JP2736943B2 - Transfer paper for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Offset printing is the mainstream in general commercial printing and high-grade printing, and coated paper such as art paper, coated paper, and cast coated paper is mainly used. This is because the surface of the coated paper is very smooth, so that when it comes into contact with the blanket roll during printing, the transferability of the ink from the roll to the coated paper is good, the image reproducibility is high, and the gloss of the image is high. And high color reproducibility. On the other hand, such a coated paper is currently not generally used as an electrophotographic transfer paper. The reason for this is that the coated paper is very smooth, so it adheres uniformly to the photoreceptor at the time of copying, etc., so that theoretically a good toner transfer image should be obtained. When applied, there is a report that the image becomes rough (Paper and Paper Times, 27, No. 4
(1984) 31-36).

One of the causes of this is that blisters (swelling of a coating layer) are generated on smooth printing coated paper because an electrophotographic image is fixed by heat. Kaisho 62-198876). This phenomenon is said to be due to the fact that the moisture in the coated paper becomes water vapor due to the low air permeability of the coated paper for printing, and the paper layer is peeled off when expanded by heating. Further, when the coated paper for printing is used as the transfer paper for electrophotography, the surface is smooth and slips between the rolls, and the running property is apt to cause trouble due to weakness of the waist or curl. As described above, the ordinary coated paper for printing is designed so as to satisfy the printing suitability, and is designed so as to satisfy the suitability for the transfer paper for electrophotography used in electrophotographic printers and copiers. Absent.

It is considered that the use of the coated paper for the transfer paper for electrophotography is effective as a method for obtaining a high-quality image only after solving the technical problems of the coated paper for printing. The application of high smoothness to the surface of coated paper is generally performed by crushing the surface with high pressure using a super calender or the like. It is weak and has a high density, and is inferior in terms of lack of volume (no bulk).

As an example of application of the coated paper to an electrophotographic transfer paper, a coated paper mainly comprising a high electric resistance resin (JP-B-57-53592, JP-B-57-55139)
No. 58-26026), but the coating amount is low and the smoothness is low, so it is close to plain paper and is not suitable for high image quality. Further, in this case, the amount of the pigment to the binder is smaller than that of a general printing coated paper, and simply increasing the coating amount does not provide high smoothness comparable to that of the printing coated paper. In general, it is not suitable for electrophotography because troubles such as blocking occur between the two.
In addition , in order to prevent blisters, there are also examples in which the average surface roughness of the coated paper is 2.0 μm or less and the air permeability is 4000 seconds or less (Japanese Patent Application Laid-Open Nos. Sho 62-1988875 and Sho 62).
-198876).

Another method for preventing blisters is to apply a moisture permeability of 50 to 500 g / m2 on both sides of a base paper having a specific air permeability.
Examples of such 2-5 g / ^{m 2} provided ² · 24 hr or good coating layer of the water vapor moisture permeability which is adjusted to the range of the coating amount is (JP-A-1-245265). However, these papers have low white paper glossiness and are smoothed with a super calender, so they do not have the same stiffness and bulk as high-quality paper, and because they have a small amount of coating, they are close to plain paper and have sufficient white paper glossiness. Since it was not obtained, it was insufficient to obtain an image quality comparable to that of high-grade printing paper.

[0007] In order to remedy the drawbacks of this, such as we are at the invention of Japanese Patent Application No. Hei 2-131253 earlier, concerning the image quality of the paper, the relevance of the moisture and air permeability and the image quality of the paper As a result of repeated investigations on the aging of the product in the actual machine, the non-film-forming resin having voids in the coating liquid was reduced to 5% by weight of the pigment.
-25% by weight, and the moisture content of the coated paper is 4-6%.
%, The air permeability is 4000 seconds or less, and the density of the coated paper is 1.1 g / cm ³ or less, so that a product with stable quality can be manufactured, and excellent images can be obtained with excellent runnability. It was disclosed that a coated paper was obtained. However, these methods do not achieve image quality comparable to that of high-grade printing paper. In particular, the glossiness of the halftone portion is lower than the glossiness of the blank portion, and it is still difficult to obtain a high image glossiness from the halftone portion to the solid portion. It was not enough.

[0008]

SUMMARY OF THE INVENTION The present invention solves these drawbacks and eliminates the need for blisters in electrophotographic printers and copiers. An object of the present invention is to provide a coated paper for electrophotographic transfer from which an image having a higher gloss than a blank portion can be obtained.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a transfer paper provided with at least one recording layer having a layer structure on a support. The outermost layer contains 30 to 100 parts by weight of synthetic silica having a specific surface area of 20 to 600 m ² / g in 100 parts by weight of the pigment, and the binder is mixed with 10 to 50 parts by weight based on 100 parts by weight of the pigment. A transfer paper coated with a coating solution by a cast coating method at a dry weight per surface of 5 to 50 g / m ^{2 and a} coated surface having a 75 ° specular gloss of 50% or more on the coated surface has more preferable characteristics. It concerns paper.

In the present invention, the synthetic silica is used as a pigment 100
The surface of the coated paper mixed with 30 parts by weight of the parts by weight is simply smoothed with a super calender (Japanese Patent Laid-Open No. 62-198876).
No.), the stiffness of the paper becomes weak, and sufficient smoothness and glossiness of white paper cannot be obtained. In addition, the air permeability of the paper decreases, causing blisters. Further, the glossiness of the image portion, particularly the image glossiness of the halftone portion, becomes lower than the glossiness of the blank portion. In contrast, higher white paper gloss by providing a coating layer by a cast coating method, without lowering the waist of paper, also without blister compromising the paper permeability is suppressed, the image glossiness particular half The image gloss of the tone portion is greatly improved.

[0011] Details of this reason are not clear, but
The specific surface area of the pigment used in the coating of coated paper is 2-3m
²/ G, at most 10m²/ G
The specific surface area of the synthetic silica used in the present invention is 20 m²/ G to
600m²/ G, very large and commonly used face
It is much larger than the fee. Synthetic silica with large specific surface areaTo
RecordVoids in the recording layer due to inclusion in the recording layer
More. The melted toner is appropriately absorbed in these voids.
This reduces unevenness on the image surface and reduces irregular reflection on the surface.
It is presumed that the image gloss decreases and the image gloss increases. this
As a result, white paper was found in cast-coated paper containing synthetic silica.
High gloss and image gloss higher than blank paper gloss
Transfer paper with high image gloss especially in the halftone area
Was successful. Specific surface area of synthetic silica is 300m²
/ G is particularly preferred. Specific surface area is 600
m²If it is larger than / g, the reason is not clear,
Especially, the glossiness of the image in the halftone area is higher than the glossiness in the blank area
Therefore, it is not suitable for the present invention.

[0012] What is synthetic silica used in the present invention?,Generally non
Crystalline silica, amorphous silica, silicic anhydride, hydrous silicic acid,
Called finely divided silica or white carbon
It is composed of a network structure of Si-O and has a certain crystal structure.
It is a silicic acid with no structure. Absorption of molten toner
20m in terms of specific surface area²/ G to 600m²/ G
Is used. The present inventionsoSynthetic silicon usedMosquito
IsSpecial production methods such as the wet method, dry method, and aerogel method
It is not limited to. The amount of synthetic silica in the coating liquid is,Pigment
It is 30 parts by weight to 100 parts by weight in 100 parts by weight.
If the amount of synthetic silica is less than 30 parts by weight,
Absorption of the melted toner into the recording layer becomes insufficient,
The glossiness of the image in the halftone area is lower than the glossiness of the blank paper
It becomes.

[0013] Pigments may be used in combination with the above-mentioned pigments, but the type thereof is not particularly limited. Examples of usable pigments include inorganic pigments such as kaolin clay, heavy calcium carbonate, light calcium carbonate, aluminum hydroxide, satin white, titanium dioxide, calcined clay, zinc oxide, barium sulfate, talc, colloidal silica, and the like. Examples of the organic pigment include styrene resins such as polystyrene and polymethylstyrene, acrylic resins such as polymethyl methacrylate and polyacrylonitrile, as well as polyvinyl chloride, polycarbonate and the like. can do. Attention should be paid to inorganic pigments having a plate-like particle form, such as kaolin clay, which reduce air permeability and cause blisters. Among organic pigments, styrene resin, acrylic resin or styrene-acrylic copolymer resin is preferable in terms of hardness, elasticity, heat resistance, and the like. Particularly, fine hollow particles made of polystyrene or styrene-methyl methacrylate copolymer are preferable. It is easy to obtain smoothness on the coating surface and is effective for lowering the density of the coating layer.

As the binder, a pigment, a resin, an emulsion, a latex, or a natural polymer which has a strong adhesive force to base paper and does not cause blocking between papers can be used alone or in combination. For example, polyvinyl alcohol, oxidized starch, esterified starch, enzyme-modified starch,
Examples include starches such as cationized starch, casein, soybean proteins, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, styrene-acrylic resins, styrene-butadiene resins, vinyl acetate resins, acrylic resins, and the like.

[0015] In addition, or blending the dye charge to adjust the hue, it is possible to blend fluorescent dyes in order to improve the feeling manner whiteness seen. Further, various assistants such as a dispersant, an antifoaming agent, a release agent, a pH adjuster, a lubricant, a water retention agent, a preservative, and the like can be added to the coating solution as needed. The amount of the binder in the coating liquid composition is 10 to 50 parts by weight based on 100 parts by weight of the pigment. If the amount of the binder is less than 10 parts by weight, the strength of the coating film becomes weak, and if it exceeds 50 parts by weight, the air permeability of the coated paper becomes too high, causing blisters.

The amount of coating is 5 to 50 g on a dry weight per side.
/ M ² , preferably 8 to 30 g / m ² , in a single-layer or multi-layer coating with an on-machine or off-machine coater. If the coating amount is less than 5 g / m ² , the coating on the surface of the base paper becomes insufficient, and a high white paper gloss cannot be obtained. When the coating amount is more than 50 g / m ² , the density of the paper increases, the air permeability increases, the occurrence of blisters and the stiffness of the paper become weak, and trouble occurs in running properties, and the function as an electrophotographic transfer paper is obtained. Disadvantages such as loss of As a production method by the cast coating method , a coagulation method, a rewetting method, and a wetting method are known, and any method can be applied to the present invention. There is no particular limitation on the coating method for obtaining the recording layer, and general coating methods such as various blade coating, roll coating, air knife coating, and bar coating are used. Can be used.

The coagulants used when using the cast coating method by the coagulation method include calcium, potassium, zinc, barium, lead, magnesium, cadmium, formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid and sulfuric acid. Each salt such as aluminum, borax, boric acid, and the like are common, but are not particularly limited. The use of a binder that solidifies effectively with these coagulants is effective in improving the coating speed and the finish of the coated surface. As base paper, acidic and neutral high-quality paper and medium paper can be used. In order to provide coating suitability as a coating base paper, the blending, adjustment, and production conditions of raw materials are determined by known methods (Japanese Patent Publication No. 55-473).
No. 85) is preferable.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. All parts in the examples are parts by weight. The measurements in the examples were performed as follows.

(1) Density: According to the method of JIS P8118. (2) Air permeability: According to the method of JIS P8117. (3) Gloss: 75 ° gloss of the coated surface was measured according to the method of JIS P8142. (4) Image glossiness: manufactured by Ricoh Co., Ltd., Artige 53
A recording test was performed using No. 30. A copy original having a dot area ratio of 10 to 100% was used, and the glossiness of the image was measured for the portions having the dot area ratios of 20%, 60%, and 100%.

(5) Glossiness evaluation: In particular, the case where the image glossiness of the halftone portion was higher than the glossiness of the blank portion was evaluated as ○, the same was evaluated as Δ, and the one with low gloss was evaluated as ×. (6) Coating layer strength: IGT printability tester (trade name I
GT A-1 type, manufactured by IGT Co., Ltd.)
0, ピ indicates that no picking occurred at a printing speed of 1.2 m / sec at an ink amount of 0.025 cc, △ indicates that the ink was slightly observed, and X indicates that the ink was completely removed. (7) Blister: Blisters with no visible foaming in the solid image area were rated as ○, and those with foaming were rated as x.

EXAMPLE 1 10 parts of heavy calcium carbonate and 10 parts of cationized starch were added to a pulp slurry consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) having a beating degree (csf) of 400 cc as base paper.
Parts and 0.1 parts of a sizing agent (alkyl ketene dimer) were added to obtain a base paper having a basis weight of 92 g / m ² . The composition of the coating liquid was a synthetic silica (trade name: Syloid 404, manufactured by Fuji Devison Co., Ltd., specific surface area: 300 m ² /
g), 20 parts of primary kaolin (trade name: Ultra White 90, manufactured by EMC), 5 parts of styrene butadiene latex and 5 parts of casein as a binder, and 2 parts of calcium stearate as a release agent, and solidified. 43%
Was prepared. The obtained coating liquid is applied to the base paper by a roll coater so that the dry solid content is 10 g / m ² ,
Then, the coated film was coagulated with a 10% aqueous solution of zinc formate as a coagulant and pressed and dried on a cast drum having a mirror surface heated to 100 ° C. while the coating film was in a wet state to obtain a recording paper having a basis weight of 102 g / m ² .

Example 2 The composition of the coating liquid was a synthetic silica (trade name: Syloid 404, manufactured by Fuji Devison, specific surface area: 300 m ² / g) as a pigment.
80 parts and first grade kaolin (trade name Ultra White 9
0, 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.
Was prepared. The obtained coating liquid was applied to the coating base paper (basis weight 92 g / m ² ) used in Example 1 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.
/ M ² of recording paper was obtained.

Example 3 The composition of the coating liquid was a synthetic silica (trade name: Fine Seal SP-20, manufactured by Tokuyama Soda Co., specific surface area: 30 m ² / g) as a pigment.
Was added as a binder, 20 parts of styrene-butadiene-based latex and 20 parts of casein, and 2 parts of calcium stearate as a release agent, to prepare a coating liquid having a solid content of 46%. The obtained coating liquid was applied to the coating base paper used in Example 1 so as to have a dry solid content of 10 g / m ² , and a recording paper having a basis weight of 102 g / m ² was obtained in the same manner as in Example 1. .

Example 4 In Example 3, the synthetic silica was prepared by changing the specific surface area to 600 m ² / g.
(Syloid 600, manufactured by Fuji Devison Co., Ltd.), 100 parts, styrene-butadiene-based latex (23 parts) and casein (20 parts) as binders, and calcium stearate (2 parts) as a release agent were added. % Of the coating solution was prepared. The resulting coating solution was applied so that the coating base paper to dry solids 5 g / m ² was used in Example 1 to obtain a recording paper having a basis weight of 97 g / m ² in the same manner as in Example 1 .

Example 5 The composition of the coating liquid was a synthetic silica (trade name: Syloid 404, manufactured by Fuji Devison, specific surface area: 300 m ² / g) as a pigment.
30 parts, 1st grade kaolin (trade name Ultra White 9
0, manufactured by EMC), 40 parts of calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Industry Co., Ltd.), 15 parts of styrene-butadiene-based latex and 10 parts of casein as a binder, and calcium stearate 2 as a release agent. Was added to prepare a coating liquid having a solid content of 54%. The obtained coating liquid was applied to the coating base paper used in Example 1 so as to have a dry solid content of 12 g / m ^2, and the basis weight was 104 g in the same manner as in Example 1.
/ M ² of recording paper was obtained.

Example 6 A pulp slurry consisting of 100 parts of hardwood bleached kraft pulp (L-BKP) having a beating degree of 400 cc as base paper was mixed with 10 parts of heavy calcium carbonate, 1 part of cationized starch, and 0.1 part of a sizing agent (alkyl ketene). The paper stock to which dimer was added was made into paper to obtain a coated base paper having a basis weight of 69 g / m ² . The coating composition is a synthetic silica (trade name: Syloid 40) as a pigment.
4. The specific surface area of 300 m ² / g manufactured by Fuji Devison
0 parts, 1st grade kaolin (trade name Ultra White 90, E
MC) (40 parts), calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Industry Co., Ltd.), 20 parts, and organic pigment (trade name: Boncoat PP-1100, manufactured by Dainippon Chemical Co., Ltd.): 10 parts.
Part, styrene butadiene latex 15 as binder
And 15 parts of casein and 2 parts of calcium stearate as a release agent were added to prepare a coating solution having a solid content of 55%. The obtained coating liquid was applied to the base paper so that the dry solid content was 40 g / m ^2, and a recording paper having a basis weight of 109 g / m ² was obtained in the same manner as in Example 1.

Comparative Example 1 A basis weight of 95.5 g / g was obtained in the same manner as in Example 1 except that the coating was performed so that the dry solid content was 3.5 g / m ^2.
to obtain a recording sheet of m ^2.

Comparative Example 2 In Example 5, the pigment composition in the coating solution was the same, and 2 parts of styrene-butadiene latex and 2 parts of casein were added as a binder, and 2 parts of calcium stearate were added as a release agent.
A coating solution having a solid content of 50% was prepared. The obtained coating solution was applied to the coating base paper used in Example 1 so as to have a dry solid content of 12 g / m ² , and a recording paper having a basis weight of 104 g / m ² was obtained in the same manner as in Example 1. .

Comparative Example 3 In Example 5, the pigment composition in the coating solution was the same. 30 parts of styrene-butadiene latex and 30 parts of casein were added as a binder, and 2 parts of calcium stearate were added as a release agent. % Of the coating solution was prepared. The obtained coating solution was applied to the coating base paper used in Example 1 so as to have a dry solid content of 20 g / m ² , and the basis weight was 112 g / m ^{2 in the same} manner as in Example 1.
Recording paper was obtained.

Comparative Example 4 The composition of the coating liquid was a synthetic silica (trade name: Syloid 4) as a pigment.
04, 5 parts of Fuji Devison Co., specific surface area 300 m ² / g), first-class kaolin (trade name Ultra White 90, E
MC) (40 parts), calcium carbonate (Brillant 15, trade name, Shiraishi Industry Co., Ltd.) 55 parts, styrene butadiene latex 15 parts as binder, casein 10
Parts, 2 parts of calcium stearate as a release agent,
A coating solution having a solid content of 58% was prepared. The obtained coating liquid was applied to the coating base paper used in Example 1 so as to have a dry solid content of 15 g / m ^2, and a recording paper having a basis weight of 107 g / m ² was obtained in the same manner as in Example 1. .

Comparative Example 5 The composition of the coating liquid was synthetic silica (trade name: Syloid 4) as a pigment.
04, 25 parts of first grade kaolin (trade name Ultra White 90, manufactured by Fuji Devison, 300 m ² / g)
40 parts of EMC Corporation), 35 parts of calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Industry Co., Ltd.), 15 parts of styrene-butadiene latex as a binder, and casein 15
Parts, 2 parts of calcium stearate as a release agent,
A coating solution having a solid content of 58% was prepared. The obtained coating liquid was applied to the coating base paper used in Example 1 so as to have a dry solid content of 15 g / m ^2, and a recording paper having a basis weight of 107 g / m ² was obtained in the same manner as in Example 1. .

[0032] to obtain a recording paper of Comparative Example 6 except that was coated to a dry solids 60 g / m ² In Example 6 Example 1 in the same manner as basis weight 129 g / m ^2.

Comparative Example 7 The coating liquid composition was a synthetic silica pigment (trade name: FK700,
30 parts of 1st grade kaolin (trade name: Ultra White 90, manufactured by EMC, manufactured by Degusa Co., Ltd., 700 m ² / g)
And 40 parts of calcium carbonate (trade name: Brilliant 1)
5, Shiraishi Industry Co., Ltd.), 11 parts of styrene butadiene latex and 11 parts of casein as a binder, and 2 parts of calcium stearate as a release agent.
% Of the coating solution was prepared. The obtained coating liquid was applied to the coating base paper used in Example 1 so as to have a dry solid content of 11 g / m ² ,
In the same manner as in Example 1, a recording paper having a basis weight of 103 g / m ² was obtained.

Comparative Example 8 The composition of the coating liquid was synthetic silica (trade name: Syloid 4) as a pigment.
04, 30 parts of a specific surface area of 300 m ² / g, manufactured by Fuji Devison Co., 70 parts of calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Industry Co., Ltd.), 22 parts of styrene-butadiene-based latex as a binder, and oxidized starch 2 To prepare a coating solution having a solid content of 56%. The obtained coating solution was used in Example 1.
Is applied with a roll coater so as to have a dry solid content of 10 g / m ^2, and is dried, and the basis weight is 102 g / m ^2.
Was obtained. Then, the coated surface was imparted smoothness using a super calender to obtain a recording paper.

[0035]

As described above, in the electrophotographic printer and copier according to the present invention, the glossiness of white paper is high, and the glossiness of the image area, particularly the glossiness of the halftone area, is higher than the glossiness of the white paper area. A good coated paper for electrophotography having good recording image quality, having stiffness and bulk was obtained. Next, Table 1 and Table 2 summarize the paper quality test results and image evaluation results of the coated papers obtained in the above Examples and Comparative Examples.

[0036]

[Table 1]

[0037]

[Table 2]

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshifumi Iimori 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Sanyo Kuni-Saku Pulp Co., Ltd. Product Development Laboratory (56) References JP-A-54-55438 (JP, A)

Claims (2)

(57) [Claims] In a transfer paper having a recording layer having at least one layer structure on a support, synthetic silica having a specific surface area of 20 to 600 m ² / g is used as a pigment on the outermost layer of the recording layer. A coating liquid containing 30 to 100 parts by weight in 100 parts by weight, and blending 10 to 50 parts by weight of a binder with respect to 100 parts by weight of a pigment, is coated on a dry solid basis on one side using a cast coating method. A transfer paper for electrophotography, which is coated at 5 to 50 g / m ² per minute. 2. The coated surface has a 75 ° specular blank glossiness of 50%.
%. The transfer paper for electrophotography according to claim 1, wherein