JPH07261540A - Image forming method - Google Patents

Abstract

PURPOSE:To prevent the sticking of a carrier, the rattling of an image, and the scattering of a toner and provide a high-quality, high-precision image excellent in the reproducibility of fine lines and an intermediate-tone image in a developing device using a two-constituent developer constituted of the toner and carrier having small grain sizes. CONSTITUTION:The magnetic flux density of a developing magnetic pole provided in a developer carrier is set to 800-1200 gauss, the tilt angle of the developing magnetic pole is set apart by 2-15 deg. from the most proximity position to an electrostatic charge image carrier and a developer carrier, the peripheral speed ratio (A) between the electrostatic charge image carrier and developer carrier is expressed by the equation: peripheral speed ratio (A): (moving speed of developer carrier)/(moving speed of electrostatic charge image carrier) X100(%), and this developing device satisfies the equation: (2D+540)/5<=A<=(2D+1340)/5, where Dmum is the weight average grain size of the magnetic carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for an electrophotographic copying machine, an electrostatic recording machine, an electrostatic printing machine and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for forming an image in an electrophotographic copying machine, an electrostatic recording machine, an electrostatic printing machine or the like, a magnetic brush developing device using a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed. Is widely used.

As one of the magnetic brush developing devices,
A non-magnetic sleeve, which is rotatably attached as a developer carrying means, and a magnet roller in which a plurality of magnetic poles fixed in the sleeve are arranged, and conveys the developer by rotating the sleeve. It is known that a magnet is arranged at a developing position facing the electrostatic image carrier. Also,
For the purpose of improving the image quality, it is known that an alternating electric field is formed at a developing position where the sleeve and the electrostatic charge image bearing member face each other, thereby preventing image swept and improving reproducibility of a halftone image. ing.

Further, since there is an increasing demand for high-quality and high-definition images, it is possible to stabilize the toner supply capacity and obtain an image with a high resolution layer by reducing the particle size of both toner and carrier. It is known that However, in this case, since the carrier has a small particle size, the carrier may adhere to the electrostatic image carrier, thereby causing an image defect. Also, the reproducibility of halftone images is poor,
There was a case where the image was poor and had a “sharpness”.

[0005]

SUMMARY OF THE INVENTION In a developing device using a two-component developer in which both the toner and carrier have a small diameter, carrier adhesion, image rubbing and toner scattering are prevented, and reproducibility of fine lines and halftone images is improved. The objective is to obtain excellent high-quality and high-definition images.

[0006]

In order to solve the problems of the present invention, the following constitutions are achieved.

(1) Using a two-component developer in which a magnetic carrier having a weight average particle diameter of 20 to 100 μm and a non-magnetic toner having a volume average particle diameter of 5 to 10 μm are mixed and facing each other with respect to an electrostatic image carrier. A developer carrier that moves and supports the developer and conveys the developer to a developing position, and a plurality of magnetic poles that are fixed inside the developer carrier and that form an alternating electric field at the developing position. In the developing device, the magnetic flux density of the developing magnetic pole provided inside the developer carrying member is set to 800 to 1200 Gauss, and the inclination angle of the developing magnetic pole is the center of the electrostatic image carrier and the developer carrying member. The weight average particle diameter of the magnetic carrier is D (μm), and the peripheral speed ratio (A) between the electrostatic image carrier and the developer carrier is set at 2 to 15 ° with respect to the line connecting the points. Use a developing device that satisfies the following "Formula 2" when defined as shown in "Formula 1" below. An image forming method characterized by the following.

[0008]

[Equation 2]

(2) The image described in (1), characterized in that the rotational movement directions of the electrostatic charge image bearing member and the developer bearing member are the same direction (so-called swiveling rotation) at the closest portions of both. Forming method.

According to the present invention, the magnetic flux density of the developing magnetic pole is set to 800 in the two-component development using the fine particle carrier and the toner.
˜1200 gauss, the inclination angle of the developing magnetic pole is 2 to 15 ° with respect to the line connecting the central points of the electrostatic image carrier and the developer carrier, and the magnetic carrier When the weight average particle size of D is set to D (μm) and the peripheral speed ratio (A) between the electrostatic image carrier and the developer carrier is determined as in the above “formula 1”, the “formula 2” is satisfied. By using an image forming method that is characterized by using a developing device, carrier adhesion to the electrostatic image carrier is suppressed, and there is no image roughness or toner scattering, and high image quality with excellent reproducibility of halftone images. A high definition image can be obtained.

Further, at this time, the rotational movement directions of the electrostatic charge image bearing member and the developer bearing member are the same in the closest portions of both, so that a high-definition image having smooth gradation can be obtained. It is more desirable because it can be done.

[0012]

[Action]

a) Developing device The developing device develops a latent image formed on the electrostatic image carrier 1 such as a photoconductor or a dielectric by electrophotography, electrostatic recording, or the like. The developing device 2, a developing sleeve 3 as a developer carrying member, a blade 4 as a developer spike height controlling member, and the like are included. That is, an opening is formed at a position of the developing device 2 close to the electrostatic image carrier 1, the developing sleeve 3 is rotatably installed in the opening, and the developing sleeve 3 is provided above the developing sleeve 3. The blade 4 is attached with a predetermined gap.

The sleeve 3 is made of a non-magnetic material, rotates in the direction of the arrow in the drawing for the development operation, and has a magnet 13 as a magnetic field generating means fixed therein. A magnetic field is formed at a developing position where the developer is applied to the charge image carrier 1 from the sleeve 3, and a magnetic brush is formed at this position.

The developing roller 31 comprises the developing sleeve 3 and a magnet 13 having a developing magnetic pole S ₁ and magnetic poles N ₁ , N ₂ , S ₂ and N ₃ for carrying a developer 8 which will be described later. ing.

The full width at half maximum of the magnetic flux density of the developing magnetic pole S ₁ is preferably within 40 °, more preferably within 35 °. When the full width at half maximum of the magnetic flux density of the developing magnetic pole is within 40 °, the image becomes clear and fine line reproducibility becomes good.

Reference numeral L is a one-dot chain line connecting the center of the developing sleeve 3 and the center of the electrostatic charge image carrier 1, and indicates the center of opposition between the developing sleeve 3 and the electrostatic charge image carrier 1, and the development is performed at this portion. The sleeve 3 and the electrostatic image carrier 1 are in the closest position, and are also the central positions of the developing area (developing position).

Θ is the angle between the developing magnetic pole and the alternate long and short dash line L with respect to the center of the developing sleeve 3, and represents the inclination angle of the developing magnetic pole. Incidentally, the case where the developing magnetic pole is upstream of the one-dot chain line L with respect to the moving direction of the developing sleeve is +, and the case where it is downstream is −.

Θ is in the range of +2 to + 15 ° or −2 to −
It is preferably in the range of 15 °. By setting θ in this range, it is possible to prevent carrier adhesion.
If θ is set outside this range, carrier adhesion will occur.

The blade 4 is made of aluminum (Al, SUS3
16) or the like, which is made of a non-magnetic material and is attached with a predetermined gap between the surface of the developing sleeve 3 and the developer 8 on the developing sleeve 3 by this gap.
Regulate the thickness of.

The measurement of the magnetic flux density in the vertical direction on the sleeve 3 was carried out by using a Gauss meter model 640 manufactured by Bell Company. That is, the axial probe connected to the Gauss meter is fixed so that the center of the sleeve 3 and the center of the probe are flush with each other while keeping a slight distance from the sleeve 3, and the magnet roller 13 is rotated to fix the axial probe on the sleeve 3. The magnetic flux density in the vertical direction can be measured in all circumferential directions.

FIG. 2 is a diagram for explaining a method of measuring the magnetic flux density Bγ in the vertical direction on the sleeve 3, which was measured using a Gauss meter model 640 manufactured by Bell Company. In the figure, the sleeve 3 is fixed horizontally, and the magnet roller 13 in the sleeve 3 is rotatably attached.

Reference numeral 17 denotes an axial probe, which is fixed so that the center of the sleeve 3 and the center of the probe 17 are substantially in the same horizontal plane while maintaining a slight distance from the sleeve 3, and is connected to the Gauss meter 16. Sleeve 3 and magnet roller 13 for measuring the magnetic flux density in the vertical direction on 3
Are substantially concentric circles, and it may be considered that the distance between the sleeve 3 and the magnet roller 13 is equal everywhere.

The magnetic velocity density (Bγ) of the developing magnetic pole is 800 to 120.
It is preferably in the range of 0 gauss. If Bγ is less than 800 gauss, the carrier cannot be sufficiently held on the developer carrying member and the carrier scatters, resulting in carrier adhesion. On the other hand, when Bγ is larger than 1200 gauss, the spike hardness of the developer becomes too large, and as a result, the rubbing force of the electrostatic image bearing member increases, and only a rough image can be obtained.

The alternating electric field means when an alternating voltage having the same polarity as the electrostatic latent image and between the highest potential and the lowest potential of the electrostatic latent image is applied between the developing sleeve and the electrostatic image carrier. It refers to the alternating electric field formed in. Furthermore, a DC voltage may be applied together with an AC voltage. By the way, the inside of the developing device 2 is divided into a developing chamber (first chamber) S-1 and a stirring chamber (second chamber) S-2 by a partition wall 5 extending in the direction perpendicular to the paper surface of FIG. A toner storage chamber S-3 is formed above S-2 with a partition wall 6 therebetween, and a replenishment toner (non-magnetic toner) 81 is stored in the toner storage chamber S-3. A supply port 6a is opened in the partition wall 6, and the supply port 6a
The replenishment toner 81 in an amount commensurate with the amount of toner consumed through a is dropped and replenished into the stirring chamber S-2. Further, the developer 8 is contained in the developing chamber S-1 and the stirring chamber S-2.

Then, in the developing chamber S-1, it is located in the bottom of the developing device 2 near the developing sleeve 3 and rotates in the direction of the arrow (counterclockwise) to rotate the developer 8 from the back side of FIG. The first transporting means 9 that is transported to the side, and the developer 8 that is above the first transporting means 9 and rotates in the direction of the arrow (counterclockwise direction) to transport the developer 8 from the front side to the back side in FIG. A second transport means 10 is provided. Further, the developer 8 is conveyed in the stirring chamber S-2 in the substantially horizontal position as in the first conveyance means 9 and in the direction of the arrow (clockwise direction) in the figure, and conveys the developer 8 from the front side to the back side in FIG. The third transport means 11 is provided. The first, second, and third conveying means 9, 10, and 11 described above are specifically configured by spiral-shaped screws.

B) Electrostatic Charge Image Bearing Member The electrostatic charge image bearing member is not particularly limited, and is an inorganic photosensitive member such as a selenium photosensitive member or an amorphous silicon photosensitive member, an organic photosensitive member usually called OPC, and other members. A dielectric or the like can be used. As the shape of the electrostatic charge image bearing member, a drum shape can be used for the inorganic photoreceptor and a drum shape or a sheet shape for the organic photoreceptor. A drum having a diameter of 10 to 200 mm is usually used.

C) Developer The developer 8 is a two-component developer composed of a non-magnetic toner 81 and a magnetic carrier 82.

The non-magnetic toner 81 has a volume average particle diameter of 5-10.
Use the μm one. The volume average particle size is 100 μm
Coulter Counter TA-II type (manufactured by Coulter Co.) was used.

On the other hand, 82 is a magnetic carrier having a weight average particle diameter of 20 to 100 μm, preferably 30 to 80 μm, and a resistance value of 10 ⁷ to
In the range of 10 ¹⁵ Ωcm, preferably in the range of 10 ⁸ ~ 10 ¹⁴ Ωcm, specifically, ferrite particles, styrene resin or acrylic resin and their copolymers (styrene-
An acrylic resin, a fluororesin, a silicone resin, or other resin coated is used.

The weight average particle diameter of the magnetic carrier is measured by the mesh method, which corresponds to the weight-based median diameter (D50).

The resistance value of the magnetic carrier was measured by using a sandwich type cell having a measuring electrode area of 4 cm ² and a gap between the electrodes of 0.4 cm, and a voltage of 1 kg was applied to one electrode while applying a voltage between both electrodes. E (V / cm) was applied and the resistance value of the magnetic carrier was determined from the current flowing in the circuit.

Further, as the resin of the toner conventionally used for this kind of application, specifically, styrene-acrylic resin, styrene-butadiene resin, ester resin,
Examples thereof include epoxy resins, and the colorant is not particularly limited, and carbon black, pigments and dyes used in this type can be used. Further, a charge control agent, wax or the like may be added if necessary. Inorganic oxide as an external additive, for example, silica, titania, alumina,
Etc. are preferably added after being hydrophobized.
Alternatively, organic fine particles may be added. The volume average particle diameter of the toner is preferably in the range of 3 to 20 μm, more preferably 5 to 10 μm from the viewpoint of image quality.

D) Regarding the relational expression (Equation 2) between the carrier weight average particle diameter (D) and the peripheral speed ratio (A): The peripheral speed ratio A of the electrostatic charge image carrier and the developer carrier is the weight average particle of the carrier. When the diameter is D (μm), (2D + 540)
It is preferably / 5 or more and (2D + 1340) / 5 or less. When the peripheral speed ratio A is smaller than (2D + 540) / 5, the non-magnetic toner is not sufficiently supplied to the developing nip portion, so that a solid image becomes rough and a stable and good image cannot be obtained. In addition, the peripheral speed ratio A is (2D + 1340)
When it is larger than / 5, toner scattering occurs, and similarly stable and good images cannot be obtained.

E) Flow of developer in the developing device This developer 8 is conveyed to the developing section, and is conveyed to the conveying magnetic pole N ₁ while being held by the developing sleeve 3.

Reference numeral 12 is a panning member for preventing the scattering of the developer and the pulling back to the upstream side, one end of which is fixed to the free end and the other end of which is fixed to the developing container 2. Is in contact with the developer at the transport magnetic pole N ₁ or upstream thereof.

The panning member 12 prevents the developer 8 carried to the carrying magnetic pole N ₁ while being held by the developing sleeve 3 from scattering when the developer 8 stands on the carrying magnetic pole N ₁ , and the developing magnetic pole S 1. ₁
Prevents pullback in the direction.

The carrier magnetic pole N ₁ and the magnetic pole N ₂ have the same pole, and a repulsive magnetic field is generated between them. Therefore, the developing sleeve 3
Then, the developer is newly supplied in the vicinity of the magnetic pole N ₂ after being agitated and mixed by the first transporting means 9 described later.

That is, the developer that has undergone the development history on the developing sleeve 3 is peeled and removed, and a sufficiently mixed new developer is constantly supplied to the developing sleeve 3, so that a stable and good image can be obtained. To be

[0039]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1 The outer diameter of the photosensitive drum 1 as an electrostatic charge image carrier is 80 mm, the outer diameter of the developing sleeve 3 as a developer carrier is 32 mm, and the half width is 35 ° inside the sleeve. The developing magnetic pole and the four magnetic poles for conveying the developer are provided, and the distance between the photosensitive drum 1 and the developing sleeve 3 is 800 μm, and the distance between the developing sleeve 3 and the spike control blade made of an aluminum material is 50.
0 μm, the peripheral speed of the photosensitive drum is 160 mm / sec,
The charging potential of the photosensitive drum is -650V, the exposure potential is -200V, and alternating voltage (frequency 2kHz, peak-to-peak voltage 2kV AC voltage, DC voltage -350 is applied to the developing sleeve 3.
Was used to form an alternating electric field at the developing position by vibrating the developer to develop the latent image. The developer is a carrier coated with styrene-acrylic resin, and the resistance value is 2 × 10 ⁹ Ω · cm (carrier A) and 1 × 10 ¹⁰ Ω · by changing the coating film thickness of the resin. cm (Carrier B), 4 × 10 ¹³ Ω ・
The magnetic carrier which is cm (carrier C) and the volume average particle size are
The magnetic flux density (Bγ) of the developing magnetic pole, the angle θ between the developing magnetic pole and the alternate long and short dash line L, and the weight average particle diameter D ( [mu] m) and the peripheral speed ratio A (%) were variously changed, and real-life evaluation was performed to evaluate carrier adhesion, toner scattering, and solid image roughness.

Since the difference in performance among the carriers A, B, and C was small, this example mainly shows the results using the carrier B, but only the representative results using the carriers A and C. Also showed.

That is, Experiment Nos. A-1 to A-1 in the present invention
Up to 8, carrier B is used, A-19 is the carrier of A-1 replaced by carrier A, and A-20 is the carrier of A-1 is replaced by carrier C. On the other hand, Experiment Nos. B-1 to B-9 outside the present invention are also the results of using the carrier B. In B-10, the carrier of B-5 is used as the carrier A,
Further, B-11 is the result of an experiment conducted by replacing the carrier of B-5 with the carrier C.

The evaluation method of carrier adhesion and toner scattering was carried out by visually observing on the copy and inside the copying machine. The symbol ◯ is good with no toner scattering or carrier adhesion, and the symbol X is visible with toner scattering or carrier adhesion. Indicates the failure confirmed in. Moreover, the evaluation method of the roughness of the solid image was evaluated by measuring the variation of the transmission density using a Sakuradensitometer (manufactured by Konica Corporation). When the variation of the transmission density is 0.30 or less, the symbol ◯ is shown, and when it is larger than 0.30, the symbol x is shown.

The results are shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1, Experiment No. A-1
In the cases of A-18, A-19, and A-20, good images were obtained without carrier adhesion, toner scattering, and solid image roughness.

On the other hand, in Experiment Nos. B-1 and B-3, since the peripheral speed ratio A was smaller than (2D + 540) / 5, only a rough image was obtained.

On the other hand, in Experiment Nos. B-2 and B-4, since the peripheral speed ratio A was larger than (2D + 1340) / 5, toner scattering occurred.

Further, in Experiment No. B-5, since the magnetic flux density Bγ of the developing magnetic pole is larger than 1200 gauss, the spike hardness of the developer becomes large, and as a result, the electrostatic charge image carrier is rubbed. The force was increased, and only a rough image was obtained.

On the other hand, in No. B-6, since the magnetic flux density Bγ of the developing magnetic pole is smaller than 800 gauss, the carrier cannot be sufficiently held on the developer carrying member and the carrier scatters. As a result, carrier adhesion occurred.

Further, in Experiment Nos. B-7 and B-9, since the inclination angle θ of the developing magnetic pole was larger than ± 15 °, carrier adhesion occurred.

In Experiment No. B-8, since the inclination angle θ of the developing magnetic pole was smaller than ± 2 °, carrier adhesion occurred.

From these results, it can be seen from B-9 and B-10 that the tendency does not change even if the carrier B is changed to A or C.

[0054]

According to the present invention, in a developing device using a two-component developer in which both the toner and the carrier are reduced in diameter, carrier adhesion, image rubbing and toner scattering are prevented, and reproducibility of fine lines and halftone images is prevented. It is possible to obtain excellent high quality and high definition images.

[Brief description of drawings]

FIG. 1 is a sectional view of a developing device of the present invention.

FIG. 2 is a diagram for explaining a method of measuring magnetic flux density.

[Explanation of symbols]

 1 electrostatic image carrier 2 developing device 3 developing sleeve 13 magnet 31 developing roller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G03G 9/08 9/10 15/09 A (72) Inventor Hiroyuki Kozuru 2970 Ishikawa-cho, Hachioji-shi, Tokyo Address Konica Stock Company

Claims (2)

[Claims] 1. A two-component developer having a magnetic carrier having a weight average particle diameter of 20 to 100 μm and a non-magnetic toner having a volume average particle diameter of 5 to 10 μm is used, and is relatively moved facing an electrostatic image carrier. A developer carrier that supports the developer and conveys the developer to a developing position; and a plurality of magnetic poles that are fixed inside the developer carrier and that form an alternating electric field at the developing position. In the image forming method using the apparatus, the magnetic flux density of the developing magnetic pole provided inside the developer carrying member is set to 800 to 1
Further, the developing magnetic pole has an inclination angle of 2 to 15 ° with respect to a line connecting the center points of the electrostatic charge image carrier and the developer carrier, and the weight average particle diameter of the magnetic carrier is When D (μm) is set and the peripheral speed ratio (A) between the electrostatic image carrier and the developer carrier is determined by the following equation 1, a developing device satisfying the following equation 2 is used. Forming method. [Equation 1] 2. The image forming method according to claim 1, wherein the rotational movement directions of the electrostatic charge image bearing member and the developer bearing member are the same in the closest portions of both.