JPS6032064A - Developing method - Google Patents

Abstract

PURPOSE:To prevent blocking and to obtain efficient developing property by carrying magnetic toner containing iron oxide of specific quantity or more and having volume resistance in a specific range at a specific moving speed in the same direction as the moving direction of the surface of an image carrier. CONSTITUTION:The magnetic toner 9 adsorbed to the surface of a non-magnetic sleeve 3 is carried in the arrow S direction by the relative rotation between the non-magnetic sleeve 3 and a parmanent magnetic member 6. The magnetic toner 9 passing through a doctor gap (d) is contacted with the surface of a photosensitive drum 1 near a developing gap D and adered to the surface to form a toner image. Although it is necessary to speed up the carrying speed of the toner 9 as possible, it is proper to set up the speed to 1.1 times or less the peripheral speed of the surface of the photosensitive drum 1. Efficient developing property is obtained by setting up the content of magnetic powder in the toner to 60wt% or more. However, if the content exceeds 80wt%, fixing property is extremely deteriorated. Considering the developing property, the volume resistance of the magnetic toner 9 is set up to 10<8>-10<12>OMEGA.cm and it is preferable to set up the grain size of the toner to 5-50mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a developing method in which an electrostatic charge image formed on the surface of an image carrier is visualized by a magnetic brush method using a one-component magnetic toner.

[Prior Art] As a copying method using electrophotography, for example, an electrostatic charge image is formed on various photoreceptors such as an Ss photoreceptor, a ZnO photoreceptor, an organic photoconductor, etc., and a magnetic brush method is used using a magnetic developer. Generally, methods are known in which a final image is obtained by developing the image and then fixing it, or by transferring the developed image onto a transfer sheet such as plain paper and then fixing it.

The magnetic developer used in this copying method is generally a two-component developer, which is a mixed powder of non-magnetic toner in which various additives such as colorants and dyes are dispersed in a magnetic carrier and fixing resin. be. However, when using this two-component developer, it is necessary to provide the developing device with a means to keep the toner concentration in the developer constant and a means to uniformly stir and mix the toner and carrier. There is a problem in that devices are becoming larger and more complex. Additionally, if carrier particles are mixed with toner for a long time, a toner film will be formed on the surface of the gearia particles, reducing the triboelectric charging properties of the carrier.
Therefore, it is necessary to replace the carrier periodically.

As a magnetic developer, it has been proposed to develop electrostatic images using a one-component magnetic toner mainly composed of resin and magnetic powder without using carrier particles (for example, in JP-A-49-1999-1).
(Refer to Publication No. 4532), it was first put to practical use in a method in which treated paper such as zinc oxide paper or electrostatic recording paper was used to directly print after development, and then it was put into practical use in an electrophotographic copying method that included the above-mentioned transfer process. It is (there is)

In a copying method including this transfer step, from the viewpoint of image quality, especially fixing properties, it is necessary to use a magnetic 1-ner with a low magnetic powder content (approximately 40% by weight or less) and a low magnetic force (e.g.,
66455) is often used. However, in order to perform good development using such a low magnetic force toner, the conveying speed of the magnetic toner is set to be at least twice the moving speed of the surface of the photoreceptor.

Therefore, when the magnetic toner passes through the doctor blade, a high pressure is applied, causing a problem of blocking.

In addition, as a method for fixing toner images, a heating fixing method using an oven or a heated roll is common, but a pressure saw fixing method is becoming more popular because it has advantages such as no preheating time and low power consumption. be.

The magnetic toner used in this pressure fixing method is required to have excellent offset resistance and storage stability, but it is particularly important to show good fixing properties at the lowest possible pressure. . Therefore, pressure-fixing magnetic toner uses resin that does not undergo plastic deformation under a specified pressure (500 k (+/cm2 or less)), and specifically waxes such as polyethylene wax, Admi wax, and microcrystalline wax are used. (For example, see JP-A-51-87042.) Also, since it is difficult to satisfy the properties with wax alone, ethylene acetate beer copolymer or ethylene acrylic copolymer, etc. It is generally used in combination with other resins. (
(For example, see Japanese Patent Publication No. 54-3373.) In this way, the pressure-fixed magnetic toner has a resin component, and since it contains at least wax, it is easily deformed when subjected to mechanical pressure, and as described above. There is a problem in that blocking is likely to occur.

[Object 1] An object of the present invention is to provide a developing method that eliminates the problems of the prior art described above and provides good developability without blocking even when using a pressure-horn fixing type magnetic toner. be.

``Summary'' The developing method of the present invention provides a non-magnetic sleeve that holds a permanent magnet member having a plurality of magnetic poles therein, facing the surface of an image carrier that moves in a predetermined direction and holds an electrostatic image. A magnetic toner mainly composed of a resin containing wax and magnetic powder is supplied onto the non-magnetic sleeve, and the magnetic toner is transferred to the surface of the image carrier by relative rotation between the permanent magnet member and the non-magnetic sleeve. and a non-magnetic sleeve, and the magnetic toner is selectively deposited on the surface of the image carrier in the opposing gap to visualize the electrostatic charge image. Contains 60% by weight or more of iron oxide as a toner and has a volume resistance of 1
Using a magnetic toner in the range of 08 to 10 Ωcm, the magnetic toner is moved in the same direction as the moving direction of the image carrier surface at the opposing interval and at a speed of 1.1 times or less than the moving speed of the image carrier surface. It is characterized by being transported at high speed.

[Configuration] E action] The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a developing device for carrying out the present invention.

In the figure, numeral 1 denotes a photosensitive drum which holds an electrostatic charge image (indicated by a cross in the figure) on its surface and moves in the direction of arrow 7 in the figure. A developing device 2 is installed around the photosensitive drum. The developing device 2 includes a non-magnetic sleeve 3 disposed facing the surface of the photoreceptor drum 1 with a gap (hereinafter referred to as a developing gear I7) D, and a permanent magnet 4 having a plurality of magnetic poles on its surface attached to a shaft 5. The permanent magnet member 6 is fixed to a permanent magnet member 6, a doctor blade 7 is disposed with a gap (hereinafter referred to as a doctor gap) d between the non-magnetic sleeve 3, and a toner 118 containing magnetic toner 9.

According to the above-mentioned developing device, the magnetic toner 9 attracted to the non-magnetic sleeve 3 is conveyed in the direction of the arrow SZj shown in the figure by the relative rotation of the non-magnetic sleeve 3 and the permanent magnet member 6. After passing through the doctor gap d, the magnetic toner 9 comes into contact with the surface of the photosensitive drum 1 near the developing gear D and adheres thereto, forming a toner image 10. After passing through the developing gap D, the magnetic toner 9 is conveyed in the direction of the arrow Sh shown in the figure and collected into the -C toner tank 8. The toner image 10 is transferred onto a transfer sheet (not shown) by a transfer means (not shown) such as a corona transfer device, and then passes through a fixing means (not shown) to obtain a final image.

The inventors of the present invention and others investigated the conditions under which good development could be carried out without blocking using the developing device shown in FIG. 1, and as a result they found a number of conditions.

First, if the conveyance speed of the magnetic toner is too fast, the magnetic toner will be subjected to a strong force when passing through the doctor gap, and blocking will likely occur. In order to prevent this, it is necessary to reduce the number of rotations of the non-magnetic sleeve as much as possible. However, if the number of rotations of the non-magnetic sleeve is reduced, the force for conveying the magnetic toner is weakened, resulting in a decrease in developing performance.

Therefore, in order to compensate for the decrease in developability, it is necessary to rotate the permanent magnet member in the same direction as the nonmagnetic sleeve. Rotating the non-magnetic sleeve in the same direction as the permanent magnet member is known, for example, as described in Japanese Patent Application Laid-Open No. 55-i26266, but according to studies by the present inventors, this toner conveying method It was confirmed that this method is extremely effective in preventing blocking.

Furthermore, in order to prevent blocking, the toner transport speed V, - expressed by the following equation (1) needs to be as fast as possible, especially when Vt=O, which is most preferable, but the circumferential speed Vp of the surface of the photoreceptor drum is -11 times or less is sufficient.

qb, D: Outside diameter of the non-magnetic sleeve (n+m) h: Toner thickness on the sleeve (orIll) P: Number of magnetic poles of the permanent magnet n,: Number of rotations of the non-magnetic sleeve (r, p, m111M=
In order to obtain good developing performance by slowing down the rotation speed of the permanent magnet part (r, p, m,) and the transport speed of the toner, the movement of the magnetic toner on the non-magnetic sleeve must be activated. It is necessary to increase the chances of the magnetic toner coming into contact with the surface of the photoconductor, so it is necessary to increase the magnetic force of the permanent magnet member, specifically, to set the magnetic force on the sleeve in the range of 00 to 1700G, and to increase the magnetic force of the permanent magnet (the rotation of the j member To increase the number, 1000r-
p, m, or more (in the case of outer diameter 29.3a+iφ), and 1-ui * should be 1Fb VQ ta / Isu - 4su h2 -j+ l 1. %Next, when implementing the above-described toner transport method, the composition of the magnetic toner is also an important factor.

In other words, according to the above-mentioned toner conveying method, the magnetic I-toner on the non-magnetic sleeve does not follow the rotation of the non-magnetic sleeve and is subjected to a force in the opposite direction to the non-magnetic sleeve due to the rotation of the permanent magnet member, so that the toner is If the content of magnetic powder is small, the movement of the magnetic toner on the non-magnetic sleeve will be reduced. As a result of studies conducted by the present inventors, it has been found that good developability can be achieved by setting the content of magnetic powder in the toner pile to 60% by weight or more (preferably 70% by weight or more). However, if the magnetic powder content m exceeds 80% by weight, the fixing properties will be extremely reduced, so it is necessary to keep it below 80% by weight.

In addition, magnetic powders include powders of metals such as iron, nickel, chromium, and cobalt, and their alloys, and various ferromagnetic powders such as ferrite i, hematite (γ-Fe 203 ), and magnetite (Fe203 and/or Fe304). However, from the viewpoint of magnetic properties and hue, it is necessary to use hematite or magnetite. Among the magnetic properties, the saturation magnetization (4πIs) is proportional to the content (2) of the magnetic powder, and is suitably in the range of 50 to 728 rAu/Q. - Mansaku Magnetic No. 7 (zHc') is determined by the type of magnetic powder, but blocking is likely to occur if it is too high.On the other hand, if it is too high, the ratio of acicular particles will increase, and the volume of magnetite will increase. increases, so 80-40
A range of 00e (preferably 100 to 3000e) is appropriate.

Furthermore, in order to be used in the pressure fixing method, at least a wax is used as the fixing resin in the present invention, but according to the studies of the present inventors, among various waxes, poly(ethylene ethylene) wax has excellent storage stability and fixing properties. It has been found that this method can best balance the characteristics and is also the most effective for preventing blocking. Furthermore, among polyethylene waxes,
It is suitable that the number average molecular weight is in the range of 4,500 to ioooo and the weight average molecular weight is in the range of 10,000 to 20,000. This is because when the molecular weight is low, the blocking prevention effect becomes weak, while when the molecular weight is high, plastic deformation becomes difficult and the fixing pressure is high (40 to 50 kg/Cll1 or more).
This is because it requires Use of this polyethylene wax also provides the effect of hardening the surface of the toner image after fixing and increasing its resistance to scratching. As the resin component, in addition to polyethylene wax, other resins such as ethylene vinyl acetate copolymer, amide wax, styrene resin, acrylic resin, etc. may be used as long as the blocking resistance and fixing properties are not impaired. can.

The magnetic toner used in the present invention contains the above-mentioned magnetic powder and resin as essential components, and optionally includes a resistance modifier such as carbon black, a fluidity modifier such as 5i02 particles, nigrosine dye and metal-containing pear dye. It may contain various additives such as a charge control agent such as (for example, see Japanese Patent Application Laid-Open No. 57-97545), and can be manufactured using these materials by a known method such as a pulverization method or a spray drying method. be able to.

The magnetic toner thus obtained can be applied to either the so-called CPC method, in which it is fixed directly after development, or the so-called C method, in which it is transferred and then fixed after development.From the viewpoint of developability. The volume resistance of magnetic toner is 10
A range of 8 to 10 Ω·am is preferable. Also, regarding toner calibration, it is best to set it in the range of 5 to 50μI, especially P
When used in the PC system, the thickness may be in the range of 5 to 30 μm.

In the present invention, the resistance of the toner is determined by placing the toner powder in a cylinder made of Teflon (trade name) with an inner diameter of 3.05vnφ.
Filled to a height of 20ml, under the load of ioogr, D
, C, the value measured in an electric field of 4000v/am. In addition, the blocking properties and storage stability of toners in Examples and Comparative Examples described below were evaluated as follows.

First, the blocking property was determined by standing upright a non-magnetic cylindrical hermetic container (outer diameter 60IIIIIIφ, inner diameter 58tIl+nφ, length 100IIIIII11) with one end sealed.
After filling the 'Or magnetic toner, the other end was sealed with an armor, and the C cylindrical container was vibrated at a frequency of 20 times/min and an amplitude of 2+11111.
The sample was vibrated up and down for 2 minutes under the following conditions, and the aggregation state of the 1-ner was observed and evaluated before and after the vibration. And 100t+ in degrees
It was evaluated by leaving it on a petri dish.

[Example 1] Polyethylene wax (weight average molecule 1111000,
Number average molecular weight 6000)...26 parts by weight Carbon black (Mitsubishi Kasei MA600) '...3
Parts by Weight The above composition was mixed in a heating kneader for 30 minutes, and then cooled and solidified. The cooled solidified product is pulverized into particles of 30 μm or less using a jet mill, and a fluidity modifier (carbon black) is added to the pulverized powder in o and o7 weight parts, mixed, and then classified to obtain a particle size distribution of 5 to 20 μm. with a volume resistance of 3X10
A magnetic toner of 9Ω·Cll1 was obtained.

Using the above magnetic toner, image evaluation was carried out in an experimental copying machine equipped with a developing device shown in Fig. M1 under the conditions of 20° C. and 60% R and H. In this case, a Se drum having an outer diameter of 120 mm was used as the photosensitive drum 1, and the drum was rotated at a circumferential speed of 1.00111111/sec. In addition, the non-magnetic sleeve 3 (a stainless steel cylinder with an outer diameter of 31.4 mm≠) is inserted in the direction of arrow X in the figure) 921', t
Rotate the permanent magnet member 6 (outer diameter 29.3
A 3a-ferrite magnet (111111φ, 8-pole symmetrical magnetization, magnetic flux density on the sleeve of 830G fixed to the shaft) was rotated at 150 Or, p, m in the same direction as the sleeve. Further, the development gap D and the doctor gap d were adjusted to 0.5IIITh and Q, 3i+m, respectively.

As the transfer paper, Sunflower manufactured by Tamako Paper Co., Ltd. was used, and for fixation, a pair of pressure rolls adjusted to a linear pressure of 18 ku/cn+ (the surface was hard chrome plated and the surface roughness was 0.83) was used.
The following grinding process was carried out using a steel roll. Furthermore, V
r is 43111m/38c'c.

Sono result: resolution 8 lines/l1lII11 solid black m degree 1.
34 and high quality images with good halftone reproducibility were obtained. Furthermore, the above-mentioned magnetic toner does not cause any problems in terms of blocking properties and storage stability.

[Comparative Example 1] A magnetic toner was prepared under the same conditions as in Example 1, except that the blending amounts of polyethylene wax and magnetite were 47 parts heavy can and 50 parts heavy lead, respectively.

Using this magnetic toner, the permanent magnet member was kept stationary and the non-magnetic sleeve was rotated at 122 r, D, lIl (V
, = 200, 6 mm/sec) except Example 1
When image evaluation was performed under the same conditions as above, the image density was 0.
．． 78, the resolution was 5.0 lines/11II11, and a good image could not be obtained.

[Example 2] Polyethylene wax (number average molecule ff 15000. weight average molecule m 1aooo>...25 parts by weight carbon black (Mitsubishi Kasei #30) total ioo parts by weight The above composition was mixed with 30 parts by weight using a two-roll heated kneader. The cooled solidified product was pulverized into particles of 30 μm or less in a di-mill, and the pulverized powder was mixed with a fluidity modifier (
A magnetic toner having a volume resistivity of 8×10 Ω·Cll1 and a grain size distribution of 5 to 20 μm was obtained by adding O1 carbon black (by weight), mixing and classifying.

Using the above magnetic toner, a permanent magnet member and a non-magnetic sleeve each having a magnetic flux density of 940G and a 3R-saw magnet with a magnetic flux density of 940G on the sleeve as the C1 permanent magnet were used.
0r, p, m and 5 Q r, 11. , m F
The image evaluation was performed in the same manner as in Example 1 except that the drum was rotated (V r = 33 mm/sea) and the circumferential speed of the 3e drum was 60 mm/sec.
Resolution 8 trees/1llIIl.

A high quality image with a solid density of 1.43 and good halftone reproducibility was obtained.

Further, the above magnetic toner did not cause any problems in terms of blocking properties and storage stability.

[Comparative Example 2] A magnetic toner was prepared under the same conditions as in Example 1, except that the proportions of polyethylene wax and magnetite were 45 parts by weight and 50 parts by weight, respectively.

Using this magnetic toner, the permanent magnet member was kept stationary and the non-magnetic sleeve was rotated at 61 r, p=m (V=
When the image was evaluated under the same conditions as in Example 1 except for 100.3 mm/sec), a satisfactory image with a density of 0.95 and a resolution of 5.6 lines/ml11 was not found.

[Effects] As described above, according to the present invention, high-quality pressure-fixed images can be obtained without blocking.

[Brief explanation of the drawing]

FIG. 1 shows an apparatus for carrying out the developing method of the present invention. FIG.

Claims (1)

[Claims] 1. A non-magnetic sleeve that moves in a predetermined direction and holds therein a permanent magnet base having a plurality of polar magnets facing the surface of the image carrier that holds the electrostatic charge image is installed. Then, a magnetic toner mainly composed of 1jAIIli containing wax and magnetic powder is supplied onto the non-magnetic sleeve, and the magnetic toner is transferred to the image carrier by relative rotation between the pre-gd permanent magnet member and the non-magnetic sleeve. In the developing method, the electrostatic charge image is visualized by conveying the magnetic toner toward an opposing gap between the image carrier surface and a non-magnetic sleeve, and selectively adhering the magnetic toner to the image carrier surface in the opposing gap. Contains 60% by weight or more of iron oxide as a toner and has a volume resistivity of 108 to 10
Using a magnetic toner in the range of Ω·Cll1, the magnetic toner is moved in the same direction as the moving direction of the image carrier surface in the opposing gap and at a speed of not more than 1.1 times the moving speed of the image carrier surface. Conveyance 1E 7S L# is applied.Saishima Onatsuji 2.Use a magnetic toner containing polyethylene wax with a number average molecular layer in the range of 4500 to ioooo and a weight average molecular weight in the range of)oooo to 20000. A developing method according to claim 1, characterized in that: