JPH08216533A - Heat transferring image receiving sheet - Google Patents

Abstract

PURPOSE: To provide color-slippage free and plain paper-like heat transferring image receiving sheet. CONSTITUTION: In a heat transferring image receiving sheet, which is produced by providing image receiving layer receiving dye migrating through sublimation from heat transfer medium under heat, on supporter consisting of wood pulp paper made mainly of wood pulp, the product of the heat shrinkage factor in the machine direction RMD of the wood pulp paper as supporter and that to the cross direction RCD is 0.20 or below and, the ratio of the heat shrinkage factor in the machine direction to that in the cross direction RCD/RMD is 2.3 or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer image-receiving sheet, and more particularly to a plain paper-like thermal transfer image-receiving sheet having no color shift.

[0002]

2. Description of the Related Art In recent years, as a means of color hard copy, an apparatus utilizing a thermal transfer recording system has been widely used because of its advantages such as light weight, compact size, no noise, excellent operability and maintainability. . This thermal transfer recording system is roughly classified into two types, which are a heat melting type and a heat transfer type or a sublimation type. In particular, the latter is excellent in reproducibility of multicolor gradation images and is printed by using a sublimation type thermal transfer type printer. The principle of such a sublimation type thermal transfer type printer is that an image is converted into an electric signal, and this electric signal is further converted into a heat signal by a thermal head.
A thermal transfer medium coated with a heat transferable dye (hereinafter referred to as an ink donor sheet) is heated, and the dye is transferred from the ink donor sheet to the image-receiving layer of the thermal transfer image-receiving sheet by sublimation or diffusion in the medium. It records information.

In a sublimation type thermal transfer type color printer, multi-tone image dots of single colors of yellow, magenta, cyan and black are overprinted by a frame sequential method, whereby a large number of red, green, blue and many others are printed. Attempts have been made to form neutral hue and density images to produce natural color photographic images.

In the color recording by the frame sequential method, the ink donor sheet and the image receiving sheet are pressed against the thermal head by the platen, and the recording is performed for each screen for each single color of the donor sheet. Therefore, in order to reproduce colors faithfully to the original image, it is important to be able to perform overprinting at an accurate position.

In recent years, from the viewpoint of increasing the printing speed,
There is a demand for improvement in sensitivity, that is, transfer density, and examples of such higher sensitivity include JP-A-62-87390 and JP-A-3-266669.
In the publication, synthetic resin films and synthetic papers such as polypropylene, polyester, and polyethylene terephthalate having a void structure produced by a biaxial stretching method are described as being effective for an image receiving sheet because they have excellent cushioning properties and heat insulating properties. ing.

However, since such a synthetic film or synthetic paper is inferior in heat resistance, curling occurs due to, for example, a drying process in laminating when a support has a multi-layer structure or an applied energy heat in printing. There was a problem. The voids of such synthetic resin film or synthetic paper are generally several to several tens of μm in thickness and several to several tens of μm in length, but the platen pressure is applied to the thermal transfer image receiving sheet during printing. When it was compressed due to cracking, minute density unevenness due to the density unevenness of the void structure occurred. Furthermore, in consideration of curl suitability, paper feedability and handling in a printer, a support such as paper, resin-coated paper, PET film, etc., has a different feel from plain paper such as PPC paper. It tends to make users feel uncomfortable.

Further, it has been conventionally known to use paper containing normal wood pulp as a main component as a support for an image receiving sheet. However, since such a support is inferior in smoothness, the surface of the image-receiving layer is poor in smoothness, and as a result, the adhesion to the donor sheet is impaired, and problems such as uneven density and white spots may occur.

Therefore, in JP-A-62-202790, the smoothness of the surface of the image receiving layer is enhanced by using the base paper having the Bekk smoothness of the surface on which the image receiving layer is provided of 50 seconds or more, and the ink transfer property is improved. Is shown to increase. Also,
JP-A-62-151393, JP-A-63-98494.
Japanese Patent Laid-Open Publication No. 9-242242 discloses that an elastic layer is provided between a support and an image-receiving layer to impart cushioning properties, and a highly sensitive image-receiving sheet can be obtained without uneven density or white spots.

However, even if the surface smoothness of the base paper is enhanced or an intermediate layer having elasticity is provided, density unevenness and white spots are improved, but a slight color shift occurs, which has been required in recent years. It has not been possible to achieve high-quality images with natural-color photo tones.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image-receiving sheet for thermal transfer, which has a pulp paper mainly composed of wood pulp as a support and has no color shift and has a plain paper-like appearance. .

[0011]

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, heat generated during printing causes non-uniform shrinkage of the pulp paper, which is a support, and as a result, It was found that color misregistration occurs during color printing.
It was also found that this color shift was irregular depending on the printed portion. Therefore, as a result of studying the relationship between shrinkage characteristics during heating and color misregistration of thermal transfer printing for pulp paper produced by various methods, it was found that not only the magnitude of shrinkage but also the anisotropy of shrinkage is an important factor. I stopped.

Therefore, it has been found that color misregistration can be suppressed by setting the heat shrinkage rate of the pulp paper as the support within a specific range, and the present invention has been completed. That is, the present invention is a thermal transfer image-receiving sheet in which an image-receiving layer for receiving a dye that migrates by sublimation from a thermal transfer medium when heated is provided on a support made of a pulp paper mainly composed of wood pulp, in which the support is used. The product of the heat shrinkage (RMD) in the machine direction and the heat shrinkage (RCD) in the cross machine direction of a certain pulp paper is 0.20 or less, and the ratio of the heat shrinkage in the cross machine direction to the machine direction (RCD / The image receiving sheet for thermal transfer is characterized in that RMD) is 2.3 or less.

The thermal shrinkage of pulp paper in the present invention means
It is a value calculated by the following mathematical formula 1 (Formula 1) from the shrinkage amount when a sample that has been conditioned for 24 hours at a temperature of 20 ° C. and a relative humidity of 65% is dried at 105 ° C. for 5 minutes.

## EQU00001 ## Thermal shrinkage (R) = dL / L.times.100 (Equation 1) Here, dL is the difference in the length of the test piece before and after drying, and L is the length of the test piece before heating. In the present invention, the heat shrinkage ratios were measured in the machine direction and the cross machine direction of the base paper and expressed as RMD and RCD, respectively.

In order to obtain a pulp paper for use in the image-receiving sheet for thermal transfer of the present invention, the heat shrinkage itself is suppressed and the heat shrinkage product (RMD x
It is necessary to achieve both a small RCD) of 0.20 or less and a thermal shrinkage ratio (RCD / RMD) of 2.3 or less by reducing the anisotropy of shrinkage.

As a method of reducing the product of heat shrinkage,
Use of pulp with high α-cellulose content, beating to give priority to cutting over swelling of fibers, increase water squeeze in press to reduce drying load in dryer, Increasing tension,
Furthermore, damp with a dryer, such as the use of a dryer without an open draw (single tier dryer) as described in Paper and Paper Technical Association, Vol. 45, No. 1, p. 78 or pp. 89-90, (1991). A method of reducing shrinkage during paper drying can be used.

As a method for reducing the heat shrinkage ratio in the machine direction and the cross machine direction, adjustment of the forming board position of the wire part, optimization of the jet / wire speed ratio, reduction of draw in the press or dryer, For example, use a dryer without the above open draw.

By using the above-mentioned methods alone or in combination, a support for a thermal transfer image-receiving sheet having the characteristics of the present invention can be obtained.

The pulp used in the present invention is NBK.
Examples include wood pulp such as P, LBKP, NBSP, LBSP, GP, and DIP, and various synthetic pulps. As a beating machine for beating pulp, a beating machine usually used for beating pulp, for example, a beater, a conical refiner, a disc refiner or the like can be used. Then, to these pulps, chemicals such as conventionally known fillers, sizing agents, dyes, dry paper strength enhancers, wet paper strength enhancers, fixing agents, and yield improvers are added as required, and a Fourdrinier paper machine is used. ,
Papermaking can be performed using a twin wire paper machine, a hybrid paper machine, a cylinder paper machine, or the like.

As the filler, for example, light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc,
Of calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide White inorganic pigment, styrene plastic pigment,
Examples thereof include acrylic plastic pigments, polyethylene, microcapsules, urea resins, and organic pigments such as melamine resins.

Examples of sizing agents include rosin sizing agents for acidic papermaking, modified rosin sizing agents for neutral papermaking, and AK.
D, ASA, cationic polymer type sizing agent and the like can be mentioned.

Further, on the surface, inorganic pigments such as silica, alumina, titanium oxide, kaolin, clay, talc, zinc oxide and barium sulfate, starch granules, cellulose powder, melamine resin microparticles, guanamine resin microparticles, urethane resin. Fine particles, epoxy resin particles, silicone resin particles, vinyl resin particles and other organic pigments, vinyl resin hollow particles, melamine resin hollow particles and other hollow pigments, starch, casein, gelatin, polyvinyl alcohol, carboxymethyl cellulose, hydroxy Water-soluble resins such as ethyl cellulose, resin emulsions such as styrene-butadiene type, acrylic type and vinyl acetate type, dispersants, cross-linking agents, dyes, fluorescent agents, ultraviolet absorbers, antioxidants, preservatives, surfactants, defoamers. Coating including agents, thickeners, conductive agents, etc. A gravure coater, roll coater, rod coater, die coater, curtain coater, which was coated by such as a blade coater may be used.

If necessary, an intermediate layer may be provided between the support and the image receiving layer of the thermal transfer image receiving sheet of the present invention in order to enhance heat insulation and cushioning. In order to enhance the heat insulating property, for example, an intermediate layer containing heat-expandable hollow particles or a hollow polymer capsule is provided. The thermally expandable hollow particles include hollow particles having a wall material made of a thermoplastic material such as vinylidene chloride-acrylonitrile copolymer, and contain a thermally expandable gas such as propane, n-butane and isobutane inside the particles. It is a hollow particle. Further, the capsule-shaped hollow polymer is a polymer having a resin such as styrene-acryl as a wall material and having water inside, and the water is evaporated into a hollow particle during drying.

In order to form the intermediate layer, the above hollow particles are mixed with the binder resins listed below and used. As the binder resin, a resin such as styrene / butadiene / acrylic copolymer, polyurethane, acrylic, vinyl chloride, vinyl acetate, vinyl chloride / vinyl acetate copolymer, polyvinyl alcohol, polyvinyl butyral, alkyd, polyester, or starch alone, Alternatively, two or more kinds can be mixed and used.

In order to improve the cushioning property, for example, silicone rubber, butadiene rubber, styrene / butadiene rubber, high styrene / butadiene rubber, butyl rubber, fluorine rubber, nitrile rubber, chloroprene rubber,
Acrylic rubber, urethane rubber, isoprene rubber, natural rubber, chlorosulfonated polyethylene, chlorinated polyethylene, chlorinated butyl rubber, polysulfide rubber, epichlorohydrin rubber, propylene oxide rubber, ethylene-vinyl acetate rubber, etc., alone or 2 More than one species can be added to the intermediate layer.

The image-receiving sheet for thermal transfer of the present invention comprises an image-receiving layer having a dyeing property to a dye sublimated and transferred by heat on a support to form an image-receiving sheet for thermal transfer.
As the binder resin having a dye-dyeing property that constitutes the image-receiving layer, any binder resin having a strong interaction with the dye and capable of stably diffusing the dye into the resin can be preferably used.

For example, those having an ester bond include polyester resin, polyacrylic ester resin,
Polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin and the like; polyurethane resin having a urethane bond; polyamide resin (nylon) having an amide bond; urea resin having a urea bond Further, as the other one having a high polarity bond, polycaprolactone resin, polystyrene resin, polyvinyl chloride, polyacrylonitrile resin, etc. can be used, or at least one of the constitutional units of the above resins is the main component. And a copolymer, for example,
It can also be used as a vinyl chloride-vinyl acetate copolymer, a styrene-butadiene copolymer, and the like, and the above resins can be used alone or in combination of two or more.

Further, the above resin is dissolved or emulsified and dispersed in an organic solvent or water and used as an emulsion, such as a gravure coater, a roll coater, a rod coater, a die coater, a curtain coater, a blade coater, an air knife coater, a slide hopper. Can be applied on the intermediate layer. The dry coating amount of the image receiving layer is 0.
It is preferably in the range of 5 to 15 g / m ² . Further, if necessary, the intermediate layer may be subjected to an easy-adhesion treatment to improve the adhesiveness to the image receiving layer.

As a method of making the intermediate layer easy to adhere, a method of modifying the intermediate layer by corona treatment, plasma treatment or the like, or a method of applying a resin having good adhesiveness to both the intermediate layer and the image receiving layer, etc. There is. As such a resin, any resin having good adhesiveness to both layers can be preferably used, but, for example, acrylic resin, vinyl chloride resin, vinyl acetate resin, urethane resin, styrene butadiene resin, Or the copolymer etc. can be illustrated.

In the present invention, a releasing agent may be added to the image receiving layer for the purpose of preventing blocking. Specific examples of the release agent include waxes such as higher fatty acid or ester thereof, amide or metal salt thereof, shellac wax, montan wax, carnauba wax, polyethylene wax and Teflon powder; fluorine-based,
Phosphate ester type surfactants; silicone oil and the like can be mentioned. Further, as the silicone oil, modified silicone oil such as amino-modified silicone, epoxy-modified silicone, alkyd-modified silicone, polyester-modified silicone and the like are also used. If necessary, a curable silicone compound can also be used as the silicone compound. Examples of the curable silicone compound include a reaction curable type, an ionizing radiation curable type, and a catalyst curable type.

Further, if necessary, additives such as dyes, pigments, wetting agents, defoaming agents, dispersants, antistatic agents, optical brighteners, ultraviolet absorbers and light stabilizers are added to the image receiving layer. It can also be contained. Especially for pigments, silica, alumina, titanium oxide, calcium carbonate, kaolin, clay,
Inorganic particles typified by zinc oxide and barium sulfate can also be added.

Further, a backing layer containing an inorganic fine powder is provided on the side of the support opposite to the image receiving layer in order to provide roll slipperiness during transfer and writing on the back side, and for the purpose of preventing static charge. Then, an antistatic agent can be added to the backing layer.
When an adhesive resin is mixed in the backing layer, it is also possible to mix the adhesive resin and an antistatic agent to cause bleeding on the resin surface, and as a result, to provide it on the resin layer. Antistatic agents include surfactants such as cationic surfactants (quaternary ammonium salts, polyamine derivatives, etc.), anionic surfactants (alkyl phosphates, etc.), zwitterionic surfactants or nonionics. Type surfactants and the like.

[0032]

The present invention relates to an image-receiving sheet for thermal transfer comprising an image-receiving layer for receiving a dye which is transferred by sublimation from a thermal transfer medium upon heating on a support made of pulp paper. By using the above, the thermal contraction at the time of thermal transfer is suppressed, and a plain paper-like image-receiving sheet for thermal transfer that does not cause color misregistration is obtained.

[0033]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the contents of the present invention are not limited to these. In addition, "parts" shown in the examples indicate parts by weight.

Example 1 Freeness of 300 mlcsf with a double disc refiner
Anionic polyacrylamide (Stargum A15, manufactured by Seikou Kagaku KK) was added to 100 parts of a mixed pulp having a weight ratio of 7: 3 of LBKP beaten up to 400 mlcsf and NBSP beaten up to 400 mlcsf (α-cellulose content 98%). .3 parts, 2.0 parts of cationic starch (Kate F, manufactured by Oji National Co., Ltd.), and alkyl ketene dimer size agent (Harcon 11-2, manufactured by Dick-Hercules).
Of 0.4% and 0.3 parts of polyamide-polyamine-epichlorohydrin resin (Kaymen S25, manufactured by Dick-Hercules) was used, and a paper making speed of 100 m /
Pulp paper having a basis weight of 110 g / m ² was produced on a fourdrinier paper machine.

At this time, the jet / wire ratio was 1.03, the moisture content at the dryer inlet was 53%, the speed difference between the press and the dryer was 1.0 m / min, and there was no open draw for drying. I went with a single tier dryer. The dried paper was subjected to a tab size treatment with a polyvinyl alcohol aqueous solution having a concentration of 3%, dried, and then smoothed with a super calendar so that the Beck smoothness was 300 seconds or more.

On the obtained pulp paper, an image receiving layer coating solution having the following composition was prepared and coated with an air knife coater so that the dry coating amount was 7 g / m ² . The thermal transfer image-receiving sheet thus obtained was used as the thermal transfer image-receiving sheet of Example 1.

[Preparation of coating liquid for image-receiving layer] Polyester emulsion (Vylonal MD-1220: Toyobo) 60 parts Polyerylene emulsion (Hydrin G-314: Chukyo Yushi) 15 parts Colloidal silica as inorganic fine particles (Snowtex O: Nissan Chemical Co., Ltd.) ) 25 parts Surfactant 5 parts

Example 2 In Example 1, the jet ratio was 1.00, the drying was an ordinary multi-cylinder dryer, the draw between the press and the dryer was 0.5 m / min, and the tension of the dryer canvas was 1.
An image receiving sheet for thermal transfer of Example 2 was manufactured by the same method except that the amount was 7 kg / cm.

Example 3 The same method as in Example 2 was repeated except that the pressurization of the press was increased to lower the moisture content at the dryer inlet to 51% and the tension of the dryer canvas was set to 1.5 kg / cm. An image-receiving sheet for thermal transfer of Example 3 was manufactured.

Comparative Examples 1 and 2 A thermal transfer image-receiving sheet was produced in the same manner as in Example 1, except that the drying was performed by a multi-cylinder dryer or a heating mirror surface dryer (Yankee dryer). These samples were used as the thermal transfer image-receiving sheets of Comparative Examples 1 and 2, respectively.

Comparative Example 3 Comparative Example 3 was repeated except that the freeness of LBKP was 250 mlcsf by viscous beating with a deluxe finer and the tension of the dryer canvas was 1.4 kg / cm. An image-receiving sheet for thermal transfer was manufactured.

Comparative Example 4 An image receiving sheet for thermal transfer of Comparative Example 4 was produced in the same manner as in Example 3, except that the jet ratio was 1.10 and the draw between the press and the dryer was 1.3 m / min. .

[Evaluation Method] The image-receiving sheet for thermal transfer thus obtained was allowed to stand at 45 ° C. for 3 days, and then a 4-color ink donor sheet (SU3-11C4H, manufactured by Mitsubishi Electric Corp.) was used.
A full-color image was printed with a sublimation thermal transfer printer (S3600-30, manufactured by Mitsubishi Electric). The four corners of the obtained image were observed with a magnifying glass, and the color shift was evaluated by visual evaluation.
Four-level evaluation was carried out, with A showing no color shift at all, B showing almost no color shift, C showing a slight color shift, and D showing a slight color shift. . As a thermal transfer image-receiving sheet which has no practical problem as a photographic image, B or more (A, B) is required.

With respect to the thermal transfer image-receiving sheets produced in Examples and Comparative Examples, the heat shrinkage ratio product and the heat shrinkage ratio, calculated from the heat shrinkage measurement results of the support pulp paper in the machine direction and the cross machine direction, The evaluation results of color misalignment evaluated according to the above evaluation method are shown in Table 1 below.

[0045]

[Table 1]

From the comparison between Example 1 and Comparative Examples 1 and 2, when a single tier dryer was used as a dryer for drying pulp paper, a pulp paper having a particularly small heat shrinkage product and heat shrinkage ratio was obtained, It is clear that an excellent image receiving sheet for thermal transfer can be produced without color shift. The pulp paper dried with the Yankee dryer of Comparative Example 2 was also inferior in curl resistance.

From the comparison between Examples 2 and 3 and Comparative Examples 1, 3 and 4, even when the pulp paper is dried by the usual multi-cylinder dryer, the papermaking conditions are adjusted and the heat shrinkage ratio product is 0.
It is clear that an excellent thermal transfer image-receiving sheet free from color misregistration can be produced by using pulp paper that simultaneously satisfies the conditions of 20 or less and the heat shrinkage ratio of 2.3 or less.

[0048]

From the above, the product of the heat shrinkage ratio (RMD) in the machine direction and the heat shrinkage ratio (RCD) in the cross machine direction of the thermal transfer image-receiving sheet of the present invention, that is, the pulp paper as the support, is 0. An image-receiving sheet for thermal transfer using pulp paper having a ratio of heat shrinkage in the cross machine direction to the machine direction (RCD / RMD) of 2.3 or less is 2.3 or less, and is an excellent plain paper sheet without color shift. It is clear that this is a thermal transfer image-receiving sheet.

Claims (1)

[Claims] 1. A thermal transfer image-receiving sheet in which an image-receiving layer for receiving a dye that migrates by sublimation from a thermal transfer medium when heated is provided on a support made of pulp paper mainly composed of wood pulp, which is the support. Machine direction heat shrinkage (RMD) and cross machine direction heat shrinkage (RCD) of pulp paper
Is 0.20 or less, and the ratio of the heat shrinkage ratio in the cross machine direction to the machine direction (RCD / RMD) is 2.3.
An image receiving sheet for thermal transfer, characterized in that: