JP5405900B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes toner and an image forming apparatus including the fixing device.

  An electrophotographic image forming apparatus that forms an image based on electrophotography (hereinafter, the electrophotographic image forming apparatus is simply referred to as an “image forming apparatus”) easily forms an image having good image quality. be able to. An image forming apparatus is widely used for a copying machine, a printer, a facsimile machine, a multifunction machine, and the like. The image forming apparatus includes, for example, a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The image forming apparatus performs a charging process, an exposure process, a development process, a transfer process, and a fixing process using the photoreceptor and these means. The image forming apparatus is an apparatus that forms an image on recording paper.

  As a fixing means for performing the fixing process, for example, a heat roller fixing type fixing device is used. The heat roller fixing type fixing device includes a fixing roller and a pressure roller. The fixing roller and the pressure roller are a pair of rollers in pressure contact with each other. At least one of the fixing roller and the pressure roller includes a heat source such as a halogen heater as a heating unit.

  In the fixing process, after the heat source heats the roller pair to a predetermined temperature required for fixing (hereinafter referred to as “fixing temperature”), a recording paper such as paper on which an unfixed toner image is formed is fixed to the fixing roller and the pressure roller. Is supplied to a fixing nip portion which is a pressure contact portion. The unfixed toner image passing through the fixing nip portion is fixed on the recording paper by heat transmitted from at least one of the fixing roller and the pressure roller and pressure by the fixing roller and the pressure roller. The portion of the fixing nip where the recording paper has passed (hereinafter referred to as “sheet passing portion”) is heated to the fixing temperature by a heating source, although the temperature is lowered.

  When a fixing roller having an elastic layer on the surface (hereinafter referred to as “elastic roller”) is used as the fixing roller, the elastic layer on the surface of the elastic roller is elastically deformed corresponding to the unevenness of the unfixed toner image at the fixing nip portion. To do. The elastic roller is in contact with the unfixed toner image so as to cover the unfixed toner image, so that the fixing property is improved for a color unfixed toner image having a larger amount of toner than a single color image.

  The elastic roller improves the releasability of the color toner that is more likely to be offset than a monochromatic image due to the strain relief effect of the elastic layer on the surface of the elastic roller. Specifically, the elastic layer that has been compressed and distorted at the fixing nip portion is released from the distortion at the exit of the fixing nip portion. Deviation occurs. As a result, the adhesive force of the elastic layer to the toner image is reduced and the releasability is improved.

  The nip shape, which is the shape of the fixing roller and the pressure roller in the fixing nip portion, is convex toward the fixing roller (reverse nip shape), thereby improving the separation performance between the fixing roller and the recording paper. As the peeling means for peeling the fixing roller and the recording paper, for example, self-stripping capable of peeling the recording paper and the fixing roller without using a peeling claw is realized, and image defects caused by the peeling means are eliminated. In a fixing device provided in an image forming apparatus capable of full color printing, for example, silicon rubber or the like is used as an elastic layer of an elastic roller.

  In a fixing device provided in an image forming apparatus capable of full-color printing, in order to cope with an increase in speed, it is necessary to widen the nip width that is the width of the fixing nip portion in the recording paper conveyance direction. As means for increasing the nip width, there are two methods of increasing the elastic layer of the elastic roller or increasing the diameter of the elastic roller. However, since the thermal conductivity of the elastic layer of the elastic roller is very low, if the elastic layer of the elastic roller having heating means inside the elastic roller is thickened, the warm-up time becomes longer. When the process speed is increased, the temperature of the fixing roller cannot follow the fixing temperature. Increasing the elastic roller diameter increases the power consumption of the heating means.

  Patent Document 1 discloses a belt fixing type fixing device including a fixing roller, a pressure roller, a heating roller, and a fixing belt. A fixing belt is stretched between the fixing roller and a heating roller including a heater for heating, and the fixing roller and the pressure roller are brought into pressure contact with each other via the fixing belt. In order to ensure a wide nip width, an elastic layer made of sponge rubber or the like of the fixing roller is provided thick and has a low hardness. In order to shorten the warm-up time, the fixing belt having a small heat capacity is heated by a heating roller as heating means. The elastic layer having a large heat capacity is not heated.

  Patent Document 2 discloses a fixing device of a belt fixing system using an elastic fixing belt that wraps color toner in order to perform clear image fixing.

JP-A-10-30796 Japanese Patent No. 3712086

  As shown in Patent Document 1, the hardness of the fixing roller is lowered in order to ensure a wide nip width. As shown in Patent Document 2, the fixing belt needs a certain degree of elasticity in order to enclose the color toner. In belt fixing, hot offset and wrapping of used paper are more likely to occur than in roller fixing, and therefore the temperature range (hereinafter referred to as “fixable temperature range”) in which good fixing can be obtained is narrow. Since the fixing temperature range for belt fixing is narrow, when the paper type, environment, or toner amount changes, poor fixing, rough images, or paper wrapping around the fixing member is likely to occur, and image quality and convenience are improved. Damaged. As a result, costly temperature control is required, recording paper is limited, toner is thinned at the expense of image quality, a large amount of wax is added, and insufficient fixing strength occurs. There is.

  In order to widen the fixable temperature range, it is necessary to instantaneously restore the fixing belt and the fixing roller, which are members in contact with the image surface, when the member in contact with the image surface is released from pressure. . When the elasticity of the fixing belt is large, the fixing belt cannot follow the restoration of the fixing roller even if the fixing roller is instantaneously restored. When the hardness of the fixing roller is low, the resilience of the fixing roller is lowered, so that the instantaneous restoring property cannot be obtained sufficiently.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device having a wider temperature range capable of fixing toner onto a member to be fixed than in the prior art, and an image forming apparatus including the fixing device.

An endless fixing belt that contacts the toner image on the fixing member and fixes the toner image on the fixing member;
A heating roller for heating the fixing belt;
The endless fixing belt is stretched together with the heating roller, and the fixing roller is in contact with the toner image on the fixing member via the fixing belt;
A pressure roller in pressure contact with the fixing roller via the fixing belt,
The fixing belt has a fluororesin layer, a rubber elastic layer, and a resin base material layer toward a contact surface with the fixing roller with reference to a contact surface in contact with the toner image on the member to be fixed,
The resin substrate layer is made of polyimide having a thickness of 50 μm or more and 90 μm or less,
The fluororesin layer is made of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether having a thickness of 5 μm or more and 20 μm or less,
The rubber elastic layer has a thickness of 30 μm to 150 μm,
With the outer diameter of the fixing belt being A mm, the fixing belt is passed through a first metal shaft having an outer diameter of 13 mm and sufficiently longer than the width of the fixing belt, and both ends of the first metal shaft are fixed. It is sufficiently longer than the fixing belt width, and the weight divided by the fixing belt width is 0. The vertical length of the fixing belt when passing through a second metal shaft of 359 g / mm and an outer diameter of 13 mm through the fixing belt so that the fixing belt extends downward is Bmm,
When S is the flexibility of the fixing belt, S = (B−A) / A
The flexibility S of the fixing belt represented by: 0.15 to 0.24 ,
In the fixing roller, a weight having an outer diameter of 11 mm and a weight of 7 g suspended from a thread of 50 cm in length is arranged so that the center of gravity of the weight is arranged on a horizontal plane including the central axis of the fixing roller in a stationary state. When at the lowest point of contact, the weight is lifted from the lowest point by a height of H1 = 10 cm, and when the weight is gently released to cause the weight to collide with the fixing roller, the height from the lowest point at which the weight rebounds. When the thickness is H2 and the repulsion coefficient of the fixing roller is R, the following equation is given: R = H2 / H1
The fixing device is characterized in that the restitution coefficient R of the fixing roller is 0.6 or more.

In the invention, it is preferable that a surface pressure of a fixing nip portion, which is a region where the pressure roller is in pressure contact with the fixing roller, is 1.4 kgf / cm ² or more.

  In the invention, it is preferable that the fixing roller has an Asker C hardness of 30 to 50 degrees.

  In the invention, it is preferable that the ratio of the weight of the toner wax to the total weight of the toner forming the toner image is 1.5% by weight or more and 4.8% by weight or less.

Further, in the present invention, the fixing roller has a surface portion in contact with the fixing belt formed of an elastic layer,
The elastic layer has a thickness dimension of 4 mm or more and 6 mm or less.

Further, in the present invention, the fixing roller has a surface portion in contact with the fixing belt formed of an elastic layer,
The ratio of the thickness dimension when the elastic layer is pressed by the pressure roller via the fixing belt and the thickness dimension when the elastic layer is not pressed is 25% or more and 35% or less. It is characterized by that.

  According to another aspect of the present invention, there is provided an image forming apparatus comprising the fixing device.

According to the present invention, the fixing belt has the outer diameter of the fixing belt A, the fixing belt is passed through the first metal shaft having an outer diameter of 13 mm and sufficiently longer than the width of the fixing belt, and both ends of the first metal shaft are fixed. In this state, it is sufficiently longer than the fixing belt width, and the weight divided by the fixing belt width is 0. When the second metal shaft having an outer diameter of 359 g / mm is passed through the fixing belt so that the fixing belt extends downward, the vertical length of the fixing belt is B, and the flexibility of the fixing belt is S. When S = (B−A) / A
The fixing belt has a flexibility S of 0.15 to 0.24 , and the fixing roller is fixed in a stationary state with a weight of 11 g and an outer diameter of 11 mm suspended on a 50 cm long thread. When it is at the lowest point that touches so that the center of gravity of the weight is placed on the horizontal plane including the central axis of the roller, lift the weight from the lowest point by a height of H1 = 10 cm, and gently release the weight to release the weight. When the height from the lowest point where the weight bounces when colliding with the fixing roller is H2, and the restitution coefficient of the fixing roller is R, the restitution coefficient R of the fixing roller represented by R = H2 / H1 Is 0.6 or more, the temperature range in which the toner can be fixed on the member to be fixed can be made wider than in the past.

  In addition, according to the present invention, since the fixing device is provided, an image forming apparatus including a fixing device having a wider temperature range capable of fixing toner onto a member to be fixed than the conventional technique is provided. it can.

The constant Chakusochi second configuration of the present invention, the thickness of the fluororesin layer is a cross-sectional view schematically showing with fixing belts that are different from the present invention. FIG. 6 is a diagram for explaining a method for measuring flexibility of the fixing belt 5. 3 is a diagram for explaining a method for measuring the resilience of the fixing roller 3. FIG. 6 is a diagram for explaining a detent 41 of the fixing belt 5. 1 is a schematic diagram schematically illustrating an image forming apparatus 1 including a fixing device. FIG. 6 is a cross-sectional view schematically showing a configuration of a fixing device 91 according to a second embodiment of the present invention. A block diagram for controlling the fixing device 91 is shown. Examples of flexibility A1 and B1 when the outer diameter of the fixing belt 5 is changed and the theoretical limit of flexibility are shown. 6 is a diagram for explaining the relationship between the shape of the elastic layer of the fixing roller 3 at the outlet of the fixing nip portion 12 and the sheet peelability. FIG.

  In the following description, parts corresponding to matters already described in the forms preceding each form may be denoted by the same reference numerals, and overlapping descriptions may be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in the preceding section. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder. Moreover, each embodiment is illustrated in order to embody the technique which concerns on this invention, and does not limit the technical scope of this invention. The technical contents according to the present invention can be variously modified within the technical scope described in the claims.

  FIG. 1 is a cross-sectional view schematically showing the configuration of the fixing device 2 according to the first embodiment of the present invention. The fixing device 2 included in the image forming apparatus 1 includes a fixing roller 3, a pressure roller 4, an endless fixing belt 5, a heating roller 6 for suspending and heating the fixing belt 5, and a heating roller 6. The first thermistor 10 and the second thermistor 10 are temperature sensors constituting temperature detection means for detecting the temperatures of the heater lamps 7a and 7b, which are heat sources for heating the pressure roller 4 and the fixing belt 5 and the pressure roller 4, respectively. The thermistor 11 is provided.

  The fixing roller 3 has a substantially cylindrical shape and has a two-layer structure in which a core metal and an elastic layer are formed from the substantially cylindrical central axis toward the outer periphery. For the metal core, a metal such as iron, stainless steel, aluminum or copper, or an alloy thereof is used. A rubber material having heat resistance such as silicon rubber or fluorine rubber is suitable for the elastic layer. In the present embodiment, the diameter of the fixing roller 3 is 30 mm. Stainless steel with a diameter of 20 mm is used for the core metal, and silicon sponge rubber with a thickness of 5 mm is used for the elastic layer. The fixing roller 3 is provided to be rotatable about a substantially cylindrical central axis, and is rotated by the rotation of the pressure roller 4. When the fixing roller 3 is in pressure contact with the pressure roller 4 via the fixing belt 5, a fixing nip portion 12, which is a portion where the fixing roller 3 and the pressure roller 4 are in contact with each other via the fixing belt 5, is formed. Is done.

  The pressure roller 4 has a substantially cylindrical shape, and has a three-layer structure in which a metal core, an elastic layer, and a release layer are formed from the substantially cylindrical central axis toward the outer periphery. A metal such as iron, stainless steel, aluminum copper, or an alloy thereof is used for the core metal. A rubber material having heat resistance such as silicon rubber or fluorine rubber is suitable for the elastic layer. A fluororesin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is suitable for the release layer. In the present embodiment, the pressure roller 4 has a diameter of 30 mm. For the metal core, iron (STKM) having a diameter of 26 mm and a wall thickness of 2 mm is used. A silicon solid rubber having a thickness of 2 mm is used for the elastic layer. A PFA tube having a thickness of 50 μm is used for the release layer.

  The heater lamp 7 a is disposed inside the pressure roller 4 and heats the pressure roller 4. When a control circuit (not shown) supplies (energizes) power to the heater lamp from a power supply circuit (not shown), the heater lamp 7a emits light, and infrared rays are emitted from the heater lamp 7a. The entire pressure roller 4 is heated when the inner peripheral surface of the pressure roller 4 absorbs infrared rays emitted from the heater lamp 7a. In the present embodiment, a heater lamp 7a with a rated power of 300 W is used.

  The pressure roller 4 is provided to be rotatable about a substantially cylindrical central axis. The pressure roller 4 is a roller-like member that is rotationally driven by a drive motor that is a drive means (not shown). The fixing roller 3 presses against the pressure roller 4 via the fixing belt 5 to form the fixing nip portion 12, and at the same time conveys the fixing belt 5 by being driven to rotate. The fixing roller 3 rotates in the opposite direction to the pressure roller 4.

  The fixing roller 3 and the pressure roller 4 are pressed against each other with a predetermined load, for example, 400N. When the fixing roller 3 and the pressure roller 4 are pressed against each other, a fixing nip portion 12 is formed. In the present embodiment, the width of the fixing nip portion 12 in the recording paper conveyance direction (hereinafter referred to as “nip width”) is 8 mm. The fixing nip portion 12 is fed with a recording paper 8 as a member to be fixed that carries an unfixed toner image. As the recording paper 8 passes through the fixing nip portion 12, the toner image is fixed on the recording paper 8. When the recording paper 8 passes through the fixing nip portion 12, the fixing belt 5 contacts the toner image forming surface of the recording paper 8, and the pressure roller 4 is a surface on the back side of the recording paper 8 from the toner image forming surface. Abut.

  The fixing belt 5 has a diameter of 50 mm when not attached. The fixing belt 5 is formed with a hollow cylindrical base material made of a heat-resistant resin such as polyimide or a metal material such as stainless steel and nickel. An elastic layer made of an elastomer material such as silicon rubber, which is excellent in heat resistance and elasticity, is formed on the surface of the base material. On the surface of the elastic layer, a release layer made of a synthetic resin material which is excellent in heat resistance and release properties, for example, a fluororesin such as PFA or PTFE is formed. The fixing belt 5 has a three-layer structure including a base material, an elastic layer, and a release layer. In the present embodiment, polyimide having a thickness of 70 μm is used as the base material, silicon rubber having a thickness of 150 μm is used as the elastic layer, and a PFA tube having a thickness of 30 μm is used as the release layer.

  The fixing belt 5 heated to a predetermined temperature by the heating roller 6 heats the recording paper 8 on which an unfixed toner image passing through the fixing nip portion 12 is formed. The fixing belt 5 is suspended by the heating roller 6 and the fixing roller 3. The fixing belt 5 follows the rotation of the pressure roller 4 and rotates in the direction of the arrow R2. When the pressure roller 4 rotates in the direction of the arrow R1 and the fixing belt 5 rotates in the direction of the arrow R2, the recording paper 8 passes through the fixing nip portion 12.

  The heating roller 6 has a substantially cylindrical shape, and has a three-layer structure in which an infrared absorption layer, a cored bar, and a protective layer are formed from the substantially cylindrical central axis toward the outer periphery. The infrared absorption layer is formed by coating and baking a heat-resistant carbon-containing paint on the inner side of the core metal. For the metal core, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. As the protective layer, a fluororesin such as PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is suitable. The protective layer prevents the polyimide layer of the fixing belt 5 and the heating roller 6 from being worn by contact between the fixing belt 5 and the heating roller 6.

  In the present embodiment, the heating roller 6 has a diameter of 28 mm, carbon black coating having a thickness of 100 μm is used as the infrared absorbing layer, and hollow aluminum having a diameter of 28 mm and a wall thickness of 1 mm is used as the core metal. . As the protective layer, a PTFE coat having a thickness of 50 μm is used.

  A heater lamp 7 b for heating the heating roller 6 is disposed inside the heating roller 6. When a control circuit (not shown) supplies (energizes) power to the heater lamp 7b from a power supply circuit (not shown), the heater lamp 7b emits light and infrared rays are emitted from the heater lamp 7b. In the heating roller 6, the entire inner surface of the heating roller 6 absorbs infrared rays emitted from the heater lamp 7b, whereby the entire heating roller 6 is heated. In the present embodiment, a heater lamp 7b with a rated power of 900 W is used. A predetermined load, for example, 50 N, is applied to the heating roller 6 in the direction opposite to the direction in which the fixing roller 3 is disposed when viewed from the heating roller 6. Since tension is applied to the fixing belt 5, the heating roller 6 rotates as the fixing belt 5 rotates.

  FIG. 2 is a diagram for explaining a method for measuring the flexibility of the fixing belt 5. FIG. 2A shows the outer diameter A of the fixing belt 5. The outer diameter A of the fixing belt 5 is preferably measured in a state in which the fixing belt 5 is not deformed due to its own weight or the like. Specifically, the outer circumference of the fixing belt 5 is measured, and the circumference is measured. A value obtained by dividing the value by 4 is defined as the outer diameter A of the fixing belt 5. FIG. 2B is a diagram illustrating the fixing belt 5 in a state where the metal pipe 21 that is the first metal shaft and the load roller 22 for measurement that is the second metal shaft are mounted.

The metal pipe 21 has an outer diameter of 13 mm and is sufficiently longer than the width of the fixing belt 5, and the both ends of the metal pipe 21 are fixed by passing the fixing belt 5 through the metal pipe 21. In this state, the measurement load roller 22 is passed under the fixing belt 5. The load roller 22 has an outer diameter of 13 mm and is longer than the width of the fixing belt 5. In the present invention, the load roller 22 has a length of 330 mm and a weight of 115 g. The fixing belt 5 for measuring flexibility has an outer diameter A of 50 mm and a belt width of 320 mm. The value obtained by dividing the weight of the load roller 22 by the width of the fixing belt 5 is 0. 359 g / mm . Here, the amount by which the load roller 22 protrudes from the fixing belt 5 is desirably the same length at one end of the fixing belt 5 and the other end. Further, it is desirable that the metal pipe 21 and the load roller 22 do not bend during the flexibility measurement.

  Assuming that the length in the vertical direction outside the fixing belt 5 through which the load roller 22 is passed is B, the value of the length B increases as the fixing belt 5 becomes softer. Here, the flexibility S of the fixing belt 5 is determined as S = (B−A) / A. The softer the fixing belt 5, the greater the value of the flexibility S. The flexibility S of the fixing belt 5 is proportional to the outer diameter A of the fixing belt 5 when the layer configuration and film thickness of the fixing belt 5 are the same. For example, when the flexibility of the fixing belt 5 having an outer diameter of 50 mm is 0.15, and the layer configuration and film thickness of the fixing belt 5 are the same, the flexibility of the fixing belt 5 having an outer diameter of 40 mm is 0.12. When the outer diameter of 5 is 60 mm, the flexibility is 0.18. However, when the outer diameter of the fixing belt 5 approaches the outer diameter of the metal pipe 21 and the load roller 22, the proportional relationship is broken. In this case, small diameter pipes and rollers are used so that the outer diameters of the metal pipe 21 and the load roller 22 are 30% or less of the outer diameter of the fixing belt 5.

  FIG. 3 is a diagram for explaining a method for measuring the resilience of the fixing roller 3. The fixing roller 3 is disposed horizontally. The spherical weight 31 is hung on a thread 32 having an outer diameter of 11 mm, a weight of 7 g, and a length of 50 cm. The spherical weight 31 is disposed so that the center of gravity of the spherical weight 31 is positioned on a horizontal plane including the central axis of the fixing roller 3 and is in contact with the fixing roller 3 in a stationary state. The position where the spherical weight 31 is arranged in this way is defined as the lowest point 33. The height at which the spherical weight 31 is suspended is adjusted so that the spherical weight 31 is positioned at the lowest point 33.

  Next, the spherical weight 31 is pulled up 10 cm from the lowest point 33 so that the thread 32 does not loosen. The height at which the spherical weight 31 is pulled up is defined as the initial height H1. The direction in which the spherical weight 31 is pulled up is a direction perpendicular to the axial direction of the fixing roller 3. When the spherical weight 31 is released gently, the spherical weight 31 hits the fixing roller 3 and rebounds. At this time, the vertical difference between the highest raised position and the lowest point is defined as a return height H2. The higher the resilience of the fixing roller 3, the higher H2. The restitution coefficient R of the fixing roller 3 is determined as R = H2 / H1. The higher the resilience of the fixing roller 3, the greater the value of the resilience coefficient R.

Table 1 shows the relationship among the flexibility S of the fixing belt 5, the restitution coefficient R of the fixing roller 3, and the fixing property, in which the outer diameter of the fixing belt 5 is 50 mm and the thickness of the fluororesin layer is different from that of the present invention . The recording paper is plain paper with a basis weight of 64 g. The paper size of the recording paper is A4. The image is provided with four-layer black of toner YMCBk at the front and rear ends in the paper transport direction, and the toner amount is 1.0 mg / cm 2. The toner wax content is 3%. The tip void is 3 mm. The fixing temperature is controlled to be constant with respect to the set temperature, but is ± 7.5 ° C. with respect to the set value and has a temperature range of 15 ° C. due to temperature fluctuations such as temperature ripple.

  The fixability is ◯ when there is no offset and a good fixed image is obtained within the above temperature fluctuation range, △ when offset occurs, and × when paper wrapping occurs immediately after fixing. . Paper output was performed in various modes such as immediately after warming up, during standby, returning from sleep, and continuous paper feeding. The fixability is good in a combination in which the flexibility S of the fixing belt 5 is 0.15 or more and the restitution coefficient R of the fixing roller 3 is 0.6 or more. That is, the desired fixability can be obtained only when the flexibility of the fixing belt 5 and the resilience of the fixing roller 3 are combined. The theoretical limit of the flexibility S is 0.418 in the case of the fixing belt 5 having an outer diameter of 50 mm, and the theoretical limit of the coefficient of restitution R is 1.

Experiments have shown that the flexibility of the fixing belt 5 changes in proportion to the outer diameter of the fixing belt 5. However, as long as the material constituting the layers of the fixing belt 5 and the thicknesses of the respective layers are the same, the conditions for good fixability do not change. Therefore, the flexibility with good fixability when the outer diameter of the fixing belt 5 is changed depends on the outer diameter, for example, 0.12 or more when the outer diameter is 40 mm and 0.18 or more when the outer diameter is 60 mm. The value of flexibility at which the fixability is good varies. When the outer diameter of the fixing belt 5 is Amm, the flexibility S that provides good fixability is S = A × 0.003.
It can be expressed as.

  A good combination when the outer diameter of the fixing belt 5 is changed is a layer configuration and a film thickness of the belt that can obtain the flexibility of the fixing belt 5 having an outer diameter of 50 mm, and when the outer diameter of the fixing belt 5 is 40 mm. The flexibility S is 0.12 or more, and when the outer diameter of the fixing belt 5 is 60 mm, the flexibility S is 0.18 or more.

Table 2 shows the relationship between the flexibility S of the fixing belt 5 and the film thickness of the belt base material in which the outer diameter of the fixing belt 5 is 50 mm and the thickness of the fluororesin layer is different from that of the present invention . Two types of polyimides, Upilex S (trademark of Ube Industries) and Kapton (trademark of Toray DuPont), were used as the belt base material. Table 2 shows the flexibility when the thickness of the polyimide is changed. The fixing belt 5 includes a polyimide base material, a silicon rubber layer having a thickness of 150 μm, and a PFA tube having a thickness of 30 μm.

  The coefficient of restitution R of the fixing roller 3 affects the hardness of the fixing roller 3, the material of the sponge rubber, the size of bubbles, and the like. For example, the restitution coefficient of the fixing roller 3 having an outer diameter of 30 mm, a sponge rubber thickness of 5 mm, and an Asker C hardness of 40 degrees is 0.6. Further, the restitution coefficient of the fixing roller 3 having an outer diameter of 30 mm, sponge rubber thickness of 5 mm, and Asker C hardness of 20 degrees is 0.5.

Table 3 shows the image evaluation when the nip surface pressure is changed using the fixing belt 5 having the flexibility S = 1.04 and the fixing roller 3 having the restitution coefficient R = 0.6. Table 4 shows whether or not gloss unevenness occurs with respect to the hardness of the fixing roller 3. By increasing the nip surface pressure, the fixability of a color unfixed toner image with a large amount of toner is improved. When the nip surface pressure is low, the fixing belt 5 is difficult to follow the unevenness of the recording paper 8, so that minute gloss unevenness occurs and the image quality deteriorates. From the image quality evaluation, the lower limit of the nip surface pressure is 1.4 kgf / cm ² (1.37E + 5 Pa).

In the case of a sponge roller, the upper limit of the nip surface pressure is determined by the durability of the fixing roller 3. The upper limit of the nip surface pressure is 2.6 kgf / cm ² (2.55E + 5 Pa). The durability of the fixing roller 3 can be determined from a decrease in the fixable range due to a decrease in the coefficient of restitution R and a decrease in the fixable temperature range due to an increase in the lower limit temperature of the fixable temperature range due to a decrease in hardness. If an offset occurs when the number of sheets to be passed is 200K (200,000), it is assumed that there is no durability.

  If the resilience of the fixing roller 3 is good, the fixable temperature range is wide. In order to ensure the resilience of the fixing roller 3, the fixing roller 3 needs to have an Asker C hardness of 30 degrees or more. Since sponge rubber has a small thermal conductivity, sponge rubber is used as the fixing roller 3. Since the heat of the fixing belt 5 heated by the heating roller 6 is not taken away by the fixing roller 3, the warm-up time is shortened.

The sponge roller is obtained by foaming silicon rubber. The upper limit of the hardness of the fixing roller 3 is a hardness at which the fixing roller 3 is manufactured in a state where bubbles of the sponge roller are uniform. The upper limit of the hardness of the fixing roller 3 is Asker C 50 degrees. If the bubbles on the sponge roller are not uniform, the hardness will be non-uniform. If the hardness is non-uniform, uneven gloss is generated, leading to a decrease in image quality. Furthermore, since the bubbles are easily crushed by using for a long time, the resilience of the fixing roller 3 is lowered. For example, when a load of 300 N is applied using the fixing roller 3 having an Asker C of 30 degrees, the surface pressure becomes 1.42 kgf / cm ² (1.39E + 5 Pa). At this time, the nip width is 6.6 mm, and the nip length is 320 mm.

  FIG. 4 is a view for explaining the detent 41 of the fixing belt 5. When the fixing belt 5 comes into contact with the detent 41 of the fixing belt 5, if the durability of the substrate is insufficient, the fixing belt 5 is cracked. In the case of Upilex S, a thickness of at least 45 μm or more is necessary as a condition that the fixing belt 5 does not crack. The cylindrical belt detent 41 is inserted into the heating roller 6 and rotates as the heating roller 6 rotates.

  When the parallelism of the fixing roller 3, the pressure roller 4 and the heating roller 6, the right / left balance of the load and the right / left balance of the belt tension are not appropriate, the fixing belt 5 moves in the axial direction, and the moving speed is large. Become. The movement of the belt can be stopped by the detent 41 in a state where the assembly accuracy of the fixing device 2 and the dimensions of each component are within the allowable ranges and are sufficiently balanced. For the stopper 41, PPS which is a heat resistant resin is used. The detent 41 is perpendicular to the end of the fixing belt 5. When the strength of the base material of the fixing belt 5 is weak, the end of the fixing belt 5 in contact with the detent 41 is cracked. Here, the thickness of the fixing belt 5 is an average value of measured values at a plurality of points in the circumferential direction of the end portion of the fixing belt 5. The measured value is preferably within a range of 10 mm from the end of the fixing belt 5. Even if a part of the thickness of the fixing belt 5 is 40 μm, if the average value is 45 μm or more, the fixing belt 5 is not cracked. Further, the thickness inside 10 mm from the end of the fixing belt 5 is thinner than 45 μm. For example, even when the thickness is 40 μm, the end crack of the fixing belt 5 does not occur.

Table 5 shows the conditions of the base material of the fixing belt 5 having good fixing property and durability when the outer diameter of the fixing belt 5 is 50 mm and the thickness of the fluororesin layer is different from that of the present invention . The silicon rubber layer has a JIS hardness of 20 degrees and a thickness of 150 μm. A PFA tube having a thickness of 30 μm is used for the release layer. An example using Upilex S manufactured by Ube Industries, Ltd. and Kapton manufactured by Toray DuPont Co., Ltd. is shown as a belt base material. The lower limit of the thickness of the substrate is determined by the durability of the substrate. The fixability is ◯ when there is no offset and a good fixed image is obtained within the above temperature fluctuation range, △ when offset occurs, and × when paper wrapping occurs immediately after fixing. . As for durability, it was evaluated as ◯ when no offset was generated up to 200K (200,000 sheets), and X when a crack occurred at the belt end. The same evaluation was made for Tables 6 to 8.

Other silicon rubber layers and release layer thicknesses can also be selected. In Table 6, the silicon rubber layer of the fixing belt 5 has a JIS hardness of 20 degrees and a thickness of 150 μm. As the release layer, a PFA tube having a thickness of 20 μm is used. In Table 7, a PFA tube having a JIS hardness of 20 degrees for the silicon rubber layer of the fixing belt 5 having a fluororesin layer thickness different from that of the present invention and having a thickness of 250 μm and a release layer of 30 μm is used. . In Table 8, the silicon rubber layer of the fixing belt 5 has a JIS hardness of 20 degrees, and a PFA coat having a thickness of 150 μm and a release layer of 20 μm is used.

  It can be seen that even when the base material is the same, the flexibility S is improved when the release layer is thinned. Further, when the silicon rubber layer is thickened, the flexibility S decreases. Furthermore, even if the release layer has the same thickness, the flexibility S of the coat is better than that of the tube. From Table 5 to Table 8, it can be seen that an appropriate film thickness of the polyimide base material is 45 to 90 μm.

  The flexibility in the above embodiment is when the fixing belt 5 has an outer diameter of 50 mm. However, when other fixing belts 5 having an outer diameter of φmm are used, Tables 1, 2, 5, 6, 7, 8 The value obtained by multiplying the flexibility S by φ / 50 is the flexibility value of the fixing belt 5 having the outer diameter φmm, and other values and the evaluation results are the same. The fixing belt 5 having an outer diameter other than 50 mm will be described with reference to Tables 9 and 10.

  Table 9 shows a good combination of flexibility and coefficient of restitution when the outer diameter of the fixing belt 5 is 40 mm. Table 10 shows a good combination of flexibility and coefficient of restitution when the outer diameter of the fixing belt 5 is 65 mm. A good combination is that the flexibility is 0.12 or more and the coefficient of restitution is 0.6 or more in the case of φ40 belt, and the flexibility is 0.2 or more and the coefficient of restitution is 0.6 or more in the case of φ65 belt. Thus, when the outer diameter of the fixing belt 5 is A, it can be seen that flexibility is required to be A * 0.003 or more.

FIG. 8 shows flexibility example A1, reference example B1 and the theoretical limit of flexibility when the outer diameter of the fixing belt 5 is changed. The horizontal axis indicates the outer diameter (mm) of the fixing belt 5, and the vertical axis indicates the flexibility index. A square indicates Example A1, and a triangle indicates Example B1. Example A1 shows the flexibility of three types of fixing belts 5 having outer diameters of 44 mm, 50 mm, and 64 mm. The fixing belt 5 is composed of Upilex S polyimide whose surface layer is 20 μm PFA coated, whose rubber layer is 150 μm, and whose base material is 50 μm. Reference example B1 shows the flexibility of three types of fixing belts 5 having outer diameters of 40 mm, 50 mm, and 65 mm. The fixing belt 5 is composed of Upilex S polyimide having a surface layer of 30 μm PFA tube, a rubber layer of 150 μm, and a base material of 50 μm. Thus, the flexibility is proportional to the outer diameter of the fixing belt 5 when the outer diameter of the fixing belt 5 is at least 40 mm to 65 mm. Both Example A1 and Reference Example B1 show good fixing performance in combination with the fixing roller 3 having a restitution coefficient of 0.6 or more.

  Table 11 shows the relationship between the thickness of the elastic layer of the fixing roller 3 and the fixing property. FIG. 9 is a diagram for explaining the relationship between the shape of the elastic layer of the fixing roller 3 at the outlet of the fixing nip portion 12 and the sheet peelability. In FIG. 9, the cores of the fixing roller 3 and the pressure roller 4 are omitted. The optimum thickness dimension of the elastic layer of the fixing roller 3 will be described.

Experimental conditions are shown below. The fixing roller 3 has an outer diameter of 30 mm, an elastic layer made of silicon sponge rubber having a thickness of 3 to 7 mm, and a core metal made of solid iron. The fixing belt 5 has a flexibility S of 0.15. The elastic layer of the fixing roller 3 is also referred to as “fixing roller elastic layer” 121 hereinafter. The configuration of the fixing belt 5 is that the polyimide layer of the base material is 50 μm thick, the rubber layer which is an elastic layer is 150 μm thick, the thickness of the fluororesin layer which is a release layer is different from the present invention, and the PFA tube is 30 μm thick. .

  The heating roller 6 has a diameter of 28 mm, a core metal of 0.7 mm thick aluminum, an infrared absorption layer of 100 μm thick carbon black paint, and a protective layer of 50 μm thick PTFE coat. The pressure roller 4 is a PFA tube having a diameter of 30 mm, an elastic layer of 1 mm thick silicon solid rubber, a core metal of 1 mm thick hollow iron, and a release layer of 50 μm. Hereinafter, the elastic layer of the pressure roller 4 is also referred to as a “pressure roller elastic layer” 122.

The process speed, that is, the fixing speed was set to 220 mm / s, and plain paper having a basis weight of 64 g was used. The image is formed with a black solid with a toner amount of 1.0 mg / cm ² at the tip in the paper transport direction by stacking four colors of cyan (C), magenta (M), yellow (Y), and black (B). The

In the fixing roller elastic layer 121, the ratio of the thickness dimension M when pressed by the pressure roller 4 via the fixing belt 5 and the thickness dimension N when not pressed is referred to as an “indentation ratio” L. . The pressing rate L of the fixing roller elastic layer 121 is
L = (N−M) / N × 100
It is represented by

  In this experiment, a load with which the pressing rate L of the fixing roller elastic layer 121 is 30% is applied to the fixing roller 3 and the pressure roller 4. The fixability was evaluated as “◯” when no toner offset and an extremely low gloss were observed within the above temperature fluctuation range, and “X” when the toner offset and an extremely low gloss were observed.

  In FIG. 9, the pressure roller 4 presses the fixing roller 3 through the fixing belt 5. The surface portion of the fixing roller 3 that contacts the fixing belt 5 is formed by the fixing roller elastic layer 121. The fixing belt 5 is not shown and will be described. The arrow R2 indicates the direction in which the fixing roller 3 rotates, and the arrow R1 indicates the direction in which the pressure roller 4 rotates.

  Since the fixing belt 5 of the present invention has excellent conformability to the deformation of the silicon sponge rubber that is the fixing roller elastic layer 121, the shape of the fixing belt 5 at the exit of the fixing nip portion 12 is the same as that of the fixing roller elastic layer 121. It is almost the same as the shape. The exit of the fixing nip portion 12 is an end portion on the downstream side where the sheet is conveyed in the fixing nip portion 12.

  At the exit of the fixing nip 12, the fixing roller elastic layer 121 and the pressure roller elastic layer 122 are in contact with each other while forming a curved surface. At the exit of the fixing nip portion 12, the larger the angle V between the tangent line 123 of the fixing roller elastic layer 121 and the tangent line 124 of the pressure roller elastic layer 122, the better the sheet peelability. By using the fixing roller 3 and the pressure roller 4 having a small diameter, the angle V can be increased to improve the peelability of the paper.

  The fixing roller elastic layer 121 in FIG. 9A is formed with a thickness dimension of 3 mm. The fixing roller elastic layer 121 is not greatly compressed even when a load is applied by the pressure roller elastic layer 122. Therefore, since the fixing roller elastic layer 121 has a small angle V at the exit of the fixing nip portion 12 and has poor paper peelability, it causes problems such as hot offset and paper winding when the fixing temperature fluctuates. It becomes easy.

  The fixing roller elastic layer 121 in FIG. 9C is formed with a thickness dimension of 7 mm. The fixing roller elastic layer 121 is pressed by the pressure roller 4 in the fixing nip portion 12 and deformed into a concave shape, whereas the fixing roller elastic layer 121 is deformed so as to bulge out in the vicinity of the exit of the fixing nip portion 12. The convex portion 125, which is a convex bulge, reduces the angle V and deteriorates the peelability of the paper.

  The fixing roller elastic layer 121 in FIG. 9B is formed with a thickness dimension of 4 mm or more and 6 mm or less. Since the angle V is larger than the angle V shown in FIGS. 9A and 9C described above, the fixing roller elastic layer 121 has reduced adhesion to the toner image and excellent paper detachability. .

  As described above, the thickness dimension of the fixing roller elastic layer 121 has an optimum thickness dimension for fixing a toner image on a sheet. The thickness dimension of the fixing roller elastic layer 121 is preferably 4 mm or more and 6 mm or less.

Table 12 shows the relationship between the indentation rate L, the fixing property, and the durability of the fixing roller elastic layer 121. Experimental conditions are shown below. The fixing roller 3 has an outer diameter of 30 mm, the fixing roller elastic layer 121 is a silicon sponge rubber having a thickness of 5 mm, and the core metal is solid iron. The fixing belt 5 has a flexibility S of 0.15. The configuration of the fixing belt 5 is that the polyimide layer of the base material is 50 μm thick, the rubber layer which is an elastic layer is 150 μm thick, the thickness of the fluororesin layer which is a release layer is different from the present invention, and the PFA tube is 30 μm thick. .

  The heating roller 6 has a diameter of 28 mm, a core metal of 0.7 mm thick aluminum, an infrared absorption layer of 100 μm thick carbon black paint, and a protective layer of 50 μm thick PTFE coat. The pressure roller 4 is 30 mm in diameter, the pressure roller elastic layer 122 is silicon solid rubber having a thickness of 1 mm, the core metal is hollow iron having a thickness of 1 mm, and the release layer is a PFA tube having a thickness of 50 μm.

The process speed, that is, the fixing speed was set to 220 mm / s, and plain paper having a basis weight of 64 g was used. The image is formed with a black solid with a toner amount of 1.0 mg / cm ² at the tip in the paper transport direction by stacking four colors of cyan (C), magenta (M), yellow (Y), and black (B). The

  In this experiment, a load with which the pressing rate L of the fixing roller elastic layer 121 is 20%, 25%, 30%, 35%, and 40% was applied to the fixing roller 3 and the pressure roller 4. The fixability was evaluated as “◯” when no toner offset and an extremely low gloss were observed within the above temperature fluctuation range, and “X” when the toner offset and an extremely low gloss were observed. Regarding the durability, when the number of sheets is 200K, the fixing property is evaluated as “good” if there is no change from the initial fixing property, and the durability is good if it deteriorates from the initial fixing property. It was set as x not being.

  The fixing roller elastic layer 121 has poor fixability when the indentation rate L is 20%, and the angle V becomes small as shown in FIG. When the pressing rate L is 40%, the fixing roller elastic layer 121 has a large load that is pressed from the pressure roller 4, and the durability is lowered.

  As described above, the pressing ratio L of the fixing roller elastic layer 121 has an optimum range for fixing performance and durability. The pressing rate L of the fixing roller elastic layer 121 is preferably 25% or more and 35% or less.

  The toner immediately after fixing at the exit of the fixing nip portion 12 is high in temperature and is sticky, so that it is difficult to separate from the fixing belt 5. In addition to the flexibility of the fixing belt 5 and the resilience of the fixing roller 3, wax added to the toner plays an important role in order to improve the releasability between the fixing belt 5 and the toner. When the amount of wax is large, the toner releasability with respect to the fixing belt 5 is improved, so that the fixable temperature range is expanded. On the other hand, when the amount of wax is large, the toner fluidity decreases. When the toner fluidity is lowered, the toner supply is delayed and the image quality is lowered. When the amount of wax is small, the toner fluidity is good, but the fixable temperature range is narrowed. This is because the releasability of the toner and the fixing belt 5 is reduced because the amount of wax is small.

  Table 13 shows the relationship among the wax amount, the fixable temperature range, and the toner fluidity. If the WAX content is 1.5% or more, there is no effect on the fixable temperature range, and if the WAX content is 4.8% or less, there is no decrease in toner fluidity.

  The toner contains at least a binder resin, a colorant, and a wax. The binder resin is not particularly limited, and a binder resin for black toner or a binder resin for color toner is used. Examples thereof include polyester resins, styrene resins such as polystyrene and styrene-acrylic acid ester copolymer resins, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyurethane, and epoxy resins.

  Alternatively, as the binder resin, a resin obtained by mixing a release agent with a raw material monomer mixture and performing a polymerization reaction may be used. In this case, it is preferable to include a polyester resin. By including a polyester resin in the binder resin, the dispersion state controllability of the release agent is improved, and a toner having further excellent fixing properties can be obtained. Furthermore, the toner can be provided with excellent durability and transparency. Binder resin can be used individually by 1 type, or can also use 2 or more types together.

  The polyester resin is not particularly limited and a known one is used. For example, a polycondensation product of polybasic acids and polyhydric alcohols can be mentioned. Polybasic acids are polybasic acids and derivatives of polybasic acids such as acid anhydrides or esterified products of polybasic acids. Polyhydric alcohols are compounds containing two or more hydroxyl groups, and include both alcohols and phenols.

  As polybasic acids, those commonly used as monomers for polyester resins can be used. Examples include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid and naphthalenedicarboxylic acid, and aliphatic carboxylic acids such as maleic anhydride, fumaric acid, succinic acid and adipic acid. used. Polybasic acids may be used alone or in combination of two or more.

  As polyhydric alcohols, those commonly used as monomers of polyester resins are used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol and glycerin, alicyclic polyhydric alcohols such as cyclohexanediol, cyclohexanedimethanol and hydrogenated bisphenol A, bisphenol Aromatic diols such as an ethylene oxide adduct of A and a propylene oxide adduct of bisphenol A are exemplified.

  “Bisphenol A” is 2,2-bis (p-hydroxyphenyl) propane. Examples of the ethylene oxide adduct of bisphenol A include polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane. Examples of the propylene oxide adduct of bisphenol A include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane. Polyhydric alcohols may be used alone or in combination of two or more.

  The polyester resin can be synthesized by a condensation polymerization reaction. For example, it can be synthesized by polycondensation reaction, specifically dehydration condensation reaction of polybasic acids and polyhydric alcohols in the presence of a catalyst in an organic solvent or without solvent. At this time, a demethanol polycondensation reaction may be carried out using a methyl esterified product of a polybasic acid as part of the polybasic acid. The polycondensation reaction between polybasic acids and polyhydric alcohols may be terminated when the acid value and softening point of the produced polyester resin reach the values in the polyester resin to be synthesized.

  In this polycondensation reaction, by appropriately changing the reaction conditions such as the blending ratio of polybasic acids and polyhydric alcohols and the reaction rate, for example, the content of carboxyl groups bonded to the terminal of the resulting polyester resin, and thus The acid value, softening point, and other physical properties of the resulting polyester resin can also be adjusted.

  In the present embodiment, the acid value of the binder resin is preferably 5 mgKOH / g or more and 30 mgKOH / g or less. When the acid value of the binder resin is less than 5 mgKOH / g, the affinity between the binder resin and the release agent is greater than when the acid value of the binder resin is 5 mgKOH / g or more. During fixing, the release agent is less likely to elute on the toner surface, and high temperature offset is likely to occur as a fixing failure. When the acid value of the binder resin exceeds 30 mgKOH / g, the functional value remaining on the toner surface increases and the moisture is easily absorbed, compared to the case where the acid value of the binder resin is less than 30 mgKOH / g. Under such conditions, the charge amount of the toner may be reduced, and charging stability may be impaired.

  Furthermore, since the dispersibility of the release agent in the binder resin tends to be lowered, if the kneading is insufficient during the production of the toner, the dispersion diameter of the release agent on the toner surface may increase. There is. When the acid value of the binder resin is 5 mg KOH / g or more and 30 mg KOH / g or less, the dispersibility of the release agent in the toner particles is set to a desired range. Specifically, the release agent on the toner surface The dispersion diameter can be stabilized to less than 300 nm, the decrease in toner charge amount under high-humidity conditions can be suppressed, and the affinity between the binder resin and the release agent to improve the fixing property Can be controlled.

  Therefore, the charging stability can be further improved and the fixing property can be improved, so that a high-definition and high-resolution high-quality image can be formed more stably over a long period of time. it can. The acid value of the binder resin is determined by the reaction conditions such as the blending ratio and reaction rate of polybasic acids and polyhydric alcohols in the case of a binder resin raw material monomer mixture, for example, a polyester resin. By appropriately changing the content, the content of the carboxyl group bonded to the terminal of the obtained binder resin, and thus the acid value of the obtained binder resin can be adjusted.

  Examples of the colorant include a yellow toner colorant, a magenta toner colorant, a cyan toner colorant, and a black toner colorant.

  Examples of the colorant for yellow toner include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 15 and C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 180, C.I. I. Organic pigments such as CI Pigment Yellow 185, inorganic pigments such as yellow iron oxide and ocher, C.I. I. Nitro dyes such as Acid Yellow 1, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, and C.I. I. Examples thereof include oil-soluble dyes such as Solvent Yellow 21.

  Examples of the colorant for magenta toner include C.I. I. Pigment red 49, C.I. I. Pigment red 57, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Basic Red 10 and C.I. I. Disperse Red 15 etc. are mentioned.

  Examples of the colorant for cyan toner include C.I. I. Pigment blue 15, C.I. I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 25, and C.I. I. Direct Blue 86 and the like can be mentioned.

  Examples of the colorant for black toner include carbon black such as channel black, roller black, disk black, gas furnace black, oil furnace black, thermal black, and acetylene black. From these various types of carbon black, an appropriate carbon black may be appropriately selected according to the design characteristics of the toner to be obtained.

  In addition to these pigments, red pigments, green pigments, and the like can be used. A coloring agent can be used individually by 1 type, or can use 2 or more types together. Two or more of the same colors can be used, and one or more of the different colors can also be used.

  The colorant in the toner used in the present invention is preferably used as a master batch. A master batch of a colorant can be produced, for example, by kneading a synthetic resin melt and a colorant. As the synthetic resin, the same kind of resin as the toner binder resin or a resin having good compatibility with the toner binder resin is used. The use ratio of the synthetic resin and the colorant is not particularly limited, but is preferably 30 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the synthetic resin. The master batch is used after being granulated to a particle size of, for example, about 2 to 3 mm.

  The content of the colorant is not particularly limited, but is preferably 4 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder resin. When using a masterbatch, it is preferable to adjust the usage amount of the masterbatch so that the content of the colorant in the toner of the present invention falls within the above range. By using the colorant in the above-mentioned range, it is possible to form a good image having a sufficient image density, high color developability and excellent image quality.

  The release agent is not particularly limited, and known ones can be used. For example, paraffin waxes and derivatives thereof, and petroleum waxes such as microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin waxes and derivatives thereof, low molecular weight polypropylene waxes and derivatives thereof, and polyolefin polymer waxes and derivatives thereof Examples thereof include hydrocarbon synthetic waxes such as derivatives, carnauba wax and derivatives thereof, and ester waxes.

  The content of the release agent used in the present invention is preferably 1.5% by weight or more and 4.8% by weight or less with respect to the total toner weight. If it is less than 1.5% by weight, the releasability of the toner with respect to the belt is lowered, and fixing offset occurs. On the other hand, if it exceeds 4.8% by weight, the fixing property is good, but the toner aggregates due to the stirring heat in the developing device, and a good image cannot be obtained. The acid value of the release agent is less than 4 mgKOH / g. When the acid value of the release agent is 4 mgKOH / g or more, the affinity between the release agent and the binder resin is higher than when the acid value of the release agent is less than 4 mgKOH / g. During fixing, the release agent is less likely to elute from the toner, and high temperature offset is likely to occur.

  The toner preferably contains a toner additive component such as a charge control agent in addition to the binder resin, the colorant, and the release agent. By containing a charge control agent, it is possible to impart preferable chargeability to the toner. As the charge control agent, a charge control agent for positive charge control or negative charge control is used.

  Examples of the charge control agent include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, triphenylmethane derivatives, guanidine salts, And charge control agents for positive charge control such as amidine salts and oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and derivatives thereof And metal salt (metal is chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long chain alkyl carboxylates, and charge control agents for controlling negative charges such as resin acid soaps. One charge control agent can be used alone, or two or more charge control agents can be used in combination.

  The amount of the charge control agent used is preferably 0.5 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the binder resin, and more preferably 0.5 parts by weight or more with respect to 100 parts by weight of the binder resin. 3 parts by weight or less. If the charge control agent is contained in an amount of more than 5 parts by weight, the carrier may be contaminated and toner scattering may occur. When the content of the charge control agent is less than 0.5 parts by weight, sufficient charging characteristics cannot be imparted to the toner.

  In this embodiment, the toner has a volume average particle diameter of 5.0 μm or more and 7.0 μm or less, and the content of toner particles having a number average particle diameter of 5.0 μm or less is less than 40% by number of all toner particles. Preferably there is. When the toner particle size distribution and number distribution satisfy this range, toner scattering is suppressed, and a high-definition and high-resolution high-quality image is formed. When the volume average particle diameter is less than 5.0 μm, toner scattering occurs due to a decrease in fluidity, and when the volume average particle diameter exceeds 7.0 μm, a sufficiently high-definition and high-resolution image is not formed. When the content of the toner particles having a number average particle diameter of 5.0 μm or less is 40% by number or more of all the toner particles, the toner scatters due to a decrease in fluidity and the fogging due to the deterioration of transfer efficiency occurs.

In the present embodiment, the toner particle content (volume%, number%) having a volume average particle diameter (D _50V ) and a number average particle diameter of 5.0 μm or less is measured by a particle size distribution manufactured by Beckman Coulter, Inc. It is measured by the device “Multisizer 3”. The measurement conditions are shown below.
Aperture diameter: 100 μm
Measurement particle number: 50000 count Analysis software: Coulter Multisizer AccuComp version 1.19 (manufactured by Beckman Coulter, Inc.)
Electrolyte: ISOTON-II (Beckman Coulter, Inc.)
Dispersant: Sodium alkyl ether sulfate

The measurement procedure was as follows: 50 ml of electrolyte, 20 mg of sample toner and 1 ml of dispersant were added to a beaker, a dispersion sample was prepared for 3 minutes with an ultrasonic disperser, and a measurement sample was prepared. Measure. From the obtained measurement results, the volume particle size distribution and number particle size distribution of the sample particles are obtained, and the volume average particle size (D _50V ) of the toner is obtained from the volume particle size distribution. Further, the content (number%) of toner particles having a number average particle diameter of 5.0 μm or less is determined from the number particle size distribution.

  For example, an external additive having functions such as powder flowability improvement, triboelectric chargeability improvement, heat resistance, long-term storability improvement, cleaning property improvement, and photoreceptor surface wear property control may be mixed with the toner. Examples of the external additive include silica fine powder, titanium oxide fine powder, and alumina fine powder. One type of external additive can be used alone, or two or more types can be used in combination.

  The external additive is added in an amount of 0.1 to 100 parts by weight of the toner particles in consideration of the charge amount necessary for the toner, the influence of the external additive on the abrasion of the photoreceptor, the environmental characteristics of the toner, and the like. 1 to 10 parts by weight is preferred, and 2.0 to less than 4.0 parts by weight is more preferred. By containing 2.0 parts by weight or more and less than 4.0 parts by weight of the external additive, the fluidity is further improved and the charging of individual toner particles can be controlled appropriately, so that the fixing property is not impaired and the fogging is not impaired. It is possible to form a high-quality image that does not occur.

  If the content of the external additive is less than 2.0 parts by weight, sufficient fluidity cannot be imparted to the toner (particularly small-diameter toner), so that the individual toner particles are not sufficiently charged and are not imaged. It becomes easy for fogging to occur at the part. When the content of the external additive is 4.0 parts by weight or more, the external additive particles tend to aggregate with each other, so that the toner surface cannot be efficiently covered and the fluidity cannot be increased. The toner particles are not sufficiently charged, and fog is likely to occur in the non-image area.

  In the toner production method, a resin composition containing at least a binder resin, a colorant, and a release agent is dry-mixed (premixed), melt-kneaded, and pulverized and classified to prepare a toner base (core). Next, the toner base (core) and the external additive are dry-mixed to obtain a desired toner. A known mixer can be used for dry mixing. For example, a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.), a super mixer (trade name, manufactured by Kawata Co., Ltd.) and a mechano mill (product) Name, Okada Seiko Co., Ltd. and other Henschel type mixing devices, Ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), and Cosmo System (trade name, Kawasaki) Heavy Industries, Ltd.).

  In the toner, the amount of the release agent added in the pre-mixing is 2.5 parts by weight or more and 6.0 parts by weight or less with respect to 100 parts by weight of the binder resin. As the kneading machine, a known kneading machine is used. For example, a general kneading machine such as a twin-screw extruder, a three-roll mill and a lab blast mill is used. For example, uniaxial or biaxial extruders such as TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, and PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), Needex ( Open roll type kneaders such as trade name, manufactured by Mitsui Mining Co., Ltd.). Among these, an open roll type kneader is preferable. The toner raw material mixture may be melt-kneaded using a plurality of kneaders.

  For toner pulverization, for example, a jet pulverizer that pulverizes using a supersonic jet stream, or coarse pulverization in a space formed between a rotor that is a rotor that rotates at high speed and a liner that is a stator. An impact pulverizer that introduces and pulverizes an object is used.

  For classification, a known classifier capable of removing excessively pulverized toner particles and coarse toner particles by classification by centrifugal force or classification by wind force is used. For example, a swirl type wind classifier (rotary type wind classifier) or the like is used. The toner may be spheroidized. As the impact spheroidizing device used for the spheroidizing treatment by mechanical impact force, a commercially available device can be used, for example, Faculty (trade name, manufactured by Hosokawa Micron Corporation) or the like is used. A commercially available device can be used as the hot air spheronizing device used for the spheroidizing treatment with hot air. For example, a surface reformer meteoreinbo (trade name, manufactured by Nippon Pneumatic Kogyo Co., Ltd.) is used.

  The spheroidizing treatment is preferably performed so that the circularity of the toner is in the above-described preferable range of circularity of the toner, specifically, 0.950 or more and 0.960 or less. Although the pulverization method is exemplified as the method for producing the toner of the present invention, the method is not particularly limited to the pulverization method. For example, a suspension polymerization method, an emulsion polymerization method, a dissolution suspension method, an ester extension polymerization method, or the like is used.

  The toner of the present invention produced as described above can be used as it is as a one-component developer, or can be mixed with a carrier and used as a two-component developer. That is, the developer that is one embodiment of the present invention includes the toner of the present invention. As a result, a developer having good fixability and good charge stability and having stable characteristics over a long period of use can be obtained, so that a developer capable of maintaining good developability can be obtained. .

  The developer is preferably a two-component developer comprising the toner of the present invention and a carrier. Since the toner of the present invention is excellent in storage stability, it is possible to obtain a two-component developer having excellent charge stability and developability by suppressing a decrease in developer fluidity. By using such a two-component developer, high-definition and high-resolution high-quality images can be stably formed over a long period of time without toner scattering.

  As the carrier constituting the two-component developer, magnetic particles are used. Specific examples of the particles having magnetism include metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum or lead. Among these, ferrite is preferable.

  A resin-coated carrier in which magnetic particles are coated with a resin, or a resin-dispersed carrier in which magnetic particles are dispersed in a resin may be used as the carrier. Although there is no restriction | limiting in particular as resin used for a resin-coated carrier, For example, an olefin resin, a styrene resin, a styrene / acrylic resin, a silicon resin, an ester resin, a fluorine-containing polymer resin, etc. are mentioned. Moreover, although it does not restrict | limit especially as resin used for a resin dispersion type carrier, For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin, etc. are mentioned.

  The shape of the carrier is preferably a spherical shape or a flat shape. Although the volume average particle diameter of the carrier is not particularly limited, it is preferably 10 μm or more and 100 μm or less, more preferably 30 μm or more and 50 μm or less in view of high image quality. When the volume average particle diameter of the carrier is less than 10 μm, the magnetic force between the carrier and the developing roller is weaker than when the volume average particle diameter of the carrier is 10 μm or more. The carrier is easily developed together with the toner.

  When the volume average particle diameter of the carrier exceeds 100 μm, there is a possibility that the individual toner particles cannot be sufficiently charged. Since the volume average particle diameter of the carrier is 10 μm or more and 100 μm or less, the chance of contact between the toner and the carrier can be increased as compared with the case where the volume average particle diameter of the carrier exceeds 100 μm. Can be controlled to provide sufficient toner chargeability. Therefore, a two-component developer having good toner developability can be obtained. When the volume average particle diameter of the carrier is 30 μm or more and 50 μm or less, the above effect can be more stably exhibited.

  In the present embodiment, the volume average particle diameter of the carrier is measured using a laser diffraction, scattering type particle size distribution measuring device Microtrac (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.).

An example of a method for producing the toner used in the present invention is shown below. Polyester resin A, 81.8 parts by weight, masterbatch (containing 40% by weight of CI Pigment Red 57: 1)
12 parts by weight, paraffin wax (release agent, trade name: HNP10, manufactured by Nippon Seiki Co., Ltd., acid value 0 mgKOH / g, melting point 75 ° C.) 5.0 parts by weight, metal alkylsalicylate (charge control agent, trade name) : BONTRON E-84, manufactured by Orient Chemical Co., Ltd.) A mixture is prepared by mixing 1.5 parts by weight with a Henschel mixer for 10 minutes. The mixture is melt-kneaded with an open roll type continuous kneader (trade name: MOS320-1800, manufactured by Mitsui Mining Co., Ltd.) to prepare a melt-kneaded product.

  The melt-kneaded product is coarsely pulverized with a cutting mill (trade name: VM-16, manufactured by Ryoko Sangyo Co., Ltd.) to prepare a coarsely pulverized product, and then the coarsely pulverized product is finely pulverized with a counter jet mill. After pulverization, the toner base (core) having a volume average particle diameter of about 6.7 μm is produced by classifying and removing the excessively pulverized toner with a rotary classifier.

  Using an impact spheroidizing device (trade name: Faculty F-600, manufactured by Hosokawa Micron Corporation), a spheroidized product of the pulverized product is produced. 100 parts by weight of toner, 2.2 parts by weight of hydrophobic silica (trade name: R-974, manufactured by Nippon Aerosil Co., Ltd.) as an external additive, and hydrophobic titanium (trade name: T-805, manufactured by Nippon Aerosil Co., Ltd.) ) A total of 3.8 parts by weight with 1.6 parts by weight is mixed with a Henschel mixer (trade name: FM mixer, manufactured by Mitsui Mining Co., Ltd.), so that an external additive is externally added to the toner. The content of WAX is 4.8% by weight based on the total weight of the toner.

  1.5 parts by weight of paraffin wax (content with respect to the total weight of the toner is 1.49% by weight), 2 parts by weight (content with respect to the total weight of the toner is 1.98% by weight), 3.5 parts by weight (toner When the content with respect to the total weight is 3.41% by weight), good fixability can be obtained, and no toner aggregation is observed in the developing device, and a good image can be obtained. The wax content is good when it is 1.5 wt% or more and 4.8 wt% or less.

  However, when 1 part by weight of the paraffin wax (the content with respect to the total weight of the toner is 1.0% by weight), a fixing offset occurs. With 5.5 parts by weight of paraffin wax (content is 5.26% by weight based on the total weight of the toner), the fixability is good, but toner agglomeration occurs in the developing device, and the toner agglomerates appear in the image. Is recognized.

  A two-component developer is produced by using a ferrite core carrier having a volume average particle diameter of 45 μm as a carrier and a V-type mixer (trade name: V) so that the coverage of the toner with respect to the carrier is 60%. -5, manufactured by Tokuju Kogyo Co., Ltd.) for 20 minutes to obtain a two-component developer containing the toner of Example 1.

  FIG. 5 is a schematic diagram schematically showing the image forming apparatus 1 including the fixing device 2. This is an example in which the image forming apparatus 1 is applied to a color multifunction peripheral. The color multifunction peripheral according to the embodiment of the present invention includes first to fourth visible image forming units 51, 52, 53, 54, an intermediate transfer belt 55, a secondary transfer unit 56, a fixing unit 2, and an internal paper feeding unit. 57 and a manual sheet feeding unit 58. The first to fourth visible image forming units 51, 52, 53, and 54, the intermediate transfer belt 55, and the secondary transfer unit 56 constitute a toner image forming unit.

  The first visible image forming unit 51 includes a photosensitive member 59, a charging unit 60, an optical system unit (not shown), a developing unit 61, and a primary transfer unit 62. Is transferred to the intermediate transfer belt 55. In the first visible image forming unit 51, a charging unit 60, a developing unit 61, and a cleaning unit 63 are arranged around a photoconductor 59 that serves as an image carrier. The optical system unit (not shown) is arranged so that the data from the light source 64 reaches the four sets of photoconductors 59, 65, 66, and 67. The primary transfer unit 62 is disposed in pressure contact with the first visible image forming unit 51 via the intermediate transfer belt 55.

  The other second to fourth visible image forming units 52, 53, 54 have the same configuration as the first visible image forming unit 51, and therefore their description is omitted. The developing unit of each unit accommodates toner of each color of yellow (Y), magenta (M), cyan (C), and black (B).

  The toner image of each color described above is transferred to the intermediate transfer belt 55 to form a color toner image. The intermediate transfer belt 55 is disposed without being bent by the tension rollers 68 and 69, and the waste toner box 70 is disposed in contact with the tension roller 69 side. The secondary transfer unit 56 transfers the color toner image formed on the intermediate transfer belt 55 to a paper body. The secondary transfer unit 56 is disposed in contact with the tension roller 68 side. The fixing unit 2 is the fixing device 2 of the present invention. The fixing unit 2 includes a fixing member 71 and a pressure member 72, and is pressed against the pressure by a pressure unit (not shown) at a predetermined pressure, and is disposed downstream of the secondary transfer unit 56.

  An image forming process using the image forming apparatus 1 will be described. After the surface of the photoconductor 59 is uniformly charged by the charging unit 60, the surface of the photoconductor 59 is laser-exposed according to image information by an optical system unit (not shown) to form an electrostatic latent image. The charging unit 60 employs a charging roller system in order to charge the surface of the photoreceptor 59 uniformly and without generating ozone as much as possible. The developing unit 61 develops the toner image on the electrostatic latent image on the photoconductor 59, and this visualized toner image is intermediate-transferred by the primary transfer unit 62 to which a bias voltage having a polarity opposite to that of the toner is applied. Transfer onto the belt 55. The other three sets of the second to fourth visible image forming units 52, 53, and 54 operate in the same manner and sequentially transfer onto the intermediate transfer belt 55.

  The toner image on the intermediate transfer belt 55 is conveyed to the secondary transfer unit 56, and separately onto a recording sheet fed from the sheet feeding roller 73 of the internal sheet feeding unit 57 or the sheet feeding roller 74 of the manual sheet feeding unit 58. Transfer is performed by applying a bias voltage having a polarity opposite to that of the toner. The recording paper carrying the transferred toner image is conveyed to the fixing unit, and is sufficiently heated by the fixing roller 3 and the pressure roller 4 so that the toner image is fused to the recording paper and discharged to the outside.

  FIG. 6 is a cross-sectional view schematically showing the configuration of the fixing device 91 according to the second embodiment of the present invention. The fixing device 91 includes a fixing belt 92 as a first endless belt and a pressure belt 93 as a second endless belt. The fixing unit includes a fixing belt 92, a fixing roller 94, and a heating roller 111, and the pressing unit includes a twin belt including a pressing roller 95 and a pressing belt 93, and a pressing roller 95 and a tension roller 96. The fixing device is configured.

  The fixing belt 92 is an endless belt-like member that is stretched between the fixing roller 94 and the heating roller 111 to form a loop-shaped movement path. The fixing belt 92 is provided so as to come into contact with the pressure belt 93 at a pressure contact point between the fixing roller 94 and the pressure roller 95, and the toner constituting the toner image carried on the recording paper 97 is heated and melted to record the recording paper. 97 to be fixed. The fixing belt 92 is driven to rotate in the direction of the arrow X by the rotational driving of the fixing roller 94 in the direction of the arrow X.

  The fixing belt 92 is a three-layer structure including a base material layer, an elastic layer, and a release layer, and is an endless belt having a thickness of 270 μm formed in a cylindrical shape having a diameter of 80 mm. The material for forming the base material layer is not particularly limited as long as it is excellent in heat resistance and durability. For example, a heat resistant synthetic resin is used. Among the heat resistant synthetic resins, polyimide (PI) or polyamideimide (PAI) is preferable. These resins are excellent in strength, heat resistance, price and the like. As for the thickness of a base material layer, 45-90 micrometers is desirable. In this embodiment, polyimide is used and the thickness is 70 μm.

The material constituting the elastic layer is not particularly limited as long as it has rubber elasticity, but is preferably superior in heat resistance. For example, silicon rubber, fluorine rubber, fluorosilicon rubber, or the like is used. Among these, silicon rubber that is particularly excellent in rubber elasticity is preferable. The elastic layer preferably has a JIS-A hardness of 1 to 60 degrees. Within the range of JIS-A hardness, it is possible to prevent poor toner fixability while preventing a decrease in strength of the elastic layer and poor adhesion. Specific examples of the silicon rubber include one-component, two-component or three-component or more silicon rubber, LTV type, RTV type or HTV type silicon rubber, condensation type or addition type silicon rubber. . The thickness of the elastic layer is preferably 30 to 150 μm. Within this thickness range, the heat insulating property can be kept low while maintaining the elastic effect of the elastic layer, so that the energy saving effect is exhibited. In the present embodiment, silicon rubber having a JIS-A hardness of 5 degrees and a thickness of 150 μm is used.

The release layer is made of a fluororesin tube. The release layer formed on the outer peripheral side of the fixing belt 92 is composed of a fluororesin tube. A release layer composed of a fluororesin tube is more durable than a release layer formed by applying a resin containing a fluororesin and firing it. When a release layer is formed by coating and baking, if an attempt is made to obtain a release layer with high dimensional accuracy, a high-precision and expensive die is required. A mold release layer with high dimensional accuracy is obtained without using a mold. The thickness of the release layer is preferably 5 to 20 μm. If the thickness of the release layer is within this range, the release layer has an appropriate strength and can follow the minute irregularities of the recording material while utilizing the elasticity of the elastic layer. In this form state, the release layer, different from the present invention, about 30μm of PFA tube thickness is used.

  As the fixing roller 94, a roller-like member formed in a cylindrical shape with a diameter of 30 mm including the cored bar 98, the elastic body layer 99 and the surface layer 100 is used. A metal having high thermal conductivity is used as the metal forming the cored bar 98. For example, aluminum or iron is used. Examples of the shape of the core metal 98 include a cylindrical shape and a columnar shape, but a cylindrical shape with a small amount of heat released from the core metal 98 is preferable.

  The material constituting the elastic layer 99 is not particularly limited as long as it has rubber elasticity, but is preferably excellent in heat resistance. For example, silicon rubber, fluorine rubber, fluorosilicon rubber and the like can be mentioned. Among these, silicon rubber having excellent rubber elasticity is particularly preferable. In order to correct the deviation of the fixing belt 92, the surface layer 100 may be provided on the elastic layer. As a result, the slidability of the surface of the fixing roller 94 is improved and the deviation of the fixing belt 92 is easily corrected.

  The material constituting the surface layer is not particularly limited as long as it is excellent in heat resistance and durability and has high slidability. For example, fluorine resin materials such as PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) and PTFE (polytetrafluoroethylene), fluorine rubber, and the like are used.

  A heating unit may be provided inside the fixing roller 94. This is because the start-up time from when the image forming apparatus 90 is turned on until the image can be formed is shortened, and the surface temperature of the fixing roller 94 is lowered due to the transfer of heat to the recording paper 97 when the toner image is fixed. This is to prevent it.

  The heating roller 111 is a roller-like member that is rotatably supported and is provided so that tension can be applied to the fixing belt 92 by a pressure unit (not shown). The heating roller 111 rotates following the rotation of the fixing belt 92 in the arrow X direction. As the heating roller 111, a metal roller made of a metal having high thermal conductivity such as aluminum or iron is used. The metal roller may have a fluororesin layer formed on the surface thereof as necessary.

  The heating roller 111 has a heating means 101 inside. As a result, the fixing belt 92 is heated. A power source (not shown) is connected to the heating means 101, and power for causing the heating means 101 to generate heat is supplied. A general heating means is used for the heating means 101. In this embodiment mode, a halogen lamp is used as the heating unit 101.

  The pressure belt 93 is stretched by a tension roller 96 and a pressure roller 95 as belt suspension members. The tension roller 96 and the pressure roller 95 are rotatably supported and supported between left and right side plates (not shown) of the fixing device 91, respectively. The pressure belt 93 rotates following the fixing belt 92. Here, by adopting a configuration in which the fixing belt 92 and the pressure belt 93 are sandwiched and conveyed by the roller pair at the most downstream portion of the fixing nip, belt slip can be prevented. The most downstream portion of the fixing nip is a portion where the pressure distribution (recording material conveyance direction) at the fixing nip is maximized.

  As the pressure roller 95, a roller-shaped member having a diameter of 30 mm including the core metal 102, the elastic body layer 103, and the surface layer 104 is used. As the material for forming the core metal 102, the elastic body layer 103, and the surface layer 104, the same metal or material as that used for forming the core metal 98, the elastic body layer 99, and the surface layer 100 of the fixing roller 94 is used. . The shape of the core metal 102 is the same as that of the core metal 98 of the fixing roller 94.

  A heating unit 105 is provided inside the pressure roller 95. This is because the start-up time from when the image forming apparatus 90 is turned on until the image can be formed is shortened, and the surface temperature of the pressure roller 95 is abrupt due to the transfer of heat to the recording paper 97 when the toner image is fixed. This is to prevent a decrease or the like. In this embodiment mode, a halogen lamp is used as the heating means 105.

  The tension roller 96 is provided with a silicon sponge layer on an iron alloy cored bar 106 having an outer diameter of 30 mm and an inner diameter of 26 mm in order to reduce the heat conductivity and reduce the heat conduction from the pressure belt 93. ing. Here, in order to form a fixing nip as an image heating nip between the fixing belt 92 and the pressure belt 93, the pressure roller 95 is pressed toward the fixing roller 94 with a predetermined pressure. Yes.

  Further, in order to obtain a wide fixing nip without increasing the size of the apparatus, a fixing pad 107 as a first pressure pad that presses the fixing belt 92 toward the pressure belt 93, and the pressure belt 93 as the fixing belt. A pressure pad 108 is provided as a second pressure pad that pressurizes the nozzle 92. The fixing pad 107 and the pressure pad 108 are arranged to be supported between left and right side plates (not shown) of the apparatus. The pressure pad 108 is pressed with a predetermined pressure in the direction of arrow Z, which is the direction of the fixing pad 107, by a pressure mechanism (not shown).

  The fixing pad 107 as the first pressure pad and the pressure pad 108 as the second pressure pad are made of PPS (polyphenylene sulfide resin). When a nip is formed by a pad that is not a rotating body, the inner peripheral surface of the belt rubs against the pad. When the friction coefficient between the belt inner peripheral surface and the pad is large, the sliding resistance increases. As a result, problems such as image misalignment, gear breakage, and drive motor power consumption increase occur. These problems are particularly remarkable in the upper and lower belt systems. For this purpose, a low friction sheet is provided on the fixing pad 107 and the pressure pad 108 which are the first pressure pads, and the low friction sheet is in contact with the belt. As a result, pad scraping due to friction with the belt can be prevented, sliding resistance can be reduced, and good belt running performance and belt durability can be obtained.

  FIG. 7 is a block diagram for controlling the fixing device 91. Power is supplied from the power supply circuit A2 to the halogen heater of the heating roller 111, and the heating roller 111 is heated. The rotating fixing belt 92 is heated by the heating roller 111. The surface temperature of the fixing belt 92 is detected by a temperature detection element such as the thermistor A109. A signal related to the temperature of the fixing belt 92 detected by the temperature detection element is input to the control circuit unit. The control circuit unit controls the power supplied from the power supply circuit to the halogen heater so that the temperature information input from the temperature detection element is maintained at a predetermined fixing temperature, so that the temperature of the fixing belt 92 is set to the predetermined fixing temperature. adjust.

  In a state where the fixing belt 92 rises to a predetermined fixing temperature and the temperature is adjusted, the recording paper 97 having an unfixed toner image is conveyed to the fixing nip between the fixing belt 92 and the pressure belt 93. The recording paper 97 is introduced with the surface carrying the unfixed toner image facing the fixing belt 92 side. The unfixed toner image on the recording paper 97 is nipped and conveyed while being in close contact with the outer peripheral surface of the fixing belt 92. The unfixed toner image is fixed on the surface of the recording paper 97 by applying heat from the fixing belt 92 and receiving pressure.

  The thermistor A 109 is provided so as to be close to the fixing belt 92 at a position facing the heating roller 111 via the fixing belt 92. The thermistor A 109 detects the temperature of the fixing belt 92. The thermistor B <b> 110 is provided so as to be close to the pressure belt 93 at a position facing the pressure roller 95 through the pressure belt 93. The thermistor B110 detects the temperature of the pressure belt 93. Detection results by the thermistor A 109 and the thermistor B 110 are input to a central processing unit (hereinafter referred to as a CPU).

  The CPU 112 determines whether or not the temperature of the thermistor A109 is within the set range from the detection result of the thermistor A109. When the temperature of the fixing belt 92 is lower than the set range, a control signal is sent to a power source connected to the heating unit A101, and electric power is supplied to the heating unit A101 to promote heat generation. When the temperature of the fixing belt 92 is higher than the set range, the presence / absence of power supply to the heating unit A101 is confirmed. When the power supply is continued, a control signal for stopping the power supply is sent.

  Further, the CPU 112 determines whether or not the temperature of the thermistor B110 is within the set range from the detection result of the thermistor B110. When the temperature of the pressure belt 93 is lower than the set range, a control signal is sent to the power source connected to the heating unit B105, and electric power is supplied to the heating unit B105 to promote heat generation. When the temperature of the fixing belt 92 is higher than the set range, the presence / absence of power supply to the heating unit B105 is confirmed. When the power supply is continued, a control signal for stopping the power supply is sent.

  A thermostat 115 (not shown) is disposed at a position facing the heating roller 111 via the fixing belt 92 and downstream of the thermistor A 109 in the rotation direction of the fixing belt 92. The thermostat 115 is provided so as to be close to the fixing belt 92 and detects an abnormal temperature increase of the fixing belt 92. The detection result by the thermostat 115 is input to the CPU 112. The CPU 112 stops the power supply from the power source connected to the heating unit A101 according to the detection result of the thermostat 115.

  The fixing mechanism including the fixing roller 94, the heating roller 111, the fixing belt 92, and the pressure roller 95 is controlled by a CPU 112 (not shown) that controls the entire operation of the image forming apparatus 90. When the CPU 112 receives an image formation instruction, the CPU 112 sends a control signal to a power supply that supplies power to the heating unit A101 and the heating unit B105 provided in the heating roller 111 and the pressure roller 95. The image forming instruction is input from an operation panel (not shown) provided on the upper surface in the vertical direction of the image forming apparatus 90 or an external device such as a computer connected to the image forming apparatus 90. The power supply that has received the control signal supplies power to activate the heating means A101 and the heating means B105.

  The heating unit A101 and the heating unit B105 heat the surfaces of the fixing roller 94, the heating roller 111, the pressure roller 95, and the fixing belt 92 so as to have respective set temperatures. When a temperature detection sensor (not shown) provided in the vicinity of the fixing roller 94 and the pressure roller 95 detects that the set temperature has been reached and the detection result is input to the CPU 112, the CPU 112 rotates the fixing roller 94. A control signal is sent to the drive means that does not, and the pressure roller 95 is rotated in the direction of the arrow Y.

  Accordingly, the fixing belt 92, the fixing roller 94, and the heating roller 111 are driven to rotate. In this state, the recording paper 97 carrying the unfixed toner image is conveyed to the fixing nip portion 12. When the recording paper 97 passes through the fixing nip portion 12, the toner constituting the toner image is heated and pressurized and fixed on the recording paper 97 to form an image.

  In the fixing device 91 shown in FIG. 7, a halogen lamp is used as the heating unit A <b> 101 inside the heating roller 111, but an external heating device may be provided on the outer periphery of the heating roller 111. Moreover, you may use the induction heating apparatus using induction heating, and may comprise combining these suitably.

As described above, the fixing belt 5 has the outer diameter of the fixing belt 5 set to A mm, and the both ends of the metal pipe 21 are fixed through the fixing belt 5 through the metal pipe 21 having an outer diameter of 13 mm and sufficiently longer than the fixing belt width. In this state, it is sufficiently longer than the fixing belt width, and the weight divided by the fixing belt width is 0. The length of the fixing belt 5 in the vertical direction when the load roller 22 of 359 g / mm and an outer diameter of 13 mm is passed through the fixing belt 5 so that the fixing belt 5 extends downward is defined as B mm. When S is given, the following formula S = (B−A) / A
The fixing belt 5 has a flexibility S of 0.15 to 0.24 , and the fixing roller 3 includes a spherical weight 31 having an outer diameter of 11 mm and a weight of 7 g suspended from a thread 32 having a length of 50 cm. In a stationary state, when the weight is at the lowest point 33 in contact with the horizontal surface including the central axis of the fixing roller 3 so that the center of gravity of the weight is disposed, the weight is lifted from the lowest point by a height of H1 = 10 cm. When the height from the lowest point 33 where the weight bounces off when the weight is caused to gently collide with the fixing roller 3 is H2, and the restitution coefficient of the fixing roller 3 is R, R = H2 / H1 Since the restitution coefficient R of the fixing roller 3 expressed by the formula (1) is 0.6 or more, the temperature range in which the toner can be fixed on the member to be fixed can be made wider than before.

Furthermore, since the surface pressure of the fixing nip portion 12 where the pressure roller 4 is in pressure contact with the fixing roller 3 is 1.4 kgf / cm ² or more, the fixing property can be improved.

  Further, since the hardness of the fixing roller 3 is 30 degrees or more and 50 degrees or less Asker C, the resilience of the fixing roller 3 is good, and the fixing property can be improved.

  Further, the fixing belt 5 has a fluororesin layer, a rubber elastic layer, and a resin base material layer toward the contact surface with the fixing roller 3 on the basis of the contact surface in contact with the toner image on the fixing member. Since the thickness of the material layer is not less than 45 μm and not more than 90 μm, the fixing belt 5 can be secured without being cracked, and the fixing property can be improved.

  Furthermore, since the ratio of the toner wax weight to the total weight of the toner forming the toner image is 1.5% by weight or more and 4.8% by weight or less, the fluidity of the toner does not decrease and the toner with respect to the fixing belt does not deteriorate. The releasability can be improved.

  Further, the surface of the fixing roller 3 in contact with the fixing belt 5 is formed by the fixing roller elastic layer 121, and the thickness dimension of the fixing roller elastic layer 121 is 4 mm or more and 6 mm or less. Can improve the fixing property of the toner. Further, the fixing roller elastic layer 121 can improve the releasability of the sheet which is a non-fixing member. As a result, the fixing device 2 can prevent problems such as hot offset and paper wrapping when the fixing temperature fluctuates.

  Further, the fixing roller 3 has a surface portion in contact with the fixing belt 5 formed by the fixing roller elastic layer 121, and the thickness dimension when the fixing roller elastic layer 121 is pressed by the pressure roller 4 through the fixing belt 5. Since the indentation ratio L, which is the ratio of M to the thickness dimension N when not pressed, is 25% or more and 35% or less, the toner fixing property is improved and the fixing roller elastic layer 121 Durability can be increased.

  Further, since the fixing device 2 is provided, it is possible to provide the image forming apparatus 1 including the fixing device 2 having a wider temperature range capable of fixing the toner on the member to be fixed than in the past.

  In this way, the image forming apparatus of the present embodiment is realized. The fixing device according to the present embodiment includes the excellent fixing device of the present invention as described above. According to the fixing device of the present invention, it is possible to widen the temperature range in which the toner fixability is good.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Fixing apparatus 3 Fixing roller 4 Pressure roller 5 Fixing belt 6,111 Heating roller 7a, 7b Heater lamp 8,97 Recording paper 9 Toner 10 First thermistor 11 Second thermistor 12 Fixing nip part 21 Metal pipe 22 Load roller for measurement 31 Spherical weight 32 Thread 33 Bottom point 41 Belt detent 51 First visible image forming unit 52 Second visible image forming unit 53 Third visible image forming unit 54 Fourth visible image forming unit 55 Intermediate transfer belt 56 Secondary transfer unit 57 Internal paper feed unit 58 Manual paper feed unit 59, 65, 66, 67 Photoconductor 60 Charging unit 61 Development unit 62 Primary transfer unit 63 Cleaning unit 64 Light source 68, 69 Tension roller 70 Waste toner BOX
DESCRIPTION OF SYMBOLS 71 Fixing member 72 Pressure member 73,74 Paper feed roller 90 Image forming apparatus 91 Fixing apparatus 92 Fixing belt 93 Pressure belt 94 Fixing roller 95 Pressure roller 96 Tension roller 98 Core metal 99 Elastic body layer 100 Surface layer 101 Heating means A
102 Metal core 103 Elastic layer 104 Surface layer 105 Heating means B
106 Metal core 107 Fixing pad 108 Pressure pad 109 Thermistor A
110 Thermistor B
111 Heating roller 112 CPU
DESCRIPTION OF SYMBOLS 113 Power supply circuit 114 Control circuit 115 Thermostat 116 Fixing roller drive motor 121 Fixing roller elastic layer 122 Pressure roller elastic layer 123 Tangent line of fixing roller elastic layer 124 Tangent line of pressure roller elastic layer 125 Convex part

Claims (7)

An endless fixing belt that contacts the toner image on the fixing member and fixes the toner image on the fixing member;
A heating roller for heating the fixing belt;
The endless fixing belt is stretched together with the heating roller, and the fixing roller is in contact with the toner image on the fixing member via the fixing belt;
A pressure roller in pressure contact with the fixing roller via the fixing belt,
The fixing belt has a fluororesin layer, a rubber elastic layer, and a resin base material layer toward a contact surface with the fixing roller with reference to a contact surface in contact with the toner image on the member to be fixed,
The resin substrate layer is made of polyimide having a thickness of 50 μm or more and 90 μm or less,
The fluororesin layer is made of a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether having a thickness of 5 μm or more and 20 μm or less,
The rubber elastic layer has a thickness of 30 μm to 150 μm,
With the outer diameter of the fixing belt being A mm, the fixing belt is passed through a first metal shaft having an outer diameter of 13 mm and sufficiently longer than the width of the fixing belt, and both ends of the first metal shaft are fixed. It is sufficiently longer than the fixing belt width, and the weight divided by the fixing belt width is 0. The vertical length of the fixing belt when passing through a second metal shaft of 359 g / mm and an outer diameter of 13 mm through the fixing belt so that the fixing belt extends downward is Bmm,
When S is the flexibility of the fixing belt, S = (B−A) / A
The flexibility S of the fixing belt represented by: 0.15 to 0.24 ,
In the fixing roller, a weight having an outer diameter of 11 mm and a weight of 7 g suspended from a thread of 50 cm in length is arranged so that the center of gravity of the weight is arranged on a horizontal plane including the central axis of the fixing roller in a stationary state. When at the lowest point of contact, the weight is lifted from the lowest point by a height of H1 = 10 cm, and when the weight is gently released to cause the weight to collide with the fixing roller, the height from the lowest point at which the weight rebounds. When the thickness is H2 and the repulsion coefficient of the fixing roller is R, the following equation is given: R = H2 / H1
A fixing device having a restitution coefficient R of 0.6 or more expressed by:   The fixing device according to claim 1, wherein a surface pressure of a fixing nip portion, which is a region where the pressure roller is in pressure contact with the fixing roller, is 1.4 kgf / cm 2 or more.   The fixing device according to claim 1, wherein the fixing roller has a hardness of Asker C of 30 degrees or more and 50 degrees or less. The ratio of the weight of the toner wax to the total weight of the toner forming the toner image is 1.5% by weight or more and 4.8% by weight or less, according to any one of claims 1 to 3. The fixing device described. In the fixing roller, a surface portion in contact with the fixing belt is formed by an elastic layer,
Thickness of the elastic layer, the fixing device according to any one of claims 1-4, characterized in that there is 4mm or more and 6mm or less. In the fixing roller, a surface portion in contact with the fixing belt is formed by an elastic layer,
The elastic layer has a pressing ratio indicating a ratio of a thickness dimension when pressed by the pressure roller via the fixing belt and a thickness dimension when not pressed to the elastic layer is 25% or more and 35 the fixing device according to any one of claims 1-4, characterized in that% or less. An image forming apparatus comprising: a fixing device according to any one of claims 1-6.

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