat energy increases. Using a heat-sensitive recording material having a color-forming agent that develops color by reacting, in a heat recording method for recording desired information in the heat-sensitive recording material, in the state where the photothermal conversion agent is localized in the microcapsules. , After preheating by supplying the heat-sensitive recording material with heat energy less than the coloring heat energy of the heat-sensitive recording material, the preheated heat-sensitive recording material is irradiated with a light beam modulated according to record information, A thermal recording method, wherein the thermal recording material is colored to a predetermined density based on thermal energy obtained from a beam. 2. The method according to claim 1, wherein the photothermal conversion agent is mixed with the color former in the microcapsules. 3. The thermal recording method according to claim 1, wherein the photothermal conversion agent is contained inside the wall of the microcapsule. 4. The thermal recording method according to claim 1, wherein the photothermal conversion agent is attached along the wall surface of the microcapsule. 5. A photothermal conversion agent for converting supplied light energy into heat energy, a color developing agent, and the color developing agent housed in a microcapsule whose substance transmittance increases as the heat energy increases. In a thermal recording device for recording desired information on the heat-sensitive recording material, using a heat-sensitive recording material having a color-forming agent that develops a color when reacted, a heat-sensitive recording in which the photothermal conversion agent is localized in the microcapsules. Preheating means for preheating the material by supplying heat energy less than the coloring heat energy of the heat-sensitive recording material, and light beam irradiation means for irradiating the preheated heat-sensitive recording material with a light beam modulated according to the recorded information. And a thermal recording device characterized by causing the thermal recording material to develop a color to a predetermined density based on the thermal energy obtained from the light beam.