JPH03146959A - Dichroic electrophotographiing method - Google Patents

Abstract

PURPOSE:To perform 2nd development without disordering a 1st toner image by charging a 1st developer electrostatically with a larger electrostatic charging quantity than a 2nd developer and forming a 1st toner image. CONSTITUTION:This dichroic electrophotographing method repeats exposure and development in order on an electrostatically charged photosensitive body by using developers of two colors to form toner image of the two colors, which are transferred together to a transfer medium and fixed. This dichroic electrophotographing method charges the 1st developer electrostatically with the larger electrostatic charging quantity than the 2nd developer to form the 1st toner image. Thus, the 1st developer which is imparted a larger electrostatic charging quantity sticks strongly on the photosensitive body, so the 1st toner image formed with it is seldom disordered even in the 2nd development. The difference in electrostatic charging quantity between the 1st and 2nd developers is preferably >=3 muc/g in absolute value and the absolute value of the electrostatic charging quantity of the 1st developer is adjusted preferably within a 10-30 muc/g range.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses two-color developers to sequentially repeat exposure and development on a charged photoconductor to form a two-color toner image.
The present invention relates to a two-color electrophotographic method for transferring and fixing all at once onto a transfer medium.

(Prior Art) Copy machines using color developers have been developed in recent years. There is also a method, such as L-' This method repeats the steps of exposure, development, and transfer.
There was a drawback that the copying time was long.

Therefore, a method has been developed in which a toner image is formed on a photoreceptor by repeating exposure and development with two color developers, and then the toner image is transferred all at once to a transfer medium (Japanese Patent Application No. 138399/1983).

(Problems to be Solved by the Invention) However, this type of method uses a magnetic brush or the like for contact development, so the photoreceptor formed by the first developer -
The toner image of H is rubbed during the second development, causing image disturbance and deterioration of image quality.

The present invention aims to solve the above-mentioned problems and provide a two-color electrophotographic method in which the second development can be performed without disturbing the first toner image.

(Means for Solving the Problems) The present invention uses two-color developers to sequentially repeat exposure and development on a charged photoreceptor to form a two-color toner image,
In a two-color electrophotographic method in which a toner image is transferred and fixed at once to a transfer medium, a first toner image is formed by imparting a higher charge amount to a first developer than a second developer. It is a two-color electrophotographic method.

(Function) In this way, the first developer to which a higher amount of charge is applied adheres more strongly to the photoreceptor, so that the first toner image formed thereon is also affected by the second contact development. Image disturbance is less likely to occur.

It is preferable that the difference in charge amount between the first developer and the second developer is 3 μc/g or more in absolute value, and the charge amount of the first developer is 10 to 30 μc/g in absolute value. It is preferable to adjust within the range of g in order to obtain a good image.

When the charge amount of the first developer is lower than 10 μc/g,
The amount of charge of the second developer must be lower than 7 μc/g, which leads to problems such as excessive image density of the second image and fogging in the J1 image area. Furthermore, if the charging i0 of the first developer is higher than 30 μc/g, a sufficient first image density cannot be obtained. Furthermore, even if the charge amount of the first developer is within the above range, if the difference in charge amount with the second developer is less than 3 μC/g, thick lines may appear in the first image. Image quality will deteriorate.

Note that it is preferable to charge the first and second developers to opposite polarities in order to prevent so-called toner contamination, in which toner of one color is developed again in a developing machine of the other color. It is also possible to have the same polarity.

The amount of charge of the developer can be adjusted as appropriate by selecting the type and amount of the charge control agent and external additives in the toner, the type of binder resin in the toner, and the type of carrier. However, it is not limited to the specific control method.

The charge amount of the developer was measured using a charge amount measuring device (TB-200) manufactured by Sili Chemical Co., Ltd.

The developer used in the present invention can be composed of the following toner and carrier. The toner can be prepared by coating colored particles with an external additive.

The main components of the colored particles are a colorant and a binder resin, and the binder resin can be any general thermoplastic resin, but specifically, styrene, chlorostyrene, etc. Styrenes; monoolefins such as ethylene, propylene, butylene, and imbutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, butyl acrylate, acrylic Esters of α-methylene aliphatic monocarboxylic acids such as dodecyl acid, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether Vinyl ethers such as;
Examples include homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc. Typical binder resins include polystyrene, styrene alkyl acrylate copolymers, etc. Examples include styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and waxes.

Colorants include, but are not limited to, carbon black, nigrosine dye, aniline blue, Calfil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine. Blue, malachite green oxalate, lamp black, rose bengal, C
, l, Pigment Red 48: I, C,! , Pigment Red 122, C,! , Pigmen 1-Red 57
:ISC,I Pigment Yellow 97,C,1,Pigment Yellow 12,C,1,Pigment Blue 15=1,C,! .

Pigment Blue 1523 can be exemplified as a representative example.

Further, a general charge control agent can also be contained in the colored particles. Typical examples include dyes such as chromium-containing dyes, and dyes with ionic structures such as cetylpyridium chloride and tetraphenylborate potassium salt.

The volume average particle diameter of the colored particles of the present invention is preferably less than about 30 μm, but is preferably in the range of 3 to 20 μm.

Further, fine silica powder or the like can be externally added to the colored particles. The silica fine powder contains the silica fine particles themselves, or silicon atoms having 1 to 3 organic groups directly bonded through silicon-carbon bonds, as described in Japanese Patent Publication No. 54-16219. Examples include silicon disulfide particles that are chemically bonded via oxygen-silicon bonds and have such silicon atoms on their surfaces. The silica fine particles may be subjected to a hydrophobic surface treatment.

Additionally, a cleaning aid may be added externally. Examples of cleaning aids include, but are not limited to, polyvinylidene fluoride powder, polymethyl methacrylate powder, and the like.

Next, as the carrier particles, particles having an average particle diameter of up to 500 μm can be used, and for example, iron, nickel, cobalt, iron oxide, ferrite, glass beads, granular silicon, etc. can be used.

Furthermore, the surfaces of these particles can be coated with a coating agent such as fluororesin or silicone resin.

(Example 1) Creation of blue developer for first development Styrene-n-butyl methacrylate-1 copolymer (70
/30) 100 parts by weight copper phthalocyanine
10 parts by weight Kaya Charge N-3 (manufactured by Nippon Kayaku,
After melting and kneading 1 part by weight of the components listed above, the components were pulverized and classified to obtain blue particles with an average particle diameter of 2 μm.

100 parts by weight of the blue particles and 1 part by weight of hydrophobic silica (R972 manufactured by Nippon Aerosil Co., Ltd.) were mixed in a Henschel mixer to obtain a negatively charged blue toner.

- On the other hand, 100 parts by weight of a carrier made of a ferrite core with an average particle size of 100 μm coated with methyl methacrylate-n-butyl methacrylate copolymer (80720) and 4 parts by weight of the above blue toner were mixed in a V-type mixer. A first blue developer was prepared by mixing.

Preparation of black developer for second development Styrene-lobyl methacrylate copolymer (70/30) 101H1f parts Carbon black Tom Hotarube upper part Cetylpyridium chloride 11 parts HR After melt-kneading the above components, finely pulverize and classify Black particles with an average particle size of 12 μm were obtained.

100 parts by weight of the black particles and aluminum oxide C
(manufactured by Nippon Aerosil Co., Ltd.) was mixed in a Henschel mixer to obtain a positively charged black toner.

On the other hand, vinylidene fluoride-trifluoroethylene copolymer (75/2
A second black developer was prepared by mixing 100 parts by weight of the carrier coated with 5) and 5 parts by weight of the above black toner using a V-type mixer.

(Example 2) 100 parts by weight of the blue particles obtained in Example 1 and 2 parts by weight of silica (11 particles R972 manufactured by Aerosil Co., Ltd.) were mixed in a Henschel mixer to obtain a negatively charged blue toner.

Thereafter, a first blue developer was prepared in the same manner as in Example 1.

Further, the second black developer used in Example 1 was used.

(Example 3) 0 100 parts by weight of the blue particles obtained in Example 1, 1 part by weight of silica (R972 manufactured by Nippon Aerosil Co., Ltd.) and 1 part by weight of tin oxide fine powder were mixed in a Henschel mixer to obtain a negatively charged mixture. A blue toner was obtained. After that, in the same manner as in Example 1, the first
A developer for development was prepared.

In addition, 100 parts by weight of the black particles obtained in Example 1 and 0.5 parts of aluminum oxide C (manufactured by Nippon Aerosil Co., Ltd.) were added.
Part by weight and 0.5 part by weight of fine tin oxide powder were mixed in a Henschel mixer to obtain a black toner for positive charging.

Thereafter, a second development preparation developer was prepared in the same manner as in Example 1.

(Comparative Example 1) 100 parts by weight of the blue particles obtained in Example 1 and 111 parts by weight of silica (1
1 part by weight of R972 (manufactured by Aerosil Co., Ltd.) and 2 parts by weight of fine tin oxide powder were mixed in a Henschel mixer to obtain a negatively charged blue toner. Thereafter, a first blue developer was prepared in the same manner as in Example 1.

Further, the second black developer used in Example 1 was used.

(Comparative Example 2) Blue particles were prepared in the same manner as in Example 1 except that Kayacharge N3 was changed to 2 parts by weight. 100 parts by weight of the old color particles and 3 parts by weight of silica (R972 manufactured by Nippon Aerosil Co., Ltd.) were mixed in a Henschel mixer to obtain a negatively charged blue toner. Thereafter, a first blue developer was prepared in the same manner as in Example 1.

Further, the second black developer used in Example 1 was used.

(Comparative Example 3) A second black developer was produced in the same manner as in Example 1, except that the amount of cetylpyridium chloride added to the black particles for the second developer in Example 1 was changed to 1.7 parts by weight. The blue developer of Example 1 was used as the first developer.

(Copy test) After measuring the amount of charge of the developer of the example and comparative example described in ``--, the developer was set in a prototype machine for two-color electrophotography, a copy test was conducted, and the image obtained by the first development was The line thickness and image density were measured to determine whether the image quality was good or bad.

In Example 1, the line thickness in the image obtained by the first development was extremely slight, and the density of the image was also sufficient.

In Example 2, the density of the image obtained by the first development was acceptable, and the line thickness in the image was extremely small.

In Example 3, the line thickness in the image obtained by the first development was acceptable, and the image density was also sufficient.

In Comparative Example 1, since the charge amount of the first developer was as low as 16 μc/g, lines in the image formed by the first development were noticeably thickened.

In Comparative Example 2, the amount of charge of the first developer was too high at 138 μc/g, and therefore a sufficient image density could not be obtained.

In Comparative Example 3, the difference in the amount of charge between the first developer and the second developer was 2.
Due to the small value of μc/g, a considerable thickening of the line was observed.

1 3 14- (Effects of the Invention) By adopting the above configuration, the present invention makes it possible to suppress line thickening in the first developed image even by the second contact development of the two-color electrophotography method. This makes it possible to form high-quality two-color images by ensuring a predetermined image density.

5 565-

Claims (3)

[Claims] (1) In a two-color electrophotographic method in which two-color developers are used to repeatedly expose and develop a charged photoreceptor in sequence to form a two-color toner image, which is then transferred and fixed all at once onto a transfer medium. , a two-color electrophotographic method characterized in that a first developer is given a higher charge amount than a second developer to form a first toner image. (2) The absolute value of the first developer is 3 μc higher than that of the second developer.
2. The two-color electrophotographic method according to claim 1, wherein the first toner image is formed by charging the first toner image to a higher value than 10 to 30 μc/g in absolute value. (3) The two-color electrophotographic method according to claim (1) or (2), characterized in that two-color developers charged with opposite polarities are used.