JP2579206B2 - Light detection automatic toner density control method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying apparatus and an image forming apparatus such as an electrostatic recording apparatus used for various applications, and more particularly to a method of mixing a toner and a carrier. Automatic toner density control method (hereinafter referred to as ATR) for maintaining a constant toner / carrier mixing ratio in a developing device that develops a latent image formed on a latent image holding member by carrying a developer formed by a developer carrying member. Things.

[Related Art] In a developing device using a two-component developer composed of a toner and a carrier, the mixing ratio of the toner and the carrier is a very important factor from the viewpoint of the developing effect. That is, when the toner density is lower than the appropriate level, the image density is lowered, and when the toner density is higher than the appropriate level, the toner cannot be charged sufficiently and fogging occurs. Therefore, in order to obtain a good image, it is necessary to accurately detect the density of the developer and control the toner density to an appropriate value.

Various proposals have been made regarding ATR,
In particular, means for detecting the color of the developer and controlling the toner replenishment amount proposed in Japanese Patent Publication No. 38-17245 is affected by environmental changes and changes in physical properties such as the bulk density of the developer due to durability. It is difficult and stable detection means. Above light detection ATR
The toner density detector shown in FIG. 1 is generally known. A lamp (light source) 3 for irradiating the developer in the transfer path 1 with light from a sensor window 2 made of a transparent material provided at a predetermined position of a developer transfer path 1 including a toner and a carrier; It comprises a first sensor 4 for receiving light reflected by the developer and a second sensor 5 for directly receiving light from the lamp 3.

Then, the toner concentration detecting device includes a first sensor 5
Detects the toner density from the difference between the voltage directly received from the lamp 3 and the output voltage. In this light detection ATR, it is preferable to use a material having the same polarity as the toner for the material of the sensor window in order to prevent the toner from adhering to the sensor window where the toner concentration detecting device and the developer come into contact.

However, it is difficult to obtain a sensor window that satisfies the above conditions and also satisfies the conditions such as transparency, strength, and workability required for the sensor window material.

Further, an additive having the same polarity as the toner may be added to the toner for the purpose of imparting charge and fluidity to the toner. In the case of rubbing, the toner adheres to the sensor window because the window material is charged to the polarity opposite to that of the additive, that is, the polarity opposite to that of the toner. For this reason, the ATR malfunctions and the toner density of the developer cannot be controlled to an appropriate value. As a result, disadvantages such as a decrease in image density or occurrence of fogging occur.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned drawbacks and to provide a developing device capable of accurately detecting the developer concentration.

[Means and Actions for Solving the Problems] As a result of earnest research, the present inventor has found that a developing device equipped with a photodetecting ATR can be used to convert a detection sensor window material into a toner and a carrier containing an additive that charges the toner to the opposite polarity to the toner. By supplying particles that charge the window material to the same polarity as the toner in the vicinity of the window in advance in an image forming apparatus using a developer, it is possible to prevent toner from adhering to the sensor window and prevent malfunction of the ATR. I found it. Hereinafter, the present invention will be described in detail.

FIG. 2 is a schematic longitudinal sectional view of the developing device, and FIG. 3 is a schematic sectional view of the developing device shown in FIG.

In FIG. 1, reference numeral 10 denotes a developing container, which is divided into a toner storing section 11 for storing toner and a developer storing section 12 for storing a developer composed of toner and carrier. The toner in the toner storage section 11 is supplied to the developer storage section 12 from the toner supply port 14 by the rotation of the toner transport member 13. The toner in the developer accommodating section 12 develops a latent image formed on a photoconductor (not shown) by a developing sleeve 15, and the developing sleeve 15 includes a magnet roller 15 having both ends fixedly supported, It comprises a non-magnetic sleeve 15 that rotates around the periphery at a predetermined peripheral speed in the direction of the arrow.

In the figure, reference numeral 16 denotes a transport pipe installed in the developing container 10 and a screw for transporting the developer in the direction of the arrow therein.
17 are provided. Reference numeral 16 'denotes a transport tube extending from the lower right end of the developing container 10 (FIG. 1) to the right end of the transport tube 16, and a screw 17' for transporting the developer in the direction of the arrow is provided therein. The developer transported by the screw 17 ′ moves from the opening 18 to the transport pipe 16. At the lower part of the developing container 10 ', there is provided a screw 17' for transporting the new toner, the toner recovered from the surface of the sleeve 15 and the carrier to the transport tube 16 'while mixing them uniformly.

A toner concentration detecting device 19 is provided on the transfer tube 16 '. The toner concentration detecting device 19 is connected to the transfer tube 16 through the window 2 attached to the transfer tube 16' as shown in FIGS.
A lamp 3 for irradiating the developer inside 6 'with light, a first sensor 4 for receiving light reflected by the developer, and a lamp 3
And the second sensor 5 that directly receives the light of the second direction.

The first and second sensors 4 and 5 output a voltage corresponding to the intensity of the received light. The first and second sensors 4 and 5 are composed of, for example, photodiodes and the like. The voltage Vb output and received by the developer 4 reflected light from the developer and the voltage Vc output by the second sensor 5 directly receiving light from the lamp 3 are adjusted in advance so that Vb = Vc. .

Next, the operation of the toner concentration detecting device will be described. When the developer conveyed in the conveying pipe 16 'by the screw 17' is higher than a predetermined toner concentration, the sensors 4, 5
Is Vb> Vc, the toner concentration detecting device 19 turns off the toner supply at this time, and when the toner concentration is lower than a predetermined toner concentration, the output voltage becomes Vb <Vc. At this time, the toner concentration detecting device 19 Turn on. By repeating these operations, the toner concentration of the developer is kept constant.

Note that the present invention is not limited to the developing device configuration and the toner concentration detecting device, but generally includes a light detection ATR using a principle of measuring reflected light of the developer through a transparent window material in contact with the developer. Applicable to all developing devices.

When the above-described toner concentration detection method is used, it is preferable to use a material having the same polarity as the toner as the material of the sensor window to electrically prevent toner adhesion. In the case of a positively charged toner system, the window material is polycarbonate, ABS resin, acrylic resin,
Nylon or the like is used. On the other hand, in the case of a negatively charged toner system, a polyfluoroethylene resin, quartz glass, or the like is used.

However, if the developer contains an external additive that has the same polarity as the toner and is more chargeable than the window material, the window material is charged to the opposite polarity to the toner, and the toner is electrically attached to the window and the ATR Will cause malfunctions. At this time, by incorporating particles having higher chargeability than the external additive into the developer, the particles rub against the window material, and the window material can be charged to the same polarity as the toner, and the toner adhesion can be reduced. Can be prevented.

In the case of a positively charged toner system, the particles used in the present invention are preferably polyvinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, or the like. In the case of a negatively charged toner system, positively chargeable resin particles such as a styrene-dimethylaminoethyl methacrylate copolymer are preferred.

The particle size of the above particles is determined using a COULTER counter
2.0μm or more measured by ELECTRONICS INC Model TA-II)
It is preferably 8.0 μm or less. If it is larger than 8.0 μm, the fluidity of the developer is affected, which is not preferable.
On the other hand, if it is smaller than 2.0 μm, the particles easily adhere to the toner and are developed as they are, so that the amount of the particles is reduced and the effect is not maintained. The added amount of the particles is 0.1% by weight or more and 0.5% or more of the starting agent obtained by mixing the carrier and the toner at a predetermined ratio.
% By weight or less is preferred. If the amount is less than 0.1% by weight, no effect can be obtained. If the amount is more than 0.5% by weight, the fluidity of the developer is adversely affected, and the reversal fog is increased.

As a method of supplying the particles, there is a method of applying the particles to the sensor window in advance, but more preferably, a method of forming a toner and a carrier into a starting agent using a mixer or the like and then sprinkling the starting agent.

When externally added to the toner used as the starter in advance, the particles strongly adhere to the toner, and thus are consumed together with the toner and the effect is not maintained. In addition, when the toner is externally added to the replenishing toner, it is not preferable to externally add a sufficient amount to obtain the effects of the present invention, since the fluidity of the toner deteriorates. On the other hand, when externally added to the carrier in advance, the effect is not obtained because the carrier is covered with the toner and the particles cannot contact the window.

The present invention can be applied to a general developing method. For example, there are a two-component developing method, a two-component AC developing method, and a method disclosed in JP-A-62-62970. As for the toner and the carrier, those generally used can be applied. For example, as for the toner, polystyrene, poly-p-
Chlorstyrene, polyvinyl toluene, styrene-p-
Homopolymers of styrene and its substituted products such as chlorostyrene copolymer and styrene vinyltoluene copolymer, and copolymers thereof; styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene −
Copolymer of styrene and acrylate such as n-butyl acrylate copolymer; styrene such as styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, and styrene-n-butyl methacrylate copolymer Copolymer of styrene and methacrylic acid ester; multi-component copolymer of styrene and acrylic acid ester and methacrylic acid ester; other styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, Styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile indene copolymer,
Styrene-copolymer of styrene such as styrene-maleic acid ester copolymer and other vinyl monomers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacryl Acids, phenolic resins, aliphatic or aliphatic hydrocarbon resins, petroleum resins, chlorinated paraffins, etc. are used alone or in combination, and if necessary, a coloring agent, a charge control agent, etc. are added to form a toner,
If necessary, a fluidity-providing agent, a lubricant, a fixing aid, or the like can be used as long as the properties of the toner are not impaired. As the carrier, iron powder and ferrite, or those obtained by coating the surface of these magnetic materials with an acrylic resin, a mixture of a fluorine resin and an acrylic resin, or a silicon resin are used.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples.

Example 1 Blue powder (toner), which is positively charged by friction with a carrier having an average particle diameter of 12 μm, is made up of 1.0% by weight of silicon dioxide treated with positively charged amino-modified silicon oil and fine particles of polyvinylidene fluoride (Coulter 0.5% by weight (counter measurement: 6.0 μm) was externally added to obtain a developer.

Next, 12 g of a mixed resin (1: 1) of a vinylidene fluoride-tetrafluoroethylene copolymer (75:25) and a methyl methacrylate copolymer is dissolved in 500 ml of an acetone-methyl ketone (1: 1) mixed solvent and coated. A liquid was prepared, and 1 kg of ferrite particles having an average particle diameter of 60 μm was coated with the coating liquid using a fluidized bed apparatus.

The edge image agent and the carrier were mixed at a weight ratio of 8: 100 to obtain a starting agent for a two-component developer. Further, 0.3 g of the polyvinylidene fluoride fine particles described above was added to 250 g of the starting agent, and the ATR window material shown in FIGS. 1 to 5 described in the text was made of polycarbonate (for the treated silicon dioxide, negatively charged, The developer is charged in a developing device using polyvinylidene fluoride fine particles), and the above developer is used as a replenishing developer. A low temperature and low humidity (15 ° C / 10 %), Normal temperature and normal humidity (22.5 ° C / 60%), and high temperature and high humidity (32.5 ° C / 85%).

As a result, a sufficient density (reflection density 1.30 to 1.40) was maintained from the beginning to the end in all three environments even when 10,000 images were output, and no image deterioration such as fogging occurred.

Comparative Example 1 Durability was carried out in the same manner as in Example 1 except that polyvinylidene fluoride fine particles were not added to the starting agent and the replenishing developer, and the same results as in Example 1 were obtained at room temperature, normal humidity, and high temperature and high humidity. However, under low temperature and low humidity, light toner adhered to the sensor window, and the ATR malfunctioned, so the density after endurance of 10,000 sheets dropped to 1.20.

Example 2 250 g of a starting agent was prepared in the same manner as in Example 1, and 1 g of polytetrafluoroethylene fine particles (7.2 μm measured by a Coulter counter) was added. By changing the material of the sensor window to polyfluoroethylene resin and performing the same durability as in Example 1, all three environments maintained a sufficient density (reflection density 1.30 to 1.40) from the beginning to the end, and image deterioration such as fog Did not happen.

Comparative Example 2 Durability was carried out in the same manner as in Example 2 except that polytetrafluoroethylene fine particles were not added to the start agent. As a result, in all three environments, vigorous toner adhesion occurred on the sensor window, and the ATR malfunctioned. 0.80 after endurance
Went down.

Example 3 Chargeable red powder (toner) with an average particle size of 13 μm
Further, 1.0% by weight of positively-charged amino-modified silicone oil-treated silicon dioxide and 0.3% by weight of fine particles of negatively-chargeable polytetrafluoroethylene (3.0 μm measured by a Coulter counter) were externally added to obtain a developer. The developer and the carrier used in Example 1 were mixed at a weight ratio of 1:10 to obtain a two-component developer starter. To 250 g of the starting agent, 0.5 g of ethylene tetrafluoride-propylene hexafluoride copolymer fine particles (5.0 μm) was added.
g, added to the developing device used in Example 1, and using the above developer as a replenishing developer, a commercially available Canon copier NP
Low temperature and low humidity (15 ℃ / 10%), normal temperature and normal humidity (22.5 ℃ / 60
%) And high temperature and high humidity (32.5 ° C./85%). As a result, a sufficient density (reflection density 1.35 to 1.40) was maintained from the beginning to the end in all three environments even when 10,000 images were output, and there was no image deterioration such as fogging.

Comparative Example 3 A toner was prepared in the same manner as in Example 3 (this is referred to as Toner A). Further, 0.5 g of the ethylene tetrafluoride-propylene hexafluoride copolymer fine particles used in Example 3 was added to Toner A. The additive (hereinafter referred to as toner B) and the carrier used in Example 3 were mixed at a weight ratio of 1:10 to obtain a start agent. The same durability as in Example 3 was performed by using 250 g of this starter and toner A as a replenishing toner. After the endurance of 10,000 sheets, the same result as in Example 3 was obtained at room temperature, normal humidity, and high temperature and high humidity. Down to 1.20.

Comparative Example 4 Using the starter of Comparative Example 3 and using toner B as the replenishing toner, the same durability as in Example 3 was performed. The same results as in Example 3 were obtained at normal temperature and normal humidity and low temperature and low humidity. However, at high temperature and high humidity, the reflection density from the initial stage to the end of 10,000
0.8-0.9.

Example 4 Black powder (toner) with an average particle size of 12 μm
Then, 0.4% by weight of negatively charged hydrophobic colloidal silica was externally added to obtain a developer. The developer and the carrier used in Example 1 were mixed at a weight ratio of 1:10 to obtain a two-component developer starter. To 220 g of the starting agent, 0.6 g of positively-chargeable fine particles of a styrene-dimethylaminoethyl methacrylate copolymer (measured by a Coulter counter of 4.0 μm) was added. In the developing device used in Example 1, only the sensor window was changed to a window made of glass (positively charged for the colloidal silica and negatively charged for the fine particles of the copolymer). The above-mentioned developer was used as a replenishing developer, and a low-temperature, low-humidity (15 ° C / 10%), normal-temperature, normal-humidity (22.
5 ° C / 60%) and high temperature and high humidity (32.5 ° C / 85%). As a result, even after endurance of 10,000 sheets, sufficient density (reflection density 1.40 to 1.45) in all three environments from the beginning to the end
And no image deterioration such as fogging was observed.

Comparative Example 3 To 200 g of the carrier used in Example 1, 0.6 g of the fine particles (4.0 μm) of the styrene-dimethylaminoethyl methacrylate copolymer used in Example 4 was externally added. The toner used in Example 4 and the carrier were mixed at a weight ratio of 1:10 to obtain a start agent. Using the starter of 220 g and the toner of Example 4 as the toner for replenishment, the same durability was carried out with the developing device and the copying machine used in Example 4. As a result, the density was drastically reduced in all three environments, and the durability was 10,000 sheets. The post-concentration dropped to 0.75.

[Effects of the Invention] As described above, according to the present invention, since the developer concentration can be accurately detected, a high-quality image can be provided for a long period of time.

[Brief description of the drawings]

FIG. 1 is a view showing a toner density detecting section of a conventional light detecting ATR, FIG. 2 is a schematic longitudinal sectional view of a developing device, FIG. 3 is a schematic sectional view of the developing device shown in FIG. FIG. 5 is a schematic diagram of a toner density detecting device.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tatsuya Tada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-63-52160 (JP, A) JP-A-63 −195341 (JP, A)

Claims (1)

(57) [Claims] An image forming apparatus using a two-component developer containing an additive for charging a toner, a carrier, and a sensor window material of a detection device for detecting a toner concentration to a polarity opposite to that of the toner, A photodetection automatic toner density control method, wherein a second additive for charging the sensor window material to the same polarity as the toner is supplied to the vicinity of the window as independent particles.