JP2003316192A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device or the like which can prevent degradation in image quality by production of air bubble pools in a transparent toner layer when the transparent toner layer is formed on a fixing belt and is transferred and fixed to a toner image carrying surface of recording paper. <P>SOLUTION: The device for forming the transparent toner layer on the fixing belt of the fixing device is installed and the transparent toner layer 5 in which a plurality of straight lines 6 penetrated from one side to the other side of the transparent toner layer line up in a direction paralleling with a feed direction E of the recording paper or toward diagonally backward is formed on the side to be superposed on the toner image carrying surface of the recording paper according to need in the fixing operation. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing a toner image carried on a recording medium such as a recording sheet by using a fixing belt, and a printer, a copying machine, a multi-function peripheral equipped with the fixing device. In relation to a typical image forming apparatus, in particular, when a transparent toner layer is formed on a fixing belt and transferred and fixed on the toner image bearing surface of a recording medium, bubbles are generated in the transparent toner layer and the image quality is improved. The present invention relates to a fixing device and the like that can prevent the deterioration of the image quality.

[0002]

2. Description of the Related Art In recent years, color image forming apparatuses utilizing electrophotography and the like have become widespread. In this type of image forming apparatus, a color image is generally formed as follows.

First, an electrostatic latent image for each color component is formed by irradiating a laser beam or the like, which is decomposed and modulated for each color component on the basis of image information, onto a photosensitive member in the form of a rotating drum, and the like. To each electrostatic latent image, toner of four colors of yellow, magenta, cyan, and black formed by mixing a pigment and the like into a thermoplastic binder resin (binder) is adhered, and each of the above colors is adhered. To form a toner image. Next, the toner images of the respective colors are transferred onto the recording paper in a state of being superposed directly or via an intermediate transfer body, and then the toner images on the recording paper are heated and pressed by a fixing device to be fixed on the recording paper. As a result, a color image is formed on the recording paper.

Further, as a fixing device in this type of image forming apparatus, a rotating heating roll and a pressure roll are mainly arranged in a state of being in pressure contact with each other, and a recording sheet to be fixed is passed through the pressure contact portion. In this state, the pressure roller and the pressure roller are placed in pressure contact with each other so as to sandwich the fixing belt which is stretched and rotated on the heating roll side. For example, a belt-combined type is used which is configured to allow the recording paper to be fixed to pass through the pressure contact portion between the pressure rolls.

By the way, in such a color image forming apparatus, for example, when forming a photographic color image, in order to form a color image having a particularly excellent glossiness, the material of the toner to be used, fixing conditions, etc. are appropriately used. A technique for forming a highly glossy photographic color image by selecting it has been proposed (Japanese Patent Laid-Open Nos. 5-142963 and 3-2.
765, JP-A-63-259575, etc.).

However, according to this proposed technique, although the glossiness of the image portion formed by the toner image can be increased, the glossiness of the non-image portion other than the image portion can be increased. Therefore, the glossiness in both the image area and the non-image area cannot be made uniform. Further, the surface of the image portion has fine irregularities left by the toner particles, and the surface is not as smooth as the image surface in a silver salt photograph or printed matter, and a smooth texture cannot be obtained.

Therefore, conventionally, for example, the following apparatus has been proposed as a means for forming an image excellent in glossiness.

That is, a transparent toner layer made of a transparent toner is formed in addition to a toner image of a colored toner forming a color image, and the transparent toner layer is transferred onto a recording sheet on which the colored toner image is formed. Image forming apparatus for fixing (JP-A-4-278967 and JP-A-5-78967)
No. 232841, JP-A-7-72696, etc.) and a clear coat device for forming a transparent resin layer on a sheet on which an image is formed (JP-A-3-130791).
Alternatively, a glossy image forming apparatus for transferring a transparent toner layer onto a sheet on which an image is formed and fixing the belt (Japanese Patent Laid-Open No. Hei 5-23284)
No. 1) and the like.

[0009]

However, in any of the images obtained by each of the above-mentioned devices, the glossiness is made uniform in both the image area and the non-image area in order to form the transparent toner layer or the transparent resin layer. However, there is a part in the image part where the difference in the height (pile height) of the toner image is large (specifically, the part where the image density is significantly different), and that part is generated when passing through the fixing pressure contact part. If the air exists so as to obstruct the path of movement of air, there is a problem in that bubbles accumulate (bubble accumulation) in a portion such as a transparent toner layer corresponding to the toner image portion. This phenomenon of bubble accumulation is likely to occur in a belt-combining type fixing device in which a recording sheet at the time of fixing is conveyed in a state of being in close contact with a fixing belt after passing through a pressure contact portion, and is cooled and then peeled off from the fixing belt. At that time, when a thick paper or a paper coated with resin is used as the recording paper, the air is less likely to escape from the back surface of each paper, which is more likely to occur. And the diameter is 10
When a bubble accumulation of more than 0 μm occurs, the bubble becomes visible and the image quality deteriorates significantly.

It is presumed that such bubble accumulation occurs due to the following mechanism. That is, as shown in FIG. 9, the transparent toner layer 2 formed on the fixing belt 200.
Air existing between the toner particles 10 and between the toner particles of the color toner image 300 carried on the recording paper 100 or between the recording paper 100 and the transparent toner layer 210 is a fixing pressure contact portion (fixing nip portion) of the fixing device. Recording paper 1 when entering N
00 and the fixing belt 200 and the like start to be pressurized and move toward the rear side of the feeding direction (passing direction) E of the recording sheet 100 so as to be squeezed out (in FIG. 9a). Dotted arrow). At this time, the air moves while growing as a mass of large bubbles, and among them, there is a portion 300 of the toner image 300 where the height difference is large.
There is a case where a cannot pass over the step due to the difference in height and cannot move to pass through the fixing nip portion N while remaining in a slight space S located on the upstream side in the feeding direction E of the portion. The air remains trapped in the transparent toner layer 210 and the like, and remains as air bubbles.

As a measure for preventing the occurrence of such bubble accumulation, it is conceivable to increase the nip pressure in the fixing nip portion or reduce the passage speed (fixing speed) of the recording paper in the fixing nip portion. However, when the nip pressure is increased, the pressure applying mechanism becomes large and the size of the apparatus is increased, and when the fixing speed is slowed, the productivity is reduced. Yes, it is not appropriate.

The present invention has been made to solve the above problems, and when a transparent toner layer is formed on a fixing belt and transferred and fixed to the toner image bearing surface of a recording medium, the transparent toner is used. An object of the present invention is to provide a fixing device and an image forming apparatus capable of preventing deterioration of image quality due to occurrence of air bubble accumulation in a layer.

[0013]

A fixing device of the present invention which can achieve the above object is a heating roll provided with a heat source, a supporting roll arranged at a predetermined distance from the heating roll, and the heating roll. And an endless fixing belt which is stretched between the supporting roll and the supporting roll and rotates, and a pressure roll arranged in pressure contact with the heating roll with the fixing belt sandwiched between the pressure roll and the fixing belt. In a fixing device that introduces a recording medium carrying a toner image to be fixed to the pressure contact portion in a posture in which the toner image bearing surface is located on the fixing belt side, and passes the toner image bearing surface of the recording medium. A transparent toner layer forming device for forming a transparent toner layer made of a transparent toner to be transferred and fixed on the fixing belt is installed, and the transparent toner layer formed by the transparent toner layer forming device is The recording medium is linearly pierced from the one end side to the other end of the transparent toner layer on the side superposed with the toner image bearing surface in a direction parallel to the feeding direction of the recording medium or obliquely rearward. It is characterized in that it is a layer in which a plurality of grooves are arranged side by side.

FIG. 1 shows the groove 6 in the transparent toner layer 5.
The typical formation pattern of is shown. In the figure, arrow E indicates the feeding direction of the recording medium, arrow J indicates the axial direction of the heating roll, and reference numeral 7 indicates the bent portion of the groove 6. The groove 6 in FIG. 1a has a pattern oriented in a direction parallel to the feeding direction E of the recording medium when superposed on the recording medium, and the groove 6 in FIG. 1c, the groove 6 in FIG. 1c is also a pattern that is also facing diagonally leftward, and the groove 6 in FIG. 1d is a pattern that is bent once at the upstream side in the feeding direction E of the recording medium, and is a groove 6a that is diagonally facing rightward. And the pattern area of the groove 6b facing diagonally leftward and rearward. 2 is the same as FIG.
FIG. 3 is a partial cross-sectional view taken along line II-II (direction orthogonal to the feeding direction of the recording medium) such as a and b. Reference numeral 8 in FIG. 2 denotes a ridge portion which is a portion between the grooves 6 and 6. FIG. 3 is a schematic explanatory view showing the structure of the groove 6. N in FIG. 3 indicates a pressure contact portion (fixing nip portion).

The transparent toner layer 5 is formed in an area corresponding to the size (planar area) of the recording medium so as to cover the entire one surface of the recording medium, or is formed in a partial area of the recording medium. It may be formed in a smaller area than the recording medium so as to cover only a specific area of the toner image.

The groove 6 in the transparent toner layer 5 is a groove continuous from one end side of the entire transparent toner layer to the other end. The grooves 6 are preferably regular (periodic) arranged in parallel at a constant pitch like a line pattern (screen pattern) as illustrated in FIG. Accordingly, the pitches may be formed differently (randomly). Further, although it is preferable that the groove 6 is a perfect straight line, even if the groove 6 is gently curved or bent in the middle due to, for example, restrictions on the forming accuracy of the transparent toner layer, it may be in a state of being approximated to a straight line as a whole. It doesn't matter. Further, the cross-sectional shape of the groove 6 is not particularly limited, but it is preferable that the groove 6 has a shape of a smooth curve. The groove 6 forms an angle (oblique intersection angle) θ with the feeding direction E of the recording medium as shown in FIG.
Is preferably set to 0 to 60 °.

The transparent toner layer forming device is not particularly limited as long as it is formed of colorless transparent toner (fine resin particles) and can form an unfixed transparent toner layer having the specific groove. Instead, for example, a toner image forming apparatus using an electrophotographic method (a device mainly including a photoconductor, a charging device, an exposure device, a developing device for transparent toner, etc.)
Can be used. The transparent toner is toner particles made of a transparent resin containing no coloring material (coloring pigment, coloring dye, black carbon particles, etc.) for the purpose of coloring due to light absorption or light scattering. The transparent toner is colorless and transparent, and is substantially colorless and transparent even when the transparency is slightly lowered depending on the type and amount of the fluidizing agent, the release agent, etc. contained in the toner particles. .

According to such a fixing device, when the transparent toner layer formed on the fixing belt at the pressure contact portion between the fixing belt and the pressure roll is superposed on the toner image carrying surface of the recording medium and transferred and fixed, The groove in the transparent toner layer functions as a groove (passage) that guides and guides the movement of air (air bubbles) squeezed out at the pressure contact portion. As a result, even if the toner image on the recording medium has a portion having a large pile height difference, the air that must pass through that portion moves well through the gap formed by the groove existing between that portion and the transparent toner layer. However, it does not remain. The groove is crushed and disappears by passing through the pressure contact portion, and is heated and melted to be transferred and fixed on the recording medium side.

Further, since the groove of the transparent toner layer is formed by penetrating from one end of the toner layer to the other end thereof, the bubbles moving along the groove eventually reach a certain end of the toner layer. Is easily discharged from the. In particular, when the groove is in a state of being penetrated obliquely rearward with respect to the feeding direction of the recording medium, the air moving through the groove so as to be squeezed out when entering the press contact portion is recorded. The recording medium or the transparent toner layer is sequentially discharged from the groove located on the upstream side of the medium in the feeding direction. This allows air to be discharged little by little and efficiently when the recording medium rushes into the pressure contact portion and passes therethrough. There is no moving air to be squeezed out and there is no danger of remaining as a large lump.

The grooves 6 in the transparent toner layer are 100 to 3
A groove having a width W of 00 μm is preferable. If the groove width W is less than 100 μm, air mass (air bubbles) with an outer diameter of 100 μm or more that is easily visible may not be removed. On the other hand, when the groove width W exceeds 300 μm, there is a problem that the groove 6 cannot be crushed and completely disappeared at the pressure contact portion and the unevenness due to the groove 6 remains after fixing and uniform gloss cannot be obtained. The depth d (before fixing) of the groove 6 is not particularly limited, but the groove 6 cannot be completely destroyed by being crushed at the pressure contact portion of the fixing and the unevenness due to the groove 6 remains after the fixing to obtain a uniform gloss. From the viewpoint of avoiding problems such as disappearance, it is preferable to set the value smaller than 50 μm.

Also, the groove in the transparent toner layer is shown in FIG.
It is preferable that all of the grooves are formed by being bent once at the upstream side in the feeding direction of the recording medium and facing diagonally opposite rear sides, as illustrated in FIG. When a groove having such a bent portion 6 is formed, the air squeezed out when entering the pressure contact portion is divided and squeezed out on both the left and right sides in the feeding direction of the recording medium and is discharged. This enables efficient air discharge. When there are two or more bent portions 6, each groove 6
All the bent portions 6 of 1 are along the feeding direction of the recording medium.
It is preferable to be configured so as to be located on two straight lines.

Further, it is preferable that the groove 6 is a groove formed so as to exist above the base layer 5a having a uniform layer thickness as illustrated in FIG. In this case, the underlayer 5
The thickness of a itself may be about 20 to 100 μm. When the transparent toner layer is formed such that the groove is located above the base layer, air is discharged at the portion where the groove 6 is formed, and the gloss of the transparent toner layer is provided at the base layer. There is an advantage that it is possible to surely realize the effect of giving a feeling.

In order to form a transparent toner layer having such a groove, when the above-mentioned electrophotographic apparatus is used as the transparent toner layer forming apparatus, for example, power modulation or pulse width modulation of the exposure apparatus is performed. Can be formed by performing. It is also possible to shift the focus of the exposure device from the normal position (defocus) to form an overlap of the exposure profiles (combined light) on the photoconductor. In the latter case, it is not necessary to perform the above-mentioned modulations like the former,
Further, it becomes possible to use an inexpensive exposure apparatus having a low resolution.

Here, the heat source in the fixing device is the heat source in both the fixing devices of the first and second inventions.
A heating roll that can be uniformly heated and maintained at a predetermined temperature (fixing heating temperature or the like) is used. This heat source may be arranged also on the pressure roll side, if necessary.

Basically, the recording medium is not particularly limited as long as it can carry the toner image to be fixed and can perform the fixing process by passing through the fixing pressure contact portion. For example, recording paper, thick paper, photographic paper, OHP sheet, etc. can be used. Further, as the recording medium, it is also possible to use a recording medium having a transparent and colorless transparent resin layer formed on at least the surface on which the toner image is carried.

The fixing device as described above forms the toner image according to the image information, and transfers the toner image to the recording medium to fix the toner image in the image forming device to form the image. It is effective to use it as a fixing device for fixing to a recording medium. In this case, the fixing device may be configured to be used inside the main body of the image forming apparatus, or may be used separately from the image forming apparatus and connected to the outside of the main body. Can be configured to.

Further, the image forming apparatus is preferably one capable of forming a color image, but may be one capable of forming only a monochrome image. Further, this image forming apparatus may use an intermediate transfer system in which a toner image formed on an image bearing member such as a photoconductor is transferred to a recording medium via an intermediate transfer member having a belt shape or a drum shape. Alternatively, the toner image on the image carrier may be directly transferred to the recording medium without using the intermediate transfer method. As the image carrier, one may be used or a plurality of images may be used.

In particular, according to the image forming apparatus equipped with the fixing device as described above, it is possible to form a high quality image which is excellent in glossiness without bubbles in the transparent toner layer. An image forming apparatus equipped with such a fixing device is suitable as a device for outputting photographic image data such as a digital still camera.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 4 shows a color image forming apparatus 1 and a fixing device 2 according to a first embodiment of the present invention. The image forming apparatus 1 can be used as a color printer, and an image forming unit such as a color copying machine, a facsimile, or a multifunction machine having various functions (print function, copy function, facsimile function, etc.). It can be used as (output unit).

<Structure of Entire Image Forming Apparatus> First, the color image forming apparatus 1 is equipped with an image forming means adopting an intermediate transfer system inside the apparatus main body 10. The image forming means includes one photosensitive drum 11 that rotates at a predetermined speed in the direction of arrow A, a charging device 12, a latent image writing device 13, a developing device 14, and a primary transfer device 15 that are arranged around the photosensitive drum 11. The main part is composed of etc.

As the photosensitive drum 11, a photosensitive drum made of an organic photosensitive material or the like is formed on the peripheral surface of a drum base having a hollow structure. As the latent image writing device 13, for example, a laser beam scanner that guides and irradiates the photosensitive drum 11 with a laser beam LB modulated based on input image information via various optical components such as an optical lens is used. . The developing device 14 includes developing devices 14Y, 14M, 14C, and 14K that store toner (developer) of each color of yellow (Y), magenta (M), cyan (C), and black (B), respectively. Rotating support 1
A rotary type developing device is used which is arranged at substantially equal intervals along the peripheral surface of No. 6. Each developing device is a two-component developing device that uses a two-component developer consisting of (colored) toner and carrier. As the toner, one having an average particle diameter of 4 to 8 μm is preferably used. As the primary transfer device 15, there is used a roll type device in which a primary transfer roll to which a primary transfer bias voltage having a polarity opposite to the charging polarity of toner is applied from a power supply device (not shown) is arranged.

Image formation by such image forming means is indicated by an arrow A.
The photosensitive surface of the photosensitive drum 11 rotating in the direction
After being uniformly charged to a predetermined potential by 2, the latent image writing device 13 forms an electrostatic latent image for each color component on the surface according to image information, and thereafter, the electrostatic latent image is formed. A toner image is formed on the photosensitive drum 11 by moving a developing device accommodating toner of a corresponding color to a developing position facing the photosensitive drum 11 and developing in a facing state. At this time, in the case of forming a single-color image consisting of toner images of one color, the above-mentioned image forming process is executed only once, whereas a color image formed by superposing toner images of plural colors is formed. If so, the above image forming process is similarly repeated for the number of the color components.

Photosensitive drum 11 formed by this image forming means
The upper toner image is transferred onto the recording paper P via the intermediate transfer belt 20. The intermediate transfer belt 20 is the photosensitive drum 1.
The primary transfer device 15 is supported by a support member (not shown) in such a state that it abuts the surface at the primary transfer position where the primary transfer device 15 is arranged, and is arranged to rotate at a predetermined speed in the direction of arrow B. . In addition, at a position of the secondary transfer position of the intermediate transfer belt 20, a backup roll 25 is in contact with the inner peripheral surface side of the belt and is in pressure contact with the outer peripheral side of the belt while sandwiching the backup roll 25 and the intermediate transfer belt 20. A secondary transfer roll 26 is installed. As the intermediate transfer belt 20, for example, a belt having a characteristic that the potential half time is 0.05 seconds or more and 1.0 seconds or less when the belt surface is uniformly charged to −500V is used.

As the intermediate transfer belt 20, there is used an endless belt formed of a synthetic resin such as polyimide containing a conductive agent such as carbon black. A secondary transfer bias voltage having the same polarity as the charging polarity of the toner is applied to the backup roll 25 from a power supply device (not shown). The secondary transfer roll 26 is disposed so that it can come into contact with and separate from the intermediate transfer belt 20, and when forming a color image in which toner images of a plurality of colors are superimposed, the toner image on the intermediate transfer belt 20 is formed. Is brought into contact with the belt 20 in accordance with the secondary transfer timing when the image is transferred onto the recording paper P, but is separated at other times.

Further, a paper feeding means for feeding the recording paper P to the secondary transfer position of the above-mentioned image forming means is provided on the lower inner side of the apparatus main body 10. The paper feeding means includes a plurality of storage trays 30 that can store the recording paper P according to conditions such as size and feeding direction, and a feeding mechanism 31 that feeds the recording paper P from each tray 30. A main portion of a paper feed path or the like constituted by a plurality of pairs of transport rolls and a transport guide member that guides and transports the recording paper P delivered from each storage tray 30 by each delivery mechanism 31 to a secondary transfer position. Has been formed. The dashed-dotted line in the figure indicates the path along which the recording paper P is conveyed.

Further, inside the apparatus main body 10, a fixing device 2, a paper conveying device 36 for conveying the recording paper P after the secondary transfer to the fixing device 2, and a recording paper P after the fixing are provided in the apparatus main body 1.
It is equipped with a pair of discharge rolls 37 and the like for discharging outside 0. Reference numeral 38 in the drawing is a discharge tray for stacking and containing the recording paper P to be discharged.

The toner image formed on the photosensitive drum 11 is
It is electrostatically primary-transferred onto the intermediate transfer belt 20 at the primary transfer position. At this time, when forming a monochromatic image, the toner image primarily transferred to the intermediate transfer belt 20 is secondarily electrostatically secondarily transferred to the recording paper P at the secondary transfer position. On the other hand, in the case of forming a color image, the toner images of a plurality of colors sequentially formed by the image forming unit are sequentially primary-transferred onto the intermediate transfer belt 20 and superposed on each other, and then the recording paper is transferred at the secondary transfer position. The image is secondarily transferred to P at once.

Next, the recording paper P on which the toner image is transferred
Is separated from the intermediate transfer belt 20 and then sent to the fixing device 2 by the sheet conveying device 36 to be fixed.
After such fixing, the sheet is conveyed by the pair of discharge rolls 37 and discharged to the discharge tray 38. A monochromatic image or a color image is formed through such a series of image forming processes.

<Structure of Fixing Device> The fixing device 2 in the color image forming apparatus 1 has the following structure.

That is, the fixing device 2 is a belt-combining type fixing device as shown in FIGS.
0, the pressure roll 45, the fixing belt 50, the peeling roll 48, and the cooler 55 constitute a main part thereof. Further, in this fixing device 2, a transparent toner layer forming device 3 for forming a transparent toner layer on the fixing belt 50 is arranged between the peeling roll 48 of the fixing belt 50 and the heating roll 40. .

The heating roll 40 has a roll structure in which a halogen lamp 42 for heating is arranged in the hollow inside of a cylindrical roll core 41 made of a metal material. In this heating roll 40, an elastic layer made of silicone rubber or the like is provided on the outer peripheral surface of the roll core material 41, if necessary,
It is possible to provide a surface layer made of fluorine resin (PFA or the like) on the outermost surface. The halogen lamp 42 is feedback-controlled so that its heating operation can be heated to a predetermined temperature based on the detection information of the surface temperature of the heating roll 40. Further, the heating roll 40 has its roll core material rotatably supported, and the rotational force of a drive motor (not shown) is transmitted through a gear train to rotate the heating roll 40 at a predetermined speed in the direction of arrow C. It is like this.

The pressure roll 45 has an elastic layer 47 made of silicone rubber or the like provided on the outer peripheral surface of a roll core member 46. The roll core member 46 is rotatably supported and is not shown. Heating roll 40 by pressure mechanism
The fixing belt 50 is pressed against the sheet at a predetermined pressure. A pressure contact portion (fixing nip portion) N is formed between the pressure roller 45 and the fixing belt 50. The pressure applied by the pressurizing mechanism is set so that the pressure in the fixing nip portion is 1 to 2 MPa.

The peeling roll 48 stretches the fixing belt 50 with a predetermined curvature and stretches the fixing belt 50 to form the belt 5.
It is a driven rotation roll for promoting peeling of the recording paper P having the toner image to be fixed, which is conveyed in a state of being in close contact with 0. The peeling roll 60 is made of aluminum, stainless steel, or the like from the viewpoint of reducing the wear of the belt 50.
It is made of metal materials such as iron and brass. Further, from the viewpoint of surely exhibiting the above-mentioned peeling promoting action by making the fixing belt 50 bent, the diameter of the roll is desirably 50 mm or less.

The fixing belt 50 has a belt structure in which a heat resistant elastic layer is provided on the outer peripheral surface of the belt base material from the viewpoint of enhancing the adhesion to the toner image on the recording paper P. The heating roll 40 is stretched around the work roll 48 so that the heating roll 40 is driven to rotate in the direction of arrow D.

In consideration of heat resistance, strength and surface smoothness, the belt base material is formed into an endless belt shape by using a heat resistant resin such as polyimide, polyamide or polyamide imide, or a metal material such as aluminum or stainless steel. The one used is used. The thickness of the base material is preferably about 15 to 250 μm. When using a belt base material made of heat resistant resin, carbon black in the resin,
The conductivity may be imparted by containing a conductivity adjusting agent such as a metal oxide powder or a graphite powder. On the other hand, the heat-resistant elastic layer is formed by coating with silicone rubber, fluororubber, etc. in consideration of ensuring releasability for toner and recording paper (especially transparent resin layer) and conformability to irregularities in the toner image. What you do is used. The layer thickness is preferably set to about 5 to 300 μm. The total thickness of the fixing belt 50 is preferably in the range of 20 to 400 μm, preferably 50 to 200 μm.
Further, the surface of the fixing belt 50 is 7
It is preferable to set the surface glossiness to be 60 degrees or more when measured with a 5 degree glossiness meter.

The cooler 55 is for rapidly cooling the recording paper P while being conveyed in a state of being in close contact with the fixing belt 50 (for example, cooling it to a temperature of 50 to 90 ° C.). As the cooler 55, a heat sink (radiating plate), a heat pipe, a cooling fan or the like can be used, but a heat sink is preferably used. As this heat sink, for example, a plurality of heat radiation fins are formed on the upper surface side in a state of being arranged substantially parallel to each other along the width direction of the fixing belt 50 (direction orthogonal to the rotation direction), and the bottom surface thereof is formed. The one made of aluminum formed as a contact (heat absorption) surface for contacting the inner peripheral surface of 50 is used. When such a heat sink is used, it is advisable to install a fan for sending air to the sink in order to remove heat from the sink.

In the fixing device 2 as described above, when an image is formed, the heating roll 40 is rotationally driven to rotate the fixing belt 50 in the direction of arrow C, and the fixing belt 5 is rotated.
A pressure roll 45 which is pressed against the heating roll 40 with 0 interposed therebetween.
Is driven to rotate. At this time, a pressure contact portion (fixing nip portion) N having a predetermined width is formed between the fixing belt 50 and the pressure roller 45 in a portion stretched around the heating roll 40.
Further, the heating roll 40 and the pressure roll 45 are heated by the halogen heater 42, so that the temperature of the fixing nip portion N becomes a predetermined heating temperature (fixing temperature: 10
0 to 200 ° C.).

The transparent toner layer forming device 3 includes a photosensitive drum 61 which rotates in the direction of the arrow as shown in FIG. 5, a charging device 62 arranged around the photosensitive drum 61, a latent image writing device 63, and a developing device. 64, the transfer device 65, and the like constitute the main part thereof.

Among them, as the photosensitive drum 61, the charging device 62 and the transfer device 65, the same ones as the photosensitive drum 11, the charging device 12 and the primary transfer device 15 in the image forming means of the image forming apparatus 1 are used.

Further, the latent image writing device 63 has an exposure unit (for example, a resolution of 400d) in which a plurality of light emitting diode elements (LEDs) are arranged in a line along the axial direction of the photosensitive drum 61.
pi LED array), and optical lens parts for guiding and irradiating light from each light emitting diode element to the photosensitive drum 61 as beam light BH. With this latent image writing device 63, the image on the photosensitive drum 61 shown in FIG.
The electrostatic latent image for forming the transparent toner layer 5 having the grooves 6 of various patterns as illustrated in FIG. The latent image pattern data of the transparent toner layer 5 is stored in advance in a storage unit or the like of an image processing unit (not shown). Transparent toner layer 5
Is usually formed as a layer having an area corresponding to the entire surface of one side of the recording paper P, but an area corresponding to a part of the recording paper P (image portion area on which a toner image is formed) for which glossiness is desired to be exhibited. May be formed as a layer. As the latent image writing device 63, a laser beam scanner can be used similarly to the latent image writing device 13 of the image forming means, but from the viewpoint of avoiding the enlargement of the device, the LED is used. It is desirable to use the device.

The developing device 64 is a two-component developing device that contains a two-component developer consisting of colorless transparent toner and carrier. As the developing device 64, a non-contact type one-component developing device that uses a one-component developer made of only transparent toner may be used. As the transparent toner, those described below are used.

Then, the fixing device 2 provided with the transparent toner layer forming device 3 carries out the following fixing.

First, when the image forming operation is started, the fixing device 2 is started as described above, and the formation of the transparent toner layer 5 by the transparent toner layer forming device 3 is started at the timing when the fixing is started. To be done.

In the transparent toner layer forming device 3, the surface of the photosensitive layer of the photosensitive drum 61 rotating in the direction of the arrow is uniformly charged to a predetermined potential by the charging device 62, and then the latent image writing device 63 charges the surface. An electrostatic latent image for forming a transparent toner layer is formed, and then the electrostatic latent image is developed by a developing device 64 to form a transparent toner layer 5 made of transparent toner on the photosensitive drum 61 (see FIG. 1). , FIG. 2) is formed. The transparent toner layer 5 has grooves 6 as shown in FIGS.
Of the image structure having

The transparent toner layer 5 formed on the photosensitive drum 61 is electrostatically transferred to the fixing belt 50 by the transfer device 65, and then conveyed to the fixing nip portion N as the fixing belt 50 rotates. . The unfixed transparent toner layer 5 formed on the fixing belt 50 is a layer having grooves 6 as illustrated in FIGS. 1 and 2 on the surface side (the surface opposite to the fixing belt). Has become.

At the fixing stage, as shown in FIG. 5, the recording paper P on which the toner image T to be fixed is transferred is fixed in a posture in which the bearing surface of the toner image T is located on the fixing belt side. Guide it through and let it pass. On the other hand, as shown in FIG. 6, the recording paper P protruding into this fixing nip portion N
The transparent toner layer 5 formed on the fixing belt 50 is superposed on the surface carrying the toner image T of FIG. Then, the recording paper P and the transparent toner layer 5 are thrust into the fixing nip portion N in a superposed state, and by passing through the fixing nip portion N, the toner image T and the transparent toner layer 5 are heated and pressed and melted. To be done.

When entering the fixing nip portion N,
The air existing between the toner image T and the toner particles of the transparent toner layer 5 and between the recording paper P and the fixing belt is finally and efficiently discharged surely through the groove 6 formed in the transparent toner layer 5. As a result, it does not remain after passing through the nip portion N. As a result, bubbles are prevented from being generated in the transparent toner layer 5 after fixing.

The recording paper P that has passed through the fixing nip portion N is conveyed while being in close contact with the outer peripheral surface of the fixing belt 50, and is peeled off from the fixing belt 50 when it reaches the peeling roll 48.

In the process from passing through the fixing nip portion N to separation, the recording paper P is conveyed from the fixing belt 50 in a state of being in close contact without being immediately separated, and is transparent to the melted toner image T. When the toner layer 5 passes through the cooler 55, it is cooled and solidified while being in close contact with the fixing belt 50. Thereby, the transparent toner layer 5
The toner image T and the toner image T are formed on the fixing belt 5 as illustrated in FIG.
The surface smoothness is excellent, following the flat surface of 0. At this time, the groove 6 of the transparent toner layer 5 disappears. After that, when the recording paper P passes through the peeling roll 48, the recording paper P is separated from the fixing belt 50 by the peeling force of the fixing belt 50 bent along the curvature of the peripheral surface of the roll 48 and the rigidity of the recording paper P itself. It is peeled off by itself.

The toner image on the recording paper P obtained after the fixing process as described above has bubbles that can be visually recognized even if there is a portion having a large density difference in the image. It is a high quality image having a uniform glossy feeling covered with the transparent toner layer 5 which does not generate

<Fixing Test> Next, the following fixing test was conducted using this fixing device 2.

In the fixing test, the heating roll 4 of the fixing device 2 is used.
A roll core material 41 having an outer diameter of 50 mm is used as 0, and a roll core material 46 is used as a pressure roll 45.
An elastic layer 47 having a thickness of mm was formed to have a roll outer diameter of 50 mm. Further, the fixing nip pressure in the fixing device 2 is set to 1.5 MPa, the rotation driving speed of the heating roll is set to 50 mm / sec (fixing speed), and the surface temperatures of the heating roll 40 and the pressure roll 45 are both halogen. The lamp 42 was set to heat to 150 ° C. At this time, the recording paper feed direction E of the fixing nip portion N
Had an average width of 5.5 mm. As the fixing belt 50, a fluorocarbon rubber is used on a polyimide base material having a thickness of 80 μm.
An endless belt having a thickness of 115 μm and a belt width of 330 mm was used, which was coated to have a thickness of μm.

As the recording paper P, art paper (made by Shin Oji Paper Co., Ltd .: OK special art paper) was used. A test image (person image) was formed on this recording paper P under the condition that the Cin = 100% portion of the image signal was 0.5 mg / cm ² . The developing device 14 includes a copying machine (manufactured by Fuji Xerox: A-Cal
The above-mentioned four-color two-component developer (average toner particle size: 7 μm) was used.

In the transparent toner layer forming device 3, an LED type writing head having a resolution of 400 dpi is used as the latent image writing device 63, and the exposure intensity is 100% at the maximum and 50% at the minimum as shown in FIG. Such a cycle is repeated so that the latent image is formed by setting the layer thickness to about 60 μm even at the minimum 50% portion, and then developing the latent image at 2.0 mg / cm 2.
^The transparent toner layer 5 was formed by developing under the developing condition of ² . The repeating unit (cycle) of the exposure intensity is shown in Table 1.
As shown in, the pixel unit is 2, 4, 6, or 8. This was set based on the fact that bubbles are formed with a diameter of about 250 μm when a transparent toner layer having no groove 6 is formed and fixed. Transparent toner layer 5 at this time
The groove 6 formed in 1 has a pattern facing diagonally rightward and rearward as illustrated in FIG. 1B, and its cross-sectional shape is a curved concave shape in a sine wave. Further, the transparent toner layer 5 was formed such that the oblique crossing angle θ of the groove 6 was each angle as shown in Table 1.

As the transparent toner, a linear polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexanedimethanol (molar ratio =
5: 4: 1, Tg = 62 degrees, Mn = 4500, Mw = 1
(000) binder resin is crushed with a jet mill and then classified with a wind-powered classifier to obtain an average particle size (d = 5
0) 11 μm transparent fine particles were prepared. The following two kinds of inorganic fine particles A and B were adhered to 100 parts by weight of the transparent fine particles by a high speed mixer. The inorganic fine particles A are SiO ₂ (the surface of which is made hydrophobic by a silane coupling agent, the average particle size is 0.05
μm, the addition amount is 1.0 part by weight). Inorganic fine particles B are Ti
O ₂ (hydrophobicizing the surface with a silane coupling agent, average particle diameter 0.02 μm, refractive index 2.5, addition amount 1.0 part by weight).

For comparison, the same test was carried out when a transparent toner layer having no groove 6 (developing amount: 2.0 mg / cm ² ) was formed (Comparative Example). Under the above conditions, fixing was performed while forming each transparent toner layer. About the test image of the person obtained at this time, by 20 evaluators,
The sensory evaluation when compared with the portrait image that is the basis of the test image was performed according to the following five-level evaluation criteria.

[0067] 1: Many air bubbles were observed and the image quality was also very poor. 2: The presence of slight air bubbles was observed and the image quality was a little poor. 3: There are very few bubbles, but the image quality is at an acceptable level. 4: Almost no bubbles were observed and the image quality was good. 5: No image of bubbles was observed and the image quality was very good.

An average value was obtained for each result of the sensory evaluation by the evaluator, and the average value was finally evaluated according to the following criteria. The results are shown in Table 1. "(200 lines)" in the table means "the groove period corresponds to 200 lines / inch". Other numbers in parentheses have the same meaning. ◯: When it is 4 or more. Δ: 2 or more and less than 4 ×: less than 2

[0069]

[Table 1]

From the results shown in Table 1, the period of the grooves of the transparent toner layer 5 (corresponding to the groove width W) is set to 4 pixel periods (converted into the groove width W of about 250 μm), and the diagonal intersection angle θ is set. It was confirmed that when the setting was made at 30 ° and 45 °, good fixing could be performed without generation of bubbles as visually observed.

[Other Embodiments] In the first embodiment, when forming the transparent toner layer 5, the transparent toner layer forming device 3 is used.
The case where the transparent toner layer 5 having the groove 6 is formed by modulating the exposure intensity of the latent image writing device 63 in the above, but other than this, for example, the latent image writing device 63 has a low resolution LED array. And the focus of the beam light BH emitted from the array is on the photosensitive drum 61.
The latent image writing device 63 made up of the array is attached so as to be located above the surface of the array, and the light emitting diodes of the array are configured to be turned on / off (alternately). You may do it. In this case, an overlap (combined light) of the exposure profiles of the beam light BH emitted from the light emitting diode which is turned on on the photosensitive drum 61 is formed, and a wavy density gradation (a cross-sectional structure such as an offset sine wave) is formed. Thus, a latent image having the above is formed, and the transparent toner layer 5 having the groove 6 can be formed. Further, in this case, a circuit for power modulation is not required, which is advantageous in cost.

Further, in the first embodiment, the case where the fixing device 2 is installed and used inside the main body 10 of the image forming apparatus 1 is illustrated, but the fixing device 2 is different from the image forming apparatus 1. After being configured as a body fixing device 2,
To be connected to the outside of the apparatus body 10 of the image forming apparatus 1,
It may be used as a so-called external type fixing device.

Furthermore, the following can be used as the transparent toner in the present invention. The binder resin that constitutes the toner particles may be substantially transparent, and examples thereof include polyester resins, polystyrene resins, polyacrylic resins, other vinyl resins, polycarbonate resins, and polyamide resins. Known resins used for general toners such as resins, polyimide resins, epoxy resins, and polyurea resins, and their copolymers are used. Among these, polyester resins are preferable because they can simultaneously satisfy the toner characteristics such as low-temperature fixability, fix strength, and storability. Further, considering that the binder resin is used together, the binder resin has a weight average molecular weight: Mw =
50,000 to 12,000 polyesters are preferred. Further, the particle size of the transparent toner is not particularly limited,
From the viewpoint of not disturbing the color toner image, 8 μm or more,
20 μm or less is desirable. When the particle size is less than 8 μm, it is necessary to apply a high electric field between the developing device and the photoconductor.
If it exceeds 20 μm, a uniform image cannot be formed.

In order to obtain a high glossiness evenly in a transparent toner, it is necessary to control the fluidity and chargeability of the toner. From the viewpoint of controlling the fluidity and chargeability of the transparent toner, it is preferable to externally add or attach one or both of the inorganic fine particles and the resin fine particles to the surface of the toner particles of the transparent toner. The inorganic fine particles are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected from known fine particles used as an external additive according to the purpose. Examples include silica, titanium dioxide, tin oxide and molybdenum oxide.
Further, in consideration of stability such as chargeability, those obtained by subjecting these inorganic fine particles to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent or the like can also be used. The organic fine particles are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected from known fine particles used as an external additive according to the purpose.
Examples of the material thereof include polyester resin, polystyrene resin, polyacrylic resin, vinyl resin, polycarbonate resin, polyamide resin, polyimide resin, epoxy resin, polyurea resin, and fluorine resin. It is particularly preferable that the average particle diameter of the inorganic fine particles and the organic fine particles is 0.005 to 1 μm. When the average particle diameter is less than 0.005 μm, when one or both of the inorganic fine particles and the resin fine particles are adhered to the surface of the transparent toner, agglomeration may occur and a desired effect may not be obtained. On the other hand, when it exceeds 1 μm, it becomes difficult to obtain a higher gloss image.

[0075]

As described above, according to the fixing device and the image forming apparatus of the present invention, even when the transparent toner layer is formed on the fixing belt and transferred and fixed on the toner image bearing surface of the recording medium, Since the transparent toner layer having a specific groove is formed, it is possible to prevent the generation of air bubbles in the transparent toner layer and deterioration of the image quality. As a result, even if there is a portion in the image where the image density condition is significantly different, it is possible to obtain a high-quality image in which the glossy feeling is uniform and smooth without depending on such a condition.

[Brief description of drawings]

FIG. 1 is an explanatory plan view showing an example of a groove formation pattern in a transparent toner layer.

FIG. 2 is a sectional view taken along line II-II of FIGS.

FIG. 3 is a schematic explanatory diagram showing a configuration of grooves in a transparent toner layer.

FIG. 4 is a schematic configuration diagram illustrating a main part of the image forming apparatus and the fixing device according to the first embodiment.

FIG. 5 is a schematic configuration diagram showing an enlarged fixing device.

FIG. 6 is a principal part explanatory view showing a fixing state in which transparent toner layers are superposed.

FIG. 7 is a partial cross-sectional view showing an image obtained by transferring and fixing a transparent toner layer.

FIG. 8 is an explanatory sectional view showing a transparent toner layer formed in a fixing test.

FIG. 9 is a schematic explanatory view showing a mechanism of occurrence of bubble accumulation.

[Explanation of symbols]

1 ... Image forming device, 2 ... Fixing device, 3 ... Transparent toner layer forming device, 5 ... Transparent toner layer, 6 ... Groove, 40 ... Heating roll, 42 ... Halogen lamp (heat source), 45 ... Pressure roll, 50 ... Fixing belt, P ... Recording paper (recording medium), T
... toner image, N ... fixing nip portion (pressure contact portion), E ... recording paper feeding direction.

Continued front page    F-term (reference) 2H005 AA21                 2H027 EA18 EB04 EC20 ED25 EE07                       EF09                 2H033 AA01 BA11 BA12 BA58 BB38                       CA26                 2H077 DB14 EA11                 2H078 AA01 BB01 CC10 DD57

Claims (5)

[Claims] 1. A heating roll provided with a heat source, and a support roll arranged at a predetermined distance from the heating roll,
A fixing belt which is stretched between the heating roll and the supporting roll at least and rotates, and a pressure roll arranged in pressure contact with the heating roll with the fixing belt sandwiched therebetween. In a fixing device that introduces a recording medium carrying a toner image to be fixed to a pressure contact portion in a posture in which the toner image bearing surface is located on the fixing belt side, and passes the toner image bearing surface of the recording medium. A transparent toner layer forming device for forming a transparent toner layer made of a transparent toner to be transferred and fixed on the fixing belt is installed, and the transparent toner layer formed by the transparent toner layer forming device is superposed on the toner image carrying surface of the recording medium. A straight line is penetrated from the one end side to the other end of the transparent toner layer in the direction parallel to the feeding direction of the recording medium or in the diagonally rearward direction to the aligned side. A fixing device, wherein the Jo groove is a layer that is present in multiple aligned state. 2. The fixing device according to claim 1, wherein the groove is a groove having a width of 100 to 300 μm. 3. A groove formed in such a manner that all of the grooves penetrating obliquely rearward are bent once at an upstream side in the feeding direction of the recording medium and are directed to opposite oblique rearward directions, respectively. The fixing device described in 1. 4. The groove is formed so as to exist above a base layer having a uniform layer thickness.
The fixing device according to any one of 1. 5. An apparatus for forming an image by forming a toner image according to image information, and transferring and fixing the toner image onto a recording medium, wherein the fixing is performed to fix the toner image onto the recording medium. An image forming apparatus comprising the fixing device according to claim 1 as an apparatus.