JP2704658B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method, for example, a multicolor image forming apparatus (color copy) for sequentially forming toner images of different colors on a photoreceptor as an image carrier to obtain a multicolor image, that is, a color image forming apparatus. The present invention relates to an image forming method suitable for a printer and an electrophotographic copying machine.

B. 2. Description of the Related Art As a conventional multicolor image forming method, a multicolor image forming method in which a plurality of toner images are superimposed and developed on the same photoconductor as an image bearing member and a transfer process is performed only once is disclosed in It is known from JP 60-76766. According to such a method, the apparatus can be reduced in size and cost, and a high-quality color image without color misregistration can be obtained.

Referring to FIG. 17, the principle of the multicolor image forming method will be described. FIG. 17 shows a change in the surface potential of the photoconductor, and exemplifies a case where the charging polarity is negative. PH indicates an exposed portion of the photoreceptor, DA indicates a non-exposed portion of the photoreceptor, and DUP indicates a rise in potential caused by the negatively charged toner adhered to the exposed portion PH in the first development.

The photoreceptor is uniformly charged by a scorotron charger, and has a constant negative surface potential -E as shown in FIG. Next, a first image exposure using a laser, a cathode ray tube, an LED or the like as a digital exposure source is given, and as shown in (b), the potential of the exposure unit PH decreases according to the amount of light. The electrostatic latent image formed in this manner is obtained by subtracting the surface potential of the unexposed portion from
The developing device to which a negative bias substantially equal to E is applied develops. As a result, the negatively charged toner T ₁ as shown in (c)
There adhered to a relatively low potential exposure portion PH, the first toner image T ₁ is formed. Region in which the toner image T ₁ is formed, the potential by negatively charged toner T ₁ is attached is rises by DUP, not in the unexposed portion DA and the same potential. Then the photosensitive member surface to which the first toner image is formed the second charging is performed by the charger, so that, regardless of the presence or absence of the toner T _1, a uniform surface potential -E. This is shown in (d). A second image exposure is performed on the surface of the photoreceptor to form an electrostatic latent image ((e)).
T ₁ second toner image is performed negatively charged developer of the toner image T ₂ of the different colors can be obtained from the. This is shown in (f). By performing the above process a plurality of times, a multicolor toner image is obtained on the photoconductor. This is simultaneously transferred onto a recording paper, and is further fixed by heating or pressing to obtain a multicolor recorded image. In this case, the photoreceptor is cleaned of toner and charges remaining on the surface and is used for the next multicolor image formation.
On the other hand, there is another method for fixing a toner image on a photoconductor.

In the method described with reference to FIG. 17, it is desirable that at least the developing step (f) be performed so that the developer layer does not contact the surface of the photoreceptor.

In the multicolor image forming method, the second and subsequent charging can be omitted. In the case where charging is repeated every time without omitting such charging, a charge removing step may be performed before charging. The exposure sources used for each image exposure may be the same or different.

The present inventor has studied the above method and found that there are the following problems. That is, in FIG. 17, when the next image exposure is performed in the step (e), if the exposure light is incident on the already formed toner image (adhered toner) as shown by a virtual line, the photosensitive member , And the exposure amount is reduced. For this reason, in the physical sense, when the next toner is superimposed on the toner that has already adhered, the amount of adhesion of the toner (that is, the amount of potential decrease due to exposure) is reduced, and the toner T ₂ on the toner T ₁ is reduced. Is reduced, and the color reproducibility is deteriorated, and the gradation is also reduced.

C. SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of improving color reproducibility, furthermore, gradation and the like while utilizing the features of superposition development.

two. In other words, according to the present invention, the Bragg angle 2θ of the X-ray diffraction spectrum with respect to CuKα characteristic X-rays (wavelength 1.541 °) is at least
Forming an electrostatic latent image by digital image exposure on an image carrier using titanyl phthalocyanine in a crystalline state showing a peak of X-ray intensity at 27.2 degrees ± 0.2 degrees as a photoconductive substance of a photosensitive layer, and forming the electrostatic latent image Repeating the development of the image, thereby superimposing a plurality of toner images on the image carrier,
The present invention relates to an image forming method for transferring the superposed toner images.

First, an example of an image forming apparatus (for example, a digital copy type multicolor image forming apparatus) usable in the present invention is shown in FIGS.
FIG. 3 will be described.

According to this apparatus, as shown in FIG. 2, in the image reading unit LE, the original 18 placed on the original table 19 receives light from the illumination light source 13 moving in the X direction, and the reflected light 20 Red through a mirror 14, a lens 15, and a color separation filter 16,
An image is formed on each of the green and blue CCD image sensors 17R, 17G, and 17B.
In these CCD image sensors, optical information is converted into a time-series electric signal and sent to an image data processing unit TR ₁ (see FIG. 3).
Here, recording image data is formed. Laser optics 10
In the laser light of the semiconductor laser 21 by the modulation unit MD based on the recording image data from the video signal processing unit TR ₂ it is modulated (in the figure, 22 is a polygon mirror). On the other hand, the surface of the image carrier 1 is uniformly charged by the scorotron band electrode 2. Subsequently, an image exposure L from the laser optical system 10 is irradiated onto the image carrier (photosensitive drum) 1. Thus, an electrostatic latent image is formed. For example, when a blue filter is set as the color separation filter 16, this electrostatic latent image is reversely developed by the developing device 31 containing yellow toner. The image carrier 1 on which the toner image has been formed is uniformly charged again by the scorotron band electrode 2, and then, for example, when a green filter is set as the color separation filter 16, the optical information read through this filter is added to the color information. Based on the image exposure L. The formed electrostatic latent image is reversely developed by a developing device 32 containing magenta toner. As a result, a two-color toner image is formed on the image carrier 1 using the yellow toner and the magenta toner. Thereafter, in the same manner, the developing device 3
In steps 3 and 34, the cyan toner and the black toner are overlaid and developed in reverse, and a four-color toner image is formed on the image carrier 1. The four-color toner image is given a charge by a pre-transfer band electrode as needed, and is transferred onto the recording paper P at once by the transfer pole 4. Recording paper P
Are separated from the image carrier 1 by the separation pole 5 and fixed by the fixing device 6. On the other hand, the image carrier 1 is cleaned by the cleaning device 8.

Although a four-color toner image has been described above, a two-color toner image or a single-color toner image may be formed in some cases.

According to FIG. 2, the control unit CT is operated by the operation unit OP, and in the image reading unit LE whose operation is controlled by this control unit, the optical information of the original 18 is converted into a time-series signal for each color, and the obtained information is obtained. the data processed by the image data processing unit TR ₁ and further into data suitable for recording the video signal processing unit TR _2.
The image forming unit RE executes the above-described process for image formation based on the control signal, transfers a toner image onto copy paper, and forms a recorded matter. The image forming unit RE employs an electrophotographic method.

In addition to the above, various kinds of preset information, especially data on the contents of functional operations such as the copy magnification and color described above, are stored in ROM (Read On
ly memory), a floppy disk, a magnetic tape, or the like, and the information in the image memory ME can be extracted and output to the image forming unit RE as needed.

In the above-described apparatus, the developing units 31 to 34 having the basic structure as shown in an enlarged view in FIG. 2 are used. In any of these developing devices, the nonmagnetic developing sleeve 41, which is a developer carrying carrier, rotates counterclockwise, and the internal magnet body 42 rotates clockwise, so that the developer 50 in the developer pool 43 is placed on the surface of the developing sleeve 41. It is attracted and transported in the direction opposite to the rotation of the magnet body 42. The thickness of the developer conveyed on the developing sleeve 41 is regulated by a layer thickness regulating blade 44 on the way to form a developer layer.

When performing development, a DC bias voltage and / or an AC voltage are applied to the developing sleeve 41 by the bias power supply 52. As a result, development is performed in the development area E, and the developer layer that has passed through the development area E is removed from the development sleeve 41 by the cleaning blade 45 and is reduced to the developer pool 43. Toner pool 43 is supplied with toner from a toner hopper (both not shown) by a toner supply roller. Further, the developer 50 in the developer pool 43 is uniformly stirred by the stirring or conveying means 46, 47, and 48, and a sufficient charge is given to the toner particles.

In the above description, the transport of the developer layer may be performed by rotating the developing sleeve 41 still or clockwise, or by rotating the magnet body 42 counterclockwise or stationary.

A one-component developer composed of magnetic toner particles may be used as the developer 50, but a two-component developer in which magnetic carrier particles and non-magnetic toner particles are mixed may be used to improve color clarity and toner charge control. Is preferably used.

The development by the developing device shown in FIG. 2 is preferably carried out by a non-contact development method, and its detailed development conditions are described in JP-A-57-147652.
Or those described in JP-A-59-181362 (however, all use a two-component developer). Also,
When a one-component developer is used, it may be the same as that described in JP-A-55-18656 or JP-B-41-9475.

When developing by the developing devices 31 to 34, the developing sleeve 41 is used.
In order to effectively control the flying of the toner by applying a bias voltage, the alternating electric field applied between the image carrier 1 and the developing sleeve 41 is set to 100 Hz to 5 KHz, and the DC bias is set to 100 Hz.
V ~ 2KV is good. Further, the gap 51 between the image carrier 1 and the developing sleeve 41 is set in the range of 10 to 2000 μm. Therefore, it is preferable that the layer thickness of the developer layer regulated by the layer thickness regulating blade 44 is smaller than the above-mentioned gap.

By using the above preferable conditions for the developing units 31 to 34, the development of the electrostatic latent image for each color by each developing unit can be performed sharply without fogging. Therefore, the recording paper P
A clear single-color image or a multicolor image is recorded.

When the developer 50 is composed of two components, the particle size of the carrier and the toner is preferably 5 to 50 μm for the former and 20 μm or less for the latter. As the carrier, a magnetic carrier or an insulating carrier coated with an insulating material can be used. When the developer 50 is used as one component, a known insulating toner can be used.

Further, the present invention is not limited to the above-described apparatus, but can be applied to other types of copying machines. The development is not limited to reversal development, but may be regular development.

The present inventor has earnestly studied the above-described color reproducibility problem in image formation in which the above-described superposition of toner images is performed on the same photosensitive member, and as a result, has reached the following recognition.

That is, since the light sensitivity of a normal photoreceptor is not so large, as shown in FIG. 17, when the amount of exposure is reduced by the adhered toner already existing during the second image exposure, The light sensitivity becomes worse accordingly. On the other hand, in the present invention, in particular, it shows high sensitivity to dot exposure by light having a relatively long wavelength such as a semiconductor laser light, and is used for development of high γ (the light attenuation characteristic of the charged potential is sharp). As a preferable photoconductive substance of the photosensitive layer (74 in FIG. 2), the peak of the X-ray intensity is obtained when the Bragg angle 2θ of the X-ray diffraction spectrum with respect to CuKα characteristic X-ray (wavelength 1.541 °) is at least 27.2 degrees ± 0.2 degrees. It is characterized by using titanyl phthalocyanine in the crystalline state shown.

This titanyl phthalocyanine also has at least 9.6
It is preferable that the peak of the X-ray intensity at each of ± 0.2 degrees and 27.2 degrees ± 0.2 degrees is preferable. Further, the X-ray intensity of the peak at 9.6 degrees ± 0.2 degrees is the X-ray intensity of the peak at 27.2 degrees ± 0.2 degrees. It is desirable that it is 40% or more.

By using such a titanyl phthalocyanine, a high-sensitivity, high-γ photoreceptor can be obtained, and a sufficient amount of adhered toner can be obtained even with a small amount of exposure. As a result, the image density is large and the color reproducibility is greatly improved. If the exposure is digital exposure (dot exposure), for example, if the recording density is 9 to 24 lines / mm, for example, 15.8 lines / mm, the obtained image is a set of a large number of dots. The gradation is determined by the area ratio of the dots. If the area ratio is small, the image density is low, and if the area ratio is large, the image density is high. Therefore, the halftone can be arbitrarily controlled by the dot area ratio. it can. In image formation using such dots, high reproducibility of one dot is required. To meet this requirement, the titanyl phthalocyanine of the present invention has a high γ (so-called on-off type).
Because of the characteristics, the dot reproducibility, that is, the gradation is also improved.

The basic structure of the titanyl phthalocyanine of the present invention may be represented by the following general formula.

General formula: (In the formula, X ¹ , X ² , X ³ and X ⁴ each represent a hydrogen atom, a halogen atom, an alkyl group or an alkoxy group, and n, m, l and k each represent an integer of 0 to 4.

The X-ray diffraction spectrum is measured under the following conditions (the same applies hereinafter). The peak here is a sharp acute-angle protrusion different from noise.

X-ray tube Cu voltage 40.0 KV current 100.0 mA Start angle 6.0 deg. Stop angle 35.0 deg. Step angle 0.02 deg. Measurement time 0.50 sec. The above X-ray diffraction spectrum is “JDX-8200”
(Manufactured by JEOL Ltd.).

Next, a method for producing the titanyl phthalocyanine according to the present invention will be described. For example, 1,3-diiminoisoindoline and sulfolane are mixed, titanium tetrapropoxide is added thereto, and the mixture is reacted under a nitrogen atmosphere. The reaction temperature is from 80C to 300C, preferably from 100C to 260C. After completion of the reaction, the mixture is left to cool, and the precipitate is collected by filtration to obtain titanyl phthalocyanine. Next, by subjecting this to a solvent treatment, the desired crystal form of titanyl phthalocyanine shown in FIGS. 10 to 13 can be obtained.

As a device used for this treatment, a homomixer, a disperser, an agitator, a ball mill, a sand mill, an attritor and the like can be used in addition to a general stirring device.

In the present invention, other carrier-generating substances may be used in addition to the above-mentioned titanyl phthalocyanine. As such a carrier-generating substance, a crystal form different from the titanyl phthalocyanine of the present invention, for example, α-type, β-type, α,
In addition to titanyl phthalocyanine such as β-mixing type and amorphous type, other phthalocyanine pigments, azo pigments, anthraquinone pigments, perylene pigments, polycyclic quinone pigments, squarium pigments and the like can be mentioned.

As the carrier transporting material in the photoreceptor of the present invention,
Various compounds can be used, and typical examples include compounds having a nitrogen-containing heterocyclic nucleus represented by oxazole, oxadiazole, thiazole, thiadiazole, imidazole and the like and a condensed ring nucleus thereof, and polyarylalkane-based compounds. , Pyrazoline compounds, hydrazone compounds, triarylamine compounds, styryl compounds, styryltriphenylamine compounds, α-phenylstyryltriphenylamine compounds, butadiene compounds, hexatriene compounds, carbazole compounds And condensed polycyclic compounds. Specific examples of these carrier transport materials include, for example, JP-A-61-107356.
Many examples can be given, including the carrier transporting substances described in (1), and the structures of particularly typical ones are shown below.

Various configurations of the photoconductor are known. The photoreceptor of the present invention can take any of these forms, but is preferably a laminated type or a dispersion type function-separated type photoreceptor. In this case, the configuration is usually as shown in FIG. 4 to FIG. The layer configuration shown in FIG. 4 is such that a carrier generation layer 72 is formed on a conductive support 71, and a carrier transport layer 73 is laminated thereon to form a photosensitive layer 74. FIG. Photosensitive layer with carrier generation layer 72 and carrier transport layer 73 reversed
74 '. FIG. 6 shows that an intermediate layer 75 is provided between the photosensitive layer 74 having the layer structure shown in FIG.
In the figure, an intermediate layer 75 is provided between the photosensitive layer 74 'having the layer structure shown in FIG. 5 and the conductive support 71. The layer structure shown in FIG. 8 is obtained by forming a photosensitive layer 74 "containing a carrier generating substance 76 and a carrier transporting substance 77, and FIG. 9 shows the structure between such a photosensitive layer 74" and a conductive support 71. Is provided with an intermediate layer 75. A protective layer (not shown) is provided on the outermost surface of the photoconductor.
May be provided.

In forming the photosensitive layer, it is effective to apply a solution in which a carrier-generating substance or a carrier-transporting substance is dissolved alone or together with a binder or an additive. However, since the solubility of the carrier-generating substance is generally low, in such a case, the carrier-generating substance is finely dispersed in an appropriate dispersion medium using a dispersion device such as an ultrasonic disperser, a ball mill, a sand mill, and a homomixer. The method of applying the liquid is effective. In this case, the binder and the additive are usually used by adding to the dispersion.

A wide variety of solvents or dispersion media can be used for forming the photosensitive layer. For example, butylamine, ethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, ethylene glycol dimethyl ether, toluene, xylene, acetophenone, chloroform, dichloromethane ,
Examples thereof include dichloroethane, trichloroethane, methanol, ethanol, propanol, and butanol.

When a binder is used for forming the carrier generation layer, the carrier transport layer, or the photosensitive layer, any binder can be selected, but a high molecular polymer that is hydrophobic and has a film forming ability is particularly desirable. Examples of such a polymer include, but are not limited to, the following.

Polycarbonate Polycarbonate Z resin Acrylic resin Methacryl resin Polyvinyl chloride Polyvinylidene chloride Polystyrene Styrene-butadiene copolymer Polyvinyl acetate Polyvinyl formal Polyvinyl butyral Polyvinyl acetal Polyvinyl carbazole Styrene-alkyd resin Silicone resin Silicone-alkyd resin Polyester phenolic resin Polyurethane Epoxy resin Vinylidene chloride -Acrylonitrile copolymer vinyl chloride-vinyl acetate copolymer vinyl chloride-vinyl acetate-maleic anhydride copolymer The ratio of the carrier generating substance to the binder is 10 to 600 w.
t% is desirable, and more preferably 50 to 400 wt%. The ratio of the carrier transporting substance to the binder is desirably 10 to 500 wt%. The thickness of the carrier generation layer is 0.01 to 20 μ
m, but more preferably 0.05 to 5 μm. The thickness of the carrier transport layer may be from 1 to 100 μm, and more preferably from 5 to 30 μm.

The photosensitive layer may contain an electron-accepting substance for the purpose of improving sensitivity, reducing residual potential, or reducing fatigue upon repeated use. Such electron accepting substances include, for example, succinic anhydride, maleic anhydride, dibromo succinic anhydride, phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride. Acid, pyromellitic anhydride, melitic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene, 1,3,5-trinitrobenzene, p-nitrobenzonitrile, picryl chloride, Quinone chlorimide,
Chloranil, bromanil, dichlordicyano-p-benzoquinone, anthraquinone, dinitroanthraquinone,
9-Fluorenylidene malonodinitrile, polynitro-
9-fluorenylidene malonodinitrile, picric acid,
o-Nitrobenzoic acid, p-nitrobenzoic acid, 3,5-dinitrobenzoic acid, pentafluorobenzoic acid, 5-nitrosalicylic acid, 3,5-dinitrosalicylic acid, phthalic acid, melitic acid, and other compounds having a large electron affinity. Can be mentioned. The addition ratio of the electron-accepting substance is preferably 0.01 to 200, more preferably 0.1 to 200, relative to the weight of the carrier-generating substance.
1-100 is preferred.

The photosensitive layer may contain a deterioration inhibitor such as an antioxidant or a light stabilizer for the purpose of improving the storage stability, durability and environmental resistance. Compounds used for such purposes include, for example, chromanol derivatives such as tocopherol and etherified or esterified compounds thereof, polyarylalkane compounds, hydroquinone derivatives and mono- and dietherified compounds thereof,
Benzophenone derivatives, benzotriazole derivatives, thioether compounds, phosphonic acid esters, phosphite esters, phenylenediamine derivatives, phenol compounds, hindered phenol compounds, linear amine compounds, cyclic amine compounds, hindered amine compounds, and the like are effective. Specific examples of particularly effective compounds include “IRGANOX 1
010 "," IRGANOX 565 "(all manufactured by Ciba-Geigy)," Sumilyzer BHT "," Sumilyzer MDP "
Hindered phenol compounds such as “Sanol LS-2626” and “Sanol LS-62”
Hindered amine compounds such as "2LD" (above, manufactured by Sankyo).

As the binder used for the intermediate layer, the protective layer, and the like, those described above for the carrier generation layer and the carrier transport layer can be used.Other polyamide resins, nylon resins, ethylene-vinyl acetate copolymers, Ethylene-based resin such as ethylene-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate-methacrylic acid copolymer,
Polyvinyl alcohol, cellulose derivatives and the like are effective.

As the conductive support 71, a metal plate, a metal drum is used, or a conductive polymer or a conductive compound such as indium oxide, or a thin layer of a metal such as aluminum or palladium is applied, deposited, or laminated. What is provided on a substrate such as paper or a plastic film can be used.

E. EXAMPLES (Synthesis Example 1) 29.2 g of 1,3-diiminoisoindoline and 200 m of sulfolane
were mixed, 17.0 g of titanium tetraisopropoxide was added, and the mixture was reacted at 140 ° C. for 2 hours under a nitrogen atmosphere. After cooling, the precipitate was collected by filtration, washed with chloroform, washed with a 2% aqueous hydrochloric acid solution, washed with water and washed with methanol, and dried to obtain 25.5 g (88.5%) of titanyl phthalocyanine. This product was dissolved in 20 times the volume of concentrated sulfuric acid, poured into 100 volumes of water to precipitate out, filtered, and then the wet cake was heated with 1,2-dichloroethane at 50 ° C. for 10 hours. Ten
The crystal type having the X-ray diffraction spectrum shown in the figure was used. This crystal had a peak intensity at 9.6 degrees at a Bragg angle 2θ of 102% of that at 27.2 degrees.

(Synthesis Example 2) 29.2 g of 1,3-diiminoisoindoline and 200 m of sulfolane
were mixed, 17.0 g of titanium tetraisopropoxide was added, and the mixture was reacted at 140 ° C. for 2 hours under a nitrogen atmosphere. After cooling, the precipitate was collected by filtration, washed with chloroform, washed with a 2% aqueous hydrochloric acid solution, washed with water and washed with methanol, and dried to obtain 25.5 g (88.5%) of titanyl phthalocyanine. This product was dissolved in a 20-fold amount of concentrated sulfuric acid, poured into 100-fold amount of water to precipitate. After filtration, the wet cake was stirred with 1,2-dichloroethane for 1 hour at room temperature to obtain an eleventh solution.
The crystal type having the X-ray diffraction spectrum shown in the figure was used. This crystal had a peak intensity at 9.6 degrees at a Bragg angle 2θ of 75% of that at 27.2 degrees.

(Synthesis Example 3) 26.6 g of phthalodinitrile and 150 ml of α-chloronaphthalene
6.5 ml of titanium tetrachloride was added dropwise to the above mixture under a nitrogen stream, and reacted at a temperature of 200 to 220 ° C. for 5 hours. The precipitate was collected by filtration, washed with α-chloronaphthalene, washed with chloroform, and then washed with methanol. Then, the mixture was refluxed in ammonia water to complete the hydrolysis, washed with water, washed with methanol, and dried to obtain 21.8 g (75.6%) of titanyl phthalocyanine. This product was dissolved in 10 times the volume of concentrated sulfuric acid, poured into 100 times the volume of water, and precipitated. The crystal type having the X-ray diffraction spectrum shown in the figure was used. This crystal has a Bragg angle 2θ of 9.6
The degree peak intensity was 45% of that of 27.2 degrees.

(Synthesis Example 4) 25.6 g of phthalodinitrile and 150 ml of α-chloronaphthalene
6.5 ml of titanium tetrachloride was added dropwise to the above mixture under a nitrogen stream, and reacted at a temperature of 200 to 220 ° C. for 5 hours. The precipitate was collected by filtration, washed with α-chloronaphthalene, washed with chloroform, and then washed with methanol. Then, after refluxing in ammonia water to complete the hydrolysis, washing with water,
After washing with methanol and drying, titanyl phthalocyanine
21.8 g (75.6%) were obtained. This product was dissolved in 10 times the volume of concentrated sulfuric acid, poured into 100 times the volume of water to precipitate. After filtration, the wet cake was stirred with o-dichlorobenzene for 1 hour at room temperature to obtain a 13th solution. The crystal type having the X-ray diffraction spectrum shown in the figure was used. This crystal had a peak intensity at 9.6 degrees at a Bragg angle 2θ of 35% of that at 27.2 degrees.

Example 1 3 parts of titanyl phthalocyanine having the X-ray diffraction pattern shown in FIG. 10 obtained in Synthesis Example 1 and a silicone resin as a binder resin (“15% xylene of KR-5240-
35 parts of butanol solution (manufactured by Shin-Etsu Chemical Co., Ltd.) and 100 parts of methyl ethyl ketone as a dispersion medium were dispersed using a sand mill, and this was applied by dip coating on an aluminum drum and a drum coated with a 0.3 μm thick polyamide resin layer. A carrier generation layer having a thickness of 0.2 μm was formed. Next, 1 part of the carrier transporting substance (2), 1.3 parts of polycarbonate resin “Iupilon Z200” (manufactured by Mitsubishi Gas Chemical Company) and a small amount of silicone oil “KF-54” (manufactured by Shin-Etsu Chemical Co., Ltd.)
A solution dissolved in 10 parts of 1,2-dichloroethane was applied using a blade coater, and after drying, a carrier transport layer having a thickness of 20 μm was formed. The photoreceptor thus obtained is referred to as Sample 1.

The spectral sensitivity distribution of the photoreceptor of Example 1 was as shown in FIG. 14, and the long wavelength sensitivity was particularly good. In addition,
The spectral sensitivity (Sλ) shown in FIG. 14 is defined as follows. That is, it is the necessary amount of light until the receiving potential 800 V falls to 400 V after exposure with monochromatic light of wavelength λ, and the exposure sensitivity at this time was defined as 0.5 μW / cm ² . Exposure E (μJ /
cm ² ) is the product of the exposure sensitivity at this time and the exposure time (t (sec)). The dark decay amount (DD) at 800 V is the amount of potential decrease when the same photoconductor is left unexposed and left for 800 seconds after charging for tsec. The spectral sensitivity Sλ was defined by the following equation.

Example 2 Instead of titanyl phthalocyanine in Example 1,
A photoconductor was obtained in the same manner as in Example 1, except that the phthalocyanine having the X-ray diffraction pattern shown in FIG. 11 and obtained in Synthesis Example 2 was used. This is designated as Sample 2.

Example 3 Similarly, a sample 3 was prepared using the crystal of FIG. 12 obtained in Synthesis Example 3.

Example 4 Similarly, a sample 4 was prepared using the crystal of FIG. 13 obtained in Synthesis Example 4.

Comparative Example 1 A photoconductor (Comparative Sample 1) was obtained in the same manner as in Example 1, except that a known X-type metal-free phthalocyanine (see Japanese Patent Publication No. 49-4338) was used instead of titanyl phthalocyanine.

As shown in FIG. 16, the X-ray diffraction spectrum of the phthalocyanine of Comparative Example 1 has peaks at the Bragg angles of 7.5 degrees, 9.1 degrees, 16.7 degrees, 17.3 degrees, and 22.3 degrees with respect to X-rays of CuKα (1.541 °). . In the specification of USP-3,357,989, the infrared absorption spectrum is shown.
m ^-1, 3 peaks between 700~750cm ^-1, 1318cm ^-1, 133
It is shown that there is a peak of equal intensity at 0 cm ^-1 .

Comparative Example 2 A known photoreceptor (Comparative Sample 2) was obtained in the same manner as in Example 1 except that a known τ-type metal-free phthalocyanine (see JP-A-58-182639) was used instead of titanyl phthalocyanine.

As shown in FIG. 16, the X-ray diffraction spectrum of the phthalocyanine of Comparative Example 2 showed that the Bragg angles of CuKα (1.541 °) with respect to X-rays were 7.6 °, 9.2 °, 16.8 °, 17.4 °, 20.4 °
And a peak at 20.9 degrees. Further, in the infrared absorption spectrum, the strongest 752 ± 2 cm ^-1 in between 700~760cm ^-1 4
Absorption bands of this, almost the same intensity absorption band of the two during 1320～1340Cm ^-1, there is a characteristic absorption band at 3288 ± 2 cm ^-1.

(Evaluation) Each sample obtained as described above was mounted on the apparatus shown in FIG. 1 and the image quality was evaluated. However, the developer and the developing conditions in this apparatus were as follows.

Developer: Carrier: Magnetite 50 wt% Resistivity 10 ¹⁶ Ω-cm Magnetic susceptibility 30 emu / g Average particle size 20 μm Toner: Styrene-vinyl acetate / benzine derivative (yellow) 10 parts by weight Charge control agent containing Non-average particle size 10 μm Magnetic toner Developing conditions: DC bias -700V AC 1.5KHz 600V Developing sleeve outer diameter 30μm Rotation speed 1000rpm. Magnetic flux density of NS magnetic pole of magnet 1000gauss Developing layer thickness (sleeve) 0.7mm Dsd (photoconductor-sleeve interval) 0.8mm And image quality evaluation was performed as follows.

(A) Color Reproducibility The amount of toner adhering to the photoreceptor at the time of monochromatic and superposition development was evaluated, and a correspondence with the image evaluation on the transfer material was taken. That is, the exposure energy is set by measuring the surface potential with respect to the exposure energy of the photoconductor, then the developing bias and the charging potential are measured, and the toners of each color (yellow Y, magenta M, cyan C) on the photoconductor drum are measured. ) And the amount of the upper layer toner attached during superposition were evaluated. At this time, the method in which the amount of toner adhered to each color is large increases the amount of toner transferred to the transfer material, so that the color reproducibility is also improved.

(B) Gradation The image density is 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.
An original having charts of 10 levels of 6, 0.7, 1.0, and 1.25 was prepared, a copy image was formed using the original, and the number of levels of gradation was determined.

(C) Resolution: 4.0 lines, 5.0 lines, 6.0 lines, 8.0 lines at equal intervals per 1 mm
In this case, the grade which can distinguish the vertical line is displayed as the resolution.

In measuring the surface potential of the photoreceptor described above,
Sensors of a surface voltmeter were inserted at positions 31 (yellow developer), 32 (magenta developer), and 33 (cyan developer) in FIG. 1, respectively, and the incident exposure energy was varied to measure the surface potential. Further, the charging potential of each photoconductor is-
Set to 800V. The incident light wavelength is 780 nm to 8
A 00 nm semiconductor laser was used. The recording dot density of this incident exposure was set so as to be 15.8 lines / 1 mm. The diameter of the photosensitive drum was 150 (mm), and the rotation speed of the drum was 140 mm / sec.

The results of measuring the surface potential are shown in Table 1 below. However, the incident exposure energy is 0, 2.5, 5, 7.5, 1
0, 12.5, and 15 (erg / cm ² ) were set as seven types.

The results are collectively shown in FIG.
Is the value at the position of the photoconductor (sample 1) according to the present invention.
4) shows that the curve of the decrease in the surface potential at the time of exposure is better than that of the comparative examples (Comparative Samples 1 and 2). From this result, the amount of light incident on the photoconductor was reduced to 15 erg / cm ²
The charging potential is -800 V, the developing bias is DC = -700 V,
Development was performed on the photoreceptor at Ac 1.5 kHz (peak-to-peak), and the toner adhesion amount was examined.

 The results are shown in Table 2 below.

From these results, the photoreceptor according to the present invention (samples 1 to
Regarding 4), even when toner adheres to the lower layer, a sufficient amount of toner adheres to the upper layer, and color reproducibility is good. However, in Comparative Samples 1 and 2, the amount of adhesion of the upper layer toner was reduced by half when superimposed as compared with the case of a single color, and the color reproducibility of the images transferred to the transfer material was higher than that of Samples 1 to 4. In terms of quality. This is because, in the case of the comparative example, since the sensitivity of the photoconductor is insufficient, the exposure amount after charging is insufficient by the base toner, and a sufficient decrease in potential does not occur.

As described above, according to the present invention, an image having excellent color reproducibility was obtained by using the above-described specific titanyl phthalocyanine in combination with the developing method of superimposing each color toner on the drum.

Table 3 below shows the results of evaluation of gradation and resolution.

From these results, when the photoconductor according to the present invention is used, an image having excellent gradation and high resolution can be obtained.

From the results described above, the results are even better in the case of Samples 1 to 3 in which the peak intensity ratio of titanyl phthalocyanine used in the present invention: 9.6 degrees / 27.2 degrees is 40% or more. Further, according to the present invention, it is possible to provide an image forming method which can sufficiently achieve color reproducibility, gradation, and resolving power by image exposure using dot exposure, is easy to implement, and is mechanically simple. In addition, there is no color shift due to superposition development.

F. Advantageous Effects of the Invention As described above, the present invention uses titanyl phthalocyanine in a crystalline state having a Bragg angle 2θ of at least 9.6 ° ± 0.2 ° and a peak at 27.2 ° ± 0.2 °, and is visible by digital exposure and overlay developing. Since an image is formed, image exposure with high γ and high sensitivity becomes possible, the amount of toner adhered to the superimposed toner image becomes sufficient, and an image with excellent color reproducibility can be obtained. In addition, the gradation and resolution are sufficiently obtained,
It is possible to provide an image forming method and an apparatus which are easy to implement and simple in terms of mechanism. In addition, by superposition development, the apparatus can be reduced in size and cost, and a high-quality color image free from color misregistration can be obtained.

[Brief description of the drawings]

1 to 15 show an embodiment of the present invention. FIG. 1 is a schematic sectional view of a copying machine, FIG. 2 is a sectional view of a main part of a developing device, and FIG. Block diagrams, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9 are sectional views showing specific examples of the layer structure of the photoreceptor used in the present invention, FIG. FIG. 11, FIG. 12, and FIG. 13 show synthesis examples 1, 2,
X-ray diffraction diagrams of titanyl phthalocyanine of the present invention obtained by the methods 3 and 4, FIG. 14 is a spectral sensitivity distribution diagram of the titanyl phthalocyanine of the present invention, and FIG. 15 is a graph showing a change in surface potential with respect to incident light energy. . FIG. 16 is an X-ray diffraction pattern of X-type and τ-type metal-free phthalocyanine, and FIG. 17 is a flow chart of a copying process. In the reference numerals shown in the drawings, 1 ... photoconductor 2 ... charger 4 ... transfer pole 5 ... separation pole 6 ... fixing device 8 ... cleaning device 10 ... laser optical system 17R, 17G, 17B ... … CCD image sensor 18… Originals 31, 32, 33, 34… Developing device 41… Developing sleeve 42… Magnet 43… Developer pool 44… Layer thickness regulating blade 71… Conductive support 72 ...... carrier generation layer 73 ...... carrier transport layer 74, 74 ', 74 "are ...... photosensitive layer 75 ...... intermediate layer L ...... image exposure E ...... developing zone T _1, T ₂ ...... toner.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihide Fujimaki 2970, Ishikawa-cho, Hachioji-shi, Tokyo Inside Konica Corporation (56) References JP-A-64-82044 (JP, A) JP-A-64-82043 (JP) , A) JP-A-64-82042 (JP, A) JP-A-64-17066 (JP, A)

Claims (1)

(57) [Claims] 1. X-rays corresponding to CuKα characteristic X-rays (wavelength 1.541 °)
An image carrier using titanyl phthalocyanine in a crystalline state showing a peak of X-ray intensity when the Bragg angle 2θ of the X-ray diffraction spectrum is at least 27.2 degrees ± 0.2 degrees as a photoconductive substance of a photosensitive layer is subjected to electrostatic image formation by digital image exposure. An image forming method in which formation of a latent image and development of the electrostatic latent image are repeated, whereby a plurality of toner images are superimposed on the image carrier, and the superimposed toner images are transferred.