JPH05286117A - Indirect transfer medium and retransfer method - Google Patents

Abstract

PURPOSE:To provide an indirect transfer medium for a retransfer method capable of sharply recording an image of high resolving power even to a receiving medium low in smoothness. CONSTITUTION:In a retransfer method wherein a thermally transferrable ink image is once formed on an indirect transfer medium and subsequently retransferred to a receiving medium, the indirect transfer medium and the receiving medium are pressed under pressure of 20kg/cm<2> or more or heated under this pressure to retransfer an image or stress is applied to both media in a lateral direction to retransfer an image. The indirect transfer medium consists of at least a rigid support and a cushioning layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transfers an image from a transfer medium to a transferred medium in thermal transfer recording to an indirect transfer medium, and then retransfers the image to the transferred medium. The present invention relates to an indirect transfer medium for clearly recording a high-resolution image on a transfer medium and a retransfer method.

[0002]

2. Description of the Related Art As a thermal transfer system, a pressure heating system using a thermal head has been put into practical use, and it has excellent features in terms of noise-free, simple mechanism, maintenance-free and dry processing. Moreover, in terms of resolution, the density of thermal heads has increased, and in recent years, resolutions of 400 to 600 DPI or more have been obtained. However, it is more difficult to increase the density of the thermal head, and the conventional thermal transfer recording system has a limit in resolution.

Therefore, a laser thermal transfer method using a laser beam as a heat source has been proposed. With this method, it is possible to focus the laser light up to several microns, so it is possible to dramatically improve the resolution. However, since the laser thermal transfer method has a limitation on the laser output, high sensitivity of the material is desired. Further, the close contact between the transfer target sheet and the sheet greatly affects the resolution of the image, so that the close contact becomes a problem particularly when a high resolution image is obtained. Conventionally, for the contact of the sheet on the exposed surface, a method of winding the sheet around a drum, pulling both ends of the sheet, or sucking air from the inside of the drum to perform vacuum contact has been considered. However, it is difficult to obtain sufficient adhesion between the transfer sheet and the transferred sheet only by these methods, and sufficient transferability cannot be obtained. Further, in order to obtain sufficient vacuum adhesion, it is possible to add fine particles of a few microns called a matte material to the image-receiving layer or the ink layer, but on the other hand, the surface becomes rough so that fine adhesion is not obtained. There were problems such as damage and uneven transfer.

In order to solve this, it is effective to give the transfer medium cushioning property to improve the adhesion, but since sufficient pressure cannot be obtained by vacuum adhesion or the like, so-called rough paper having low surface smoothness is used. In contrast, the current situation is that it is not a fundamental solution.

A method of recording an image on an intermediate transfer medium and then pressure-sensitively transferring it to any transfer medium such as rough paper is disclosed in JP-A-54-127334, JP-A-54-161946 and JP-A-61-295094. Same as 63-
No. 128987, etc., it was difficult to form a high-resolution image of the order of several μm, which is equivalent to laser recording, and to retransfer the image by these methods.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is a retransfer method capable of clearly recording a high-resolution image even on a transfer medium having a low smoothness,
And to provide an indirect transfer medium therefor.

[0007]

The above object of the present invention is achieved by the following configurations.

(1) In a retransfer method in which a thermal transferable ink image is once formed on an indirect transfer medium, and then the image is retransferred to the transfer medium, a retransfer method is performed between the indirect transfer medium and the transfer medium.
A re-transfer method in which pressure or heat is applied at 20 kg / cm ² or more, or an image is re-transferred while applying pressure or heat and pressure and applying lateral stress.

(2) As means for applying a lateral stress, a projection-shaped unevenness is brought into contact with the indirect transfer medium or the transfer medium, or the relative speed between the indirect transfer medium side and the transfer medium side of the pressure device. The retransfer method according to (1), in which

(3) In a retransfer method in which a heat transferable ink image is once formed on an indirect transfer medium and then the image is retransferred to a transfer medium, the indirect transfer medium comprises at least a rigid support and a cushioning layer. Indirect transfer medium.

(4) The indirect transfer medium according to (3), wherein the image recording surface of the indirect transfer medium has a thermoplastic elastomer having a glass transition point of 30 ° C. or lower.

The present invention will be described in more detail below.

First, an indirect transfer medium required for primary recording and retransfer of a high resolution image will be described.

The indirect transfer medium must be provided with the contradictory performance that the recorded image can be efficiently held and can be efficiently retransferred to a desired transfer medium. JP-A-61-295094 discloses a silicone rubber roll having low wettability as a means for achieving this. Silicone rubber rolls, etc. are also highly flexible and can be fitted to some degree to the fine irregularities of the medium to be transferred. It cannot be retransferred. According to our study, silicone rubber, Teflon, water-repellent silicone resin coating, etc. have excellent retransferability, but primary transfer is not possible unless a method with a large transfer pressure such as a word processor is used, and transfer must be done only by vacuum adhesion. It was found that it was almost impossible to transfer by the laser thermal transfer method, which is required.

Glass transition point (Tg) as an indirect transfer medium
Thermoplastic elastomer with a temperature of 30 ℃ or less (Thermoplastic el
astmer; TPE) is preferred. TPE has both a rubber component having elasticity in the molecule = a soft segment (soft phase) and a molecular restraint component for preventing plastic deformation = a hard segment (hard phase). It has properties. Specifically, styrene type (Styrene block copolymer; SBC), olefin type (Thermoplastic elastmer olefin; TPO), urethane type (Thermoplastic elastmer urethane; TPU),
Polyester type (Thermoplastic elastmer polyester;
TPEE), polyamide type (Thermoplastic elastmer p
olyamide; TPAE), 1,2-polybutadiene system, PVC system (Thermoplastic elastmer vinyl chloride; TPV)
C), fluorine type (fluorine rubber; FKM), and other ionomer resins. These configurations are as follows. SBC: Polybutadiene, polyisoprene, and polyolefin are used for the soft segment, and polystyrene is used for the hard segment.

TPO: polypropylene or polyethylene for the hard segment and EPDM (Ethy
Lene propylene dien terpolymer) is used.

TPU: A polymer chain composed of diisocyanate and short-chain glycol serves as a hard segment, and a polymer chain composed of diisocyanate and a polyol serves as a soft segment.

TPEE: A high melting point and highly crystalline aromatic polyester (eg polybutylene terephthalate) is used for the hard segment, and an amorphous polyether (Tg-70 ° C. or lower) (eg polytetramethylene ether glycol) is used for the soft segment.

TPAE: Nylon is used for the hard segment and polyester or polyol is used for the soft segment.

Fluorine type: Fluorine rubber is used as a soft segment,
Fluorine resin is used for the hard segment.

Among the above, 1,2-polybutadiene TP
E is particularly preferred.

These TPEs show good retransferability even by a retransfer method such as an ordinary laminating method, but a further excellent retransfer property can be obtained by the following retransfer method.

It is also effective to provide a cushion layer between the support and the support for the purpose of improving the retransfer property.

Next is a method of retransfer to another transfer medium. In the present invention, the pressure is 20 kg / cm ² or more, or pressure or heating is applied.
It is characterized in that pressure is applied, or a stress in the lateral direction is applied simultaneously while applying pressure. As a result, a desirable adhesive force relationship for transfer is generated between the transfer medium, the ink, and the indirect transfer medium, and clear transfer is possible. In order to obtain a lateral pressure, it is effective to give a slight difference in peripheral speed to the transfer roller, to lay an uneven surface on the mesh as an underlay, or to use a roller having fine protrusions.

[0025]

The present invention will be described below with reference to examples.
The embodiment is not limited to this.

Example 1 (Preparation of Ink Sheet) 50 μm of transparent PET (polyethylene terephthalate: diamond T-50) and 30 μm of EVA (ethylene-vinyl acetate copolymer) having a VA (vinyl acetate) content of 14% as a cushion layer. On the EVA surface of the extrusion-laminated support, the following coating solution was applied as a photothermal conversion layer so that the dry coating amount would be 0.5 g / m ² .

At this time, the transmission density at 830 nm was 0.9.
In addition, a weight part represents a weight part of solid content. The EVA surface had surface smoothness so that the average roughness Ra was 0.5 μm or less. The better the surface smoothness, the better the transfer.

Light-to-heat conversion layer coating liquid Carbon black aqueous dispersion 2.1 parts by weight PVA (cation-modified: Kuraray L-506) 4.9 parts by weight Fluorine-based surfactant 0.1 parts by weight Water 100 parts by weight This light-to-heat conversion layer is made of PVA-based polymer. By using as a binder, it is possible to prevent the photothermal conversion material (carbon black) from scattering during light irradiation, and to improve the peeling of the ink layer.

In order to improve the adhesion of the photothermal conversion layer to the support or the cushion layer, an adhesive layer may be provided between them or an adhesive material may be added to the photothermal conversion layer.

As the photothermal conversion material, dyes having absorption in the near infrared region are preferably used in addition to carbon black. Specifically, cyanine dyes, anthraquinone dyes, squarylium dyes, croconium dyes, azurenium dyes, indoaniline metal complex dyes, phthalocyanine dyes, naphthalocyanine metal complex dyes, dithiol metal complex dyes, intermolecular dyes. Examples include CT dyes. It is preferable to introduce a sulfo group or the like into these dyes to make them water-soluble, since they can be used in an aqueous photothermal conversion layer.

Next, the ink layer shown below was dried to an amount of 0.
It was applied so as to be 7 g / m ² .

Ink layer coating liquid Magenta pigment dispersion 30 parts by weight Petroleum resin (Harumi Kasei: DS-90) 57 parts by weight Paraffin wax dispersion 5 parts by weight EVA (VA 40%) 5 parts by weight Dioctyl phthalate 3 parts by weight Methyl ethyl ketone 400 parts by weight Part (preparation of indirect transfer medium) 50 μm transparent PET (diamond T-
50) was subjected to an adhesive treatment, and then a 30 μm film of 1,2-polybutadiene resin (Nippon Synthetic Rubber: Melvac RB-840) was also used as a cushion layer and an indirect transfer layer to form an indirect transfer medium. At this time as well, laminating precision was provided, and the average surface roughness Ra was set to 0.5 μm or less.

(Formation of Image) (Primary Transfer of Ink to Indirect Transfer Medium) The above sheet is superposed on a flat plate by a vacuum pump and brought into close contact with each other, and exposed and peeled under the following conditions to form an image. .. Decompression degree
It was 500 torr.

(Exposure condition) Light source: 100 mW semiconductor laser (oscillation wavelength, 830 nm) Exposure direction: Incident from the back of the ink sheet Exposure part light intensity: 50 mW Beam diameter: 1 / e ² 10 μm Exposure time: 0.5-10 μsec Pulse width 3.0 It was possible to transfer a solid image beautifully in μsec or more.

Further, the indirect transfer medium is made to face a printing paper (Mitsubishi Toku Ryokan art paper), and the temperature is 90 ° C., the pressure is 30 kg / cm ² , and the speed is 3 cm.
When re-transferred by applying heat and pressure at 1 / sec, almost 1
00% image retransferred. Laser transfer and retransfer were also possible for halftone dot images equivalent to 180 lines.

Comparative Example 1 The ink sheet used in Example 1 and the printing paper were brought into close contact with each other by vacuum contact, and a transfer experiment was conducted in the same manner. Transfer was possible in 4.0 μsec or more, but the recessed part of the paper was not transferred, and a perfect image could not be obtained.

Example 2 A transfer image was similarly obtained using the ink sheet and indirect transfer medium used in Example 1, and retransfer was performed under the following conditions.

A metal roll having a depth of 30 μm and a 300-mesh lattice pattern and a heat-resistant rubber having a rubber hardness of 90 degrees were held by a roll attached to the metal roll with a thickness of 1 mm, and the pressure was 20.
Retransfer was performed at a speed of kg / cm ² , 90 ° C., and 2 cm / sec, with the indirect transfer medium and the fine paper facing each other. As a result, the ink image was clearly retransferred to the paper.

Example 3 A transfer image was similarly obtained using the ink sheet and the indirect transfer medium used in Example 1, and retransfer was performed under the following conditions.

A smooth metal roll and a heat-resistant rubber having a rubber hardness of 90 degrees are held by a roll attached to a metal roll with a thickness of 1 mm, and the pressure is 5 kg / cm ² , at 90 ° C., and the speed of 2 cm / sec is an indirect transfer medium. And the high-quality paper was faced to retransfer.
At this time, a drive motor was attached so that the rolls and the rolls had a slight relative speed. As a result, the ink image was clearly retransferred to the paper.

Comparative Example 2 Example 1 except that the following was used as the indirect transfer medium.
I went the same way.

(Indirect transfer medium) E on a transparent base of 75 μm
VA (VA content 14%) was extrusion laminated to a thickness of 30 μm, which also served as a cushion layer. The image lacked sharpness due to uneven transfer in the primary transfer with a laser.

Example 4 On the indirect transfer medium used in Comparative Example 2, 10% 1,2-polybutadiene (Japan Synthetic Rubber: RB-830) toluene solution was applied and dried to a dry film thickness of 1 μm. An indirect transfer medium was obtained. When this was used and carried out in the same manner as in Example 1, clear primary transfer images and retransfer images were obtained.

[0044]

The transfer medium having an ink layer and the indirect transfer medium are superposed on a base material, wound around a cylindrical drum, and scanning-exposed with a beam while rotating (or in close contact with a flat plate, and plane scanning exposure). According to the retransfer method of the present invention, in which a high-resolution image of micron order is transferred from the transfer medium to the indirect transfer medium, and then the recorded image is further transferred to the transfer medium, the direct transfer from the transfer medium to the transfer medium is performed. High-resolution images can be obtained even on high-quality paper that is difficult to transfer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sota Kawakami 1st Sakura-cho, Hino City, Tokyo Konica Stock Company In-house

Claims (4)

[Claims] 1. A retransfer method in which a thermal transferable ink image is once formed on an indirect transfer medium, and then the image is retransferred to the transfer medium.
A retransfer method comprising applying pressure or heat and pressure at kg / cm ² or more, or applying pressure in the horizontal direction while applying pressure or heat and pressure, and retransferring an image. 2. As means for applying a lateral stress, a projection-shaped unevenness is brought into contact with an indirect transfer medium or a transfer medium, or the relative speed between the indirect transfer medium side and the transfer medium side of the pressure device is set. The retransfer method according to claim 1, wherein the retransfer is slightly changed. 3. A retransfer method in which a thermal transferable ink image is once formed on an indirect transfer medium and then the image is retransferred to a transfer medium, wherein the indirect transfer medium comprises at least a rigid support and a cushioning layer. An indirect transfer medium characterized by. 4. The indirect transfer medium according to claim 3, wherein the image recording surface of the indirect transfer medium has a thermoplastic elastomer having a glass transition point of 30 ° C. or lower.