JPH02113264A - Three-color image recording method - Google Patents

Abstract

PURPOSE:To record an excellent three-color image at low cost by forming and visualizing electrostatic latent images corresponding to alpha- and beta-color images in a light exposing process by using a composite photosensitive body, and then developing and visualizing an electrostatic latent image corresponding to a black image in a uniform exposing process. CONSTITUTION:The composite photosensitive body 10 is formed by laminating 1st and 2nd photoconductive layers 1A and 1B on a conductive substrate 1K in order; and the photosensitive layer 1A becomes a conductor when irradiated with A-color light and the photoconductor layer 1B becomes a conductor when irradiated with B-color light. The photoconductive layers 1A and 1B are charged in the opposite directions to nearly equal potentials, the A-color light is switched to high intensity, and the B-color light is switched to high intensity, low intensity, and 0. Exposure is combined by combining them to form the electrostatic latent images corresponding to an alpha color and a beta color, and those images are visualized with alpha-color and beta-color toner particles TR and TB. Then uniform exposure is carried out by using C-color light which is transmitted through the photoconductive layer 1B to make the photoconductive layer 1A conductive to form the electrostatic latent image corresponding to black picture elements, and the image is visualized with black toner TN. Consequently, the three-color image which has small dislocation is easily obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a three-color image recording method.

[Prior Art] Various methods have been proposed for writing on a photoconductive photoreceptor using light to record a three-color image.

[Problems to be Solved by the Invention] However, conventionally proposed methods9, such as the method disclosed in Japanese Patent Application Laid-open No. 15853/1983, involve a drum-shaped or belt-shaped photoreceptor rotating once. During the process, charging, writing, and development are repeated three times in succession, which requires three writing devices, which increases the cost of the device and has problems such as less freedom in device design layout. .

There is also the problem that positional deviations tend to occur between images of different colors, and that a page memory for images is required because the writing positions are different.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a novel three-color image recording method that can be realized at low cost and that can record good three-color images.

[Means to solve the problem] The present invention will be explained below.

The three-color image recording method of the present invention is a method for recording three-color images of black, α color, and β color, and the method according to claim 1 and 2 also includes a composite photoreceptor.

This composite photoreceptor has first and second photoconductive layers on a conductive substrate. A second photoconductive layer is provided over the first photoconductive layer. An intermediate layer for carrier trapping may be provided between the first and second photoconductive eyebrows. The second photoconductive layer and the intermediate layer provided as necessary are such that the first photoconductive layer becomes a conductor when the composite photoreceptor is irradiated with A color light, and the second photoconductive layer becomes a conductor when the composite photoreceptor is irradiated with B color light. fJ is made so that the conductive layer becomes a conductor.

The method of claim 1.2 also includes a charging step and an exposure step.

A first development step, a uniform exposure step, and a second development step.

It has a transfer process.

Each of these steps is performed in the above order.

First, to explain the method of claim 1, the first . The second light guides are charged in opposite directions and to approximately equal potentials.

Charging the photoconductive layer refers to forming an electric double layer through the photoconductive layer. As a result of this charging step, the surface potential of the composite photoreceptor becomes approximately zero.

Next, an exposure step is performed on the composite photoreceptor using A color light and B color light.

The light intensity of A color light can be switched between strong and 0, and B
The intensity of the colored light can be switched between strong, weak, and zero.

Then, the composite photoreceptor is connected to each pixel of black, white, α color, and β color, so that black: (A color light intensity; 0, B color light intensity) O) White: (A
Color light intensity; strong, B color light intensity; strong) α color = (A color light intensity; 0, B color light intensity; strong) β color = (A color light intensity; strong, B
By exposing with a combination of color light intensities (weak), an electrostatic latent image corresponding to the α-color image and an electrostatic latent image corresponding to the β-color image are formed.

In the first development step, the electrostatic latent image corresponding to the α-color image and the electrostatic latent image corresponding to the β-color image are visualized using α-color toner and β-color toner that are charged to predetermined polarities opposite to each other. do.

In the subsequent uniform exposure step, the composite photoreceptor is uniformly exposed to C color light that passes through the second photoconductive layer and turns the first photoconductive layer into a conductor, thereby forming an electrostatic latent image corresponding to the β color image. An electrostatic latent image corresponding to a black pixel is formed with the same polarity and larger potential distribution.

Then, this electrostatic latent image corresponding to the black pixel is visualized with black toner in a second developing step under a development bias potential higher than the potential of the electrostatic latent image corresponding to the β color image.

The three-color toner image thus obtained on the composite photoreceptor is transferred and fixed onto transfer paper in the subsequent transfer step.

In the method of claim 2, after performing the same charging step as the charging step of claim 1, an exposure step is performed as follows.

That is, using A color light whose light intensity can be switched between strong, weak, and O, and B color light whose light intensity can be switched between strong and 0, black, white, α
The above composite photoreceptor is arranged in correspondence to each pixel of color and β color.Black = (A color light intensity; 0.B color light intensity, 0) White: (A color light intensity; strong, B color light intensity 1 strong) α color : (A color light intensity;
Weak: B color light intensity Strong) β color: (A color light intensity; strong, B color light intensity O) Exposure is performed to create an electrostatic latent image corresponding to the α color image and an electrostatic latent image corresponding to the β color image. form.

Subsequently, in a first developing step, each of the electrostatic latent images is visualized using α color toner and β color toner that are charged to predetermined polarities opposite to each other.

In the subsequent uniform exposure step, the composite photoreceptor is uniformly exposed to D color light that turns only the second photoconductive layer into a conductor, and the composite photoconductor is uniformly exposed to D color light that makes only the second photoconductive layer conductive, thereby forming an electrostatic latent image of the same polarity and higher potential than the electrostatic latent image corresponding to the α color image. An electrostatic latent image corresponding to a black pixel is formed by the distribution of .

The electrostatic latent image corresponding to the black pixel is visualized with black toner in a second development step under a development bias potential greater than the potential of the electrostatic latent image corresponding to the α color image.

The three-color toner image thus obtained on the composite photoreceptor is transferred onto transfer paper in a transfer process and fixed.

[Function] The three-color image recording method of the present invention uses a composite photoreceptor as described above, and forms electrostatic latent images corresponding to α and β color images as photoreceptor surface potential distributions with opposite polarities through an exposure step. Then, these are visualized by the first developing step. After that, the electrostatic latent image corresponding to the black image written during the exposure process is made visible as a potential distribution by the uniform exposure process, and this is visualized in the second development process. The development bias voltage is manipulated to prevent further black toner from depositing on top of the image.

Referring to FIG. 1, reference numeral 10 indicates a composite photoreceptor.

The composite photoconductor 10 has first photoconductive layers IA and 1B laminated in this order on a conductive substrate IK, and when the composite photoconductor 10 is irradiated with A color light, the photoconductive layer IA becomes conductive. The photoconductive layer 1B is prepared so that it becomes a conductor when the photoconductive layer 1B is made into a conductor and irradiated with B color light.

The method of claim 1 is carried out as follows.

First, while uniformly irradiating this composite photoreceptor 10 with B color light,
For example, when positive charging is performed, the photoconductive layer 1B has become a conductor due to the irradiation with B color light, so this charging causes the first
As shown in FIG. 1, an electric double layer is formed via the photoconductive layer IA. In this state, it is said that the photoconductive layer IA is charged. Next, in the dark, when charging is performed with a negative polarity opposite to the previous charging, the photoconductive layer IA is charged as shown in FIG. 1 (II). , IB are charged in opposite directions. Some of the positive carriers trapped at the boundary between the photoconductive layers IA and IB are connected to the conductive substrate IK and the photoconductor @JL.
The charging process is the process of charging the photoconductive layers IA and 1B in opposite directions, forming a pair with the negative charge at the boundary of A, and forming a pair with the other negative charge on the surface of the photoconductive layer 18. This charging step is performed so that the charging directions of the photoconductive layers IA and IB are opposite to each other, that is, the dipole moments of the electric double layer formed through each photoconductive layer are opposite to each other, and each light is The charging is performed so that the charging potentials of the conductive layers 1^ and 1B are approximately equal, that is, the absolute values of the charging potentials are approximately equal. As a result, the surface potential of the composite photoreceptor after the charging process becomes approximately O.

Next, in the exposure step, exposure is performed using A and B color lights.

In order to make the explanation more concrete, in the following explanation, the alpha color will be referred to as red,
Let the β color be blue.

As shown in Figure 1 (III), in the exposure process black, white,
Exposure with A color light and exposure with B color light are performed for each color pixel of red and blue as follows.

That is, no exposure is performed on black pixels.

Therefore, even after the exposure process, the black pixel portion maintains the surface potential after the charging process, that is, approximately O potential.

A white pixel portion is exposed to both A and B color light at an intensity of r. Due to this exposure, the photoconductive layers l^ and IB are made conductive by the A and B color lights, respectively, and their charged states are eliminated, so that the surface potential of these portions becomes approximately 0 potential after the exposure process.

Next, the portion corresponding to the red pixel is exposed to B color light with an intensity distribution r strong J, and the intensity of A color light is set to 0. In other words, exposure to A color light is not performed. Therefore, in this region, only the photoconductive layer IB becomes a conductor and its charged state is eliminated, and the photoconductive layer IA
The charging potential appears as the photoreceptor surface potential. Therefore, the surface potential of this portion becomes positive after the exposure process.

In addition, the blue pixel area is exposed to [strong] A color light and [weak J B color light. Then, in this part, the charged state of the photoconductive layer IA is canceled by the strong A color light, and the photoconductive layer IB The charged state of is partially resolved by "weak" B color light, but the charged potential of the photoconductive layer IB does not become 0, so the photoreceptor surface potential at this location is the negative electrode of the charged potential of the photoconductive layer IB. It becomes sex. This negative potential is smaller in absolute value than the initial charging potential of the photoconductive layer IB.

Next, as shown in FIG. 1 (rv), development is performed using negatively charged red toner TR to visualize the electrostatic latent image corresponding to the red pixel.

Furthermore, as shown in FIG. 1(V), the electrostatic latent image corresponding to the blue pixel is visualized using the blue toner TB charged with a positive TI. The steps shown in FIGS. 1(IV) and 1(V) are the first developing step.

Subsequently, as shown in FIG. 1(m), a uniform exposure process using C color light is performed.

This C color light turns the photoconductive layer IA into a conductor, and the photoconductive layer IA becomes a conductor.
B selects light that does not become a conductor. Further, it is desirable that the C color light be light that is well absorbed by the red toner.

Through this uniform exposure step, the charged state of the photoconductive layer IA is released, and the charged potential of the photoconductive layer IB appears as a surface potential at the black pixel portion. This potential is the initial charging potential charged during the charging process. Therefore, the potential of the electrostatic latent image corresponding to the black pixel has the same polarity as the potential of the electrostatic latent image corresponding to the blue pixel described above, but is larger in absolute value than the potential of the blue pixel portion.

Therefore, as shown in FIG. 1 (VII), by performing development with positively charged black toner τN under a developing bias potential higher than the potential of the blue pixel portion, only this electrostatic latent image corresponding to the black pixel can be visualized. That is, this is the second developing step.

In this way, a three-color image is formed on the surface of the composite photoreceptor 10 using the three types of toner: red, blue, and black. but.

Among the toners, the red toner and the other toners are charged oppositely, so before transfer, pre-transfer charging is performed to align the polarity of each toner to, for example, positive polarity. ), a desired three-color recorded image can be obtained by transferring the visible image onto the transfer paper S and fixing it.

The method of claim 2 differs from the method of claim 1 in that it includes an exposure step;
There are differences in the uniform exposure process and the second development process.

That is, in the method of claim 2, after the above-mentioned charging process explained with reference to FIGS. 1(I) and (II), an exposure process is performed as follows. Exposure is performed, and the white pixel portion is exposed to both A and B color light at an intensity of just over 1. That is, the exposure conditions for these black pixels and white pixels are the same as in the method of claim 1.

Next, the portion corresponding to the red pixel is exposed to B color light with an intensity distribution r of "strong", and the intensity of the A color light is set to "weak".

Then, in this part, the state of charge of the photoconductive layer IB is strong B.
The charge state of the photoconductive layer IA is partially resolved by the A color light of 1 level, but the charge potential of the lead 'H-/11 A does not reach 0, and therefore the photoreceptor surface at this location is The potential has the positive polarity of the charging potential of the photoconductive layer IA.

This positive potential is smaller in absolute value than the initial charging potential of the photoconductive layer IA. In addition, the blue pixel area is exposed to A color light of 1 strong, and in this area, only the photoconductive layer 1^ becomes a conductor and its charged state is eliminated, and the charged potential of the photoconductive layer IB becomes the photoreceptor surface potential. Appears as.

Therefore, the surface potential of this portion becomes negative after the exposure process.

In this way, the electrostatic latent image corresponding to the red pixel and the electrostatic latent image corresponding to the blue pixel are formed as photoreceptor surface potentials of opposite polarity.
Next, these are visualized using red toner TR1 and blue toner TB in the same manner as in the first developing step.

In the subsequent uniform exposure step, the composite photoreceptor is uniformly irradiated with D color light. The D color light is light that only makes the photoconductive layer IB conductive, but it is desirable that the light is well absorbed by the blue toner. Through this uniform exposure step, the charged state of the photoconductive layer IB is released, and the positive electrode The electrostatic latent image corresponding to the black pixel becomes apparent as the surface potential of the black pixel. The potential of this electrostatic latent image is the charging potential of the photoconductive layer IA on the side of the charging process, and is higher than the potential of the electrostatic latent image corresponding to the red pixel.

Therefore, by performing development with the black toner TN while applying a potential higher than the electrostatic latent image corresponding to the red pixel as a developing bias, only the electrostatic latent image corresponding to the black pixel can be visualized. The rest is claim 1
A desired three-color image can be obtained by performing the same transfer process as the one described above.

[Example] Hereinafter, description will be given based on specific examples.

A composite photoreceptor as shown in FIG. 2 (1) was prototyped. Since there is no risk of confusion, the same reference numerals as in FIG. 1 will be used in the explanation.

The first photoconductive layer IA formed on the conductive substrate IK is of a functionally separated type, and is composed of a layered carrier transport layer IAI and a carrier generation layer IA2.

Further, an intermediate layer IC is formed between the first photoconductive layer IA and the second photoconductive layer IB.

This composite photoreceptor was formed as follows. As the conductive substrate IK, a resin film with an A1 layer deposited on the surface was used. First, a carrier generation layer IAI was formed on this conductive substrate 1. This carrier generation layer
A phenylstilbene compound having the structural formula as shown in Figure (II) is used as a donor, polycarbonate is used as a binder, and a solution of these dissolved in tetrahydrofuran is sprayed onto the conductive substrate IK and dried to a thickness of 20 μm. was formed.

Next, a carrier generation layer IA is placed on this carrier transport layer.
2, a pigment having the structural formula as shown in FIG. 1 (III) was dissolved in tetrahydrofuran together with a binder, and the mixture was spray-dried to a thickness of 0.1 μm.

On top of that, a layer of polyamide with a thickness of 0.5 mm is applied as an intermediate layer IC.
It was formed to a thickness of 3μ by a spray method.

Finally, a layer of eutectic OPc was formed to a thickness of 20 μm as the second photoconductive layer IB. Eutectic OPC consists of polycarbonate as binder, thiapyrylium salt as dye,
The above phenylstilbene compound and eutectic OPC were dissolved in a solution as a donor and formed by a spray method.

FIG. 2(rv) shows the spectral sensitivity of the first photoconductive layer IA, and FIG. 2(V) shows the spectral sensitivity of the second photoconductive layer IB and the intermediate layer IC.
FIG. 2 (VI) shows the spectral sensitivity of the second photoconductive layer IB.

As is clear from these figures, the photoconductive layer IB of the prototype composite photoreceptor 10 allows light with a wavelength of 780 nm to pass through nine layers,
Absorbs 97% of light with a wavelength of 878 nm. Furthermore, the photoconductive layer IIA has high sensitivity to light having a wavelength of 780 nm that passes through the photoconductive layer IB and the intermediate layer 1C. Therefore, light with a wavelength of 780 nm can be used as the above-mentioned A color light,
In addition, the light with a wavelength of 678nra can be used as B color light, and the light with a wavelength of 460nr@ can be used for the photoconductive layer IB and the intermediate layer IC.
and makes the photoconductive layer IA a good conductor. Therefore, this light with a wavelength of 460 nm can be used as the above-mentioned C color light.

Now, the above-mentioned composite photoreceptor 10 is constructed in the form of a belt.

A device as shown in FIG. 3 was constructed.

In FIG. 3, while rotating the PJ combined photoreceptor 10 in the 10 meter direction, first uniformly irradiate the photoreceptor with white light from the quenching lamp 30 to perform optical static elimination, and then the charger 12
Positive charging is performed while uniformly irradiating light with a wavelength longer than 880 nm. Light with a wavelength of 680 nm or more is obtained by filtering the light from the lamp 12B with a filter 12. Note that this charging occurs when the surface potential of the composite photoreceptor 10 is +1600
Do this so that it forms a V.

Next, when the charger 14 performs negative charging so that the surface potential becomes 0, the photoconductive layer IA becomes +5o.
ovt: The photoconductive layer IB is charged with -800V.

Subsequently, an exposure process is performed using the optical writing device 1B.

The optical sending device 16 has a wavelength of 678 nm as shown in FIG.
, a light source device 161 that combines a semiconductor laser that emits laser light of 780 nm and a collimating lens system.
A parallel beam is obtained from 162, which is combined by a dichroic mirror 163, a one-rotation polygon mirror 164, and an fθ lens 1.
65, the composite photoreceptor 10 can be optically scanned and written. In addition, you should write black, white, red,
The blue image signal is obtained by reading a document having three-color images of red, blue, and black on a white background.

The laser beams have wavelengths of 780 nm and 678 nm.

The strength can be changed as shown below.

Pixel 780nm 678n＋＊Black
OO White Strong Strong Red O Strong Blue Strong Weak However, 1 strong is the light intensity that can reduce the charging potential of the photoconductive layer from ±800v to ±50v, and 1 weak is the light intensity that can reduce the charging potential of the photoconductive layer from ±800v to ±50v. The intensity is approximately 400v.

As a result, the surface potential of the photoreceptor after the exposure step is +aoov at the electrostatic latent image area corresponding to the red pixel, -400 V at the electrostatic latent image area corresponding to the blue pixel, and approximately 0 at other areas.

Among the electrostatic latent images thus formed, the electrostatic latent image corresponding to the red pixel is developed by a developing device 18 using red toner. The developing device 18 is a known NSP developing device.

This is contact development.

Subsequently, the electrostatic latent image corresponding to the blue pixel is developed by a developing device 20 using blue toner.

Next, the white light from the lamp 22 is filtered by a filter 221 to uniformly expose the composite photoreceptor 10 to light having a wavelength of 460±1 one. As a result, the electrostatic latent image corresponding to the black pixel is manifested as a surface potential of 1800V. This potential is the charging potential of the photoconductive layer 18.

This electrostatic latent image corresponding to the black pixel is visualized with black toner by the developing device 24. At this time, -400V is applied to the developing section as a developing bias potential. This prevents the electrostatic latent image corresponding to the blue pixel from being further developed with black toner.

Although the developing devices 20 and 24 were NSP developing devices, the developing gap was controlled to 50±10 μm using a spacer. Thereby, subsequent development can be performed without affecting the toner image obtained in the previous development.

A three-color image is thus formed on the composite photoreceptor 10.

The toner that makes up this three-color image is transferred to the pre-transfer charger 2.
6 allows you to align the polarity to positive polarity.

The transfer paper S is attracted to the transfer belt 32 by the charger 34 and conveyed, the toner image is transferred by the transfer charger 33, it is separated from the transfer belt 32 by the 1-separation charger 40, and the three-color image is fixed by the fixing device 42. after,
Expelled from the device.

After the visible image has been transferred, the composite photoreceptor 10 is cleaned by a cleaning device 28.
The residual toner is removed.

Further, the transfer belt 32 is neutralized by a static eliminator 36 and cleaned by a cleaner 38 .

I was able to obtain a good three-color image by implementing the above process.

During the exposure process, a little less than 1 ounce of light with a wavelength of 780 nm is applied to the red pixel area.
The latent image potential is set to +400■ by parallel writing, and the blue pixel area is not exposed to light with a wavelength of 678 nm, and the uniform exposure process is uniformly exposed to light with a wavelength of 680±10 nm, so that it corresponds to black pixels. A good three-color image could also be obtained by the method of claim 2, in which an electrostatic latent image is formed as a potential distribution of 10 aoov and developed with a bias voltage of +400V.

Note that the conveyance of the transfer paper S can be switched back by the transfer belt 32 to repeat transfer a plurality of times, and by utilizing this, it is possible to record a mixed color image of red and blue.

[Effects of the Invention] As described above, according to the present invention, a novel three-color image recording method can be provided. Since the method of the present invention has the above-described configuration, the exposure process is simple and a three-color image with little positional shift of color images can be easily and reliably obtained.

Note that writing using A color light and B color light can be done using the method described in the example,
Arrays of LDs or LEDs that emit these lights may be arranged close to each other, and writing using A color light and writing using B color light may be performed with a slight temporal shift.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention, FIG. 2 is a diagram for explaining a composite photoreceptor used in an example, and FIG. 3 is a diagram showing an example of an apparatus for carrying out the present invention. FIG. 4 is a diagram for explaining the optical writing device. 10. Composite photoreceptor, 60. conductive substrate, IA,
,,first photoconductive layer, IB,,second photoconductive layer,T
R, Red toner, TB, Blue toner, TN, Black toner, S90. Transfer paper introduction/z, figure (V) 3 (Cm Sae J)

Claims (1)

[Claims] 1. First and second photoconductive layers are disposed on a conductive substrate with the second photoconductive layer facing upward, and the first photoconductive layer is irradiated with A color light. Using a composite photoreceptor prepared such that the second photoconductive layer becomes a conductor when irradiated with B-color light, the first and second photoconductive layers are oriented in opposite directions to each other and approximately Using a charging process to charge to the same potential, A color light whose light intensity can be switched between strong and 0, and B color light whose light intensity can be switched between strong, weak and 0, black, white, α color, β color, etc.
The above composite photoreceptor is arranged corresponding to each color pixel: Black: (A color light intensity; 0, B color light intensity; 0) White: (A color light intensity; strong, B color light intensity: strong) α color: (A Color light intensity; 0, B color light intensity; strong) β color: (A
an exposure step of forming an electrostatic latent image corresponding to the α-color image and an electrostatic latent image corresponding to the β-color image by exposing with a combination of intensity of color light intensity: strong, B color light intensity: weak; A first developing step in which the electrostatic latent image is visualized using α color toner and β color toner charged to opposite predetermined polarities; The composite photoreceptor is uniformly exposed to C-color light that makes the photoconductive layer of the image conductive, and has the same polarity as the electrostatic latent image corresponding to the β-color image.
A uniform exposure step of forming an electrostatic latent image corresponding to a black pixel using a larger potential distribution, and a developing bias that is larger than the potential of the electrostatic latent image corresponding to the β-color image to form an electrostatic latent image corresponding to the black pixel. A three-color image recording method comprising: a second developing step of visualizing with black toner under a potential; and a step of transferring and fixing the three-color toner image obtained on the composite photoreceptor onto transfer paper. 2. Dispose the first and second photoconductive layers on a conductive substrate with the second photoconductive layer on the upper side, and when irradiated with A color light, the first photoconductive layer becomes a conductor and becomes a B color light. Charging in which the first and second photoconductive layers are charged in opposite directions and to approximately the same potential using a composite photoreceptor prepared such that the second photoconductive layer becomes a conductor when irradiated with Using A color light whose light intensity can be switched between strong, weak and 0, and B color light whose light intensity can be switched between strong and 0, black, white, α color, β color
The above composite photoreceptor is arranged corresponding to each color pixel: Black: (A color light intensity; 0, B color light intensity; 0) White: (A color light intensity; strong, B color light intensity: strong) α color: (A Color light intensity; weak: B color light intensity; strong) β color: (A
an exposure step of forming an electrostatic latent image corresponding to an α-color image and an electrostatic latent image corresponding to a β-color image by exposing with an intensity combination of color light intensity: strong, B color light intensity: 0; A first developing step in which the latent image is visualized with α color toner and β color toner charged to predetermined polarities opposite to each other; and After the first developing step, only the second photoconductive layer is made into a conductor. a uniform exposure step of uniformly exposing the composite photoreceptor to D-color light to form an electrostatic latent image corresponding to black pixels with the same polarity as the electrostatic latent image corresponding to the α-color image and with a larger potential distribution; , a second development step in which the electrostatic latent image corresponding to the black pixel is visualized with black toner under a development bias potential greater than the potential of the electrostatic latent image corresponding to the α-color image; A three-color image recording method, comprising the step of transferring and fixing the three-color toner image onto a transfer paper.