GB2343756A

GB2343756A - Thermal image transfer medium

Info

Publication number: GB2343756A
Application number: GB9926655A
Authority: GB
Inventors: Mitsuru Naruse; Keiichi Shiokawa; Kazuyoshi Inamura; Hiroshi Tohmatsu; Katsushi Shishido
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1998-11-11
Filing date: 1999-11-10
Publication date: 2000-05-17
Anticipated expiration: 2019-11-10
Also published as: GB9926655D0; DE19954103A1; FR2785566A1; GB2343756A9; GB2343756B; DE19954103B4; FR2785566B1

Abstract

The thermal image transfer recording medium has a support 22, an intermediate layer 33 and an ink layer 44. The intermediate layer contains a thermofusible material, such as microcrystalline wax, mixed with a polymer resin, for example a polyester resin, and forms the top layer 33 of the ink image 7 when it has been transferred to the image receiving member 1. The ink image has optimum resistance to damage by rubbing or scratching when the dynamic friction coeficient is in the range 0.120 - 0.165.

Description

2343756

TITLE OF THE INVENTI THEPIAU IMAGE TRANSFER, RECORDING MEDIUM

BACKGROUND OF THE INVENTI Field of the Invention

The present invention relates to a thermal image transfer recording medium, and more particularly to a thermal image transfer recording medium which is suitable for a printer equipped with an edge-type line thermal head, and capable of producing high quality images on an image receiving member with a small surface energy, that is, with a high surface smoothness.

Discussion of BaCkgroun The thermal image transfer recording method using a thermal head is widely employed because there is no noise development, the printing apparatus is small and not expensive, the maintenance is easy, and the produced image can show stable quality.

The thermal image transfer recording method includes the steps of (a) heating a thermal image transfer recording medium imagewise by means of a thermal head with the ink layer of the recording medium being in - 1 contact with an image receiving member, and (b) peeling the ink layer from the thermal image transfer recording medium, thereby transferring an ink image to the image receiving member.

For thermal image transfer recording, an edge-type thermal head has become prevalent in the market of the printing apparatus in recent years, because the mechanism of the apparatus itself can be made relatively simple and the cost is advantageous.

In the printer equipped with the edge-type thermal head, the abovementioned steps (a) and (b) are subsequently carried out very speedily, so that the ink layer is separated from the thermal image transfer recording medium before the ink layer is completely melted and sufficiently transferred to the image receiving member. The result is that the ink image formed on the image receiving member shows poor image fixing performance, and easily peels off when rubbed or scratched. in particular, when the ink image is formed on an image receiving member with a small surface energy, for example, a PET-coated paper, the ink is not deposited well on the image receiving member.

To solve the shortcomings caused by the edge-type - 2 - thermal head as mentioned above, it is proposed to enhance the adhesion of the ink layer for use in the thermal image transfer recording medium, for example, by employing an ethylene - vinyl acetate copolymer (EVA) as the binder resin for the ink layer as disclosed in Japanese Laid-Open Patent Application 4-82789. The effect of this proposal is still insufficient. On the contrary, there produces another problem that the ink layer of the recording medium sticks to the image receiving member to stain it during the non-printing operation because the ink layer of the recording medium is pressed against the image receiving member by means of a thermal head.

Further, in Japanese Patent Publication 4-73390 and Japanese Patent No. 2606849, it is proposed to improve the image fixing performance by providing a thermofusible layer (or heat-softening layer) that comprises a wax with a penetration of 5 or less as the main component between the support and the ink layer of the recording medium. This method cannot produce such a sufficient effect as expected.

SUMARY OF THE IWMNTI

Accordingly, a first object of the present invention - 3 - is to provide a thermal image transfer recording medium capable of printing high quality images by use of a printer equipped with an edge- type thermal head, without staining an image receiving member by the pressure application to the image receiving member during the nonprinting operation.

A second object of the present invention is to provide a thermal image transfer recording medium capable of forming a high quality ink image on an image receiving member with a small surface energy.

The above-mentioned first and second objects of the nresent invention can be achieved by a thermal image transfer recording medium comprising a support, an intermediate layer formed thereon comprising a thermofusible material and a resin, and a thermofusible ink layer formed on the intermediate layer, capable of forming an ink image on an image receiving member, with the surface of the ink image exhibiting a dynamic friction coefficient in a range of 0.120 to 0.165.

It is preferable that the resin for use in the intermediate layer comprise a polyester resin.

The aforementioned polyester resin may have a weight-average molecular weight of 7,500 to 10,000. - 4 - It is preferable that the thermofusible material for use in the intermediate layer comprise microcrystalline wax.

It is preferable that the thermofusible material for use in the intermediate layer be prepared in the form of particles dispersed in an aqueous emulsion. The intermediate layer may be formed by coating an aqueous coating liquid comprising the above-mentioned aqueous emulsion.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view showing one embodiment of a thermal image transfer recording medium according to the present invention.

FIG. 2 is a schematic cross-sectional view of an ink image formed on an image receiving member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic cross-sectional view showing one embodiment of a thermal image transfer recording medium according to the present invention. In the thermal image transfer recording medium 6 of FIG. 1, an intermediate layer 33 and a thermofusible ink layer 44 are successively overlaid on a support 22, and a backcoat is provided on the back side of the support 22, opposite to the side of the intermediate layer 33 with respect to the support 22.

When an ink image is formed on an image receiving member using the thermal image transfer recording medium shown in FIG. 1, the ink image is formed on the image receiving member as illustrated in FIG. 2. Namely, the thermofusible ink layer 44 and the intermediate layer 33, which constitute an ink image 7, are transferred to an image receiving member 1 and deposited thereon in such a configuration that the thermofusible ink layer 44 is covered with the intermediate layer 33. The intermediate layer 33 is fused to remove the thermofusible ink layer 44 from the main body of the thermal image transfer recording medium 6, and the fused intermediate layer 33 is thereafter set on the thermofusible ink layer 44 when - 6 the ink image 7 is formed on the image receiving member 1.

According to the present invention, by decreasing the surface energy of the intermediate layer 33, that is, the surface portion of the ink image 7 when viewed form the transferred image side, the slip characteristics of the surface of the transferred ink image are increased to prevent the transferred image from peeling off when rubbed or scratched.

The inventors of the present invention have found that the intermediate layer constitutes the surface portion of the transferred image, and that when the dynamic friction coefficient of the surface portion of the image is too large, the scratch resistance of the image becomes poor. As the results of the intensive studies, it has been discovered that when the surface portion of the ink image shows a dynamic friction coefficient of 0.165 or less, the transferred ink image does not easily peel off from the image receiving member by rubbing or scratching. When the dynamic friction coefficient of the surface portion of the ink image is in the range of 0.120 to 0.165, the peeling problem of the transferred ink image can be solved, and the thermal image transfer performance is excellent, so that the - 7 - image Quality is Satisfactory for practical use.

To obtain such an intermediate layer as constitutes the surface portion of the ink image with the above specified dynamic friction coefficient, the following methods are preferably employed. The method (1) is to employ as a resin for use in the intermediate layer a polyester resin, preferably in an amount of 7 to 20 wt%, more preferably 10 to 15 wt%, of the entire weight of the intermediate layer on a dry basis. The method (2) is to employ as a thermofusible material for use in the intermediate layer a microcrystalline wax with an average particle size of 0.1 to I pm, preferably in an amount of 7 to 20 wt% of the entire weight of the intermediate layer on a dry basis. The aforementioned methods (1) and (2) may be employed alone or in combination. Thus, the scratch resistance of the transferred ink image can be improved, and the thermal image transfer performance is satisfactory.

In the method (1), when the content of the polyester resin is less than 7 wt%, the dynamic friction coefficient tends to increase, so that the scratch resistance cannot be sufficiently improved. when the content of the polyester resin exceeds 20 wt%, the - 8 - thermal image transfer performance is lowered, thereby impairing the image quality of the obtained ink image.

Furthermore, it is preferable that the polyester resin have a weightaverage molecular weight of 7,500 to 10,000. When the weight-average molecular weight of the employed polyester resin is within the abovementioned range, the image receiving member can be prevented from being stained with the ink by the pressure application during the non-printing operation, and the thermal image transfer performance is satisfactory.

In the method (2), when the amount of microcrystalline wax is less than 7 wt%, the scratch resistance cannot be improved; while when the amount thereof exceeds 20 wt%, the thermal image transfer performance is lowered.

The dynamic friction coefficient referred in the present invention is measured by the following method: An ink image is printed on a commercially available image receiving member "PET WH50(A) PAT1 8 LKY1" (Trademark), made by Lintec Corporation, by a printer "B-572" (Trademark), made by Toshiba TEC Corporation. Using a measuring apparatus, "Automatic Friction Abrasion Analyzer DFM-SS" (Trademark), made by KYOWA INTERFACE 9 - SCIENCE CO., LTD.), a stainless ball with a diameter of 2 mm was brought into contact with the surface of the printed ink image under the application of a load of 200 Q, with the stainless ball being moved at a speed of 0.1 M/s.

In the intermediate layer, any conventional thermofusible material is usable as long as the dynamic friction coefficient specified in the present invention can be obtained.

Specific examples of the thermofusible material for use in the present invention are natural waxes and synthetic waxes such as paraffin wax, microcrystalline wax, carnauba wax, ceresin wax, oxidized wax, ester wax, polyethylene wax, candelilla wax, Japan wax, beeswax, and montan wax.

In particular, the waxes which exhibit the rate of penetration of 3 or less are preferably employed in the present invention. For example, candelilla wax (with a penetration of 1), carnauba wax (with a penetration in a range of 0.8 to 1.6), polyethylene wax (with a penetration of 3 or less), Fischer-Tropsch wax (with a penetration in a range of 0.9 to 3), and hardened castor oil wax (with a penetration of less than 1) are - 10 preferable. Of these waxes, the above-mentioned microcrystalline wax is particularly advantageous.

Further, the waxes may be used in combination so as to obtain the penetration of 3 or less. For example, a mixture of the waxes may show the rate of penetration of 3 or less even if the mixture comprises a paraffin wax with a rate of penetration of 9.

As previously mentioned, it is preferable to employ a polyester resin as the resin component in the intermediate layer. Other conventional resins may be used as long as the dynamic friction coefficient is within the specified range.

Examples of the resin for use in the intermediate layer include polyester resin, acrylic resin, polyethylene resin, ethylene - vinyl acetate copolymer, ethylene - acrylate copolymer, polyurethane, cellulose, vinyl chloride - vinyl acetate copolymer, petroleum resin, rosin and derivatives thereof, and polyamide.

These resins may be used alone or in combination.

When necessary, the intermediate layer may further comprise carbon black, an organic or inorganic pigment, and a variety of dyes for coloring the intermediate layer, and additives, for example, a softener such as a - 11 - plasticizer, and a surfactant such as an anti-foaming agent.

It is preferable that the deposition amount of the intermediate layer be in the range of about 0.5 to 2 g/M2. When the deposition amount of the intermediate layer is within the above-mentioned range, the printing characteristics are stable.

The thermofusible ink layer for use in the present invention comprises the same conventional thermofusible materials as mentioned in the explanation of the intermediate layer, and a resin.

Specific examples of the resin for use in the thermofusible ink layer include acrylic resin, polyester resin, polyethylene resin, ethylene vinyl acetate copolymer, ethylene - acrylate copolymer, polyurethane, cellulose, vinyl chloride - vinyl acetate copolymer, petroleum resin, rosin and derivatives thereof, and polyamide.

These resins may be used alone or in combination.

As the coloring agent for use in the thermofusible ink layer, at least one coloring agent may be appropriately selected from the group consisting of carbon black, organic or inorganic pigments, and a - 12 - variety of dyes.

Any conventional film or paper may be used as the support of the thermal image transfer recording medium according to the present invention. For example, there can be preferably employed a polyester film made of polyethylene terephthalate, a polycarbonate film, a triacetyl cellulose film, a polyimide film, and a polyamide film.

As illustrated in FIG. 1, the thermal image transfer recording medium may further comprise a backccat layer which is provided as a heat-resistant lubricating layer on the back surface of the support, opposite to the intermediate layer with respect to the support. Owing to the backcoat layer, the support can be protected from high temperature when heat is applied thereto using an edge-type line thermal head, and the recording medium can be smoothly transported.

Specific examples of the material for use in the backcoat layer are silicone oil, silicone rubber, silicone resin, polyimide, epoxy resin, phenolic resin, melamine resin, and cellulose. The backcoat layer may be provided on the back surface of the support by coating any of the abovementioned oil or resin in the form of a - 13 - thin film.

The thermal image transfer recording medium of the present invention may further comprise an undercoat layer which is interposed between the support and the intermediate layer, or between the intermediate layer and the thermofusible ink layer as a primer coating layer and/or heat insulating layer.

Furthermore, the thermal image transfer recording medium of the present invention may further comprise a top layer which is provided on the thermofusible ink layer to improve the adhesion of the thermofusible ink layer to an image receiving member when an ink image is formed thereon.

Other features of this invention will become apparent in the course of the following description of exemplary embodiments, which are given for illustration t 4 of the invention and are no Lntended to be limiting thereof.

Example I (Formation of intermediate layer] The following components were dispersed in a ball mill for 14 hours, so that a coating liquid for - 14 intermediate layer was prepared.

Parts by Weight Carnauba wax 3.0 Candelilla wax 2.0 Linear saturated polyester resin (weight-average molecular weight: 20000, Tg: 10'C) 0.5 Methyl ethyl ketone 18 The thus prepared coating liquid was coated on a PET film serving as the support by a wire bar, and dried, whereby an intermediate layer with a deposition amount of 1.5 g/M2 was provided on the PET film. [Formation of thermofusible ink layer] The following components were dispersed in a ball mill for 14 hours, so that a coating liquid for thermofusible ink layer was prepared. In the preparation of the coating liquid, the candelilla wax was previously dissolved to some extent in toluene.

Parts by Weiaht Carbon black 1.5 Candelilla wax 3.0 Ethylene - vinyl acetate copolymer resin (content of vinyl acetate: 28 wt%) 4.0 Rosin ester resin (melting point: 1250C) 1.5 Toluene 67 The thus prepared coating liquid was coated on the above obtained intermediate layer by a wire bar, and dried, whereby a thermofusible ink layer with a deposition amount of 1.5 g/M2 was provided on the intermediate layer. (Formation of backcoat laver] A silicone resin was coated by a wire bar on the back surface of the PET film, opposite to the intermediate layer bearing surface, to have a deposition amount of 0.05 g/M2 on a dry basis, so that a backcoat layer was provided on the rear side of the PET film.

Thus, a thermal image transfer recording medium No. I according to the present invention was obtained.

Example 2

The procedure for preparation of the thermal image transfer recording medium No. 1 in Example 1 was repeated except that the formulation for the intermediate layer coating liquid in Example 1 was changed as follows:

Parts by Weight Carnauba wax 2.4 Candelilla wax 1.6 Microcrystalline wax 1.0 Methyl ethyl ketone 18 Thus, a thermal image transfer recording medium No. 2 according to the present invention was obtained.

Examp.le 3 The procedure for preparation of the thermal image transfer recording medium No. 1 in Example 1 was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following fomulation:

PaLts by Weight Aqueous emulsion of polyester resin prepared by diluting a polyester resin emulsion with water (solid content: 20 wt%) (polyester resin with weight-average molecular weight: 8500, Tg: 6C) 1.5 Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 39 wt%) 6.5 Water 1.0 Ethanol 1.0 Thus, a thermal image transfer recording medium No. 3 according to the present invention was obtained.

Example 4

The procedure for preparation of the thermal image transfer recording medium No. 3 in Example 3 was repeated except that the polyester resin for use in the formulation for the intermediate layer coating liquid in Example 3 was replaced by a polyester resin with a weight-average molecular weight of 6500 and a glass transition temperature (Tg) of 40'C.

Thus, a thermal image transfer recording medium No. 4 according to the present invention was obtained.

Example 5

The procedure for preparation of the thermal image transfer recording medium No. 3 in Example 3 was repeated except that the polyester resin for use in the formulation for the intermediate layer coating liquid in Example 3 was replaced by a polyester resin with a weight-average molecular weight of 12000 and a glass transition temperature (Tg) of 60C.

Thus, a thermal image transfer recording medium No. - 18 - according to the present invention was obtained.

Example 6 The procedure for preparation of the thermal image transfer recording medium No. I in Example 1 was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following formulation:

Parts by Weiahr Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 39 wt%) 5.2 Emulsion of microcrystalline wax (with a particle diameter of 0.5 pm) (solid content: 30 wt%) 1.76 Water 1.0 Ethanol 1.0 Thus, a thermal image transfer recording medium No.

6 according to the present invention was obtained.

Example 7

The procedure for preparation of the thermal image transfer recording medium No."l in Example I was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following formulation:

Parts by Weight Aqueous emulsion of carnauba wax/candelille wax (6/4) (solid content: 39 wt%) 6.15 Aqueous emulsion of polyester resin (same as employed in Example 3) (solid content: 20 wt%) 3.0 Water 1.0 Ethanol 1.0 Thus, a thermal image transfer recording medium No.

7 according to the present invention was obtained.

Example 8

The procedure for preparation of the thermal image transfer recording medium No. I in Example I was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following fon- nulation:

Parts by Weig ht Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 3 9 wtO/o) 5.92 Aqueous emulsion of polyester resin (same as employed in Example 3) (solid content: 20 wtI/6) 3.45 Water 0.78 Ethanol 1.00 Thus, a thermal image recording medium No. 8 according to the present invention was obtained.

Example

The procedure for preparation of the thermal image transfer recording medium No. I in Example 1 was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following formulation:

Parts by Weight Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 39 wt%) 5.2 Emulsion of microcrystalline wax (with a particle diameter of 0.5 pm) (solid content: 30 wt%) 0.852 Water 1.0 Ethanol 1.0 Thus, a thermal image transfer recording medium No. 9 according to the present invention was obtained.

Example 10

The procedure for preparation of the thermal image transfer recording medium No. 1 in Example 1 was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following formulationi Parts by Weight Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 39 wt%) 6.1 Emulsion of microcrystalline wax (with a particle diameter of 0.5 pm) (solid content: 30 wt%) 0.58 Water 1.0 Ethanol 1.0 Thus, a thermal image transfer recording medium No. 10 according to the present invention was obtained.

Comparative Example I The procedure for preparation of the thermal image 22 - transfer recording medium No. I in Example 1 was repeated except that the formulation for the intermediate layer coating liquid in Example 1 was changed as follows:

Parts by Weight Carnauba wax 3.0 Candelilla wax 2.0 Methyl ethyl ketone 18.0 Thus, a comparative thermal image transfer recording medium No. 1 was obtained.

Comparative Example 2 The following components were heated to melt the waxes, and thereafter dispersed in a ball mill for 14 hours, so that a coating liquid for intermediate layer was prepared.

Parts by Weight Carnauba wax 3.0 Candelilla wax 2.0 Methyl ethyl ketone 18.0 The thus prepared coating liquid was coated on the same PET film as employed in Example 1 by a wire bar, and dried, whereby an intermediate layer with a deposition - 23 - amount of 1.5 g/m' on a dry basis was provided on the PET f ilm.

After that, the thermofusible ink layer and the backcoat layer were provided in the same manner as in Example 1.

Thus, a comparative thermal image transfer recording medium No. 2 was obtained.

Comparative Example 3 The procedure for preparation of the thermal image transfer recording medium No. 1 in Example 1 was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following formulation:

Parts by WeiQht Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 39 wt%) 5.2 Water 1.0 Ethanol 1.0 Thus, a comparative thermal image transfer recording medium No. 3 was obtained.

Comparative Example 4 The procedure for preparation of the thermal image 24 transfer recording medium No. I in Example 1 was repeated except that a coating liquid for intermediate layer was prepared by simply mixing all the components listed in the following fori-nulation:

Parts by Weight Aqueous emulsion of carnauba wax/candelilla wax (6/4) (solid content: 39 wt%) 7.15 Aqueous emulsion of polyester resin (same as employed in Example 3) (solid content: 20 wt%) 1.05 Water 1.0 Ethanol 1.0 Thus, a comparative thermal image transfer recording medium No. 4 was obtained.

Using the above-mentioned thermal image transfer recording media No. 1 to No. 10 according to the present invention and comparative thermal image transfer recording media No. 1 to No. 4, the following measurement and evaluation tests were carried out. (1) Dynamic friction coefficient The dynamic friction coefficient of the surface of the obtained ink image was measured by the abovementioned method.

(2) Scratch resistance An ink image was formed on an image receiving member (Trademark "PET WHSO (A) PAT 1 8 LKY1" made by Lintec Corporation) using a commercially available printer (Trademark "B-572" made by Toshiba TEC Corporation) The ink image thus formed was scratched with the nails, and the scratch resistance was evaluated on the following organoleptic scale: @: To peel the ink image from the image receiving member required much labor. 0: The scratch resistance of the ink image was sufficiently high for practical use. L: The scratch resistance of the ink image was slightly low, but evaluated as acceptable for practical use. X: The ink image peeled off from the image receiving member by several scratching operations, and the scratch resistance was evaluated as unacceptable for practical use. (3) Thermal image transfer performance An ink image was formed on an image receiving member of which the surface smoothness is low, that is, the socalled vellum paper, using a commercially available printer (Trademark "B-572" made by Toshiba TEC Corporation). The presence of non-printed spots in the obtained ink image was checked by visual inspection. Namely, the thermal image transfer performance was evaluated in terms of the image quality. 0: Non-printed spots were scarcely observed. Z: Several non-printed spots were observed, but it was evaluated as acceptable for practical use. X: There were partially observed non-printed spots, and the number of non-printed spots was evaluated as unacceptable for practical use. (4) Stain of image receiving member by pressure application This evaluation was carried out using the thermal image transfer recording media Nos. 1, 3, 4, 5, and 7 according to the present invention, and the comparative thermal image transfer recording medium No. 4.

A cast coated paper was set in a commercially available printer (Trademark "B-572" made by Toshiba TEC Corporation), and allowed to stand at 40'C and 50%RH for 10 minutes with the platen being in pressure contact with the image receiving sheet.

The printing was started ten minutes later. It was - 27 - visually inspected whether the portion of the image receiving sheet with which the platen had been brought into pressure contact was stained or not. The degree of stain was eva'Luated on the following scale: 0: There was no stain. L: The stain in the form of a dotted line was slightly observed, but evaluated as acceptable for practical use. X: The stain appeared in the form of a straight line, and the degree of stain was evaluated as unacceptable for practical use.

The results are shown in TABLE 1.

TABLE 1

Intermediate Layer of Dynamic Evaluation Results Recording Medium Friction Resin Weight on Coeffi- Scratch Thermal Stain of (Weight dry basis cient of resist- image sheet by on dry of micro- Ink Image ance transfer platen basis) crystalline perform- pressure wax ance Polyester Ex. 1 Mw:20000, 0.148 0 0 Tg:10'C (10 wt.%) Ex. 2 20 wt.% 0.130 @ 0 Polyester Ex. 3 Mw:8500, 0.148 @ 0 0 Tg:60C (10 wt.%) I Polyester Ex. 4 r 0.153 0 0 0 Mw:6500, Tg:40C (10 wt.%) Polyester Ex. 5 Mw:12000, 0.165 0 0 Tg:60C (10 wt.%) Ex. 6 20 wt.% 0.138 @ 0 Polyester Ex. 7 Mw:8500, 0.160 0 0 1 Tg:60C (20 wt.%) Polyester Ex. 8 Mw:8500, 0.158 0 0 Tg:60C (23 wt.%) Ex. 9 10 wt.% 0.160 0 0 Ex. 10 7 wt.% 0.165 0 - 0 Comp.

Ex. I 0.20 X 0 Comp.

Ex. 2 Mixture of waxes 0.180 X 0 Comp. Ex. 3 0.210 X 0 Polyester Comp. Mw:8500, Ex. 4 Tg:60C 0.170 X 0 (7 wt.%)

As previously explained, when the thermal image transfer recording medium of the present invention is employed, ink images with high scratch resistance can be formed on an image receiving sheet, for example, even on a PET-coated paper of which the adhesion to the ink image is poor. In this case, the thermal image transfer performance is also excellent, so that the image quality of the obtained ink image is satisfactory.

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Claims

WHAT IS CLAIMED IS:

1. A thermal image transfer recording medium comprising a support, an intermediate layer formed thereon comprising a thermofusible material and a resin, and a thermofusible ink layer formed on said intermediate layer, capable of forming an ink image on an image receiving member, with a surface portion of said ink image exhibiting a dynamic friction coefficient in a range of 0.120 to 0.165.

2. The thermal image transfer recording medium as claimed in Claim 1, wherein said resin for use in said intermediate layer comprises a polyester resin.

3. The thermal image transfer recording medium as claimed in Claim 2, wherein said polyester resin has a weight-average molecular weight of 7, 500 to 10,000.

4. The thermal image transfer recording medium as claimed in Claim 1, wherein said thermofusible material for use in said intermediate layer comprises microcrystalline wax.

31 - S. The thermal image transfer recording medium as claimed in Claim 1, wherein said thermofusible material -or use in said intermediate layer is in the form of particles dispersed in an aqueous emulsion, and said intermediate layer is formed by coating an aqueous coating liquid comprising said aqueous emulsion.

6. A thermal image transfer recording medium substantially as herein described with reference to the accompanying drawings.

7. A thermal image transfer recording medium substantially as herein described with reference to Examples I A 0.

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