JP2000279878A - Continuous production of powder coated sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably provide a powder-coated sheet comprising a powder coating material and having a coating film with a smooth surface and good luster provided on a substrate sheet without coating defects. SOLUTION: In this production method, while being fed in a prescribed direction, a substrate sheet 1 is coated with a powder coating material in dry coating process and led to a first fixing apparatus 9 comprising a first pressurizing roller and a first fixing roller. After being pressurized and heated between the rollers to heat and melt the powder coating material on the substrate sheet, the substrate sheet is further led to a second fixing apparatus 12 comprising a second pressurizing roller and a second fixing roller to pressurize and heat the resultant sheet again and the powder coating material on the substrate sheet is heated, melted and fixed again on the substrate sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a powder-coated sheet, and more particularly to a method for producing a coating film having powder coating, having no coating defects and having a smooth and glossy surface. The present invention relates to a method for continuously producing a powder coated sheet capable of stably obtaining a powder coated sheet provided on the sheet.

[0002]

2. Description of the Related Art In recent years, in order to record information such as characters and images on a base sheet, as a new method, an ink sheet having an image of a sublimable dye is superposed on the image side on an image receiving sheet, and the ink sheet is printed. Various methods have been used, such as a sublimable dye thermal transfer method in which the image is thermally transferred to an image receiving sheet by heating with a thermal head, and a method in which an inkjet ink is caused to fly from a nozzle and adhere to the image receiving sheet. However, conventionally, in such a recording method, a dedicated image receiving sheet provided with an ink receiving layer for receiving the ink on a base sheet is used.

That is, such an image receiving sheet is conventionally manufactured by wet-coating a solution containing a resin, a pigment, a filler and the like on an appropriate base sheet and heating and drying the solution. Such dedicated image receiving sheets are expensive, and recently, for example, Japanese Patent Application Laid-Open No.
As described in Japanese Patent No. 3031, a powder coating is dry-coated on a base sheet by, for example, an electrostatic spray method, melted by heating, and fixed, and is applied on the base sheet as an ink receiving layer. A method of forming a resin coating has been proposed.

According to such a method, an image receiving sheet can be obtained easily and at low cost. However, unevenness of the surface of the base sheet, variation in the particle size of the powder coating used, and unevenness in the thickness of the coating can be obtained. In addition to the above, when foreign matter adheres to the base material sheet, when a powder coating that has been dry-coated on the base material sheet is heated and melted and fixed, a cold offset or hot offset occurs. The powder coating on the sheet is transferred to the fixing roll, and as a result, a minute portion where the coating film has peeled off on the base sheet, that is, a coating film defect occurs. For example, a powder coating is dry-coated on a base sheet having minute foreign substances adhered to the surface, and the base sheet is guided to a fixing device, and when the powder coating is heated and pressed, the foreign substances are fixed together with the powder coating. The film is transferred to a roll, and a coating film defect occurs corresponding to the foreign matter. When the above-described sublimable dye is thermally transferred to an image receiving sheet having such a coating film defect, or the ink jet ink is caused to fly and adhere, and recording is performed, an image referred to as a “white spot” corresponding to the defect is formed. Defects occur.

[0005] Before the dry coating of the powder coating, even if foreign substances do not adhere to the substrate sheet, or if the coating film of the powder coating has remarkable irregularities on the surface, it is subjected to a sublimation type thermal transfer image receiving method. When used as a sheet, it does not adhere to the ink sheet, so that an accurate and clear thermal transfer image is not formed.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a sublimation dye thermal transfer image-receiving sheet or an ink-jet recording image-receiving sheet having a resin coating film as a receiving layer formed on a base sheet using a powder coating. Including, in general, the powder coating is dry-coated on the substrate sheet, heated and melted, is made to solve the above-described problems in the production of the powder coating sheet consisting of fixing, A method for continuously producing a powder coating sheet comprising a powder coating, having no coating defects, and having a smooth and glossy coating film on a substrate sheet. The purpose is to provide.

[0007]

According to the present invention, a powder coating is dry-coated on a base sheet while the base sheet is running in a predetermined direction, and the base sheet is subjected to the first method. It is led to a first fixing device composed of a pressure roller and a first fixing roller, and heated under pressure between the rollers to heat and melt the powder coating material on the base sheet and fix it on the base sheet. The sheet thus obtained is further guided to a second fixing device including a second pressure roller and a second fixing roller, and is again pressurized and heated between the rollers to form a powder on the base sheet. A method for continuously producing a powder coated sheet, characterized in that a coating material is heated and melted and re-fixed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a powder coating contains a resin. As this resin, a resin appropriately selected according to the use and required characteristics of the obtained powder coated sheet is used. In the present invention, for example, a saturated polyester resin, a polyamide resin, a (meth) acrylic resin, Polyurethane resin, polyvinyl alcohol resin, polyvinyl acetal resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride / vinyl acetate copolymer resin, vinylidene chloride resin, polystyrene resin, styrene / acryl copolymer resin, styrene / butadiene copolymer One or more selected from styrene resins such as resins, polyethylene resins, ethylene / vinyl acetate copolymer resins, cellulose resins, epoxy resins and the like are preferably used. However, it is not limited to these.

In the present invention, the powder coating preferably contains a coloring agent. As the colorant, a white colorant is preferably used to give a white ground color to the base sheet. As such a white colorant, for example,
Zinc white, titanium oxide, tin oxide, antimony white, zinc sulfide, barium carbonate, clay, silica, white carbon, talc, alumina, barite, and the like are used, and usually, titanium oxide is preferably used. However, if necessary, a colored colorant can be used to give the base sheet a colored ground color. Such colorants are
In powder coatings, it is usually added in the range of 0.5 to 30% by weight, preferably 5 to 25% by weight.

Further, according to the present invention, the powder coating is dry-coated on the surface of the base sheet, melted by heating, and fixed as necessary so that no offset occurs when fixing. And an anti-offset agent. As the anti-offset agent, usually, various waxes having a melting point in the range of 50 to 150 ° C. are preferably used. Specific examples include paraffin wax, polyolefin wax such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, higher fatty acids, higher alcohols, and the like. Such an offset preventing agent,
Usually, in powder coatings, it is used in the range of 0.1 to 20% by weight, preferably 0.5 to 10% by weight.

When the powder coated sheet according to the present invention is used as a sublimable dye thermal transfer image-receiving sheet, in order to impart releasability from the ink sheet to the receiving layer, an internal release agent such as silicone oil is used. Alternatively, the reactants can be blended.

[0012] The above resin is usually used in an amount of 100 to 100% together with a coloring agent and, if necessary, an anti-offset agent and other additives.
The powder coating material used in the present invention is melt-kneaded at a temperature of about 200 ° C., preferably about 130 to 180 ° C. for several minutes, usually about 3 to 5 minutes, cooled, pulverized, and classified to obtain a powder coating used in the present invention. Obtainable. The powder coating has an average particle diameter in the range of 0.1 to 30 μm, preferably 1 to 30 μm.
25 μm, most preferably 5-20 μm
In the range.

According to the present invention, such a powder coating can be dry-coated on a substrate sheet and fixed to form a powder coating sheet. A powder mixture obtained by mixing inorganic fine particles and coating the surface of a powder coating with the inorganic fine particles is dry-coated on a substrate and fixed to obtain a powder coated sheet.

More specifically, when the powder coating sheet according to the present invention is used as a sublimation dye thermal transfer image receiving sheet, a powder mixture is prepared by mixing hydrophobic inorganic fine particles with the powder coating.
This is dry-coated on a base sheet, melted by heating, and fixed to obtain an image receiving sheet. According to such an image receiving sheet, when the ink receiving sheet is superimposed on the ink sheet, the ink sheet is heated, and the image of the ink sheet is thermally transferred to the image receiving sheet, the receiving layer has high releasability.

The above-mentioned hydrophobic inorganic fine particles preferably have an average particle diameter in the range of 1 nm to 1 μm.
Usually, it is used in an amount of 1 to 12 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the powder coating. Examples of such hydrophobic fine particles include, for example, anhydrous silica, titanium dioxide, aluminum oxide, calcium carbonate, etc., whose surfaces have been subjected to hydrophobic treatment. These can be easily obtained as commercial products.

On the other hand, when the powder coating sheet according to the present invention is used as an image receiving sheet for aqueous ink jet recording, a powder mixture is prepared by mixing hydrophilic inorganic fine particles with the powder coating, and this is mixed with a base material sheet. To form an image receiving sheet. According to such an image receiving sheet, the powder coating has a mutually fused coating film on the base sheet, with the inorganic fine particles on the surface thereof having a gap therebetween, and the powder coating. The surface of the receptor layer, which is a coating film of the above, is also coated with the hydrophilic inorganic fine particles. Therefore, if the aqueous inkjet ink adheres to such an image receiving sheet, the aqueous ink medium is adsorbed by the hydrophilic inorganic fine particles while penetrating into the coating film along the gap, so that the image receiving sheet is , Has excellent ink absorbency, while the dyes and pigments in the ink also
Since it is adsorbed and supported by the hydrophilic inorganic fine particles of the coating film, a clear image with high density can be formed.

The hydrophilic inorganic fine particles also preferably have an average particle diameter in the range of 1 nm to 1 μm.
Usually, it is used in an amount of 1 to 12 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the powder coating. Examples of such hydrophilic fine particles include anhydrous silica, titanium dioxide, aluminum oxide, calcium carbonate, and the like. These can be easily obtained as commercial products.

Since such a powder mixture is also a kind of powder coating, in the present invention, this powder mixture is also called a powder coating.

In the present invention, the substrate is usually
Paper, synthetic paper, synthetic resin sheet and the like are preferably used.
The paper is not particularly limited as long as it is made of ordinary cellulose fiber, and in addition to plain paper, high-quality paper,
Including coated paper. Examples of plain paper include ordinary PPC copy paper, paper subjected to calendering to improve the smoothness of the surface of the PPC copy paper, and thermal transfer word processor paper and coated paper that have already been surface-treated. Can be mentioned. As the synthetic resin sheet, for example, polyester, polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate,
Examples include sheets made of polycarbonate, polyamide, and the like. Examples of the synthetic paper include those obtained by extruding a mixture of a polyolefin resin or other synthetic resin as a resin component, a required inorganic filler, and the like. In particular, by using paper as the base material, the sublimable dye thermal transfer image-receiving sheet according to the present invention can be manufactured at low cost.

In the present invention, in order to dry-coat a powder coating composition containing inorganic fine particles on a substrate, for example, electrostatic coating such as electrostatic spraying or electrostatic immersion, spraying, spraying, etc. Powder coating such as coating method, dispersion method, powder melt lamination method, dusting method, cascade method, magnetic brush developing method,
An electrophotographic method such as a powder cloud method and an open chamber method can be used.

Among these dry coatings, in the present invention, for example, an electrostatic spray method can be preferably used. This electrostatic spraying method is a kind of powder coating, and specifically, a powder mixture according to the present invention, which is atomized at the tip of a spray gun, that is, a powder comprising a powder coating composition and inorganic fine particles. The body mixture is transported by air, and a negative high voltage (for example, -50 to -90 kV) is applied to a needle electrode incorporated at the tip of the spray gun to negatively charge the powder mixture. A grounded electrode is placed along the back surface of the substrate, and thus the negatively charged powder mixture is carried to the substrate and electrostatically deposited by the electric field present between the spray gun and the grounded electrode. It is.

FIG. 1 shows an example of a preferred apparatus configuration for carrying out the present invention. By winding a base sheet, for example, plain paper 1 from a paper feed roll 2 to a take-up roll 3 so as to have a constant traveling speed, the paper travels in a certain direction. Then, for example, the powder paint is dry-coated on the paper using the electrostatic spraying device 5. Next, the paper coated with the powder coating is guided to the preheating device 6 and heated to an appropriate preheating temperature.
Next, this is guided to a first fixing device 9 composed of a fixing roller 7 and a pressure roller (backup roller) 8, where the powder coating is heated and pressed on paper between the rollers to form a powder coating. The toner is fixed on paper, and further guided to a second fixing device 12 including a fixing roller 10 and a pressure roller (backup roller) 11, and heated and pressed again between the rollers to fix the powder coating material on paper. Let it. The powder coated paper 13 thus obtained may be used, if necessary, with a cooling roller 13.
Is wound up on the winding roll 14.

In the present invention, the first and second fixing devices each comprise a fixing roller and a pressure roller. Usually, the fixing roller has a heating means inside,
The surface of a metal tube made of aluminum or the like is covered with a relatively thin wall of a fluororesin such as polytetrafluoroethylene. On the other hand, the pressure roller is usually formed by coating the surface of a metal tube made of steel, aluminum or the like with a relatively thick silicone rubber, or further coating the surface with a fluororesin such as polytetrafluoroethylene. It becomes. The pressure roller,
If necessary, a heating means may be provided inside. According to the present invention, the base sheet on which the powder coating is dry-coated is guided to the first and second fixing devices, and the powder coating is applied to the second fixing device.
Press and heat several times to fix on the base sheet.

The surface temperature of the fixing roller is preferably 40 to 120 degrees higher than the melting start temperature of the resin used for the powder coating.
Temperature is suitable, the nip width between the fixing roller and the pressure roller is suitably in the range of 0.5 to 15.0 mm,
The pressure of the nip is suitably in the range of 0.5 to 11 kgf / cm ² . Further, according to the present invention, in order to effectively eliminate defects in the coating film on the base material sheet by performing the second fixing after the first fixing, the second fixing device fixes the fixing. It is preferable that either one or both of the temperature of the roller and the pressure between the fixing roller and the pressing roller be equal to or higher than that in the first fixing device.

[0025]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 (Preparation of powder coating composition and powder mixture) Saturated polyester resin (NE-382 manufactured by Kao Corporation, acid value 8.9 mgK)
OH / g, glass transition point 62.6 ° C, melting start temperature 99
C) 89 parts by weight, wax as an anti-offset agent (Viscol 550P manufactured by Sanyo Chemical Industries, Ltd., melting point 150)
C) 4 parts by weight and 7 parts by weight of titanium oxide as a white pigment were mixed and stirred with a mixer, and then mixed with a biaxial melt kneader to obtain 1 part.
Melt kneading was performed at 50 to 160 ° C. for 3 to 5 minutes. After cooling, the obtained kneaded product was pulverized and classified to obtain an average particle size of 10%.
A μm white powder coating composition was obtained. 100 parts by weight of this white powder coating composition was added to hydrophobic anhydrous silica (H-2000 / 4 manufactured by Clariant Japan KK, average particle diameter 16n).
m) A powder mixture was prepared by mixing 3 parts by weight.

(Manufacture of image receiving paper for thermal transfer recording of sublimable dye)
The above white powder mixture was adhered to the entire surface of a commercially available plain paper using a commercially available electrostatic spray device, and preheated.
m / min to the first fixing device, a fixing roll temperature of 160 ° C., a nip length between the fixing roll and the pressure roll of 240 mm, a nip width of 5 mm, and a pressing force between the nips of 2 k.
After the first-stage fixing was performed under the condition of gf / cm ² , the fixing device was guided to a second fixing device, and the second-stage fixing was performed under the same conditions as the first fixing conditions. In the first and second fixing devices, the fixing roll uses a 40 mm-diameter aluminum tube provided with a heating means inside and coated with a polytetrafluoroethylene resin, and the pressure roll has an inside. The surface of an aluminum tube having an outer diameter of 40 mm provided with a heating means was coated with silicone rubber to a thickness of 5 mm, and the surface was further coated with a polytetrafluoroethylene resin.

As described above, the surface roughness and the surface unevenness of the image receiving sheet obtained by performing only one fixing operation and the image receiving sheet obtained by performing the fixing operation twice were measured. The surface roughness was measured using a contour surface roughness measuring machine (manufactured by Tokyo Seimitsu Co., Ltd.) under the conditions of a paper feed speed of 3 mm / sec, a drive speed of 0.3 mm / sec, a drive distance of 10 mm, and a needle tip R of 1 μm. It was measured. As shown in FIG. 2, the surface of the image receiving sheet that has been fixed once has a significant convex portion, but the surface of the image receiving sheet that has been fixed twice has no significant convex portion, as shown in FIG. , Are uniformly smooth.

The surface irregularities were photographed with a high-resolution digital microscope (VH-6300 manufactured by Keyence Corporation) at a magnification of 800 times. As shown in FIG. 4 showing the surface of the image receiving sheet fixed once, many convex portions are observed, and the distribution of the convex portions is biased. However, according to the image receiving sheet fixed twice, FIG. As shown on the surface, the number of protrusions was small and the distribution was uniform.

Further, as a result of measuring the gloss of the surface of the image receiving sheet, as shown in Table 1, the surface gloss of the image receiving sheet fixed twice was compared with that of the image receiving sheet fixed only once. It is also excellent.

[0031]

[Table 1]

Using an image receiving sheet obtained by performing only one fixing operation and an image receiving sheet obtained by performing two fixing operations, an image is formed on the image receiving sheet by thermal transfer of a sublimation dye, and the density thereof is reduced. As a result, it was found that the image density of the image receiving sheet obtained by performing the fixing twice was improved.

[0033]

As described above, according to the method of the present invention,
After the powder coating is dry-coated on the base sheet, the powder coating is heated and melted twice and fixed, so that there is no coating film defect. When such a powder coated sheet according to the present invention is used, for example, as an image receiving sheet for sublimable dye thermal transfer recording or ink jet recording, image defects called white spots do not occur. Furthermore, since the powder coating sheet according to the method of the present invention has a smooth surface, for example, when used as an image receiving sheet for sublimable dye thermal transfer recording, it has excellent adhesion to the ink sheet, so that it is accurate and sharp. An image can be formed. Further, the powder coating sheet according to the present invention has excellent gloss.

[Brief description of the drawings]

FIG. 1 shows an example of a preferred apparatus configuration for carrying out the method of the present invention.

FIG. 2 is a chart showing the surface roughness of an image receiving sheet obtained by performing only one fixing.

FIG. 3 is a chart showing the surface roughness of an image receiving sheet obtained by performing fixing twice according to the present invention.

FIG. 4 is a photograph showing the surface of an image receiving sheet obtained by performing only one fixing.

FIG. 5 is a photograph showing the surface of an image receiving sheet obtained by performing fixing twice.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Plain paper (base sheet), 2 ... Paper supply roll, 3 ... Take-up roll, 4 ... Coating booth, 5 ... Electrostatic spray device, 6 ...
Preheating device, 7 fixing roller, 8 pressure roller, 9 first
Fixing device, 10: fixing roller, 11: pressure roller, 1
2 ... second fixing device, 13 ... powder coated paper.

Claims (1)

[Claims] 1. While running a base material sheet in a predetermined direction,
A powder coating is dry-coated on the substrate sheet, and the substrate sheet is guided to a first fixing device including a first pressure roller and a first fixing roller, and heated under pressure between the rollers. do it,
The powder coating on the base sheet is melted by heating and fixed on the base sheet, and the sheet thus obtained is further guided to a second fixing device including a second pressure roller and a second fixing roller. And again applying pressure and heating between the rollers to heat and melt the powder coating on the base sheet and re-fix the powder coating.