JPH0485071A - Heat sensitive transfer material - Google Patents

Abstract

PURPOSE:To permit a good printing without lowering the density of the surface of an ink transferred to a printing medium by coloring shell or thermally expandable substances in the same color as a thermally meltable ink layer. CONSTITUTION:An ink ribbon 400 is heated from the side of a base film 450 by the Joule heat generated by a heating resistor 366 formed on a thermal head 360. In doing so, the heat is transmitted through a base film 450 to a thermally meltable ink layer 410 to soften and melt this ink layer and, at the same time, expand microcapsules 420, enclosing therein thermally expandable substances 430, dispersed in the thermally meltable ink layer 410, whereby the molten ink is fused on the surface of recording paper P by the ink layer 410. In the image dot formed on the recording paper P after separation of the ink ribbon 400, even if the expanded microcapsules 420 are exposed on the ink surface of the image dot, its effect on the printing density can be reduced, since the microcapsules 420 (shell 440 and thermally expandable substance 430) and the ink layer 410 are colored in the same color.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thermal transfer material used in a thermal transfer recording type image forming apparatus.

(Prior art) In recent years, image forming devices such as printers and facsimiles using thermal transfer recording methods have become popular because they do not make noise during operation, are low in cost, easy to reduce in size and weight, and have excellent operability and maintainability. It is becoming widespread.

This thermal transfer method generally uses a thermal transfer material (hereinafter referred to as an ink ribbon) that has a heat-melting ink layer on a sheet-like support, and selectively transfers this ink ribbon using a thermal head or the like. The ink layer is heated to melt the ink layer, and the melted ink is transferred onto a recording medium to record an image according to the heated shape.

However, conventional ink ribbons have a problem in that print quality deteriorates on recording media with poor surface smoothness. Therefore, in order to be able to perform good printing even on recording media with poor surface smoothness, thermal expansion ink is made of a shell containing a thermal expansion substance in a heat-melting ink layer or in a separate layer. (hereinafter referred to as microcapsules).

) has been developed.

When this ink ribbon is heated by a thermal head, the ink layer melts and the microcapsules expand, and the pressure causes the molten ink to be pressed and adhered to the recording medium, resulting in a smooth surface. Good printing can be performed even on recording media with poor quality.

(Problems to be Solved by the Invention) However, even with the ink ribbon containing the above-mentioned microcapsules, there have been unresolved problems as listed below.

■ Conventional shells are colorless and transparent, but because they are made of fine particles, they appear white to the naked eye. For this reason, if the shell is exposed on the ink surface transferred to the recording medium, it will have a negative effect on the ink density, and in the worst case, for example, in the case of a black ink ribbon,
Black ink looks gray. The same applies to the thermal expansion material included in the shell.

■In order to reduce the amount of ink ribbon consumed, the ink ribbon may be transported at a speed slower than the transport speed of the recording medium, but in such cases, the ink ribbon and the recording medium will rub against each other. , so-called background fog occurs, in which melted ink adheres to non-recording areas of the recording medium, staining the surface of the recording medium.

■If the microcapsules do not expand sufficiently, the molten ink cannot be firmly pressed against the recording medium, making it impossible to obtain good print quality.

The present invention was made to solve such problems,
The present invention provides a thermal transfer material capable of printing with good print quality.

[Structure of the Invention] (Means for Solving Problem R) The present invention provides a thermally expandable material having at least a heat-melting ink layer on a support and comprising a shell and a thermally expandable material contained in the shell. In the heat-sensitive transfer material provided with a transfer surface containing particles, the shell and the heat-melting ink layer are formed in the same color.

A second invention provides a thermal transfer material in which a transfer surface is provided on a support, the transfer surface having at least a heat-melting ink layer and containing heat-expandable particles consisting of a shell and a heat-expandable material contained in the shell. In this case, the thermally expandable material and the thermally meltable ink layer are formed in the same color.

A third invention includes a support, a heat-melt ink layer containing heat-expandable particles laminated on the support, and a softening temperature of the heat-melt ink layer laminated on the heat-melt ink layer. The overcoat layer is higher than the overcoat layer.

A fourth invention provides a support, a heat-melt ink layer containing heat-expandable particles laminated on the support, and an almost colorless and transparent overcoat layer laminated on the heat-melt ink layer. It is equipped with the following.

Furthermore, a fifth aspect of the present invention provides a thermal transfer material in which a transfer surface having at least a heat-melting ink layer and containing heat-expandable particles is provided on a support, wherein the expansion start temperature of the heat-expandable particles is The temperature is higher than the softening temperature of the heat-melting ink layer.

(Function) In the first invention, since the shell is formed in the same color as the heat-melting ink layer, even if the shell is exposed on the surface of the ink transferred to the recording medium, the density of the ink does not decrease. .

In the second invention, since the thermally expandable material is formed to have the same color as the heat-melting ink layer, the density of the ink does not decrease as well.

In the third invention, an overcoat layer having a softening temperature higher than that of the heat-melt ink layer is laminated on the heat-melt ink layer containing heat-expandable particles. It is possible to prevent the layer from melting and adhering to the recording medium.

In the fourth invention, since a colorless and transparent overcoat layer is laminated on the heat-melting ink layer containing heat-expandable particles, even if the overcoat layer is rubbed off by the recording medium, No deterioration of print quality.

In the fifth invention, since the expansion start temperature of the heat-expandable particles is higher than the softening temperature of the heat-fusible ink layer, the heat-fusible particles start expanding after the heat-fusible ink layer has softened and melted. The heat-expandable particles can reliably expand and press the molten ink onto the recording medium.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Image forming apparatus FIG. 1 shows an image forming apparatus 10 according to an embodiment of the present invention.
FIG. The configuration will be explained below.

The recording paper cassette 60 stores recording paper P.

Further, as a conveyance mechanism for this recording paper P, there is a take-out mechanism 70 that sends out the recording paper P from the cassette 60, a separation mechanism 90 that separates and conveys the recording paper P taken out from the cassette 60 one by one, and a PET (polyethylene terephthalate). ,
Drum 100, which has a conductive material such as polyimide formed on its surface and conveys recording paper P while adsorbing it to its surface.
a pinch roller 110 that presses the recording paper P against the drum 100, a peeling claw 130 that peels off the recording paper P from the drum 100, and a tray 15.
There is a paper discharge mechanism 140 for discharging the recording paper P on the top of the recording paper P.

Further, around the drum 100, there are a recording paper detection sensor 120 that detects the leading and trailing edges of the recording paper P, a monochrome printing mechanism 300 that prints only colors, and a color printing mechanism 600 that performs color printing. It is located.

Furthermore, the image forming apparatus 10 includes an interface for receiving image signals from the outside, an electric circuit 200 for controlling the entire apparatus, a power supply 280 for supplying power to each part of the apparatus, and a control panel for performing various operations of the apparatus. 29
0 is set.

Next, the operation in the above configuration will be explained. The recording paper P is transferred to the recording paper cassette 60 by the take-out mechanism 70 and the separation mechanism 90.
The sheets are taken out one by one from the pinch roller 110 and the drum 10.
Due to the suction action of 0, it is wound around the drum 100 which rotates in the direction indicated by the arrow in the figure.

Next, in the case of printing only in - color, after being printed by the monochrome printing mechanism 300, it is peeled off from the drum 100 by the peeling claw 130, and is discharged onto the tray 150 by the paper discharge mechanism 140.

On the other hand, in the case of multicolor printing, the peeling claw 130 is moved to a position away from the drum 100 indicated by the broken line by a solenoid (not shown), and the recording paper P is transferred to the drum 100 without being printed by the monochrome printing mechanism 300. It reaches the color printing mechanism 600 while being wound, and first,
The first color is printed. Further, as the drum 100 rotates, the color printing mechanism 600 prints the second and third colors, and the monochrome printing mechanism 300 prints black, and then the peeling claw 130 moves to the position shown by the solid line to remove the recording paper P from the drum. It is peeled off from 100 and discharged onto tray 150.

The configuration and operation of each part will be explained in detail below.

Monochrome Printing Mechanism FIG. 2 is a sectional view showing the monochrome printing mechanism 300. The configuration will be explained below.

The ink ribbon 400 has one end wound around a supply roll 310, is held between a pair of supply rollers 330 and 330, is in contact with a preheater 340, and is placed between a thermal head 360 biased by a compression coil spring 350 and the drum 100. ,
and a pair of collection rollers 370 and 370, and the other end is wound onto a collection roll 380.

The supply roller pair 330, 330 is directly connected to and driven by a motor (not shown), and the collection roller pair 37o1370 and the collection roll 380 are driven via a slip clutch (not shown). The conveying speed of these ink ribbon conveying sections is determined by the relationship: circumferential speed of drum 100 > conveying speed of collection roller pair 370, 370 and collection roller 380, conveyance speed of supply roller pair 330, 330, when there is no slippage due to the slipping clutch. The ink ribbon 40 is released by the slipping clutch.
It is configured so that a constant tension is applied to the 0. Further, the conveyance speed of the pair of supply rollers 330, 330, which defines the conveyance speed of the ink ribbon 400, is set to 0.1 to 0.9 times the circumferential speed of the drum 100, particularly 0.2
It is preferable to set the range to 0.5 times.

The compression coil spring 350 biases the thermal head 360 against the drum 100 with a value smaller than the normal pressing force, and the value is set to 20 to 150 g/c, or particularly 50 to 100 g/c. It is preferable that

The preheater 340 has a resistor 34 that is longer than the width of the recording paper P.
1 is wrapped and hardened with cement 342, and the outside is further covered with a Teflon sheet 343 with low frictional resistance. The surface temperature of the preheater 340 is the same as that of the ink ribbon 400.
The temperature is controlled to be lower than the ink melting point of the ink ribbon 400 by a temperature control thermistor 344 attached to the side surface of the surface that comes into contact with the ink ribbon 400 .

In addition, 367 is a drive circuit mounting part in which the drive circuit of the thermal head 360 is mounted.

Next, the operation of the monochrome printing mechanism 300 having the above configuration will be explained.

Before the recording paper P wrapped around the drum 100 reaches the thermal head 360, the motor that drives the monochrome printing mechanism 300 is stopped, and the ink ribbon 400 is in a state of sliding relative to the drum 100. It is said that Then, the recording paper is detected by the detection signal from the recording paper detection sensor 120 and the delay timer in the electric circuit 200.
At the point when the thermal head 360 reaches the thermal head 360, the motor rotates, and the supply roller pair 330, 330 and the collection roller pair 37
0.370 and the collection roll 380 are the ink ribbon 40
0 at a slower speed than the drum 100. Further, the recording paper P is detected by the thermal head 360 by a detection signal from the recording paper detection sensor 120 and a delay timer in the electric circuit 200.
When the ink ribbon 400 has passed through, the motor is stopped and the conveyance of the ink ribbon 400 is stopped.

Conveyance of the ink ribbon 4° is temporarily stopped for non-image areas that are not printed, such as between lines, under control from the electric circuit 200.

Immediately before reaching the thermal head 360, the ink ribbon 400 is heated by a preheater 340 to a temperature slightly lower than the melting point of the ink, and then printed on the recording paper P by the thermal head 360. Therefore, a good transferred image can be obtained even with less heating by the thermal head 360, and high-speed recording is also possible.

FIG. 3 is a sectional view showing the structure of the ink ribbon 400.

As shown in the figure, the ink ribbon 400 has an overcoat layer 47o (hereinafter referred to as a coat layer 470).

), a thermofusible ink layer 410 that softens and melts due to heat,
It is composed of microcapsules 420 that expand rapidly when heated and a base film 450 as a support for these, and the microcapsules 420 are dispersed so as to be in contact with the base film 450.

As for the form of dispersion, the heat-fusible ink layer 410 may be thicker than the particle size of the microcapsules 420, as shown in FIG. 3(a); The thickness of the layer 410 may be the same (FIG. 4(b)), or the heat-melting ink layer 410 may be made thinner than the particle size of the microcapsules 420.
20 (FIG. 2(C)), or the microcapsules 420 may be exposed from the heat-melting ink layer 410 (FIG. 4(D)).

The coating layer 470 has a softening temperature that is higher than that of the heat-melting ink layer 410.
Alternatively, the color of the coating layer 470 can be made colorless and transparent. The coat layer 470, which has a softening temperature higher than that of the heat-melting ink layer 410, is made of, for example, a coloring material or a binder. The colorless and transparent coating layer 470 is made of, for example, a binder that does not contain a colorant. As the coloring material and the binder, the above-mentioned heat-melting ink layer 410 is used.
Pigments, dyes, waxes, resins, etc. used in The thickness of the coating layer 470 is preferably set to 10 μm or less, particularly 0.1 to 5 μm.

The particle size of the microcapsules 420 is 1 to 30μ before expansion.
m1 (1 to 10 μm), and the maximum particle size after expansion is 2 to 1
00 μm1 (10 to 60 μm), heat-melting ink layer 41
The thickness of 0 is set to 1 to 20 μm1 (2 to 10 μm), and it is particularly preferable to set it to the value shown in parentheses. In addition, as for the amount of dispersion, the heat-melting ink layer 410
When the total is 100 parts, 1 microcapsule 420 is
It is preferable that it is dispersed in 30 parts.

The heat-melting ink layer 410 consists of a colorant and a binder. Examples of colorants include pigments such as carbon black,
Other examples include the substances disclosed in JP-A No. 60-25792, such as nigrosine dye, lamp black, or any colorant commonly used in the field of printing and copying, such as various dyes; All dyes and pigments can be used. Further, as a binder, for example, JP-A-59-2
Substances disclosed in Japanese Patent No. 01894 (in parentheses below), such as waxes such as carnauba wax, paraffin, Sasol wax, and microcrystalline wax, can be used.

(Carnauba wax, paraffin, Sasol wax,
Waxes such as microcrystalline wax and castor wax, stearic acid.

Valmitic acid, lauric acid, aluminum stearate, lead stearate, barium stearate, zinc stearate, zinc valmitate.

Higher fatty acids such as methyl hydroxystearate and glycerol monohydroxystearate or their metal salts, derivatives such as esters, polyethylene, polypropylene, polyisobutylene.

Polyethylene wax, polyethylene oxide, polytetrafluoroethylene, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer.

Thermoplastic resins made of single or copolymers of olefins, such as ethylene-vinyl acetate copolymers, or derivatives thereof, are used. ) Other examples (including specific examples) include beeswax, candelilla wax, polyethylene wax, hollow wax, auriculie wax, ester wax,
Oxidized wax, waxes such as montan wax, osikelite, ceresin, higher alcohols such as valmityl alcohol, stearyl alcohol, behenyl alcohol, eicosatru, higher fatty acid esters such as cetyl balmitate, myricyl valmitate, cetyl stearate, myricyl stearate, acetamide. , amides of propionic acid amide, balmitic acid amide, stearic acid amide, cellulose resins (ethyl cellulose, etc.), terpene resins, polyester resins, rosin resins, epoxy resins, vinyl resins (vinyl acetate resin, vinyl chloride) resin, vinyl chloride vinyl acetate copolymer resin, vinyl butyral resin, polyvinyl stearate, etc.), butadiene resin, aromatic petroleum resin, low molecular weight petroleum resin, ketone resin, styrene resin, aliphatic hydrogen carbonate resin , polyamide resin, polystyrene resin, ester resin, acrylic resin, sulfone resin, polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, ester gum, rosin maleic acid resin, rosin phenolic resin, phenolic resin, terpene resin, cyclopetane diene resin, aroma family resin,
Resins such as urea resin and silicone resin, higher amines such as stearylamine, styrene-butadiene copolymer,
Examples include high molecular weight polymers such as acetate butyrate, polyvinyl alcohol, and the like. These binders may be used alone or in combination of two or more.

As the base film 450, for example, a plastic film such as polyethylene terephthalate, polyimide, polyester, polycarbonate, triacetyl cellulose, nylon, or cellophane, or thin paper such as capacitor paper, glassine paper, or parchment paper can be used. Its thickness is 2
15 μm, particularly preferably 3 to 6 μm.

Furthermore, the base film 450 may be provided with a heat-resistant layer made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melanin resin, polyester resin, vinyl ester resin, nitrocellulose, etc. on the surface that contacts the thermal head 360, for example. It is possible to improve the 450 heat resistance of the base film.

The ink ribbon 400 in this embodiment is obtained by, for example, a known hot melt coating method or solvent coating method. In the hot-melt coating method, the coating liquid mainly composed of the above-mentioned binder and colorant obtained under heating is heated to a temperature below the expansion start temperature so that the microcapsules 420 encapsulating the thermally expandable substance 430 do not expand thermally.
Disperse the microcapsules 420 in the heat-melting ink layer 410 to form a coating liquid containing the microcapsules 420 and forming the heat-melting ink layer 410 and the coating layer 470 (mainly containing the binder) at a temperature and condition below the expansion start temperature. It can be obtained by applying this using a bar coater or the like in this order and drying it.

In the solvent coating method, microcapsules 420 encapsulating the thermally expandable substance 430 are dispersed in a paint liquid containing a binder and a colorant dissolved in a solvent as main components, and the microcapsules 420 encapsulating the thermally expandable substance 430 are contained. It is obtained by preparing a coating liquid that becomes the heat-melting ink layer 410, applying it using a bar coater or the like in the same order as in the hot-melt coating method, and drying it.

Further, in the above-described ink ribbon 400, only the case where the heat-melting ink layer 410 formed on the base film 450 is one layer has been described, but it may have a multilayer (two or more layers) structure as necessary. I can bring it.

Next, the microcapsule 420 will be explained in more detail.

Thermal expansion material 430 encapsulated in microcapsules 420
A thermally decomposable blowing agent or a volatile liquid with a low boiling point is used.As a blowing agent, a blowing agent compound that generates gas by thermal decomposition, which is commonly used in fields such as resin processing, is used. It can also be used in the present invention. Further, as the volatile liquid, an evaporative/volatile blowing agent compound commonly used in fields such as resin processing can be used.

Thermally decomposable blowing agents include organic blowing agents such as diazoamino derivatives, azo compounds, sulfone hydrazide compounds, and nitroso compounds, and inorganic blowing agents such as bicarbonates, carbonates, and azides. Specific examples of organic blowing agents include diazoamino derivatives such as 1,3〜bis-biphenylyltriazine, diazoaminobenzene, and 1-methyl-3-phenyltriazine, and azo compounds such as azobishexahydrobenzodinitrile, Sulfone hydrazide compounds such as azodicarbonamide, azobisisobutylnitrile, diazoaminobenzene, diazoic acid amide, etc. include benzenesulfonic acid hydrazide, 4,4-bis(hydrazinosulfonyl)diphenyl ether, p-1-luenesulfonylhydrazide, benzenesulfonyl hydrazide, p, p
-oxybisbenzenesulfonylhydrazide, diphenylsulfone SS'disulfonylhydrazide, 4,4-
Oxybisbenzenesulfonyl hydrazide, etc., and nitroso compounds such as N, N=-dinitroso-N, N--dimethylterephthalamide, N,N-dinitrosopentaethylenetetramine, N,N-dimethyl-N, N--dinitroterephthalamide, etc. can be mentioned.

Specific examples of inorganic blowing agents include bicarbonates such as sodium bicarbonate, sodium bicarbonate, ammonium bicarbonate, and sodium bicarbonate; carbonates such as sodium bicarbonate, ammonium carbonate, and magnesium carbonate; and azides such as CaN6, Examples include B a N b. Examples of volatile liquids with low boiling points include isobutane;
Substances disclosed in Publication No. 792, such as propane,
Pentane, hexane, etc. can be used. Other specific examples include trichlorofluoromethane, dichlorofluoromethane,
Examples include dichlorotetrafluoroethane, normal butane, butylene, carbon dioxide, acetone, methylene chloride, trichlorofluoromethane, trichlorotrifluoromethane, petroleum ether, and the like. These blowing agents may be used alone or in combination of two or more.

In general, a low boiling point volatile liquid is a liquid near normal temperature and normal pressure, or a low boiling point volatile liquid to be included in the microcapsules 420 used in the ink ribbon 400 of the present invention is particularly suitable at room temperature and normal pressure. Preferred are gaseous substances that become liquid under pressure equal to or higher than normal pressure (for example, inside a microcapsule), such as isobutane, neopentane, propane, freons, and the like.

FIG. 4 shows the viscosity of the heat-melting ink layer 410 and the shell 44.
It schematically shows the elastic limit stress of 0.

As shown in the figure, as the heat from the thermal head 360 is transferred to the thermofusible ink layer 410, the temperature of the printing area rises (tO), and then immediately drops when the heat application ends (t3). do. The viscosity of the hot melt ink layer 410 is
It starts to decrease from the softening temperature TI (tl) of the binder, and increases as the temperature decreases. Further, the elastic limit stress of the shell 440 starts to fall below the softening temperature T2 (t2) later than the time (tl) at which the binder starts to soften, and increases as the temperature decreases. Therefore, the expansion of the microcapsules 420 starts from the time (t2') when the internal pressure exceeds the strength of the shell 440 after the shell 440 has softened.
The expansion continues until the internal pressure becomes equal to atmospheric pressure, but if the temperature drops too quickly, the expansion stops when the internal pressure at that time falls below the strength of the shell 440 (t4). Therefore, in order to completely expand the microcapsules 420, it is necessary to maintain the temperature at a high temperature for a sufficient period of time until the expansion is completed.

By the way, as described above, when the expansion start temperature of the microcapsules 420 is equal to or higher than the softening temperature of the binder, the microcapsules 420 expand after the binder is softened, so there is no problem with ink transfer. However, if the temperature is lower than the softening temperature of the binder, the binder expands before it softens. For this reason, when the microcapsules 420 protrude from the ink layer 410 (FIG. 3(d)), only the protruding portions swell, making it impossible to obtain the effect of pushing out the ink. Furthermore, in the case of the microcapsules 420 completely embedded in the ink layer 410 (FIG. 3(a)), the start of fat expansion is delayed, making it difficult to completely expand the microcapsules 420. Therefore, it is desirable that the expansion start temperature of the microcapsules 420 containing the thermally expandable material 430 is equal to or higher than the softening temperature of the binder. In particular, the temperature difference from the softening temperature of the binder is preferably in the range of 0°C to 50°C, and the softening temperature of the binder of the hot-melt ink layer 410 is usually set to 55°C to 150°C. If the softening temperature of the binder is 55°C, 55°C to 10
5℃, 150℃ if the softening temperature of the binder is 150℃
The range of the temperature at which the microcapsules 420 start expanding is preferably 200°C.

Microcapsules 420 containing a foaming agent can be obtained by a known microencapsulation method. For example, in the case of an aqueous type, a spray drying method involves spray drying a dispersion obtained by dispersing a non-aqueous blowing agent in the form of a suspension or emulsion into an aqueous solution that becomes a shell material;
Other methods include phase separation method, ponbrex coacervation method,
Examples include interfacial polymerization method, in 5 situ polymerization method, and the like.

Microcapsule 420 containing a low boiling point volatile liquid
There are two types: one is a low boiling point volatile liquid itself, and the other is one in which resin particles are impregnated with a low boiling point volatile liquid. When a low boiling point volatile liquid itself is encapsulated, it can be obtained by a known microencapsulation method. For example, in the case of an aqueous solution type,
The spray drying method involves spray drying a dispersion obtained by dispersing a low-boiling point volatile liquid (insoluble in water) in the form of a suspension or emulsion into an aqueous solution that serves as a shell material.Other methods include the phase separation method and bombrex core cell. Examples include vation method, interfacial polymerization method, etc.
This is disclosed in detail in Publication No. 24, etc.

Further, as the monomer that becomes the shell 440 of the microcapsules 420 obtained by polymerization, for example,
Substances disclosed in Publication No. 26524, such as alkenyl aromatics such as styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, ar-vinylxylene, ar-chlorostyrene, ar-bromostyrene, etc. , vinylbenzyl chloride, styrene-derived compounds such as p-tert-butylstyrene, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, propyl methacrylate, butyl methacrylate, lauryl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate Acrylate substances such as vinyl acetate, vinyl butyrate, vinyl acetate, vinyl laurate, vinyl myrilate, vinyl propionate and other esters, and vinyl chloride, vinylidene chloride, vinyl bromide, acrylonitrile, etc. .

In addition, the following substances can be mentioned as specific materials for the shell formed in the phase separation method, interfacial polymerization method, and in sHυ polymerization method.

Phase separation method: polyvinyl acetate, styrene-maleic acid copolymer, benzyl cellulose, ethyl cellulose, polyethylene, nitrocellulose, ketone resin, polymethyl methacrylate, polyamide resin, acrylonitrile-styrene copolymer, vinylidene chloride-acrylonitrile copolymer, Epoxy resin, etc. Pombrex coacervation method: Gelatin, acrylic resin Interfacial polymerization method: Polyamide, polysulfonamide, 7 polyurea, polyurethane, polyester, polyamide urethane, polyamide urea, polysulfonamide urea, polyester sulfonate, etc. In 5 ltu polymerization method: Boristyrene, polyurethane,
When impregnating fine resin particles with urea-formalin, etc., for example, a method of adding a volatile liquid during suspension polymerization of an appropriate monomer (Japanese Patent Publication No. 3B-3190), beads obtained by suspension polymerization, etc. There is a method (Japanese Patent Publication No. 36-10628) in which a volatile liquid is added after swelling with a solvent or the like. Also,
If necessary, there is a method in which the resin is made fine and then impregnated with a volatile liquid.

Furthermore, if necessary, a foaming aid may be added to reduce the decomposition temperature of the foaming agent.

Examples include compounds that have the effect of lowering the decomposition temperature, such as substances disclosed in JP-A-60-25792, such as oxalic acid, lactic acid, and citric acid. Furthermore, if necessary, it may contain a dispersant to facilitate dispersion, etc.
Surface treatment such as coating with a coloring agent can be performed. Similarly, a dispersant and a filler can be contained in the binder as required.

Furthermore, the microcapsules 420 can be colored in the same color as the heat-melting ink layer 410. The form of coloring is as shown in FIG. 5, in which the shell 440 is colored (
a)), coloring of the thermal expansion material 430 with a low boiling point ((b) in the same figure), and coloring of both ((C) in the same figure).

Coloring agents used for coloring include inorganic pigments (natural, chromate, ferrocyanic compounds, oxides, sulfides,
sulfates, silicates, metal powders, etc.), organic pigments (natural dye lakes, nitroso-based, azo-based, phthalocyanine-based, condensed polycyclic systems, basic dye lakes, mordant dyes, vat dyes, etc.), etc. Examples of dyes include water-soluble dyes and oil-soluble dyes.

Specific examples of inorganic pigments include natural pigments such as rare earth pigments,
Chromates such as yellow lead, zinc yellow, barium erochrome orange, molybdenum red, and chromium green, ferrocyanic compounds such as navy blue, titanium oxide, titanium yellow, titanium white, red iron oxide, yellow iron oxide, zinc ferrite,
Oxides such as zinc white, iron black, cobalt blue, chromium oxide, spinel green, sulfides such as cadmium yellow, cadmium orange, cadmium red, sulfates such as barium sulfate, silicates such as calcium silicate, ultramarine, Examples include metal powders such as bronze and aluminum, and carbon black.

Specific examples of organic pigments include natural dye lakes such as mada lake, nitroso pigments such as naphthol green and naphthol orange, benzidine Yeo-G, Hansa Yellow G, Hansa Yellow 10G, Palkan Orange,
Rake Red R1 Rake Red C Ruki Red D1 Watching Red, Brilliant Carmino 6B, Binocular Orange, Bordeaux 10B (Bon Maroon) and other soluble azo (azo lake) systems, Vilarozin Red, Rose Red, Toluidine Red, ITR Red, Toluidine Red (Lake Red 4R), l-Luidine Maroon, Brilliant Faist Scarlet, Lake Bordeaux 5B,
Insoluble azo pigments such as insoluble azo pigments, condensed azo pigments such as phthalocyanine pigments such as phthalocyanine blue, phthalocyanine green, brominated phthalocyanine green, fast sky blue, anthraquinone pigments such as thren blue, perylene pigments such as berylene maroon, Perinone pigments such as perinone orange, quinacridone pigments such as quinacridone and dimethylquinacridone, dioxazine pigments such as dioxazine violet, condensed polycyclic pigments such as isoindolinone pigments and quinophthalone pigments, rhodamine 6B lake, rhodamine lake B1 malachite green, etc. basic dye lake,
Examples include mordant dye pigments such as alizarin lake, vat dye pigments such as indane screen, indigo blue, and anthinthrone orange, fluorescent pigments, azine pigments (diamond black), and green gold.

Specific examples of water-soluble dyes include basic dyes such as Rhodamine B, acidic dyes such as Orange ■, fluorescent dyes, etc. Specific examples of oil-soluble dyes include monoazo dyes such as Fast Orange R1 Oil Red and Oil Elo. , anthraquinone dyes such as anthraquinone blue and anthraquinone violet, azine dyes such as nigrosine and insulin, basic, acidic, and metal complex compound dyes.

Shell 44 of microcapsule 420 containing a foaming agent
A known microencapsulation method is used to color 0. For example, in the case of an aqueous type, there is a spray drying method in which a non-aqueous blowing agent is dispersed in the form of a suspension or emulsion into an aqueous solution containing a colorant to form a shell material, and then the resulting dispersion is spray-dried. Examples include separation method, bombex funacervation method, interfacial polymerization method, and in 5 situ polymerization method.

Microcapsule 420 containing a low boiling point volatile liquid
The shell 440 can be colored using a low boiling point volatile liquid itself, or by impregnating resin particles with a low boiling point volatile liquid. When a low boiling point volatile liquid itself is encapsulated, it can be obtained by a known microencapsulation method. For example, in the case of an aqueous solution, a low boiling point volatile liquid (insoluble in water)
is obtained by dispersing it in the form of a suspension or emulsion in an aqueous solution that becomes a shell material containing a colorant, and when the microcapsules 420 contain a low-boiling point volatile liquid, a low-boiling point volatile liquid. The spray drying method involves spray drying a dispersion obtained by dispersing a mixture (insoluble in water) of a liquid and a coloring agent in the form of a suspension or emulsion into an aqueous solution that serves as a shell substance.Other methods include the phase separation method, and the Pombrex core. Examples include cervation method and interfacial polymerization method. Examples of the monomer that becomes the shell 440 of the microcapsules 420 obtained by polymerization include the substances disclosed in Japanese Patent Publication No. 42-26524;
For example, vinylidene chloride, acrylonitrile, etc. are easily colored. In the case of impregnating fine resin particles, for example, the above-mentioned Japanese Patent Publication No. 33-319.0, Japanese Patent Publication No. 36-1062
There are methods such as Publication No. 8.

Furthermore, the foaming aid can be colored to adjust the decomposition temperature of the foaming agent. For example, compounds that have the effect of lowering the decomposition temperature, such as substances disclosed in JP-A-60-25792, such as oxalic acid, lactic acid, and citric acid, are colored. Similarly, the dispersant and filler can also be colored.

Other methods for coloring the shell 440 include dyeing the shell 440 after the microcapsules 420 are formed, or coating the surface of the shell.

When dyeing with a dye, the microcapsules 420 encapsulating a thermally expandable material obtained by the above method without a coloring agent are dyed using a known dyeing method, such as a direct method, a mordant method, a reduction method, or an oxidation method. It can be colored by dyeing, color development method, reaction method, etc.

The method for coating the surface of the shell 440 is as follows:
Coating methods include a wet method that utilizes the bonding force due to the action of liquid and solid bridges of the binder, a dry method that utilizes the bonding force due to the action of van der Waals forces, electrostatic forces, and mechanical chemicals, coating methods, and well-known microencapsulation methods. Can be mentioned.

In addition, in the above-described ink ribbon 400, only the case where the heat-melting ink layer 410 formed on the base film 450 is one layer has been described, or it may have a multilayer (two or more layers) structure as necessary. You can also do it.

Next, the operation during recording when using the ink ribbon having the above configuration will be described.

FIG. 6 is a cross-sectional view showing the state of the ink ribbon 400 during printing and peeling.

The ink ribbon 400 is heated from the base film 450 side by Joule heat generated from the heating resistor 366 formed on the thermal head 360. This results in
Heat-melt ink layer 410 via base film 450
Heat is transferred to soften and melt the thermofusible ink layer 410, and the microcapsules 420 containing the thermally expandable substance 430 dispersed within the thermofusible ink layer 410 also expand, causing the thermofusible ink layer 410 to expand. The melted ink is attached to the surface of the recording paper P. In addition, microcapsule 42
0 has elasticity when heated (transferred) and is more easily deformed than the material of the hot-melt ink layer 410, so it does not expand while remaining spherical, but expands while deforming into a water pillow shape as shown in FIG. go. Therefore, the microcapsules 42 deform and expand.
0 causes the melted ink of the heat-melting ink layer 410 to be pushed into and adhere to the recesses on the surface of the recording paper 2, so good print quality can be obtained even on the recording paper P with low surface smoothness. . Furthermore, as the microcapsules 420 expand, the contact area between the melted ink of the heat-melting ink layer 410 and the base film 450 decreases, reducing the adhesive force and improving the releasability from the base film 450. This also contributes to obtaining good print quality.

Furthermore, on the pixel dots formed on the recording paper P after the ink ribbon 400 is peeled off, the expanded microcapsules 420 are exposed on the ink surface of the pixel, and the microcapsules 420
If the colors of the coloring materials of the heat-melting ink layer 410 are different from each other, the density of the image dots will be affected.

However, according to the ink ribbon 400 of this embodiment, since the microcapsules 420 (shell 440, thermal expansion material 430) and the ink layer 410 are made the same color (colored), the influence on the density is extremely small.

Next, the principle of printing will be explained in detail using a schematic cross-sectional view of the recording paper P1 ink ribbon 400 and the thermal head 360 shown in FIG. In this example, the conveying speed of the ink ribbon 400 will be explained as 0.5 times the circumferential speed of the drum.

First, when the heating resistor of the thermal head 360 is energized, Joule heat is generated there, and the heat is transmitted to the heat-fusible ink layer 410 via the base film 450 of the ink ribbon 400 (FIG. 4(a)).

Next, the heat melts the heat-melting ink layer 410 and turns it into ink, and the microcapsules 420 expand to increase the volume of that portion. As a result, the melted ink of the heat-melting ink layer 410 is ejected from the surface of the ink ribbon 400 and is pressed against the uneven surface of the recording paper P (FIG. 4(b)). Since the ink ribbon 400 is conveyed at a speed 0.5 times that of the recording paper P, the ink is stretched and attached to the surface of the recording paper P after one line period (FIG. 4(C)). As time elapses, the ink undergoes cohesive failure at the expanded microcapsules 420, and a pixel of one pixel is formed on the surface of the recording paper. Further, most of the microcapsules 420 remain in the ink ribbon 400 because they are blocked by the unmelted heat-fusible ink layer 410 (FIG. 4(d)).

The ink stretched and attached to the recording paper P mentioned above (see figure (
In C) and (d) of the same figure, the ink on the surface of the recording paper P escapes through the recording paper P and hardens immediately, but the non-printing area around the print is affected by the heat generated by thermal diffusion. As a result, it hardens to some extent and becomes sticky. Therefore, overcoat layer 4
If there is no 70, the sticky ink in the non-printing area will
It adheres to the recording paper P, causing background smearing, and staining the recording paper P. The ink layer 410 has a heat-melting temperature of the present invention.
In the ink ribbon 400 in which a higher overcoat layer 470 is laminated, heat due to thermal diffusion in non-printing areas is
Since the overcoat layer 470 does not soften, it does not become sticky, thereby preventing stains. Further, the colorless and transparent overcoat layer 470 is coated with the heat-melting ink layer 410.
Colorless overcoat layer 4 even when laminated on top
70 is only rubbed off, there is no background fogging, and this prevents stains.

In the ink ribbon 400 of this example, the dispersion form of the microcapsules 420 was presented as being in contact with the base film (Fig. 3), but the case shown in Fig. 8 (a) ) to (C), the particles may be dispersed (including protruding) in a floating state within the heat-melting ink layer 410 without contacting each other.

In the above description, these are examples presented, and the present invention is not limited thereto.

[Effects of the Invention] According to the present invention, since the shell or the thermally expandable material has the same color as the heat-melting ink layer, the density of the ink surface transferred to the recording medium does not decrease and good printing can be achieved. It can be carried out.

In addition, since an overcoat layer with a softening temperature higher than that of the heat-melt ink layer is laminated on the heat-melt ink layer containing heat-expandable particles, the heat-melt ink layer in the non-recording area is melted. It is possible to prevent the overcoat layer from adhering to the recording medium, and since the overcoat layer is almost colorless and transparent, even if the overcoat layer is rubbed off, the print quality will not deteriorate.

Furthermore, since the swelling start temperature of the heat-expandable particles is higher than the softening temperature of the heat-fusible ink layer, the heat-expandable particles start expanding after the heat-fusible ink layer has sufficiently softened and melted. can be expanded reliably, improving printing quality.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view showing the configuration of a monochrome printing mechanism, and FIG. 3 is a sectional view showing the configuration of a monochrome printing mechanism. A cross-sectional view showing the structure of the provided ink ribbon, FIG. 4 is a view schematically showing the viscosity of the heat-melting ink layer and the elastic limit stress of the shell, and FIG. 5 is a view showing the form of coloring of the microcapsules. FIG. 6 is a cross-sectional view showing the state of the ink ribbon during printing and peeling, and FIG. 7 is a cross-sectional schematic diagram of the recording paper, ink ribbon, and thermal head to explain the principle of printing.
FIGS. 8(a) to 8(C) are diagrams showing microcapsules floating in the heat-melting ink layer. DESCRIPTION OF SYMBOLS 10... Image forming apparatus, 300... Monochrome printing mechanism, 400... Ink ribbon, 410... Heat melting ink layer, 420... Microcapsule, 43
0...thermal expansion material, 440...shell, 450...
Base film, 470...coat layer. Applicant Toshiba Corporation Toshiba Intelligent Technology Corporation

Claims (5)

[Claims] (1) A thermal transfer material having, on a support, a transfer surface having at least a heat-fusible ink layer and containing heat-expandable particles consisting of a shell and a heat-expandable substance contained in the shell, A heat-sensitive transfer material, characterized in that the shell and the heat-melting ink layer are formed in the same color. (2) A thermal transfer material having, on a support, a transfer surface having at least a heat-fusible ink layer and containing heat-expandable particles made of a shell and a heat-expandable substance contained in the shell; A heat-sensitive transfer material, characterized in that a thermally expandable material and the heat-melting ink layer are formed in the same color. (3) a support, a heat-melt ink layer containing heat-expandable particles laminated on the support, and a softening temperature of the layer laminated on the heat-melt ink layer that is higher than that of the heat-melt ink layer; A thermal transfer material characterized by comprising a high overcoat layer. (4) Comprising a support, a heat-melt ink layer containing thermally expandable particles laminated on the support, and an almost colorless and transparent overcoat layer laminated on the heat-melt ink layer. A heat-sensitive transfer material characterized by: (5) In a heat-sensitive transfer material in which a transfer surface having at least a heat-melting ink layer and containing heat-expandable particles is provided on a support, the expansion start temperature of the heat-expandable particles is higher than the temperature at which the heat-melt ink layer starts to expand. A heat-sensitive transfer material characterized by having a softening temperature or higher.