JPH04219285A - dye thermal transfer receiving sheet - Google Patents

Abstract

PURPOSE:To obtain a high sensitivity thermal transfer print of high quality by setting the Bekk smoothness of a stretched sheet to 5000 sec or more, the void volume from the surface of said sheet up to 30mum to 15-50% and the Bekk smoothness of a coating layer of a dyeing resin to 5000 sec or more. CONSTITUTION:A molten mixture of a thermoplastic resin such as a saturated polyester resin and inorg. pigment is formed into a sheet by a melting extrusion laminator and the sheet is further stretched to obtain a stretched sheet having a void structure and a coating layer of a dyeing resin is provided to the surface with Bekk smoothness of 5000 sec or more of the stretched sheet. The void volume from the surface of the stretched sheet up to 30mum is set to 15-50% and the Bekk smoothness of the surface of the dyeing resin layer is set to 5000 sec or more. This dye thermal transfer receiving sheet is excellent in the gradation properties of an image and the uniformity of low density and high density and a high sensitivity thermal transfer print of high quality can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a full-color printer that receives image-forming dyes such as thermally transferred sublimation dyes and prints high-resolution halftone images with high fidelity and high sensitivity. This invention relates to an image receiving sheet.

[Problems to be solved by conventional technology and inventions] Development of high-quality color hard copies and printers using a dye thermal transfer method is progressing. The dye thermal transfer method uses an ink sheet with dye layers of three colors: yellow, magenta, and cyan, by continuously controlling the thermal energy of the thermal head and continuously changing the amount of dye of each color transferred by heat. Achieves full color density gradation images.

In order to obtain high-quality images, research is being carried out on image-receiving paper that has a dye-dyed layer that has a high dye transfer speed and dye amount, and has good storage stability.

In such a printer, a receiving sheet having a dyeable surface coating layer is superimposed on an ink sheet having a sublimable dye layer so that the dyed layer is in contact with the dye side of the ink sheet, and electricity is applied corresponding to the image. An image is formed by transferring dye at a desired density onto a receiving sheet using heat according to a signal.

Monolayer or multilayer films comprising uniaxially oriented and/or biaxially oriented film layers based on polyolefins, e.g. polypropylene, containing inorganic pigments to improve resolution and fidelity. It has been proposed to use a synthetic paper made of .

Such an image-receiving sheet has advantages such as uniform thickness, flexibility, and lower thermal conductivity than paper made of cellulose pulp due to the void structure unique to synthetic paper. Therefore, it has the advantage that a uniform and high-density image can be obtained.

However, it contains existing polypropylene as the main component, and 1
When a single-layer or multi-layer structure film made of axially or biaxially stretched film is used as a substrate, the void structure on the surface of the film is exposed, causing unstable image formation and problems, and also affecting the uniformity of the resulting print. There were drawbacks that made it worse.

There has been a desire for a technique that uses synthetic paper with an exposed void structure on the surface as a sheet-like substrate as described above, and eliminates drawbacks such as image non-uniformity while taking advantage of high sensitivity.

[Means and effects for solving the problem] In order to solve the above problems, the present inventors have developed a coating layer of a dye-dyeable resin, a stretched sheet containing voids containing a thermoplastic polymer as a main component. In the sheets laminated in this order, the stretched sheet has a Beck smoothness of 5000 seconds or more, a porosity of 15% to 50% from the surface of the stretched sheet to 30 μm, and a Beck smoothness of the dyeable resin coating layer. Smoothness is 5000
It has been found that a dye thermal transfer image-receiving sheet characterized by a transfer resistance of at least 2 seconds is effective.

The porosity of the stretched sheet was determined using the following formula.

ρ0: Film density before stretching ρ1: Film density after stretching The image receiving sheet of the present invention has a Bekk smoothness of the stretched sheet of 50.
00 seconds or more, the porosity between 30 μm from the surface of the stretched sheet is 15% or more and 50% or less, and the Bekk smoothness of the dyeable resin coating layer is 5000 seconds or more. For color printers, we have completed a recording sheet that prints high-resolution halftones faithfully and with high sensitivity, solving the drawbacks of conventional printers.

The thickness of the image-receiving sheet of the present invention is appropriately selected depending on the application such as color printing, computer graphics, labels, cards, etc., but it is generally preferably 40 to 250 μm.

The Bekk smoothness of conventionally used stretched sheets containing voids and mainly composed of thermoplastic polymers is 300 to 100.
The normal time was about 0 seconds.

As a synthetic paper, this paper has excellent writability and
This is to expose voids on the surface where an excessively smooth surface is undesirable in order to improve printability.

The present inventors succeeded in reducing the exposure of the void structure in the outermost layer without considering writability or printability, so that the porosity remains high, that is, the sheet contains voids and the smoothness is reduced. It has been found that a stretched sheet containing voids and containing thermoplastic polymer as a main component can be obtained for 3000 seconds or more, more preferably 5000 seconds or more.

In the image-receiving sheet of the present invention, the necessary conditions for achieving uniformity of the transferred image are the flatness of the outermost layer represented by the smoothness of the stretched sheet, which is necessary to improve resolution, and the fidelity of transfer. In order to improve reliability, the above-mentioned relationship is established with the porosity of the surface layer (in the present invention, the measure is up to 30 μm from the surface). If these two conditions are met,
The image receiving sheet and its base material have not been seen before, but
The present inventors have achieved smoothness on the surface by smoothing only the top layer of the surface of the base material and maintaining a void structure underneath.
This has succeeded in achieving both high porosity.

As a result, the adhesion of the thermal head is improved, and the applied thermal energy is controlled and diffused onto the dots, increasing the temperature of the ink layer and receiving layer accurately and uniformly, resulting in more uniform printed images. The clarity could be improved.

The stretched sheet may be used alone as a base sheet, or
If there is a risk of thermal deformation or thermal shrinkage occurring due to temperature, as occurs during thermal transfer, a multilayer structure laminated with other heat-resistant and strong sheets such as paper or plastic film may be used as the base sheet. good.

Further, the stretched sheet itself may be a multilayer sheet, for example, composed of a stretched sheet having a high porosity and serving as a surface layer, and a stretched sheet having a high density and serving as a core. In this case, in order to improve the fidelity and reliability of transfer, the porosity and smoothness of the surface layer (in the present invention, the measure is up to 30 μm from the surface) should be set in the above relationship.

The porosity or the volume ratio of voids is determined from the relationship between the true specific gravity of the raw material and the apparent thickness of the layer, and has a great influence on the heat insulation properties and compressibility of the film layer.

The porosity of the surface layer of the stretched film is 15% or more and 50% or less, more preferably 25% or more and 40% or less.

The thickness of the base sheet used in the present invention is generally 20 to 3
00 μm, and the thickness of the core material is preferably 15 to 200 μm.

The base sheet in the present invention is characterized by having a fine void structure and being smooth. As a method for forming a fine void structure in a stretched sheet, it is preferable to incorporate an inorganic pigment or other incompatible polymer into the thermoplastic resin. The method of forming a stretched sheet with such a void structure is to melt and extrude a melted mixture of thermoplastic resin and inorganic pigment into a sheet using a laminator, and then stretch it in one or two axes to form a stretched sheet with a void structure. There is a method of forming a stretched sheet.

The thermoplastic resin used for the stretched sheet is mainly composed of polypropylene or polyethylene terephthalate, which has good crystallinity, good stretchability, and easily forms voids.
A suitable small amount of other thermoplastic resin is used in combination and stretched to produce a sheet containing voids.

The content of incompatible particles such as pigments in the resin layer is 1 by volume.
It is preferably 0% or less. If the amount is too large, the strength will be insufficient and problems such as breakage of the film will occur. As the inorganic pigment, a pigment having an average particle size of 20 μm or less is preferable, and examples thereof include calcium carbonate, clay, diatomaceous earth, titanium oxide, aluminum hydroxide, and silica.

The uppermost part contains as a main component a thermoplastic resin capable of receiving and fixing a thermal transfer image-forming dye, and 3 to 2
A top coating layer (dye image-receiving layer) is formed having a thickness of 0 μm, preferably 5 to 10 μm.

As the thermoplastic resin forming the upper coating layer, a polyester resin such as a saturated polyester resin (trademark: VYLON 200, manufactured by Toyobo Co., Ltd.) is used. The dye-receptive thermoplastic resin may optionally contain additives, such as
Polydimethylsiloxane copolymer resin (trademark: SH-
3746, manufactured by Toray Dow Corning Silicone Co., Ltd.), etc. may be included.

〔Example〕

The invention will be further illustrated by the following examples.

Stretched film production example-1 65% by weight of polypropylene with a melt index of 0.8
, 15% by weight of low-density polyethylene was blended with 20% by weight of calcium carbonate having an average particle diameter of 3 μm, melt-extruded using an extruder at 270 degrees, and cooled to obtain an unstretched sheet containing almost no voids. 1 from 150 degrees
A stretched sheet containing voids was obtained by biaxially stretching at a temperature of 70 degrees. The porosity was 25% and was almost uniform in the thickness direction of the sheet. The smoothness was 6000 seconds on one side and 2500 seconds on the other side.

The thickness was 50μ.

Example-1 The film obtained in Stretched Film Production Example-1 was applied to both sides of a 50μ thick polyethylene phthalate film using a polyester adhesive so that the surface with a smoothness of 6000 seconds was on the outside. A base sheet was produced by pasting together using a dry lamination method.

On top of this, paint-1 is applied as a dye-dyed layer with a solid content of 5 g/m2.
A sublimation dye-receiving sheet was obtained by coating and drying using a die coating method at a ratio of .

Paint-1 Saturated polyester resin (Vylon 200, Toyobo Co., Ltd.) 100 parts Silicone resin (SH-3746, Toray Dow Corning Silicone Co., Ltd.) 5 parts Toluene 500 parts Methyl ethyl ketone 100 parts Example 2 Film 2 of Production Example-1
A base sheet was produced by dry laminating the sheets together using a polyester adhesive so that the surface with a smoothness of 6000 seconds was on the outside. Paint-1 was applied thereon as a dye-dyed layer using a die coating method at a solid content of 5 g/m<2 >and dried to obtain a sublimation dye-receiving sheet.

Comparative Example-1 As a base, the thickness was 150 μm, the porosity of the surface layer was 25%,
Synthetic paper YUPO FPG150 with a smoothness of 550 seconds was used.

On top of that, paint-1 is applied as a dye-dyed layer with a solid content of 5 g/m2.
A sublimation dye-receiving sheet was obtained by coating and drying using a die coating method at a ratio of .

Comparative Example-2 A non-stretched polypropylene film with a thickness of 38 μm, a surface layer porosity of 0%, and a smoothness of 3000 seconds was used as the base, and the films were bonded together in the same manner as in Example-1 to produce a base sheet. , on which paint-1 is applied as a dye-dyed layer at a solid content of 5
A sublimation dye-receiving sheet was obtained by coating and drying by a die coating method at a ratio of g/m2.

Evaluation A commercially available sublimation thermal transfer printer was used to print halftone single-color and overlapping color images of each color. This image was visually evaluated, especially the image clarity of the dots and the uniformity of the density of halftones.

The evaluation results are shown in Table 1 on a 5-grade scale.

〔Effect of the invention〕

The thermal transfer image-receiving sheet of the present invention has excellent image gradation and uniformity at low density and high density, and overcomes the drawbacks of conventional methods, which have excellent brightness and uniformity of printed images. This makes high-quality, highly sensitive thermal transfer printing possible.

Patent applicant: Oji Paper Co., Ltd. Agent Hiroshi Nakamoto

Claims (1)

[Claims] Claim 1: A coating layer of a dye-dyeable resin is provided on the surface of a stretched sheet containing a board mainly composed of a thermoplastic polymer and having a Beck smoothness of 5000 seconds or more, and
1. A dye thermal transfer image-receiving sheet, characterized in that the porosity up to 0 μm is 15% or more and 50% or less, and the Bekk smoothness of the surface of the dyeable resin layer is 5000 seconds or more.