JPH0650406B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on amorphous silicon (hereinafter a-Si).
The present invention relates to an image forming method in electrophotography using a photoconductor.

In electrophotography, generally, a photoconductive substance is used, an electric latent image is formed on a photoconductor by various means, and then the latent image is developed with a toner, and if necessary, a transfer material such as paper. After the toner image is transferred onto, the copy is fixed by heating or pressure. In addition, the step of removing the toner remaining on the photoconductor after the transfer is an important step for practical use in electrophotography. Photoconductive materials that are currently known as electrophotographic photoreceptors include Se and Cd.
S, organic photoconductor, a-Si, and the like. a-Si has high photosensitivity over the entire visible light range, high surface hardness, and is expected to have a long life, but the film thickness of a-Si is limited in terms of productivity, cost, and performance, and the surface potential is high. There is also a tendency that the dark decay is fast in addition to being low. Therefore, a
In the electrophotographic method using the —Si photoconductor, the resin having a high triboelectric charging property can be used for the binder resin of the toner. However, due to corona discharge, aS
i When charging the surface of the photoconductor, sufficient measures have not yet been taken against deterioration of the photoconductor surface due to generation of ozone, etc. In addition, a-Si is expected to have high hardness. The surface is easily scratched, and even invisible scratches may be reflected in the image.Therefore, except for the deteriorated part of the photoconductor surface, there is no scratch reflected in the image, and the photoconductor surface is always kept in a desired state. A cleaning process is desired.

An object of the present invention is to provide an image forming method including a cleaning process suitable for an a-Si photoconductor.

The present invention externally adds strontium titanate to a toner using a-Si photoconductor as a latent image holding layer and polyester as a binder resin to remove a deteriorated portion on the a-Si photoconductor to form an image. It is an image forming method including a cleaning step for keeping the surface of the photoreceptor at a desired state without adversely affecting it.

a-Si has a Vickers hardness of 1500 to 2000, and has a printing durability of 200,000 to 500,000 sheets, which is several times that of the CdS photoconductor, which is said to have the most durability and abrasion resistance so far. However, due to its high sensitivity, even minute scratches and deterioration of the surface adversely affect the image.

Therefore, the present inventors have studied various resins and inorganic compounds and found that the removal of the deteriorated portion of the a-Si photoconductor is
It has been found that the intended purpose can be effectively achieved by using a polyester resin as a toner binder resin and combining the toner and strontium titanate independently of the hardness of the inorganic compound. The present invention has been reached. With polyester resin and fine powders of cerium oxide, alumina, aluminum silicate, etc., it has been difficult to damage the photoreceptor and adversely affect the image, or to sufficiently remove the deteriorated portion. In addition, styrene-acrylic resin and epoxy resin have poor image quality such as image deletion and low density, and even if strontium titanate, which was effective in polyester resin, is added, a-Si
The photoconductor could not be cleaned sufficiently and satisfactory results could not be obtained.

As a cleaning method, known methods such as a fur brush cleaning, a magnetic brush cleaning, a blade cleaning and a rubbing cleaning can be used, and the rubbing cleaning is particularly suitable for the a-Si photosensitive member.

There is no clear reason why externally adding strontium titanate to a toner using a polyester resin can always keep the a-Si photoconductor surface in a desirable state. However, in the transfer step, when the negatively charged toner on the photoconductor is transferred onto the transfer material by setting the back side of the transfer material to a high potential, the positively charged strontium titanate fine powder is transferred onto the transfer material. Either the toner moves from the toner to the surface of the photoconductor or the toner on the photoconductor, or due to variations in external addition, the toner to which a larger amount of strontium titanate adheres remains on the photoconductor surface during transfer,
Due to any of the causes, strontium titanate remains on the photoconductor that has finished the transfer process in a larger proportion than when externally added. In fact, the toner collected by the cleaning device contained strontium titanate in a proportion higher than the amount of external addition.

From the above, in the cleaning step of the a-Si photoconductor, the combination of the toner itself using the polyester resin and the strontium titanate fine powder present in a higher proportion than that at the time of external addition gives good results. It is considered that the result suitable for cleaning the Si photoconductor is obtained.

The method of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an example of a copying apparatus or a recording apparatus to which the image forming method according to the present invention can be applied.
Of course, it is not limited to this.

Reference numeral 1 denotes a latent image (electrostatic image) holder, which is a photosensitive drum including a photoconductive layer, and not limited to a drum shape, but may be a sheet shape or a belt shape. 2 is a known photosensitive charging device, 3
Is an optical image irradiation device for projecting an original image, an optical image, or a light beam modulated by an image signal. As a result, an electrostatic image is formed on the photoconductor 1. A developing device 4 has a toner holding member 4a, which forms a toner particle image according to the electrostatic image on the photoconductor 1. Reference numeral 5 is a device for transferring the toner image onto the transfer material 6. Incidentally, in order to improve transferability, electric charges may be applied to the developed image in advance by corona discharge or the like before transfer. Further, the electrostatic image on the photoconductor 1 is once transferred to another image carrier, and this is made into a visible image by the developing device 4. It is also possible to employ a so-called electrostatic image transfer system. Reference numeral 7 denotes a fixing device for fixing the toner image on the transfer target member 6, which is composed of at least two rollers having heating and pressing means. A cleaning device 8 has a rubbing means such as a urethane rubber roller for cleaning and removing the residual toner on the photoconductor 1 after the transfer and reusing the photoconductor 1.

Each step of the electrophotographic method applied to the method of the present invention will be described below.

First, an a-Si photoconductor is used as the electrophotographic photoconductor used in the step of forming an electrical latent image. A- used in the present invention
The Si photoconductor has a photoconductive layer of 5 to 20 μm on the substrate,
It preferably has an a-Si layer of 10 to 18 μm. At this time, if necessary, hydrogen, oxygen, boron, nitrogen, phosphorus, and other elements may be introduced individually or in combination during the formation of a-Si to impart new characteristics in order to adapt the characteristics to practical use. Is also good. Further, as a structure of the a-Si photosensitive member, a charge injection preventing layer may be provided below the a-Si layer to prevent the intrusion of charges from the substrate.

Next, the developing process used in the present invention will be specifically described with reference to examples. FIG. 2 is a sectional view showing one embodiment of the developing process used in the present invention. In the figure, the latent image holding surface 1
Is moved in the direction of the arrow, the multi-pole permanent magnet 9 is fixed so as not to rotate. Therefore, by rotating the non-magnetic cylinder 4b which is the toner holding member (sleeve) in the same direction as the latent image holding surface 1, The one-component insulating magnetic toner 11 sent from the developing container 12 is applied onto the non-magnetic cylindrical surface, and friction between the cylindrical surface and the toner particles gives the toner particles a charge having a polarity opposite to the electrostatic image charge. Further, the doctor blade 10 made of iron is brought close to the cylindrical surface (interval 50 μ to 500 μ),
By arranging the multi-pole permanent magnet 9 so as to face one magnetic pole (S pole in the figure), the toner layer can be made thin (3
0 μ-300 μ) and regulate it uniformly. By adjusting the rotational speed of the cylinder 4b, the surface speed and preferably the internal speed of the toner layer is made substantially equal to or close to the speed of the electrostatic image holding surface. Permanent magnets may be used as the doctor blade 10 instead of iron to form the opposing magnetic poles, and another toner coating method may be used instead of the blade. Further, in the developing section, an AC bias may be applied between the toner holding member and the electrostatic holding surface. The developing process according to the present invention is described in JP-A-54-42141 and JP-A-55-1865.
It is described in detail in Japanese Patent Publication No. 6 and the like.

In the present invention, the polyester resin as the binder resin for toner is composed mainly of dicarboxylic acids and polycarboxylic acids represented by phthalic acids as an acid component among the acid components and alcohol components constituting the binder resin. It is composed mainly of an etherified diphenol mixture as a component.

In particular, the etherified diphenol is mainly composed of propoxylated bisphenol and is partially mixed with ethoxylated bisphenol. In addition to these, as a special component, alkyl-substituted dicarboxylic acid and diol are included.

The phthalic acid-based dicarboxylic acids as the main constituent raw material of the polyester are 1,2-benzenedicarboxylic acid and its anhydride, 1,3-benzenedicarboxylic acid, 1,4
-Benzenecarboxylic acid and esterified products thereof can be used equally. Also, aliphatic dicarboxylic acids can be mixed within the range of less than 40 mol% of the dicarboxylic acids, and examples thereof include fumaric acid, maleic acid, succinic acid, cyclohexanedicarboxylic acid, malonic acid, glutaric acid and Anhydrides of these acids can be used.

The usable etherified diphenols are polyoxystyrene (6) -2,2-bis (4-hydroxyphenyl) propane and polyhydroxybutylene (2)-.
2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (3) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3)-
Bis (4-hydroxyphenyl) thioether, polyoxyethylene (2) -2,6-dichloro-4-hydroxyphenyl, 2 ', 3', 6'-trichloro-4'-hydroxyphenylmethane, polyoxy Propylene (3)
-2-Bromo-4-hydroxyphenyl, 4-hydroxyphenyl ether, polyoxyethylene (2,5)-
p, p-bisphenol, polyoxybutylene (4) bis (4-hydroxyphenyl) ketone, polyoxystyrene (7) -bis (4-hydroxyphenyl) ether, polyoxypentylene (3) -2, 2-bis (2,
6-diaiodo-4-hydroxyphenyl) propane and polyoxypropylene (2,2) 2,2-bis (4-
Hydroxyphenyl) propane.

One group of etherified diphenols are etherified bisphenols. A preferred group of etherified bisphenols are ethoxylated or propoxylated, having 2-3 moles of oxyethylene or oxypropylene per mole of bisphenol and having propylene or sulfone groups as substituents. . An example of this group is polyoxyethylene (2,5) -bis (2,6-dibromo-4).
-Hydroxyphenyl) sulfone, polyoxypropylene (3) -2,2-bis (2,6-difluoro-4-hydroxyphenyl) propane and polyoxyethylene (1,5) -polyoxypropylene (1,0 ) -Bis (4-hydroxyphenyl) sulfone.

Another preferred group of etherified bisphenols falling into the group characterized by the above formula is polyoxypropylene-
2,2'-bis (4-hydroxyphenyl) propane and polyoxyethylene or polyoxypropylene 2,2-bis (4-hydroxy, 2,6-dichlorophenyl) propane (oxyalkylene units per mole of bisphenol) The number is 2.1 to 2.5).

Examples of tricarboxylic or higher polycarboxylic acids, including their esters, 1,2,4-benzenetricarboxylic acid, 1,2,5-
Benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenecarboxylic acid,
1,2,4-naphthalene tricarboxylic acid, 1,2,4-
Butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxylic propane, 1,3-dicarboxyl-2-methyl-2-methylenecarboxylic propane, tetra (methylenecarboxylic) methane , 1,2,7,8-octanetetracarboxylic acid and the like can be used. More preferably, at least 60 mol% of the polycarboxylic acid is one selected from trimellitic acid, pyromellitic acid and their anhydrides.

Further, as the polyol having 3 or more valences, 3 to 1 carbon atoms are used.
Polyhydroxy compounds containing 2 and 3 to 9 hydroxyl groups are applicable. A preferred group of polyhydroxy compounds are sugar alcohols and their anhydrides. Examples of these polyhydroxy compounds are sorbitol, 1,2,5,6-hexanetetrol, glycerin, 1,4-sorbitan, pentaerythritol, xylitol, sucrose, 1,2,4-butanetriol,
1,2,5-pentanetriol, erythro 1,2,3
Butanetriol and threo-1,2,3-butanetriol. More preferably, at least 60 mol% of the polyol is selected from glycerin, pentaerythritol, and sorbitol.

Further, these polycarboxylic acids or polyols having a valence of 3 or more account for 40 mol% in the acid or / and alcohol components.
Should not be exceeded.

The alkyl-substituted dicarboxylic acid has 6 to 6 carbon atoms.
18 alkyl groups substituted succinic acid, maleic acid,
Examples include fumaric acid and acid anhydrides thereof. As the alkyl number of carbon atoms is larger, the triboelectric charging ability is more effective even if added in a small amount. If the action is too strong, the toner will be excessively charged, and problems will occur during transfer. Therefore, the amount must be strictly within the above range.

As the alkyl-substituted diol, glycols substituted with an alkyl group having 6 to 18 carbon atoms can be equally used, and ethylene glycol is particularly preferable. It has the same effects as those of the alkyl-substituted dicarboxylic acid.

The strontium titanate fine particles have an average particle size of 0.3.
To 5.0, preferably 0.3 to 2.0 μ, and it is preferable to add 1 to 5% by weight to the toner. Further, a hydrophobic colloidal silica fine powder may be externally added to the toner for the purpose of improving the free flowing property of the powder.

Examples of the charge control agent that can be used in the toner used in the present invention include organic salts or complexes containing a divalent or higher valent metal. Al, Ba, Ca, C as effective metal species
d, Co, Cr, Cu, Fe, Hg, Mg, Mn, N
Examples thereof include polyvalent compounds such as i, Pb, Sn, Sr and Zn. As the organometallic compound, carboxylate salts, alkoxylates, organometallic complexes and xylate compounds of the above metals are effective, and examples thereof include zinc acetate, magnesium acetate, calcium acetate, aluminum acetate, magnesium stearate, calcium stearate, stearin. Acid aluminum, aluminum isopropoxide, aluminum acetylacetonate, iron (II) acetylacetonate, chromium 3,5-ditertiary-butylsalicylate, chromium 3,5-ditertiary-butylstearate, etc., especially acetylacetone metal complex, Salicylic acid metal salts are preferred. The amount added should not exceed 4% by weight with respect to the binder resin in order to avoid adversely affecting the triboelectrification property, and if it is 0.2% or less, the substantial effect disappears.

Further, known thermoplastic resins in a range not impairing the performance of the present invention, that is, 40% by weight or less in the binder resin, for example, polyester resin, urethane resin, epoxy resin, ethylene-ethyl acrylate resin, phenol resin, styrene other than the present invention. -Butadiene resin, xylene resin, butyral resin, etc. may be used by mixing or modification. The blending amount of these known thermoplastic resins is more preferably not more than 20% by weight in the binder for toner. Among these thermoplastic resins, styrene-acrylic resin is preferable.

As the colorant used in the toner of the present invention, all known colorants can be used, and examples thereof include carbon black, iron black, nigrosine, benzidine yellow, quinacridone, rhodamine B, and phthalocyanine blue.

In order to use the toner of the present invention as a magnetic toner,
Magnetic powder may be included. As such magnetic powder, a substance that is magnetized when placed in a magnetic field is used.
There are powders of ferromagnetic metals such as iron, cobalt and nickel, and compounds such as magnetite, hematite and ferrite. When using an iron oxide magnetic material as a coloring agent,
It is preferable that the toner contains 20 to 80% by weight.

Further, the toner of the present invention is mixed with carrier particles such as iron powder, glass beads, nickel powder, and ferrite powder, if necessary, and used as a developer for an electric latent image.

The developed image obtained in the developing step is transferred to a transfer material such as paper using an electrostatic transfer method such as corona transfer or bias roll transfer.

On the other hand, the transferred image on the transfer target member is fixed by a known method such as a pressure heating roll method, an open chamber method, and a flash fixing method.

Hereinafter, the present invention will be specifically described with reference to resin production examples, examples, and comparative examples, but these do not limit the present invention in any way. All used parts are parts by weight.

[Production Example 1] Polyoxypropylene (2,5) -2,2-bis (4-)
545 parts of hydroxyphenyl) propane were placed in a four-necked flask, a stirrer, a condenser, a thermometer, and a gas introduction tube were set and placed in a mantle heater. After purging the inside of the reaction vessel with nitrogen gas, when the content was adjusted to 50 to 60 ° C., 135 parts of terephthalic acid and 77 parts of succinic acid (C ₁₆ H ₃₀ O ₄ ) substituted with a C ₁₂ alkyl group were used. Then, 38 parts of trimellitic acid was added so that the amount of carboxyl group was 0.9 equivalent to 1 equivalent of hydroxyl group. 2 this mixture system
The mixture was heated and stirred at 10 ° C. After removing the water of reaction, after about 5 hours, the reaction was traced by measuring the acid value every hour in order to see the end point of the reaction. The reaction was cooled to room temperature when the acid number was about 30. Then, a polyester resin was obtained by a conventional method.

[Production Example 2] Polyoxypropylene (2,5) -2,2-bis (4-hydroxyphenyl) was prepared in the same manner as in Production Example 1.
545 parts of propane were put into a flask, and nitrogen replacement and 50
C. Heating was performed. 135 parts of isophthalic acid, C ₁₂
77 parts of succinic acid substituted with the alkyl group and 38 parts of trimellitic acid were added, and the mixture was heated and stirred at 210 ° C. for reaction, and after completion of the reaction, it was cooled to room temperature. Then, a polyester resin was obtained by a conventional method.

(Example 1) Polyester resin of Production Example 1 100 parts Acetylacetone iron 2 parts Carbon black 8 parts A mixture having the above composition was kneaded by heating with a roll mill.
After allowing this to cool, it was coarsely crushed with a cutter mill and finely pulverized with an ultrasonic jet mill to obtain a toner having an average particle size of about 8μ.

To this toner, 3% by weight of strontium titanate having an average particle diameter of 1.0 μm was added and externally added with a coffee mill. 15 parts of the toner thus obtained was mixed with 85 parts by weight of carrier iron powder to obtain a two-component developer. Next, a photosensitive drum provided with an a-Si photoconductive layer having a film thickness of 15 μm was provided on the substrate. Using a modified NP-5000 machine, a durability test by repeated copying was performed.
No damage appears on the Si photoconductor, and the image quality is good.
When the surface of the i photoreceptor was observed, no deteriorated portion was found.

(Example 2) Polyester resin of Production Example 1 100 parts 3,5-ditersialybutylchromium salicylate 3 parts Magnetite 60 parts A mixture having the above composition was prepared according to a conventional method to give an average particle size of about 1
A 0 μ single-component magnetic toner was obtained.

3% by weight of strontium titanate having an average particle diameter of 1.0 μ was externally added to this toner. Using this, an evaluation test was conducted as follows.

On the surface of an a-Si photosensitive drum, which has a charge injection prevention layer of 1.0μ on an aluminum substrate, a film thickness of 20μ, and an a-Si photoconductive layer containing boron,
The drum is charged uniformly by corona discharge of +6 KV at a linear surface velocity of 168 mm / sec, and then the original image is irradiated to form a latent image on the surface of the photoconductor. As shown in FIG. 2, sleeve diameter 50 mm, sleeve surface magnetic flux density 70
A developing device having a distance of 0.2 mm between a sleeve made of 0 Gauss and an iron cutting blade and a sleeve made of aluminum was set to a distance between the surface of the a-Si photosensitive drum and the sleeve of 0.25 mm, and development was performed using the developer. Then, the powder image was transferred while irradiating a direct current of +7 KV from the back surface of the transfer paper, and further fixed between the heating rollers. As the cleaning method, the rubbing cleaning shown in FIG. 1 was used. As a result, even after running 100,000 sheets, the image did not show the scratches on the drum, and almost no deterioration components due to corona discharge such as nitrogen oxides were observed on the surface of the a-Si photoconductor.

Example 3 Except for using the polyester resin of Production Example 2,
When performed in the same manner as in Example 1, neither scratch nor deterioration component on the drum surface was observed.

Example 4 The same results were obtained as in Example 2, except that 1% by weight of strontium titanate fine powder having an average particle size of 2.0 μ was externally added.

Example 5 5% by weight of strontium titanate having an average particle size of 1.0 μm
Good results were obtained by the same procedure as in Example 2 except that external addition was performed.

(Comparative Example 1) The same operation as in Example 1 was carried out except that a styrene-acrylic resin, which had been widely used in the past, was used, but the image quality was deteriorated due to drum scratches after 10,000 sheets of durability.

(Comparative Example 2) The same operation as in Example 2 was carried out except that an epoxy resin was used, but when the drum surface was examined at a durability of 9000 sheets, a deteriorated portion due to corona discharge was observed.

(Comparative Example 3) The same operation as in Example 2 was carried out except that a toner to which strontium titanate was not added externally was used, and when the drum surface was examined at a durability of 20,000 sheets, a deteriorated portion was recognized.

(Comparative Example 4) The same operation as in Example 2 was carried out except that 6% by weight of strontium titanate having an average particle size of 3 μm was externally added. As a result, a drum scratch was generated at a durability of 5,000 sheets.

(Comparative Example 5) The same operation as in Example 2 was performed except that cerium oxide was externally added instead of strontium titanate, and a drum scratch was generated at a durability of 15,000 sheets.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an example of a copying apparatus to which the image forming method of the present invention can be applied. FIG. 2 shows a sectional view of one embodiment of the developing process used in the present invention. DESCRIPTION OF SYMBOLS 1 ... Latent image carrier, 4 ... Developing device, 4a ... Toner holding member, 4b ... Non-magnetic cylinder, 9 ... Magnetrol, 10 ... Doctor blade, 11 ... Insulating magnetic toner.

Claims (3)

[Claims] 1. A step of forming an electrical latent image on a latent image holding layer, a step of developing the latent image with a toner disposed on a toner holding member, and a step of transferring the obtained toner image to a subject member. And a step of removing the toner remaining on the surface of the latent image holding layer after transfer, using an amorphous silicon photoreceptor as the latent image holding layer,
The latent image formed on the amorphous silicon photoconductor is used as a binder resin of the toner, with (A) an acid or alcohol component of 40 mol% or less of a trivalent or more polycarboxylic acid and / or a trivalent or more polyol. (B) 60 mol% or more of dicarboxylic acids based on phthalic acid; (C) 30 mol% or less of an alkyl-substituted dicarboxylic acid and / or alkyl-substituted diol in an acid or alcohol component; and (D) etherified diphenols. Developed by adding a fine powder of strontium titanate to a toner using a non-linearized low melting point polyester resin obtained from a system containing,
An image forming method comprising: transferring and cleaning the photoconductor after the transfer. 2. Strontium titanate has an average particle size of 0.3.
The image forming method according to claim 1, wherein the image forming method has ˜5.0 μm. 3. The image forming method according to claim 1, wherein 1 to 5% by weight of strontium titanate is added to the toner.