JPH04321081A - Pressure transfer device - Google Patents

Abstract

PURPOSE:To realize a small-sized and lightened pressure transfer device by pressing a recording sheet with uniform sufficient transfer pressure through the use of a back roller having a small diameter, on a pressure transfer device used for a transfer type recorder for obtaining a toner image formed on a toner image carrier, on the recording sheet by means of a pressure transfer in such a manner that the recording sheet is abutted on the toner image carrier, and pressed by a pressurizing device from the back of the recording sheet. CONSTITUTION:The pressurizing device is composed of the back roller 6 coming into contact with the recording sheet, and plural pressure rollers 11, 12, and 13, parallely arranged in the shaft direction of the back roller 6, and distributably pressed on plural load applying parts.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure transfer device used in a recording apparatus that transfers a toner image on a toner image carrier onto a recording paper by pressure transfer to obtain a toner image on the recording paper.

0002

2. Description of the Related Art Electrostatic and electrophotographic recording devices are known as devices that transfer a toner image on a toner image carrier to a recording paper by pressure transfer to obtain a toner image on the recording paper. . In these devices, by using pressure transfer, good transfer characteristics can be achieved even on recording paper with poor smoothness, and a clear toner image can be obtained on the recording paper.

0003

However, pressure transfer requires a large pressing force. Therefore, in order to obtain the necessary pressing force uniformly on the recording paper, the pressing device of the pressure transfer device must be constructed of a member having high rigidity and must be pressed with a strong spring. For this reason, the pressure transfer device has the problem of becoming larger and heavier.

This will be explained using FIG. 4. The toner image carrier 401 is made of a photoreceptor, and the recording paper 402 comes into contact with the toner image carrier 401 and is pressed from behind by a back roller 403 . The toner image previously formed on the toner image carrier 401 is pressure-transferred onto the recording paper 402 by contact pressure generated between the recording paper 402 and the toner image carrier 401 . At this time, the back roller 403 needs to press the recording paper with uniform pressure. Therefore, it is composed of a cylindrical member with a uniform diameter of 2R. When loads C and D are applied to the shaft end, a bending moment is applied to the shaft to cause it to curve. As a result, if the bending rigidity of the back roller 403 is not sufficiently high, the pressure will be small at the center, and furthermore, a gap will occur. prevent this,
In order to obtain good transfer characteristics over the entire length of the back roller 403, it is necessary to configure the back roller 403 with a large diameter roller. The magnitude of the contact pressure generated between two members that are in contact with each other under pressure depends on the contact area.If the load is the same, the contact pressure when a roller with a large radius of curvature is brought into contact with a roller with a small radius of curvature is It will be smaller than when they are in contact with each other.

Therefore, if the diameter of the back roller is made small in order to obtain the necessary contact pressure, the bending rigidity of the back roller becomes insufficient, and if the diameter of the back roller is increased, it is necessary to increase the applied load. For this reason, the pressure transfer device has become larger and heavier.

An object of the present invention is to solve this problem and to realize a pressure transfer device that is small, lightweight, and can provide sufficient transfer pressure.

[0007]

[Means for Solving the Problems] The pressure transfer device of the present invention transfers a toner image formed on a toner image carrier by bringing a recording paper into contact with the toner image carrier and applying pressure from behind the recording paper. A pressure transfer device used in a transfer type recording device that obtains a toner image on the recording paper by pressure transfer, in which the pressure device is arranged in parallel with a back roller that contacts the recording paper in the axial direction of the back roller. It is composed of a plurality of pressure rollers.

[0008]

[Example] An example of the present invention will be explained.

FIG. 1 is a perspective view of a wet type recording apparatus according to an embodiment of the present invention.

A charging device 2, an exposure device 3 consisting of a laser scanner, a developer supply device 4, an elastic drum 5 serving as a toner image carrier are arranged around a photoconductor drum 1 made of a photoconductor.
A photosensitive drum cleaning device 7, a pressure device 10, and an elastic drum cleaning device 9 are arranged in this order.

As shown in FIG. 3, the photosensitive drum 1 includes an amorphous selenium photosensitive layer 10 around an aluminum tube 100.
1 was deposited. It is configured to rotate in the direction of arrow A.

The developer supply device 4 guides a wet developer (hereinafter also referred to as developer) stored in a developer container 8 having a built-in supply pump to a coating head 202 serving as a developer supply means, and supplies the wet developer to a coating head 202 serving as a developer supply means. 1. Discharge onto the outer peripheral surface.

The configuration of the coating head 202 is shown in FIG. The coating head 202 is provided with the opening of the slit 72 facing the photosensitive drum 1 . The piezoelectric ceramic plate 121 and the metal plate 122 face each other across the microgap of the slit 72. The piezoelectric ceramic plate 121 has electrodes 123, 1 on both sides.
24, and when a high frequency voltage is applied between them, the arrow F
It expands and contracts in the direction of . In this embodiment, the piezoelectric ceramic plate 1
As 21, a PZT plate having a thickness of 1 mm is used, a wet type developer 56 is supplied to a gap of 20 μm, and the wet type developer 56 is driven at 1.8 MHz and vibrated in the direction of arrow F to fly as droplets.

The wet developer 56 consists of Label 1255 of Columbia Carbon Co., Ltd. and ethyl cellulose as pigments in a high resistance, low dielectric constant aliphatic hydrocarbon solvent (for example, Exxon Chemical Co.'s Isopar G) as a dispersion medium. It is composed of toner particles dispersed together with an organic amine charge control agent. The apparatus of this embodiment uses positively charged toner particles.

As shown in FIG. 3, the elastic drum 5 has an elastic layer 116 on a metal tube 112. This is composed of a conductive layer 113 made of conductive urethane rubber in which a conductive compound is dispersed, and an insulating layer 114 made of a fluororesin coating layer as the outermost layer, and comes into contact with the photoreceptor drum 1 under pressure. , arrow B at the same speed as photoconductor drum 1
Rotate in the direction of.

The charging device 2 is composed of an elastic conductive roller to which a predetermined voltage is applied by a high voltage power source, and charges the surface of the photosensitive drum 1.

The exposure device 3 is composed of a laser beam scanner, and forms an electrostatic latent image on the photosensitive drum 1 by controlling a laser beam according to image data from a computer and performing selective exposure. The pressure device 10 includes a back roller 6 made of a metal roller, and 3 coaxially separated and juxtaposed with each other.
The pressure roller 11, 12, and 13, a compression spring 14 that presses the pressure roller 11, and a slider 15 are constructed. (Sliders and compression springs for the pressure rollers 12 and 13 are omitted from illustration.) The slider 15 is connected to the spring receiver 16
is slidably supported inside. Pressure roller 1
The pressure roller 11 is pressed toward the back roller 6 by the force of the compression spring 14 while preventing the axial movement of the roller 1 .

The pressure roller 11 is composed of a metal roller 19 having a shaft 17 passing through it through a plastic bush 18 around the periphery. Both ends of the shaft 17 are pressed by the semicircular opening of the slider 15.

Next, the operation will be explained.

The charging device 2 charges the photosensitive drum 1 to a positive potential. In the exposure step, an electrostatic latent image corresponding to the image is formed on the photoreceptor drum 1. As a result of neutralizing the surface charge in the exposed portion, an electrostatic latent image is formed on the photoreceptor drum 1.

The toner image forming operation will be explained with reference to FIG. The surface of the photoreceptor drum 1 is uniformly charged with a positive charge and has a positive surface potential (+500 V in this embodiment), and after the exposure process, the exposure section 105 has a substantially ground potential (for example, +4
0V), and the non-exposed portion 104 is at a positive potential (+50V in this embodiment).
0V) and enters the contact portion 117 with the elastic drum 5. The contact portion 117 holds the wet developer 56 supplied from the coating head 202 . The elastic drum 5 is powered by a power source 102
Therefore, the positive potential is maintained at a value lower than the positive potential of the non-exposed area (+50 V in this embodiment). The wet developer layer 56 is
Since it has a positive charge, when it passes through the contact part 117 between the photoreceptor drum 1 and the elastic drum 5, it is directed toward the photoreceptor drum 1 in the exposed area and towards the elastic drum in the non-exposed area, depending on the electrostatic force. 5 receives an electrostatic force. As a result,
A developer layer 1 is applied to the elastic drum 5 in the area corresponding to the non-exposed area.
09 is attached. On the other hand, an electrostatic force acts on the exposed area so that the developer adheres to the photoreceptor drum 1, but due to the above potential relationship, the attraction force between the photoreceptor drum 1 and the developer is not large, so the contact area It is subjected to a squeezing action by the pressing force of 117 and is peeled off and removed. On the other hand, the carrier liquid is also subjected to a throttling action, and movement of the contact portion 117 downstream is prevented. These stay in the retention part 115 on the upstream side of the contact part 117.

The recording paper 21 is conveyed to the transfer area as the toner image is formed, and the toner image is transferred from the elastic drum 5 to the recording paper 21 under pressure by the pressure device 10. That is, the toner image is pressurized by the pressure roller 6 and generates adhesion force with the recording paper 21 due to the pressure, and the toner image is pressed by the elastic drum 5.
The image is transferred from the recording paper 21 to the recording paper 21.

Residual toner on the photosensitive drum 10 and elastic drum 5 is removed by a photosensitive drum cleaning device 7 and an elastic drum cleaning device 9.

The pressure transfer device 10 of this embodiment applies pressure to the back roller 6 in a distributed manner using three pressure rollers 11, 12, and 13. The bending rigidity of the pressure roller and the amount of bending deformation of the back roller 11 determined from the load are used as an index of the non-uniformity of the transfer pressure, and by using the analytical formula for the amount of bending displacement in the case of a beam supported at both ends, the following equation is approximated. can be evaluated.

(Transfer pressure non-uniformity) = (load) / ((distance between load application points) cubed) On the other hand, the contact area is proportional to the radius of curvature of the back roller 11, and the contact pressure is inversely proportional to the contact area. Then, the transfer pressure (peak value) is expressed by the following equation.

(Transfer pressure) = (Load) / (Back roller radius of curvature) In the case where a load is applied to both ends of the back roller as shown in the conventional example,
Comparing the case of this example, the distance between the load application points is 1/
2, the bending displacement becomes 1/8, which can be considered as an eight-fold increase in rigidity. The pressure roller 11 is the back roller 6
Considering that it is a line contact (rather than a point contact), the equivalent rigidity of the back roller configured in this embodiment can be considered to be even higher. Therefore, a roller with a small diameter is used as the back roller 6 to generate high contact pressure (transfer pressure) uniformly over the entire length with a small load. Furthermore, by pressing with a large number of back rollers, a more uniform pressure distribution can be obtained.

Furthermore, in a transfer type recording device using a liquid developer as in this embodiment, the transferred image quality depends more on the contact between the toner image carrier and the recording paper than in the case of a device using a dry developer. Sensitive to the state. For this reason, in the apparatus of this embodiment, the toner image carrier is made of an elastic material that deforms following the irregularities of the recording paper. At this time, the structure of the present invention reduces the diameter of the back roller, reduces the area of the elastic material in contact with it, and reduces the range of high contact pressure exerted by the back roller, thereby reducing the mechanical strength of the elastic material. It can reduce the load and provide high durability. Furthermore, by reducing the transfer pressure area, the recording paper passes through the pressure transfer process in a short time. Therefore, it is possible to prevent image distortion and the like due to relative displacement between the recording paper and the toner image carrier, and to improve the quality of the transferred image. Therefore, it is particularly effective to use the pressure transfer device of the present invention in a transfer type recording device using a wet developer.

[0028]

Effects of the Invention The wet recording device of the present invention generates high contact pressure with a small load by pressing the back roller with a plurality of pressure rollers arranged in parallel in the axial direction, thereby creating a compact and lightweight pressure transfer device. This has the effect that it can be realized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a wet recording device equipped with a pressure transfer device of the present invention.

FIG. 2 is a sectional view showing the operation of a coating head used in a wet recording device equipped with a pressure transfer device of the present invention.

FIG. 3 is a diagram showing the operation of forming a toner image in a wet recording device equipped with the pressure transfer device of the present invention.

FIG. 4 is a diagram illustrating a pressure transfer operation of a recording device equipped with a conventional pressure transfer device.

[Explanation of symbols]

1: Photosensitive drum 4: Developer supply device 5: Elastic drum (toner image carrier) 6
: Back roller 10 : Pressure device 11, 12, 13 : Pressure roller 14 : Compression spring 15 : Slider 16 : Spring receiver 17 : Shaft 18 : Plastic bush 19
: Metal roller

Claims (1)

[Claims] 1. A toner image formed on a toner image carrier is transferred by pressure transfer by bringing a recording paper into contact with the toner image carrier and pressing the recording paper from behind with a pressure device. In a pressure transfer device used in a transfer type recording device that obtains a toner image on paper, the pressure device is composed of a back roller that contacts the recording paper and a plurality of pressure rollers that are arranged in parallel in the axial direction of the back roller. A pressure transfer device characterized by: