JP2964515B2 - Electrostatic latent image forming body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image forming body that forms a latent image by a local difference in charge state, and more particularly to an improvement in latent image forming accuracy. Things.

2. Description of the Related Art An electrostatic latent image forming body has a photosensitive layer that is chargeable and that becomes photoconductive upon exposure. This photosensitive layer usually has an insulating property, but when exposed to light, electrons and holes can move, the charge on the photosensitive layer surface is canceled out, and a local difference in the state of charge occurs on the photosensitive layer surface, resulting in static electricity. An electrostatic latent image is formed. A photosensitive drum used in an electrophotographic apparatus is one example. This photosensitive drum is formed by forming a photosensitive layer on the surface of a conductive substrate, and after uniformly charging the photosensitive layer,
When exposure is performed in accordance with image data, electrons and holes are generated in the photosensitive layer, and combined with positive ions or negative ions on the surface of the photosensitive layer to form an electrostatic latent image corresponding to an image to be recorded. The electrostatic latent image is developed by attaching a toner having a charge opposite to the surface charge to the surface of the photosensitive layer, and an image is recorded.

However, when the photosensitive layer is exposed to light and produces photoconductivity,
Electrons or holes may spread and move in the photosensitive layer from the portion where the light hits. For this reason, there is a problem that the charge is canceled even in a portion other than the portion of the photosensitive layer surface to which the light is applied, and an electrostatic latent image which does not correspond to the exposure pattern with high accuracy is formed.

An object of the present invention is to provide an electrostatic latent image forming body and an electrostatic latent image forming apparatus capable of forming an electrostatic latent image accurately corresponding to an exposure pattern.

Means for Solving the Problems According to the first aspect of the present invention, in order to solve the above-mentioned problems, a photosensitive layer of an electrostatic latent image forming body is formed by a plurality of photosensitive layers separated by an insulator crossing the surface thereof. In addition, the insulator shall contain a photo-curable resin and a sensitizing dye that increases the sensitivity of the photo-polymerization reaction of the photo-curable resin, and the sensitizing dye provides light shielding. It is characterized by the following.

The invention according to claim 2 is characterized in that each of the plurality of photosensitive cells includes a charge generation layer that generates a charge by exposure, and a charge transport layer that transports the charge generated by the charge generation layer. It is characterized by the following.

According to a third aspect of the present invention, there is provided an electrostatic latent image forming apparatus including: an electrostatic latent image forming body; and an exposure device that irradiates the electrostatic latent image forming body with an exposure beam to expose the electrostatic latent image forming body. The photosensitive layer of the body is composed of a large number of photosensitive cells separated by an insulator crossing the surface thereof, and the insulator has a light-shielding property, and the size of the photosensitive cell is exposed. It is characterized in that it is smaller than the beam exposure spot.

Function and Effect of the Invention In the electrostatic latent image forming body according to the first aspect of the present invention, since the photosensitive layer is composed of a large number of photosensitive cells insulated by an insulator, electrons or holes are exposed to the photosensitive cells to which they belong. It moves only inside and cancels the charge on the surface of the photosensitive cell. Electrons or holes do not move to portions of the photosensitive layer other than the portions where the light has hit, and do not cancel the charges. In addition, since the insulator has a light-shielding property, light irradiated on each photosensitive cell is prevented from being transmitted through the insulator and diffused into an adjacent cell due to reflection inside the photosensitive cell. The light-shielding property of the insulator can be obtained by using a sensitizing dye that increases the sensitivity of the photopolymerization reaction of the photocurable resin, and an electrostatic latent image corresponding to the exposure pattern with high accuracy can be obtained at low cost.

In the electrostatic latent image forming body according to the second aspect of the present invention, each of the plurality of photosensitive cells has a charge generation layer that generates a charge by exposure, and a charge transport that transports the charge generated by the charge generation layer. When exposed to light, the charge generation layer generates charges, and the generated charges are transported by the charge transport layer to form an electrostatic latent image. Therefore, it is not necessary to charge the reverse side of the photosensitive layer with a charge having a polarity opposite to that of the front side, and the configuration of the electrostatic latent image forming apparatus can be simplified accordingly.

In the electrostatic latent image forming apparatus according to the third aspect of the present invention,
The size of the photosensitive cells is made smaller than the exposure spot of the exposure beam, and the insulator that separates many photosensitive cells has a light-shielding property, preventing the charge and light of each photosensitive cell from spreading to adjacent photosensitive cells. Therefore, while increasing the exposure spot of the exposure beam, high resolution is obtained by exposing only the necessary portion of the photosensitive layer as much as possible, compared with the case where the resolution is improved by reducing the exposure spot of the exposure beam, An electrostatic latent image corresponding to the exposure pattern with extremely high precision is formed at low cost.

Embodiment Hereinafter, a case where the present invention is applied to a photosensitive drum of a laser printer will be described in detail with reference to the drawings.

In FIG. 4, reference numeral 10 denotes a housing of the laser printer device, and a laser scanner unit 12 is provided at an upper portion in the housing 10. Laser scanner unit 12
Has a semiconductor laser, a collimator lens, a polygon mirror, etc., and as shown by a dashed line, a laser beam emitted from the unit 12 is reflected by a reflection mirror 14 and passes through a slit 16 to form an electrostatic latent image forming body. The photosensitive drum 18 is exposed. The photosensitive drum 18 has a cylindrical shape, is rotatably supported by the housing 10 by a shaft 20, and is rotated by a driving device (not shown), and is uniformly exposed by a pre-exposure lamp 22 prior to exposure. In addition, the surface is negatively charged by the corotron 24. The laser beam is emitted according to image data created in advance, and an electrostatic latent image corresponding to an image to be recorded is formed on the surface of the photosensitive drum 18 depending on the presence or absence of electric charge. The formation of the electrostatic latent image will be described later. The electrostatic latent image formed on the photosensitive drum 18 is developed by applying a toner 30 by a developing device 28, and the toner image obtained thereby is transferred to a recording paper 34 charged by a transfer corotron 32, The recording paper 34 on which the image is fixed is discharged to a paper discharge tray 40. Reference numeral 42 denotes a cleaner for removing the toner remaining on the surface of the photosensitive drum 18 after the transfer of the toner image to the recording paper 34.

As shown in FIG. 3, the photosensitive drum 18 has a cylindrical shape, and has a photosensitive layer 52 on the surface of a conductive substrate 50 made of aluminum.
Is formed. The photosensitive layer 52 is composed of a large number of photosensitive cells 56 separated by a grid 54 orthogonal to the surface thereof, as schematically shown in FIG. As shown in FIG. 2, the photosensitive cell 56 has a charge generation layer 58 and a charge transport layer 60, and the lattice body 54 is made of a synthetic resin as described later.
It has light-shielding properties and insulating properties. Also,
This laser printer device has a resolution of 300 DPI, a minimum spot diameter of the laser beam is 85 μm, and the lattice of the lattice body 54 is 1 μm.
The side is a 28 μm square.

Next, the structure of the photosensitive drum 18 will be described. Although the photosensitive drum 18 is actually cylindrical, it is shown in a rectangular shape in the following description. First, as shown in FIG. 5, one surface of the conductive base material 50 is immersed in a tank filled with a photocurable resin to form a photocurable resin tank 62. As the photocurable resin, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate and the like are used. This photocurable resin contains a polymerization initiator and a sensitizing dye. As the polymerization initiator, diaryl ketone derivatives such as benzophenone, miheras ketone, benzoyl methyl ether, isopropylxanthone and isopropylthioxanthone, benzolylalkyl ether, and ketocoumarin compounds are used. Ethylene blue or the like is used as a sensitizing dye. The sensitizing dye is added to increase the sensitivity of the photopolymerization reaction of the photocurable resin and to provide a light-shielding property, and a dye that prevents transmission of light of that wavelength is selected according to the wavelength of the laser beam. For example, if light at 660 nm (red) is used for exposure, methylene blue is used to absorb the exposure light.

Next, a mask 64 is put on the photocurable resin layer 62 as shown in FIG. The mask 64 is formed of a lattice-like portion 66 which has a lattice shape and allows transmission of light, and a large number of light-shielding portions 68 which are square and surrounded by the lattice-like portion 66 and do not transmit light. . Therefore, when light is applied to the photo-curable resin layer 62 with the mask 64 covered, only the portion corresponding to the lattice-shaped portion 66 is cured, and a cured portion 70 is formed as shown in FIG. Subsequently, the photocurable resin layer 62 is washed,
Rinse the uncured resin covered with. As a result, as shown in FIG. 8, a grid 54 having a light-shielding property and an insulating property is formed on the conductive substrate 50.

The conductive base material 50 on which the lattice body 54 is formed as described above is combined with a condensed polycyclic pigment such as a perylene-based or anthantrone-based pigment or an azo pigment as a carrier-forming material, and a polyester or phenol resin as a binder resin. Immerse in a tank filled with a mixture with petital resin, etc.
A container-like charge generation layer 58 is formed as shown in FIG.

Then, it is further immersed in a tank filled with a mixture of a heterocyclic, hydrazone or arylamine carrier transport material and a binder resin such as polycarbonate, polyester or methacrylic resin. As a result, the space in the charge generation layer 58 is filled with the carrier transport material as shown in FIG. 10, and the surface is subjected to finish processing and dried, as shown in FIG. 11, on the conductive base material 50. As a result, the photosensitive drum 18 having a large number of photosensitive cells 56 separated by the lattice 54 is obtained.

The photosensitive drum 18 formed as described above is
, Negative ions are attached to the surface as shown in FIG. When the photosensitive drum 18 is exposed according to the exposure pattern, the laser beam is absorbed by the charge generation layer 58 of the photosensitive cell 56 to which the laser beam has been applied, as shown in FIG. 13, and electron-hole pairs are generated. The electrons escape through the conductive substrate 50, while the holes move through the charge transport layer 60 and combine with the negative ions on the surface of the photosensitive drum 18 to cancel the charge. At this time, since a large number of photosensitive cells 56 are separated from each other by a lattice body 54, which is a light-shielding insulator, light incident on the photosensitive cells 56 at the time of exposure propagates only within the photosensitive cells 56 and travels through the charge generating layer. The holes generated by the absorption by the holes 58 move only in the charge transport layer 60 of the photosensitive cells 56 and move to the photosensitive drum 18.
It will bind to negative ions on the surface. Due to the diffusion of light, light is absorbed in a portion other than the portion of the photosensitive layer 52 which has been irradiated with light, generating an electron-hole pair or causing the charge generation layer 58
The generated holes do not move to a portion other than the portion where the light that caused the holes hits and cancel out the electric charge, and only the photosensitive cells 56 where the light hits as shown in FIG. As a result, the electrostatic latent image corresponding to the exposure pattern is formed on the surface of the photosensitive drum 18. In particular, in the photosensitive drum 18, one of the photosensitive cells 56
Since the length of each side is set to one third of the spot diameter of the laser beam, the spread of light and the movement of holes are small, and a highly accurate electrostatic latent image can be obtained.

FIG. 15 shows the potential of the photosensitive drum 18 at the time of exposure when a stripe pattern having a width of one dot is printed at every other dot. As is clear from this figure, the potential of the photosensitive cell 56 irradiated with the laser beam 72 increases due to the cancellation of the electric charge, whereas the potential of the photosensitive cell 56 between the adjacent laser beams 72 is the initial potential before the exposure. And an electrostatic latent image corresponding to the exposure pattern with high accuracy is formed.

On the other hand, in the conventional photosensitive drum 80, as shown in FIG. 16, a photosensitive layer 84 which is not separated by a light-shielding insulator is formed on a conductive base material 82, and a laser beam 72 is applied every other dot. Even if the light is diffused, the holes spread and move as well, and the charges are canceled out in portions other than the portions of the photosensitive layer 84 to which the light is applied, so that the potential is increased. As a result, the potential difference between the portion where the laser beam 72 hits and the portion where the laser beam 72 does not hit is small, and toner adheres to the portion where the laser beam 72 does not hit during development, and an unclear stripe pattern is recorded.

As described above, according to the laser printer of this embodiment, an electrostatic latent image corresponding to an exposure pattern can be formed with high accuracy, and even a fine line or a fine figure can be clearly recorded. The effect of improving the quality is obtained.

Although the photosensitive cells have a square shape in the above embodiment, they may have other shapes such as a triangular shape and a hexagonal shape.

Furthermore, the electrostatic latent image forming body is not limited to the drum shape, but may be a belt shape or a plate shape.

Further, in the above embodiment, the electrostatic latent image forming body is formed by forming the photosensitive layer on the conductive base material, but may be formed only by the photosensitive layer. In this case, when the photosensitive layer is charged, the electrostatic latent image forming body is supported on a conductive support, and positive ions and negative ions are respectively attached to the opposite surfaces. These positive ions or negative ions can move in the photosensitive layer by exposure, and combine to cancel the electric charge to form an electrostatic latent image.

Furthermore, the present invention can be applied to an electrostatic latent image forming body of an electrophotographic apparatus other than a laser printer apparatus and an electrostatic latent image forming body used for an application other than the electrophotographic apparatus.

In addition, without departing from the scope of the claims, the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a photosensitive drum of a laser printer according to one embodiment of the present invention. FIG. 2 is an enlarged front sectional view showing a main part of the photosensitive drum. Third
The figure is a perspective view of the photosensitive drum. FIG. 4 is a front sectional view schematically showing the laser printer. Fifth
FIG. 6, FIG. 7, FIG. 8, FIG. 9, FIG.
FIG. 11 is a diagram for explaining the manufacturing process of the photosensitive drum.
FIG. 12 is a view showing a state in which the photosensitive drum is charged, FIG. 13 is a view showing exposure, and FIG. 14 is a view showing a state in which an electrostatic latent image is formed. FIG. 15 is a diagram showing a potential when the photosensitive drum is exposed. FIG. 16 is a diagram showing a potential when a conventional photosensitive drum is exposed. 18: photosensitive drum, 50: conductive substrate 52: photosensitive layer, 54: lattice 56: photosensitive cell, 58: charge generation layer 60: charge transport layer

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Claims (3)

(57) [Claims] 1. An electrostatic latent image forming body having a photosensitive layer that is chargeable and generates photoconductivity upon exposure, and forms an electrostatic latent image, wherein the photosensitive layer intersects the surface of the photosensitive layer. In addition to being composed of a large number of photosensitive cells separated by an insulator, the insulator contains a photocurable resin and a sensitizing dye that increases the sensitivity of a photopolymerization reaction of the photocurable resin. An electrostatic latent image forming body characterized in that a light-shielding property is imparted by a dye. 2. A method according to claim 1, wherein each of said plurality of photosensitive cells includes a charge generating layer for generating a charge by exposure and a charge transporting layer for transferring the charge generated by said charge generating layer. The electrostatic latent image forming body according to claim 1, wherein 3. An electrostatic latent image forming body having a photosensitive layer that is chargeable and generates photoconductivity upon exposure, and on which an electrostatic latent image is formed, and an exposure beam is applied to the electrostatic latent image forming body. An exposure device that irradiates and exposes the photosensitive layer, wherein the photosensitive layer comprises a large number of photosensitive cells separated by an insulator crossing the surface thereof, and the insulator is An electrostatic latent image forming apparatus having a light shielding property, and wherein the size of the photosensitive cell is made smaller than the exposure spot of the exposure beam.