JP2012098435A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus employing an electrophotographic system, capable of forming an image of high picture quality with extremely high graininess while preventing uneven density or tone variation even in a halftone image on a large screen.SOLUTION: The image forming apparatus employs a digital system using an electrophotographic photoreceptor having a photosensitive layer on a cylindrical substrate and a plurality of kinds of toners for electrostatic latent image development. The substrate has a processed pattern formed along the center axis on an outer circumference face thereof, and the pattern satisfies formula (1): ΔL≥10 μm, where ΔL represents a difference in processing periods in the center axis direction in an image region on the cylindrical substrate. At least one kind of the toners has a light transmittance of 40% or more and 90% or less by the following measurement method. The method for measuring a light transmittance is carried out by forming a fixed image with a toner deposition amount of 4.0 g/mon a polyethylene terephthalate (PET) sheet and measuring the light transmittance of the fixed image.

Description

  The present invention relates to an image forming apparatus using an electrophotographic photosensitive member (hereinafter sometimes simply referred to as a photosensitive member) and toner capable of forming an extremely high-quality image in the light printing field.

  In recent years, the image quality of a printing system using a dry electrophotographic system has been improved, and has been widely used in the printing field with a relatively small number of copies. As a result, the required image quality level has risen to an unthinkable range and has been used in unusual ways such as printing on coated paper, images with almost no white background, and subtle tones (colors). Many uses such as mass printing have been made. Along with this, the occurrence of problems and requests that have not been pointed out in the past or at all has increased.

  One of them is density unevenness and color tone variation due to unintended minute density changes. Conventionally, there has been a problem with halftone images, etc., but it is a case where extremely high image quality is required on a large screen such as posters and calendars created exclusively by offset printing. It was not a problem in formation.

  As a cause of subtle density unevenness and color tone fluctuation in electrophotographic image formation, there are generation of interference stripes (patterns) that exist on the exposure pattern and the surface of the photoreceptor substrate, which are considered to be due to the cutting cycle. Although the interference streak (pattern) may have occurred before, it is a light streak that has not been a problem in the past. However, these issues have become a problem today due to the above-mentioned background.

  This is a problem that occurs frequently in recent years due to the combination of required quality for improving the uniformity of intermediate colors, improved performance of the image forming apparatus, and the use of coated paper in electrophotographic image formation. Is in a hurry. In particular, in a color image in which toner superposition is normally used, unevenness in the toner amount causes not only the density of the image but also the color tone to fluctuate. Naturally, when the image size is increased, color unevenness is more easily noticeable.

  After all, because it has been used in fields that do not require as high image quality as the printing field, such as office documents and personal documents, the problems that have not been regarded as a problem in electrophotographic image forming apparatuses, It is thought that it has become apparent because it has been used in the light printing field.

  By the way, looking back on countermeasures against interference streaks and stripes in the field of electrophotographic photoreceptors, the surface of the substrate of the photoreceptor has been roughened by cutting or blasting (for example, Patent Documents 1 to 4). ). The countermeasures shown in these figures also correspond to the countermeasures against failures such as image unevenness and color tone fluctuation that are regarded as problems in the present invention. However, even if conventionally known cutting is applied, the periodicity of the surface shape of the substrate remains, so the effect is limited.

  In the case of blasting, since hard particles are blown, particles and fragments thereof bite and remain on the surface of the photoreceptor substrate, and burrs are generated on the collision mark. It is likely to cause. Therefore, it is not sufficient as a countermeasure for a field requiring high image quality, such as the large-screen halftone image printing described above.

Japanese Patent No. 3480618 JP 2001-235858 A JP 2003-173037 A JP 2003-91085 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic image forming apparatus capable of forming a high-quality image with extremely good graininess without causing density unevenness and color tone fluctuation even in a large-screen halftone image. That is.

  According to the study of the present inventor, there are a plurality of color unevenness generation mechanisms that can be perceived by humans in the electrophotographic process, and there is a case where another one emerges when one that has been seen under certain conditions is improved. is there. All improvement is difficult only by improvement of the photosensitive member, and it seems impossible to achieve the object unless it is combined with improvement of the toner and the image forming method. For example, a color tone (color tone) that has recently been attracting attention and is a topic of attention is an impression of a color that is a combination of lightness, saturation, and graininess of the color. It is difficult to solve by just making the quantity distribution uniform.

  As a result of intensive studies by the inventors, it has been found that the object of the present invention can be achieved by adopting the following configuration.

(1)
A digital image forming apparatus using at least an electrophotographic photosensitive member having a photosensitive layer on a cylindrical substrate, and a plurality of types of electrostatic latent image developing toners,
The substrate has a processed shape formed on the outer peripheral surface along the central axis, and the shape satisfies Formula 1;
Formula 1 ... ΔL ≧ 10μm
(Where ΔL is the difference in machining cycle in the central axis direction within the image area of the cylindrical substrate)
An image forming apparatus wherein at least one of the toners has a light transmittance of 40% or more and 90% or less by the following measurement method.
<Light transmittance measurement method>
The light transmittance of a fixed image having a toner adhesion amount of 4.0 g / m ² formed on a polyethylene terephthalate (PET) sheet is measured.

(2)
The image forming apparatus according to (1), wherein the electrophotographic photoreceptor is an electrophotographic photoreceptor having at least a cylindrical substrate, an intermediate layer, and a photosensitive layer, and the intermediate layer includes particles.

(3)
The image forming apparatus according to (1), wherein the electrostatic latent image developing toner is produced by associatively fusing at least resin particles produced by suspension emulsion polymerization and colorant particles.

  According to the present invention, it is possible to provide an electrophotographic image forming apparatus capable of forming a high-quality image that does not cause density unevenness even in a large-screen halftone image and has extremely good graininess.

The image figure of the stripe-shaped density nonuniformity of the last screen made into a subject by this invention. The schematic diagram explaining the film thickness fluctuation | variation of the electric charge generation layer by the cutting pitch of an electroconductive base | substrate surface. The figure explaining the measuring method of (DELTA) L in this invention. 1 is a configuration diagram of an example color image forming apparatus used in the present invention. FIG.

  The present invention will be further described below.

  The present invention occurs when an electrophotographic image forming apparatus is used and applied to a field requiring extremely high image quality such as light printing for forming an image on a transfer medium having high flatness such as coated paper. It was made to solve a problem that was discovered.

  In order to obtain an extremely high quality image, it is effective to use at least one gray toner as the toner used for image formation. However, when the image quality is improved by performing such a correspondence, the density unevenness and the color tone fluctuation in the halftone image are emphasized, which has not been known so far, and the density unevenness and the color tone in the halftone image are enhanced. It has been found that it is necessary to prevent the occurrence of fluctuations more strongly. To that end, we found that the width of the periodic unevenness generated by cutting on the surface of the cylindrical body of the photosensitive member was varied to some extent, and that there was a certain appropriate range for the density of gray toner, and further investigations were made to determine its limit value. The structure of the present invention is obtained.

  The configuration of the present invention (mainly the configuration of claim 1) is as described later. However, a processed shape in which a cylindrical substrate of the photosensitive member (hereinafter also referred to as a substrate only) is formed along its central axis. Means that when the surface of the substrate is shaped by cutting, an uneven shape is produced to bring the cutting tool into contact with the substrate while rotating the substrate about the central axis. To change the machining cycle width, the relative movement speed of the cutting tool is changed. That is, in order to vary ΔL, cutting is performed while changing the feed speed of the cutting tool and / or the rotational speed of the substrate to be cut.

  Hereinafter, the substrate processing of the present invention will be further described.

  The cutting process of the cylindrical substrate is a process in which the cutting tool abuts while rotating around the substrate as the central axis. However, the dimensional accuracy is set to a desired level, and the substrate surface is made fresh except for the oxide film on the substrate surface. Is carried out for the purpose of making the desired shape. The substrate finished by the conventional cutting process has a processed surface shape regularly formed in the direction along its central axis, and the film thickness of the layer formed on the substrate has regularity reflecting the processed surface shape. And the reflection does not disappear easily even when the layers are stacked.

  In a widely used stacked organic electrophotographic photosensitive member, if the charge generation layer has such a film thickness periodicity, it interferes with the periodicity of the screen of input light and causes minute and periodic potential unevenness. Occurs. This is visualized as fine and periodic color unevenness in a high-quality image. FIG. 1 is a diagram for explaining streaky density unevenness on the final screen, which is a problem in the present invention.

  For example, when an intermediate layer is provided on a photosensitive substrate and a charge generation layer is formed on the intermediate layer (UCL), the surface shape of the base is the surface shape of the intermediate layer. It is mainly determined by the shape of the processed surface and the composition of the intermediate layer (FIG. 2 illustrates this case).

  For this reason, if an intermediate layer containing fine particles is used, a random convex shape derived from the shape of the fine particles appears on the surface of the intermediate layer, and the shape periodicity derived from the substrate can be reduced. It is effective in reducing failures.

  In any case, it is extremely effective to reduce the regularity of the processed surface shape.

  In order to set ΔL, which is an index of irregularity, to 10 μm or more, it is necessary to frequently change the machining cycle width when the surface of the substrate is shaped by cutting. For this purpose, an instruction to frequently change the moving speed of the cutting tool with respect to the surface of the photosensitive member during processing may be added.

For example, in the case of a CNC lathe that indicates the moving speed X (mm / rev) of the tool and its indicated position Y (mm), (X ₁ , Y ₁ ), (X ₂ , Y ₂ ),... (X _n , Y _n ) and n blocks are programmed. For example, in the m-th block, when (Y _{m + 1} −Y _m ) / X _m is not an integer, the byte movement speed is reduced to enable switching at the end point of the block, and the command speed is indicated in the next m + 1-th block. Speed up to X _{m + 1} is performed. This can be used to change the moving speed of the byte.

  In the case of an analog lathe that is not CNC, it is possible to change the moving speed of the tool by outputting the motor voltage that controls the moving speed of the tool through, for example, a circuit that switches a plurality of resistors. Further, for example, it is possible to move the byte using a power source that can output a voltage having a specified waveform.

In order to further reduce the periodicity, it is desirable that the instruction interval for changing the moving speed is not constant. This is for instance the case of the CNC lathes By not constant Y _n, in the case of the analog lathe using a plurality of timers for switching, or a an output waveform can be complicated by the superposition like the different waveforms This can be achieved by using a power source.

  Further, setting ΔL to 10 μm or more can be realized by appropriately changing the rotation of the conductive substrate during processing. This can be achieved by the same means as in the analog lathe described above.

  ΔL tends to be larger than the indicated value difference of the tool moving speed because the above-mentioned deceleration is applied in the case of the above-mentioned CNC lathe, and because of the overshoot when changing the voltage in the case of the above-mentioned analog lathe. it is conceivable that.

  Moreover, although ΔL tends to increase as the number of rotations of the substrate increases, it is considered that this is due to the influence of wobbling or wah of the rotating body.

  This limit range is Δ ≧ 10 μm because, if it is less than 10 μm, image unevenness due to interference and color tone fluctuation at the time of a color image occur. Further, the upper limit value is currently limited by the performance of the substrate processing machine, but there seems to be no limit due to the effect of the invention.

In addition, at least one of the toners is a gray toner having a light transmittance of 40% or more and 90% or less of a fixed image formed on a polyethylene terephthalate (PET) sheet with a toner adhesion amount of 4.0 g / m ^2. . Gray toner with a light transmittance of less than 40% is similar to the conventional black toner and has a small amount of adhesion, and the effect of the variation is large. The effect of improving the graininess decreases because the amount is too large and the variation at the time of transfer increases.

[Measurement method of ΔL]
First, a method for measuring ΔL will be described.

  The machining cycle difference ΔL in the central axis direction in the image area of the cylindrical substrate in the present invention is calculated by reading the machining cycle from the cross-sectional curve or roughness curve of the machined surface as illustrated in FIG. Can do. That is, attention is paid to the repetitive shape and period from the spectrum diagram of FIG. 3A, and the period length is read by increasing the magnification appropriately. In the case of the lower spectrum diagram (FIG. 3B), the lateral magnification is set to 4 times.

  The measurement location may be any location within the image area of the cylindrical substrate, and may be one location or multiple locations. In the present invention, ΔL in Equation 1 may be calculated from the total machining cycle read from each measurement location. When there is only one measurement location, a plurality of machining cycles read from the measurement location. It may be calculated from

  The measurement length of the machined surface may be any length as long as the machining cycle can be read. However, when the number of measurement points is one, the length at which the machining cycle can be read at least 5 cycles is preferable, and 10 cycles or more are particularly preferable. .

  As the measurement location, for example, the vicinity of the center of the cylindrical base in the axial direction is selected, and for the measurement length, for example, about 4 mm is selected.

  In addition, the measurement of the cross-section curve or the roughness curve is not particularly limited as long as the machining cycle can be read from each curve, but for example, a non-contact type using a stylus type surface roughness measuring instrument, a laser, etc. A surface analysis device or the like is used.

Examples of using a stylus type surface roughness measuring instrument include the following conditions.
Measuring instrument: Tokyo Seimitsu Surfcom 1400D
Measurement mode: Ten-point surface roughness measurement (JIS'01 standard; Rzjis)
Measurement length: 4.0 mm
Cut-off: 0.8mm (Gaussian)
Measurement speed: 0.3 mm / sec
In the present invention, the difference between the maximum value and the minimum value of the cutting cycle read from the cross-sectional curve or roughness curve measured in this way is defined as ΔL.

[Transparency of gray toner]
The transmittance measured in the fixed image portion formed by the gray toner formed on the PET sheet is calculated as follows.

For example, using a spectrophotometer “U-3500” (manufactured by Hitachi High-Tech Fielding Co., Ltd.), a visible spectral transmittance is measured using a PET sheet on which toner is not carried as a reference, and a spectral transmittance at a wavelength of 600 nm is obtained. . Next, in the same manner, a spectral transmittance at a wavelength of 600 nm is obtained for an image fixed on a PET sheet with a toner adhesion amount of 4 g / m ² , and a fixed image on the PET sheet when the spectral transmittance of the reference is 100%. The spectral transmittance is referred to as “light transmittance” in the present invention (hereinafter sometimes simply referred to as transmittance). In the present invention, a commercially available multifunction machine “bizhub PRO C6500” (manufactured by Konica Minolta Business Technologies) or a modified machine thereof is used to form an image, but the present invention is not limited to this.

  The toner adhesion amount is a value obtained by blowing off the toner from a PET sheet in which the toner is not fixed and dividing the mass difference before and after the blow-off by the image area. However, in the case where it is difficult to sample the PET sheet in which the toner is not fixed due to the structure of the image forming apparatus, the fixed image on the PET sheet is a solvent that does not dissolve the PET sheet but dissolves the toner resin, For example, it can be calculated by washing and removing with methyl ethyl ketone and dividing the mass difference before and after the removal by the image area.

  Here, a PET sheet having a thickness of about 0.1 mm and not subjected to roughness processing or coating processing is used. Specifically, “3M Transparency Film PP2500 A4 size” (manufactured by Sumitomo 3M Limited) was used.

In the present invention, the transmittance of the gray toner formed on the PET sheet measured in the fixed image portion with a toner adhesion amount of 4.0 g / m ² is in the range of 40% to 90%, preferably 60%. It is in the range of ˜85%.

  When the transmittance measured in the fixed image portion by the gray toner is in the above range, the graininess in the halftone image such as a soft tone image or a dull tone image is improved and the color uniformity is improved. Rather, the problem related to the uniformity of the color image that has been masked in the prior art is brought to light, and as one of them, a phenomenon in which interference streaks are more conspicuous than in the past has occurred.

  In addition, when forming a halftone image such as a soft tone image and a dull tone image, it is preferable that the dots formed by the color toner and the dots formed by the gray toner overlap with each other at a rate of 5 to 50%. However, even when the color toner dots and the gray toner dots do not overlap and are adjacent to each other, the brightness and darkness of the grain is reduced and the graininess is excellent compared to the case of using the black toner dots. An image can be formed.

  Here, a preferred usage of the gray toner according to the image forming method of the present invention will be described.

That is, when the maximum value of the development potential of the black toner and _{V max,} the dot latent image with a less than 1/4 of the potential of _{V max} at 1/256 or more _{V max,} converted as dots only the gray toner is developed Is done. The dot latent image with less than half of the potential of V _max at 1/4 or more of V _max, is used in combination with gray toner and a black toner, the toner adhesion amount of gray toner (developer amount), black toner It is preferable to use the toner after adjusting it so as to be larger than the toner adhesion amount (development amount). Then, the dot latent image with 1/2 or more of the potential of V _max, only the black toner is converted as dots development.

V _max is the difference between the developing bias potential applied to the developing roller and the photosensitive member potential at the maximum exposure in the case of the reversal development method.

  Gray toner may be used for character images and monochrome images that were previously formed by black toner, but in dots that can be replaced with black toner by overlapping yellow, magenta, and cyan dots, the dot potential is set as described above. Accordingly, it is particularly preferable to use the black toner and the gray toner in a shared manner.

  There are many parts common to cyan, magenta, yellow, and black toners for the production method and general characteristics of the gray toner, which will be described later.

  Here, a description will be given focusing on slightly different parts. When carbon black is used as the colorant contained in the gray toner particles constituting the gray toner, the carbon black is added to 100 parts by mass of the binder resin from the viewpoint of controlling the transmittance of the fixed image portion by the gray toner. It is preferable that 0.03-2.0 mass parts is contained with respect to it, More preferably, it is 0.05-0.54 mass parts.

  A black dye can also be used as the colorant contained in the toner particles constituting the gray toner. In the case of using a black dye, the colorant in the toner particles dissolves in the binder resin, so that the transparency is improved. Therefore, in order to obtain the same transmission density as carbon black, the black dye is used as the binder resin 100. It is preferable that 0.08-0.42 mass part is contained with respect to a mass part.

  Preferred black dyes include C.I. I. Direct Black (hereinafter referred to as “DBk”)-19, DBk-38, DBk-71, DBk-74, DBk-75, DBk-90, DBk-112, DBk-117, DBk-154, Acid Black (hereinafter referred to as “DBk”). , "ABk")-2, ABk-24, ABk-31, ABk-52 and the like.

  Further, a white pigment such as titanium oxide can be used in combination as a colorant for the gray toner. However, since the white pigment is difficult to control the transmittance, the white pigment content is 100 parts by mass of the binder resin. It is preferable to keep it below 2 parts by mass.

[Configuration of photoconductor]
The general structure of the photoreceptor will be described below.

  In the present invention, the photoconductor is often a so-called organic photoconductor containing at least one of a known organic charge generating material and organic charge transporting material. Hereinafter, the organic photoreceptor will be described.

  The organophotoreceptor of the present invention has at least a photosensitive layer on a conductive substrate, or further a protective layer sequentially laminated. Specifically, the layer structure as shown below is exemplified. Can do.

1) Layer structure in which a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated as an intermediate layer and a photosensitive layer on a conductive substrate.
2) A layer structure in which an intermediate layer, a single layer containing a charge transport material and a charge generation material as a photosensitive layer, and a protective layer are sequentially laminated on a conductive substrate.

  Hereinafter, the constitution of the organic photoreceptor and the compound to be used will be described focusing on the above 1).

(Conductive substrate)
The conductive substrate (also referred to as a conductive support) of the photoreceptor used in the present invention has a cylindrical shape having conductivity, and has a processed shape regularly formed along the central axis on the outer peripheral surface by cutting. Any material may be used as long as it has, for example, a material obtained by molding a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel into a drum shape.

(Middle layer)
In the present invention, an intermediate layer having a barrier function and an adhesive function may be provided between the conductive substrate and the photosensitive layer. Considering various types of failure prevention, it can be said that providing an intermediate layer is a preferable mode.

  The intermediate layer can be formed by dip coating or the like by dissolving a known binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane, alkyd-melamine, or epoxy in a known solvent. Of these, an alcohol-soluble polyamide resin is preferred.

  Moreover, various fine particles (metal oxide particles and the like) can be contained for the purpose of adjusting the resistance of the intermediate layer. For example, various metal oxides such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide. Fine particles such as indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide can be used.

  These fine particles may be used alone or in combination of two or more. When two or more types are mixed, it may take the form of a solid solution or fusion. The average particle size of such fine particles is preferably 0.3 μm or less, more preferably 0.1 μm or less. These fine particles may be surface-treated with an inorganic compound or an organic compound in a single or multiple manner.

  Examples of the solvent used for the intermediate layer include known ones. For example, when alcohol-soluble polyamide is used for the binder, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec -C1-C4 alcohols, such as butanol, are excellent in the solubility and application | coating performance of polyamide, and are preferable. In addition, in order to improve the coating properties and storage properties of the liquid, the dispersibility of the fine particles, etc., co-solvents that can be used in combination with the above-mentioned solvent to obtain preferable effects include benzyl alcohol, toluene, methylene chloride, cyclohexanone, tetrahydrofuran, and the like. Can be mentioned.

  The density | concentration of binder resin is suitably selected according to the film thickness and production rate of an intermediate | middle layer.

  When the inorganic particles are dispersed, the mixing ratio of the inorganic particles with respect to the binder resin is preferably 20 to 400 parts by volume, more preferably 40 to 200 parts by volume with respect to 100 parts by volume of the binder resin.

  As a means for dispersing the inorganic particles, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The intermediate layer coating solution can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating.

  The thickness of the intermediate layer is preferably from 0.1 to 30 μm, more preferably from 0.3 to 15 μm.

(Charge generation layer)
The charge generation layer used in the present invention preferably contains a charge generation material and a binder resin, and is formed by dispersing and coating the charge generation material in a binder resin solution.

  Examples of the charge generation material include, but are not limited to, azo raw materials, quinone pigments, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and phthalocyanine pigments. These charge generating substances can be used alone or in a form dispersed in a known resin.

  As the binder resin of the charge generation layer, a known resin can be used, for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, Polyurethane resins, phenol resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (eg, vinyl chloride-vinyl acetate copolymer resins, chlorides) Vinyl-vinyl acetate-maleic anhydride copolymer resin) and poly-vinylcarbazole resin, but are not limited thereto.

  The charge generation layer is formed by dispersing a charge generation material in a solution in which a binder resin is dissolved in a solvent using a disperser to prepare a coating solution, and applying the coating solution to a certain film thickness using a coating device. It is preferable to prepare the film by drying.

  Solvents for dissolving and coating the binder resin used in the charge generation layer include, for example, toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, Examples include butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine, but are not limited thereto.

  As a means for dispersing the charge generating material, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The mixing ratio of the charge generating material to the binder resin is preferably 1 to 600 parts by weight, more preferably 50 to 500 parts by weight based on 100 parts by weight of the binder resin. The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating. It can also be formed by vacuum deposition of the pigment.

(Charge transport layer)
The charge transport layer used in the photoreceptor of the present invention contains a charge transport material (CTM) and a binder resin, and is formed by dissolving and coating the charge transport material in a binder resin solution.

  Examples of charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds Oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1- Two or more kinds of vinylpyrene, poly-9-vinylanthracene, triphenylamine derivatives and the like may be mixed and used.

  A known resin can be used as the binder resin for the charge transport layer, and polycarbonate resin, polyarylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylate resin, and styrene-methacrylic acid. Examples include ester copolymer resins, and polycarbonate resins are preferred. Further, BPA, BPZ, dimethyl BPA, BPA-dimethyl BPA copolymer and the like are preferable in terms of crack resistance, wear resistance, and charging characteristics.

  The charge transport layer is preferably formed by dissolving the binder resin and the charge transport material to prepare a coating solution, applying the coating solution to a certain film thickness with a coating machine, and drying the coating film.

  Examples of the solvent for dissolving the binder resin and the charge transport material include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, and tetrahydrofuran. 1,4-dioxane, 1,3-dioxolane, pyridine, diethylamine, and the like, but are not limited thereto.

  The mixing ratio of the charge transport material to the binder resin is preferably 10 to 500 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the binder resin.

  The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  An antioxidant, an electronic conductive agent, a stabilizer and the like may be added to the charge transport layer. As the antioxidant, those described in JP-A No. 2000-305291, and as the electronic conductive agent, those described in JP-A Nos. 50-137543 and 58-76483 are preferable.

(Protective layer)
The photoreceptor of the present invention may be provided with a protective layer on the outermost surface as necessary.

[Toner used in the present invention]
The toner used in the present invention contains at least a resin and a colorant. Further, the toner used in the present invention preferably has a volume-based median diameter (D ₅₀ ) of 2.0 to 7.5 μm. These points are the same for the gray toner and the other cyan, magenta, yellow, and black toners, and the same applies to other points.

  The small-diameter toner that faithfully reproduces a minute dot image is preferably produced by a polymerization method capable of adding an operation for controlling the particle size and shape in the production process. Among them, emulsion polymerization association fusion in which resin fine particles of around 120 nm are formed in advance by an emulsion polymerization method, etc., and toner is prepared through a step of agglomerating the resin fine particles to form particles of a predetermined size. The method is one of effective production methods.

  Hereinafter, a procedure for preparing a toner by an emulsion polymerization association fusion method, which is often used in the preparation of the toner of the present invention, will be described. Toner preparation is performed through the following steps.

(1) Preparation process of resin fine particle A dispersion (2) Preparation process of resin fine particle B dispersion (3) Preparation process of colorant fine particle dispersion (4) Aggregation / fusion process of resin fine particles (5) Aging process ( 6) Cooling step (7) Cleaning step (8) Drying step (9) External additive treatment step Hereinafter, each step will be described.

(1) Production process of resin fine particle A dispersion The resin fine particle A is a resin fine particle that is first added to the reaction system in the aggregation step described later. This step is a polymerization monomer that forms the resin fine particle A. This is a step of forming resin fine particles having a size of, for example, about 120 nm by introducing into an aqueous medium and performing polymerization. The resin fine particles A can also be formed by containing a wax. In this case, the wax is contained by dissolving or dispersing the wax in a polymerizable monomer and polymerizing it in an aqueous medium. Resin fine particles are formed.

(2) Production Step of Resin Fine Particle B Dispersion The resin fine particles B are resin fine particles added during the aggregation of the resin fine particles A that were first added to the reaction system in the aggregation step described later. The production method of the resin fine particles B is basically the same as the production method of the resin fine particles A, but the resin fine particles having a value different from the glass transition temperature of the resin fine particles A are formed. In the production of the resin fine particles B, it is preferable to form resin fine particles having a value higher than the glass transition temperature of the resin fine particles A.

(3) Colorant particle dispersion preparation step In this step, the colorant is dispersed in an aqueous medium to prepare a colorant particle dispersion having a size of, for example, about 110 nm.

(4) Aggregation / fusion process of resin fine particles This process is a process of agglomerating resin fine particles and colorant particles in an aqueous medium, and fusing these aggregated particles to obtain particles. This is a step corresponding to the “step of agglomerating resin fine particles”.

  In this step, an alkali metal salt, an alkaline earth metal salt, or the like is added as an aggregating agent to an aqueous medium in which resin fine particles and colorant particles are present, and then the glass transition point of the resin fine particles is higher than the glass transition point. In addition, by heating to a temperature equal to or higher than the melting peak temperature (° C.) of the mixture, the agglomeration proceeds, and at the same time, the resin fine particles are fused.

  In this step, the toner according to the present invention in which spherical toner and non-spherical toner are mixed can be produced by performing particle formation according to the following procedure.

  That is, the resin fine particles A and the colorant particles prepared by the above-described procedure are first added to the reaction system, and an aggregating agent such as magnesium chloride is added to aggregate the resin fine particles A to form particles. Then, during the aggregation of the resin fine particles A, the resin fine particles B having a glass transition temperature different from that of the resin fine particles A added first are added, and further the aggregation of the resin fine particles is continued.

In addition, when the resin fine particles are added, the size of the aggregate composed of the resin fine particles A added first is 30% to 50% of the median diameter (D ₅₀ ) of the final target toner based on the volume. Is preferred.

  When the particle size of the particles reaches a target size, aggregation is stopped by adding a salt such as salt. The addition amount of the resin fine particles B is preferably 2 to 90% by mass with respect to the resin fine particles A.

(5) Ripening step This step is a step of aging until the shape of the particles has a desired average circularity by heat-treating the reaction system subsequent to the aggregation / fusion step.

(6) Cooling step This step is a step of cooling (rapid cooling) the dispersion of the particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

(7) Washing step This step includes a step of solid-liquid separation of the particles from the particle dispersion cooled to a predetermined temperature in the above step, and a surfactant or the like from the particles solid-liquid separated into wet cake-like aggregates. It consists of a cleaning process for removing deposits such as aggregating agents.

  In the washing treatment, the filtrate is washed with water until the electric conductivity of the filtrate becomes 10 μS / cm or less. Examples of the filtration method include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, and a filtration method using a filter press and the like, and are not particularly limited.

(8) Drying step This step is a step of drying the washed particles to obtain dried particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like.

  The moisture of the dried particles is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, when the dried particles are aggregated with weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

(9) External additive treatment step This step is a step of preparing a toner by mixing the dried particles with an external additive as necessary. As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  Next, the resin, colorant, wax and the like constituting the toner according to the present invention will be described with specific examples.

  First, as a resin that can be used in the toner according to the present invention, a polymer obtained by polymerizing a polymerizable monomer as described below can be used.

  The resin according to the present invention contains a polymer obtained by polymerizing at least one polymerizable monomer as a constituent component. Examples of the polymerizable monomer include styrene, o-methylstyrene, m- Methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, p Styrene or styrene derivatives such as -n-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, methyl methacrylate, ethyl methacrylate, methacryl N-butyl acid, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, Methacrylate derivatives such as n-octyl acrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, acrylic Acrylate derivatives such as isopropyl acid, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, Olefins such as ethylene, propylene and isobutylene, vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate, vinyl such as vinyl methyl ether and vinyl ethyl ether Vinyl ketones such as ethers, vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, vinyl compounds such as vinyl naphthalene, vinyl pyridine, etc. And acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These vinyl monomers can be used alone or in combination.

  Moreover, it is also possible to use combining what has an ionic dissociation group as a polymerizable monomer which comprises resin. For example, it has a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group of the monomer, and specifically includes acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid. Acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy And propyl methacrylate.

  Furthermore, multifunctional such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a crosslinkable resin by using a functional vinyl.

  Known colorants can be used for the toner according to the present invention. Specific colorants are shown below.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite.

  Examples of the colorant for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48; 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the colorant for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Further, as a colorant for green or cyan, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

  These colorants can be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

  Examples of the wax that can be used in the toner according to the present invention include conventionally known waxes. Specific examples include polyolefin waxes such as polyethylene wax and polypropylene wax, long-chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, and trimethylolpropane. Tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellit Ester waxes such as acid tristearyl and distearyl maleate, ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. Such as amide waxes.

  The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  The toner according to the present invention may be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 80 μm.

  The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to.

[Image forming apparatus]
The image forming method of the present invention uses a set of toners including at least a specific gray toner and a black toner, and forms a latent image on a photosensitive member, and forms a black toner. Development process for developing the electrostatic latent image with black toner to develop, development process for developing the electrostatic latent image with gray toner to form a gray toner image, and fixing for fixing the black toner image and the gray toner image In the case of forming a color image, a development process using a color toner composed of yellow toner and / or cyan toner and / or magenta toner and a fixing process for fixing the color toner image are performed. Specifically, the process of transferring the toner image formed by developing the electrostatic latent image formed on the photoreceptor with toner onto the image support is repeated twice or more using different color toners. By forming a toner image on the image support, an image support carrying the toner image is obtained, and this toner image is fixed to the image support.

  Such an image forming method can be executed in the following image forming apparatus.

  FIG. 4 is an explanatory sectional view showing an example of the configuration of the image forming apparatus used in the image forming method of the present invention.

  This image forming apparatus is a so-called direct transfer type full-color image forming apparatus that does not use an intermediate transfer member, in which five sets of image forming units 18Y, 18M, 18C, 18G, and 18Bk are provided along the conveying belt 15A. It is.

  Each of the image forming units 18Y, 18M, 18C, 18G, and 18Bk is a photoconductor of the present invention in which a photosensitive layer is formed on the outer peripheral surface of a cylindrical substrate, and is transported by power from a driving source (not shown). The photosensitive drums 10Y, 10M, 10C, 10G, and 10Bk driven by the belt 15A and rotated clockwise with the substrate grounded are arranged in a direction orthogonal to the moving direction and the same as the toner. Chargers 11Y, 11M, 11C, 11G, and 11Bk made of, for example, scorotron chargers that apply a uniform potential to the surfaces of the photosensitive drums 10Y, 10M, 10C, 10G, and 10Bk by polar corona discharge, and photosensitive The photosensitive drums 10Y, 10M are uniformly charged by scanning in parallel with the rotation axes of the body drums 10Y, 10M, 10C, 10G, 10Bk. An exposure device 12Y, 12M, 12C, 12G, 12Bk made of, for example, a polygon mirror and a rotating developing sleeve (for example, a polygon mirror) are formed by performing image exposure on the surface of 10C, 10G, 10Bk based on image data. And a developing unit 13Y, 13M, 13C, 13G, and 13Bk that conveys toner held on the surface to the surfaces of the photosensitive drums 10Y, 10M, 10C, 10G, and 10Bk. Yes.

  In FIG. 4, 19Y, 19M, 19C, 19G, and 19Bk are cleaning devices.

  Here, a yellow toner image is formed by the image forming unit 18Y, a magenta toner image is formed by the image forming unit 18M, and a cyan toner image is formed by the image forming unit 18C. The unit 18G forms a gray toner image, and the image forming unit 18Bk forms a black toner image.

  As the conveying belt 15A for conveying the image support P, a conductive film such as carbon black is added to a polymer film such as polyimide, polycarbonate or PVdF, or a synthetic rubber such as silicone rubber or fluorine rubber to impart conductivity. These may be used, and may be in the form of a drum or a belt, but is preferably in the form of a belt from the viewpoint of freedom in device design.

  In addition, the surface of the conveyor belt 15A is preferably appropriately roughened, and for example, the ten-point surface roughness Rzjis is preferably 0.5 to 2 μm. By making the surface of the transport belt 15A rough in this way, the adhesion between the image support P and the transport belt 15A becomes high, and the image support P swings on the transport belt 15A. Is suppressed, and the transferability of the toner image from the photosensitive drums 10Y, 10M, 10C, 10G, and 10Bk to the image support P can be improved.

  In such an image forming apparatus, first, the toner images of the respective colors formed on the photosensitive drums 10Y, 10M, 10C, 10G, and 10Bk of the image forming units 18Y, 18M, 18C, 18G, and 18Bk are timed. In addition, a color toner image is formed on the image support P by sequentially transferring and superimposing on the image support P transported by the transport belt 15A by the transfer units 14Y, 14M, 14C, 14G, and 14Bk. The

  The image support P on which the color toner image is carried has a predetermined interval from the discharging portion by the AC discharger 15B provided on the downstream side of the transfer region with the image forming unit 18Bk of the transfer belt 15A and the transfer portion 15D. Due to the separation action of the separation claw 15C provided via the separation claw 15C, the separation claw 15C is separated from the conveyance belt 15A, conveyed to the conveyance unit 15D, and conveyed to the fixing device 16 via the conveyance unit 15D.

  In the fixing device 16, the image support P is sandwiched in the nip portion N formed by the heating roll 16 a and the pressure roll 16 b and heat and pressure are applied, so that the image support P is superposed on the image support P. After the color toner image is fixed, it is discharged out of the apparatus.

  The fixing temperature in the fixing device 16 is preferably 110 to 200 ° C, and more preferably 120 to 160 ° C.

  The image forming method of the present invention is not limited to the above. For example, an electrostatic latent image is formed on an electrostatic latent image carrier, and the electrostatic latent image is visualized with toner. Examples include an image forming method based on a so-called intermediate transfer method in which a toner image is obtained, and the toner image is transferred to an intermediate transfer member and then transferred onto an image support such as paper and fixed to form an image. it can.

  In the image forming method of the present invention, in the fixed image formed on the image support, the development steps are performed in a prescribed order so that the image with black toner overlaps the upper layer side with respect to the image with gray toner. Is preferred.

  Specifically, in the image forming method using the intermediate transfer type image forming apparatus, it is preferable to perform the development process using black toner and the developing process using gray toner, and the image forming method using the direct transfer type image forming apparatus. Is preferably performed in the order of a development step using gray toner and a development step using black toner. By performing the development steps in such an order, more continuous gradation can be obtained in a portion desired to be expressed softly, and a clear contour can be given to a portion desired to be expressed sharply.

  Further, in the case of forming a color image, in the fixed image formed on the image support, the development steps are performed in a prescribed order so that the image by the gray toner overlaps the upper layer side than the image by the color toner. Preferably, it is done.

  Specifically, in an image forming method using an intermediate transfer type image forming apparatus, it is preferable to perform a developing process using a gray toner, a developing process using a yellow toner, a developing process using a cyan toner, and a developing process using a magenta toner. In the image forming method using the direct transfer type image forming apparatus as shown in FIG. 3, the developing process is performed in the order of the developing process using yellow toner, the developing process using cyan toner, the developing process using magenta toner, and the developing process using gray toner. Is preferred. By performing the development process in the above order, as described above, when the gray toner image is superimposed on the color toner image and the image is formed, the degree of dullness of the lower color toner image is determined as the adhesion of the gray toner. The amount and the area ratio of overlapping dots can be adjusted.

  According to the image forming method as described above, it is possible to form a high-quality image with little gloss difference between the highlight portion and the shadow portion, uniform and three-dimensionality, and further, a soft tone image and a dull tone image, etc. Even when a halftone image is formed, an image excellent in prevention of density unevenness and color tone variation can be formed.

  The image forming apparatus of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers. The present invention can be widely applied to such devices.

  Next, the present invention will be further described with reference to typical embodiments and performances of the present invention. However, the configuration of the present invention is not limited to these.

  In the text, “part” means “part by mass”.

<Preparation of substrate 1>
An aluminum alloy blank having a length of 362 mm was mounted on an analog lathe, and was cut with a diamond sintered tool so that the outer diameter was 59.95 mm and the surface Rzjis was 0.75 μm.

  The spindle speed at this time is 4500 rpm, and the feed rate instruction value of the cutting tool is a machining distance-speed instruction value, 0.5 mm-0.340 mm / rev, 1.6 mm-0.350 mm / rev, 2.8 mm-0. . 340mm / rev, 1.1mm-0.350mm / rev, 2.5mm-0.340mm / rev, a circuit combining timer and resistance, etc. so that it repeats 3.2mm-0.350mm / rev Voltage was input to the tool moving motor. ΔL was 30 μm.

  ΔL uses the Surfcom 1400D manufactured by Tokyo Seimitsu Co., Ltd., RzJIS'01 standard, roughness measurement, measurement length 20.0mm, cut-off 0.08mm (Gaussian), measurement speed 0.3mm / sec. It is the difference between the maximum value and the minimum value of the cutting cycle, which is performed at the center and read from the obtained roughness curve.

<Preparation of substrate 2>
Substrate 2 was produced in the same manner except that the speed indication value of 0.350 mm / rev was all replaced with 0.343 mm / rev under the production conditions of substrate 1. ΔL was 9 μm.

<Preparation of substrate 3>
Substrate 2 was manufactured in the same manner except that the speed indication value of 0.350 mm / rev was all replaced with 0.345 mm / rev under the manufacturing conditions of substrate 1. ΔL was 11 μm.

(Preparation of the substrate 4)
The lathe spindle rotation speed was 4500 rpm, an aluminum alloy base tube was mounted on a CNC lathe, and was cut with a diamond sintered tool so that the surface Rzjis was 0.80 μm.

In this case, as the start of the base pipe end, bytes of the feed program, the relationship of the machining distance / byte feed rate indicated ^{value, 1 st conditions: 2mm / 300μm / rev → 2} nd conditions: 1.8mm / 310μm / rev → 3 ^rd condition: 2 mm / 320 μm / rev → 4 ^th condition: 1.8 mm / 310 μm / rev The increase / decrease of the condition was repeated. At this time, ΔL was 55 μm, and the surface Rzjis was 0.80.

(Preparation of the substrates 5 and 6)
In the manufacturing conditions of the base 4, the same change as in the processing of the base 4 is made except that the change in the bite feed speed instruction value is changed from 1st to 4 sh so that Rzjis becomes 0.75 and 0.85, respectively. Thus, the substrates 5 and 6 were produced. Table 1 also shows the ΔL and surface roughness of the substrate.

<Production of photoconductor>
(Formation of intermediate layer)
1 part by weight of binder resin (N-1) is added to 20 parts by weight of ethanol / n-propyl alcohol / tetrahydrofuran (45:20:35 volume ratio), dissolved with stirring, and then surfaced with 5% by weight of methyl hydrogen polysiloxane. 4.2 parts by mass of the treated rutile titanium oxide particles were mixed, and the mixed solution was dispersed using a bead mill. At this time, zirconia beads having an average particle diameter of 0.5 mm were used and dispersed at a filling rate of 80%, a peripheral speed setting of 4 m / sec, and a mill residence time of 3 hours to prepare an intermediate layer coating solution. The same solution was filtered through a filter using a polypropylene filter medium having a filtration accuracy of 10 μm, and then the intermediate layer coating solution was applied to the outer periphery after washing the “base 1” prepared above by a dip coating method at 120 ° C. Was dried for 20 minutes to form an “intermediate layer” having a dry film thickness of 2 μm.

(Formation of charge generation layer)
The following components were mixed and dispersed using a sand mill disperser to prepare a charge generation layer coating solution. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.

Y-titanyl phthalocyanine (a titanyl phthalosin pigment having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in the spectrum of X-ray diffraction by Cu-Kα characteristic X-ray) 20 parts by mass Polyvinyl butyral (BX -1, manufactured by Sekisui Chemical Co., Ltd.) 10 parts by mass Methyl ethyl ketone 700 parts by mass Cyclohexanone 300 parts by mass (formation of charge transport layer)
The following components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method and dried at 120 ° C. for 70 minutes to form a charge transport layer having a dry film thickness of 20 μm.

Charge transport material (the following structure) 50 parts by mass Polycarbonate resin “Iupilon-Z300” (manufactured by Mitsubishi Gas Chemical Company) 100 parts by mass Antioxidant (2,6-di-t-butyl-4-methylphenol) 8 parts by mass Tetrahydrofuran / Toluene (volume ratio 8/2) 750 parts by mass

  This is the photoconductor No. Set to 1.

  In the same manner, changing the substrate 1 to the substrates 2 to 6, the photosensitive member No. 2-6 were produced.

<Gray toner production example 1>
[Preparation of Resin Particle A]
(First stage polymerization)
A 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device was charged with a solution prepared by dissolving 8 g of sodium dodecyl sulfate in 3 L of ion-exchanged water while stirring at a rate of 230 rpm under a nitrogen stream. The temperature was raised to 80 ° C. After the temperature increase, a solution in which 10 g of potassium persulfate was dissolved in 200 g of ion-exchanged water was added, and the liquid temperature was set to 80 ° C. again.
Styrene 480g
n-Butyl acrylate 250g
Mecacrylic acid 68.0g
n-octyl-3-mercaptopropionate 16.0 g
After the monomer mixture liquid was dropped over 1 hour, polymerization was performed by heating and stirring at 80 ° C. for 2 hours to prepare resin particles [1H].

(Second stage polymerization)
A 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device was charged with a solution of 7 g of polyoxyethylene (2) sodium dodecyl ether sulfate in 800 ml of ion-exchanged water and heated to 98 ° C. 260 g of the resin particles [1H],
Styrene 245g
120g of n-butyl acrylate
n-octyl-3-mercaptopropionate 1.5 g
Paraffin wax A 95g
Ester wax A 480g
A solution prepared by dissolving a monomer mixture consisting of 90 ° C. was added, and the mixture was dispersed and dispersed for 1 hour by a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. A dispersion liquid containing oil droplets) was prepared.

  Next, an initiator solution in which 6 g of potassium persulfate was dissolved in 200 ml of ion-exchanged water was added to this dispersion, and the system was polymerized by heating and stirring at 82 ° C. for 1 hour to obtain resin particles [1HM]. Got.

(Third stage polymerization)
Furthermore, a solution in which 11 g of potassium persulfate was dissolved in 400 ml of ion-exchanged water was added, and under a temperature condition of 82 ° C.,
Styrene 435g
n-Butyl acrylate 130g
Methacrylic acid 33g
n-octyl-3-mercaptopropionate 8 g
A monomer mixture consisting of was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, followed by cooling to 28 ° C. to obtain resin particles [A].

[Preparation of Resin Particle B]
(First stage polymerization)
A solution of 2.3 g of sodium dodecyl sulfate dissolved in 3 L of ion-exchanged water was charged into a 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introduction device, and stirred at a stirring speed of 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. After the temperature increase, a solution in which 10 g of potassium persulfate was dissolved in 200 g of ion-exchanged water was added, and the liquid temperature was set to 80 ° C. again.
Styrene 520g
210g of n-butyl acrylate
Methacrylic acid 68.0g
n-octyl-3-mercaptopropionate 16.0 g
After the monomer mixture liquid was dropped over 1 hour, polymerization was carried out by heating and stirring at 80 ° C. for 2 hours to prepare resin particles [B].

(Preparation of colorant dispersion)
90 g of sodium dodecyl sulfate was dissolved in 1600 ml of ion exchange water with stirring. While stirring this solution, 84 g of carbon black “Regal 330R” (manufactured by Cabot) is gradually added as a colorant, and then dispersed using a stirrer “Claremix” (manufactured by M Technique). Thus, a dispersion of colorant fine particles (hereinafter referred to as “colorant dispersion [1]”) was prepared. The particle diameter of the colorant fine particles in this colorant dispersion [1] was 110 nm as measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

[Aggregation / fusion process]
In a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device, 300 g of resin particles [A] in terms of solid content, 1400 g of ion-exchanged water, and 120 g of “colorant dispersion [1]” Then, a solution prepared by dissolving 3 g of sodium polyoxyethylene (2) dodecyl ether sulfate in 120 ml of ion-exchanged water was added, the liquid temperature was adjusted to 30 ° C., and the pH was adjusted to 10 by adding a 5N aqueous sodium hydroxide solution. did. Next, an aqueous solution in which 35 g of magnesium chloride was dissolved in 35 ml of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After holding for 3 minutes, the temperature was raised and the system was heated to 90 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 90 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Beckman Coulter), and 260 g of resin particles [B] were added when the volume-based median diameter reached 3.1 μm. Further, the particle growth reaction was continued. When the desired particle size is reached, an aqueous solution in which 150 g of sodium chloride is dissolved in 600 ml of ion-exchanged water is added to stop particle growth, and further, the mixture is heated and stirred at a liquid temperature of 98 ° C. as a fusing step. The fusion between the particles was allowed to proceed until the circularity was 0.965 as measured by “FPIA-2100” (manufactured by Sysmex). Thereafter, the solution was cooled to 30 ° C., hydrochloric acid was added to adjust the pH to 4.0, and stirring was stopped.

[Washing and drying process]
The particles generated in the aggregation / fusion process were solid-liquid separated with a basket type centrifugal separator “MARK III model number 60 × 40” (manufactured by Matsumoto Kikai Co., Ltd.) to form a wet cake of toner base particles. The wet cake was washed with ion exchange water at 45 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket-type centrifuge, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). The toner base particles [1] were prepared by drying until the amount reached 0.5% by mass.

[External additive treatment process]
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the toner base particles [1], and the mixture is added using a Henschel mixer. By mixing, a gray toner [1] according to the present invention was produced. The softening point of gray toner [1] was 110 ° C.

<Gray developer production example 1>
The gray toner [1] is mixed with a ferrite carrier having a volume-based median diameter of 60 μm coated with a silicone resin by a V-type mixer so that the concentration of the gray toner is 6% by mass, and the gray developer [1]. Was prepared.

<Gray toner production example 2>
A gray toner [2] was prepared in the same manner as in Production Example 1 of the gray toner, except that the charging amount of the colorant “Regal 330R” (Cabot) was changed to 72 g.

<Gray toner production example 3>
A gray toner [3] was prepared in the same manner as in Production Example 1 of the gray toner, except that the charging amount of the colorant “Regal 330R” (Cabot) was changed to 15 g.

<Gray toner production example 4>
A gray toner [4] was produced in the same manner as in Production Example 1 of the gray toner, except that the charging amount of the colorant “Regal 330R” (manufactured by Cabot) was changed to 6.3 g.

<Gray developer production examples 2 to 4>
Each of the above gray toners [2], [3], and [4] is coated with a silicone resin and a volume-based median diameter 60 μm ferrite carrier, and the V-type mixer is adjusted so that each toner concentration becomes 6% by mass. To prepare a gray developer [2], [3], [4].

<Black toner production example 1>
Black toner [1] was prepared in the same manner as in Gray toner production example 1 except that 1680 g of “Regal 330R” (Cabot Corporation) was used as the black colorant.

<Production Example 1 of Yellow Toner>
Yellow toner [1] was prepared in the same manner as in Gray toner production example 1 except that 1680 g of “CI Pigment Yellow 74” was used as the yellow colorant.

<Cyan toner production example 1>
Cyan toner [1] was prepared in the same manner as in Gray toner production example 1 except that the silicon phthalocyanine compound represented by 1600 g of the above formula (1-2) was used as the cyan colorant.

<Magenta toner production example 1>
Magenta toner [1] was prepared in the same manner as in Gray toner production example 1 except that the compound represented by the above formula (3-2) 1720 g was used as the magenta colorant.

<Production Example 1 of Black Developer, Yellow Developer, Cyan Developer, and Magenta Developer>
Each of the above black toner [1], yellow toner [1], cyan toner [1] and magenta toner [1] is coated with a silicone resin-coated volume-based median diameter 60 μm ferrite carrier, and the density of each toner. The black developer [1], yellow developer [1], cyan developer [1], and magenta developer [1] were prepared by mixing with a V-type mixer so that the amount of toner was 6% by mass.

[Performance evaluation]
One of the gray developers [1] to [4] obtained as described above, a black developer [1], a yellow developer [1], a cyan developer [1] and a magenta developer [1]. And developing a digital multi-function peripheral “bizhub PRO C6501” (manufactured by Konica Minolta Business Technologies, Inc.) and providing each toner with an image forming unit of gray toner The following (1) and (2) were evaluated. The fixing temperature in the fixing process was 180 ° C. Further, the transmittance value measured in the fixed image portion of the gray toner adhesion amount 4.0 g / m ² formed on the PET sheet by the gray toner measured by the above-described procedure is 35% for [1], [ 2] was 42%, [3] was 85%, and [4] was 92%.

(Performance evaluation)
The above-mentioned modified machine of bizhub PRO C6501 manufactured by Konica Minolta Business Technologies, Inc. and the A3 size of “POD gross coat (100 g / m ² )” manufactured by Oji Paper Co., Ltd. are used.
(1) Graininess evaluation Web Safe Color soft tone color code, # cc6666, # cc9966, # cccc66, # 99cc66, # 66cc66, # 66cc99, # 66cccc, # 6699cc, and dull tone color code, # 996666, # The patch images of 999966, # 669966, # 6699999, # 666699, and # 996699 were output in the printer mode, and the respective graininess was comprehensively determined. The results of visual evaluation based on the following criteria are shown in Table 2.

OK: 5 people visually evaluated that 3 or more people had no roughness due to graininess NG; 5 people visually evaluated that 3 people or more had roughness due to graininess (2) Density unevenness and color variation (interference) Line) Evaluation The developer for the black developer of bizhub PRO C6501 manufactured by Konica Minolta Business Technologies, Ltd. is the gray developer [1], and the black photoreceptor is the above-mentioned photoreceptor No. 1 and changing the density of the black (Bk) halftone image and the cyan image halftone image on a “POD gloss coat (100 g / m ² )” manufactured by Oji Paper Co., Ltd. for visual evaluation. did. The same evaluation was performed on other photoreceptors.

  Table 2 shows the results of evaluation based on the following criteria.

○: Diagonal streak is not seen at all △: Diagonal streak is seen slightly, but there is no problem in actual use ×: Diagonal streak is seen, there is a problem in actual use

  Photoconductor No. 1 (ΔL: 30 μm), No. 1 3 (ΔL: 11 μm), No. 3 4 (ΔL: 55 μm), No. 4 5 (ΔL: 35 μm), No. 5 When 6 (ΔL: 25 μm) was used, and a combination of gray toner [2] (transmittance: 42%) or gray toner [3] (transmittance: 85%), good results were obtained. That is, when the photoconductor and toner in the present invention were used, all the characteristic evaluations were good.

10Y, 10M, 10C, 10G, 10Bk Photosensitive drum 11Y, 11M, 11C, 11G, 11Bk Charger 12Y, 12M, 12C, 12G, 12Bk Exposure unit 13Y, 13M, 13C, 13G, 13Bk Developer 14Y, 14M, 14C , 14G, 14Bk Transfer device 15A Conveyor belt 15B AC static eliminator 15C Separation claw 15D Conveyor 16 Fixing device 16a Heating roll 16b Pressure roll 18Y, 18M, 18C, 18G, 18Bk Image forming unit 19Y, 19M, 19C, 19G, 19Bk Cleaning device N Nip part P Image support

Claims (3)

A digital image forming apparatus using at least an electrophotographic photosensitive member having a photosensitive layer on a cylindrical substrate, and a plurality of types of electrostatic latent image developing toners,
The substrate has a processed shape formed on the outer peripheral surface along the central axis, and the shape satisfies Formula 1;
Formula 1 ... ΔL ≧ 10μm
(However, ΔL is the difference in machining cycle in the central axis direction within the image area of the cylindrical substrate.)
An image forming apparatus wherein at least one of the toners has a light transmittance of 40% or more and 90% or less by the following measurement method.
<Light transmittance measurement method>
The light transmittance of a fixed image having a toner adhesion amount of 4.0 g / m ² formed on a polyethylene terephthalate (PET) sheet is measured.   2. The image forming apparatus according to claim 1, wherein the electrophotographic photosensitive member is an electrophotographic photosensitive member having at least a cylindrical substrate, an intermediate layer, and a photosensitive layer, and the intermediate layer includes particles.   2. The image forming apparatus according to claim 1, wherein the electrostatic latent image developing toner is produced by associatively fusing at least resin particles produced by suspension emulsion polymerization and colorant particles.

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