JPH04275573A - Brush electrifier - Google Patents

Abstract

PURPOSE:To prevent the loosening of an electrifying brush and to suppress the occurrence of a brush line-like image noise by providing processing and recessing parts on the inner surface of a supporting plate setting the end part of the eletrifying brush in the moving direction of the surface of a drum. CONSTITUTION:The supporting plates 24 and 25 supporting the end part of a fixed type electrifying brush 20 coming into contact with the surface of the photosensitive drum 1 to electrify it, are provided. The projecting/recessing parts for preventing the loosening of the end part of the brush are provided on the inner surfaces of the supporting plates 24 and 25 coming into contact with the brush 20. As the degree of the projecting/recessing parts, the maximum surface roughness of approximately 2-40mum, is desired, with respect to the brush hairs 21 normally used. On the other hand, even if the projecting and recessing parts are formed like dispersed spots, the projecting and recessing parts can be along the direction of brush hairs, as well. Thus, on the end part of the electrifying brush, each brush hair top end is set, and further, each brush hair is prevented from being deviated/grouped by the vibration, etc., of a device, so that the surface of an electrostatic latent image carrier is electrified in an uniform state without having unevenness, by that.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush charging device for charging the surface of an electrostatic latent image carrier in an image forming apparatus such as a copying machine or a printer.

0002

2. Description of the Related Art In image forming apparatuses such as copying machines and printers, an electrostatic latent image bearing member such as a photoreceptor drum is charged by a charging device, and the charged area is exposed to image light to form an electrostatic latent image.
Developing the latent image into a visible image and transferring it to a transfer material,
Make it stick. Various types of charging devices are known, but they can be roughly divided into corona charging devices that use corona discharge, and devices that use a charging brush, charging roller, or rotationally driven endless charging belt to generate an electrostatic latent image. It is divided into contact type charging devices that are brought into contact with the surface of the carrier.

Charging devices using corona discharge have the advantage of being able to perform stable charging, but they also generate a large amount of ozone, which causes deterioration of the electrostatic latent image carrier and has an adverse effect on the human body. For this reason, contact charging devices are attracting attention because they generate significantly less ozone than corona charging devices. Among these, brush charging devices, particularly brush charging devices having a fixed charging brush that contacts and charges the surface of a moving electrostatic latent image carrier, are attracting attention because of their relatively simple structure.

Generally, the structure is as shown in FIG. 11, in which a base fabric A on which a large number of charged brush bristles F are implanted is fixed to a back plate P made of aluminum or the like with an adhesive or the like. Brush B contacts moving surface S of electrostatic latent image carrier PC.

[0005]

However, the brush charging device has the following problems. That is, in the charging brush B, ideally, the ends B1 and B2 should be aligned as shown in FIG. 11, but in reality, as shown in FIG. At the upstream end B1 of the brush, some parts (a) come loose so as to protrude upstream in the X direction in the figure, some parts (b) come loose further downstream, and at the side end B2, some parts (a) come loose from the inside of the brush. It is scattered to the outside in the Y direction in the figure.

[0006] Such disintegration of charged brushes is particularly likely to occur due to grouping of brush bristles due to long-term use. One possible cause of grouping is that toner components, paper dust, oily components from the fixing device, etc. adhere to the bristles of the brush, and the bristles adhere to each other. usually,
Since the brush bristles are flocked in pile units, each of which is a bundle of a plurality of bristles, it is thought that it is easy to group the brush bristles into bundles of the pile unit. It is also conceivable that the brush bristles may be deformed due to heat, pressure, vibration, etc. applied to the bristles over a long period of time, resulting in grouping.

[0007] When the charging brush B comes apart in this way, discharge starts preferentially at the protruding portion (a) according to Passien's law, and as a result, the position corresponding to the concave portion (b) around the protruding portion (a) also starts discharging. Because it is charged to some extent, the discharge threshold voltage cannot be reached at the recessed portion (b), and no discharge occurs.As a result, uneven charging occurs in the width direction Y of the electrostatic latent image carrier, and this charging Due to the pattern, noise in the form of shading streaks occurs in the final image.

Note that Japanese Patent Laid-Open No. 105566/1984 teaches a support plate that supports the downstream end of the charging brush in the direction of movement of the surface of the electrostatic latent image carrier as a means for preventing the charging brush from falling down. The surface of this support plate that comes into contact with the brush is not subjected to any kind of surface treatment, and even this cannot prevent the brush that is in contact with the surface from coming apart in the Y direction in FIG. 12.

Accordingly, the present invention provides a brush charging device including a fixed charging brush that contacts and charges the surface of a moving electrostatic latent image carrier, which It is an object of the present invention to provide a brush charging device which can prevent the occurrence of image noise in the form of brush lines as much as possible.

0010

[Means for Solving the Problems] According to the above-mentioned object, the present invention provides a brush charging device including a fixed charging brush that contacts and charges the surface of a moving electrostatic latent image carrier. Provided is a brush charging device, characterized in that a support member supporting an end of the charging brush is provided, and an inner surface of the support member that comes into contact with the brush is provided with unevenness for preventing the end of the charging brush from coming loose. It is something to do.

[0011] The brush end where the support member is provided is
It is at least one of the upstream side, downstream side, and both ends of the charging brush. The degree of unevenness on the inner surface of the support member may be as long as it can prevent the brush bristles from coming loose.
Maximum surface roughness Rma based on the 0601-1970 standard
It is preferable that x is about 2 to 40 μm. Moreover, the unevenness may be formed in the form of scattered dots or may consist of a large number of uneven lines along the original direction of the brush bristles, and the state thereof is not particularly limited.

0012

[Function] According to the brush charging device of the present invention, the tips of the brush bristles are aligned at the end of the charging brush provided with the support member, and the inner surface of the support member is uneven, so that each brush This prevents the hairs from being deviated and grouped together due to device vibration, etc., and the surface of the electrostatic latent image carrier is uniformly charged.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. All of the embodiments described below are used by being incorporated into a printer whose schematic configuration is shown in FIG. First, the printer shown in FIG. 1 will be explained. The printer shown in FIG. 1 includes a photosensitive drum 1, which is an electrostatic latent image carrier, in the center thereof, and this drum is rotationally driven in the direction of arrow CW by a driving means (not shown). A brush charging device 2, a developing device 3, a transfer charger 4, a cleaning device 5, and an eraser 6 are arranged in this order around the drum 1. The charging device 2 is a charging device according to the present invention.

An optical system 7 is arranged above the photosensitive drum 1, and this optical system includes a semiconductor laser generator, a polygon mirror, a toroidal lens, a half mirror, a spherical mirror, a folding mirror, and a reflecting mirror in a housing 71. An exposure slit is formed on the floor of the housing 71, from which the charging device 2 and the developing device 3 are arranged.
The photoreceptor drum 1 can be exposed to an image through the gap.

On the right side of the photosensitive drum 1 in the figure, there are a pair of timing rollers 81, a pair of intermediate rollers 82, and a paper feed cassette 83.
are arranged in sequence, and a paper feed roller 84 faces the paper feed cassette 83. Furthermore, a pair of fixing rollers 91 and a pair of paper discharge rollers 92 are sequentially arranged on the left side of the photosensitive drum 1 in the drawing, and a paper discharge tray 93 faces the pair of paper discharge rollers 92 .

According to this printer, the surface of the photosensitive drum 1 is charged to a predetermined potential by the charging device 2, and the charged area is exposed to image light from the optical system 7 to form an electrostatic latent image. The electrostatic latent image thus formed is developed into a toner image by the developing device 3, and transferred to a transfer area facing the transfer charger 4. On the other hand, from the paper feed cassette 83 to the paper feed roller 84
Transfer paper (in this example, width 210 mm and length 298 mm)
is sent in the longitudinal direction. ) is pulled out, passes through an intermediate roller pair 82 and reaches a timing roller pair 81, where it is sent to the transfer area in synchronization with the toner image on the drum 1. Thus, in the transfer area, the toner image on the drum 1 is transferred onto the transfer paper by the action of the transfer charger 4, and the transfer paper reaches the fixing roller pair 91, where the toner image is fixed, and then the paper is ejected by the paper ejection roller pair 92. The paper is discharged to the paper tray 93.

After the toner image is transferred to the transfer paper, the toner remaining on the photosensitive drum 1 is cleaned by a cleaning device 5, and the residual charge is erased by an eraser 6. The system speed of the printer (peripheral speed of the photosensitive drum 1) is 3.5 cm/sec, and the developing device 3 is a contact type developing device using a one-component developer, and performs reversal development.

In this example, the photosensitive drum 1 was manufactured as follows, and is a functionally separated organic photosensitive member for negative charging that is sensitive to long wavelength light. First, 1 part by weight of τ-type metal-free phthalocyanine, polyvinyl butyral resin (
degree of acetylation 3 mol% or less, degree of butylation 70 mol%, degree of polymerization 1000) 2 parts by weight, and 10 parts by weight of tetrahydrofuran
0 parts by weight was placed in a ball mill pot and dispersed for 24 hours.
A photosensitive coating liquid was obtained. This has an outer diameter of 30 mm and a length of 240 mm.
The charge generation layer was coated on the entire surface of a cylindrical aluminum substrate using a dipping method and then dried to form a charge generation layer having a thickness of 0.4 μm.

Next, the structural formula is written on this charge generation layer.

00
20]

[Chemical formula 1]

8 parts by weight of the hydrazone compound shown below, orange dye (Sumiplast Orange 12
; manufactured by Sumitomo Chemical Co., Ltd.) and 10 parts by weight of polycarbonate resin (Panlite L-1250; manufactured by Teijin Kasei Ltd.) dissolved in a solvent consisting of 180 parts by weight of tetrahydrofuran. A charge transport layer having a thickness of 18 μm was formed by coating and drying the photoreceptor drum 1.

Here, the τ-type metal-free phthalocyanine is Cu
When using Kα1/Ni X-rays with a wavelength of 1.541 Å, the Bragg angle (2θ ± 0.2 degrees) was 7.6, 9.2,
It has an X-ray diffraction pattern showing strong peaks at 16.8, 17.4, 20.4 and 20.9. In particular, the infrared absorption spectrum is between 700 and 760 cm-1.
1 ± 2 cm-1 is the strongest four absorption bands, 1320 ~
It has two absorption bands of approximately equal intensity between 1340 cm-1 and a characteristic absorption at 3288±3 cm-1.

[0023] The electrostatic latent image carrier to which the charging device of the present invention can be applied is not limited to those described above. In an imaging system using a long wavelength light source such as a laser optical system or an LED array, a photoreceptor with long wavelength sensitivity as described above may be used, or a liquid crystal shutter array, PLZT shutter array, etc. may be used to convert visible light into a light source. imaging system,
Alternatively, in a visible light imaging system using a lens and mirror optical system used in normal analog PPC, a photoreceptor having sensitivity in the spectral range may be used.

The structure is not limited in any way, and the photoreceptor may be of the above-mentioned functionally separated type or may have a single layer structure. Furthermore, all known materials such as charge generating materials and charge transporting materials can be used. That is, hydrazone,
Organic materials such as styryl compounds as charge transport materials can also be used.

A surface protective layer may be provided on the outermost surface of the photoreceptor, and examples of such materials include resins such as ultraviolet curable resins, room temperature curable resins, and thermosetting resins; Resin with resistance adjustment material dispersed inside, materials made of metal oxides, metal sulfides, etc. thinned by vapor deposition or ion plating in vacuum, and plasma polymerization of hydrocarbon gases. An amorphous carbon film etc. can be used.

The substrate material is not particularly limited as long as it has conductivity, and the shape may vary depending on the image forming system.
It may be in the shape of a drum, a flat plate, or a belt. Further, when the light source used is coherent light, the surface of the substrate may be roughened or blackened to prevent the generation of so-called interference patterns.

In this example, the toner used in the developing device 3 is of a negatively charged type, and includes 100 parts by weight of bisphenol A type polyester resin, 5 parts by weight of carbon black MA#8 (manufactured by Mitsubishi Chemical Corporation), Bontron S-3
4 (manufactured by Orient Chemical Industries, Ltd.) 3 parts by weight, and 2.5 parts by weight of Viscol TS-200 (manufactured by Sanyo Chemical Industries, Ltd.)
A composition consisting of parts by weight is kneaded by a known method,
The average particle size after crushing and classification is 10 μm, and the particle size is 7 to 13 μm.
Toner particles having a distribution of 80% by weight in the range of 0.75% by weight of hydrophobic silica (Tanolux 500, manufactured by Talco) as a fluidizing agent are added to the toner particles,
The mixture was mixed and stirred using a homogenizer.

[0028] Such toner was stored in the developing device 3 and developed. Next, the brush charging device 2 in the printer will be explained. For example, as shown in FIG. 2, the charging device 2 according to the present invention has a charging brush 2.
0 can be constructed from a belt-shaped pile cloth. The pile cloth can be obtained, for example, by weaving brush bristles 21 made of conductive fibers of 3 to 10 deniers onto a base cloth 22, and further coating the back surface of the base cloth with a conductive adhesive.

Furthermore, the brush bristles can be bundled, for example, from 50 to 100, and woven into the warp threads 22a of the base fabric 22 in a V-shape as shown in FIG. 3, or in a W-shape as shown in FIG. The brush 20 is fixed to the back plate by the adhesive. The material of the brush bristles is not particularly limited as long as it has appropriate conductivity.

Examples of such conductive materials include metal wires such as tungsten, stainless steel, gold, platinum, iron, copper, and aluminum. In addition, as conductive resin materials, fibers such as rayon, nylon, acetate, copper ammonia, vinylidene, vinylon, fluoroethylene, Promix, benzoate, polyurethane, polyester, polyethylene, polyvinyl chloride, polyclar, polynosic, polypropylene, etc. ,Carbon black,
It is possible to use carbon fibers, metal powders, metal whiskers, metal oxides, semiconductor materials, etc. in which a resistance adjuster is dispersed. In this case, a desired resistance value can be obtained depending on the amount of dispersion. Furthermore, the resistance adjuster may be coated on the surface of the fiber instead of being dispersed inside the fiber.

Next, specific examples of the charging device 2 according to the present invention will be sequentially explained together with comparative examples.
A method of evaluating image noise in the form of brush lines based on uneven charging on the surface of a photoreceptor drum will be described below. Image noise is evaluated as follows. Using the printer, after charging by the charging device 2, a repeating pattern of 2 dots on (lit) and 2 dots off (lights out) is written in the main scanning direction using the laser from the optical system 7, and the same is written in the sub-scanning direction. 2 dots on (lit), 2 dots off (unlit)
Adjust the laser lighting timing to obtain the writing pattern. Thereafter, a print image as shown in FIG. 5 is obtained through reversal development, transfer, and fixing processes.

Let WM be the maximum width in the main scanning direction of a minute black solid pattern consisting of 2 dots x 2 dots on this print image. The standard deviation of WM of 30 small solid black patterns continuous in the main scanning direction is defined as σ, and the following ranking of brush-streaked image noise is performed based on σ. standard deviation σ
Evaluation symbol
0μm≦σ<10μm
A 10
μm≦σ B
If the standard deviation σ is large, it means that the width of the fine black solid in the main scanning direction varies in the main scanning direction. Here, the A-rank indicates a good condition in which brush-like noise is not recognized on the image.

Next, Examples and Comparative Examples will be sequentially explained. Example 1 A brush bristle material containing 12 wt% of conductive carbon powder based on the total weight has an electrical resistivity of approximately 1 x 105 Ω.
Made of 6-denier rayon fiber. As shown in FIGS. 6 and 7, the fibers 21 are woven into a base fabric 22 with a thickness of 0.5 mm using a W weave as shown in FIG. W=9mm
, height h1=7mm, fiber density in the center 15000/
A charging brush 20 of cm2 is formed, a conductive adhesive is coated on the back side of the base fabric 22, and the base fabric 22 is coated with the adhesive.
An aluminum back plate 23 with a thickness t=1 mm
Fixed.

Further, an upstream support plate 24 and a downstream support plate 25 are provided at right angles to the upstream end 231 and downstream end 232 of the back plate 23, respectively, in the surface movement direction of the photosensitive drum 1. It was erected. Each of these support plates is also made of aluminum, has a thickness of 1 mm, and has the same length in the axial direction of the photoreceptor drum as the length of the back plate 23.

The upstream and downstream support plates 24 and 25 have the same height, and the protruding amount h2 of the brush bristles 21 from their free ends is 1 mm. In the examples and comparative examples described below, the thickness of the support plate is 1 mm, and the protrusion amount h2 of the brush bristles from the free end of the support plate is similarly 1 mm. Further, the inner surfaces of each of the support plates 24 and 25 were provided with irregularities by sandblasting. FIG. 8 is a partially enlarged view showing the unevenness of the sandblasted inner surface. The maximum surface roughness Rmax of the inner surface is 2.0 μm. In addition,
This surface roughness was measured using a surface roughness meter (Surfcom 550A) manufactured by Tokyo Seimitsu Co., Ltd. according to "JIS-B-0601-1970".
The maximum height (Rmax) was obtained by measuring. The measurement of surface roughness in the following explanation is also similar to this.

The support plate is not limited to aluminum as in this example, but may be made of metal such as iron, nickel, or phosphor bronze. In addition, in this case, in order to provide unevenness on the inner surface of the support plate, in addition to the sandblasting treatment in this example, a bite treatment,
Processes such as etching and embossing can be used. Example 2 As shown in FIG. 9, the downstream support plate 25 in Example 1
, and the maximum surface roughness of the inner surface of the upstream support plate 24 was reduced to 40
It is expressed in μm.

Example 3 The maximum surface roughness of each inner surface of the support plates 24 and 25 in Example 1 was set to 10 μm. Example 4 The maximum surface roughness of each inner surface of the support plates 24 and 25 of Example 1 was set to 40 μm.

Example 5 As shown in FIG. 10, in place of the upstream and downstream support plates 24 and 25 of Example 1, polyethylene films 26 and 27 with a thickness of 0.3 mm and embossed inner surfaces were provided. It is something that The maximum surface roughness of the inner surface of each support plate is 2.0μm
It is. In this way, the support plate may be made of resin, or may be made of polyester, polycarbonate, etc. in addition to polyethylene. Further, in this case, in order to provide unevenness on the inner surface, various surface treatments such as those described in Example 1 can be employed, but by embossing as in this example, it is easy to form uniform unevenness on the resin surface.

Example 6 The roughness of the inner surface of each support plate was set to 20 μm in Example 5. Example 7 In Example 5, the roughness of the inner surface of each support plate was set to 40 μm. Comparative Example 1 Upstream and downstream support plates 24 and 25 in Example 1
The inner surface is a substantially smooth surface with a maximum surface roughness of 0.02 μm.

Comparative Example 2 In Example 2, the inner surface of the upstream support plate 24 was made substantially smooth with a maximum surface roughness of 0.02 μm. Comparative Example 3 Upstream and downstream support plates 26 and 27 in Example 5
Each inner surface is a substantially smooth surface with a maximum surface roughness of 0.01 μm.

[0041] Examples 1 to 7 and Comparative Examples 1 to 7 explained above
3 is assembled into the printer shown in FIG.
It was charged to about 0V. Then, print out under a developing bias of -300V.
Image noise (brush line noise) for each image after 0 images
was evaluated using the method described above, and the results shown in Table 1 were obtained.

[0042]

[Table 1]

As can be seen from Table 1, in Examples 1 to 7, the brush-streaked image noise is improved compared to Comparative Examples 1 to 3, not only at the initial stage of printing but even after 5,000 sheets have been printed. . This is because in Examples 1 to 7, the upstream support plate is provided, and its inner surface is provided with unevenness, so that the upstream end of the charging brush 20 in the direction of movement of the surface of the photoreceptor drum is supported and aligned. This is thought to be due to the fact that the drum surface is prevented from dispersing both in the direction of movement of the drum surface and in the direction across it.

[0044] It is also conceivable to provide side end support members for supporting and aligning both end portions of the charging brush in a direction transverse to the direction of movement of the surface of the electrostatic latent image carrier, to prevent them from coming apart; however, in that case, The inner surface of the support member may also be provided with irregularities similar to those described above to prevent the brushes from coming apart or grouping.

[0045]

As explained above, according to the present invention, there is provided a brush charging device equipped with a fixed type charging brush that contacts and charges the surface of a moving electrostatic latent image carrier. Accordingly, it is possible to provide a device that can prevent the end portion of the charging brush from coming loose, charge the surface of the electrostatic latent image carrier evenly and uniformly, and suppress the generation of image noise in the form of brush streaks.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an example of a printer that incorporates and uses a charging device according to the present invention.

FIG. 2 is a perspective view of a typical example of a charging brush in a charging device.

FIG. 3 is an explanatory diagram showing an example of a state in which brush bristles are planted on a base fabric.

FIG. 4 is an explanatory diagram showing another example of the state in which brush bristles are planted on the base fabric.

FIG. 5 is a diagram of an example of a printed image for performing image noise evaluation.

FIG. 6 is a perspective view of one embodiment.

FIG. 7 is a side view of the embodiment shown in FIG. 6;

8 is a partially enlarged view showing the unevenness of the inner surface of the support plate in the embodiment shown in FIG. 6; FIG.

FIG. 9 is a side view of another embodiment.

FIG. 10 is a side view of still another embodiment.

FIG. 11 is an explanatory diagram of a conventional example.

FIG. 12 is an explanatory diagram of brush disintegration in the conventional example of FIG. 11;

[Explanation of symbols]

1 Photoreceptor drum 2　Brush charging device 20 Charged brush 21 Brush hair 22 Base fabric 23 Back plate 24 Upstream support plate 25 Downstream support plate 26 Upstream support plate 27 Downstream support plate

Claims (1)

[Claims] 1. A brush charging device comprising a fixed charging brush that contacts and charges the surface of a moving electrostatic latent image carrier, comprising: a support member that supports an end of the charging brush; A brush charging device characterized in that an inner surface of the support member that contacts the brush is provided with unevenness for preventing an end portion of the charging brush from coming loose.