JPS58149061A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To provide a developer causing no edge effect even after making a large number of copies in color copying using a toner having chromatic colors, by using a carrier having low reflectance in a near IF region and a specified current value. CONSTITUTION:Density of a developer is detected with a reflection density detector 5 as reflection density when a light receiving element, such as a photodiode, receives the reflected light of a near IF region emitted from a lamp 6. A current value of a carrier is obtd. by placing 1kg carrier 34 on a magnetic drum 33 rotated in 50-100rpm and measuring it. A carrier having 115-145muA, a flat shape, and, preferably, <=25% reflectance in 700-800nm region is widely different in reflectance from chromatic colors, and much larger in friction between each particle of the carrier as compared with ordinary spherical carrier particles, because its particles are smooth on the surfaces and flat shapes. As a result, when the developer using this carrier is employed, always stable developing density can be retained, and image quality superior in gradation, small in edge effect, and good in reproducibility of solid parts can be retained even after making a large number of copies.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic developer, and more specifically, the present invention relates to a developer for electrophotography, and more specifically, the developer disclosed in Japanese Patent No. 2297691, which is useful when developing with a magnetic brush development method.
As described in Japanese Patent Publication No. 42-23910, Special Publication No. 43-24748, etc., electrostatic charge is uniformly applied to the photoconductive layer by corona discharge, and a light image spread on the original is exposed to this. By doing so, the charge on the exposed portion is extinguished and latent scratches are formed. The electrostatic latent image thus obtained is developed by allowing a finely powdered electrostatic substance and, in some cases, toner to adhere thereto. The toner is colored by the electrostatic latent scratches depending on the amount of charge on the photoconductive layer, forming a toner image with shading. This toner image is transferred to a supporting surface such as paper or cloth as required, and permanently fixed to the supporting surface using a suitable fixing means such as heating, pressure, solvent treatment, or overcoating. This toner image can also be fixed onto the photoconductive layer if it is still desired to omit the toner self-transfer step.

In the development of electrostatic latent scratches, the toner is mixed with carrier having relatively large particles and used as an electrophotographic developer. The compositions of both the toner and the carrier are chosen such that, due to their mutual contact friction, the toner assumes a polarity opposite to the charge on the photoconductive layer. Also, as a result of contact friction between the two,
The carrier electrostatically adheres the toner to the surface, transports the toner as a developer through the developing device, and supplies the toner onto the photoconductive layer.5 Many methods of developing the developer are known. Particularly typical developing methods include the cascade development method described in U.S. Pat. No. 2,618,552, the magnetic puxi method described in U.S. Pat. No. 2,874,063, the touchdown method described in U.S. Pat. No. 2,895,847, and other fur brush development methods. as,
The cascade method and the magnetic brush method are known. In the cascade method, non-magnetic particles such as glass peas are used, and fine powder toner is attached to the surface to form a developer. When this developer cascades over the surface of the photoconductive layer carrying the electrostatic latent image, the toner selectively adheres only to the charged portions of the electrostatic latent image and does not adhere to the uncharged portions, thereby performing development.

Further, the magnetic brush method uses magnetic particles such as steel and ferrite as carriers. A developer consisting of toner and magnetic carrier is held by a magnet, and the magnetic field of the magnet arranges the developer in a brush shape. When this magnetic brush comes into contact with the electrostatic latent image surface on the photoconductive layer, only the toner is attracted from the brush to the electrostatic latent image for development.)
It is something.

Touchdown development is a method in which the developing agent 'klFm is conveyed by a support 1-- such as a web or sheet to a support surface and developed according to the electrostatic latent image.

In conventional technology, if a two-component developer is used to continuously copy a large number of sheets using an electronic copying device, good images with clear and good image quality can be obtained initially, but after tens of thousands of sheets have been copied, Capri's A two-component developer with sufficient durability has not yet been obtained, resulting in images with significant edge effects and poor gradation and clarity.

Especially in color copying using chromatic toner, continuous gradation is a factor that does not greatly affect image quality.
In the conventional technology, after a large number of images are continuously copied, an edge effect appears in the image, resulting in a poor image with no gradation and only the peripheral area of the image being emphasized.

Currently, in order to improve durability in continuous copying of a large number of sheets, studies are being carried out particularly on carriers, and many reports have been made. For example, it has been proposed that the surface of a substance used as a carrier is coated and used as a carrier. However, even such carriers do not satisfy all required characteristics such as triboelectric properties and mechanical properties, and coated carriers generally have many flat areas because edge effects tend to appear in images. , it cannot be used as a color developer where gradation is important.An object of the present invention is to provide a developer that has durability in copying a large number of sheets. An object of the present invention is to provide a developer that does not cause edge effects after copying a large number of sheets in color copying using a toner having the following properties.

Another object is to provide a developer that can maintain stable developer concentration at all times when using an optical density sensing type developer concentration control device. - The percentage value is based on an electrophotographic developer containing a carrier that has a low reflectance in the near-infrared region and a current value of 115 to 145 μA.

To measure the carrier current value in the present invention, an apparatus as shown in FIG. 8 is used. That is, the test carrier 34 is placed on a magnetic drum 33 which has a magnetic pole width inside 1 and is wrapped with a non-magnetic sleeve 32, and is rotated at a rotational speed of 50 to 1100 rpm.

At this time, the gap with the stator 35 is about 2.0 to 5.0.

In the figure, E is a 200V DC power supply, ■ is a minute voltage at, and R is a standard resistance, and a resistance at 1 is used. This type of device is used to measure the current value of iron powder while the magnetic drum is rotating.

Electricity 11 is the formula below You can find it from ■.

Further, the spectral reflectance measurement of the carrier and toner applied to the present invention was carried out using a digital double beam self-six-spectrophotometer needle (trade name: UVIDEC-505, manufactured by JASCO Corporation).

FIG. 1 is an explanatory diagram of a developing device to which an optical density sensing type developer concentration control device is applied. In the same figure, a developing device 1 uses a magnetic brush method to apply paper developer onto a photoreceptor drum 4 using a fixed magnet 2 and a sleeve 3 rotating around the fixed magnet 2, so that an electrostatic latent image on the photoreceptor is formed. I am visualized. In the current gII agent T, for example, the carrier is iron powder, and the toner is mainly composed of 4, which is obtained by mixing a resin with a coloring agent and pulverizing the mixture to about loμ. The developer concentration is determined by the reflection density detector 5.
Accordingly, the reflected light from the rung 6 is detected as the reflection density received by the light receiving element 7 such as a photodiode.

To explain in more detail, the reflection density detector 5 is equipped with a developer reference density plate, and the detection control circuit 8 detects the difference between the reflection density currently obtained and the reflection density obtained from the reference density plate. The signal is then converted into a predetermined control signal to drive the replenishment motor 9. Further, the motor 9 rotates the robot gear and drives the conveyance screw 'L11 provided at the lower part of the toner hopper 12, thereby replenishing a predetermined amount of replenishment developer T1 into the current dispensing device. When the light receiving element 7 receives the reflected light from the lamp 6, the developer 2o contact surface "3ti"
In terms of stray light, it is sometimes important to use a near-infrared filter that transmits light with wavelengths longer than 700 nm. The reflectance of the carrier must be significantly different from that of the toner, and the reflectance of the carrier must be sufficiently lower than that of the toner.This is because the difference in spectral reflectance between the carrier and toner in the near-infrared region is If it is small, a phenomenon occurs in which the reflected density of the received light hardly changes even if the toner concentration in the developer decreases.Even if the amount of toner in the developer substantially decreases and scratches and unevenness occur, , the detected reflection density cannot distinguish between the spectral reflectance of carrier and toner, and is always judged to be within the standard value. 7oo~800n
cyan toner has a large spectral reflectance in the vicinity of m, but cyan toner has a low spectral reflectance in that region, so when using an optical density detection type density control device, care must be taken when selecting a carrier. A carrier that meets the needs and has as low a reflectance as possible must be chosen.

An object of the present invention is to provide a developer characterized by using a density control device as described above and using a carrier that can maintain stable developer-vertical orientation, especially when a large number of copies are made using chromatic toner. .

The object of the present invention is to have a current value of 115 to 145 μA, a flat shape, and a reflectance of preferably 25 inches or less in the near-infrared region of 700 to 800 nm. This can be achieved using an electrophotographic developer characterized by the use of a carrier.

The carrier used in the present invention, which has a flat shape and has a current value of 115 to 145 μA, can obtain a high current value that could not be achieved with conventional spherical, nodular, or coated carriers. This is probably because the carrier surface is smooth and flat, so the contact between the carriers is much larger than in spherical carriers, which makes it easier for current to flow, resulting in a high current value. As a result, when using this developer, the image quality was as follows.
It has excellent gradation, little edge effect, and good reproducibility in the flat area, and its performance is maintained even after copying a large number of sheets.

The carrier used in the present invention is flat and has a current value of u5~1
45 μA (more preferably 12 to 130 μA) and a particle size of 70 μ or less (more preferably 60 μ or less, particularly preferably 50 μ to 20 μ) can be used. Further, the reflectance in the near-infrared region of 700 to 800 nm is preferably 25 inches or less (more preferably 20% or less).

The material of the carrier used in the present invention is, for example, iron, 61
All known ferromagnetic materials can be used, including metals such as 4, r-ferrite, Ba-ferrite, Sr-ferrite, and other ferromagnetic compounds.

All known toners can be used in the invention, but examples of the binder resin for the toner include monomers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene. Coalescence: Styrene-P-chlorostyrene copolymer, styrene-globylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Polymer, styrene-butyl acrylate copolymer, styrene-
Octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether co-polymer, Copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, 1'! ″0x-y-vy;
i'#**#;
Polyamide, polyacrylic W1411 M&, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. can be used alone or in combination.

Colorants used in toner include carbon black, nigrosine dye, lamp black, Sudan black SM,
First-kai Yellow G, Penjijishi Yellow, Pigment Yellow, India First Orange, Irgazine Red, Balanitroaniline Red, Toluidine
Red, Carmine FB1 Permanent) - Bordeaux FRR
, to:'Gmento Orange R1 Resole Rez)'
2 G, Rake Φ Red C, Rhodamine FB.

rhodamine B lake, methyl violet) B lake,
Phthalocyanine blue, pigment blue, brilliant green B1 phthalocyanine, oil yellow GG, fbon first yellow CGG,
Kayaset Y 963, Kayaset YG1 Sumiplast Niro G G-Zapon Fast Orange RR, Oil Scarlet, Sumigerast Orange G, Orazole Brown B1 Pomelo Fast Scarlet CG1
Aizensbiron @Red BEH, Oil Pink OP
1. All known dyes and dyes such as Victoria Blue F 4 R, First Ken Blue 5007, Sudan Blue, and Oil Peacock Blue can be used.

The invention will now be described in more detail by way of an illustrative example.

[Example 1] It has a flat shape and has a current value of 130 μA (at), 750
An iron powder carrier having a spectral reflectance of 8 at nrrr-800 nm and a magenta toner were mixed to prepare a developer. The particle size of the carrier at this time is 60 μm or less.

When this agent was continuously copied using an NP-color copying machine (manufactured by Canon), the image quality with excellent gradation and little edge effect, which was the same as the initial image quality, was maintained for 10,000 copies.

Furthermore, as shown in Figure 2, the developer density change at that time showed stable movement with an error of 1%.[Example 2] It had a flat shape, a current value of 117 μA, and a particle size distribution of 250 μ to 15 μ. An iron powder carrier having a spectral reflectance of 13% or less in the range of 700 nm to 780 nm and a yellow toner were mixed to prepare a developer. When this was subjected to a durability test in the same manner as in Example 1, it showed a stable change in the developer concentration as shown in Figure 3, and the image quality after 6,000 sheets was excellent with good gradation. there were.

[Example 3] The current value was 135μA, the particle size was 60μ or less, and the
20 nm to 800 nrn, an iron powder carrier with a light reflectance of 25% is mixed with magenta toner and used as a developer.
When a large number of copies were made using a P-color copying machine, 9,000 copies with excellent gradation and sharp edges were produced. Further, the developer concentration change at that time was stable, as shown in FIG. 4, within the tolerance of 1 difference ±1.5 well.

[Example 4] The same carrier as in Example 1 was used and mixed with cyan toner to prepare a developer. A large number of 10,000 copies of this were made using an NP-color copying machine, but the same good image quality as the initial one was maintained.

The developer concentration was kept stable as shown in FIG.

It has a flat shape, has a current value of 120uIL, and has a current value of 750uIL.
When a durability test was carried out on an NP-color copying machine using a combination of iron powder carrier and cyan toner with a spectral reflectance of 3 sand on the surface, the developer concentration was extremely unstable as shown in Figure 6. Ta.

Figure 6 is also a graph showing the results of adjusting the density each time the developer concentration showed an abnormal value during the durability test. However, with 500 sheets, the density decreased but the image was good with little edge effect.

[Special Soft 1112] Spherical, current value 100mm, Tol, 70G-800n
When a large number of copies were made in the same manner as in Example 1 using a combination of a carrier with an mO spectral reflectance of 5- and a magenta toner, 500 Oij images were color copies with remarkable continuous gradation with edge effects. It was a poor image. The 3jL co-drug level remained stable as shown in Figure 7.

[Brief explanation of the drawing]

Figure 1s1 is a diagram of a nine developing device O1g to which an optical III degree detection type developer concentration control device is applied. JII2~$1711 is the toner chain g for the number of durable sheets.
Graph showing changes. The jIB diagram shows 1! of the device that measures the carrier otm value. Ming diagram. 1...IA imager 5...Reflection am detector 34.
...ΦYaria T...Developer T1...Replenishment fA agent applicant Canon Co., Ltd. Taikyu is listed in the number of pages Fuku & Eifunan Saiga Kai

Claims (1)

[Claims] Low reflectance in near-infrared region, current value 115-14
An electrophotographic developer containing a carrier of 511A.