JPH01207779A - Method for forming resistor heating body layer for heat fixing roller - Google Patents

Abstract

PURPOSE:To suppress the generation of heat accumulation and hot offset on a part exceeding paper feeding width by forming a resistor heating body material sheet reduced at the volume weight of the resistor heating body material in a paper passing area on its center part by a printing method, transferring said sheet to the outer periphery of a cylindrical supporting body and then heating and sintering the resistor heating body material on the supporting body. CONSTITUTION:In case of transferring the resistor heating body material to be printed on transfer paper to a supporting body roller core, multilayer printing is executed by a net point printing method or the like so that the volume weight is reduced in the paper passing area on the center part or printing is executed by a multilayer printing method so that the film thickness of the 2nd layer or after is thinned at its center part. Since paper carrying routes are formed by guide plates 24 on both the sides of the holding part of a heat roller 1 and a pressure roller 10 in a fixing device, a toner image 21 formed on the surface of paper 20 carried to the paper carrying routes is fixed by pressure and heating. Consequently, the generation of hot offset can be prevented.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a heating fixing roll of a fixing device used in equipment using an electrophotographic process such as an electrophotographic copying machine, a facsimile machine, and a printer. This invention relates to a method for forming layers.

[Prior Art] In an electrophotographic process, a toner image formed on a photoreceptor is generally transferred onto a recording support, such as paper, by a transfer device, and then, if necessary, the toner image is fixed on the surface of the paper to form a desired image. I have obtained a copy etc.

Known methods for fixing toner images include a heat fixing method, a pressure fixing method, and a solvent fixing method.

The heat fixing method is a method in which toner is melted by heating and adhered to paper, and is widely adopted.

There are various heat fixing methods, such as a hot air fixing method, an oven fixing method, and a heated roll fixing method, but the heated roll fixing method is the most common.

A heating roll type fixing device that has been commonly used in the past consists of a III heating roll 1 and a pressure roll 10, as shown in FIG. When the paper 20 is sandwiched and conveyed between the 1/11 loaf roll 10 and the paper 20, it is heated and pressurized to fix and cover the unfixed toner image 21 on the surface of the paper 20 transferred from the photosensitive drum. It is.

In the heating roll type fixing device using this type of internal heating element 25, a lamp such as a halogen lamp is used as the heating element (heat source). In order to raise the temperature to
It takes approximately 10 minutes for the ohm to come up. Therefore, there is a lost time during which no copying operation can be performed from when the operator turns on the switch until it warms up. In addition, because heat loss is large, power consumption is relatively large, and furthermore, a temperature control device, a surface temperature sensor, etc. are required, and the use of expensive halogen lamps increases costs and makes the structure extremely complicated. It also has drawbacks such as low reliability against failures.

As another heating method, has a method been proposed in which a heating element is formed from a semiconductor ceramic material having self-temperature control characteristics (PTC characteristics) near the outer peripheral surface of the heating roll, and heating is performed from near the surface of the roll? It is difficult to actually obtain a PTC ceramic material whose resistance rises to a desired value, and especially when forming a film-like heating element on the roll surface, it is extremely difficult to control the resistance value.
For example, when the h1 value is set to 180'C, if the rising temperature of the resistor deviates from 180°C by only a few degrees, there is a problem in that it becomes impossible to heat the heating element by energizing it.

Therefore, the present inventors created and experimented with a heating roll for heat fixing in which a thin film-like resistance heating layer was provided on the outer periphery of a cylindrical support, and found that the warm-up time was significantly shortened.
It has been confirmed that it saves power, simplifies the structure, lowers costs, and improves reliability, and it is extremely easy to control temperature.

However, in order to put into practical use a heating fixing roll provided with such a thin resistance heating layer, it is extremely important to form the resistance heating layer on the support with high precision and productivity. becomes.

Furthermore, in order to shorten the warm-up time, materials with low thermal conductivity such as ceramic and enamel are suitable as the material for the support roll core. That is, thermal conductivity 1
．． 2 to 10.8 Kcal/m, h, °C is suitable.

[Problems to be Solved by the Invention] However, when a roll core with low thermal conductivity such as a ceramic core is employed, there are the following drawbacks. In other words, when continuous copying is performed with paper of a size smaller than the maximum paper passing area on the heat fixing roll, the temperature of the non-paper passing area of the roll rises, but because the roll core has low thermal conductivity, there is no heat transfer to that area. As the heat is accumulated, the heat-resistant temperature of the release layer on the surface (260 to 280' in the case of Teflon)
If the temperature exceeds C), the release layer will deteriorate and be damaged.

Furthermore, if a copy is made using a large size sheet after passing a small size sheet, the developer (toner) becomes hot offset and lands on the fixing roll side, resulting in a copy defect.

Therefore, an object of the present invention is to improve the above-mentioned defect of poor heat distribution in the axial direction in a heat fixing roll in which a resistive heating element layer is provided on a ceramic core, and to prevent heat accumulation and hot offset in the area beyond the paper passing section. It is an object of the present invention to provide a heat fixing roll that is less likely to cause this.

[Means for Solving the Problems] The present inventors formed a ceramic core by a printing method that controls the volumetric density of the resistance heating element material on the ceramic core in accordance with the temperature distribution in the axial direction of the heating roll during fixing. The problem of surface marking was solved by using and covering the resistive heating element sheet.

That is, the present invention uses a printing method to form a resistance heating element material sheet in which the volume of the resistance heating element material is small in the paper passing area at the center, and then spreads this resistance heating element material sheet around the outer periphery of a cylindrical support. There is a method for forming a resistive heating element layer of a heating fixing roll, which comprises heating and baking the resistive heating element material on the support after transferring the resistive heating element to the support.

The method for forming a resistive heating element layer of the present invention will be explained according to the T diagram shown in FIG.

The raw materials for the resistance heating element material used in the method of the present invention are conductive particles, glass powder, and a vehicle.

As the conductive particles, various metal powders, metal oxide powders, metal oxide powders, metal oxide powders, etc. can be used.

Such conductive particles include A(j, Pd, Ni,
Metal powder such as Cu, AI, Cr, RuO2, M2 Ru
Metal oxides such as 2 o□ x (M is 3i, pb, 3a, etc.), nickel-boron alloy (hereinafter referred to as NiB).
Examples include metal borides such as, metal phosphides such as nickel-phosphorus alloy (hereinafter referred to as NiP), and the like. Among these, preferred is Ni or Ni-based compound powder, which has a large TCR value, and particularly preferred is NiB, which is low in cost and changes to Ni when fired in the atmosphere. B is N
This prevents oxidation of i and allows firing in the atmosphere.

Hereinafter, the case where NiB is mainly used will be explained in detail.

NiB can be present in almost any ratio of Ni to B, but NiB suitable as a raw material for the resistance heating element of the heat fixing roll of the present invention has a B content in the range of 1 to 20% by weight. Commercially available N1B (B content: about 10 to 12% by weight) is preferably used. If the B content is less than 1% by weight, Ni will be oxidized during the firing process in the atmosphere, producing non-conductive nickel oxide, so the firing conditions (firing speed, firing temperature, firing atmosphere, etc.) must be strictly controlled. There is. Furthermore, if the content of 8 in NiB exceeds 20% by weight, the hygroscopic component becomes hygroscopic, resulting in poor moisture resistance, which is not preferable.

The glass binder is fused to the surface of the ceramic or enamel used as a support by firing.
It is used to form a strong resistance heating layer, and preferably a material whose coefficient of thermal expansion is close to that of the support material is selected and used.

The proportions of NiB and glass binder used can vary within wide limits. That is, the ratio of NiB is 10 to 9
It is used within a range of 6% by weight, preferably 20 to 80% by weight (therefore, the glass binder is 4 to 90% by weight, preferably 20 to 80% by weight).

The vehicle is used as a printing improver to print well on the transfer sheet by making a paste of powdered glass binder and NiB.

As a vehicle, materials commonly used in the printing field, such as 2 to 15 parts by weight of a binder such as ethyl cellulose, nitrocellulose, or acrylic resin, are mixed with 100 parts by weight of a solvent such as butylcalcitol acetate, carpitol acetate, or terpineol. A dissolved solution is used.

The amount used is the total amount of NiB and glass binder (100
5 to 70 parts by weight.

The vehicle, NiB powder, and glass binder powder are uniformly mixed using a stirrer such as a Raikai machine or a three-roll stirrer to form a paste. After degassing if necessary, a uniform thin film is formed on the transfer paper using a printing method. to print. Any general printing method can be used as the printing method, but it is particularly suitable for its productivity, ability to form a long-life film thickness of about 10 to 30 μm, and highly accurate film thickness control (±1 μTrL). A screen printing method using a silk screen or the like is preferred.

In the present invention, when the volumetric weight of the resistance heating element material printed on the transfer paper is later transferred to the support roll core, printing is performed for a long time using a halftone printing method or the like so that it is reduced in the central oil paper area. Alternatively, printing is performed using the multilayer printing method 11 so that the thickness of the second and subsequent layers becomes thinner in the center.

Normally, temperature control without any practical problems is possible by a two-layer multilayer printing method.

The film thickness (dry) of pastes 1 to 1 to be formed on the transfer sheet is 5 to 100 μm, preferably 15 to 40 μm, and the difference in film thickness between the center and both ends is about 5 to 10 μm.

This level of film thickness difference has no effect on fixing performance.

If the film thickness is less than 5 μm, disconnection is likely to occur due to thermal stress during energization.

On the other hand, if the thickness exceeds 100 μm, smooth transfer to the support will not be possible, and the heat capacity will increase when used as a heating fixing roll, resulting in a long warm-up time.

After drying the paste print on the transfer sheet at room temperature or by heating, if desired, a resin liquid is applied to the surface by top printing45, dried and reinforced, and then divided to fit the shape of the support roll core. disconnected.

The support roll core is made of pipe-shaped ceramic made of alumina or mullite, or aluminum whose surface is insulated with enamel or other inorganic material.
Metal such as stainless steel.

After coating the surface of the support roll core with a transfer liquid (water, etc.), the above-mentioned transfer sheet is wound around the support roll core while rotating, a dry paste is applied thereto, and the transfer is performed, followed by drying at room temperature or heating and baking.

As mentioned above, when using NiB, calcination 1 is performed in the atmosphere.
However, when using Ni powder etc., a non-oxidizing atmosphere (
It is necessary to sinter in N2, Ar gas, etc.).

The firing temperature and time may vary depending on the conductive or non-conductive particles used, the type of glass binder, the film thickness of the transfer paste, etc.
The temperature is 00 to 950°C, usually 600 to 700°C, and the baking time is about 10 minutes to 3 hours in total.

Through this firing step, a solid layer containing a conductive material in a glass binder to form a conductive path is fused to the surface of the support roll to form a resistive heating element layer. When using NiB powder, this firing converts it into N1Bh (Nl) in the glass binder to form a heat generating layer.

[Example] Examples of a heating fixing roll in which a resistance heating layer is provided on the surface of a support roll by the method of the present invention and a fixing device using the roll will be described below with reference to the drawings.

FIG. 3 is a front sectional view of an example of a fixing device equipped with the heat fixing roll of the present invention.

This fixing device has a configuration in which a heating roll 1 and a pressure roll 10 are opposed to each other, similar to conventional fixing devices. The heating tube 1 has a cylindrical mullite core with a diameter of 25 mm, a length of 250 mm, and a wall thickness of 1.5 m, and a resistive heating element layer of the present invention (thickness: 16 μm) uniformly coated over the entire surface.
) and further has a Teflon release layer 4 with a thickness of 200 m.

The resistance heating element layer was formed by the following method.

NiB powder (B content 10.5Φ amount%, average particle size 1 μm)
30% by weight crow flour binder (matched to the coefficient of thermal expansion of the mullite core, average particle size 5 μm) 50% by weight Vehicle consisting of ethyl cellulose and terpineol 20% by weight After uniformly mixing the above ingredients using a Raikai machine, A base was printed on the transfer sheet using a 200-mesh silk screen to a film thickness of 24 μm (when dry) from the paste that had been left to stand and defoamed, and was dried at room temperature for 1 day.

Next, using a paste having the same composition as the base material, two layers of resistance heating elements were printed on both ends of the roll, which are exposed to high temperatures, using a halftone dot printing method, and then dried.

Next, this was cut to match the size of a mullite core, and transferred by rotating it around a mullite core coated with an aqueous resin solution, followed by drying at 100° C. for 15 minutes. next,
The temperature was raised to 680'C in air over 25 minutes, kept at that temperature for 10 minutes, fired, and cooled to room temperature for 25 minutes, resulting in a uniform heating resistor layer (T
CR3500ppm/'C> was formed.

Cylindrical electrodes 5° 5a are provided on both sides of the ceramic core 2, and the cylindrical electrodes and the heat generating layer are connected by conductive wires 6.
, 6a. The cylindrical electrodes 5, 5a are in contact with sliding bearings 7, 7a that support the heating roll 1, and the sliding bearings 7.7a are each connected with a conductive wire 8 from a power source.
, 8a are connected.

The frames 15, 158 of the copying machine are each provided with a bearing housing 16, 16a formed of an insulating member,
The above-mentioned slide bearings 7, 7a are supported by the bearing housing. The conductors 8 and 8a are connected through holes 17.17a formed in the bearing housing, and a drive gear 18 is fixed roughly on the outside of the bearing housing 16, and this gear meshes with the motor side gear 19. heating roll 1
It is designed to rotate.

The pressure roll 10 formed opposite to the heating roll 1 is
As shown in FIG. 4(a), it is formed by covering the surface of a metal core 11 with an elastic body 12, and is supported by bearing members 13 on both sides so that it can rotate freely. The heating roll 1 rotates as the heating roll 1 rotates.

The pressure roll 10 is made of a metal core with a diameter of 15 m, the surface of which is coated with silicone sponge to a thickness of 5 mm, and a spring or the like is used to prevent eggs of 5K9 from coming into contact with the heating roll.

Further, as shown in FIG. 4(a), the fixing device has a paper transport path formed by guide plates 24 on both sides of the sandwiching portion between the heating roll 1 and the pressure roll 10, and the paper transport path is The toner image 21 formed on the surface of the paper 20 being conveyed along the path is fixed by applying pressure and heating.

Around the heating roll 1, there is a temperature sensor 22 for temperature control, and a peeling claw 23 for peeling off the copy after fixing.
etc. are provided.

In the 1J11 heat fixing device with the above configuration, the electrode 5°5
When a voltage of 100V was applied to a, 20V was applied in about 20 seconds.
It reaches 0'C, and the power at that time is about 500WV'Ct.
Tsu lko.

200 in the case of a method using a conventional halogen lamp.
900 to 1000 W is required to obtain ℃, and approximately 5
Compared to the time it took ~10 minutes, the heat fixing roll of the present invention allows copying to be started in a fraction of the time of the conventional method, and the power consumption can be reduced by several tens of percent. .

Furthermore, after testing 30,000 sheets of continuous copying, the output of the heating element decreased by less than 1%, indicating that it has an extremely long life.

In addition, even during continuous copying of small-sized paper, the area printed with two layers of halftone dots has a slightly lower resistance value, so the amount of heat generated can be controlled to a low level, and the non-oiled paper area does not become hot unlike conventional methods, resulting in good copying. It has become clear that it can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the flow of the method for forming a resistance heating layer on a heat fixing roll according to the present invention, FIG. 2 is a schematic diagram of a conventional heat roll type fixing device, and FIG. FIG. 4(a) is a schematic side sectional view, and FIG. 4(b) is a perspective view of the heating roll portion of FIG. 4(.). It is. Marks in the figure @: 1.1a... Heating roll; 2... Ceramic core; 3... Resistance heating element layer; 4... Release layer: 5.5a
... Cylindrical electrode: 6.6a... Conductor near, 7a...
・Sliding bearing; 8... Conductor: 10', 10a...
Pressure roll; 11...Metal core; 12...Elastic body; 13.13a...Bearing; 14...Shaft: 15.
158... Frame: 16.16a... Bearing housing; 17... Hole; 18... Drive gear:
19...Motor side gear: 20...Paper; 21.
... Toner image; 22 ... Temperature sensor; 23.
... Peeling claw; 24... Kite board; 25... Internal heating element. Figure 1 Figure 2

Claims (1)

[Claims] Using a printing method, a sheet of resistance heating element material whose volumetric weight is smaller in the paper passing area at the center is formed, and after this sheet of resistance heating element material is transferred to the outer periphery of a cylindrical support, it is supported. A method for forming a resistance heating element layer of a heating fixing roll, which comprises heating and baking a resistance heating element material on the body.