JPS5988749A - Developing agent - Google Patents

Abstract

PURPOSE:To obtain a carrier which is stable and is negatively electrostatically charged by incorporating styrene more in the carrier of a developing agent consisting of a magnetic carrier contg. carbon black having specific pH or above and styrene polymer and a toner cong. a styrene-acryl copolymer and a coloring agent. CONSTITUTION:A developer wherein % of the styrene monomer in the carrier is larger by >=10% than % of the styrene monomer in the toner is prepd. of a developer consisting of the magnetic carrier which is a copolymer resin of 60wt% a styrene monomer and a monomer, such as (meth)acrylate, acrylonitrile or the like, and has 5,000-200,000 average Mw., 2,000-1000,000 average Mn, and 10- 40mu average grain size and contains magnetic powder and carbon black having >=5 pH as well as a toner which contains a copolymer resin of 20-80wt% styrene monomer and (meth)acrylate monomer and a coloring agent (pigment or dye) and has 5,000-20,000 average Mn, 30,000-500,000 average Mw. and 40- 70 deg.C glass transition temp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer for developing electrostatic latent images, and more particularly to a two-component dry developer comprising carrier particles and toner.

Methods of obtaining copies by electrophotography or electrostatic recording are known. This method develops an electrostatic latent image formed on a photoconductor or electrostatic recording medium with a developer to obtain a toner image.
This toner iron is transferred to transfer paper and then fixed to obtain a copy.

As this developer, a developer consisting of two components, a carrier and a toner, is generally used.

By stirring the developer in the developer, frictional electrification is generated between the carrier and the toner, giving the toner an electric charge of the opposite polarity to the electrostatic latent phenomenon and adhering to the latent image. Develop.

Conventionally, among such developers, Q Egiaria has been used which has a particle size larger than that of toner. but.

When a carrier whose particle size is larger than that of the toner is used, there is a drawback that one-tone reproduction is poor (and toner tends to adhere to the background area).

In recent years, in order to solve these drawbacks, developers have been proposed in which the particle size of the carrier is approximately the same as that of the toner. For example, as a developer used in magnetic brush development, the average particle size of the binder resin and magnetic powder is 5 to 3.
A developer is known in which a small particle diameter carrier of 0 μm is mixed with a toner having an average particle diameter of 5 to 20 μm. This kind of reality
Although the electrostatic agent solves the above-mentioned drawbacks, it has a narrow tolerance range due to the amount of charge required for the toner to adhere to the latent image (if the amount of charge is too large, the image density decreases and the background of the carrier Also, if the amount of charge is too small, toner scattering or toner adhesion to the background area may occur.Also, because the tolerance range is narrow, such phenomena occur even under normal phenomenon conditions. It was something.

In addition, in recent years, organic photoreceptors have been used as photoreceptors, and in this case, the a1 polarity is negative and the toner must be positively charged, that is, the carrier must be configured to be negatively charged. As an attempt to negatively charge a carrier using the aforementioned developer having a small carrier particle size, a method is known in which a charge control agent is added to the toner. In this method, carbon black, which is usually added to toner, is negatively chargeable, and even if a charge control agent is added, it is difficult to obtain a positively chargeable toner (and it is difficult to obtain a toner with uniform chargeability). For this reason, the present inventors have investigated the use of the same binder resin in the toner and carrier as a phenomenon agent using a small particle size carrier, but since the carrier is used repeatedly in the current device, When used for a long time, the amount of charge changes, which affects the developed image.

The purpose of the present invention is to provide a developer having a size of s5, which has the disadvantages of the conventional ones, and which prevents the reduction in image density and the adhesion of background areas in developers using small particle diameter carriers. This is what we provide. A further object of the present invention is to provide a developer in which the carrier is stable and can be negatively charged.

The purpose of the present invention is to obtain a styrenic polymer, magnetic powder and PH5
It is made of a mixture of a magnetic carrier containing the above carbon black and a toner containing a styrene-acrylic copolymer and a colorant, and the styrene amount ratio of the styrene polymer in the magnetic carrier is styrene-acrylic in the toner. This can be achieved by using a dry developer characterized in that the ratio of styrene content is greater than that of the acrylic copolymer.

The styrene polymer used as the binder resin component of the magnetic carrier used in the present invention has a sterene content of 60 wt% or more. 1 "The styrenic polymer obtained by combining has a molecular weight of @-5,000~2
00,000, preferably 50,00 (1-150.
000, Mu = 2,000 to 100,000, preferably 20,000 to 50,000, and the glass transition temperature (Ty) is 30 to 100° C1, preferably C5
It is preferable to use one with a temperature of 0 to 100°C. The content of this styrene polymer in the magnetic carrier has a great effect on the saturation magnetic flux density of the gearia particles, so care must be taken. Blend weight ratio: 20:80 to 60:4
0. Preferably the ratio is 2°:80 to 40:60. This is because if the content of the styrene polymer is less than 20 weight vertical parts, the binder is too small (too much, the binding ability cannot be obtained and the carrier particles may become too large), resulting in the problem of poor production. This is because if the amount exceeds 100%, sufficient magnetism will not be obtained and transportability will deteriorate.In addition, for styrene-based polymers, styrene, vinyltoluene, halokenated styrene, α-methylstyrene, etc. Polymer or acrylic ester, methacrylic ester as required.

Copolymers with copolymerizable monomer components such as butadiene, acrylonitrile, maleic anhydride/acid, vinyl chloride, polyester, etc. can be used. Among these, those using acrylic esters and methacrylic esters as copolymerization components are preferred. This is because by using a styrene polymer similar to the styrene-acrylic copolymer used in the toner, the toner can easily reach the acceptable range of the amount of charge required to adhere to a@. .

The carrier magnetic powder used in the present invention suitably has an average particle size of 0.1 to 3 μm. As magnetic powder,
Fine powders of magnetite, ferrite, iron, nickel, chromium dioxide, γ-hematite, cobalt, etc. can be used. Among them, magnetite is preferred because it is inexpensive and can be used stably.

The carbon black used in the carrier in the present invention is optimally one having a pH of 5 or more.

If carbon black with kX and PH of 5 or less is used, the negative chargeability of the carrier becomes thick.

This is because the image density is low F and the carrier adheres to the background area. The effects of carbon black in the carrier include control of chargeability and conductivity of the carrier. P.H.
By using carbon black of 5 or more, it becomes possible to control the amount of charge necessary for the toner to adhere to the AF image within a narrow tolerance range. In addition, the carbon black in the carrier quickly releases the residual charge in the carrier that occurs when the toner moves to the reservoir.

It becomes possible to impart stable charging properties to toners that are sequentially added. The blending amount of carbon black is 1 to 10 wt%, preferably 2 to 8 wt%, based on the mixture of binder resin and magnetic powder. The reason for this is that if the amount of carbon black is less than 1 wt%, the chargeability control and conductivity control described above cannot be achieved.

Moreover, if it exceeds 10 wt%, the conductivity becomes thick, and carrier adhesion to the photoreceptor occurs due to electrostatic induction from the latent f-phase, and the charging effect imparted to the toner decreases, resulting in toner scattering,
This is because the toner adheres to the background area. Specific carbon blacks used in the carrier include furnace black, channel black, acetylene black, thermal black, etc., and commercially available ones can be used.

In addition, dyes, charge control agents, etc. may be added as necessary.

The carrier of the present invention can be mixed with a toner to obtain stable negative chargeability, and can withstand long-term use, especially without carrier adhesion to the photoreceptor.The carrier has an average particle size of 10 to 40 μm, preferably 20 to 35 μm.If it is less than 10 μm, the magnetic force per gear 9 will be small.

If the thickness exceeds 40 μm, the sharpness of the image will be lost and the image quality will deteriorate, and when the toner density is increased, the toner will tend to adhere to the background area. .

The carrier of the present invention can be produced by mixing, pulverizing and then classifying, dissolving a styrene polymer in a solvent, spray drying a suspension in which magnetic powder and carbon black are dispersed, and then classifying the styrene polymer. When polymerizing the system polymer, any method of dispersing magnetic powder or carbon black in a monomer may be used.

The toner used in the present invention is configured so that it can be positively charged and has good fixing properties, particularly hot roll fixing properties. The binder resin for the toner is preferably a styrene-acrylic copolymer, particularly a styrene-acrylic copolymer with a styrene content of 20 to 80 wt%, and may also be a ternary or quaternary copolymer with other monomers. . The copolymerization reaction includes random copolymerization, block copolymerization, graft copolymerization, or a combination thereof. Examples of the styrene monomer of the styrene-acrylic copolymer include styrenes such as styrene, vinyltoluene, α-methylstyrene, and chlorostyrene; examples of the acrylic monomer include methyl methacrylate and ethyl methacrylate.

Examples include monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl 9-acrylate, and dodecyl acrylate. Also polyethylene,
Examples include graft copolymers of polypropylene, ethylene-propylene copolymers, and ethylene-acetic acid e-vinyl copolymers, and graft copolymers of the above-mentioned crystalline polymers, styrene-acrylics, and polyesters. Other resins may also be used in combination. When mixing other resins to form a binder resin, the styrene-acrylic polymer is configured to be the main resin component. The styrene-acrylic copolymer has a glass transition point (Tp) of 40 to 70°C, a number average molecular weight of 5,000 to 20,000, and a weight average molecular weight of 30,000 to 500,000. Manufactured by fA.

The colorant used in the toner may be any suitable pigment or E-technical dye, with sufficient pigment to color the binder resin, generally up to 25 wt of the toner, preferably 1.
As the coloring agent used in an amount of ~20wt, for example, Car1? Examples include black dye, nigrosine dye, aniline blue, phthalocyanine/blue, and the like.

Further, in order to impart positive chargeability to the toner, it is preferable to add an imperial control agent such as a quaternary ammonium salt or a nigrosine dye.

The average particle size of the toner is preferably 5 to 20 μm.

This is because if the average particle size is less than 5 μm, the fluidity of the toner will deteriorate and the toner will adhere to the background area, and if the average particle size exceeds 20 μm, the sharpness of one image will be lost and the image quality will deteriorate. It is. The toner manufacturing method is similar to the carrier manufacturing method described above.

The toner used in the present invention exhibits stable positive (tF?W) properties when mixed and stirred with the above-described carrier.

In the present invention, the styrene content ratio of the styrene polymer used in the magnetic carrier (i.e., the weight percentage of the styrene component)
is required to be at least 10 wt % greater than the styrene binding (ie, the weight % of the styrene component) of the styrene-acrylic copolymer used in the toner. This is because when the styrene number ratio of the carrier is high, m of the carrier surface is
The styrene polymer coats the magnetic powder with a thickness of at least several tens of microns, and the styrene-acrylic copolymer of the toner and the styrene polymer of the carrier come into frictional contact. This is because when the styrene liquid ratio of the carrier is high, it is possible to give the carrier stable negative elasticity. When the styrene content ratio of the styrene-combined body of the carrier is less than the styrene content ratio of the styrene-acrylic copolymer of the toner, or the total is at most 10
When the amount is less than % by weight, the toner's charging property decreases, toner scattering and toner adhesion to the background area occur, resulting in deterioration of image quality.

In the developer of the present invention, the toner and carrier are mixed in a ratio of 2:98 to 40:60, preferably 5:95 to 35:6.
It can be used in any weight ratio within the range of 5. Toner is 2wt
If it is less than 40 wt %, the one-plane image density will be insufficient, and if it exceeds 40 wt %, toner scattering and toner adhesion to the background will occur. Further, in the developer of the present invention, colloidal silica or the like may be added for the purpose of improving the fluidity of a lubricant and toner using a cleaning method. As a cleaning lubricant, for example, a fine powder of fatty acid, fatty acid metal salt, polyolefin, etc. is added to the toner in an amount of 2 wt% or less, preferably 0.1 to 1. It is used by adding Owt%.

The developer of the present invention is preferably used for developing a negative latent image formed on a CdS, ZnO1 organic photoreceptor. It can also be used as a reversal developer for positive latent images on Ses Se alloy photoreceptors.

In one example of a developing method using the developer of the present invention, an electrostatic latent image formed on a photoreceptor or an electrostatic recording medium is developed using a magnetic brush developing device. In the developer of the present invention, since the carrier is negatively charged and the toner is positively charged, the toner is attracted to the negative latent image, development is performed, and the toner image is transferred to the transfer paper and then fixed. .

In the developer of the present invention, the amount of styrene in the binder resin of the carrier and toner is contained in a larger proportion in the carrier, and carbon black with a pH of 5 or more is contained, and the charge amount is within an allowable range. It can be applied to a narrow range of development methods. Another effect is that the toner charge amount is stabilized, and as is clear from FIG. 1, the image quality equivalent to printing is maintained even after 100,000 copies are made.

In FIG. 1, A indicates that the amount of toner waste is stable when continuous copying is performed using the developer according to the present invention. For comparison, similar measurements were performed on developer B, in which the amount of styrene in the styrene polymer in the carrier was lower than that in the toner. In addition, developer C, which uses carbon black with a pH of 5 or less in the carrier, had a high toner charge, and the charge rate increased further with copying. , the carrier adhered to the photoreceptor, and the amount of carrier contributing to development decreased, resulting in a decrease in image density.

Next, the present invention will be specifically explained using examples.

Example 1 Preparation of carrier Stre/-n-butyl methacrylate
65'0) 35 parts by weight magnetite 65 parts by weight carbon black (BLACKPEARL manufactured by Giyabonoto)
S 880, )') 18.0 ) 5 Electrical welded parts were mixed, melted and kneaded, pulverized, and classified for 1 time to obtain an average particle size of 2.
A magnetic carrier of 4.0 μm was obtained.

Example 2 Preparation of carrier styrene-acrylic rl! 22-ethylhegicyl copolymer (styrene content 85 wt%, M'W = 150. old) 0,
Tg60℃) 25 parts by weight magnetite 75 parts by weight Carbo Black (RAVEN1500 manufactured by Columbia,
PH6) 3 parts by weight were mixed and carried out in the same manner as in Example 1 to obtain a gearia with an average particle size of 22.5 μm.

Example 3 Preparation of carrier Styrene-n-butyl acrylate copolymer (styrene content 80 wt%, Ra = 50,000, Tg 55°C) 30 parts by weight Magnetite 70 parts by weight Carbon black (RAVEN5250 manufactured by Columbia)
, PH2) were mixed in the same manner as in Example 1 to obtain a carrier having an average particle size of 26 μm.

Example 4 Preparation of toner Stere/-ethyl methacrylate copolymer (styrene l
70 wt% -Mw =407000, Tg 7
0°C) 93-layer vertical carbon black (REGAL330, P made by Gearbot)
H8,5) 5 parts by weight of nigrosine dye and 2 parts by weight were mixed and the same procedure as in Example 1 was carried out to obtain a toner having an average particle size of 11 μm.

Example 5 Preparation of toner Polyglobylene-sterene-methacrylic+II n-butyl graft copolymer (styrene content 5515-wt%, Mw = 30,000, Tg 55°C)
91 parts carbon black 8 parts quaternary ammonium salt 1 part by weight were mixed and the same procedure as in Example 1 was carried out to obtain an average particle size of 9.5 Jim.

A copying test was conducted using the carrier and toner produced in Examples 1 to 5 above as the developer in Examples 1 to 6 in combinations shown in Table 1.

The test method was to use a magnetic brush phenomenon device equipped with an electromagnetic agent stirring device to continuously generate one negative polarity electrostatic phenomenon, and test 2,000 sheets, 10,000 sheets, 20,000 sheets, respectively. In addition to measuring the toner charge in the developer at the time of 30,000, 50,000, 70,000, and 100,000 sheets, the image on the transfer paper and the developer on the surface of the photoreceptor before transfer are transferred to tape. The results are shown in Tables 1 and 2.

The image quality of the carrier and toner combinations of Examples 1-5.2-4.2-5, which had no abnormalities related to the present invention among the phenomena of Examples 1 to 6 in the table, was excellent in gradation and density. High (no fogging on the skin 17- 16- 18-

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the amount of toner charge in the developer and the number of copies. Symbols in the figure: A... Developer of the present invention; B... Developer in which the styrene liquid ratio in the toner is higher than the styrene amount ratio in the carrier; C...
...A developer in which the carbon black in the carrier has a pH of 5 or more.

Claims (1)

[Claims] Consisting of a mixture of a magnetic carrier containing a styrene polymer, magnetic powder, and carbon black with a pH of 5 or more, and a toner containing a styrene-acrylic copolymer and a colorant, the styrene polymer in the magnetic carrier A dry type developer characterized in that the amount ratio of styrene is greater than the amount ratio of styrene in the styrene-acrylic copolymer in the toner.