JP2658069B2 - Transfer type thermal recording method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a transfer type thermal recording method.

2. Description of the Related Art Conventional transfer-type thermal recording methods in this field include, for example, "Thermal Ink-Transfer Imaging" (Y. Tokunaga).
And K. Sugiyama, IEEE Transactions On
Trans.on Electron Device
s), Vol. ED-27, PP. 218-222, 1980), on one surface of a sheet-like heat-resistant substrate, 20% by weight of carnauba wax and 40% by weight of ester wax as a binder material. %, Mineral oil 10% by weight, other adjuvants 10% by weight
A heat transfer layer (thickness of about 3 μm) made of an ink material in which a pigment is mixed with the hot melt binder material by 20% by weight using a hot melt material made of Paper is used as the image receiving body.

Problems to be Solved by the Invention In the conventional transfer type thermal recording method, when performing area gradation recording by changing the area of the transferred and recorded dots, there is a problem that the friction resistance of the recorded image is insufficient. Fixing property). In addition, when two or more colors are overprinted in color printing, there is a problem that the riding (trapping) of the upper color ink becomes unstable. Further, in the conventional transfer-type thermal recording method, when the transfer-type thermal sheet (hereinafter, referred to as a sheet) is peeled off from the recording medium, there is a problem that the peeling between the sheet and the recording medium becomes unstable and the image quality deteriorates. there were.

The fixability and the image quality vary greatly depending on the thickness of the thermal transfer layer of the transfer type thermal sheet.

When performing area gradation recording by changing the area of the thermal transfer layer (recording dot) on which the transfer recording is performed, in the saturation density recording, the friction resistance of the dot for connecting the recording dots does not matter so much, In density recording, recording dots are transferred independently without being connected to adjacent dots. For example, when the recording dots are rubbed with a nail or the like, the dots are squashed laterally and stain the paper surface, thereby deteriorating the image quality.
Therefore, there is a problem in image fixing property. This has a greater effect when the thickness of the recording dot is larger than the area of the recording dot. The area of dots in the low-density region tends to become smaller and smaller in order to improve the gradation and the resolution by area gradation recording. The problem of insufficiency becomes important.

When two or more colors are overprinted in color printing, halftone density printing is performed in the same manner as described above.
Since the recording dots are transferred independently without being connected to the adjacent dots, when recording the upper color from above the lower color
A step is formed on the surface of the recording medium between the portion with and without the undercolor, and the phenomenon that the upper color is transferred only on the protruding undercolor occurs, and the riding (trapping) of the upper color ink becomes unstable. There was a problem.

Further, when the transfer type thermal sheet and the recording medium are peeled off after recording, a part of the thermal transfer layer is peeled off from the base material of the sheet and transferred to the recording medium. And the breaking strength inside the thermal transfer layer. When the thickness of the thermal transfer layer is large, the peeling resistance increases due to an increase in the breaking strength inside the thermal transfer layer, and a large force is required for the peeling of the sheet after transfer recording. Transfer becomes unstable and the image quality deteriorates.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a transfer type thermal recording method capable of obtaining a high-quality recorded image with a high fixing property that overcomes the conventional problems.

Means for Solving the Problems The present invention, in order to solve the above problems, a transfer-type heat-sensitive sheet provided with a thermal transfer layer containing a coloring material and a binder material on one surface of a substrate, a recording medium and And heating the thermal transfer layer from the other surface side of the substrate via the substrate in a state where the thermal transfer layer of the transfer type thermal sheet and the recording medium are pressed against each other, and then the transfer type thermal sensitive In a thermal recording method for recording by peeling off the sheet and the recording medium,
The thermal transfer layer of the transfer type heat-sensitive sheet was formed to a thickness of 1.0 to 0.6 μm using a material obtained by mixing a coloring material at 30 to 50% by weight with a binder material made of a hot melt material.

According to the present invention, by setting the thickness of the thermal transfer layer to a predetermined value, it is possible to improve the fixing property of the image, the ink trapping, and the sheet peeling property.

The transfer type heat-sensitive sheet is required to have a sufficient recording density. In order to perform recording at a saturation recording density of 1.5 or more, when a pigment is used as a coloring material, for example, it is necessary that the pigment of 0.3 g / m2 or more is contained in the thermal transfer layer in a state of being sufficiently dispersed with the binder material. is there. Therefore, when setting the thickness of the thermal transfer layer, it is necessary to simultaneously consider the weight ratio of the coloring material in the thermal transfer layer.

Two phenomena can be considered for the fixing property of an image.
One is a phenomenon that, when rubbed with a nail or the like, the recording dots are squashed laterally and stain the paper surface, thereby deteriorating the image quality. This has a particularly large effect when the thickness of the recording dot is large relative to the area of the recording dot. The other is that the strength of the recording dots is reduced because the content of the coloring material in the recording dots is too large, and the surface of the recording dots is rubbed off when the image surface is rubbed with a rough surface or the like, and the surroundings are again removed. Is a phenomenon that the image quality is deteriorated by adhering to the paper surface. This has nothing to do with the size of the recording dots. Therefore, under the condition that the pigment of 0.3 g / m2 or more is contained in the thermal transfer layer in a state of being sufficiently dispersed with the binder material, both the thickness of the recording dots, that is, the thickness of the thermal transfer layer, and the content of the coloring material in the thermal transfer layer are included. By optimally selecting the conditions, it is possible to obtain a condition under which the above two phenomena are most unlikely to occur, that is, a condition under which image fixability is the best.

Regarding ink trapping, when recording an upper color from above a lower color, if the step formed on the surface of the recording medium is reduced in a portion where the lower color is present and in a portion where the lower color is not present, the lower color recording dot surface and the recording medium surface can be reduced. Both have relatively uniform contact with the surface of the overcolor thermal transfer layer, thereby improving the trapping characteristics. For that purpose, the thickness of the thermal transfer layer for forming undercolor dots may be reduced.

As the peeling resistance, when the thickness of the thermal transfer layer is reduced, the breaking strength inside the thermal transfer layer, that is, the peeling resistance, decreases, and the deterioration of the image quality can be reduced. Further, by reducing the thickness of the thermal transfer layer, heat is easily transmitted to the surface of the thermal transfer layer, and there is an advantage that recording sensitivity is improved.

From the physical properties of the binder material, as a method for improving the fixability of the recorded image, it is conceivable to include a material having a large elongation at break (elongation at break) and a high strength (rupture strength). Vinyl acetate is the most effective. However, the peel resistance of the sheet is higher than other materials. Therefore, it is very important to make the peeling resistance equal to or less than the conventional one in combination with the method of thinning the thermal transfer layer according to the present invention. Therefore, if the friction resistance is considered to be particularly important among the conventional problems, the combination of the above-mentioned material and the thickness of the thermal transfer layer of the present invention is most effective. Regarding the recording sensitivity, it is assumed that the inclusion of a resin having a melt viscosity of 300 centipoise or less at 100 ° C. in the binder material contributes to higher sensitivity.

1. Embodiment FIG. 1 is a conceptual sectional view illustrating an embodiment of the present invention.

A transfer-resistant heat-sensitive sheet 5 having a binder 2 on one surface of a base material 1 and a thermal transfer layer 4 composed of a coloring material 3 composed of a pigment, a dye, or both, and a material constituting the binder 2 The thermal transfer layer 4 and the fixing layer 6 are opposed to each other using a recording medium 7 coated with a fixing layer 6 compatible with at least a part of the sheet 5 and the sheet 5 and the recording medium 7 between a heat source 8 and a platen 9. FIG.

As the substrate 1, for example, a film such as polyethylene terephthalate (PET), a polyimide film, a polycarbonate film, a polyamide film, or a cellulose film having a thickness of 2 to 10 μm, or a capacitor paper is used.

The binder material 4 is, for example, at least room temperature (0 to 35 ° C.)
Is formed of a single or a plurality of types of hot melt materials so as to be solid and have reduced viscosity when heated, and to impart adhesion to a recording medium and transfer adhesion. Its melting point or softening point is selected in the range of 20 to 150 ° C, preferably 30 to 120 ° C. When the melting point or softening point is lower than 20 ° C., the thermal transfer layer transferred and recorded on the recording medium is liable to soften or set off during storage of the recorded material. This requires energy and makes thermal transfer recording with a thermal head or the like difficult.

Examples of hot melt materials include carnauba wax, beeswax, solid paraffin, waxes such as microwax, low molecular weight polyethylene, petroleum resin, polyamide resin, rosin-modified resin, polyvinyl acetate resin, polyvinyl chloride resin, polyvinyl chloride Polymer resins, polyvinyl butyral resin, epoxy resin, polyester resin, acrylic resin, ethyl cellulose, polyethylene glycol, polyacrylamide, resins such as polyvinylpyrrolidone,
And styrene / acrylic copolymer resins such as amide / acrylic acid fatty acid amide modified resins, styrene / methacrylic copolymer resins, acrylic resins, methacrylic resins, unsaturated carboxylic acid resins, and unsaturated carboxylic acid ester resins Denature at least one of the groups to 100
Resins and the like having a melt viscosity at 300C of 300 mPa · sec or less are used. These hot melt materials can be used alone or in combination of two or more as needed.
The denaturation referred to herein is fatty acid amide, 2,2-bis (4 ′
-Oxyphenyl) propane or a bisphenol derivative such as bis (4'-oxyphenyl) methane is reacted with the resin. In particular, a resin obtained by reacting a long-chain fatty acid amide with the above resin is effective. As the long-chain fatty acid amide, an acid amide having 10 to 40 carbon atoms such as lauric acid amide, oleic acid amide, and erucic acid amide is used.

In addition to the above-mentioned hot melt material, the binder material 2 has, for example, a property that the viscosity decreases with increasing temperature and the adhesiveness increases, and the adhesive material (polybutene, polyisobutylene, etc.) which is fluid at normal temperature (for example, 25 ° C.) , Polybutadiene, silicone oil, etc.), surfactants, softeners such as stearic acid and lanolin, plasticizers such as n-octyl phthalate (DOP), dibutyl phthalate (DBP), tricresyl phosphate (TPC), aerosil, talc And the like are appropriately mixed.

Auxiliary particles may be included in the thermal transfer layer. The auxiliary particles are appropriately selected, for example, from the above-mentioned hot melt materials. In this case, the auxiliary particles have a lower viscosity at a temperature higher than the softening point than the binder material 4, are not completely compatible with the binder material 4 at room temperature, are solid at room temperature, and are particulate in the binder material 4 at room temperature. Material is selected so as to be mixed and dispersed.
An effective choice is to make auxiliary particles using waxes whose viscosity tends to decrease at a temperature higher than the softening point, or modified resins such as the above-mentioned fatty acid amide modified resin of styrene / methacrylic copolymer, and a binder material. No. 4 is configured so that the ratio of the hot melt material containing no waxes or the above-mentioned modified resins and having a melt viscosity (for example, about 100 ° C.) of 1000 mPa · sec or more is large. . The melt viscosity (for example, about 100 ° C.) of the binder material 2 is 100
If it is less than 0 mPa · sec, the thermal transfer layer becomes brittle at room temperature, and the transferred thermal transfer layer has poor fixability.

Further, the heat transfer layer may contain heat-resistant auxiliary particles. These particles have an effect of easily breaking the thermal transfer layer 4 apart. Furthermore, when the particles have a particle size larger than the thickness of the layer formed by the thermal transfer layer 4, in addition to the above-described effects, the particles also act as transfer auxiliary particles for mainly transferring the particles. In this case, as the material of the particles, for example, aluminum oxide, titanium oxide,
Examples thereof include calcium carbonate, silicon dioxide, polymer carbonate, nylon, guanamine resin, and polypropylene. The size of the particles is preferably within 20 μm. If it is larger than 20 μm, the heat capacity of the particles becomes too large,
Low sensitivity.

As the coloring material 3, organic or inorganic pigments, water-soluble dyes or oil-soluble dyes used in ordinary printing inks and paints,
Further, a mixture of these plural kinds is appropriately selected. For example, carbon black and diamond black are used as pigments in black transfer recording, and CI Solvent B is used as dyes.
Use lack 3 etc. For full-color recording, for example, a thermal transfer layer 4 of each of three primary colors of a pigment or a dye or a mixture thereof, and furthermore, four primary colors including black is arranged on a substrate 1 in a plane-sequential manner, and these are recorded in order. This can be easily performed by superimposing and transferring onto a medium.

When the temperature rise control is performed by a thermal head, the substrate 1
In order to prevent the back surface from melting to cause sticking or to run smoothly, a heat-resistant lubricating layer such as a polysulfone resin mixed with silica fine powder is set to a thickness of, for example, about 1 μm. be able to.

Furthermore, when the temperature rise control is performed by energizing a conductive base material, metal powder or carbon black is dispersed in a plastic film such as PET or polymer carbonate to impart conductivity to the base material. Or a substrate in which a conductive resistance layer is disposed on the back surface of the substrate can be used.

As a recording medium, plain paper, coated paper, art paper, synthetic paper or a polymer film having excellent surface smoothness, and a fixing layer containing a hot melt material provided on the surface to which the ink material is transferred based on these, are provided. A material having improved transferability of the ink material is used.

The material of the fixing layer 8 may be any material that is compatible with at least one of the materials contained in the binder material 4. Therefore, it is convenient to use the same material as any of the contained materials. The term “compatible” as used herein does not necessarily mean complete compatibility, and may be partially compatible.

 Hereinafter, specific examples will be described.

Example-1 As a resin A of the binder material 2, a vinyl acetate resin Gohsenil E50Y8 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., glass transition point:
3030 ° C., polymerization degree 1800, melt viscosity (160 ° C.): 106 mPa · sec or more) 2.1 parts by weight, resin B: fatty acid amide-modified resin perfector of styrene / acrylic copolymer 6030-1
(Hitachi Chemical Industries, Ltd., melting point 77 ° C, melt viscosity (100
° C): 20 parts by weight of 20 mPa · sec) powder, 0.47 to 12.6 parts by weight of a cyan pigment (CI Pigment Blue 15) as a coloring material 3,
The mixed material to which 48 to 72 parts by weight of ethyl acetate is added as a solvent is heated to about 50 ° C. to completely melt the hot melt material, and is well mixed and dispersed at room temperature by a ball mill.

Using a commercially available bar coater, this mixed solution is layered at room temperature on a substrate 1 having a heat-resistant lubricating layer on the back surface of a PET film having a thickness of 9 μm, and ethyl acetate is removed by evaporation. The coating thickness of the obtained thermal transfer layer 4 is about 0.4 to 3.0 μm on average. The weight of the thermal transfer layer was obtained by subtracting the weight of the substrate from the weight of the sheet after coating and drying, and divided by the specific gravity of the thermal transfer layer material to obtain the thermal transfer layer thickness. Therefore, even when there are irregularities on the surface of the thermal transfer layer, an averaged thickness is required.

A coated paper having a fixing layer (coating thickness: 4 μm) made of the above-mentioned vinyl acetate resin Gohsenil E50Y8 on the surface of a polypropylene synthetic paper having a thickness of 150 μm as a substrate is used as a recording medium, and the sheet is formed on the fixing layer. And transfer recording was performed using a thermal head. The thermal head has a linear recording density of 4 dots / mm. The applied power per heating resistive element is 0.4 W, the main scanning recording density is 16.7 ms / line, the sub scanning recording density is 4 dots / mm, and the recording signal is It is pulse width modulated (PWM) with 6 bits, and its maximum pulse width is 4 ms.

Auxiliary particles are formed on the sheet by precipitation of resin B. Resin A due to the part of auxiliary particles whose viscosity has been reduced
As a result, the image can be transferred onto the surface of the recording medium with an area corresponding to the size of the auxiliary particles. The area of the thermal transfer layer to be transferred depends on the number of auxiliary particles whose viscosity is to be reduced. Since the area is proportional to the amount of heat applied from the thermal head, it increases with the pulse width of a signal applied to the thermal head.
Therefore, as the recording density characteristics, the transfer recording density rises smoothly from the paper surface reflection density (D0) by pulse width modulation recording, shows the highest transfer recording density when the pulse width Pw is 3.3 ms, and shows good continuous gradation. Was.

FIG. 2 shows the relationship among the thickness of the thermal transfer layer, the pigment content, the amount of the applied pigment, and the saturation recording density.

As is apparent from the figure, the saturated recording density substantially corresponds to the amount of the coating pigment, but when the pigment content exceeds 50%, the amount of the coating pigment necessary for obtaining the same recording density gradually increases.
It is considered that the excessively high pigment content causes insufficient dispersion with the binder material.

Table 1 shows the relationship between the thickness of the thermal transfer layer, the pigment content, and the friction resistance, trapping characteristics and sheet releasability of the image. In each sample, the coating pigment amount was 0.3 g / m2. For the evaluation of the rub resistance, the recorded image of the halftone density and the rubbing white cotton cloth were rubbed against each other using a rubbing tester according to the dyeing fastness test method for rubbing (JIS L 0849). The degree of coloring of the cotton cloth was determined by comparing it with the gray scale for staining. This result corresponds to a decrease in image quality due to various types of friction. The evaluation of the trapping was performed by measuring the variation in the transfer recording density of the upper color when various densities were recorded in the lower color. Regarding the sheet releasability, various images were actually recorded by a printer for evaluating recording characteristics, and the effect of the sheet peeling on the image quality was examined.

For comparison, a hot melt material consisting of 20% by weight of carnauba wax, 40% by weight of ester wax, 10% by weight of mineral oil, and 10% by weight of other auxiliaries was used as a binder material, and a pigment was used as a coloring material. Of the transfer type heat-sensitive sheet formed by a hot melt coating method using a thermal transfer layer (having a thickness of about 4 μm) in which is mixed 20% by weight, and a recording image when plain paper is used as a recording medium.

As can be seen from the table, when the thermal transfer layer thickness is 1.5 μm or less and the pigment content is 60% or less, the friction resistance is improved to grade 4 or more, and when the thermal transfer layer thickness is 0.85 μm or less and 45% or less, it is improved to grade 4-5. I do. Further, both the trapping characteristics and the sheet releasability are improved when the thickness of the thermal transfer layer is reduced. It can be seen that the characteristics of the conventional transfer type thermal recording method are worse than those described above, and that there is a great difference particularly in the fixing property.

From these results, the optimum values of the thermal transfer layer thickness and the pigment content were 1.5 to 0.5 μm and 20 to 60%, respectively, and 1.0 to 0.6 μm.
m, 30 to 50% is better, 0.85 to 0.75 μm, 35 to
45% gives the best properties.

Magenta color (CI Pigment)
ment Red 57), yellow (CI Pigment Yellow 1)
2), similar results were obtained using a black (carbon black) pigment. Similar results were obtained when a dye was used as the coloring material instead of the pigment.

In terms of material, as described above, the resin B is vinyl acetate, and a part of the binder material 2 and the fixing layer 6 are compatible with each other. The friction resistance is improved.

In the present embodiment, the area gradation recording in the unit of the auxiliary particles is enabled by the physical properties of the binder material and the configuration of the auxiliary particles contained in the binder material. The same applies to the case where tone recording is realized, and the same effect can be obtained when area gradation recording is performed by a dither method or the like.

FIG. 1 shows the case where the fixing layer 6 is applied,
When the base material of the recording medium 7 is a material compatible with the binder material 2, it is not necessary to apply the fixing layer 6. As the heat source 8, a thermal head, a laser beam, or the like is provided. The platen 9 is installed in order to equalize the pressure of the heat reduction 8, and rubber is generally used as the material.

Effect of the Invention As described above, in the present invention, the heat transfer layer of the transfer type heat-sensitive sheet is formed by adding a coloring material to a hot melt binder material.
It is possible to improve the fixability of the image by forming a thickness of 1.0 to 0.6 μm with the material mixed with 50% by weight, and to realize the improvement of the image quality by the stability of the ink trapping and the stability of the sheet peeling. be able to.

[Brief description of the drawings]

FIG. 1 is a conceptual cross-sectional view of an apparatus in which a transfer-type thermal recording method according to an embodiment of the present invention is performed, and FIG. 2 is a diagram illustrating a thermal transfer layer thickness, a pigment content, and the like when recording is performed using a sheet of the apparatus. FIG. 3 is a characteristic diagram showing a relationship between the amount of a coating pigment and a saturation recording density. DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Binder material, 3 ... Color material, 4 ... Thermal transfer layer, 5 ... Transfer type heat-sensitive sheet, 6 ... Fixing layer, 7 ... Recording medium, 8 ... Heat source, 9 ...... Platen

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Nobuyoshi Taguchi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-206693 (JP, A) JP-A-61-54990 (JP, A) JP-A-57-105395 (JP, A) JP-A-61-217290 (JP, A) JP-A-61-8386 (JP, A) JP-A-61-51385 (JP, A) JP-A-61-158498 (JP, A) JP-A-63-51182 (JP, A) JP-A-60-232994 (JP, A) JP-A-62-21595 (JP, A) JP-A-62-220387 (JP, A) JP-A-60-9798 (JP, A) JP-A-58-108184 (JP, A) JP-A-58-71186 (JP, A) JP-A-63-288780 (JP, A) JP-A-54-41941 JP, A)

Claims (3)

(57) [Claims] 1. A transfer type heat-sensitive sheet having a heat transfer layer containing a colorant and a binder on one surface of a base material, and a recording medium, wherein the heat transfer layer and the heat transfer layer of the transfer type heat-sensitive sheet are used. And heating the thermal transfer layer through the base material in a state where the recording medium is pressed against the recording medium, and thereafter, the transfer type thermal sheet and the recording medium are peeled off and the recording medium is transferred and recorded. The heat transfer layer of the heat-sensitive sheet is made of a binder material made of hot melt
A transfer-type thermosensitive recording method, wherein a material mixed at 50% by weight is formed to a thickness of 1.0 to 0.6 μm. 2. The recording medium according to claim 1, wherein a fixing layer compatible with the thermal transfer layer is provided on a surface layer of the recording medium.
The transfer type thermal recording method described in the above item. 3. A hot melt material comprising a resin A and a resin B, wherein the resin A is a styrene / acrylic co-aggregate resin, a styrene / methacrylic copolymer resin, an acrylic resin, a methacrylic resin, an unsaturated carboxylic acid resin, A resin characterized in that at least one of the group consisting of unsaturated carboxylic acid ester resins is modified to have a melt viscosity at 100 ° C. of 300 mPa · sec or less, and the resin B is a vinyl acetate resin. 3. The transfer type thermal recording method according to claim 1 or 2.