JP3499482B2 - Two-component developer and developing device using the developer - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to, for example, a developing device using a two-component developer及beauty the developer used in the image forming process in the image forming apparatus such as a copying machine or a printer of an electrophotographic system.

[0002]

2. Description of the Related Art Developing systems used in electrophotographic image forming processes are roughly classified into two-component developing systems and one-component developing systems. The two-component developing method is used by mixing a carrier made of a magnetic material such as Fe (iron) and ferrite as a developer with a toner.
In addition, the charging characteristic of the developer is adjusted by changing the mixing ratio of the carrier and the toner. And
The developing method using such a two-component developer is excellent in the developing characteristics and gradation reproducibility of thin lines and solid images, and is also suitable for forming color images.

On the other hand, in the one-component developing system, since only the toner is used as the developer, it is not necessary to mix and agitate the toner and the carrier, and further, it is not necessary to control the toner concentration or replace the toner. Has the advantage. Also,
There are two types of one-component developing methods, one using magnetic toner and the other using non-magnetic toner. In addition to the advantages described above, the method using a magnetic toner not only facilitates the formation of a uniform toner layer and also facilitates the transport of the toner, but also uses the magnetic binding force of the toner.
There is an advantage that it is possible to easily control the adhesion (so-called “fogging”) and the scattering of the toner on the background portion.

However, in the method using the magnetic toner,
Since the magnetic toner contains magnetic powder, it is not suitable for forming a color image. Therefore, at present, a two-component developing method or a non-magnetic one-component developing method is predominant as a developing method in color image formation.

When the two-component developer used in the two-component developing system is manufactured, it is carried out by mixing the toner and the carrier at a predetermined mixing ratio, mixing time and mixing rotation speed. It usually takes several months before the user actually puts the manufactured two-component developer into the toner replenishing device and supplies it to the developing device for use. In this way, if the two-component developer is left for several months from the time of manufacture, the charge of the developer leaks, and as shown by a thin line (b) in FIG. The charge amount is lower than that at the beginning of manufacturing. Depending on the type of two-component developer, 30% of the initial design value
To about 70%.

When copying is performed on a recording paper in an image forming apparatus using such a two-component developer, the charge amount of the two-component developer is lower than the designed value, so that toner scattering or White background fogging (“fogging” that occurs on white background) is likely to occur. In addition, the initial image density formed on the recording paper, that is, the image density during a certain period of time when the image forming apparatus is first used, becomes high, resulting in an image with a gamma with insufficient gradation. It causes problems such as being lost.

Further, when copying is repeatedly performed on the recording paper in this state, the charge amount of the two-component developer increases, and when the number of copies on the recording paper reaches several hundreds, as shown in FIG. It tends to saturate to a certain value, as shown by the diagonal lines. However, when the toner (start developer toner) of the initial two-component developer (hereinafter referred to as start developer) initially charged into the developing device runs low, the toner for start developer is supplied from the toner replenishing device. When the same two-component developer (hereinafter referred to as replenishment toner) is replenished, the difference in charge amount between the start developer toner and the replenishment toner increases,
The image characteristics will also change significantly.

In particular, in recent image forming apparatuses such as personal copying machines and printers, in order to shorten the time from turning on the power to the apparatus main body until the copying becomes possible, that is, the so-called "ready time", power is supplied to the apparatus main body. There are many models that are ready for copying immediately when is turned on. Therefore, in such a device, since the two-component developer in the developing device is not sufficiently agitated, the charge amount of the two-component developer cannot be sufficiently increased, which tends to promote the above-mentioned problems. is there.

Therefore, in order to solve the above-mentioned conventional problems, for example, as disclosed in Japanese Patent No. 2772016 (hereinafter referred to as a prior art), when a two-component developer is manufactured, a toner is used. The mixing time of the toner and the carrier is set in an appropriate range so that the toner and the carrier are sufficiently mixed, and further control is performed so that excessive stirring is not performed. There is a structure having a structure that prevents the scattering of particles, fog, and decrease in density.

[0010]

However, in the invention described in the above-mentioned prior art, when the two-component developer is manufactured, the mixing conditions of the toner and the carrier are simply agitated under appropriate conditions. If the start developer is left alone for several months, the charge amount of the start developer is reduced, and problems such as toner scattering and fog may occur during the initial copying.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an appropriate difference in charging characteristics between a toner for a start developer and a replenishment toner, and to perform start development. By setting the charge amount of the toner of the developer to be higher than the charge amount of the replenishment toner, toner scattering and fog that occur when image formation is performed with a two-component developer left for several months after manufacturing as before. Alternatively, there is provided a developing device using a two-component developer及beauty the developer to the the image density is high can be reliably prevented.

[0012]

In order to solve the above problems, the first invention is used in a developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier, and A two-component developer comprising at least a toner and a carrier,
Number of parts of colorant contained in toner for start developer
Relative to the number of parts of the colorant contained in the replenishing toner
It is characterized in that it is set to 5 to 30% by weight reduction .

[0013]

[0014]

A second invention uses the two-component developer described above.
And a developing device .

[0016]

In the present invention, the toner of the two-component developer (the toner for the start developer) which is initially charged in the developing device.
Is set to be higher than the charge amount of the replenishment toner that is sequentially replenished thereafter. As the method, firstly, in the toner manufacturing process, the number of constituents of the colorant of the toner for the starting developer is set to be smaller than the number of constituents of the colorant of the replenishment toner. The colorant generally has a lower resistance than the binder resin, and the volume resistivity of the toner for the starting developer can be increased by reducing the number of constituents of the colorant of the toner for the starting developer to be smaller than that of the replenishing toner. it can. In general, when the volume resistivity of the toner increases, the amount of leak of electric charge decreases and the amount of charge increases.

As a second method, in the toner manufacturing process, the product of the mixing time and the mixing rotational speed when mixing the binder resin, the colorant, the charge control, etc. is determined by the value of the toner for the start developer and the replenishment toner. And are set to different values. The value of the product of the mixing time and the mixing speed represents the strength of mixing (stirring) of each material such as the binder resin, the colorant, and the charge control agent, and the value of this product causes the dispersion of each material. Property changes, and the charge amount of the manufactured toner changes. Particularly, in the case of a positive polarity toner, when the materials are agitated strongly in the step of mixing the materials, aggregation of the colorant occurs around the charge control agent, the chargeability of the charge control agent is lowered, and the charge amount of the toner is lowered. I will end up. Therefore, when the toner for the starting developer is manufactured, the value of the product of the mixing time and the mixing rotation speed is set to a value smaller than that of the replenishing toner. Therefore, the charge amount of the toner for the start developer is higher than that of the replenishment toner.

The toner for the starting developer produced by the above method is mixed with a carrier and used as a two-component developer. In this two-component developer, the charge amount of the toner for the start developer is set higher than that of the replenishment toner, so that the charge amount does not decrease much even if it is left for a long period of time. Therefore, even if an image is formed by leaving it for several months after the production, the toner scattering and fog, which have been conventionally observed, are reduced, and an image having sufficient gradation can be obtained.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic view showing a main part of an image forming process portion in an electrophotographic image forming apparatus using a two-component developer according to the present invention.

As shown in FIG. 1, reference numeral 1 is an image forming unit, and an electrostatic latent image carrier 2 made of a photoconductor is rotatably arranged in the image forming unit 1 in a direction indicated by a solid arrow. ing. The electrostatic latent image carrier 2 has a cylindrical drum 3 made of a metal such as aluminum as a base material, and selenium (Se) or an organic photoconductor (OPC: OPC) on the outer peripheral surface of the cylindrical drum 3.
And a photoreceptive layer 4 formed by coating a thin film of Organic Photo-Conductor or the like.

Around the electrostatic latent image carrier 2, a charging member 5, an exposing member 6, a developing device 20, which will be described later, a transfer member 7, a cleaning member 8 and a charge removing member 9 are arranged in this order along the rotation direction thereof. It is arranged. The charging member 5 is composed of, for example, a charging wire such as a tungsten wire, a corona charger formed of a metal shield plate or a grid plate, a charging roller, or a charging brush. The exposure member 6 may be, for example, a laser or an LED (Light Em).
It is composed of a lighting diode). The transfer member 7 is composed of, for example, a corona charger, a charging roller, or a charging brush. The cleaning member 8 is a cleaning blade, and the discharging member 9 is a discharging lamp.

In the image forming process in the image forming section 1 described above, first, the surface of the electrostatic latent image carrier 2 is charged with the charging member 5.
Are uniformly charged to a predetermined potential. Then, an electrostatic latent image is formed on the electrostatic latent image carrier 2 by light irradiation from the exposure member 6 according to the image information. The electrostatic latent image formed on the electrostatic latent image carrier 2 is developed from the inside of the developing device 20 by a developing electric field formed between the electrostatic latent image carrier 2 and the developing device 20. Toner) moves and is visualized as a toner image. The toner image is transferred onto the recording medium P such as paper by the transfer member 7, and the recording medium P after the transfer is transferred.
Is conveyed to the fixing member 10 side, and the toner image is fixed on the recording medium P by the fixing member 10.

The recording medium P after fixing is discharged to a paper discharge unit (not shown). On the other hand, residual toner remaining on the electrostatic latent image carrier 2 after transfer is scraped off by the cleaning member 8 and collected. After cleaning, the charge on the surface of the electrostatic latent image carrier 2 is removed by the charge removing member 9,
The surface of the electrostatic latent image carrier 2 after the charge elimination is again charged uniformly to a predetermined potential by the charging member 5, and is statically irradiated by the light irradiation from the exposure member 6 according to the next image information. An electrostatic latent image is formed on the electrostatic latent image carrier 2.

The two-component developer according to the present invention is supplied to the developing device 20 described above. As shown in FIG. 2, the developing device 20 has a developing device 21, and a magnet roller 22 is fixed in the developing device 21. The magnet roller 22 is provided with a magnet 23 inside, and a sleeve 24 is provided outside the magnet roller 22. Then, the developer T in the developing device 21 is attached onto the sleeve 24,
As the sleeve 24 rotates, the developer T is transported to the developing area A between the developer T and the electrostatic latent image carrier 2. Further, a soft developer brush is formed in the developing area A between the electrostatic latent image carrier 2 and the sleeve 24, and the electrostatic latent image carrier 2 is rubbed by the developer brush. The electrostatic latent image is developed. Further, a doctor blade 25 is provided on the sleeve 24, and the doctor blade 25 controls the layer thickness of the developer T adhering to the sleeve 24.

In the developing device 21, a stirring roller 26 is provided.
Is rotatably arranged at a position adjacent to the sleeve 24. The agitating roller 26 serves as a developer T in the developing device 21.
Is stirred.

In this case, the developer T initially charged in the developing device 21 is a so-called "start developer toner", and the replenishment toner Ts is the toner concentration sensor (see FIG. According to the detection result (not shown), a predetermined amount of toner is supplied from the toner replenishing device 27 into the developing device 21. Then, the replenishment toner Ts supplied into the developing device 21 is mixed with the carrier by the stirring roller 26 to form a developer.

That is, at the first stage when the main body of the apparatus starts to be activated, development is performed only with the toner T for the start developer. Then, the toner T for the start developer in the developing device 21 decreases, and the replenishment toner Ts is gradually supplied into the developing device 21 and mixed with the toner T for the starting developer, and finally the inside of the developing device 21 It replaces the replenishment toner Ts.

Therefore, in the first embodiment of the present invention, the charge amount of the toner T for start developer which is initially charged in the developing device 21 is set higher than the charge amount of the replenishment toner Ts. Then, as a method thereof, first, when the toner is manufactured, the number of constituent parts of the colorant of the start developer toner T is set to be smaller than the number of constituent parts of the colorant of the replenishment toner Ts. That is, normally, the resistance of the colorant is lower than that of the binder resin.
The volume resistivity of the start developer toner T can be set higher than that of the replenishment toner Ts by setting the number smaller than the number of parts of the colorant of s. As a result, it is possible to reduce the decrease in the charge amount of the developer due to being left for a long period of time, as compared with the case where the same toner as the starting developer toner T is used as the replenishment toner Ts.

If the number of constituent parts of the colorant is reduced in this way, the charge amount of the toner T for the starting developer also becomes higher than the charge amount of the replenishment toner Ts, and the image density after leaving for a long time becomes darker than necessary. It never happens. Further, when the number of copies is piled up as before, the difference from the initial image density is reduced.

In this case, the transition of the charge amount of the toner T for the starting developer is as shown by the thick line (a) in FIG. That is, the two-component development was carried out in which the initial charge amount of the two-component developer was the same as that of the conventional start developer toner T and the number of the colorant components of the replenishment toner Ts was the same. The charge amount of the developer becomes higher than the charge amount (thin line (b) in FIG. 3), and even when left for a long time (several months), the charge amount of the toner T for start developer is kept higher than before. can do. Further, the toner T for the starting developer has decreased as the number of copies has been increased.
Then, the replenishment toner Ts is replenished little by little, and gradually replaced with the replenishment toner Ts. Therefore, the charging characteristic of the developer gradually approaches the replenishment toner Ts and is completely replaced with the replenishment toner Ts after several hundreds of sheets, and the charging characteristic becomes that of the replenishment toner Ts. Then, at this point, an image having the same image quality as that of the conventional one is obtained.

By the way, as the number of copies increases from the initial stage of copying, the toner T for start developer is contained in the developer.
And replenishment toner Ts are mixed. The toner T for the starting developer and the replenishment toner Ts have the same toner constituent material,
Since only the content of the colorant is different, other than the charging characteristics of the developer, it does not change significantly, and no further problems occur.

Further, the number of constituent parts of the colorant contained in the start developer toner T and the replenishment toner Ts is made smaller than in the conventional case so that the resistance of the toner is increased, that is, both charge amounts are increased. If set, as shown by the dotted line (c) in FIG. 3, as the number of copies increases, the charge amount of the developer increases and the image density decreases. The number of parts of the colorant contained in the toner T for start developer should be reduced to 5 to 30% by weight, preferably 10 to 20% by weight, relative to the number of parts of the colorant contained in the replenishment toner Ts. Is desirable. When the number of constituent parts of the colorant of the start developer toner T is 5% by weight or less with respect to the number of constituent parts of the colorant of the replenishment toner Ts, charging characteristics of the start developer toner T and the replenishment toner Ts, etc. Since the difference in performance is small, the desired effect cannot be obtained. On the other hand, when the content is 30% by weight or more, the performance difference in the charging characteristics and the like between the toner T for start developer and the replenishment toner Ts becomes too large, which causes a problem that the initial image density decreases.

In the second embodiment of the present invention, when the starting developer toner T is manufactured, the product of the mixing time and the mixing rotation speed is made different from the replenishment toner Ts, and the replenishment toner Ts is manufactured. Set smaller than the value of. As a result, the charging characteristics of the start developer toner T and the replenishment toner Ts are changed, and the same effect as when the number of constituent parts of the colorant is changed as in the above-described first embodiment is obtained.
Here, the "product" of the mixing time and the number of mixing revolutions when manufacturing the toner represents the so-called mixing strength, and the larger the value of the product, the stronger the stirring force. .

That is, when the stirring force is changed during the production of the developer, the agglomeration state of the components such as the colorant and the charge control agent in the toner is changed, which causes the charge characteristic (resistance) of the developer.
Also changes. For this reason, such a developer can be selectively used as the start developer toner T and the replenishment toner Ts.

In particular, when a toner having a positive charging polarity is used, in the mixing step, the charge control agent is positively charged while the colorant (for example, carbon black) is
Normally, it is negatively charged with respect to the charge control agent. For this reason, the stronger the stirring in the mixing process, the more the charge control agent and the colorant attract each other by electrostatic force, and the colorant aggregates around the charge control agent, resulting in poor chargeability of the charge control agent (charge Amount will be lower). Therefore, in the present invention, the stirring at the time of manufacturing the start developer toner T is weaker than the stirring at the time of manufacturing the replenishment toner Ts, that is,
By reducing the value of the product of the mixing time and the number of rotations of the mixing, the chargeability of the toner T for the starting developer can be improved.
It should be higher than s. As a result, the initial charge amount of the start developer toner T becomes higher than that of the replenishment toner Ts, and moreover, the rise of charge can be increased.

The material of the toner according to the present invention is not particularly limited, but typical examples of the material include the following materials. When a magnetic toner is used instead of the two-component developer, magnetite, ferrite, etc. are further added to the following.

(Embodiment 1) Next, the first embodiment of the present invention described above.
The method for producing the two-component developer in the above embodiment will be specifically described. In this case, the toner T for the start developer is
For example: * Binder resin: Styrene acrylic resin 100 parts (weight part) * Coloring agent: Carbon black 6 parts (weight part) * Charge control agent: Nigrosine 3 parts (weight part) * Wax: Low molecular weight polyethylene 3 parts (weight) Part) as an ingredient. Then, these components are charged into a super mixer, the mixing speed is 600 rpm, and the mixing time is 5
Set to minutes and after dry mixing, with a twin-screw extruder,
Heat, melt and knead. Then, the kneaded product is cooled and solidified, coarsely pulverized to a particle size of about 2 mm by a feather mill, further finely pulverized by a jet mill, and toner having a particle size of 5 μm or less is cut by a rotor classifier to obtain a volume. Average particle size is 10μ
m powder is obtained. Further, a toner is manufactured by mixing 100 parts of this toner powder and 0.2 part of hydrophobic silica.

The volume resistivity of the toner thus manufactured was 1.80 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 20 μC / g. Further, the charge amount after leaving the toner T for start developer for about two months was about 15 μC / g.

On the other hand, as the toner of the replenishment toner Ts,
For example: * Binder resin: Styrene acrylic resin 100 parts (weight part) * Coloring agent: Carbon black 7 parts (weight part) * Charge control agent: Nigrosine 3 parts (weight part) * Wax: Low molecular weight polyethylene 3 parts (weight) Part) is used as a component to reduce the content of the colorant in the toner component of the toner T for start developer described above, and the toner is manufactured under the same conditions as the toner T for start developer described above. The volume resistivity of the toner thus manufactured is
It was 1.65 × 10 ¹¹ Ω · cm.

Using the toner T for start developer and the replenishment toner Ts described above, 3000 sheets were copied by a copying machine (Personal copying machine Z85 made by Sharp), and the examples in Table 1 below were obtained. As shown by the evaluation result of No. 1, no initial fog on the white background and toner scattering were visually observed as in the past, and a good result in which the image density was stable was obtained.

[0042]

[Table 1]

As a result, the number of constituent parts of the colorant contained in the toner for the start developer is smaller than that of the toner for replenishment.
For example, by setting it to 14% by weight reduction, as described above, it is set to 5 to 30% by weight, preferably 10 to 20% by weight with respect to the number of constituent parts of the colorant contained in the replenishing toner. By doing so, it becomes possible to effectively eliminate the conventional problems.

(Example 2) In this Example 2, the colorant of the toner for the starting developer in Example 1 was increased by 0.5 parts by weight, * Binder resin: Styrene acrylic resin 100 parts (parts by weight) * Coloring agent: Carbon black 6.5 parts (parts by weight) * Charge control agent: Nigrosine 3 parts (parts by weight) * Wax: Low molecular weight polyethylene 3 parts (parts by weight) and the same conditions as in Example 1 To produce toner.

The volume resistivity of the toner thus manufactured was 1.74 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 19 μC / g. In addition, the charge amount after leaving the toner T for start developer for about two months was about 13 μC / g.

Then, by using the above-mentioned toner T for start developer and the replenishment toner Ts similar to that of the first embodiment, the toner is 300 in a copying machine (a Sharp personal copying machine Z85).
When 0 copies were made, as shown in the evaluation results of Example 2 in Table 2 below, some initial white background fog was observed, but no toner scattering was observed and the image density was also found. Stable and good results were obtained.

[0047]

[Table 2]

As a result, the number of constituent parts of the colorant contained in the toner for the start developer is smaller than that of the toner for replenishment.
For example, by setting 7% by weight reduction, as described above, 5 to 30% by weight, preferably 10 to 20% by weight, relative to the number of parts of the colorant contained in the replenishing toner.
If it is set to a decrease, it becomes possible to effectively eliminate the conventional defect.

(Example 3) In Example 3, the colorant of the toner for the starting developer in Example 1 was reduced by 1.0 part by weight, and * binder resin: styrene acrylic resin 100 parts (part by weight). * Coloring agent: carbon black 5 parts (parts by weight) * Charge control agent: nigrosine 3 parts (parts by weight) * Wax: low molecular weight polyethylene 3 parts (parts by weight) under the same conditions as in Example 1. Toner is manufactured.

The thus-produced toner had a volume resistivity of 2.10 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 25 μC / g. In addition, the charge amount after leaving the toner T for start developer for about two months was about 19 μC / g.

Then, by using the toner T for the starting developer described above and the replenishment toner Ts similar to that in the first embodiment, 300 is set in a copying machine (Personal copying machine Z85 made by Sharp).
When 0 sheets were copied, as shown in the evaluation results of Example 3 in Table 3 below, white background fog and toner scattering as before were not seen, and good results were obtained, but the initial image The concentration was a little low.

[0052]

[Table 3]

As a result, the number of constituent parts of the colorant contained in the toner for the start developer is smaller than that of the toner for replenishment.
For example, by setting the reduction to 29% by weight, as described above, the reduction is set to 5 to 30% by weight, preferably 10 to 20% by weight with respect to the number of constituent parts of the colorant contained in the replenishing toner. By doing so, it becomes possible to effectively eliminate the conventional problems.

(Comparative Example 1) In Comparative Example 1, the toner T for start developer and the replenishment toner Ts are commonly used, and the same components as those of the replenishment toner of Example 1 are used.
A toner was manufactured, and 6 parts of such a toner and 100 parts of the iron powder-based carrier were mixed with a Nauta mixer for about 30 minutes to obtain a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 18 μC / g. The charge amount after the toner T for start developer was left standing for about 2 months was about 11 μC / g.

Then, using the toner T for start developer and the replenishment toner Ts described above, 3000 copies were made by a copying machine (Personal copying machine Z85 made by Sharp), and a comparative example in Table 4 below. As shown in the evaluation result of No. 1, white background fog and toner scattering were visually confirmed in several sheets from the initial stage, and the image density at the initial stage was high and the image had a high gamma.

[0056]

[Table 4]

(Comparative Example 2) In Comparative Example 2, the toner for the starting developer is, for example, * binder resin: styrene-acrylic resin 100 parts (part by weight) * coloring agent: carbon black 6.8 parts ( (Parts by weight) * Charge control agent: Nigrosine 3 parts (part by weight) * Wax: Low molecular weight polyethylene 3 parts (parts by weight). Then, these components are charged into a super mixer, the mixing speed is 600 rpm, and the mixing time is 5
Set to minutes and after dry mixing, with a twin-screw extruder,
Heat, melt and knead. Then, the kneaded product is cooled and solidified, coarsely pulverized to a particle size of about 2 mm by a feather mill, further finely pulverized by a jet mill, and toner having a particle size of 5 μm or less is cut by a rotor classifier to obtain a volume. Average particle size is 10μ
m powder is obtained. Further, a toner is manufactured by mixing 100 parts of this toner powder and 0.2 part of hydrophobic silica.

The volume resistivity of the toner thus manufactured was 1.67 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 19 μC / g. In addition, the charge amount after the toner T for start developer was left standing for about two months was about 12 μC / g.

Then, using the above-mentioned toner T for start developer and the replenishment toner Ts having the same components as in Example 1, the amount is 30 by a copying machine (Personal copying machine Z85 made by Sharp).
00 copies were made, but Comparative Example 2 in Table 5 below
As shown in the evaluation result of 1., the white background fog and toner scattering were visually confirmed in several sheets from the initial stage, and the initial image density was also high, and the image had a high gamma.

[0060]

[Table 5]

As a result, the number of constituent parts of the colorant contained in the toner for the start developer is smaller than that of the toner for replenishment.
For example, it was confirmed that the effect cannot be expected unless the amount is set to 3% by weight reduction and the amount of the colorant contained in the replenishment toner is reduced to 5 to 30% by weight.

Comparative Example 3 In this Comparative Example 3, the toner for the start developer is, for example, * binder resin: styrene acrylic resin 100 parts (parts by weight) * colorant: carbon black 4.5 parts (parts by weight) Parts) * Charge control agent: Nigrosine 3 parts (parts by weight) * Wax: Low molecular weight polyethylene 3 parts (parts by weight). Then, these components are charged into a super mixer, the mixing speed is 600 rpm, and the mixing time is 5
Set to minutes and after dry mixing, with a twin-screw extruder,
Heat, melt and knead. Then, the kneaded product is cooled and solidified, coarsely pulverized to a particle size of about 2 mm by a feather mill, further finely pulverized by a jet mill, and toner having a particle size of 5 μm or less is cut by a rotor classifier to obtain a volume. Average particle size is 10μ
m powder is obtained. Further, a toner is manufactured by mixing 100 parts of this toner powder and 0.2 part of hydrophobic silica.

The volume resistivity of the toner thus manufactured was 2.39 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 28 μC / g. In addition, the charge amount after leaving the toner T for start developer for about two months was about 23 μC / g.

Then, using the toner T for start developer described above and the replenishment toner Ts having the same components as in the first embodiment, the amount is 30 by using a copying machine (Personal copying machine Z85 manufactured by Sharp).
00 copies were made, but Comparative Example 3 in Table 6 below.
As shown in the evaluation result of 1., the problem that the initial image density was low occurred.

[0065]

[Table 6]

As a result, the number of constituent parts of the colorant contained in the toner for the start developer is smaller than that of the toner for replenishment.
For example, it has been confirmed that the effect cannot be expected unless it is set to 35% by weight reduction and 5 to 30% by weight reduction with respect to the number of constituent parts of the colorant contained in the toner for replenishment.

(Example 4) This example 4 relates to a method for producing a two-component developer according to the second embodiment of the present invention described above. In this case, the toner for the start developer is, for example, * binder resin. : Styrene acrylic resin 100 parts (parts by weight) * Coloring agent: Carbon black 7 parts (parts by weight) * Charge control agent: Nigrosine 2 parts (parts by weight) * Wax: Low molecular weight polyethylene 2 parts (parts by weight) as a component To do. Then, these ingredients are put into a super mixer, the mixing speed is 600 rpm, and the mixing time is 2
Set to minutes and after dry mixing, with a twin-screw extruder,
Heat, melt and knead. Then, the kneaded product is cooled and solidified, coarsely pulverized to a particle size of about 2 mm by a feather mill, further finely pulverized by a jet mill, and toner having a particle size of 5 μm or less is cut by a rotor classifier to obtain a volume. Average particle size is 10μ
m powder is obtained. Further, a toner is manufactured by mixing 100 parts of this toner powder and 0.2 part of hydrophobic silica.

The volume resistivity of the toner thus manufactured was 2.80 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. The charge amount of the toner T for start developer at that time was about 23 μC / g. The charge amount after the toner T for start developer was left standing for about two months was about 14 μC / g.

On the other hand, as the toner of the replenishment toner Ts,
The same component as the toner for the starting developer described above is charged into the super mixer, the mixing rotation speed is set to 600 rpm and the mixing time is set to 5 minutes, and the volume average is set in the same manner as the toner for the starting developer. A powder toner having a particle size of 10 μm is manufactured.

Then, using the toner T for start developer and the replenishment toner Ts described above, 3000 copies were made by a copying machine (Personal copying machine Z85 made by Sharp). As shown by the evaluation result of No. 4, no initial fog on the white background or toner scattering was visually observed, and a good result in which the image density was stable was obtained.

[0071]

[Table 7]

As a result, by making the product of the mixing time by the super mixer and the like in the mixing process of the toner for the start developer and the mixing rotation speed smaller than that of the toner for replenishment, the problems as before can be effectively obtained. It becomes possible to eliminate it.

(Example 5) This example 5 is another example of the above-mentioned example 4, and in this case, the toner for the start developer is, for example, * binder resin: styrene / n.butyl acryl. Resin 100 parts (parts by weight) * Coloring agent: Carbon black 7 parts (parts by weight) * Charge control agent: Nigrosine 2 parts (parts by weight) * Wax: Low molecular weight polyethylene 2 parts (parts by weight). Then, these components are put into a super mixer, the mixing speed is 300 rpm, and the mixing time is 5
Set to minutes and after dry mixing, with a twin-screw extruder,
Heat, melt and knead. Then, the kneaded product is cooled and solidified, coarsely pulverized to a particle size of about 2 mm by a feather mill, further finely pulverized by a jet mill, and toner having a particle size of 5 μm or less is cut by a rotor classifier to obtain a volume. Average particle size is 10μ
m powder is obtained. Further, a toner is manufactured by mixing 100 parts of this toner powder and 0.3 part of hydrophobic silica.

The volume resistivity of the toner thus manufactured was 2.90 × 10 ¹¹ Ω · cm. And
6 parts of such a toner and 100 parts of an iron powder type carrier were mixed with a Nauta mixer for about 30 minutes to prepare a toner T for a start developer. The charge amount of the toner T for start developer at that time was about 24 μC / g. In addition, the charge amount after the toner T for start developer was allowed to stand for about two months was about 16 μC / g.

On the other hand, as the toner of the replenishment toner Ts,
The same component as the toner for the starting developer described above is charged into the super mixer, the mixing rotation speed is set to 600 rpm and the mixing time is set to 5 minutes, and the volume average is set in the same manner as the toner for the starting developer. A powder toner having a particle size of 10 μm is manufactured.

Then, using the above-mentioned start developer toner T and replenishment toner Ts, 3000 copies were made by a copying machine (Sharp personal copying machine Z85), and the examples in Table 8 below were obtained. As shown in the evaluation result of No. 5, the initial fog on the white background and the toner scattering were not visually observed, and the image density was stable and good results were obtained.

[0077]

[Table 8]

As a result, by making the product of the mixing time by the super mixer or the like and the mixing rotation speed in the mixing process of the toner for the start developer smaller than that of the toner for replenishment, the problems as before can be effectively achieved. It becomes possible to eliminate it.

(Comparative Example 4) In Comparative Example 4, the mixing time by the super mixer or the like in the toner mixing step of the above-described Example 4 was compared with the mixing rotation speed. The toner is the same as the replenishment toner Ts and is used as the toner for the start developer in the fourth embodiment.
A toner having a volume average particle diameter of 10 μm is manufactured by using the same component as the replenishment toner of (1). Then, 6 parts of such a toner and 100 parts of the iron powder-based carrier were mixed with a Nauta mixer for about 20 minutes to prepare a toner T for a start developer. At that time, the charge amount of the toner T for start developer was about 20 μC / g. The charge amount after the toner T for start developer was left standing for about two months was about 14 μC / g.

Then, using the toner T for start developer and the replenishment toner Ts described above, 3,000 copies were made by a copying machine (Personal copying machine Z85 made by Sharp), and comparative examples in Table 9 below. As shown in the evaluation result of No. 4, white background fog and toner scattering were observed in several sheets from the initial stage.

[0081]

[Table 9]

It is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0083]

As is apparent from the above description, according to the first aspect of the present invention, by changing the content of the colorant contained in the toner, the charge amount of the toner of the start developer is made higher than that of the replenishment toner. Since it can be easily set to a high value, it is possible to suppress white background fog and toner scattering at the initial stage when forming an image. Can be formed.

[0084]

[0085]

According to the second invention, by making the content of the colorant contained in the toner of the start developer smaller than that of the replenishment toner, the charge amount of the toner of the start developer becomes higher than that of the replenishment toner. So that it can be easily set. By using such a two-component developer, it is possible to prevent white background fogging and toner scattering at the initial stage as before when performing image formation after leaving it for a long period of several months, and the subsequent image. Also in the formation, an image with good image quality can be formed.

[0087]

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus having an image forming process of a two-component developer according to the present invention.

FIG. 2 is a schematic configuration diagram showing a developing device according to the present invention.

FIG. 3 is an explanatory diagram showing, in comparison, changes in the amount of charge of a two-component developer according to the present invention and a conventional two-component developer when left for a long period of time.

[Explanation of symbols]

1 Image forming section 2 Electrostatic latent image carrier 3 cylindrical drum 4 Photoconductor 5 charging member 6 Exposure member 7 Transfer member 8 cleaning members 9 Static eliminator 10 Fixing member 20 Developing device 21 Developing device 22 Magnet roller 23 Magnet 24 sleeves 25 doctor blade 26 Worship roller 27 Toner supply device A development area P recording medium T-start developer (two-component developer) Ts replenishment toner

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] 1. A two-component developer used in a developing device for developing an electrostatic latent image formed on an electrostatic latent image carrier and comprising at least a toner and a carrier . Number of parts of colorant contained in toner
Relative to the number of parts of the colorant contained in the replenishing toner
A two-component developer characterized by being set to a reduction of 5 to 30% by weight . 2. A two-component developer according to claim 1 is used.
And a developing device .