JPH0384570A - developing device - Google Patents

Abstract

PURPOSE:To stabilize the triboelectrification of toner by forming the surface shape of a developing sleeve by forming a smooth projection part and recessed part with fine raised parts. CONSTITUTION:On the surface of the developer carrier 3, the projection part with the smooth surface and the recessed part which has a surface where the fine raised parts are formed are formed, a developer 6 is properly charged by the friction between the smooth surface of the projection part and the developer 6, and while the developer 6 is securely carried by the recessed part, the developer 6 is prevented from being electrified too much by the fine raised parts formed on the surface of the recessed part. Then a developer supply and peeling means is arranged in slide contact with the developer carrier 3 to peel the developer 6 off the developer carrier 3. Consequently, the triboelectric charge quantity (triboelectrification) of the developer can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device that performs development using a dry developer.

[Prior Art] Various types of dry-component developing devices have been proposed and put into practical use. However, in any development method, it is extremely difficult to form a thin layer of dry one-component developer. However, now that there is a need to improve the clarity and resolution of developed images, thin-layer type dry single-component developers*
Development of Type 3 and its equipment has become essential, and several measures have been proposed in response.

For example, there is a device as shown in Japanese Patent Application Laid-Open No. 54-43038. In this device, a rubber or metal elastic blade, which is a developer regulating means, is brought into contact with a developing sleeve, which is a developer carrier, and the developer (hereinafter referred to as toner) is allowed to enter and pass through the abutting portion onto the developing sleeve. A thin toner layer is formed on the toner, and a triboelectric charge (hereinafter referred to as triboelectric charge) is applied to the toner at the contact portion.

In such an apparatus, when using magnetic toner, if a magnet is provided in the developing sleeve, the toner can be supplied onto the developing sleeve by the magnetic force of the magnet. However, there is a problem in that the use of non-magnetic toner requires a new and more convenient supply means. Therefore, the applicant proposed the developing device shown in FIG.
59). In such an apparatus, a supply roller serving as a developer supplying and separating means is arranged in contact with the developing sleeve upstream of the contact portion between the elastic plate and the developing sleeve in the rotational direction of the developing sleeve, and supplies toner to the developing sleeve and removes the toner from the developing sleeve. The undeveloped toner on the top is being stripped off. With such a simple configuration, it has become possible to faithfully reproduce high-density, wide-area solid black images and to always provide stable images.

Furthermore, the developing sleeve of the conventional device described above is subjected to sandblasting treatment using amorphous blast particles (hereinafter referred to as amorphous particles) having sharp edges such as angular powder particles to roughen the surface. A device has also been proposed that further stabilizes the conveyance ability while keeping the component developers in an appropriate electrically charged state.

[Problem to be Solved by the Invention] However, the particle size is #400 (the particle size standard is based on JIS R6001 abrasive material) on the developing sleeve.

The same applies to the particle size below. ) using a surface-roughened development sleeve sandblasted with irregularly shaped particles.
When an image development durability test was conducted using a developing device using a non-magnetic component toner as a developer and brought into contact with the above-mentioned developing sleeve, which is an elastic blade and a supply roller, the following problematic phenomena were found. occured.

- After continuous copying, the image density decreased and fogging started occurring after about 500 copies.

(2) After removing the toner from the entire circumference of the developing sleeve surface using the developing device in (2) above, the developing sleeve was further cleaned with a solvent and an image was formed, and the image density was recovered.

First of all, regarding the above phenomenon (2), we measured the amount of triboelectric charge (hereinafter referred to as "triboelectric charge") of the toner on the developing sleeve, and found that at the above-mentioned number of copies, the triboelectric charge at the start of copying was about to reach its peak, and the decrease in triboelectric charge was due to the decrease in image density. I found out that it was lowering the height and causing fogging.

Further, when the surface of the developing sleeve at this time was observed using an electron microscope or the like, it was found that something was embedded in the uneven parts of the surface, especially in the recessed parts, as shown in FIG. Analysis of this substance revealed that it was a resin binder in the toner ingredients. Since both the binder covering the recesses and the toner are made of resin, the resins often come into contact with each other, making it impossible to obtain sufficient charging and reducing the triboelectric charge. It was found that the resin adhered particularly strongly to the deep parts of the recesses, and because the plastic was irregularly shaped, the sharp shape further strengthened the adhesion. It was also found that the deep and sharply shaped recesses were only scraped off by the supply roller.

The toner carried and conveyed on the developing sleeve in the above state is subjected to friction with the toner (resin) attached to the surface layer of the developing sleeve (or embedded in the recess) under the contact pressure between the elastic blade and the developing sleeve. This results in toner with an unstable charging state (low charge or charged with opposite polarity).

As a result, when these toners contribute to development in the developing section, there is a problem of low density and fogging.

Next, it has been found that sharp shapes cause resin to adhere to the surface of the developing sleeve, so if you use a developing sleeve with a smooth uneven surface using regular particles instead of irregularly shaped particles for sandblasting, you can achieve the above-mentioned results. It was thought that the problem would be resolved. Therefore, as described in JP-A-57-116:172, using regular shaped blast particles (hereinafter referred to as regular shaped particles) having a smooth surface like granular powder particles, particle size #
When image development and durability were performed using a developing sleeve that had been subjected to a sandal last treatment at 40°, a good image could be provided. However, when a toner with a small particle size is used as a developer in order to further improve image quality, the following new problems arise under special conditions.

■When copying an original with a lot of white background and extremely low toner consumption in a low-humidity environment, the image density immediately decreased.

This phenomenon occurred more markedly when a rubber roller was used as the supply roller.

Therefore, when we observed the surface of the developing sleeve for phenomenon (2), we found that toner particles were still attached to the surface, and when we measured the tribo, it was found that at the above-mentioned number of copies, it was considerably higher than the tribo of the applied toner layer at the start of copying. This was confirmed. In other words, phenomenon (2) occurs because when toner with a small particle size is used under conditions of low humidity, the toner becomes excessively charged (hereinafter referred to as charge-up).

This is because, as shown in FIG. 7, the toner is captured in the recesses on the smooth surface, which increases the frequency with which the toner rolls on the developing sleeve, increasing the amount of charge on the toner. In particular, when the particle size of the toner is reduced, the above-mentioned tendency is accelerated, and the amount of charge may increase significantly more than the appropriate amount. Such toner has a large mirroring force with respect to the developing sleeve, and when non-contact development is performed, the flying rate decreases at the same developing bias as when using a developing sleeve subjected to irregular shape blasting.

As a result, the amount of toner that passes through the development area while remaining attached to the development sleeve increases. There is also a problem in that even if an attempt is made to scrape off the toner having a large mirroring force that has returned into the developer supply container with a supply roller, it cannot be easily scraped off because of its strong adhesion to the developing sleeve.

As mentioned above, when a rubber roller is used as a supply roller, the charge-up phenomenon becomes more pronounced.The reason why the charge-up phenomenon becomes more pronounced is that the toner that has been charged up and has a large reflection force is scraped off with a strong force, and the This seems to be because the contact width (hereinafter referred to as nip width) of the rubber roller was widened and the toner was forced onto the developing sleeve instead.

In addition, if you widen the nip width between the developing sleeve and the supply roller in an attempt to sufficiently scrape off toner that has strongly adhered to the developing sleeve, or increase the relative speed difference between the developing sleeve and the supply roller, the driving torque increases and the developing Problems such as increased damage to the sleeve and supply roller (decreased durability) were occurring.

Incidentally, the above-mentioned phenomena (1) to (4) similarly occurred when a one-component magnetic toner was used as the developer.

The present invention provides a developing device that forms a good image by appropriately charging the toner without excessively charging up the toner while increasing the conveying ability of the developing sleeve, and by reliably peeling off the toner adhering to the developing sleeve. It is intended to.

[Means for Solving the Problems] According to the present invention, the above objects include: a developer supply container having an opening in the front and storing a monocomponent developer; and a developer supply container rotatably disposed in the opening. a developer carrier for carrying and transporting a developer; a developer carrier disposed behind the developer carrier so as to be in sliding contact with the developer carrier; supplying the developer to the developer carrier; and the developer carrier. A developer supplying and separating means made of an elastic body for peeling off the developer on the developer carrier, and a developer regulating means for regulating the passage of the developer on the developer carrier in contact with the developer carrier. In the developing device, the above-mentioned developer carrier is achieved by forming, on the surface thereof, convex portions having a smooth surface and concave portions having a rough surface with fine undulations.

[Function] The present invention forms a convex portion having a smooth surface and a concave portion having a surface with fine undulations on the surface of the developer carrier, and allows the smooth surface of the convex portion to interact with the developer. The developer is triboelectrically charged appropriately by the friction of the recess, and while the developer is reliably transported by the recess, the fine undulations formed on the surface of the recess prevent excessive charging of the developer. Further, since the developer supply and peeling means is disposed in sliding contact with the developer carrier, the developer on the developer carrier is peeled off and the amount of charge of the developer is stabilized.

[Embodiment] Hereinafter, a first embodiment of the present invention will be described based on FIGS. 1 and 2 of the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a photosensitive drum as a latent image carrier that rotates in the direction of arrow A. As shown in FIG. The photosensitive drum 1 may be, for example, a so-called xerographic photoconductor on which an electrostatic latent image is formed by the Carlson process, or a photoconductor having an insulating layer on the surface on which an electrostatic latent image is formed by the NP process described in Japanese Patent Publication No. 42-23910. , an insulator on which a latent image is formed by an electrostatic recording method, an insulator on which an electrostatic latent image is transferred by a transfer method, an electrostatic latent image (or potential latent image) or a magnetic latent image is formed and retained by any other appropriate method. It is a member that has been installed.

A developing device is arranged opposite to the photosensitive drum l,
The developing device includes a developer supply container (hereinafter referred to as container).
2, a developing sleeve 3 as a developer carrying member, an elastic blade 4 as a developer regulating means, and a supply roller 5 as a developer supplying and separating means.

The container 2 has an opening extending in the longitudinal direction of the developing device (direction perpendicular to the paper surface), and the developing sleeve 3 is inserted into the opening.
or has been set up. The developing sleeve 3 is made of a non-magnetic material such as aluminum and has a surface as described below. The developing sleeve 3 is horizontally installed in the opening in FIG. 1, with its right half-circumferential surface protruding into the container 2, and its left half-circumferential surface exposed outside the container 2, and rotatably supported on a bearing. It is rotationally driven in the direction of arrow B. The developing sleeve 3 is not limited to a cylindrical body (sleeve), but may be in the form of an endless belt that is rotationally driven. Alternatively, a conductive rubber roller may be used. The surface of the developing sleeve 3 exposed outside the container is connected to the photosensitive drum l.
They face each other with a gap on the surface.

A supply roller 5 is disposed behind the developing sleeve 3 so as to rotate in sliding contact with the surface of the developing sleeve 3 entering the container at a sliding contact portion S. The supply roller 5 rotates in the same direction as the developing sleeve 3 and supplies the developer to the developing sleeve 3.
The toner on the developing sleeve 3 is peeled off by supplying the toner to the developing sleeve 3 and making elastic contact with the developing sleeve 3.

An elastic blade 4 is disposed in contact with the developing sleeve 3 at a contact portion T downstream of the sliding contact portion S between the supply roller 5 and the developing sleeve 3 in the rotational direction of the developing sleeve 3. , the passage of the developer on the developing sleeve 3 is restricted at the corresponding contact portion T.

First, in this embodiment, the toner 6 supplied to the vicinity of the developing sleeve 3 by the rotation of the supply roller 5 is conveyed to the sliding contact portion S of the supply roller 5 by the rotation of the developing sleeve 3, and is then conveyed to the sliding contact portion S of the supply roller 5. It enters the contact portion T with the sleeve 3 and is supported on the surface of the developing sleeve 3.

Further, when the toner 6 passes through the contact portion T between the elastic blade 4 and the developing sleeve 3, it comes into sliding contact with the surface of the developing sleeve 3 by the elastic blade 4, and is further subjected to frictional electrification. In this way, the toner 6 can be sufficiently triboelectrically charged.

The toner 6 that has been sufficiently triboelectrically charged in this manner passes through the contact portion T and is formed as a thin layer of toner on the developing sleeve 3, and is conveyed to the developing portion F facing the photosensitive drum 1 on the developing sleeve 3E. It will be done. In the developing section F, some toner is consumed by the developing operation, and other toner is collected from the lower part of the developing sleeve 3 as the developing sleeve 3 rotates. A sealing member 7 is provided in this collection portion to allow the toner that has not been consumed during development to pass into the container 2, and to prevent the toner 6 in the container 2 from leaking from the lower part of the container 2. The collected toner on the developing sleeve 3 is scraped off by elastic contact at the sliding contact portion S between the supply roller 5 and the developing sleeve 3.

Most of the scraped off toner 6 is conveyed as the supply roller 5 rotates, mixes with the toner in the container 2, and the charge of the charged toner is dispersed. At the same time, new toner is supplied onto the developing sleeve 3, where the elastic blade 4 and the developing sleeve 3 come into contact with each other, and the toner is again applied with a triboelectric effect and made into a thin layer, and then transported to the developing section.

In this way, the undeveloped toner on the developing sleeve is scraped off, so that the toner on the developing sleeve 3 is replaced, and excessive charging of the toner, that is, charge-up, is prevented.

Next, the developing sleeve of this embodiment will be explained in detail.

In this embodiment, as shown in FIG. 2, the surface shape of the developing sleeve is formed by convex portions having smooth surfaces (hereinafter referred to as smooth convex portions) and concave portions having surfaces formed by fine undulations. be done. When a developing sleeve having such a shape is used, the toner conveyed to the vicinity of the developing sleeve by the supply roller enters the contact portion of the elastic blade as the developing sleeve rotates. At this time, the toner rolls on the smooth-surfaced convex portion of the developing sleeve, and the toner is pulled out from under the pressure of the elastic blade by an appropriate conveying force in the concave portion which is provided with tribo and has minute undulations.

The triboelectric effect on the toner is mainly caused by these smooth convex portions, or because the smooth convex portions are randomly distributed, the surface of the developing sleeve that has been blasted with regular particles (only the concave portions that have been relatively smoothed) is applied to the toner. surface), the toner is not charged. Therefore, the mirroring force is not so large, and the toner on the developing sleeve can be easily scraped off by the sponge acid supply roller. Furthermore, since the fine undulations of the recessed portions are not sharp and deep undulations when irregular roughness is applied, the toner resin is not embedded in the recessed portions to a great extent. Also, even if it is embedded,
It is easier to scrape off the sponge with a supply roller than when irregular-shaped blasting is applied.

The fine undulations reduce the frequency of contact between the surface of the recessed portion and the toner, thereby preventing the toner from being charged up. The roughness of the unevenness on the surface of the developing sleeve, ie, the height of the smooth convex portion, is 0.1 to 1 times the average particle size of the toner, and the pitch pressure gid of the convex portion is 0.1 times the average particle size of the toner. 5
~5 times, and the height h2 of the fine undulations in the recess is 0.01 to 0.3 times the average particle size of the toner, and the pitch pressure * d2 is 0.02S1 times the average particle size of the toner h> hx, d
It is preferable that the range satisfies +>d2. If it is outside this range, appropriate triboelectricity will not be applied on the developing sleeve.

For example, ht, hz are below the lower limit range, d,,d
When , exceeds the upper limit range, the toner tends to be excessively charged, and conversely, when ht, h2, upper limit, d,, d, exceed the lower limit range, the toner resin may be fused (contaminated) or triboelectric. shows a decreasing trend.

Next, an experimental example conducted under the following conditions based on this example will be described.

In this experimental example, an aluminum developing sleeve with a diameter of 20 m5 was used, and the surface was first coated with particle size #150 (the particle size standard is JI
Depends on the SR6001 abrasive. The same applies to the particle size below. ) particles were used to form thick irregularities, and then blasting was performed again using particles with a particle size of #600 to form fine undulations. In addition, the surface was mirror-polished as a final step to smooth out the convex portions. The shape characteristics of the surface of this developing three are that the height of the convex portion h□ is approximately 5 tsubo ugly, the pitch gap d is approximately 30 ru, and the height of fine undulations h2
or about IILm, and the pitch gap d2 is about 5Lm. Note that the method for forming this shape is not limited to the above-mentioned method; for example, a method may be used in which irregularities are formed by random erosion using a chemical engineering/inching method, and then the convex portions are polished to a mirror surface.

Next, as a material for the elastic blade 4, rubber having a JIS hardness of 40 to 80 degrees, preferably 50 to 70'' is suitable for stably forming a thin layer of developer.Elastic blade 4
The end portion of the developer sleeve 3 is biased so as to come into contact with the developing sleeve 3 .

Note that the end of the blade mentioned above refers to the tip of the blade,
This is the vicinity including the tip or the vicinity of the tip not including the tip. Further, the pressure setting of the elastic blade on the developing sleeve (linear pressure in the direction of the generating sleeve of the developing sleeve) is preferably set to 5 to 200 g/m, and in the experimental example, it was set to 50 g/m.

As the material for the supply roller 5, a sponge roller with a skeleton structure having a low degree of foaming (high density) is preferable.

In this example, a 5 m thick urethane foam (density 0.025 g/c1) wound around a core rod was used. This sponge roller makes soft contact with the developing sleeve, and the effective contact width is 1 to 10 mm, and in the example, it was set to 4 mm. Note that in order to improve the peeling off of undeveloped toner on the developing sleeve, it is preferable that the sponge roller circumferential speed and the developing sleeve circumferential speed have a relative speed, and the relative speed with respect to the developing sleeve is 5 to 600 mm/
see is effective, and was set to 150 mm/sec in this experimental example.

The toner is made of a copolymer of styrene/acrylic resin and styrene butadiene resin and a pigment with an average particle size of 12 JL.
A toner in which 1.5% of colloidal silica was externally added to toner powder was used.

The developing method in this experimental example is, for example,
32375, that is, by applying an alternating current with a superimposed direct current between the photosensitive drum 1 and the developing sleeve 3, a thin layer of toner on the developing sleeve 3 is transferred to an electrostatic latent image on the photosensitive tram l in the form of an image. A so-called non-contact development method was used. In addition, a contact development method may also be used.

The above device was installed in a Canon Co., Ltd. NP1215 copying machine, and a frequency of 1800H was used as a bias power source.
z, -2 to an AC voltage with a peak-to-peak voltage of 130 V.
Using a superimposed DC current of 50 V, the surface potential of the latent image on the photosensitive drum l was set to -540 V in the dark area and -150 V in the bright area, and the distance between the developing sleeve 3 and the photosensitive drum L was set to 250 p.
-ta was set, and development was performed by non-contact development.

As a result, a uniform coated layer of about 1 OJL was obtained on the developing sleeve, and when the charge amount of this layer was measured by the Tlow-off method, the charge amount was +15 ILc/g. This amount of charge is sufficient to obtain a good image.

Moreover, the obtained image was a good image with a reflection density of 1.3.

Furthermore, when images were formed on 2,000 sheets continuously, the toner charge amount continued to be maintained at 15 to 204 c/g, and good images were obtained without sleeve ghost or density loss until the final image was formed. I was able to get it.

In addition, in a low humidity environment, the same type of toner as mentioned above has an average particle size of 8.
When development was carried out using toner with a small particle size, there was no abnormal increase in the amount of triboelectric charge of the toner until 1000 images were formed, and the amount of charge was maintained at +ta~+22←c/g. It was possible to obtain images without thinning, fogging, or dripping.

Next, a second embodiment of the present invention will be described using FIG. 3.

This embodiment differs from the first embodiment in that the surface shape of the developing sleeve is formed only by minute depressions in which the minute undulations within the depressions have been treated to be relatively smooth, as shown in FIG. Even with such a shape, the ability to apply triboelectric force to the toner and the ability to peel it off are the same as those in the first embodiment, and especially when the particle size of the toner is made smaller, the effect on peeling is further improved. In addition, the formation method is, for example, after blasting with amorphous particles with a particle size of #150, particles with a particle size of #600 to #80 are used.
Blast again with regular particles from the mouth. After that, there are methods such as mirror polishing the surface.

Next, a third embodiment of the present invention will be described.

In this example, the material of the supply roller is a fur brush structure.
For example, this embodiment differs from the first embodiment in that rayon fiber or the like is used. However, in this case, if the width of contact with the developing sleeve is too wide (increasing the contact pressure), the brush will become fatigued over time, so it is preferable to lower the contact pressure than the sponge roller.

Finally, a fourth embodiment of the present invention will be described using FIG. 4.

In this embodiment, a magnetic toner is used as the developer. In this case, as shown in FIG. 4, the magnetic roller 8 is held and fixed within the developing sleeve and its magnetic force is utilized to transport the toner, and the magnetic force can also be utilized in the developing section. The functions and effects of the supply roller are the same as in the first embodiment.

Note that a fur brush was used as the supply roller 5 in FIG. 4.

[Effects of the Invention] As explained above, in the present invention, a developing agent is used, and a thin layer of toner is formed, the toner is applied, and the toner is peeled off using an elastic blade and a sponge or fur brush-like supply roller. In the device, by forming the surface shape of the developing sleeve with smooth convex portions and concave portions having fine undulations, it is possible to provide triboelectricity in the smooth convex portions and to carry the toner appropriately in the concave portions with fine undulations. It was possible to separate the functions of the toner and stabilize the toner tribodies, which is a distant relative. Furthermore, by using a sponge or fur brush-like roller as the supply roller, the effect of stripping off the toner in the recesses having fine undulations is improved, and it becomes possible to stabilize the tribo over time. By adopting this configuration, it has become possible to always provide stable images even when the toner particle size is reduced or there are environmental changes.

Furthermore, even when toner that requires light load application, such as capsule toner for pressure fixing, is used, by forming the surface of the developing sleeve in the above-described shape, it is now possible to prevent the developing sleeve from fusing or the like.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the device according to the first embodiment of the present invention, FIG. 2 is a schematic cross-sectional enlarged view of the surface shape of the developing sleeve of the device shown in FIG. 1, and FIG. 3 is the surface shape of the developing sleeve of the device of the second embodiment. FIG. 4 is a schematic cross-sectional view of the device of the fourth embodiment,
FIG. 5 is an enlarged schematic cross-sectional view of the surface shape of the developing sleeve of a conventional device, FIG. 6 is an enlarged schematic cross-sectional view of the surface shape of the developing sleeve of another conventional device, and FIG. 7 is a schematic cross-sectional view of another conventional device. It is a diagram.

Claims (7)

[Claims] (1) A developer supply container having an opening in the front and storing a one-component developer, a developer carrier rotatably disposed in the opening to carry and transport the developer, and the developer carrier. a developer supply comprising an elastic body disposed so as to be in sliding contact with the developer carrier at the rear of the body and supplying the developer to the developer carrier and peeling off the developer from the developer carrier; In a developing device including a peeling means and a developer regulating means that comes into contact with the developer carrier and restricts the passage of the developer on the developer carrier, the surface of the developer carrier has a surface. A developing device characterized in that a convex portion having a smooth surface and a concave portion having a rough surface with minute undulations are formed. (2) The height h1 of the smooth convex portion is 0.1 to 1 times the average particle size of the one-component developer, the pitch distance d1 of the convex portion is 0.5 to 5 times the average particle size, and the concave portion Height h2 of minute undulations within
is 0.01 to 0.3 times the average grain size, the distance d2 between the pitches of fine undulations is 0.02 to 1 times the average grain size, h1 is larger than h2, and d2 than d
1. The developing device according to claim 1, wherein the developing device is satisfied that 1 is large. (3) A claim that the surface shape of the developer carrier has a convex part and a concave part, the convex part consists of a smooth surface, and the concave part consists of a fine concave area treated to be relatively smooth. The developing device according to item (1). (4) The developing device according to claim (1), wherein the one-component developer is a non-magnetic developer. (5) The developing device according to any one of claims (1) to (3), wherein the developer supply and peeling means is formed of an elastic body. (6) Claims (1) to (3) wherein the developer supplying and peeling means is a sponge roller having a foam skeleton structure.
). (7) The developing device according to any one of claims (1) to (3), wherein the developer supply and peeling means is formed of a fur brush.