JPH0950162A - Image forming method - Google Patents

Abstract

(57) [Summary] [Purpose] To separate and remove the toner mixed in the developer to form a clear two-color image. [Structure] As the first toner of the first developer, one that is charged to the opposite polarity to the second toner when mixed in the second developer is used, and the mixing ratio of the second developer is set to a predetermined value. So that the first toner can be electrically separated from the second developer. The first toner mixed in the second developer is surely separated and removed to form a two-color image with little color mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming method, and more particularly to an image forming method suitable for two-color development.

[0002]

2. Description of the Related Art A two-component developer consisting of a toner and a carrier is used to repeatedly charge, expose and develop a photoreceptor.
There are electrophotographic devices that form color toner images. In this electrophotographic apparatus, when a second developer is applied on the photoconductor when the second toner image is formed on the photoconductor on which the first toner image is formed, a developing process is performed. The second developer scrapes off the first toner image formed on the body, and the first toner mixes in the second developer,
In the second toner image formed by developing, color mixture due to the mixed first toner occurs. Then, the first toner mixed in the second developer is accumulated in the second developer, and the amount thereof increases with time, so that the second toner image gradually has a degree of color mixture. However, there is a problem in that it becomes impossible to form a clear two-color toner image.

As a method for solving this problem, Japanese Patent Publication No. 6
In Japanese Patent Laid-Open No. 3-56542, the toner concentration of the first developer is made lower than the toner concentration of the second developer, and the charge amount of the toner of the first developer is changed to the charge amount of the toner of the second developer. By making it larger than the first
The toner adhesion force of the second developer is further increased, and the adhesion force of the toner to the carrier of the second developer is decreased, so that the first toner is separated from the photosensitive drum during the development by the second developer,
It is proposed to prevent the color mixture from being mixed in the developer and reduce the occurrence of color mixture.

Further, Japanese Patent Publication No. 4-1907 / 1992 discloses another method for reducing color mixture. In this method, when the first toner image and the second toner image are formed, the first toner and the second toner are charged to the same polarity, but the first toner is contained in the second developer. When the first toner is mixed, the charge amount of the mixed first toner is set from near zero to the opposite polarity to the charge polarity of the second toner. Then, the toner having a charge amount near zero is removed from the second developing device by the air flow, or the toner having the opposite polarity to the second toner is electrically separated and removed. Also,
Another method disclosed in Japanese Examined Patent Publication (Kokoku) No. 63-56543 is to use a first toner having a polarity opposite to that of the second toner by adhering the first toner to a region on the surface of the photosensitive drum where the charge remains. It is proposed to remove the first toner mixed in the second developer. In these examples, it is necessary to use, as the first toner, a material whose charge polarity is reversed by frictional charging with the second developer, but as such a material, the second toner and the second carrier are used. A material is selected so that the charge amount when combined is larger than the charge amount when the first toner and the second carrier are combined. However, in combination with the second carrier,
Although the charge amount of the second toner is larger than the charge amount of the first toner, on the contrary, a phenomenon occurs in which the charge polarity of the second toner is reversed, and the desired effect is obtained. There was nothing.

The above conventional example is a case where the first and second toner images are formed by reversal development-reversal development or regular development-regular development, and two types of toner having the same charging polarity are used.

On the other hand, a method of preventing color mixture when toners having different charging polarities are used as the first toner and the second toner is disclosed in JP-A-59-214049 and JP-A-6-62.
It is disclosed in Japanese Patent Publication No. 3-292161. This method uses such a developer that the carrier of the second developer lies between the first toner and the second toner on the triboelectric series. As a result, even if the first toner is mixed in the second developer, its charge polarity is not reversed, so that the second toner can be electrically separated, and the second toner is hardly mixed in the second developer.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to
The charge polarity of the first toner mixed in the second developer is surely opposite to that of the second toner, and the color mixing is small even if the first toner is mixed in the second developer. It is to provide a two-color image forming method.

[0008]

A feature of the present invention is that after a first toner image is formed on a photoconductor by a first developer, a second toner image is formed on the photoconductor on which the first toner image is formed. In the image forming method for forming the second toner image with the second developer, the first toner of the first developer, which is charged to the opposite polarity to the second toner when mixed in the second developer, is used. In addition, the mixing ratio of the second developer is set to a predetermined value so that the first toner can be electrically separated from the second developer.

[0009]

The first toner mixed in the second developer is charged to the opposite polarity to the second toner by frictional charging with the second toner, and is electrically attracted.
The second toner image can be removed from the second developer by a method of adhering it to a region where the second toner image is not formed (image background portion).

Therefore, even if the first toner is mixed in the second developer, the mixed toner is not removed and accumulated, so that the second toner image is not mixed and clear. It is possible to form two color toner images.

[0011]

EXAMPLES First, the relationship between the charge amount and the toner mixing ratio will be described, and then the relationship with the conditions for preventing color mixing will be described.

How to determine the relationship between the charge amount Q / M and the toner mixture ratio T / C (weight of toner / weight of carrier) will be described.

Consider a developer in which m1 (g) toner and m2 (g) carrier are mixed. The toner mixing ratio T / C can be expressed by Equation 3.

[0014]

(Equation 3)

The phenomenon in which the toner is charged by the friction between the toner and the carrier will be described with reference to the model of FIG. This model is a charging model in which the amount of electrons moving during contact is determined by the work function difference between toner and carrier and the number of surface states. The work function is the minimum energy for releasing electrons into the vacuum, and is shown by W1 and W2 in FIG.
The number of surface states indicates how many electrons are present in the unit energy width or there is a place where the electrons enter, and it is indicated by N1 and N2 in FIG. It is considered that the frictional electrification of the toner and the carrier is such that when the toner and the carrier come into contact with each other, the electrons move from the smaller work function to the larger work function, and the movement of the electrons ends when the work function difference after the movement becomes zero. There is. This idea is based on the model of FIG. 5, assuming that the toner and carrier are each a container containing water, and if the bottom of this container is connected with a pipe, the water moves from a higher water level to a lower water level. It is very similar to the movement of water ending when the water levels in the containers coincide. Water is an electron,
The distance from the top of the container to the surface of the water corresponds to the work function.

When the work function of the carrier is smaller than that of the toner as shown in FIG. 5, electrons move from the carrier to the toner. The amount of charge transferred, Q, can be calculated from the model above,

[0017]

(Equation 4)

[0018] Here, N1 and N2 are the surface state numbers of the toner and the carrier, W1 and W2 are the work functions of the toner and the carrier, and e is the absolute value of the electronic charge.
This formula is published by Baifukan, A. R. See Bryce, Akira Miyake and Wataru Segawa, co-translation “Electrical Properties of Polymers” on page 177.

Amount of charge Q / M per unit weight of toner
Can be obtained by dividing Q by m1 and becomes:

[0020]

(Equation 5)

Next, a relational expression with T / C will be derived. Assuming that the number of surface states per unit weight of toner and carrier is n1 and n2, the following relationships exist between the weights m1 and m2 and the number of surface states N1 and N2.

[0022]

(Equation 6)

[0023]

(Equation 7)

From Equations 3, 6 and 7,

[0025]

(Equation 8)

## EQU1 ## Eliminate m1 from number 5 and then number 8
Using the relational expression of

[0027]

[Equation 9]

## EQU1 ## The numerator of the number 9 is Q / M (0), the n1 / n2 of the numerator is Lch, and

[0029]

(Equation 10)

[0030]

[Equation 11]

[Mathematical formula-see original document]

[0032]

(Equation 12)

## EQU1 ## This is an equation representing the relationship between the toner charge amount Q / M and the toner mixture ratio T / C. From this equation 12, it is understood that Q / M (0) is the value of Q / M extrapolated to the toner mixture ratio T / C = 0. Also, from Equation 12, L
It can be seen that ch represents the degree of decrease in Q / M as the mixing ratio T / C increases. The larger the value, the more the mixing ratio T / C.
The Q / M is greatly decreased with an increase in the toner charge and is considered to be a load for charging the toner.

Developers having different toner mixing ratios T / C were prepared by combining various toners and carriers, and the charge amount Q / M thereof was measured by the blow-off method. Measurement error is 10%
It is a degree.

[0035]

[Table 1]

Table 1 shows the results. Table 1 shows
Applying the least squares method to the measurement result, Q / M (0)
And Lch. Err in Table 1 is Q / M
It is the root mean square error between the calculated value using (0) and Lch and the measured value. Usually, the value obtained by multiplying the root mean square error by 3 is estimated as the error, and accordingly, from Table 1, the difference between the Q / M calculated by Equation 12 and the actually measured value is within 10% on average. I understand. This is in good agreement when the measurement variation of Q / M is taken into consideration. Therefore, Q / M and T / C
It can be seen that the relationship of is expressed by Equation 12.

Next, the same analysis as described above is performed to find the conditions for reversing the charge polarity of the mixed toner. Here, considering negatively charged toner, the second color toner is A, the first color toner is B, and the carrier is C. In addition, toner A,
When B is combined with carrier C, B is charged to have a negative polarity. Further, in order to reverse the charge polarity of the toner B to the positive polarity, the magnitude of the work function is WA>WB> WC as shown in FIG.

The Q / M of toners A and B can be calculated as follows. Assuming that electrons move so that there is no difference in work function, the energy level WF after the movement of electrons is

[0039]

(Equation 13)

Then, the charge amount Q accumulated in the toner A is
A is

[0041]

[Equation 14]

It becomes Similar to the above analysis, the following relationship exists between the toner / carrier surface state number N and the toner / carrier weight m.

[0043]

(Equation 15)

In Expression 15, nA, nB and nC are the number of surface states per unit weight.

The charge amount Q / MA of the toner A is Q
It can be obtained by dividing A by mA,

[0046]

(Equation 16)

It becomes Equation 16 can be rewritten as follows.

[0048]

[Equation 17]

By the way, the toner A for the carrier C,
When Q / M of B is extrapolated to T / C = 0,

[0050]

(Equation 18)

[0051]

[Equation 19]

Is as follows. By rewriting Eq. 17 using this and Eq. 15, the Q / M of toner A is as follows.

[0053]

(Equation 20)

Similarly, the following equation is obtained for Q / MB.

[0055]

(Equation 21)

By the way, the toner considered here is a negatively charged toner, and Q / M (0, A, C) <0, Q / M
Since (0, B, C) <0, the second term on the right side of the equations (20) and (21) shifts the values of Q / MA and Q / MB from the negative direction to the positive direction (decreases the absolute value). To work. That is, it is a term indicating charge polarity reversal.

Next, the conditions for reversing the charging polarity of the mixed toner B and for positively charging the toner B will be determined.

First, the following conditions

[0059]

(Equation 22)

The following equation is obtained by applying the equations (20) and (21).

[0061]

(Equation 23)

[0062]

(Equation 24)

[Mathematical formula-see original document] Equations 23 and 24 are divided by nC.mC, and the following relationship is established: Charging load coefficient: LchAC = nA / nC, LchBC =
Using the nB / nC mixing ratio: T / C = mA / mC mixing ratio: M / T = mB / mA, the following can be rewritten.

[0064]

(Equation 25)

[0065]

(Equation 26)

First, a condition for satisfying the equation 25 is obtained. Swap the terms of the equation to get the following equation:

[0067]

[Equation 27]

M / T> 0, T / C> 0, -Q / M (0,
Since A, C)> 0, the following two cases are conceivable as conditions under which Expression 27 holds.

(Case 1) LchBC · Q / M (0,
A, C) -LchAC · Q / M (0, B, C)>
If 0

[0070]

[Equation 28]

(Case 2) LchBC · Q / M (0,
A, C) -LchAC · Q / M (0, B, C) <
If 0

[0072]

(Equation 29)

Next, the condition is obtained from the equation 26. Similar to the previous equation, the terms of the equation are exchanged to obtain the following equation.

[0074]

[Equation 30]

Since T / C> 0, it is necessary to satisfy the equation 30.

[0076]

[Equation 31]

That is, The condition is the same as (case 2) under the condition of Expression 27.

At this time, the following condition is obtained for T / C.

[0079]

(Equation 32)

After all, the conditions that both equations 25 and 26 are satisfied are represented by equations 31 and 32. This is a condition for the toner B to be positively charged.

Next, returning to the equation 26 before rewriting to the equation 32, it is rewritten as follows.

[0082]

[Expression 33]

This equation shows the Q / M-T / C characteristics of Toner B as shown in FIG.
When Q / M is approximated to be inversely proportional to T / C, the toner A is equal to or more than the mixing ratio T / C (R) at the point where the Q / M-T / C characteristic which does not approximate the toner A intersects. And carrier C
It is necessary to set the mixing ratio of. This is the condition for reversing the charge polarity of the mixed toner.
The condition is satisfied when the mixing ratio of the toner of the second color developer and the carrier is larger than the value of T / C (R) calculated by Equation 32. In such a case, the second color developer is satisfied. It is possible to reverse the charge polarity of the first-color toner mixed in the developer. This is because the mixed toner B is negatively charged with respect to the carrier C,
Since the toner A is positively charged, it is easy to understand that the charging polarity of the mixed toner is determined by the degree of charging with both. That is, if the ratio of the toner A is small, the mixed toner B is negatively charged mainly by frictional charging with the carrier, and if the mixing ratio is large and the ratio of the toner A is large, the mixed toner B is The frictional charging with the toner A is mainly charged to the positive polarity.

Since the mixing ratio is a positive value,
If the value of T / C (R) calculated in step 1 is a negative value, it means that there is no condition for reversing the charge polarity of the toner of the first color mixed in with the developer of the second color. Therefore, in such a case, as described above, it is impossible to reverse the charge polarity of the mixed toner by frictional charging with the toner and separate the mixed toner from the second developer.

An embodiment of the present invention in which mixed toner is separated by such charge control will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows, as a first embodiment, an example of a two-color image forming apparatus for carrying out the image forming method according to the present invention. In this two-color image forming apparatus, OPC having a negative charging characteristic is used for the photosensitive drum 1, and a developer using negatively charging toner is used as the first and second toners. The photosensitive drum 1 is installed so as to rotate at a constant speed in the clockwise direction, and its surface is first uniformly charged with a negative polarity by the first charger 2 and then the image of the first color by the first exposure device 3. Light corresponding to the data is irradiated to form a first electrostatic latent image, and the first developing device 4 develops with a first developer to form a first toner image. Then the second
The second exposure unit 6 is charged again with the negative polarity by the charger 5.
Is irradiated with light corresponding to the image data of the second color to form a second electrostatic latent image.
And the second toner image is formed.

The two-color toner image formed by the first toner image and the second toner image formed on the photosensitive drum 1 by the above procedure is transferred onto the recording medium 12 such as paper by the transfer device 8 and then fixed by the fixing device 10. Is fixed in. Photosensitive drum 1 after transfer
Is used for the next two-color image formation after the toner remaining on the surface is removed by the cleaner 9.

In such a two-color image formation, when the surface of the photosensitive drum 1 is rubbed with the developer of the second developing device 7 when the second toner image is formed and the developing step is executed, the photosensitive drum is already formed. A part of the first toner is scraped off from the first toner image already formed on the first toner image and is taken into the second developer of the second developing device 7.

By the way, this two-color image forming apparatus is
Table 2 shows the mixing ratio dependence of the charge amount due to the triboelectrification of the first toner included in the second developer, the second toner included in the second developer, and the second carrier of the second developer. It has the characteristics shown in.

[0090]

[Table 2]

From this characteristic, the mixing ratio T /
When C (R) is calculated, it becomes 0.016. Also, the second
The developer uses a binder type carrier in which magnetic powder is dispersed in resin, and the mixing ratio is 0.04 to 0.0
It is set between 8 and 8 to ensure a predetermined development (image) density. The mixing ratio of this second developer is 0.016.
As described above, when the first toner is mixed in the second developer, the triboelectrification polarity of the first toner can be reversed to the positive polarity. In fact, the first developer mixed with the first toner is forcibly mixed, and the developer is sandwiched between two parallel electrodes to apply a high voltage, so that the mixed first toner is mixed with the negative electrode. Could be separated to the side.

Therefore, as shown in FIG. 2, the negative polarity charged first toner mixed in the second developer is changed in polarity from negative polarity to positive polarity by frictional charging with the second toner. Then, as described above, the first
The toner can be removed from the second developer by an electric suction method or a method of adhering it to a region (image background portion) where the second toner image is not formed on the photosensitive drum 1.

Therefore, even if the first toner is mixed in the second developer, the mixed toner is not removed and accumulated, so that the second toner image is not mixed and clear. It is possible to form two color toner images.

(Embodiment 2) Next, as a second embodiment,
An example of a two-color image forming apparatus using toners having different charging polarities as the first toner and the second toner will be described with reference to FIG.

The main constituent elements of this second embodiment are also shown in FIG.
This is the same as the first embodiment shown in FIG. In this embodiment, the second charger 5 installed between the first developing device 4 and the second exposing device 6 in the first embodiment is omitted, and instead, the second developing device 7 is provided in the subsequent stage. A pre-transfer charger 11 is installed. The pre-transfer charger 11 is a charger for adjusting the charging polarities of the first toner and the second toner formed on the photosensitive drum 1 to one polarity.

The two-color image forming apparatus forms a toner image in the following order. In the second embodiment as well, similar to the first embodiment, the case where the OPC having the negative charging characteristic is used for the photosensitive drum 1 will be described. Further, a case where a positively charged toner is used as the first toner and a negatively charged toner is used as the second toner will be described.

The photosensitive drum 1 is installed so as to rotate at a constant speed in the clockwise direction, the surface of the photosensitive drum 1 is uniformly negatively charged by the first charger 2, and the image of the first color is imaged by the first exposure device 3. Light corresponding to the data is emitted to form a first electrostatic latent image. At this time, the amount of light irradiated by the first exposure device 3 is controlled so that the charge (charge amount) of the light-irradiated portion on the photosensitive drum 1 disappears by about half. Next, the first developing device 4 develops with the first developer, and the positively charged first toner adheres (regularly) to the area where the light remains on the photosensitive drum 1 without being irradiated with light. developing)
I do.

Next, the surface of the photosensitive drum 1 is the second exposure device 6
Thus, light corresponding to the image data of the second color is emitted to form a second electrostatic latent image on the photosensitive drum 1. At this time, the amount of light emitted by the second exposure unit 6 is controlled so that the charge on the portion of the photosensitive drum 1 irradiated with the light is almost lost. The surface of the photosensitive drum 1 on which the second electrostatic latent image is formed is developed by the second developer by the second developer, and the second toner charged with negative polarity is attached. This second toner adheres (reverse development) to the area where the light is irradiated on the photosensitive drum 1 and the charge has disappeared.

The two-color toner image formed by the first positively charged toner and the second negatively charged toner formed on the photosensitive drum 1 by the above procedure is directly transferred to the recording medium 12 when electrostatically transferred. Only the toner image of one charging polarity is transferred. The pre-transfer charger 11 aligns the two toner images with either positive or negative charging polarity so that both toner images are electrostatically transferred. The first and second toners having the same charging polarity are transferred to the recording medium 12 such as paper by the transfer device 8 and fixed by the fixing device 10. After the transfer, the photosensitive drum 1 is used for forming the next toner image after the toner remaining on the surface of the photosensitive drum 1 is removed by the cleaner 9.

In this two-color image formation, the first toner and the second toner have different charging polarities. Therefore, when the second electrostatic latent image formed on the surface of the photosensitive drum 1 is developed by the second developer of the second developing device 7, the first electrostatic latent image formed on the photosensitive drum 1 is already formed. The toner image of (1) is electrically repelled by the second carrier of the second developer, and thus is hardly scraped off. However, since the first toner has the opposite polarity to the second toner, the first toner is associated with the second toner and the second toner
It may be mixed in the second developer of the developing machine 7.

By the way, in this embodiment, the same second developer as that used in the first embodiment is used.
The same toner is used, but the first carrier is the first
The toner of (1) is positively charged. For example, a carrier coated with a fluorine-based resin is used. By using such a carrier, the first toner can be positively charged.

In this embodiment, the first toner is the second toner.
When mixed in the developer, the first toner becomes positive in the second developer as described in the first embodiment. Therefore, as shown in FIG. 4, the positively charged first toner mixed in the second developer is maintained in the positive polarity by the frictional charging with the second toner, and as described above,
The first toner having the positive polarity of the charging polarity is secondly developed by a method of electrically attracting it or a method of adhering it to a region (image background portion) where the second toner image is not formed on the photosensitive drum 1. It is removed from the agent.

Therefore, also in the case of this second embodiment, the first
Even if the toner of No. 2 is mixed in the second developer, it is not removed and accumulated, so that the second toner image is not mixed in color and a clear two-color toner image can be formed. .

In this embodiment, the system in which the exposure is divided into two is described. However, a three-level electrostatic latent image is formed on the photosensitive drum 1 by one exposure in which the exposure amount is controlled. The same method can be applied to a method of forming toner images of two colors by performing normal development and reversal development.

(Comparative Example 1) As Comparative Example 1, the case where the developers shown in Table 3 are used will be described.

[0106]

[Table 3]

This toner is the same as in Table 2, but the carrier coating is modified. Then, the value of T / C (R) calculated by the equation 32 is 0.126. Second
A value of 0.126 is too large as the mixing ratio of the developer, which causes scattering of toner and contamination of the image background portion. A proper mixing ratio of the second developer is about 0.06 from the viewpoint of ensuring a predetermined image density and not causing toner scattering or background contamination.
Therefore, since the value is smaller than 0.126, the charging polarity of the first toner mixed in the second developer is not reversed, and
Since it cannot be separated from the developer, it is accumulated and mixed in the second toner image, and an unclear second toner image is formed.

(Comparative Example 2) As Comparative Example 2, the case where the developers shown in Table 4 are used will be described.

[0109]

[Table 4]

With this developer, T / C calculated by the equation 32
The value of (R) is -0.034. The mixing ratio must be a positive value, and this negative value means that
In the developers of Table 4, it means that the charge polarity of the first toner does not reverse due to friction with the second toner.
In fact, when the first toner and the second toner are mixed directly and then a high voltage is applied with the two parallel electrodes sandwiched between them,
The first toner adhered to the positive electrode and the second toner adhered to the negative electrode. That is, in this case, the first toner was more likely to be negatively charged than the second toner. Therefore, also in this comparative example, the charging polarity of the first toner mixed in the second developer does not reverse and cannot be separated from the second developer, so that it accumulates in the developer. The second toner image is mixed with the second toner image, and an unclear second toner image is formed.

[0111]

As described above, according to the present invention, it is possible to reliably separate and remove the first toner mixed in the second developer, and obtain a two-color image with little color mixture. You can

[Brief description of drawings]

FIG. 1 is a schematic view of a two-color image forming apparatus for explaining a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the reversal of the charge polarity of the mixed toner in the first embodiment of the present invention.

FIG. 3 is a schematic view of a two-color image forming apparatus for explaining a second embodiment of the present invention.

FIG. 4 is a diagram illustrating inversion of charging polarity of mixed toner according to a second embodiment of the present invention.

FIG. 5 is a model diagram of triboelectric charging of toner.

FIG. 6 is a model diagram of triboelectric charging when mixed toner is present.

FIG. 7 is a characteristic diagram illustrating the relationship between the charge polarity reversal of mixed toner and the mixing ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 1st charging device 3 1st exposing device 4 1st developing device 5 2nd charging device 6 2nd exposing device 7 2nd developing device 8 Transfer device 9 Cleaner 10 Fixing device 11 Pre-transfer charging device 12 Recording medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Ouchi 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Nititsu Koki Co., Ltd.

Claims (3)

[Claims] 1. A first toner image is formed on a photoconductor by a first developer, and then a second toner image is formed on the photoconductor on which the first toner image is formed by a second developer. In the image forming method for forming, a two-component developer including a toner and a carrier is used as the second developer, and the toner and the carrier of the second developer are combined using the parameter estimation method of the least square method. In order to apply the relationship between the charge amount Q / M of the toner of No. 2 and the weight mixing ratio T / C of the toner and the carrier to the equation 1,
/ M (0) and Lch are calculated and Q / M (0, A),
LchA, and the charge amount Q / of the first toner when the first toner and the carrier of the second developer are combined in the same manner.
The Q / M (0) and Lch of the equation 1 are calculated so that the relationship between M and the weight mixing ratio T / C is applied to the equation 1, and Q / M (0) is calculated as Q / M.
(0, B), LchB, and T calculated by Equation 2
/ C (R) is positive, and the developer is used in a mixing ratio in which the weight mixing ratio of the second developer is larger than T / C (R). [Equation 1] [Equation 2] 2. The image forming method according to claim 1, wherein
When forming the second toner image and the second toner image, the first toner and the second toner are charged to the same polarity and used.
An image forming method, characterized in that the first toner and the second toner are toners that are charged to the same polarity with respect to the carrier of the second developer. 3. The image forming method according to claim 1, wherein
When forming the second toner image and the second toner image, the first toner and the second toner are used by being charged with different polarities.
An image forming method, characterized in that the first toner and the second toner are toners that are charged to the same polarity with respect to the carrier of the second developer.