JP4479185B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to an improvement of an image forming apparatus that forms an image on a so-called embossed sheet in which an uneven surface is formed as a recording material.

Conventionally, in a color copying machine, a printer, or the like, when a dedicated sheet such as high-quality paper is used as a recording material, each part such as development conditions and transfer conditions is optimized so as to obtain the best image quality.
Conventionally, as an example of focusing on the surface of the recording material to achieve good image formation, the transfer current is increased or the transfer pressure is increased depending on the surface roughness, texture and smoothness of the recording sheet. Furthermore, a method of controlling exposure conditions and development conditions so as to increase the amount of toner before sheet transfer has been proposed (see, for example, Patent Documents 1 to 3).
By the way, as a recording material used in the recent graphic arts market, an embossed sheet with a concavo-convex pattern on the surface using a mold has been frequently used. Conventionally, it is excellent on an embossed sheet by xerography. No presentation has been made to form an image.

JP 2002-156839 A (column of embodiment of the invention, FIG. 2, FIG. 3) JP 2002-202638 A (column of embodiment of the invention) Japanese Patent Laid-Open No. 2001-337496 (column of embodiment of the invention, FIG. 1) Japanese Examined Patent Publication No. 46-41679 (Detailed Description of the Invention, FIG. 2)

Among Patent Documents 1 to 3 mentioned above, in the Patent Document 1, depending on the surface roughness of the recording sheet, by changing the pressing force and the transfer time for transferring, when the coarse registration sheet surface, the pressing force There have been proposals to obtain a good image by making it stronger or by increasing the transfer time. However, even if the transfer conditions are changed in this way and an image is formed on the embossed sheet so as to increase the amount of toner, the unevenness of the surface is so deep that image omission in the recesses cannot be solved.
Japanese Patent Application Laid-Open No. 2004-228561 proposes preventing transfer failure and fixing failure by increasing the transfer current or fixing temperature during image formation on special paper such as thick paper and envelopes. However, even if an image is formed on the embossed sheet by this method, the toner thickness on the surface only increases and the image omission in the concave portion is not eliminated.
Further, Patent Document 3 proposes changing the image forming conditions in order to reduce the influence of the texture of the recording sheet itself. However, this method does not provide a solution to the embossed sheet even if it has an effect on the texture, and image omission occurs.

As a method of dealing with these problems from another viewpoint, a method of pressing the elastic layer to the concave portion of the embossed sheet by providing a sufficiently soft elastic layer on the surface of the intermediate transfer member is also conceivable (see, for example, Patent Document 4). .
However, in this configuration, friction between the photosensitive member and the intermediate transfer member increases, and image quality deterioration such as pixel position deviation occurs. Further, when the frequency of the concavo-convex pattern is high and the amplitude is large, that is, when the embossed concavo-convex portions are arranged densely and deeply, even if the elastic layer of the intermediate transfer member is sufficiently soft and thick, the embossed sheet surface is It is not possible to follow up and image omission is not improved.

In this way, the embossed sheet is a coated paper or non-coated paper that has been subjected to unevenness processing, so its shape and paper quality vary, and surface roughness, texture and smoothness alone are accurate surface unevenness. Cannot be judged correctly.
Further, some embossed sheets have a concave portion of 100 μm or more. For example, even if the transfer current is increased, the discharge due to the gap between the toner and the embossed sheet causes image quality degradation, and image omission cannot be improved sufficiently.
On the other hand, even if the transfer pressure is increased, the normally used intermediate transfer belt such as a polyimide resin cannot follow the unevenness of the embossed sheet and the gap does not disappear, so the image omission is not improved.
Furthermore, even if the exposure and development conditions are changed and the amount of toner is increased, the change in the toner layer thickness is small compared to the depth of the embossed sheet recess. Will not improve. Further, since the toner layer thickness is increased, the transfer efficiency is deteriorated and the image omission is also deteriorated.
The present invention has been made in order to solve the above technical problem, and provides an image forming apparatus for forming a good image with no image omission on an embossed sheet having a concavo-convex surface. It is to provide.

That is, according to the present invention, as shown in FIG. 1, an image forming means 2 for electrostatically transferring a toner image on an image carrier onto a recording material 1 to form an image, and a type of the recording material 1 depending the mode selecting means 3 for selecting embossed sheet mode or a non-embossed sheet mode, the case where the mode selecting means 3 is embossed sheet mode is selected, the layer thickness of the non-embossed sheet mode of the toner image on said image bearing member And image forming control means 4 for controlling the image forming means 2 so as to be smaller than the case where is selected.

In such technical means, the image forming means 2 includes a process of transferring and fixing to the recording material 1 from each process of charging, exposure and development on the image carrier.
Further, the mode selection means 3 may be input in such a manner that the information of the recording material 1 is manually input using a switch or the like, or in a mode in which the result of separately determining the recording material 1 is input automatically. There is no problem.
Further, the mode selection means 3 selects whether or not the recording material 1 is an embossed sheet on the basis of information such as the thickness of the recording material 1 and the surface unevenness depth. For example, the recording material 1 is selected manually. It is also possible to determine the surface irregularity depth and thickness change amount based on the information such as the model number, for example, automatically, from the surface roughness by CCD camera etc. from the uneven depth and thickness variation amount etc. Even if it is an aspect to judge, it does not interfere. Note that the information for selecting the mode as to whether the sheet is an embossed sheet may be based on one piece of information or may be based on a plurality of pieces of information.

In the present invention, the embossed sheet mode may be one type or may be a mode provided with a plurality of types. In the latter case, it is usually preferable that the image forming conditions include a plurality of different conditions.
Note that the embossed sheet refers to a sheet having a concavo-convex pattern on the surface using a mold, and includes ordinary paper that includes so-called embossed paper, such as art paper or coated paper, which has been subjected to concavo-convex processing with a mold. The resack 66 and bosses handled by sales companies and the like correspond to this.
Furthermore, when the unevenness depth is less than 30 μm, it is not necessary to change the image forming conditions related to the present invention by performing the conventional transfer conditions and the like, and the unevenness depth is preferably 30 μm or more. It is preferable to perform image formation in the embossed sheet mode using an embossed sheet as an embossed sheet.

In the present invention, from the viewpoint of preventing image omission on the embossed sheet, when the embossed sheet mode is selected, the layer thickness of the toner image on the image carrier is made smaller than when the non-embossed sheet mode is selected. It is preferable to control the image means 2.
In order to reduce the layer thickness of the toner image, the exposure amount on the image carrier is changed to be weaker than that in the case where the non-embossed sheet mode is selected, and the developing bias is selected in the non-embossed sheet mode. There is a mode of changing in a direction of weakening as compared with the case of the case, and both may be performed simultaneously, or only one of the modes may be performed.
Further, the exposure amount may be changed by changing the beam intensity, the beam spot size, or the like in an embodiment using a laser beam, for example.

Further, as another aspect of reducing the layer thickness of the toner image, when the embossed sheet mode is selected, by removing the lower color, the three-color mixed portion of Y (yellow), M (magenta), and C (cyan) is changed to K (black). ). When the non-embossed sheet mode is selected, the under color removal is not performed.

Further, the mode selection unit 3 may include a determination unit 5 that automatically determines whether or not the recording material 1 is an embossed sheet, and a mode in which the determination is made based on the unevenness depth of the recording material 1 is possible. .
And in the aspect which automatically discriminate | determines by the uneven | corrugated depth of the recording material 1, the aspect which judges the image from a CCD camera etc. using a frequency analyzer, an image analyzer, etc. is possible, for example.

As described above, according to the present invention, the toner image on the image carrier is electrostatically transferred onto the recording material and has an image forming means for forming an image. When the embossed sheet mode or non-embossed sheet mode is selected and the embossed sheet mode is selected, the toner image layer thickness on the image carrier is made smaller than when the non-embossed sheet mode is selected. Since the image means is controlled, it is possible to obtain a layer thickness of the toner image that matches the embossed sheet, and even if the recording material is an embossed sheet, a good image with improved image omission is formed. be able to.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the present invention is applied.
In FIG. 1, an image forming apparatus 10 includes an image forming unit 11 capable of forming a color image.
In the present embodiment, the image forming unit 11 is provided with an image reading unit 26 for reading a document on the upper portion of the apparatus main body 20, and a document feeding device for feeding a document to the image reading unit 26 above the image reading unit 26. 27, an image forming module 21 is disposed inside the apparatus main body 20, and multistage sheet supply trays 31 to 34 are disposed below the image forming module 21, and the apparatus main body 20 side is also provided. A manual feed tray 35 is disposed in the opening and closing direction.

  The image forming module 21 used in the present embodiment employs, for example, an electrophotographic system, and includes a photosensitive drum 22 that forms and supports each color component toner image, and each color component on the photosensitive drum 22. The toner images are sequentially primary transferred to the intermediate transfer belt 23, and the multi-color component toner image on the intermediate transfer belt 23 is secondarily transferred to a recording sheet by a secondary transfer device 24 including, for example, a secondary transfer roll. It is intended to lead to.

Here, around the photosensitive drum 22, a charger 221 for charging the photosensitive drum 22, an exposure device 222 such as a laser scanning device for writing an electrostatic latent image on the photosensitive drum 22, and each color component toner are accommodated. A developing device 223 that visualizes the electrostatic latent image on the photosensitive drum 22, a primary transfer device 224 made of, for example, a transfer roll that transfers each color component toner image on the photosensitive drum 22 onto the intermediate transfer belt 23, and Electrophotographic devices such as a cleaner 225 for cleaning residual toner on the photosensitive drum 22 are sequentially arranged.
The intermediate transfer belt 23 is stretched and circulated on a plurality of stretching rolls, and the secondary transfer device 24 is disposed opposite to each other with one stretching roll as a backup roll. Reference numeral 231 denotes a cleaner for cleaning the intermediate transfer belt 23.

Furthermore, in the present embodiment, the conveyance path 40 from the sheet supply trays 31 to 34 is directed upward from the side of the manual feed tray 35 of the apparatus main body 20, and passes through the secondary transfer portion of the image forming module 21 and the fixing unit 25. A reverse conveyance path 42 that is provided in a substantially Y shape on the lower side near the exit of the main conveyance path 41 and conveys the recording sheet by reversing the front and back of the recording sheet. There is provided a return conveyance path 43 that is connected to a part of the reverse conveyance path 42 and returns the recording sheet with the front and back reversed to the main conveyance path 41 in front of the image forming module 21 again.
Here, a registration roll 44 that transports the recording sheet after positioning is provided upstream of the secondary transfer site of the main transport path 41, and a transport belt 45 that transports to the fixing unit 25 is provided downstream of the secondary transfer site. Each transport path 40 is provided with an appropriate number of transport rolls 46. A reversing mechanism 100 for reversing and transporting the front and back of the recording sheet is disposed in the reversing transport path 42.
Note that the recording sheet delivery unit from the manual feed tray 35 is connected in communication with the horizontal portion of the main conveyance path 41. In the present embodiment, when an embossed sheet is applied as the recording sheet, the manual feed tray 35 is manually connected. The embossed sheet is inserted into the apparatus main body 20 by insertion.

Furthermore, in the present embodiment, as shown in FIG. 3, the control device 60 is configured by, for example, a microcomputer system (CPU 61, ROM 62, RAM 63, input / output interfaces 64, 65). An image forming program in the mode, an image forming program in the non-embossed sheet mode, an under color removal program, and the like are stored in advance.
The control device 60 takes in signals from the embossed sheet selection switch 71 and the undercolor removal selection switch 72 provided on the apparatus main body 20 (see FIG. 2) side to the CPU 61 via the input interface 64, and the CPU 61 However, when the recording sheet is an embossed sheet, the image forming control in the embossed sheet mode is performed. When the recording sheet is a non-embossed sheet, the image forming control is performed in the normal non-embossed sheet mode. The image forming conditions for the exposure amount 76, the developing bias 77, and the under color removal 78 are controlled via the output interface 65.

Next, the operation of the image forming apparatus according to the present embodiment will be described with reference to FIGS.
Now, after setting the embossed sheet on the manual feed tray 35, various selection switches, specifically, the embossed sheet selection switch 71 shown in FIG. 3 is selected and operated (step S1).
The control device 60 confirms that the embossed sheet has been applied to the recording sheet under the signal, and changes the exposure amount and the developing bias (steps S2 to S4).
At this time, in the case of an embossed sheet, the exposure amount and the developing bias are changed in the direction of weakening.
In this example, both the exposure amount and the development bias are changed. However, even if only one of them is changed, the toner layer thickness may be reduced. Furthermore, in this example, the embossed sheet mode is one type, but there may be a plurality of types.

After the image forming conditions are changed as described above, the exposure of the photosensitive drum 22 by the exposure device 222 is weakened in exposure amount, and further, the developing bias in the developing device 223 is weakened. The toner layer on the drum 22 is formed thinner than usual (steps S5 and S6).
The thinned toner image is transferred onto the intermediate transfer belt 23 by the primary transfer device 224, and then transferred onto the embossed sheet conveyed from the manual feed tray 35 by the secondary transfer device 24 (Step S7, S8).
The embossed sheet onto which the toner image has been transferred passes through the transport roll 45, is fixed by the fixing unit 25, and is then discharged to the discharge tray 52 (step S9).
If an embossed sheet is not selected, the process proceeds from step S2 to the exposure process in step S5.

As described above, when the toner layer thickness is reduced, the charge held by the entire toner layer is reduced, and the electrostatic adhesion between the intermediate transfer belt 23 and the toner is weakened. Transfer efficiency is improved.
FIGS. 5A and 5B are schematic views showing the transfer process to the embossed sheet when the toner layer thickness is different. In FIG. 5A, when the toner layer thickness is thick, the electrostatic transfer force between the intermediate transfer belt 23 and the toner is strong, so the secondary transfer roll 24 in the concave portion (portion (A) in the figure) of the embossed sheet. The electrostatic attractive force (due to the transfer bias) that pulls the toner to the side becomes relatively weak, and the toner transfer to the concave portion becomes insufficient. On the other hand, as shown in FIG. 5B, when the toner layer thickness is thin, the electrostatic adhesion force between the intermediate transfer belt 23 and the toner becomes weak, and the toner is transferred to the concave portion of the embossed sheet. Become.

Therefore, there is no need to increase the transfer current more than necessary or increase the pressing force of the intermediate transfer belt 23, and it is not necessary to have a soft layer such as a rubber layer on the surface of the intermediate transfer belt 23. Even if they are not necessarily brought into contact with each other, occurrence of image omission due to transfer failure is suppressed.
In addition, by reducing the toner layer thickness, the amount of toner transferred onto the embossed sheet decreases and the color reproducibility decreases, but the embossed sheets that are normally used may have colors such as ivory and beige. Because there are many, the market demand for color reproduction is low, which is not a problem in practical use.
Therefore, as in the present case, by reducing the toner layer thickness in the case of an embossed sheet, it is possible to form an image with no image loss and smooth image quality.

By the way, although the embodiment in which the under color removal is not performed has been described in the present embodiment, it is also possible to perform the under color removal.
6A and 6B are diagrams for explaining undercolor removal, FIG. 6A is a conceptual diagram thereof, and FIG. 6B shows an operation flow.
For example, as shown in FIG. 6B, when the lower color removal selection switch 72 is operated, the control device 60 can remove the lower color (Y (yellow), M (magenta), C (cyan)). Control for converting the color mixture portion) to K (black) is performed (steps S11 and S12).
Then, K (black) toner development is performed (step S16). If under color removal is not selected, normal Y (yellow) toner development, M (magenta) toner development, and C (cyan) toner development are performed (steps S13 to S15).
At this time, by removing the under color, the toner layer thickness is reduced as shown in FIG.
Therefore, this under color removal is also useful in the direction of suppressing image omission on the embossed sheet.

  In the present embodiment, as shown in FIG. 2, a mode in which a single photosensitive drum 22 is used for the rotary development is shown. However, for example, a so-called tandem type in which a plurality of photosensitive drums are each provided with a developing device. Also in the image forming apparatus, it is possible to form an image with no image omission on the embossed sheet by reducing the toner layer thickness as in the present embodiment.

Embodiment 2
The image forming apparatus according to the present embodiment is configured in substantially the same manner as in the first embodiment, and is different from the first embodiment in the mode of the embossed sheet selection switch, and the operation screen display as shown in FIG. For example, an embossed sheet to be used is manually selected by a touch panel.

As shown in FIG. 7, various types of embossed sheets are shown on the display selection switch 73 having a touch panel. In this example, Boss, Rezac 66, Grande, Gilesse, Stripe, Colky, Hammertone GA, and Firmi are shown, but not limited to this, other names may be used as long as they are normally used as an embossed sheet. It is also possible to use it.
Then, the image forming conditions of the exposure amount 76 and the developing bias 77 are changed through the control device 80 based on the signal from the display selection switch 73.

  In the present embodiment, the image forming conditions for achieving the optimum toner layer thickness are incorporated in the control device 80 in advance depending on the type of the embossed sheet indicated by the display selection switch 73, so that the embossed sheet to be used is used. The image can be formed without image omission only by selecting the type of the image using the display selection switch 73.

Embodiment 3
The image forming apparatus according to the present embodiment is configured in substantially the same manner as in the first embodiment. However, unlike the first embodiment, as shown in FIG. 8, the control apparatus 90 automatically determines the embossed sheet. The frequency analysis device 83 is provided.
In the figure, a CCD camera 82 and a frequency analysis device 83 are disposed in the image forming apparatus main body (not shown), and the control sheet 90 causes the recording sheet 81 based on the frequency analysis result of the conveyed recording sheet 81. It is configured to automatically determine whether or not the image is an embossed sheet and process whether or not to change the image forming condition based on the signal.

As shown in FIG. 9, the control device 90 is constituted by, for example, a microcomputer system (CPU 91, ROM 92, RAM 93, input / output interfaces 94, 95), and the ROM 92 determines whether or not it is an embossed sheet. A program, an image forming program in the embossed sheet mode, an image forming program in the non-embossed sheet mode, an under color removal program, and the like are stored in advance.
The control device 90 takes in signals from the frequency analysis device 83, the under color removal selection switch 72, and the like to the CPU 91 via the input interface 94. When the recording sheet 81 is an embossed sheet, the CPU 91 embossed sheet. A predetermined processing program is executed so as to perform image formation control in the mode, and when the recording sheet 81 is a non-embossed sheet, image formation control in the normal non-embossed sheet mode is performed via the output interface 95. Thus, the image forming conditions of the exposure amount 76, the developing bias 77, and the under color removal 78 are controlled.
In the present embodiment, it is configured to determine whether or not the sheet is an embossed sheet by analyzing the surface unevenness depth of the recording sheet 81 by the frequency analyzer 83.

Here, the operation | movement about the embossed sheet discrimination | determination effect | action in this Embodiment is demonstrated based on FIG.
When the image is captured by the CCD camera 82, the content is subjected to surface analysis by the frequency analysis device 83, and it is determined whether or not the recording sheet 81 used in the control device is an embossed sheet based on the information ( Steps S21 to S23).
Further, in the case of an embossed sheet, it is divided into two depending on whether the unevenness is shallow or deep, and an appropriate exposure amount is selected (steps S24 to S26).
Then, exposure with the selected exposure amount is performed, and development, primary transfer, secondary transfer, and fixing are performed (steps S27 to S31).

Furthermore, the effect | action which confirms the uneven | corrugated depth of an embossed sheet is demonstrated in detail using FIG.
In the present embodiment, when an image of the recording sheet 81 conveyed by the CCD camera 82 is captured, a grayscale image corresponding to the depth of the unevenness is obtained. In this case, the image becomes whiter as the unevenness becomes shallower and becomes darker as the deeper ones. This density difference is converted into the depth of the unevenness by the frequency analysis device 83.
Usually, since the embossed sheet forms a pattern (unevenness) when passing between molds (rolls) with an uneven pattern, the above-described grayscale image has a certain frequency component. Therefore, by performing the frequency analysis, it is possible to determine that the recording sheet 81 having a peak at a certain frequency is an embossed sheet.
Note that if the unevenness is 30 μm or more, the grayscale image becomes clearer, so that discrimination by frequency analysis becomes easier.

If the control device 90 determines that the sheet is an embossed sheet based on information from the frequency analysis device 83, the image forming condition is changed in a direction that reduces the exposure amount.
In this example, the frequency analysis device 83 is used and the unevenness depth of the recording sheet 81 is observed. However, instead of the frequency analysis device 83, the unevenness creepage distance or the like is measured by an image analysis device, for example. By doing so, it is possible to use a substitute value for the unevenness depth.
Also in this embodiment, it is possible to remove the under color by operating the under color removal selection switch 72.

  As described above, in this embodiment as well, since the toner layer thickness is reduced when the recording sheet 81 is an embossed sheet by performing the processing as described above, there is no image omission and image quality is the same as in the first embodiment. Smooth image formation becomes possible.

FIG. 11 shows the contents of using an embossed sheet and confirming the correlation between the toner layer thickness and the missing image.
In this embodiment, DocuCenterColor manufactured by Fuji Xerox Co., Ltd.
500 remodeling machines were used, and a resack 66 and a boss that are usually handled by a paper sales company such as Takeo Co., Ltd. were used as an embossed sheet.
Under normal conditions, the toner layer thickness is less than 10 μm for a single color (C, M, Y, K), less than 15 μm for a secondary color (R, G, B), and 20 μm for a tertiary color (PB). It is weak.
The image omission evaluation was determined as the image omission grade as follows.
G1 is no image omission, G2 is a level between G1 and the next G3, G3 is an image omission but is not concerned, G4 is a level between G3 and the next G5, G5 is an image omission It was classified as terrible, and G1 to G3 were determined as acceptable levels.

As a result of the evaluation, as shown in FIG. 11, the image omission grade was improved by reducing the thickness of the toner layer in both the resac 66 and the boss. In the case of the resac 66 and the boss, the boss has deeper irregularities, and even if the toner layer thickness is reduced from 15 μm to 10 μm and 5 μm, the result is that the one-rank image loss is inferior to that of the resac 66, and the practical toner layer thickness Was found to be 10 μm or less for the Rezac 66 and 5 μm or less for the boss.
Further, the color reproduction at this time was inferior to usual, but at a level where there was no practical problem.

1 is an explanatory diagram showing an outline of an image forming apparatus according to the present invention. 1 is an explanatory diagram showing Embodiment 1 of an image forming apparatus to which the present invention is applied. 3 is a block diagram of a control device according to Embodiment 1. FIG. 3 is a flowchart illustrating an image forming method according to the first embodiment. (A) and (b) are explanatory views showing toner transfer onto an embossed sheet. (A) is a conceptual diagram showing under color removal, and (b) is a flowchart of the under color removal method. It is explanatory drawing which shows the embossing sheet manual input means in Embodiment 2 of the image forming apparatus to which this invention was applied. It is explanatory drawing which shows the recording material automatic discrimination means in Embodiment 3 of the image forming apparatus to which this invention was applied. FIG. 10 is a block diagram of a control device according to a third embodiment. 10 is a flowchart illustrating an image forming method according to the third embodiment. It is explanatory drawing which shows the evaluation result of Example 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Recording material, 2 ... Image formation means, 3 ... Mode selection means, 4 ... Image formation control means, 5 ... Discrimination means

Claims (4)

An image forming means for electrostatically transferring a toner image on an image carrier onto a recording material to form an image;
Mode selection means for selecting an embossed sheet mode or a non-embossed sheet mode according to the type of recording material;
If embossed sheet mode is selected by the mode selecting means, work for allowed to control the imaging means so as to reduce as compared with the case where the layer thickness of the toner image on the image bearing member is non-embossed sheet mode is selected An image forming apparatus comprising: an image control unit. The image forming apparatus according to claim 1.
The image forming control means controls the image forming means so that when the embossed sheet mode is selected, the exposure amount is changed in a direction to be weaker than that when the non-embossed sheet mode is selected. apparatus. The image forming apparatus according to claim 1.
The image forming control means controls the image forming means so that when the embossed sheet mode is selected, the developing bias is changed in a direction to be weaker than when the non-embossed sheet mode is selected. apparatus. The image forming apparatus according to claim 1.
The image forming control means controls the image forming means to perform undercolor removal when the embossed sheet mode is selected, and not to perform undercolor removal when the non-embossed sheet mode is selected. Image forming apparatus.

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