JP2003207955A - Image forming device - Google Patents

Abstract

(57) [Summary] [Problem] To control the gloss to make the gloss uniform in the entire image area of an electrophotograph and to reduce uneven gloss between an image portion (halftone, high density portion) and a non-image portion (recording paper). Lost
Improve image quality. SOLUTION: A photosensitive drum 1 is formed by a toner image forming means.
When the toner images formed on the recording mediums a to 1d are transferred to the recording paper P by the transfer unit 3 and the transferred toner images are fixed and smoothed by the fixing device 5, the temperature of the rollers 51 and 52 is selected by the selection unit. A suitable recording paper P having a different gloss is selected in accordance with fixing conditions and smoothing conditions, such as the feeding speed of the recording paper P, the release agent application amount, and the roller pressing load.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of controlling a gloss of a toner image fixed on an image supporting substrate. 2. Description of the Related Art Generally, silver halide photography and printing have a wide color reproduction space and good graininess and gloss uniformity.
It is well known that image quality is excellent. On the other hand, it is difficult for electrophotography to obtain image quality comparable to silver halide photography or printing. This will be described with reference to actual measurement results shown in FIGS. 5 to 8. In FIG. 5, when the horizontal axis represents the image density, the vertical axis represents the gloss, and a single color tone of cyan is used as a sample, The relationship between gloss and density of each image of silver halide photography, printing and electrophotography is shown. The gloss was measured using a commercially available gloss meter, and the image density was measured using a Macbeth reflection densitometer RD948. As is apparent from the figure, the gloss of the silver halide photograph is very high at about 100, the gloss of the print is about 30 and the gloss of the electrophotograph is a very low value of about 10. FIG. 6 shows the relationship between the image density of a silver halide photograph and normalized gloss, FIG. 7 shows the relationship between the image density of printing and normalized gloss, and FIG. 8 shows the image density of electrophotography and normalized gloss. Indicates the relationship with gross. According to this, in the case of the silver halide photograph of FIG. 6, the gloss is very stable in the entire image area.
In the case of the printing of FIG. 7, the gloss in the low-density region (0 to 0.6) is slightly lower than that of the silver halide photograph, gradually increases until the image density becomes about 1.0, and saturates therefrom. I have.
Further, in the case of the electrophotography shown in FIG. 8, in the low-density region, it is constant at about 30% of the maximum value.
~ 1.2), the gloss sharply increases and the image density becomes 1.3.
Saturated to a degree. The gloss difference between the low-density region and the high-density region causes uneven gloss in the low-density portion and the high-density portion of the electrophotographic image, which is unnatural. In order to reduce the gloss difference between the low-density region and the high-density region, Japanese Patent Application Laid-Open No. 08-171306 discloses a method for changing the fixing condition according to the maximum value of the image gloss after fixing. According to the above method, the gloss of the recording paper and the image high density portion becomes uniform. [0005] However, the situation is different regarding the halftone of an image. The toner has a smooth surface and no irregularities, and has a high light reflectivity. However, since the area where the toner is applied is small from the low density to the halftone of the electrophotographic image, the gloss is the surface property of the recording paper P and the toner. Is determined by the shape of the isolated dot. On the other hand, as the image density increases, the area on which the toner is applied increases, so that the gloss increases without being greatly influenced by the surface properties of the recording paper P. Since the gloss of the recording paper P greatly depends on properties such as surface properties and materials, the gloss can be increased up to about 100 by applying a coating agent such as a resin on the recording paper P. In particular, in the case of high gloss paper such as cast-coated paper, the gloss in the low density portion and the high density portion becomes high as shown in FIG. 9, and the gloss unevenness becomes remarkable. In the halftone, the toner is isolated and the light is scattered, so that the gloss is reduced. The gloss of the high-density portion changes when the toner surface is melted. The gloss of the high density portion can be easily changed by changing the fixing conditions (temperature, speed) of the fixing device (FIG. 10). On the other hand, the situation is different in the halftone. As shown in FIG. 11, even if the fixing condition (temperature and speed) is changed to change the melting state of the toner, the gloss does not fluctuate more sensitively in the high density region. Therefore, depending on the type of paper, it is not possible to make the gloss uniform over the entire density range only by changing the fixing conditions of the fixing device. As described above, the mechanism of generation of gloss in electrophotography differs between low, medium and high density regions of an image. It is difficult to make the gloss uniform in all concentration ranges. [0011] The uneven gloss deteriorates the image quality of the electrophotography and gives a poor impression as compared with silver halide photography and printing. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. By controlling the gloss in the low, medium, and high density areas, the gloss in the entire image density area of an electrophotograph can be made uniform. It is an object of the present invention to provide an image forming apparatus capable of eliminating unevenness in gloss and improving image quality. The conventional gloss control is performed by simply changing the fixing condition, thereby changing only the gloss of the high density portion regardless of the type of paper. [0014] This patent focuses on making the gloss uniform even in the entire density range, and thus the idea is different from the conventional one. In order to achieve the above object, an image forming apparatus according to the present invention provides a toner image formed on an image carrier by a toner image forming means, and an image supporting means for transferring the toner image by a transfer means. In an electrophotographic image forming apparatus, the toner image after transfer is fixed to an image supporting substrate by a fixing unit, and the surface of the toner image after fixing is smoothed by a smoothing unit. An image forming apparatus comprising: a selection unit that selects a fixing condition and a smoothing condition according to a maximum value of gloss of a recording material and an image portion. Preferably, there is provided a supply unit for supplying a plurality of types of image support base materials having different properties, and the selection unit is configured to supply one of the plurality of supply units in accordance with the fixing condition. I chose it. (Function) Based on the above-described configuration, the selection means can appropriately change the gloss depending on the fixing conditions such as the temperature of the roller, the conveying speed of the image supporting base material, the amount of the release agent applied, and the roller pressing load. Select a suitable image support substrate. The selection means selects one of the supply means having a plurality of types of image support base materials having different properties according to the fixing conditions, and supplies a desired image support base material. Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic configuration diagram showing a four-color full-color laser beam printer as an embodiment of an image forming apparatus according to the present invention. FIG. FIG. 3 is a schematic configuration diagram showing a fixing unit according to the first embodiment. The laser beam printer shown in FIGS. 1 to 3 has four image forming stations Pa, Pb, Pc, P
d is provided. Each image forming station Pa, P
b, Pc, and Pd are provided around chargers 12a, 12b, 12c, 12d, cleaners 4a, 4b, around electrophotographic photosensitive members (hereinafter, referred to as "photosensitive drums") 1a, 1b, 1c, and 1d as image carriers. 4c, 4d and developing devices 2a, 2b,
2c and 2d are provided. The photosensitive drums 1a, 1b, 1c, 1d
Below the transfer belt 31 so as to be in contact with them.
Is provided. The transfer belt 31 sequentially transports the recording paper P, which is an image supporting base material, to each of the photosensitive drums 1a, 1b, 1c, and 1d. Each image forming station Pa, Pb, P
The images formed on the photosensitive drums 1a, 1b, 1c, 1d in c and Pd are transferred to the recording paper P on the transfer belt 31. That is, each of the image forming stations Pa, Pb, Pc, and Pd for forming an image of each color of magenta, cyan, yellow, and black respectively has the photosensitive drum 1a,
1b, 1c and 1d are arranged.
a, 1b, 1c and 1d are rotatably supported in the direction of the arrow. The photosensitive drums 1a, 1b, 1c, 1d
Around the chargers 12a, 12a,
12b, 12c, 12d and developing devices 2a, 2b, 2
c, 2d and cleaners 4a, 4b, 4c, 4d, and each photosensitive drum 1 between the developing devices 2a, 2b, 2c, 2d and the cleaners 4a, 4b, 4c, 4d.
The transfer section 3 is disposed below the transfer points a, 1b, 1c, and 1d. This transfer unit 3 is provided at each image forming station Pa, P
The transfer belt 31 and transfer chargers 3a, 3b, 3c and 3d are common recording paper transport means for b, Pc and Pd. Further, the laser beam printer includes:
A plurality of supply means, namely, a paper feed cassette 61 and an arrow R
A manual paper feed tray 61a that can be pulled out in the direction 61a is provided, and one of high, medium and low gloss recording papers P is mounted on the paper feed cassette 61 or the manual paper feed tray 61a. The recording paper P is supported on the transfer belt 31 and is connected to each of the image forming stations Pa, Pb, Pc,
In the process of passing through the Pd, the photosensitive drums 1a, 1b, 1
The toner images of each color formed on c and 1d are sequentially transferred. When this transfer step is completed, the recording paper P
Is transported to the fixing device 5 by a transport belt 62 which is separated from the transfer belt 31 and serves as recording paper guide means. As shown in FIG. 3, the fixing device 5 includes a fixing roller 51 rotatably supported, a pressure roller 52 that rotates while being in pressure contact with the fixing roller 51, and a release agent that is a release agent supply and application unit. Coating device 53 and roller cleaning devices 54 and 55
This is a configuration including: Heaters 56 and 57 such as halogen lamps are provided inside the fixing roller 51 and the pressure roller 52, respectively. Thermistors 58 and 59 are in contact with the fixing roller 51 and the pressure roller 52, respectively, and the voltages applied to the heaters 56 and 57 via the temperature control device 60 are controlled to control the fixing roller 51 and the pressure roller 52. The surface temperature is adjusted. The fixing roller 51 is in contact with a release agent application device 53 that applies silicon oil as a release agent to the surface of the fixing roller 51.
When the recording paper P is conveyed by the printer and passes between the fixing roller 51 and the pressure roller 52, the toner is
On the surface. The release agent coating device 53 is connected to a coating amount control device 63 for controlling the amount of silicone oil applied to the surface of the fixing roller 51. A drive motor (not shown) that drives the fixing roller 51 and the pressure roller 52 has a conveyance speed of the recording paper P, that is, a fixing motor 51 and a pressure roller 52 that press and heat both front and back surfaces of the recording paper P. A speed control device 64 for controlling the rotation speed is connected. Thus, the unfixed toner image on the surface of the recording paper P is melted and fixed, and a full-color image is formed on the recording paper P. The recording paper P on which the full-color image has been fixed
Is separated from the pressure roller 52 by the separation claw 68 and passes through the halftone gloss control member. The halftone gloss control member is an upper roller 1 rotatably supported.
01 and a lower roller 102 which rotates while being pressed against the upper roller. A heater such as a halogen lamp may be disposed on the upper and lower rollers to control the temperature of the upper and lower rollers. The recording paper exits the upper and lower rollers 101 and 102 and is discharged outside the printer. Fixing for controlling high-density area gloss,
The pressure member surface layer is preferably made of silicone rubber or fluorine rubber having rubber elasticity. Since the surface layer has elasticity, when the unfixed image comes to the fixing nip, the surface layer rubber itself is heated so as to wrap the toner, so that the toner is excellent in melting and fixing the toner. Excellent in glossing in high density areas where the amount of toner applied is large. On the other hand, in the half tone, even if the toner is wrapped and the heat is efficiently transmitted, the toner is isolated on the recording paper and the swelling of the toner remains, so that the gloss is reduced (FIG. 12). The upper and lower roller surface materials of the next halftone gloss control member are preferably harder than the fixing and pressing members 101 and 102. For example, fluorine resin and the like can be given. Since the surface material is harder than the toner, the toner is crushed (FIG. 13). Since the toner is fixed along the recording material surface, light is not scattered and gloss can be increased. As described above, the functions are separated into two sets of members, and heat is supplied at the initial stage, and gross is generated in the high concentration part.
Thereafter, the toner in the halftone portion is crushed to generate gloss. A gross selection mode switch (not shown) as selection means is provided on the operation display of the laser beam printer, and by selecting one of the gross selection mode switches, the fixing roller 51 and the pressing roller 52 are switched. The fixing conditions such as the temperature, the conveying speed of the recording paper P between the fixing roller 51 and the pressing roller 52, the amount of silicone oil applied, and the pressing load between the fixing roller 51 and the pressing roller 52 are controlled. That is, when any one of the gloss selection mode switches is operated, the voltage applied to the heaters 56 and 57 is controlled via the temperature control device 60 so as to achieve the desired gloss, or the speed control device 64 is used. The conveying speed of the recording paper P is controlled by varying the rotation speed of the fixing roller 51, or the amount of silicone oil applied to the surface of the fixing roller 51 is controlled via the application amount control device 63. Further, the contact pressure of the halftone gloss control section is controlled. The fixing roller 51 having a soft surface layer controls the gloss of the high-density toner portion, and the upper roller 101 having a hard surface layer controls the halftone gloss. The selection means for controlling the fixing conditions is provided with a recording sheet P optimal for the fixing conditions.
Alternatively, a function of selectively feeding paper from the manual paper feed tray 61a or the like is provided so that the gloss of the color output image of the electrophotograph is brought close to excellent image formation similar to silver halide photography or printing. In this case, if there is no optimal recording paper P, a display requesting the supply of the optimal recording paper P is displayed on the operation display. As the recording paper P to be used, there are cast-coated paper, coated paper, high-quality paper, and the like in descending order of gloss.
With the above operation, the gloss of the non-image portion (recording paper) and the high density portion (solid toner portion) are determined. The conditions of the smooth member after fixing (high hardness surface layer) are determined so as to match the gloss. When the high gloss mode is set, (gloss control when using cast coated paper) ・ Recording material Cast coated paper basis weight 150 g / m 2 gloss 50% ・ High density gloss control part Condition roller diameter 60φ nip 7mm surface layer Material Silicone rubber Fixing temperature 180 ° C Fixing speed 45mm / s ・ Contrast gloss control part condition Roller diameter 40φ Nip 4mm Surface layer PFA load 50N / mm Fig. 14 shows the relationship between image density and gloss of cast coated paper obtained under the above conditions. Shown in As shown in FIG. 14, under the initial fixing condition,
The halftone gloss drops, and uniform gloss cannot be achieved. By passing through the second-stage halftone gloss control member, the halftone gloss increased. On the other hand, the high-density part and the low-density part were hardly affected, so that the gloss was uniform over the entire density range. The resulting image had less unevenness like printing, and the impression was remarkably improved. (Embodiment 2) When the low gloss is selected, the fixing conditions of the fixing device 5 are set as follows. The surface temperature of the fixing roller 51 and the pressure roller 52 is set to 150 ° C., and the recording paper conveyance speed is set to 90 mm / s. Smooth member load 3
Gloss 10 coated paper is used as the recording paper P for eliminating the gloss difference between the non-image area and the image area under this fixing condition.
After forming a 16-tone color toner image on the coated paper by the developing devices 2a, 2b, 2c, 2d and the transfer section 3 shown in FIG. 2, the toner is melted by the fixing device 5 shown in FIG.
Fixed on coated paper. FIG. 4 shows the result of measuring the gloss image density dependency of the 16 gradation image. This figure is
The gloss is standardized with a maximum gloss of 1. As can be seen from the figure, the gloss of the non-image area (white coated paper) and the gloss of the image area (high image density area) are almost the same. Further, when passing through the smoothing member, the gloss of the halftone portion also increases. (Embodiment 3) In this embodiment, the high density gloss control member is a belt fixing device (FIG. 1).
5). As for the conditions for using the belt fixing device, it is desired that the fixing nip load be low pressure in view of problems such as paper transportability. Since the nip width is large, the amount of heat that can be supplied to the recording paper is larger than that of the roller pair system, so that the toner is more likely to be melted. Therefore, the contents of the first and second embodiments are applied. When the high gloss mode is selected as an example, (gloss control when cast coated paper is used) Recording material Cast coated paper basis weight 150 g / m 2 gloss 50% ・ High density gloss control section nip 25 mm fixing temperature 180 ℃ Fixing speed 150mm / s ・ Condition of halftone gloss control part Roller diameter 40φ Nip 4mm Surface layer PFA load 50N / mm Fig. 16 shows how the gloss in the halftone area changes when passing through the halftone gloss control part. As described above in this embodiment, even if the fixing member for performing the high density gloss control is a belt, the gloss of the recording material, the half tone, and the high density area can be made closer, so that the printed image becomes glossy. There was no unevenness and it looked good. As described above, according to the present invention, in the toner image output method using the electrophotographic method, the fixing condition and the smoothing are determined according to the maximum value of the gloss of the recording paper and the image area. By selecting the conditions, the gloss in the non-image area, halftone, and high density areas can be made uniform, so the difference in gloss between the white background area and the solid toner area, which has been a problem in color images by electrophotography, can be reduced. Thus, it is possible to form an image having an excellent appearance equivalent to silver halide photography and printing. The selection means selects one of the supply means for supplying a plurality of kinds of image support base materials having different properties according to the fixing conditions, so that the non-image portion, the half tone, and the high density The gross of the parts almost match, and it looks natural without any uneven gloss. In particular, in the case of a belt fixing method or a non-contact heating method in which the toner must be fixed at a low pressure, it is difficult to control the halftone gloss, and uneven gloss is generated in the low density, halftone, and high density areas. It's easy to do. The method of the present invention in which the above-mentioned smoothing member is disposed after these fixing devices is very effective for uniformizing gloss.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram illustrating a developing / transferring unit according to the embodiment. FIG. 3 is a schematic configuration diagram illustrating a fixing unit according to the embodiment. FIG. 4 is a gloss image of a 16-gradation image. FIG. 5 is a diagram showing the result of measuring the density dependency. FIG. 5 is a diagram showing the relationship between the gloss and the density of each image of a silver halide photograph, a print, and an electrophotograph when a single color tone of cyan is used as a sample. 6 is a diagram showing the relationship between the image density of the silver halide photograph and the normalized gloss. FIG. 7 is a diagram showing the relationship between the image density of the print and the normalized gloss. FIG. 9 is a diagram showing the relationship between the density and gloss of cast-coated paper in the electrophotographic image forming method. FIG. 10 is a relationship between the high-density portion gloss and the fixing speed of the cast-coated paper in the electrophotographic image forming method. FIG. 11 FIG. 12 shows the relationship between halftone gloss and fixing speed of cast coated paper in electrophotographic image formation. FIG. 12 shows scattering. FIG. 13 shows scattering. FIG. 14 Gloss with halftone gloss control. FIG. 15 is a diagram showing a system of a belt fixing device according to a third embodiment. FIG. 16 is a diagram showing a gloss / density relationship when a halftone gloss control is provided. Pb, Pc, Pd Image forming stations 1a, 1b, 1c, 1d Electrophotographic photosensitive members 12a, 12b, 12c, 12d as image bearing members Chargers 4a, 4b, 4c, 4d Cleaners

Continuation of front page    F term (reference) 2H027 DA12 DA50 EA12 EB04 EC06                       EC20 ED17 ED25 EF06 EF09                 2H030 AB02 AD04 AD05                 2H033 AA01 BA07 BA29 BB01 CA07                       CA16 CA18 CA30 CA35 CA48

Claims (1)

Claims: 1. A plurality of supply means for supplying a plurality of types of image support base materials having different properties, respectively, and a transfer means for transferring a toner image formed on an image carrier by a toner image forming means. An image forming apparatus of an electrophotographic system in which a toner image after transfer is fixed to the image supporting substrate by a fixing unit by a fixing unit, and the toner image surface after the fixing is smoothed by a smoothing unit. In the fixing device, according to the maximum value of the gloss of the recording material and the image area, a selecting means for selecting a fixing condition, a selecting means for selecting the smoothing condition of the smoothing device, and the fixing condition and the smoothing condition according to the fixing condition An image forming apparatus, wherein one supply unit is selected from a plurality of supply units.