JP2004102316A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve efficiency of transfer of a toner image from a transfer body to be transfering to a transfer body to be transfered. <P>SOLUTION: The image forming apparatus comprises a photoreceptor 101, a charger 102 which charges the surface of the photoreceptor 101, an optical system 103 which forms an electrostatic latent image on the charged surface of the photoreceptor 101, a developing device 104 which supplies a toner to the surface of the photoreceptor 101 with the formed electrostatic latent image to form a toner image, a film forming device 105 which converts the toner image into a film, and a transfer device which transfers the toner image converted into a film to a recording medium 110 while applying shearing stress to the toner image. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an image forming method and an image forming apparatus.

(4) A wet image forming apparatus using a liquid developer can use a submicron-sized fine toner that cannot be realized by a dry method, so that high image quality can be realized. In addition, since the ratio of the pigment to the resin in the toner particles is higher than that of the dry type, sufficient image density can be obtained with a small amount of toner, which is economical, and the glass transition temperature of the resin of the toner used is low. Since the temperature at which the toner is fixed on the paper can be set low, there are also advantages such as energy saving.

On the other hand, the conventional wet image forming apparatus still has some essential problems. One of these problems is deterioration of image quality in the transfer unit. Conventionally, the liquid developer adhering to the photoreceptor has been directly transferred to the sheet by the action of an electric field, so that uneven transfer due to an electric field fluctuation according to the unevenness of the sheet surface has occurred. In addition, transfer failure is likely to occur due to environmental dependence such as temperature and humidity of a place where the sheet is used and variations in electric characteristics of paper. As a result, the image quality of the transferred image in the transfer unit has been significantly deteriorated.

In order to solve such a problem, an apparatus which transfers the image temporarily from a photoconductor to an intermediate transfer medium by an electric field, and then transfers the image from the intermediate transfer medium to a recording medium such as paper using pressure or heat and pressure is used. And U.S. Patent Nos. 5,148,222, 5,166,734, and 5,208,637. Since it is relatively easy to configure the intermediate transfer medium with a material that has a smooth surface and little variation or fluctuation in electrical resistance, the image quality is significantly degraded by the transfer means compared to the case of direct transfer to paper by an electric field. To be improved.

Furthermore, since the solvent attached to the intermediate transfer medium can be vaporized or sucked by heating or suction of air before transfer to the paper using pressure or using pressure and heat, Solvent adhesion to paper can also be significantly reduced.

In addition, Japanese Patent Publication No. 46-41679 and Japanese Patent Application Laid-Open No. 62-280882 disclose transfer from a photoconductor to an intermediate transfer medium and transfer from an intermediate transfer medium to a recording medium without using electric field transfer. In both cases, an apparatus for performing transfer by pressure or transfer by pressure and heat is disclosed. In this case, since the transfer is performed only by pressure or only by pressure and heat, the problem seen in the case of electric field transfer does not occur.

However, the following problems are actually encountered even in an apparatus in which an image is temporarily transferred from a photoconductor to an intermediate transfer medium by an electric field, and then the image is transferred from the intermediate transfer medium to a recording medium such as paper using pressure or using pressure and heat. Is left. In other words, when transferring the toner image on the photoconductor to the intermediate transfer medium, although a high transfer efficiency is obtained for a single color toner image, an image in which a plurality of color toner images are sequentially superimposed on the photoconductor is transferred. In such a case, there is a disadvantage that the transfer efficiency is reduced or transfer unevenness occurs. When transferring an image in which toner images of a plurality of colors are sequentially superimposed on a photoreceptor, the number of times the toner image is fixed is usually fixed each time the toner image of each color is developed. Is different depending on the color, and such an electric field is different. For this reason, it is necessary to superimpose the toner images on the intermediate transfer medium, and in that case, misregistration for each color becomes a problem, and the process speed is reduced.

Further, in both the transfer from the photoconductor to the intermediate transfer medium and the transfer from the intermediate transfer medium to the recording medium, in a device that performs transfer by pressure, or transfer by pressure and heat, the transfer from the photoconductor to the intermediate transfer medium, Regardless of the transfer from the intermediate transfer medium to the recording medium, it is important that the solvent is removed to some extent from the toner image before the transfer to form a film.

ト ナ ー Since the toner image formed on the photoreceptor has an increased adhesive force to the surface of the photoreceptor, high pressure and heat are required for transferring the toner image. This can be solved to some extent by optimizing the surface energy of the photoreceptor and the intermediate transfer medium, but it reduces the room for material selection, making it difficult to reduce equipment costs and maintain recording reliability. Was one of the causes.

As described above, in an apparatus for temporarily transferring an image from a photoreceptor to an intermediate transfer medium by an electric field, and then transferring the image from the intermediate transfer medium to a recording medium such as paper by using pressure or using pressure and heat, Can not solve all the problems that arise.

Further, in an apparatus that transfers both the transfer from the photoreceptor to the intermediate transfer medium and the transfer from the intermediate transfer medium to the recording medium by the action of pressure, or the action of pressure and heat, various devices generated by applying an electric field are used. Although problems can be avoided, high pressure and heat are required to obtain high transfer efficiency, and in order to alleviate the conditions, there is less room for selection of materials used as constituent members.

Therefore, the present invention provides a process of forming an electrostatic latent image on the surface of an electrostatic latent image holding member, and supplying a toner image to the electrostatic latent image by a developing unit to form a toner image on the surface of the electrostatic latent image holding member. Developing, removing the solvent of the developed toner image and drying the toner image, and applying the shear stress to the dried toner image to transfer the toner image from the surface of the electrostatic latent image holding member. An image forming method comprising: a first transfer step of transferring onto an intermediate transfer medium; and a second transfer step of transferring the toner image from the surface of the intermediate transfer medium onto a recording medium. .

The surface speed of the electrostatic latent image holding member may be different from the surface speed of the intermediate transfer medium.

Further, in the first transfer step, an elastic layer is provided on the intermediate transfer medium in a non-fixed state, and pressure is applied in a direction perpendicular to a surface of the intermediate transfer medium in contact with the toner image, so that the toner image is formed. The toner image may be transferred from the electrostatic latent image holding member to the intermediate transfer medium by extending in the tangential direction of the surface in contact with the toner image.

The toner image formed on the surface of the electrostatic latent image holding member may be a toner image including a carrier liquid and toner particles.

Further, the present invention provides an electrostatic latent image holding member, a charger for charging the surface of the electrostatic latent image holding member, and an optical device for forming an electrostatic latent image on the charged surface of the electrostatic latent image holding member. Developing means for supplying a liquid toner to the surface of the electrostatic latent image holding member on which the electrostatic latent image is formed to form a toner image, and removing a solvent of the toner image formed on the surface of the latent image holding member Means for drying the toner image; first transfer means for transferring the toner image on the surface of the electrostatic latent image holding member onto an intermediate transfer medium while applying a shear stress to the dried toner image; And a second transfer means for transferring the toner image on the intermediate transfer medium onto a recording medium.

(4) The surface speed of the electrostatic latent image carrier may be different from the surface speed of the intermediate transfer medium.

The first transfer unit has an elastic layer provided in a non-fixed state on the intermediate transfer medium, and applies pressure in a direction perpendicular to a surface of the intermediate transfer medium that comes into contact with the toner image so that the toner image is The toner image may be transferred from the surface of the electrostatic latent image holding member to the intermediate transfer medium by extending the contact surface in a tangential direction.

The toner image formed on the surface of the electrostatic latent image holding member may be composed of a carrier liquid and toner particles.

ADVANTAGE OF THE INVENTION According to the image forming apparatus of this invention, when transferring a toner image from a transfer receiving body to a transfer body, the transfer efficiency of a toner image to a transfer body is improved by applying a shear stress to a toner image. Can be done. Therefore, a stable image can be formed on the recording medium.

EXAMPLES Hereinafter, examples of the present invention will be described in detail, but the present invention is not limited to these examples.

First, a first embodiment of the present invention will be described. FIG. 1 shows the configuration of the first embodiment.

The image forming apparatus according to the present exemplary embodiment includes a photosensitive member 101 as an electrostatic latent image holding member, a charger 102 that uniformly charges the surface of the photosensitive member 101 around the photosensitive member 101, and a light corresponding to an image signal with respect to the charged charge. An optical system device 103 that irradiates and forms an electrostatic latent image; a developing unit 104 that forms a toner image on the surface of the photoconductor 101 by applying liquid toner to the surface of the photoconductor 101 on which the electrostatic latent image is formed; Filming means 105 for forming the formed toner image into a film, intermediate transfer medium 106 as a first transfer means for transferring the filmed toner image, and collecting residual toner on the surface of photoreceptor 101 Cleaning means 107 and a charge removing means 108 for removing the charged charges on the surface of the photoconductor 101. Here, the film forming means may be a means for removing the carrier liquid and drying the toner image. The film forming means may be a means for removing the carrier liquid and drying the toner image. The film formation in the present invention means that the solvent of the toner is removed to some extent, and a state in which a cohesive force or an adhesive force is exerted on the toner particles. It refers to heating to a temperature higher than the transition point to obtain a state in which tackiness is imparted.

Further, a pressure roller 109 as a second transfer unit for applying pressure is provided at a position different from the contact position of the intermediate transfer medium 106 with the photoconductor 101, and the intermediate transfer medium 106 and the pressure roller The recording medium 110 is conveyed to the recording medium 109.

The photoreceptor 101 has a photosensitive layer 112 having a thickness of about 10 to about 40 μm on the surface of a metal drum 111 made of aluminum or the like, and preferably a release layer having a thickness of about 5 μm or less made of a fluorine-based resin, a silicone-based resin or the like. It has a layer 113.

The developing means 104 has a toner holding member 115 for holding the liquid toner 114 and a developing roller 116 for supplying the liquid toner 114 to the release layer 113 on the surface of the photoconductor 101.

The toner image forming unit 105 includes a squeezing unit 117 that performs fogging of the toner image formed by the developing unit 104 and regulates the thickness of the liquid toner, and determines an adhesive force of the squeezed toner image to the surface of the release layer 113. A toner image fixing means 118 for heating the fixed toner image to remove the solvent from the toner image. Further, the toner image heating unit 119 is provided in a non-contact state with respect to the photoconductor 101, and may be a light irradiation unit such as a halogen lamp.

The liquid toner 114 is obtained by dispersing toner particles having a diameter of about 2 μm or less containing a pigment component in a carrier liquid such as an insulating hydrocarbon solvent. In the case of this embodiment, the toner particles are dispersed in a solvent. Positively charged. In addition, the toner particles are moved in the carrier liquid by the developing means, so that a toner image composed of toner particles obtained by visualizing the electrostatic latent image is formed.

The intermediate transfer medium 106 includes a metal roller 120 and an elastic layer 121 formed on the surface thereof and having a thickness of about 1 mm or less, such as urethane rubber, fluorine rubber, epichlorohydrin rubber, or silicone rubber. On the inner surface of the metal roller 120, a heater 122 composed of a halogen lamp or the like is provided.

The pressure roller 109 is preferably a metal roller, or an elastic layer is preferably formed on the surface of the metal roller. Further, a heater is provided on the inner surface to heat the entire roller to about 60 to about 100 ° C. Is more preferred.

The photosensitive member 101, the intermediate transfer medium 106, and the pressure roller 109 are independently rotated by independent drive mechanisms (not shown).

Next, an image forming process performed by the image forming apparatus according to the present embodiment will be described.

First, the surface of the photoconductor 101 is uniformly charged to about +800 V by the charger 102.

Next, the potential of the image portion is reduced to about +200 V by the optical system device 103, and an electrostatic latent image is formed on the surface of the release layer 113.

(4) In the developing means 104, the developing roller 116 is held with a gap of about 150 μm provided with respect to the surface of the release layer 113, and this gap is filled with the liquid toner 114 supplied by the developing roller 116. Since a voltage of about +500 V is applied to the developing roller 116, when the electrostatic latent image passes through a region where the photosensitive member 101 and the developing roller 116 are in contact with each other via the liquid toner 114, in the image portion, the photosensitive member 101 Since an electric field is formed in the direction toward 101 and in the direction from the photoreceptor 101 to the developing roller 116 in the non-image portion, the toner particles in the positively charged liquid toner 114 adhere only to the image portion. As a result, a toner image is formed on the surface of the release layer 113 after passing through the developing unit 104. At this time, the potential of the image section rises to about + 300V.

(4) In the metal roller provided as the next squeezing means 117, the metal roller is provided through a gap of about 50 μm from the surface of the release layer 113, and a voltage of about +200 V is applied. When the liquid toner image approaches the squeezing means 117, a strong electric field is formed in the direction from the surface of the release layer 113 to the metal roller. However, since a strong electric field is formed particularly in the non-image area, the liquid image floats in the non-image area. Charged toner particles are collected. At the same time, the thickness of the toner image is regulated and the toner image is made thinner.

{Circle around (2)} In the toner image fixing means 118, the surface potential of the toner image is charged to about +800 V using the same charge applying means as the charger. Due to this surface charge, an electric field is formed in the image portion of the toner image from the surface of the toner image toward the metal drum 111 in the photoconductor 101, so that the toner particles in the toner image approach the surface of the release layer 113, and As the image force acting between the drum 111 and the drum 111 increases, the image is fixed more strongly.

(4) Next, in the toner image heating means 119, the toner image is heated to about 70 ° C., and most of the solvent contained in the toner image is removed. The toner image is formed into a film through the squeezing unit 117, the toner image fixing unit 118, and the toner image heating unit 119. That is, the toner image is formed into a film by removing about 80% or more of the solvent from the state after the development.

Generally, a liquid toner uses toner particles having a low glass transition point. The toner particles are swelled and dispersed in the carrier liquid, but act between the toner particles as the carrier liquid is removed. The cohesive force acts greatly, and the film is integrated into a film. In this case, the heating unit 119 is not always necessary, and the removal of the carrier liquid may be promoted by, for example, a blowing unit. Further, in the case of toner particles having a high glass transition point, the cohesive force acting between the toner particles does not become sufficiently large only by removing the solvent, but the adhesive force is increased by heating the toner particles to a temperature higher than the glass transition temperature. Adhesive force acts between the toner particles to form a film. The heating for increasing the adhesive strength may be performed by heating the intermediate transfer medium 106.

The toner image formed into a film is then transported to a region where the photoconductor 101 and the intermediate transfer medium 106 are in contact. Alternatively, the toner image on the photoreceptor 101 is heated in a region where the intermediate transfer medium 106 and the photoreceptor 106 are in contact with each other to form a film.

In this area, the pressure from a load of about 20 to 60 kgf in terms of A4 width and the heat from the intermediate transfer medium 106 heated to a temperature equal to or higher than the glass transition point of the toner particles, for example, about 70 ° C. by the heater 122 provided therein, are generated. Supplied. By heating the intermediate transfer medium 106 in this manner, the adhesive force of the toner particles is increased, and the adhesive force to the intermediate transfer medium 106 is increased. At this time, it is preferable to increase the adhesion of the toner particles to the intermediate transfer medium without increasing the adhesion of the toner particles to the photoconductor 101 by keeping the photoconductor 101 below the glass transition point.

FIG. 2 is an enlarged view of a portion where the photoconductor 101 and the intermediate transfer medium 106 are in contact with each other. As shown in FIG. 2, the surface velocity v ₁ of the photosensitive member 101 is set to be larger than the surface velocity v ₂ of the intermediate transfer medium 106. Such speed difference provided when at the interface between the toner image 201 and the release layer 113 surface as shown in FIG. 2 such force f ₁ of the same direction as the moving direction of the photosensitive member 101. On the other hand, at the interface between the toner image 201 and the elastic layer 121 surface acts to move the direction opposite to the direction of force f ₂ of the photosensitive member 101, the toner image 201 is subjected to a shear stress. Due to this shearing stress, the adhesive force of the toner image 201 to the surface of the release layer 113 is reduced, and the toner image 201 can be easily separated from the surface of the release layer 113, so that the first transfer step is performed. In order to exert a shearing stress, the magnitudes of v ₁ and v ₂ may be made different. However, when the present inventors conducted an experiment, it was found that, when v ₁ > v ₂ , the peeling property of the toner image 201 was particularly high. Was high. The speed ratio, v ₂ / v ₁ , is set to about 0.8 to 0.98, and more preferably about 0.9 to 0.95 so that sufficient shear stress is applied to the toner image 201 and the image is not disturbed. It is desirable to do.

In FIG. 1, when the photoconductor 101 is further rotated, the residual toner remaining on the surface of the release layer 113 that has not been transferred is removed by the cleaning unit 107, and the residual charge is removed by the charge removing unit 108.

On the other hand, the intermediate transfer medium 106 having received the transfer of the toner image rotates in the direction of the arrow in FIG. 1 to convey the toner image to a region in contact with the recording medium 110 supported by the pressure roller 109, and A pressure is applied to the image under a load of about 40 to 100 kgf in terms of A4 width.

FIG. 3 is an enlarged view of a portion where the intermediate transfer medium 106, the recording medium 110, and the pressure roller 109 are in contact. As shown in FIG. 3, the surface speed v ₃ of the pressure roller 109 is set lower than the surface speed v ₂ of the intermediate transfer medium 106. By the frictional force acting at the interface of the pressure roller 109 and the recording medium 110, when such speed of the recording medium 110 is v _3, the upper and lower surfaces of the toner image, a force acting in the tangential direction of the intermediate transfer medium 106 Since the directions are opposite to each other, a shear stress can be applied to the toner image. Then, the toner image is easily subjected to the second shear transfer step from the intermediate transfer medium 106 to the surface of the recording medium 110, and an image is formed on the recording medium 110.

In this way, in the area where the photoconductor 101 and the intermediate transfer medium 106 and the area where the intermediate transfer medium 106 and the recording medium 110 supported by the pressure roller 109 are in contact with each other, in addition to the action of pressure and heat, Shear stress acts in the direction of rotation of. For this reason, it is easy to separate the toner image from the transfer side and transfer the toner image to the transfer side, and it is possible to improve the transfer efficiency of the toner image. In the transfer step from the intermediate transfer medium 106 to the recording medium 110, when the pressure roller 109 is heated, it is possible to suppress a decrease in the temperature of the toner image on the surface of the intermediate transfer medium 106 due to the contact with the recording medium 110. Transfer efficiency can also be improved.

By the way, when a speed difference is provided between the transfer side and the transfer side as shown in FIGS. 2 and 3, the size of the toner image on the transfer side is different from the size of the toner image on the transfer side. I will. As shown in Figure 2, before and after the transfer from the toner image 201 is the release layer 113 to the elastic layer 121, contracts in accordance with the ratio of the velocity ratio _v 2 / _{v 1.} Similarly, as shown in FIG. 3, the toner image 201 contracts before and after the transfer from the elastic layer 121 to the recording medium 110 in accordance with the ratio v ₃ / v ₂ . Therefore, the toner image on the surface of the recording medium 110 changes at a ratio of v ₃ / v ₁ from the original image.

Therefore, in order to make the toner image on the surface of the recording medium 110 the same as the original image, an electrostatic latent image deformed from the original image is formed in advance in consideration of the deformation rate of the toner image at the time of transfer. It is also possible to make the image finally obtained on the recording medium 110 equal to the original image.

Next, a second embodiment of the present invention will be described. FIG. 4 shows the configuration of the second embodiment. In FIG. 4, portions common to those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The image forming apparatus of this embodiment performs the transfer from the photoconductor 101 to the intermediate transfer medium 106 using an electric field, and then transfers the toner image on the surface of the intermediate transfer medium 106 to the recording medium 110 by pressure and heat. The configuration is the same as that of FIG. 1 except that the toner image heating unit is not provided near the photoconductor and a toner image heating unit 401 is provided in a non-contact state with the intermediate transfer medium 106 as shown in FIG. is there.

The toner image formed on the surface of the release layer 113 as in the first embodiment is conveyed through the squeezing unit 117 and the toner image fixing unit 118 to a position close to the intermediate transfer medium 106. A gap of about 50 μm or less is provided between the photoreceptor 101 and the intermediate transfer medium 106 as the first transfer unit, but the gap is determined by the solvent contained in the toner image of the liquid toner formed on the surface of the release layer 113. It is full. A voltage of about 600 V is applied between the photoreceptor 101 and the intermediate transfer medium 106, and the toner particles in the liquid toner undergo a transfer process by electrophoresis and move to the surface of the elastic layer 121.

The toner image transferred to the intermediate transfer medium 106 in this way is heated to 70 ° C. or more by heat from the toner image heating unit 119 and the heater 122 inside the intermediate transfer medium 106 to be formed into a film. The toner image formed into a film is transferred to the recording medium 110 by the same operation as in the first embodiment, and a final image is obtained. Also in the present embodiment, a shear stress acts between the intermediate transfer medium 106 and the recording medium 110 supported by the pressure roller 109, and a good image can be obtained.

Next, a third embodiment of the present invention will be described. FIG. 5 shows the configuration of the third embodiment. FIG. 5 is an enlarged view of the vicinity of the intermediate transfer medium 106 in FIG.

The basic configuration of the image forming apparatus of this embodiment is the same as that of the first embodiment, but is a component of the intermediate transfer medium 106 as shown in FIG. An elastic layer 121 as a second transfer unit is provided in a non-fixed state with respect to a metal roller 120 at a contact position with the recording medium 110. The difference is that the surface speeds of 106 and the pressure roller 109 are all equal.

Next, the principle of operation in this embodiment will be described with reference to FIGS. 6, 7, and 8. FIG.

First, as shown in FIG. 6, the intermediate transfer medium 106 and the toner image 201 on the surface of the release layer 113 move to the contact position with the rotation.

Next, as shown in FIG. 7, pressure P is applied at the contact position between the intermediate transfer medium 106 and the photoconductor 101, and the elastic layer 121 on the surface of the intermediate transfer medium 106 is compressed in the thickness direction. At this time, since the elastic layer 121 is provided in a non-fixed state with the metal roller 120, a force also acts in the tangential direction of the intermediate transfer medium 106, and the elastic layer 121 expands in this direction. Therefore, the elastic layer 121 comes into contact with the toner image 201 on the surface of the release layer 113 while being extended in the tangential direction of the intermediate transfer medium 106.

Further, as shown in FIG. 8, when the intermediate transfer medium 106 and the photoconductor 101 are brought into a non-contact state as they move, the pressure applied to the elastic layer 121 is released, and the elastic layer 121 returns to the original state. Thus, it contracts along the tangential direction of the intermediate transfer medium 106 and expands in the thickness direction. By a series of actions, a shear stress accompanying the contraction of the elastic layer 121 acts on the interface between the release layer 113 and the toner image 201, and the adhesion of the toner image 201 to the surface of the release layer 113 is weakened. The process is performed, and peels off and moves to the elastic layer 121.

こ と By making the elastic layer 121 of the intermediate transfer medium 106 not adhered to the metal roller 120 in this manner, it is possible to apply a greater force in the tangential direction of the intermediate transfer medium 106. Therefore, the toner image 201 is subjected to not only the action of the force in the thickness direction of the elastic layer 121 but also the action of the shear stress in the tangential direction, thereby facilitating the transfer.

The transfer of the toner image from the intermediate transfer medium 106 to the recording medium 110 is exactly the same, and the same shear stress acts between the elastic layer 121 and the recording medium 110 supported by the pressure roller 109 at the contact position between the two. Accordingly, the second transfer step is performed, and the toner image can be easily transferred to the recording medium 110.

(4) When a material having higher elasticity is used for the elastic layer 121, a shear stress can be more effectively applied, and the elastic layer 121 may be appropriately selected in consideration of the strength of the material. For example, it is desirable that the elastic layer 121 has a hardness of about 40 to 60 degrees and a thickness of about 0.1 to 1 mm, which is defined by the type A of JIS K-6301.

In the present embodiment, when the release layer 113 and the elastic layer 121 or the elastic layer 121 and the recording medium 110 supported by the pressure roller 109 come into contact with each other during transfer and pressure is applied, the elastic layer 121 contracts, Along with the elongation, the size of the toner image 201 in contact therewith changes before and after the transfer.

In order to match the original image with the image on the recording medium 110, the pressure applied between the photoconductor 101 and the intermediate transfer medium 106 and the pressure applied between the intermediate transfer medium 106 and the pressure roller 109 are set to the same value. It is preferably about 70 kgf in A4 width conversion. In general, the pressure required for transfer from the photoconductor 101 to the intermediate transfer medium 106 is smaller than the pressure required for transfer from the intermediate transfer medium 106 to the recording medium 110. For example, the former requires about 20 to about 60 kgf in A4 width conversion, while the latter requires about 40 to about 100 kgf. In such a case, the rate of change in the size of the image before and after the transfer is different between the two transfers. In this case, the size of the image may be changed in advance when the electrostatic latent image is formed.

Next, a fourth embodiment of the present invention will be described. FIG. 9 shows the configuration of the fourth embodiment. In FIG. 9, portions common to FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The image forming apparatus of the present embodiment directly transfers the photosensitive member 101 to the recording medium 110 by using pressure and heat without using an intermediate transfer medium.

The pressure roller 109, which is a transfer unit, includes a metal roller 901 and an elastic layer 902 formed on the surface of the metal roller 901, and a heater 903 is provided inside the roller 901.

Through the same process as in the first embodiment, the toner image formed on the surface of the release layer 113 is moved to a region where the release layer 113 is in contact with the recording medium 110 supported by the pressure roller 109. Then, it receives a pressure due to a load of about 60 to 100 kgf in A4 width conversion.

Here, the surface speed of the pressure roller 109 is set lower than the surface speed of the photoconductor 101, and the recording medium 110 is slower than the photoconductor 101 due to the frictional force acting between the pressure roller 109 and the recording medium 110. Set to move. With this setting, the directions of the forces acting on the upper and lower surfaces of the toner image in the tangential direction of the photoconductor 101 are opposite to each other, so that a shear stress can be applied to the toner image.

Therefore, even in the case where the transfer is performed directly from the photoreceptor 101 to the recording medium 110 by pressure and heat, the shear transfer process is performed by applying the shear stress, so that the transfer efficiency can be improved.

Next, a fifth embodiment of the present invention will be described. FIG. 10 shows the configuration of the fifth embodiment.

画像 The image forming apparatus of this embodiment uses a dry image forming method to transfer the image to the intermediate transfer medium, and then to the recording medium.

FIG. 10 illustrates the configuration of the apparatus according to the present embodiment. The image forming apparatus according to the present exemplary embodiment includes a photoconductor 101, a charger 102 that uniformly charges the photoconductor 101, and an optical device that irradiates the charged charge with light according to an image signal to form an electrostatic latent image. System unit 103, developing means 1001 for supplying a toner powder to form a toner image from an electrostatic latent image on release layer 113 on the surface of photoconductor 101, intermediate transfer medium 1002 for transferring the toner image, photoconductor 101 There is a charge removing means 108 for removing charged charges on the surface, and a cleaning means 107 for collecting residual toner on the release layer 113 on the surface of the photoreceptor 101.

The pressure roller 109 for applying pressure by contacting the intermediate transfer medium 1002 preferably has a heater inside. The recording medium 110 is conveyed between the intermediate transfer medium 1002 and the pressure roller 109 as a second transfer unit.

The intermediate transfer medium 1002 includes an intermediate transfer belt 1003, a first transfer roller 1004 as a first transfer unit, and a second transfer roller 1005. The intermediate transfer belt 1003 is made of the same material as the elastic layer 121 of the first embodiment, and preferably has a resistivity of about 10 ¹⁰ to 10 ¹² Ωcm.

The second transfer roller 1005 has a heater 1006 such as a halogen lamp inside, and rotates at a surface speed different from the surface speed of the pressure roller 109.

{Circle around (4)} The toner image heating means 1007 for fusing the toner image while the intermediate transfer belt 1003 moves from the contact position with the release layer 113 to the contact position with the recording medium 110 is provided. As shown in FIG. 10, the toner image heating unit 1007 may be provided with a light irradiation unit in a non-contact manner, or may be provided with a heat roller having a heater therein in contact with the intermediate transfer belt 1003.

Next, an image forming process performed by the image forming apparatus according to the present embodiment will be described.

{Circle around (1)} First, a toner image is formed on the surface of the release layer 113 by using a powder toner through a process of a normal dry image forming method.

A predetermined transfer voltage is applied to the first transfer roller 1004, and the toner image is subjected to a first transfer process by an electric field formed between the photoconductor 101 and the intermediate transfer belt 1003, and the intermediate transfer belt 1003 Transferred to the surface.

(4) The toner image transferred to the surface of the intermediate transfer belt 1003 is heated when passing through the toner image heating means 1007, and is melted and formed into a film.

The toner image formed into a film is subjected to the action of pressure applied between the intermediate transfer belt 1003 supported by the second transfer roller 1005 and the recording medium 110 supported by the pressure roller 109, and the speed of both rollers is increased. The difference causes the effect of shear stress along the direction of rotation of the roller. As a result, the toner image on the intermediate transfer belt 1003 is easily transferred onto the recording medium 110, and is fixed on the recording medium 110 as a final image.

In a dry image forming apparatus using a powder toner as a developer, a toner image is usually in a powder state until it is thermally fixed on the surface of a recording medium. By forming into a film, image disturbance due to scattering of toner at the time of transfer can be eliminated, and a higher quality image can be obtained. This toner image formed into a film can be easily transferred by applying a shear stress to the toner image as in the present embodiment.

In the first embodiment, as shown in FIG. 1, the toner image heating means 119 is provided in a non-contact state with respect to the photoreceptor 101, but as shown in FIG. It can also be configured. FIG. 11 shows a configuration diagram of the sixth embodiment, in which a roller 1101 having a heater inside is provided in place of the toner image heating means 119 provided in a non-contact state in FIG. The surface of the roller 1101 is made of a material such as a silicone resin to which a toner image is extremely unlikely to adhere, and the roller 1101 is pressed against the surface of the photoreceptor 101 with a pressure that does not disturb the toner image of about 10 kgf or less in A4 width conversion.

FIG. 12 shows a seventh embodiment, in which a voltage is applied to a toner image heating means 1201 composed of a roller instead of the toner image heating means provided in a non-contact state in FIG. It is also possible to simultaneously perform fixing of the toner image by voltage and formation of a film by heating. With such a configuration, it is possible to form a toner image into a film without disturbing the toner image without providing a toner image fixing unit.

Although the photosensitive member has been described as an example of the electrostatic latent image holder, the electrostatic latent image holder according to the present invention is not particularly limited to the photosensitive member. Can be used. In this case, an electrostatic latent image is formed on the surface of the electrostatic latent image holding member by providing, instead of the charging unit and the exposure unit, a unit capable of supplying a charge according to an image signal, such as an ion flow head. It becomes possible. Further, for the subsequent processes such as the developing process, the same processes as those using the above-described photoconductor may be applied.

FIG. 1 is a configuration diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a first diagram illustrating a shear stress acting on a toner image. FIG. 5 is a second diagram illustrating the shear stress acting on the toner image. FIG. 9 is a configuration diagram of an image forming apparatus according to a second embodiment of the present invention. FIG. 9 is a configuration diagram of an image forming apparatus according to a third embodiment of the present invention. FIG. 4 is a diagram for explaining transfer of a toner image from a photoconductor surface to an intermediate transfer medium surface. FIG. 4 is a diagram for explaining transfer of a toner image from a photoconductor surface to an intermediate transfer medium surface. FIG. 4 is a diagram for explaining transfer of a toner image from a photoconductor surface to an intermediate transfer medium surface. FIG. 9 is a configuration diagram of an image forming apparatus according to a fourth embodiment of the present invention. FIG. 13 is a configuration diagram of an image forming apparatus according to a fifth embodiment of the present invention. FIG. 13 is a configuration diagram of an image forming apparatus according to a sixth embodiment of the present invention. FIG. 13 is a configuration diagram of an image forming apparatus according to a seventh embodiment of the present invention.

Explanation of reference numerals

101 photoconductor 102 charger 103 optical system 104 developing means 105 film forming means 106 intermediate transfer medium 107 cleaning means 108 static elimination means 109 pressure roller 110 recording medium 111 metal drum 112 Photosensitive layer 113 release layer 114 liquid toner 115 toner holding member 116 developing roller 117 squeezing means 118 toner image fixing means 119 toner image heating means 120 metal roller 121 elastic layer 122 heater 201 toner Image 401 toner image heating means 901 metal roller 902 elastic layer 903 heater 1001 developing means 1002 intermediate transfer medium 1003 intermediate transfer belt 1004 first transfer roller 1005 second transfer roller 1006 heater 1007 ... toner image heating means 1101 ... roller 1201 Toner image heating means

Claims (4)

Forming an electrostatic latent image on the surface of the electrostatic latent image holding member, and developing a toner image on the surface of the electrostatic latent image holding member by supplying a toner image to the electrostatic latent image by developing means; Removing the solvent of the developed toner image and drying the toner image; and applying the shear stress to the dried toner image to transfer the toner image from the surface of the electrostatic latent image holding member onto an intermediate transfer medium. An image forming method comprising: a first transfer step of transferring a toner image; and a second transfer step of transferring the toner image from the surface of the intermediate transfer medium onto a recording medium. The image forming method according to claim 1, wherein the intermediate transfer medium has an elastic layer having a thickness of 1 mm or less formed on the surface. An electrostatic latent image holding member, a charger for charging the surface of the electrostatic latent image holding member, an optical device for forming an electrostatic latent image on the charged surface of the electrostatic latent image holding member, and the electrostatic latent image holding member. Developing means for supplying a liquid toner to the surface of the electrostatic latent image holding member on which an image is formed to form a toner image; and removing the solvent of the toner image formed on the surface of the latent image holding member to remove the toner image. Means for drying; first transfer means for transferring the toner image on the surface of the electrostatic latent image holding member onto an intermediate transfer medium while applying a shear stress to the dried toner image; An image forming apparatus comprising: a second transfer unit configured to transfer the toner image onto a recording medium. 4. The image forming apparatus according to claim 3, wherein the intermediate transfer medium has an elastic layer having a thickness of 1 mm or less formed on a surface.

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