JPS6017472A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent effectively an offset development to a rotating body by providing a means for applying a parting agent and a charge control property agent to a pair of rotating bodies for forming a fixing device. CONSTITUTION:A heat resisting release property resin layer 11 is provided on the surface of a heating roller 1, and an elastic body layer 21 is provided on the surface of a pressure roller 2. On the other hand, an offset preventing device 6 which has contained separately a charge control property release agent 61 being a charge control property agent, and a release agent 63, respectively is provided on the heating roller 1. In this state, as the heating roller 1 rotates, the release agent 63 is applied to the surface of the heating roller 1 from the preventing device 6, and thereafter, the charge control property release agent 61 is applied. Subsequently, the release agent 61 is applied in a press-contacting area (d) on the surface of the pressure roller 2. In this way, an offset development to a rotating body is prevented effectively. In this regard, even when the offset preventing device is provided on the pressure roller side, the same effect can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device installed in a recording device such as an electrophotographic device or an electrostatic recording device, and more specifically, a fixing device for fixing an object to be fixed, such as an unfixed image, to a recording material. The present invention relates to a fixing device that extremely effectively prevents offset of an object to be fixed that occurs in a rotating body that is subject to heat treatment, pressure treatment, or heating and pressure treatment.

Conventionally, a method for preventing the offset phenomenon to the first and second rotating bodies such as rollers and belts that perform fixing action is disclosed in Japanese Patent Laid-Open No. 55
No. 55374 and Japanese Unexamined Patent Publication No. 55-96970 disclose a recording material such as a roller that contacts the image surface of a copy paper with an object to be fixed supported by the copy paper, such as a toner image, and an image of the same polarity. It is known to apply a bias voltage using a corotron, or to apply a bias voltage with a polarity opposite to that of the toner to a roller on the opposite side of the toner image surface.

In other words, in the conventional device, a charge is forcibly applied from the outside of the rotating body. If the voltage is applied using a corona charger such as a corotron, the device becomes larger, more complicated, and more expensive, and if the corona charger becomes dirty, spark discharge and IJ-resistance are likely to occur, resulting in poor reliability and safety. So it was alright. Furthermore, when the voltage was applied using a bias roll, the practical effect was small and the bias roll was easily soiled, making it impractical.

Another proposal is to charge the roller material on the side that contacts the toner image surface of the recording paper to the same polarity as the toner using a frictional charging system. 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
The proposal has not been put into practical use.

The present invention satisfactorily improves the above-mentioned conventional drawbacks with a simple configuration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that extremely effectively prevents the offset phenomenon to a rotating body and has stable fixing performance over a long period of time.

Another object of the present invention is to prevent image disturbances such as blurring caused during fixing. An object of the present invention is to provide a fixing device capable of producing high-quality copies.

The mold releasability of the first rotary body is improved by applying a structure in which the mold release agent is selectively applied to the first rotary body and the charge-controlling ginseng agent is selectively applied to the second rotary body. to improve, and
By varying or maintaining the friction charging polarity of the second rotating body, it is possible to very effectively prevent the object to be fixed, such as toner or resin material, from being offset to the rotating body due to adhesive force and electrostatic force.

The details of the present invention will be explained below with reference to the drawings.

An example of an electrophotographic apparatus to which the fixing device according to the present invention can be applied is shown below.

The photosensitive material for forming an electrostatic latent image and the forming process shown in FIG. 1 are based on those described in Japanese Patent Publication No. 42-23910, but are not limited thereto. No. 2040, No. 42-19748, No. 43-24748, No. 45-37957
No. 49-27048, No. 44-1343
Publication No. 7, Publication No. 45-24077, Publication No. 43-179
No. 47, No. 45-25236, and other well-known methods can be applied. A description of the illustrated device will be added.

A photosensitive drum 9tri, which has a photosensitive layer provided on a metal cylinder, is uniformly positively charged by a secondary charger 10, and then simultaneously re-charged by a secondary charger 11 which provides a charge with a polarity opposite to that of the primary charger 10. , a lamp 12 illuminates the original image, and this light image is applied to the photosensitive layer via an optical system 13. As a result, an electrostatic latent image is formed on the surface insulating layer of the photosensitive drum 9 due to the difference in surface charge density according to the light and dark pattern of the light image, and then the entire surface of the photosensitive layer is uniformly covered with the full surface exposure lamp 14. By exposing it to light, a difference is created in the surface potential depending on the brightness of the original image, forming an electrostatic latent image with high contrast.
Next, due to frictional charging with the developing sleeve 151 in the developing device 15, the latent image is developed with negatively charged toner and made visible. The development process was based on the developing method or apparatus described in JP-A-55-18656, JP-A-55-18657, JP-A-55-18678, and JP-A-55-18679, respectively. .

Next, a transfer charger 18 applies a positive charge to the back side of a recording material 17 such as paper supplied from a cassette 16, and the visible image on the photosensitive drum is transferred onto the recording material by the electrostatic attraction force. The transferred toner image is transferred to rollers 1 and 2.
It is heat-fixed by

The drum 9 is cleaned by the grade cleaning means 19 and reused.

FIG. 2 is an explanatory diagram of the heat fixing device in FIG. 1.

A heating roller 1 has a heating heater 3 such as a halogen heater inside, and rotates in the direction of the arrow in response to a driving force from a driving motor (not shown). 2 is heater 3 for low heating
A pressure roller with a built-in roller presses against the heating roller 1 and rotates in sliding contact.

This heating roller 1 has a relatively thin heat-resistant release resin layer 1, such as polytetrafluoroethylene resin (PTFE) or PFA, on the outer peripheral surface of a hollow roller core 1 made of metal such as aluminum, stainless steel, or steel. It is provided with a thickness of 80μ. The pressure roller 2 is rotatably supported by a bearing (not shown). This roller 2 is pressed into contact with the heating roller l by a known pressure means at least during fixing, and the metal roller core 2
2. An elastic layer such as silicone rubber, rubber, or silicone rubber on the outer periphery of the mic. It is a relatively thick set of (for each religious organization). One purpose of this configuration is to secure the protrusion (d) in the pressure contact area with the heating roller.

A temperature sensing element 4 such as a thermistor or thermocouple is disposed in contact with the outer peripheral surface of the heating roller 1, and its detection signal is guided to a known control means (not shown) to control the temperature of the outer peripheral surface of the heating roller 1 ( The toner image is maintained at the melting temperature by controlling the output of the heater 3 or the voltage applied thereto. 5. ．． Reference numeral 52 denotes a separating claw that reliably separates the copy paper from the roller after fixing.

6, when fixing the recording material, the toner image T on the recording material is
A storage section 62 for storing an offset material 6 to the fixing roller 1, and a release agent 6. and a storage section 64 that stores the .

Further, each of the storage portions 62.6° of the offset prevention device 6 has an opening extending in the longitudinal direction of the roller.
,6. Polytetrafluoroethylene continuous porous tube 61 +
Continuous porous tetrafluoroethylene membrane containing 610 6.
．． 6. It has a loose coating amount control member 65°6. A configuration for applying a release agent (63°64, 68.610.612) is provided on the upstream side in the rotational direction of the fixing roller.
However, on the downstream side there is a configuration for applying a charge control mold release agent (61
, 62, 6y-69, 611).

Therefore, the mold release agent 6. After applying a small amount of charge control mold release agent 6I
is applied in a small amount. To simplify the explanation, the surface of the heating roller has a coated layer of mold release agent 63 and a coated layer of charge-controlling mold release agent 61 stacked thereon. The surface of the heating roller having this coating layer is coated on the surface of the pressure roller 2 in the pressure contact region d where it contacts the pressure roller 2 with a charge control mold release agent 6. is applied substantially.

The charge controllable mold release agent 61 maintains the surface potential of the pressure roller 2 at a polarity for preventing offset of the toner image T.

At this time, the surface of the heating roller 1 mainly prevents an offset phenomenon due to the stickiness of the toner image T, and the surface of the pressure roller 2 prevents an offset phenomenon due to the potential relationship of the toner image.

In other words, by selectively applying two types of release agents to the fixing heating roller 1 and pressure roller 2 in this way, it was possible to largely eliminate the cause of offset occurrence. Moreover, the second
In the illustrated embodiment, since the application means has an integral structure, it can be manufactured at low cost and the mold release agent can be reliably supplied.

In addition, the storage sections 62 and 64 are filled with urethane foam, etc., to prevent the charge control mold release agent 6I and the mold release agent 6° from spilling outside the storage container due to vibrations such as when the machine is moved. A saw breakage prevention member 6+11612 is provided.

A guide plate 7 is inclined upward so as to guide the copy paper P bearing a toner image toward the heating roller 1 side.

As a result of research into preventing toner offset, the forces related to toner offset are predominantly due to the adhesive force between the roller and the toner and the electrostatic force that the toner receives. It was confirmed that the toner offset to the roller has a very large dependence on the surface potential of the roller. Considering the roller as a coaxial cylinder, the surface potential V of the roller is v=(l!Og(几/r)/2πε
. εrI! )・Q ・・・・・・(1) It can be expressed as follows.

From the above equation (11), it can be seen that the larger the wall thickness (R-r) and/or the smaller the dielectric constant, the higher the potential of the roller is charged.

In the configuration of this example, the insulating coating layer of the heating roller is relatively thin, and the insulating layer of the pressure roller is relatively thick. By controlling the release agent and applying a release agent to the heating roller, it is possible to minimize toner offset to the heating roller. This makes it possible to make high-quality copies that prevent

In the case shown in FIG. 2, the toner image has negative polarity and the release agent 6. l
A thin film of the mold release agent 6 is formed on the surface of the heating roller 1 by sequentially applying a small amount of the mold release agent 6□ with positive charge control property to the surface of the heating roller 1, and the mold release agent 6 is brought into pressure contact with the heating roller. A positive charge control mold release agent is transferred to the surface of the rotating pressure roller 2.

The frictional polarity of the pressure roller with the copy paper, which has a rubber surface layer that has a relatively small capacitance and is easily charged to a high negative potential, is reversed using a positive charge control release agent, and the pressure roller is charged with a positive charge. By charging the toner to a high potential, it has become possible to minimize toner offset to the heating roller and to obtain high-quality copies without image holes such as blurring.

As the mold release agent 6s applicable to this example, all conventionally used general ones can be used, such as dimethyl silicone oil, methylphenyl silicone oil, fluorosilicone oil, and their like. Mixtures can be used.

As the charge control mold release agent (having positive characteristics) of this embodiment, one that has mold release properties and is positioned in a positive order compared to the recording material in the triboelectrification series can be applied.

For example, as a positive charge controllable m-type agent, a dimethyl silicone oil in which some of the methyl groups are replaced with amino groups (
(hereinafter referred to as amine-modified silicone oil) can be used.

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

i) Atype fi) Btype X, y: Positive integer, R', R'': Alkyl group Btype
Commercially available products include, for example, K
F393. KF857. KF859 (both manufactured by Shin-Etsu Chemical KK), and Atype 1, for example, K
F864. Examples include: , methylphenyl silicone oil, fluorosilicone oil, and the like can be used. or,
In addition to the above, examples of silicone oils containing amine groups include amide-modified silicone (e.g. KF3935. Shin-Etsu Membrane) and silicone diamine (e.g. X-22-1
61, Shin-Etsu Chemical Co., Ltd. Membrane), etc. can also be used. Alternatively, silicone oil treated with a silane coupling agent containing an amino group as shown below may be used.

H, NCH, CH, CH, 8i (OCH,).

H, NCH, CH, CH, St (QC, H,).

CH.

■ H, NCH2CH, CH, Si (OCH,).

H,NC0NHCH1CH2CH,Si (QC2H,
),.

H2NCH2Cl-12NHCH2CH,,CH,Si
(OCHL)3H2NCH,CH,NHCH,CH2
NHCH,CH,CH28i (OCH8)sH11C
20COCH, CH2NHCH2CH2CH, 8i (
OCHl)3(H,Co)sSiCH,CH2C
H, -NHCH.

(H,CO), 5iCi(,CH2CruN HCH
2H3CNHCH,0M2CH,Si (QC2H,)
.

H,N (0171,CH2Nu), CH2CH,
CH,8i (OCf(,).

H,C-NHCONHC,)mu5i(OCR,)3-fold,
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 above charge control mold release agent 63 can be used alone, but it can also be added to conventionally commonly used mold release agents such as dimethyl silicone oil, methylphenyl silicone oil, fluorosilicone oil, etc. It is possible. In this case, in addition to being able to arbitrarily select properties such as thermal stability and viscosity, it is also possible to reduce the cost by relatively reducing the amount of relatively expensive amino-modified oil used. I can do it. For example, dimethyl silicone oil KF96H (25
Viscosity at ℃ 10,000aS) (Shin-Etsu Chemical KK
It was confirmed that a sample in which 10'wt% of the compound (manufactured by M.D.) was added could also be applied to the present invention as a charge-controllable mold release agent. Of course, the lower limit of the amount added is not limited to the above-mentioned value, and even a small amount can be used as a charge control mold release agent by appropriate combination.

In addition to the above-mentioned amino-modified silicone oil, charge control agents that can be applied to the present invention include, for example, a charge control agent (positive charging property) having the structural formula shown below, such as dimethyl silicone oil, etc. It may also be added to the agent.

NCL-3 (OLOA 313) Polybutene 0LOA5080 Nylon 12 Duomin (Lion Armor Co.) ・ Armac CR R is an alkyl group ■, fatty acid monoethanolamide R-CO-NH-CH2CL (20H For example, R as CIl~c1□ lauric acid, etc.■, fatty acid jetanolamide, for example, R is C, C, lauric acid, etc. The amount of these additions is 100 parts by weight of silicone oil.
It is effective even in a very small amount of about -8 parts by weight.

The effects of the embodiments of the present invention will be shown below using specific numerical examples. In Figure 2, the heating roller is a roller with an outer diameter of 60 m coated with a 30 μm thick PF'A coating on an aluminum core metal with a wall thickness of 7mm, and the pressure roller is a roller with an outer diameter of 60 m on a stainless steel hollow core metal. Using a roller coated with heat-vulcanized silicone rubber, both rollers are brought into pressure contact with each other at a total pressure of 60 K7, and a sheet of plain paper (A
3 sizes) at 23 sheets/min (roller peripheral speed 270fi/5e
The fixing process was performed at the speed of c). Also, the porous tetrafluoroethylene membrane 6 of the offset prevention device 6? *68
The permeate flow from -1v is )tagen -Po1seu
From the formula of iJe, V = nxHr'5T78 nz n: number of filter pores, where H: pressure (cxH, 0) r: pore diameter S2 filtration area T: filtration time n: liquid viscosity l! : Film thickness x V-thickness.

In this example, the tetrafluoroethylene porous membrane 6□.

66, and tetrafluoroethylene porous tube 6°.

As 610, those shown in Table 19 and Table 2 were used (amount of mold release agent 6>amount of charge control mold release agent 6).

Table 1 ゛Table 2 In addition, as the charge control mold release agent 6I, one having a skeleton structure of type A of the amino-modified silicone oil described above, a viscosity of 350oC8 at 25°C, and an amine equivalent of 2000 was used (Shin-Etsu Chemical Co., Ltd.). Tomo KF861).

On the other hand, mold release agent 6. As the material, dimethyl silicone oil having a viscosity of 10,0 OOC8 at 25° C. was used (Shin-Etsu Kagakuyu KF96H). When copying starts, both rollers rotate under pressure, and before the copy paper passes between the rollers, dimethyl silicone oil 6 is applied to the surface of the heating roller.
3 is supplied, and then amine-modified silicone oil 61 is supplied to the upper layer thereof. Next, most of the amine-modified silicone oil in the upper layer in the nip portion migrates to the surface of the pressure roller. Furthermore, it was confirmed that the amino-modified silicone oil that had once migrated to the pressure roller hardly migrated to the fixing roller during subsequent rotations, but preferentially adhered to the pressure roller.

A toner image of 300 cm per sheet was formed on A3 plain paper under the above conditions (Canon Test Chart NA-2:
After establishing the conditions in which offset is most likely to occur,
The toner offset rate was 0.03% or less, and no problems occurred. The toner offset rate referred to here is as follows.

Also, the surface potential of the pressure roller after passing 99 sheets is +600.
The surface potential of the heating roller was -300V, and the surface potential of the paper was +180V.

The above results are considered to result in a decrease in offset due to the following factors. That is, when a positively charged positive latent image is transferred onto plain paper after being developed with negative toner, the plain paper is given a positive charge and is transferred by electrostatic attraction with the negative toner.

That is, at this point, the plain paper is positively charged. After this, during the fixing process, when the plain paper P passes through the nip section, frictional peeling occurs between the paper P and the pressure roller 2, causing it to be charged by friction, and at this time, amino-modified silicone oil mixed with silicone oil, which is a charge-controlling mold release agent, comes into play. The pressure roller becomes highly charged. In other words, the plain paper P is negatively charged, which is opposite to the positive charge that should hold the negatively charged toner. As mentioned above, the present inventors found that when the offset is a charge amount, the surface of the pressure roller, which has a smaller capacitance than the paper, will have a much larger potential than the paper. It exerts a large electrostatic attraction on the negative toner on plain paper so that the charge on the back side can be ignored. In other words, during fixing, the negative toner is strongly held on the paper surface, so offset can be prevented. Moreover, due to the above-mentioned effect, there was almost no scattering or disturbance of the image during fixing, and high-quality copies were obtained. Then, continue copying to Rainbow with the above conditions and make 100,000
Even after sheet feeding, there was no change at all from the initial state, with very little offset, and high quality copies were obtained. In the above case, the roller surface temperature was 180°C while the paper was being passed through the paper, but the temperature of the charge-controlling mold release agent in the container 21 was about 100°C, and there was almost no decomposition of the amino groups, resulting in good long-term results. Obtained. Further, in the above example, the consumption amount of amine-modified silicone oil was 2×10 g/1 sheet, and the consumption amount of silicone oil was 1×10 g/1 sheet.

Next, as a comparative example, a system in which the amino-modified silicone oil was removed from this example, that is, mold release agent 6s, was applied in the same manner, and when the material @TjU control mold release agent 6I was not applied, the system was When paper was passed in the same manner as in the example, the toner offset rate was 0.6X, and 20 times more toner was offset to the fixing roller than in the example of 50 sheets. There was still some blurring in the image, which increased as the sheets continued to pass. This is due to the fact that the surface potential of the pressure roller increases toward the negative side as the sheets are continuously fed. Also, the surface potential of the pressure roller after passing 99 sheets is:
-6000V or more (approximately -4000V when one sheet passes) The surface potential of the heating roller is -200V, and the surface potential of the paper is +2
It was 10V.

The reason for the above is that due to the frictional separation charging with the paper, the surface of the pressure roller has a very large negative potential compared to the paper. Due to the negative toner being applied to the fixing roller, the negative toner is transferred to the fixing roller, resulting in image disturbances such as offset and blurring.

FIG. 3 shows another embodiment of the present invention, in which an offset prevention device is provided on the pressure roller 2 side. Components that are the same as those in FIG. 2 are indicated by the same numbers.

Similar to the embodiment shown in FIG.
．． It consists of a storage section 82 that stores the mold release agent 8s, and a storage section 84 that stores the mold release agent 8s on the downstream side of the storage section 82.

When a copy signal is input, both rollers l and 2 rotate,
First, a heat-resistant felt 85 and a charge-controlling mold release agent 8 are applied to the surface of the pressure mill 2. is supplied, and then a metering blade 86 forms a uniform thin film of charge control mold release agent on the pressure roller surface.

(Then, the mold release agent 83 is supplied to the upper layer of the thin film from the heat-resistant felt 8., and then the mold release agent 83 is supplied onto the charge-controllable mold release agent thin film on the surface of the pressure roller by the metering blade 8. thin films are laminated.Next, at the nip part,
A part of the thin film of the mold release agent 8 transfers to the surface of the heating roller 1. Heat-resistant felt 8. ,8. As the material, general heat-resistant felts such as Nomex felt and Teflon felt can be used. Metering blade 8. , 8°, general heat-resistant blades such as furan rubber blades, fluorosilicone rubber blades, and silicone rubber blades can be used.

Further, in this embodiment, the charge control mold release agent 81 is as follows:
In 100 parts of dimethyl silicone oil (Shin-Etsu Chemical Exhibition KF96H) with a viscosity of 10,00C8 at 25°C, the above A type, amino-modified silicone oil (Shin-Etsu Chemical Exhibition KF857) with a viscosity of 70C8 at 25°C. , 0
．． A mixture of O1iti and in part was used. Mold release agent 8. The viscosity at 25℃ is 10,0OOC8
Dimethyl silicone oil (Shin-Etsu Chemical Exhibition KF96) 1)
was used.

When we conducted an experiment similar to the example shown in FIG. 2, the toner offset vehicle had O.
Similar good results were obtained even when oooo sheets were passed.

In addition, in this implementation, the anti-offset agent applicator was installed only on the heating roller side or the pressure roller side in order to make it more compact. Even if a controllable mold release agent application device is provided separately, the same results as in the previous example can be obtained. Furthermore, the present invention is applicable not only to the heat fixing device described above but also to a pressure fixing device having a pair of fixing rollers.

In the above embodiment, a positive charge-controlling release agent is used to reverse the chargeability of the pressure roller, which has a large influence on negative toner when it comes into contact with the recording material, and stabilize its surface potential. However, the present invention has a method for the opposite case, that is, to stabilize the charging of the pressure roller to be negative with respect to positive toner, and to suppress changes in the surface potential of the pressure roller. Also included are embodiments in which stabilization is achieved.

As a specific example, if a charge-controlling release agent with negative characteristics (for example, a release agent containing fine silica powder, etc.) is used as the charge-controlling release agent shown in Figure 2.3 above, the pressure roller will be able to interact with the recording material. It is negatively charged by friction and can withstand changes over time and maintain a stable surface potential state. In this way, instead of changing the polarity of the pressure roller, the polarity is strongly supplied, so that the surface potential of the fixing rotor can be actively stabilized, and there is little offset over a long period of time. Surface stains on rotating bodies (fixing roller, pressure roller, pressure belt, belt-shaped rotating body) can be largely prevented.

Further, according to the present invention, a high quality fixed image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram illustrating an example of an image forming apparatus to which the present invention can be used for JN, and FIGS. 2 and 3 are detailed explanatory diagrams of the present invention. 1 is a heating roller, 2 is a pressure roller, 3.3' is a heater,
1. % is a heat-resistant mold release resin layer, 21 is an elastic layer, 6.8 is an offset prevention device%, 61+81 is a charge control mold release agent, and 6s and 83 are mold release agents.

Claims (4)

[Claims] (1) In a fixing device that fixes an object to be fixed to a recording material, the fixing device has a first rotating body having a releasable surface and a second rotating body having an elastic surface. A fixing device comprising means for applying a release agent and a charge control agent to the second rotating body. (2) the applying means is provided on the surface of the first rotating body;
Claim 1, further comprising a release agent application means and a charge control agent application means in sequence in the rotational direction of the first rotating body.
Fixing device as described in section. (3) the applying means is provided on the surface of the second rotating body;
Claim 1, further comprising a charge control agent application means and a release agent application means in sequence with respect to the rotational direction of the second rotating body.
Fixing device as described in section. (4) The application means includes a release agent application means on the surface of the first rotor, and a charge controllable application means on the surface of the second rotor.
A fixing device according to claim 1.