JPH05131766A - Thermal transfer paper and production thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a coated paper for thermal transfer, which is suitable as a transfer paper for a thermal transfer printer and a copying machine and has high white paper glossiness and high image glossiness and excellent image reproducibility. In a transfer paper in which a recording layer having at least one layer structure is provided on a support, the outermost layer of the recording layer is at least 100 parts by weight of a pigment and 10 to 50 binders.
5 to 50 g / dry solid content per side
m ² provided, 30 to 100% by weight of the pigment is synthetic silica having a specific surface area of 20 to 600 m ² / g, and the outermost surface layer has a 75 ° specular white paper glossiness of 5
A thermal transfer paper having a content of 0% or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer type thermal transfer paper, and more particularly to a high gloss thermal transfer paper suitable for a thermal transfer type thermal transfer printer and a copying machine.

[0002]

2. Description of the Related Art In general thermal transfer printers and copiers of the melt transfer system, high-quality paper having a high smoothness that has been surface-treated with a super calendar or the like is used as a recording transfer paper. It is known that the image quality becomes clear when the time is 100 seconds or more. This is because by increasing the smoothness of the recording surface, the adhesiveness between the paper and the ink ribbon at the time of recording is increased, the transfer of the ink to the transfer paper surface is increased, and the reproducibility of the solid image is improved, The image reproducibility of the halftone portion is insufficient.

On the other hand, coated paper having high smoothness and gloss is not currently used as a melt transfer type thermal transfer paper under the present circumstances. The reason for this is that the surface smoothness of the coated paper is extremely high, so that it will adhere evenly to the ink ribbon during recording, so theoretically a good ink transfer image should be obtained, but in reality Is non-uniform and the image reproducibility is not sufficient.

The non-uniformity of ink transfer is remarkable especially in art paper for printing and cast coated paper having high smoothness and gloss. In these papers, since the coated paper surface has few irregularities and voids, the melted ink does not cling to the transfer paper, and the ink once transferred to the paper is retransferred to the ink ribbon. This is because

As described above, the usual coated paper for printing is designed to satisfy the printing suitability, and is not designed to satisfy the suitability for the transfer paper for the thermal transfer printer of the melt transfer system or the copying machine. Therefore, if these technical problems of coated paper for printing are solved, by using the coated paper as a thermal transfer printer of a melt transfer system or a transfer paper for a copying machine, a higher quality image than ever can be obtained. It is thought that it can be obtained.

In general coated paper, when imparting high smoothness to the coated paper surface, the smoothness is usually imparted by crushing the surface with a high pressure using a super calender or the like. Therefore, in terms of paper quality, coated paper is inferior in that it is not as stiff as high-quality paper, and it has a high density and lacks volume feeling (no bulkiness). The balance with the glossiness of the image area is very poor, and it is not possible to obtain high image quality comparable to that of ordinary offset printing.

[0007]

As a result of various studies to solve the above-mentioned drawbacks, the present inventors have cast-coated a coating solution so that a certain amount or more of synthetic silica having a specific surface area is contained. According to the above, it was found that good results can be obtained, and the present invention has been achieved.

Therefore, a first object of the present invention is to provide a high quality image having high blank paper glossiness and high image glossiness as well as excellent image reproducibility when using a thermal transfer printer or a copying machine of a melt transfer system. It is to provide a coated paper for thermal transfer that can be obtained. A second object of the present invention is to provide a method for producing coated paper useful for thermal transfer.

[0009]

The above-mentioned various objects of the present invention are, in a transfer paper provided with a recording layer having at least one layer constitution on a support, in which the outermost layer of the recording layer is at least pigment 100. A layer comprising 5 to 50 parts by weight of a binder and 10 to 50 parts by weight of a binder and having a dry solid content of 5 to 50 g / m ^{2 on} one side, wherein 30 to 100% by weight of the pigment has a specific surface area of 20 to 600 m ² / It was achieved by a thermal transfer paper and a method for producing the same, which is g synthetic silica and has a surface gloss of 75 ° specular white paper of 50% or more.

The synthetic silica used in the present invention is generally referred to as amorphous silica, amorphous silica, silicic acid anhydride, hydrous silica, fine powder silica, or white carbon, and has a Si--O network shape. It is a silicic acid that has a structure and does not have a certain crystal structure. From the viewpoint of transferability of the melted ink, it is preferable that the specific surface area using a synthetic silica of ^{20~600m 2 / g, 20~300m 2 /} g
Those in the range of are particularly preferable. Specific surface area of 600m ²
If it is larger than / g or if the specific surface area is 20 m ² / g or less, the reason is not clear, but the image reproducibility especially in the halftone portion is deteriorated, which is not preferable.

The synthetic silica used in the present invention may be produced by any method such as a wet method, a dry method and an airgel method, and the production method is not particularly limited. Further, in the present invention, the compounding amount of the synthetic silica in the coating liquid is 30 to 100 in 100 parts by weight of the pigment.
Parts by weight. When the amount of the synthetic silica in the pigment is less than 30 parts by weight (that is, less than 30% by weight), the transfer of the melted ink to the recording layer becomes insufficient, and the image reproducibility especially in the halftone part is become worse.

The type of pigment that can be used in combination with the above synthetic silica is not particularly limited. Examples of pigments that can be used in combination include kaolin, clay, ground calcium carbonate,
Inorganic pigments such as light calcium carbonate, aluminum hydroxide, satin white, titanium dioxide, calcined clay, zinc oxide, barium sulfate, talc, colloidal silica, styrene resin fine particles such as polystyrene and polymethylstyrene, and polymethacryl Examples thereof include fine particles of acrylic resin such as methyl acid and polyacrylonitrile, and organic pigments such as fine particles of polyvinyl chloride and polycarbonate. These pigments can be used together in any ratio.

Among the organic pigments, fine particles of styrene resin, acrylic resin or styrene-acrylic copolymer resin are preferable from the viewpoint of hardness, elasticity and heat resistance, and polystyrene or styrene-methyl methacrylate copolymer is particularly preferable. When the hollow microparticles made of coalesce are used, the coating surface is likely to have smoothness, and it is effective in reducing the density of the coating layer.

As the binder, a resin, an emulsion, a latex, a natural polymer or the like, which has a strong adhesion to the pigment and the base paper and does not cause blocking between the paper and between the paper and the ink ribbon, is used alone or in combination. can do. Examples of such a binder include polyvinyl alcohol, oxidized starch, esterified starch, enzyme-modified starch, starch such as cationized starch, casein, soybean proteins, carboxymethyl cellulose, fibrin derivatives such as hydroxyethyl cellulose, and the like. Examples thereof include styrene-acrylic resin, styrene-butadiene resin, vinyl acetate resin, acrylic resin and the like.

The content of the binder in the coating composition is pigment 10
It is preferably 10 to 50 parts by weight with respect to 0 parts by weight. If the compounding amount of the binder is less than 10 parts by weight, the coating film strength will be weak, and if it exceeds 50 parts by weight, the coating properties will be adversely affected. In the present invention, it is also possible to mix a dye or a colored pigment for the purpose of adjusting the hue, or a fluorescent dye for the purpose of improving the whiteness of the visual sense.

The coating composition containing the above components can be easily prepared by a known method. In the present invention, if necessary, various auxiliary agents such as a dispersant, a defoaming agent, a release agent, a pH adjusting agent, a lubricant, a water retention agent, an antiseptic agent, etc. in the paint may impair the effects of the present invention. Further addition can be made within the range not present.

In the present invention, the coating liquid prepared as described above is coated on a support to form a recording layer. In this case, the surface of the coated paper coated with the coating liquid is Simply smoothing with a super calendar (Japanese Patent Laid-Open No. 62-198876) weakens the stiffness of the paper, and it is not possible to obtain sufficient white paper glossiness, and the transportability in the printer and copier is reduced due to the reduction of the stiffness of the paper. It causes problems such as failure. Further, not only is the transferability of the ink inferior, a good image cannot be obtained, but the balance of the glossiness between the image portion and the blank sheet portion becomes extremely poor.

On the other hand, when the coating layer is formed by the cast coating method using the above-mentioned coating liquid, the glossiness of the paper is not deteriorated and the glossiness of the white paper is very high. Further, the balance of glossiness between the white paper portion and the image portion, which has good ink transferability, becomes very good, and the thermal transfer paper of the present invention can be easily obtained.

Although the details of the reason are not clear, the specific surface area of the pigment generally used in the coating material of coated paper is 2 to 3 m.
² / g, not more than 10m ² / g at most,
The specific surface area of the synthetic silica used in the present invention is 20 to 600 m.
^{Since it is 2} / g, which is much larger than that of commonly used pigments, it can be estimated as follows.

That is, when the coating layer is provided by the casting method, synthetic silica having a large specific surface area is contained in the recording layer as it is, so that the number of voids in the recording layer becomes very large. Therefore, the transferability of the ink becomes good, and the unevenness of the image surface is reduced by the proper absorption of the ink melted in the voids, so that the irregular reflection on the surface is reduced and the image glossiness is increased. Inferred.

The coating amount is such that the dry weight per one side is 5 to 50.
g / m ^2, is preferably a single-layer or multi-layer coating on-machine or off-machine coater such that 8~30g / m ^2. When the coating amount is less than 5 g / m ² , the coating on the surface of the thick paper is insufficient and high white paper gloss cannot be obtained. On the other hand, when the coating amount exceeds 50 g / m ² , the density of the paper increases and the stiffness of the paper becomes weak, which causes troubles in running properties and loses the function as a transfer paper.

As a method for cast coating, a known method such as a coagulation method, a rewetting method, or a wetting method may be appropriately used. The coating method for obtaining the recording layer is not particularly limited,
A general coating method, for example, a coating method such as various blade coating, roll coating, air knife coating, bar coating or the like can be adopted.

As the coagulant used when the cast coating method by the coagulation method is used, formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, calcium, zinc, barium,
Lead, magnesium, cadmium, and various sulfates such as aluminum, further potassium sulfate, potassium citrate, borax, boric acid and the like are generally, in the present invention,
It is not particularly limited to these. Further, when a binder that effectively coagulates with these coagulants is selected and used, it is effective for improving the coating speed and the finishing state of the coated surface.

As the base paper, acidic and neutral high-quality papers, medium-quality papers, etc. can be used, but in order to have coating suitability as a base paper for coating, known methods such as blending, adjustment, manufacturing conditions, etc. It is preferable to use the paper prepared according to (Japanese Patent Publication No. 55-47385).

[0025]

As described in detail above, the thermal transfer paper of the present invention has good ink transferability even though the white paper glossiness is extremely high, and also has excellent glossiness in the image area.
It has a good balance of glossiness between the white paper portion and the image portion and can obtain a high quality image, and is particularly suitable as a thermal transfer paper for a melt transfer type thermal transfer printer or a copying machine.

[0026]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. All parts in the examples are parts by weight. or,
Each measurement in the examples was performed as follows.

(1) Density: Measured according to the method of JIS P8118. (2) Smoothness: Measured according to the method of JIS P8119. (3) Gloss: The 75 ° gloss of the coated surface was measured according to the method of JIS P8142.

(4) Image glossiness: Using a color thermal printer M4234-10 manufactured by Mitsubishi Electric Corporation, patterns having halftone dot area ratios of 25%, 50% and 100% were recorded, respectively, and glossiness of each portion was recorded. The degree was measured.

(5) Evaluation of image reproducibility: In particular, the degree of transfer of ink in a portion having a halftone dot area ratio of 25% was visually evaluated, and ○ was uniformly recorded and ○ was partially omitted. Δ: The ink having almost no ink transfer was marked with x.

(6) Coat layer strength: Using an IGT printability tester (IGT A-1 type, manufactured by IGT Corporation), ink tack was 10 and ink amount was 0.02.
When the printing speed was 5 cc and the printing speed was 1.2 m / sec, those in which picking did not occur were evaluated as ◯, those in which picking was slightly observed were evaluated as Δ, and those in which the transferred ink was completely removed were evaluated as x.

Example 1. As base paper, beating degree 400cc
Of hardwood bleached kraft pulp (L-BKP) of 100 parts was added to a pulp slurry containing 10 parts of ground calcium carbonate, 1 part of cationized starch and 0.1 part of sizing agent (alkyl ketene dimer) to make paper. Basis weight 92g /
A coated base paper of m ² was obtained.

On the other hand, as a pigment, synthetic silica (trade name Syloid 404: manufactured by Fuji Davisson Co., Ltd., specific surface area 3)
(80 m ² / g) and ² parts of 1st grade kaolin (trade name Ultra White 90: manufactured by EMC Corporation)
0 parts, styrene-butadiene latex 5 as a binder
And 5 parts of casein and 2 parts of calcium stearate as a release agent were added to prepare a coating liquid having a solid content of 43%.

The obtained coating solution was coated on the above-mentioned base paper with a roll coater so that the dry solid content was 10 g / m ^2, and then coagulated using a 10% aqueous solution of zinc formate as a coagulant, While the coating film was in a wet state, it was pressed against a cast drum having a mirror surface heated to 100 ° C. and dried to obtain a transfer paper having a basis weight of 102 g / m ² .

Example 2. Synthetic silica as a pigment (trade name 404: manufactured by Fuji Davison Co., Ltd., specific surface area 300 m
80 parts of ² / g) and 20 parts of first-class kaolin (trade name Ultra White 90: manufactured by EMC Co., Ltd.),
15 parts of styrene-butadiene-based latex and 15 parts of casein as a binder and 2 parts of calcium stearate as a release agent were added to prepare a coating liquid having a solid content of 42%.
The coating liquid thus obtained was used in Example 1 for coating base paper (92 g /
in m ^2), the outer was coated by a roll coater so that the dry solid content of 15 g / m ² Example 1 basis weight in the same manner as 1
A transfer paper of 07 g / m ² was obtained.

Example 3. 100 parts of synthetic silica (trade name: Fineseal SP-20: manufactured by Tokuyama Soda Co., Ltd., specific surface area: 30 m ² / g) as a pigment, 20 parts of a styrene-butadiene latex as a binder and 20 parts of casein, and a steer as a release agent. 2 parts of calcium phosphate was added to prepare a paint having a solid content of 46%. The resulting paint, the outer the coating base paper to dry solids was coated by a roll coater so that the 10 g / m ² was used in Example 1, Example 1 in the same manner as basis weight 102 g / m ² The transfer paper of was obtained.

Example 4. The synthetic silica used in Example 3 had a specific surface area of 600 m ² / g (trade name: Syloid 600:
(Manufactured by Fuji Devison Co., Ltd.), and 23 parts of styrene-butadiene latex and 20 parts of casein as a binder and 2 parts of calcium stearate as a release agent were added to prepare a coating liquid having a solid content of 40%. The obtained coating liquid was applied to the coated base paper used in Example 1 to obtain a dry solid content of 5 g.
/ Outside were coated with a roll coater so that m ² is to obtain a transfer paper having a basis weight of 97 g / m ² in the same manner as in Example 1.

Example 5. Synthetic silica as a pigment (trade name 404: manufactured by Fuji Davison Co., Ltd., specific surface area 300 m
30 parts of ² / g), 40 parts of first-class kaolin (trade name Ultra White 90: manufactured by EMC Co., Ltd.) and 30 parts of calcium carbonate (trade name Brilliant 15: manufactured by Shiraishi Industry Co., Ltd.) Add 15 parts of styrene-butadiene latex and 10 parts of casein as a binder and 2 parts of calcium stearate as a release agent, and solid content is 54%.
The coating liquid of was prepared. 104 g of basis weight was obtained in the same manner as in Example 1 except that the obtained coating liquid was applied to the coated base paper used in Example 1 with a roll coater so that the dry solid content was 12 g / m ^2. A transfer paper of / m ² was obtained.

Example 6. As base paper, beating degree 400cc
Of hardwood bleached kraft pulp (L-BKP) into a pulp slurry containing 10 parts of heavy calcium carbonate, 1 part of cationized starch and 0.1 part of sizing agent (alkyl ketene dimer) to make paper. , Basis weight 69g
A coated base paper of / m ² was obtained.

On the other hand, as a pigment, synthetic silica (trade name Cyloid 404: manufactured by Fuji Davisson Co., Ltd., specific surface area 3)
00m ² / g) 30 parts, 1st grade kaolin (trade name Ultra White 90: manufactured by EMC Corporation) 40 parts,
20 parts of calcium carbonate (brand name Brilliant 15: manufactured by Shiraishi Industry Co., Ltd.) and organic pigment (brand name Boncoat PP)
-1100: manufactured by Dainippon Chemical Co., Ltd.), 15 parts of a styrene-butadiene latex and 15 parts of casein as a binder, and 2 parts of calcium stearate as a release agent are added to prepare a coating liquid having a solid content of 55%. did. The resulting coating liquid, outside the dry base paper solids was coated by a roll coater so that the 40 g / m ^2, in the same manner as in Example 1, a transfer paper having a basis weight of 109 g / m ² Obtained.

Comparative Example 1. A transfer paper having a basis weight of 95.5 g / m ² was obtained in exactly the same manner as in Example 1 except that coating was performed with a roll coater so that the dry solid content was 3.5 g / m ² .

Comparative Example 2. A coating solution was prepared in the same manner as in Example 5 except that 2 parts of styrene-butadiene latex and 2 parts of casein as a binder and 2 parts of calcium stearate as a release agent were added to form a coating solution having a solid content of 50%. Prepared. The obtained coating liquid was applied to the coating base paper used in Example 1,
The grammage was 10 in the same manner as in Example 1 except that the coating was carried out by a roll coater so that the dry solid content was 12 g / m ^2.
A transfer paper of 4 g / m ² was obtained.

Comparative Example 3. A coating solution was prepared in exactly the same manner as in Example 5 except that 30 parts of styrene-butadiene latex and 30 parts of casein as a binder and 2 parts of calcium stearate as a release agent were added to form a coating solution having a solid content of 50%. Prepared. The obtained coating liquid was applied to the coated base paper used in Example 1 by a roll coater so that the dry solid content was 20 g / m ² , and the basis weight was the same as in Example 1. 1
A transfer paper of 12 g / m ² was obtained.

Comparative Example 4. 5 parts of synthetic silica (trade name Syloid 404: manufactured by Fuji Davison Co., Ltd., specific surface area 300 m ² / g) as a pigment, 40 parts of primary kaolin (trade name Ultra White 90: manufactured by EMC Co., Ltd.) and calcium carbonate 55 parts (trade name: Brilliant 15: manufactured by Shiraishi Kogyo Co., Ltd.), 15 parts styrene-butadiene latex and 10 parts casein as a binder, and 2 parts calcium stearate as a release agent are added, and a solid content is 5
An 8% coating liquid was prepared. The obtained coating liquid was used in Example 1
A transfer paper having a basis weight of 107 g / m ² was obtained in exactly the same manner as in Example 1 except that the coated base paper used in 1 was coated with a roll coater so that the dry solid content was 15 g / m ² .

Comparative Example 5. Synthetic silica (trade name: Syloid 404: manufactured by Fuji Davison Co., Ltd., specific surface area: 300 m ² / g) 25 parts as a pigment, first-class kaolin (trade name: Ultra White 90: manufactured by EMC Co., Ltd.) 40
Parts and calcium carbonate (trade name Brilliant 15: manufactured by Shiraishi Kogyo Co., Ltd.), 35 parts of styrene-butadiene latex as a binder, 15 parts of casein and 2 parts of calcium stearate as a release agent, and a solid content of 58%. The coating liquid of was prepared. The obtained coating liquid was applied to the coated base paper used in Example 1 by a roll coater so that the dry solid content was 15 g / m ² , and the basis weight was 107 g in the same manner as in Example 1. A transfer paper of / m ² was obtained.

Comparative Example 6. Dry solids was applied so that the 60 g / m ² outside in the same manner as in Example 1 to obtain a transfer paper having a basis weight of 129 g / m ²

Comparative Example 7. Synthetic silica as a pigment (trade name FK700: manufactured by Degussa Co., Ltd., specific surface area 700 m ²
/ G) 30 parts, 1st grade kaolin (trade name Ultra White 90: manufactured by EMC Co., Ltd.) 40 parts and calcium carbonate (trade name Brilliant 15: manufactured by Shiraishi Industry Co., Ltd.) 30 parts, as a binder 11 parts of styrene-butadiene-based latex and 11 parts of casein and 2 parts of calcium stearate as a release agent were added to prepare a coating liquid having a solid content of 60%. The obtained coating liquid was applied to the coated base paper used in Example 1 by a roll coater so that the dry solid content was 11 g / m ² , and the same procedure as in Example 1 was carried out.
A transfer paper having a basis weight of 103 g / m ² was obtained.

Comparative Example 8. 30 parts of synthetic silica (trade name Cyloid 404: manufactured by Fuji Davison Co., Ltd., specific surface area: 300 m ² / g) and 70 parts of calcium carbonate (trade name: Brilliant 15: manufactured by Shiraishi Industry Co., Ltd.) as a pigment, and styrene butadiene as a binder 22 parts of system latex and 2 parts of oxidized starch were added to prepare a coating liquid having a solid content of 56%. The obtained coating liquid was coated on the coated base paper used in Example 1 with a roll coater so that the dry solid content was 10 g / m ^2, and dried to obtain a coating having a basis weight of 102 g / m ² . Got the paper. Then, a super calender was used to impart smoothness to the coated surface to obtain a transfer paper.

Table 1 shows the results of a summary of the coating liquid formulations, the specific surface areas and the coating amounts of the synthetic silicas used for the transfer papers of the above Examples and Comparative Examples.
The values in the column of pigment in the table are synthetic silica / kaolin /
It represents calcium carbonate / organic pigment, and the value in the column of binder represents latex / casein.

[0049]

[Table 1]

Table 2 shows the results of the paper quality test and the image evaluation of the coated paper obtained.

[Table 2]

The results shown in Table 2 indicate that not only the white glossiness of the transfer paper of the present invention is high, but also the stiffness and bulkiness of the transfer paper are extremely high, and the glossiness of the recorded image portion is high, and the image quality is high. It proves to be excellent.

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Claims (2)

[Claims] 1. A transfer paper comprising a support and a recording layer having at least one layer structure, wherein the outermost layer of the recording layer is at least 100 parts by weight of a pigment and 10 to 10 parts by weight of a binder.
50 parts by weight, 5-50 dry solids per side
g / m ² provided layer, which is 30 to 10 of the pigment.
0% by weight is a synthetic silica having a specific surface area of 20 to 600 m ² / g, and the surface of the outermost layer has a 75 ° specular white paper glossiness of 50% or more. 2. The method for producing a thermal transfer paper according to claim 1, wherein the outermost layer is provided by a cast coating method.