JPH09114267A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain chromaticity from differing and to reproduce the recorded image of a desired color by optically detecting the characteristic depending on the kind of a material to be recorded based on spectral reflectance and controlling the transfer of the recorded image in accordance with the detected result. SOLUTION: When a kind discriminating command signal 26 for discriminating the kind of a transfer sheet 1 is supplied to a controller 24 from a control part 30 having a CPU function on the device side before the image is formed by an image forming device in a paper kind detecting device 20, a white light source 21 is turned on and irradiates the uppermost surface of the sheet 1 kept in a housing cassette 2. Thus, reflected light is made incident on photodetector 22 through a blue filter 23. A current which is photoelectrically converted in accordance with received light quantity by the photodetector 22 is inputted in the controller 24, and the kind of the sheet 1 related to the chromaticity is discriminated. Then, a kind discriminating signal 25 is outputted from the controller 24 to the control part 30. Thereafter, the sheet 1 is fed from the cassette 2 to a developing mechanism by a feeding roller 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus such as a copying machine, a printer, a fax machine, etc., which is an electrophotographic type and forms a fixed image on a recording material such as a printing machine.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration example of a conventional full-color laser beam printer to which an electrophotographic technique is applied. Here, 1 is a recording material (hereinafter, referred to as a transfer sheet) which is held in the accommodating cassette 2 in an accumulated state, and 3 feeds the transfer sheets 1 located in the uppermost layer from the accommodating cassette 2 one by one. The feeding rollers 4 are resist rollers that temporarily stop the leading end of the transfer sheet 1 fed by the feeding roller 3 and transfer the transfer sheet 1 to the transfer drum 5 at a transfer timing. 6 is a photosensitive drum for transferring a recorded image onto the transfer sheet 1 held by the transfer drum 5,
In the case of this example, 7 stores toners of cyan (C), magenta (M), yellow (Y) and black (Bk) for each of the sleeves 7C, 7M, 7Y and 7Bk. A color-specific developing device for forming an electrostatic latent image.

Reference numeral 8 is a laser scanner, and the laser scanner 8 modulates the intensity of the laser beam 9 based on an image information signal sent from a host device (not shown),
By projecting the modulated laser beam 9 onto the photosensitive drum 6, an electrostatic latent image is formed for each color. 10 is a transfer sheet 1
A fixing roller for fixing the toner image transferred on the upper surface, a discharging roller 11 and a discharging tray 12. 13
Is a charger, and the charger 13 charges the photosensitive drum 6 with a potential for forming an electrostatic latent image.

An electric field formed by the voltage applied to the sleeves 7C to 7Bk and the surface potential charged by the charger 13 on the electrostatic latent image of each color formed on the photosensitive drum 6 by the above-described structure. The image is selectively visualized by means of, and the visualized image is transferred to the transfer sheet on the transfer drum 5.
Repeated for the four colors C and Bk. Therefore, the density of the image transferred at this time depends on the above-mentioned electric field strength, the characteristics of the toner of each color, and the sleeves 7C to 7C of the developing device 7.
It is almost determined by the amount of toner supplied from Bk.

Although not shown, the image is not directly transferred from the photosensitive drum to the transfer sheet, but is once transferred from the photosensitive drum to the intermediate transfer member and then retransferred from the intermediate transfer member onto the transfer sheet. There is also a laser beam printer. In any case, the chromaticity of the image fixed on the transfer sheet also depends on the characteristics of the toner, process conditions relating to development and transfer, and other factors set in advance in the model. In addition to the above, the chromaticity is also affected by the type of transfer sheet used.

[0006]

However, in the conventional image forming apparatus as described above, the characteristics relating to the paper quality, particularly the color, differ depending on the type of the transfer sheet used, and thus the difference in the characteristics is transferred to the image. Affect the color of
It has been confirmed by experiments that the chromaticity between the transfer sheet and the image has the following relationship.

1) For example, when a brownish recycled paper or the like is used as a transfer sheet, such a transfer sheet has a chromaticity difference of about ΔE = 10 as a color difference measurement value compared to a pure white transfer sheet, and is visually observed. However, the recycled paper is more yellowish. Therefore, when an image is formed on such two types of transfer sheets under the same conditions, the entire color of the image is affected by the color peculiar to the formed transfer sheet, and in the above case, the recycled paper is used. Has a yellowish color, which is different from the desired color.

2) The transfer sheet has different spectral characteristics by a spectrophotometer depending on the type, and in particular, the spectral reflection characteristics greatly differ in a short wavelength range. For example, as shown in FIG. In B and C, the change in reflectance becomes significant near the wavelengths of 430 to 440. In general terms, the higher the reflectance as a whole, the closer it is to pure white. Here, the horizontal axis represents wavelength, and the vertical axis represents reflectance or transmittance in%, respectively. In the short wavelength region 400 nm to 600 nm, regions of blue-green, blue, and violet colors are used, and in the long wavelength region. 600 nm to 700 nm represents red, orange, and yellowish color regions.

The object of the present invention is to suppress the difference in the chromaticity of the transferred and recorded image due to the above-mentioned characteristics of the recording material, particularly the characteristics relating to the color, and to reproduce the recorded image of a desired color. An object is to provide an image forming apparatus.

[0010]

In order to achieve such an object, a first invention of the present application is to form an electrostatic latent image according to a recording signal, develop the electrostatic latent image and record the electrostatic latent image. In an image forming apparatus capable of transferring an image onto a recording material, a paper type detecting means for optically detecting a characteristic of the recording material depending on the paper type based on spectral reflectance, and a detection result by the paper type detecting means. And a control means for controlling the transfer of the recorded image in accordance with the above.

A second invention according to the present application is an image formation capable of forming an electrostatic latent image according to a recording signal, developing the electrostatic latent image, and transferring the recorded image onto a recording material. In the apparatus, a paper type detection unit that optically detects a characteristic of the recording material depending on the paper type based on spectral reflectance, and a control that controls transfer of the recorded image according to a detection result of the paper type detection unit. And a filter for three colors of blue, red, and green that transmits reflected light from the recording material.

Furthermore, a third invention according to the present application is an image capable of forming an electrostatic latent image according to a recording signal, developing the electrostatic latent image, and transferring the recorded image onto a recording material. In the forming apparatus, a paper type detection unit that optically detects the characteristics of the recording material depending on the paper type based on spectral reflectance, and the transfer of the recorded image is controlled according to the detection result of the paper type detection unit. A control means, wherein the control means forms the electrostatic latent image, changes a bias voltage to develop the electrostatic latent image, and changes a hue of the recorded image. It is a thing.

According to the first aspect of the invention, the paper type detection means detects the color characteristics of the recording material based on the spectral reflectance, and the recorded image on the recording material is detected according to the detection result. Transcription is controlled.

According to the second invention, a plurality of color filters are provided for detecting the color characteristics based on the spectral reflectance of the paper type detecting means, so that the recording material is colored in advance. It is also possible to obtain an appropriate detection result depending on the color characteristics.

Furthermore, according to the third aspect of the invention, the control means controls so as to change the bias voltage relating to the development on the basis of the result detected by the paper type detection means, whereby the recorded image to be transferred is transferred. It is possible to output the same hue as desired regardless of the hue of the recording material.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an example of the structure around a transfer sheet storage cassette 2 according to the present invention. Here, 20 is an optical detection device (hereinafter referred to as a paper type detection device) for detecting the paper type of the transfer sheet 1. The paper type detection device 20 is arranged above the transfer sheets 1 accumulated in the storage cassette 2 as shown in this figure. 21 is a white light source that projects light onto the accumulated transfer sheet 1 at an angle of approximately 45 °, 2
2 is a light receiving element for receiving the light reflected from the surface of the transfer sheet 1, 23 is disposed on the optical path immediately before the light receiving element 22,
A blue (color) filter that absorbs and transmits a part of the reflected light spectral energy from the surface of the transfer sheet 1;
Transfer sheet 1 by inputting a current according to the amount of light received from 2.
Is a controller for sending the type discrimination signal 25, and 26 is a type discrimination command signal for the transfer sheet 1 to the controller 24.

In the paper type detection device 20 having such a configuration, the type determination command signal 26 of the transfer sheet 1 is sent to the controller 24 from the control unit 30 having a CPU function on the device side before the image formation by the image forming device. Then, the white light source 21 is turned on, and the storage cassette 2 is irradiated with the uppermost surface of the transfer sheet 1 kept in the accumulated state. Thus, the reflected light is incident on the light receiving element 22 via the blue filter 23.
Thus, the current photoelectrically converted by the light receiving element 22 in accordance with the amount of received light is input to the controller 24, and the type related to the chromaticity of the transfer sheet 1 is determined here as described later, and the type determination signal 25 is sent. It is output from the controller 24 to the control unit 30. Then, after this, transfer sheet 1
Is fed from the storage cassette 2 to the developing mechanism shown in FIG. 5 by the feeding roller 3.

Next, the operation of the blue filter applied to this embodiment will be described with reference to FIG.

As described above, FIG. 2 shows the spectral characteristics for the three types of transfer sheets 1 (A, B, C), and these spectral characteristics all have wavelengths of 420 to 44.
The change in reflectance is greatest between 0 nm. Meanwhile, blue as the spectral characteristics of the spectral characteristics are known to be higher in transmittance at a wavelength of 410~450nm as blue (color) filter 23, the spectral transmittance characteristics as shown in the figure C _B Become a rate. That is, it can be seen that the blue filter 23 having the above-mentioned spectral characteristic is suitable for the discrimination in the wavelength region of 420 to 440 nm where the change (difference) in reflectance becomes the largest as the spectral characteristic of the transfer sheet. Therefore, the reflected light is received by the light receiving element 22 via the blue filter 23, and is further received by the controller 2
When the signal value of the transfer sheet 1 in the above wavelength range is set to 1, the signal values of the transfer sheets 2 and 3 have the ratio values as shown in the following Table 1, respectively. Can be clearly distinguished.

[0021]

[Table 1]

In the transfer sheet type discriminating method according to the first embodiment, when the transfer sheet contains a fluorescent substance, the transfer sheet type discriminating signal value becomes particularly large, and the transfer sheet contains a lot of waste paper. However, the transfer sheet discrimination signal is particularly small for recycled paper or the like in which the bleaching agent is not used much.

According to the above-described first embodiment, the transfer sheet is irradiated with white light, and the reflected light is passed through the blue filter 23 to obtain the reflected light in the wavelength region having the largest difference between the transfer sheets. Thus, the type of the transfer sheet can be accurately determined by extracting the light as the transfer sheet type determination signal 25 for each of the transfer sheets 1 to 3 according to the light amount.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the first embodiment, since the white light is emitted toward the transfer sheet 1 and the reflected light is received by the light receiving element 22 through only the blue filter 23, 420-
Only reflected light in a short wavelength region such as 440 nm is detected, and when chromatic color paper is used as the transfer sheet 1, there is a risk of making an incorrect decision.

Therefore, in order to reduce such an influence,
In the second embodiment, the reflected light of the transfer sheet 1 is received through the blue filter, the red filter and the green filter, and the color information of the transfer sheet 1 is transferred to the plurality of transfer sheet discrimination signals 125.
As a result, the color of the transfer sheet 1 can be more accurately discriminated by taking it out from the controller 124.

In FIG. 3, the paper type detecting device 120 includes a white light source 21, a blue filter 23B (23), and a red filter 2.
The transfer sheet discrimination signal 125 from the controller 124 is composed of three sets of light receiving elements 22B, 22R and 22G which are received through the respective color filters of the 3R and the green filter 23G.
It is output as a combination of three types of signals corresponding to 3G.

Next, a third embodiment will be described with reference to FIG.

This embodiment is intended to obtain the same hue as the color of the image fixed on the transfer sheet 1, regardless of the color of the transfer sheet itself which differs depending on the type of the transfer sheet 1. That is, in this embodiment, the first
As described in the embodiment, when the control unit 30 receives the transfer sheet type discrimination signal 25 detected by the paper type detection device, the developing applied according to the signal 25 for the cyan and magenta color developers. Make the bias slightly change. FIG. 4 shows the applied developing bias. The solid line shown in the figure is for superimposing the AC voltage Vpp on the DC voltage Vdc and applying it to the developing sleeves 7C to 7Bk (see FIG. 5) in the conventional image formation. As described above, when it is small, the developing bias for charging the cyan and magenta developers is ΔV1 as indicated by the broken line.
By changing dc and ΔV1pp, the developing characteristics of only cyan and magenta colors are increased. As a result, for example, in a transfer sheet such as recycled paper that is slightly yellowish because it does not contain a bleaching agent, the type determination signal 25 of the transfer sheet is reduced, and the developability of cyan color and magenta color is increased accordingly. The density becomes darker, and the change in density offsets the yellow color which is the color of the transfer sheet, and the image color becomes almost the same hue in terms of chromaticity even if the type of the transfer sheet is different. When the type determination signal 25 of the transfer sheet is large, the transfer sheet 1 is formed because of the fluorescent substance as described above.
However, the developing bias applied to the cyan and magenta developers is changed by ΔV2dc and ΔV2pp, respectively, as indicated by the alternate long and short dash line, to reduce the developability of cyan and magenta and strengthen yellow. This allows the image colors to have almost the same hue in terms of chromaticity.

In the above example, the developing sheet bias for the cyan and magenta developers is changed by the transfer sheet type discriminating signal 25 through the blue filter 23, but the three types of filters described in the second embodiment are used. In the system using, the control unit 30 selects the signal of the filter with the largest output, and changes the developing bias of each developer according to the relative difference with the output of another filter. When the red filter 23R is selected, the developing bias for the yellow and magenta developers is changed, and when the green filter 23G is selected, the developing bias for the yellow and cyan developers is changed.

[0031]

As described above, according to the first aspect of the present invention, the paper type detecting means for optically detecting the characteristics of the recording material depending on the paper type based on the spectral reflectance, and the paper type detecting means. Since the control means controls the transfer of the recorded image according to the detection result of the means, it is possible to clearly discriminate different characteristics depending on the type of the transfer sheet.

Further, according to the second invention, in the first invention, the paper type detecting means has filters of three colors of blue, red and green for transmitting the reflected light from the recording material. ,
The characteristics of a transfer sheet which is colored in advance can be clearly discriminated.

Further, according to a third invention, in the first or second invention, the control means forms the electrostatic latent image, and a bias voltage for developing the electrostatic latent image. Since the hue of the recorded image is changed by changing the image forming apparatus, even if the transfer characteristics of the transfer sheet are different, an image forming apparatus capable of reproducing an image having the same hue based on the determination result by the paper type detecting unit. Offering is now possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration example of a paper type detection device according to a first embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing spectral characteristics of a transfer sheet and a filter according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration example of a paper type detection device according to a second embodiment of the present invention.

FIG. 4 is a waveform diagram showing, as an example, changes in the developing bias according to the third embodiment of the present invention.

FIG. 5 is a configuration diagram showing an example of an electrophotographic printer to which the present invention can be applied.

[Explanation of symbols]

1 Recording material (transfer sheet) 2 Storage cassette 5 Transfer drum 6 Photosensitive drum 7 Color developing device 7C, 7M, 7Y, 7Bk (development) sleeve 8 Laser scanner 13 Charger 20 Paper type detector 21 White light source 22 Light receiving element 23 Blue (color) filter 23B, 23R, 23G filter 24 Controller 30 Control unit ΔV1dc, ΔV1pp, ΔV2dc, ΔV2pp Development bias change amount

Claims (5)

[Claims] 1. An image forming apparatus capable of forming an electrostatic latent image in response to a recording signal, developing the electrostatic latent image, and transferring the recorded image onto a recording material, the paper type of the recording material. A sheet type detecting means for optically detecting the characteristics of the above based on the spectral reflectance, and a control means for controlling the transfer of the recorded image according to the detection result by the sheet type detecting means. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the paper type detection unit includes at least a blue filter that transmits reflected light from the recording material. 3. The image forming apparatus according to claim 1, wherein the paper type detection unit has filters of three colors of blue, red, and green that transmit reflected light from the recording material. 4. The control means forms the electrostatic latent image, changes a bias voltage to develop the electrostatic latent image, and changes the hue of the recorded image. The image forming apparatus according to any one of items 1 to 3. 5. The recorded image is a color recorded image,
The image forming apparatus according to claim 1, wherein the recorded image can be transferred according to a recording signal for each color.