JPH06135165A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To improve multiple characteristics by controlling an ink flow out quantity in thermal transfer by a method wherein a heat fusible ink layer having a heat fusible material and a coloring agent as main components is provided on a base material and a fine crater structured resin coating of which a peripheral part is thicker than its central part is provided thereon. CONSTITUTION:In a thermal transfer recording medium, a thermal fusible ink layer 4 which has a thermal fusible material and a coloring agent as main components, and is provided on a base material 2 is prevented from peeling off from the base material 2, and besides a fine crater structure 6 of which a peripheral part is thicker than its central part is provided to a resin coating 5 on the ink layer 4 in order to control an ink flow out quantity in thermal transfer recording. Though, general thermoplastic resin is used as resin of such the resin coating 5, in order to form a fine crater structure 6 of which a peripheral part is thicker than its central part on the resin coating 5, for example, the resin is dissolved in a volatile solvent such as methyl ethyl ketone or the like. The resin solution is applied onto the ink layer 4 by an ordinary application system, and dried by air to form the fine crater structure 6.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermal transfer recording medium,
More specifically, the present invention relates to a thermal transfer recording medium in which a resin coating having a specific structure is provided on a heat-meltable ink layer so that a high-density image can be obtained by printing many times.

[0002]

2. Description of the Related Art Among recording devices such as printers and facsimiles, those utilizing a thermal transfer recording system have been widely used as devices which can be downsized, reduced in price, and reduced in maintenance. The thermal transfer recording medium used in the thermal transfer recording apparatus is generally one in which a thermal transferable ink layer (thermofusible ink layer) is simply provided on a support, and therefore the ink layer is heated by one use. There was a problem in running cost because the entire part was transferred to the receiving paper (plain paper etc.) and could not be used repeatedly. Therefore, the emergence of a thermal transfer recording medium that can be repeatedly used has been demanded, and various types of multiple-printing thermal transfer recording media have been proposed so far.

Some of them are (1) JP-A-54.
-68253, JP-A-55-105579, JP-A-60-40293, etc., a fine porous ink layer is provided on a support, and the heat-meltable ink is gradually added. It was made to exude, (2)
A method in which a porous film is provided on an ink layer on a support so as to control the outflow amount of ink, as disclosed in JP-A-58-212993, and (3) JP-A-60-127.
No. 191, JP-A-60-127192, etc., a plurality of ink layers are provided through a plurality of adhesive layers, and the adhesive layers and the ink layers are gradually peeled off to expose a new ink layer. Those that can be transferred and transferred are proposed. However, the thermal transfer recording medium of the above (1) has a drawback that it is difficult to seep out the ink with repeated use and the print density gradually decreases. In the thermal transfer recording medium (2), when the pore size of the porous film is increased in order to increase the printing density, the mechanical strength is lowered and the ink layer is peeled off. The thermal transfer recording medium (3) has a drawback that the transfer amount of the heat-meltable ink is not constant for each printing.

Further, most of the conventional thermal transfer recording media correspond to a serial thermal head used in a recording device such as a word processor, and like a line thermal bed used in a recording device such as a facsimile or a bar code printer. If the peeling time after heating the thermal transfer recording medium and the receiving paper (recording paper) is long, there is a drawback that the peeling of the ink layer occurs during peeling, and further, the image density decreases. Among the conventional techniques, in the thermal transfer recording mediums of (1) and (2), as disclosed in JP-A-63-137891, a thermosoftening resin is provided between the support and the ink layer. There is also proposed an example in which an intermediate adhesive layer is provided to prevent peeling of the ink layer. However, in this case, during thermal transfer recording,
In the multi-time thermal transfer recording medium in which the heat loss due to the intermediate adhesive layer is large and the ink coating layer is thicker than the one-time ribbon, the thermal sensitivity is remarkably reduced, and it is necessary to reduce the ink amount or increase the applied energy accordingly.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to prevent thermal peeling of an ink layer, maintain high printing density even when repeated thermal transfer printing is performed without increasing the applied energy, and reduce thermal density. A recording medium is provided.

[0006]

In the thermal transfer recording medium of the present invention, a heat fusible ink layer containing a heat fusible substance and a colorant as a main component is provided on a support, and a peripheral portion is provided on the ink layer. A resin film having a fine crater structure thicker than the central portion is provided.

Further, in the thermal transfer recording medium of the present invention, a heat-meltable ink layer containing a heat-meltable substance and a colorant as a main component is provided on a support, and a through hole and a peripheral portion are mainly formed on the ink layer. It is also useful to provide a resin coating having a fine crater structure thicker than the part, and to disperse a release agent on the resin coating.

The present invention will be described in more detail below.
1, 2 and 3 are schematic sectional views of three typical examples of the thermal transfer recording medium according to the present invention. In the figure, 11, 12 and 13 are thermal transfer recording media, 2 is a support, 3 is a heat resistant protective layer, 4 is an ink layer (thermofusible ink layer), 5 is a resin coating, 6 is a peripheral part from the center part. Thick fine crater structure,
Reference numeral 7 represents a through hole, and 8 represents a release agent.

As shown in FIG. 1, the first thermal transfer recording medium 11 of the present invention prevents the ink layer 4 from peeling from the support 2 and controls the amount of ink outflow during thermal transfer recording. The resin coating 5 on the ink layer 4 is provided with a fine crater structure 6 whose peripheral portion is thicker than the central portion. As a resin for such a resin film 5, a general thermoplastic resin can be used, but a vinyl chloride-vinyl acetate copolymer, a polyester resin, a polycarbonate resin, a cellulose resin or the like is preferable.

In order to form the fine crater structure 6 in which the peripheral portion is thicker than the central portion in the resin coating 5, for example, the resin as described above is dissolved in a volatile solvent such as methyl ethyl ketone, and this resin solution is placed on the ink layer 4. Apply by a normal coating method (wire bar coating method, gravure coating method, etc.),
Then, it may be dried with air having a relative humidity of 30 to 90% RH.

In the fine crater structure 6, the crater diameter is preferably in the range of 0.01 to 10 μm, and the number of craters per unit area (400 μm ² ) is preferably in the range of 30 to 300. preferable. If the maximum diameter of the crater is smaller than 0.01 μm or if the number of crater structures 6 per unit area (400 μm ² ) is less than 30, the ink hardly leaks from the ink layer 4 and the image density is lowered. . On the contrary, when the maximum diameter of the crater structure 6 is larger than 10 μm or when the number of craters per unit area (400 μm ² ) is more than 300, the amount of ink seeping out from the ink layer 4 increases, and the number of times of mulching is extremely large. Less. Crater structure 6
The maximum diameter and the number of crater structures 6 per unit area (400 μm ² ) can be controlled by adjusting the relative humidity of the air during the formation of the resin coating 5 and the flow rate / flow rate of the air. The coating amount of the resin coating 5 is 0.0
It is preferable to regulate the amount to ² to 0.50 g / m ² . 0.02g /
If it is less than m ^2, the mechanical strength of the resin coating 5 becomes weak,
Peeling of the ink layer 4 is likely to occur, and 0.50 g / m ²
If the amount is larger, the thermal sensitivity becomes lower, resulting in an unclear image with low image density.

The second thermal transfer recording medium 12 of the present invention, as shown in FIG. 2, has a resin coating 5 on the ink layer 4 in order to enable high density printing, especially in a large number of thermal transfer recordings. The through hole 7 and the fine crater structure 6 thicker than the peripheral portion are provided in the. If only the fine crater structure 6 whose peripheral portion is thicker than the central portion is formed on the resin film 5, if the energy at the time of printing is small, the portion of the crater structure 6 cannot be sometimes broken and the ink from the ink layer 4 may not be broken. The ink is not supplied as expected, and the density of the printed image becomes low. Therefore, in the thermal transfer recording medium 12 of FIG.
A resin coating having through holes (through holes reaching the ink layer 4 from the surface) 7 together with the fine crater structure 6 is provided on the ink layer 5 so that ink can be supplied even when the energy is low.

The through holes 7 can be formed in the same manner as the fine crater structure 6 except that water, alcohols such as methanol and ethanol are added to the resin solution, and the resin film is dried. Relative air humidity of 4
It can be adjusted by adjusting to 0 to 80% RH. Also in this thermal transfer recording medium 12, the crater diameter of the fine crater structure 6 in which the peripheral portion is thicker than the central portion has a crater diameter of 0.01 to 1
It is similar to the thermal transfer recording medium 11 shown in FIG. 1 that the number of craters per unit area (400 μm ² ) of 0 μm is preferably in the range of 30 to 300. The number of through holes is 10 to 150 per unit area (400 μm ² ).
The range of the number is suitable, and the diameter is suitably about 0.1 to 3.0 μm.

As shown in FIG. 3, the third thermal transfer recording medium 13 of the present invention is separated from the resin film 5 so that the thermal transfer recording medium and the receiving paper can be easily separated from each other after the thermal transfer recording operation. The mold agent 8 is contained or attached. If the resin coating 5 is thin, when the heat is applied from the thermal head, a part of the resin may soften and be fixed on the receiving paper, and in severe cases, the entire ink layer 5 is transferred to the receiving paper side. Particularly, at low printing speed and high energy, this development is remarkable. By including or adhering the release agent 8 to the resin film 5, such inconvenience can be avoided.
The release agent 8 may be scattered in the thermal transfer recording medium shown in FIG.

As the release agent 8, an organic lubricant or an inorganic lubricant is preferably used. As an organic or inorganic lubricant,
Beeswax, carnauba wax, whale wax, wood wax, candelilla wax, nuka wax, montan wax, paraffin wax, polyethylene wax, oxidized wax,
Natural waxes such as ozokerite, ceresin, ester wax, petroleum wax, synthetic wax, higher fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, frommenic acid, behenylic acid, stearyl alcohol and behenyl alcohol. In addition to higher alcohols, higher amides such as stearamide and oleinamide, esters such as higher fatty acid esters of glycerin and sorbitan, inorganic pigments such as silica, calcium carbonate, talc and kaolin, and fine particles such as fluororesins. You can Among these, a particularly preferable mold release agent is one containing wax as a main component. This is because when the release agent 8 containing wax as a main component is used, heat is applied from the thermal head,
This is because a part of the surface of the wax that is in contact with the receiving paper is melted and can be more closely attached to the receiving paper, so that a thermal transfer image with good resolution is obtained. On the other hand, it is considered that when the thermal transfer recording medium 13 separates from the receiving paper, the release agent containing wax as a main component solidifies, so that the transfer of the ink layer 4 can be prevented by the action of a spacer. A wax-based release agent has a penetration of 2 at 25 ° C.
By using the following, it is possible to prevent the resin film 5 from moving to the back surface, that is, so-called blocking phenomenon in a normal product state.

The scattered release agent 8 is preferably granular.
The particle size is 0.1 to 20 μm, preferably 3 to 10 μm. If it is smaller than 0.1 μm, the function as a spacer is impaired, and the entire transfer of the ink layer 4 easily occurs,
On the other hand, if it is larger than 20 μm, the adhesiveness to the receiving paper is deteriorated and the resolution is deteriorated.

Since the thermal transfer recording medium 13 has the release agent 8 scattered on the resin coating 5, the thermal transfer recording medium 13 has excellent releasability from the receiving paper after thermal transfer recording and prevents the entire transfer of the ink layer to the receiving paper. However, it is preferable to impart adhesiveness to the support 2 to the ink layer 4 itself in order to prevent the entire transfer of the ink layer more reliably. This is
This is achieved by adding a substance having tackiness or adhesiveness to the ink layer 4 in contact with the support 2. Examples of the substance having tackiness or adhesiveness to the support 2 include polymer substances and wax-like substances, preferably polymer adhesives such as ethylene-vinyl acetate copolymer and microcrystalline wax. Can be mentioned. The amount of such a tacky or adhesive substance added is appropriately determined according to the number of times of repeated printing and the printing conditions. However, in the case of application to a printer equipped with a normal line thermal head, in the case of a polymer adhesive the ink layer 5 to 50% by weight, and in the case of microcrystalline wax, 5 to 70% by weight in the ink layer. In the case of a polymer adhesive, if the amount added is too large, the density of the transferred image will decrease, while if the amount added is too small, the adhesion of the ink layer 4 to the support 2 will decrease. In the case of the microcrystalline wax, if the addition amount is too small, the adhesive force of the ink layer 4 to the support 2 is lowered, while if it is too large, problems such as blocking occur.

FIG. 4 shows the thermal transfer recording medium 13 shown in FIG.
The surface structure of was taken by a micrograph and examined. Here, the white thin annular portion is a fine crater whose peripheral portion is thicker than the central portion, and the irregular white portion is a release agent scattered.

In the present invention, two or more ink layers 4 are provided on the support 2 in order to enable high-density printing in a large number of thermal transfers, and the heat-meltable ink component of the ink layer 4 is melted. It is preferable that the ink layer having a higher viscosity be closer to the support 2. In this case, the melt viscosity of the ink layer can be adjusted by adding a thickener to the ink layer and appropriately selecting the type and addition amount of the thickener at that time. As the thickener, an adhesive or sticky substance that is solid at room temperature is used. Something like this:
In addition to various polymers, organic substances having a high melt viscosity such as the above-mentioned microcrystalline wax can be shown.
The thickener preferably used in the present invention is an ethylene-vinyl acetate copolymer, and particularly has a melt flow rate (MF) (JIS K 6760) of 10 g / 10 mi.
It is preferable to use one having an n or more, preferably 100 g / 10 min or more.

The thermal transfer recording medium of the present invention can be manufactured by a conventionally known method. That is, a predetermined ink layer 4 is formed on the support 2 (preferably a “heat resistant substrate”).
Is formed, and is formed thereon according to the method for forming the resin coating. In this case, the ink layer 4 may be composed of one layer, but it is preferable that the ink layer 4 is formed of two or more layers as described above, and the melt viscosity of the ink layer closer to the support 2 is increased.

The colorant forming the thermal transfer ink layer 4 is
Although it can be appropriately selected from known pigments and dyes, it is common to use carbon black or a phthalocyanine-based pigment as the pigment, and the dye is a direct dye, an acid dye, a basic dye, a disperse dye, or an oil. Soluble dyes and the like are generally used.

Vehicle components constituting the ink layer 4 include natural waxes such as beeswax, carnauba wax, whale wax, wood wax, candelilla wax, nuka wax, montan wax, paraffin wax, polyethylene wax, oxidized wax, ozokerite and ceresin. , Ester waxes and the like are generally used. In addition to these, higher fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, flomenic acid and behenylic acid, higher alcohols such as stearyl alcohol and behenyl alcohol, stearamide and Higher amides such as oleinamide and esters such as higher fatty acid esters of glycerin and sorbitan are also used.

The coating amount of the thermal transfer ink layer 4 has to be appropriately set in consideration of various factors such as the number of times of printing and thermal sensitivity, but in general, the dry weight of the entire thermal transfer ink layer is 4 to 12 g / m ² is good, and in the case of a two-layer structure, each layer is 2
˜7 g / m ^2, about 3 to 5 g / m ^{2 for} each layer.

As the support 2 used in the present invention, known heat-resistant materials such as plastic films of polyester, polycarbonate, triacetyl cellulose, nylon and polyimide, cellophane, sulfuric acid paper, condenser paper and the like can be used. The thickness of the support 2 is preferably about 2 to 15 μm in consideration of heat sensitivity and mechanical strength.

The heat-resistant protective layer 3 made of silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose or the like is provided on the surface of the support 2 in contact with the thermal head. It is also possible to further improve the heat resistance of. A suitable thickness of the heat-resistant protective layer is about 0.01 to 2.0 μm.

[0026]

EXAMPLES Next, the present invention will be specifically described by way of examples. All parts and% herein are based on weight.

Example 1 (Coating liquid A) Carbon black 15 parts Lanolin fatty acid monoglyceride (mp = 73 ° C.) 25 parts Candelilla wax 20 parts Microcrystalline wax (mp = 83 ° C.) 30 parts Ethylene-vinyl acetate copolymer 10 Parts (melt flow rate: 2,500 g / 10 min) After filling the above components in a sand mill vessel, the temperature was set to 110.
Dispersion was performed while maintaining the temperature at ℃ to obtain a heat-meltable ink component (coating liquid A).

(Coating Liquid B) Carbon black 10 parts Candelilla wax 40 parts Lanolin fatty acid monoglyceride (mp = 73 ° C.) 50 parts After filling the above components in a sand mill vessel, the temperature is set to 110.
Dispersion was carried out by keeping at ℃. 20 parts of this dispersion was crushed, added to 80 parts of a methylethylketone / toluene (2/1) mixed solvent, dissolved by heating and then cooled to obtain a coating liquid B by dispersing at 25 ° C.

(Coating liquid C) Cellulose acetate propionate 3 parts Methyl ethyl ketone 97 parts The above components were mixed to obtain a coating liquid C.

Next, after coating a PET film having a thickness of about 5.5 μm on the other surface of the base material, one surface of which has been heat-treated,
Is applied by the hot melt coating method to about 3 g / m
A thermal transfer ink layer of ² was obtained. Subsequently, the coating liquid B is applied with a bar coater and then dried at 80 ° C. to obtain about 4 g /
A m ² thermal transfer ink layer was laminated. The coating liquid C is also coated with a bar coater in the same manner, and then air having a relative humidity of 30% RH, a wind speed of 2 m / sec, and a temperature of 20 ° C. is uniformly applied for 10 seconds to be dried to form a resin film of about 0.2 g / m ^2. A thermal transfer recording medium was prepared by laminating the layers. When the cross section of this thermal transfer recording medium was analyzed by a TEM photograph and the surface was analyzed by a SEM photograph, it was confirmed that a resin coating having a fine crater structure in the peripheral portion was thicker than in the central portion. The diameter of fine craters is about 0.05 μm, and the number of craters per unit area (400 μm ² ) is about 20.
It was 0.

Example 2 In Example 1, the coating liquid C was dried under the relative humidity of 80.
% RH, wind speed 2m / sec, temperature 10 ℃ 10
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that it was uniformly applied for a second and dried. As a result, the diameter of the fine crater of the formed resin coating was about 9 μm and the unit area (400
The number of craters per μm ² ) was about 50.

Example 3 In Example 1, the coating liquid C was dried under the relative humidity of 50.
% RH, wind speed 2m / sec, temperature 10 ℃ 10
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that it was uniformly applied for a second and dried. As a result, the diameter of the fine crater of the formed resin coating is about 3 μm, and the unit area (400
The number of craters per μm ² ) was about 100.

Example 4 In Example 1, the composition of the coating liquid C was changed to the following coating liquid D, and the drying conditions were relative humidity of 25% RH and wind speed of 2 m / se.
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that air having a temperature of 10 ° C. was uniformly applied for 10 seconds to be dried. As a result, the diameter of the fine craters in the formed resin coating was about 2 μm, and the number of craters per unit area (400 μm ² ) was about 35. (Coating liquid D) Cellulose acetate propionate 3 parts Methyl ethyl ketone 93 parts Methanol 4 parts

Example 5 In Example 4, the coating liquid D was dried under the relative humidity of 80.
% RH, wind speed 2m / sec, temperature 10 ℃ 10
A thermal transfer recording medium was obtained in the same manner as in Example 4 except that the coating was uniformly applied for a second and dried. As a result, the diameter of the fine crater of the formed resin coating is about 6 μm and the unit area (400
The number of craters per μm ² ) was about 280.

Example 6 In Example 1, the composition of the coating liquid C was changed to the coating liquid E described below, and the drying conditions were set to a relative humidity of 50% RH and a wind speed of 2 m / se.
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that air having a temperature of 20 ° C. was uniformly applied for 10 seconds to be dried. As a result, the number of fine craters in the formed resin film was about 100. Further, it was confirmed by TEM and SEM that through holes were formed, and the number of through holes was about 20 per unit area (400 μm ² ). (Coating liquid E) Cellulose acetate propionate 3 parts Methyl ethyl ketone 89 parts Methanol 4 parts Water 4 parts

Example 7 A thermal transfer recording medium was obtained in the same manner as in Example 3 except that the composition of the coating liquid C was changed to the coating liquid F described below. As a result, the diameter of the fine craters of the formed resin coating was about 2 μm, and the number of craters per unit area (400 μm ² ) was about 80. The presence of spacer particles was also confirmed by SEM photographs. (Coating liquid F) Cellulose acetate propionate 3 parts Vinyl chloride powder (Nippon Zeon Co., PGR-121) 2 parts Methyl ethyl ketone 95 parts

Example 8 A thermal transfer recording medium was obtained in the same manner as in Example 3 except that the composition of the coating liquid C was changed to the coating liquid G described below.
As a result, the diameter of the fine craters in the formed resin film was about 3 μm, and the number of craters per unit area (400 μm ² ) was about 100. (Coating liquid G) Cellulose acetate propionate 3 parts Paraffin wax aqueous dispersion (solid content 30%, average particle size about 3 μm) 8 parts Methyl ethyl ketone 91 parts

Example 9 A thermal transfer recording medium was obtained in the same manner as in Example 3 except that the composition of the coating liquid C was changed to the coating liquid H described below.
As a result, the diameter of the fine craters in the formed resin film was about 3 μm, and the number of craters per unit area (400 μm ² ) was about 100. (Coating liquid H) Cellulose acetate propionate 3 parts Carnauba wax aqueous dispersion (solid content 30%, average particle size about 4 μm) 8 parts Methyl ethyl ketone 91 parts

Example 10 A thermal transfer recording medium was obtained in the same manner as in Example 6 except that the composition of the coating liquid E was changed to the coating liquid I described below.
As a result, the fine crater diameter of the formed resin film was about 3 μm, and the number of craters per unit area (400 μm ² ) was about 120. The number of through holes was about 30 per unit area (400 μm ² ). (Coating liquid I) Cellulose acetate propionate 3 parts Carnauba wax aqueous dispersion (solid content 30%, average particle size about 4 μm) 8 parts Methyl ethyl ketone 85 parts Methanol 4 parts

Comparative Example 1 In Example 1, the coating liquid C was dried under the relative humidity of 10
% RH, wind speed 2m / sec, temperature 10 ℃ 10
A thermal transfer recording medium was obtained in the same manner as in Example 1 except that it was uniformly applied for a second and dried. As a result, fine craters and / or through holes could not be confirmed in the formed resin film.

Comparative Example 2 In Example 4, the coating liquid D was dried under the relative humidity of 90.
% RH, wind speed 2m / sec, temperature 10 ℃ 10
A thermal transfer recording medium was obtained in the same manner as in Example 4 except that it was uniformly applied for a second and dried. As a result, in the formed resin film, a number of through holes were cut innumerably, and the film had low mechanical strength.

These 12 types of thermal transfer recording media were mounted on a line thermal head, and the same spot was printed 5 times under the following conditions. [Printing conditions] Thermal head: Line thin film head type (8dot /
mm) Platen pressure: 330 gf / cm Peeling angle of thermal transfer recording medium: 45 ° (to transfer paper) Applied energy: 18 mj / mm ² , 15 mj / mm ² Printing speed: 4 inch / sec Transfer paper: coated paper ( Bristow absorption 4.00 ml:
j. TAPPI, No. 51, first grade liquid paraffin used / Beck smoothness 2000 sec) Printing pattern: CODE39 parallel bar coat (Na
print 2dot) All solid (6 mm × 7 mm) 4 printing environment temperature: 20 ° C., 60% RH The density of the solid portion of the printed material was evaluated by RD-914 of Macbeth. The total transfer of the ink layer was visually evaluated. The resolution of the printed image was visually evaluated for the presence or absence of white spots in the CODE39 parallel barcode. Blocking is performed by stacking a polyethylene terephthalate film on the surface of each thermal transfer recording medium so as to face each other with a load of 2 kg / cm.
^{At 2} , the sample was left standing at 50 ° C. for 24 hours, cooled, and then visually confirmed and evaluated. The results are summarized in Tables 1 and 2.

[0043]

[Table 1]

In Examples 1 to 6, the bar code reproducibility was excellent and the image density up to the fifth printing was relatively high. Above all, in Example 3, it could be put to practical use. Further, in Examples 7 to 10, the bar code reproducibility was further excellent, and among them, Examples 9 and 10 had no ink layer full transfer, no white spots in the image, and excellent blocking resistance, which was extremely impractical. It was a high thermal transfer recording medium for multi-use printing. In Comparative Example 1, only an image with low density can be obtained, and
In Comparative Example 2, the image density became low after the fourth time, and only images with extremely bad multiplicity were obtained.

[0045]

[Table 2]

In Examples 6 and 10, even when the applied energy is low, the tendency of the image density to decrease is extremely small as compared with the high applied energy (18 mj / mm ² ), and an image having stable multi-printing characteristics can be obtained.

[0047]

In the thermal transfer recording medium according to the present invention, the resin film having a fine crater structure in which the peripheral portion is thicker than the central portion is formed in the uppermost layer, and the ink layer is prevented from separating from the base material (support). At the same time, the multi-characteristics are improved by controlling the ink outflow amount at the time of thermal transfer. In the thermal transfer recording medium according to the second aspect, a resin coating having a through hole and a fine crater structure in which the peripheral portion is thicker than the central portion is formed in the uppermost layer, and a high density image can be obtained even with low applied energy. In the thermal transfer recording medium according to the third aspect, the amount of ink outflowing from the ink layer becomes appropriate by setting the coating amount of the uppermost layer within a certain range. The thermal transfer recording medium according to claim 4 or 5, wherein the diameter of the fine crater structure or the number of craters per unit area (400 μm ² ) in the resin coating is regulated to achieve a high print image density and maintain the number of multiple times. You can In the thermal transfer recording medium according to claim 6, the release agent is scattered on the resin coating,
The entire transfer of the ink layer can be prevented. In the thermal transfer recording medium according to the seventh aspect, a release agent containing wax as a main component provides a clear image with excellent resolution, that is, less white spots. The thermal transfer recording medium according to claim 8 comprises a release agent at 25 ° C.
By using a wax having a penetration of 2 or less as a main component, the blocking resistance is further improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of a thermal transfer recording medium according to the present invention.

FIG. 2 is a sectional view of another example of the thermal transfer recording medium according to the present invention.

FIG. 3 is a sectional view of still another example of the thermal transfer recording medium according to the present invention.

FIG. 4 is a micrograph showing the surface structure of a thermal transfer recording medium according to the present invention.

[Explanation of symbols]

 2 Support 3 Heat Resistant Protective Layer 4 Ink Layer 5 Resin Protective Layer 6 Fine Crater Structure with Periphery Thicker than Center 7 Through Hole 8 Release Agent 11, 12, 13 Thermal Transfer Recording Medium

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masahiro Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (8)

[Claims] 1. A heat-meltable ink layer containing a heat-meltable substance and a colorant as a main component is provided on a support, and a resin coating having a fine crater structure whose peripheral portion is thicker than the central portion is provided on the ink layer. A thermal transfer recording medium provided. 2. The thermal transfer recording medium according to claim 1, wherein the resin film further has a through hole. 3. The coating amount of the resin coating is 0.02 to 0.
The thermal transfer recording medium according to claim 1, which has a weight of 50 g / m ² . 4. In a fine crater structure in which the peripheral portion is thicker than the central portion, the diameter of the crater is 0.01 to 1.
The thermal transfer recording medium according to claim 1, which has a thickness of 0 μm. 5. The thermal transfer recording medium according to claim 1, wherein in the fine crater structure in which the peripheral portion is thicker than the central portion, the number of craters per 400 μm ² is 30 to 300. 6. The thermal transfer recording medium according to claim 1, wherein a release agent is scattered on the resin film. 7. The thermal transfer recording medium according to claim 6, wherein the release agent contains wax as a main component. 8. The thermal transfer recording medium according to claim 7, wherein the release agent containing wax as a main component has a penetration of 2 or less at 25 ° C.