JPH0720723A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To provide a new electrostatic latent image developing device of a noncontact liquid developing system capable of excellently developing even the parts of a high image density and high resolution. CONSTITUTION:Plural developing means composed of one set of developing rollers 20 and 24 disposed in close proximity to the surface of a latent image carrier 1 across a developing gap in a prescribed developing part and holding a thin film-like developing liquid on the peripheries and rotated in a prescrived direction, that is, rotated to impart the held developing liquid to a developing part and liquid film forming means forming a developing liquid film thinner than the developing gap, on the peripheries of the developing rollers by squeezing rollers 21 and 25 disposed in the proximity to the developing rollers 20 and 24 are arranged along the moving direction of the surface of the latent image carrier 1, to form a developing means train the developing liquid is supplied onto the peripheries of the developing rollers 20 and 24 in each developing means and the developing conditions of each developing means are set so as to attain development in at least two different kinds of developing conditions, in the developing means train.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developing device.

[0002]

2. Description of the Related Art To develop an electrostatic latent image formed on a latent image carrier such as a photoconductive photoconductor, a developing solution in which toner is dispersed in a dispersion medium is held on the peripheral surface of a developing roller. There is a developing method in which an electrostatic latent image is visualized with the toner by supplying the latent image bearing surface to the surface of the developing roller in the developing section. That is, a method is known in which the thickness of the developer film formed on the peripheral surface of the developing roller is made smaller than that of the "developing gap" to perform development (Japanese Patent Laid-Open No. 55-143565). This developing system is hereinafter referred to as "non-contact liquid developing system".

In the non-contact liquid developing system, there is a gap between the developing solution film formed on the peripheral surface of the developing roller and the surface of the latent image carrier, and when the charges forming the electrostatic latent image reach the developing section, Due to the action of the electric field due to the electric charges, the developer film projects so as to "extend" toward the electric charges and adheres to the latent image carrier to develop the electrostatic latent image.

However, when the non-contact liquid developing method is actually carried out by using a developing roller having a smooth peripheral surface, the developed image has "developing unevenness" such as so-called "white spots". Appeared, and it was found that a good visible image could not be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and effectively eliminates development unevenness such as white spots, and makes it possible to improve a portion having high image density and a portion having high resolution. It is an object of the present invention to provide a new non-contact liquid developing system electrostatic latent image developing device capable of developing.

[0006]

SUMMARY OF THE INVENTION The electrostatic latent image developing device of the present invention "provides a developing solution held on the peripheral surface of a developing roller to a latent image carrier to form a static image formed on the latent image carrier. An apparatus for developing a latent electrostatic image to obtain a toner image "having a developing device array and a developing solution supplying device.

The "developing means array" is composed of a plurality of sets of developing means.
It is arranged along the moving direction of the surface of the latent image carrier. One set of "developing means" is composed of a developing roller and a liquid film forming means. The "developing roller" has a smooth peripheral surface and is disposed in close proximity to the surface of the latent image carrier in a predetermined developing section with a developing gap, and the developing solution is formed into a thin film on the peripheral surface. By holding and rotating in a predetermined direction, the held developing solution is brought to the developing section. The "liquid film forming means" forms a developing liquid film thinner than the developing gap on the peripheral surface of the developing roller by a squeeze roller provided close to the developing roller.

The "developing solution supply means" is a means for supplying the developing solution to the peripheral surface of the developing roller in each of the plurality of developing means constituting the developing means array. In the developing means array, the developing conditions of each developing means are set so that "development is performed under at least two different developing conditions".

In order to realize different developing states in the developing means train, "the developing solution having a higher toner concentration may be supplied to the developing means having a faster developing order" (claim 2). "By applying a voltage between the developing roller and the squeeze roller in each developing means and making the voltage different according to the developing means, the developing roller of the developing means having a faster developing order can develop a toner having a higher toner density. Forming a liquid film ”(claim 3).

A developing bias voltage having a polarity opposite to that of the latent image charge can be applied to the developing roller of each developing means, and "the magnitude of the developing bias voltage is varied depending on the developing means".
Alternatively, the size of the developing gap may be varied depending on the developing means (claim 5). Alternatively, the number of rotations of the developing roller can be changed according to the developing means (claim 6), and the number of rotations of the squeeze roller can be changed according to the developing means (claim 7). .

Further, "the diameter of the developing roller may be varied depending on the developing means" (claim 8), or "the squeeze gap between the developing roller and the squeeze roller may be varied depending on the developing means". Good (Claim 9).

In each developing means in the electrostatic latent image developing apparatus of the present invention, "the peripheral surface of the developing roller is very close to the surface of the latent image carrier" means that the size of the developing gap is 100 .mu.m.
It means m or less, preferably 50 μm or less. Further, as the latent image carrier, in addition to a photoconductive photosensitive member, a dielectric layer provided on a conductive substrate (an electrostatic latent image can be formed by position-selective charging with a multi-needle electrode or the like).
Can be used.

[0013]

In the conventional non-contact liquid developing system, the reason why uneven development such as "white spot" mentioned above occurs is considered as follows. FIG. 1C shows the state of the developing unit of the conventional non-contact liquid developing system as an explanatory diagram. Latent image carrier 1
An electrostatic latent image due to a positive charge (indicated by a + sign) is formed on. The gap between the surface of the latent image carrier 1 and the peripheral surface of the developing roller 2, that is, the developing gap is 100 to 400 μm, and the developer film of the developer 3 is thick accordingly.

When the developing solution 3 held as a developing solution film on the circumferential surface of the developing roller 2 and the circumferential surface of the latent image carrier 1 come close to each other in the developing section, the developing solution 3 becomes as shown in FIG. 1 (c). , Projecting so as to extend toward the latent image charge forming the electrostatic latent image and adhering to the peripheral surface of the latent image carrier to visualize the electrostatic latent image.

By the way, if the developing solution 3 is projected so as to extend toward a part of the latent image charge, the projecting of the developing solution is less likely to be formed in the vicinity of this projecting portion. That is, when one protrusion 3A is formed on the developer 3 as shown in the figure, the surface of the developer film around the protrusion 3A is recessed toward the peripheral surface of the developing roller 2, In the "dash portion", the resultant force of the surface tension acts toward the outside of the developer film, so that the pressure becomes low, and the developer 3 around the protrusion 3A is transferred to the protrusion 3A.
Pull to the side.

The protrusion 3A attracts the developer 3 and takes it in and continues to grow. However, since the developer 3 is strongly attracted to the protrusion 3A side in a portion in the immediate vicinity of the protrusion 3A, another protrusion is difficult to be formed. In the visible image obtained as a result of development, a so-called "white spot" portion is generated around the portion visualized by the protrusion 3A, and when the electrostatic latent image is a so-called "solid portion", the white spot is uneven. It appears in the form of unevenness and causes uneven development. Note that FIG. 1C shows the protrusion 3A.
Shows a state immediately before contact with the surface of the latent image carrier 1.

In the present invention, as described above, in each developing means, the developing roller is provided in the developing section "close to the surface of the latent image carrier with a developing gap therebetween", The gap is 100 μm or less, preferably 5
The thickness of the developer film also becomes smaller as the thickness becomes smaller than 0 μm.

Therefore, as shown in FIG. 1B, when a protrusion is formed on the developer film, the depression formed around the protrusion is the "bottom" of the developer film, that is, the circumference of the developing roller 2. It reaches the surface, and the protrusion and the developer film are cut at this portion. Therefore, even if one protrusion is formed on the developer film, the influence of the protrusion formation is small, and the protrusions on the developer film can occur close to each other depending on the latent image charge. Development failure such as “” does not occur.

On the other hand, however, the absolute amount of the developer adhering to the surface of the latent image carrier during development is small as the thickness of the developer film becomes extremely thin. As described above, since the amount of the developer that adheres to the electrostatic latent image is the minimum necessary, a portion of the electrostatic latent image having a high resolution is visualized with an extremely high resolution, but the so-called “solid portion” has a The density of the visual image tends to be insufficient, and the place that should be pure black is "dark gray"
A situation may occur in which development is performed only to a moderate density.

Therefore, in the present invention, "the developing conditions of each developing means are set so that the developing is performed under at least two different developing conditions in the developing means train", and a high image density is obtained in a portion requiring a high image density. In order to obtain a toner image of image density, and in areas where high resolution is required,
A toner image having a high resolution is obtained.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 (a) shows only a characteristic part of one embodiment of the invention described in claims 1 and 2. A "photoconductive photosensitive member" as a latent image carrier, which is denoted by reference numeral 1, is formed in a drum shape and rotates in the direction of an arrow, and is provided with a charging unit and an exposing unit (an original image exposure method for irradiating an original optical image with an original image). Or a writing method using a light beam), and an electrostatic latent image developing device 50 forms a toner image corresponding to the electrostatic latent image. The toner image is transferred onto the transfer paper by a transfer unit (not shown).

The casing 5 of the electrostatic latent image developing device 50 is
It is divided into upper and lower two stages by the middle partition member 5A. The developing roller 20, the squeeze roller 21, and the scrapers 22 and 23 are provided in the upper part partitioned by the middle partition member 5A.

The developing roller 20 is driven to rotate in a counterclockwise direction at a predetermined rotational speed by bringing the peripheral surface of the developing roller 20 into close proximity to the peripheral surface of the photosensitive member 1 through a developing gap of 100 μm or less by an appropriate spacer. The squeeze roller 21 has a peripheral surface that is close to the upper peripheral surface of the developing roller 20 with a predetermined gap.
It is driven to rotate counterclockwise at a predetermined rotation speed. A base of the scraper 22 is held by the casing 5, and a tip of the scraper 22 is brought into contact with the peripheral surface of the squeeze roller 21. The scraper 23 whose base is held by the casing 5 has its tip end abutted on the peripheral surface of the developing roller 20 and forms a "developer pool" with the right peripheral surface of the developing roller 20.

Similarly, the developing roller 24, the squeeze roller 25, and the scrapers 26 and 27 are provided in the lower portion partitioned by the intermediate partition member 5A. The developing roller 24 is driven to rotate counterclockwise by an appropriate spacer so that the peripheral surface is very close to the peripheral surface of the photoconductor 1 through a developing gap of 100 μm or less. Squeeze roller 25
Is driven to rotate counterclockwise at a predetermined rotational speed, with its peripheral surface being close to the upper peripheral surface of the developing roller 24 with a predetermined gap.

The base of the scraper 26 is held by the partition member 5A, and the tip of the scraper 26 is in contact with the peripheral surface of the squeeze roller 25. The scraper 27 whose base is held by the casing 5 has its tip end abutted against the peripheral surface of the developing roller 24, and forms a "developer pool" with the right peripheral surface of the developing roller 24.

"Liquid film forming means" for the developing roller 20
The squeeze roller 21 and the scraper 22 constituting the
Together with the developing roller 20, a set of "developing means" is configured. Further, the squeeze roller 25 and the scraper 26, which form the “liquid film forming means” for the developing roller 24, form another set of “developing means” together with the developing roller 24. Therefore, the developing section is provided with two sets of developing means along the moving direction of the surface of the photoconductor 1.

The "developer" is a dispersion medium (Isopar: trade name) in which toner is dispersed, and the developer tank 3 is used.
Stored in 3,34. The developing solution 3A stored in the developing solution tank 34 is pumped up by the pump 31 and supplied by the nozzle 28 to the "developing solution reservoir" in the upper developing means. A part of the supplied developer 3A is used for development, but a surplus part flows down onto the partition member 5A and returns to the inside of the developer tank 34 via the drain.

Developer 3 stored in developer tank 33
B is pumped up by the pump 30, and by the nozzle 29,
It is supplied to the "developer pool" in the lower developing means. A part of the supplied developer 3B is used for development, but the surplus part flows down to the bottom of the casing 5, and returns to the inside of the developer tank 33 via the drain.

Therefore, the partition member 5A and the scraper 23
The nozzle 28, the pump 31, the developing solution tank 34, and the drain constitute a supplying means for supplying the developing solution to the upper developing means, and the casing 5, the scraper 27, the nozzle 29, the pump 30, and the developing solution tank 33. And drain
A supply means for supplying the developing solution to the lower development means is configured. And these supply means constitute the "developing solution supply means" as a whole.

In this embodiment, the developing roller 2
The development gaps for 0 and 24 are set to have the same size. Further, the developing rollers 20 and 24 are both metal rollers having a smooth peripheral surface.

Now, the developer 3A stored in the developer tank 34 and the developer 3B stored in the developer tank 33.
And toner density are different from each other. The developer 3A has "high toner concentration" as compared with the toner concentration in the normal developer.
In other words, the developing solution 3B has substantially the same toner concentration as in a normal developing solution.

The developing solution 3A supplied to the developing solution reservoir wets the peripheral surface of the developing roller 20 and moves with the counterclockwise rotation of the developing roller 20, and the surplus portion is removed by the squeeze roller 21, and the developing roller is removed. A developer film that is thinner than the developing gap is formed on the peripheral surface of 20, and is brought to the developing portion by the rotation of the developing roller 20, and the electrostatic latent image on the photoconductor 1 is developed by the non-contact liquid developing method.

The developer 3A has a higher toner concentration than a normal developer, and has a low fluidity and a large surface tension as much as the toner solid content. Therefore, the formation of protrusions on the developer film for performing non-contact liquid development requires a larger electric field than in the case of a normal developer. Therefore, the developer 3A
Means that only a portion of the electrostatic latent image having a large latent image charge, that is, a “solid portion” or a portion corresponding to a high image density is selectively developed, but the developer 3A has a high toner concentration. So
The density of the toner image formed on the developed portion is sufficiently high.

On the other hand, the developing solution 3B supplied from the developing solution tank 33 to the developing solution reservoir moves with the counterclockwise rotation of the developing roller 24, the surplus portion is removed by the squeeze roller 25, and A developer film thinner than the developing gap is formed on the peripheral surface, and is brought to the developing section by the rotation of the developing roller 24, and the electrostatic latent image on the photoconductor 1 is developed by the non-contact liquid developing method.

Since the developing solution 3B has a toner concentration similar to that of a normal developing solution, a portion having a small latent image charge in the electrostatic latent image, that is, a "high resolution portion" or a "low density portion" is also effective. develop. However, the area where the image density is high is already in the developer 3
Since the latent image charge is effectively neutralized by the toner of A, the development in these portions is hardly performed.

In this way, the developing solution 3A having a high toner density is applied to the portion having a high image density, and the developing solution 3B having a relatively low toner density is applied to the portion having a low image density or a high resolution.
In this way, it is possible to obtain a good toner image which is appropriately developed, has excellent resolution, and has a high image density in a solid portion.

This embodiment is further modified so that three or more sets of developing means are arranged along the moving direction of the surface of the photoconductor 1 and the developing solution having a higher toner concentration is supplied to the developing means having a faster developing order. You can also choose to do so.

FIG. 2 shows an embodiment of the invention described in claims 1 and 3. In order to avoid complications, if you think that there is no fear of confusion,
The same reference numerals as in FIG. 1 are used.

The feature of this embodiment is that, firstly, the developer 3 having a "higher toner concentration than that in a normal developer" is stored in the developer tank in both the upper developing means and the lower developing means. Nozzle 2 pumped from 33 by pump 30
Secondly, the squeeze rollers 21 and 25 are supplied to the DC voltage sources 36 and 3 respectively.
5 is to apply a voltage. For this purpose
Each of the squeeze rollers 21 and 25 has a conductive portion. The developing rollers 20 and 24 are both grounded.

The electrostatic latent image on the photoconductor 1 is composed of positive charges, and the toner in the developer 3 is negatively charged. The DC voltage power supply 36 applies a negative voltage to the squeeze roller 21, and the DC voltage power supply 35 applies a positive voltage to the squeeze roller 25.

Therefore, when the developer film is formed on the developing roller 20 by the squeeze roller 21, the toner in the developer 3 is electrophoresed to the developing roller 20 side by the action of the electric field from the squeeze roller 21 toward the developing roller 20. Then, a high toner concentration region is formed on the peripheral surface of the developing roller 20. Therefore, the toner concentration in the developer film formed on the peripheral surface of the developing roller 20 is higher than the toner concentration in the developer 3. In other words, the developing solution 3 is the developing roller 2
It is “concentrated” by the voltage between 0 and the squeeze roller 21 and is formed as a developer film on the developing roller 20.

When the squeeze roller 25 forms a developer film on the developing roller 24, the toner in the developer 3 is electrophoresed to the squeeze roller 25 side by the action of the electric field from the developing roller 24 toward the squeeze roller 25. Then
A low toner concentration region is formed on the peripheral surface of the developing roller 24. Therefore, the toner concentration in the developer film formed on the peripheral surface of the developing roller 24 is lower than the toner concentration in the developer 3. That is, the developing solution 3 is “diluted” by the voltage between the developing roller 24 and the squeeze roller 25, and is formed as a developing solution film on the developing roller 24.

In this way, a developer film having a high toner concentration is formed on the developing roller 20 and a developer film having a low toner concentration is formed on the developing roller 24, which corresponds to FIG. Similarly to the embodiment described above, a portion having a high image density is a developer film having a high toner concentration, and a portion having a low image density or a portion having a high resolution is a developer film having a relatively low toner concentration. It is possible to obtain a good toner image which is developed and has excellent resolution and high image density in a solid portion.

The DC voltage power sources 35 and 36 are variable voltage power sources, and the voltage value applied to the squeeze rollers 21 and 25 is changed to change the toner concentration in the developer film formed on the developing rollers 20 and 24. Can be adjustable.

This embodiment is further modified so that three or more sets of developing means are arranged along the moving direction of the surface of the photoconductor 1, and the developing means having a faster developing order is provided with a developer film having a higher toner concentration. It can also be formed.

According to the third aspect of the invention, since the common developing solution can be supplied to all the developing means, the developing solution supplying means can be simplified as compared with the case of the second aspect of the invention.

The inventions described in claims 1, 2 and 3 can promote the effect by various methods. For example, in FIG.
In the embodiment shown in FIG. 1A, as in the embodiment shown in FIG.
A DC voltage power supply 38,
A developing bias voltage having a polarity opposite to that of the latent image charge may be applied by 37 to make the magnitude of the developing bias voltage different depending on the developing means (claim 4). In the non-contact liquid development system, the protrusions formed on the developer film are easier to form as the magnitude of the electric field formed in the developing portion is larger. Therefore, increasing the magnitude of the developing bias voltage leads to increasing the density of the toner image obtained by development.

Therefore, by applying the developing bias voltage,
The efficiency of development by the developing rollers 20 and 24 can be increased, and the development speed can be improved while maintaining the effect of the invention described in claim 1. Of course, the developing bias voltage can be adjusted to be used for adjusting the toner image density.

Alternatively, in the embodiment shown in FIGS. 1A, 2 and 3, the size of the developing gap for each of the developing rollers 20 and 24 may be changed (claim 5). In the non-contact liquid development method, the larger the development gap,
Since the image density of the formed toner image tends to be low, this can be used to set the development gap according to the developing means, and more appropriate development can be executed in each developing means. .

Further, as in the embodiment shown in FIG. 4, the driving means 60, 61 for the developing rollers 20, 24 may be separate, and the number of revolutions of the developing rollers 20, 24 may be varied depending on the developing means ( Claim 6). This can be applied to any of the embodiments shown in FIG. 1 (a), FIG. 2 and FIG.

Making the number of rotations of the developing roller different means that "the amount of developer brought to the developing section by each developing roller per unit time" is different. For example, in the toner image to be formed, when the image having a high image density occupies a large proportion, the developing roller 2
When the developer has a high toner concentration and is used for the development by 0, a large supply amount is required. In such a case, the number of rotations of the developing roller 20 is set to be large so that the required amount of developing solution is brought to the developing section.

The developing roller 2 is driven by the driving means 60, 61.
The number of rotations 0 and 24 can be variably set, and the properties required for a toner image (resolution, image density, halftone, etc.)
It goes without saying that the number of rotations of the developing rollers 20 and 24 can be adjusted.

As in the embodiment shown in FIG. 5, the driving means 62, 63 for the squeeze rollers 21, 25 may be separate, and the number of revolutions of the squeeze rollers 21, 25 may be varied according to the developing means (claims). 7). This is also shown in FIG.
It can be applied to any of the embodiments shown in FIGS.

Differentiating the rotation speed of the squeeze roller means changing the thickness of the developer film formed on the developing roller. For example, as in the above-described example, in the toner image to be formed, when the image having a high image density occupies a large proportion, the developing solution having a high toner density provided by the developing roller 20 has a large amount. Supply is needed. Therefore, in such a case, the number of rotations of the squeeze roller 21 is set to be small so that the developer film formed on the developing roller 20 is thickened so that a necessary amount of the developer is brought to the developing section. Of.

The number of rotations of the squeeze rollers 21 and 25 can be variably set by the driving means 62 and 63, and the number of rotations of the squeeze rollers 21 and 25 can be changed according to the properties required for the toner image (resolution, image density, halftone, etc.). It may be adjusted.

Similarly, the squeeze gap between the squeeze roller 21 and the developing roller 20 is set to the squeeze roller 25.
The squeeze gap between the developing roller 24 and the developing roller 24 may be different, and the thicknesses of the developer films formed on the developing rollers 20 and 24 may be different from each other (claim 9).

As in the embodiment shown in FIG. 6, the developing roller 2
It is also possible to make the roller diameter of 00 and the roller diameter of the developing roller 24 different (claim 8). As described above, at the developing position by the developing roller 200 where the development is first performed, the development is performed with the developer having a high toner concentration, and the developer having a high toner concentration has a fluidity due to the large toner solid content. The surface tension is low, the surface tension is high, and the number of times the projections of the developer film are formed tends to be small.

In such a case, as in the embodiment shown in FIG. 6, by increasing the roller diameter of the developing roller 200 for the first development, the developing roller 200 and the photosensitive member 1 are moved in the moving direction of the photosensitive member surface. By setting a large "developing area" adjacent to each other, a toner image having a desired image density can be obtained by compensating the number of times of protrusion formation with the length of the developing area.

The embodiment of FIGS. 3 to 7 described above is
Both can be easily expanded even when three or more sets of developing means are used. Further, in the embodiment based on the third aspect of the invention, the middle partition member 5A can be omitted if the developer flowing from the upper developing means does not affect the liquid film formation in the lower developing means. In that case, the base of the scraper 26 is held by the casing 5.

[0060]

As described above, according to the present invention, a novel electrostatic latent image developing device can be provided. The present invention is configured as described above, so that a toner image having a high image density can be obtained in a portion requiring high image density, and a toner image having a high resolution can be obtained in a portion requiring high resolution. Therefore, it is possible to satisfactorily develop a portion having a high image density and a portion having a high resolution. The inventions of claims 4 to 9 can effectively promote the effects of the inventions of claims 1 to 3.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of the invention described in claims 1 and 2 and the operation of the invention.

FIG. 2 is a diagram for explaining one embodiment of the invention described in claims 1 and 3;

FIG. 3 is a diagram for explaining one embodiment of the invention described in claims 1, 2 and 4.

FIG. 4 is a diagram for explaining one embodiment of the invention according to claim 6;

FIG. 5 is a diagram for explaining one embodiment of the invention according to claim 7;

FIG. 6 is a diagram for explaining one embodiment of the invention according to claim 8;

[Explanation of symbols]

 1 Photoreceptor (latent image carrier) 20,24 Developing roller 21,25 Squeeze roller 3A, 3B Developer

Claims (9)

[Claims] 1. An apparatus for obtaining a toner image by supplying a developer held on a peripheral surface of a developing roller to a latent image carrier to develop an electrostatic latent image formed on the latent image carrier. , Which has a smooth peripheral surface and is arranged in close proximity to the surface of the latent image carrier at a predetermined developing section with a developing gap, and holds the developer in a thin film on the peripheral surface in a predetermined direction. By rotating the developing roller to bring the retained developing solution to the developing section, and a squeeze roller provided close to the developing roller, a developing solution film thinner than the developing gap is formed on the peripheral surface of the developing roller. A plurality of developing means, one set including the liquid film forming means to be formed, is arranged along the moving direction of the surface of the latent image carrier, and a developing roller in each of the plurality of developing means. Developer supply means for supplying the developer to the peripheral surface The a, in the developing unit sequence, as developed by at least two different development conditions is carried out, an electrostatic latent image developing apparatus characterized by setting the developing conditions of each developing unit. 2. The electrostatic latent image developing device according to claim 1, wherein the developing conditions are made different by supplying a developing solution having a higher toner concentration to a developing means having a faster developing order. Electrostatic latent image developing device. 3. The electrostatic latent image developing device according to claim 1, wherein a voltage is applied between the developing roller and the squeeze roller in each developing means, and the voltage is made different according to the developing means. An electrostatic latent image developing device characterized in that development conditions are made different by forming a developer film having a higher toner concentration on a developing roller of a developing means having a higher order. 4. The electrostatic latent image developing device according to claim 2, wherein a developing bias voltage having a polarity opposite to that of the latent image charge is applied to the developing roller of each developing means, and the magnitude of the developing bias voltage is changed. An electrostatic latent image developing device characterized in that the electrostatic latent image developing device is different according to the type. 5. The electrostatic latent image developing device according to claim 2, 3 or 4, wherein the size of the developing gap is varied depending on the developing means. 6. The electrostatic latent image developing device according to claim 2, 3 or 4 or 5, wherein the number of rotations of the developing roller is varied depending on the developing means. 7. The electrostatic latent image developing device according to claim 2, 3 or 4 or 5, wherein the number of revolutions of the squeeze roller is varied depending on the developing means. 8. An electrostatic latent image developing device according to claim 2, 3 or 4 or 5 or 6 or 7, wherein the diameter of the developing roller is varied depending on the developing means. apparatus. 9. The electrostatic latent image developing device according to claim 2, 3 or 4 or 5 or 6 or 7 or 8, wherein the squeeze gap between the developing roller and the squeeze roller is different depending on the developing means. Electrostatic latent image developing device.