JP2002014550A - Device and method for transfer, and device and method for image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device by which pre-transfer due to defective close contact between an intermediate transfer belt 41 and transfer paper 100 on the upstream side of the intermediate transfer belt 41 in a moving direction than a secondary transfer nip N is effectively suppressed to a level at which it is not confirmed by visualizing. SOLUTION: The secondary transfer roller 51 is brought into press-contact with the intermediate transfer belt 41 so that the non-winding part of the intermediate transfer belt 41 to a secondary transfer opposed roller 46 on an assumption that the secondary transfer roller 51 does not exist is partially brought into contact with the secondary transfer opposed roller 46 on the side of a nip entrance, and the caught amount of the secondary transfer opposed roller 46 by the secondary transfer roller is set as 0.2 to 3.0 (mm), and also an angle θ1 obtained by the extended line of the intermediate transfer belt 41 in the moving direction just before coming into contact with the secondary transfer roller 51 and a nip entrance tangent line is set as >=5 ( deg.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for transferring a visible image from a belt-like visible image carrier such as a photosensitive belt or an intermediate transfer belt of an image forming apparatus to a recording member such as transfer paper. The present invention relates to a transfer method, and an image forming apparatus and an image forming method using the transfer method.

[0002]

2. Description of the Related Art Conventionally, as a transfer device used in an image forming apparatus such as a copying machine, a printer, a facsimile, etc.
A transfer device as shown is known. In the figure, the transfer device includes an intermediate transfer belt 41 as a belt-shaped visible image carrier, a secondary transfer roller 51 as an elastic roller,
A secondary transfer facing roller 46 as a biting roller, a plurality of stretching rollers (not shown), and the like are provided. The intermediate transfer belt 41 is formed in an endless belt shape, and is stretched around the plurality of stretching rollers and the secondary transfer facing roller 46 and is moved endlessly in the direction of the arrow in FIG. A toner image (not shown) as a visible image is primarily transferred to S. The secondary transfer opposing roller 46 formed of a rigid material such as metal cuts into a secondary transfer roller 51 formed of an elastic member to form a secondary transfer nip N. A secondary transfer bias having a polarity opposite to that of the toner constituting the toner image is applied to the secondary transfer roller 51 by a power supply (not shown). A secondary transfer electric field is formed.

The toner image primary-transferred onto the intermediate transfer belt 41 enters the secondary transfer nip N as the intermediate transfer belt 41 moves endlessly. On the other hand, the transfer paper 100 is conveyed from the pair of registration rollers (not shown) between the front surface S in the secondary transfer nip N and the secondary transfer roller 51 in consideration of the timing of this approach. With this conveyance, the toner image and the transfer paper 10 are transferred at the secondary transfer nip N.
0 is brought into close contact, and the toner image
Secondary transfer is performed from the intermediate transfer belt 41 to the transfer paper 100 by the action of the next transfer electric field or the like. Note that a secondary transfer bias having the same polarity as the toner may be applied to the secondary transfer facing roller 46 to form a secondary transfer electric field.

In the transfer apparatus having the above configuration, the above-mentioned 2
In addition to the next transfer nip N, the secondary transfer electric field also acts on the upstream and downstream regions in the transfer paper transport direction. When a gap G is formed between the front surface S of the intermediate transfer belt 41 and the transfer paper 100 on the upstream side of the secondary transfer nip N, the toner (not shown) is caused by the action of the secondary transfer electric field. There is a case where a phenomenon called so-called pre-transfer, in which the image is flying and transferred from the front surface S to the transfer paper 100, occurs. In particular, when a full-color image is formed by superimposing the black, magenta, cyan, and yellow toner images sequentially on the intermediate transfer belt 41 and forming a primary color image, the toner image is formed on the intermediate transfer belt 41 more than when a single-color image is formed. , The pre-transfer is likely to occur. Most of the pre-transferred toner adheres to a position displaced from the original attachment position on the transfer paper 100, resulting in transfer dust scattered around the original image, blurring of image edges, full-color image Or the color of the image may be impaired, thereby deteriorating the image quality.

[0005] Incidentally, referring to FIG.
Although the pre-transfer that occurs when the toner image is transferred from No. 1 to the transfer paper 100 has been described, the same pre-transfer may occur in the following cases. That is, for example, when a toner image is directly transferred from a photosensitive belt to a recording member such as transfer paper without using an intermediate transfer belt, a belt-shaped visible image carrier and a recording member are placed in a nip formed by two rollers. This is the case where a visible image is transferred while being sandwiched.

Therefore, a recording member such as the transfer paper 100 should be brought into close contact with the visible image carrier upstream of the nip such as the secondary transfer nip N and then sent out toward the nip. General.

[0007]

However, even if the recording member is brought into close contact with the visible image carrier upstream of the nip, a poor transfer may occur immediately before the recording member enters the nip and pre-transfer may occur. Was. In particular, as the diameter of the biting roller such as the secondary transfer opposing roller 46 is reduced, poor adhesion between the recording member and the visible image carrier tends to easily occur immediately before the nip.

The inventors of the present invention have conducted intensive studies on the causes of such poor adhesion and found the following phenomena. That is, as shown in FIG. 16, in the secondary transfer nip N in which the secondary transfer opposing roller 46 is cut into the secondary transfer roller 51, the transfer paper 100 is not a secondary transfer roller 51 deformed into a concave shape, but a circular shape. 2 while maintaining
It moves along the circular orbit of the next transfer opposing roller 46 (strictly speaking, it moves along a circular orbit offset outward from the circular orbit by the thickness of the intermediate transfer belt 41). When the transfer paper 100 is moved in this way at the secondary transfer nip N,
It has been found that the nip non-entering portion of the transfer paper 100 is caused to take an attitude that is similar to the nip entrance tangent L1 depending on the strength of the waist. The nip entrance tangent line L1 is defined as a rotation center point P2 of the secondary transfer facing roller 46,
A line orthogonal to the straight line L2 connecting the nip entrance point P1 at the position of the nip entrance point P1. The nip entrance point P1 is a contact point between the back surface of the intermediate transfer belt 41 and the transfer paper 100 at the position where the two rollers start sandwiching the belt. In FIG. 16, the nip entrance tangent line L1 is located on the intermediate transfer belt 41 on the upstream side of the nip.
It is located between the front surface S and the secondary transfer roller 51. Therefore, the leading end of the transfer paper 100 enters the secondary transfer nip N, and the non-entry portion of the transfer paper
If it is set to 1, the nip non-entry portion that has been in close contact with the intermediate transfer belt 41 will be separated from the intermediate transfer belt 41, and poor adhesion between the nip non-entry portion and the intermediate transfer belt 41 will occur. It is.

FIG. 17 shows a circle C1, a circle C2 having a smaller diameter and being in contact with and inscribed at a contact point P3, and a tangent L3 contacting the circles C1 and C2 at the contact point P3. From this figure, it can be understood that the distance between the circle and the region before and after the contact point P3 at the tangent line L3 increases as the diameter of the circle decreases. Circles C1 and C2 correspond to the secondary transfer facing roller 46 in the transfer device of FIG. 15, the contact point P3 corresponds to the nip entrance point P1, and the tangent line L3 corresponds to the nip entrance tangent line L1. Therefore, as the diameter of the secondary transfer opposing roller 46 becomes smaller, the gap between the intermediate transfer belt 41 and the transfer paper 100 on the upstream side of the nip becomes larger, and the above-mentioned poor adhesion is more likely to occur.

In FIG. 16 described above, if the nip entrance tangent line L1 is positioned closer to the rotation center point P2 of the secondary transfer opposing roller than the front surface of the intermediate transfer belt 41, the nip of the transfer paper 100 is not The entry portion can be made to follow the nip entrance tangent line L <b> 1 to positively adhere to the intermediate transfer belt 41.

The present inventors have examined how the nip entrance tangent line L1 can be positioned closer to the rotation center point P2 than the front surface of the intermediate transfer belt 41. I found something like that. That is, FIG.
As shown in (a), when a configuration in which the intermediate transfer belt 41 is simply wound around the secondary transfer opposed roller 46 is considered,
The belt portion upstream of the winding start point P6 of the belt with respect to the secondary transfer opposing roller 46 is tangent to the secondary transfer opposing roller at the winding start point P6. When the nip entrance point P1 is set downstream from the winding start point P6, the nip entrance tangent line L1 is set to the intermediate transfer belt 41.
It is located between the front surface and the secondary transfer roller (not shown), and pre-transfer is induced. Therefore, the nip entrance point P1 is gradually moved upstream from the state shown in the figure, and the nip entrance tangent L1 is gradually brought closer to the intermediate transfer belt 41. Then, when the nip entrance point P1 is moved to substantially the same position as the winding start point P6, the nip entrance tangent L1 can be exactly overlapped with the front surface of the intermediate transfer belt 41 on the upstream side of the nip.

However, it is not enough to simply superimpose, and in order to positively bring the transfer paper (not shown) into close contact with the intermediate transfer belt 41, the nip entrance point P1 is moved further upstream and the nip entrance tangent L1 is It is necessary to move the intermediate transfer belt 41 toward the rotation center point P2 from the front surface.
In order to move the nip entrance point P1 in this way, as shown in FIG. 1B, the belt portion (the non-wound belt portion) that has not been wound around the secondary transfer roller 46 until then is moved to the secondary It is necessary that the transfer roller 51 be brought into contact with the secondary transfer roller 46 on the nip entrance side by pressing. Therefore, the nip entrance tangent line L1 is
In order to position the non-wound belt portion on the rotation center point P2 side of the front surface of the first transfer roller 51 on the assumption that there is no secondary transfer roller 51, the non-wound belt portion is pressed by the secondary transfer roller 51 at the nip entrance side. Partial secondary transfer roller 4
6 need to be contacted. When brought into contact in this way,
As shown in FIG.
Is pressed against the front surface of the intermediate transfer belt 41, and the intermediate transfer belt 41 is bent in an S-order from the upstream side of the nip to the inside of the nip.

As a transfer device in which the intermediate transfer belt 41 is bent in an S-shape, a transfer device described in Japanese Patent Application Laid-Open No. 9-90780 is known. In this publication, figures similar to FIGS. 18 (a) and (b) are described as figures showing an embodiment apparatus. This embodiment avoids pre-transfer caused by poor adhesion between the intermediate transfer belt 41 and the transfer paper 100 on the upstream side of the nip. As shown in each figure, the embodiment apparatus includes a secondary transfer roller 51.
The non-wound portion of the intermediate transfer belt 41 in the case where it is assumed that there is no contact is partially brought into contact with the secondary transfer opposing roller 46 on the nip entrance side by the pressure contact of the secondary transfer roller 51. Therefore, on the upstream side of the nip, a nip entrance tangent (not shown) is positioned closer to the rotation center of the secondary transfer opposing roller 46 than the intermediate transfer belt 41, and the transfer paper 100 is positively brought into close contact with the intermediate transfer belt 41. become.

However, this publication describes an operation that is not related to the nip entrance tangent as an operation for improving the adhesion between the transfer paper 100 and the intermediate transfer belt 41 on the upstream side of the nip. Specifically, "the transfer paper (100) bends in an S-shape so as to follow the shape of the intermediate transfer belt (41) bent from immediately before the transfer nip to the rear end of the transfer nip. (41) and transfer paper (100)
Is improved not only in the transfer area but also immediately before the transfer area. The effect is described.

As shown in FIG. 19, this operation is performed in the pre-contact area R between the intermediate transfer belt 41 and the secondary transfer roller 51 downstream of the nip entrance point P1.
, The transfer paper 100 can be forcibly brought into close contact with the intermediate transfer belt 41 on the upstream side of the nip. Certainly, prior to entering the secondary transfer nip, for the transfer paper portion that has entered the pre-contact area R,
Although the transfer paper portion is forcibly brought into close contact with the intermediate transfer belt 41, the transfer paper portion before entering the pre-transfer region R is not forcibly brought into close contact with the intermediate transfer belt 41 by being pinched. Therefore, if the length of the pre-adhesion region R is too short only by the operation described in the publication, the pre-transfer may occur because the forced adhesion region on the nip upstream side of the transfer paper 100 is insufficient. This means that the length of the pre-adhesion region R must be secured to some extent.

However, as the length of the pre-contact area R is increased, the S-shaped bent portion of the intermediate transfer belt 41 is bent with a larger curvature. There is a possibility that a streak is generated or a color shift occurs in a full-color transfer image. Even in the experiments conducted by the present inventors, when the curvature was increased to a certain extent, horizontal stripes and color shift occurred in the transferred image. These streaks and color shifts are caused by the curvature being too large,
At or near the secondary transfer nip, the intermediate transfer belt 5
This is caused by an excessive pressure applied to the transfer paper 1 or the transfer paper, causing either one to slip slightly (hereinafter, these are referred to as "streaks caused by pressure near the nip").

The present inventors, even when the pre-adhesion region R is relatively short, do not provide the operation described in the above publication but transfer paper 10
It has been considered that the transfer paper 100 can be positively brought into close contact with the intermediate transfer belt 41 on the upstream side of the nip by the action of making the nip non-entering portion of 0 the nip entrance tangent line L1. Then, as shown in FIG. 2, the secondary transfer nip N was formed so that the pre-adhesion region R was slightly generated, and a secondary transfer image was formed. Then, depending on the magnitude of the angle θ1 between the extension line L5 in the moving direction of the front surface S of the intermediate transfer belt 41 and the tangent line L1 at the nip just before contact with the secondary transfer roller 51, the nip upstream side may be illustrated. The transfer paper that was not used could be positively brought into close contact with the intermediate transfer belt 41 due to its stiffness. However, it was found that if the angle θ1 was too small, the adhesion was insufficient. Theoretically, the transfer paper can be positively brought into close contact with the intermediate transfer belt 41 simply by slightly shifting the nip entrance tangent line L1 to the rotation center point 2 side of the front surface S, but actually, In this case, it is considered that the angle θ1 needs to be increased to some extent because the rotation speed of both rollers and the belt influences.

Therefore, the present inventors have examined the occurrence of transfer dust due to the above-mentioned poor adhesion while setting the angle θ1 to various values. Table 1 shows the results of this test. In this test, the radius r1 = 15 [m
m], a secondary transfer roller 51, and a radius r2 = 15 [mm]
And the thickness Tb = 0.15 [m
m] using the intermediate transfer belt 41 and plain paper. The secondary transfer roller 5 of the secondary transfer opposing roller 46
The amount K of biting into 1 was adjusted by the hardness and pressing force of the secondary transfer roller 51. The bite amount K was calculated as "r1 + Tb + r2- (distance M between the centers of both rollers)". Furthermore, the occurrence of transfer dust was investigated, and the occurrence of "streaks due to pressure near the nip" was evaluated as "x (notably observed)", "△ (slightly observed)", "○ not observed" No. rank samples were prepared, and the test was repeated ten times to investigate.

[Table 1]

In the results of the transfer dust in Table 1, "x" indicates that the transfer dust could be confirmed visually, and "△" indicates that the transfer dust was confirmed.
It shows that the transfer dust was able to be confirmed for the first time by the double loupe, and "」 "shows that the transfer dust was not able to be confirmed even by the 10-fold loupe.

As shown in Table 1, under the condition of “0.2 mm ≦ bite amount K ≦ 3.0 mm”, the angle θ1 is set to 5 [°].
With the above setting, it was found that the pre-transfer (transfer dust) caused by the above-mentioned poor adhesion can be effectively suppressed to a level at which visual confirmation is not possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and a first object of the present invention is to provide a structure in which a visible image carrier and a recording member are located upstream of a nip in a moving direction of the visible image carrier. An object of the present invention is to provide a transfer device, a transfer method, an image forming apparatus, and an image forming method that can effectively suppress pre-transfer caused by poor adhesion to the image to a level at which pre-transfer cannot be visually confirmed.

A second object of the present invention is to provide, in addition to the first object, a transfer device capable of effectively suppressing "streaks or the like caused by pressure near the nip".

[0023]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the first aspect of the present invention, there is provided an elastic roller rotatably disposed and rotatably disposed so as to bite into the elastic roller to form a nip. A transfer roller for applying a transfer bias to one of the rollers in order to form a transfer electric field between the two rollers; and a peripheral surface of the transfer roller for carrying a visible image on the front surface. A belt-like visible image carrier that is sandwiched between the nips while moving so as to wind around a part of the surface, and between the elastic roller in the nip and the front surface that is in contact with the elastic roller. In a transfer device that sandwiches a recording member conveyed toward the space between the recording member and the visible image carried on the front surface and transfers the visible image to the recording member,
Assuming that the elastic roller is not provided, the elastic roller is provided with the visible image carrier so that a non-wound portion of the visible image carrier with respect to the bite roller is partially brought into contact with the bite roller on the nip entrance side. The body is pressed against the body, and the amount of the biting roller biting into the elastic roller is set to 0.
It is set to 2 [mm] or more and 3.0 [mm] or less, and
An angle θ1 between an extended line in the moving direction of the visible image carrier immediately before contacting the elastic roller and a tangent to the nip entrance is set to 5 [°] or more.

In this transfer device, the elastic roller is pressed against the visible image carrier so that the non-wound portion of the visible image carrier around the bite roller is partially brought into contact with the bite roller on the nip entrance side. Thus, the nip entrance tangent at the upstream side of the nip is located closer to the rotation center of the biting roller than the front surface of the visible image carrier. Further, the bite roller is made to bite into the elastic roller with a bite amount of 0.2 [mm] or more and 3.0 [mm] or less, and the angle θ1 is made 5 [°] or more, whereby the table shown above is obtained. 1 satisfies the condition of “5 ° ≦ angle θ1”. Therefore, it is possible to effectively suppress the pre-transfer caused by the poor adhesion between the visible image carrier and the recording member upstream of the nip in the moving direction of the visible image carrier to a level at which pre-transfer cannot be visually confirmed.

According to a second aspect of the present invention, in the transfer apparatus of the first aspect, the angle θ
1 is set to 25 [°] or less.

In this transfer device, "25 ° ≧
The angle θ1 ”is satisfied, and“ streaks or the like due to the pressure near the nip ”can be effectively suppressed.

According to a third aspect of the present invention, in the transfer device of the second aspect, the angle θ1 is set to be 15 ° or more and 20 ° or less.

In this transfer apparatus, "1" in Table 1 is used.
5 ° ≦ angle θ1 ≦ 20 ° ”
It is possible to avoid the occurrence of the pre-transfer caused by the above-mentioned poor adhesion immediately before the nip and the occurrence of “streaks or the like caused by the pressure near the nip”.

However, also in this transfer apparatus, there is a possibility that pre-transfer may occur depending on the attitude of the recording member in a region upstream of the nip and relatively far from the nip. Specifically, for example, when the recording member enters the nip after being brought into close contact with the elastic roller instead of the visible image carrier, the recording member is separated from the elastic roller so as to follow the nip entrance tangent just before the nip. Although it is in close contact with the image carrier, it is in close contact with the elastic roller at a position relatively far from the nip, and is in a state of being separated from the visible image carrier. Therefore, in such a case, pre-transfer may occur at a position relatively far from the nip.

Further, immediately before the nip, even if the recording member is to be brought into close contact with the visible image carrier due to its stiffness, the recording member is caused by the speed difference between the linear speed inside the nip and the conveying speed toward the nip. There is also a possibility that the recording member may be deflected to separate the recording member from the visible image carrier and cause poor adhesion. Specifically, the conveying speed of the recording member toward the nip is generally set higher than the linear speed inside the nip for the purpose of suppressing the recording member slip in the nip. With this setting, the recording member is naturally bent upstream of the nip. Then, this bending causes separation from the visible image carrier.

Therefore, the invention of claim 4 is based on claims 1 and 2
Or, in the transfer device of 3, the two guide plates facing each other are provided, and the recording member is caused to pass between the guide plates before the recording member enters the nip, so that the recording member is connected to the nip. The guide is guided toward the visible image carrier on the upstream side in the predetermined direction.

In this transfer device, the recording member is guided toward the visible image carrier on the upstream side of the nip by the two guide plates, so that the recording member and the visible member are relatively away from the nip. Adhesion with the image carrier can be promoted.
Further, when the conveying speed of the recording member toward the nip is higher than the linear speed inside the nip, the recording member is bent at a portion on the upstream side in the conveying direction from a portion where the contact with the visible image carrier is started. Thus, the bending of the recording member immediately before the nip can be suppressed.

According to a fifth aspect of the present invention, there is provided the transfer device according to the first, second, third or fourth aspect of the present invention, wherein the visible image carrier is positioned from the center of the winding around the biting roller when the elastic roller is not provided. Also, the rotation center of the elastic roller is located on the upstream side in the moving direction of the visible image carrier.

In this transfer device, it is assumed that there is no elastic roller by positioning the center of the nip upstream of the winding center of the visible image carrier around the bite roller in the moving direction of the visible image carrier. In such a case, the non-wound portion of the visible image carrier with respect to the biting roller is easily brought into partial contact with the biting roller on the nip entrance side. More specifically, an example using a secondary transfer opposing roller, a secondary transfer roller, and an intermediate transfer belt will be described. As shown in FIG. In the state where the belt is naturally wound, the winding center in the belt moving direction is the position of P8. From this state, as shown in FIG. 3B, while the rotation center point P7 of the secondary transfer roller 51 is positioned on the winding center line L4, the intermediate transfer that has not been in contact with the secondary transfer opposing roller until then. The non-wound portion of the belt 41 is pressed against the secondary transfer roller 51 by the secondary transfer roller
In order to make the secondary transfer roller 51 contact with the secondary transfer roller 51, the secondary transfer roller 51 having a considerably large diameter must be deformed greatly. In such a configuration, there is a possibility that uneven rotation of the secondary transfer roller 51 may occur due to excessive nip pressure, deformation unevenness of the secondary transfer roller 51, and the like. On the other hand, as shown in FIG. 3C, when the secondary transfer nip N is formed while the rotation center point P7 of the secondary transfer roller 51 is positioned upstream of the winding center line L4 in the belt moving direction, the comparison is made. Target diameter 2
The non-wound portion can be brought into contact with the secondary transfer facing roller using the secondary transfer roller 51 and without significantly deforming the secondary transfer roller. Therefore, it is easy to partially contact the non-wound portion on the nip entrance side with the secondary transfer facing roller.

The invention of claim 6 is the invention of claims 1, 2, 3, and 4.
Or the transfer device of 5, wherein an intermediate transfer belt is provided as the visible image carrier, and a contact / separation unit that contacts / separates the elastic roller from / to the front surface of the intermediate transfer belt;
Immediately after the elastic roller is brought into contact with the front surface, the elastic roller is rotated at a linear speed that does not cause a relative speed difference between the elastic roller and the front surface. A mechanism is provided in which the entirety is moved along the front surface so that the biting roller gradually bites into the elastic roller.

In this transfer apparatus, the provision of contact / separation means for bringing the elastic roller and the intermediate transfer belt into and out of contact provides the primary transfer to the intermediate transfer belt several times in a state where both are separated. After transferring the superimposed image, the two are brought into contact with each other and the superimposed image can be collectively transferred to the recording member. Therefore, the superimposed image obtained by repeating the primary transfer can be secondarily transferred onto the recording member. However, when the elastic roller is brought into contact with the front surface of the intermediate transfer belt, excessive stress may be applied to the intermediate transfer belt. Specifically, an example using a secondary transfer facing roller and a secondary transfer roller will be described. As shown in FIG. 4A, the intermediate transfer belt 41 is directed toward the secondary transfer roller 51 on the upstream side of the nip. From the biased state, the intermediate transfer belt 41
When the secondary transfer roller 51 and the secondary transfer roller 51 are separated from each other, the state shown in FIG. That is, a part of the winding portion of the intermediate transfer belt 41 around the secondary transfer opposing roller 46 is
The state is separated from the next transfer opposing roller 46. From this state, in order to return to the state shown in FIG. 4A again, the secondary transfer roller 51 is brought into contact with the intermediate transfer belt 41 portion (non-wound portion) not backed up by the secondary transfer opposing roller 46 at a stretch. I do. Then, a large tension is applied to the intermediate transfer belt 41 to apply an excessive stress. Therefore, in this transfer device, after the elastic roller is brought into contact with the intermediate transfer belt, the elastic roller is moved along the front surface of the intermediate transfer belt, and the biting roller is gradually moved into and out of the elastic roller. Means. In such a configuration, first, the elastic roller is brought into contact with the intermediate transfer belt portion that is backed up by the biting roller, and then moved along the front surface thereof, thereby slightly reducing the tension on the intermediate transfer belt. It becomes possible to give each. Therefore, the elastic roller can be brought into contact with the front surface of the intermediate transfer belt without applying excessive stress to the intermediate transfer belt. When the elastic roller is moved along the front surface of the intermediate transfer belt, the front surface may be damaged by the rubbing between the two. Since the elastic roller is rotated at such a linear velocity as not to cause the damage, the front surface can be prevented from being damaged due to the rubbing.

By the way, the present inventors have conducted intensive studies and found that
In the transfer device according to the first aspect, in addition to the above-mentioned "streaks and the like caused by the pressure near the nip", a horizontal band caused by friction of a guide plate of a thick paper as a recording member, separation of a thick paper guide, a difference in a nip linear velocity, and the like. It has been found that stripes and color shift may occur.

Horizontal band-shaped streaks and color shifts caused by friction of the guide plate of thick paper (hereinafter referred to as "streaks caused by guide plate friction")
Means cardboard and guides it to the nip upstream
These are horizontal stripes or color shifts caused by friction with a single guide plate. This "streak caused by friction of the guide plate"
The cause of the occurrence will be described as follows using an example using a secondary transfer facing roller, an intermediate transfer belt, and a secondary transfer roller. That is, as shown in FIG. 5, the thick paper 101 between the two guide plates (the upper guide plate 52 and the lower upper guide plate 53).
And the thick paper 101 after passing through
If the transport direction is different, the thick paper 101
3 is bent around the end or its vicinity. Even if such a posture is adopted, it does not cause a serious problem when plain paper having relatively excellent flexibility is used as the recording member. However, when the thick paper 101 which is stiffer than the plain paper is used, the upper guide plate 52 in the thick paper 101 is used.
The frictional resistance of the contact portion with the upper and lower guide plates 53 is abnormally increased, and the thick paper 101 being transported is delicately slipped, thereby causing horizontal stripes or color shift. Also, if this frictional resistance is increased to a predetermined level,
The thick paper 101 is continuously slipped to cause a conveyance failure. This frictional resistance increases as the bending angle of the thick paper 101 decreases.

The inventors of the present invention aimed at finding effective conditions for suppressing "striations and the like caused by guide plate friction" and inability to transport the thick paper 101 (inability to transport due to friction in the guide plate).
The following tests were performed. That is, 13 as the thick paper 100
Using 5 kg paper or a government-made postcard, under the condition that the angle θ1 is set to a value that does not cause “streak due to pressure near the nip”, the angle θ2 is set to various values, and The color shift and the state of occurrence of conveyance failure were examined. The angle θ2 is, as shown in FIG. 6, a first contact point P4 where the upper guide plate makes the strongest contact with the thick paper 101, and a second contact point where the lower guide plate makes the strongest contact with the thick paper 101. Of the two corners formed by the curve L6 connecting the three points of the contact point P5 and the nip entry point P1, the angle is the angle facing the elastic roller. The test results are shown in Table 2 below.

[Table 2] As shown in Table 2, it was found that if the angle θ2 was set to 140 ° or more, the inability to transport the thick paper (135 kg paper or government-made postcard) 101 due to the friction of the guide plate could be avoided. However, under the condition of “180 ° ≦ angle θ”, on the upstream side of the nip, the thick paper 101 is not transferred to the intermediate transfer belt 41 by the two guide plates but to the secondary transfer nip N or 2.
Since the guide is directed to the next transfer roller 51, the characteristic configuration of the transfer device according to the second aspect is not provided. Therefore, under the condition of “180 ° ≦ angle θ” as shown in Table 2, transfer dust due to pre-transfer occurs.

According to a seventh aspect of the present invention, there is provided the transfer device according to the fourth, fifth or sixth aspect of the present invention, comprising the two guide plates, wherein the recording member is conveyed while being sandwiched by the nip. A first contact point, which is a part of the contacting guide plate that makes the strongest contact with the recording member, and a first contact point of the recording plate that contacts the surface of the recording member opposite to the recording surface; Of the two angles formed by the curve connecting the three points of the second contact point, which is the site of the strongest contact, and the nip entry point, the angle θ2 of the angle facing the elastic roller is 140 [° ] Or more and less than 180 [°].

This transfer apparatus satisfies the condition of “140 ° ≦ angle θ2 <180 °” in Table 2 above, and as long as plain paper, 135 kg paper or an official postcard is used as a recording member, the friction of the guide plate is increased. Can prevent the recording member from being unable to be conveyed.

According to an eighth aspect of the present invention, in the transfer device of the seventh aspect, the angle θ2 is set to 155 [°] or more.

This transfer device satisfies the condition of “155 ° ≦ angle θ2 <180 °” in Table 2 above, and as long as plain paper, 135 kg paper, or an official postcard is used as a recording member, the “guide plate” is used. The occurrence of "streaks or the like" caused by friction can be avoided.

However, also in this transfer device, if 135 kg paper or a postcard made thicker than an official postcard is used as a recording member, there is a possibility that "streaks or the like caused by friction of the guide plate" may occur. Therefore, the present inventors conducted a similar test using 200 kg paper as the thick paper 101. The test results are shown in Table 3 below.

[Table 3]

As shown in Table 3, the angle θ2 is set to 160
It has been found that, when set to [°], even when 200 kg paper is used as the thick paper, it is possible to avoid “streaks and the like due to guide plate friction” and to be unable to convey due to guide plate friction.

Therefore, a ninth aspect of the present invention is the transfer apparatus of the eighth aspect, wherein the angle θ2 is set to 160 °.

In this transfer apparatus, as long as plain paper, 135 kg paper, government-made postcard or 200 kg paper is used as the recording member, "streaks and the like caused by guide plate friction" It is possible to avoid the inability to carry.

On the other hand, the above-described horizontal band-shaped streaks or color shifts caused by the separation of the thick paper (hereinafter referred to as “stripe caused by the separation of the guides”) are caused by vibrations when the thick paper is separated from the guide plate. Horizontal stripes and color shifts caused by the The cause of the occurrence of "streaks or the like due to guide separation" will be described below with reference to an example using a secondary transfer opposing roller, an intermediate transfer belt, a secondary transfer roller, and thick paper. That is, as shown in FIG. 7, when the thick paper 101, which is stiffer than plain paper, separates from the upper guide plate 52 in the upstream of the nip as the paper is conveyed, the thick paper 101 is immediately released from the regulating force of the upper guide plate 52. The rear end portion jumps up toward the intermediate transfer belt 41 and vibrates so as to follow the posture of the preceding portion. This vibration is transmitted to the close contact portion between the intermediate transfer belt 41 and the thick paper 101 immediately before the nip, and the two are delicately repeatedly contacted and separated, so that a horizontal band-shaped streak or color shift occurs.

In order to suppress such “streaks or the like caused by separation of the guide”, the tip of the upper guide plate 52 is brought as close as possible to the intermediate transfer belt 41, and the thick paper 101 at the time of separation is removed.
It is conceivable to minimize the amount of bounce of the ascending. However, when the leading end of the upper guide plate 52 is brought closer to the intermediate transfer belt 41, the toner scattered from the intermediate transfer belt 41 easily stains the vicinity of the leading end. Upper guide plate 5
If the vicinity of the leading end of No. 2 is contaminated with toner, the toner rubs against a recording member such as the thick paper 101 that contacts the vicinity of the leading end, and a rubbed stain image is generated. In particular, when the thick paper 101 is used as the recording member, the thick paper 101 is rubbed violently with the toner adhering to the vicinity of the leading end, so that a rubbed stain image is easily generated. On the other hand, as a method of suppressing toner adhesion to the guide plate, a method of applying a bias having a polarity opposite to that of the toner to the guide plate is known. However, this method requires a new dedicated bias applying unit, which is costly. It will be high.

According to a tenth aspect of the present invention, in the transfer device of the fourth, fifth, sixth, seventh, eighth or ninth aspect, the recording member is conveyed while being sandwiched by the nip. The end of the guide plate, which is in contact with the recording surface, on the downstream side in the recording member moving direction is formed of a flexible member.

In this transfer apparatus, before the recording member such as thick paper separates from the guide plate such as the upper guide plate 52 which comes into contact with the recording surface of the recording member, the end of the guide plate is removed. The flexible member is urged toward the rear end of the recording member to flex flexibly toward the visible image carrier such as the intermediate transfer belt 41. When the flexible member bends in this manner, the jump of the rear end of the recording member when separating from the flexible member is reduced, and the vibration of the recording member caused by the jump is suppressed. As a result, "streaks or the like due to the guide separation" can also be suppressed.
When the flexible member bends, its tip approaches the visible image carrier, but the approach time is short, and
The visible image carrier portion facing the leading end when approaching is not an image area corresponding to the recording member but a non-image area, and therefore does not carry a visible image. For this reason, compared to the case where the tip of the guide plate is always kept close to the visible image carrier, adhesion of a coloring substance such as toner to the tip can be suppressed, and generation of a stain image can be suppressed. Therefore, in this transfer device, it is possible to suppress "streaks and the like caused by separation of the guide" while suppressing the generation of a stained image caused by staining the tip of the guide plate with the coloring substance. Further, the stain image can be suppressed without providing a bias applying unit to the guide plate.

However, depending on the thickness of the recording member, the flexible member cannot be flexed sufficiently, and the effect of suppressing "streaks or the like caused by the separation of the guide" cannot be sufficiently exhibited or the flexure is excessively flexed. Therefore, there is a possibility that the toner may be brought into contact with the visible image carrier and stained with a coloring substance. Therefore, the present inventors have examined the relationship between the difference in thickness of the recording member and the occurrence of "streaks and the like caused by separation of the guide" and the occurrence of a stain image. Then, in this test, the difference between the flexure amount of the flexible member when the thinnest recording member was used and the flexure amount of the flexible member when the thickest recording member was used was 0.5 [ mm], the amount of flexure of the flexible member when a relatively thin recording member is used is insufficient, and “streaks or the like due to separation of the guide” is generated.
Further, it was found that when the above difference exceeded 3.0 [mm], the amount of flexure of the flexible member when a relatively thick recording member was used was excessive, and a stain image was generated.

In view of this test result, a transfer device according to a tenth aspect of the present invention is the transfer device according to the tenth aspect, wherein upper and lower limits of the thickness of the usable recording member are designated, and the flexible member is brought into contact with the lower limit of the recording member. The difference between the amount of deflection of the flexible member and the amount of deflection of the flexible member due to contact with the upper limit recording member is 0.5
The flexible member adjusted to be not less than [mm] and not more than 3.0 [mm] is provided.

In this transfer apparatus, the upper and lower limits of the thickness of the usable recording member are specified, for example, by being specified in the main body of the apparatus or in an instruction manual, and the recording member having a thickness within the specified range is used. As far as possible, it is possible to suppress "streaks or the like caused by separation of the guide" due to the difference in the amount of flexure of the flexible member and the above-described stained image.

On the other hand, the above-mentioned horizontal band-shaped streaks or color shifts (hereinafter, referred to as “stripes caused by the nip linear speed difference”) caused by the nip linear speed difference are defined as the intermediate transfer belt 41 in the nip during transfer. Is a horizontal band-shaped streak or color shift caused by a linear velocity difference between a visible image carrier such as the above and an elastic roller such as the secondary transfer roller 51. The cause of the occurrence of “streaks or the like due to the difference in nip linear velocity” will be described below.
That is, if there is a linear velocity difference (nip linear velocity difference) between the visible image carrier and the elastic roller in the nip, the two rub against each other while being brought into close contact with each other by the nip pressure. This rubbing causes a slight speed difference between the visible image carrier and the recording member sandwiched between the nips, resulting in "streaks or the like due to the nip linear speed difference". In particular, as in the transfer device according to the present invention, when the visible image carrier is brought into close contact with the elastic roller even immediately before the nip,
Since a slight speed difference is generated even at the contact portion, "streaks or the like due to the nip linear speed difference" is more likely to occur. Also, if there is a difference in the nip linear velocity, a stretched image having expansion and contraction in the recording member conveyance direction is likely to be generated. Specifically, although the cause is unknown, when the thickness of the recording member is relatively thick, the conveying speed of the recording member by the nip is increased, so that an elongated image is easily generated, and when the thickness is relatively thin, The conveyance speed is reduced, and a contracted image is easily generated.

Therefore, the present inventors conducted tests on the occurrence of horizontal band-shaped streaks and color shifts when no nip linear velocity difference was provided and when various nip linear velocity differences were provided. . The results of this test are shown in Table 4 below.

[Table 4]

In Table 4, "Nip linear velocity difference = 100.
"00%" indicates that there is no nip linear velocity difference. Table 4
As shown in FIG.
Just by setting [%], “difference due to the difference in nip linear velocity” is slightly recognized. It can be seen that in order to avoid this, the difference in nip linear velocity must be eliminated. Since it is extremely difficult to completely eliminate the nip linear velocity difference, if it is 100.10 [%] or less, it may be considered that there is no nip linear velocity difference.

In view of the test results, the invention of claim 12 is based on claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Alternatively, in the transfer device according to the eleventh aspect, the linear velocity of the visible image carrier and the linear velocity of the elastic roller during transfer are set to be the same.

In this transfer device, since there is no rubbing between the visible image carrier and the elastic roller in the nip, a delicate speed difference does not occur between the two.
The occurrence of "streaks or the like due to the nip linear velocity difference" can be avoided. In addition, it is possible to avoid the occurrence of a stretched image due to the nip linear velocity difference.

However, the difference in nip linear velocity may be intentionally provided in order to reduce the cohesive force of a coloring substance such as toner in the nip. Specifically, a superimposed image having a relatively large amount of the coloring substance attached thereto is collectively secondarily transferred,
When a character image or a line image is transferred to an OHP sheet, a hollow image in which a part of the image is not partially transferred easily occurs. The cause of the occurrence of the hollow image will be described with reference to an example in which toner is used as a coloring substance.
That is, in the nip, the transfer is performed while applying the nip pressure to the toner image, so that the toner particles constituting the toner image are positively aggregated. When the visible image carrier and the recording member are separated from each other at the nip exit, each toner particle aggregates with a remarkably strong cohesive force, and the adhesive force between the visible image carrier and the toner and the cohesive force between each toner particle But,
If the adhesive force between the toner and the recording member is exceeded, the toner may not be transferred onto the recording member and may remain on the visible image carrier. Then, a hollow image occurs due to the residual. In the case of a superimposed image, more toner is attached than in a normal image, and the cohesive force between the toner particles in the nip is increased, so that a hollow image is easily generated. Also, in the case of an OHP sheet, unlike a transfer paper or the like which can penetrate the toner into the paper fibers, the smooth surface of the OHP sheet weakens the adhesive force with the toner, so that a hollow image easily occurs. . Further, since the character image and the line image 8 (especially the vertical line image) are easily given a concentrated weight in the nip, a hollow image on the OHP sheet is more likely to occur. On the other hand, if a nip linear velocity difference is provided, a shift stress acts on the toner layer in the toner image,
The agglomerated toner layer can be collapsed to reduce the aggregating power of the toner. As a result, it is possible to suppress the occurrence of a blank image.

Accordingly, the present inventors have developed a nip linear velocity difference when a full-color character image is transferred using plain paper (Ricoh: Type 6000 70W) or OHP sheet (Ricoh: PPC-FC). A test was conducted to investigate the relationship between the occurrence state of the hollow image and the occurrence state of "streaks and the like due to the difference in nip linear velocity". Table 5 shows the results of this test. In addition, about the result of the hollow image,
A sample of the rank was created and judged. Further, as an intermediate transfer belt as a visible image carrier, an elastic belt having an elastic layer and a lower layer coated on a surface layer constituting a front surface and an inelastic belt having only the lower layer coated on the surface layer were used. .

[Table 5]

In the results of the hollow image in Table 5, "○"
Indicates that no hollow image is generated, and “△” indicates that a slight hollow image is generated. As shown in Table 5, the nip linear velocity difference (10
(0.80%), it is possible to avoid the occurrence of a hollow image due to toner aggregation on both plain paper and the OHP sheet, but “streaks or the like due to a difference in nip linear velocity” occur. Let me do it. Further, when the nip linear velocity difference is not provided (100.00%), although "streaks or the like caused by the nip linear velocity difference" can be avoided, a hollow image is generated on the OHP sheet. On the other hand, when the elastic belt is used, it can be seen that the occurrence of the hollow image on the OHP sheet is sufficiently suppressed even though the nip linear velocity difference is not provided. Because the elastic layer is flexibly deformed in the nip according to the thickness of the character image, the weight on the character image is reduced and the cohesive force of the toner is not so strong. The occurrence of "streaks" was suppressed.

In view of the test results, the invention of claim 13 is the transfer device of claim 12, wherein the visible image carrier is constituted by at least a surface layer forming the front surface and an elastic layer. It is characterized by the following.

In this transfer device, the elastic layer is flexibly deformed in the nip according to the thickness of the visible image.
Aggregation of a coloring substance such as toner constituting the visible image can be suppressed, and generation of “streaks or the like due to a difference in nip linear velocity” can be suppressed. Also, since there is no nip linear velocity difference,
It is possible to avoid "streaks or the like caused by the difference in nip linear velocity" or generation of a stretched image caused by the difference in nip linear velocity.

According to a fourteenth aspect of the present invention, there is provided a nip forming step in which a rotatable biting roller is bitten by a rotatable elastic roller to form a nip; A step of moving the image carrier so as to be wound around a part of the peripheral surface of the biting roller and sandwiching the image carrier in the nip; and applying a transfer bias to one of the rollers to form a transfer electric field between the two rollers. Applying the recording member, and conveying the recording member between the elastic roller in the nip and the front surface that is in contact with the elastic roller, and sandwiching the recording member. Transferring the visible image to the recording member, wherein in the nip forming step, the visible image carrier is not wound around the biting roller when the elastic roller is assumed to be absent. The so as to partially contact with the bite roller at the nip inlet side, the bite roller 0.
The elastic roller is pressed against the visible image carrier while being bitten into the elastic roller by a bite amount of 2 mm or more and 3.0 mm or less, and the visible image immediately before contacting the elastic roller is pressed. The angle θ1 between the extension line in the moving direction of the carrier and the tangent to the nip entrance is set to 5 [°] or more.

In this transfer method, pre-transfer caused by poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the conveying step is visually observed by the same operation as the transfer device of the first aspect. Can be effectively suppressed to a level where it is not confirmed.

According to a fifteenth aspect of the present invention, there is provided a latent image carrier for carrying a latent image, a developing means for developing the latent image on the latent image carrier, and a visual image obtained by the development. 3. An image forming apparatus comprising: a transfer device for transferring a latent image carrier, which is a carrier, directly to a recording member via an intermediate transfer member, which is a visible image carrier, to a recording member. , 3, 4, 5, 6, 7, 8, 9, 10, 11, 1
It is characterized in that two or thirteen transfer devices are provided.

In this image forming apparatus, the pre-transfer caused by poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the transfer device is suppressed by the same operation as the transfer device of the first aspect. be able to.

According to a sixteenth aspect of the present invention, there is provided a step of carrying a visible image on a front surface of a belt-shaped visible image carrier, and a step of making a rotatable elastic roller bite a rotatable biting roller to form a nip. A nip forming step of forming, and a step of sandwiching the visible image carrier holding the visible image in the nip while moving the visible image carrier to be wound around a part of the peripheral surface of the biting roller; and Applying a transfer bias to the elastic roller to form a transfer electric field, and conveying and nipping the recording member between the elastic roller in the nip and the front surface in contact with the elastic roller. In an image forming method for forming an image on the recording member by performing a conveying step and a step of transferring a visible image of the front surface to the recording member at the nip, the nip forming step includes: Assuming there is no elastic roller In such a case, the bite roller is set to 0.2 mm or more and 3.0 mm so that the non-wound portion of the visible image carrier with respect to the bite roller is partially brought into contact with the bite roller at the nip entrance side. The elastic roller is pressed against the visible image carrier while being bitten into the elastic roller by the following bite amount, and the extension line in the moving direction of the visible image carrier immediately before contacting the elastic roller; The angle θ1 with the tangent is set to 5 [°] or more.

In this image forming method, the pre-transfer caused by the poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the transporting step is visually observed by the same operation as the transfer device of the first aspect. Can be effectively suppressed to a level where it is not confirmed.

[0071]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic color printer (hereinafter, referred to as a color printer) as an image forming apparatus will be described. First,
The schematic configuration and operation of the color printer according to the present embodiment will be described with reference to FIG. This color printer 1
Are a photoconductor unit 10, a writing optical unit 20,
Developing unit 30, transfer unit 4 as transfer device
0, fixing unit 60, double-sided printing paper reversing unit 7
0, a transfer paper cassette 80, a manual feed tray 83, and the like. Black: black (hereinafter, referred to as Bk), Cyan: cyan (hereinafter, referred to as C), Mage
nta: Magenta (hereinafter referred to as M), Yellow:
The yellow (hereinafter, referred to as Y) color image is sequentially visualized on the photoreceptor belt 11 of the photoreceptor unit 10, and these are superimposed to form a final four-color full-color image.

The photoreceptor belt 11 rotates clockwise as indicated by an arrow A. Around the photoreceptor cleaning device 1
2, a charging roller 13, a developing unit 30, a transfer unit 40 and the like are arranged. The photoreceptor belt 11 includes a driving roller 14, a primary transfer opposing roller 15, a tension roller 16
It is stretched between and rotated in the direction of arrow A with the rotation of the drive motor. When the photoconductive belt 11 having a seam is used, a seam mark is provided in a non-image forming area at the end of the photoconductive belt 11 and detected by a sensor (not shown). It is preferable that the optical writing be performed later.

The writing optical unit 20 includes a semiconductor laser 21, a laser light emission drive control unit (not shown), a polygon mirror 22, three reflection mirrors 23a, b, c, and the like. A color image data from a personal computer (not shown) or the like is received and converted into an optical signal. Based on the color signal, optical writing corresponding to each color image is performed on the photosensitive belt 11 to form an electrostatic latent image.

The developing unit 30 includes a Bk developing device 31
K, C developing device 31C, M developing device 31M, Y developing device 31
Y, moving each developing unit in the left-right direction in the figure to move the photosensitive belt 1
1 is provided with a contact / separation mechanism (not shown) for performing a contact / separation operation. Each of the developing units 31K, C, M, and Y includes a developing sleeve 32K, C, M, and Y that rotates while supporting a developer on the surface to develop an electrostatic latent image on the surface of the photoreceptor belt 11. Developer paddles 33K, C, M, and Y that rotate to pump and stir the toner, and developer storage cases 34K, C, M, and Y that store the toner. In the illustrated example, a Bk developing device 31K containing black toner, a C developing device 31C containing cyan toner, an M developing device 31M containing magenta toner, and a M developing device 31M containing magenta toner in order from the lower side of the apparatus main body.
The Y developing device 31Y contains yellow toner. The toner in each of the developing units 31K, C, M, and Y is charged to a predetermined polarity. On the other hand, each developing sleeve 32K,
A developing bias is applied to C, M, and Y by a developing bias power supply (not shown), and the developing sleeves 32K, C, M, and
Y is biased at a predetermined potential with respect to the photosensitive belt 11.

The contact / separation mechanism of the developing unit 30 includes:
When an electromagnetic clutch (not shown) for transmitting a drive from a motor (not shown) to each of the developing units 31K, C, M, and Y is turned on, the driving force of the electromagnetic clutch 34K, C, M, and
Y is moved to the photoreceptor belt 11 side (right side in the figure). At the time of development, each developing unit 31K, C, M, Y
The selected one of them moves and comes into contact with the photoreceptor belt 11. On the other hand, when the electromagnetic clutch is turned off to cancel the drive transmission, the developing device that has been in contact with the photoreceptor belt 11 moves in a direction away from the photoreceptor belt 11 (left side in the figure).

In the standby state of the main body of the color printer, the developing unit 30 is set at a position where all the developing units 31K, C, M, and Y are separated from the photoreceptor belt 11. Optical writing with a laser beam and formation of an electrostatic latent image are started based on the image data (hereinafter, an electrostatic latent image based on Bk image data is referred to as a Bk electrostatic latent image, and the same applies to C, M, and Y). Before the front end of the electrostatic latent image reaches the Bk development position so as to enable development from the front end of the Bk electrostatic latent image, the Bk developing sleeve 32K starts rotating, and the Bk electrostatic latent image is filled with Bk toner. develop. Thereafter, the developing operation of the Bk electrostatic latent image area is continued.
When the trailing edge of the electrostatic latent image passes the Bk development position, Bk
The developing device 31K is separated from the photosensitive belt 11, and the developing device of the next color immediately contacts the photosensitive belt 11. This is completed at least before the leading end of the electrostatic latent image based on the next image data reaches the developing position.

The transfer unit 40 includes an intermediate transfer belt 41, a belt cleaning device 42, a position detecting sensor 43, a driving roller 44, a primary transfer roller 45, a secondary transfer opposed roller 46, a secondary transfer opposed roller 46, and a cleaning unit. An opposing roller 47, a waste toner tank 49, a secondary transfer roller 51, an upper guide plate 52, a lower guide plate 53, a secondary transfer bias applying unit (not shown), a secondary transfer roller contacting / separating unit, and the like are provided.

The intermediate transfer belt 41 as a visible image carrier is stretched around a driving roller 44, a primary transfer roller 45, a secondary transfer opposing roller 46 serving as a biting roller, and a cleaning opposing roller 47. The drive roller 44 is rotated in the direction of arrow B in FIG. A plurality of position detection marks (not shown) are provided in an area where an image is not transferred near the belt edge of the intermediate transfer belt 41, and any one of these position detection marks (image forming The position detection sensor 43 detects a position detection mark which first passed through the position detection sensor 43 at the start of the operation, and starts image formation at this detection timing.

The belt cleaning device 42 includes a cleaning brush 42a, a contact / separation mechanism (not shown), and the like.
During the next transfer and during the first transfer of the second, third, and fourth color images to the intermediate transfer belt 41, the cleaning brush 42a is separated from the surface of the intermediate transfer belt 41 by the contact / separation mechanism.
Away from each other. The toner cleaned from the surface of the intermediate transfer belt 41 by the belt cleaning device 42 is stored in a waste toner tank 49 provided inside the transfer unit 40.

The secondary transfer roller contacting / separating means also performs the primary transfer of the first color Bk image onto the intermediate transfer belt 41.
And the images of the second, third, and fourth colors are
During the next transfer, the secondary transfer roller 51 is separated from the surface of the intermediate transfer belt 41. The secondary transfer roller 51 is moved to the intermediate transfer belt 41 before the full-color transfer image formed by the superimposed primary transfer on the intermediate transfer belt 41 reaches the position facing the secondary transfer facing roller 46. To the transfer surface (front surface).
Due to this contact, the secondary transfer opposing roller 46 formed of a rigid material such as metal cuts into the secondary transfer roller 51 formed of an elastic material via the intermediate transfer belt 41 to form a secondary transfer nip. .

A transfer paper (not shown) as a recording member is stored in the transfer paper cassette 80, and is conveyed toward a registration roller pair 82 by paper feed rollers 81a, 81b, and 81c.

The manual feed tray 83 is provided on the right side of the main body of the color printer 1 so as to be openable and closable, and sends out OHP paper or thick paper to the pair of registration rollers 82.

The registration roller pair 82 is used to transfer a recording member such as transfer paper sent from the transfer cassette 80 or the manual feed tray 83 to the full-color transfer image on the intermediate transfer belt 4.
The sheet is sent to the secondary transfer nip at a timing when it is sandwiched by the secondary transfer nip with the movement of 1. The secondary transfer bias applying unit of the transfer unit 40 applies a secondary transfer bias having a polarity opposite to that of the toner to the secondary transfer roller 51, and connects the secondary transfer roller 51 in contact with the intermediate transfer belt 41 to the secondary transfer roller 51. A secondary transfer electric field is formed between the transfer counter roller 46 and the transfer counter roller 46. In the secondary transfer nip, the full-color transfer image sandwiched between the transfer surface of the intermediate transfer belt 41 and the transfer paper is separated from the transfer surface of the intermediate transfer belt 41 by the action of the nip internal pressure and the secondary transfer electric field. It is secondarily transferred to transfer paper.

Each of the above units can be easily detached from the apparatus. For example, in FIG. 8, when removing the transfer unit 40, the front cover (not shown) is opened, and the unit can be easily removed by sliding the unit from the back side to the front side of the paper.

In the color printer 1 having the above configuration,
When the image forming operation is started, first, the photosensitive belt 11 is rotated clockwise as indicated by an arrow A, and the intermediate transfer belt 41 is rotated counterclockwise as indicated by an arrow B. And the photoreceptor belt 1
A Bk toner image, a C toner image, an M toner image, and a Y toner image are sequentially formed on 1, and primary-transferred onto the intermediate transfer belt 41. It is general to gradually increase the primary transfer bias applied to the primary transfer roller 45 at the time of the primary transfer of the superimposition. However, depending on the resistance characteristics of the intermediate transfer belt 41, a predetermined primary transfer bias is applied. A transfer bias may be applied.

The Bk toner image is formed as follows. That is, the charging roller 13 to which a charging bias is applied by a power supply (not shown) rotates while contacting the photosensitive belt 11 to uniformly charge the surface thereof. The surface of the charged photoreceptor belt 11 is exposed to a laser beam LD based on a Bk color image signal. By this exposure, a charge proportional to the exposure amount is lost from the exposed portion of the photoreceptor belt 11 which is initially uniformly charged, and a Bk electrostatic latent image is formed. When the Bk toner on the Bk developing sleeve 32K comes into contact with the Bk electrostatic latent image as the photosensitive belt 11 moves, the Bk electrostatic latent image is developed into a Bk toner image. The developed Bk toner image is transferred to the primary transfer facing roller 15 and the primary transfer roller 4.
5 comes in contact with the intermediate transfer belt 41 at the primary transfer position where the primary transfer nip is formed by contacting via two belts (photosensitive belt 11 and intermediate transfer belt). This one
At the next transfer position, a primary transfer bias is applied to the primary transfer roller 45 by a power supply (not shown), and a primary transfer electric field is formed between the two rollers. The Bk toner image in contact with the intermediate transfer belt 41 is primarily transferred onto the intermediate transfer belt 41 by the action of the nip internal pressure and the primary transfer electric field.

Some untransferred residual toner on the photoreceptor belt 11 is cleaned by the photoreceptor cleaning device 12 in preparation for reuse of the photoreceptor belt 11. The collected toner is stored in a waste toner tank (not shown) via a collection pipe.

On the photosensitive belt 11 side, the process proceeds to the C image forming step after the Bk image forming step, and the position detecting sensor 4
In accordance with the detection timing of 3, the writing by the laser light LD with the C image data is performed, and a C electrostatic latent image is formed. Then, after the trailing end of the previous Bk electrostatic latent image has passed and before the leading end of the C electrostatic latent image has arrived, the Bk developing device retreats from the developing position, and the C developing device C moves to the developing position. And the C electrostatic latent image is developed with C toner. Thereafter, the development of the C electrostatic latent image area is continued, but when the rear end of the C electrostatic latent image passes, the C developing device C is retracted from the developing position as in the case of the Bk developing device B. Then, the next M developing device M is moved to the developing position. This is also completed before the leading end of the next M electrostatic latent image reaches the developing position. The M and Y image forming processes are the same as those of the above-described Bk and C processes, respectively, because the operations of forming and developing the electrostatic latent image are omitted.

In the secondary transfer nip, the intermediate transfer belt 41
The transfer paper on which the full-color transfer image is secondarily transferred from
After passing through the secondary transfer nip, the toner is sent to the fixing unit 60, and when passing between the fixing belt 61 and the pressure roller 62 controlled at a predetermined temperature, the full-color transfer image is fused and fixed. (Arrow C direction). Then, the sheets are stacked on the sheet discharge tray 84 face down.

When double-sided printing is performed, the transfer paper that has passed through the fixing unit 60 is guided by the double-sided switching claw 85 in the direction of arrow D, and the double-sided printing paper reversing unit 7 is moved.
Sent to 0. After the rear end of the transfer paper has passed the reversing switching claw 71, the reversing roller pair 72 stops, and the transfer paper also stops. Then, the reversing roller pair 72 starts reversing after a certain blank time, and the transfer paper starts to switch back. At this time, the reversing switching claw 71 is switched, and the transfer paper is guided in the direction of arrow E and sent to the registration roller pair 82. The transfer paper sent to the pair of registration rollers 82 stands by at the nip of the pair of registration rollers 82 in a state where the transfer paper is turned upside down. And
The registration roller pair 82 is driven at a predetermined timing,
After the transfer paper is sent to the secondary transfer position and the four-color superimposed toner image is collectively transferred from the intermediate transfer belt 41, the toner image is fused and fixed by the fixing unit 60 and sent out of the apparatus main body.

The surface of the photoreceptor belt 11 that has passed the primary transfer position is cleaned by a photoreceptor cleaning device 12, and is uniformly discharged by a discharge lamp (not shown).
Further, the surface of the intermediate transfer belt 41 after the transfer of the toner image to the transfer paper is cleaned by pressing the cleaning brush 42a of the belt cleaning device 42 by the contact / separation mechanism. The toner cleaned from the intermediate transfer belt 41 is stored in a waste toner tank 49.

Next, the color printer 1 according to the present embodiment
Will be described. FIG. 9 is a schematic diagram showing a peripheral configuration of the secondary transfer nip of the color printer 1. The transfer paper (not shown) enters the secondary transfer nip N from the right side in the figure as shown by the arrow in the figure. As shown in the drawing, in the color printer 1, the secondary transfer facing roller 46 formed of a rigid material cuts into a secondary transfer roller 51 which is an elastic roller formed of an elastic material to form a secondary transfer nip N. The nip portion of the recording member such as transfer paper (not shown) moves along the circular orbit of the secondary transfer opposed roller 46 in the nip. The recording member that moves in this manner has a nip entrance tangent line L corresponding to a portion immediately before being sandwiched by the nip (a portion immediately before the nip enters).
Have a posture that mimics 1.

When the intermediate transfer belt 41 is naturally wrapped around the secondary transfer opposing roller 46, the non-wound portion that should not originally come into contact with the intermediate transfer belt 41 is pressed against the secondary transfer roller 51 at the nip entrance side. Thus, the toner is brought into contact with the secondary transfer opposing roller 46 and taken into the nip. For this reason, the nip entrance tangent line L1 is located closer to the rotation center point P2 than the transfer surface S of the intermediate transfer belt 41.

When the leading end of the transfer paper (not shown) enters the secondary transfer nip N and moves along the circular orbit of the secondary transfer opposing roller in the nip, the part immediately before the nip enters has a strong waist. By doing so, the posture is made to follow the nip entrance tangent line L1. Then, the portion immediately before the nip entry positively contacts the transfer surface L7 of the intermediate transfer belt 41. Therefore, pre-transfer caused by poor adhesion between the intermediate transfer belt and the recording member on the upstream side of the nip can be suppressed.

This color printer has a 2
The rotation center point P7 of the next transfer roller 51 is positioned upstream of the center line L4 around which the intermediate transfer belt 41 is wound around the secondary transfer opposing roller 46 in the belt movement direction. The non-wound portion is easily brought into contact with the secondary transfer facing roller 46.

The intermediate transfer belt 41 on the upstream side of the nip
The intermediate transfer belt 41 has a secondary transfer roller 51
There is provided an urging member 48 for urging toward.

The bite amount of the secondary transfer opposing roller 46 into the secondary transfer roller 51 (including the thickness of the intermediate transfer belt 41) is 0.2 [mm] or more and 3.0 [m].
m] is set in the following range. The angle θ1 between the nip entrance tangent L1 and the transfer surface S of the intermediate transfer belt 41
Is set in the range of 15 ° to 20 °. By these settings, Table 1 shown earlier
Has the condition of “15 ° ≦ angle θ1 ≦ 20 °”,
In addition to avoiding the occurrence of pre-transfer caused by the above-mentioned poor adhesion, it also avoids "streaks and the like caused by pressure near the nip".

FIG. 10 shows a modification of the urging member 48.
FIG. 2 is a schematic diagram showing one roller and an intermediate transfer belt 41 together. In the figure, the urging member 48 is a driven urging roller that rotates in contact with the back surface of the intermediate transfer belt 41. In such a driven urging roller, the intermediate transfer belt 4
1 does not rub against the back surface, and the back surface can be prevented from being damaged by the rubbing.

Next, a description will be given of a color printer of each embodiment in which a more characteristic configuration is added to the color printer 1 according to this embodiment. [Embodiment 1] FIGS. 11A to 11C are schematic diagrams each showing a peripheral configuration of a secondary transfer nip in a color printer of Embodiment 1. FIG. In FIG. 11A,
The secondary transfer roller 51 separated from the intermediate transfer belt 41 is brought into contact with the intermediate transfer belt 41 as follows by a secondary transfer roller contacting / separating unit (not shown). That is, first, as shown in FIG.
The intermediate transfer belt 41 is backed up by the secondary transfer opposing roller 46 and is brought into contact therewith. And FIG.
As shown in FIG. 1C, the intermediate transfer belt 41 is moved to a target stop position along the transfer surface, and a tension is gradually applied to the intermediate transfer belt 41. During this movement, the secondary transfer roller 51 is driven or driven to rotate at a linear speed that does not cause a relative speed difference with the transfer surface of the intermediate transfer belt 41. In such a configuration,
The secondary transfer roller 51 can be brought into contact with the intermediate transfer belt 41 without applying excessive stress to the intermediate transfer belt 41.

As a transfer device capable of suppressing the application of excessive stress as described above, a transfer device disclosed in Japanese Patent Application Laid-Open No. Hei 10-133497 is known. However, this publication does not mention the rotation of the moving secondary transfer roller (transfer roll), and depending on the presence or absence of rotation and the rotation speed,
There is a possibility that the transfer surface may be damaged by rubbing against the intermediate transfer belt 41 during the movement. On the other hand, in the color printer of the first embodiment, since the moving secondary transfer roller 46 is rotated at such a speed that the secondary transfer roller 46 does not rub against the intermediate transfer belt 41, it is possible to avoid the occurrence of such damage.

[Embodiment 2] FIG. 12 is a schematic diagram showing a peripheral configuration of a secondary transfer nip in a color printer according to Embodiment 2 of the present invention. In the drawing, P4 indicates a first contact point, which is a portion of the upper guide plate 52 that comes into contact with the recording surface of the cardboard 101 serving as a recording member, where the cardboard 101 comes into strongest contact with the cardboard 101. Further, P5 indicates a second contact point which is a portion of the lower guide plate 53 that comes into contact with the non-recording surface of the thick paper 101, where the strongest contact is made with the thick paper 101. Also, P1
Indicates a nip entrance point P1 in the secondary transfer nip N. These first contact point P4, second contact point P5,
Of the two corners formed by the curve L6 with the nip entrance point P1, the angle θ2 of the corner facing the secondary transfer facing roller is set to 160 [°]. In such a configuration, the thick paper 1 is formed by the two guide plates 52 and 53.
01 is guided toward the intermediate transfer belt 41 upstream of the secondary transfer nip N. Unlike the case where the cardboard 101 is guided toward the secondary transfer roller 51, the cardboard 101 may promote the close contact between the cardboard 101 and the intermediate transfer belt 41 even at a position relatively far from the secondary transfer nip N. it can. In addition, the cardboard 101 is bent not immediately before the nip but in a portion downstream of the contact start point with the intermediate transfer belt 41 in the transport direction, so that the deflection immediately before the nip can be suppressed. Further, the angle θ2 is set to 160
As set in [°], as shown in the test shown in Table 3, as long as plain paper, 135 kg paper, government-made postcard, or 200 kg paper is used as the recording member, the “stripe caused by the friction of the guide plate” is used. And the like, and the inability to transport the recording member due to the friction of the guide plate can be avoided.

[Embodiment 3] FIG. 13 is a schematic view showing a peripheral configuration of a secondary transfer nip N in a color printer according to Embodiment 3 of the present invention. In the figure, the tip of the upper guide plate 52 (the tip on the downstream side in the moving direction of the thick paper 101) is a 0.1 [mm] thick mylar, a polyurethane sheet, a flexible resin sheet,
It is formed of a flexible member 52a such as a rubber sheet.
The guide plate portion other than the tip is formed of a rigid material such as plastic, and the amount x of the flexible member 52a protruding from the rigid material is set to 10 [mm]. In such a configuration, the thick paper 101 has the first contact point P4 and the second
It is transported while sequentially contacting the contact point P5 and the nip entrance point P1.

As shown in FIG. 13, when the rear end of the thick paper 101 as a recording member passes over the flexible member 52a, it is urged toward the intermediate transfer belt 41, and The flexible member 52a flexes flexibly toward the intermediate transfer belt 41. When the flexible member 52a bends in this way, the jump of the rear end of the thick paper 101 when separating from the flexible member 52a is reduced, and as a result, the vibration of the thick paper 101 caused by the jump is suppressed. This allows
“Streaks or the like due to guide separation” can also be suppressed.

In the color printer according to the third embodiment,
A sticker is affixed to the printer body (not shown). For example, this seal is written as "Please use paper of thickness from xx mm to xx mm". You have specified a lower limit. The upper and lower limits are also specified in an instruction manual (not shown). In addition, the difference between the amount of deflection of the flexible member 52a due to contact with the recording member having the lower limit thickness and the amount of deflection due to contact with the recording member having the upper limit thickness is 0.5 [mm] or more and 3.0 [mm]. mm]
Its flexibility has been adjusted as follows.

In the present color printer having the above-described structure, the generation of a stained image caused by the tip of the upper guide plate 52 being too close to the intermediate transfer belt 41 and being stained with the toner is suppressed while the “streak caused by the guide separation” is suppressed. Etc. "can be suppressed. In addition, the stain image can be suppressed without providing a bias applying unit to the upper guide plate 52. Further, as long as a recording member having a thickness within the specified range is used, it is possible to suppress "streaks or the like caused by separation of the guide" due to a difference in the amount of flexure of the flexible member 52a and the above-described stained image.

By applying a conductive treatment to the surface of the flexible member 52a and applying a bias having a polarity opposite to that of the toner,
The generation of the stain image may be suppressed more reliably. Also, using a thin metal plate as the flexible member 52a,
A spring or the like may be brought into contact with this to adjust its flexibility.

[Fourth Embodiment] FIG. 14 is a sectional view showing an intermediate transfer belt in a color printer according to a fourth embodiment.
In the figure, the intermediate transfer belt 41 is composed of a surface layer 41a constituting a transfer surface, an elastic layer 41b made of an elastic material such as rubber or elastomer, and a lower layer 41c.

The present color printer is configured to move a secondary transfer roller (not shown) and the intermediate transfer belt 41 at the same linear speed during the secondary transfer. That is, a difference in nip linear velocity does not occur during the secondary transfer.

In the present color printer having the above-described structure, the intermediate transfer belt 41 is flexibly deformed in the secondary transfer nip according to the thickness of the full-color transfer image, and the “due to the difference in the nip linear velocity caused by the aggregation of toner”. It is possible to avoid the occurrence of "streaks and the like caused by the nip linear velocity difference" and the occurrence of stretched images caused by the nip linear velocity difference while suppressing the occurrence of the "streaks and the like".

The material used for the surface layer 41a is not limited, but it is desirable to use a material that reduces the adhesion of the toner to the transfer surface to enhance the secondary transferability. As such a material, for example, one or two or more of polyurethane, polyester, epoxy resin and the like are used, and a material which reduces surface energy and enhances lubricity, for example, a fluororesin, a fluorine compound, fluorocarbon, titanium dioxide, One type or two or more types of powder particles such as silicon carbide can be dispersed and used. Further, a surface layer having a large amount of fluorine may be formed on the surface by a heat treatment such as a fluorine rubber material to reduce the surface energy.

As elastic materials such as rubber and elastomer in the elastic layer 41b, butyl rubber, fluorine rubber, acrylic rubber, ethylene-propylene terpolymer (EPDM), nitrile rubber (NBR), acrylonitrile-butadiene-styrene rubber natural rubber , Isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydride Phosphorus rubber, silicone rubber, fluorine rubber, polysulfide rubber, polynorbornene rubber, hydrogenated nitrile rubber, thermoplastic elastomer (for example, polystyrene, polyolefin, polyvinyl chloride) , Polyurethane, polyamide, polyurea, polyester, fluorocarbon resin, etc.)
One type or two or more types selected from the group consisting of, for example, can be used. However, it is not limited to these.

The material of the lower layer 41c is ethylene.
= Fluorinated resins such as tetrafluoroethylene copolymer (ETFE) and polyvinylidene difluoride (PVDF), polycarbonate, polystyrene, chloropolystyrene, poly-
α-methylstyrene, styrene-butadiene copolymer,
Styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-
Acrylic ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic ester copolymer (styrene-methyl methacrylate copolymer, styrene-methacrylic) Styrene-based resins (styrene or styrene-substituted products) such as ethyl acrylate copolymer, styrene-phenyl methacrylate copolymer, styrene-α-methyl methyl acrylate copolymer, styrene-acrylonitrile-acrylate copolymer , A methacrylate resin, a butyl methacrylate resin, an ethyl acrylate resin, a butyl acrylate resin,
Modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, rosin-modified maleic resin, Phenolic resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin and polyvinyl butyral resin,
One or more kinds selected from the group consisting of polyamide resins, modified polyphenylene oxide resins, and the like can be used. However, it is not limited to these.

The elastic layer 41b and the lower layer 41c may contain a conductive agent for adjusting the resistance as required, but there is no particular limitation on the type of the conductive agent for adjusting the resistance.
For example, carbon black, graphite, metal powder such as aluminum and nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, potassium titanate, antimony oxide-tin oxide composite oxide (ATO), indium oxide-tin oxide composite oxide Examples of the conductive metal oxide such as an article (ITO) and the conductive metal oxide include insulating fine particles such as barium sulfate, magnesium silicate, and calcium carbonate.

The method for manufacturing the intermediate transfer belt 41 is not particularly limited. A centrifugal molding method in which a material is poured into a rotating cylindrical mold to form an endless belt, a spray coating method for forming a thin surface layer 41a, a dipping method in which a cylindrical mold is immersed in a material solution and pulled up, It may be formed by a casting method of injecting a material into a mold or an outer mold, a method of wrapping a compound around a cylindrical mold, and performing a vulcanization polishing treatment. Further, these and other methods may be formed in combination.

For reference, a method of manufacturing the elastic intermediate transfer belt used in the test shown in Table 5 will be described. First, polyvinylidene difluoride (PVDF): 10
A cylindrical mold is immersed in a dispersion obtained by uniformly dispersing 18 parts by weight of carbon black, 3 parts by weight of a dispersant, and 400 parts by weight of toluene with respect to 0 parts by weight, and immerses the cylindrical mold in 10 [mm / sec].
c], gently lift it up, dry it at room temperature,
m] to form a uniform film of PVDF. Then, the mold on which this film is formed is immersed again in the above-mentioned dispersion liquid and 10 [m
m / sec], dry at room temperature for 15 minutes.
A lower layer 41c made of a PVDF film having a thickness of 0 [μm] was formed. Then, 100 parts by weight of a polyurethane prepolymer, 3 parts by weight of a curing agent (isocyanate), 20 parts by weight of carbon black, 3 parts by weight of a dispersant, and 500 parts by weight of methyl ethyl ketone (MEK) were uniformly mixed. The mold in which the lower layer 41c having a thickness of 150 [μm] was formed was immersed in the dispersed liquid, and was gently pulled up at 30 [mm / sec], followed by air drying. By repeating this operation,
The lower layer 41c made of PVDF having a thickness of 50 [μm] has 15
An elastic layer 41b made of 0 [μm] urethane polymer was covered. Further, a polyurethane prepolymer: 100 parts by weight, a curing agent (isocyanate): 3 parts by weight, PT
FE fine powder: 50 parts by weight, dispersant: 4 parts by weight,
MEK: A mold in which the lower layer 41c and the elastic layer 41b are formed is immersed in a dispersion liquid in which 500 parts by weight is uniformly dispersed.
After being gently pulled up at 0 [mm / sec], it was naturally dried. This operation is repeated to form a 5 [μm] thick PTFE
A surface layer 41a made of urethane polymer made of a film was covered. Finally, after drying the belt film composed of these layers at room temperature, crosslinking is performed at 130 [° C.] for 2 hours to form the lower layer 41c.
= 150 [μm] thick, elastic layer 41b = 150 [μm]
The intermediate transfer belt 41 having a three-layer structure having a thickness and a surface layer 41a = 5 [μm] was manufactured.

For reference, a method of manufacturing the inelastic intermediate transfer belt used in the test shown in Table 5 will be described. First, a cylindrical mold is immersed in a dispersion in which 18 parts by weight of carbon black, 3 parts by weight of a dispersant, and 400 parts by weight of toluene are uniformly dispersed with respect to 100 parts by weight of PVDF, and 10 [ mm / sec], and was gently pulled up and dried at room temperature to form a uniform PVDF film having a thickness of 75 [μm]. Then, the mold on which this film is formed is immersed again in the above dispersion liquid, gently pulled up at 10 [mm / sec], dried at room temperature, and dried to a thickness of 150 [μm].
A lower layer made of VDF was formed. Next, 100 parts by weight of a polyurethane prepolymer, 3 parts by weight of a curing agent (isocyanate), 50 parts by weight of PTFE fine powder, 4 parts by weight of a dispersant, and 500 parts by weight of MEK are uniformly dispersed. Immerse the mold with this lower layer in the dispersion liquid
After being pulled up at 30 [mm / sec], it was naturally dried. This operation is repeated to form a 5 [μm] thick PTFE
A surface layer made of a urethane polymer consisting of a film was coated on the lower layer. Finally, after drying these layers at room temperature,
After crosslinking for a time, the lower layer = 150 [μm] thick, the surface layer =
An intermediate transfer belt having a two-layer structure having a thickness of 5 [μm] was manufactured.

As a method of reducing the permanent deformation (elongation) of the intermediate transfer belt due to use, a method of using a material having relatively low elongation in the lower layer 41c, or a method of using a core material for reducing the elongation in the lower layer 41c is used. And the like. As the core material, natural fibers such as cotton and silk, polyester fibers, nylon fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers,
From the group consisting of polyvinylidene chloride fiber, polyurethane fiber, polyacetal fiber, synthetic fiber such as polyfluoroethylene fiber and phenol fiber, inorganic fiber such as carbon fiber, glass fiber and boron fiber, and metal fiber such as iron fiber and copper fiber. Those formed into a woven fabric or a thread using one or more selected ones are mentioned. Of course, it is not limited to these materials.

Regarding the manner of twisting in the form of a thread, any twisting method such as a method of twisting a plurality of filaments, single twisting, ply twisting and twin twisting may be used. Further, for example, fibers of a material selected from the above-described material group may be blended. Of course, the core material may be used after being subjected to an appropriate conductive treatment. Furthermore, as for the woven fabric, any woven fabric formed by any weaving method, such as knitting or cross-weaving, can be used.

[0119] The method of incorporating the core material is as follows.
There is no particular limitation. For example, a method in which a tubular woven fabric is covered with a mold or the like and a lower layer is provided thereon, or a method in which the tubular woven fabric is immersed in liquid rubber or the like to provide a lower layer on one or both surfaces of the core layer And a method in which a yarn is spirally wound around a mold at an arbitrary pitch and a lower layer is provided thereon.

The thickness of the elastic layer 41b depends on its hardness, but if it is too thick, the expansion and contraction of the surface becomes large and cracks are easily generated in the surface layer 41a. Also, the amount of expansion and contraction increases, and the expansion and contraction of the image increases. In order to suppress these cracks and expansion and contraction of the image, it is desirable to provide the elastic layer 41b with a thickness of less than about 1 [mm].

In the embodiments and examples described above, the color printer including the intermediate transfer belt 41 as the visible image carrier has been described. It goes without saying that the present invention is also applicable to an image forming apparatus that performs direct transfer.

The secondary transfer roller 5 which is an elastic roller
1 is applied with a secondary transfer bias having a polarity opposite to that of the toner.
Although the color printer that forms the next transfer electric field has been described, the present invention is also applicable to an image forming apparatus that forms a transfer electric field by applying a transfer bias having the same polarity as a visible substance such as toner to a biting roller.

[0123]

According to the present invention, claims 1, 2, 3, 4, 5, 6, 7,
According to the invention of 8, 9, 10, 11, 12 or 13, pre-transfer caused by poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the moving direction of the visible image carrier is visually observed. There is an excellent effect that it can be effectively suppressed to a level at which it cannot be confirmed by the above.

In particular, according to the invention of claim 2 or 3,
There is an excellent effect that "streaks or the like due to the pressure near the nip" can be effectively suppressed.

According to the third aspect of the present invention, it is possible to avoid the occurrence of pre-transfer caused by the above-mentioned poor adhesion immediately before the nip, and to prevent "streaks or the like caused by pressure near the nip".
There is an excellent effect that the occurrence of phenomena can be avoided.

In particular, according to the fourth aspect of the present invention, the adhesion between the recording member and the visible image carrier is promoted even at a position relatively distant from the nip. Has an excellent effect that it can be suppressed. Also, even when the conveying speed of the recording member toward the nip is higher than the linear speed inside the nip,
Since it is possible to suppress the bending of the recording member immediately before the nip, it is possible to suppress the above-mentioned poor adhesion due to the speed difference between the linear speed inside the nip and the transport speed toward the nip, and to suppress the pre-transfer caused by this. There is an excellent effect that it can be done.

According to the fifth aspect of the present invention, the non-winding portion of the visible image carrier with respect to the biting roller when the elastic roller is not provided partially contacts the biting roller at the nip entrance side. There is an excellent effect that it is easy to cause.

In particular, according to the invention of claim 6, there is an excellent effect that the superimposed image obtained by repeating the primary transfer can be secondarily transferred onto the recording member. Further, there is an excellent effect that the elastic roller can be brought into contact with the front surface of the intermediate transfer belt without giving excessive stress to the intermediate transfer belt. Further, there is an excellent effect that the front surface can be prevented from being damaged due to sliding friction between the elastic roller and the front surface of the intermediate transfer belt.

According to the seventh, eighth or ninth aspect of the invention, as long as plain paper, 135 kg paper or an official postcard is used as the recording member, it is possible to avoid the inability to transport the recording member due to the friction of the guide plate. There is an excellent effect that can be.

In particular, according to the eighth or ninth aspect of the invention, as long as plain paper, 135 kg paper or an official postcard is used as a recording member, it is possible to avoid the occurrence of "streaks or the like caused by friction of the guide plate". There is an excellent effect that it can be done.

According to the ninth aspect of the present invention, as a recording member, plain paper, 135 kg paper, a government-made postcard or
As long as 00 kg paper is used, there is an excellent effect that it is possible to avoid "streaks or the like caused by guide plate friction" and to prevent the recording member from being unable to be conveyed due to guide plate friction.

In particular, according to the tenth or eleventh aspect of the present invention, it is possible to suppress "streaks or the like due to guide separation" while suppressing the generation of a stain image caused by staining the tip of the guide plate with a coloring substance. There is an excellent effect that can be. In addition, this stained image has an excellent effect that it can be suppressed without providing a bias applying unit to the guide plate.

According to the eleventh aspect of the present invention, as long as a recording member having a thickness within a specified range is used,
There is an excellent effect that it is possible to suppress "streaks or the like caused by separation of the guide" due to the difference in the amount of flexure of the flexible member and the above-mentioned stained image.

In particular, according to the twelfth or thirteenth aspect, there is an excellent effect that generation of "streaks or the like due to a difference in nip linear velocity" can be avoided. Further, there is an excellent effect that generation of a stretched image due to a difference in nip linear velocity can be avoided.

Further, in particular, according to the invention of claim 13,
Excellent in that the occurrence of "streaks caused by the nip linear velocity difference" and the occurrence of "streaks caused by the nip linear velocity difference" can be suppressed while avoiding the occurrence of a stretched image caused by the nip linear velocity difference. effective.

In particular, according to the fourteenth aspect of the present invention, the pre-transfer caused by the occurrence of poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the transporting step is reduced to a level at which pre-transfer cannot be visually confirmed. There is an excellent effect that it can be effectively suppressed.

According to the fifteenth aspect of the present invention, it is possible to suppress the pre-transfer caused by poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the transfer device. effective.

In particular, according to the sixteenth aspect of the present invention, the pre-transfer caused by the occurrence of poor adhesion between the visible image carrier and the recording member on the upstream side of the nip in the transport step is reduced to a level at which pre-transfer cannot be visually confirmed. There is an excellent effect that it can be effectively suppressed.

[Brief description of the drawings]

FIG. 1A is a schematic diagram showing a state in which an intermediate transfer belt is naturally wound around a secondary transfer opposing roller. 4B is a schematic diagram illustrating a state in which the non-wound belt portion of FIG. 4A is brought into contact with the secondary transfer roller at the nip entrance side by the pressure contact of the secondary transfer roller 51. FIG.

FIG. 2 is a schematic diagram showing a secondary transfer nip N formed so as to generate a small amount of a pre-contact region R together with an angle θ1.

FIG. 3A is a center line L around which an intermediate transfer belt is wound;
FIG. FIG. 4B is a schematic diagram illustrating a main part of the transfer device configured to generate a pre-contact area while the rotation center point P7 of the secondary transfer roller is positioned on the center line L4 around the winding; FIG. 3C is a schematic diagram illustrating a main part of the transfer device according to the present invention.

FIG. 4A is a schematic diagram illustrating a contact state between an intermediate transfer belt and a secondary transfer roller in the same transfer device. (B)
FIG. 3 is a schematic diagram showing a state in which an intermediate transfer belt and a secondary transfer roller are separated from each other in the transfer device.

FIG. 5 is a schematic diagram illustrating a direction in which thick paper is transported between guide plates in the transfer device and a direction in which thick paper is transported after passing between the guide plates.

FIG. 6 is a schematic diagram illustrating an angle θ2 in the transfer device.

FIG. 7 is a schematic diagram illustrating the principle of generation of “streaks or the like caused by guide separation” in a conventional transfer device.

FIG. 8 is a schematic configuration diagram of a color printer according to the embodiment.

FIG. 9 is a schematic diagram showing a peripheral configuration of a secondary transfer nip in the color printer.

FIG. 10 is a schematic diagram showing a modification of the urging member of the color printer together with two rollers and an intermediate transfer belt.

FIGS. 11A to 11C each show Example 1;
FIG. 2 is a schematic diagram showing a peripheral configuration of a secondary transfer nip in the color printer according to the first embodiment.

FIG. 12 is a schematic diagram illustrating a peripheral configuration of a secondary transfer nip in the color printer according to the second embodiment.

FIG. 13 is a schematic diagram illustrating a peripheral configuration of a secondary transfer nip in a color printer according to a third embodiment.

FIG. 14 is an enlarged sectional view showing an intermediate transfer belt of the color printer according to the fourth embodiment.

FIG. 15 is a configuration diagram illustrating a main configuration of a conventional transfer device.

FIG. 16 is a schematic diagram illustrating a relationship between a secondary transfer nip and a nip entrance tangent in the transfer device.

FIG. 17 shows a circle C1, a circle C2 smaller in diameter and in contact with and inscribed at a contact point P3, and a circle C at the contact point P3.
FIG. 1 is a plan view showing a tangent line L3 tangent to C2.

FIGS. 18 (a) and (b) are Japanese Unexamined Patent Publication No. 9-9 / 1997, respectively.
FIG. 2 is a cross-sectional view illustrating a configuration around a nip in a transfer device described in Japanese Patent Application Laid-Open No. 0780/07.

FIG. 19 is a schematic view showing a pre-contact area R in the transfer device.

[Explanation of symbols]

41 Intermediate Transfer Belt (Visible Image Carrier) 41a Surface Layer 41b Elastic Layer 46 Secondary Transfer Opposing Roller (Bite Roller) 48 Biasing Member 51 Secondary Transfer Roller (Elastic Roller) 52 Upper Guide Plate 52a Flexible Member 53 Lower Guide plate 100 Transfer paper (recording member) 101 Cardboard (recording member) P1 Nip entrance point P2 Rotation center point (Rotation center of biting roller) P4 First contact point P5 Second contact point P7 Rotation center point (Rotation center of elastic roller) L1 Nip entrance tangent line L4 Wrap center line N Secondary transfer nip (nip)

Continued on the front page (72) Inventor Hiromi Ogiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hiroshi Ono 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Mitsuru Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Ryuta Takeichi 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Invention Person Toshiaki Motohashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Katsuya 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. 2H032 AA05 AA14 BA09 BA19 BA23

Claims (16)

[Claims] 1. An elastic roller rotatably disposed, a bite roller rotatably disposed so as to bite into the elastic roller, or one of the rollers for forming a transfer electric field between the two rollers. Transfer bias applying means for applying a transfer bias to the roller, and a belt-like shape which is held between the nip while moving so as to carry a visible image on the front surface and wind around a part of the peripheral surface of the biting roller. And a recording member conveyed between the elastic roller in the nip and the front surface that is in contact with the elastic roller. In the transfer device for transferring the visible image carried on the surface to the recording member, the non-wound portion of the visible image carrier with respect to the biting roller when the elastic roller is assumed to be absent is formed at the nip entrance side. The bite The elastic roller is pressed against the visible image carrier so as to make contact with the roller, and the biting amount of the biting roller with respect to the elastic roller is set to 0.2 mm or more and 3.0 mm or less. And an angle θ1 between an extended line in the moving direction of the visible image carrier immediately before contacting the elastic roller and a tangent to the nip entrance is set to 5 [°] or more. 2. The transfer apparatus according to claim 1, wherein the angle θ
1 is set to 25 [°] or less. 3. The transfer device according to claim 2, wherein the angle θ
A transfer device, wherein 1 is set to 15 ° or more and 20 ° or less. 4. The transfer device according to claim 1, wherein:
By providing two guide plates opposed to each other and passing the recording member between the guide plates before the recording member enters the nip, the recording member is located upstream of the nip in the predetermined direction. A transfer device for guiding the toner image toward the visible image carrier on the side of the transfer device. 5. The transfer device according to claim 1, wherein the elastic roller is located at a position higher than the center of the visible image carrier wound around the biting roller when the elastic roller is not provided. Wherein the rotation center of the transfer device is located on the upstream side in the moving direction of the visible image carrier. 6. The transfer apparatus according to claim 1, wherein an intermediate transfer belt is provided as the visible image carrier, and the elastic roller is in contact with a front surface of the intermediate transfer belt. Immediately after the elastic roller is brought into contact with the front surface, the elastic roller has a linear velocity that does not cause a relative speed difference between the elastic roller and the front surface. A transfer device for moving the entire elastic roller along the front surface while rotating the roller so that the bite roller gradually bites into the elastic roller. 7. The apparatus according to claim 4, further comprising two guide plates.
Or the transfer device of 6, wherein a first contact point that is a portion of the guide plate that comes into contact with the recording surface of the recording member conveyed while being sandwiched by the nip, the portion being in strongest contact with the recording member; It is formed by a curve connecting three points of a second contact point, which is a portion of the guide plate which is in contact with the recording member on the side opposite to the recording surface of the recording member, and a nip entrance point. Of the two corners, the angle θ2 of the corner facing the elastic roller is 140 [°].
As described above, the transfer device is less than 180 [°]. 8. The transfer device according to claim 7, wherein the angle θ
2. The transfer device, wherein 2 is set to 155 [°] or more. 9. The transfer apparatus according to claim 8, wherein the angle θ
2 is set to 160 [°]. 10. The apparatus according to claim 4, further comprising two guide plates.
In the transfer device of 5, 6, 7, 8 or 9, the end of the guide plate, which is in contact with the recording surface of the recording member conveyed while being sandwiched by the nip, on the downstream side in the recording member moving direction is flexible. A transfer device comprising a conductive member. 11. A transfer apparatus according to claim 10, wherein upper and lower limits of the thickness of the usable recording member are designated, and the amount of flexure of the flexible member due to contact with the lower limit of the recording member and the upper limit of the recording member. A transfer member provided with the flexible member having a difference from a deflection amount of the flexible member due to contact with the flexible member of not less than 0.5 [mm] and not more than 3.0 [mm]. . 12. The method of claim 1, 2, 3, 4, 5, 6, 7,
8. The transfer device according to claim 8, wherein the linear speed of the visible image carrier and the linear speed of the elastic roller during transfer are set to the same speed. 13. The transfer device according to claim 12, wherein the visible image carrier is constituted by at least a surface layer forming the front surface and an elastic layer. 14. A nip forming step of forming a nip by cutting a rotatable biting roller into a rotatable elastic roller; and a belt-shaped visible image carrier having a visible image on a front surface thereof. A step of sandwiching the nip while moving so as to be wound around a part of the peripheral surface of the biting roller, and a step of applying a transfer bias to one of the rollers to form a transfer electric field between the two rollers; A conveying step of conveying the recording member between the elastic roller in the nip and the front surface that is in contact with the elastic roller and sandwiching the recording member, and forming a visible image of the front surface in the nip; And a step of transferring to a recording member, wherein in the nip forming step, the non-wound portion of the visible image carrier with respect to the biting roller when the elastic roller is assumed to be absent at the nip entrance side. Min to so as to contact with the bite roller, the bite roller 0.2 [mm] or more,
The elastic roller is pressed against the visible image carrier while biting into the elastic roller with a bite amount of 3.0 [mm] or less, and the moving direction of the visible image carrier is extended just before contacting the elastic roller. Angle θ between the line and the tangent to the nip entrance
A transfer method, wherein 1 is 5 [°] or more. 15. A latent image carrier for carrying a latent image, developing means for developing the latent image on the latent image carrier, and a visible image obtained by development, An image forming apparatus comprising: a transfer device for transferring a latent image carrier directly or via an intermediate transfer member that is a visible image carrier to a recording member, wherein the transfer device is used as the transfer device. 5,
An image forming apparatus provided with 6, 7, 8, 9, 10, 11, 12 or 13 transfer devices. 16. A step of carrying a visible image on the front surface of a belt-shaped visible image carrier, and a step of forming a nip by making a rotatable elastic roller bit into a rotatable biting roller. Moving the visible image carrier bearing the visible image around the part of the peripheral surface of the biting roller so as to be sandwiched in the nip, and forming a transfer electric field between the two rollers. Applying a transfer bias to one of the rollers, and conveying the recording member between the elastic roller in the nip and the front surface that is in contact with the elastic roller. Transferring the visible image of the front surface to the recording member at the nip to form an image on the recording member, wherein in the nip forming step, the elastic roller is If you assume there is no The biting roller is 0.2 [mm] or more and 3.0 [mm] such that the non-wound portion of the visible image carrier with respect to the biting roller is partially brought into contact with the biting roller on the nip entrance side. The elastic roller is pressed against the visible image carrier while biting into the elastic roller with the following bite amount, and the extension line in the moving direction of the visible image carrier immediately before contacting the elastic roller, and the nip entrance tangent line Wherein the angle θ1 is 5 [°] or more.