JPH0656535B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device, and in particular, a recording material (for example, paper) carrying an object to be fixed (for example, toner) is nipped and conveyed between a pair of rotating bodies (for example, rollers or endless belts). The present invention relates to a fixing device in which a fixed material is fixed on a recording material, and a movable web-shaped moving member is brought into contact with the rotating body on the side where the fixed material contacts.

In this type of fixing device, an offset phenomenon occurs in which toner particles forming a toner image adhere to the rotating body. Conventionally, in order to prevent this offset phenomenon, a release layer (tetrafluoroethylene, silicone rubber, etc.) or a release liquid (eg, silicone oil) has been applied to the surface of the rotating body, but the effect is insufficient. Met.

Further, as disclosed in JP-A-55-55374 and JP-A-55-96970, a bias voltage having the same polarity as that of the toner image is externally applied to a rotating body that comes into contact with the toner image. There is one that applies a bias potential having a polarity opposite to that of the toner image to the opposite side, that is, the rotating body that is in contact with the back surface of the recording material.

However, when a bias voltage is applied with a corona charger such as a corotron, not only does the device become large, complicated, and costly, but when the corona charger becomes dirty, spark discharge and leaks easily occur, resulting in reliability and safety. It was scarce. Further, when the bias roll was applied, the practical effect was small, and the bias roll was easily soiled, which was not practical. Furthermore, when the rotating body is pressed against the roller at a high pressure to fix the toner at a relatively high speed, the frictional force increases and the electrostatic force that affects the charged toner increases, which easily causes a complicated electric field change. The offset prevention effect becomes unstable. Moreover, the use of the bias voltage within the range of the limited electric power has a disadvantage that various restrictions are imposed on other devices such as a charger, an exposure lamp, and a heater.

The present invention has been proposed in view of the above, and an object thereof is to provide a fixing device capable of stably obtaining a toner offset prevention effect with a simple structure and preventing toner scattering to obtain a high quality fixed image. To do.

According to the present invention, a conventional offset has a simple structure, that is, a web-shaped moving member that moves by contacting a rotating body for fixing or a rotating body such as a coating roller or a coating belt contacting the rotating body for fixing prevents offset. It is an extremely novel and highly inventive step characterized by a structure containing a triboelectrification agent that forms an electric field for at least one of the fixing rotators.

Embodiments of the present invention will be described below with reference to the drawings. First,
With reference to FIG. 1, a very schematic structure of an example of an electrophotographic copying machine to which the fixing device of the present invention is applied will be described. In FIG. 1, a photosensitive drum 20 having a photosensitive layer provided on a metal cylinder is uniformly positively charged by a primary charging device, and then recharged by a secondary charging device 22 which gives a charging having a polarity opposite to that of the primary charging device 21. At the same time, the original image is irradiated by the lamp 23, and this light image is given to the photosensitive layer via the optical system 13. As a result, an electrostatic latent image due to the difference in surface charge density is formed on the surface insulating layer of the photosensitive drum 20 according to the pattern of light and dark of the light image, and then the entire surface of the photosensitive layer is made uniform by the whole surface exposure lamp 14. by exposure, the difference to form a high electrostatic latent image contrast caused to the surface potential in accordance with brightness of the original image, then the frictional charging with the developing sleeve 15 ₁ in the developing unit 15, the non-polar The latent image is developed and visualized by the charged toner.

Then, the toner image is positively charged by the transfer charger 18 on the back surface of the supporting material 17 such as paper supplied from the cassette 24, and the visible image on the photosensitive drum is transferred onto the supporting material by the electrostatic attraction force. Transfer and transfer the transferred toner image to rollers 1 and 2
To fix the heat.

The drum 20 is cleaned by the blade cleaning means 19 and reused.

FIG. 2 is a schematic view showing an example of the fixing device for heat fixing. In FIG. 2, the fixing roller 1 has a heater 3 for heating such as a halogen heater therein, and receives a driving force from a driving motor (not shown) to rotate in the direction of the arrow. The fixing roller 1 is aluminum, stainless steel, silicone rubber on the outer peripheral surface of the same metallic hollow roller core 1 _1, fluorine rubber, heat-resistant elastic layer, such as a fluorosilicone silicone rubber, or P
TFE, is provided with a heat-resistant resin layer _{1 2} of PFA or the like 15~1000μ thickness.

The pressure roller 2 is rotatably supported by a bearing (not shown). The roller 2 is pressed against the at least fixed by a known pressurizing means to the fixing roller 1, the metallic roller core 2 ₁
Silicone rubber on the outer peripheral surface of fluorine rubber, a relatively thick elastic layer 2 _2, such as a fluorosilicone silicone rubber (e.g. 5mm~10mm
The degree is provided. This configuration is intended to secure a pressure contact area with the fixing roller. A temperature sensitive element 4 such as a thermistor or a thermocouple is arranged in contact with the outer peripheral surface of the fixing roller 1, and a detection signal of the temperature sensitive element 4 is guided to a known control means (not shown) to change the temperature of the outer peripheral surface of the fixing roller 1 to Heater 3
Of the toner image or by controlling the applied voltage or the like).

Reference numeral 5 denotes a cleaning unit for removing foreign matter such as offset toner and paper dust adhered to the surface of the fixing roller from the roller surface, which is made of heat-resistant non-woven fabric such as Nomex (registered trademark) or Himeron (registered trademark), and is made of dimethyl silicone oil. and using the cleaning web 5 ₁ are impregnated with a release agent such as. The cleaning web 5 ₁ does not necessarily have to be impregnated with a release agent.

The cleaning web 5 ₁ silicone rubber, fluorine rubber, in contact with the fixing roller fluorosilicone silicone rubber, the pushing of an elastic silicone rubber sponge by the roller 5 _2. Also, the web 5 _1, the winding roller 5 ₃ given drive to move to vary the trace increments its contact position from the supply roller 5 _4, always new surface of the cleaning web 5 ₁ comes into contact with the fixing roller .

The guide plate 6 is inclined upward so as to guide the recording material P (support plate 17) carrying the unfixed toner image T between the rollers 1 and 2. The guide plate 7 is inclined upward so as to guide the recording material P passing between the rollers 1 and 2 to a transport path (not shown). The wrap preventing member 8 intended to prevent the recording material P are attached fixing roller 1 wound, it is biased so that the tip end portion ₈₁ abuts on the fixing roller 1 by a biasing member (not shown).

In the embodiment wherein the impregnated amino-modified silicone oil, which is an example of a charge control release agent in the cleaning web 5 ₁ in the above-described fixing device. This impregnation may be performed not only on the entire surface of the web but also intermittently as shown in FIG. In this case, the interval a: the impregnation width b is 5: 1 to 200:
1 is appropriate.

By the way, the present inventors have confirmed that the offset of the toner due to the electrostatic force largely depends on the surface potential of the roller, the recording material, or the like. Generally, the surface potential of the roller is
When it is regarded as a coaxial cylinder, it can be expressed as V = {log (R / r) / 2πεoεrl} · Q.
...... (1) (where R is the outer diameter of the roller (m), r is the inner diameter of the insulating surface coating layer (m), ε = 8.854 × 10 ⁻¹² F / m, εr is the relative permittivity, and l is the insulation. Length of Functional Coating) From the above formula (1), it can be seen that the roller is charged to a higher potential as the wall thickness (Rr) becomes larger and / or the relative dielectric constant becomes smaller.

Te is at the arrangement shown, the insulating cover layer 1 ₂ of the fixing roller 1 is not much charging relatively thin. In contrast, since the insulating layer 2 ₂ of the pressure roller 2 is relatively thick, charged by slight adhesion of the charge control release agent, to form a large surface potential. Therefore, by controlling the triboelectrification polarity of the pressure roller with the charge controllable release agent, it becomes possible to minimize the toner offset to the fixing roller. or,
Along with that, it is possible to prevent image disturbance such as fly dust that mainly occurs during fixing. Therefore, it is possible to obtain a high quality copy.

In the illustrated example, the recording material P has a negatively charged toner T. The rollers 1 and 2 are rotated in the direction of the arrow, and at the same time, the cleaning web 5 ₁ is moved in the direction of the arrow to release the positive charge controllability. Mold 5 ₁₂ from web 5 ₁ to roller 1
Transfer from roller 1 to roller 2. As a result, the pressure roller 2 has a relatively small electrostatic capacity and is easily charged to a high potential.
The polarity of triboelectrification against copy paper is reversed by controlling the charge controllable release agent, and the pressure roller is charged to a positive high potential. Therefore, it is possible to minimize the electrostatic offset to the pressure roller and obtain a high-quality copy without image distortion such as black spots.

The effects of the present embodiment will be shown below by specific numerical examples.

As a fixing roller in FIG. 2, a roller having an outer diameter of 60 mm, which is obtained by applying a PFA coating having a thickness of 30 μm on an aluminum core metal having a thickness of 7 mm,
As a pressure roller, a roller with a thickness of 5 mm and a heat-vulcanizing silicon rubber coating on a stainless steel hollow core is used. Both rollers are pressed against each other at a total pressure of 60 kg, and plain paper (A3 size)
The fixing process was performed at a speed of 3 sheets / minute (roller peripheral speed: 270 mm / sec).

Further, as the release agent 5 ₁₁ and the charge controllable release agent 5 _{12 with which the} web 5 ₁ is impregnated, the following are used.

Release agent 5 ₁₁ : Dimethyl silicone oil with viscosity of 10,000cs at 25 ℃ (KF96H manufactured by Shin-Etsu Chemical) Charge control release agent 5
₁₂ - 25 in viscosity ℃ is 1200Cs, amino-modified silicone oil of an amino equivalent of 3,500 (amino (%) 0.5%) (Toray
The SF8417) and the release agent 5 _11, 1: 100 a blend in. As shown in FIG. 3, a web 5 ₁ was impregnated with a charge controllable release agent 5 ₁₂ periodically (intermittently) with an interval a = 100 mm and an impregnation width b = 5 mm. The web feed speed was 0.5 mm / min.

Under the above conditions, when a toner image of 300 mg per sheet was formed on A3 plain paper (a condition where offset is most likely to occur) was fixed, no problem occurred.

The table below shows a comparison of the toner offset amounts when 50,000 copies are continuously made.

A, (conventional example) ... Web 5 ₁ Mold release agent with viscosity of 10,000cs only (dimethyl silicone oil Shin-Etsu Chemical KF96H) B, charge controllable release agent only (amino-modified silicone oil Toray SF8417) C ₁ , charge control A blending ratio of 5 ₁₂ : 5 ₁₁ : 1 ₁₁ C: a mold release agent (amino-modified silicone oil Toray SF8417) 5 ₁₂ and a release agent with a viscosity of 10,000cs (dimethyl silicone oil, Shin-Etsu Chemical KF96H) 5 _{11 2} , 〃 1: 100 C ₃ , 〃 1: 1,000 C ₄ , 〃 1: 10,000 D, the above-mentioned periodic (intermittent) impregnation (KF96H & SF8417a: b
= 100mm: 5mm) The reason why the above comparison result is obtained.

Since it is applied from the fixing roller side (although amino-modified silicone oil tends to adhere preferentially to the pressure roller side having silicone rubber on the peripheral surface at the nip portion,
Nevertheless, amino-modified silicone oil adheres to the surface of the fixing roller.

If the amount of this amino-modified silicone oil attached is too large,
Due to the activity and chargeability of the amino group, the toner offset to the fixing roller tends to increase.

That is, in the area B, the surface potential of the pressure roller is + 6000V.
Since it is charged more than the above, a good electric field is formed to prevent toner offset, but since a small amount of amino-modified silicone oil adheres to the fixing roller side as well, due to its activity, the offset is about 1/8. is there.

Next, by diluting the amino-modified oil with silicone oil, the pressure roller can be charged to a sufficient potential to prevent toner offset, and the surface of the fixing roller is adversely affected by the amino-modified silicone. It is possible to create a state in which oil hardly adheres.

That is, in the C ₁ to C ₃ region, the toner offset can be reduced to 1/15 as compared with the conventional case where only general silicone oil is attached.

As it is further diluted, it becomes impossible to charge the pressure roller to a potential that can prevent offset well,
(That is, the effect of the amino group disappears), and the toner offset approaches the conventional example.

In the above experiment, the tendency is seen in the C ₄ region. That is, when the web is impregnated with a blended liquid of silicone oil and amino-modified oil, a particularly effective blending ratio is a case where 10 ¹ to 10 ^{3 of} amino-modified silicone oil is blended with ¹ silicone oil.

When the web is intermittently (intermittently) impregnated with a charge controllable release agent such as amino-modified silicone oil, the toner offset is further reduced to 1/20 or less. This is because the amino-modified silicone oil once attached to the pressure roller 2 keeps the potential of +6000 V or more, which is good for preventing offset, during the subsequent copying of about 2000 sheets. On the other hand, a small amount of amino-modified silicone oil that has adhered to the fixing roller side will soon be removed from the surface of the fixing roller by passing the paper, and will not adversely affect the offset. Therefore, the toner offset amount is
Reduced to less than 1/20. Then, when the amino-modified silicone oil adhering to the surface of the pressure roller gradually decreases, new amino-modified silicone oil is applied again, and the offset prevention effect is continuously maintained.

In addition to toner offset, it is also effective for preventing image dust.

FIG. 4 shows a manufacturing method for impregnating the web 50 used in the present invention with a release agent and a charge controllable release agent.

In FIG. 4, the base web 50 before being impregnated with oil is shown.
Is conveyed to the offset prevention liquid application section 53 through the tension rollers 51 and 52. In order to prevent wrinkling of the base web, the inlet guide 531 has an arc shape such that the central portion in the web feeding direction is closer to the roller 536 and the left and right side portions are farther.

The dimethyl silicone oil 533 in the offset prevention liquid storage container 532 moves from the pumping roller 534 to the application roller 535 made of fluorine rubber, and is nipped and conveyed by the pressure contact roller 536 and the application roller 535 made of metal, the web feed speed, the roller 534, By controlling the pressure contact force of 535 and the like, the web is impregnated with an appropriate amount of oil. The pressure contact roller 536 has a mechanism for releasing pressure on the web and is pressed against the application roller 535 only when it is desired to impregnate the web with oil.

The offset prevention liquid 533 is applied in the offset prevention liquid application section 53.
The web 50 impregnated with is then conveyed to a charge controllable release agent application section 54.

In the portion 54, a charge controllable release agent such as amino-modified silicone oil impregnated in an oil-containing member 541 such as felt is used.
It is held by a holding member 542, and is appropriately brought into contact with or separated from the web by using the shaft 543 as a rotation fulcrum, and impregnated with a charge controllable release agent intermittently (intermittently) in the web longitudinal direction.

After that, the web passes through the roller 55 and is wound around the winding shaft 56 in an appropriate length.

The contact / separation of the roller 536 with respect to the web, the contact / separation of the oil impregnating member 541 with respect to the web, and the appropriate length of the web wound around the take-up shaft in the steps described above are performed by a control circuit (not shown) according to the counter 57. Be seen. Further, the above impregnation step is only an example, and the method of manufacturing the web applicable to the fixing device of the present invention may be performed by another method.

The charge controllable release agent includes, in addition to those in which a charge agent is dispersed or mixed in a release liquid (typically, silicone oil), or chemically bonded, and the following, Includes all those similar to the technical idea of the present invention.

<Group of Charge Controllable Release Agents> The following is a list of charge controllable release agents positioned in a higher order than the recording material in the triboelectric charging series. As the charge control release agent, dimethyl silicone oil in which a part of the methyl group is replaced with amino group (hereinafter referred to as amino-modified silicone oil) can be used.

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

(i) Type A (ii) Type B x, y ,; positive integer, R ′, R ″; alkyl group Examples of A type are KF864, X-22-3801 (both manufactured by Shin-Etsu Chemical Co., Ltd.), SF8417 (Tole Silicone) Co., Ltd. etc. In addition, examples of B type are trade names KF393, KF
857 and KF859 (both manufactured by Shin-Etsu Chemical Co., Ltd.) are available. Further, those which are subjected to amino modification are preferably releasing agents such as methylphenyl silicone oil in addition to dimethyl silicone oil, which can be used in this embodiment.

In addition, amide-modified silicone (eg, KF3935 Shin-Etsu Chemical Co., Ltd. trade name) is used as silicone oil having amino groups.
Silicone diamine (for example, X-22-161, trade name of Shin-Etsu Chemical Co., Ltd.) and the like can be used.

Other than the above examples, a charge controllable release agent obtained by treating silicone oil with an amino group-containing silane coupling agent shown below can be given.

H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ H ₂ NCH ₂ CH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ H ₂ NCONHCH ₂ CH ₂ CH ₂ Si (OCH ₂ H ₅ ) ₃ H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂・ Si (OCH ₃ )
₃ H ₅ C ₂ OCOCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (O ・ CH ₃ ) ₃ H ₅ C ₂ OCOCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂・ CH ₂ CH ₂ Si (O
CH ₃ ) ₃ H ₅ C ₂ OCHOCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂・ CH ₂ NHCH ₂ CH
₂ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) H ₃ COCOCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂ CH ₂・ CH ₂ Si (OCH
₃ ) ₃ H ₃ CNHCH ₂ CH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ H ₂ N (CH ₂ CH ₂ NH) ₂ CH ₂ CH ₂ CH ₂ Si (O ・ CH ₃ ) ₃ H ₃ C-NHCONHC ₃ H ₆ Si (OCH ₃ ) ₃ The alkoxy group in the above mixture may be a chlorine atom. These silane coupling agents may be used alone or in a mixture of two or more.

The above-mentioned charge controllable release agent can be used alone, but the charge controllable release agent can be used as a conventional release agent generally used such as dimethyl silicone oil, methylphenyl silicone oil and fluorosilicone oil. Those to which a mold agent is added are also applicable. In this case, properties such as thermal stability and viscosity can be arbitrarily selected, and the amount can be reduced by relatively reducing the amount of relatively expensive amino-modified oil used. For example, SF8417 (amino equivalent 3500 / amino (%) 0.5, manufactured by Toray Silicone KK.) Has a viscosity of 10,000cs at 25 ° C dimethyl silicone oil KF96H viscosity at 25 ° C 10,000cs
It was confirmed that even a sample obtained by adding 10 ³ wt% to (manufactured by Shin-Etsu Chemical Co., Ltd.) can be applied to the present invention as a charge control release agent. Of course, the lower limit of the addition amount is not limited to the above value, and it is possible to apply as a charge controllable release agent even with a smaller addition amount by an appropriate combination.

Further, a charge control agent having the following structural formula may be added to a release agent such as dimethyl silicone oil.

・ NCL-3 (OLOA 313) ・ OLOA 5080 ・ Nylon 12 ・ Duo Min (Lion Armor) ・ Mamanc C I. Fatty acid monoethanolamide _{R-CO-NH-CH 2} CH 2 OH for example lauryl acid _C 11 _{-C 17} as R II. Fatty acid diethanolamide CH ₂ CH ₂ OH R-CO-N CH ₂ CH ₂ OH For example, C _{11 to} C ₁₇ laurimic acid as R, etc. Has a preventive effect. For example, even about 10 ⁻³ parts by weight with respect to 100 parts by weight of silicone oil is sufficiently effective.

<Group 2 of Charge Controllable Release Agents> The following is a list of charge controllable release agents positioned in a negative order relative to the recording material in the triboelectrification series.

A silicone oil having a halogen element group such as a halide-modified silicone oil is suitable, and one having a chlorine atom is particularly suitable. Also in this example, dimethyl silicone oil, fluorosilicone oil, methylphenyl silicone oil or the like may be used as well as silicone oil which is subject to modification.

In addition, there is a silicone oil to which a fluorine-based surfactant is added.

Further, fluorosilione oil is effective as a negative charging agent, and it may be added to silicone oil.

As an example of use for forming an electric field having these offset prevention effects, the following may be used when the roller surface on the side in contact with the toner image is a resin material and the surface of the pressurizing rotary member is a rubber material.

When the toner has a negative polarity in the structure shown in FIG.
At least one of the charge controllable release agent group 1> may be contained. Similarly, when the toner has a positive polarity,
It suffices to include at least one selected from the group consisting of <charge controllable release agent second group> in the web.

Also, in the case of other configurations, regarding the polarity of the toner, the rotating body having the same polarity as the toner is in contact with the toner, and the rotating body having the opposite polarity to the toner is in direct contact with the toner. Rather, it is to use each rotating body on the side in contact with the recording material.

As described above in detail, according to the present invention, the charge controllable release agent is attached to the pair of rotating bodies that nip and convey the recording material carrying the unfixed toner image, and the rotating body surface on the back surface of the recording material is attached. Since the toner image is frictionally charged to a potential having a polarity opposite to that of the charge of the unfixed toner image, toner offset and image scattering can be prevented, and an image of good quality can be obtained for a long period of time. Further, since the moving member of the rotating body that is in contact with the unfixed toner image is used as the means for attaching the charge controllable release agent, it is possible to obtain the effect that no special attaching means is required.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an electrophotographic copying machine to which the fixing device of the present invention is applied, FIG. 2 is a front view of the fixing device, FIG. 3 is a perspective view of a cleaning web, and FIG. It is a front view which shows an example of the manufacturing apparatus of a cleaning web. 1, 2 are rotating bodies, 5 (50) is a cleaning web, 5 ₁₁
Release agent, 5 ₁₂ charge control release agent, T is unfixed toner image, P is a recording material.

Claims (1)

[Claims] 1. A fixing device, comprising: a pair of rotating bodies for holding and fixing an object to be fixed having a predetermined polarity, and a cleaning web for cleaning the surface of the rotating body on the side in contact with the object to be fixed. A fixing device characterized by containing a triboelectrifying agent intermittently in the web.