JPH0833680B2 - Toner for developing electrostatic image and method for developing electrostatic image using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a toner for developing an electrostatic charge image, which visualizes and visualizes an electrostatic charge image formed by an electrophotographic method, an electrostatic printing method, an electrostatic recording method or the like. And a method of developing an electrostatic charge image using the same.

<Prior Art> Conventionally, in a copying machine or the like using an electrophotographic method, an electrostatic charge image formed on a photoconductor is treated with a toner containing a binder resin, a colorant, etc. and a magnetic carrier such as iron powder or ferrite powder. A dry developing method is widely used in which the developer is used for visualization. One of the dry developing methods is a magnetic brush method which is excellent in gradation reproducibility and image quality.

This magnetic brush development method, as shown in FIG.
The electrostatic charge image formed on the photoconductor drum (1) by charging and exposure is developed by a developer (3) containing toner and carrier contained in a developing device (2). More specifically, in the developing device (2), a stirring roller (4) for uniformizing the developer (3) is incorporated, and the developing device (2) faces the photoconductor drum (1) and A developing sleeve (5) is arranged at a predetermined distance.
This developing sleeve (5) is made of a magnet or the like,
The carrier in the developer (3) forms a magnetic brush arranged in a chain, and the toner is attached to the carrier by frictional charging. Further, in order to smoothly develop the electrostatic charge image formed on the photoconductor drum (1), the length of the magnetic brush is regulated by the spike control plate (6). By bringing the toner into contact with the drum (1), the toner is transferred to the electrostatic charge image on the photosensitive drum (1), and the electrostatic charge image is developed.

In the developing device (2), the magnetic permeability of the developer is set at a predetermined position in contact with the flowing developer (3).
By utilizing the fact that it is proportional to the proportion of the magnetic carrier in the developer (3) and inversely proportional to the toner concentration,
A magnetic sensor (7) for detecting the toner concentration in the developer (3) is attached. The magnetic sensor (7) utilizes the fact that the frequency output by the transmitting coil inside the magnetic sensor (7) changes in accordance with the magnetic permeability of the developer (3), and uses this change as a voltage output. And is used to digitize and display the toner concentration in the developer (3) as a voltage value. Further, in order to prevent the toner concentration in the developer (3) from being lowered due to the development, and thus the image density from being lowered, the toner concentration in the developer (3) is below a predetermined value, that is, Agent (3)
The sensor (7) indicates that the magnetic permeability of
, The replenishment toner (10) stored in the hopper (9) is replenished by the toner replenishing roller (11), and the development is performed while adjusting the toner concentration in the developer (3) within a predetermined range. There is.

<Problems to be Solved by the Invention> However, in the conventional developing method, due to the variation in the magnetic sensor, the toner replenishment is started immediately after the start developer is set, and the toner density becomes excessive, resulting in image fog and toner. May be scattered, or the toner supply instruction lamp may light up. To solve the above problem, the toner replenishment start voltage V1 is set higher than the output voltage V0 of the start developer. For this reason, the toner concentration of the developer during continuous copying is controlled to be lower than the toner concentration of the start developer, which causes a decrease in image density. further,
When the toner used as the starting developer is used as it is as the replenishing toner as in the above-mentioned conventional method, the toner can be developed while controlling the toner concentration in the developer within a predetermined range, but the development and the replenishment of the toner are repeated. If this is done, the tendency of so-called spent formation, in which the toner sticks to the carrier due to friction between the carrier in the developer and the toner, increases significantly. When this spent occurs, not only does the electric resistance of the developer increase and the charging characteristics of the toner change, but also the toner concentration that effectively acts on image formation decreases substantially. There is a problem that

<Objects of the Invention> The first invention is made in view of the above problems, and a toner suitable for replenishment can be easily prepared, and a high-quality image can be obtained for a long time even if development and replenishment are repeated. It is an object of the present invention to provide an electrostatic charge image developing toner that can be extended.

Further, a second aspect of the present invention uses the above-mentioned electrostatic image developing toner as a replenishing toner, and while maintaining the toner concentration in the developer within a predetermined range, it is possible to develop a high quality image for a long period of time. The purpose is to provide a method.

<Means and Actions for Solving Problems> In order to achieve the above object, the first invention is a powder toner to be replenished to a start developer including a powder toner and a carrier, and the bulk toner of the developer is used. The bulk density increasing fine powder substance which increases the density is added to 100 parts by weight of the powder toner for replenishment in the range of the addition weight part z satisfying the following formula by the toner for developing an electrostatic image to obtain the above-mentioned conventional products. To solve the problem of.

z ≧ y + 0.05 (parts by weight) [y is the part by weight of the fine powder substance capable of increasing the bulk density with respect to 100 parts by weight of the powder toner in the starting developer. According to the electrostatic charge image developing toner having the above structure,
To the powder toner for replenishment, a fine powder substance for increasing the bulk density for increasing the bulk density of the developer is added within the range of the added weight part z. Even if the toner in the developer is mixed, the fine powder substance is present between the toner in the developer and the carrier to improve the fluidity of the toner and prevent the toner from becoming a toner. Toner charging characteristics and image characteristics do not change. In addition, the fine powder substance is added to the powder toner in an amount of z by weight.
A toner for developing an electrostatic charge image suitable as a toner for replenishment can be produced only by adding the toner within the range.

A second aspect of the invention is to develop an electrostatic charge image using a start developer composed of powder toner and carrier, and detect the toner concentration when the toner concentration in the developer drops below a predetermined value. In the method of developing an electrostatic charge image, which continues developing while adjusting the toner concentration in the developer within a predetermined range by replenishing the replenishing powder toner based on the detection signal of the sensor, the replenishing powder toner As a powder toner, a fine powder substance capable of increasing the bulk density for increasing the bulk density of the developer is used as a powder toner.
The conventional problems described above are solved by a developing method of an electrostatic charge image using 100 parts by weight of an additive added in the range of added weight parts z satisfying the following formula.

z ≧ y + 0.05 (parts by weight) [y is the part by weight of the fine powder substance capable of increasing the bulk density with respect to 100 parts by weight of the powder toner in the starting developer. According to the second generation developing method, when the sensor detects that the toner concentration in the developer has dropped to a predetermined value or less, the bulk density increasing fine powder substance for increasing the bulk density of the developer is Since the powder toner for replenishment added in the range of the addition weight part z is replenished and the bulk density and the packing density of the developer are increased, the ratio of the carrier in the unit volume of the developer is increased. Therefore, the sensor erroneously detects that the toner concentration is equal to or lower than the predetermined value, even though the toner concentration is not equal to or lower than the predetermined value. That is, the toner concentration in the developer is artificially detected to be lower than a predetermined value by the sensor. As a result, the powder toner for replenishment can be replenished and developed while the toner concentration in the developer is substantially high. Moreover, since the fine powder substance is added to the replenishing powder toner, the toner is prevented from being spent, and the substantial toner concentration in the developer can be prevented from decreasing.

 The present invention will be described in detail below.

The electrostatic image developing toner of the first invention comprises a powder toner containing a binder resin, a colorant and other additives, and a bulk density increasing fine powder substance for increasing the bulk density of the developer.

Examples of the binder resin include styrene polymers, acrylic polymers, styrene-acrylic copolymers, polyethylene, chlorinated polyethylene, polypropylene, olefin polymers such as ionomers, polyvinyl chloride, polyesters, polyamides, polyurethanes. Examples include various polymers such as epoxy resin, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, phenol resin, rosin-modified phenol resin, xylene resin, rosin-modified maleic acid resin, rosin ester, and petroleum resin.

Examples of the unsaturated monomer used in the polymer include styrene, α-methylstyrene, o-methylstyrene, p-
Styrene-based monomers such as methylstyrene, p-methoxystyrene, p-chlorostyrene; acrylic acid, methyl acrylate, ethyl acrylate, -n-butyl acrylate,
Isobutyl acrylate, -n-octyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate,
Stearyl acrylate, cyclohexyl acrylate, phenyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, glycidyl acrylate, diethylaminoethyl acrylate, acrylamide, acrylonitrile, methacrylic acid, methyl methacrylate, methacrylic acid Ethyl, methacrylic acid-n-
Butyl, isobutyl methacrylate, methacrylic acid-n-
Octyl, 2-ethylhexyl methacrylate, dodecyl methacrylate, stearyl methacrylate, cycloxyl methacrylate, phenyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, diethylaminoethyl methacrylate, etc. Acrylic or methacrylic monomers; carboxylic acids having unsaturated double bonds such as maleic acid, fumaric acid, crotonic acid, itaconic acid or their alkyl esters or their alkyl esters; olefins such as ethylene, propylene or butadiene Monomer;
Examples thereof include vinyl acetate, vinyl chloride, vinylidene chloride, vinylpyrrolidone, vinylnaphthalene and the like. The above monomers are used alone or in combination of two or more.

Among the above-mentioned polymers, those having a styrene example polymer, an acrylic polymer, a styrene-acrylic copolymer or the like as a main component are preferable. These polymers preferably have a weight average molecular weight of 30,000 to 200,000, particularly 50,000 to 150,000, and are used alone or in combination of two or more.

Among the above-mentioned polymers, rosin ester, rosin-modified phenol resin, rosin maleic acid resin, epoxy resin, polyester, fibrin-based polymer, polyether resin and the like are used for improving the triboelectric charging property of the toner. It is useful.

When the powder toner is a heat fixing toner, the polymer has a softening point of 50 to 200 ° C., preferably a softening point of 70 to 1
Those having 70 ° C. are preferred.

When the powder toner is pressure fixing toner,
Polymers that are easily plastically deformed, such as olefin polymers such as polyethylene and polypropylene, and polyamides are mainly used. This polymer is another polymer such as polyvinyl acetate, ethylene-vinyl acetate copolymer, hydrogenated polystyrene, polymer such as hydrogenated rosin ester, aliphatic, alicyclic or aromatic petroleum resin. May be contained.

Examples of the colorant include carbon black, lamp black (CINo.77266), chrome yellow (CINo.14090), and Hansa yellow (CINo.11660, 11).
680, etc.), Benzidine Yellow (CI No. 21100, etc.),
Slene Yellow G (CINo.70600), Quinoline Yellow (CINo.47005), Permanent Orange GTR (CINo.
12305), Pyrazolone Orange (CINo.21110), Balkan Orange (CINo.21160), Watch Young Red (CINo.15865), Permanent Red (CINo.1231)
0), Brilliant Carmine 3B (CINo.16105), Brilliant Carmine 6B (CINo.15850) DuPont Oil Red (CINo.26105), Pyrazolone Red (CINo.211)
20), Resole Red (CI No.15630), Rhodamine B
Rake (CINo.45170), Rake Red C (CINo.155
85), Rose Bengal (CINo.45435), Aniline Blue (CINo.50405), Ultramarine Blue (CINo.7)
7103), Calco Oil Blue (CINo.azoec Blue
3), Methylene Blue Chloride (CINo.52015), Phthalocyanine Blue (CINo.74160), Phthalocyanine Green (CINo.74260), Macalide Green Oxalate (CINo.42000), and CISolvent Yellow 6
Examples include oil-soluble dyes such as 0, CISolvent Red 27, and CISolvent Blue 35. These colorants are used alone or in combination of two or more, and used in an amount such that a sufficient image density can be obtained, for example, 1 to 30% by weight, preferably 2 to 20% by weight.

When the powder toner is a magnetic toner, a magnetic substance is used together with the colorant or in place of the colorant. The magnetic substance may be any material that exhibits magnetism or is magnetizable. For example, ferrite, magnetite, and other iron, cobalt, nickel, manganese, and other ferromagnets, alloys, or these metals. Examples thereof include compounds containing. These magnetic materials have an average particle size of 0.
It has a size of about 1 to 1 μm, and is used generally in an amount of 20 to 75% by weight, preferably 40 to 70% by weight, as a mixture of one or more kinds.

In order to control the charge of the electrostatic image developing toner,
The above powder toner preferably contains a charge control agent as another additive. As the charge control agent,
For example, nigrosine dye (CINo.50415B), oil black (CINo.26150), oil-soluble dyes such as spirone black, naphthenic acid, salicylic acid, octylic acid, fatty acids described below, manganese, iron, cobalt, lead of resin acids, Examples include metal soaps such as metal salts of zinc, cerium, calcium, nickel and the like, metal-containing azo dyes, pyrimidine compounds, metal chelates of alkylsalicylic acid, etc., and those containing 0.1 to 5% by weight based on the binder resin. preferable.

Further, the powder toner preferably contains an offset preventive agent in order to prevent the toner from adhering to the fixing roller. Examples of the anti-offset agent include various waxes such as low molecular weight polypropylene, low molecular weight polyethylene, and paraffin wax, low molecular weight olefin polymers of olefin monomers having 4 or more carbon atoms, silicone oil, and the like. 0.
Those containing 5 to 15% by weight are preferable.

A fine powder substance capable of increasing the bulk density is added to the powder toner. As this fine powder substance, the bulk density and the packing density of the developer are increased after the replenishment without adversely affecting the characteristics of the toner, the photoreceptor and the image characteristics, and the ratio of the carrier per unit volume of the developer is increased. And, as long as it can prevent the spent of the toner, any can be used, for example, talc, kaolin, barium sulfate or the like, aluminum silicate, surface-treated aluminum silicate, calcium carbonate, Antimony trioxide, barium titanate, calcium titanate, strontium titanate, magnesium oxide, calcium silicate, zinc oxide, zirconium oxide and the like are preferable, and particularly,
Silica, alumina and titanium oxide, which have improved toner and developer fluidity and toner charging characteristics and have excellent image characteristics, are preferable. The bulk density increasing fine powder substance is preferably one which has been subjected to a hydrophobic treatment from the viewpoint of toner stability. The bulk density increasing fine powder substance may be used alone or in combination of two or more.

The fine powder substance acts as a bearing by interposing between the toner and the carrier in the developer, improving the fluidity of the toner and increasing the packing density of the toner and the developer.

The fine powder substance may have an appropriate bulk density, but a substance having a bulk density of 30 to 200 g / l, particularly about 50 to 150 g / l is preferable. If the bulk density is less than 30 g / l, the fluidity of the toner becomes insufficient, and if it exceeds 200 g / l, it is difficult to increase the volume of the carrier in the developer with a small amount.

The fine powder substance may have an appropriate particle size, but one having an average particle size of 1 to 100 μm, particularly 5 to 50 mμ is preferable. When the particle diameter of the fine powder substance is out of the above range, it is difficult to increase the bulk density and the packing density of the developer, and it is not possible to sufficiently prevent the toner from being spent.

A preferred specific example of the fine powder substance is "Aerosil R972" (trade name, manufactured by Nippon Aerosil Co., Ltd.) (average particle size 16
mμ), “Aluminum oxide C” (average particle size 20 m
μ), "Titanium oxide P25" (average particle size 30m
μ) and the like can be exemplified.

The fine powder substance is 100 parts by weight of the powder toner,
It is added within the range of added weight part z satisfying the following formula.

z ≧ y + 0.05 (parts by weight) [y is the part by weight of the fine powder substance capable of increasing the bulk density with respect to 100 parts by weight of the powder toner in the starting developer. That is, the added weight part z of the fine powder substance with respect to 100 parts by weight of the powder toner for replenishment needs to be 0.05 parts by weight or more more than the added weight part y with respect to 100 parts by weight of the powder toner for the start developer. is there.

If the added weight part of the fine powder substance does not satisfy the above range, the fluidity of the toner is not sufficiently improved, and the toner cannot be spent. The added weight part z of the fine powder substance to 100 parts by weight of the powder toner is preferably in the range of 0.05 ≦ z ≦ 2 (parts by weight). If the charge weight part z of the fine powder substance is less than 0.05 part by weight, not only the fluidity of the toner cannot be sufficiently improved, but also the bulk density of the developer,
It is difficult to increase the packing density and increase the volume of the carrier in the developer. On the other hand, if it exceeds 2% by weight, the triboelectric chargeability between the toner and the carrier deteriorates, and the sufficient triboelectric charge required for the toner cannot be obtained, causing the toner to scatter and stain the inside of the copying machine.

In addition, in order to protect the photoconductor,
A fatty acid metal salt may be added.

As the fatty acid of the fatty acid metal salt, a saturated or unsaturated fatty acid having 8 to 36 carbon atoms, for example, caprylic acid, capric acid, undecylic acid, lauric acid, tridecyl acid, myristic acid, palmitic acid, steariic acid, behenic acid, Lignoceric acid, serotic acid, montanic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, erucic acid, ricinoleic acid, dihydroxystearic acid, cyclic fatty acids,
Examples thereof include dibasic acids or dimer acids which are dimers of the above unsaturated fatty acids. Of the above fatty acids, saturated fatty acids, especially stearic acid, are preferred.

Further, as the metal of the fatty acid metal salt, zinc, lead,
Iron, copper, tin, cadmium, aluminum, calcium,
Various metals such as magnesium, nickel, cobalt, manganese, lithium and barium can be exemplified. Of the above metals, zinc is preferred.

The fatty acid metal salt is 0.0 per 100 parts by weight of the toner.
1 to 10 parts by weight is added.

Further, in order to improve the fluidity of the toner, the surface of the toner may be treated with a compound having a low surface tension such as a silane coupling agent, silicone or a fluorine compound. Furthermore, the powder toner may be heat-treated to smooth the corners of the toner, if desired.

The above powder toner has a particle size of 1 to 30 μm, preferably 5 to 30 μm.
It has a thickness of ~ 25 μm.

The electrostatic image developing toner of the present invention is used in combination with a replenishing powder toner, in particular, the electrostatic image developing toner described above and a start developer consisting of a carrier such as magnetic powder represented by iron powder. It is suitable as a powder toner for replenishment. The toner for the electrostatic image developer thus generated can also be used as the toner for the start developer. In that case,
The addition weight part y of the bulk density increasing fine powder substance to 100 parts by weight of the powder toner is preferably 0 ≦ y ≦ 1.25 (parts by weight). That is, in the powder toner for the starting developer, it is preferable that the fine powder substance is not added or the fine powder substance is added in the range of 1.25 wt% or less.

The second invention relating to the developing method will be described below.

In the developing method of the present invention, a start developer and a replenishing powder toner that is replenished when the toner concentration in the developer is lowered and the image density is lowered are used.

The start developer comprises toner and carrier, and various conventionally used developers can be used.
As the starting developer, a developer containing 2 to 10% by weight of toner and 90 to 98% by weight of carrier can be used.

Examples of the carrier include glass beads, an uncoated carrier such as oxidized or unoxidized iron powder, or a magnetic substance such as iron, nickel, cobalt, or ferrite, an acrylic polymer, a fluoropolymer, a polymer such as polyester. Although a coated carrier coated with (1) is used, an uncoated or coated magnetic material such as iron or ferrite is preferable in order to detect and control the toner concentration in the developer. The carrier usually has a particle size of 50 to 2000 μm.

As the replenishing powder toner, the electrostatic image developing toner of the first invention is used. In this toner for developing an electrostatic image, a fine powder substance capable of increasing bulk density is used as a powder toner.
Expressed in terms of added parts by weight to 0 parts by weight, as described above, z ≧ y + 0.05 (parts by weight) [y is a fine powder substance capable of increasing the bulk density with respect to 100 parts by weight of the powder toner in the starting developer. It is an addition weight part of. As described above, replenishment to the start developer not only increases the bulk density and packing density of the developer and prevents the toner from being spent, but also improves the fluidity of the toner. , The triboelectric chargeability and the image characteristics can also be improved.

Then, using the above-mentioned start developer and replenishing powder toner, development is carried out by a known development method such as the magnetic brush method which dies in FIG.

Taking the developing method shown in FIG. 3 as an example, the toner concentration in the developer (3), the amount of the fine powder substance added to the powder toner, and the magnetic sensor (7) are described.
The relationship with the sensor output voltage is as shown in FIGS. 1 and 2. However, FIG. 1 shows a developer using toner with an addition amount of the fine powder substance of 0.7 parts by weight, and FIG. 2 shows a developer with a toner concentration of 4.5% by weight. The hydrophobic silica (“Aerosil R972”, trade name of Nippon Aerosil Co., Ltd.) is used as the fine powder substance.

As is apparent from FIGS. 1 and 2, the sensor output voltage is inversely proportional to the toner concentration in the developer (proportional to the ratio of carriers). Further, the sensor output voltage is proportional to the addition amount of the bulk density increasing fine powder substance because the bulk density and the packing density of the developer are increased by adding silica which is the bulk density increasing fine powder substance.

Therefore, the sensor output voltage indicated by the start developer is V0,
It is assumed that the replenishment start voltage for replenishing the replenishment powder toner to control the toner concentration in the developer is V1, and the sensor output voltage produced by the replenishment powder toner is V2. (However, | V2-V1 | ≦ 0.5, V2> V0). Also, the toner density of the start developer is x0, the first replenishment start voltage V1
Assuming that the toner concentration in the developer is x1, and the toner concentration in the developer in which the toner in the start developer is replaced by the powder toner for replenishment is x2 (x0≈x2> x1), the start developer is As the toner is consumed and the toner density decreases as the toner is developed, and the ratio of the magnetic powder as the carrier increases, the sensor output voltage gradually increases and reaches V0 to V1. When the sensor output voltage reaches V1 and the toner concentration reaches x1, the replenishment powder toner is replenished.

Further, when the development and the replenishment of the replenishing powder toner are continued, the bulk density of the developer is gradually increased because the replenishing powder toner contains the fine powder substance capable of increasing the bulk density. Also grows. Then, in the state where the toner in the developer is substantially replaced by the powder toner for replenishment, if the toner concentration is the same, the sensor output voltage has a relation of V2> V0, so the replenishment start voltage V1 should be maintained. The powder toner for replenishment is replenished, and the toner concentration in the developer becomes higher than the toner concentration x1 in the developer at the start of the first toner replenishment. That is, unlike the case of using the replenishment toner to which the bulk density increasing fine powder substance is not added, although the sensor erroneously detects that the toner concentration during development is less than x1,
The actual toner concentration in the developer is higher than the toner concentration x1 at which the replenishing powder toner is replenished, and the toner concentration x0 in the start developer is maintained at approximately the same state (X0 ≈ X2) while developing. The process will proceed.

Moreover, since the replenishing powder toner contains a fine powder substance that improves the fluidity and triboelectricity of the toner, replenishment of the replenishing powder toner and subsequent toner development by repeated development. Can be prevented. Therefore, even if the powder toner for replenishment is replenished and the development is repeated, it is possible to prevent the toner characteristic from changing and the image density from being lowered. The bulk density increasing powder substance is consumed in a predetermined amount together with the toner during development.

In the magnetic brush development method, the predetermined voltage V1 at which the replenishing powder toner is replenished is appropriately set according to the toner concentration in the developer, the addition amount of the bulk density increasing fine powder substance, and the desired image density. However, it is preferable to set the relation between the powder toner for replenishment and the sensor output voltage V2 of the developer prepared with the same toner concentration as the starting developer to satisfy the following expression.

When | V2-V1 | ≦ 0.5 (V) | V2-V1 | exceeds 0.5 (V), it becomes difficult to control the toner concentration in the developer within a predetermined range.

When the above magnetic sensor is used, the sensor output voltage is usually ± 1.5 V depending on the developer and the developing device.
Since there are cases in which there is some variation, in order to accurately control the toner concentration in the developer, in particular, | V2-V1 | ≦ 0.25
It is preferable to set the sensor output voltage to about (V).

The electrostatic toner image developing toner of the first invention is preferably used as the powder toner of the start developer. In this case, since the toner in the start developer and the replenishing powder toner have substantially the same composition, the fluidity of the toner,
There is no difference in characteristics such as triboelectrification characteristics, and there is an advantage that a uniform image can be obtained even if a large number of sheets are copied.

The powder toner for the starting developer, which is used in combination with the powder toner for replenishment described above, contains the addition amount of the fine powdery substance for increasing the bulk density y to 100 parts by weight of the powder toner.
However, as described above, it is preferable that 0 ≦ y ≦ 1.25 (parts by weight).

On the other hand, the added weight part z of the fine powder substance with respect to 100 parts by weight of the powder toner for replenishment is z ≧ y + 0.05 in order to detect the toner density with a sensor particularly accurately and control the toner density within a predetermined range. Even within the range of (parts by weight), it is particularly preferable that z ≦ y + 0.50 (parts by weight).

That is, the added weight part z of the fine powder part to 100 parts by weight of the replenishment powder toner is the powder toner for the start developer
It is necessary to add 0.05 parts by weight or more to 100 parts by weight, but it is not preferable to add a large amount exceeding 1.50 parts by weight.

When the above magnetic sensor is used, it is preferable to use a carrier made of uncoated or coated magnetic powder, as described above, in order to control the toner concentration in the developer with high accuracy. In that case, it is preferable that the fine powder substance is made of a material insensitive to the sensor. That is, in the above example, it is preferable to be composed of a material that does not exhibit magnetism or does not magnetize, such as silica, aluminum oxide, or titanium oxide.

Further, the term "sensor for detecting the toner concentration in the developer" means that the powder density for increasing the bulk density of the developer is added to the powder toner for replenishment, and therefore the capacity of the developer is detected. A level sensor for detecting the weight of the developer or a sensor for detecting the electrostatic capacity of the developer may be used, but the above magnetic sensor capable of accurately controlling the toner concentration is preferable.

The method of replenishing the replenishment toner is not limited to the replenishment roller that continuously replenishes the replenishment toner as described above, and may be a method capable of intermittently replenishing the replenishment toner by a predetermined amount.

The toner is developed by a conventionally known developing method, for example, a cascade developing method, a hair brush developing method, a magnetic brush developing method, or the like.

<Example> Hereinafter, the present invention will be described in more detail with reference to Examples.

Example Preparation of Start Developer and Replenishing Toner 90% by weight of styrene-acrylic copolymer as binder resin, 7.5% by weight of carbon black as colorant, 1.5% by weight of polypropylene as anti-offset agent, and as charge control agent A powder toner having an average particle diameter of 12 μm was prepared by a conventional method using 1.0% by weight of the metal-containing dye of (1).

To 100 parts by weight of this powder toner, 0.7 parts by weight of hydrophobic silica (Aerosil R972, a product name of Nippon Aerosil Co., Ltd.) as a fine powder substance for increasing the bulk density was added, and the mixture was mixed with a Henschel mixer (Mitsui Miike). After stirring at high speed, surface treatment was performed, foreign matters, aggregates, etc. were removed by a vibrating screen to prepare a toner for a start developer. This toner and average particle size
A starting developer having a toner concentration of 4.5% by weight was prepared by uniformly mixing with a ball mill using a 80 μm ferrite carrier (manufactured by Nippon Iron Powder Co., Ltd.).

Further, to 100 parts by weight of the powder toner, 1.5 parts by weight of the above-mentioned hydrophobic silica was added, high-speed stirring was carried out with a Henschel mixer, surface treatment was performed, and foreign matters, aggregates, etc. were removed by a vibrating sieve, and a powder for replenishment was added. A body toner was prepared.

Running test The above-mentioned start developer was stored in a developing device of a DC-111 type copying machine manufactured by Mita Kogyo Co., Ltd. equipped with a magnetic sensor, and it was left idle for 3 minutes to measure the sensor output. . For reference, a developer containing 4.5% by weight of replenishment toner was prepared in the same manner as the above-mentioned start developer, and the sensor output was measured in the same manner as above, and showed 8.5V. In the above copying machine, the toner replenishment start voltage at which replenishment toner is replenished is set to 8.5V.

Then, the start developer is stored in the developing device of the copying machine, the replenishing powder toner is stored in the hopper arranged above the developing device, and A- When a running test was performed using 4 sizes, the results shown in FIG. 4 were obtained. That is, the initial sensor output voltage shows 6.5V,
The image density was 1.5. After that, when copying was continued without replenishing the powder toner for replenishment, the sensor output voltage increased, the toner concentration in the developer decreased, and the image density gradually decreased. Then, when 100 sheets were copied, the sensor output voltage was 8.5 V, the toner concentration in the developer was 3% by weight, and the image concentration was also reduced to 1.25. In addition,
As described above, since the sensor output voltage reached the toner replenishment start voltage, the replenishment powder toner was replenished. After that, when copying was continued, powder toner for replenishment was replenished from the hopper to the developing device according to the consumption of toner in the developer while maintaining the toner replenishment start voltage of 8.5 V, The toner concentration gradually increased from 3% by weight, and at the 1,000th copy, the toner concentration in the original developer was restored to 4.5% by weight, and the image concentration was also restored to the initial image concentration of 1.5. .

Also, when the sensor output voltage 8.5V and the toner concentration in the developer of 4.5% by weight were maintained and the development was continued, 2
An image density of 1.43 was shown when copying 000 sheets.

Comparative Example On the other hand, without using the replenishing powder toner of the present invention,
A running test was conducted in the same manner as in the above-mentioned example using the above-mentioned toner for start developer as the replenishing toner, and the result as shown in FIG. 5 was obtained. That is,
At the 100th copy, the image density drops to 1.25 and
After that, development was carried out without recovering the toner density and the image density in the developer to the original values, and the 20,000th copy image showed an image density of 1.2.

<Effects of the Invention> As described above, according to the toner for developing an electrostatic charge image of the first invention, the powder density toner is added with the predetermined addition weight of the bulk density increasing fine powder substance for increasing the bulk density of the developer. Since it is added within the range of parts, the fluidity of the toner is improved, the spent of the toner can be prevented, and the charging characteristics and image characteristics of the toner do not change. Therefore, even if development and replenishment are repeated,
It is possible to form a high-quality image for a long time without causing the spent toner. Further, a toner suitable for replenishment can be easily prepared simply by adding the above-mentioned bulk density increasing fine powder substance to the powder toner.

Further, according to the second occurrence, as the replenishing powder toner, the toner to which the bulk density increasing fine powder substance for increasing the bulk density of the developer is added within the predetermined addition weight part is used. By supplying the powder toner for use, the bulk density and the packing density of the developer can be increased and the spent of the toner can be prevented. Also, when the powder toner for replenishment is replenished, the sensor detects the toner concentration in the developer pseudo low, so that the powder toner for replenishment is further replenished and the toner concentration in the developer is substantially reduced. It can be developed in a high state. Therefore, while maintaining the toner concentration in the developer within a predetermined range, a high-quality image can be formed for a long period of time without lowering the image concentration, which is a unique effect of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the toner concentration in the developer and the sensor output voltage, FIG. 2 is a diagram showing the relationship between the addition amount of the fine powder substance in the developer and the sensor output voltage, and FIG. FIG. 4 is a schematic diagram showing a developing mechanism by a magnetic brush method, FIG. 4 is a diagram showing a result of an example, and FIG. 5 is a diagram showing a result of a comparative example.

Continuation of the front page (56) Reference JP 59-220765 (JP, A) JP 61-28958 (JP, A) JP 59-137305 (JP, A) JP 59-100454 (JP , A) JP-A-60-216367 (JP, A) JP-A-54-76166 (JP, A)

Claims (8)

[Claims] 1. A powder toner to be replenished to a starting developer comprising a powder toner and a carrier, wherein a bulk density increasing fine powder substance for increasing the bulk density of the developer is a powder toner for replenishment. A toner for developing an electrostatic charge image, characterized in that the toner is added within a range of added weight part z satisfying the following formula to weight part. z ≧ y + 0.05 (parts by weight) [y is the part by weight of the fine powder substance capable of increasing the bulk density with respect to 100 parts by weight of the powder toner in the starting developer. ] 2. The static toner according to claim 1, wherein the added weight part z of the fine powder substance to 100 parts by weight of the powder toner for replenishment is within the range of 0.05 ≦ z ≦ 2 (parts by weight). Toner for charge image development. 3. The addition weight part y of the fine powder substance to 100 weight parts of the powder toner in the starting developer is within the range of 0 ≦ y ≦ 1.25 (parts by weight). Claims 1 or 2
6. The toner for developing an electrostatic charge image according to the item. 4. Any of claims 1 to 3 wherein the finely powdered material is selected from the group consisting of silica having a bulk density of 30 to 200 g / l, aluminum oxide and titanium oxide. The toner for developing an electrostatic image as described in 1. 5. The toner for developing an electrostatic charge image according to claim 1, wherein the fine powder substance has a particle size of 1 to 100 mμ. 6. An electrostatic charge image is developed using a start developer composed of powder toner and a carrier, and when a toner concentration in the developer drops below a predetermined value, detection by a sensor for detecting the toner concentration. In the method of developing an electrostatic charge image, which continues developing while adjusting the toner concentration in the developer within a predetermined range by replenishing powder toner for replenishment based on a signal, An electrostatic charge, characterized in that a bulk density increasing fine powder substance for increasing the bulk density of an agent is added to 100 parts by weight of powder toner in an addition weight part z range satisfying the following formula. Image development method. z ≧ y + 0.05 (parts by weight) [y is the part by weight of the fine powder substance capable of increasing the bulk density with respect to 100 parts by weight of the powder toner in the starting developer. ] 7. The method of developing an electrostatic charge image according to claim 6, wherein the carrier is magnetic powder. 8. The method for developing an electrostatic charge image according to claim 6 or 7, wherein the sensor is a magnetic sensor.