JPS63210864A - image forming device - Google Patents

Abstract

PURPOSE:To decrease the film thickness of photoreceptive layers of an A-Si photosensitive body so that the cost reduction, etc., of a product are facilitated and the degradation in the quality thereof is obviated by using the photoreceptive layers having specific film thickness and bringing a conductive member applied with a voltage into contact with the surface of the photosensitive body to execute the uniform electric charge treatment of the photosensitive body. CONSTITUTION:The amorphous silicon base photosensitive body (A-Si photosensitive body) 1 which is constituted basically of silicon atoms and has the photoreceptive layers 1b-1d formed to <=20mum and >=10mum film thicknesses is used as the photosensitive body 1. Each of the photoreceptive layers is constituted of a charge injection blocking layer 1b, a photosensitive layer 1c and a surface protective layer 1d. The uniform electric charge of such body 1 is executed by bringing the conductive member 2 applied with the voltage into contact with the surface of the body 1. The body 1 having the thin layers 1b-1d, hence low cost is thereby used. Good image formation is permitted by using the contact electric charge in place of corona electric charge which has many problems as the means for the charge treatment of said body.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to an image forming apparatus that forms an image by applying an image forming process that includes a step of uniformly charging the surface of a photoreceptor.

More specifically, the present invention relates to an image forming apparatus that uses an amorphous silicon-based photoreceptor (A-Si photoreceptor) composed of silicon atoms as a matrix and uniformly charges the photoreceptor by contact charging.

[Conventional technology]

Conventionally, an electrophotographic device, which is a typical image forming device of this kind, has a photoreceptor such as a rotating drum type that is charged, exposed to light, and
An image is formed by applying an image forming process of development, and the formed image on the surface of the photoreceptor is transferred to the surface of a transfer material and fixed to obtain an image-formed product (copy).

Photoreceptors include Cd5-resin dispersion system, ZnO-resin dispersion system, Se vapor deposition system, 5e-Te, 24-coating system, Se-A
There are various types such as sM type, 0PC (organic photoconductor) type, and A-9i type, which are in practical use.

As a charging device for a photoreceptor, most electrophotographic devices currently in practical use use a corona charger whose main components are a thin wire electrode such as a gold-plated tungsten wire and a shield plate.

Although charging treatment using a corona charger has good uniform charging properties, it has the following problems.

1) Application of high voltage In order to obtain a surface potential of, for example, 500 to 700 V to the photoreceptor, it is necessary to apply a high voltage of DC 4 to 8 KV to the wire electrode. Maintain a close distance between the wire electrode and the shield plate to prevent leakage to the shield plate and main body (5)
If the above measures are taken, the charger itself will become larger and the use of highly insulated cables will become essential.

2) Most of the discharge current from the wire electrode with poor power efficiency flows to the shield plate,
The corona current flowing toward the photoreceptor, which is the object to be charged, accounts for only about 5 to 30% of the total discharge current, resulting in poor power efficiency.

3) Wire contamination A wire electrode with a large curvature (generally one with a diameter of 60 to 100 μm is used) is used to increase the discharge efficiency, but the high electric field formed on the wire surface causes damage to the inside of the device, such as The wire surface becomes dirty by collecting minute dust such as toner particles, paper fiber pieces, and corona discharge products. Wire contamination tends to cause uneven discharge, adversely affecting the quality of halftone images, and also causing image unevenness, white spots, black lines, etc.

Therefore, it is necessary to clean the wires and the inside of the charger quite frequently.

4) Generation of corona discharge products A considerable amount of ozone is generated as a result of corona discharge.

Ozone oxidizes nitrogen in the air to produce nitrogen oxides (NOx)
etc. Furthermore, the produced nitrogen resistant material reacts with moisture in the air to produce nitric acid and the like. Corona discharge products such as ozone and its by-products, such as nitrogen oxides and nitric acid, adhere to or act on the photoreceptor surface and surrounding equipment surfaces, causing alteration and deterioration of the photoreceptor surface, simmering of the equipment, etc. cause Adhesion of corona discharge products to the photoreceptor surface lowers the resistance of the photoreceptor surface, lowering the charge retention ability and causing image blurring. In addition, the corona discharge products adhering to the inner surface of the shield plate of the corona charger volatilize and liberate not only when the electrophotographic device is in operation but also during rest periods such as at night, and this corresponds to the discharge opening of the charger. It adheres to the surface of the photoreceptor and lowers the resistance of that portion of the photoreceptor. For this reason, it is well known that the first copy that is first output when the apparatus is restarted after the apparatus has been shut down causes blurring of the image in the portion corresponding to the opening of the charger during the halt of the apparatus.

When the photoreceptor used is an A-3i photoreceptor, the above-mentioned problems due to corona discharge products become particularly severe. That is, A-
The A-9i photoreceptor has lower charging ability than other Cd5-resin dispersion system photoreceptors, and therefore the charging treatment using corona discharge for the A-9i photoreceptor is more difficult than for the other photoreceptors mentioned above. Also, a configuration is adopted in which the amount of discharge (charging) current is significantly increased. The A-9i photoreceptor is often used particularly in high-speed electrophotographic equipment, and the amount of discharge current in such cases can be as high as 2000 lA. Since there is a proportional relationship between the amount of discharge current and the amount of ozone generated, the photoreceptor is
-3i photoreceptor, and in a system in which it is charged by corona discharge, the amount of ozone generated is particularly large, and therefore the problem caused by the generation of corona discharge products becomes particularly large.

In order to prevent or reduce the harmful effects caused by corona discharge products as described above, fan means for actively eliminating generated ozone,
It is necessary to equip the apparatus with equipment such as an absorption/decomposition filter means and a drum heater means.

5) Limitations of device miniaturization and cost reduction In the corona charging method, there are limits to miniaturization and cost reduction of the corona charger itself, and space constraints for its installation.
There is a limit to miniaturization and cost reduction of the entire image forming apparatus due to the necessity of providing an ozone removal device and the like. In addition, the operating environment (temperature, humidity, etc.) may vary due to use outdoors or inside a vehicle.
The corona charging method is likely to be adversely affected by such environmental changes.

Therefore, recently, instead of using a corona charger which has many problems as mentioned above, a contact (or direct) charging method has been introduced, in other words, a method of charging the object to be charged by contacting it with a conductive member to which a voltage is applied is applied to the surface of the object to be charged. Various methods have been researched and proposed in which charging is performed to a desired potential by directly injecting charges.

For example, a method of charging a photoreceptor by bringing a voltage-applied brush into contact with it (JP-A-58-104348, JP-A No. 57-1999)
No. 87951), separation property of bringing multiple voltage application contacts into contact (Japanese Patent Application Laid-open No. 139156/1983), reducing the amount of ozone and at the same time rubbing and polishing the surface of the photoreceptor to eliminate image blurring by seeding. Method of charging while charging (JP-A-58-15097
No. 5), and other Japanese Patent Application Laid-open Nos. 178287-1987 and 5B-
104351, No. 58-40588, etc.

In the contact charging method, the voltage applied to the conductive member in order to obtain a desired charging potential on the surface of the charged object is A-9i, which has a low charging ability.
In the case of a photoreceptor, a low potential of a fraction or less of the voltage that must be applied to a corona charger to obtain a similar charging potential is sufficient, and power efficiency is high ( For example, the charge caused by corona discharge is 800~
2000g A/DCe6-8Kv (50-150gA/DC ÷ 0.5-1.5 Kl/ is sufficient), and the conductive member that is in contact with the photoreceptor surface has a rubber hardness of 15-80 degrees (JIS) Is).・Electrical resistance 105~1
06Ω conductive rubber member such as roller type or pad type,
If a voltage is supplied to the conductive rubber member from a constant voltage power source to contact charge the surface of the photoreceptor, the above-mentioned effects are remarkable, and efficient charging, that is, a high dark potential, which has been difficult in the past, can be achieved. This method has the advantage of generating only a small amount of ozone, and is promising as a charging treatment method in place of corona charging, which has many problems.

Especially high hardness (Vickers hardness 1) like A-Si photoconductor.
000 or more) is considered to be suitable as a charging treatment method for objects with excellent fist abrasion resistance.

A-Si photoconductors, both blocking type and high resistance type, are extremely superior in deterioration resistance, abrasion resistance, hardness, scratch resistance, impact resistance, etc., as compared to other photoconductors. Therefore, even if the A-Si photoreceptor is pressed against a conductive member for charging, its characteristics deteriorate due to crystallization of the photosensitive layer.

There are no problems such as indentation, scratches, abrasion, or contamination or deterioration during fusion due to chemical reactions with the surface material of the conductive member, and there is no problem with the mechanical contact and release of the conductive member against the photoreceptor. It is also resistant to impact effects.

[Problem that the invention seeks to solve]

Regarding the A-5i photoreceptor, as shown in the model diagram of the calendar structure in FIG.
, a photosensitive layer (A-Si photoconductive layer) 102 and a surface protective layer 1d are laminated in this order, so-called blocking type photoreceptor 1 is generally used. The charge injection blocking type 1b prevents the injection of electrons through the surface protective layer 1.
d plays the role of blocking the injection of holes. In addition to this blocking type, there is a single layer so-called high resistance type. The high-resistance type has a high resistance made by doping the A-Si layer with oxidants, etc.
It holds electric charge.

Since the positive type A-Si photoreceptor can have a pure photosensitive layer IC, effective countermeasures can be taken against optical memory and photodeterioration, and it is generally more widely used than the single layer type.

The charge injection blocking layer 1b, photosensitive PtI C, and surface protection layer 1d of the blocking type A-Si photoconductor 1 are combined, and the high resistance type A-Si photosensitive layer of the single layer type A-Si photoconductor is combined. It is called a photoreceptive layer.

Conventionally, regarding the general blocking type A-Sig light body used by applying corona charging, in order to ensure the required charging surface potential and to make it durable with good voltage resistance. Regarding the photoreceptive layer, those having the specifications shown in the table below are used.

However, the photoreceptive layer (lb ÷ 10
◆ld) is at least 24 gm or more overall,
The layer thickness is relatively large, and it takes a long time, approximately 6 to 8 hours, to form the photoreceptor layer during the production of the photoreceptor, which is a major cause of a significant increase in the manufacturing cost of the photoreceptor. It has become. The same can be said of the single layer type A-S i photoreceptor.

Therefore, if the A-9i photoreceptor can be manufactured at low cost, and contact charging can be used as a charging processing method instead of corona charging, which has many problems, and good images can be produced, an ideal image forming apparatus can be constructed. Can be done.

The present invention accomplishes this.

Summary: Structure of the Invention [Means for Solving Problems] The present invention provides an image forming apparatus that forms an image by applying an image forming process including a step of uniformly charging the surface of a photoreceptor, in which silicon atoms are used as the photoreceptor. An amorphous silicon-based photoreceptor having a photoreceptor layer having a film thickness of 20 JLm or less and 10 μm or more is used, and the photoreceptor is uniformly charged using a conductive method in which a voltage is applied to the surface of the photoreceptor. The gist of the present invention is an image forming apparatus characterized in that image forming is performed by bringing a sexual member into contact with the image forming apparatus.

[For production]

The conventional A-9i photoconductor described above, which has a relatively thick photoreceptive layer and is expensive to manufacture, was subjected to corona charging treatment using a corona charger and brought into contact with a roller-type conductive member to which a voltage was applied. I-V characteristics (relationship between the current processing required for charging and the charged surface potential V of the photoreceptor) during N main processing (hereinafter referred to as roller charging), and v-■
The characteristics (the relationship between the applied voltage V required for charging and the charged surface potential V of the photoreceptor) are shown in solid line graphs in FIGS. 4 and 5, respectively.

As is clear from this characteristic graph, there is a region where the saturation state occurs in corona charging, whereas this is hardly observed in roller charging.

This is the photoreceptive layer (1b+1c+Id) of the A-5i photoreceptor.
(7) R9/'i! We believe that this includes the suggestion that it is possible to easily obtain a predetermined charged surface potential even in a photoconductor that is smaller than that of a conventional photoconductor.
Regarding the photoreceptive layer of the i photoreceptor, the A-9i photoreceptor has a thin photoreceptor layer in which the thickness of each of the charge injection blocking layer 1b, photosensitive layer IC, and surface protective layer 1d constituting the photoreceptor layer is %. t-V characteristics and v when the photoreceptor was prepared and similarly subjected to corona charging treatment and when roller charging was performed.
-■I tried measuring the characteristics.

The results are shown in broken line graphs in FIGS. 4 and 5.

In other words, a thin photoreceptor with a photoreceptor layer that is thinner than the conventional one,
When it is charged by corona charging, it is not possible to secure a charged surface potential of 400V when the standard photoreceptor dark area potential is 400V, but when it is charged by roller charging, it can be sufficiently secured. is possible.

Specifically, even if the thickness of the photoreceptive layer is made as thin as 201 Lm or less and 104 Lm or more, when the photoreceptor is charged by roller charging, that is, contact charging, the dark area potential of the photoreceptor (400 V) is maintained.
It turns out that it is possible to secure This also applies to high-resistance amorphous silicon (for example, using atoms such as oxygen, nitrogen, and carbon as constituent atoms).

The thinner the photoreceptor layer is, the shorter the time required to form the layer during production of the photoreceptor, and the lower the cost of the photoreceptor. If the photoreceptive layer has a thickness of 20 gm or more, the effect of shortening the film formation time will be small, and if it has a thickness of 10 gm or less, it will be difficult to secure a predetermined photoreceptor dark area potential even with roller charging.

On the other hand, by making the photoreceptive layer thinner, the voltage resistance of the photoreceptor layer decreases, and the applied voltage during roller charging is restricted.

Literature (Solidstate technology)
According to
The withstand electric field (value of dielectric breakdown voltage per unit layer thickness) of the charge injection blocking layer 1b,! =The photosensitive layers 1c are almost equal, and one surface protective layer 1d is about one order of magnitude larger than the others. That is, photosensitive layer 1
The surface protective layer 1d has an electric field strength about 10 times larger than that of the surface protective layer 1d.
However, in reality, only about three times as much electric field is applied, and compared to the photosensitive layer 1c, the withstand electric field is almost the same for electric field injection! layer i
About 1.5 times as much electric field is applied to b. For this reason, when dielectric breakdown occurs in the A-S i photoreceptor, it is considered that the field injection blocking layer tb is often the first to be broken down.

Therefore, since voltage application in roller charging is performed up to MAX1, 5 KV, it is desirable that the charge injection blocking layer 1b has a thickness of 3 to 5 gm, and the surface protective layer 1d, which is representative of SiC, also has a thickness of 3 to 5 gm.
．． It is desirable to provide a hole of about 5 to 2 μm.

Thus, in an image forming apparatus using an A-S i photoreceptor as a photoreceptor, a photoreceptor with a thin photoreceptive layer and therefore low cost is used, and the charging treatment method is a contact method instead of corona charging, which has many problems. It is possible to construct a device that can produce good images by applying a band.

〔Example〕

FIG. 1 is a schematic diagram of one example of an image forming apparatus according to the present invention, and this example is a contact charging type/transfer type electronic thickening apparatus using a rotating drum type A-Si photoreceptor.

(2) is a drum-type photoreceptor that is rotated around a shaft 1e at a predetermined circumferential speed in the direction of the center arrow; during the rotation process, the contact charging device 2 uniformly charges its circumferential surface to a predetermined positive or negative surface potential; After being processed, electrostatic latent images corresponding to the exposed image pattern are sequentially formed by being subjected to light image exposure L (slit exposure Φ laser beam scanning exposure, etc.) by an image exposure device (not shown) in the image exposure section 3. It is formed. The latent image is in developer 4
The toner is developed, and the developed image is sequentially transferred onto the surface of the transfer material P, which is synchronously conveyed from a paper feeding means section (not shown) to a transfer charger section 6 via a conveyance section 5. The transfer material P that has undergone the image transfer is sequentially separated from one surface of the photoreceptor by the separation charger 7, is introduced into an image fixing means (not shown) in the conveying section 8, and is printed out outside the machine as an image formed product. . After the image has been transferred, the photoreceptor surface is cleaned by a cleaning device 9, then subjected to full-surface light irradiation (excluding 7tt exposure, eraser) by a pre-exposure device 10, uniformly charged again by a charging device 2, and repeatedly used for image formation. be done.

A. Photoreceptor 1 The Dorato type A-5i photoreceptor 1 of this example has a charge injection blocking layer (B2 doped with 3000 pμm) on the outer peripheral surface of a high-purity All cylinder (aluminum cylinder) la as a base.

0:4000 pμm doped) lb to 3gm, A-9i
Photosensitive layer IC: 15 μm, surface protective layer (SiC layer) l
d is sequentially formed with each film thickness of 0.5 m.

Therefore, the thickness of the photoreceptive layer (lb◆lc+1d) is 1
It was thin at 8.5 gm and had a withstand voltage of 1.7 KV.

Also, the electric field strength of each layer 1b, lc, and ld is 120V/120V in order.
'μ, aov/p, 220V/g.

B. Contact type charging device 2 In this example, it is a conductive roller contact type, and a metal core made of SUS or the like is used as the shaft rod 22, and a conductive elastic material layer 21 (in this example, an electric resistance 105Ω・Rubber hardness 45°
(JIS)Is) EPD14. The outer peripheral surface of the roller is integrally covered with conductive urethane rubber (Luxkin CF3700, which has a surface precision and wear-resistant finish) and is applied to one surface of the photoreceptor with a predetermined pressure (for example, a linear pressure of 0).
, 01 to 0.2 kg/c+*) and are kept in constant pressure contact.

In this example, the conductive roller 2 is driven to rotate with the rotation of the photoreceptor 1, but the roller 2 is kept in pressure contact with the photoreceptor 1 and is actively driven by a drive source at a predetermined circumferential speed. The photoconductor 1 may be driven to rotate in the forward or reverse direction of rotation, or may be pressed against the rotating photoconductor 1 non-rotation. As shown in FIGS. 3(a) and 3(b), it is also possible to use a pad member that presses against one surface of the photoreceptor in a non-rotational manner.

Reference numeral 23 denotes a power source for applying voltage to the conductive roller 2. The circumferential surface of the photoreceptor 1 is uniformly charged in a contact manner as the photoreceptor 1 rotates by contact with the conductive roller 2 to which a voltage is applied from the power supply 23 .

Contact charging by the conductive roller is characterized in that discharge starts at any continuous gap due to the difference in curvature between the photoreceptor 1 and the roller 2, and the discharge is stably maintained in a certain gap region by the applied voltage. In the case of the brush method, it is a collection of point contacts, whereas in the roller method, a rigid roller is brought into pressure contact with the photoconductor, and the positioning of gaps, etc. for surface contact is stable, and there is no tip discharge. Durability is also improved.

By using a conductive rubber roller as the conductive roller 2, the followability to the photoreceptor is improved, and the gap caused by the difference in curvature is also stabilized.

Silicone rubber, urethane rubber, etc. can be used as the conductive rubber material, but it is preferable to select urethane rubber rather than silicone rubber to prevent uneven charging due to oil seepage and from the viewpoint of wear resistance. By using , it is easy to make the conductive roller 2 have a relative speed difference with the photoreceptor 1, and it is possible to reduce uneven charging due to rotational play of the roller 2, etc. produces the effect of scraping off corona products.

It has been found that the hardness (JIS) is preferably 15 to 80 degrees, particularly 45 to 55 degrees, so that the pressure mechanism can be set stably. It has also been found that by increasing the resistance value to 105 to 106 Ω, dielectric breakdown can be prevented, and high-quality images can be obtained without uneven charging. Particularly in the case of the A-5i photoreceptor, there is a protective resistance effect of the rush current to the abnormal growth part called the spherical protrusion, which is unique to the A-Si photoreceptor, and there is no problem that the resistance is too high and causes uneven supply voltage. The A-9i photoreceptor, which has nearly twice the current flowing through the same roller contact charging than other photoreceptors, makes it an extremely suitable contact charging roller.

The voltage applied to the conductive roller 2 may be only DC (direct current), but it may be DC (direct current) with an AC (alternating current) component superimposed on the DC component.
+AC voltage can give better results.

DC component 500-1 (100V and AC1 & C100-1
8QOHz, 800-1800V p-p) DC+
By applying pressure to ACffi 71, a good image without uneven charging was obtained.

In particular, Vp-p has a great effect, and when it is 1400V P-P or more, it can cover dirt on the conductive roller 25 and almost eliminate charging unevenness caused by rotation of the roller.

A-9, a rotating drum type with a photoreceptive layer of 28 μm as a C1 image forming photoreceptor.
An existing laser copying machine (Canon NP9030.30 cps, process speed 18
0m5/5ee), and replaced the photoreceptor with a photoreceptor with a photoreceptive layer of 18.5 gm as in item A, and replaced the corona charger as a charging device with the conductive roller contact type charging device as in item B. This was replaced with a laser copying machine having the configuration shown in the example in FIG.

DC+ to the conductive roller 2 of the modified laser copying machine described in E. 1.
When a voltage of 3 KV was applied and the photoconductor L was subjected to contact charging to produce an image, a dark area potential of 400 V was obtained, and the static electricity was removed (bright area potential) to 50 V by a 4 μJ/C112 laser mist. The actual current was 200 pA, and a good image was output.

In addition, the voltage applied to the conductive roller 2 is DC■8QOV.
D1600Hz -1200V P-P (1) A
When the C voltage was set to the Noceta DC+AC superimposed voltage, it was possible to effectively prevent charging unevenness due to surface dirt on the roller 2, and a good image was output.

Laser copy 411 before modification (A- of photoreceptive layer 28JLm)
Si photoreceptor, corona charging treatment) is 4 at DC■0.9KV.
A dark potential of 00v can be obtained, 2.8 #LJ
/cm2 laser exposure removes static electricity (bright area potential) to 50V, the current at this time is t3oga, and a good image is output. In this laser copying machine, only the photoreceptor was replaced with the photoreceptor with a photoreceptive layer of 18.5 JLm as described in item A above, and this was subjected to corona charging treatment to produce an image.
Even if the voltage applied to the corona charger was set to 8 KV or higher, it was not possible to secure a dark potential of 400 cm on the photoreceptor, and the output image was only of very low density.

C. By applying contact charging to the A-Si photoreceptor as described in detail of the invention, A-Si film thickness can be reduced with low voltage and current.
It is now possible to maintain the same potential as before on the photoreceptor, which eliminates the need for high-voltage transformers, ozone extraction fans, etc., reducing costs on the equipment side.
Manufacturing costs can be easily reduced by reducing the film thickness of the A-9i photoreceptor, making it possible to provide a low-cost image forming apparatus without deterioration in quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an example of a laser copying machine according to the present invention, FIG. 2 is a schematic diagram of the layer configuration of an A-9i photoreceptor (blocking type),
Figures 3 (false) and (b) are cross-sectional views of configuration examples of conductive members for contact charging other than roller type, respectively, and Figure 4 is the I-V of the photoreceptor.
The characteristic graph in FIG. 5 is the same V-■ characteristic graph. 1 is a rotating drum type A-9i photoreceptor, 1a is a base, 1b
is a charge injection blocking layer, lc is a photosensitive layer (A-Si photoconductive layer)
, 1d is a surface protective layer, 2 is a contact charging device (roller type)
, 23 is a voltage applying power source.

Claims (3)

[Claims] (1) In an image forming apparatus that forms an image by applying an image forming process that includes a step of uniformly charging the surface of a photoreceptor, the photoreceptor is an amorphous silicon-based photoreceptor composed of silicon atoms as a matrix, and Image formation characterized by using a receptor layer having a thickness of 20 μm or less and 10 μm or more, and uniformly charging the photoreceptor by bringing a conductive member to which a voltage is applied into contact with the surface of the photoreceptor. Device. (2) The image forming apparatus according to claim 1, wherein the surface protective layer of the light-receiving layer contains carbon. (3) The conductive member is a roller body consisting of a metal core and a conductive rubber layer wrapped around it with a rubber hardness of 15 to 80 degrees and an electrical resistance value of 10^5 to 10^6 Ω. The image forming apparatus according to claim 1, wherein the image forming apparatus is brought into contact with each other in a freely rolling manner or in a non-rotating manner.