Patent Application
20060288896
1. Field of the Invention
The present invention relates to a technique to form a toner image or an electrostatic latent image on a substrate.
2. Description of the Background Art
An electrophotographic printer which forms a toner image on printing paper by irradiating a photosensitive drum having an electrically-charged photosensitive material with light to form an electrostatic latent image, applying toner to the electrostatic latent image to make the image apparent as a toner image and then transferring the image to the printing paper has been conventionally used. For transferring a toner image to printing paper, such a printer uses a transferring method using electric field, where an electric field is formed by bringing the printing paper into contact with an outer peripheral surface of a photosensitive drum while applying a potential to one side of the printing paper opposite to the photosensitive drum at a predetermined transfer position and then toner which is a mass of charged particles (or charged particles in liquid) is moved from the photosensitive material to the printing paper.
It is known, however, that depending on the potential applied to the printing paper in transferring the toner image, the electric field locally becomes strong to cause discharge in a gap between the photosensitive drum and the printing paper in the vicinity of the transfer position and this disturbs the toner image. Then, a technique to suppress such discharge in the gap between the photosensitive drum and the printing paper immediately after being separated from the photosensitive drum is disclosed in, for example, “Principles and Application of Electrophotography Technique” edited by Society of Electrophotography of Japan, CORONA PUBLISHING CO., LTD, 1988, pp. 186-189 (Document 1) and “Latest Technique for Electrophotography Process and Optimal Design and Application & Development of Apparatus” by Hiroshi TAKAHARA, Keiei Kaihatsu Center Shuppanbu (Management and Development Center, Publishing Section), Jun. 30, 1989, p. 6652 (Document 2), where an AC corona discharger is provided on a side of printing paper opposite to a photosensitive drum in the downstream of a transfer position and electric charges applied to the printing paper from other DC corona discharger in transfer are thereby quickly removed in the downstream. Also known is a technique to suppress discharge, where printing paper is bent with small curvature in the vicinity of a transfer position and moved along its surface, to sharply increase the width of a gap between the photosensitive drum and the printing paper as the distance from the transfer position becomes larger along a tangential direction of the photosensitive drum at the transfer position.
Other than electrophotography known is a technique to form an electrostatic latent image on a drum having a dielectric layer, using a multistylus which is a set of pin electrodes.
The printing technique which utilizes the transferring method using electric field has begun to be used in various fields from printing by general-type image output devices (image printers) to patterning for industrial production such as printed circuit boards, color filters for liquid crystal panel or textile printing, because of its simplicity which allows a free change of pattern only by changing electronic data without using any plate and its high speed and high-resolution output.
Japanese Patent Application Laid Open Gazette No. 58-57783 discloses a method of forming patterns for printed circuit board, which uses electrophotography to eliminate the necessity of processes of applying and removing a photoresist, mask coating or the like. Japanese Patent Application Laid Open Gazette No. 5-283838 discloses a method of forming patterns for printed circuit board, where a toner image is formed by electrophotographic printing, to mask a photoresist part corresponding to a conductive pattern, and this prevents defects such as positional errors of the conductive pattern or the like. Japanese Patent Application Laid Open Gazette No. 7-254768 discloses a technique of preventing disturbance of patterns caused in a transferring process of a method of manufacturing a circuit board, where charged particles are induced to the board (substrate) in accordance with an image signal to form an image of charged particles corresponding to a pattern and the electrostatic latent image is thereby directly supplied with developer, regardless of thickness of the board, for development. Japanese Translation of a PCT, No. 2002-527783 discloses a technique of performing electrostatic printing on a glass substrate with a functional (high-performance) material which is liquid toner in manufacturing color filters for liquid crystal panel. Japanese Patent Application Laid Open Gazette No. 5-27474 discloses a method of electrophotographic textile printing and toner for the textile printing.
A printed circuit board and a color filter are formed of rigid flat materials. As a method of transfer onto such a rigid flat panel, a roller transfer which is transfer using pressure and electric field, a transfer using heat and pressure through an intermediate transfer belt and the like have been suggested. For the printed circuit board and the color filter, however, a printing with much higher dimensional accuracy than that in a case of general-type images is required, but it is difficult, in the roller transfer or the transfer through the intermediate transfer belt, to achieve the required accuracy, because of conveyance error due to transfer pressure and cumulative error due to use of the transfer belt.
On the other hand, when a photosensitive drum and an object to which an image is transferred are made closer to each other or separated with applying a potential, an electric field is concentrated in a gap between them and there is a probability that discharge should occur in a gap of certain size, depending on the magnitude of the electric field. Since a potential required for transfer onto a material having a large thickness and low dielectric constant, such as a printed circuit board or glass of color filter, is so high, a large electric field is formed in a wide range of the gap ahead and behind a transfer position between the photosensitive drum and the object to which an image is transferred and discharge is thereby caused to break the image.
In the techniques of Document 1 and Document 2, since the AC corona discharger uses a high-voltage alternating current, there is a problem of easily causing noise in a printer. Further, since a glass substrate can not be bent along its surface, the above method in which an object is moved while being bent with small curvature in the vicinity of the transfer position can not be used.
Though there is a possible technique where a loop member like a flat belt with high capacitance is provided as an intermediate transfer member and a toner image on a photosensitive material which is another loop member provided along an outer periphery of a photosensitive drum is once transferred to the intermediate transfer member with a relatively low transfer bias and then the toner image is transferred from the intermediate transfer member to the glass substrate, even in such a case, when the toner image is transferred to the glass substrate, a relatively large transfer potential is required, and this easily causes discharge disadvantageously.
The present invention is intended for an image forming apparatus for forming a toner image or an electrostatic latent image on a substrate. It is an object of the present invention to transfer an image from a loop member to a substrate with high accuracy in transferring an original image from the loop member having an outer peripheral surface on which the original image is formed as a form of toner image or electrostatic latent image to the substrate.
According to the present invention, the image forming apparatus comprises an original image holding part for rotatingly moving a loop member like a cylindrical drum or a flat belt along its outer peripheral surface on which an original image which is a toner image or an electrostatic latent image to be transferred is formed, a moving mechanism for bringing one main surface of the substrate closest to the outer peripheral surface at a predetermined transfer position while moving the substrate at the same speed as a portion of the loop member goes at the transfer position in a traveling direction along the one main surface which is the same direction as the portion of the loop member, and a transfer part for transferring the original image on the outer peripheral surface to the substrate at the transfer position while applying a potential to a surface of the substrate opposite to the one main surface, the potential having a distribution where the difference between the potential and a surface potential of the loop member gradually decreases as the distance from the transfer position toward the traveling direction or one direction opposite to the traveling direction becomes larger.
In the image forming apparatus, since the potential having the distribution where the difference between the potential and the surface potential of the loop member gradually decreases as the distance from the transfer position toward one direction becomes larger is given to the substrate, it is possible to prevent (suppress) discharge from occurring in a gap between the loop member and the substrate in the vicinity of the transfer position and transfer the original image from the loop member on the substrate with high accuracy.
According to one preferred embodiment, the image forming apparatus further comprises a supporting member having a contact surface which comes into contact with the surface of the substrate opposite to the one main surface in the vicinity of the transfer position and the supporting member is formed of a semiconductor material having a constant thickness, and the transfer part comprises a first potential applying part for applying a first potential to a position on a surface of the supporting member opposite to the contact surface, which is closest to the transfer position, and a second potential applying part for applying a second potential which is nearer to the surface potential of the loop member than the first potential to the supporting member at a position away from the first potential applying part at a predetermined distance toward the one direction, to generate a potential having the distribution on the supporting member.
This makes it possible to easily apply the potential having the distribution to the substrate.
More preferably, a distribution of the potential which is applied by the transfer part to the surface of the substrate opposite to the one main surface further has a distribution where the difference between the potential and a surface potential of the loop member gradually decreases as the distance from the transfer position toward a direction opposite to the one direction becomes larger.
In this case, the image forming apparatus in accordance with a preferred embodiment further comprises a supporting member having a contact surface which comes into contact with a surface of the substrate opposite to the one main surface in the vicinity of the transfer position and the supporting member is formed of a semiconductor material having a constant thickness, and the transfer part comprises a first potential applying part for applying a first potential to a position on a surface of the supporting member opposite to the contact surface, which is closest to the transfer position, and two second potential applying parts for applying a second potential which is nearer to the surface potential of the loop member than the first potential to the supporting member at positions away from the first potential applying part at a predetermined distance toward the one direction and a direction opposite to the one direction, respectively, to generate a potential having the distribution on the supporting member.
According to another preferred embodiment of the present invention, the image forming apparatus further comprises a substrate holding part for holding the substrate on a flat holding surface formed on a member having rigidity, and in the image forming apparatus, the moving mechanism moves the substrate holding part to move the substrate and the transfer part is a potential applying mechanism for applying the potential to the holding surface.
In the image forming apparatus, since the substrate is held on the flat holding surface formed on the member having rigidity, it is possible to transfer the original image from the loop member to the substrate with high accuracy.
According to one preferred embodiment, the potential applying mechanism comprises a plurality of linear electrodes each extending in a direction orthogonal to the traveling direction, which are arranged in the traveling direction at a regular pitch in the substrate holding part, a resistance material covering the plurality of linear electrodes and having a surface which serves as the holding surface, and a potential applying electrode shift mechanism for applying a first potential to one of the plurality of linear electrodes which is located at the transfer position, applying a second potential which is nearer to a surface potential of the loop member than the first potential to one of the plurality of linear electrodes which is located away from the transfer position at a predetermined distance in the traveling direction or a direction opposite to the traveling direction, and sequentially shifting a linear electrode to which the first potential is applied and a linear electrode to which the second potential is applied in synchronization with the movement of the substrate holding part.
Preferably, adjacent two of the plurality of linear electrodes are connected to each other with a resistance element having a resistance value lower than that of the resistance material located between adjacent two linear electrodes.
In the image forming apparatus, since the linear electrodes are covered with the resistance material, it is possible to easily generate a potential having an ideal distribution to prevent discharge.
According to another preferred embodiment, a potential applying mechanism comprises a plurality of linear electrodes exposed from the holding surface and arranged in the traveling direction at a regular pitch, each extending in a direction orthogonal to the traveling direction, an insulator interposed among the plurality of linear electrodes to form the holding surface together with the linear electrodes, a plurality of resistance elements each for connecting adjacent two of the plurality of linear electrodes, and a potential applying electrode shift mechanism for applying a first potential to one of the plurality of linear electrodes which is located at the transfer position, applying a second potential which is nearer to a surface potential of the loop member than the first potential to one of the plurality of linear electrodes which is located away from the transfer position at a predetermined distance in the traveling direction or a direction opposite to the traveling direction, and sequentially shifting the linear electrode to which the first potential is applied and the linear electrode to which the second potential is applied in synchronization with the movement of the substrate holding part.
In the above two preferable potential applying mechanisms, a second potential which is nearer to a surface potential of the loop member than the first potential may be applied to ones of the plurality of linear electrodes which are located away from the transfer position at a predetermined distance toward the traveling direction and a direction opposite to the traveling direction. With this, the difference between the surface potential of the loop member and the potential of the holding surface gradually decreases as the distance from the transfer position in both directions becomes larger, and it is possible to prevent discharge from occurring in both the traveling direction side and the opposite side of the transfer position.
In the image forming apparatus, preferably, the original image is a toner image formed by applying liquid toner to an electrostatic latent image on the outer peripheral surface.
The present invention is also intended for an image forming method for forming a toner image or an electrostatic latent image on a substrate.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The image forming apparatus 1 of
The image forming apparatus 1 further comprises a process unit 3 which is so provided as to face the glass substrate 9 on the support belt 201, for forming a toner image of color of R, G or B on a photosensitive drum by electrophotography, and a transfer part 4 for applying a potential to a portion of the support belt 201 which faces the process unit 3 (i.e., a portion having the contact surface).
The process unit 3 comprises a photosensitive drum (photoconductor drum) 31 having a diameter of 250 mm, which is connected to a not-shown motor through a reduction gear, and the photosensitive drum 31 is supported rotatably around a rotation axis J1 parallel to the X direction. The photosensitive drum 31 has a drum body 311 formed of metal such as aluminum, with the rotation axis J1 as its center, and the drum body 311 is electrically grounded. Onto an outer peripheral surface of the drum body 311, for example, a single-layer organic photosensitive material having phthalocyanine pigment (hereinafter, referred to simply as a “photosensitive material 312”) is uniformly applied (or vapor-deposited). The diameter of the photosensitive drum 31 is not limited to 250 mm, but preferably, it should range from 200 mm to 400 mm. The photosensitive material 312 may be formed of an inorganic photosensitive material such as amorphous silicon, other than the single-layer organic photosensitive material having phthalocyanine pigment.
The process unit 3 further has a drum charger 32 which is so provided as to face the photosensitive drum 31, and the drum charger 32 generates ion to charge the photosensitive material 312. Around the photosensitive drum 31, clockwise from the drum charger 32 arranged are a latent image forming part 33 for emitting light for image formation to form an electrostatic latent image on the photosensitive material 312, a developing part 34 for applying liquid toner (e.g., wet toner dispersed in an insulating isoparaffin solvent (carrier solvent)) to the electrostatic latent image formed on the photosensitive material 312 to develop the image, a cleaner 35 for cleaning a surface of the photosensitive material 312 and a drum discharger 36 for emitting light to remove electric charges from the photosensitive material 312. The developing part 34 is connected to a toner feeder (not shown) for supplying liquid toner which is a developing liquid.
The glass substrate 9 on the support belt 201 comes closest to the outer peripheral surface of the photosensitive material 312 between the developing part 34 and the cleaner 35 on a moving path of portions of the photosensitive material 312. As discussed later, since the toner on the outer peripheral surface of the photosensitive material 312 is transferred onto an upper surface of the glass substrate 9 at a position where the photosensitive material 312 and the glass substrate 9 come closest to each other, the position where the photosensitive material 312 and the glass substrate 9 come closest to each other is referred to as a transfer position in the following discussion and one main surface of the glass substrate 9 to which the toner is transferred is referred to simply as an upper surface (not necessarily a surface whose normal is physically directed upward). The transfer position is a position fixed relatively to the process unit 3.
The transfer part 4 has a transfer potential applying part (first potential applying part) 41 for applying a transfer potential (e.g., (+3000) V) which is the first potential to the same position as the transfer position in the Y direction on a surface of a portion of the support belt 201 on the side of the process unit 3 opposite to the contact surface and two auxiliary potential applying parts (second potential applying part) 42 for applying the second potential (e.g., (−1000) V) (hereinafter, referred to as “auxiliary potential”) to positions away from the position to which the transfer potential is applied by the transfer potential applying part 41 at the same distance (e.g., 4 cm) in the (+Y) direction and the (−Y) direction, respectively.
In the image forming apparatus 1 of
The drum charger 32 sequentially applies electric charges to a portion of the photosensitive material 312 which reaches a position facing it (hereinafter, referred to as a “target part”), to uniformly charge a surface of the target part with e.g., (−700) V (Step S112). The charged target part is continuously moved to an irradiation position of the latent image forming part 33. The latent image forming part 33 has an LED array in which a plurality of light emitting diodes (LEDs) for emitting light of predetermined wavelength are arranged, as a light source. The latent image forming part 33 receives image data corresponding to the color of toner of the process unit 3 out of the image data of color components generated from an image indicating a pattern of color filter and emits light for image formation in accordance with this image data toward the photosensitive material 312. In the portion of the target part of the photosensitive material 312 which is irradiated with light, the electric charges on the surface are moved inside the photosensitive material 312 and removed. Since part of the photosensitive material 312 which is not irradiated with light keeps the state of being charged, an image of distribution of electric charges (i.e., an electrostatic latent image) is formed on the surface of the photosensitive material 312 (Step S113). The light source of the latent image forming part 33 is not necessarily limited to an LED but may be e.g., a semiconductor laser, combination of a lamp and a liquid crystal shutter, or the like.
The part (target part) of the photosensitive drum 31 on which the electrostatic latent image is formed is moved to a position facing the developing part 34, and then a developing roller 341 of the developing part 34 applies liquid toner (toner which is dispersed in a solvent and charged) to the electrostatic latent image (Step S114). At this time, the toner charged to have the same polarity as the surface of the photosensitive material 312 is attached to only a portion of the target part on the photosensitive material 312 in which the electric charges are removed, to develop the electrostatic latent image. In other words, a toner image is formed on the target part of the photosensitive material 312. There may be another case where the charged toner should be attached to the charged portion on the photosensitive material 312.
After that, the target part reaches the transfer position which is closest to the upper surface of the glass substrate 9 and moves exactly in the (+Y) direction at a speed in accordance with the rotation speed of the photosensitive drum 31 (the speed in a tangential direction in a section of the outer peripheral surface of the photosensitive drum 31 which is orthogonal to the rotation axis J1) at the transfer position. The substrate moving mechanism 202 moves the glass substrate 9 on the support belt 201 along the upper surface in the (+Y) direction, which is the same direction as the target part moves toward, as a traveling direction at the same speed as the target part goes at the transfer position, and the transfer roller 413 of
As discussed earlier, since the transfer potential applying part 41 applies a positive transfer potential to the support belt 201 and the auxiliary potential applying part 42 applies a negative auxiliary potential having the polarity reverse to that of the transfer potential to the support belt 201, a constant current is carried from the transfer roller 413 to the auxiliary roller 423 through the semiconductor support belt 201 having a constant thickness. At this time, in the support belt 201, the difference between the potential at the transfer position and the potential at a position away from the transfer position in the Y direction (i.e., voltage) is the product of the resistance in a range from the transfer position of the support belt 201 to this position and the current flowing in the support belt 201, and the resistance in this range is proportional to the distance from the transfer position to this position in the Y direction. Therefore, as shown in
Since the auxiliary potential A2 is nearer to a surface potential A0 of the photosensitive material 312 than the transfer potential A1, a potential having a distribution where (the absolute value of) the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position P1 toward the (−Y) direction becomes larger (hereinafter, the potential indicating the whole distribution generated in the support belt 201 is referred to as a “distribution potential”) is generated on the contact surface of the support belt 201 and this distribution potential is given to a (lower) surface of the glass substrate 9 opposite to the upper surface thereof. In the present preferred embodiment, since the surface potential A0 of the photosensitive material 312 takes a value between the value of the transfer potential A1 and that of the auxiliary potential A2, a range of the distribution potential where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position P1 in the (−Y) direction becomes larger (hereinafter, referred to as a “potential difference decreasing range”) is exactly from the transfer position P1 to a position P0 where the potential becomes A0. If the auxiliary potential takes a value between the value of the transfer potential and that of the surface potential of the photosensitive material 312, the potential difference decreasing range is from the transfer position P1 to the position P2 with which the auxiliary roller 423 on the (−Y) side comes into contact.
With the above distribution potential, on the upper surface of the glass substrate 9, a potential having a polarity reverse to that of the toner is generated at the transfer position, and the toner on the target part of the photosensitive material 312 is thereby moved to the upper surface of the glass substrate 9 (Step S115). In the potential difference decreasing range in the vicinity of the transfer position, since the difference between the surface potential of the photosensitive material 312 and the potential on the upper surface of the glass substrate 9, i.e., a voltage (bias) which is applied to a gap between the outer peripheral surface of the photosensitive material 312 and the upper surface of the glass substrate 9 gradually decreases as the distance from the transfer position toward the (−Y) direction becomes larger and the width of the gap gradually increases, the electric field in this gap sharply decreases as the distance from the transfer position toward the (−Y) direction becomes larger. In the image forming apparatus 1, the potential on the (+Y) side of the transfer position has the same distribution as the above, and it is therefore possible to prevent (or suppress) the discharge caused by a phenomenon in which the electric field applied to the gap between the outer peripheral surface of the photosensitive material 312 and the upper surface of the glass substrate 9 in the vicinity of the transfer position on both (+Y) and (−Y) sides becomes an electric breakdown field of this gap or higher.
The target part is continuously moved to the position of the cleaner 35 of
Since the operations of Steps S112 to S115 are performed almost concurrently on the portions on the photosensitive material 312 and each of the operations is continuously performed on the portions of the photosensitive material 312 which sequentially reach the transfer position, the whole of toner image on the outer peripheral surface of the photosensitive material 312 is eventually transferred to the upper surface of the glass substrate 9 at the transfer position. When printing on the whole of glass substrate 9 is completed, the rotation of the photosensitive drum 31 is stopped and the substrate moving mechanism 202 is also stopped, and this puts an end to the printing operation of the image forming apparatus 1 (Steps S116a and S116b). Thus, a toner image of one color is completely formed entirely on the upper surface of the glass substrate 9.
As discussed earlier, actually, three image forming apparatus 1 corresponding to the three colors, R, G and B, are prepared, and when formation of the toner image of one color is completed on the glass substrate 9, the glass substrate 9 is carried to the next image forming apparatus for formation of a toner image of next color. With this operation, the toner image of three colors, R, G and B is formed on the glass substrate 9 by the three image forming apparatus and finally fused by heating with a fusing unit to be fixed on the glass substrate 9. Then, a color filter is completed.
Depending on, however, the design of the image forming apparatus and the setting condition such as the distance between the transfer roller 413 and the auxiliary roller 423 in the Y direction or the magnitude of the transfer potential and the auxiliary potential, there is a possible case where the electric field applied to the close vicinity of the transfer position should become an electric breakdown field or higher in the gap between the outer peripheral surface of the photosensitive material 312 and the upper surface of the glass substrate 9. Even if such a design or a setting condition can not be avoided, it is possible to prevent discharge from occurring between the outer peripheral surface of the photosensitive material 312 and the upper surface of the glass substrate 9 in the close vicinity of the transfer position by making the carrier solvent of liquid toner full (the same applies to the image forming apparatuses discussed later). From such a viewpoint, it is preferable that the toner image formed by the image forming apparatus 1 should be formed by applying liquid toner to the electrostatic latent image on the outer peripheral surface of the photosensitive material 312. It is natural, depending on the design of the image forming apparatus and the setting condition, that powder toner (toner which is charged, not being dispersed in a carrier solvent) may be used.
As discussed above, in the image forming apparatus 1 of
Further in the image forming apparatus 1, since the auxiliary potential applied to the support belt 201 by the auxiliary potential applying part 42 has a polarity reverse to that of the transfer potential applied by the transfer potential applying part 41, the distribution potential having sharper gradient than that in a case where the transfer potential and the auxiliary potential have the same polarity is generated in the support belt 201, and it is therefore possible to further prevent discharge from occurring in the gap between the photosensitive material 312 and the glass substrate 9 in the vicinity of the transfer position.
When the toner image on the outer peripheral surface of the photosensitive material 312 is transferred onto the glass substrate 9 at the transfer position, electric charges (discharge ions) are applied by the corona discharger 415 to a position on a surface of the support belt 201 opposite to the contact surface, which is closest to the transfer position with the support belt 201 and the glass substrate 9 interposed between itself and the photosensitive drum 31, and the transfer potential is thereby applied to the position in a manner out of contact with the support belt 201. With this operation, a potential having a distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position toward both the (+Y) and (−Y) directions becomes larger is generated in the support belt 201 and is applied to a surface of the glass substrate 9 opposite to the upper surface. As a result, discharge is prevented from occurring in the gap between the photosensitive material 312 and the glass substrate 9 in the vicinity of the transfer position and it is thereby possible to transfer the toner image onto the glass substrate 9 with high accuracy.
The transfer roller 413 or the auxiliary roller 423 is provided in the transfer potential applying part 41 and the two auxiliary potential applying parts 42 in the transfer part 4 of
In the image forming apparatus 1a of
Thus, in the image forming apparatuses 1 and 1a, the photosensitive drum 31 or the intermediate transfer part 25 operates as an original image holding part which rotatingly moves the loop member like a cylindrical drum or a flat belt along its outer peripheral surface on which an original image which is the toner image or the electrostatic latent image to be transferred to the glass substrate 9 is formed and the original image which is an object to be transferred to the glass substrate 9 is thereby moved to the transfer position and transferred onto the glass substrate 9. There may be another case where a multistylus which is a set of pin electrodes is provided as the latent image forming part and a loop member formed of a dielectric material is provided in the original image holding part and a voltage is applied to the pin electrodes which face the outer peripheral surface of the loop member with a gap interposed therebetween to cause discharge between the tips of the pin electrodes and the loop member, and the electric charges are thereby applied to the outer peripheral surface of the loop member to form an electrostatic latent image.
Though the image forming apparatuses 1 and 1a of the first and second preferred embodiments have been discussed above, the image forming apparatuses 1 and 1a allow various variations other than the above examples.
In the first and second preferred embodiments, the transfer potential and the auxiliary potential are applied to the semiconductor support belt 201 to cause the distribution potential in the support belt 201, which has a distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position in the Y direction becomes larger, and thus the distribution potential can be easily applied to a surface of the glass substrate 9 opposite to the upper surface. In the image forming apparatuses 1 and 1a, however, another technique may be used to cause the distribution potential in the contact surface of the support belt. In an image forming apparatus of
As still another exemplary technique to generate the distribution potential on the contact surface of the support belt, in an image forming apparatus of
Thus, in the image forming apparatus, a transfer part for applying a distribution potential to the glass substrate 9 can be realized with various constitutions. Though the support belt 201 can stably and appropriately support even a large-size glass substrate 9 by bring its contact surface into contact with the lower surface of the glass substrate 9 opposite to the upper surface in the above preferred embodiments, in order to hold an outer edge of the glass substrate 9 or support the glass substrate 9 by a plurality of rollers each extending in the X direction, which are arranged in the Y direction, and the like, a transfer part which directly applies the distribution potential to the lower surface of the glass substrate 9 may be provided.
Though the auxiliary potential having a polarity reverse to that of the transfer potential is applied to the support belt 201 by the auxiliary roller 423 (or the brush 425) of the auxiliary potential applying part 42 in the above first and second preferred embodiments, there may be another case where the auxiliary potential supply part 424 is omitted and the auxiliary roller 423 is grounded in the auxiliary potential applying part 42, to apply a ground potential to the support belt 201 as the auxiliary potential. This makes it possible to simplify the construction of the auxiliary potential applying part 42 and apply the distribution potential having a sharp gradient to the glass substrate 9.
Though the distribution potential having the distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position on both sides of the transfer position in the Y direction parallel to the traveling direction of the glass substrate 9 in image formation becomes larger is given to the glass substrate 9 in the above first and second preferred embodiments, the distribution potential may be given only to the (+Y) side or the (−Y) side of the transfer position. From the viewpoint that the toner image should be transferred from the photosensitive material 312 to the glass substrate 9 with high accuracy, however, it is preferable that the distribution potential having like distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position toward not only one direction but also the opposite direction becomes larger should be given to the glass substrate 9 and the discharge should be prevented from occurring in the gap between the photosensitive material 312 and the glass substrate 9 on both the (+Y) and (−Y) sides of the transfer position, like in the above first and second preferred embodiments.
In the image forming apparatuses 1 and 1a, a stage formed of e.g., a semiconductor material having a constant thickness, on which the glass substrate 9 is placed, may be provided, where the transfer part 4 generates the distribution potential. In this case, the substrate moving mechanism is realized as a mechanism which horizontally moves the stage in the Y direction with a linear motor, combination of a ball screw mechanism and a motor or the like. Thus, as a supporting member having a contact surface which comes into contact with the glass substrate 9 in the vicinity of the transfer position and a moving mechanism for moving the glass substrate 9 in the tangential direction of the loop-shaped photosensitive material 312 (or the intermediate transfer member 251) at the transfer position where the glass substrate 9 comes closest to the outer peripheral surface of the photosensitive material 312, various elements may be used. Depending on the design of the image forming apparatus 1 or 1a, there may be a case where the glass substrate 9 is fixed and the transfer part and the process unit are moved relatively to the glass substrate 9 in the Y direction, to form the toner image on the glass substrate 9.
The image forming apparatuses 1 and 1a may be used for some purposes other than manufacture of color filters, and an object to be processed in the image forming apparatus 1 or 1a may be a semiconductor substrate, a printed circuit board or the like, other than the glass substrate 9. In the image forming apparatuses 1 and 1a, since the discharge in the vicinity of the transfer position is prevented, even if a substrate having low capacitance, which is formed of a thick material or a material whose relative dielectric constant is low, is an object, it is possible to transfer and form a toner image or an electrostatic latent image on the substrate with high accuracy by applying a high transfer potential. Thus, substrates of various materials can be processed.
The image forming apparatus 1b comprises a substrate holding part 21 for holding a lower surface (a main surface on the (−Z) side) of the glass substrate 9 having a thickness of e.g., 0.3 to 0.7 mm by vacuum adsorption with a flat holding surface 210, a substrate moving mechanism 26 provided on a surface block 11, for horizontally moving the substrate holding part 21 in the Y direction of
The process unit 3 is the same as that in the first preferred embodiment and comprises the photosensitive drum 31 having the drum body 311 and the photosensitive material 312. The photosensitive drum 31 is supported rotatably around the rotation axis J1 in parallel to the X direction of
Like in the first preferred embodiment, the glass substrate 9 on the substrate holding part 21 comes closest to the outer peripheral surface of the photosensitive material 312 between the developing part 34 and the cleaner 35 in the moving path of portions of the photosensitive material 312, and this position is the transfer position where the toner on the outer peripheral surface of the photosensitive material 312 is transferred to the upper surface of the glass substrate 9. The transfer position is a position fixed relatively to the process unit 3.
Surfaces of the linear electrodes 222 and a surface of the insulating member 221 are flush with each other, and these surfaces are covered with a resistance material 223 and a surface of the resistance material 223 is the holding surface 210 for holding the glass substrate 9. The holding surface 210 is a surface formed on a member having rigidity and including the resistance material 223 and the constituents therebelow and thereby prevented from being bent by the pressure in transfer. As shown in
As shown in
The transfer potential roller 225 and the auxiliary potential rollers 226 are each formed by covering the surrounding of a center electrode to which the transfer potential or the auxiliary potential is applied with a conductive elastic material (e.g., rubber). With this, even if the roller is located between adjacent linear electrodes 222, the roller is deformed, to always come into contact with any one of the linear electrodes 222 while the substrate holding part 21 is moved. As a result, the transfer potential and the auxiliary potential are continuously applied to any ones of the linear electrodes 222 while the substrate holding part 21 is moved. In a case where the width of the linear electrode 222 is 1 mm and the pitch of the linear electrodes 222 is 2 mm, for example, a contact width of the transfer potential roller 225 in the Y direction is 1.1 mm or larger. If the transfer potential roller 225 comes into contact with three or more linear electrodes 222 at the same time, a high potential is disadvantageously applied to a position other than the transfer position, and it is therefore preferable that the contact width of the transfer potential roller 225 should be limited to 2.9 mm or smaller.
Since the transfer potential roller 225 and the auxiliary potential rollers 226 are each formed of an elastic material, it is possible to easily apply a desired potential to the linear electrodes 222 without giving any damage on the linear electrodes 222. Each of the transfer potential roller 225 and the auxiliary potential rollers 226 may be a conductor-type sponge roller which becomes flat across the adjacent linear electrodes 222, other than the conductive rubber roller.
The insulating member 221, the linear electrodes 222, the resistance material 223, the resistance elements 224, the transfer potential roller 225, the auxiliary potential rollers 226, the transfer potential power supply 227, the auxiliary potential power supplies 228 and the like constitute the potential applying mechanism 22 for applying a potential having a predetermined distribution for transferring the toner image from the photosensitive drum 31 to the glass substrate 9 to the holding surface 210.
In the image forming apparatus 1b of
The drum charger 32 sequentially applies electric charges to a portion of the photosensitive material 312 which reaches a position facing it (hereinafter, referred to as a “target part”), to uniformly charge a surface of the target part (Step S213). The charged target part is continuously moved to an irradiation position of light from the latent image forming part 33. The latent image forming part 33 has an LED array in which a plurality of light emitting diodes (LEDs) for emitting light of predetermined wavelength are arranged, as a light source. The latent image forming part 33 receives image data corresponding to the color of toner of the process unit 3 out of the image data of color components generated from an image indicating a pattern of color filter and emits light for image formation in accordance with this image data toward the photosensitive material 312. In the portion of the target part of the photosensitive material 312 which is irradiated with light, the electric charges on the surface are moved inside the photosensitive material 312 and removed. Since part of the photosensitive material 312 which is not irradiated with light keeps the state of being charged, an image of distribution of electric charges (i.e., an electrostatic latent image) is formed on the surface of the photosensitive material 312 (Step S214). The light source of the latent image forming part 33 is not necessarily limited to an LED but may be e.g., a semiconductor laser, combination of a lamp and a liquid crystal shutter, or the like.
The part (target part) of the photosensitive drum 31 on which the electrostatic latent image is formed is moved to a position facing the developing part 34, and then the developing roller 341 of the developing part 34 applies liquid toner (toner which is dispersed in a solvent and charged) to the electrostatic latent image (Step S215). At this time, the toner charged to have the same polarity as the surface of the photosensitive material 312 is attached to only a portion of the target part on the photosensitive material 312 in which the electric charges are removed, to develop the electrostatic latent image. In other words, a toner image is formed on the target part of the photosensitive material 312. There may be another case where the toner charged to have a polarity reverse to that of the surface of the photosensitive material 312 should be attached to the charged portion on the photosensitive material 312.
After that, the target part reaches the transfer position which is closest to the upper surface of the glass substrate 9 and moves exactly in the (+Y) direction at a speed in accordance with the rotation speed of the photosensitive drum 31 (the speed in a tangential direction in a section of the outer peripheral surface of the photosensitive drum 31 which is orthogonal to the rotation axis J1) at the transfer position. The substrate moving mechanism 26 moves the glass substrate 9 along the upper surface in the (+Y) direction which is the traveling direction of the target part at the same speed as the target part goes at the transfer position, and the target part of the photosensitive material 312 thereby comes into contact with the upper surface of the glass substrate 9 at the transfer position (these two may not necessarily come into contact with each other, and the same applies to the following). At this time, a potential having a distribution discussed later is applied to a main surface (lower surface) of the glass substrate 9 opposite to the upper surface by the resistance material 223 and the linear electrodes 222 through the transfer potential roller 225 and the auxiliary potential rollers 226, and the upper surface of the glass substrate 9 thereby has a potential having a polarity reverse to that of toner at the transfer position. As a result, the toner on the target part of the photosensitive material 312 is moved to the upper surface of the glass substrate 9, to achieve a transfer using electric field (Step S216). The functions of the potential applying mechanism 22 including the transfer potential roller 225, the auxiliary potential rollers 226 and the like in transferring toner to the glass substrate 9 will be discussed in detail after the description of the whole operation of the image forming apparatus 1b.
The target part is continuously moved to the position of the cleaner 35 and the cleaner 35 cleans the surface of the photosensitive material 312 by removing unnecessary substances such as toner remaining in the target part of the photosensitive material 312 (in other words, toner not transferred to the glass substrate 9) and the photosensitive material 312 is thereby mechanically turned back to the initial state. Then, the photosensitive material 312 is irradiated with light by the drum discharger 36 having combination of a lamp and a filter, or an LED or the like, to be cleared of electric charges, and electrically turned back to the initial state.
Since the operations of Steps S213 to S216 are performed almost concurrently on the portions on the photosensitive material 312 and each of the operations is continuously performed on the portions of the photosensitive material 312 which sequentially reach the transfer position, the whole of toner image on the outer peripheral surface of the photosensitive material 312 is eventually transferred to the upper surface of the glass substrate 9 at the transfer position. When printing on the whole of glass substrate 9 is completed, the rotation of the photosensitive drum 31 is stopped and the substrate moving mechanism 26 is also stopped, and this puts an end to the printing operation of the image forming apparatus 1b (Steps S217a and S217b). Thus, a toner image of one color is completely formed entirely on the upper surface of the glass substrate 9.
As discussed earlier, actually, three image forming apparatuses corresponding to the three colors, R, G and B, are prepared, and when formation of the toner image of one color is completed on the glass substrate 9, the glass substrate 9 is carried to the next image forming apparatus for formation of a toner image of next color. With this operation, the toner image of three colors, R, G and B is formed on the glass substrate 9 by the three image forming apparatuses and finally fused by heating with the fusing unit to be fixed on the glass substrate 9. Then, a color filter is completed.
Next, detailed discussion will be made on a function of the potential applying mechanism 22 in the image forming apparatus 1b, referring to
The auxiliary potential applied by the auxiliary potential roller 226 is a potential having a polarity reverse to that of the transfer potential as shown in
Thus, the potential having the distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position toward the traveling direction of the substrate holding part 21 and its opposite direction becomes larger is given to a surface (lower surface) of the glass substrate 9 opposite to the upper surface through the holding surface 210. As a result, also on the upper surface of the glass substrate 9, the potential having the distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position toward the traveling direction of the substrate holding part 21 and its opposite direction becomes larger is (indirectly) given. Since the gap between the outer peripheral surface of the photosensitive material 312 and the upper surface of the glass substrate 9 gradually increases as the distance from the transfer position becomes larger, the electric field in the gap sharply becomes small as the distance from the transfer position becomes larger. As a result, it is possible to prevent (or suppress) the discharge caused by a phenomenon in which the electric field in the gap between the outer peripheral surface of the photosensitive material 312 and the glass substrate 9 becomes an electric breakdown field of this gap or higher in the vicinity of the transfer position, and the toner image can be thereby transferred to the glass substrate 9 with high accuracy.
The potential on the photosensitive drum 31 may be one between the transfer potential and the auxiliary potential, and in this case, the potential having the distribution where the difference between the potential and the surface potential of the photosensitive material 312 gradually decreases as the distance from the transfer position becomes larger until some midpoint in a range from the transfer potential roller 225 to the auxiliary potential roller 226 is given to the upper surface of the glass substrate 9. Since the upper surface of the insulating member 221 is covered with the resistance material 223 and the glass substrate 9 is held thereon, actually, in the distribution of the potential on the upper surface of the glass substrate 9, the maximum value and the minimum value of the potential approximate to the ground potential, as compared with the distribution of the potentials shown in the upper side of
The resistance value of the resistance element 224 should be a value lower than the resistance value of the resistance material 223 between adjacent two linear electrodes 222 (not lower than 103Ω and not higher than 109Ω, preferably not lower than 105Ω and not higher than 109Ω, e.g., 108Ω). This makes the current more easily flow in the resistance element 224, to stably form a desired distribution of potential on the upper surface. By covering the surfaces of the linear electrodes 222 with the resistance material 223, it is possible to easily form a potential having an ideal smooth distribution to prevent the discharge, and even when the transfer potential roller 225 is located between adjacent two linear electrodes 222, it is possible to easily uniformize a local distribution of potential at the transfer position. If a stable distribution of potential can be formed, naturally, the resistance element 224 may be omitted.
When the substrate holding part 21 is moved by the substrate moving mechanism 26 in the traveling direction ((+Y) direction) with the above distribution of potential formed, in synchronization with the movement of the substrate holding part 21, the linear electrodes 222 to which the transfer potential and the auxiliary potential are applied are sequentially shifted relatively in the (−Y) direction while the relative relation in position between the transfer potential roller 225 and the auxiliary potential roller 226 is maintained, and the distribution of potential formed around the transfer position is maintained. As a result, the whole of toner image can be stably transferred from the photosensitive drum 31 to the glass substrate 9.
As discussed above, in the image forming apparatus 1b of the present preferred embodiment, since the glass substrate 9 is held on the flat holding surface 210 formed on a member having rigidity, it is possible to transfer the toner image from the photosensitive drum 31 to the glass substrate 9 with high accuracy, preventing a shift of the glass substrate 9. Further, since the potential having the distribution where the difference between the potential and the surface potential of the photosensitive drum 31 gradually decreases as the distance from the transfer position becomes larger is given to the upper surface of the glass substrate 9, it is possible to prevent discharge from occurring on the traveling direction side of the transfer position and the opposite side and therefore possible to prevent disturbance in the toner image transferred on the glass substrate 9 and the toner image on the photosensitive material 311 which is to be transferred.
For manufacturing a color filter in the image forming apparatus 1c, like in the image forming apparatus 1b of
In the image forming apparatus 1c, like in the image forming apparatus 1b, adjacent two out of the linear electrodes 222 are connected to each other with the resistance element 224 (see
In the image forming apparatus 1c, since the resistance material 223 is omitted, the construction of the apparatus can be simplified. If an object to which an image is transferred is the glass substrate 9, since the object has a sufficient thickness, it is possible to smooth the distribution of potential on the upper surface of the glass substrate 9 even without the resistance material 223.
In the image forming apparatus Id of
In the image forming apparatus 1d of
Thus, in the image forming apparatuses 1b to 1d, the photosensitive drum 31 or the intermediate transfer part 25 operates as the original image holding part which rotatingly moves the loop member like a cylindrical drum or a flat belt along its outer peripheral surface on which an original image which is the toner image or the electrostatic latent image to be transferred to the glass substrate 9 is formed and the original image which is an object to be transferred to the glass substrate 9 is thereby moved to the transfer position and transferred onto the glass substrate 9. There may be another case where a multistylus which is a set of pin electrodes is provided as the latent image forming part and a loop member formed of a dielectric material is provided in the original image holding part and a voltage is applied to the pin electrodes which face the outer peripheral surface of the loop member with a gap interposed therebetween to cause discharge between the tips of the pin electrodes and the loop member, and the electric charges are thereby applied to the outer peripheral surface of the loop member to form an electrostatic latent image.
Though the image forming apparatuses 1b to 1d of the third to fifth preferred embodiments have been discussed above, the image forming apparatuses 1b to 1d allow various variations other than the above examples.
Though the auxiliary potential rollers 226 are provided on both sides of the transfer position in the Y direction parallel to the traveling direction of the glass substrate 9 in image formation in the third to fifth preferred embodiments, the auxiliary potential roller 226 may be provided only on the (+Y) or (−Y) side of the transfer position. From the viewpoint that the toner image should be transferred from the photosensitive material 312 onto the glass substrate 9 with high accuracy, however, it is preferable that not only the auxiliary potential roller 226 on one side of the transfer position but also another like auxiliary potential roller 226 on the other side should be provided and the discharge occurring in the gap between the photosensitive material 312 and the glass substrate 9 should be prevented from both the (+Y) and (−Y) sides of the transfer position like in the third to fifth preferred embodiments.
A plurality of linear electrodes 222 in the image forming apparatus 1b do not have to be exposed from the insulating member 221 but may be buried in the resistance material 223 as shown in
The through holes 221a to adsorb the glass substrate 9 to the holding surface 210 do not have to be formed only in the insulating member 221 interposed among a plurality of linear electrodes 222, and if the diameter of the through hole 221a is sufficiently smaller than the width of the linear electrode 222, the through hole 221a may be formed in the linear electrode 222. The glass substrate 9 may be mechanically held on the holding surface 210.
Though the number of rollers which come into contact with the linear electrodes 222 is three in the three to fifth preferred embodiments, four or more rollers may be provided on the linear electrodes 222 in order to obtain a stabler distribution of potentials.
The potential applying mechanism 22 does not necessarily have to be one having rollers (the transfer potential roller 225 and the auxiliary potential rollers 226) but may be a conductive brush, and as shown in
The photosensitive drum 31 may not come into contact with the glass substrate 9 at the transfer position but there may be another case, for example, where the photosensitive drum 31 approximates to the glass substrate 9 with a very small gap therebetween at the transfer position and the gap is filled with the liquid for transfer. If there is no probability of discharge, only a predetermined potential may be applied to the holding surface 210 in the substrate holding part 21 at least at the transfer position.
The image forming apparatuses 1b to 1d may be used for some purposes other than manufacture of color filters, and an object to be processed in the image forming apparatuses 1b to 1d may be a semiconductor substrate, a printed circuit board or the like, other than the glass substrate 9. In the image forming apparatuses 1b to 1d, since the discharge in the vicinity of the transfer position is prevented, even if a substrate having low capacitance, which is formed of a thick material or a material whose relative dielectric constant is low, is an object, it is possible to transfer and form a toner image or an electrostatic latent image on the substrate with high accuracy by applying a high transfer potential. Thus, substrates of various materials can be processed.
While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.
This application claims priority benefit under 35 U.S.C. Section 119 of Japanese Patent Application No. 2005-184806 and Japanese Patent Application No. 2005-184807 filed in the Japan Patent Office on Jun. 24, 2005, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2005-184806 | Jun 2005 | JP | national |
| P2005-184807 | Jun 2005 | JP | national |
