JPH04464A - Electrophotographic image forming device - Google Patents

Abstract

PURPOSE:To obtain an electrohotographic image forming device which corrects the fluctuation of a surface potential with high accuracy and forms a stable image by controlling exposing light quantity based on the correction value of the specified exposing light quantity stored by a control means at the time of forming an image. CONSTITUTION:Immediately after the device starts, the surface of a photosensitive body 34A is electrostatically charged by a corona charger 35 and the surface potential is detected by a surface potential sensor 32. Next, a host computer 22 reads the surface potential at a measuring point after exposure in specified timing, estimates the surface potential at the measuring point at the time of developing, and compares it with the target surface potential at the time of developing, then it decides the correction value of the exposing light quantity, which is stored in a memory 15. Thus, the CPU 22 controls the exposing light quantity based on the correction value of the exposing light quantity stored in the memory 15 at the time of forming the image. Therefore, the fluctuation of the surface potential caused by the optical attenuation characteristic of the photosensitive body is corrected with high accuracy and the stable image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic image forming apparatus that forms an electrostatic latent image on the surface of a photoreceptor and forms a toner image using this electrostatic latent image.

[Prior art]

Conventionally, electrophotographic image forming apparatuses have been applied to many copying machines, printers, etc. due to their simplicity, high speed, and low cost. In particular, wet-type electrophotographic image forming apparatuses have higher resolution than dry-type electrophotographic image forming apparatuses, and are therefore known to be suitable for electrophotographic image forming apparatuses that require high image quality.

In addition, when applying the above-mentioned wet electrophotographic image forming apparatus to fields that require extremely high image quality, such as commercial printing proofs, it is necessary to produce uniform and stable static images over a large area of at least A3 size or larger. It is necessary to form an electrolatent image and a toner image.

[Problem to be solved by the invention]

However, in the photoconductors used in the above-mentioned electrophotographic image forming apparatus, due to differences in light attenuation characteristics inherent to the photoconductors, changes in light attenuation characteristics due to environmental fluctuations (temperature fluctuations, humidity fluctuations), number of image formations, etc. The surface potential of the photoreceptor changes slightly at the time. For this reason, it has been extremely difficult to obtain stable images. Furthermore, fluctuations in the surface potential of the photoreceptor due to the light attenuation characteristics of the photoreceptor can be avoided by correction of variations in charging voltage and exposure amount between electrophotographic image forming apparatuses, and by environmental fluctuations (temperature fluctuations). and humidity fluctuations)
There is a problem in that the problem cannot be sufficiently improved by correcting the charging voltage or the like.

The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain an electrophotographic image forming apparatus that is capable of highly accurately correcting fluctuations in surface potential due to the light attenuation characteristics of a photoreceptor, and is capable of forming stable images. be.

[Means to solve the problem]

The electrophotographic image forming apparatus according to the present invention is an electrophotographic image forming apparatus that forms an electrostatic latent image on the surface of a photoreceptor and forms a toner image using the electrostatic latent image 9. a light source that exposes the surface of the photoconductor at a predetermined timing; a surface potential detection device that is disposed at a position facing the surface of the photoconductor and detects the surface potential of the photoconductor; A measuring point on the charged surface of the photoreceptor is exposed to the light source, and the surface potential of the measuring point after exposure is read at a predetermined timing, and the surface potential of the measuring point during development is estimated, and this surface potential is set as a target. a calculation means for determining a correction value for the exposure light amount by comparing the surface potential during development; a storage means for storing the correction value for the exposure light amount determined by the calculation means; and a correction value for the exposure light amount stored in the storage means. The present invention is characterized by being provided with an exposure light amount control means for controlling the exposure light amount during image formation based on the value.

[Effect]

According to the above means, at a predetermined timing by the charging means,
For example, immediately after the apparatus is started up, the surface of the photoreceptor is charged, and the points at which the surface potential of the charged photoreceptor is measured are exposed to light from a light source. A surface potential detection means detects the surface potential measurement point of the exposed photoreceptor.

Next, the calculation means reads the surface potential of the measurement point after exposure at a predetermined timing, estimates the surface potential of the measurement point during development, compares this surface potential with the target surface potential during development, and calculates the amount of exposure light. A correction value for the amount of exposure light is determined, and the correction value for the amount of exposure light is stored in the storage means. Thereby, during image formation, the exposure light amount control means controls the exposure light amount based on the exposure light amount correction value stored in the storage means.

Therefore, variations in surface potential due to the light attenuation characteristics of the photoreceptor can be corrected with high accuracy, and stable images can be formed.

The surface potential of the measurement point during development is determined by stopping the photoreceptor at a position facing the surface potential detection means, reading the surface potential of the measurement point into the calculation means after the time when the measurement point reaches the development position, and calculating the surface potential of the measurement point. The potential is estimated to be the surface potential at the measurement point during development. Alternatively, one or more surface potential detection means extract at least two or more surface potentials at the same position on the surface of the photoreceptor at predetermined time intervals, calculate a light attenuation characteristic curve, and perform development from this light attenuation characteristic curve. The surface potential at the measurement point at the time may be estimated.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a layout diagram of each processing section constituting a wet type electrophotographic image forming apparatus as an electrophotographic image forming apparatus according to a first embodiment of the present invention.

Exposure section 10 forming part of a wet electrophotographic image forming apparatus
is connected to a semiconductor laser 12, a control unit 14 for controlling the output state of the semiconductor laser 12, a condenser lens 16.26, a scanning lens 28, a reflection mirror 24.30, and a buffer 19, and receives the incident laser beam. It records image information supplied from a multi-AOM (acousto-optic modulator) 18 that divides the ultrasound into a plurality of parts according to the frequency of the ultrasound, a polygon mirror 20, and a host computer 22 that serves as calculation means and exposure light amount control means. photosensitive drum 3
A memory 15 serves as a storage means for storing a charging voltage correction value for correcting the dark decay characteristic of the photoconductor 34A on the outer circumferential surface of No. 4, and an exposure light amount correction value for correcting the light decay characteristic of the photoconductor 34A. .

As the semiconductor laser 12, for example, Al-Ga-A
s laser can be used. A laser beam emitted from the semiconductor laser 12 is irradiated onto the multi-AOM 18 via a condensing lens 16. Further, ultrasonic waves of different frequencies generated according to the image information stored in the memory 15 are supplied to the multi-AOM 18. This causes the laser beam to be diffracted in different directions depending on the frequency of the ultrasound.

Further, the light intensity of the laser beam is modulated by the multi-AOM 18 based on the exposure light amount correction value stored in the memory 15. Therefore, by modulating this laser beam, the optical attenuation characteristic of the photoreceptor 34A is corrected.

This laser beam is condensed by a condensing lens 26, and is further incident on a polygon mirror 20 rotating at high speed via a reflection mirror 24. The laser beam reflected by the polygon mirror 20 is sent to the scanning lens 28 and the reflection mirror 3.
0 to the image forming area on the surface of the photosensitive drum 34. In this embodiment, since a multi-AOM is used, a plurality of (eg, eight) laser beams are scanned simultaneously.

The photosensitive drum 34 is connected to a drive means (not shown), and is rotated clockwise in FIG. 1 (in the six directions of arrows in FIG. 1) by this drive means. Further, the rotation angle of the photosensitive drum 340 (the rotational position of the photosensitive drum 34 from the home position) is detected by a well-known photosensitive drum rotational position detection device, and is manually input to the host computer 22 at any time.

A photoreceptor 34A is provided on the outer peripheral surface of the photoreceptor drum 34 made of aluminum. As the photoreceptor 34, a well-known organic photoconductor or inorganic photoconductor can be used.

It is also possible to use a dielectric material charged with a charging needle.

Organic photoconductors include a variety of well-known organic photoconductors. Specifically, “Research Disclosure J
(Research Disclosure) Magazine #10
938 (May 1973 issue, page 61 et seq., an article entitled "Electrophotographic Elements, Materials and Processes").

For example, poly-N-vinylcarbazole and 2.4.7-) are in practical use. Electrophotographic photoreceptor consisting of J nitrofluoren-9-one (U.S. Pat. No. 3,4
84.237), poly-N-vinylcarbazole sensitized with pyrylium salt dye (Special Publication No. 4 g-256
58), an electrophotographic photoreceptor containing an organic pigment as a main component (Japanese Patent Application Laid-Open No. 49-37543), an electrophotographic photoreceptor containing a eutectic complex consisting of a dye and a resin as a main component (Japanese Patent Application Laid-Open No. 47-107)
No. 35), an electrophotographic photoreceptor in which copper phthalocyanine is dispersed in a resin; Others, Journal of the Society of Electrophotography, Volume 25, No. 3 (1986), 6
There are substances described on pages 2 to 76.

In addition, as the inorganic photoconductor used in the present invention, "Electro Photography J (rElectro-p
photography J R, M, 5chaffer
(Author, Focal Press (London))
(1975), pages 260 to 374, etc., various inorganic compounds are representative. Specific examples include zinc oxide, zinc sulfide, cadmium sulfide, selenium, selenium-tellurium alloy, selenium-arsenic alloy, selenium-tellurium-arsenic alloy, and the like.

In addition, amorphous silicon can also be used. This amorphous silicon has fast dark decay but can be used repeatedly, so it is suitable for this embodiment.

A corona charger 35 serving as a charging means is disposed upstream in the rotational direction of the photoreceptor at a position where the laser beam is incident on the photoreceptor 34A. This corona charger 35 is equipped with a corona wire and a grid wire, and the corona charger 35 is connected to an AC
and connected to a DC power source. Further, the corona charger 35 is connected to the host computer 22, and the discharge voltage is controlled by the host computer 22 based on the correction value of the charging voltage stored in the memory 15.

As a result, the photosensitive drum 34 before electrostatic latent image formation is rotated clockwise in FIG. 1 after the surface of the photosensitive member 34A is uniformly charged positively or negatively by the corona charger 35.

Further, as will be described later, by connecting the corona charger 35 to a DC power source and applying a charge having the same polarity as the toner through DC corona discharge, the charge on the toner can be strengthened (precharge).

Further, as will be described later, by connecting the corona charger 35 to an AC power source and performing AC corona discharge, the photoreceptor 34A
The charges on the photoreceptor are neutralized, and the residual potential on the photoreceptor can be removed (static charge removal).

A surface potential sensor 32 as a surface potential detection means is arranged downstream of the corona charger 35 (on the rotational direction side of the photoconductor drum 34), and this surface potential sensor 32 detects the surface potential of the photoconductor 34A. 8 is now possible. Further, the surface potential sensor 32 is connected to the host computer 22, and based on the surface potential detected by the surface potential sensor 32, the surface potential measurement point of the photoreceptor 34A is stopped at a position facing the surface potential sensor 32,
The surface potential of the measurement point after the time when the measurement point reaches the development position is read into the host computer 22, the surface potential at the time of development is estimated, and the estimated surface potential at the time of development and the target surface potential at the time of development are calculated. After comparison, a correction value for the charging voltage is determined and stored in the memory 15.

Further, at a position facing the surface potential measurement point of the photoconductor 34A on the opposite side of the photoconductor drum 34 of the surface potential sensor 32,
A lamp 33 is arranged as a light source. This lamp 33 is connected to the host computer 22, and is configured to expose the surface potential measuring point of the photoreceptor 34A charged by the corona charger 35 for a predetermined period of time.

After exposure with the lamp 33, the surface potential measurement point of the photoreceptor 34A is stopped at a position facing the surface potential sensor 32, and the surface potential of the measurement point after the time when the measurement point reaches the development position is measured by the host computer. 22 and estimate the surface potential during development based on the light attenuation characteristics of the photoreceptor 34A.
The estimated surface potential at the time of development is compared with the target surface potential at the time of development when light irradiation is performed.
Determine the correction value of the exposure light amount to correct the light attenuation characteristics of 4A,
The information is stored in the memory 15.

The part of the photoconductor 34A where the laser beam is incident becomes conductive and the charge on the surface disappears, causing the photoconductor 34A to become conductive.
An electrostatic latent image is formed on the surface of 4A.

As shown in FIG.
1 is placed. By irradiating the photoreceptor 34A with light from the exposure lamp 11, the charges on the photoreceptor 34A can be neutralized (photostatic charge removal). This optical charge removal has the same function as the charge removal by the corona charger 35, and can perform pre-exposure to improve the transfer efficiency of the toner attached to the photoreceptor 34A, as will be described later.

As shown in FIG.
A pre-wet device 50 is provided downstream of the position where the light is incident (on the rotational direction side of the photosensitive drum 34 with respect to the incident position). This pre-wetting device 50 is adapted to apply a carrier liquid, which is a dispersion medium for liquid developer, for the purpose of preventing toner from adhering to non-image areas and improving transferability of toner images onto a transfer material.

A developer unit 36 is arranged downstream of the pre-wet device 50 (on the rotational direction side of the photosensitive drum 34).

The developer unit 36 includes a box with an open top, and a liquid developer 38 is housed in the box. This liquid developer 38 has four types of toner particle colors: blank, yellow magenta, and cyan. As this liquid developer 38, a known developer can be used, such as Japanese Patent Publication No. 35-5511, Japanese Patent Publication No. 35-1
3424, Special Publication No. 50-40017, Special Publication No. 49-98
634, JP 58-129438, JP 61-18
0248, and the developer disclosed in Fundamentals and Applications of Electrophotographic Technology (Electrophotographic Society Enri, Corona Publishing (1988)).

These liquid developers generally include a carrier liquid, a colorant that forms toner particles, a coating agent made of a polymeric resin that provides fixation properties for the colorant, and a coating agent that promotes the dispersion of toner particles and works to stabilize the dispersion. It consists of a dispersant to control the polarity and charge amount of the toner particles, and a charge control agent to control the polarity and charge amount of the toner particles.

As the coating agent, various known resins can be used, but in particular, Japanese Patent Application Laid-Open No. 61-180248 and Japanese Patent Application No. 63-4
1272, copolymers of ethylene and (meth)acrylic acid, copolymers of ethylene and vinyl acetate, copolymers of ethylene and ethyl acrylate, and ethylene and (meth)acrylic acid esters disclosed in Japanese Patent Application No. 63-41273. Ethylene-based copolymers such as a copolymer of , a terpolymer of ethylene/(meth)acrylic acid/(meth)acrylic acid ester are preferred. The amount of toner particles in the developer is not particularly limited, but is 0.1 to 200 g/l per developer 11.

(i.e. 5 to 10 DOO of carrier liquid per toner particle)
cc. ) Various known charge control agents can be used, and their weight concentration is 0.01 to 10 g per 1 liter of developer.
1, preferably 0.01 to 1 g.

Further, various known dispersants can be used, and the weight concentration thereof is preferably 0.01 to 50 g, preferably 0.1 to 10 g, per 1β of the developer.

A plurality of developing rollers 40 are arranged in the developer unit 36 and extend in the axial direction of the photosensitive drum 34 and correspond to the image forming area of the photosensitive member 34A. This developing roller 4
A part of the outer circumferential surface of 0 is immersed in liquid developer 38.

These developing rollers 40 are rotated by a drive mechanism (not shown).

Further, the developing roller 40 is moved by a mechanism (not shown) from a position where the developing roller 40 is away from the image forming area to a position where it contacts the image forming area (see FIG. 1), and the liquid developer 38 is moved through the developing roller 40. It is designed so that it can be applied to the image forming area. Further, the developing roller 40 is moved from the contact state to a state away from the image forming area (movement in the direction of arrow B in FIG. 1) by a mechanism not shown. By changing the type of developer unit 36 through this movement, four types of coloring can be achieved.

A squeeze device 41 having an air jet section 41A extending in the axial direction of the photosensitive drum 34 and facing the image forming area is disposed on the side of the developer unit 36 in the rotational direction of the photosensitive drum 34. The excess liquid developer 38 supplied to the tank is removed and discharged to a waste liquid tank.

A squeeze device 4 extending in the axial direction of the photosensitive drum 34 is provided on the downstream side of the squeeze device 41 in the rotational direction of the photosensitive drum 34.
3 is placed. The squeeze device 43 has an air jet section 4.
3A is formed, and a liquid developer discharge path 43B and a rinse liquid discharge path 43C are formed with this air jet portion 43A sandwiched therebetween.

These air jetting portions 43A1, liquid developer discharge path 43B,
The rinse liquid discharge path 43C extends in the axial direction of the photosensitive drum 34 and faces the image forming area. The liquid developer discharge path 43B and the rinse liquid discharge path 43C are connected to a waste liquid tank (not shown), and the air jetted from the air jet section 43A is blown onto the excess liquid developer and rinse liquid attached to the photoreceptor 34A. The liquid developer and the rinsing liquid are supplied through the liquid developer discharge path 43B and the rinse liquid discharge path 4, respectively.
3C to the waste tank.

A rinse liquid unit 42 is arranged downstream of the squeeze device 43 in the rotational direction of the photosensitive drum 34 . The rinsing liquid unit 42 includes a box with an open top. A rinsing liquid 44 is contained in this box. As the rinsing liquid 44, a non-polar non-aqueous solvent having an electrical resistance of 1×10 9 Ω·am or more and a dielectric constant of 3 or less can be used.

Examples of the non-aqueous solvent include solvents such as straight or branched aliphatic hydrocarbons, aliphatic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons, but there are concerns regarding volatility, safety, odor, etc. From the point of view, octane, isooctane, decane, isodecane, dodecane, isododecane, nonane, isoparaffin-based petroleum solvents Isopar E, Isopar G1 Isopar H1 Isopar L (A, Invar RL)
soper" is a product name of Exxon Corporation), Tsurpets 10
01 Shell Silua 1 (manufactured by Shell) and the like are suitable.

A plurality of rinse rollers 46 are arranged in the rinse liquid unit 42 so as to face the image forming area and extend in the axial direction of the photosensitive drum 34 . A portion of the outer peripheral surface of this rinse roller 46 is immersed in the rinse liquid 44. The rinse roller 46 is connected to the rinse roller 4 by a mechanism (not shown).
6 is moved from a position away from the image forming area to a position in contact with the image forming area shown in FIG.
can be applied to the image forming area via a rinse roller 46.

Further, the rinse roller 46 is moved by a mechanism (not shown) from the contact state to a state away from the image forming area (the first
(movement in the direction of arrow C in the figure).

Further, the rinse roller 46 is brought into contact with the image forming area during development processing and is moved away from the image forming area by a mechanism not shown.

On the downstream side (rotational direction side of the photosensitive drum 34) of the rinsing liquid unit 42 (7), there is a squeeze device 62 having an air jet section 62A extending in the axial direction of the photosensitive drum 34 and facing the image forming area. It is located. The rinsing liquid supplied to the image forming area is removed from the image forming area by the air ejected from the air ejecting portion 62A and is guided to a waste liquid tank (not shown).

An exhaust duct 66 that constitutes a part of the drying processing section 64 is arranged downstream of the squeeze device 62 (on the rotational direction side of the g-light drum 34). The exhaust duct 66 has an arc-shaped opening 66B having a radius of curvature equal to the distance between the photoreceptor 34A and the photoreceptor 34A on the side facing the photoreceptor 34A.

Further, on the downstream side of the exhaust duct 66 in the drum rotation direction, there is an intake chamber 6 that constitutes the drying processing section 64 together with the exhaust duct 66.
8 is placed.

The side of this intake chamber 68 opposite to the photosensitive drum 34 is connected to a blower (not shown), and the side of the photosensitive drum 34 is connected to an exhaust duct 66.
It faces the air inlet opening 66A on the downstream side. Air sent from the air inlet opening 66A (arrow W in FIG. 1) passes through the opening 66B and is blown onto the photoreceptor 34A, thereby drying the wet photoreceptor 34A.

The air sent to the photoreceptor 34 is discharged to the outside of the apparatus via the air discharge port 66C.

A transfer unit 70 is arranged downstream of the intake chamber 68 (on the rotational direction side of the photosensitive drum 34). The transfer section 70 is moved by a drive mechanism (not shown) in the direction toward and away from the outer periphery of the photoreceptor 34A (in the direction of the arrow in FIG. 1).

A pair of transfer rollers 72 extending in the axial direction of the photosensitive drum 34 are provided in the transfer section 70 in close proximity to the photosensitive member 34A. A transfer guide 74 extending in a direction away from the photosensitive drum 34 is arranged above the transfer rollers 72 . The transfer guide 74 includes a tray 7 for storing transfer materials.
The transfer material set on the tray 75 is guided by a transfer guide 74, reaches a position where it is held between the transfer roller 72 and the photoreceptor 34A, and is transferred.

A cleaning section 76 is arranged downstream of the transfer roller 72 (on the rotational direction side of the photosensitive drum 34), and on the downstream side of this cleaning section 76 (on the rotational direction side of the optical drum 34).
A cleaning brush 77 is arranged. The cleaning section 76 is equipped with a take-up roller 78 and a web roller 79. A cleaning web 82 made of nonwoven fabric or the like is wound around the take-up roller 78 and the web roller 79.

Further, the cleaning section 76 is provided with a cleaning roller 84 having a plurality of through holes 84A formed therein so as to extend in the axial direction of the photosensitive drum 34.

This cleaning roller 84 has the above-mentioned isopar G.
Contains a carrier liquid such as This cleaning roller 84 is wound around the middle part of the cleaning web 82. The cleaning roller 84 faces the image forming area via the cleaning web 82. The cleaning unit 76 is moved by a drive mechanism (not shown) in a direction in which it comes into contact with the outer peripheral surface of the photoreceptor 34A and in a direction in which it separates (in the direction of arrow G in FIG. 1).

In the cleaning process, the cleaning roller 84 is driven by the mechanism described above to a position close to the photoreceptor 34A, and the cleaning web 82 comes into contact with the photoreceptor 34A. Further, the cleaning web 82 is wound clockwise by the winding roller 78. The cleaning roller 84 is rotated clockwise following the winding operation, and with this rotation, the carrier liquid flows out from the through hole 84A. By sliding the portion of the cleaning web 82 impregnated with the carrier liquid along the surface of the photoreceptor 34A, residual toner and the like after transfer are removed.

A cleaning brush 77 is arranged downstream of the cleaning section 76 (on the rotational direction side of the photosensitive drum 34). The cleaning brush 77 is constructed by planting a large number of animal hairs on the cylindrical surface of a cylindrical body, extends in the axial direction of the photosensitive drum 34, and is brought into contact with the outer circumferential surface of the photosensitive member 34A by a drive mechanism (not shown). direction and departure direction (first
(in the direction of arrow H in the figure). In a cleaning step to be described later, a cleaning brush 77 is slid along the surface of the photoreceptor 34A to remove foreign matter attached to the photoreceptor 34A without disturbing the toner image formed on the photoreceptor 34A.

The operation of this embodiment will be explained below.

In this embodiment, the charging voltage correction value and the exposure light amount correction value are calculated and stored in the memory 15 using the following method when the wet type electrophotographic image forming apparatus is started up or every predetermined period of time has elapsed after the start-up.

The procedure for calculating the charging voltage correction value and the exposure light amount correction value and storing them in the memory 15 will be explained according to the flowchart of FIG.

First, the photosensitive drum 34 is rotated to completely eliminate static electricity from the photosensitive member 34A (Step 100), and then the corona charger 35
A predetermined measurement point on the photoreceptor 34A is charged with a predetermined voltage (step 102).

When the measurement point of the photoconductor 34A reaches a position opposite to the surface potential sensor 32, the photoconductor drum 34 is stopped, and the surface potential sensor 32 starts detecting the surface potential of the measurement point (step 104).

As shown in FIG. 2, the surface potential (VO) of the measurement point after the time (T1) when the measurement point reaches the developing roller 40 is read into the host computer 22 (step 106).

The ratio (ΔV=V1/VO) between this surface potential (VO) and the target surface potential (vl) during development is calculated (step 108), and the correction value of the charging voltage (DO) (D1=ΔV−D
O) is calculated (step 110) and stored in the memory 15 (step 112).

The photosensitive drum 34 is rotated again to eliminate static electricity from the photosensitive member 34A (step 112).

Thereafter, a predetermined measurement point on the photoreceptor 34A is charged with a predetermined voltage by the corona charger 35 (step 114).

When the measurement point of the photoconductor 34A reaches a position facing the surface potential sensor 32, charging is stopped, the photoconductor drum 34 is stopped, and the surface potential sensor 32 starts detecting the surface potential at the measurement point (step 116). .

As shown in FIG. 2, after the time (T2) when the measurement point reaches the exposure position by the exposure section 10, the lamp 33 is turned on and the measurement point is exposed for a predetermined time (step 118).

Furthermore, the surface potential (EO) of the measurement point after the time (T3) when the measurement point reaches the development position after exposure is read into the host computer 22 (step 120).

The ratio (△E=E 1/EO) between this surface potential (EO) and the target surface potential (El) during development is calculated (step 122), and the correction value for the exposure light amount (LO) (L1=ΔE
-DL) is calculated (step 124) and stored in the memory 15 (step 126).

Correction value (Dl) of the charging voltage stored in this memory 15
The following image forming process is performed based on the exposure light amount correction value (Ll).

In this embodiment, after a black image is formed, yellow, magenta, and cyan images are formed superimposed on the black image. Further, in this embodiment, a developer containing negatively charged toner particles is used.

First, a case will be described in which a black image is formed on the photoreceptor 34A. Image information of the image to be copied is supplied from the host computer 22.

When a transfer start switch (not shown) is turned on, the photosensitive drum 34 is rotated clockwise in FIG. 1 by a driving means (not shown), the corona charger 35 is activated, and
C. The photoreceptor 34A is positively charged by corona discharge (Charging in FIG. 4(A)). In this case, the corona charger 35
The discharge voltage is controlled by the host computer 22 based on the charging voltage correction value (Dl) stored in the memory 15. Therefore, it is possible to highly accurately correct a decrease in the surface potential of the photoreceptor 34A during development due to dark decay characteristics.

When the image forming portion of the photoreceptor 34A, whose surface is uniformly and positively charged, is positioned at the exposure position, the laser beam emitted from the semiconductor laser 12 is modulated according to image information, thereby exposing the photoreceptor 34A to an image. (Figure 4 (A) exposure).

In this case, the exposure light amount of the laser beam is controlled by the host computer 22 based on the exposure light amount correction value (Ll) stored in the memory 15. Therefore, it is possible to highly accurately correct a decrease in the surface potential of the photoreceptor 34A during development due to the light attenuation characteristic. Therefore, a stable image can be formed in the development process described later.

When the surface of the photoreceptor 34A is imagewise exposed, the portion irradiated with the laser beam becomes conductive, and the positive charges on the surface move to form an electrostatic latent image corresponding to image information.

The photoreceptor 34A, on which the electrostatic latent image is formed, is further
The photoreceptor 3 is rotated clockwise in the figure, and the pre-wet device 50
The carrier liquid is uniformly applied to the surface of 4A.

The pre-wet portion of the photoreceptor 34A further rotates clockwise in FIG. 1 and reaches a position corresponding to the developer unit 36. In this case, a developer unit 36 containing a liquid developer containing blank toner particles is arranged in advance. This developer unit 36 applies a liquid developer containing black toner particles to the area where the electrostatic latent image is formed via a developing roller 40 (FIG. 4(A) development).
.

As a result, negatively charged toner particles in the developer adhere to the image area where the electrostatic latent image is formed, and the electrostatic latent image is visualized, resulting in a toner image corresponding to the image area or non-image area. is formed (FIG. 5(A)).

The portion of the photoreceptor 34A on which the toner image is formed further rotates clockwise in FIG. 1 and reaches a position corresponding to the squeeze device 41. The area where the toner image is formed is squeezed by being blown with air from the air jetting section 41A, thereby guiding the excess liquid developer 38 to a tank (not shown) (FIG. 4(A) Squeeze 1).

The portion of the photoreceptor 34 on which the toner image is formed further rotates clockwise in FIG. 1 and reaches a position corresponding to the rinse liquid unit 42 filled with the rinse liquid 44. Photoreceptor 34
A rinsing liquid 44 is supplied to the surface of the photoreceptor 34A via a rinse roller 46, and the developer containing unnecessary toner particles adhering to the portion of the photoreceptor 34A other than the image area to which the toner is to be adhered is washed away (see Fig. 4). (A) Rinse).

The excess rinsing liquid 44 supplied to the photoconductor 34A is flowed downstream along the outer peripheral surface of the photoconductor 34A, but is removed from the surface of the photoconductor 34A by air jetted from the air jet section 43A of the squeeze device 42. and the discharge path 43C
is discharged to a waste liquid tank (not shown) via the
A) Squeeze 2).

The photoreceptor 34A further rotates clockwise in FIG. 1 and faces the opening 66A of the exhaust duct 66.

From this opening 66A, dry air supplied from a blower (not shown) is blown onto the surface of the photoreceptor 34A. This dry air dries the moist surface of the photoreceptor 34A (FIG. 4(A) drying).

From this state, the photoreceptor 34A is further rotated clockwise in FIG. 1, and the photoreceptor 34A shifts to the second rotation. In this second round, only the drying process is performed (Fig. 4 (B)
dry).

This drying evaporates the rinsing liquid and carrier liquid existing between the toner particles forming the electrostatic latent image, increasing the interaction (bonding force) between the toner particles.
As the photoreceptor 34A rotates around the circumference, the portions of the photoreceptor 34A that face the corona charger 35 are charge-removed by AC corona discharge by the corona charger 35 (FIG. 4(C) charge removal).

Further, the light emitted from the exposure lamp 11 is supplied to this charge-eliminated portion, and the charge remaining on the dust light body 34A after the charge removal is removed (FIG. 4(C) optical charge removal). Thereafter, the drying process is continued until the third rotation is completed.

Next, the process moves to the second color (yellow) image formation process (
4th lap). In this second color application process, first, the cleaning brush 77 is moved onto the photoreceptor 3 by a drive mechanism (not shown).
The foreign matter attached to the photoreceptor 34A is removed by sliding along the surface of the photoreceptor 4A (FIG. 4(D) puff). As the photoreceptor 34A rotates, the portion of the photoreceptor 34A from which the foreign matter has been removed is sequentially charged (charging in FIG. 4(D)) and exposed (N light in FIG. 4(D)) in the same manner as described above. An electrostatic latent image is formed on the photoreceptor 34A.

As before, the area on the photoreceptor 34A where the electrostatic latent image is formed is pre-wet (pre-wet in FIG. 4(D)) before the development process to prevent toner particles from adhering to the non-image area. After that, the development is performed, and a toner image of yellow toner particles is formed on the photoreceptor 34A, superimposed on the toner image formed of the black toner particles (Fig. 4 (D) Development, 5 Figure (B)). At this time, the developer unit 36 is moved so that the unit containing the developer containing yellow toner comes into contact with the surface of the photoreceptor 34A. After that, squeeze 1 (Figure 4 (D) squeeze 1) and rinse (Figure 4 (D)) as described above.
D) rinsing), squeeze 2 (FIG. 14 (D) squeeze), and drying treatment (FIG. 4 (D) drying).

Next, in the same way as in the process of applying toner particles of the first color, the photoreceptor 3
Drying is carried out during the fifth rotation of 4A (Drying in Fig. 4 (E)), and further, in the 6th rotation period, static electricity is removed (Fig. 4 (F) Static removal) and light exposure (Fig. 4 (F) light exposure) and drying.

In the same way as applying the second color liquid developer, apply the third color (
A liquid developer containing toner particles of magenta is applied. As a result, a toner image of magenta toner particles is formed on the photoreceptor 34A, superimposed on the toner image formed of the yellow toner particles. As a result, three toner layers of black, yellow, and magenta toner particles are formed on the photoreceptor 34A (FIG. 5(C)).

When applying the fourth color (cyan), that is, the final color, use a puff (removal of foreign matter with a cleaning brush) (see Figure 4) in the same way as when applying the second and third colors. (G) puff), charging (Fig. 4 (G) charging), exposure (Fig. 4)
After performing pre-wetting (Fig. 4 (G) Pre-wet) and preventing toner particles from adhering to non-image areas, development (Fig. 4 (G) Development) is performed. A toner image of cyan toner particles is formed on the photoreceptor 34A, superimposed on the toner image formed of the magenta toner particles.

As a result, toner layers of four colors, blank, yellow, magenta, and cyan, are formed on the photoreceptor 34A. After that, the same squeeze 1 as above (Figure 4 (G) squeeze 1)
, Rinse (Figure 4 (G) Rinse), Squeeze 2 (
Figure 4 (G) Squeeze 2), drying (Figure 4 (G) Drying)
will be done. The above operations are performed while the photosensitive drum 34A rotates once. The drying process is performed within the period in which the photoreceptor 34A is further rotated once clockwise in FIG.
Figure 4 (H) drying). This second and final color rotation is only for drying.

The photoreceptor 34A is further rotated and moves to the third rotation. In this third rotation, first the corona charger 35
An electric charge having the same polarity as that of the toner is applied to the photoconductor 34A by DC corona discharge caused by the DC corona discharge.
precharge) is performed.

The portion of the photoreceptor 34A that is not precharged is further
It rotates clockwise in the figure and reaches a position corresponding to the exposure lamp 11. The light emitted from the exposure lamp 11 is applied to the photoreceptor 34A.
and pre-exposure is performed.

The pre-exposed portion of the photoreceptor 34A further rotates clockwise in FIG. 1 and reaches a position corresponding to the pre-wet device 50. As described above, the droplet-shaped carrier liquid is ejected from the pre-wetting device 50 and applied to the pre-exposed area, thereby performing pre-wetting before transfer.

On the other hand, the transfer material guided by the guide 74 to a position where it is sandwiched between the photoconductor 34A and the roller 72 is sandwiched by the portion of the photoconductor 34A where the toner particle layers of the four colors are formed, and the transfer material is A transferred image is formed by the toner layer (FIG. 5(D)). As a result, an original image is formed on the surface of the transfer material.

Further, the photosensitive drum 34A is rotated clockwise in FIG. 1 to proceed to a cleaning process. In this cleaning step, web cleaning is performed and further drying processing is performed to bring the photoreceptor to the initial state before exposure as shown in FIG. 4(A).

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 to 8.

Incidentally, the same members as in the first embodiment are given the same reference numerals and the description thereof will be omitted.

As shown in FIG. 6, in this embodiment, a surface potential sensor 86 as a surface potential detection means is connected to the exposure lamp 11.
The photosensitive drum 34 is disposed on the downstream side in the rotational direction.

This surface potential sensor 86 is connected to the host computer 22 similarly to the surface potential sensor 32. Further, in this embodiment, the exposure lamp 11 also serves as a light source for determining the light attenuation characteristics of the photoreceptor 34A, and the lamp 33 of the first embodiment is omitted.

Next, the procedure for calculating the charging voltage correction value and the exposure light amount correction value and storing them in the memory 15 in this embodiment will be explained according to the flowchart of FIG. 8.

The following process is performed when the wet type electrophotographic image forming apparatus is started up or every predetermined period of time has elapsed after startup.

First, the counter N of the host computer 22 is cleared (step 130).

The developing roller 40, the rinsing roller 46, the transfer section 70, the cleaning section 76, and the cleaning brush 77 are moved in the directions of arrows B, C, D, and GSH in FIG. 6, respectively, and are separated from the photosensitive drum 34 (step 132).

Next, the photoreceptor 34A is completely neutralized in step 134).
After that, the photosensitive drum 34 is rotated and the corona charger 35
A predetermined measurement point on the photoreceptor 34A is charged with a predetermined voltage (step 136).

The surface potential at the measurement point of the photoreceptor 34A is detected by the surface potential sensor 32.86.
) The surface potentials of the measurement points immediately after charging (E2, E3
) into the host computer 22 (step 14
0). Similarly, the surface potentials (E4, E5) of the measurement points after the photosensitive drum 34 rotates once are measured by the host computer 22.
(step 140.141.142.144
).

The host computer 22 calculates the surface potentials at the four points (E2,
E3, E4, E5), the dark decay characteristic curve F of the photoreceptor 34A shown in FIG. 7(A) is calculated (step 1).
46).

Furthermore, the surface potential (V2) of the development time is calculated using this dark decay characteristic curve F, and the calculated surface potential (V2)
and the target surface potential during development (v3) (ΔV
= V3/V2) (step 148), and calculate the correction value (Dl) of the charging voltage (step 150).
5 (step 152).

Next, the counter N of the host computer 22 is cleared (step 158).

The photoreceptor 34A is completely neutralized (step 160), and then the photoreceptor drum 34 is rotated and the corona charger 35 charges a predetermined measurement point on the photoreceptor 34A with a predetermined voltage (step 162).

The exposure lamp 11 is turned on for a predetermined period of time, and the measurement point is exposed to a predetermined amount of light (step 164).

The surface potential at the measurement point of the photoreceptor 34A is detected by the surface potential sensor 32.86 (Step 166), FIG. 7(B)
The surface potential (E 6 , E
7) is loaded into the host computer 22 (step 168). Similarly, the surface potentials (E8, E9) of the measurement points after the photosensitive drum 34 has rotated once are read into the host computer 22 (steps 168, 170, 172.
174).

The host computer 22 determines the surface potential at the four points (E6
. A+ (1e t) A2
t)α・・・・(1) Here, A+, A2, and α are constants, and vO is the initial charge amount.

By substituting the surface potentials at the four points (E6, E7, E8, E9) and determining the respective constants A+, A2, and α, the light attenuation characteristic curve G of the photoreceptor 34A shown in FIG. 7(B) is obtained. Calculate (step 176).

Furthermore, the surface potential (V4) of the development time is calculated using this light attenuation characteristic curve G, and the calculated surface potential (V4)
and the target surface potential during development (V5) (ΔV
= V5/V4) (step 178), and calculate the correction value (Ll) for the exposure light amount (step 180).
5 (step 182).

Correction value (Dl) of the charging voltage stored in this memory 15
Based on the exposure light amount correction value (Ll), the host computer 22 controls the corona charger 35 and the multi-AOM 18.
is controlled, and image forming processing is performed in the same manner as in the first embodiment.

Although negatively charged toner particles are used in each of the above embodiments, positively charged toner particles may also be used. In this case, the photoreceptor 34A is negatively charged.

Further, in the second embodiment, the charging voltage correction value and the exposure light amount correction value are calculated by the above method when the wet electrophotographic image forming apparatus is started up or every predetermined period of time after the start-up, and are stored in the memory 15. However, instead of this, the photoreceptor 3 after development
During idle rotation for drying in step 4, the charging voltage correction value and the exposure light amount correction value may be calculated using the above method and stored in the memory 15. In this case, FIGS. 9(A) and 9(B)
As shown, the surface potential measurement point (P) of the photoreceptor 34A
is the non-image portion 34B (the shaded portion in FIGS. 9(A) and 9(B)) of the photoreceptor 34A.

Further, in the second embodiment, the surface potential sensor 32.8
6 are disposed on the downstream side of the photoconductor drum 34 of the corona charger 35 in the rotation direction, but instead of this, one or three or more surface potential sensors 32 are disposed at a position facing the photoconductor 34A, When the surface potential measurement point (P) reaches the position facing each surface potential sensor, the surface potential measurement point (P)
) may be read into the host computer 22.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration, it is possible to accurately correct variations in the surface potential due to the light attenuation characteristics of the photoreceptor, and it is possible to obtain an excellent effect that a stable image can be formed.

[Brief explanation of drawings]

FIG. 1 is a layout diagram of each processing section constituting a wet electrophotographic image forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a photosensitive diagram of the wet electrophotographic image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a graph showing the dark attenuation characteristics and light attenuation characteristics of the human body; FIG.
Figures (A) to 4 (J) are explanatory diagrams for explaining the operation of the wet electrophotographic image forming apparatus, and Figures 5 (A) to 5 (D
) is a cross-sectional view showing the process of forming four-layer images on a photoreceptor, FIG. 7(A) and 7(B) are graphs showing the dark attenuation characteristics and light attenuation characteristics of the photoreceptor of the wet type electrophotographic image forming apparatus according to the second embodiment of the present invention, and FIG. FIG. 3 is a flowchart showing a procedure for calculating and storing correction values in a memory in a wet electrophotographic image forming apparatus according to a second embodiment. 11...Exposure lamp, 15...Memory, 18...Multi-AOM. 22... Host computer, 32.86... Surface potential sensor, 33... Lamp, 34... Photosensitive drum, 34A... Photosensitive member, 35... Corona charger.

Claims (1)

[Claims] (1) An electrophotographic image forming apparatus that forms an electrostatic latent image on the surface of a photoreceptor and forms a toner image using the electrostatic latent image, the apparatus comprising: a charging means that charges the surface of the photoreceptor at a predetermined timing; a light source that exposes the surface of the photoreceptor, a surface potential detection means that is disposed at a position facing the surface of the photoreceptor and detects the surface potential of the photoreceptor, and measurement of the surface of the photoreceptor charged by the charging means. A point is exposed to the light source, the surface potential of the measurement point after exposure is read at a predetermined timing, the surface potential of the measurement point at the time of development is estimated, and this surface potential is compared with the target surface potential at the time of development. a calculation means for determining a correction value for the exposure light amount; a storage means for storing the correction value for the exposure light amount determined by the calculation means; An electrophotographic image forming apparatus comprising: an exposure light amount control means for controlling the amount of light.