JPS6014270A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording device (such as an electrophotographic device or an electrostatic recording device).
(for example, copying machines, facsimile machines, laser beam printers, etc.), specifically in rotating bodies that undergo heat treatment, pressure treatment, or heating and pressure treatment to fix objects to be fixed, such as unfixed single-sided images, on recording materials. The present invention relates to an image forming apparatus having a fixing device that extremely effectively prevents offset of an object to be fixed and image part blur.

Conventionally, a method for preventing the offset phenomenon of a rotating body such as a roller or belt that performs a fixing action is disclosed in Japanese Patent Application Laid-Open No. 55-5'53.
It is disclosed in Japanese Patent Application Laid-open No. 74 and Japanese Patent Application Laid-Open No. 55-96970. A system in which a corotron applies a bias voltage of the same polarity as the fixed object supported by the copy paper, such as a toner image, to a roller that comes into contact with the image surface of the recording material, such as copy paper.
Alternatively, it is known to apply a bias voltage of opposite polarity to the roller on the side opposite to the toner image area.

Other proposals include a method in which the material of the roller on the side that comes into contact with the toner image area of the recording paper is made of a triboelectrostatic type material that is abrasively charged with the toner; This is a method of adding positively charged materials such as. However, with this method, no method has yet been found that effectively obtains the offset prevention effect while maintaining various physical properties as in the first method described above. That is, the second proposal has not been put into practical use.

On the other hand, in recent years, miniaturized image forming apparatuses (for example, printers, copiers, microrecorders, and laser beam recorders) have become important in terms of material and cost savings.

The inventors have found that in such a small device, applying the above-described prevention method results in an extremely increased occurrence rate of offset. In particular, cleaning of these offset toners must be improved compared to conventional methods, which causes many problems.

The purpose of the present invention is to solve this problem, which required a great deal of cost and time to find out the cause of such a problem, and which can significantly prevent the occurrence of offset and improve the formation An object of the present invention is to provide an image forming apparatus that can stably obtain images.

The present invention utilizes a unit that forms a toner image of a specific polarity on one surface of a recording material by giving the recording material a polarity opposite to that of the toner image (for example, a transfer charger applies a charge opposite to that of the toner image to the recording material). The charging polarity of the rotating body that is in contact with the back side of the toner image surface for a recording material whose length is greater than the distance between the toner image transfer section (where the toner is applied, etc.) and the fixing section that fixes the toner image onto the recording material. It is characterized in that it has a charge control means for making the polarity the same as the specific polarity of the toner image on the recording material.

The present invention can prevent image disturbances (for example, toner scattering) that occur during fixing to obtain high-quality images, and can also satisfactorily prevent offset and improve mold release properties during rotation itself.

Hereinafter, the present invention will be explained in detail while explaining the present invention in detail.

FIG. 1 is a side view of the main parts of an electrophotographic copying apparatus to which an embodiment of the present invention is applied.

The apparatus shown in the figure is a copying apparatus using an electrophotographic method, in which a photosensitive drum 2 having a photoconductive layer provided on a conductive drum base is supported rotatably in the direction of the arrow. Around this drum 2, corona dischargers 3,
A short focus optical element array 4, a developing device 5, a transfer corona discharge device 6, and a cleaning device 7 are provided. In this apparatus 1, a photosensitive drum 2, a discharger 3, a developer 5, and a cleaner 7 are integrally supported as a process kit 20 by a casing 8 made of electrically insulating and opaque black AB8 resin. There is. This casing 8 is guided and supported by guide rails 9 fixed to the main body, and is attached to and removed from the main body.

The process kit mentioned above includes the photoconductor, which has a limited number of repeated uses due to deterioration, the developer, which handles toner that needs to be replenished due to consumption, and the cleaning of the discharge electrode due to toner and oxide adhesion. One or more of the necessary process means such as a corona discharger are combined to form a structure independent of the main body, and this structure is detachably attached to the main body and is called a process kit.

For example, in the above-mentioned copying machine, the photosensitive drum is N
The case where the mold (positive) 0PC1 & light body is used is described. The surface of the photosensitive drum 2 is uniformly charged with a negative polarity by the corona discharger 3, and then the original is placed on the reciprocating document table io (the optical system may be relatively movable) at the top of the main body of the apparatus. The drum 2 is exposed to the reflected light through the element array 4 to form a negative latent image. The formed negative latent image is developed with positive toner in the developing device 5, and the developed image is transferred onto a transfer material such as plain paper by a transfer corona discharger 6 of negative polarity. The transfer material is supplied one sheet at a time to the transfer material supply tray 12 by the operator's manual operation, and then transferred to the transfer material supply tray 12 by the conveyance roller 13.
and is conveyed to the transfer section via the timing roller 14.

The transfer material that has been transferred is separated by a separating means 15,
The paper is sent to a fixing device 17 via a moving path 16 and fixed thereon, and then sent out onto a paper ejection tray 19 via an ejection roller 18 . Furthermore, the distance l between the transfer section 6 and the fixing section 17 is the transfer material (
In this example, the length is set to be sufficiently shorter than the length (Japanese Industrial Standard B5 size, which is a frequently used size). As a minimum condition, it is set that there is at least a period when the transfer material PLt stays in the transfer section and the fixing section at the same time. At least when the transfer material is held by the fixing device 17, its rear end is charged with a polarity opposite to that of the toner image. Further, in this example, the total process speed was set to 60 mm/h.

FIG. 2 is a perspective view showing the attachment/detachment relationship between the main body of the apparatus and the process killer (20). This is done by drawing out 8. Arrow 22 in the diagram
indicates the direction of movement of the housing when the process kit is attached or removed.

3 is an enlarged view of the fixing device of this embodiment. 2) l-1: outer diameter 24-ttrm, wall thickness 1
．． 6 tMI aluminum core bar 23. On top, 30 μm thick P
FA coating 23. Fusing roller without flange,
24 is a heat-vulcanized silicone sponge with a wall thickness of 4 mm and a sponge hardness (ASKI (It C) of 20 degrees) on an aluminum core bar with an outer diameter of 14 m+.It is completely covered, and on its outer periphery, a wall thickness of 111111 is used. % This is a pressure roller coated with room temperature vulcanizable silicone rubber 24. with a rubber hardness of 50 degrees (JIS hardness).

Both rollers 23 and 24 are pressed against each other at a total pressure of 5 Kf, and rotated together while being pressed during copying.

The fixing roller 23 is %1. A 1KW halogen lamp 25 is installed inside, and the output of the halogen lamp 25 is controlled by a temperature detection element 26 such as a thermistor that is in contact with the fixing roller 23 and a temperature control means (not shown), so that the surface of the fixing roller is controlled. The temperature is adjusted to the optimum temperature for fusing.

Moreover, by adopting the configuration of this embodiment, it is possible to shorten the time from when the power is turned on until the surface temperature of the fixing roller reaches the temperature at which the toner can be melted to about 15 seconds. . Therefore, even if the power is turned off at the end of the copy operation, the next copy can be made without waiting (on-demand type device).

27 is a positive characteristic type charge control mold release agent 2 which will be described in detail later.
7. It is an application member that also serves as a cleaning member and contains heat-resistant felt 27 such as Nomex or Teflon.
．． It consists of

A transfer material P such as plain paper carrying a positive (positive polarity) toner image T is conveyed between both rollers, and after the toner image T is fixed, a separation claw 28 is placed in contact with or close to the roller surface. ．． .

282 to ensure separation.

At this time, as is clear from FIG. 3, the fixing roller 23 is arranged so as to be in contact with the supporting surface side of the unfixed toner image T of the transfer material P, and the pressure roller 24 is arranged so as to be in contact with the back surface side of the transfer material P. .

In this embodiment, since the toner image T is of positive polarity and the transfer corona discharger 6 is of negative polarity, the transfer material P enters the fixing device I7 while being substantially tinged with negative polarity by the charger 6. do.

However, in the fixing device 17, since the rollers 23 and 24 are both rotating in pressure contact, the surfaces of each roller form a predetermined surface potential as appropriate. When the transfer material P entered the fixing device 17 in this state while being affected by the discharge device, an extremely large amount of toner offset occurred.

As a result of intensive research to solve this problem, the inventors of the present invention have found that a means such as a transfer corona discharger 6 that continues to provide a substantially large polarity to a toner image support material such as the transfer material P acts. It has been found that a major factor is that the recording material supporting the toner image is held between a pair of rollers of the fixing device under the condition that the toner image is being held.

In other words, this offset phenomenon is caused by the roller pair and the recording material (
The present invention was achieved by focusing on the fact that this problem can be solved by controlling the charge to an appropriate balance, since this is caused by the strong electrostatic force caused by the surface potential of paper (paper, etc.). That is, the present invention has means for substantially charging the recording material so that the recording material supports the toner image and prevents offset.

This can be achieved by stripping the roller surface of the fixing device, applying a charge-controlling release agent, or treating the roller surface, or adding a charging agent or a charge-controlling release agent to the inside of the roller. There are some that add or have the same amount, and the toner offset is drastically reduced due to the charged electrostatic force.

More specific examples will be given below.

(Example 1) In FIG. 3, an application member 27 made of Nomex felt
Inside, a charge control mold release agent 27. Dimethyl silicone oil (Shin-Etsu Chemical Co., Ltd. KF96H) with a viscosity of i, o, o o o as at 25°C and j~, a viscosity of 70C8 at 25°C and an amine equivalent h1
Amino-modified silicone oil with a weight of 830 (Shin-Etsu Chemical Department K)
1l1''857, a positive characteristic type (to be described later), was mixed with 11 parts (-) and impregnated with 1.51.

Under the above conditions, using A4 plain paper as a toner image support material, a toner image of 15o7η was formed per sheet (conditions that are very likely to cause offset) and was fixed. The offset ratio was less than 0.005 and no problems occurred.

The toner offset rate referred to here is as follows.

Also, when I investigated the surface potential during paper passing, paper P was -1800V, fixing 0-ra 23flj:, +250V.
, /JII pressure roller 24u, +700v.

In other words, in this embodiment, by applying a positive charge-controllable release agent from the fixing roller side, the fixing roller and rotation are pressed against each other from the start of the copying operation until the copy paper reaches the fixing section. The positive charge-controlling mold release agent can also be transferred to the pressurizing roller to reverse the polarity of frictional charging between the pressurizing roller and the paper, which tends to be negatively charged. Therefore, while being subjected to transfer corona, the negative charge on the copy paper being conveyed between both rollers is not reduced.More precisely, due to the friction zone between the fixing roller and the pressure roller,
By strengthening the negative charge on the copy paper, we were able to increase the electrostatic attraction between the negative charge on the copy paper and the toner image on the copy paper. . As a result, the toner offset to the fixing roller was minimized, and a high-quality copy was obtained in which image disturbances such as blurring that occurred during fixing were prevented.

In the configuration of this embodiment, the potential of the pressure roller is relatively small because the speed is slow and the pressure contact force of both rollers is small, and the distance between the transfer section and the fixing section is small. Since it is sufficiently short compared to the majesty, the electric potential of the paper is relatively large even in the fixing section due to the influence of the transfer corona. Toner offset due to p'R force is vF for the surface potential of the regular roller, and ■ for the surface potential of the paper.

Then, the contrast between the two is Suwachi (Vp −
VF) Te, large, t: So approximation Te#, (VP-V,,)
The larger the value of is minus full, the smaller the toner offset is, and when (Vp-Vrr□) is on the plus side by as much as of, the toner offset increases dramatically.

In (Example 1), the fixing roller was positively charged by the charge-controlling release agent, and both rollers were in the positive order in the frictional charging series with respect to the copy paper, so that the fixing roller was not attached to the copy paper. Because the copy paper is charged to a high negative potential due to the injection of negative charge and the injection of negative market from the negative transfer corona, the potential contrast (VP-VF) is -2050V, and the positively charged toner is relies on electrostatic force to adhere closely to the copy paper, making it possible to drastically reduce offset.

In Example 1, the effect of the charge control release agent impregnated into the coating member remained even after 5,000 copies were made, and toner offset was less than 0.005%. .

Preferably, the surface of the moving path 16 is also coated with the recording material.
) It is preferable to configure the recording material so that it is charged to a potential having a polarity opposite to that of the recording material.

As the charge control mold release agent 17 described above, one that has mold release properties and is located in a higher order than that of the recording material in the triboelectrification series can be used.

For example, as a charge control mold release agent, dimethyl silicone oil in which some of the methyl groups have been replaced with amino groups VcIif (hereinafter referred to as amine-modified silicone oil) can be used, as shown in Example 1. be.

An example of the skeleton structure of amine-modified silicone oil is shown below.

+ ) A type ti) B type Examples of commercially available B type products include Kp3g3. ■cFss7. KF859(
Both products are manufactured by Shin-Etsu Chemical Co., Ltd.), and Atype products include, for example, KF864. X-22-3801 (all manufactured by Shin-Etsu Chemical KK) 8FB 4.1.7 (
)-resilicon oil), etc.

In addition, although dimethyl silicone oil is used as the base silicone oil in h)a, it is not limited to this, and mold release agents such as methylphenyl silicone oil and fluorosilicone oil can also be used.

In addition to the above, amide-modified silicone (for example, KF 3935.
(manufactured by Shin-Etsu Chemical), silicone diamine (for example, X-
22-161, Shin-Etsu Chemical M), etc. can also be used.

Alternatively, a silicone oil treated with a silane coupling agent containing amine 7 groups shown below may be used.

6 Go! i go ml'' go po ho go go go (H,C
O), Si CH2C)-I, CH, -NHCI-
1゜1 (t-i,co)s si C14,CH2CJ-I
2-NHCH2H, CNl-ICl3. Chi, C.I.
-I, Si (QC2H,).

H2N(CH2CH2NH), CH2Cl, CH,5i
(OCH,), H,C-NHCONI-1c, H,8
i (OCH,)s Furthermore, the alkoxy group of the above compound may be a chlorine atom. These silane coupling agents may be used alone or in a mixed system of two or more. The charge control mold release agent described above can be used alone, but as shown in Example 1, It is also possible to use conventional mold release agents such as dimethyl silicone oil, methylphenyl silicone oil, fluorosilicone oil, etc., which are added to commonly used mold release agents. In this case, in addition to being able to arbitrarily select properties such as thermal stability and viscosity,
By relatively reducing the amount of relatively expensive amine-modified oil used, it is also possible to lower the cost. for example,
5F8417 (amino equivalent 3500/amino (trout 0.
5. Toray Silicone KK) dimethyl silicone oil KF96H (viscosity 10,000C8 at 25°C)
) (It was confirmed that a sample in which 10 wt% was added to Shin-Etsu Chemical Co., Ltd. 1 (manufactured by I) can be applied to the present invention as a charge control mold release agent.Of course, the lower limit of the amount added is limited to the above value. By appropriate combination, it is possible to use it as a charge control mold release agent even in a small amount.

In addition to the above-mentioned amine-modified silicone oil, charge control mold release agents that can be applied to the present invention include, for example, a charge control agent having the structural formula shown below added to a mold release agent such as dimethyl silicone oil. Anything is fine.

, NOT, -3(OLOA, 313) R is polybutene. 0LOA5080 I1 O Nylon 12 O Duomin (Lion Armor Co.) O Armac CR R is an alkyl group J, fatty acid monoethanolamide R, -CO-NH-OH7CH20H For example, I7 is a H6 fatty acid such as C1 to C87 lauric acid Jetanolamide For example, as R, lauric acid of CIl to C17, etc. The amount of these added is 1 per 100 parts by weight of silicone oil.
It is effective even with a very small amount of about 0-3 parts by weight.

(Comparative Example 1) Application member 27. As a mold release agent, dimethyl silicone oil (Shin-Etsu Chemical Exhibition KF96H) with a viscosity of 10 and ooocs at 25°C, which has been commonly used in the past, was used.
When paper was passed in the same manner as in Example 1 with the same configuration as in Example 1, except that a material impregnated with 1.59 Toner offset occurred to the extent that 272 could not be retained, and toner that could not be cleaned adhered to the copy paper, resulting in a significant deterioration in copy quality. In addition, the copy image quality was also inferior to that of Example 1, since the fixing roller was offset in a circular manner around the image area.

In addition, the surface potential of copy paper when paper is passed is -450V,
Fixing o-rubber 300V, pressure o-rubber 9o.

V, and the potential contrast (VP-VF) is -15
Although the potential was still negative at 0 V, a toner offset of 12 times or more occurred as compared to the example.

(Example 2) In Example 1, when the transfer corona discharger 6 of negative polarity is used for the positive toner image T, the potential of the roller pair is set to the opposite polarity with respect to the paper, and the polarity of the fixing roller 23 and the toner image are changed. The pressure roller 24 applies a positive frictional charge to the paper P by making the polarity the same as that of the paper P, but the second embodiment shows the opposite case.

That is, a second embodiment is a case where a positive transfer corona discharger 6 is used for a negative toner image T. In this case, a negative charge control release agent and a negative charge agent were used as described above (Example 1) so that the potential of the roller pair was opposite to the paper.
You can give it like this.

Further, in Example 1.2, the charge controllable release agent was applied from the fixing roller side, but the same effect can be obtained even if it is applied from the pressure roller side.

As described above, in the present invention, the distance between the transfer section and the fixing section is sufficiently short compared to the length of the copy paper (substantially even in the fixing section, the toner image support material as the recording material is This method is effective for image forming apparatuses in which the potential of the transfer material is relatively high, and has an especially excellent offset prevention effect particularly when the surface potential of the pressure roller is relatively low. In this embodiment, if the surface potential of the pressure roller is three times or less compared to the paper potential, the potential of the pressure roller is ignored as described above, and the electrostatic force of the toner on the roller is ignored. The magnitude of the offset can be indicated by the potential contrast (vP-vv) between the paper and the fixing roller. In addition, configurations where the surface potential of the pressure roller is low include those where the speed is slow and/or the pressure contact force between both rollers is small (generally common in low-speed machines), and where the surface potential of the pressure roller is low. The insulation coating such as silicone rubber or Teflon is thin,
In the case of a fixing device configured such that the pressure roller has a small capacitance (the surface potential of the pressure roller is approximately V=(l!r
g(] can also be expressed as /r ) /2yr εogrl I Q).

Or, the resistance of the pressure roller surface coating layer may be low (due to a low-resistance agent, etc.).

The above-mentioned charge control means may be operated (addition, kneading, filling, swelling) during production of the roller.

The present invention is also applicable to compaction.

The present invention provides a first rotating body (roller or belt) on the toner image side.
Focusing on the surface potential of the second rotating body (roller or belt) on the back side of the recording material 1-1 At least a charge control means is provided to make the charging polarity of the surface of the second rotating body the same as that of the toner image. Therefore, it is possible to stabilize the surface potential of the recording material and obtain an excellent image and an excellent offset prevention effect.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of one embodiment of the present invention, and FIG.
FIG. 3 is a perspective view of the embodiment, and FIG. 3 is an enlarged explanatory view of the main part of FIG. 1. 1 is a copying device, 2 is a photosensitive drum, 6 is a transfer corona discharger, llj is a fixing device, 23 is a fixing roller, 24 is a pressure roller, l! is the distance between the transfer section and the fixing section, T is the toner image,
P is transfer material.

Claims (2)

[Claims] (1) A section that forms a toner image with a specific polarity on one side of a recording material by giving the recording material a polarity opposite to that of the toner image, and A fixing section having a first rotating body that contacts and a second rotating body that conveys the recording material with the first rotating body in contact with the other surface of the recording material, and a distance that is greater than the distance between the forming section and the fixing section. An image forming apparatus comprising: a means for controlling charging so that the charging polarity of the second rotating body is the same as a specific polarity of a toner image on the recording material with respect to a length of the recording material. (2) The image forming apparatus according to claim 1, wherein the first rotating body has a material on its surface that is charged to the same polarity as the specific polarity of the toner image.