JP2000275969A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always realize excellent transfer characteristic and the output of a high- quality image by directly transferring a visible image to a body to be transferred by heat and pressure in a state where a solvent remains and heating the visible image after the body to be transferred passes through a transfer part. SOLUTION: After an image carrier 1 is uniformly electrified, it is exposed 3a with a laser beam modulated in terms of image, so that an electrostatic latent image is formed on the surface of the image carrier 1. The electrostatic latent image is made visualizable by a developing device 4a storing liquid developer. A toner image formed on the image carrier 1 is transferred to paper 8 by a transfer means 6 in a state where the fixed solvent is included regardless of the existence of a transparent resin applying means. Specified pressure is applied to the toner image on the image carrier 1 by the transfer roller 6, and the toner image is transferred to the paper by the heat and the pressure. The solvent where the transferred image remains continues to be heated by the heating means 12 of the transfer roller in a state where the paper is attracted to the transfer roller, and is evaporated on the transfer roller. Thereafter, the paper is peeled from the surface of the transfer roller by a peeling means 14 and ejected to the outside of a machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a liquid developer.

[0002]

2. Description of the Related Art In recent years, electrophotographic apparatuses and electrostatic recording apparatuses using liquid developers have advantages that cannot be realized by a dry system, and their values have recently been reviewed. In other words, extremely fine toner of submicron size can be used, so that high image quality can be realized, and sufficient image density can be obtained with a small amount of toner, so that it is economical and has a print-like texture. This is the main advantage of the wet image forming apparatus.

[0003] On the other hand, the conventional liquid image forming apparatus using liquid toner has several problems, and for this reason, dry technology has been allowed to stand alone for a long time. One of these problems is a problem in transfer means.

[0004] The first problem in transfer is deterioration of image quality. That is, in the related art, since the developer adhered on the image carrier is directly transferred to the sheet by the electric field by the transfer unit, the transfer unevenness due to the electric field fluctuation according to the unevenness of the sheet surface has occurred. In addition, due to variations in the electrical characteristics of the paper and environmental dependency, transfer defects are likely to occur, and the quality of the transferred image has been significantly degraded.

In order to solve such a problem, there has been proposed an apparatus for temporarily transferring the image from an image carrier to an intermediate transfer medium and then transferring the image to a sheet. US Patent No. 5,148,22
Nos. 5,166,734, 5,208,637, etc. disclose devices for transferring an image from an image carrier to an intermediate transfer medium by an electric field, and then transferring to a sheet by pressure (and heat). I have.

Further, Japanese Patent Publication No. 46-41679 and Japanese Patent Application Laid-Open No. 62-280882 disclose an apparatus using pressure (and heat) for both transfer to an intermediate transfer medium and transfer to paper without using electric field transfer. Is disclosed. According to this method, it is relatively easy to form the intermediate transfer medium from a material having a smooth surface and a small variation or variation in electric resistance.
Image quality degradation due to transfer is dramatically improved. Even when the image is transferred to the intermediate transfer medium by pressure and heat, the deterioration of the image quality is significantly suppressed.

However, these proposals still have the following problems. First, providing an intermediate transfer medium complicates the process. In addition, the image quality fluctuates with the deterioration of the intermediate transfer medium, which lowers the reliability of the system. Since an intermediate transfer medium generally requires elasticity and release properties, a silicone-based or fluorine-based release layer is provided on the surface of an elastic layer of rubber or the like, but its durability is inferior to other components.

Further, when transferring the toner image from the intermediate transfer medium to the paper, it is difficult to obtain 100% transfer efficiency, and a cleaner for removing the toner remaining on the intermediate transfer medium after the transfer is required. . The durability of the intermediate transfer medium is further reduced by the damage caused by the cleaner.

In order to solve the problem relating to such an intermediate transfer medium, there has been proposed an apparatus for directly transferring a toner image from an image carrier to an image carrier (paper) by heat and pressure. U.S. Pat. No. 5,608,507 discloses an apparatus for directly transferring an image formed by a liquid toner from an image carrier having a release layer on the surface to a sheet by heat and pressure. In this apparatus, the liquid toner image adhered to the latent image on the photoreceptor surface is completely dried (dry out) and then transferred to the paper, so that the solvent does not adhere to the paper and harmful solvent vapor Is not released outside the aircraft.

However, according to the follow-up test conducted by the present inventors,
This apparatus also has the following problems. First,
It is difficult to transfer a toner image to paper with pressure (and heat) in a state where the solvent is completely dried, and as described in detail in the patent, it is necessary to improve the transfer efficiency by using a photosensitive layer. Is formed on the elastic backing layer, and the adhesion between the paper surface and the toner is required to be improved by utilizing the elastic deformation.

In this case, the photoconductor layer is repeatedly deformed along with the deformation of the elastic body under the pressure of the pressing member pressed against the back surface of the sheet, so that the binder resin constituting the photoconductor undergoes fatigue destruction, The life of the photoconductor is significantly shortened. Since the photoreceptor needs to have flexibility, a metal-based photoreceptor such as amorphous silicon or selenium cannot be used, and a binder-based photoreceptor such as an organic photoreceptor must be used. Lifetime improvement is difficult.

Further, in order to obtain good transfer efficiency, the surface layer of the photoreceptor must be made of a material having a remarkably high releasability, and it has been extremely difficult to achieve both a high photoreceptivity and a high release layer.

[0013]

As described above, even the devices disclosed so far have various problems in practical use. SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and to provide an image forming apparatus capable of stably realizing good transfer characteristics and high-quality image output in wet electrophotography.

[0014]

According to a first aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on an image carrier, and a liquid developer on the electrostatic latent image. A developing unit that forms a visible image by supplying, a transfer unit that directly transfers the visible image to a transfer object by heat and pressure in a state where a solvent remains, and a transfer unit that transfers the visible image to the transfer unit. Means for heating the visible image after passing through the image forming apparatus.

In such an image forming apparatus, the visible image after the transfer is heated by a heating means provided separately, the visible image is continuously heated after the transfer in the transfer section, or the transfer target is heated. The visible image is heated by heating the transfer unit after the transfer in a state where the transfer target is adsorbed to the transfer unit that transfers the transfer unit to the transfer unit. As a result, even if the transfer is performed with a high-speed machine exceeding 40 cpm, the solvent continues to evaporate even after the transfer, so that the solvent vapor evaporates almost completely there and harmful vapor is released outside the machine. Can be prevented. The transfer is preferably performed in a state where the solvent remains in the visible image at a ratio of 10 to 80%.

According to a second aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image. Transport means for transporting the object to be transferred to the transfer unit, and the object to be transferred,
Suction means for suctioning to the transfer means prior to transfer,
A heating unit that heats the transport unit, and a transfer unit that transfers the visible image to a transfer target by heat and pressure,
An image forming apparatus is provided, in which the transfer unit is heated by the heating unit so that the transfer target body is heated prior to transfer.

In such an image forming apparatus, the paper is mainly preheated by adsorbing the paper to the heated transfer roller before the transfer. As a result, the paper is sufficiently heated prior to the transfer without providing a special paper preheating device,
Even in a high-speed machine exceeding 40 cpm, stable simultaneous transfer and fixing can be performed.

According to a third aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image. Transport means for transporting the object to be transferred to the transfer unit, and the object to be transferred,
Suction means for suctioning to the transfer means prior to transfer,
A heating unit that heats the transfer unit, a transfer unit that directly transfers the visible image to the transfer target by heat and pressure in a state where the solvent remains, and after the transfer target passes through a transfer unit. Comprising a means for heating the visible image, by heating the conveying means by the heating means,
An image forming apparatus is provided in which the transfer target is heated prior to transfer.

Such an image forming apparatus is a combination of the image forming apparatus according to the first aspect of the invention and the image forming apparatus according to the second aspect of the present invention. Fixing becomes possible.

According to a fourth aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image. Transfer means for transferring the visible image to a transfer target, wherein the liquid developer is a mixture of a solvent having a boiling point of T1 ° C. and a solvent having a boiling point of T2 ° C. higher than T1 ° C. Before the transfer, the visible image is heated at T3 ° C. which is lower than T2 ° C., and at the time of transfer or at least one of after transfer,
(T3 + T2-T1) Provided is an image forming apparatus further comprising means for heating at a temperature of not less than (C3).

In such an image forming apparatus, a large amount of a solvent having a low boiling point is evaporated before transfer to secure a stable residual amount of the solvent in a short time. At the time of transfer or after transfer, by heating at a higher temperature than before transfer, the solvent having a high boiling point is also evaporated, and the solvent is prevented from being discharged outside the apparatus. This enables stable offset transfer.

The fifth invention is the same as the fourth invention, and includes a latent image forming means for forming an electrostatic latent image on the image carrier,
A developing unit that forms a visible image by supplying a liquid developer to the electrostatic latent image; and a transfer unit that transfers the visible image to a transfer target, wherein the liquid developer has a boiling point. Contains a mixed solvent obtained by mixing a solvent having a temperature of Ta ° C. and a solvent having a boiling point of Tb higher than Ta, and heating the visible image at a temperature equal to or higher than Ta ° C. and lower than Tb ° C. before transfer, and at least during transfer or after transfer. In any one of the above embodiments, there is provided an image forming apparatus further comprising a unit for heating at Tb ° C. or higher.

Such an image forming apparatus can expect the same effect as the image forming apparatus according to the fourth aspect.

According to a sixth aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image. Transferring means for transferring the visible image to a transfer-receiving member, and applying a substantially transparent resin onto the image bearing member before the development.
And a second transparent resin applying means for applying a substantially transparent resin on the image carrier on which the visible image is formed after the development, wherein the first transparent resin applying means comprises: The molecular weight of the resin applied by the transparent resin applying means is smaller than the molecular weight of the resin applied by the second transparent resin applying means.

Such an image forming apparatus has a first applying means for applying a substantially transparent resin before the development of a visible image and a second applying means for applying the resin after the development. The molecular weight of the resin applied by the first applying means in contact with the carrier is made smaller than the resin applied by the second applying means in contact with the object to be transferred, so that the resin can be easily separated from the middle of the resin during transfer. The purpose of the present invention is to improve the separation of the transfer-receiving member from the holding of the latent image when the transfer is performed using the resin.

According to a seventh aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on an image carrier, and a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image. Transfer means for transferring the visible image to an object to be transferred by an electric field, and transparent resin applying means for applying a substantially transparent resin on the image carrier before the development. Image forming apparatus. In particular, after a visible image of a plurality of colors is overlaid on the latent image forming means and developed, the image is transferred to a transfer object by an electric field.

In such an image forming apparatus, when a visible image, in particular, a visible image of a plurality of colors is superimposed and developed on an image carrier, and the image is transferred to a transfer object by an electric field, the image is transferred to the image carrier. Before the visible image is developed, a substantially transparent resin is applied. Even if the transfer efficiency does not reach 100%, most of the transfer residue becomes a transparent resin. Transfer efficiency 1
00% can be obtained.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be shown, and the present invention will be described in detail. FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. In FIG. 1, an image carrier 1 is a photosensitive drum in which an organic or amorphous silicon-based photosensitive layer is provided on a conductive substrate. The image carrier 1 is uniformly charged by a well-known corona charger or scorotron charger 2a, and then is exposed to an image-modulated laser beam 3a to form an electrostatic latent image on the surface.

Thereafter, the electrostatic latent image is visualized by the developing device 4a that stores the liquid developer. The liquid developer is, for example, Exoper G, L,
Metallic soap for charge control and an acrylic resin with a glass transfer point in the range of −50 ° C. to 50 ° C. added with a pigment are dispersed in a hydrocarbon-based insulating solvent such as M or Norper 12, 13, 15 or the like. What can be used.

The liquid developer or toner adhering to the electrostatic latent image may reach the transfer means as it is and may be transferred to the sheet by the transfer device 5, but here the second charger 2b and the second laser A second electrostatic latent image is formed by exposure 3b, and is formed by a second developing device 4b that stores a second developer of a different color from the liquid developer stored in the first developing device 4a. develop. Therefore, after the second development, two color toner images are formed on the image carrier 1.

Similarly, a third charger 2c, a third laser exposure 3c, a third developing device 4c, a fourth charger 2c
d, fourth laser exposure 3d, and fourth developing device 4d perform third, fourth charging, exposure, and development, and a full-color toner image is formed on image carrier 1.

In the conventional wet image forming apparatus, the thickness of the toner image formed on the surface of the image carrier 1 by the developing means is at most about 0.4 μm, and is 0.1 μm or less in the constant density image area. That was not uncommon. Therefore, when these toner images are transferred to plain paper having irregularities of several tens of μm on the surface, how to bring the toner particles into contact with the paper surface has been an important issue.

In the conventional electric field transfer, a sufficient amount of solvent is supplied to the paper and the solvent penetrates into the concave portions of the paper, so that toner particles can adhere to the concave portions of the paper by electrophoresis (= transfer). However, as a result, the paper was discharged outside the machine while absorbing a large amount of solvent, and this caused an environmental problem due to the solvent vapor.

In the transfer by pressure (and heat), the toner can be transferred to the paper after the solvent has been sufficiently removed in advance.
An extremely thin toner layer having a thickness of about 1 μm must be adhered to a paper recess having a depth of several tens of μm. for that reason,
It has been an essential condition that the image carrier and the intermediate transfer medium are made of an elastic body, and the elastic body is deformed under a high pressure so that the toner contacts the concave portion of the paper.

This request has caused problems relating to durability and stability of the image carrier and the intermediate transfer medium as described above.
The present inventors have conducted intensive studies to solve these problems, and as a result, have obtained the following knowledge. That is,
Even in the wet process, if the thickness of the toner image transferred to the paper is in the range of 0.3 μm to 20 μm, more preferably in the range of 1 μm to 10 μm, the surface of the image carrier or the intermediate transfer medium may be rigid or flexible. Even if the toner is composed of a low material, good transfer to plain paper can be realized, and even if the thickness of the toner image is less than 0.3 μm, the transfer to plain paper can be performed if the solvent is contained in a certain range. I found that it was possible to some extent.

That is, the image layer thickness is increased by applying a transparent resin to the toner image, and furthermore, the toner image can be transferred to plain paper by controlling the amount of the remaining solvent to a certain level. It becomes. However, if the transfer is carried out mainly in a high-speed machine with the solvent remaining in this way, the above-described problem of the solvent being discharged out of the machine occurs, so the present invention has been applied.

First, regarding the first embodiment of the present invention,
This will be described with reference to FIG. As described above, the toner image formed on the image carrier is transferred to the sheet 8 by the transfer unit 6 in a state containing a certain solvent regardless of the presence or absence of the transparent resin applying unit. Reference numeral 6 denotes a transfer roller which also serves as a paper conveying unit.

The transfer roller has a structure in which an elastic sheet having a hardness of about 40 to 90 ° or a rigid body is wound around an elastic sheet, the surface is made of a dielectric material, the inside is made of a conductive member, and is grounded. ing. The paper is electrostatically attracted to a transfer roller serving as a transfer unit and a transfer unit by a suction roller 15. At this time, the suction roller has a hardness of 30 ° or more and a resistance of 0.
With a conductive elastic or rigid roller of about 10e9Ω,
A potential difference of 500 to 3 kv is applied to the transfer roller.

Next, a predetermined pressure (0.3 kg / cm or more and 15 kg / cm or less) is applied to the toner image on the image carrier by the transfer roller 6, and the toner image is transferred to paper by heat and pressure. You. Next, the solvent in which the transferred image remains remains heated by the transfer roller heating means 12 in a state where the paper is adsorbed to the transfer roller.
Evaporates almost completely on the transfer roller.

Thereafter, the paper is peeled off from the surface of the transfer roller by the peeling means 14, and is discharged outside the machine. Here, the peeling means 14 uses a corona charger to which a bias including an AC bias (500 to 10 kv) is applied. However, since the image is fixed, the charge is removed by a contact charger such as a roller or a brush. Alternatively, it may be peeled off by a mechanical means such as a peeling nail. Also, even if an excessive bias is applied to these, the image will not be disturbed.

As the paper suction means, the electrostatic suction is described here, but other methods may be used. For example,
A method of vacuuming the paper by making a fine hole in the roller, a method of mechanically gripping the front and rear edges of the paper, or a method of gripping the front end of the paper and combining it with electrostatic suction, It is conceivable to make the surface of the transfer roller sticky. The paper does not need to be absorbed prior to the transfer, and may be made to adhere to the transfer roller by making contact at the transfer nip as shown in FIG.

FIG. 2 shows an example in which a belt is used as the conveying means. The belt is a belt made of rubber or resin having a volume resistance of about 10 ⁷ to 10 ¹³ Ω, for example, a belt made of polyimide resin. The paper electrostatically attracted to the belt by the attracting roller 15 to which the bias is applied,
It is heated by the heating means 12 and is transferred by heat and pressure in the transfer area.

The paper after the transfer is continuously heated by the heating means while being adsorbed on the belt, and after the remaining solvent is almost completely evaporated, the paper is separated from the belt and discharged. When a belt is used, the paper can be separated from the belt by using the curvature of the driving roller and the driven roller of the belt, so that a neutralizing member or the like for peeling can be omitted.

FIG. 3 shows the transfer characteristics when the temperature of the image bearing member is changed when the temperature of the transfer member (transfer roller) is changed. A transparent resin is applied on the toner image so that the layer thickness of the entire image is 1
The results are shown in FIG. The horizontal axis shows the remaining amount of the solvent in the toner image, and the vertical axis shows the transfer efficiency. The load of the transfer roller is about 2 kg per 1 μm in the longitudinal direction of the transfer roller, and the transfer speed is 100 mm / sec.

From FIG. 3, it can be seen that, in the case of plain paper having a rough surface, transfer cannot be performed even if the amount of the remaining solvent is too small or too large, and there is an optimum condition for the amount of the remaining solvent. When the image carrier is heated to slightly heat the toner image before the transfer, the transfer performance is improved. On plain paper, the optimum value of the residual amount of the solvent is 0.3 to 0.3 mg / cm ^{2. In} terms of weight conversion ratio, when the specific gravity of the toner is about 0.8, the solid content is 2
0 to 45% and the solvent 55 to 80%. Also, when transferring to art paper with relatively good smoothness,
It is 0.01 to 0.3 mg / cm ² , and the weight conversion ratio is 20 to 90% of solid content and 10 to 80% of solvent.

Similarly, FIG. 4 shows the result of a similar experiment conducted using only the toner without providing the transparent resin. In this case, the toner layer thickness was about 0.1 to 0.3 μm, but the transfer efficiency was low for both plain paper and art paper, but it was possible to transfer to some extent if the residual amount of solvent was kept at a constant value. You can see that there is.

FIG. 4 shows the transfer characteristics when the layer thicknesses of the toner and the transparent resin are changed. From FIG. 4, it can be seen that good transfer was achieved if the amount of solvent was constant without the transparent resin. However, the margin is very narrow, and when the toner layer thickness is less than 0.3 μm, 0.15 mg /
cm ² , the weight conversion ratio is 20% solids, and the solvent 8
0%, and the transfer efficiency has not reached 100%.

On the other hand, when the transparent resin is applied to the toner image to reduce the layer thickness to about 3 μm, the margin of the optimum value of the remaining solvent amount is widened, but the weight conversion ratio between the solid content and the solvent is as described above. The same tendency as in the case of 1 μm is obtained.

That is, when the toner image is heated prior to the transfer, the transfer efficiency is improved, and the specific gravity ratio of the optimum solvent remaining amount of the toner image immediately before the transfer is determined by the following equation. When the thickness is 1 μm or more, the tendency becomes almost the same. If the solid content is 20 to 90% and the solvent is 10 to 80%, preferably fixed to the same conditions and can also be used for plain paper,
It is understood that the solid content is preferably 20 to 45% and the solvent is preferably 55 to 80%.

FIG. 5 shows an example of a color image printing apparatus adopting a method of forming a toner image for each color by one rotation of the image carrier. In the color image printing apparatus shown in FIG. 5, the image carrier is provided with a detachable cleaner, a residual solvent amount adjustment device before transfer, and a transfer device. It is supposed to be.

The image carrier uniformly charged by the corona charger is subjected to an exposure process corresponding to each color, and the first color is developed. Thereafter, charging is further performed, exposure is performed at a position corresponding to the image portion, and a transparent resin is applied. At this time, the drying means, the transfer device, and the cleaner are separated from the image carrier, and the image carrier rotates once by one rotation.
Charging, development, and application of a transparent resin are performed.

After the above operation is repeated for all colors (3 to 4 colors), the drying means, the transfer device, and the cleaner are brought into contact with the image carrier, and transfer to paper is performed. In such an apparatus, since there is only one transparent resin coating device and the coating can be performed for each color, the thickness of the transparent resin layer can be easily increased. When the transparent resin is developed under the same conditions and method as a normal developing device, the coating thickness is about 0.5 μm. Here, if this is applied for every four colors, the thickness becomes 2 μm, which is sufficient for transfer to plain paper.

Further, by controlling the number of times of application depending on the type of paper, wasteful transparent resin can be avoided. For example, in the case of relatively smooth art paper,
After the development of all colors is completed, the transfer can be sufficiently performed by applying the transparent resin only once. Some paper types do not require transparent resin. On plain paper with poor smoothness, a transparent resin is applied for each color to make 2μ
m is obtained. Although the paper type can be automatically detected by using a gloss meter or the like, generally, inputting by a user or providing a dedicated paper feed tray is lower and more reliable. Is the way.

The first embodiment described above can be applied to a case where only ordinary toner is used, but is very effective when such a transparent resin is applied. This is because, in the transfer in the case where the transparent resin is applied, the toner image contains a large amount of solvent at the time of transfer, so that it is not sufficiently dried only at the time of transfer.

As in the present embodiment, it is necessary to evaporate the solvent after transfer by the heat source of the transfer roller or the conveying means, or to newly install a fixing device after transfer. In this embodiment, since the visible image is directly transferred from the image carrier to the transfer target, it is difficult to heat the toner image before the transfer. As mentioned above, heating the visible image before transfer improves the transfer efficiency.However, no matter how small the heat capacity of the image carrier, such as the belt photoreceptor, the temperature is, if the temperature is too high, other processes such as development will be performed. There is concern about the impact on Therefore, the present embodiment in which the transfer roller and the conveying means are mainly heated and the paper is adsorbed thereon to increase the transfer efficiency becomes important.

Next, a second embodiment of the present invention will be described.
This will be described in detail with reference to the drawings. The present embodiment is characterized in that an object to be transferred, such as paper, is preheated before transfer, and achieves good transfer even in a high-speed machine exceeding 40 cpm. As a method,
This is almost the same as the first embodiment shown in FIGS. 1 and 2, that is, before transfer, paper is adsorbed to a transfer means such as a transfer roller or a transfer belt, and the transfer means is heated in that state. As a result, the paper is warmed before transfer and reaches the transfer area in a sufficiently heated state.

The image forming apparatus shown in FIGS. 1 and 2 has a structure in which the paper is attracted to the conveying means before the transfer, and the image forming apparatus shown in FIG. If there is, the paper is preheated, and this embodiment is applied, and if not, only the first embodiment is applied.

FIG. 6 shows the difference in transfer characteristics depending on the presence or absence of preheating of paper when the transfer speed is 100 mm / sec and 300 mm / sec. From FIG. 6, an experiment was performed in a state in which the layer thickness of the entire image was reduced to 1 μm by applying a transparent resin, and there was no significant difference between the two at 100 mm / sec. It can be seen that the transfer efficiency was clearly improved.

The present embodiment is applicable not only to the case where a visible image is directly transferred from an image carrier to paper, but also to the transfer from an intermediate transfer medium to paper. However, at the time of transfer, the direct transfer method containing a larger amount of solvent has a greater effect, and as in the example shown in FIGS. 1 and 2, the first embodiment and the second embodiment are combined, and before and after transfer. By heating the paper by the method described above, it is possible to achieve both stable transfer even in a high-speed machine and keeping solvent vapor out of the machine.

Next, a third embodiment of the present invention will be described. In the present embodiment, two or more kinds of solvents are mixed and used. As a solvent for a normal liquid developer, for example, an insulating solvent such as Isopar G, H, K, L, M or Norpar 12, 13, 15, or the like manufactured by Exxon is used. These solvents are mixtures of paraffinic hydrocarbons such as dodecane and undecane, and of course, those having slightly different physical properties such as boiling points are mixed.

Accordingly, the concept of mixing two or more solvents having different boiling points is already known. Also,
The concept of adding a trace amount of a solvent with an extremely far boiling point is
It is disclosed in JP-T-10-508119. But,
When transferring a liquid toner image from an intermediate transfer member to paper by heat and pressure, a very small amount (0.2 to 2%) of a high-boiling solvent is left in the intermediate transfer member to remove the intermediate transfer member. By not drying completely at all times, the durability of the intermediate transfer member is improved, and the life is extended.

In the present embodiment, on the other hand, the difference in boiling point is utilized when creating a state in which the liquid developer contains a certain solvent before the transfer. Tokiohei 10-5
Unlike the technique disclosed in 08119, the purpose of use of the solvent is different, the difference in the boiling points of the solvents to be mixed is small, and a small amount of a solvent having a high boiling point that does not evaporate at room temperature is used. Mix slowly evaporating levels of solvent at equivalent levels.

FIG. 7A shows an image forming apparatus according to this embodiment. In FIG. 7A, the transfer of the toner image on the image carrier after the development process is adjusted to a constant solvent amount as described above, regardless of the presence or absence of the transparent resin. In many cases, this adjusting means is a drying means having a heat source, and is shown as a drying means 20 in FIGS. 7A and 7B.

Here, when the ratio of the solid content of the toner image and the solvent adjusted before transfer is 30%: 70%, a mixture of a solvent having a low boiling point (boiling point T1 ° C.) and a solvent having a high boiling point (boiling point T2 ° C.) The ratio is set to about 3: 7 to 1: 1 and the toner image on the image carrier is heated at a temperature lower than T2 ° C. (T3 ° C.) by the above-mentioned drying means.

At this time, T3 ° C. does not necessarily need to be higher than T1 ° C. This is because the solvent evaporates exponentially as the solvent gets closer to the boiling point even at a temperature lower than the boiling point. Thus, most of the low boiling point solvent contained in the toner image is dried before the transfer, and the ratio between the solid content and the solvent can be adjusted relatively stably.

Thereafter, in the transfer area, the paper is heated at a temperature of T3 ° C. or higher (T4 ° C.). At this time, in order to evaporate faster and including the solvent having a high boiling point, T4 and T4 are heated.
It is effective to make the temperature difference from 3 larger than the temperature difference (T2−T1) between the boiling point (T2) of the high boiling solvent and the boiling point (T1) of the low boiling solvent.

That is, by setting the temperature as described above, the solvent having a high boiling point evaporates after the transfer, because the solvent having a high boiling point evaporates after the transfer, and the solvent having a high boiling point evaporates after the transfer. Is not released out of the machine.

In experiments conducted by the present inventors, Isopar G
And Isopar L in a 1: 1 ratio. The boiling point of Isopar G is 155 to 175 ° C, and Isopar L is 1
88-207 ° C. In this case, the drying temperature before the transfer is set to 60 ° C., the isoper G is substantially evaporated, and a large amount of the isoper L having a relatively high boiling point remains, so that the remaining amount of the solvent before the transfer is adjusted relatively stably. I was able to.

Then, with a configuration as shown in FIG.
When the temperature of the transfer roller was set to 75 ° C., the solvent did not completely evaporate just by passing through the transfer portion, and the image was peeled off when the discharged paper was rubbed with a finger. Then, when the temperature of the transfer roller was set to 95 ° C., the solvent evaporated almost completely in the transfer portion, the image was sufficiently fixed at the same time as the transfer, and the solvent vapor did not leak out.

The fourth embodiment of the present invention is also performed for the same purpose as the third embodiment. FIG. 7B illustrates an image forming apparatus according to the present embodiment. In this embodiment, the transfer can be performed at a higher speed than in the third embodiment, and the heating temperature before the transfer is set to the boiling point (Ta) of the low-boiling solvent.
° C) or higher and lower than the boiling point (Tb ° C) of the high boiling point solvent. As a result, the low-boiling solvent evaporates rapidly before the transfer, leaving almost only the high-boiling solvent. Thereafter, after the transfer portion or after the transfer, the high-boiling solvent is almost completely evaporated by heating at a temperature higher than the boiling point (Tb ° C.) of the high-boiling solvent.

FIG. 7B shows an example in which a fixing device is further provided after passing through the transfer section. However, as shown in FIG. 7A, the transfer section may be heated at Tb ° C. or higher. . In the experiment by the inventor, the same mixed solvent as in the third embodiment was used,
Heating temperature before transfer is equal to or higher than Ta ° C. and lower than Tb ° C. 18
When the temperature was set to 0 ° C., the amount of the remaining solvent could be adjusted even in a high-speed process. Then, when the heating temperature after the transfer was set to 210 ° C., 300 mm /
Even at a speed exceeding sec, the solvent evaporated almost completely, and good transfer / fixing became possible.

That is, in order to realize the process according to the present embodiment in a high-speed machine, the heating temperature before the transfer is set to be equal to or higher than the boiling point of the solvent having a low boiling point, and the heating temperature after the transfer section or after the transfer is adjusted to the boiling point. By setting the temperature higher than the boiling point (Tb ° C.) of the high solvent, more preferable results can be obtained.

Next, a fifth embodiment of the present invention will be described. In the present embodiment, a transparent resin is applied. As described above, when a transparent resin is applied, good transfer can be realized regardless of the type of paper.However, depending on the type of paper, the paper is easily attached to an image carrier such as a photoconductor, and Separation becomes difficult. FIG. 9A is a schematic diagram when the paper is stuck to the photoconductor. In the case of art paper on which a thin film is pasted, the paper separates from it.

Therefore, in this embodiment, as shown in FIG. 8, the first transparent resin is applied to the image carrier by the transparent resin applying device 4 before the toner image is developed, and then the toner image is formed. After the development, the second transparent resin is finally applied by the transparent resin applying device 9. At this time,
By making the molecular weight of the first transparent resin smaller than that of the second transparent resin, the first transparent resin is easily separated in the resin layer during transfer. The schematic diagram is shown in FIG. With such a configuration, even if the transparent resin adheres to the image carrier, the toner image is separated from the paper in the middle of the first transparent resin layer, so that the separation of the paper is improved.

It is generally desirable for the transparent resin to have a toner charging characteristic and a viscoelastic characteristic of a resin component close to those of a colored developer. Therefore, it is preferable to use a resin obtained by removing a pigment from toner. The molecular weight of the toner used in the experiment by the inventor and the acrylic resin used for the conventional transparent resin is 6
When it was transferred to art paper using the same resin as the first resin, the paper was stuck to the photoreceptor and could not be separated well.

Therefore, the molecular weight of the acrylic resin used for the first transparent resin was set to A1 sample:
60000 (Mw), A2 sample: molecular weight 20,000
４０40000 (Mw), A3 sample: molecular weight 1000
When the sample was lowered to 0 to 20000 (Mw), the separation of the paper was improved in the samples A2 and A3.

At this time, on the photoreceptor after transfer, FIG.
As shown in the schematic diagram of (b), some transparent resin remained, and the first transparent resin layer having a small molecular weight was separated and transferred. In this way, by interposing a resin having a smaller molecular weight than the resin used for the toner between the toner image and the image carrier, the paper can be easily separated from the photoconductor.

The sixth embodiment of the present invention relates to an apparatus for developing an image of a plurality of colors on an image carrier and then transferring the image to a transfer target at a time.
0 is shown. On the photoreceptor (a belt-shaped photoreceptor in this embodiment), there is a transparent resin applying means 4 before developing the toner image. First, the photoreceptor is uniformly charged by the charger 2 and then exposed. Then, the transparent resin is applied to the image portion by the transparent resin applying means 4. At this time, the transparent resin may be applied to the entire surface instead of the image portion.

Thereafter, charging, exposure, and development of each color toner are successively performed to form a color image on the photosensitive member.
The formed color image is transferred by an electric field in a transfer unit via a means for adjusting the amount of the remaining solvent, which is omitted in the drawing. At this time, in the transfer by the electric field, the transfer efficiency does not become 100% due to the influence of the resistance and the surface roughness of the paper.

However, since a transparent resin is provided on the photosensitive member side of the color image, 100% transfer of the visible image can be achieved even if the transparent resin portion is left untransferred. This conceptual diagram is shown in FIG. At this time, the transfer efficiency of the electric field transfer is 70 to 80%. Therefore, when the transfer efficiency is 70% by further applying a transparent resin in a portion where the three colors completely overlap with each other by the same means as the development, The substantial transfer efficiency is 70/100 × 0.75 = 93%.

In the same manner, the portion where two colors are overlapped is
0/100 × 0.67 = 100% or more, and in fact, there is almost no portion where three or more colors are overlapped. Even if three colors are overlapped, if the transfer efficiency is 75% or more, practically 10% is obtained.
In most cases, the transfer efficiency is 10% because the transfer is 0%.
0% can be achieved.

Although the transfer object was treated as paper here,
This may be something like an intermediate transfer member. The transfer efficiency of the intermediate transfer member is better than that of paper, and the transfer efficiency is stable. However, since 100% transfer is originally difficult, the application of the present embodiment enables substantially 100% transfer at all times. It can be said that it is a sure method.

In all of the above-described examples of applying a transparent resin, the transparent resin may be applied to the entire surface. However, although a new exposure means is required, the transparent resin is applied only to the image area. By selectively applying, the transparent resin is not wasted. Further, as described in the first embodiment, when the amount of the transparent resin applied is detected by detecting the type of paper, the transparent resin is not unnecessarily consumed. As a means for detecting the type of paper, a simple and inexpensive method can be used such as inputting by a user, setting a paper feed cassette to a special paper or plain paper specification, or the like.

As a means for adjusting the coating film of the transparent resin, when a normal developing device is used, the process conditions (peripheral speed and applied bias of the developing roller and squeeze roller, and those rollers and the image carrier) Adjustment of the gap). Further, the method of changing the number of application circuits as described above, or the application method itself such as spraying with an ink jet nozzle may be changed.

Although the optimum amount of the remaining solvent before the transfer is described in the first embodiment, the range described above can be applied to all the embodiments.

[0086]

As described above in detail, according to the present invention, a flexible image composed of a liquid developer can be transferred from an image carrier to an image carrier with high efficiency, and paper can be discharged. The solvent does not adhere to the waste paper, and an image forming apparatus having high image quality and being environmentally friendly can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of another example of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a solvent amount and transfer efficiency.

FIG. 4 is a characteristic diagram showing a relationship between a solvent amount and transfer efficiency.

FIG. 5 is a diagram illustrating a configuration of another example of the image forming apparatus according to the first embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between a solvent amount and transfer efficiency.

FIG. 7 is a diagram illustrating a configuration of an image forming apparatus according to a third embodiment of the present invention.

FIG. 8 is a diagram illustrating a configuration of an image forming apparatus according to a fifth embodiment of the present invention.

FIG. 9 is a schematic diagram of transfer according to a fifth embodiment of the present invention.

FIG. 10 is a diagram illustrating a configuration of an image forming apparatus according to a sixth embodiment of the present invention.

FIG. 11 is a schematic diagram of transfer according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Image carrier 2, 2a, 2b, 2c, 2d ... Charger 3, 3a, 3b, 3c, 3d ... Exposure 4a, 4b, 4c, 4d ... Developing device 4 ... Transparent resin provision device 5 ... Pre-transfer heating device Reference Signs List 6 Transfer means 8 Paper 9 Transparent resin applying device 10 Transparent developer 11 Transparent resin applying roller 12 Heating means 14 Paper peeling means 15 Suction roller 16 Adsorption bias applying means 17 Paper assisting means

Claims (15)

[Claims] A latent image forming means for forming an electrostatic latent image on an image carrier; a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image; Transfer means for directly transferring an image to a transfer object by heat and pressure in a state where a solvent remains; and a means for heating the visible image after the transfer object passes through a transfer portion. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the transfer unit continuously heats the visible image transferred to the transfer target while being in contact with the transfer target. . 3. A transfer means for transferring a transferred object, an adsorption means for adsorbing the transferred object on the transfer means, and a heating means for heating the transfer means, wherein the transfer means is provided by the heating means. 3. The image forming apparatus according to claim 1, wherein the visible image is heated after the transfer target passes through the transfer unit by being heated. 4. 4. A latent image forming means for forming an electrostatic latent image on an image carrier, a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image, and a transferred object Transport means for transporting the transfer medium to the transfer unit, suction means for attracting the transfer object to the transport means prior to transfer, heating means for heating the transport means, and the visible image by heat and pressure. An image forming apparatus comprising: a transfer unit that transfers the image to a transfer target; and the transfer unit is heated by the heating unit, whereby the transfer target is heated prior to the transfer. 5. A latent image forming means for forming an electrostatic latent image on an image carrier, a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image, and a transferred object Transport means for transporting the transfer medium to the transfer unit, an adsorption means for adsorbing the object to be transferred to the transport means prior to transfer, a heating means for heating the transport means, and the visible image remaining in a solvent. A transfer unit for directly transferring the transferred object to the transferred object by heat and pressure in a state, and a unit for heating the visible image after the transferred object has passed through a transfer unit; An image forming apparatus, wherein the transfer target is heated prior to transfer by heating the means. 6. The image forming apparatus according to claim 1, further comprising a unit for heating the visible image before the image is transferred to the object. 7. A latent image forming unit for forming an electrostatic latent image on an image carrier, a developing unit for forming a visible image by supplying a liquid developer to the electrostatic latent image, Transfer means for transferring an image to a transfer object,
The liquid developer includes a solvent having a boiling point of T1 ° C. and a solvent having a boiling point of T1.
A mixed solvent obtained by mixing a solvent having a T2 ° C higher than 0 ° C,
Before the transfer, the visible image is heated at T3 ° C, which is lower than T2 ° C, and at the time of transfer or at least one of after transfer,
(T3 + T2-T1) An image forming apparatus further comprising means for heating at a temperature of not less than (° C.) ° C. 8. A latent image forming means for forming an electrostatic latent image on an image carrier, a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image, Transfer means for transferring a visual image to a transfer target, the liquid developer includes a solvent having a boiling point of Ta ° C. and a mixed solvent obtained by mixing a solvent having a boiling point of Tb higher than Ta, and Heating the visible image at Ta ° C or higher and lower than Tb ° C;
An image forming apparatus, further comprising means for heating at or above Tb ° C. during transfer or at least after transfer. 9. The apparatus according to claim 1, further comprising a transparent resin applying means for applying a substantially transparent resin to the visible image before the transfer. Image forming apparatus. 10. A latent image forming means for forming an electrostatic latent image; a developing means for forming a visible image by supplying a liquid developer to the electrostatic latent image on the image carrier; Transfer means for transferring an image to a transfer-receiving member; first transparent resin applying means for applying a substantially transparent resin onto the image carrier before the development; and A second transparent resin applying means for applying a substantially transparent resin on the image carrier on which the image is formed, wherein the molecular weight of the resin applied by the first transparent resin applying means is equal to the 2. An image forming apparatus characterized in that the molecular weight is smaller than the molecular weight of the resin applied by the transparent resin applying means. 11. A latent image forming unit for forming an electrostatic latent image on an image carrier, a developing unit for forming a visible image by supplying a liquid developer to the electrostatic latent image, and An image forming apparatus comprising: a transfer unit for transferring an image to an object to be transferred by an electric field; and a transparent resin applying unit for applying a substantially transparent resin onto the image carrier before the development. apparatus. 12. An image forming apparatus according to claim 11, wherein a visible image of a plurality of colors is superimposed and developed on said latent image forming means, and then transferred to a transfer object by an electric field. 13. The method according to claim 9, wherein said substantially transparent resin is applied only to an image area of said visible image.
13. The image forming apparatus according to any one of items 12 to 12. 14. A detecting means for discriminating the type of the object to be transferred, and a thickness of a substantially transparent resin applied to the visible image is varied in a range of 0 to 20 μm by a signal of the detecting means. 14. The image forming apparatus according to claim 9, further comprising a unit. 15. The resin according to claim 15, wherein said resin is substantially transparent to the visible image.
Solids ranging from 0% to 90%, and 10% to 80%
The image forming apparatus according to any one of claims 9 to 14, further comprising a squeezing means for adjusting the amount of the solvent component so as to reach the transfer means in a state containing the solvent component in the range of%. apparatus.