JPH04369665A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an excellent color image by fixing a supporting member for a developer carrier which supports a developer carrier and which keeps a gap between the developer carrier and an image carrier constant. CONSTITUTION:Developer is one-component developer having a sharp melting characteristic and the developer carrier supporting member 21 which is set for supporting the developer carrier 7 and keeping the gap between the carrier 7 and the image carrier 1 constant is fixed. Then, it is favorable that the apparent viscosity of the developer at 90 deg.C is 5X10<6> poise and it is specially favorable that the absolute value of difference between the apparent viscosity P1 of the developer at 90 deg.C and the apparent viscosity P2 at 100 deg.C is within the range of 2m10<5> < ¦P1-P2¦ < 4X10<6>. This, the sharp melting type toner can be used and the excellent image can be obtained by it. Besides, the excellent sealing of the toner can be achieved by simple constitution.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention generally relates to an electrophotographic image forming apparatus, and in particular, to an electrophotographic image forming apparatus that visualizes a latent image formed on an image carrier using a one-component developer and has high image clarity. The present invention is suitably implemented in a color image forming apparatus that can obtain images and has a simple structure.

0002

2. Description of the Related Art Conventionally, various electrophotographic color image forming apparatuses have been proposed, and some have been commercialized, one example of which is shown in FIG.

In this example, as an image carrier, an electrophotographic photosensitive drum 1 having a photoconductive layer provided on a conductive substrate is rotatably disposed, and an electrophotographic image forming means is provided around the drum 1 to form a color image. is formed.

That is, the photosensitive drum 1 is uniformly charged by the primary charger 2. Next, image exposure 3 is performed based on the image information of the first color, magenta, to form a latent image. Next, this latent image is visualized by a magenta developer 4A.

On the other hand, a transfer material P is held in advance on the transfer drum 19, and the magenta toner image on the photosensitive drum 1 is transferred onto the transfer material P under the action of the transfer charger 5. On the other hand, the transfer residual toner on the photosensitive drum 1 is cleaned by a cleaner 6. After cleaning, the photosensitive drum 1 is uniformly charged again by the charger 2, and image exposure 3 is performed based on the image information of the second color, cyan, to form a latent image.

At this time, the magenta developing device 4A is as shown in FIG.
1, the cyan developing device 4B is once retracted downward in the direction of arrow a, and then the cyan developing device 4B is moved in the direction of arrow b together with other developing devices and placed in a position facing the photosensitive drum 1, and the cyan latent image described above is The image is visualized by the cyan developer 4B. The cyan toner image is superimposed and transferred onto the transfer material P held by the transfer drum 19. Transfer residual toner on the photosensitive drum 1 is cleaned by a cleaner 6.

Thereafter, in the same manner, the latent image of the third color, yellow, is made into a toner image by the yellow developer 4C and transferred onto the transfer material P, and the fourth color, black, is visualized by the black developer 4D. , transfer onto a transfer material.

[0008] Yellow, magenta, cyan, black 4
The transfer material P to which the colored toner images have been transferred is separated from the transfer drum 19 and fixed by the fixing device 8 to obtain a permanent image.

[0009] In the above-mentioned apparatus, a magnetic brush development using a two-component developer containing a mixture of non-magnetic toner and magnetic particles is used as the color developing device. Therefore, only the developing device that performs development is placed close to the photosensitive drum 1, the magnetic brush of this developing device comes into contact with the photosensitive drum 1, and the other developing devices are maintained apart from the photosensitive drum 1. Ru. Therefore, when developing the next color, the previous developing device is once retracted from the photosensitive drum, and then the next developing device is moved from a position away from the photosensitive drum to a position closest to the photosensitive drum, and then The magnetic brush was configured to move toward the photosensitive drum so that it came into contact with the photosensitive drum.

[0010] As mentioned above, in a color image forming apparatus having such a configuration, a two-component developer is used, so in order to prevent color mixing, the developer which does not perform development is moved to a retracted position from the photosensitive drum. An evacuation mechanism was essential. As a developing method that does not require such a retracting mechanism for the developing device,
There is a non-contact development method using a one-component developer.

Referring to FIG. 12, the non-contact developing method is as follows.
A gap (hereinafter referred to as "SD gap") is provided between the photosensitive drum 1 and the developing sleeve 7 as a developer carrier provided in the developing device 4, and while this SD gap is maintained,
This is a method of forming an electric field between the photosensitive drum 1 and the developing sleeve 7 and causing the toner on the developing sleeve 7 to fly to the photosensitive drum 1 to develop an image.Normally, the toner on the developing sleeve 7 does not move onto the photosensitive drum 1 unless an electric field is formed. will be kept in contact with. Therefore, when forming a color image, there is no need to move the developing device that is not performing development to the retracted position.

As shown in FIG. 12, the SD gap is
Rollers 133 are provided at both ends of the developing sleeve 7 so as to abut against the circumference of the photosensitive drum 1.
By designing the outer diameter of No. 3 to an appropriate size, it can be set to a predetermined size.

[0013] In order to obtain a good color image, it is preferable that the toners of each color melt in a short time during fixing and mix together. When comparing the color mixing properties of toners, in the case of color images, the light transmittance of the image on transparency paper (hereinafter referred to as "trapen") on which the toner image is fixed is often used.

Therefore, the apparent viscosity at 90° C. of the image on the trapen to which the toner image is fixed is 5×10 4
〜5×106 poise, preferably 25×104〜
2 x 106 poise, more preferably 105 to 106
poise, and the apparent viscosity at 100°C is 104 ~
5×105 poise, preferably 104 to 3.0×1
05 poise, more preferably 104 to 2×105
Color O with extremely good light transmittance when poise
HP is obtained, and even as a full color toner, good results are obtained in fixing properties, color mixing properties, and high temperature offset resistance.

[0015] Apparent viscosity P1 at 90°C and 100
The absolute value of the difference from the apparent viscosity P2 at °C is 2×10
It is particularly preferable that the range is 5<|P1-P2|<4×106.

Dyes or pigments can be used as coloring agents. For example, phthalocyanine blue, industhrene blue, beacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow can be used. Its content is 12 parts by weight or less, preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the binder resin so as to sensitively affect the light transmittance of the OHP film.

By using the above-mentioned color image forming toner, the so-called "sharp melt type" toner, fixing properties,
Good color mixing results have been obtained.

The above-mentioned "apparent viscosity" was defined based on the measurement method described below.

A flow tester model CFT-500 (manufactured by Shimadzu Corporation) was used. The sample is a 60 mesh pass product with a thickness of about 1.
Weigh 0-1.5g. Using a molder, make 100
Pressure is applied at a rate of kg/cm2 for 1 minute.

[0020] This pressurized sample is subjected to flow tester measurement under the following conditions at normal temperature and normal humidity (temperature of about 20 to 30°C, humidity of 30 to 70% RH) to obtain a humidity-apparent viscosity curve. From the obtained smooth curve, the apparent viscosity at 90° C. and 100° C. is determined, and this is used as the apparent viscosity of the sample with respect to humidity.

RATE TEMP 6.0D/
M (℃1 minute) SET TEMP
70.0DEG(℃)MAX TEMP
200.0DEGINTERVAL
3.0DEGPREHEAT
300.0SEC (seconds) LOAD
20.0KGF (kg) DIE
(DIA) 1.0MM (mm
)DIE(LENG) 1.0MM
PLUNGER 1.0C
M2 (cm2)

Furthermore, in the conventional color image forming apparatus, as a sealing means for preventing toner from scattering from the developing device 4, a toner seal made of wool felt is installed at the end of the developing sleeve 7. Ta.

[0023]

[Problems to be Solved by the Invention] However, in a conventional color image forming apparatus that employs a non-contact development method using a one-component developer, as can be understood from FIG.
In order to maintain the gap, a roller 133 having the same rotation center as the developing sleeve 7 was pressed against the photosensitive drum 1;
Since both the roller 133 and the photosensitive drum 1 rotate, a seal to prevent toner leakage cannot be formed at the abutting portion. Therefore, when the scattered toner adheres to the pressing portion of the photosensitive drum 1, a layer of toner is formed between the photosensitive drum 1 and the rollers 133, resulting in a wide SD gap.

Furthermore, due to the pressing force and frictional heat between the roller 133 and the photosensitive drum 1, the toner may melt and adhere to the photosensitive drum 1 or the periphery of the roller 133, so-called fusion. Once fusion has occurred, it is difficult to remove it, and on the contrary, the amount of fusion tends to increase.

In an image forming apparatus for obtaining particularly good color images, sharp melt type toners that melt well at low temperatures, that is, have low viscosity, are preferred from the viewpoint of the light transmittance of the toner described above. The amount of toner adhesion that occurs between the contact portion of the photosensitive drum 133 and the photosensitive drum 133 is much greater than that when rollers are used in a normal monochrome image forming apparatus. Not only is it not maintained accurately, but the SD gap widens. As a result, image unevenness may occur, and the electric field for causing the toner to fly may become weak, resulting in a decrease in density.

[0026] Furthermore, as mentioned above, toner for color image formation having sharp melt characteristics is likely to cause fusion. If a method is used in which the flow of toner is blocked by making contact with the developing sleeve, the toner will get clogged between the developing sleeve and the wool felt, and as a result, the toner will easily fuse to the felt and the developing sleeve, and the torque will increase. This caused problems such as close-ups and a decrease in the toner sealing effect.

Therefore, an object of the present invention is to use a sharp melt type toner, to obtain a good color image, and to achieve a good toner seal with a simple structure. It is an object of the present invention to provide an image forming apparatus which is free from torque increase due to toner fusion, maintains an SD gap with a sufficiently high precision, and can always form high-quality images.

[0028]

Means for Solving the Problems The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention:
It has an image carrier on which a latent image is formed, and at least one developing device arranged around the image carrier and converting the latent image on the image carrier into a visible image, and the developing device is a developing device. In the image forming apparatus, the image forming apparatus includes a developer carrier that carries a developer and transports the developer toward the image carrier, and the developer carrier and the image carrier are arranged in a non-contact state with a predetermined gap between them. The developer is a one-component developer having sharp melt characteristics, and a developer carrier is provided to support the developer carrier and maintain a constant gap between the developer carrier and the image carrier. The image forming apparatus is characterized in that a supporting member is fixed. Preferably, the developer has an apparent viscosity at 90°C of 5×10 6 poise or less, and particularly preferably, the developer has an apparent viscosity at 90°C of P1 and 1
The absolute value of the difference from the apparent viscosity P2 at 00°C is 2×
The range is 105 <|P1 −P2 |<4×106.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image forming apparatus according to the present invention will be explained in more detail below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention. This embodiment is a color image forming apparatus using a laser beam as a light source. More specifically, the surface of the electrophotographic photosensitive drum 1, which is an image carrier, is uniformly charged to VD=-700V by the primary charger 2. Next, image exposure 3 is performed based on the image information of the first color magenta, and V
L=-50V, and a latent image is formed on the photosensitive drum 1. Next, this latent image is made into a visible toner image by reversal development with magenta toner in a magenta developer 4C.

On the other hand, a transfer material P is held in advance on the transfer drum 19, and the magenta toner image on the photosensitive drum 1 is transferred onto the transfer material P under the action of the transfer charger 5. On the other hand, the transfer residual toner on the photosensitive drum 1 is cleaned by a cleaner 6.

After cleaning, the photosensitive drum 1 is uniformly charged again by the charger 2, and image exposure 3 is performed based on the image information of the second color, cyan, to form a latent image. Next, this latent image is visualized with cyan toner in a cyan developer 4B. The cyan toner image is superimposed and transferred onto the transfer material P held by the transfer drum 19. Transfer residual toner on the photosensitive drum 1 is cleaned by a cleaner 6.

In the same manner, the latent image of the third color, yellow, is visualized with toner by the yellow developer 4A and transferred onto the transfer material P, and the latent image of the fourth color, black, is made into a toner image by the yellow developer 4D.
The toner is made into a visible image and transferred onto the transfer material P. The transfer material P to which the four-color toner images of yellow, magenta, cyan, and black have been transferred is separated from the transfer drum 19 and fixed by a fixing device (not shown) to form a permanent image.

Next, the developing units 4 (4A, 4B, 4C, 4D)
) will be explained. In this embodiment, since the configuration of each developing device is the same, the yellow developing device 4A will be described.

The developing device 4A includes a toner container 10A,
An opening 12 formed at a position facing the photosensitive drum 1 includes a developing roller 7A that conveys the one-component developer, that is, the toner, in the toner container 10A toward the photosensitive drum 1. In this embodiment, the developing roller 7A is a conductive sleeve made of aluminum. Further, the toner container 10A includes a toner conveying member 11A and an application roller 9A for conveying toner near the developing sleeve 7A. Application roller 9A
rotates at a relative speed to the rotatable sleeve 7A, and applies negative polarity non-magnetic one-component toner as a one-component developer stored in the toner container 10A onto the sleeve 7A. In order to perform this application well, it is preferable that the application roller 9A be subjected to a sponge-like process, a knurling process, or a brush-like process. The applied toner is regulated to a predetermined layer thickness by an elastic blade 8A made of urethane rubber, phosphor bronze, or the like. In addition, sleeve 7A
A sheet 16A is disposed below the toner container 10A to prevent the toner from spewing out.

The sleeve 7A and the photosensitive drum 1 are kept in a non-contact state and are maintained at an interval of 100 to 500 μm. The toner regulated to a predetermined layer thickness by the blade 8A is transferred to the photosensitive drum 1 by rotation of the sleeve 7A.
The photosensitive drum 1 is transported to the developing position opposite to the photosensitive drum 1.
It is attached to the upper electrostatic latent image and developed to visualize the electrostatic latent image as a toner image. During development, a developing bias is applied to the sleeve 7A from a bias power supply 17 controlled by a bias control device 18.

Cyan developer 4B, magenta developer 4
C. The black developer 4D is also the same as the yellow developer 4.
It is constructed in the same manner as A, and each component that performs the same function is indicated by the same number and a letter is attached for each toner color.

The developing bias is a DC voltage VDC plus an AC voltage VP-P (voltage from peak to peak), and VDC is -500V to -100V, VP-P.
is several hundred V to several KV. When the distance T between the photosensitive drum 1 and the sleeve 7, that is, the S-D gap is 300 μm, the AC voltage required to obtain a good image is VP-P = 1200V.
~2400V, preferably VP-P =1600V~
It is 2000V.

The amount of charge Q/M (μc/g) possessed by the non-magnetic one-component toner used in this example is Q/M=-5 to -30.
μc/g, amount of toner on sleeve M/S (mg/cm2
) is M/S=0.3 to 1.5 mg/cm2.

In the present invention, sharp melt type toner is used to obtain good color images;
It is important to maintain the SD gap accurately. Therefore, in the present invention, the S-D with the configuration shown in FIGS.
Gap retaining means are employed.

That is, in the embodiment shown in FIG. 2, as will be better understood with reference to FIG. are fixed with screws 22, etc., and thereby the photosensitive drum 1 and sleeve 7 are held at a constant S-D.
A gap is maintained. In this state, as shown in FIG. 3, the photosensitive drum shaft 23 and the sleeve 7 are each connected to a drive system (not shown). In addition, photosensitive drum 1
The method for driving the sleeve 7 is not limited to the method shown in FIG. 3, but may also be performed by, for example, using a member that serves as a flange and a gear at the end of the photosensitive drum 1 and transmitting the drive to the gear. good.

FIG. 4 shows an embodiment in which the SD gap holding means according to the present invention is applied to the color image forming apparatus shown in FIG. Developer device 4 for each color toner (4A, 4B, 4C)
, 4D), each developing sleeve 7A, 7B, 7C, 7D is
Sleeve support members 21A, 21B, 21C, 2, respectively
It is independently fixed and positioned with respect to the side plate 20 by 1D.

By providing the S-D gap holding means according to the present invention, even if sharp melt type toner suitable for color images is used, fluctuation and widening of the S-D gap due to toner fusion etc. can be prevented. This makes it possible to obtain good color images with good uniformity.

As shown in FIG. 5, the toner application area on the developing sleeve 7 is preferably equal to or slightly wider than the maximum image forming width and wider than the width of the photosensitive drum 1 between the side plates 20, 20. Narrower is better.

Furthermore, since it is preferable that the friction between the sleeve support member 21 and the sleeve 7 be small, the support portion of the support member 21 may be molded from a resin with low frictional resistance, such as a fluororesin such as PTFE. More preferably, by using a method such as pouring a lubricant such as grease, the developing sleeve 7 can be rotated more smoothly, and good sleeve retention can be achieved.

FIG. 6 shows a second embodiment of the present invention. In this embodiment, the photosensitive drum 1 and each developing sleeve 7A, 7B, 7C, 7D of each color toner developing device 4 are supported by a single member by a bush 24.

FIG. 7 shows a perspective view of the bush 24. As shown in FIG. 7, the bush 24 has a photosensitive drum opening 25 and developing sleeve openings 26A, 26B, and 26C.
, 26D, the photosensitive drum 1 is formed in the photosensitive drum opening 25, and the developing sleeve openings 26A, 26B, 26
Developing sleeves 7A, 7B, 7C, and 7D are fitted into C and 26D, respectively, and the photosensitive drum 1 and sleeve 7 are positioned.

The other end of the photosensitive drum 1 and the developing sleeve 7 is also configured to support the photosensitive drum 1 and the sleeve 7 with a member similar to the bush 24, but in order to transmit driving force to each, Through holes are formed in the other photosensitive drum opening 25 and the developing sleeve openings 26A to 26D, so that they can be connected to a drive system.

Therefore, in this embodiment, the SD gap is between the photosensitive drum opening 25 and each sleeve opening 26A to 26D.
The SD gap is determined by simply inserting the photosensitive drum and the sleeve. Also, other components and image forming processes necessary for the image forming apparatus in this embodiment are the same as those in the first embodiment, and therefore are omitted in this embodiment.

In the second embodiment having the above-described structure and operation, the part that maintains the SD gap is attached to the photosensitive drum 1.
Since only one is required for each end of the developing sleeve 7, the structure is simple and easy to assemble. Furthermore, if the bush 24 is made of hard resin and manufactured by molding, mass production is high and costs are low. Furthermore, if the resin surface is coated with a fluororesin such as PTFE, which has good slip properties, both the photosensitive drum and sleeve can rotate smoothly without S-D gap vibration, and have the advantage of improved durability. It also has

A third embodiment of the present invention is shown in FIGS. 8 and 9. This embodiment has the same configuration as the first embodiment, but the toner seal member 27 is attached to the rotating shaft 28 of the application roller 9.
and the sleeve 7 are sealed. Further, the toner seal member 27 is fitted with the toner container 10, so that the toner does not leak from the gap between the seal member 27 and the container 10.

Conventionally, as a sealing method at the end of such a sleeve, the flow of toner has been obstructed by wrapping a plate-shaped material such as wool felt around the developing sleeve about half a circumference, or so-called "surface contact." However, in the present invention, a sharp melt type toner is used to obtain a good color image, so if the sealing method uses surface contact, once the toner enters the sealing part, it is likely to cause fusion, resulting in rotation of the sleeve. The torque increases, which may cause uneven rotation or, in the worst case, tooth skipping of the drive transmission gear.

Therefore, in this embodiment, in order to make full use of sharp melt type toner suitable for color image output, a sealing member 27 as shown in FIGS. 9 and 10 is used.
It is better to use A cross-sectional view of this seal member 27 along line XX in the figure is shown in FIG. As can be seen from this figure, the seal member 27 has a lip portion 27a formed on the bearing side and is in line contact with the shaft 28, thereby preventing the toner from flowing outward. The principle of this sealing method will be explained with reference to FIG.
7a receives the force in the direction of the solid line arrow, and the edge of the lip portion 27 seals the shaft 28. By using such a toner sealing method that utilizes line contact, it is possible to reduce torque increase due to toner fusion, etc., and it becomes possible to use sharp melt type toner. As the seal member 27 of the type shown in FIG. 10, what is generally called an oil seal can be used, and is a member well known to those skilled in the art and widely used in press machines, injection molding machines, etc. .

By using the present embodiment described above, it is possible to further reduce toner scattering to the sleeve support member 21 that positions the sleeve, and as a result, highly accurate S-D gap maintenance can be achieved. is achieved, thereby making it possible to form good color images using sharp melt type toner.

The toner seal means described in connection with the third embodiment can also be used in the second embodiment described above, and similar effects can be obtained.

Further, although each of the above embodiments has been described with respect to a color image forming apparatus, the present invention can also be suitably implemented in a monochromatic image forming apparatus such as black and white.

[0057]

Effects of the Invention The image forming apparatus according to the present invention configured as described above can use sharp melt type toner, thereby making it possible to obtain good color images, and has a simple configuration. A good toner seal is achieved, there is no torque increase due to toner fusion, etc., and the SD gap can be maintained with a sufficiently high precision, so that high quality images can always be formed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a side view showing the sleeve support member.

FIG. 3 is a top view showing the relationship among a sleeve support member, a developing sleeve, and a photosensitive drum according to the first embodiment of the present invention.

FIG. 4 is a side view showing a sleeve support member applied to a color image forming apparatus.

FIG. 5 is a top view of a sleeve support member, a developing sleeve, and a photosensitive drum showing a toner application area.

FIG. 6 is a side view of the SD gap retaining means according to the second embodiment of the invention.

FIG. 7 is a perspective view of the SD gap holding means.

FIG. 8 is a top view showing the relationship among a sleeve support member, a developing sleeve, a toner seal member, and a photosensitive drum according to a third embodiment of the present invention.

FIG. 9 is a side view of the toner seal member.

FIG. 10 is a cross-sectional view of the toner seal member.

FIG. 11 is a longitudinal sectional view of a conventional color image forming apparatus.

FIG. 12 is a top view showing a conventional SD gap holding means using rollers.

[Explanation of symbols]

1 Image carrier 4 Developing device 7 Developer carrier (developing sleeve) 9 Application roller 10
toner container

Claims (1)

[Claims] 1. An image carrier having an image carrier on which a latent image is formed, and at least one developing device arranged around the image carrier and converting the latent image on the image carrier into a visible image, The developing device has a developer carrier that carries developer and transports the developer toward the image carrier, and the developer carrier and the image carrier are arranged in a non-contact state with a predetermined gap between them. In the forming device, the developer is a one-component developer having sharp melt characteristics, and for supporting the developer carrier and maintaining a constant gap between the developer carrier and the image carrier. An image forming apparatus characterized in that a developer carrier supporting member is fixed.