JPH08137197A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of uniformly electrifying an electrostatic latent image carrier by restraining the grouping of the bristles of an electrifying brush in an electrifying device. CONSTITUTION: In this image forming device, an electrostatic latent image is formed by performing image-exposure on the electrostatic latent image carrier 1 whose surface is electrified by the contact type brush electrifying device 2, and the latent image is developed to be a visible image by a developing device 4. The visible image is transferred to a transfer material 7, and the residual developer remaining on the image carrier 1 after transfer is removed by the developing device 4. In the electrifying device 2, the bristles constituting the rotating brush for electrification 21 are bundled and implanted at many parts of a ground fabric. When it is assumed that the shortest distance and the longest distance of the implanting interval between the adjacent bundles out of the bundles are Lmin and Lmax, respectively, a condition 0.44<=Lmin/ Lmax<=1 is satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as an electrophotographic copying machine or a printer, an electrostatic latent image carrier such as a photosensitive drum is charged by a charging device, and an image is exposed in the charged area. Then, an electrostatic latent image is formed, the latent image is developed into a visible image, which is transferred to a transfer material and fixed. After the transfer, the developer remaining on the surface of the electrostatic latent image carrier is removed by a cleaning device.

Recently, in response to demands for compactness and cost reduction of the apparatus, various apparatuses without the cleaning apparatus have been proposed. For example, Japanese Patent Laid-Open No. 3-4283 teaches a so-called cleanerless image forming apparatus in which a developing device also serves as a cleaning device.

[0004]

However, such a cleanerless image forming apparatus has the following problems. That is, in the cleanerless configuration, the developer remaining on the electrostatic latent image carrier after the visible image transfer reaches the charging device as it is, and the charging device contacts the electrostatic latent image carrier with the charging brush. In the case of the contact type brush charging device having the above, the residual developer adheres to the brush bristles of the charging brush, so that grouping of brush bristles (a phenomenon of sticking to each other) occurs during overlapping of image formation, and an electrostatic latent image is formed. Uneven charging of the carrier occurs. This charge unevenness finally appears as image noise such as image density unevenness and deteriorates the image quality.

In order to solve such a problem, a brush type charging device is not adopted but a corona charging device, a roller,
It is possible to employ a charging device including a charging member such as a blade, but the residual developer appears as a so-called memory at the time of the next image formation unless the residual developer is dispersed before charging. In this respect, a corona charging device cannot be expected to have a residual developer scattering effect, and a charging device such as a roller or a blade cannot be expected to have a residual developer scattering effect. Therefore, in the cleanerless configuration, the contact type brush charging device having an effect of scattering the residual developer is suitable.

Therefore, in the present invention, an electrostatic latent image is formed by exposing the electrostatic latent image bearing member whose surface is charged by a contact type brush charging device to an image, and the latent image is developed by a developing device to be visible. An image forming apparatus, which is configured to transfer an image, transfer the visible image to a transfer material, and allow the developing device to remove residual developer remaining on the electrostatic latent image carrier after the transfer. An object of the present invention is to provide an image forming apparatus capable of suppressing grouping of brush bristles of a charging brush in a charging device and uniformly charging the electrostatic latent image bearing member accordingly.

[0007]

As a result of repeated research aimed at solving the above-mentioned problems, the present inventor found that brush bristles were formed on each of a large number of parts of a base member such as a base cloth as a charging brush body in a brush charging device. A bundle is planted, and at that time, the shortest distance is Lmin and the longest distance is Lm among the planting intervals of the bundles adjacent to each other.
It has been found that if the brush body is configured to satisfy the condition of 0.44 ≦ Lmin / Lmax ≦ 1, where ax is set, image unevenness due to grouping of brush bristles by the residual developer is suppressed.

The present invention is based on this finding. An electrostatic latent image is formed on a latent electrostatic image bearing member whose surface is charged by a contact type brush charging device to form an electrostatic latent image, and the latent image is developed by a developing device. Develop it into a visible image, transfer the visible image to a transfer material,
In the image forming apparatus, which allows the developing device to remove the residual developer remaining on the electrostatic latent image carrier after the transfer, in the contact type brush charging device, the bristles of the contact type brush charging device have a large number of base members. They are planted in a bundle in each of the parts, and the shortest distance is Lmin and the longest distance is Lmax among the planting intervals of adjacent ones of those bundles.
In this case, the image forming apparatus is characterized by satisfying the condition of 0.44 ≦ Lmin / Lmax ≦ 1.

Here, each element in this image forming apparatus will be further described. Regarding the structure and material of the brush body: Although various structures of the brush body constituting the contact type brush charging device are conceivable, from the viewpoint of making strength, productivity, flocking density and the like desirable, so-called velveteen weave Representative examples are those having substantially the same structure. That is, as shown in FIG. 3 (A), it is a BM1 in which a large number of piles P of brush bristles are woven in a base cloth B1 as a base member at intervals. In addition, as shown in FIG. 3B, a flexible sheet-shaped synthetic resin base member B2 in which a large number of piles P of brush bristles are planted at intervals may be considered. The present invention can be applied also to these brush bodies in which piles are planted at a regular pitch.

In any case, as a typical example, each pile may be formed by bundling about 20 to 200 brush bristles having a diameter of about 10 μm. When the brush body BM1 of the type shown in FIG. 3 (A) is adopted, as a typical example of the method of weaving the pile P into the base cloth B1, as shown in FIG. There is a so-called V-shaped weave in which P is woven in a V-shape, and a so-called W-shaped weave in which each pile P is woven in a yarn S constituting a base fabric B1 as shown in FIG. Brush bristles are less likely to come off in W-shaped weaves than in V-shaped weaves.

Further, as a special weaving method, as shown in FIG. 6 (A), each pile P may be inserted into the base fabric B1 and the piles may be knotted on the back side of the base fabric. In addition, as a modified example of the V-shaped weave and the W-shaped weave (with different pile pitches) shown in FIGS. 4 and 5, FIGS.
The weave shown in (F) is also conceivable. 6B is a weave in which the base cloth yarn S and the pile P are not in a parallel relationship, and productivity is poor, but when applying a coating treatment to the back surface of the base cloth,
It is considered that the flow of the coating liquid along the yarn becomes complicated and uniform coating is easy. Further, the one shown in FIG. 6 (C) is V shown in FIG.
The pile P is thinned out in the character weaving, and FIG.
6D shows the weave of FIG. 6C in which the stitches of the base fabric thread S for hooking the pile P are increased during V-shaped weaving, and the one of FIG. The pile P is thinned out in the vertical direction with respect to FIG.
In the case of (F), the distance between the hooks for hooking the pile P and the V-shaped weave is different from that in FIG. 6 (E).

In addition to the above, it is possible to adopt a method in which the pile pitch is changed by various methods such as mixing different weaves, changing the yarn diameter of the base cloth, and mixing piles of different diameters. As the material of the brush bristles in the contact type brush charging device, the charging ability of the electrostatic latent image carrier, its surface hardness and size, the positional relationship with other elements of the charging device, the system speed of the device, etc. are taken into consideration. , Suitable electrical resistivity, flexibility, hardness, shape, so that a desired charging amount can be obtained by applying a charging voltage such as a DC component only or a voltage containing a DC component and an AC component, It is sufficient to select one having strength, and the material is not particularly limited.

As the conductive metal brush bristle material, tungsten, stainless steel, gold, platinum, aluminum, iron,
Metal fibers such as copper can be used while appropriately adjusting the length or fiber diameter. The conductive resin brush bristle materials include rayon, polyamide, acetate, copper ammonia, vinylidene, vinylon, fluorinated ethylene, benzoate, polyurethane, polyester, polyethylene,
In fibers made of polyvinyl chloride, polypropylene, etc.,
It is possible to use a material in which a resistance adjusting agent such as carbon black, carbon fiber, metal powder, metal whiskers, metal oxide, or semiconductor material is dispersed. In this case, a desired resistance value can be appropriately obtained depending on the amount of dispersion. Further, instead of dispersion, the fiber surface may be coated with a resistance adjusting material.

The electrical resistivity of such a fiber material is usually about 1 in terms of volume resistivity in order to obtain good charging performance.
It is set to be not more than ⁰⁹ Ωcm, preferably not more than 10 ⁷ Ωcm. In addition, the cross-sectional shape of the fiber is easy to make in the manufacturing process, such as a circle, an ellipse, a wrinkle-shaped circle, a polygon, a flat shape, or a shape having a cavity inside, as long as the chargeability is not impaired. You can choose a shape. Regarding Support and Rotation of Brush Body As for the brush bodies BM1 and BM2 as illustrated in FIG. 3, for example, as shown in FIG. 7A, rotationally driven conductive metal, conductive synthetic resin, surface 7 is spirally wound around the surface of the conductive core rod R1 made of an insulating material or the like subjected to conductive treatment, or flatly wound as shown in FIG.
As shown in FIG. 7C, it is formed in a tubular shape in advance and is attached by a conductive adhesive, such as by fitting, or as shown in FIG. 7D, conductive metal, conductive synthetic resin, surface Is rolled into a cylindrical shape and wound around its surface, and the brush body end edge is sandwiched between the abutting edges of the plate-like body to prevent caulking, and these are rotated. It is also possible to drive. Also at this time, it may be adhered with a conductive adhesive. Further, as shown in FIG. 7 (E), the brush body is formed in advance into an endless belt shape, and at least one of them is rotationally driven.
It is also conceivable to wind the pulleys R3 and R4, at least one of which is made of a conductive material such as a conductive metal, a conductive synthetic resin, or an insulator whose surface is subjected to a conductive treatment. further,
As shown in FIG. 7 (F), a brush body BM having a predetermined area size.
1 or BM2 is bonded to a conductive substrate R5 made of a conductive metal, a conductive synthetic resin, an insulating material whose surface is conductively treated, or the like arranged in a fixed position with respect to the electrostatic latent image carrier, by a conductive adhesive. Can also be considered. Further, a similar brush can be obtained by fixing the conductive adhesive instead of the conductive adhesive and fixing the conductive adhesive to the substrate at the rear end.

The rotating brush or fixed brush thus obtained is brought into contact with the surface of the electrostatic latent image carrier (photoreceptor drum in the illustrated example) PC as illustrated in FIGS. 8 (A) to 8 (E). . FIG. 8A shows a state in which one roller-type rotating brush RB is in contact. FIG. 8B shows a state in which two roller-type rotating brushes RB are in contact with each other. When a plurality of rotating brushes are brought into contact with each other as described above, the present invention may be applied to the brush on the most upstream side in the surface moving direction of the electrostatic latent image carrier.

Further, FIG. 8C shows a state in which a belt-shaped rotating brush BB is contacted so that the line connecting the pulleys R3 and R4 supporting the belt-shaped rotating brush BB is arranged at a right angle to the rotation axis of the photosensitive drum. Is shown. FIG. 8D shows a state in which the belt-shaped rotary brush BB is contacted so that the line connecting the pulleys R3 and R4 supporting the belt-shaped rotary brush BB is arranged parallel to the rotation axis of the photoconductor drum. FIG. 8E shows a state in which the fixed brush FB is brought into contact with the photosensitive drum PC. The present invention can also be applied to these. The shortest distance Lmin among the planting intervals of mutually adjacent brush bristles in the contact type brush charging device
And the maximum distance Lmax are determined as follows.

That is, as illustrated in each of FIG. 9 to FIG. 13, an arbitrary brush bristle bundle is set to A among the bundles of brush bristle which are coming out from the same position in the brush body, and the brush bristle closest to A is set. When a polygon having a corner of the bundle is formed so as to pass through the bundle B and surround the bundle A, the bundle A at the center of the polygon
From the closest bundle B on the polygon to the shortest distance L
min, and the distance between the bundle C and the bundle A farthest from the bundle A among the brush bristle bundles on the polygonal line is Lmax.
However, such a polygon has a maximum area with all interior angles less than 180 degrees. For example, in the example shown in FIG. 9, the polygon indicated by the solid line has a larger area than the polygon indicated by the alternate long and short dash line (triangle), so the polygon indicated by the solid line is selected.
Furthermore, the brush bristle bundles other than A do not exist in the polygon.

If a plurality of types of polygons can be considered even under such conditions, the one with the largest Lmax among them can be Lmax.
Choose as. Applied AC (AC) component In charging the electrostatic latent image bearing member, generally, it is better to apply a charging voltage including an AC component than a case where a DC voltage is simply applied to the brush charging device. A stable charge can be obtained. Therefore, also in the present invention, FIG.
As illustrated in, for example, alternating current (AC) power supply P _AC and direct current (D)
C) It is possible to apply a voltage in a state in which both voltages are superimposed to the brush charging device by using the power source P _DC . In this case, the DC component is usually 300 V to 1500
A voltage selected from the range of about V is applied with a polarity according to the charging polarity of the electrostatic latent image carrier.

As the AC component, it is usually in the form of being superposed on the DC component, and is usually 500 V to 1 peak-to-peak.
An alternating voltage having an amplitude selected from the range of about 500 V is applied. Not only the peak-to-peak value of the AC component, but also the frequency, the resistance value of the rotating brush material, the electrostatic capacity of the brush material, the contact resistance between the rotating brush and the photosensitive member, the driving speed of the rotating brush and the photosensitive member. Etc.,
It may be appropriately selected, and a frequency selected from the range of about 5 to 5000 Hz is usually adopted.

The waveform of the AC component is not particularly limited as long as the requirements of the system entanglement are taken into consideration. As shown in FIG. 15, (A) a rectangular waveform,
(B) sinusoidal, (C) sawtooth,
(D) Half-sine waveform, (E) Sawtooth waveform including time constant, (F) Rectangular waveform including time constant,
Examples include (G) a waveform in which a sub-waveform is superimposed on the main waveform, and (H) a waveform in which peak-to-peak pulsates. A typical example of the electrostatic latent image carrier is a photoconductor having a drum shape. As a photoconductor that can be used in the present invention, a semiconductor laser beam (wavelength: 780 nm), which will be described in detail in Examples later, is used. And a function-separated type organic photoreceptor having good sensitivity to long-wavelength light such as LED light (wavelength 680 nm). However, the invention is not limited to such a function-separated type organic photoconductor.

As for the sensitivity range of the photoconductor, a semiconductor laser (780 nm) optical system and an LED array (680 nm)
In an image forming system using long-wavelength light such as an optical system, a photoreceptor having the above-mentioned long-wavelength sensitivity may be used. For example, visible light is used as a light source in a liquid crystal shutter array, a PLZT shutter array, or the like. Image forming system, image forming system using a visible light laser as a light source, image forming system using a phosphor light emitting array as a light source, or analog image formation using visible light and lens / mirror optical system commonly used in general copying machines. In a system or the like, a photoreceptor having sensitivity in the visible range may be used.

Regarding the constitution of the photoconductor, in addition to the function-separated type organic photoconductor in which the charge transport layer is separately provided on the charge generation layer, a so-called reverse type in which the charge generation layer is provided on the charge transport layer is used. It may be a laminated type photoreceptor or a so-called single-layer type photoreceptor having both a charge generation function and a charge transport function. Further, as the charge generating material, the charge transporting material, the binder resin, the additive and the like, known materials may be appropriately selected according to the purpose. Further, the photosensitive material is not limited to the organic material, but zinc oxide, cadmium sulfide,
An inorganic material such as a selenium-based alloy, an amorphous silicon-based alloy, or an amorphous germanium-based alloy may be used.

The photoreceptor applicable to the present invention may further be provided with a surface protective layer in order to improve durability, environment resistance, etc., and may have charging performance, image quality, adhesion to a substrate, etc. An undercoat layer may be provided for improvement. As a material for such a surface protective layer or an undercoat layer,
A resin such as an ultraviolet curable resin, a room temperature curable resin or a thermosetting resin, a mixed resin in which a resistance adjusting material is dispersed in the resin,
Uses vacuum thin film materials made by thinning metal oxides, metal sulfides, etc. in vacuum by vapor deposition or ion plating, amorphous carbon film produced by plasma polymerization method, amorphous silicon carbide film, etc. can do.

The substrate of the photoconductor applicable to the present invention is not particularly limited as long as it is a photoconductor support having a conductive surface, and the shape may be a flat plate shape other than the cylindrical shape. It may be a belt shape. Further, the surface of the substrate may be roughened, oxidized, colored, or the like.

[0025]

According to the image forming apparatus of the present invention, an image is formed similarly to the conventional image forming apparatus. However, the developer remaining on the electrostatic latent image carrier after the transfer of the visible image to the transfer material is removed by the developing device. Further, in the contact type brush charging device used, brush bristles are planted in a bundle on each of a large number of portions of the base member in the charging brush. When the shortest distance is set to Lmin and the longest distance is set to Lmax, the setting interval is set to satisfy the condition of 0.44 ≦ Lmin / Lmax ≦ 1. Grouping of the brush bristles of the charging brush due to the residual developer remaining is suppressed, and the electrostatic latent image carrier can be uniformly charged accordingly.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a printer according to the present invention. The printer P1 has a photosensitive drum 1 at the center. The drum 1 is rotationally driven in the direction of arrow a (counterclockwise) in the figure by a driving device (not shown). Around the drum, a brush charging device 2, an exposure device 3, a developing device 4,
Transfer chargers 5 are sequentially arranged.

The brush charging device 2 includes a rotating brush 21, and the rotating brush is in contact with the surface of the photosensitive drum 1. The rotating brush 21 is applied with a charging voltage from a power source (not shown), and is rotated in the opposite direction to the photosensitive drum 1 by a driving device (not shown), in other words, in the contact area with the photosensitive drum 1, the photosensitive drum 1 is rotated. The surface of the photosensitive drum 1 is uniformly rotated by -500 while being rotated in the drum surface moving direction.
It can be charged to ~ -1000 (V).

The rotating brush 21 is of a roller type in which a brush body of the type shown in FIG. 3A is wound around and fixed on a conductive core rod which is rotationally driven, and which is electrically connected to the core rod by a conductive adhesive. In the brush body portion, conductive brush bristles are bundled and woven into the base cloth. The shortest distance Lmin and the longest distance Lmax among the planting intervals of the adjacent ones in the brush bristle bundle are 0.44 ≦ L.
The condition of min / Lmax ≦ 1 is satisfied.

The exposure device 3 uses a generally known semiconductor laser. Here, the surface of the photosensitive drum 1 charged to -600 (V) is irradiated with a laser beam for the image portion to about -50. It is adjusted so as to decrease to (V). The developing device 4 is a one-component developing device that performs reversal development. The driving roller 42 supported by the casing 41 and driven to rotate in the direction of arrow b (clockwise) in the drawing has an inner diameter slightly larger than the outer diameter of the roller. A flexible developing sleeve 43 is externally fitted, and both ends of the sleeve are pressed against the drive roller 42 from the inside of the casing 41 by the pressing belt member 44 to form a slack portion 430 on the opposite side, and this slack portion is exposed to light. It is in contact with the body drum 1. Further, a metal regulating blade 45 is in contact with the developing sleeve 43 in the casing 41.

The toner T, which is a one-component developer accommodated in the casing 41, is supplied to the toner conveying roller 47 while being stirred by the stirring member 46 which is driven to rotate counterclockwise in the figure, and the roller 47 in the figure. The toner T is moved to the developing sleeve 43 side while being rotationally driven in the clockwise direction. The developing sleeve 43 is driven to rotate in the same direction as the driving roller due to frictional force as the driving roller 42 rotates, while the regulation blade 45 frictionally charges the toner T while adhering a certain amount on the developing sleeve 43. The developing sleeve 43 sequentially supplies the toner T to the contact portion with the photosensitive drum 1 by its rotation. A developing bias voltage of −250 V is applied to the developing sleeve 43 from a power source (not shown).

The photoconductor drum 1 is a function-separated type organic photoconductor for negative charging having good sensitivity to long-wavelength light such as semiconductor laser light (wavelength 780 nm) and LED light (wavelength 680 nm). It is manufactured as follows. First, 1 part by weight of τ (tau) type metal-free phthalocyanine, 2 parts by weight of polyvinyl butyral resin, and 100 parts by weight of tetrahydrofuran were put in a ball mill pot to prepare 2 parts.
Dispersed for 4 hours to obtain a photosensitive coating solution. At this time, the viscosity of the photosensitive coating liquid was 15 cp at 20 ° C. As the polyvinyl butyral resin, a resin having an acetylation degree of 3 mol% or less, a butylation degree of 70 mol% and a polymerization degree of 1000 was used.

This coating solution was applied to an outer diameter of 30 mm and a length of 240 m.
m, the thickness of 0.8 mm is applied to the surface of an alumite cylindrical substrate by the dipping method, and the film thickness after drying is 0.4 μm.
The charge generation layer of was formed. The cylindrical substrate used here is an aluminum alloy containing 0.7% by weight of magnesium and 0.4% by weight of silicon, and the drying condition is 20 ° C.
In the circulating air for about 30 minutes.

Next, on this charge generation layer, 8 parts by weight of a hydrazone compound represented by the following structural formula (Formula 1), 0.1 part by weight of an orange dye (Sumiplast Orange 12, manufactured by Sumitomo Chemical Co., Ltd.), and a polycarbonate resin (Panlite) were used. L-1250; manufactured by Teijin Chemicals Ltd.) 10 parts by weight of a coating solution prepared by dissolving 180 parts by weight of tetrahydrofuran in a solvent is applied by a dipping method and dried to form a charge transport layer having a thickness of 28 μm. did. The viscosity of the coating liquid at this time was 240 cp at 20 ° C., and the drying condition was 30 minutes in circulating air at 100 ° C.

[0034]

Embedded image

As described above, the function-separated type negatively chargeable organic photosensitive drum 1 in which the charge generation layer and the charge transport layer were sequentially laminated on the conductive substrate was produced. Here, the τ-type metal-free phthalocyanine used for preparing the charge generation layer is CuK.
When an X-ray having a wavelength of α / Ni of 1.541Å is used, the Bragg angle (2θ ± 0.2 degrees) is 7.6, 9.2, 16.
It has an X-ray diffraction pattern showing strong peaks at 8, 17.4, 20.4 and 20.9 degrees. In the infrared absorption spectrum, the 751 absorption band of ± 2 cm ^-1 strongest four during 700~760cm ^-1, 1320
Almost absorption band of the same intensity of two during ~1340cm ^-1, and those having a characteristic absorption band at 3288 ± 3 cm ^-1.

The toner used in the developing device 4 is as follows. This toner is a negative charging type non-translucent non-magnetic black toner, and is bisphenol A type polyester resin 100.
Parts by weight, carbon black (MA # 8; manufactured by Mitsubishi Kasei Co., Ltd.) 5 parts by weight, and a charge control agent (Bontron S-3
4; 3 parts by weight of Orient Chemical Industry Co., Ltd. and wax (Viscor TS-200; Sanyo Chemical Industry Co., Ltd.)
A composition consisting of 2.5 parts by weight is kneaded, pulverized and classified by a known method to give an average particle size of 10 μm of 7 to 13
Toner particles having a distribution of 80% by weight in the range of μm were produced, and hydrophobic silica (manufactured by Gabosil Co., Ltd .: Talanox 500) of 0.75 was added to the toner particles as a fluidizing agent.
It was added by weight% and mixed and stirred by a homogenizer.

The developer and the developing method that can be used in the image forming apparatus according to the present invention are not limited to this. Depending on the polarity of the photoconductor and the image formation process used,
It is possible to appropriately select and employ a positively charged toner, a translucent toner, a magnetic toner, a two-component developing method, a regular developing method, or the like. Regarding color, not only black toner but also color toners such as yellow, magenta, and cyan can be appropriately selected and used. Further, the toner shape may be an irregular shape or a specific shape such as a spherical toner. Further, for the purpose of improving cleaning performance, a lubricant such as polyvinylidene fluoride may be mixed.

Next, FIG. 2 shows a schematic configuration of another printer according to the present invention. This printer P2 is the same as the printer P1 shown in FIG. 1, except that the charging device 2 is replaced by a contact brush charging device 20 of the type shown in FIG. .
The other structure is the same as that of the printer P1 in FIG. 1, and the same parts are designated by the same reference numerals as in FIG. Also,
The toner used in the developing device 4 is also the same.

Also in the fixed brush 22 of the charging device 20, conductive brush bristles are bundled and woven into the base cloth in the brush body portion. The shortest distance Lmin and the longest distance Lmax among the planting intervals of the adjacent ones of the brush bristle bundles are 0.44 ≦ Lmi.
The condition of n / Lmax ≦ 1 is satisfied. According to the printers P1 and P2 described above, the surface of the photosensitive drum 1 that is driven and rotated is uniformly charged to the surface potential −600 (V) by the brush charging devices 2 and 20, and then the exposure device 3 performs image exposure. And an electrostatic latent image is formed.
The surface potential of the exposed portion drops to about -50 (V). The electrostatic latent image thus formed is developed in the developing device 4 under a developing bias voltage of -250 (V) to become a toner image. In this development, the toner T on the developing sleeve 43 adheres to the electrostatic latent image with a potential difference ΔV = 200 (V).

The toner image thus formed is transferred by the transfer charger 5 to the paper 7 supplied from the transfer paper supply means (not shown), and the transferred paper 7 is separated by the separating means (known per se). It is separated from the photoconductor drum 1 by (not shown), and the process proceeds to a fixing device (not shown) where the toner image is fixed and then discharged. However, all the toner on the photoconductor drum 1 is not transferred onto the paper 7 by the transfer charger 5, and is usually 10 to 10.
20% of the toner remains on the photosensitive drum 1 as residual toner. This residual toner is charged by the charging devices 2 and 20,
Further, if necessary, after passing through the image exposure process by the exposure device 3, it reaches the developing device 4 again, and the residual toner in the non-image portion is collected by the developing sleeve 43.

When charging and exposing are performed with the residual toner remaining on the photosensitive drum 1, the brush charging device 2 will be referred to as the problem that the portion with the residual toner may not be charged or may not be exposed. , 20 and the fixed brush 22 disturb the residual toner, so there is no problem. If a contact charging device such as a corona charger, a charging roller, or a charging blade is used, a dispersal member is required. However, if such a brush charging device is used, there is also a dispersal effect, and therefore the dispersal member is not necessary.

In these printers P1 and P2, the condition of 0.44 ≦ Lmin / Lmax ≦ 1 is satisfied as described above, and therefore, after the toner image is transferred, the toner for charging due to the toner remaining on the photosensitive drum 1 is charged. Grouping of the brush bristles of the brushes 21 and 22 is suppressed, and the photosensitive drum 1 can be uniformly charged by that amount, and a high-quality image in which image unevenness is suppressed can be formed.

Next, using the printer P1 or P2, the charging voltage applied to the contact type brush charging device 2, 20 and the material and thickness of the brush bristles of the charging device are set to the following common conditions 1, 2. 3, and the arrangement of the brush bristle bundles was within the range of 0.44 to 1 in the value of Lmin / Lmax, and as a comparative example, image formation was carried out by using an image outside the range. did. This will be explained below.

As an image evaluation method, an image after 500 sheets of character patterns having a B / W ratio of 5% are output by the printer is evaluated. The evaluation image is 300 as shown in FIG.
A halftone dot image of 1 on and 3 off in dpi was used, and image unevenness was evaluated in the following 5 grades (to). FIG.
6, the regular length of one side of one dot l = 84.7.
μm.

Image unevenness is considerably severely observed by the naked eye and is not practical. Image unevenness is visually observed and is not practical. Image unevenness is visually observed, but is within the practicable limit. A little image unevenness is seen in the image, but it is not a noticeable image Good image in which no image unevenness is seen visually When the brush charging device is the following common condition 1, the printer P1 is used, and the rotating brush of the charging device 2 is used. As described above, the charging voltage applied to 21 is a direct current (DC) voltage superimposed with an alternating current (AC) voltage, and the DC component is −
600 V, AC component was 1.5 kV, and frequency was 100 Hz.

The rotating brush 21 is rotated in the opposite direction to the photosensitive drum 1 as described above. Therefore, the mutual contact portions of the two move in the forward direction (the same direction). Brush bristle thickness: 6 denier (600d / 100f) Brush bristle material: Conductive carbon dispersed in rayon Brush resistance: 10 ⁶ to 10 ⁷ Ωcm Brush bristle length: 5 mm To the brush bristle 1 Amount of pushing in: 1 mm Rotational speed of rotating brush 21: 3 of rotation speed of photosensitive drum
Double Experimental Example 1 A rotating brush having a brush bundle arranged as shown in FIG. 9 was used. The planting interval of the brush bundle is Lmin / Lmax =
It is 1.0. Images using this brush were evaluated. Experimental Example 2 A rotating brush having a brush bundle arranged as shown in FIG. 10 was used. The brush bundling interval is Lmin / Lmax
= 0.6. Images using this brush were evaluated. Experimental Example 3 A rotating brush having a brush bundle arranged as shown in FIG. 11 was used. The brush bundling interval is Lmin / Lmax
= 0.44. Images using this brush were evaluated. Comparative Experimental Example 1 A rotating brush having a brush bundle arranged as shown in FIG. 12 was used. The brush bundling interval is Lmin / Lmax
= 0.40. Images using this brush were evaluated. Comparative Experimental Example 2 A rotating brush having a brush bundle arranged as shown in FIG. 13 was used. The brush bundling interval is Lmin / Lmax
= 0.2. Images using this brush were evaluated. When the brush charging device is in the following common condition 2, the printer P1 or P2 is adopted, and the charging device 2, 20
The charging voltage applied to the rotating brush 21 and the fixed brush 22 was only DC component -1100V, and AC component was not applied. Other conditions were the same as the common condition 1. Experimental Example 4 In the printer P1, a rotating brush having a brush bundle arranged as shown in FIG. 9 was used. The planting interval of the brush bundle is
Lmin / Lmax = 1.0. Images using this brush were evaluated. Experimental Example 5 In the printer P1, a rotating brush having a brush bundle arranged as shown in FIG. 10 was used. The planting interval of the brush bundle is Lmin / Lmax = 0.6. Images using this brush were evaluated. Experimental Example 6 In the printer P1, a rotating brush having a brush bundle arranged as shown in FIG. 11 was used. The planting interval of the brush bundle is Lmin / Lmax = 0.44. Images using this brush were evaluated. Comparative Experimental Example 3 In the printer P2, a fixed brush having a brush bundle arranged as shown in FIG. 12 was used. The planting interval of the brush bundle is Lmin / Lmax = 0.4. Images using this brush were evaluated. Comparative Experimental Example 4 In the printer P1, a rotating brush having a brush bundle arranged as shown in FIG. 13 was used. The planting interval of the brush bundle is Lmin / Lmax = 0.2. Images using this brush were evaluated. When the brush charging device has the following common condition 3, the printer P2 is adopted, and the fixed brush 22 of the charging device 20 is used.
As described above, the charging voltage applied to the DC voltage is a direct current (DC) voltage superimposed with an alternating current (AC) voltage. The DC component is -600 V, the AC component is 1.5 kV, and the frequency is 100 Hz.
And

Brush bristle thickness: 6 denier (600 d /
100f) Brush bristle material: Conductive carbon dispersed in rayon Brush resistance: 10 ⁶ to 10 ⁷ Ωcm Brush bristle length: 5 mm Pushing amount of brush bristle into drum 1: 1 mm Experimental example 7 Brush bundle A fixed brush having an arrangement as shown in FIG. 9 was used. The planting interval of the brush bundle is Lmin / Lmax =
It is 1.0. Images using this brush were evaluated. Experimental Example 8 A fixed brush having a brush bundle arranged as shown in FIG. 11 was used. The brush bundling interval is Lmin / Lmax
= 0.44. Images using this brush were evaluated. Comparative Experimental Example 5 A fixed brush having a brush bundle arranged as shown in FIG. 12 was used. The brush bundling interval is Lmin / Lmax
= 0.40. Images using this brush were evaluated. From the above results, Lmin / Lmax ≧ 0.4
It can be seen that when the value is 4, uneven charging is reduced and a good image is obtained. In particular, Lmin / Lmax ≧ 0.6 or more is good, and it is understood that the rotating brush is better than the fixed brush.

[0048]

According to the present invention, the electrostatic latent image bearing member whose surface is charged by the contact type brush charging device is imagewise exposed to form an electrostatic latent image, and the latent image is developed by the developing device. An image forming apparatus, wherein a visible image is formed, the visible image is transferred to a transfer material, and after the transfer, the residual developer remaining on the electrostatic latent image carrier is removed by the developing device. It is possible to provide an image forming apparatus capable of suppressing image unevenness due to grouping of brush bristles of the charging brush in the charging device and uniformly charging the electrostatic latent image carrier by that amount.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a main part of a printer which is an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a main part of a printer which is another embodiment of the present invention.

FIG. 3 is a diagram showing a structural example of a brush body adopted in the charging device, and FIG. 3A shows a structure in which a pile is woven into a base cloth,
FIG. 1B shows a structure in which a pile is woven into a synthetic resin base member.

FIG. 4 shows an example of V-shaped weaving of a pile into a base cloth in a brush body of the type shown in FIG. 3A, where FIG. 4A is a schematic sectional view of the brush body, and FIG. FIG. 3 is a schematic plan view of the brush body.

FIG. 5 shows an example of W-shaped weaving of a pile into a base cloth in a brush body of the type shown in FIG. 3A, where FIG. 5A is a schematic sectional view of the brush body, and FIG. FIG. 3 is a schematic plan view of the brush body.

FIG. 6A to FIG. 6F are diagrams showing another example of how to weave the pile into the base cloth in the brush body.

7A to FIG. 7F are respectively shown in FIG.
It illustrates a method of forming a brush body as shown in FIGS. 3A and 3B on a rotating brush body or a fixed brush body.

8A to 8E are diagrams showing examples of a mode in which a rotating brush body or a fixed brush body as shown in FIG. 7 is brought into contact with a photoconductor.

FIG. 9 is a diagram showing a method for obtaining the maximum Lmax and the minimum Lmin of the planting intervals of the brush bristle bundle in the charging brush.

FIG. 10 is a diagram showing a method for obtaining Lmax and Lmin in a charging brush in which a brush bristle bundle is implanted in a state different from that shown in FIG. 9;

FIG. 11 is a diagram showing a method of obtaining Lmax and Lmin in a charging brush in which a brush bristle bundle is further implanted.

FIG. 12 is a diagram showing a method for obtaining Lmax and Lmin in a charging brush in which a brush bristle bundle is further implanted.

FIG. 13 is a diagram showing a method of obtaining Lmax and Lmin in a charging brush in which a brush bristle bundle is further implanted.

FIG. 14 is a diagram showing an example of a power supply configuration when a charging voltage in which a DC voltage is superimposed with an AC voltage is applied to the brush charging device.

FIGS. 15A to 15H are diagrams showing waveform examples of the AC component applied to the charging device.

FIG. 16 is a diagram showing an example of a halftone dot pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor drum (electrostatic latent image carrier) 2, 20 Contact type brush charging device 21 Rotating brush 22 Fixed brush P Pile (bunch of brush bristles) B1 Base cloth (base member) B2 Synthetic resin base member A, B, C Brush bunch P _AC AC power supply P _DC DC power supply 3 Exposure device 4 Developing device 5 Transfer charger 7 Transfer paper

Claims (1)

[Claims] 1. An electrostatic latent image carrier is imagewise exposed to light by a contact brush charging device to form an electrostatic latent image, and the latent image is developed by a developing device to be visualized. In the image forming apparatus, in which the visible image is transferred to a transfer material, and after the transfer, the developer remaining on the electrostatic latent image carrier is removed by the developing device, the contact brush charging device is , The brush bristles are planted in a bundle in each of a large number of parts of the base member, and the shortest distance among the planting intervals of adjacent ones of these bundles is Lmin,
An image forming apparatus which satisfies a condition of 0.44 ≦ Lmin / Lmax ≦ 1 when the longest distance is Lmax.