JPH0486852A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the unevenness of density caused by the unevenness of pressure and fault in forming a layer by providing an abutting member which abuts on a developing roller and which is constituted of a projecting surface whose abutting part has non-circular cross section and an elastic member for pressing the abutting member to the developing roller in a developer layer forming means. CONSTITUTION:In a developing device 11, the thin layer of non-magnetic toner is formed on the surface of the developing roller 12 and allowed to contact with the surface of a photosensitive drum 13 so as to perform development. The non-magnetic toner 15 is supplied to the developing roller 12 by a toner supply roller 17, and a toner carrying quantity is regulated by a blade 18. At the same time, the toner 15 is triboelectrified. The blade 18 consists of a flat spring 25, and the abutting member 26 is fixed along a longitudinal direction at one end, and elastic sealing materials 27a and 27b are fixed on both sides. In the abutting member 26, the projecting surface which projects from the spring 25 and whose cross-sectional shape is non circular is formed. The sealing materials 27a and 27b are provided so that they may nearly as high as the abutting member 26 or a little higher than the member 26 and the hardness thereof may set to be low and the movement of the toner toward both ends is surely sealed.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device that visualizes an electrostatic latent image in an electrophotographic device or an electrostatic recording device, and particularly relates to a developing device that visualizes an electrostatic latent image in an electrophotographic device or an electrostatic recording device. The present invention relates to a developing device that can be used to obtain high-quality images.

(Prior art) As one of the conventional developing methods using a one-component developer,
Pressure development method
ent) is known. This method is characterized in that an electrostatic latent image and a toner carrier having a thin layer of toner particles are brought into contact at substantially zero relative velocity. This method is disclosed, for example, in US Pat. No. 3,152,012, US Pat. This method is
It has many advantages such as the device can be simplified and miniaturized, and since no magnetic material is required, the toner can be easily colored.

In this pressure development method, development is performed by pressing or bringing the toner carrier (developing roller) into contact with the electrostatic latent image, so it is necessary to use a developing roller having appropriate 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 in order to avoid damaging it. Further, in order to obtain the well-known developing electrode effect and bias effect, it is preferable to provide a conductive layer on or near the surface of the developing roller and apply a bias voltage as necessary.

(Problem to be Solved by the Invention) However, when a conductive layer is provided on the surface of an elastic roller, the conductive layer is pressed and rubbed by an electrostatic latent image holder or a blade for forming a thin toner layer, which causes scratches. Damage such as
Even if the bias conductivity is maintained by making the elastic body conductive, density unevenness, fogging, and scratch marks will appear on the image in a relatively short period of time.

In addition, in the above-mentioned pressurized thickness development method, the blade for forming a thin toner layer has conventionally had a convex curved surface with a circular cross section (hereinafter referred to as a single R shape) at the contact portion with the developing roller. What you have is disclosed. Such a blade has the advantage of being able to smoothly press the toner against the developing roller to form a toner layer due to the sliding friction between the developing roller and the blade. There is a problem in that it is easily affected by the accuracy of straightness, and uneven density (uneven layer thickness) and poor layer formation are likely to occur due to uneven pressure in the longitudinal direction. Uneven layer thickness directly leads to non-uniformity in the amount of charge, causing concentration fluctuations and soil burrs.

The present invention was made to solve these conventional problems, and it is possible to obtain high-quality images without defective images such as density unevenness and ground blur, and also to avoid deterioration of image quality even after long-term use. The purpose of the present invention is to provide a developing device that does not.

[Structure of the Invention] (Means for Solving the Problems) A developing device of the present invention includes a developing roller disposed opposite to an electrostatic latent image holder, and a developing device that forms a thin layer of developer on the surface of the developing roller. a developer thin layer forming means, the electrostatic latent image formed on the electrostatic latent image carrier by bringing the developer thin layer formed on the developing roller close to or in contact with the electrostatic latent image carrier. In the developing device for visualizing an image, the developer layer forming means includes a contact member whose contact portion that contacts the developing roller is constituted by a convex surface having a non-circular cross-sectional shape, and this contact member. and an elastic member that presses the developing roller against the developing roller.

(Function) The developing device of the present invention having the above configuration can elastically rub the toner conveyed on the developing roller with excellent followability even if parts with lower precision than conventional parts are used. Pressure (frictional force) regulates the amount of toner passing through and triboelectrically charges the toner. As a result, more uniform thin layer formation and reliable frictional electrification are achieved, resulting in high-quality images with no defective images such as density unevenness or ground blur, and image quality maintained even after long-term use. No deterioration occurs.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a contact-type component nonmagnetic developing device which is an embodiment of the present invention.

The developing device 11 includes a developing roller 12 having conductivity and elasticity.
A thin layer of non-magnetic toner is formed on the surface of the developing roller 12, and development is performed by bringing this into contact with the surface of the photoreceptor drum 13. Therefore, a developer carrier, a magnetic roller, a toner density control device, etc. are unnecessary, and miniaturization and price reduction are possible.

A developing process using the developing device 11 will be described below.

The non-magnetic toner 15 in the toner container 14 is sent to a toner supply roller 17 while being stirred by a mixer 16, and is supplied to the developing roller 12 by the toner supply roller 17.

A part of this toner 15 is adhered and conveyed as the developing roller 12 rotates due to mechanical conveying force by the developing roller 12 and electrostatic force due to charging caused by friction with the developing roller surface and other members, and is attached to the blade 18. reach. here,
The blade 18 regulates the amount of toner conveyed and at the same time triboelectrically charges the toner 15.

Note that the blade 18 is attached to the first blade holder 18a1.
It is held by a spacer 18b and a second blade holder 18c, and is brought into contact with the developing roller 12. The layer forming member including the blade 18 will be described in detail later.

As described above, the toner supply roller 17 has two roles: supplying toner to the developing roller 12 and scraping off toner on the developing roller 12 after development. , 1 around the metal shaft 17a
Density 0.045g/c with conductivity of 0.06Ω・C or less
d, a roller having a soft polyurethane foam layer 17b with a cell count of about 50 to 60 cells/25i+m;
Contact depth with respect to the developing roller 12: 0.2 to 1,0
A good image can be obtained by setting the rotation speed to about 1/2 to 4 times the speed in the opposite direction to the developing roller 12, and applying a bias voltage of the same potential as the developing roller 12 or up to about 100 volts. Since this bias voltage contributes to the amount of toner transferred, it is preferable to confirm and adjust it experimentally. In addition, in this example,
The free end of the blade 18 is in a so-called "against" position, where it precedes the rotation of the developing roller 12.
It may also be a so-called with position.

Further, in this embodiment, the negatively charged organic photoreceptor drum 1
3 to perform reversal development. For this reason, a negatively charged toner is used as the toner 15, and a material that is easily negatively charged is used as the blade 18.

Further, the developing bias potential is set to -130 to 300 V with respect to the surface potential of the photoreceptor drum 13 of -350 to 70 V,
Power is supplied to the metal shaft 12a of the developing roller 12 via a protective resistor of 3 to 10 megohms. In this example, extremely high development sensitivity is obtained, and a maximum density of about 1.4 can be stably obtained at a surface potential of -500 .mu. and a bias voltage of 200 V.

The developing roller 12 is pressed against the photoreceptor drum 13 to the extent that it forms a contact width (developing nip) of approximately 1 to 5 μl, and in this state, the speed of the photoreceptor drum 13 is approximately 1 to 4 degrees. It is rotating in the direction of the arrow (vlth). For this reason, the toner particles are also subjected to friction at the development position and are triboelectrically charged, resulting in extremely sharp images with little fog. The toner remaining after development is scraped through a recovery blade (Mylar film) 19 and returned to the inside of the developing device.

In addition, in FIG. 1, 21 is the first blade holder 18.
It is a baffle plate attached to the blade 18, and it also comes into contact with the foam material 22 made of maltbrene etc. attached to the back surface of the blade 18, thereby sealing the toner and sealing the blade 1.
This is to suppress the vibration of the developing roller 8 and to form a good toner layer on the developing roller 12.

Further, the blade 18 is pressed against the developing roller 12 by the rotating shaft 23 of the first blade holder 18a and a plurality of compression springs 24 for applying pressure.

The plurality of compression springs 24 are set lower than the spring constant of the thin plate spring material of the blade 18, so that even if the contact portion of the blade 18 wears, the pressing force hardly changes.
A good toner layer can be maintained.

FIG. 2 is a perspective view showing the blade 18.

The blade 18 is made of a thin plate spring 25 made of stainless steel, beryllium copper, phosphor bronze, etc.
A contact member (chip) 26 made of a rubber elastic body or resin having a JIS-A hardness of 30 to 85 degrees, such as silicone rubber or urethane, is fixed along the longitudinal direction to one end of the tip 5. There is. Furthermore, elastic sealing materials 27a and 27b made of urethane foam or the like are fixed to both sides of the chip 26. In this embodiment, the thin plate spring 25 is made of phosphor bronze and has a plate thickness of about 0.2 mm, but a thin plate spring 25 of about 0.1 to 2 mm thick can be used depending on the shape.

The chip 26 is attached to a thin plate spring 25 as shown in FIG.
The cross section of the contact portion has a radius r of 0.5 to 0.5 on the upstream side with respect to the rotational direction of the developing roller 12. 3mm
(r1 = 1.5 m + g in this example), and the downstream contact radius r2 is 2 to 10 mm (r2 - 8 m in this example).
).

The elastic sealing materials 27a and 27b are provided so as to be approximately the same height or slightly higher than the chip 26, and have a low hardness. The structure is such that it can reliably seal against movement.

In the blade 18, the chip 26 is attached to the developing roller 12.
If the toner layer is not pressed securely against the toner layer, uneven formation will occur.

As described above, it has been experimentally confirmed that when a conventional blade is used, if the straightness of the portion that contacts the developing roller 12 is 50 μm or less, unevenness in the toner layer shape can be ignored. However, the precision that can be achieved using current manufacturing technology is limited to about 100 μm, which causes uneven formation of the toner layer.

In contrast, in the blade 18 of this embodiment, a tip 26 is mounted on a highly elastic thin plate spring 25, and the contact section has a special cross-sectional shape in which the curvature changes continuously as described above. Therefore, even if the precision of the chip 26 is 100 μm, the elasticity of the thin plate spring 25 compensates for pressure (load) unevenness, so it easily follows the movement of the developing roller 12 and ensures an even toner layer. Formation can be performed.

This is because the curvature of the first half of the protrusion is set to a suitable radius to regulate the amount of toner passing, and then the radius of the second half of the protrusion is larger than the first half and makes contact with the developing roller 12 on a wider surface. This is because the toner layer regulated in the first half can be reliably rubbed and charged.

By changing the shape of the front and rear parts of the chip 26 and dividing the functions in this way, it becomes possible to control the amount of toner conveyance (layer thickness) and the amount of charge more efficiently and easily than before. .

Note that although the accuracy in the normal direction to the tangent between the developing roller 12 and the chip 26 can be easily guaranteed as described above, the accuracy in the tangential direction is likely to appear as pressure unevenness. Therefore, in the blade 18 of this embodiment, as shown in FIG. 4, the chip 26 is mounted at a distance dl from the end of the thin plate spring 25, and this distance is fixed by molding or bonding. The thin plate spring 2 can be used as a presser and for positioning when
5 in the lateral direction and accuracy in the tangential direction to the developing roller 12.

This interval d1 is related to the size of the layer thickness, but if dl is too large, the entire blade will be pushed up by the pressure caused by the toner flow, resulting in poor layer formation.
It may be about 5 degrees, preferably about 0.5 to 2 degrees. The optimum value of this interval is actually determined by the weight, the curvature (radius) of the tip 26, and the like.

Further, the length Lp in the longitudinal direction of the chip 26 is the length Lp of the thin plate spring 2.
For the length Lc in the longitudinal direction of 5, d2+ shown in FIG.
It is shorter by d3 minutes. That is, Lc −Lp +d2+d
3, and the above-mentioned elastic sealing material 2 is used in the d2 and 63 parts.
7a and 27b are pasted.

Note that if the length of d2+d3 is too long, the developing device itself will become large. Also, considering the sealing ability, at least 2
Since about m+g is required, d2+d.

is preferably about 4 to 30 II11, preferably about 4 to 20 II. Also, the length L of the chip 26 at this time
p is larger than the effective developing width, and the length Lc of the thin plate spring 25 is set to be equal to the width of the developing roller 12 or long enough to cover the side seal (not shown) of the developing roller 12.

Next, details of other main components of the developing device 11 will be explained.

FIG. 5 is a perspective sectional view of the developing roller 12 of the developing device 11 shown in FIG. In the developing system of this embodiment, the first characteristics required of the developing roller 12 are "conductivity and elasticity", and the simplest configuration that satisfies these requirements is a metal shaft and a conductive rubber roller. However, in order to convey the toner while being pressed against the surface, the surface needs to be smooth, so in this embodiment, as shown in FIG. 5, an elastic layer is provided around the metal shaft 12a. A two-layer structure including a conductive layer 12b and a surface conductive layer 12c is adopted.

There are two types of elastic layer 12b, one that is electrically conductive and one that is not, but it is preferable to use one that is electrically conductive in consideration of the possibility that the surface electrically conductive layer 12c may be peeled off or scratched.

Further, since the elastic layer 12b is in pressure contact with the blade 18 and the photosensitive drum 13, if the rubber hardness is high, a large load is required to obtain a predetermined nip, which also leads to an increase in developer torque. In addition, permanent distortion (%) as defined by JISK8301 due to packaging or being left for a long time becomes a problem, and if it exceeds approximately 10%, uneven development roller cycles will occur in the image. Therefore, the compressive strain (%) of the elastic layer 12b must be 10% or less, preferably 5% or less. Rubber hardness and permanent set (%
), there is a general tendency that the larger the rubber hardness, the smaller the permanent deformation, so the balance between the materials and each other is important.

After the developing roller 12 is deformed by the blade 18, it is sent to the developing section of the photoreceptor drum 13, but if it remains deformed, it will affect the development, so the deformation must be recovered by then.

Therefore, the rubber hardness of the elastic layer 12b is 35'' or less, preferably 30'' or less, and the rubber hardness of the conductive layer 12c is 35'' or less, preferably 30° or less.

The conductive layer 12c is formed by applying a conductive urethane paint to the surface of the elastic layer 12b by spraying or dipping, and since it comes into direct contact with the toner and photoconductor, it is free of plasticizers, sulfurizing agents, process oil, etc. It must not stain the toner or photoreceptor by seeping out.

The surface smoothness of the conductive layer 12c is 3 to 5 μmRz
The following is desirable; if it is more than that, the pattern of surface irregularities tends to appear in the image. In order to achieve a smoothness of 3 μmRz, it is conceivable to attach a sufficiently thick conductive layer 12c to the elastic layer 12b and then finish it to a predetermined outer diameter and surface roughness through post-processing (polishing). In order to realize this without post-processing because the cost would be high, the elastic layer 12b
This can be achieved by optimally selecting the surface roughness of the conductive layer 12c, the thickness of the conductive layer 12c, and the viscosity of the paint. That is, the lower the viscosity of the paint and the greater the surface roughness of the elastic layer 12b, the greater the thickness of the conductive layer 12c must be. As for the viscosity of the paint in the barrel forming the conductive layer 12c, the same paint must be used with different viscosity (varying the amount of dilution) depending on the method of applying the paint to the surface of the elastic body 12b.

As a study on the resistance of the developing roller 12, a developing experiment was conducted by interposing a resistor with an arbitrary resistance value between the developing bias power source and the metal shaft 12a, and the correlation between the potential on the developing roller surface, the resistance value, and the image was determined. Obtained. The result is the 6th
As shown in the figure. Incidentally, the voltage of the developing bias power supply at this time was -200 cm.

As is clear from FIG. 6, at a resistance value of 10"Ω or more, the development of a white solid image (portion where the photoreceptor potential is 1,500μ) and a black solid image (the portion where the photoreceptor potential is 0 to 40μ) At different times, the developing roller surface potential shows different values, and tends to approach the white background latent image potential for solid white images and the black solid latent image potential for solid black images.In other words, for images with large area image areas, The potential difference between the latent image potential in the image area and the surface potential of the developing roller becomes small, resulting in a low-density image.On the other hand, in the case of a thin line image where the area of the image area is small, the surface potential of the developing roller approaches the latent image potential in the white background area, resulting in an image with low density. As the potential difference between the two and

Such fluctuations in the surface potential of the developing roller are caused by the current flowing through the resistor during development.

During black solid development, negatively charged toner particles are transferred from the developing roller 12 to the photoreceptor drum 13;
A current flows from 2 to the developing bias power supply. During white solid development, the surface charge of the photosensitive drum 13 is removed by the developing roller 12, and a current flows from the developing bias power source to the developing roller 12.

Such a current generates a potential difference across the resistor, resulting in the above-mentioned fluctuation in the surface potential of the developing roller. This tendency was remarkable at 1×10 8 Ω or more.

That is, the actual resistance value between the metal shaft 12a and the surface conductive layer 12c is 1×10 8 Ω or less, preferably 1×
It was confirmed that good images can be obtained when the resistance is 10'Ω or less. Since the resistance value between the metal shaft 12a and the surface conductive layer 1.2c is 1×10 8 Ω or less, the resistance value of the conductive elastic layer 12b and the surface conductive layer 12c is equal to the resistance value between the metal shaft 12a and the elastic layer 12b1. Layer 12b and conductive layer 1
1 x 106Ω due to the 2c adhesive layer and brimer etc.
Unless it is lower than (1), a good image cannot be achieved.

In other words, a satisfactory result was obtained if the total resistance between the metal shaft 12a and the surface conductive layer 12C was less than lXl06Ω·C.

From the above, in the developing roller 12, the elastic layer 12b has a rubber hardness (JIS-^) of 35° or less and an elongation of 25°.
Conductive silicone rubber with a resistance of about 0 to 500% and a resistance value of 1 x 106 ohms or less is used, and the conductive layer 12c is a conductive polyurethane paint, such as "Subarex" manufactured by Nippon Miractron Co., Ltd., with a resistance value of 104 to 105 ohms. ·mouth,
A rubber with an elongation of about 100 to 400% was used, and the rubber hardness of the entire developing roller 12 was around 30 to 40''.Also, the elastic layer 12b with a surface roughness of 5 to 10 μm was coated by spray coating. By forming the conductive layer 12c with a film thickness of about 50 to 120 μm, the surface roughness is almost reduced.
A developing roller 12 of 3 μmRz has been realized, and good images have been obtained.

As described above, in this embodiment, a metal shaft coated with conductive silicone rubber and conductive polyurethane paint was used as the developing roller 12, but the developing roller 12 may be used as long as it satisfies the characteristics described above. Not done.

Next, a further different embodiment of the blade 18 will be described.

The shape of the tip (contact portion) of the tip 26 of the blade 18 in the embodiment described above has two different cross-sectional shapes in the first half and the second half.
Although it is configured with one semi-cylindrical shape, it may be configured with three or more curved surfaces. Moreover, it is not necessary to combine only cylindrical surfaces with different radii, and what is important is that the first half of the chip 26 (
The shape of the cross section from the upstream side to the latter half (downstream side) is composed of a continuous and smooth curved surface, such as a quadratic curved surface like an elliptical cylinder divided in half, or a combination of this and a cylinder. However, the shape may meet the above-mentioned purpose. Note that this shape is only the tip abutting portion, and does not limit the shape of the pedestal portion that receives the cylindrical protrusion. That is, the shape of the entire chip 26 is not limited.

FIG. 7 shows the configuration of the blade 18 of another embodiment. The blade 18 of this embodiment has an end of a support plate 29 made of a 1.2 mm thick iron plate that is rigid and has little elasticity in the working pressure range. A chip 30 made of silicone rubber and having a tip radius r1 of 11 mm and a rear end radius r2 of 8 mm is provided at the tip 30, and is configured to be pressed against the developing roller 12 at an angle close to perpendicular to the developing roller 12. In this case as well, the effects and actions are generally the same as in the above-described embodiment, and the curvature of the front half and the curvature of the rear half are selected so as to facilitate different functions.

FIG. 8 shows the configuration of the blade 18 of still another embodiment, in which the blade 18 of this embodiment has a thin plate spring 25.
At the end of the developing roller 12, the upstream abutting cylindrical part has a radius r1 of 0.5 to 4 m, and the downstream abutting cylindrical part radius r2 of 2 to 10 m (rl <"2"). It is equipped with a chip 31 composed of surfaces of different curvatures that satisfy the conditions,
This structure allows the first small (sharp) cylindrical part (rl)
This makes it possible to efficiently regulate the amount of toner conveyed (that is, it is easy to regulate the layer thickness), and then the second large (sloping) cylindrical part (r2) rubs the regulated toner over a wider contact width. Therefore, the toner is charged more reliably, and a stable image with less fluctuation can be obtained even when the environment changes.

On the other hand, the abutting part of conventional contact-type layer forming members consists of edges (a combination of straight lines) or a single cylindrical surface, and when the edges are abutted, it is necessary to use extremely high-precision edges. It is extremely difficult to manufacture because of uneven toner layer thickness, and the contact area is small, resulting in rapid wear and poor long-term stability. Further, when a contact portion (having a large curvature, that is, a small radius) is used alone, although layer formation is relatively easy, charging becomes unstable and wear is relatively quick. Small curvature (
In other words, if a contact part (with a large radius) is used alone, wear will be reduced, but the layer thickness will become too thick, which will require applying a strong load to the blade, resulting in an increase in driving torque. This method has disadvantages in that it tends to cause side effects such as toner sticking to the developing roller or blade (filming).

Although the above has been described based on the embodiments, the present invention also includes the chips 26, 30, 3 that constitute the contact portion with the developing roller 12.
By giving the convex surface of 1 (abutting member) a different curved surface structure, the functions required of the layer forming member can be shared and designed, compared to the conventional one that only has a single curved surface. Separation of functions allows a greater degree of freedom in design, does not require high precision as in the past, makes it easier to maintain precision, and has a longer lifespan.

In the above embodiments, contact type one-component development was explained as an example of the development method, but the present invention is not limited to the peeling embodiment. The present invention can be similarly applied to any developing system, and can be effective in all developing systems that employ a contact type developer (toner) layer forming member.

[Effects of the Invention] As explained above, according to the developing device of the present invention, more uniform thin layer formation and reliable frictional electrification can be performed, resulting in high-quality images without defective images such as density unevenness and ground force blur. It is possible to obtain high-quality images and to perform development without deterioration of image quality even after long-term use.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a developing device according to an embodiment of the present invention;
2 to 4 are diagrams showing the configuration of the blade of the developing device shown in FIG. 1, FIG. 5 is a diagram showing the configuration of the developing roller of the developing device shown in FIG. 1, and FIG. 6 is a diagram showing the developing roller potential. Graphs showing the correlation between resistance values and images, Figures 7 to 8
The figure is a diagram showing the configuration of a blade in another embodiment. 11...Developing device 12...
......Developing roller 13...
・Photoreceptor drum 18...Blade 25...Thin plate spring 26...
・・・・・・Abutting member (chip) applicant
Toshiba Corporation

Claims (3)

[Claims] (1) A developing roller disposed opposite to the electrostatic latent image holder;
and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, and by bringing the developer thin layer formed on the developing roller close to or in contact with the electrostatic latent image carrier. In the developing device that visualizes the electrostatic latent image formed on the electrostatic latent image holder, the developer layer forming means has a convex contact portion that contacts the developing roller and has a non-circular cross-sectional shape. A developing device comprising: a contact member formed by a surface; and an elastic member that presses the contact member against the developing roller. (2) a developing roller disposed opposite to the electrostatic latent image holder;
and a developer thin layer forming means for forming a developer thin layer on the surface of the developing roller, and by bringing the developer thin layer formed on the developing roller close to or in contact with the electrostatic latent image carrier. In the developing device for visualizing the electrostatic latent image formed on the electrostatic latent image holder, the surface of the developing roller is made of an elastic member, and the developer layer forming means is brought into contact with the developing roller. A developing device comprising: an abutting member whose abutting portion is constituted by a convex surface having a non-circular cross-sectional shape; and a pressing member that elastically presses the abutting member against the developing roller. (3) The convex surface of the contact portion of the developer layer forming means has a curvature larger on the upstream side with respect to the rotating direction of the developing roller than on the downstream side. 3. The developing device according to claim 1 or claim 2.