JPH03170980A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To surely peel off a transfer material after the transfer from an image holding body by specifying the outside diameter of the image holding body. CONSTITUTION:A toner image on a photosensitive drum 1 is transferred to a transfer part is accordance with a rotation of the photosensitive drum 1, and on the other hand, as for paper P, its timing is taken by a resist roller 3, and it is always guided and carried to the transfer part from a stable position by an entry guide 4. In the transfer part, the toner image is fixed electrostatically to the paper P, and after the transfer, the toner image is fixed to the paper P, and the paper P is discharged to the outside of the device. In this case, the outside diameter of the photosensitive drum 1 is set to <=60mm, and desirably, set to <=54mm. In such a way, by a transfer roller, a transfer material after the transfer can be peeled off surely from the photosensitive drum by only flexural rigidity of the transfer material, and a transfer image being free from deterioration of a picture quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electrophotographic apparatus, and particularly to an electrophotographic apparatus using a transfer roller as a transfer means.

(Prior Art) An electrophotographic apparatus capable of recording an image on plain paper requires a step of transferring a toner image on a photosensitive drum to a transfer material that is an image receiving sheet.

In this step, a charged toner image formed on a photoreceptor drum is transferred to a transfer material using electrostatic force.

Methods for generating electrostatic force include a method using a corona charger and a method using a transfer roller (US Pat. No. 2,626).
No. 865).

The method using a corona charger has a simple device structure and is therefore widely used in general copying machines. In this method, corona ions are generated from the back side of a transfer material using a corona charger, and a toner image is transferred onto the transfer material by an electric field generated by the corona ions applied to the transfer material. At this time,
Even if the amount of corona ions generated from the corona charger is the same, the amount of corona ions held differs depending on the electrical resistance of the transfer material, and the strength of the transfer electric field differs. Therefore, the toner transfer efficiency also differs.

Generally, the electrical resistance of plain paper used as a transfer material changes greatly due to changes in environmental humidity. Therefore, a phenomenon in which image density changes due to changes in environmental humidity often occurs. Further, when the transfer material comes into contact with or leaves the photoreceptor drum, gas discharge occurs due to the charging of the transfer material, and the toner transferred to the transfer material is scattered, resulting in a problem that the toner image is disturbed.

On the other hand, in the method using a transfer roller, a conductive roller to which a bias voltage is applied is used to press the transfer material against the surface of the photoreceptor drum, thereby forming an electric field between the transfer material and the photoreceptor drum to form a toner image. is transferred onto a transfer material. Since this method hardly transfers the transfer material, it is possible to obtain stable transfer efficiency against changes in environmental humidity. Further, since the transfer material is conveyed while being pressed by the transfer roller, the contact state between the photoreceptor drum and the transfer material is uniform and stable, and therefore there is an advantage that toner scattering and the like are essentially less.

(Problems to be Solved by the Invention) As described above, the transfer method using a transfer roller has various advantages over the method using a corona charger, but it is difficult to completely separate the transfer material from the photoreceptor drum after transfer. However, there was a problem in that paper jams occurred, especially in low-humidity environments.

The reason why the transfer material cannot be peeled off from the photoreceptor drum after transfer is
This is because the transfer material is charged by the applied voltage and comes into close contact with the photoreceptor drum due to electrostatic force.

In the method using a corona charger, an AC charge eliminator (AC corona charger) is installed immediately after the transfer charger to remove the charge for transfer at the transfer section (the contact area between the photoreceptor drum and the transfer material). The transfer material is peeled off from the photosensitive drum by removing static electricity from the transfer material almost simultaneously. In the method using a transfer roller, it is possible to solve this problem by eliminating static electricity from the transfer material in the same way as with a corona charger, but in reality, since the transfer roller covers the transfer area, it is impossible to eliminate AC electricity. It is not possible to use static eliminating means such as electric appliances.

Another method of peeling off the transfer material when using a transfer roller is to forcefully peel off the transfer material by guiding it with tape or the like for about 10 mm on one side. There is a problem that the area becomes a non-image area.

Another problem with the method using a transfer roller is that it is affected by changes in environmental humidity.

That is, even in the method using a transfer roller, there was a problem in that in a humid environment, the electrical resistance of paper as a transfer material decreased significantly, and a large amount of electric charge was applied from the transfer roller to the paper, resulting in a decrease in transfer efficiency. .

An object of the present invention is to provide an electrophotographic apparatus that can obtain transferred images with high transfer efficiency and no deterioration in image quality.

Structure of the Invention C] (Means for Solving the Problems) The present invention includes an image carrier that carries a developer image, a transfer roller that transfers the developer image to a transfer material, and a transfer roller that transfers the developer image to a transfer material. Provided is an electrophotographic apparatus in which a transfer material is peeled from an image carrier with bending rigidity of , wherein the outer diameter of the image carrier is 60 mm or less.

In the electrophotographic apparatus of the present invention, the outer diameter of the image carrier is 54 mm.
It is particularly preferable that it is less than mm.

Further, the present invention provides an image carrier that carries a developer image, a guide member that guides a transfer material onto the image carrier, a transfer roller that transfers the developer image to the transfer material, and the guide member. An electrophotographic apparatus is provided, which includes means for applying a bias voltage having a polarity opposite to the charging polarity of the developer image to a transfer roller.

(Function) In the electrophotographic apparatus of the present invention, the transfer material after being transferred by the transfer roller is peeled off from the photosensitive drum only by the bending rigidity of the transfer material. As a result of repeated research on the releasability of the transfer material in this case, the present inventors found that the outer diameter of the photoreceptor drum greatly affects the releasability of the transfer material, and that it is possible to reduce the outer diameter of the photoreceptor drum. It has been found that the releasability increases. Then, various experiments were conducted regarding the outer diameter of the photoreceptor drum and the releasability of the transfer material, and the present invention was completed. That is, in the electrophotographic apparatus of the present invention, the outer diameter of the photoreceptor drum is 60 mm or less, so that the transfer material after transfer can be reliably peeled off from the photoreceptor drum. Further, when the outer diameter of the photoreceptor drum is 54 mm or less, the releasability of the transfer material is particularly good.

Further, in the electrophotographic apparatus of the present invention, a guide member for guiding the transfer material is provided on the image carrier that carries the developer image. Therefore, the transfer material enters the image carrier stably. Further, a bias voltage having a polarity opposite to the charge polarity of the developer image is applied to the guide member and a transfer roller for transferring the developer image to the transfer material. This prevents the electric charge applied to the transfer material from the transfer roller from leaking to the guide member when it is humid, preventing the transfer electric field from decreasing, and as a result, it is possible to transfer toner images with high transfer efficiency. It is.

(Examples) Hereinafter, various embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing the configuration of a transfer section when the present invention is applied to a laser beam printer. In FIG. 1, reference numeral 1 denotes a photoconductor drum rotating in the direction of the arrow, 2 a transfer roller that is brought into pressure contact with the photoconductor drum 1 and rotates following the photoconductor drum 1 due to this pressure contact force, and 3 a transfer roller that rotates following the photoconductor drum 1. , a pair of registration rollers 4 that sends out the supplied paper P (transfer material) at a predetermined timing; 4 is made of aluminum; a pair of entry guides that guide the paper P to the pressure contact portion of the photosensitive drum 1 and the transfer roller 2; 5 is a bias power supply that supplies and applies a bias voltage to the transfer roller 2;
indicates a post-transfer guide that guides the paper P after transfer to a fixing device (not shown).

Although not shown, it is well known that means required for repeated image formation, such as charging means, image exposure means (laser exposure), developing means, and cleaning means, are arranged around the photoreceptor drum 1. That's right.

In the laser *beam* printer shown in FIG. 1, the photoreceptor drum 1 is an organic photoreceptor (OPC) with an outer diameter of 36 mm, and rotates at a peripheral speed of 48 mm/sec. Transfer roller 2
has an outer diameter of 18 mm, and a core metal 28 made of stainless steel.
It is integrated with this core metal 28 and has a resistivity of approximately 106Ω・c.
It is composed of an elastic layer 2b made of soft conductive urethane rubber of m and a resistance layer 2C made of a fluorine-based resin, which is integrated with this elastic layer 2b and has a thickness of about 100 μm and a resistivity of about 10 9 Ω·cm. The resistance per unit area between the core bar 28 and the resistance layer 2c is approximately 107Ω/cm2. Furthermore, the rubber strength of the transfer roller 2 is approximately 10" (
JIS-A), and is softly pressed against the photosensitive drum 1 by a spring (not shown) at a constant pressure of about 30 g/cm (linear pressure per lcm in the axial direction of the roller).

The polarity of the bias voltage applied to the transfer roller 2 from the bias power supply 5 is opposite to the charged polarity of the toner image (not shown) on the photoreceptor drum, and in this embodiment, the photoreceptor is an OPC. , is charged with negative polarity and forms an electrostatic latent image by imagewise exposure using a laser optical system.
The polarity of the bias voltage is positive because the portion where the charge has disappeared is reversely developed by the negatively charged toner.

The toner image on the photoconductor drum 1 is transferred to the transfer section (the pressure contact section between the photoconductor drum 1 and the transfer roller 2) as the photoconductor drum 1 rotates, while the paper P is transferred to the transfer section (the pressure contact section between the photoconductor drum 1 and the transfer roller 2).
The timing is determined by , and the entry guide 4 always guides and conveys the paper to the transfer section from a stable position. In the transfer section, the toner image is electrostatically transferred onto the paper P. After the transfer, the toner image is fixed on the paper P, and the paper P is discharged from the apparatus.

Using the laser beam printer explained above, 30
When a peel test was conducted on various types of printer paper weighing from 100 g/m2 to 100 g/m'' under a low humidity environment of 10° C. and 20% RH, no paper jam occurred with any of the printer papers.

Next, the outer diameter of the photoreceptor drum 1 is set to 54 mm, 60 mm+
Using a laser beam printer modified to 65mm,
Peeling test was conducted under similar conditions, roller outer diameter 5 5r
With the r+m photoreceptor drum, results almost the same as those with an outer diameter of 3 mm were obtained, and with the outer diameter of 160 mm, results sufficient for practical use were obtained. However, the outer diameter is 6
With a 5mm sensing body drum, paper jams occur and the outer diameter is 60mm.
A photoreceptor drum exceeding mmN is undesirable.
It was.

Although OPCI was used as the photoreceptor in the above embodiments, it is also possible to use an inorganic photoreceptor such as Se.

FIG. 2 is a sectional view schematically showing the configuration of a copying section when the present invention is applied to a copying machine. Figure 1: Laser shown in IS
t11 of the transfer section of the beam printer! The differences from G are that the SE photoconductor tram 11 is used as the photoconductor drum, that the length of the transfer roller 2 is 28 mm, and that the transfer roller 2 is A conveyance means consisting of a conveyance belt 16 and a conveyance belt drive roller 17 is used instead of the guide 6, and a bias voltage is applied not only to the transfer roller 2 but also to the entry guide 4. The rest of the structure is the same as that shown in FIG. Although not shown in the drawings, the image exposure is not laser exposure, but is performed using reflected light from the original.

The polarity of the bias voltage applied from the bias power supply 5 to the transfer roller 2 and the entrance guide 4 is opposite to the charging polarity of the toner image (not shown) on the photoreceptor drum, and in this embodiment, the photoreceptor is Since it is Se, it is charged to a positive polarity, and an electrostatic latent image is formed by imagewise exposure of the reflected light from the original, and is developed by a toner charged to a negative polarity, so the polarity of the bias voltage is positive. It is.

The toner image on the photoreceptor drum 11 is transferred to a transfer section (photoreceptor drum 11 and transfer roller 2) as the photoreceptor drum 11 rotates.
On the other hand, the paper P is timed by the registration rollers 3, and is always guided and conveyed from a stable position to the transfer part by the entry guide 4.

In the transfer section, the toner image is electrostatically transferred to the paper P,
After the transfer, the paper P is transported by the transport belt l6 to the fixing device, where the toner image is fixed on the paper P, and the paper P is discharged from the apparatus.

Using the electrophotographic apparatus shown in FIG. 2 as described above, we evaluated the transfer efficiency when the same bias voltage as that applied to the transfer roller 2 was applied to the approach guide 4 and when the approach guide 4 was grounded. I changed the results and compared the two. That is,
First, normal temperature and humidity (20℃, 55%RH) and low temperature and low humidity (
(10℃, 20%RH), there is almost no difference between applying a bias voltage and when grounding, and the temperature is 1200~
A transfer efficiency of 85% or more was obtained at a bias voltage (transfer voltage) of 200V. In addition, the transfer efficiency is solid I! It was determined from the weight ratio of the amount of developed toner and the amount of transferred toner of the L image.

On the other hand, under high temperature and high humidity (30° C., 85% RH), a large difference in transfer efficiency was observed between when a bias voltage was applied and when it was grounded.

Although Se is used as the photoreceptor in the embodiment shown in FIG. 2, it is also possible to use OPC.

FIG. 3 is a graph showing the transfer efficiency versus bias voltage (transfer voltage) when bias voltage is applied to the approach guide 4 and when it is grounded at high temperatures (30° C., 85% RH). It is.

As is clear from Fig. 3, when the approach guide 4 is grounded, the transfer efficiency is extremely low, whereas when a bias voltage is applied, the transfer efficiency is different between normal temperature and normal humidity and low temperature and low humidity. Exactly the same properties were obtained.

Figure 4 and '! Figure J5 is a sectional view showing a copying machine according to still another embodiment of the present invention. The copying machine shown in FIG. 4 is an example in which transfer is performed above the photosensitive drum 11.
Reference numeral 26 indicates a post-transfer guide. FIG. 5 shows an example in which transfer is performed on the side of the photosensitive drum 11. In either case, the same effects as the copying machine shown in FIG. 2 can be obtained.

Although various embodiments of the present invention have been shown above, the present invention is not limited to these. For example, the material, structure, and manufacturing method of the transfer roller may be any as long as a transfer roller with appropriate elasticity and electrical resistance can be obtained. Moreover, the shape and structure of the entry guide may be of any type as long as it can exhibit the same effect. Furthermore, the image carrier is not limited to a photosensitive drum, and an ion projection head using a dielectric drum may be used to form an electrostatic latent image.

[Effects of the Invention] As explained above, according to the present invention, by setting the outer diameter of the image carrier to 60 mm or less, the transfer agent after transfer can be removed from the image carrier without using any special peeling means. The paper can be removed reliably and paper jams can be prevented. Furthermore, by applying the bias voltage applied to the transfer roller to the entry guide as well, it is possible to prevent a decrease in transfer efficiency in the case of high humidity.

That is, according to the electrophotographic apparatus of the present invention, it is possible to obtain a transferred image with high transfer efficiency and no deterioration in image quality, and it can be suitably applied to copying machines, printers, and the like.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a transfer section of a laser printer according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a transfer section of a copying machine according to another embodiment of the present invention, and FIG. Graphs showing the relationship between bias voltage and transfer efficiency of a copying machine, and FIGS. 4 and 5 are cross-sectional views showing a transfer section of a copying machine according to still another embodiment of the present invention. 1... Photosensitive drum, 2... Transfer roller, 3...
Registration roller, 4... Entry guide, 5... Bias power supply, 6... Post-transfer guide

Claims (2)

[Claims] (1) An electrophotographic device that includes an image carrier that carries a developer image and a transfer roller that transfers the developer image to a transfer material, and that peels the transfer material from the image carrier using the bending rigidity of the transfer material. An electrophotographic apparatus, wherein the image carrier has an outer diameter of 60 mm or less. (2) An image carrier that carries a developer image, a guide member that guides a transfer material onto the image carrier, a transfer roller that transfers the developer image to the transfer material, and the guide member and the transfer roller. and means for applying a bias voltage having a polarity opposite to that of the developer image.