JP3121680B2 - Dye thermal transfer image receiving sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dye thermal transfer image receiving sheet (hereinafter, referred to as an image receiving sheet). More specifically, the present invention relates to an image receiving sheet capable of receiving a clear image with high density and no density unevenness.

[0002]

2. Description of the Related Art In recent years, the development of a thermal transfer type high-quality color hard copy, in particular, a dye thermal transfer type printer has been rapidly progressing. In the dye thermal transfer printer, the sublimation dye layers of three colors (yellow, magenta, and cyan) are heated by continuously controlling the heating energy of the thermal head, and the transfer amount of the dye of each color is changed to change the density. It is possible to form a full-color image of gradation.

[0003] With such a dye thermal transfer printer,
In order to form high-quality prints on an image receiving sheet at a high speed, it is known to use a biaxially stretched film mainly composed of a thermoplastic resin such as polyolefin and having a large number of minute voids as a base material of the image receiving sheet. Have been. The image receiving sheet is provided with an image receiving layer containing a thermoplastic resin as a main component on the substrate. An image receiving sheet using such a base material has uniform thickness, flexibility, and advantages such as a lower thermal conductivity than that using a paper made of cellulose fiber or the like as a base material. There is an advantage that a uniform and high density print can be obtained.

[0004] However, such a biaxially stretched film is
When used as a base material of an image receiving sheet that requires high image reproducibility, residual stress during stretching is relaxed by heating during printing, and heat shrinks in the stretching direction. As a result, curling or wrinkling occurs on the image receiving sheet. This causes troubles such as a paper jam of the image receiving sheet traveling in the printer.

In order to improve the above-mentioned drawback of curling or wrinkling, a sheet obtained by laminating and stretching a stretched film on a screen of a core material having a relatively small heat shrinkage or a core material having a large elastic modulus is used as a base material. It is known. However, such a base material has a disadvantage that curling occurs due to a difference in shrinkage due to heat or the like because sheets having different heat shrinkage are laminated. Therefore, even if the heat shrinkage of the stretched film laminated on the front and back is the same,
At the time of printing, since heating is performed only on the front side, the temperature differs between the front side and the back side of the image receiving sheet. As a result, there is a difference in the heat shrinkage between the front and back sides, causing curling.
Furthermore, since the stretched film is laminated on the front and back of the core material,
There is also a drawback that the manufacturing cost increases significantly.

In order to improve the curl during printing and the unevenness in the density of an image, Japanese Patent Laid-Open No. 2-106397 has been proposed.
, JP-A-2-307786, and US Patent 477
No. 4224 proposes to use a base material in which a polyolefin resin is laminated on paper. When this is used as a base material of an image receiving sheet, curling resistance is improved, but paper fiber is used. There have been problems such as uneven print density due to unevenness and a decrease in print density.

Further, US Pat. No. 4,999,335 describes that a print density is improved by using a base material obtained by laminating a blend of polyethylene and polypropylene on paper. The improvement was insufficient.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a problem of curling when a biaxially stretched film is used as a base material for an image receiving sheet, a density unevenness when a paper laminated with a polyolefin resin is used, and Another object of the present invention is to provide an image receiving sheet capable of solving the problem of print density reduction and obtaining excellent image quality.

[0009]

The dye thermal transfer image-receiving sheet of the present invention is formed on a base paper containing cellulose pulp as a main component, and on at least one surface of the base paper,
A resin coating layer containing a thermoplastic resin as a main component, and formed on the resin coating layer, and receives a thermal transfer image-forming dye, having an image receiving layer to be dyed, the resin coating layer, It is characterized by including a plurality of layers simultaneously formed on a base paper by coextrusion lamination.

The image-receiving sheet of the present invention has a multilayer structure in which a resin coating layer constituting the base material is simultaneously formed on a base paper by co-extrusion lamination, thereby improving sensitivity and improving density unevenness. The occurrence is prevented. In particular, the above effect is improved by combining the polyethylene resin layer and the polypropylene resin layer. Further, in the method for producing an image receiving sheet of the present invention,
It is possible to improve productivity and performance by simultaneously forming a plurality of layers on base paper by using coextrusion lamination and laminating the layers.

[0011] Coextrusion lamination is a process in which two or more types of resins or resins of the same type but having different performances are supplied from two or more extruders into a specially designed die.
This is a method in which a plurality of laminar flows of the resin melted inside or outside the die are superposed to form a multilayer structure, and then a single film is formed. Therefore, each resin layer of the obtained resin coating layer forms an independent layer laminated and united with each other.

[0012] Coextrusion laminations are classified into T-die casting, inflation (with or without stretching), in-die and out-die lamination as coextrusion processes, multi-manifold methods, feedblock methods, and the like. However, an actual manufacturing method often uses these combinations.

The thermoplastic resin used for forming the resin coating layer of the present invention may be a homopolymer such as low-density polyethylene, high-density polyethylene, polypropylene, polybutene, polypentene, or an ethylene-polypropylene copolymer which can be extrusion-coated. Copolymers of two or more olefins such as, or a linear low-density polyethylene composed of a copolymer of ethylene and α-olefin, and a mixture of two or more of these are used. Melt index materials can be used alone or in combination. In particular, when the polyethylene resin layer and the polypropylene resin layer are combined, the performance of the image receiving sheet is greatly improved. That is, when these resins are combined to form a multilayer structure, a resin coating layer effective for obtaining an image receiving sheet having both excellent sensitivity and image quality, which cannot be obtained in the case of a single layer structure, can be obtained.

A typical structure of a resin coating layer for an image receiving sheet is as follows: a base layer containing cellulose pulp as a main component, a polyethylene layer / polypropylene layer two-layer laminate layer,
Examples of the multilayer structure include a polypropylene layer / polyethylene layer two-layer laminate layer, a polyethylene layer / polypropylene layer / polyethylene layer three-layer laminate layer, and a polypropylene layer / polyethylene layer / polypropylene layer three-layer laminate layer. It may be a combination of resins.

The thickness of the resin coating layer is not particularly limited,
The thickness of each layer is 5 to 20 μm, and the total thickness is preferably 60 μm or less, and more preferably 10 to 40 μm. Further, a single-layer or multi-layer resin coating layer may be provided on the back surface of the base paper for an image receiving sheet in order to prevent curling.

It is preferable to add a white pigment to the resin coating layer of the present invention in order to improve the whiteness of the image receiving sheet. White pigments used for this purpose include titanium oxide, zinc oxide, talc, calcium carbonate and the like. Furthermore, in the present invention, a resin metal salt such as stearic acid amide or zinc stearate, an antioxidant such as hindered phenol, a pigment or dye such as cobalt blue or ultramarine blue may be added to the resin coating layer.

Further, in order to improve the adhesion between the resin coating layer and the image receiving layer, a coating layer made of various hydrophilic resins and hydrophobic resins may be provided between the two layers.

The type of cellulose pulp used for producing the base paper of the present invention is not particularly limited. For example, wood pulp, waste paper pulp, and the like obtained by subjecting hardwood or softwood to chemical or mechanical treatment are used. Non-wood natural pulp such as hemp and cotton, and synthetic pulp using polyethylene or polypropylene as a raw material can be used. These pulp may be used alone or in combination of several kinds.

In addition to the above-mentioned cellulose pulp, various fibers such as organic fibers such as acrylic fibers, rayon fibers, phenol fibers, polyamide fibers, and polyester fibers, and inorganic fibers such as glass fibers, carbon fibers, and alumina fibers. It may be mixed, but from the viewpoint of papermaking properties,
Base paper containing 50% by weight or more of cellulose pulp is preferred. In the process of producing base paper, various retention aids, paper strength agents, sizing agents, fillers, etc. can be appropriately selected and used, and further, dyes, pH adjusters, slime control agents, defoamers, etc. are required. Can be used according to

Further, it is also allowed to apply starch, polyvinyl alcohol, a surface sizing agent, a pigment, etc. to the base paper surface by a size press, a gate roll, a blade coater, an air knife coater or the like. The basis weight of the base paper is not particularly limited, but is preferably from 60 to 250 g / m ² .

The image receiving sheet of the present invention is produced by providing an image receiving layer on the surface of the resin coating layer. As a resin used for forming the image receiving layer, the dyeing property of the dye is good,
It is required that the transfer speed is high, the obtained image density is high, the discoloration of the obtained image by heat is small, and the running property of the obtained image receiving sheet is good. Specifically, it is preferable to use a thermoplastic saturated polyester resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-based resin such as a vinyl chloride-vinyl propionate copolymer, and other polycarbonate resins, polyvinyl acetal, polyamide, and the like.
A polyacrylate, an active energy ray-curable resin and the like can also be used.

In the image receiving layer of the present invention, a crosslinking agent, a lubricant, a release agent, and / or a pigment of a resin may be added, if necessary, for the purpose of preventing fusion with the ink sheet due to heat during printing. It may be added. Further, other additives, for example, pigments, fluorescent dyes, dyes such as blue and violet, ultraviolet absorbers and / or antioxidants, and the like can be added as necessary. These additives may be mixed with the main component of the image receiving layer, or may be provided as a separate coating layer above or below the image receiving layer.

The thickness of the image receiving layer is preferably from 1 to 10 μm, more preferably from 2 to 6 μm. If the thickness of the image receiving layer is less than 1 μm, there are disadvantages such as a decrease in the density and sensitivity of the obtained image and a decrease in the gloss of the printed surface. When the thickness exceeds 10 μm, the effect is saturated and not only is uneconomical, but also decreases the strength of the image receiving layer.

Further, in order to prevent static electricity from being generated during traveling of the image receiving sheet in the printer and causing a trouble in traveling, a layer containing an antistatic agent may be provided on at least one surface of the image receiving sheet. As the antistatic agent, a cationic hydrophilic polymer is advantageously used.

[0025]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited thereto.

[0026] Examples 1-3 and in each of Comparative Examples 1-3 Examples 1-3 and Comparative Examples 1-3, on the back surface of quality paper having a basis weight of 150 g / m ^2, a polyethylene resin 25 g / m ² The resin was coated by an extrusion lamination method so as to have an application amount of, and a backside resin coating layer was formed. Then, anatase-type titanium dioxide was applied to the surface of the high-quality paper according to the resin type, coating amount, and coating method shown in Table 1.
A resin coating layer having a multilayer structure containing 0% is formed, and the surface of the resin coating layer is subjected to a corona discharge treatment. Then, a coating composition for forming an image receiving layer having the following composition is applied in an amount of 6 g after drying. / M ² , using a wire bar to apply and dry to form an image receiving layer, thereby producing an image receiving sheet. In addition, among the resin types shown in Table 1, PE represents polyethylene, PP represents polypropylene, and EVA represents ethylene-vinyl acetate copolymer.

The image-receiving layer forming coating composition sets formed amount Polyester resin 100 parts by weight (trademark: Byron 200, manufactured by Toyobo Co., Ltd.) silicone oil 3 parts by weight (trademark: KF393, manufactured by Shin-Etsu Silicone Co.) Isocyanate 5 parts by weight ( Trademark: Takenate D-110N, manufactured by Takeda Pharmaceutical) 300 parts by weight of toluene

The image receiving sheets obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were each provided with a step pattern of a color bar signal generator (manufactured by Shibazoku Co., Ltd., trade name: C13A2) by a thermal transfer printer (manufactured by Fuji Film). , Trademark: VP7
100), and the print image obtained was evaluated for print density and density unevenness. Table 1 shows the results.

The print density and density unevenness were measured as follows. 1. Print density: The maximum density of the printed image is determined by a Macbeth densitometer (RD-914, Kollmorgen Cor).
p. Manufactured). 2. Density non-uniformity: Density non-uniformity of a printed image was observed, and a visual evaluation was performed in three steps: 3 for good quality, 2 for general quality, and 1 for poor quality.

[0030]

[Table 1]

[0031]

The dye thermal transfer image-receiving sheet of the present invention is suitable for recording a clear print image having a high density and no density unevenness, and is extremely excellent in practical use.

Continuation of the front page (72) Inventor Koji Narita 1-10-6 Shinonome, Koto-ku, Tokyo Oji Paper Co., Ltd. Examiner in the Product Research Laboratory Shiro Kimura (56) References JP-A-2-86493 (JP, A) JP-A-2-133699 (JP, A) JP-A-2-225087 (JP, A) JP-A-2-50891 (JP, A) JP-A-6-15785 (JP, A) JP-A-3-61038 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. A base paper containing cellulose pulp as a main component, a resin coating layer formed on at least one surface of the base paper and containing a thermoplastic resin as a main component, and formed on the resin coating layer, And an image receiving layer for receiving and dyeing a thermal transfer image-forming dye, wherein the resin coating layer includes a plurality of layers formed simultaneously on the base paper by co-extrusion lamination. Thermal transfer image receiving sheet.