JPH04208960A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a high-quality image and to prevent the image from being deteriorated even when a device is used for a long time by making the layer thickness of the conductive layer of a developing roller larger than the particle diameter of toner. CONSTITUTION:In a contact type one component non-magnetic developing device, the developing roller 109 is constituted of a metallic shaft 109a, an elastic layer 109b formed on the shaft 109a and a conductive layer 109c. When the layer thickness of the conductive layer is smaller than the particle diameter of the toner used, a load applied to a toner layer forming blade must be made large in order to obtain the excellent image, and the load applied to the developing roller is large. Therefore, stress is caused in the conductive layer, the peeling of the conductive layer occurs because of the stress, and durability is not obtained. By setting the layer thickness of the conductive layer at a value larger than the particle diameter of the toner, the excellent image is obtained and such a state is maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Field of Application) The present invention relates to a developing device for visualizing an electrostatic latent image in an electrophotographic device or an electrostatic recording device, and in particular, to The present invention relates to a developing device capable of forming high-quality images.

(Prior Art) As one of the developing methods using a one-component developer, the pressure development method (IrIIpression Developme
nt) is known. This method is characterized by bringing the electrostatic latent image into contact with the developer particles or developer carrier at substantially zero relative peripheral velocity, and since no magnetic material is required, the device can be simplified and miniaturized. Not only is this possible, but it also has many advantages, such as the ease of coloring the developer.

In the above-mentioned pressure development method, since development is carried out by pressing or bringing the developer carrier into contact with the electrostatic latent image, it is necessary to use a developing roller having elasticity and conductivity. Particularly when the electrostatic latent image holder is a rigid body, it is essential that the developing roller be made of an elastic body to avoid damaging it. Furthermore, as is well known, in order to obtain a developing electrode effect or a bias effect in the developing roller, it is desirable to provide a conductive layer on or near the surface of the developing roller and apply a bias voltage as necessary. Furthermore, since the charge is applied to the developer by frictional charging between the developing roller and the developer layer forming blade, it is possible to ensure a constant nip width by bringing the developer layer forming blade into pressure contact with the developing roller. is necessary.

In order to impart a sufficient charge to the developer, it is desirable to use a material of the triboelectric series that matches the polarity of the charge.

However, when a conductive layer is provided on the surface of the developing roller, since the developing roller itself has elasticity, in order to impart a sufficient amount of charge to the toner, the blade must be sufficiently pressed against the developing roller to make contact between the blade and the conductive layer. The width must be made sufficiently wide, which increases the torque applied to the motor that rotates the developing roller. In addition, since the pressing force of the blade against the developing roller increases, damage such as scratches is likely to occur in the conductive layer, and even if the conductivity of the bias is maintained by making the elastic body conductive, there will be uneven density and marks of fogging. etc. appear on the image, making it impossible to obtain good images for a long period of time.

(Problems to be Solved by the Invention) The present invention has been made to solve the problems of the prior art as described above. It is an object of the present invention to provide a one-component type developing device that can obtain high-quality images without images and that does not cause deterioration of the images even after long-term use.

[Structure of the Invention] (Means for Solving the Problems) A developing device of the present invention includes a developing roller that is disposed opposite to an image carrier and has a conductive layer, and a thin developer layer made of toner is formed on the developing roller. and a developer thin layer forming means,
A developing device that visualizes a latent image by bringing a thin layer of developer formed on the developing roller close to or in contact with an image carrier, wherein the layer thickness of the conductive layer is determined and the particle diameter of the toner is determined by A developing device characterized by satisfying the relationship r<L.

(Function) According to the developing device of the present invention, it is possible to prevent the occurrence of streaks, scratches, and peeling of the conductive layer. Further, by making the thickness of the conductive layer larger than the developer particle diameter, the contact width between the toner and the conductive layer can be increased without increasing the pressing force of the blade unnecessarily. By using a developing roller like 2, it is possible to impart sufficient charge to the developer, and it is possible to obtain high-quality images without defective images such as uneven image density and fog in non-image areas. This makes it possible to obtain high-quality images over a long period of time.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of a contact type component non-magnetic developing device 103. The developing device in this embodiment performs development by forming a thin layer of non-magnetic developer on the surface of a developing roller 109 having conductivity and elasticity, and bringing this into contact with the surface of the photoreceptor 102. . This device does not require a carrier, Mg roller, developer concentration control, etc., and can be made smaller and lower in price. The developing process will be explained below.

As shown in FIG. 1, the non-magnetic developer 113 in the developer container 112 is sent to the developer supply roller 111 while being stirred by the mixer 114, and is supplied to the development roller 109 by the developer supply roller 111. . This developer 113
As the developing roller 109 rotates, a part of the toner is adhered and conveyed by the mechanical conveying force of the developing roller 109 and the electrostatic force caused by charging caused by friction between the developing roller surface and other members. Thereafter, the amount of developer conveyed is regulated by the blade 110 held by the blade holder A 117, the spacer 118, and the blade holder B 119 and brought into contact with the developing roller 109, and at the same time, the developer is triboelectrically charged due to friction therebetween. This apparatus uses a negatively charged organic photoreceptor drum 102 to perform reversal development. Therefore, a negatively charged developer is used as the developer, and the blade 110 is also made of a material that easily imparts a negative charge.

FIG. 2 is a perspective sectional view of the developing roller 109.

As shown in FIG. 2, the developing roller 109 includes a metal shaft 109a, an elastic layer 109b formed on the metal shaft 109a, and a conductive layer 109C provided on the elastic layer. The developing bias potential is -200 V with respect to the photoreceptor surface potential of -500 V, which is applied to the metal shaft (109a) of the developing roller 109 through a protective resistor.
As shown in FIG. 1, the developing roller 109 comes into contact with the photoreceptor 102 about 1 to 4 times in the direction of the arrow at a speed of about 1.2 to 4 times the photoreceptor drum 102. It has a width (developing nip) and rotates in contact. Since the developer particles are also charged at the development position, extremely sharp images with little fogging can be obtained.

The remaining developer is scraped off by a cover blade (Mylar film) 115 and returned to the inside of the developing device. Furthermore, if the developer falls from the developing roller 109 for some reason, it will stain the inside of the machine or the transfer paper, so a member 116 such as a plasticizer that reacts with the developer and fuses the developer is attached at the bottom. This overcomes the above problems and has the advantage that even if the developing device 103 is placed upside down, the developer will not fall. In FIG. 1, 121 is a buckle plate attached to the blade holder A, which seals the developer and prevents vibrations of the blade 110 by coming into contact with a foam material 123 made of maltbrene or the like attached to the back side of the blade 110. This allows a good developer layer to be formed on the developing roller 109.

Further, the blade 110 is connected to the rotating shaft 1 of the blade holder 117.
17a and a plurality of compression springs 120 for applying pressure to the developing roller 109.

Since the spring constant of the compression spring 120 is lower than the spring constant of the thin plate spring material of the blade 110, the pressing force hardly changes even if the contact portion of the blade 110 wears, making it possible to maintain a good developer layer. There is.

Next, the toner thin layer forming blade and the developing roller, which are the main components of the developing device 103 according to the present invention, will be explained.

FIG. 3(a) is a perspective view showing one embodiment of the developer thin layer forming blade used in the present invention, and FIG. 3(b) is a perspective view showing an example of the developing roller and developer thin film forming blade used in the present invention. FIG. 3 is a schematic diagram showing a state of contact. As shown in FIG. 3(b), the developer thin layer forming blade 110 has a thin plate spring 110a made of, for example, stainless steel, beryllium copper, or phosphor bronze plate, and is formed at the tip of the thin plate spring 110a made of, for example, silicone rubber or urethane rubber. The chip 110b is made of a rubber elastic body or resin having a JIS-A hardness of 30 to 85 degrees.

As shown in FIG. 3(a), this chip 110b is bonded to one end along the elongated direction on one surface of the above-mentioned thin plate spring 110a having bidirectional surfaces. A sealing material 110c made of urethane foam is attached to the flat spring 110a from one surface to the other so as to seal both ends of the chip 110b. Note that the chip 110b can be attached using methods such as adhesion, fitting, or clamping, and any method may be used as long as it can be attached accurately. Preferably, a stainless steel plate with a thickness of 0.15 mm can be used as the thin plate spring 110a. The thickness of the thin plate spring 110a is 0.1 to 2 depending on the shape.
It is possible to use something of about 1. chip 110
b is formed using silicone rubber with a JIS-A standard of 80°, and the contact portion with the developing roller (that is, the chip 110
At least two parts whose centers are on the same straight line (tips of b)
It is composed of three or more curved surfaces. FIG. 2b is an enlarged view of the tip of the tip 110b in this embodiment, and as can be seen from this figure, the radius 11I111R1 and the radius 2o
It is composed of IiIII and R2. The radius R1 and the radius R2 are calculated using the following formula R2(01111)≧R1(+nm)x
By satisfying 5, the influence of tip wear can be ignored. Note that the chip 1 is used as the sealing material 110c.
Chip 110b can be made thicker by using a chip thicker than 10b
When the developer is pressed against the developing roller, movement of the developer toward both ends can be reliably sealed. Since the sealing material 110C is disposed so as to wrap the tip of the developer thin layer forming blade 110 in this way, it is possible to prevent peeling off due to the conveyance of the developer and to realize a stable seal with a long life.

Further, since the developer thin layer forming blade 110 of the present invention has the chip 110b mounted on the thin plate spring 110a, it is possible to easily and reliably form an even developer layer by the elasticity of the thin plate spring 110b. is possible. However, the accuracy in the tangential direction between the developing roller and the chip 110b is important because it causes pressure unevenness, which affects the developer layer and the image.

FIG. 4 is a diagram showing the arrangement of chips in the developer forming blade used in the present invention. In the developer thin layer forming blade 110 of the present invention, as shown in FIG. 4, the chip 110bl is mounted from a position spaced apart by dl from the tip of the thin plate spring 110a. This spacing is used as a hold down and for positioning when mounting by molding or gluing. By sufficiently performing this holding and positioning, it is possible to improve the mounting structure of the thin plate spring in the lateral direction and the accuracy in the tangential direction with respect to the aforementioned developing roller. Note that if dl is too large, the pressure caused by the flow of the developer will cause poor layer formation, so it is preferably 0.5 m+s to 5 mm%.
About m to 2 mm is good. In this embodiment, dl is set to 0.5 dragon. Further, the length Lp in the longitudinal direction of the tip 110b is shorter than the length Lc in the longitudinal direction of the thin plate spring 110a by d2+d3. That is, Lc-Lp 10d20d3, and the sealing member 110C made of the above-mentioned urethane foam is attached to the dl and 63 parts. dl
and d3 are preferably 3 dragons or more each considering the seal width, so d2+d3 is 6 to 30Il11
1, preferably about 6 to 20 m+w. Further, the length Lp of the chip 110b at this time is set to be larger than the effective development width, and the length Lc of the thin plate spring 110c is set to be long enough to cover the side seal of the developing roller.

In the developing device of the present invention, the developing roller 109 is required to have conductivity and elasticity. The simplest configuration that satisfies this is a combination of a metal shaft and a conductive rubber roller, but in order to obtain a sufficient contact width with the photoreceptor drum, the rubber hardness is preferably 50° or less according to the JIS standard, and the developer The surface needs to be smooth because it is conveyed while being pressed against the surface of the developing roller. Therefore, as shown in FIG. 2, in the developing roller used in the present invention, an elastic layer 10 is provided around the metal shaft 109a.
9b and a surface conductive layer 109c.

When selecting the elastic layer 109b of such a developing roller, there are two options: one that is conductive and one that is not. However, considering the possibility that the conductive layer 109c may be peeled off or scratched, the elastic layer 109b should also be selected. It is preferable that it is conductive. Further, the elastic layer 109b
10 and the photoreceptor 102, permanent distortion (%) shown in JIS standard 6301 due to packaging or being left for a long time becomes a problem, and if it exceeds 10%, uneven development roller cycles may occur on the image Therefore, the compressive strain (%) of the elastic layer 109b is 10% or less, preferably 5%.
% or less is better. There is generally a relationship between the rubber hardness and permanent set (%) such that the larger the rubber hardness, the smaller the permanent set, so the balance between the materials and each other is important. As described above, conductive urethane rubber was selected in this embodiment as a material having the characteristics required for the elastic layer 109b, but it is also possible to use other conductive EPDM rubber, conductive silicone rubber, etc.

The elastic layer 109 b made of conductive silicone rubber used in the present invention had a hardness of 30° with a type A hardness needle according to JIS standard 630117, and an outer diameter of 18 mm.

In addition, the electrical resistance value of conductive silicone rubber is determined by the contact width of the above elastic roller with a stainless steel roller with a diameter of 60 mm.
Calculated by measuring the current observed when the metal shafts of both rollers are placed in parallel and a potential difference of 100V is created between the metal shafts. The result is 3-4x103Ω.
・It was (1). Moreover, the permanent set was 2.5% as a result of measurement using the measuring method shown in Jl5K6301.

Further, since the conductive layer 109C of the developing roller directly contacts the developer and the photoreceptor, a material is selected that will not contaminate the developer or the photoreceptor by seeping out plasticizer, vulcanizing agent, process oil, etc. The surface smoothness of the conductive layer 109c is 3.
If it is less than μm Rz or preferably more than that, a pattern of surface irregularities tends to appear in the image. Smoothness 3μta R
In order to realize z, a method can be considered in which a sufficiently thick conductive layer 109c is attached to the elastic layer 109b and then finished to a predetermined outer diameter and surface roughness through post-processing (polishing), but this method is costly. Therefore, it is better to form the conductive layer 109C without post-processing. The surface roughness of the elastic layer 109b, the thickness of the conductive layer 109C, and the conductive layer 109C
The viscosity of the paint used for the formulation must be optimally selected. FIG. 5a to FIG. 5C are elastic layer 109b.
FIG. 6 is a diagram illustrating a typical method for forming a conductive layer 109c thereon. Fig. 5a shows the method of application by spraying,
FIG. 5 shows a dipping method, and FIG. 5C shows a knife method. The viscosity of the paint in each method is as follows: spray method, dipping method ≦ Knifetsu method, and when the paint film thickness is T (μm) and the surface roughness of the elastic layer 109b is S (μm Rz), in the spray method, If T≧l0XS and T≧5XS are satisfied in the dipping method and the knife method, it is possible to make the surface smoothness of the conductive layer 3 μtn Rz.

The conductive layer 109c is formed by dispersing conductive carbon fine particles in polyurethane resin to form a conductive layer 109c of 10 Ω (maximum).
A conductive polyurethane paint is applied to the surface of the elastic layer 109b made of conductive silicone rubber, and after drying, heat treatment is performed to form the conductive layer 109c.
was formed. This conductive polyurethane paint is a solution type based on thermoplastic polyurethane.

First, a diluting solvent is added to a stock solution of conductive polyurethane paint to prepare a paint having an appropriate viscosity. Next, after thoroughly stirring this diluted paint, it was applied onto the surface of the elastic layer 106b, which had been washed with a solvent, using a dipping method. The pulling speed of the elastic layer 109b is 3.5
mm/sec.

After application, dry in the air for about 30 minutes, then heat at 100°C.
Heat treatment was performed for 20 minutes. As a result, the layer thickness is 30-35
A conductive layer 109c having a thickness of μm was obtained.

The layer thickness of the conductive layer 109c can be varied from 5 μm to 5 μm by changing the pulling speed of the dipping method and the viscosity of the paint.
It is adjustable up to a range of 300 μm.

Through the above steps, the metal shirt 109a and the conductive layer 109 are formed.
The resistance value between c is 5 x 10” Ω・mark, the rubber hardness is 35° with A type hardness needle of JIS standard 6301, and the surface roughness is 3 μm.
A developing roller 109 of Rz was obtained.

The non-magnetic toner 113 used here is obtained by mixing, dispersing, and crushing and classifying carbon, a charge control agent, and wax in an epoxy resin. The volume average particle size of this toner is 11.5 μm, which is a 50% volume particle size measured using a TA-n type Coulter counter manufactured by Coulter Electronics.

Next, a so-called laser printer is used, which forms a latent image by irradiating an organic photoreceptor with a negatively charged surface with a laser beam, and converts this into a visible image using a reversal development method.
An example in which the contact-type component nonmagnetic developing device 103 is applied will be described.

The potential of the image area, that is, the potential of the exposed area is -80V1. The potential of the non-image area, that is, the potential of the unexposed area is -500V.

When reversal development was performed with the developing bias set to -200 V, the contact width between the photosensitive drum 102 and the developing roller 109 set to 1.5 mm, and the circumferential speed ratio between the photosensitive drum 102 and the developing roller 1:2.5, the image A printed sample was obtained with a density of 1.4 and an extremely sharp line image and a solid image with no unevenness with no fogging at all. Furthermore, as a result of a life test of 10,000 sheets with this image forming apparatus, it was possible to obtain an extremely good image equivalent to the initial image even after the life test was completed.

FIG. 6 is a graph showing the relationship between the image density and the amount of charge of the developer from the initial stage up to 10,000 copies.

The image density was measured for a solid image, and the charge amount of the developer was measured by using a charge amount measuring device 200 shown in FIG. 7(b) for 10 rotations of the roller. As shown in FIG. 7(a), this charge amount measuring device 200 includes a Faraday gauge 2 which is a conductive container having a suction pump 201 and an opening 203 provided opposite to a developing roller 109.
02, the developer on the developing roller 109 is suctioned and repaired by the Faraday cage 202, and the average charge amount per unit weight of the developer is measured from the charge generated by electrostatic induction.

As is clear from this graph, by using the above-mentioned developing device, it is possible to obtain an image forming apparatus in which the image density and charge amount hardly change even after 10,000 sheets have been printed, and the image condition is good.

Next, for comparison, the layer thickness of the conductive layer was changed from 5.0 μm to 20 μm.
An attempt was made to form an image under the same conditions as above, varying it down to 0μ. Incidentally, the particle diameter r of the toner is 11.5 μm.

(Other conditions being the same) The results are shown in Table 1.

In the early stage of Table 1, a printed sample having an image density of 1.4, an extremely sharp line image with no fogging, and a uniform solid image with no unevenness was obtained as in the case of the above-mentioned developing device.

However, when a developing roller with a conductive layer thickness of 10 μm or less was used, cracks appeared on the surface of the developing roller after 2,000 sheets were printed, and these scratches began to appear on the images. Also, after 3,000 sheets have been printed, peeling occurs due to these cracks, and in the areas where the conductive layer has peeled off, the toner sticks to the elastic layer, making it impossible to develop in those areas, and 10,000 sheets are finished. At the time, the image quality was very poor. However, when the thickness was 15 μm or more, such problems did not occur, and there was no significant change in the image condition even after 10,000 copies were printed.

As is clear from this experimental result, when the thickness of the conductive layer is smaller than the particle size of the toner used, the relationship between the thickness of the conductive layer and the particle size r of the toner is expressed as r<L. If not satisfied, in order to obtain a good image, the load applied to the toner layer forming blade must be increased compared to the developing device of the present invention, and the large load applied to the developing roller causes stress to the conductive layer. Therefore, problems such as peeling of the conductive layer occurred. As described above, it was confirmed that the developing device not according to the present invention did not have durability for 10,000 sheets.

From the above experimental results, good images can be obtained by setting the thickness of the conductive layer to a value larger than the particle size of the toner.
It was also confirmed that this state could be maintained for a long period of time.

As described above, in one embodiment of the present invention, the developing roller 1
The toner thin layer forming blade 110 for 09 is Agai
nst position, but in the present invention, the present invention is not limited thereto, and may be a W i t position.

Furthermore, although the shape of the tip of the tip 110b of the toner thin layer forming blade 110 in this embodiment has a curved surface with an elliptical cross section, if the contact portion with the developing roller 109 is not flat, it will have a parabolic shape. There is no problem as long as it has a surface or a semicircular shape, and the chip 110b may be configured to come into contact with a plurality of developing rollers.

[Effects of the Invention] As explained above, according to the present invention, the developer is sufficiently charged, and stable high-quality images can be obtained without image defects such as uneven image density or fogging and without deterioration even after long-term use. It is possible to provide a developing device that can obtain an image.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a developing device showing an embodiment of the present invention;
FIG. 2 is a partially cutaway sectional view showing an example of a developing roller used in the present invention, FIG. 3(a) is a perspective view showing an example of a developer thin layer forming blade used in the present invention, and FIG. figure(
b) is a schematic diagram showing the state of contact between the developing roller and the developer thin film forming blade used in the present invention, and FIG. A plan view showing the arrangement of FIG. 5(a)
FIGS. 5(c) to 5(c) are schematic diagrams showing various methods of forming a conductive layer on the elastic layer of the developing roller, and FIG. 6 is a graph showing the relationship between image density and developer charge amount with respect to the number of sheets on which images are formed. 7(a) is a schematic diagram showing a method for measuring the amount of charge of the developer on the developing roller, and FIG. 7(b) is a schematic diagram showing the method for measuring the amount of charge of the developer on the developing roller. FIG. 2 is a perspective view of the device. 109...Developing roller, 109a...Metal shaft, 109b...Elastic body layer, 109c...Conductive layer, 1
10...Blade, 110a...Thin plate spring material, 11
0b...Chip, 110c...Sealing material, 110d...
... Elastic body layer, 110e... Charged layer. Applicant's Representative Patent Attorney Takehiko Suzuej11Figure 3Figure 4Figure 5Figure 6

Claims (1)

[Claims] A developing roller disposed opposite to the image carrier and having a conductive layer; and a developer thin layer forming means for forming a developer thin layer of toner on the developing roller, the developing roller formed on the developing roller. A developing device that visualizes a latent image by bringing a thin agent layer close to or in contact with an image carrier, where the thickness of the conductive layer is L and the particle size of the toner is r,
A developing device characterized by satisfying the relationship r<L.