JP2696399B2 - Image forming method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method and an image forming apparatus, 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
Also, the present invention relates to an image forming method and apparatus suitable for a monochrome printer and an electrophotographic copying machine.

B. 2. Description of the Related Art In a conventional image forming method, a halftone image is necessary to enhance the quality, but none of the methods proposed so far is satisfactory.

For example, in the method disclosed in Japanese Patent Laid-Open Publication No. 50-25112, the accuracy of gradation reproduction is reduced due to a delay in the response of the device. Further, the publication discloses that an analog video signal is linearly converted into a pulse width modulation (PWM) signal. However, in the halftone printing process, a nonlinear distortion is used. Even if a transform is used (especially if the linear transform is used in a laser beam print engine), good results cannot be obtained.

Therefore, to obtain high quality halftone prints,
Although a non-linear conversion is required, the method disclosed in the above publication has to use a different triangular wave in continuous scanning in order to perform the non-linear conversion, and the configuration is complicated.

On the other hand, in pulse width modulation (PWM), laser output is performed in two values, ON and OFF, and gradation is obtained by controlling the oscillation time. The advantage is that when the laser output is turned on, the surface potential of the photoreceptor is brought into a saturated state, so that a potential change depending on temperature and humidity can be ignored and the stability is excellent. However, the disadvantage is that the peak value of the pulse decreases as the pulse width becomes shorter, and the potential may be expressed in an analog manner as shown in FIG. In order to avoid this, it is necessary to keep the output constant and make the spot diameter as small as possible.

In pulse width modulation, one dot is divided into, for example, 256 to give gradation. For example, if the recording density is 400 dpi (dot / in
In the case of ch), as shown in FIG. 21, 256 types of dot exposure (digital exposure) are performed. In this case, if the dots are subdivided, the exposure energy decreases and the sensitivity also decreases. In other words, in the reversal development, the development electric field (V _DC bias−V _L (exposure portion potential)) decreases, and the amount of the developer attached decreases. This will be described with reference to FIG. 22. As the dot width becomes smaller (that is, the PWM output becomes smaller and the pulse width becomes smaller), the actual toner adhesion amount becomes smaller than the ideal toner adhesion amount, and (Halftones)
In addition, uniform gradation cannot be obtained.

C. SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus which exhibit a sufficient response to scanning by the above-described pulse width modulation method and can obtain good halftones and the like.

D. In other words, the present invention relates to an image forming method for forming an electrostatic latent image on an image carrier by charging and image exposure and visualizing the electrostatic latent image. As a photoconductive substance, 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 ±
The image exposure is performed by digital exposure using titanyl phthalocyanine in a crystalline state showing an X-ray intensity peak at 0.2 degrees, and the length of a scan line segment is controlled by pulse width modulation during the digital exposure. The present invention relates to an image forming method.

In addition, the present invention provides that the Bragg angle 2θ of the X-ray diffraction spectrum with respect to CuKα characteristic X-ray (wavelength 1.541 °) is at least 2
Along the image carrier using titanyl phthalocyanine in a crystalline state showing a peak of X-ray intensity at 7.2 degrees ± 0.2 degrees as a photoconductive substance of the photosensitive layer, a charging unit, a digital exposure unit, and a developing unit are provided. Also provided is an image forming apparatus arranged, wherein the digital exposure means has a scanning line generating section for generating an exposure scanning line, and wherein the length of the segment of the exposure scanning line is controlled according to a pulse width modulation signal. Is what you do.

The Bragg angle 2θ of the X-ray diffraction spectrum for CuKα characteristic X-rays (wavelength 1.541 °) is at least 9.6 degrees ± 0.2.
And titanyl phthalocyanine in a crystalline state showing an X-ray intensity peak at 27.2 ° ± 0.2 °, respectively.

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 is PWM-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, color separation filter 16
When the blue filter is set as, this electrostatic latent image is inverted by the developing device 31 containing yellow toner. The image carrier 1 having the toner image formed thereon 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,
It receives an image exposure L based on the optical information read through this filter. 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, cyan and black toners are superimposed and developed in reverse by the developing units 33 and 34 in the same manner, and a four-color toner image is formed on the image carrier 1. 4
The color toner image is given a charge by a pre-transfer band electrode as required, and is transferred onto the recording paper P at once by the transfer pole 4. The recording paper P is 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. 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). 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.

Next, the PWM method in the laser exposure system will be described in detail with reference to FIGS.

In FIG. 4, reference numeral 61 denotes the above-mentioned video signal processing unit TR ₂
A / D (analog / digital) conversion of analog image data from a CCD image sensor or a video camera, and outputs a digital video signal of a predetermined bit, as described above. This digital signal may be temporarily stored in a memory, or may be input from an external device through communication or the like. The signal from the digital data output device 61 is used as an address of the digital lookup table 69 for γ correction. An output from the look-up table 69, for example, an 8-bit output representing 256 levels of gray scale is output by the D / A converter 62.
Each pixel is converted into an analog signal for each pixel, and each obtained pixel is relatively sequentially input to one terminal of the circuit 64. At the same time, a triangular analog reference pattern signal is generated from the pattern signal generator 63 at a period corresponding to the predetermined pitch of the halftone dots, and is input to the other terminal of the comparison circuit 64. On the other hand, the reference clock from the reference clock generation circuit 66 is synchronized with the horizontal synchronization signal generated for each line by the horizontal synchronization signal generation circuit 65, and the timing signal generation circuit 67
For example, the countdown is performed in a quarter cycle.
The counted-down signal (pixel clock) is used for the transfer clock of the digital video signal and the latch of the D / A converter 62. Note that the horizontal synchronization signal in this example is
Since this apparatus is applied to copying using a laser beam, it corresponds to a known beam detect signal. Comparison circuit
At 64, the level of the analog converted analog video signal is compared with the level of the triangular wave pattern signal, and a pulse width modulation signal is output. This pulse width modulated signal is
Raster scan print section for modulating laser beam
It is input to 68 laser modulation circuits. As a result, the laser beam is turned on / off in accordance with the pulse width, and an electrostatic latent image corresponding to a halftone image is formed on the photoconductor of the raster scan printing unit 68.

As described above, by converting a digital image signal into an analog image signal once and comparing it with a triangular wave signal having a predetermined period, almost continuous or linear pulse width modulation becomes possible, and a high gradation image output is obtained. Can be The pulse width modulation controls the length of the segment of the exposure scan line (that is, the exposure dot for the photoconductor).

Further, since a pattern signal synchronization clock (halftone clock) synchronized with the horizontal synchronization signal is formed using a reference clock having a higher frequency than the frequency of the pattern signal synchronization clock for generating a pattern signal (for example, a triangular wave), The fluctuation (jitter) of the signal of the pattern generated from the pattern signal generation circuit 43, for example, the deviation (offset) between the pattern signals of the first and second lines is less than one-twelfth of the period of the pattern signal in this embodiment. . This accuracy is
A line screen is required to be formed evenly and smoothly for each line to ensure reproduction of high quality halftone.

Thus, the density information is accurately pulse-width modulated, and the above-described semiconductor laser 21 emits a laser beam modulated in accordance with the pulse-width modulation signal. The light beam modulated by the semiconductor laser 21 is collimated by a collimating lens (not shown), subjected to light deflection by a polygon mirror 22 having a plurality of reflecting surfaces, and further subjected to image exposure on the photosensitive drum 1 by an imaging lens. Do.

The present inventor has described that in the image formation as described above,
When laser exposure by PWM (pulse width modulation) is combined with titanyl phthalocyanine described later,
It has been found that a sufficient response is exhibited even when the pulse width is shortened, a halftone is sufficiently output, and a high resolution can be obtained.

That is, the light speed (especially, sensitivity to long-wavelength light such as a semiconductor laser) is not so large in a normal photoreceptor, and therefore, when the pulse width modulation is shortened as described above, the exposure amount ( Insufficient exposure energy) reduces the decrease in the surface potential of the photoreceptor. On the other hand, titanyl phthalocyanine used in the present invention has an X-ray intensity peak at a Bragg angle 2θ of at least 9.6 ° ± 0.2 ° and 27.2 ° ± 0.2 ° in the X-ray diffraction spectrum with respect to CuKα characteristic X-ray (wavelength 1.541 °). And has high sensitivity to dot exposure with light of a relatively long wavelength such as a semiconductor laser beam and high γ (the light attenuation characteristic of the charged potential is sharp). The titanyl phthalocyanine desirably has a peak X-ray intensity at 9.6 degrees ± 0.2 degrees which is 40% or more of a peak X-ray intensity at 27.2 degrees ± 0.2 degrees.

By using such titanyl phthalocyanine, a highly sensitive photoreceptor can be obtained, a sufficient amount of toner adhered can be obtained even with a small exposure amount, and each dot is formed with a high density even by the above-described PWM type dot exposure. Further, the gradation of an image, which is a set of a large number of dots, is primarily determined by the output level of the dots. However, since the titanyl phthalocyanine has high sensitivity and high γ characteristics, The output level can be reproduced more faithfully.

That is, in image formation using such dots, 1
It is required that the dot reproducibility be high. However, since the titanyl phthalocyanine of the present invention has high sensitivity and high γ degree (so-called on-off type) characteristics, Good reproducibility.

The basic structure of the titanyl phthalocyanine of the present invention may be represented by the following general color 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, titanyl phthalocyanine of the target crystal type shown in FIGS. 12 to 15 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-mixture type and armophas 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,
Although various things can be used, various things can be used, and typical examples include nitrogen-containing heterocyclic nuclei represented by oxazole, oxadiazole, thiazole, thiadiazole, imidazole and the like, and fused ring nuclei thereof. , A polyarylalkane compound, a pyrazoline compound, a hydrazone compound, a triarylamine compound, a styryl compound, a styryltriphenylamine compound, an α-phenylstyryltriphenylamine compound, a butadiene compound, Hexatriene compounds, carbazole compounds, condensed polycyclic compounds, and the like. Specific examples of these carrier transporting substances include, for example, the carrier transporting substance described in JP-A-61-107356, and many of them can be mentioned. Particularly representative structures 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 FIGS. 6 to 11. The layer configuration shown in FIG. 6 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, and FIG. Photosensitive layer with carrier generation layer 72 and carrier transport layer 73 reversed
74 '. FIG. 8 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. The layer structure shown in FIG. 10 is obtained by forming a photosensitive layer 74 ″ containing a carrier generating substance 76 and a carrier transporting substance 77, and FIG. 11 shows a 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, ethylene 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 Methacrylic 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 Phenol 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, clamanol 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 101
0 "," IRGANOX 565 "(all made by Ciba-Geigy)," Sumilyzer BHT "," Sumilyzer MDP "
Hindered phenol compounds such as “Sanol LS-2626” and “Sanol LS-622L”
H "(above, manufactured by Sankyo) and the like.

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. 12
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, filtered, and then the wet cake was stirred with 1,2-dichloroethane for 1 hour at room temperature for 13 hours.
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 to precipitate out, and after filtration, the wet cake was stirred with 1,2-dichloroethane at room temperature for 1 hour to obtain a 14th solution. 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, 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 to precipitate, filtered, and then the wet cake was stirred with o-dichlorobenzene for 1 hour at room temperature for 15 hours. 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 35% of that of 27.2 degrees.

Example 1 3 parts of titanyl phthalocyanine having the X-ray diffraction pattern of FIG. 12 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 Sample 1 was 16th.
As shown in the figure, the long wavelength sensitivity was particularly good.

The spectral sensitivity (Sλ) shown in FIG. 16 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 . The exposure amount E (μJ / cm ² ) depends on the exposure sensitivity and the exposure time (t (se
c)). Also, the dark attenuation at 800V (DD)
Is the amount of potential decrease when the same photoreceptor is not exposed and left for 800 sec. 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. 13 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. 14 obtained in Synthesis Example 3.

Example 4 Similarly, a sample 4 was prepared using the crystal of FIG. 15 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. 19, 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. 19, the X-ray diffraction spectrum of the phthalocyanine of Comparative Example 2 shows 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 a color copy DC-8010 (manufactured by Konica) remodeling machine equipped with a writing system capable of outputting up to 256 gradations per dot with linear pulse width modulation. And evaluated.

The charging potential of the photoconductor is -800V for all photoconductors.
The voltage applied to the sleeve during development is DC-700V, AC 1.
5 kHz (peak-to-peak) alternating field development. The developer used in the product of DC-8010 was used, and the exposure energy to the image carrier was 255/255 and 15 erg / cm ^2.
And

In this case, by performing pulse width modulation, It was expressed.

The results are shown in FIG. Here, the horizontal axis represents the output level of pulse width modulation, and the vertical axis represents the image density. The toner was developed with a red toner. The image density was measured using a Sakura densitometer (amber filter), and the white paper was measured at CD (copy density) = 0.

From the above equation (1), it can be seen that the smaller the value of a, the smaller the image exposure energy, but the samples 1 to 4 according to the present invention have almost the same gradient γ and high γ. Moreover, since the image density is high, the gradation is uniform and good. On the other hand, in the comparative sample, γ rapidly rises from 150/255,
It can be seen that the gradation is inferior. Furthermore, the image density is ≦
Only 1.0 is obtained, and there is a practical problem. In the comparative sample 1, the image density cannot be obtained unless the output level is further increased. The photoreceptors of Samples 1 and 2 having low sensitivity have a narrow developing area, and particularly at a level of 150/255 or less, the density and gradation cannot be obtained.

FIG. 18 shows the above sample 1, comparative samples 1 and 2
The results obtained by measuring the surface potential of the photoreceptor in relation to the exposure output level are shown below. It is clear that the sensitivity of the photoreceptor of the present invention is excellent, and that the output level is more preferably 100/255 or more.

Furthermore, in image formation by dot exposure, 4.0, 5.0, 6.3
Print controller that outputs 8.0 and 8.0
Connected to -8010 and evaluated the image resolution. The results are shown in the table below (however, the PWM output level is 255/255 and the energy is
15erg / cm ^2).

It can be seen that the resolving power of the sample according to the present invention is all better than that of the comparative sample.

Samples 1 to 3 having a peak intensity ratio of 9.6 degrees / 27.2 degrees of 40% or more of titanyl phthalocyanine used in the present invention.
In the case of the above, the result is further improved.

F. As described above, the present invention performs digital exposure by pulse width modulation using titanyl phthalocyanine in a crystalline state having peaks at least at Bragg angle 2θ of 9.6 ° ± 0.2 ° and 27.2 ° ± 0.2 °. Therefore, the light sensitivity of the photosensitive layer is improved and the sensitivity becomes high even if the pulse width is small, and since it has an appropriate γ, an excellent halftone image can be obtained, and the grayscale information of the image can be expressed in high gradation. And can be reproduced uniformly,
Also, high resolution can be obtained.

[Brief description of the drawings]

1 to 18 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. FIG. 4 is a block diagram of a PWM type modulation signal generating circuit, FIG. 5 is a signal waveform diagram of each part thereof, FIG. 6, FIG. 7, FIG. 8, FIG. 9, FIG. FIG. 11 is a cross-sectional view showing a specific example of the layer configuration of the photoreceptor used in the present invention. FIG. 12, FIG. 13, FIG. 14, FIG.
X-ray diffraction diagrams of titanyl phthalocyanine of the present invention obtained by 3 and 4, FIG. 16 is a spectral sensitivity distribution diagram of titanyl phthalocyanine of the present invention, FIG. 17 is a graph showing a comparison of copy density with respect to PWM output level, FIG. 18 is a graph showing a comparison of the photoconductor surface potential with respect to the PWM output level. FIG. 19 is an X-ray diffraction diagram of X-type and τ-type metal-free phthalocyanine, FIG. 20 is a graph showing the photoenergy photoreceptor surface potential with respect to the spot diameter of dot exposure, FIG.
(B) is a schematic diagram showing a dot pattern in each system, FIG.
FIGS. 22 (A) and (B) are schematic diagrams showing a comparison of the amount of developer adhesion at each PWM output level. 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… Document 21… Semiconductor lasers 31, 32, 33, 34… Developer 41… Developing sleeve 42… Magnet 43… Developer reservoir 44… Layer thickness regulating blade 61… Digital data output device 62 D / A converter 63 Triangular wave generation circuit 64 Comparator 65 Horizontal synchronization signal generation circuit 67 Timing signal generation circuit 68 Raster scan printing unit 71 Conductive support 72 Carrier generation layer 73 Carrier transport layer 74, 74 ', 74 "... Photosensitive layer 75 ... Intermediate layer L ... Image exposure E ... Development area.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihide Fujimaki 2970 Ishikawacho, Hachioji City, Tokyo Inside Konica Corporation (56) References JP-A-1-82044 (JP, A) JP-A-1-82043 (JP) JP-A-1-82042 (JP, A) JP-A-1-17066 (JP, A) JP-A-3-6570 (JP, A) JP-A-2-309362 (JP, A) JP-A-2-289658 (JP, A) JP-A-2-267563 (JP, A) JP-A-2-216159 (JP, A) JP-A-2-215867 (JP, A) JP-A-2-215866 (JP, A A) JP-A-2-198453 (JP, A) JP-A-2-198452 (JP, A) JP-A-1-299874 (JP, A) JP-A-1-207755 (JP, A)

Claims (2)

(57) [Claims] An image forming method for forming an electrostatic latent image on an image carrier by charging and image exposure, and for visualizing the electrostatic latent image, comprises the steps of: As the substance, titanyl phthalocyanine in a crystalline state showing an X-ray intensity peak at least at a Bragg angle 2θ of at least 27.2 ° ± 0.2 ° in an X-ray diffraction spectrum with respect to CuKα characteristic X-ray (wavelength 1.541 °) is used, and the image exposure is performed digitally. An image forming method, wherein the length of a scanning line segment is controlled by pulse width modulation during the digital exposure. 2. X-rays corresponding to CuKα characteristic X-rays (wavelength 1.541 °)
A charging means along an image carrier using titanyl phthalocyanine in a crystalline state showing a peak of X-ray intensity at least at a Bragg angle 2θ of X-ray diffraction spectrum of at least 27.2 ° ± 0.2 ° as a photoconductive substance of a photosensitive layer, Digital exposure means and development means are arranged, wherein the digital exposure means has a scan line generating section for generating exposure scan lines, and the length of the segments of the exposure scan lines is controlled according to a pulse width modulation signal. Image forming apparatus configured as described above.