JP2000103177A - Ink image receiving sheet for molten thermal transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an ink image receiving sheet for the melt thermal transfer in which unevenness in gray level of highlight section is scarce, a high recording density can be obtained and the gradation reproductivity and dot reproductivity are superior in the case a thermal head is brought into contact with the image receiving sheet through a transfer ink-ribbon and the sheet is used for a printer of large contact pressure. SOLUTION: An ink image receiving sheet is provided with a sheet-shaped substrate and a porous ink acceptive layer formed of a resin-containing liquid composed mainly of water dispersive resin at least on one face of the sheet- shaped substrate, and the average pore diameter on the surface of the porous ink acceptive layer is 0.5-30 μm, and the uneven thickness of the sheet-shaped substrate is measured continuously by a thickness gause for a film, when its measurement signal is obtained by a frequency analyser, the integral value (PY value) of power spectrum at the 1-12.5 mm wavelength is 10 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink image receiving sheet for fusing thermal transfer. More specifically, the present invention is applied to a printer for fusion heat transfer using a thermal head, particularly when the thermal head and the image receiving sheet are in contact with each other via the transfer ink ribbon, and the contact pressure is large. The present invention relates to an ink receiving sheet for a fusion heat transfer, which has less uneven shading in a highlight portion, obtains a high recording density, and has excellent tone reproducibility and dot reproducibility.

[0002]

2. Description of the Related Art A fusion heat transfer recording method using an ink image-receiving sheet for fusion heat transfer and a thermal head is widely used in word processor printers and label printers because of its simple mechanism and easy maintenance. High quality paper has been mainly used as the image receiving sheet for the system. However, in recent years, ink jet recording, sublimation type thermal transfer recording,
High-quality full-color images have been strongly desired in various recording methods such as a laser recording method.

[0003] In the fusion thermal transfer recording system, various devices have been devised in order to cope with full color printing.
Speaking of printers, from the method of obtaining gradation without changing the size of one dot, which has been frequently used,
A printer adopting a variable dot system (so-called variable dot system) for changing the size of each dot has been developed. For example, a G6800-40 type printer (trade name) manufactured by Mitsubishi Electric Corporation corresponds to this system. In addition, in full-color recording from low applied energy to high applied energy, the ink receiving sheet for melt thermal transfer has excellent dot reproducibility, which allows the dot shape of the melt-transferred ink to be faithfully reproduced, and transfers a sufficient amount of ink. Therefore, high recording density is required as an important quality of a recorded image.

[0004] In view of the above background, it is necessary to appropriately respond to the characteristics of the ink receiving sheet for fusing thermal transfer. For example, if a normal printing uncoated paper is used for a variable dot printer, the recording density may be reduced due to low heat insulation and the dot reproducibility may be poor due to insufficient cushioning. May be. On the other hand, if the surface is too rough, a phenomenon that causes a portion where the ink is not transferred, that is, a drop is likely to occur. Any of these causes a poor dot reproducibility.
In addition to the decrease in recording density due to the poor dot reproducibility as described above, a decrease in recording density due to low ink absorbency of the molten ink receiving layer may occur.

As an attempt to solve these problems, it has been proposed to provide an undercoat layer containing hollow particles on a sheet-like support (JP-A-2-89690, JP-A-64-27996). Gazette). However, this attempt is still insufficient in improving the cushioning property and the heat insulating property of the ink image receiving sheet for fusion thermal transfer. In addition, in this attempt, when the hollow particles are dissolved in an organic solvent or the like of the receiving layer, a polymer material having organic solvent resistance is used as an adhesive for the hollow particles, or on the layer containing the hollow particles. It is necessary to provide an organic solvent-resistant polymer layer on the substrate, which poses a manufacturing problem.

As another attempt to solve the above-mentioned problem, a resin layer containing components eluted in water is formed on a sheet-like support mainly composed of plastic, and a water-soluble component is formed from the resin layer. To elute and form micropores,
It has also been proposed to improve the ink receiving capacity of the image receiving sheet for fusion thermal transfer by using the method (Japanese Patent Laid-Open No. 2-412).
No. 87). However, in this case, the maximum density is still insufficient, or there is a drawback such as lack of gloss in the recorded image, and the quality required for the ink receiving sheet for fusion thermal transfer has not been satisfied. In addition, since the ink receiving sheet for fusion heat transfer is mainly composed of plastic,
Recycling is also difficult.

On the other hand, by changing the size of the dot as in the prior art,
Printers that do not use the
The contact pressure between the thermal head and the recording paper surface
The transfer of dots onto the recording paper surface
To ensure good dot reproducibility, gradation reproducibility,
Some of them try to meet the demands such as recording density. For example,
Alp, which is called a micro dry printer
MD-1000 (trade name), MD-1300 manufactured by SUDENKI
(Product name), MD-2000J (Product name) Printer, etc.
Corresponds to this method. This method is also used for dot transfer.
Contact pressure between the ink ribbon and the surface of the recording paper
The printer adopting the above variable dot method
Unlike the melt transfer type ink image receiving sheet for
High-quality recorded images without much need for insulation or heat insulation
It is said that there is an advantage that an image can be obtained. This method
The contact pressure of the thermal head is approximately several tens kg / c.
m ^TwoVariable, but the variable
Several kg / cm for dot-type printer^TwoAnd low
It is estimated to be. However, the contact between the ink ribbon and the surface of the recording paper
When images are recorded with a printer with a high tactile pressure,
Due to uneven thickness of the sheet-shaped support, the ink ribbon
The adhesion of the layer may not be uniform,
The image quality may be different or deformed,
However, there is a problem that the image quality decreases and a good recorded image cannot be obtained.
In the future, even though the variable dot method will be used,
Thermal head and fusion transfer type image receiving sheet
High contact pressure, which combines the advantages of both
Melt transfer printer that can produce high-quality full-color images
Could be developed.

As the image receiving sheet for a printer in which the contact pressure of the thermal head is high, a high quality paper or a dedicated sheet obtained by coating a molten ink receiving layer containing a pigment on a paper-based support is used. Since the transferability of the molten ink from the low density portion to the halftone recording portion is not always sufficient, there is also a problem that it has not been able to respond to the market demand for high image quality.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the drawbacks of the prior art and, in a printer for fusion heat transfer using a thermal head, in particular, the thermal head and the image receiving sheet come into contact via a transfer ink ribbon. When used in a printer with a large contact pressure, the ink receiving sheet for fusion thermal transfer has less uneven shading in the highlight area, high recording density, and excellent tone reproducibility and dot reproducibility. It is intended to provide.

[0010]

Means for Solving the Problems An ink-receiving sheet for fusion thermal transfer according to the present invention comprises a sheet-like support and a porous sheet formed on at least one surface thereof from a resin-containing liquid containing a water-dispersible resin as a main component. A porous ink receiving layer, wherein the average pore diameter of the surface of the porous ink receiving layer is 0.5 to 30.
μm, and the thickness unevenness of the sheet-like support is continuously measured by a film thickness gauge, and a measurement signal obtained by analyzing the measurement signal with a frequency analyzer is obtained. The integrated value (PY value) of the power spectrum at a wavelength of 1 to 12.5 mm is 10 μm or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to achieve the above object, and as a result, in recording with a printer for fusion heat transfer, unevenness of highlights has been reduced by optimizing a sheet-like support. They have found that they can be improved and have completed the present invention. That is, in order to obtain an ink image receiving sheet for melt thermal transfer having a good surface smoothness,
It is effective to use a sheet-like support having a specific surface smoothness. In this case, the surface of the sheet-like support has an integral (PY value) of a power spectrum at a wavelength of 1 to 12.5 mm of 10 μm. Hereinafter, the present inventors have found that it is necessary to use those having a diameter of preferably 5 μm or less, and have completed the present invention.

The porous ink receiving layer according to the present invention has a high flexibility due to its structure, and provides good adhesion between the ink ribbon and the receiving layer at the time of recording with a fusion heat transfer type printer. Excellent in nature. However, a printer for fusion heat transfer (MD-1 manufactured by Alps Electric Co., Ltd.) in which the contact pressure of the thermal head is several tens kg / cm ^2.
000, MD-1300, MD-2000J, etc. (all are trade names), the receiving layer may be crushed during recording. At this time, when a sheet-like support having a surface with a large thickness unevenness with a PY value exceeding 10 μm is used, the degree of adhesion between the ink ribbon and the receiving layer may not be uniform due to the uneven thickness of the sheet-like support. In some cases, the sizes of the dots may be different or deformed, and the image quality may deteriorate, and an excellent recorded image may not be obtained.

The PY value on the surface of the sheet-shaped support is a root mean square value of input signal values in a designated wavelength region, that is, 1 to 12.5 mm. In order to measure the PY value, the thickness unevenness of the sheet-shaped support is continuously measured using a film thickness gauge (for example, a paper thickness gauge manufactured by Anritsu Co., Ltd.), and the obtained measurement signal value is measured. And a frequency analyzer (for example, a product of Ono Sokki Co., Ltd., trademark: CF-940). In this case, the PY value is the voltage (Vrms)
Since this value is expressed as a value, it can be converted into the depth of peak-to-valley, which is uneven thickness, by multiplying this voltage value by 28.8 μm / V.

Examples of the sheet-like support used in the present invention include papers such as paper containing pulp as a main component, coated paper, laminated paper, and the like, plastic films such as polyolefin, methacrylate, cellulose acetate, and the like. And porous synthetic resin films such as foamed polyethylene terephthalate film, foamed polypropylene film and the like, which are made of synthetic paper made of styrene and pigment. These sheet-like supports are less susceptible to shrinkage and expansion due to temperature changes than papers and, unlike papers, are isotropic materials, so that they do not easily cause curling and twisting. However, unlike paper having pulp as a main component as a sheet-like support, it is generally not recyclable.

The pulp used in the present invention is a virgin chemical pulp (CP: hardwood bleached kraft pulp,
Softwood bleached kraft pulp, hardwood unbleached kraft pulp,
Softwood unbleached kraft pulp, hardwood bleached sulfite pulp, softwood bleached sulfite pulp, hardwood unbleached sulfite pulp, softwood unbleached sulfite pulp, etc. Mechanical pulp (MP: pulp prepared by mechanically treating wood and other fiber materials, such as ground pulp, chemical ground pulp, chemimechanical pulp, and semi-chemical pulp) may be contained. Waste paper pulp, fine paper, fine coated paper, medium paper that has been dissociated from unprinted waste paper such as top white, special white, medium white, etc., which is generated in bookbinding, printing plants, cutting mills, etc. High quality paper, medium quality coated paper,
Pulp deinked after disintegrating used paper, newspaper used paper, etc. printed on flat paper, letterpress, intaglio printing, electrophotographic method, thermal method, thermal transfer method, pressure-sensitive recording method, ink jet recording method, carbon paper, etc. (Hereinafter abbreviated as DIP)
Etc. can also be used. Further, pulp treated with non-wood such as bacas, kenaf, bamboo, rice straw and the like can also be used.

Fillers which can be used in the pulp-based sheet-like support of the present invention include calcium carbonate such as heavy calcium carbonate, light calcium carbonate, chalk, clay, calcined clay, pyrophyllite, and cellulite. Inorganic fillers such as silicates such as cite and talc, and organic pigments such as urea resin can be used, but are not limited thereto.

When a coating layer is formed on a sheet-like support containing pulp as a main component and used as the sheet-like support of the present invention, various kinds of pigments used in ordinary general coated paper, For example, calcium carbonates such as heavy calcium carbonate and light calcium carbonate, clays, calcined clays, silicic acids such as pyrophyllite, sericite, talc, etc., inorganic fillers, and organic pigments such as urea resin alone or in combination of two or more kinds Can be used.

When the adhesive is used after coating, a water-soluble adhesive, an emulsion, a latex, or the like, which has a strong adhesive force to a base material or an additive such as a pigment and has a low blocking property, is used alone or as a mixture. Can be used. For example, acrylic polymers, conjugated diene polymers, vinyl polymers, urethane polymers, and derivatives thereof, such as polyacrylates, polymethacrylates, styrene-butadiene copolymers (SBR latex ), Acrylonitrile-butadiene copolymer (NBR)
Latex), methyl methacrylate-butadiene copolymer (MBR latex), styrene-acrylate copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene-acryl Water-dispersible resins such as copolymers, polyvinylidene chloride, polyurethane, urethane-acrylic copolymers, and polyvinyl alcohols having various molecular weights and degrees of saponification and derivatives thereof, starch and derivatives thereof (starch oxide, cation Various modified starches such as modified starch), cellulose and its derivatives (methoxycellulose, carboxymethylcellulose, methylcellulose, ethylcellulose and the like), and water-soluble resins such as polyethylene glycol, but are not limited thereto. Not.

As the coating method, for example, an on-machine coater provided with a coating device such as gate roll coating, size press coating, blade coating, air knife coating, roll coating, bar coating, reverse coating, etc. Any of off-machine coaters such as roll coating, gravure coating, and curtain coating can be employed.

The internal sizing agent used in the present invention includes:
A sizing agent such as a rosin sizing agent, a synthetic sizing agent, a petroleum resin sizing agent, a neutral sizing agent can be used, and an appropriate sizing agent such as a sulfate band and a cationized starch is combined with a fixing agent for fibers. Can be used.

In the present invention, the porous ink-receiving layer formed on the sheet-shaped support contains a water-dispersible resin or a water-dispersible resin and a pigment as main components. Such a porous ink receiving layer includes a water-dispersed resin,
Apply mechanical stirring to the liquid material containing the pigment as necessary,
A large number of fine air bubbles can be formed, dispersed and contained therein, and the air-containing resin liquid can be applied to a sheet-like support and dried to form the resin.

In the present invention, the term “water-dispersible resin” used for forming the porous ink-receiving layer refers to an interface containing a hydrophilic functional group in the skeleton of the molecular chain or an interface such as an emulsifier added during synthesis. Polymers or oligomers such as aqueous emulsions and colloidal dispersions (microemulsions) that are stably dispersed in water as a medium by the effect of the activator. As the water-dispersible resin usable in the present invention,
For example, polyurethane resin, urethane-acrylic copolymer, styrene-butadiene copolymer (SBR latex), acrylonitrile-butadiene copolymer (NBR)
Latex), methyl methacrylate-butadiene copolymer (MBR latex), styrene-acryl copolymer, polyacrylate, polymethacrylate, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate Examples include, but are not limited to, copolymers, polyvinylidene chloride, and the like. These water-dispersed resins can be used alone or as a mixture of two or more, if necessary.

The above-mentioned water-dispersible resin and various known aqueous resins can be mixed and used in accordance with the required level of recording performance or the suitability of the printer. That is,
One or more aqueous resins as exemplified below can be used in combination with the water-dispersible resin. As an aqueous resin,
For example, polyvinyl alcohols and derivatives thereof of various molecular weights and degrees of saponification, various modified starches such as starch or oxidized starch, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, and water-soluble such as polyethylene glycol Resin, even glue,
Casein, soy protein, gelatin, sodium alginate and the like can be used, but are not limited thereto.

In the present invention, examples of the pigment which can be contained in the porous ink receiving layer include zinc oxide, titanium oxide, calcium carbonate, silicic acid, silicate, clay, talc, mica, calcined clay, and aluminum hydroxide. Inorganic pigments such as barium sulfate, lithopone, colloidal silica, etc., processed into various shapes and structures such as polystyrene, polyethylene, polypropylene, epoxy resin, styrene-acrylic copolymer, etc. In the type of plastic pigment, or plastic pigment having a hollow structure,
Organic pigments, such as so-called heat-expandable particles, and starch powder, cellulose powder, and the like, which contain a gas that expands by heating in the hollow portion and thereby expands the plastic pigment itself, but are not limited thereto. Not something. Among them, fine silica, colloidal silica, and the like are preferable because the effect of suppressing the blocking of the porous ink receiving layer can be obtained with a small amount of use. These pigments can be used alone or as a mixture of two or more, if necessary.

The porous ink receiving layer in the present invention, as inferred from the structure thereof, is not inherently strong in coating film strength. Therefore, when various pigments are blended, the coating film strength is further reduced. This may cause troubles such as peeling of the transfer ink image. Therefore, when the porous ink receiving layer is formed by adding various pigments to the water-dispersed resin-containing liquid, the compounding amount may be appropriately adjusted in consideration of the overall quality of the ink image receiving sheet for fusion thermal transfer. You just have to decide.

If necessary, a known viscosity modifier, dispersant, dye, water-proofing agent, lubricant, plasticizer and the like are added to the liquid containing the resin or the mixture of the resin and the pigment before the formation of the bubbles. be able to.

The coating amount of the porous ink receiving layer formed on at least one surface of the sheet-like support is 2 g / m ^2.
It is preferable that it is above. There is no particular upper limit on the amount of coating. In general, a foam-containing liquid having a low expansion ratio (volume after foaming with respect to the volume of the resin-containing stock solution before foaming) is low.
When the same coating amount is obtained as compared with the bubble-containing liquid having a high expansion ratio, the volume of the coating material is small, so that it becomes difficult to cover the surface of the sheet-like support. When the coating amount is less than 2 g / m ² , it may be difficult to sufficiently coat the surface of the sheet-like support, and the ink-receiving sheet for fusion thermal transfer on the surface having appropriate smoothness may not be obtained. May not be obtained. On the other hand, the upper limit of the coating amount is not particularly limited. However, if the thickness of the porous ink receiving layer is too large, it may be economically disadvantageous, and may be appropriately selected according to the required performance.

The mechanism of developing the excellent ink transfer characteristics of the ink receiving sheet for heat transfer in the present invention is as follows.
It is considered that physical characteristics such as structural characteristics and compression characteristics of the porous ink receiving layer and the ink image-receiving sheet for fusion thermal transfer are involved. In terms of structural characteristics, the surface of the porous ink receiving layer formed on the sheet-like support has a large number of fine pores, so that there is absorption of molten ink by capillary force, Since a large number of pores contained in the ink receiving layer communicate with each other to form open cells, the permeability of the molten ink into the porous ink receiving layer is improved, and the ink receiving capacity is high. Is considered to be expressed.

In this regard, the size of the pores on the surface of the porous ink receiving layer formed on the ink receiving sheet for fusion thermal transfer is related to the ink receiving ability. That is, when the molten ink is transferred, in order to form a good image on the ink-receiving sheet for fusion thermal transfer of the present invention, the average pore diameter of the surface of the porous ink receiving layer is in the range of 0.5 to 30 μm. And more preferably 1.0 to 20
μm, more preferably 1.0 to 5.0 μm.
m.

The pore diameter on the surface of the porous ink receiving layer is related to the ability to capture the molten ink by capillary action due to its size, and the smaller the pores, the greater the ability. However, when the average pore diameter is less than 0.5 μm, the ink absorbing ability is poor, and transfer failure may occur. On the other hand, when the average pore diameter is larger than 30 μm and the pore size is too large, the desired recording image density may not be obtained because the transfer ink is buried in the pores.
The pore diameter on the surface of the porous ink receiving layer can be measured using an optical microscope or a scanning electron microscope and an image analyzer.

In the present invention, as a device for forming, containing and dispersing air bubbles in a water-dispersed resin-containing liquid, for example, a confectionery foaming machine having a stirring blade rotating while carrying out planetary motion, generally used in emulsification dispersion and the like is used. A batch type stirrer such as a homomixer and a Cowles dissolver may be used. When performing continuous production on an industrial scale, mechanical stirring is performed while continuously feeding a mixture of air and a resin-containing liquid into a closed system, and air can be dispersed and mixed into fine bubbles. The device is preferred. For example, a multi-cylinder continuous foaming machine with a slit from Gaston County of the United States of America (a rotor having a cylindrical and a slit similar to the stator on the side is provided in the gap between the cylindrical multi-layered stator with a slit on the side. Fitting, rotating the rotor at a high speed, feeding the resin-containing liquid and air, and stirring and stirring the resin liquid and air when passing through the slit, thereby dispersing and mixing air in the resin-containing liquid), Double cylindrical continuous foaming machine made by Aikosha Seisakusho in Japan, Stoke in the Netherlands, etc. (consisting of a rotor with pins and an outer tube with pins, containing the resin fed into the cylinder by rotating the rotor at high speed A type in which air is dispersed and mixed in a resin-containing liquid by stirring the liquid and air can be used, and any of these devices is effective in producing a bubble-containing resin liquid. There is no problem at all Te, not particularly strict restrictions when equipment selection.

In the above-mentioned various foaming machines, as a method of adjusting the size of the bubbles dispersed in the bubble-containing resin liquid, in the case of a batch type stirring device, the composition and properties of the resin-containing liquid (surfactant) The point is to select the addition rate and type of the resin, the viscosity of the resin mixture, the rotation speed, the rotation continuation time, and the like. The expansion ratio can also be adjusted substantially by the above factors. On the other hand, in the case of a continuous foaming machine, the composition, properties, rotation speed, and residence time of the resin-containing liquid and air in the apparatus (stirring rate, stirring rate, type, viscosity of the resin mixture, etc.) The size of the bubble can be adjusted by (time) or the like. For example, when stirring at the same rotation speed, and when the ratio between the amount of the resin-containing liquid and the amount of air to be sent to the device is constant, the bubbles are smaller as the total amount of feed is smaller and the stirring time in the device is longer. Tend to be. The expansion ratio can be adjusted by selecting the ratio between the amount of the resin-containing liquid and the amount of air to be fed into the apparatus.

The size of the pores on the surface of the porous ink receiving layer depends on the formation of bubbles, the composition of the water-dispersed resin mixture before the dispersion treatment, that is, the type and blending ratio of the materials, and the process from coating to drying. In the amount of solids remaining as a component directly related to the thickness of the film in the porous ink receiving layer,
Alternatively, it is often affected by various factors such as the expansion ratio and the coating method. The size of the pores on the surface of the porous ink receiving layer in the present invention is also related to the size of the bubbles in the bubble-containing resin liquid obtained by mechanical stirring. Since the pores on the surface of the porous ink receiving layer after processing and drying become smaller,
The bubble-containing state of the water-dispersed resin-containing mixture is not particularly limited, but the size of the bubbles is the same as that of the surface of the porous ink receiving layer, that is, the average diameter is 0.5 to 30 μm.
m are preferably dispersed and mixed.
More preferably, the average diameter is 1.0 to 20 μm, and even more preferably, the average diameter is 1.0 to 5.0 μm.
The size of the contained bubbles can be measured with an image analyzer by photographing a part of the bubble-containing resin liquid with an optical microscope.

In the formation of the bubble-containing resin liquid, the equipment for mechanical stirring is insufficient, so that the desired bubble-containing state cannot be obtained, or the stability of the bubbles in the bubble-containing resin liquid is low. For the purpose of improving the surfactant, it can be appropriately selected and blended from a wide range of surfactants called foam stabilizers and foaming agents. As such surfactants, higher fatty acids, modified higher fatty acids, and alkali salts of higher fatty acids (for example, higher fatty acid ammonium salts) have the effect of enhancing the foaming properties of the resin-containing liquid, and the bubbles dispersed and contained. Can be used because of its high effect of improving the stability. There is no particular limitation on the selection, but it is preferable to select one that does not hinder the fluidity of the resin-containing mixed liquid or impair coating workability. The amount of the surfactant, such as the foam stabilizer and the foaming agent, is 0 to 30% by weight of the solid content of the surfactant based on 100 parts by weight of the solid content of the resin solution or the mixed solution of the resin solution and the pigment. Parts by weight, more preferably 1 to 20 parts by weight. Even if the amount of the surfactant added exceeds 30 parts by weight, the effect is saturated and the cost may be disadvantageous.

The coating method for forming the porous ink receiving layer on at least one surface of the sheet-like support includes a Meyer bar method, a gravure roll method, a knife method, a reverse roll method, a blade method, and an extrusion method. Method, gate roll method, 2 roll size press method,
Any known method such as a casting method can be selected.

Further, on one surface of the sheet-like support,
Coating the above-mentioned bubble-containing mixed solution, when drying to produce an image receiving sheet for a printer for fusion heat transfer of the present invention, coating,
In steps such as drying and winding, the image receiving sheet itself may curl with the porous ink receiving layer inside or outside. In this case, if the image receiving sheet is used after being processed into an image receiving sheet of a predetermined size by cutting, not only the appearance is not good, but also the paper feeding to the printer is not performed normally or the inside of the printer such as a paper jam is caused. In some cases, troubles such as poor running performance may occur.

In order to prevent various troubles caused by such curling, a curling preventing layer may be applied or laminated on the back surface of the sheet, that is, on the surface opposite to the porous ink receiving layer. The material, forming method, coating amount, and laminating amount of the curl prevention layer are not particularly limited, but the type and thickness of the sheet-like support, or the properties of the porous ink receiving layer, that is, the material composition, expansion ratio, coating Optimization can be achieved in consideration of various factors such as the amount of work.

On the other hand, forming a porous ink-receiving layer on both sides of a sheet-like support under the same conditions of material composition, expansion ratio, coating amount, etc. is very advantageous from the viewpoint of curl control. become. In addition, since a good recorded image can be formed on both sides of one image receiving sheet, there is an advantage that it can be used for various purposes and has a great economic effect.

[0039]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. In the examples and comparative examples, "parts" means "parts by solid weight" with respect to the solid content of the resin unless otherwise specified.

Example 1 An aqueous resin mixture having the following composition (solid content: 3
1%) to a continuous foaming machine (trade name: Turbo Whip TW-7)
0, manufactured by Aikosha Manufacturing Co., Ltd.)
The mixture was mixed with air at pm and stirred to perform a foaming treatment so that the foaming ratio became 3.0 times.

Aqueous resin mixture liquid Resin: 100 parts of water-dispersed polyurethane resin (trade name: Adekabon Titer HUX-381, manufactured by Asahi Denka Kogyo KK) Foam stabilizer: higher fatty acid ammonium salt type 5 parts (trade name: Boncoat F) -1, Dainippon Ink and Chemicals, Inc.) Thickener: carboxymethylcellulose 3 parts (trade name: AG gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

After foaming the above bubble-containing resin mixture,
Immediately, a paper support having a PY value of 2.8 μm (120.0 g / m
² ) The amount of coating after drying with an applicator bar is 10 g
/ M ² and dried. Further, on the opposite side to which the cell-containing resin mixture was applied, a coating for a curl prevention layer (solid content concentration: 5%) having the following composition was dried so that the coating amount after drying was 3 g / m ^2. Coating was performed with a Mayer bar to prepare an ink image-receiving sheet for fusion thermal transfer.

Paint for anti-curl layer Oxidized starch (trade name: Oji Ace C, manufactured by Oji Cornstarch) 100 parts Polyvinyl alcohol (trade name: PVA117, manufactured by Kuraray Co.) 20 parts

Example 2 An aqueous resin mixture having the following composition (solid content: 3
1%) was subjected to the same foaming treatment as in Example 1, and as a support, commercially available high-quality paper (trade name: Marshmallow, 104.7 g)
/ M ² , PY value 7.5 μm, manufactured by Oji Paper Co., Ltd.), and an ink receiving sheet for fusion thermal transfer was produced in the same manner as in Example 1.

Aqueous resin mixture liquid Resin: 100 parts of water-dispersed polyurethane resin (trade name: Adekabon Titer HUX-381, manufactured by Asahi Denka Kogyo KK) Foam stabilizer: higher fatty acid ammonium salt-based 5 parts (trade name: Boncoat F) -1, Dainippon Ink and Chemicals, Inc.) Thickener: carboxymethylcellulose 3 parts (trade name: AG gum, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Pigment: clay (trade name: HT clay, manufactured by Ryosan Shoji Co., Ltd.) 10 copies

Example 3 As a paper support, commercially available synthetic paper (trade name: YUPO FPG11)
0, a PY value of 1.7 μm, manufactured by Oji Yuka Synthetic Paper Co., Ltd.), except that an ink image-receiving sheet for fusion heat transfer was produced in the same manner as in Example 1.

Example 4 An aqueous resin mixture having the same composition as in Example 1 was mixed with the same apparatus as in Example 1 at a stirring speed of 1500 rpm.
Then, the mixture was mixed with air and stirred to perform a foaming treatment so that the foaming ratio became 1.2 times. Immediately after the foaming treatment, the composition was coated on the same paper support as in Example 1 with an applicator bar so that the coating amount after drying was 10 g / m ² . Further, an anti-curl paint (solid content of 5%) having the same composition as in Example 1 was applied to the opposite side to which the above-mentioned bubble-containing resin mixture was applied.
%) Was applied using a Mayer bar so that the coating amount after drying was 4 g / m ² .

Example 5 The same foaming treatment as in Example 1 was performed on an aqueous resin mixture having the same composition as in Example 1. Immediately after the foaming treatment, the same paper support as in Example 1 (PY value: surface 2.8 μm,
On the back surface (2.9 μm), coating was performed with an applicator bar so that the coating amount after drying was 10 g / m ² . further,
The same bubble-containing resin mixture was applied to the back side of the surface coated with the bubble-containing resin mixture so that the coating amount after drying with an applicator bar was 10 g / m ² .

Comparative Example 1 An aqueous resin-containing mixed solution having the same composition as in Example 1 was developed.
Without foaming, the same paper support as in Example 1 was used for application.
Coating amount after drying with a locator bar is 10 g / m ^Twobecome
Coated as follows. Furthermore, the above-mentioned bubble-containing resin mixture is
A car having the same composition as in Example 1 on the coated opposite side
Coating amount after drying the anti-fouling paint (solids concentration 5%)
g / m^TwoCoating with a Mayer bar so that
A transfer ink image-receiving sheet was prepared.

Comparative Example 2 Commercially available high quality paper (trade name: OK Prince,
Except for using 104.7 g / m ² , PY value of 14.0 μm, manufactured by Oji Paper Co., Ltd., an ink image-receiving sheet for fusion thermal transfer was prepared in the same manner as in Example 1.

Comparative Example 3 A commercially available Xerox paper (trade name: R paper (recycled PPC paper), PY value 18.0 μm, manufactured by Fuji Xerox Co., Ltd.) was used as the paper support in the same manner as in Example 1. An ink image-receiving sheet for fusion heat transfer was prepared.

Comparative Example 4 An aqueous resin mixture having the same composition as in Example 1 was stirred at 400 rpm using the same apparatus as in Example 1.
Then, the mixture was mixed with air and stirred to perform a foaming treatment so that the foaming ratio became 3.0 times. Immediately after the foaming treatment, the composition was coated on the same paper support as in Example 1 with an applicator bar so that the coating amount after drying was 10 g / m ² . Further, an anti-curl paint (solid content of 5%) having the same composition as in Example 1 was applied to the opposite side to which the above-mentioned bubble-containing resin mixture was applied.
%) Was dried with a Mayer bar so that the coating amount after drying was 3 g / m ² , and dried to produce an ink image-receiving sheet for fusion thermal transfer.

Measurement and evaluation method (PY value measurement method) A sample was measured at 50 cm (MD direction).
The film was sampled at 5 cm (in the CD direction), the film was measured for thickness unevenness using a thickness gauge (manufactured by Anritsu), and the obtained measurement signal was analyzed using a frequency analyzer (manufactured by Ono Sokki Co., Ltd.). The details of the film thickness gauge and the measurement conditions were as follows. Film feeder (manufactured by Anritsu) Sample feed speed 25 mm / sec Ball 5 mm diameter metal Pressurized 36 g / chip Micrometer: K306C (same as above) Sensitivity range ± 15 μm Recorder: K310B (same as above) Sensitivity range 0.5 V / cm and frequency The analysis equipment and analysis conditions were as follows. Frequency analyzer CF-940 (manufactured by Ono Sokki Co., Ltd.) Input signal DC2V, 1K (16 points) / dual To convert the power spectrum value obtained by this device into the depth of peaks to valleys Calculated by multiplying by 28.8 (μm / V).

Measurement and Evaluation of Ink Receiving Sheet for Melt Thermal Transfer For the ink receiving sheets for melt thermal transfer of Examples 1 to 5 and Comparative Examples 1 to 4, the expansion ratio of the bubble-containing resin mixed liquid and the resulting melt thermal transfer sheet were measured. Various properties of the ink receiving sheet were measured or evaluated by the following methods. The results are shown in Table 1.

(Expansion Ratio) The expansion ratio was determined by dividing the weight of 100 ml of the aqueous resin mixture (stock solution) before the expansion treatment by the weight of 100 ml of the aqueous resin mixture containing bubbles after the expansion treatment.

(Average pore diameter) The pore diameter of the surface of the porous ink receiving layer was determined by depositing a vapor deposition device (trade name: Ion Sputter E-102, After depositing gold using Hitachi Ltd., an optical microscope (trade name: BH-
2. After taking a photograph at a magnification of 470 times using Olympus Corporation, the outline of the pores on the surface is accurately drawn on a transparent film with a black pen or the like, and further, a drum scanner (trade name: The contour information of the pores is optically read by a 2605 type drum scan densitometer, manufactured by Abe Design Co., Ltd., and measured using an image analyzer (trade name: Luzex III, manufactured by Nireco Co.). The value was determined and defined as the average pore diameter. The area to be measured was 0.06 mm ² (200 μm ×
300 μm). The shape of the pores formed on the porous ink receiving layer surface is not necessarily a perfect circle,
The pore diameter was expressed as a circle equivalent diameter based on the area within the contour of the pore obtained by image analysis.

(Recording Performance) Examples 1 to 5 and Comparative Example 1
4 to 20 ° C., relative humidity 65% for the ink image receiving sheet having a porous ink receiving layer obtained in
And then supply it to a thermal transfer color printer (trade name: MD1000, manufactured by Alps Electric Co., Ltd.), and apply a transparent film to the surface of the image at 1200 dpi resolution after image transfer. In addition, melt transfer recording was performed by setting to a function of imparting gloss to an image by applying heat with a thermal head. The reflection density of the obtained ink transfer image was measured with a Macbeth reflection densitometer and evaluated visually as described below. In the following evaluation criteria, ◎ and ○ have a better level of performance than the conventional technology. Δ and × are not suitable for practical use at a problematic level. (1) C (cyan), M (magenta), Y (yellow)
, The C + M, C + Y, M + Y double color, and C + M + Y triple color have gradation densities of 10 to 100.
% (Solid density portion) to produce a fused transfer recorded image with a gradation pattern of 10 steps, and a Macbeth reflection densitometer R
The reflection density was measured using D-914 (trade name), and C +
The maximum reflection density of the M + Y triple color portion and the gradation reproducibility of each single color portion, each double color portion and each triple color portion were evaluated. The gradation was evaluated in four stages of ◎, △, Δ, and × in order from the one that was reproduced well. (2) The dot reproducibility was evaluated by observing the dots of the ink transferred from the ink ribbon to the receiving layer, and in the order of ◎, △, Δ, and ×, in order from the one that was reproduced well similarly to the gradation reproducibility.
It was evaluated on a scale. (3) Regarding the peeling of the coating layer, the image area after the melt transfer recording was observed, and the presence or absence of white spots in the image accompanying the peeling was evaluated.

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[Table 1]

As is apparent from Table 1, the ink receiving sheet for fusion thermal transfer having the porous ink receiving layer obtained in each of the examples has little unevenness in the density of highlights, recording density, gradation reproducibility, and dots. Excellent reproducibility and various recording performances such as peeling of the coating layer. (Examples 1 to 5)

On the other hand, when the foaming treatment was not performed (Comparative Example 1), the recording density and the performance such as the peeling of the coating layer were not much different from those of the porous ink image receiving sheet of the present invention, but the highlight portion was shaded. Unevenness occurs, and tone reproducibility and dot reproducibility are inferior. Even when the PY value of the support exceeds 10 μm, even in the case of a melt thermal transfer type ink receiving sheet having a porous ink receiving layer, unevenness in density of highlights and gradation reproducibility are inferior (Comparative Examples 2 and 3). . Also, even when the PY value of the support is 10 μm or less, if the average pore diameter on the surface of the receiving layer exceeds 30 μm, a high recording density cannot be obtained, and the density unevenness of the highlight portion and the gradation reproducibility are poor. Inferior. It is presumed that the transfer ink was buried in the pores (Comparative Example 4).

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EFFECT OF THE INVENTION When the ink image-receiving sheet for melt thermal transfer according to the present invention is used in a printer of a thermal melt transfer system in which the contact pressure between the thermal head and the image-receiving sheet is high, the unevenness of the highlight portion is small, and the high recording density Thus, a thermal transfer image recorded matter having excellent tone reproducibility can be obtained, and its practical value is extremely high.

Claims (1)

[Claims] 1. An ink image receiving sheet for fusion thermal transfer comprising a sheet-like support and, on at least one surface thereof, a porous ink receiving layer formed from a resin-containing liquid containing a water-dispersible resin as a main component, The average pore diameter of the surface of the porous ink receiving layer is 0.5 to 30 μm, and the thickness unevenness of the sheet-like support is continuously measured by a film thickness gauge, and the measurement signal is subjected to frequency analysis. When determined by analysis with a machine, the surface of the sheet-like support, wavelength 1 ~
The integrated value of the power spectrum at 12.5 mm (PY
(Value) is 10 μm or less.