JPH063844A - Image forming method - Google Patents

Abstract

(57) [Abstract] [Purpose] Spot exposure is performed by an exposure beam based on a digital signal to form a spot-like image with high sharpness. [Structure] A phthalocyanine derivative in which the benzene nucleus of a phthalocyanine and a phthalocyanine molecule is substituted with an electron-withdrawing group, and the number of electron-withdrawing groups is 0.5 or less and 0.001 or more with respect to the total of phthalocyanine units of the phthalocyanine and the phthalocyanine derivative. After mixing with an acid that dissolves phthalocyanine in the following composition ratio, a photoreceptor 11 composed of a phthalocyanine-based composition deposited by water or a poor solvent substance is positively charged at 12 and then at 13 based on a digital signal. An image is formed by spot exposure with a beam and development at 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electrophotography, electrostatic recording,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using a positively chargeable photoconductor applied to electrostatic printing, etc. Regarding

[0002]

2. Description of the Related Art A photoconductor having a photosensitive layer formed by dispersing a photoconductive organic pigment in a binder resin is known, for example, from Japanese Patent Publication No. 56-20543. The publication describes that a photoconductive phthalocyanine-based pigment is used as the photoconductive organic pigment and a novolac type phenol resin is used as the binder resin, whereby a photoreceptor having excellent gradation and repetitive characteristics can be obtained. ing.

By the way, as a photoconductor applied to electrophotography, as shown in FIG. 4 (a), one showing a so-called low γ type light attenuation characteristic in which light attenuation is slow, and FIG. 4 (b) are shown. As shown, the light decay is slow at the beginning of exposure,
It is known to exhibit a so-called high γ type optical attenuation characteristic that becomes steep in the middle and the latter stages.

The photoreceptor described in the above publication exhibits the low γ-type light attenuation characteristic shown in FIG. 4A, and is excellent in gradation and repetitive characteristics. Like the selenium-based vapor deposition photoreceptor shown, it is preferably used in a repetitive transfer type copying machine or the like.

On the other hand, the photosensitive member having the high γ type light attenuation characteristic of FIG. 4B has characteristics such that the light attenuation is steep in the latter stage of exposure and has a high gamma characteristic, and is repeatedly used. It is not used effectively because it has a drawback that the light attenuation curve changes and deteriorates in the process.

In recent years, in the field of electrophotography and the like, research and development of an image forming method employing a digital system, which enables easy image quality improvement, alteration inspection, editing, etc., and enables high quality image formation, has been actively conducted. . In this image forming method, a beam of, for example, a laser, an LED array, a liquid crystal shutter, or preferably a semiconductor laser is modulated by a digital image signal from a computer or a copy original, and spot exposure is performed on a uniformly charged photoreceptor. To form a dot-shaped electrostatic latent image, which is developed with toner to form a dot-shaped image.

As shown in FIG. 5 (a), the beam modulated by the digital image signal has a luminance distribution that approximates to a pulse having a normal distribution with a skirt extending to the left and right. For example, in the case of a semiconductor laser beam, , Usually 50 to 1 at a brightness of 1 to 5 mW
It has an extremely narrow pulse width of 00 μm. Such a pulse is usually spot-exposed on a photoconductor applied to electrophotography to form a dot-shaped electrostatic latent image, which is preferably developed by a reversal development method to form a dot-shaped image, Images often have poor sharpness. This tendency is low γ
Remarkably when using a photoconductor that exhibits a type light attenuation characteristic,
The narrower the pulse width of the exposure beam is, the more remarkable it is.

On one side of FIGS. 5 (b) to 5 (d), the potential distribution of a dot-shaped electrostatic latent image when spot exposure is performed by a semiconductor laser beam using a photoconductor having a low γ type optical attenuation characteristic. (B-1), a dot-shaped image image (C-1), and a dot overlapping line image (D-1) are shown.
Similar to the above, a case where a photoconductor having a high γ type light attenuation characteristic is used is shown on the second side of FIGS. 4B to 4D. As can be seen from the figure, the potential distribution of the dot-shaped electrostatic latent image and the dot-shaped or line-shaped image of the photoconductor exhibiting the low γ-type light attenuation characteristic are unclear due to the digital method. Is inconvenient for the formation of the image.

[0009]

From such a point of view, the inventors of the present invention have replaced the photoconductor having a low γ-type optical attenuation characteristic with a high photopolymer having a relatively high gamma characteristic as shown in FIG. 4B. We have earnestly conducted research on a technique for improving the sharpness of a dot-shaped image by using a photoconductor having a γ-type light attenuation characteristic.

As the photoreceptor exhibiting the high γ-type light attenuation characteristic, for example, a photoconductive inorganic material such as zinc oxide, titanium oxide or cadmium sulfide, or a photoconductive organic material such as a phthalocyanine pigment is used in a usual electrophotography. There is known a photoreceptor having a photosensitive layer formed by being dispersed and contained in a thermoplastic binder resin applied to.

However, these photoconductors exhibiting high γ-type light attenuation characteristics have been developed for use in ordinary electrophotography, and therefore the gamma characteristics are insufficient and the repetitive characteristics are inferior. There is. In particular, a photoconductor using a photoconductive inorganic material has relatively coarse particles of the photoconductive inorganic material and only has a moderate gamma characteristic, and is not suitable for forming a dot-shaped image by a digital method. Totally inappropriate.

Further, as described in the above-mentioned publication, the photoconductor exhibiting the high γ type light attenuation characteristic generally has a drawback that the repetitive characteristic is poor and the fatigue deterioration is large.

The present invention has been made based on the above circumstances, and its objects are as follows.

It is an object of the present invention to provide an image forming method capable of stably forming a dot-shaped image having excellent sharpness many times by spot exposure with an exposure beam.

[0015]

In order to achieve the above object, the positively chargeable photosensitive member used in the image forming method of the present invention is a phthalocyanine derivative in which benzene nucleus of phthalocyanine and phthalocyanine molecule is substituted by an electron withdrawing group. Was dissolved in an acid capable of dissolving phthalocyanine at a composition ratio such that the number of electron-withdrawing groups was 0.5 or less and 0.001 or more with respect to the total of phthalocyanine units of the phthalocyanine and the phthalocyanine derivative, followed by water or a poor solvent substance. The phthalocyanine-based composition deposited by the method is dispersed and contained in a binder resin.

In the image forming method of the present invention, the surface of the photoconductor containing the phthalocyanine-based composition is positively charged, and the surface of the positively chargeable photoconductor is spot-exposed by an exposure beam based on a digital signal. To form an electrostatic latent image,
It is characterized by including a series of steps of developing the formed electrostatic latent image with a developer.

[0017]

In the image forming method of the present invention, a phthalocyanine derivative substituted with an electron-withdrawing group is used as a positively chargeable photoreceptor, and the number of electron-withdrawing groups is 0.5 or less with respect to the total of all phthalocyanine units. As a result of using a phthalocyanine-based composition in which phthalocyanine and phthalocyanine were dissolved in an acid at a composition ratio of 001 or more and then precipitated with water or a poor solvent, it was found that the sensitivity characteristics were almost flat for some period in the early stage of exposure. It exhibits damping properties, but surprisingly,
In the middle and the latter half of the exposure, the light attenuation characteristic is changed to an extremely high sensitivity, and the light attenuation characteristic is decreased substantially linearly, and as a result, an extremely high γ characteristic is exhibited.

Although the reason why such excellent properties are exhibited is not fully clarified, carriers generated on the surface of the photoconductive organic pigment at the initial stage of exposure are
Light attenuation is suppressed by being temporarily trapped on the surface of the pigment, and the carrier trap becomes saturated in the middle and the latter half of the exposure, resulting in avalanche phenomenon all at once, causing a nearly linear fall. It is presumed that it exhibits a light attenuation characteristic that

Therefore, after the surface of the photoconductor is positively and uniformly charged, the surface is spot-exposed with an exposure beam on the basis of a digital signal to form a dot-shaped electrostatic latent image. When developed by the reversal development method and visualized, a dot-shaped image with extremely high sharpness is obtained.

FIG. 2 shows the preferred photoreceptor characteristics obtained with the photoreceptor used in the present invention.

The maximum light energy among the light energies that can maintain the surface potential at about the same level as the initial charging V ₀ is E
_{1. The} minimum light energy among the light energies that can drop the surface potential to the residual potential V _res (about 30 V) is defined as E ₂ . The smaller E ₁ is, the better the photosensitivity is, and E ₂
The smaller the difference ΔE of −E _1, the higher the γ-type photoreceptor can be. In this evaluation method, ΔE is preferably 20 μJ / cm ² or less.

(Phthalocyanine composition) The phthalocyanine used in the present invention includes metal-free phthalocyanine,
And phthalocyanine complexes of phthalocyanine with copper, nickel, cobalt, tin, zinc, iron, lead, magnesium, titanium and oxides / halides of the above metals, and also a mixture thereof. Phthalocyanine is a compound well known as a pigment, and in the present invention, both phthalocyanine called crude and pigmented phthalocyanine can be used.

The phthalocyanine derivative used in the present invention is one in which the benzene nucleus of the phthalocyanine molecule is substituted with an electron withdrawing group. The electron-withdrawing group is a substituent having a positive substituent constant δ according to Hammett's rule. Above all δ
Is preferably +0.2 or more. Examples of such an electron-withdrawing group include a nitro group, a cyano group, a halogen atom, a sulfone group and a carboxyl group.
This phthalocyanine derivative is
As a phthalocyanine raw material, phthalonitrile, phthalic acid, phthalic anhydride, and phthalimide, which are substituted with the above-mentioned substituents, phthalonitrile, phthalic acid, phthalic anhydride,
It can be obtained by using phthalimide or partly in combination. The method for producing the phthalocyanine derivative is also not particularly limited. The number of electron-withdrawing substituents in one molecule of the phthalocyanine derivative is 1 to 16.

The composition ratio of the phthalocyanine and the phthalocyanine derivative is such that the number of electron-withdrawing groups of the phthalocyanine derivative is 0.5 or less, preferably 0.2 or less for the synthesis of the phthalocyanine and the phthalocyanine unit of the phthalocyanine derivative. The ratio is set to 0.001 or more, preferably 0.002 or more.

Examples of the phthalocyanine-dissolving acid used in the present invention include inorganic acids such as sulfuric acid and alkylsulfonic acids such as methanesulfonic acid, ethanesulfonic acid and propanesulfonic acid, and halogenated alkylsulfonic acids in which these are halogen-substituted. , And organic acids such as alkylbenzene sulfonic acid. It is also possible to use a mixed acid of an aromatic organic acid such as toluenesulfonic acid / benzenesulfonic acid and at least one organic acid selected from the above alkylsulfonic acid / halogenated alkylsulfonic acid / alkylbenzenesulfonic acid. The mixing ratio of the aromatic organic acid and the organic acid is preferably 1 to 6 parts by weight, more preferably 1 to 4 parts by weight, with respect to 10 parts by weight of the organic acid. If it is 6 parts by weight or more, the aromatic organic acid is not uniformly dissolved in the organic acid.

The phthalocyanine composition used in the present invention is obtained by dissolving the phthalocyanine and the phthalocyanine derivative in the above proportions in an acid and then precipitating with water or a poor solvent to obtain a phthalocyanine photoconductive composition.

The amount of the acid used for dissolving the phthalocyanine and the phthalocyanine derivative is 5 to 30 with respect to 1 part by weight of the phthalocyanine and the phthalocyanine derivative.
Weight is preferable, and 10 to 20 parts is more preferable.

When the phthalocyanine and the phthalocyanine derivative are dissolved in the acid in the above ratio, the temperature is preferably 0 to 30 ° C., and the solution is dissolved with sufficient stirring. The stirring time is preferably 0.5 to 3 hours.

Then, water or a poor solvent substance is deposited, and the poor solvent to be reprecipitated is preferably water, but is not particularly limited as long as it is a solvent which does not dissolve phthalocyanine. For example, methanol / ethanol / acetone / methyl ethyl ketone is preferable. The amount of the poor solvent is preferably 3 to 30 times the amount of the acid, and 5
More preferably, the amount is about 15 times.

As a method of precipitation, for example, the acid solution is transferred to a dropping funnel and slowly dropped into a poor solvent such as water which is sufficiently stirred. The poor solvent temperature at that time is 0 to 20 ° C.
Is preferred. After the dropping, the mixture is stirred for a while, and the time is preferably 0.5 to 3 hours. The deposited phthalocyanine photoconductive composition is filtered, washed with water, dried and isolated.

(Photoreceptor) FIG. 3 shows a specific example of the constitution of the photoreceptor used in the present invention, 1 is a conductive support, 2 is an undercoat layer, 3 is a photoreceptor layer, and 4 is a crosslinked resin layer. Is. In this example, an undercoat layer 2 is provided on a conductive support 1, a photoconductor layer 3 is provided on the undercoat layer 2, and a crosslinked resin layer 4 is further provided thereon.

The conductive support 1 is made of aluminum,
A metal plate made of steel, copper, or the like or a drum is used, but it may be a paper or plastic film on which a metal layer is laminated or vapor-deposited.

Further, as the undercoat layer 2, for example, the following resins which are usually used in a photosensitive layer for electrophotography can be used.

(1) Polyvinyl alcohol (poval), polyvinyl methyl ether, polyvinyl ethyl ether and other vinyl polymers

(2) Nitrogen-containing vinyl polymers such as polyvinylamine, poly-N-vinylimidazole, polyvinylpyridine (quaternary salt), polyvinylpyrrolidone and vinylpyrrolidone-vinyl acetate copolymer.

(3) Polyether type polymers such as polyethylene oxide, polyethylene glycol, polypropylene glycol

(4) Acrylic acid-based polymers such as polyacrylic acid and its salts, polyacrylamide, poly-β-hydroxyethyl acrylate, etc.

(5) Polymethacrylic acid and its salts,
Methacrylic acid-based polymers such as polymethacrylamide, poly-β-hydroxyethyl methacrylate, and polyhydroxypropyl methacrylate

(6) Ether fibrin-based polymers such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cell sauce and hydroxypropyl methyl cellulose

(7) Polyethyleneimine-based polymers such as polyethyleneimine

(8) Polyalanine, polyserine, poly-
L-glutamic acid, poly- (hydroxyethyl) -L-
Polyamino acids such as glutamine, poly-δ-carboxymethyl-L-cysteine, polyproline, lysine-tyrosine copolymer, glutamic acid-lysine-alanine copolymer, silk fibroin and casein

(9) Starch and its derivatives such as starch acetate, hydroxyethyl starch, starch acetate, hydroxyethyl starch, amine starch and phosphate starch

(10) Polymer soluble in a mixed solvent of water and alcohol such as soluble nylon and methoxymethyl nylon (8 type nylon) which are polyamides

In the undercoat layer 2, +700 to +2,0
It is desirable to have hole mobility so as to withstand a high electrification of 00 V, for example, in the case of positive electrification, to prevent injection of electrons from the conductive support 1 and to obtain excellent light attenuation characteristics due to avalanche phenomenon.

The photoreceptor layer 3 contains a phthalocyanine-based composition, a binder resin, and an antioxidant, which is optionally used, in an amount of 0.01 to 1 μm using a solvent for the binder resin.
It is formed by mixing and dispersing in the form of fine particles to prepare a coating liquid, coating the coating liquid on the undercoat layer 2, drying and optionally heat treating.

The crosslinked resin layer is prepared by dissolving a crosslinked resin and an antioxidant used as necessary in a solvent to prepare a coating solution, coating the coating solution on the photoreceptor layer 3 and drying the coating solution. Is formed by heat treatment.

[0047]

EXAMPLES The present invention will be specifically described below with reference to reference examples and examples of the present invention, but the embodiments of the present invention are not limited thereto.

Reference Example 1 of Photoreceptor (Production of Phthalocyanine-Based Composition) 40 g of copper phthalocyanine and 4-nitrophthalic anhydride produced by a method called the Weyler method using phthalic anhydride, cupric chloride and urea. 0.8 g of tetranitrocopper phthalocyanine prepared in the same manner as above was dissolved in 440 g of methanesulfonic acid with sufficient stirring. Pour the dissolved liquid into 2,000 g of water,
A composition of copper phthalocyanine and tetranitrocopper phthalocyanine was deposited, filtered, washed with water, and dried at 60 ° C. to obtain 39.8 g of a phthalocyanine composition.

(Photoreceptor) Phthalocyanine composition 5.3 g Antioxidant 0.2 g 2,2-thio-diethylene-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] -Polyester resin solution 19g Almatex, P-645 (manufactured by Mitsui Toatsu) -Melamine resin solution 7g Uban, 20HS (manufactured by Mitsui Toatsu) -Cyclohexanone 100g

The above-mentioned materials are mixed to prepare glass beads 200.
g was added and dispersed by a pent mixer for 4 hours to prepare a coating liquid for the photoreceptor layer.

On the other hand, an aluminum drum-shaped conductive support having a diameter of 80 mm was used, and an undercoat layer made of soluble nylon and having a thickness of 0.1 μm was formed on the surface thereof. On the undercoat layer, the coating liquid for the photoreceptor layer was dried to a film thickness of 2
It was coated so as to have a thickness of 0 μm and dried at 200 ° C. for 3 hours to form a photoconductor layer.

Next, a fluororesin (Sephral coat A1
01-B, Central Glass) 10 g, isocyanate resin (Coronate HX, Nippon Polyurethane) 0.7
g and 0.3 g of the antioxidant represented by the structural formula (a) were dissolved in 50 g of cyclohexanone to prepare a coating solution for the crosslinked resin layer.

[0053]

[Chemical 1]

The coating solution for the crosslinked resin layer was applied on the photoreceptor layer so that the film thickness after drying was 1 μm, and dried to produce a positively chargeable photoreceptor for use in the present invention.

A positively chargeable photoconductor for testing used in the present invention was manufactured in the same manner as above except that an aluminum foil having a thickness of 90 μm was used as the conductive support.

(Evaluation) The positively charged photoreceptor for this test was mounted on "Cynthia-55" (manufactured by Gentec), and a charging / exposure test was conducted to measure the electrostatic characteristics of the photoreceptor for the test. did. The results were good as shown in Table 1 below.

Reference Example 2 of Photoreceptor (Production of Phthalocyanine Composition) Copper Phthalocyanine 4
0 g, tetranitro copper phthalocyanine 0.8 g consisting of methane sulfonic acid / paratoluene sulfonic acid in a weight ratio of 8
It was dissolved in 440 g of an organic mixed acid of / 2 with sufficient stirring. The dissolved liquid is poured into 2,000 g of water to precipitate a copper phthalocyanine composition, which is then filtered and washed with water at 60 ° C.
It was dried in a vacuum to obtain 39.6 g of a phthalocyanine composition.

(Photoreceptor) As in Reference Example 1, a drum shape,
A positively charged photoreceptor for testing was manufactured.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results were good as shown in Table 1 below.

Reference Example 3 of Photoreceptor (Production of Phthalocyanine Composition) Copper Phthalocyanine 4
0 g of octachlorocopper phthalocyanine was dissolved in 440 g of methanesulfonic acid with sufficient stirring. The dissolved liquid was poured into 2,000 g of water to deposit a copper phthalocyanine composition, which was then filtered, washed with water, and dried at 60 ° C. to obtain 39.0 g of a phthalocyanine composition.

(Photoreceptor) As in Reference Example 1, drum-shaped,
A positively charged photoreceptor for testing was manufactured.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results were good as shown in Table 1 below.

Reference Example 4 of Photoreceptor (Production of Phthalocyanine Composition) The phthalocyanine composition of Reference Example 1 was used.

(Photoreceptor) In the same manner as in Reference Example 1, except that the polyester resin and the melamine resin were changed to a fluororesin and an isocyanate resin in the preparation of the coating solution for the photoreceptor layer, the drum-shaped positive resin used in the present invention was similarly used. A chargeable photoreceptor and a test positively charged photoreceptor used in the present invention were produced.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results were good as shown in Table 1 below.

Reference Example 5 of Photoreceptor (Production of Phthalocyanine Composition) The phthalocyanine composition of Example 2 was used.

(Photoreceptor) As in Reference Example 4, drum shape,
A positively charged photoreceptor for testing was manufactured.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results were good as shown in Table 1 below.

Reference Example 6 of Photoreceptor (Production of Phthalocyanine Composition) The phthalocyanine composition of Reference Example 1 was used.

(Photoreceptor) In the preparation of the coating solution for the crosslinked resin layer of Reference Example 1, the compound of the following structural formula (b) was used as the antioxidant instead of the compound of the structural formula (a). In the same manner as in Reference Example 1, a drum-shaped, test positively charging photosensitive member used in the present invention was manufactured.

[0071]

[Chemical 2]

(Evaluation) Evaluation was carried out in the same manner as in Example 1. The results were good as shown in Table 1 below.

Reference Example 7 of Photoreceptor (Production of Phthalocyanine Composition) The phthalocyanine composition of Reference Example 2 was used.

(Photoreceptor) As in Reference Example 6, drum-shaped,
A positively charged photoreceptor for testing was manufactured.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results were good as shown in Table 1 below.

Comparative Example 1 40 g of copper phthalocyanine was dissolved in 440 g of methanesulfonic acid with sufficient stirring. Dissolve the liquid in water 2,000
After depositing the copper phthalocyanine composition on the g,
It was filtered, washed with water, and dried at 60 ° C. to obtain 39.0 g of a phthalocyanine-based photoconductive composition.

(Photoreceptor) As in Reference Example 1, drum-shaped,
A positively charged photoreceptor for testing was manufactured.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results are as shown in the following Table 1, high sharpness large E ₂ -E ₁ could not be obtained.

Comparative Example 2 Unsubstituted copper phthalocyanine 40 and tetranitrocopper phthalocyanine 0.8 g were dissolved in 98% concentrated sulfuric acid 440 with sufficient stirring. The dissolved liquid is poured into 2,000 water to precipitate a copper phthalocyanine composition, which is then filtered and washed with water.
After drying at 0 ° C., 39 g of a composition was obtained.

(Photoreceptor) As in Reference Example 1, drum-shaped,
A positively charged photoreceptor for testing was manufactured.

(Evaluation) Evaluation was carried out in the same manner as in Reference Example 1.
The results are as shown in the following Table 1, high sharpness large E ₂ -E ₁ could not be obtained.

[0082]

[Table 1]

As can be seen from the results in Table 1, the positively charging photosensitive material according to the present invention has an excellent high γ characteristic in which the initial charge V ₀ is high and E ₂ -E ₁ is 20 or less. Have.

[0084]

【Example】

 Image Forming Method The image forming method of the present invention will be described with reference to FIG.

In the present invention, by using the specific photoconductor 11 shown in FIG.
It is uniformly charged in the range of + 2,000V at 12, and the surface of this photoconductor is spot-exposed at 13 by an exposure beam based on a digital signal to form a dot-shaped electrostatic latent image, This electrostatic latent image is developed with a developer at 14, then transferred onto a recording medium 15 such as paper at 16 and fixed at 17 to form a dot-shaped image. After the transfer, the photosensitive member is cleaned with a cleaning blade, a cleaning brush, or the like at 18 to form a clean surface, and then subjected to a charging step again to be used for forming the next image.

In the exposure process, there are a laser printer system, an optical shutter array system, a liquid crystal shutter array system, an LED system and the like. When the laser printer system is applied, for example, a digital signal corresponding to an image from a computer is used. The modulated laser beam spot-exposes the uniformly charged surface of the photoconductor to form a dot-shaped electrostatic latent image. When a digital copying machine system is applied, the surface of a uniformly charged photoconductor is spot-exposed by a laser beam modulated by a digital signal corresponding to an image from a copy original to form a dot-shaped image. Form an electrostatic latent image.

A semiconductor laser can be particularly preferably used as the exposure beam. That is, since the semiconductor laser can form a laser beam having an extremely narrow pulse width, it is possible to form a dot-shaped electrostatic latent image with high sharpness.

In the developing step, the dot-shaped electrostatic latent image formed on the photosensitive member by spot exposure with the exposure beam is subjected to one-component or two-component development containing fine particle toner having an average particle size of 1 to 20 μm. Develop with agent.

As a developing system, a contact reversal developing system may be adopted, or toner images of respective colors may be formed on an exposed body in a superposed manner, and the toner images may be collectively transferred onto a transfer material and fixed to form a color image. In a color image forming method for forming an image, a method may be adopted in which a high frequency AC bias is applied to a developing area to cause toner to fly and non-contact reversal development is performed (see JP-A-58-184381). .

Further, in the present invention, even when the contact reversal developing method is adopted, it is preferable to apply an AC bias to the developing area for development, and the toner acts as a latent image on the photoreceptor due to the action of the AC bias. Development is carried out by being pressed against the surface from the vertical direction, and there is an advantage that the entire latent image surface is uniformly and sharply developed.

According to the image forming method of the present invention, the photoconductor has an excellent high γ characteristic, and the excellent high γ characteristic is stably exhibited even when the image is repeatedly formed many times. Therefore, by spot-exposing the surface of the photoconductor with the exposure beam based on the digital signal,
It is possible to form a high sharpness dot-shaped electrostatic latent image without fringes, and as a result, it is possible to form an image with high sharpness.

Example The drum-shaped positively charging photoreceptors obtained in Reference Examples 1 to 7 were mounted on digital laser printers, and the surface of the photoreceptor 11 was positively and uniformly charged at 12, and The surface of the photoconductor is exposed with a semiconductor laser beam modulated by a digital signal in 13 to form a dot-shaped electrostatic latent image, and this electrostatic latent image has an average particle diameter of 12 μm.
The non-magnetic toner and the two-component developer consisting of a resin-coated ferrite carrier having an average particle diameter of 100 μm were used, and a DC bias voltage of 600 V was applied between the developing gaps, and the contact reversal development method was used to develop at 14, This is transferred to plain paper at 16 and fixed at 17,
A black and white image was formed.

The above operation was repeated 100,000 times, and the sharpness of the obtained black and white image was examined.
When any of the photoconductors was used, excellent images with high sharpness were obtained to the end. That is, the reproduced image of the 5.5-point original Chinese character document was excellent in reproducibility from the initial image to the image after 100,000 times.

Comparative Example 3 In the example of the present invention, a black and white image was continuously produced in the same manner except that the photosensitive member for comparison having a drum shape obtained in Comparative Example 1 was changed to the positive photosensitive member. When formed, only an image with poor sharpness was obtained. That is, 5.5
The copy image of the original Kanji character manuscript at Point was an image that was difficult to read because the Kanji was partially crushed from the initial image.

Comparative Example 4 Black and white images were continuously formed in the same manner as in the example of the present invention except that the drum-shaped comparative positively charging photosensitive member obtained in Comparative Example 2 was used as the photosensitive member. When formed, the image had poor sharpness as in Comparative Example 3 and was difficult to read from the initial image.

[0096]

EFFECTS OF THE INVENTION A photoconductor having a so-called high γ-type attenuation characteristic in which the light attenuation is steep in the middle and the second half of exposure is used.
In addition, spot exposure with a beam for exposure provides a highly sharp dot-shaped electrostatic latent image without fringes, and as a result, a digital-ready image with high sharpness can be repeatedly formed.

[Brief description of drawings]

FIG. 1 is a diagram showing each step of an image forming method characterized by using a novel photoconductor having a digital-compatible characteristic.

FIG. 2 is a graph showing preferable photosensitivity characteristics of the photoconductor used in the present invention.

FIG. 3 is a diagram showing a configuration example of a positively charged single-layer type photosensitive member used in the present invention.

FIG. 4 is a graph showing light attenuation characteristics of a photoconductor used for electrophotography, in which (a) shows low γ type light attenuation characteristics and (b) shows high γ type light attenuation characteristics.

5A and 5B are diagrams showing respective image forming modes when spot exposure is performed on a low-gamma-value photoconductor (1 side) and a high-gamma-value photoconductor (2 side), in which FIG. The exposure energy distribution which is normally distributed, (b) in the figure shows the potential of the electrostatic latent image, (c) shows the dot-shaped image image, and (d) shows the line-shaped image image. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive support 2 Undercoat layer 3 Photoconductor layer 4 Crosslinked resin layer 10 Support drum 11 Photoreceptor according to the present invention 12 Uniform charging 13 Spot exposure 14 Development 15 Recording medium such as paper 16 Transfer 17 Fixing 18 Cleaning

Claims (1)

[Claims] 1. A phthalocyanine derivative in which a benzene nucleus of a phthalocyanine and a phthalocyanine molecule is substituted with an electron withdrawing group, and the number of electron withdrawing groups is 0.5 or less and 0.001 with respect to the total of phthalocyanine units of the phthalocyanine and the phthalocyanine derivative. After the phthalocyanine is dissolved in an acid capable of dissolving the phthalocyanine in the above composition ratio, the photoreceptor containing the phthalocyanine-based composition precipitated in water or a poor solvent in the binder resin is positively charged, and the positively charged photoreceptor is obtained. A digital-compatible characteristic characterized by including a series of steps of forming an electrostatic latent image by spot-exposing the surface of the substrate with an exposure beam based on a digital signal and developing the formed electrostatic latent image with a developer. And an image forming method capable of expressing.