JPS6385568A - Electrophotographic black insulating paper and electrophotographic copying method using it - Google Patents

Abstract

PURPOSE:To facilitate formation of a reversed image by using black insulating paper specified in intrinsic surface resistivity and intrinsic volume resistivity. CONSTITUTION:The black insulating paper to be used has an intrinsic surface resistivity of >=10<9>OMEGA and an intrinsic volume resistivity of >=5X10<9>OMEGA.cm, and it is prepared by mixing into a paper pulp material an insulating black pigment obtained by coating a conductive black pigment, such as carbon black, with an insulating transparent resin, such as a styrenic copolymer, and making paper in the paper-making process, and alternatively, it is prepared by coating or impregnating conductive black paper with an insulating transparent resin, laminating an insulating transparent film on said paper, or printing, coating, or impregnating white paper with the insulating black pigment.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a black insulating paper for electrophotography that allows color images, especially inverted images, to be obtained on black paper in the electrophotographic copying process, and electrophotographic copying using the same. Regarding the method.

(Prior Art) In the electrophotographic copying method, in addition to the usual positive image copying system that forms a positive electrostatic latent image from a positive original to obtain a positive copy, there is a system that uses a negative original such as microfilm or a laser beam or There are reversal image copying systems in which a negative electrostatic latent image is formed by a light image, such as a light emitting diode array, and then reversed to produce a positive copy.

A typical copying machine is equipped with only a normal image copying system, and is based on the premise that a positive original with a white background area is obtained from an original with a positive white background area.

Therefore, it is impossible to obtain a white positive image of the background from a black negative image of the background. however.

Slides and some foreign pamphlets or catalogs have negative image originals, which are difficult to read if the original image is copied. Therefore, it is desirable to provide these originals with a positive image by copying an inverted image.

For this reason, a copying machine that has both a normal image copying system and a reverse image copying system has been proposed. Two types of copying machines include, for example, a copying machine equipped with a photoreceptor and a charging device that can be charged to both positive and negative polarities. However, there are only a limited number of photoreceptors that can be charged to one polarity, and their sensitivity and durability are limited. Significant differences occur in the sensitivity and other electrophotographic characteristics of the photoreceptor when it is positively charged and negatively charged.

It becomes difficult to adjust the density and image quality of the normal image and the inverted image to a constant value. Copying machines using toner of both positive and negative polarities are also known. However, this copying machine requires two types of toner and also requires electrical control such as switching the application of bias voltage to the developing section. in this way,
A copying machine that has both a normal image copying system and a reverse image copying system requires complicated mechanisms and controls.

In order to solve this problem, 1. After forming a desired color area on a transfer paper using a colored toner (for example, black toner) using a normal normal image copying machine.

Attempts have been made to copy an image onto this area using a toner of a different color than the colored toner (for example, white toner versus black toner). However, this method requires two copies, making the operation complicated. By copying twice,
The resulting copied image has wrinkles and curls.

One possible method for obtaining a reversed image using a normal copying machine is to copy an image onto black paper using white toner. However, black paper generally contains carbon blank for the purpose of improving color development and preventing static electricity. Therefore, this black paper is conductive and cannot transfer a toner image using an electrophotographic copying machine.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and its purpose is to provide an electrophotographic black color that can be used in an electrophotographic copying machine to transfer images. An object of the present invention is to provide an insulating paper and an electrophotographic copying method using the same. Another object of the present invention is to provide a black insulating paper for electrophotography which can produce a reversed image using a conventional copying machine, and an electrophotographic copying method using the same.

(Means for Solving the Problems) The present invention involves preparing a black insulating paper in place of the conventional black paper which is 9gL conductive, and using this black insulating paper to make copies using a normal image copying machine. By.

A clear inverted image can be obtained by simplifying the section. It was completed based on the inventor's knowledge.

The electrophotographic black insulating paper of the present invention has a two-surface specific resistance value of 1.
09Ω or more and the volume specific resistance value is 5×109Ω・
1 or more, thereby achieving the above object.

The electrophotographic copying method of the present invention is an electrophotographic copying method using the above-mentioned black insulating paper, and includes copying a reversed image with white toner on the black insulating paper, thereby achieving the above-mentioned object. be done.

In the electrophotographic copying process, the electrical resistance value of transfer paper influences the transfer efficiency and image quality of toner images or electrostatic latent images. If the electrical resistance of the transfer paper is not high enough, the charge from the transfer corotron or bias roll will pass through the paper to ground, thereby not creating the electric field necessary to cause transfer.

Therefore, the transfer efficiency decreases. Also, if the electrical resistance value of the transfer paper is too low, charge will leak through the paper.

The transfer electric field is reduced and the toner image is removed. The relationship between the surface specific resistance value (Ω) of the transfer paper and the transfer efficiency (C%) is
As shown in the figure. The surface specific resistance value (Ω) of the transfer paper and the incidence of toner image removal (%) when copying using this transfer paper.
) is shown in Figure 2. As is clear from FIGS. 1 and 2.

The transfer efficiency of the transfer paper reaches a surface specific resistance value of around 109Ω, and decreases significantly below this value. Similarly, the incidence of toner image omission increases rapidly below 109Ω. For this reason, the black insulating paper of the present invention was set to have a specific resistance value of 2 surfaces of 10 9 Ω or more. Also the volume resistivity value.

Based on similar data, 5X109Ω・cl! It is considered to be 1 or more. If the surface resistivity of the black insulating paper falls below 109Ω, or if the volume resistivity falls below 5×109Ω, the transfer efficiency will decrease even when copying using this black insulating paper, resulting in sharp images. An electrophotographic copy image cannot be obtained.

The toner image also comes off.

This black insulating paper is obtained by mixing an insulating black pigment with raw pulp in one known paper manufacturing process, for example two.

In the paper manufacturing process, raw pulp is suspended in water and then beaten. The beaten pulp is mixed with size, filler, dye, etc.

Next, it is made into paper and rolled or cut.

A roll or cut paper is obtained, respectively. During the blending process in the manufacture of this paper, the insulating black pigment is
It is added to beaten raw pulp along with fillers, dyes, etc. Insulating black pigment.

For example, it can be obtained by coating a conductive black pigment such as carbon black, graphite, cyanine black, CuCr20a, CuFe2O4-Cu with an insulating transparent resin. Examples of insulating transparent resins include polystyrene; styrenic copolymers such as polystyrene-butadiene copolymer and styrene-acrylic copolymer; polyethylene, polyethylene-vinyl acetate copolymer, and polyethylene-vinyl alcohol copolymer. Examples include ethylene copolymers; phenolic resins; epoxy resins; allyl phthalate resins; polyamide resins; polyester resins; and maleic acid resins. To coat the electrically conductive black pigment with the insulating transparent resin, a method similar to that used for manufacturing ordinary electrophotographic toners is used. In this method, first, a conductive black pigment and an insulating transparent resin are mixed in a mixer, and then heated and melted and kneaded in a hot roll mill.

Next, the kneaded material is pulverized with a feather mill or jet mill, and then classified for 1 time to obtain an insulating black pigment with a desired particle size. By classification, the insulating black pigment has an average particle size of 10 μm.
The following is preferable. If it exceeds 10 μm, a clear electrophotographic copy image cannot be obtained even if it is copied using black insulating paper made using this insulating black pigment.

The black insulating paper of the present invention can also be obtained by coating or impregnating conductive black paper with an insulating transparent resin.

The same resin as the resin used for coating the conductive black pigment is used as the insulating transparent resin. This resin.

It is usually dissolved in a suitable solvent and coated or impregnated onto conductive black paper. Black insulating paper can also be obtained by laminating an insulating transparent film on conductive black paper. As the insulating transparent film, polyethylene terephthalate poly4-methylpentene-1, polyolefin resin, etc. are formed into a film and used. Alternatively, the resin film for film may be formed on both sides of the conductive black paper by a lamination method such as an extrusion lamination method.

The black insulating paper of the present invention can also be obtained by printing, coating or impregnating white paper with an insulating black pigment.

As the white paper, ordinary transfer paper used for copying electrophotographs is used. The same material as the insulating black pigment mixed with the raw material pulp in the method for obtaining black insulating paper described above is used for the insulating black pigment.

The method for preparing this insulating black pigment is also as described above.

It is obtained by coating a conductive black pigment such as carbon black or graphite with an insulating transparent resin. The same resin as described above is used as the insulating transparent resin.

The black insulating paper thus obtained is used as a transfer paper in a normal electrophotographic copying process. Using this black insulating paper, an inverted image is copied using a conventional copying machine, for example, in a first-order manner.

By exposing the original, an electrostatic latent image corresponding to the original image is formed on the photoreceptor. This latent image is developed using, for example, white toner. This toner image is then electrostatically transferred to black insulating paper and heat fused. As a result, an inverted image of the original image (a negative image for a positive original) is formed on the black insulating paper. The electrophotographic copying process uses known processes and does not require any special operations, except for the use of white toner.

White toner contains white colorant, binder resin, and compounding agents (
charge control agent, mold release agent, etc.).

The white coloring agents in this toner include zinc white, titanium oxide, tin oxide, antimony white, and zinc sulfide.

Zinc oxide, barium carbonate, clay, silica, white carbon, talc, alumina, pallite, etc. are used.

As the charge control agent for this toner, a known colorless or white agent is used as it does not adversely affect the color tone of the white toner. For the purpose of positive charge control, organic compounds having a basic nitrogen atom 1, such as basic dyes and aminobilin.

Pyrimidine compounds, polynuclear polyamine compounds, aminosilanes, or fillers surface-treated with these are used, and for the purpose of controlling negative charge.

Carboxy group-containing compound 2 such as a metal chelate of alkyl salicylic acid is used. These charge control agents are preferably used in an amount of 1 to 10% by weight per toner.

Further, as a releasing agent for this toner, silicone oil, low molecular weight olefin resins, various waxes, etc. are used.

The white toner is made by melting and kneading the above components and cooling them.

This is obtained by crushing and classifying. It can also be obtained by dispersing toner ingredients in a resin solution and then spray granulating the resultant.

For example, a resin similar to the insulating transparent resin described above is used as the binder resin for the white toner.

(Example) The present invention will be described below with reference to examples.

Styrene-acrylic copolymer (Bryolide ACL)
100 parts by weight of carbon black (manufactured by Gutdeyer)
Printex L+manufactured by Degussa) 20 parts by weight of the above formulation was blended, pre-mixed using a Henschel mixer, then melt-kneaded using a twin-screw extruder and allowed to cool.

This kneaded product was coarsely ground using a cutting mill and then finely ground using an ultrasonic jet mill PJM-100 to obtain an insulating black pigment with an average particle size of 8 μm.

This insulating black pigment was blended with the size, filler, dye, etc. into a beaten raw material bulb.

Next, black insulating paper was obtained using a known paper manufacturing process.

The surface specific resistance value of the obtained black insulating paper was 1.5×101
0Ω, and the volume resistivity value is 2. l×10”Ω・cm
Met.

Using this black insulating paper as a transfer paper, a white image was formed on the black insulating paper using a white toner containing titanium oxide as a white coloring agent by a normal copying method. The white images were clear and no wrinkles or curls were observed in the 9 images.

Actual observation ±1 Commercially available conductive black paper with carbon blank dispersed (Belcourt 702 surface specific resistance value 1.5 to 2 x 101'Ω)
1 volume specific resistance value 1.2 x 109Ω・(to)).

A 20% by weight methanol solution of polyvinyl butyral was applied. The coating was carried out on both sides of conductive black paper in a layer thickness of 2 to 10 μm or more.

The surface specific resistance value of the obtained black insulating paper was 1.2×10I
OΩ, and the volume resistivity value is 1.8 x 10”Ω・
It was the mouth.

Using this black insulating paper as a transfer paper, a white image was formed on the black insulating paper by a normal copying method using a white toner containing titanium oxide as a white colorant. This white image was clear and no wrinkles or curls were observed in one image.

20% methanol by weight of next JU Kensho polyvinyl ethylene? A black insulating paper was obtained in the same manner as in Example 2, except that a 20% by weight methanol solution of polyvinylpyrrolidone was used instead of the solution.

The surface specific resistance value of the obtained black insulating paper was 8.0×109
Ω, and the volume resistivity value was 1.5×10 days Ω·am.

Using this black insulating paper as a transfer paper, a white image was formed on the black insulating paper by a normal copying method using a white toner containing titanium oxide as a white colorant. This white image was clear and no wrinkles or curls were observed in one image.

20tt% ethanol of Tinehei Kando polyvinyl ethylene? A black insulating paper was obtained in the same manner as in Example 2, except that a 20% methanol solution of an acrylic polymer (L-53P) was used instead of the liquid solution.

The surface specific resistance value of the obtained black insulating paper was 3.0×101
0Ω, and the volume resistivity was 5.2×10”Ω·mouth.

Using this black insulating paper as a transfer paper, a white image was formed on the black insulating paper by a normal copying method using a white toner containing titanium oxide as a white colorant. This white image was clear and no wrinkles or curls were observed in one image.

Back cover ±1 The insulating black pigment obtained in Example 1 was dissolved in toluene at a concentration of 25% by weight. This solution was applied to a thickness of 5 μm on ordinary white transfer paper for electrophotographic copying.

The surface specific resistance value of the obtained black insulating paper was 4.8×10I
0 Ω, and the volume-specific resistivity value was 5.6×10” Ω.

Using this black insulating paper as a transfer paper, a white image was formed on the black insulating paper using a white toner containing titanium oxide as a white coloring agent by a normal copying method. This white image was clear and no wrinkles or curls were observed in one image.

(Effect of the invention) The electrophotographic black insulating paper of the present invention is thus prepared.

Since it has excellent insulation properties, a reversed image can be easily obtained by using this as a transfer paper and performing normal electrophotographic copying using white toner. Unlike conventional methods, there is no need for special copying machines or complicated controls. There is no need to copy twice. The obtained copied image is clear with few wrinkles and curls.

As a result, the electrophotographic copying method using the black insulating paper of the present invention is useful in obtaining a positive image copy from a negative original.

4. Figure 1 is a graph showing the relationship between the surface resistivity value of transfer paper and the transfer efficiency when electrophotographic copying is performed using this transfer paper, and Figure 2 is 2 is a graph showing the relationship between the surface resistivity value of a transfer paper and the incidence of toner image omission when electrophotographic copying is performed using this transfer paper.

that's all

Claims (1)

[Claims] 1. A black insulating paper for electrophotography having a surface resistivity of 10^9 Ω or more and a volume resistivity of 5 x 10^9 Ω·cm or more. 2. Claim 1, which is obtained by mixing an insulating black pigment with the beaten raw material pulp in a mixing step in paper manufacturing in which size, filler, dye, etc. are blended with the beaten raw material pulp. Black insulating paper for electrophotography. 3. The black insulating paper for electrophotography according to claim 1, which is obtained by coating or impregnating a conductive black paper with an insulating transparent resin. 4. The black insulating paper for electrophotography according to claim 1, which is obtained by laminating an insulating transparent film on a conductive black paper. 5. The black insulating paper for electrophotography according to claim 1, which is obtained by printing, coating, or impregnating white paper with an insulating black pigment. 6. Claim 2 or 5, wherein the insulating black pigment is formed by coating a conductive black pigment with an insulating transparent resin.
Black insulating paper for electrophotography as described in any of the above. 7. The conductive black pigment is carbon black, graphite cyanine black, CuCr_2O_4 and C
The black insulating paper for electrophotography according to claim 6, which is at least one of uFe_2O_4-CuMn_2O_4. 8. An electrophotographic copying method using black insulating paper for electrophotography having a surface resistivity value of 10^9Ω or more and a volume resistivity value of 5×10^9Ω·cm or more, the method comprising: An electrophotographic copying method comprising copying a reversed image with white toner. 9. The black insulating paper is obtained by mixing an insulating black pigment with the beaten raw material pulp in a blending process in paper manufacturing in which size, filler, dye, etc. are mixed with the beaten raw material pulp. The electrophotographic copying method according to scope item 8. 10. The electrophotographic copying method according to claim 8, wherein the black insulating paper is obtained by coating or impregnating conductive black paper with an insulating transparent resin. 11. The electrophotographic copying method according to claim 8, wherein the black insulating paper is obtained by laminating an insulating transparent film on a conductive black paper. 12. The electrophotographic copying method according to claim 8, wherein the black insulating paper is obtained by printing, coating, or impregnating white paper with an insulating black pigment. 13. The electrophotographic copying method according to claim 9 or 12, wherein the insulating black pigment is a conductive black pigment coated with an insulating transparent resin. 14. The electrophotographic copying method according to claim 13, wherein the conductive black pigment is at least one of carbon black, graphite cyanine black, CuCr_2O_4, and CuFe_2O_4-CuMn_2O_4.