JPH03241380A - Heating device - Google Patents

Abstract

PURPOSE:To prevent the degradation of a film and simultaneously to smoothly transport the film by specifying the surface roughness of a part where a heating body adheres to the heat resistant film. CONSTITUTION:A transfer material sheet P on which an unfixed toner image Ta is carried is guided by a guide 29 and advances between the fixing film 24 of the press-contacting part N of the heating body 20 and a pressure roller 28 and the pressure roller 28. The unfixed toner image Ta is heated to be softened and fused on the press-contacting part N, and becomes a toner image Tc completely fixed on a cooled/solidified sheet P before it is ejected. At this time, the surface roughness R2 (the average roughness of ten pieces measured in accordance with JIS-BO 601) of the part where, at least, the heating body 20 adheres to the heat resistant film 24 is set at 0.3mum<=R2<=3mum. Thus, the degradation of the durability of the film 24 at an early stage caused by over- abrasion and the unstabilization of the transport are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heating device that applies thermal energy to a material to be heated, such as a recording material, through a heat-resistant film.

This device is an image heating fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, or a fax machine, that is, it is made of heat-melting resin, etc., by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. Recording materials (electrofax sheets, electrostatic recording sheets,
An unfixed toner image corresponding to the desired image information, formed directly or indirectly (transfer) on the surface of a transfer material sheet, printing paper, etc., is permanently fixed to the surface of the recording material that carries the image. It can be used as an image fixing device that performs heat fixing processing.

Further, the present invention is not limited to an image fixing device, and can be widely used as a means/device for heat-treating a material to be heated such as an image carrier, such as a device for heating a recording material carrying an image to modify its surface properties.

(Prior Art) Conventionally, a heating device for a recording material, for example, for heat-fixing an image, includes a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and pressed against the heating roller. By,
A heated roller system that heats the recording material while nipping and conveying it is often used.

In addition, various methods and configurations such as a flash heating method, an oven heating method, and a hot plate heating method are known and are in practical use.

Held heating systems are also known, as disclosed in US Pat. No. 3,518,191. This is because: (1) the toner image is brought into contact with the heating web and heated to its melting point, (2) the toner is cooled to a relatively high viscosity after melting, and (2) the toner tends to adhere to the heating web. This method allows the adhesive to be fixed without causing offset by peeling it off from the heating web in a weakened state.

Recently, a heating element (thermal heater, hereinafter referred to as heater) that is fixedly supported, a heat-resistant film (fixing film) that is conveyed while being in pressure contact with the heater, and a recording material is closely attached to the heater through the film. An apparatus having a method and configuration that heats and fixes an unfixed image formed and supported on the surface of the recording material by applying heat from a heater to the recording material through the film. heating method) has been devised.

For example, Japanese Patent Application Laid-Open No. 63-3131 related to the applicant's previous proposal
The system, device, etc. disclosed in Publication No. 82 belongs to this category, and includes a thin heat-resistant film (sheet), a means for moving the film, and a fixed support arrangement on one side of the film with the film inside. and a pressure member disposed on the other side facing the heater to bring the image-bearing surface of the recording material to which the image is to be fixed into close contact with the heater through the film, and the film is At least when performing image fixing, the recording material to be image-fixed is conveyed and introduced between the film and the pressure member, and the heater and the pressure member are moved at the same speed in the same direction as the recording material to which the image is to be fixed. The image-bearing surface of the recording material is heated by the heater through the film by passing through a fixing nip section as a fixing section formed by pressure contact with the recording material, and heat energy is applied to the visible image (unfixed toner image). This heating means/device is basically applied to the film, softens and melts it, and then separates the film and recording material after passing through the fixing section at a separation point.

In such film heating type equipment, a low heat capacity heating element can be used as the heater, which results in lower power consumption and less wait time compared to conventional contact heating type devices such as heat roller type or belt heating type. This method is effective because it has advantages such as being able to shorten the time (quick start) and solving various drawbacks of other conventional devices.

The heater as a heating element is formed by coating a low heat capacity current-carrying heating resistor in a linear or band shape on a heat resistant, good thermal conductivity, low heat capacity insulating substrate (base material) such as ceramic. A heater having a low heat capacity of the above embodiment is used, and when the resistor is energized, the temperature of the surface of the heater rapidly rises to the required fixing temperature because the heat capacity of the resistor and the substrate is small.

The heat-resistant film in contact with the heater also has a small heat capacity, and thermal energy from the heater side is effectively transmitted via the film to the recording material that is in pressure contact with the film, thereby performing thermal fixation of the image.

The heater temperature is controlled using an energization control configuration in which the heater temperature is detected by a temperature sensing element, and the energization to the energized heating resistor is controlled based on the temperature detection information to control the temperature of the heater to a predetermined fixing temperature. .

(Problems to be Solved by the Invention) However, in the film heating type device in which the film is slid on a fixedly supported heater, the film may deteriorate due to abrasion in the sliding part, and wear particles may be generated. For example, in an image fixing device, this may have an adverse effect on the image.

Furthermore, if the surface of the heater is made too smooth to prevent film abrasion, the adhesion between the film and the heater will improve, increasing frictional force, which may reduce the durability of the gears and motors that drive the film. There were problems such as not being able to drive the film smoothly.

An object of the present invention is to solve the above-mentioned problems in a film heating type heating device.

(Means for Solving the Problems) The present invention provides a heat-resistant film that is driven to feed in close contact with a heating body that is disposed in a fixedly supported manner. It is a heating device that applies thermal energy to the heated body from the heating body side through the heat-resistant film by passing the heating body in close contact with the heating body. The heating device is characterized in that Rz (ten-point average roughness measured according to JIS-BO601) or 0, -3 μm≦Rz≦3 μm.

(Function) That is, the surface roughness Rz of at least the portion of the heating body (heater) that comes into close contact with the heat-resistant film is set to 0.3 μm≦Rz≦3 μm, preferably 0.7 μm≦Rz52 μm, as described above. This optimizes the sliding balance between the heating element and the film, reduces early durability deterioration of the film and generation of abrasion powder due to excessive wear, and prevents excessive frictional force between the heating element and the film. The present invention was completed based on the discovery that the instability of the backward drive of the film and the significant deterioration of the durability of the gears, motors, etc. of the drive unit due to this can be prevented.

If Rz > 3 μm, the film will wear out early, and film abrasion powder will be generated, which will greatly reduce the durability of the film, and in image fixing devices, it will cause image defects such as uneven gloss and poor fixing. .

If Rz<3 μm, the frictional force between the heating body and the film becomes excessive, reducing the durability of gears, motors, etc. of the film traveling drive unit, and also causing instability in film transport or inability to move the film.

(Example) <Example 1> (1) Example of image forming apparatus (FIG. 2) First, an example of an image forming apparatus using a heating device according to the present invention as a fixing device for an unfixed image will be described.

The apparatus of this example is an electrophotographic copying apparatus with a reciprocating document table, a rotating tram type, and a transfer type.

In FIG. 2, reference numeral 100 denotes an apparatus housing, and numeral 1 denotes a reciprocating document mounting table made of a transparent plate member such as a glass plate, which is disposed on the upper plate 100a of the housing. are driven to reciprocate at predetermined speeds in the right direction a and the left direction a' in the drawing, respectively.

G is a document, which is placed by placing the image side to be copied facing down on the top surface of the document table 1 according to a predetermined placement standard, and placing the document pressure bonding plate 1a on top of it and pressing it down. .

Reference numeral 100b denotes a slit opening, which serves as a document illumination section, and is opened on the surface of the top plate 100a of the machine casing, with its length extending in a direction perpendicular to the direction of reciprocating movement of the document table 1 (direction perpendicular to the plane of the paper). The downward image surface of the document G set on the document platform 1 passes through the position of the slit opening 100b sequentially from the right side to the left side during the forward movement of the document platform 1 to the right side a. During the passage, the light from the lamp 7 is received through the slit opening 100b and the transparent original table 1, and the document is illuminated and scanned. The light reflected from the document surface of the illumination scanning light is imaged and exposed on the surface of the photosensitive drum 3 by the short focus and small diameter imaging element array 2.

The photosensitive drum 3 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is driven to rotate clockwise as shown by an arrow around a central support shaft 3a at a predetermined circumferential speed, and is charged during the rotation process. The image-forming exposed original image is formed on the surface of the photosensitive drum 3 by being subjected to a positive or negative charging process by the charger 4, and the image-forming exposure (slit exposure) of the original image on the charged surface thereof. Electrostatic latent images corresponding to the images are sequentially formed.

This electrostatic latent image is sequentially visualized by a developing device 5 using toner made of a resin or the like that softens and melts when heated, and the developed toner image is transferred to a location where a transfer discharger 8 is provided as a transfer section. I will do it.

S is a cassette in which transfer material sheets P as recording materials are stacked and stored, and the sheets in the cassette are fed and fed one by one by the rotation of the feeding roller 6, and then are transferred to the drum 3 by the registration roller 9. The timing is set so that when the tip of the toner image forming section reaches the transfer discharger 8, the tip of the transfer material sheet P also reaches the open position of the transfer discharger 8 and the photosensitive tram 3, so that they coincide. Feeds synchronously. Then, the toner image on the photosensitive drum 3 side is sequentially transferred onto the surface of the fed sheet by the transfer discharger 8.

The sheet to which the toner image has been transferred in the transfer section 8 is sequentially separated from the surface of the photosensitive drum 3 by a separating means (not shown), and is guided by a conveying device 10 to a fixing device 11 (to be described later) to remove the unfixed toner image carried thereon. After the heat-fixing process, the image is discharged onto a paper discharge tray 12 outside the machine as an image-formed product (copy).

On the other hand, the surface of the photosensitive drum 3 after the toner image is transferred is subjected to removal of adhered contaminants such as residual toner by a cleaning device 13, and is used repeatedly for image formation.

(2) Fixing device 11 (Figs. 1 and 2) 24 is an endless belt-shaped fixing film, which is arranged between a drive roller 25 on the left side, a driven roller 26 on the right side, and below between the drive roller 25 and the driven roller 26. A low heat capacity linear heating body 20 as a heating body is suspended between the three members 25, 26, and 20 parallel to each other. The fixing film 24 will be described in detail in section (4) below.

The driven roller 26 is an endless belt-shaped fixing film 2.
The fixing film 24 is fixed clockwise at a predetermined circumferential speed as the drive roller 25 rotates clockwise, that is, the unfixed toner image Ta conveyed from the image forming section 8 side. wrinkles, meandering, etc. at the same peripheral speed as the conveyance speed of the transfer material sheet P carrying the
Rotation is driven without speed delay.

The drive roller 25 is a metal roller coated with a heat-resistant material having a high coefficient of friction, such as silicone rubber, against the film 24, and the driven roller 26 is a metal roller coated with a heat-resistant material having a high coefficient of friction, such as silicone rubber, etc. It is.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer such as silicone rubber with good mold releasability as a pressure member. The lower surface is pressed against the lower surface by a biasing means (not shown) with a total pressure of, for example, 4 to 7 kg, and is rotated in a forward counterclockwise direction in the conveying direction of the transfer material sheet P.

The heating element 20 is a low heat capacity linear heating element whose length is in the direction (width direction of the film) that intersects the plane movement direction of the film 24, and includes a heater substrate 21, a current-carrying heating resistor (heating element) 2
2. It consists of a temperature measuring element 23, etc., and is fixedly supported by being attached to a heater support 27.

The heater support 27 has heat insulation properties, high heat resistance, and rigidity to thermally support the heating body 20 with respect to the fixing device 11 and the image forming device, and is made of, for example, pps (polyphenylene sulfide), PAI (polyamideimide), PI (polyimide). ), PEEK (polyetheretherketone), liquid crystal polymer, and other highly heat-resistant resins, and composite materials of these resins and ceramics, metals, glass, etc.

The heater board 21 is a heat-resistant, insulating, low heat capacity, and high thermal conductive member, and has a thickness of 1 mm and a width of 10 m, for example.
・It is an alumina substrate with a length of 240 cm.

The heating element 22 is formed of, for example, Ag/Pd (
electrically resistive material such as silver palladium) or Ta2N to a thickness of approximately 1.
It is coated to a thickness of 0 μm and a width of 1 to 3 mm by screen printing, etc., and then a layer of heat-resistant glass 21a is applied as a surface protective layer for about 100 μm.
It is coated with μm coating.

The outer surface of this heat-resistant glass layer 21a is the contact sliding surface of the heat-resistant film 24 in the heating element 20 of this example, and the roughness of the outer surface of this glass layer 21a is set according to the present invention. This will be explained in detail in section (5) below.

For example, the temperature sensing element 23 is mounted on the upper surface of the substrate 21 (the heating element 22
It is a low heat capacity temperature measuring resistor such as a PT film, which is coated by screen printing or the like on the substantially central part of the surface opposite to the surface on which the temperature sensor is provided.

As the temperature measuring element, a thermistor having a low heat capacity or the like may be arranged in contact with the substrate 21.

In the case of the heating element 20 of this example, electricity is applied to the heating element 22 which is linear or strip-shaped from both ends in the elongated direction.
2 to generate heat over almost its entire length. AClooV is used for energization.
According to the temperature detected by the temperature measuring element 23, the energization power is controlled by controlling the phase angle of energization by an energization control circuit (not shown) including a triac.

(3) Fixing Execution Operation The device performs an image forming operation in response to an image forming start signal, and the transfer material sheet P carrying an unfixed toner image Ta on its upper surface is conveyed from the transfer section 8 to the fixing device 11 through a guide 29.
The pressure contact portion N between the heating body 20 and the pressure roller 28 is guided by
The toner enters between the fixing film 24 and the pressure roller 28, and the unfixed toner image surface comes into close contact with the lower surface of the fixing film 24, which is rotating in the same direction at the same speed as the conveyance speed of the sheet P, causing surface misalignment. fixing film 24 without causing wrinkles.
The heating body 20 and the pressure roller 28 pass through the mutual pressure contact portion N of the heating body 20 and the pressure roller 28 while being subjected to a clamping force.

Since the heating body 20 is energized and heated at a predetermined timing in response to an image formation start signal, the toner image Ta is heated at the pressure contact portion N.
It is heated to become a softened and melted image Tb.

The running direction of the fixing film 24 is turned at an acute angle (bending angle θ is approximately 45°) at an edge portion S of the heater support 27 having a large curvature (the radius of curvature is approximately 2 mm). Therefore, the sheet P conveyed through the pressure contact portion N while overlapping the fixing film 24 is separated from the fixing film 24 by the curvature at the edge portion S, and is discharged to the paper discharge tray 12.

By the time the sheet is ejected, the toner has sufficiently cooled and solidified, and the sheet P
The toner image is completely fixed (toner image Tc).

The toner used in this example has a sufficiently high viscosity when melted by heating, so even if the toner temperature when separated from the fixing film 24 is higher than the melting point of the toner, the adhesion force between the toners is sufficient to maintain the adhesion of the toner to the fixing film. Therefore, when the fixing film 24 and the sheet P are separated, toner offset with respect to the fixing film 24 does not substantially occur.

Furthermore, in this example, the heat capacity of the heating element 22 and the substrate 21 of the heating element 20 is small, and these are also thermally supported by the support 27. Toner melting point (or sheet P
Since the temperature is raised to a sufficiently high temperature with respect to the fixing temperature of
Moreover, it also prevents the temperature inside the aircraft from rising.

(4) Regarding the fixing film 24 The fixing film 24 is a single layer with a total thickness of 100 μm or less, preferably 40 μm or less, and has heat resistance, mold releasability, durability, etc., in order to reduce heat capacity and achieve quick start performance. Alternatively, a composite layer film can be used. FIG. 4 is a schematic diagram of the layer structure of an example of a composite layer film, and this example is a two-layer structure film. 24a is a heat-resistant layer serving as a base film of the fixing film, and 24b is a release layer laminated on the outer surface (the surface facing the toner image) of the heat-resistant layer 24a.

The heat-resistant layer 24a is made of, for example, polyimide, polyetheretherketone (PEEK), polyethersulfone (PES).
), polyetherimide (PE■), polyparabanic acid (
A film with excellent strength and heat resistance, such as a highly heat-resistant resin film such as PPA), can be used.

The release layer 24b is preferably made of PTFE (polytetrafluoroethylene), a fluororesin such as PFA-FEP, a silicone resin, etc. The linear layer 24b is laminated onto the heat-resistant layer 24a using an adhesive laminate of a release layer film or a release layer material. Lamination using film forming techniques such as electrostatic painting (coating), vapor deposition, and CVD,
This can be done by forming a two-layer film by co-extruding the heat-resistant layer material and the release layer material.

Since the thickness of the heat-resistant layer 24a is set to be thicker than the thickness of the release layer 24b, the total thickness of the film can be reduced while maintaining the strength of the film, and the efficiency of heat transfer from the heating body to the recording material is high.

Note that the surface resistance of the release layer 24b is preferably io'°Ω or less. The release layer 24b is formed by mixing a conductive agent such as carbon black, graphite, or conductive whiskers.
The resistance value of the surface may be lowered. In this case, charging of the toner contacting surface of the fixing film 24 can be prevented. When the toner contacting surface of the fixing film 24 is insulative, the surface of the fixing film is electrically charged, which may disturb the toner image on the sheet P or transfer the toner image to the fixing film 24 (so-called charge offset). However, these problems can be avoided by taking the above measures.

(5) Surface Roughness of Heating Body 20 In the apparatus of this embodiment, the heat-resistant film 24 slides in close contact with the outer surface of the above-mentioned surface protection layer 21a of the heater, which is the heating body 20.

Therefore, in this embodiment, the surface protective layer 21a of the heater 20 is
By baking a heat-resistant glass layer as a surface protective layer applied on the heating element 22 by a screen printing method in a clean room at a temperature close to the softening temperature of the glass, the surface roughness becomes 0.7 μm≦Rz52 μm. It is formed like this.

Generally, a rough surface is formed when foreign matter gets mixed in during firing or when the temperature changes suddenly. However, according to experiments conducted by the present inventors, it is possible to use a heater 20 in which the surface roughness of the surface protective layer 21a is Rz>3 μm. If you continue to form images for a long time with a device that has
The film will wear out and the image will be adversely affected. Here, the negative effects include abrasion powder generated between the heater 20 and the film 24, and the thickness of the film 24 becoming thinner in some areas, resulting in areas with different melting states of toner, resulting in uneven gloss and poor fixing. be. Further, if image fixing is continued using such a heater, scratches may be formed on the inner surface of the film, which may cause the film to break.

On the other hand, heat-resistant glass has a high softening temperature of about 10 io.

When fired with C), a smooth surface is formed, but Rz〈
When the thickness is 3 μm, the adhesion between the film 24 and the heater 20 (the outer surface of the surface protective layer 21a) is too good, and the frictional force between the film and the heater becomes large, making it difficult to transport the film smoothly.

That is, the film 24 does not move at the same speed as the drive roller 25, but may slide or vibrate.

Further, there is a drawback that the load on the gears and motor for rotating the drive roller 25 increases, and the durable life of these components is shortened.

By setting the surface roughness Rz of the surface protective layer 21a, which is at least the part of the heater 20 that comes into close contact with the film 24, to 0.3 μm≦Rz≦3 μm, preferably 0.7 μm≦Rz≦2 μm, The sliding balance between the heater 20 and the film 24 is optimized, reducing early durability deterioration of the film due to excessive wear and generation of abrasion powder. This also prevents instability of the film transport drive and significant deterioration of the durability of the gears, motors, etc. of the drive unit.

<Example 2> In the above <Example 1>, the surface protective layer 2 of the heater 20
Although the heater with the desired surface roughness was formed by controlling the firing conditions of the heat-resistant glass layer 1a, a complicated device is required to control the firing conditions in this way.

In this embodiment, a heater having a desired surface roughness is formed at low cost using a simple device by firing a heat-resistant glass layer and then polishing its surface.

For example, even if a heat-resistant glass layer 21a (R, H = 0.4 μm) with a rough surface due to minute dust etc. is formed during firing, the
By polishing the outer surface of the glass layer 21a using DIAMOND TOOLS MFG.

It is better to polish in the same direction (vertical direction) as the feeding direction of the film 24, as shown by arrow A in Fig. 3, to reduce the sliding wear of the film 24 and to reduce the frictional force. Therefore, it is preferable.

However, polishing in the longitudinal direction B (horizontal direction) of the heater, which is perpendicular to the six directions, has the advantage that polishing can be done more easily and in a shorter time.

(Effects of the Invention) As described above, according to the present invention, in a film heating type heating device, the sliding balance between the heating body and the film is optimized, which prevents early durability deterioration of the film due to excessive wear and wear particles. In addition to reducing the occurrence of this, it also prevents instability of the film running drive and a significant decrease in the durability of the gears and motors of the drive unit due to excessive frictional force between the heating element and the film. Prevented. Therefore, for example, it can be effectively used as an image heating fixing device which has advantages such as being durable and less likely to cause uneven gloss or poor fixing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of a heating device according to the present invention utilized as an image fixing device. FIG. 2 is a schematic diagram of the configuration of an example of an image forming device using the device. FIG. 3 is a partially cutaway plan view of the heating element. FIG. 4 is a schematic diagram of the layer structure of the fixing film. 11 is an image fixing device (heating device), 20 is a heating element (heater), 21 is a heater substrate, 22 is a heating element, 21a is a surface protective layer (heat-resistant glass layer), 23 is a horizontal groove element, 27 is a heater support , 24 is a heat-resistant fixing film, 25 is a driving roller, 26 is a driven roller, 28 is a pressure roller, and P is a recording material as a heated material.

Claims (1)

[Claims] (1) A material to be heated, such as a recording material, is brought into close contact with the surface opposite to the heating body side of a heat-resistant film that is driven to be fed in close contact with a heating body that is placed in fixed support, and passed through the heating body position. It is a heating device that applies thermal energy to the heated object from the heating body side through the heat-resistant film, and the surface roughness R_ of at least the part of the heating body that comes into close contact with the heat-resistant film is
A heating device characterized in that z (ten-point average roughness measured according to JIS-B0601) is 0.3 μm≦R_z≦3 μm.