JPS63113480A - Development system for electrostatic latent image - Google Patents

Abstract

PURPOSE:To obtain a distinct image which is superior in sharpness of characters, in resolving power, and in image gradation by using carriers having small particle diameter and carriers having large particle diameter, inhibiting the large-size carriers from passing by a 1st blade prior to the conveyance of a developer to a development area, and adjusting a developer to prescribed layer thickness. CONSTITUTION:The small-size carriers of small mean particle size and the large-size carriers of large means particle size and used as carriers. Then, the 1st blade 14 inhibits the large-size carriers of the developer 1 on a developer carrier body 4 from being passed prior to the conveyance of the developer 1 to the development area, the developer is adjusted to the prescribed layer thickness. Consequently, even when the large-size carriers are used, the distance between a photosensitive body 9 and the developer carrier body 4 can be shortened and a sharp copy image is obtained which is superior in sharpness of characters, in resolving power, and in image gradation.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to electrophotography, electrostatic printing, electrostatic recording, etc., in which an electrostatic latent image formed on a photoreceptor is transferred to a powder toner and a carrier. The present invention relates to a method for developing an electrostatic latent image using a two-component developer comprising:

<Prior art> Conventionally, in copying machines and the like that utilize electrophotography, a dry development method is used to visualize an electrostatic charge image formed on a photoconductor using a developer consisting of powder toner and carrier, especially for gradation reproduction. Magnetic brush development is widely used because of its excellent properties and image quality.

This magnetic brush development method is performed by developing an electrostatic latent image formed on a photoreceptor by charging and exposure with a developer containing toner and magnetic carrier contained in a developing device. More specifically, a rotatable developer carrier that supports the developer as a magnetic brush is disposed facing the photoreceptor and spaced apart from it by a predetermined distance, and the developer is spread in a predetermined layer on the developer carrier. The developer is formed thickly, and as the developer carrier rotates, the developer is conveyed to a developing area to develop the electrostatic latent image formed on the photoreceptor. Note that, in order to control the toner concentration of the developer within a predetermined range, a magnetic sensor that detects the toner concentration is usually installed inside the developer. In development in the development area, the smaller the distance between the photoreceptor and the developer carrier, the better the sharpness and resolution of characters, the better the gradation of the image, and the clearer the copied image can be obtained. The developer formed as a magnetic brush on the developer carrier is cut into predetermined lengths by a blade to reduce the layer thickness of the developer.

On the other hand, in order to reduce the layer thickness of the developer, it has been proposed to use a small particle carrier having an average particle diameter of about 30 μm, for example.

However, when the above small particle diameter carrier is used, the fluidity of the developer becomes poor, the mixability with replenishment toner, and the frictional charging properties of the toner are poor. becomes difficult to control. In addition, if the gap between the developer carrier and the blade is made small in order to reduce the distance between the photoreceptor and the developer carrier, when dust or paper dust gets mixed in during development,
White streaks appear on the developer on the developer carrier, making it impossible to obtain uniform copied images.

Therefore, as magnetic carriers, those having an average particle diameter of about 100 μm are widely used because they have excellent developer fluidity and toner triboelectric charging properties, and easy control of toner concentration.

<Problems to be solved by the invention> However, when using the above conventional magnetic carrier,
Since the particle size of the carrier is large, the gap between the developer carrier and the blade, through which the developer passes, is controlled by the particle size of the carrier. However, it is not possible to reduce the layer thickness of the developer formed as a magnetic brush to a predetermined value or less. Also,
If the layer thickness of the developer is less than a predetermined value, the carrier will clog the blade portion, and a sliver-shaped portion will appear on the developer carrier where no magnetic brush is formed, resulting in white spots in the image. Therefore, there have been problems in that the sharpness of characters, resolution, and gradation of images are poor, and it is difficult to obtain clear copied images.

Purpose This invention has been made in view of the above problems, and even if a large particle carrier is used as the carrier, the distance between the photoreceptor and the developer carrier can be reduced, and the sharpness of characters etc. can be reduced. An object of the present invention is to provide an electrostatic latent image development method that can obtain clear copied images with excellent resolution and image gradation.

Means and operation for solving the above problems> In order to achieve the above object, the electrostatic latent image development method of the present invention is such that a developer consisting of toner and carrier is deposited in a predetermined layer on a developer carrier. In a developing method in which an electrostatic latent image formed on a photoreceptor is developed by forming a thick layer and transporting it to a developing area, the carriers include a small carrier with a small average particle diameter and a large carrier with a large average particle diameter. In addition, prior to conveying the developer to the development area, a blade is used to suppress the passage of large-particle carriers among the developer on the developer carrier, and the developer is adjusted to a predetermined layer thickness. It is characterized by this.

According to the electrostatic latent image development method having the above configuration, a small particle carrier with a small average particle diameter and a large particle carrier with a large average particle diameter are used as carriers, so the small particle carrier is used. Despite this, the fluidity of the developer, the triboelectric charging properties of the toner, etc. do not deteriorate. Furthermore, before the developer is conveyed to the developing area, the blade prevents the large particle carrier from passing among the developer on the developer carrier, so that the large particle carrier enters the developing area by the blade. This can be prevented, and the fluidity of the developer can be maintained by returning the large particle carrier to the developer before being transported. As mentioned above, the developer contains a small particle carrier and a large particle carrier and has good fluidity, so even if the gap between the developer carrier and the blade is small, the developer passes smoothly through the gap. Therefore, by adjusting the gap between the developer carrier and the blade, it is possible to adjust the thickness of the developer formed on the developer carrier to a predetermined layer thickness. The distance can be reduced.

<Example> The present invention will be described in detail below based on the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of an electrostatic latent image development method using a magnetic brush development method, in which a developer (1) consisting of toner and magnetic carrier is contained in a developing device (2). A rotatable stirring member (3) is disposed inside the developing device (2) in order to homogenize the developer (1). , developer (1)
A developer carrier (4) carrying the developer as a magnetic brush is rotatably arranged. That is, the developer carrier (4
) is composed of a rotatable non-magnetic developing sleeve (5) that carries developer, and a magnetic roll (6) consisting of a plurality of magnets fixed within this developing sleeve (5). The magnetic carrier is magnetically attracted in a state where the toner is attached due to electrification, thereby forming a magnetic brush that stands up on the developing sleeve (5). In this example, the developing sleeve (9) is rotationally driven in the counterclockwise direction.
), at least one of the magnetic rolls (6) may be rotatable.

As the developing sleeve [5] rotates, the developer (1) is applied to the drum base opening and the drum base ('7).
A photosensitive layer (8) formed on the photosensitive layer (8) of the photosensitive body (9) is formed on the photosensitive layer (8) of the photosensitive body (9) by contacting or bringing it close to the surface of the photosensitive body (9) which is rotationally driven in a clockwise direction. The electrostatic latent image is conveyed to a development area where the electrostatic latent image is developed.

Further, as the electrostatic latent image is developed, the toner concentration of the developer (1) decreases, so the toner concentration of the developer (1) is controlled within a predetermined range to form a homogeneous copy image over a long period of time. Therefore, a magnetic sensor (10) is attached to a member (17) provided at a predetermined location within the developing device (2). This magnetic sensor (10) utilizes the fact that magnetic permeability changes in proportion to the proportion of magnetic carrier in the developer (1) per unit volume and the amount of developer (1) passing through per unit time. The change in inductance of the pickup coil is output as a change in DC voltage.

When the toner concentration detected by the magnetic sensor (10) is below a predetermined value, the hopper (11
) The replenishment toner (12) stored in the hopper (
11) The developer (1) of the developing device (2) is replenished by a replenishment roller (13) rotatably provided in the lower opening.
) is attached facing toward the developer (1) of the developing device (2).

In addition, in order to improve the fluidity of the developer (1), the mixability with the replenishment toner, and the triboelectric charging characteristics of the toner, and to accurately detect and control the toner concentration by the magnetic sensor (lO). As the magnetic carrier, a mixture of a small carrier having a small average particle size and a large carrier having a large average particle size is used.

The average particle diameter of the small particle carrier and the large particle carrier is preferably such that the average particle diameter of the large particle carrier is 2 to 5 times larger than the average particle diameter of the small particle carrier. If the average particle diameter of the large particle carrier is outside the above range, the fluidity, triboelectric charging properties, etc. of the developer will not be sufficient. In particular, the small particle size carrier preferably has an average particle size of 20 to 40 μm, and the large particle size carrier preferably has an average particle size of 40 to 300 μm, particularly 70 to 200 μm. The average particle size of the small particle carrier is 2
If it is less than 0 μm, not only will the triboelectricity with the toner not be sufficient, but it will also tend to transfer to the photoreceptor side during development, resulting in a large amount of carrier consumption.If the average particle size exceeds 40 μm, the sharpness of characters will deteriorate and the image Quality deteriorates. Furthermore, if the average particle diameter of the large particle carrier is less than 40 μm, the fluidity of the developer will decrease, making it difficult to accurately control the toner concentration, and if it exceeds 300 μm, the triboelectric charging property with the toner will decrease. descend.

The small particle size carrier and the large particle size carrier may have overlapping portions in terms of particle size distribution, or may have different peaks in particle size distribution. Also,
The mixing ratio of the above small particle size carrier and large particle size carrier is:
It can be selected as appropriate depending on the desired fluidity of the developer, but in order to improve the fluidity of the developer, a small particle size carrier, a large particle size carrier 15-8515-15 (
(parts by weight), particularly preferably 30 to 70 (parts by weight). The small particle size carrier is less than 15 parts by weight;
Not only is it impossible to reduce the layer thickness of the developer on the developer carrier (4), but also the photosensitive layer (8) and the developing sleeve (5)
It becomes difficult to form a high-quality image. Moreover, if it exceeds 85 parts by weight, it becomes difficult to precisely control the fluidity of the developer, the triboelectricity of the toner, and the toner concentration.

Further, the large particle carrier in the developer (1) is prevented from being transported to the development area, and the developer is transported to the development area while being formed as a magnetic brush on the developer carrier (4). In order to form a clear copy image with excellent sharpness of characters, resolution, and image gradation using a developer consisting of a small-particle carrier and toner with a thin developer layer, the developer carrier is A blade (14) is disposed opposite to the developing sleeve (5) of (4) with a predetermined gap J therebetween. The above blade (
14), the magnetic brush formed on the developer carrier (4) is cut into a predetermined thickness, and the magnetic brush formed on the developer carrier (4) is
Of the developer (1) conveyed as the developer (1) rotates, the large particle carrier is transported between the developer sleeve (5) and the blade (14).
). Therefore, between the developing sleeve [S and the blade (14) 111j
By adjusting lJ, the layer thickness of the developer [1) made of toner and small particle carrier formed as a magnetic brush on the developing sleeve (5) is made thinner, and the developer is transported to the developing area. Therefore, the distance between the developing sleeve (5) of the developer carrier (4) and the photosensitive layer (8) of the photoreceptor (9) can be reduced. The above developing sleeve (5
] and the blade (14) can be set appropriately depending on the particle size of the large particle carrier, but in order to reliably suppress the passage of the large particle carrier, It is preferable that the average particle diameter of the carrier is 6 times or less. In addition, in order to reduce the distance between the developing sleeve (S) and the photosensitive layer (8) and obtain a high quality image, the gap J is set to 0.2 to 0.
．． Preferably, it is 8 mm.

Note that a small amount of large particle carrier is mixed into the developer that has passed through the gap J between the developing sleeve (opening and blade (14)) to the extent that it does not adversely affect the development in the developing area. Good too.

Further, reference numeral (16) is a guide member that guides the large particle carrier whose passage is suppressed by the blade (14) into the developing device (2).

As described above, the developer conveyed to the development area consists of small-particle carrier and toner, so the smaller the carrier particle size, the more small-particle carrier is transferred to the photoconductor along with toner in the development process. 9) and may be consumed. Therefore, in order to keep the composition of the developer constant, it is preferable to use a toner containing 0 to 15 2% by weight of small particle size carrier as the replenishment toner.

According to the electrostatic latent image development method of the above embodiment, even if a large particle carrier is used as the carrier, the blade (14)
This makes it possible to prevent the large particle carrier from being transported to the developing area, and also to adjust the layer thickness of the developer formed on the developing sleeve [S], which is composed of the small particle carrier and toner. Therefore, the distance between the photosensitive layer (8) and the developing sleeve (S) can be reduced.Also, since the large particle carrier is guided by the guide member (16) and returns to the developing device (2), , the fluidity characteristics of the developer (1) in the developing device (2), the charging characteristics of the toner, etc. are good,
The toner concentration of the developer [1] can be accurately detected by the magnetic sensor (10), and the toner concentration can be accurately controlled by replenishing the replenishment toner (12) in the hopper (11) with the replenishment roller (13). can do. Therefore, the toner concentration can be accurately controlled and the photosensitive layer [81
This, combined with the fact that the distance to the developer carrier (4) can be reduced, forms a clear copy image with excellent sharpness of characters, resolution, and image gradation.

Note that the photoreceptor] 9) is not limited to the illustrated drum shape, but may be in the shape of an endless belt.

The powder toner has an average particle diameter of 1 to 30 μm, preferably 5 to 25 μm, and may be either a heat fixable toner or a pressure fixable toner. The above-mentioned carrier may be glass beads, etc., but it may also be an uncoated carrier such as oxidized or unoxidized iron powder, or a magnetic material such as iron, nickel, cobalt, ferrite, etc., such as acrylic polymer, fluorine-based Coated carriers coated with polymers, such as polyesters, are preferred. Further, the developer used usually has a toner concentration of 2 to 15% by weight.

Further, the electrostatic latent image development method of the present invention is not limited to the magnetic brush development method described above, but can also be applied to conventionally known development methods such as cascade development method.

Experimental Examples> The present invention will be described in more detail below based on experimental examples.

A heat-fixable toner having an average particle size of lo μm was used as the powder toner, and a small magnetic carrier having an average particle size of 30 μm and a large magnetic carrier having an average particle size of 120 μm were used as the carrier. In addition, toner density 10 consisting of the following carrier composition
A developer of % by weight was prepared.

Developer I:: Particle size carrier developer ■:: Particle size carrier developer ■: Small particle size Kiku 9F 50 Carrier consisting of 50Tt1 part and the layer thickness of the developer on the developer sleeve shown in Fig. 1 above. Using the developing device shown in Figure 1, we investigated the minimum size of cutting the ears to form a uniform magnetic brush of developer on the developing sleeve by adjusting the gap J between the developing sleeve and the blade. is the second-
As shown in Figure 1, the thickness was 0.2 mm for the developer I, and 0.8 mm for the developer II. In addition, the developer I
For Sn, the above-mentioned gap l is 0.4 mms 1.1
mm, the layer thickness of the developer, that is, the layer thickness of the magnetic brush, and the cutting dimension, that is, the gap between the developing sleeve and the blade, were equal.

On the other hand, as shown in Figure 2-2, in developer Ⅰ, despite having many large particle carriers, the minimum cutting size is 0.25 mm, which is slightly larger than in developer I, and the magnetic The layer thickness and the cutting size of the brush are the same as the developer I above, and the gap l.
They became equal when they were 0.4 mm. Furthermore, when the gap J was set to about 0.7 mm, a small amount of large particle carrier was mixed into the developer that passed through the blade. It has been found that the gap between the blade and the blade can be set to 0.25 to 0.7 mm.

As mentioned above, even though a large particle size carrier is used, by mixing a small particle size carrier and a large particle size carrier, the minimum ear cutting size and the layer thickness of the magnetic brush can be reduced in the case of a small particle size carrier. The layer thickness of the magnetic brush formed on the developing sleeve and, as a result, the distance between the developing sleeve and the photosensitive layer could be reduced.

Note that the layer thickness of the magnetic brush is the average value of the layer thickness at the peaks and the layer thickness at the valleys of the magnetic brush formed on the developing sleeve.

Control of Toner Concentration When the relationship between toner concentration and sensor output voltage was investigated using the developing device equipped with the magnetic sensor of the above embodiment, the results shown in FIG. 3 were obtained. That is, the toner concentration and the sensor output voltage are in an inversely proportional relationship.

In addition, in FIG. 3, the sensor output voltage shown by the developer made only of carrier is shown as 100.

In addition, while changing the toner concentration of the developer, the sensor output voltage of the developer consisting only of carrier was set to 13V, and changes in the sensor output voltage were investigated.
The results shown in the figure were obtained. That is, in developer A using a small particle diameter carrier, the sensor output voltage was small, and in developer I with a toner concentration of 10% by weight, it showed a value of 1 V or less. Further, the sensor output voltage of the developer B using a large particle/diameter carrier was high, and the above developer (2) with a toner concentration of 10% by weight showed 5 to 6V. On the other hand, small particle carrier 50
Developer C using a heavy part and a large particle diameter carrier 50 heavy part
In this case, although there are many small particle size carriers, the sensor output voltage is close to the sensor output voltage of the above developer B using large particle size carriers, and the sensor output voltage is about 5V for the above developer (2) with a toner concentration of 10% by weight. Indicated.

When the fluidity of the developer was examined by the angle of repose, it was found that the developer I had poor fluidity, while the developer II had good fluidity. Further, it was found that the developer (3) exhibited fluidity close to that of the developer (H).

In addition, when developing using the above-mentioned developing device while adjusting the layer thickness of the developer with the above-mentioned blade and replenishing replenishment toner, it was found that the toner concentration was controlled accurately using developer I. While it was difficult to
It was found that the toner density could be precisely controlled using the developers (1) and (2). Note that the toner of the developer described above was used as the replenishment toner.

Image characteristics As mentioned above, the set gap between the developing sleeve and the blade j
However, since it is limited by the particle size of the carrier used, when developing using each developer, the gap between the developing sleeve and the blade was set as follows.

Developer I: J -0.4mm Developer ■: No 1.1mm Developer M: J -0.4mm When developed using the above developing device, Developer I
Initially, the sharpness of the characters was good, but when replenishing the toner, the mixability of the replenishment toner and developer and the fluidity of the developer were poor, and repeated development resulted in white streaks and fogging on the image. The toner density has changed significantly. In addition, in developer (2), the particle size of the carrier was large, and the distance between the developing sleeve and the photosensitive layer could not be made small, resulting in images with poor character sharpness, poor resolution, and poor gradation.

On the other hand, with developer ■, it is possible to control the toner concentration with high precision, and the distance between the developing sleeve and the photosensitive layer can be reduced, resulting in excellent character sharpness, resolution, and gradation. A clear image was obtained.

<Effects of the Invention> As described above, according to the electrostatic latent image development method of the present invention, since a small particle carrier with a small average particle diameter and a large particle carrier with a large average particle diameter are used, the developer The fluidity of the toner, the mixability with replenishment toner, the triboelectric charging properties of the toner, etc. do not deteriorate. Furthermore, before the developer is conveyed to the developing area, the large particle carrier can be prevented from entering the developing area, and the toner can be separated from the small particle carrier formed on the developer carrier by the blade. Since the layer thickness of the developer can be adjusted to a predetermined thickness, development can be performed with a small distance between the photoreceptor and the developer carrier. Therefore, even if a large-particle carrier is used as the carrier, the distance between the photoreceptor and the developer carrier can be made small, and a clear copied image with excellent sharpness of characters, resolution, and image gradation can be obtained. It has the unique effect of being able to

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIGS. 2-1 to 4 are diagrams showing experimental results, respectively. ]1]...Developer, [4]...Developer carrier, ]9
)...Photoreceptor, (14)...Blade.

Claims (1)

[Claims] 1. A developer consisting of toner and carrier is formed in a predetermined layer thickness on a developer carrier and transported to a development area to develop an electrostatic latent image formed on a photoreceptor. In the developing method, a small particle carrier having a small average particle diameter and a large particle carrier having a large average particle diameter are used as the carriers, and prior to conveying the developer to the development area, the carrier is coated on the developer carrier. An electrostatic latent image development method characterized by controlling the passage of large-particle carrier among the developer using a blade and adjusting the developer to a predetermined layer thickness. 2. The electrostatic latent image development method according to claim 1, wherein the gap between the developer carrier and the blade is 6 times or less the average particle diameter of the large particle carrier. 3. The electrostatic latent image development method according to claim 1, wherein the gap between the developer carrier and the blade is 0.2 to 0.8 mm. 4. The small particle size carrier has an average particle size of 20 to 40 μm,
Claim 1 above, wherein the large particle size carrier has an average particle size of 70 to 300 μm.
Developing method of electrostatic latent image as described in . 5. The electrostatic latent image development method according to claim 1 or 4, wherein the carrier is a magnetic carrier.