JPH03168759A - Toner for developing electrostatic charge image and developer - Google Patents

Abstract

PURPOSE:To obtain a uniform image density by specifying the ratio of the volume average diameter of the toner and the diameter corresponding to the equiprojected area circle of the toner when this toner is triboelectrostatically charged by a friction member. CONSTITUTION:The fine granular toner is used by being triboelectrostatically charged by the friction member. The ratio Dp97.5/Dv50 of the volume average diameter Dv50 of this toner and the diameter Dp97.5 corresponding to the equiprojected area circle of the toner when this toner is triboelectrostatically charged by the friction member is specified to <=1.6. The volume average diameter Dv50 is the grain size corresponding to the ball of the volume equal to the volume of the toner particles of the size in which 50% of the number of the toner particles measured by integrating the toner particles of the small grain sizes is incorporated in the grain size distribution of the toner simple substance. The grain size incorporated therein with 97.5% of the number of the toner particles measured by projecting the triboelectrostatically charged toner particles separated from a developer and dropped onto paper by an image analyzer, measuring the grain size corresponding to the circle of the area equal to the area of this toner particle and integrating the number from the min. grain size is defined as Dp97.5. The generation of the unequal images by the coarse toners is obviated in this way and the uniform solid images are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a toner used in an image forming apparatus such as an electrophotographic copying machine and a developer using the toner. In particular, the present invention relates to a toner and a developer using the toner for making the image density uniform.

(Prior Art) In an image forming device such as an electrophotographic copying machine, a developer containing a binder resin and a coloring agent is generally used as a developer for visualizing an electrostatic latent image formed on a photoreceptor using a dry development method. A fine toner consisting of additives is used. The toner obtains a desired charge by friction with the friction member, and is developed by adhering to the electrostatic latent image formed on the photoreceptor through charging and exposure steps. The obtained toner image is transferred to a support such as transfer paper, and then fixed onto the support by a fixing means. In this way, a copy of the original is obtained.

Conventionally, the particle size has been reduced to 1 for the purpose of making the image density of copies uniform.
Toner particles of about 0 μm are used. (B) Even if toner with such a uniform particle size is used, the particle size of the toner is low, and the shape and fluidity of the toner particles are low. Due to variations in charging characteristics and other factors, toner images formed by dry development methods have problems in that the solid image portions are non-uniform and have poor graininess. In order to solve this problem, Japanese Patent Application Laid-Open No. 62-284363
In the publication, we focused on the correlation between toner particle size and fluidity,
It has been proposed to use toner with a degree of cohesion of 1.5 or less. Cohesion degree refers to the ratio of the average particle size of the toner particles resulting from free fall from the toner cloud to the average particle size of the toner used (cohesion degree = cloud average particle size / average particle size of the toner used). diameter). However, the degree of cohesion is 1.5
Even when the following toners were used, the uniformity of the image density was not sufficient, and the image density was uneven, especially in the intermediate tones, and was not fully satisfactory.

According to the findings of the inventor of the present invention, the uniformity of a solid image is influenced not only by the physical properties of the toner alone, but also by the overall physical properties during development, including the triboelectric charging characteristics between the toner and the friction member. it is conceivable that.

The present invention is intended to solve the above-mentioned problems, and its purpose is to provide a toner and a developer that can provide uniform image density by evaluating the toner as a triboelectrically charged toner.

(Means for Solving the Problems) According to the present invention, there is provided a toner for developing an electrostatic image in which a fine particle toner is triboelectrically charged by a triboelectric charging member, and the volume average diameter Dv50 of the toner is Equivalent projected area circle equivalent diameter Dpqt. of toner when triboelectrically charged by a friction member. Ratio to s D P 97. S/Dv5
. Provided is a toner in which the particle diameter is 1.6 or less.

Furthermore, according to the present invention, there is provided a developer for developing electrostatic images containing the above toner and carrier.

(Function) The reason why the overall physical properties of the toner as a developer in a triboelectrically charged state, rather than the physical properties of the toner alone, influences the image characteristics is presumed to be as follows. Toner has
Contains various additives such as colorants and charge control agents. Therefore, when the toner and the friction member are frictionally charged, the toner may be charged to the opposite polarity depending on the type of Pj friction member used. These toners charged with opposite polarities adhere to each other and aggregate to form coarse particles. Therefore, even if the toner alone has a uniform particle size, depending on the type of friction member used, the developer may contain coarse toner particles, which may cause the final image to be uneven. do.

This was confirmed by measuring the charge distribution of the toner in a state where the fine particle toner and the friction member were frictionally charged, and by examining the correlation between the charge distribution of the toner and the uniformity of the solid image area. . Based on this, the present invention was completed by focusing on the charging characteristics of toner and evaluating not only the toner itself but also the toner triboelectrically charged by the friction member.

The toner of the present invention has a volume average diameter DV of the toner alone. and the equivalent projected area circle diameter D of the toner when the friction member is triboelectrically charged p91. Regarding 5, I am satisfied with the second one. The triboelectrically charged toner is obtained as follows. For example, when the friction member is a carrier, nitrogen gas is sprayed onto a developer consisting of toner and carrier to separate the charged toner from the carrier due to friction with the carrier, and then an electric field is applied to the toner so that it falls onto the paper. Obtained by letting

DP*? ．． s/Dv5. ≦1.6 The volume average diameter Dv50 in the formula is the particle size distribution obtained as a result of measuring a single toner with a Coulter counter, where 50% of the number of measured toner particles is accumulated from toner particles with a small particle size. The particle size corresponds to a sphere having the same volume as the volume of toner particles of the included size. Equivalent projected area circle equivalent diameter D P 9 in the formula? ．． S is determined as follows. The triboelectrically charged toner particles separated from the developer and falling onto the paper are projected by an image analysis device, and the particle diameter corresponding to a circle having the same area as the toner particles is measured. Then, the particle size that includes 97.5% of the number of measured toner particles is calculated from the minimum particle size by D P 9? ．． It is defined as s. Toner with this value exceeding 1.6 contains coarse particles that adhere and aggregate due to reverse polarity charging as a result of frictional charging with a friction member.

(Preferred Embodiment of the Invention) The toner used in the present invention is a powder toner in which additives such as colorants are dispersed in a binder resin, which has been conventionally used in dry development methods.

Binder resins include styrene polymers, acrylic polymers, styrene-acrylic polymers, chlorinated polyethylene, polypropylene, olefin polymers such as ionomers, polyvinyl chloride, polyester, polyacid, polyurethane, and epoxy. resin, diacryl phthalate resin,
Various polymers such as silicone resin, ketone resin, polyvinyl butyral resin, phenol resin, rosin-modified phenol resin, xylene resin, rosin-modified maleic acid resin, and rosin ester are used. These resins are arbitrarily selected depending on the fixing method and other required properties. Among these, styrene polymers, acrylic polymers, and styrene-acrylic polymers are preferred, and styrene-acrylic polymers are particularly preferred. The weight average molecular weight of these resins is preferably from 30,000 to 200,000, particularly preferably from soooo to 150,000. One type of polymer or a mixture of two or more types may be used.

As the coloring agent to be dispersed in the binder resin, the following known pigments and dyes used in this field (hereinafter simply referred to as colored pigments) can be used.

Black pigments: carbon plaque, acetylene black, lamp black, aniline black.

Yellow pigments; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, teftol yellow S1 Hansa yellow 10G, benzidine yellow G, quinoline yellow lake, permanent yellow NGO, tartrazine rake.

Orange pigment; red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, penzidine orange G1 indanthrene brilliant orange GK, red pigment; red pigment, red cadmium red, red lead. , mercury cadmium sulfide, Permanent Orange 4R, Vilazolone Red, Lysole Red, Watching Red Calcium Salt, Lake Red D1 Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B. , purple pigment; manganese purple, first violet B1 methyl violet lake.

Blue pigments; navy blue, cobalt blue, American blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, first sky blue, indansemb blue BC
, green pigment; chrome green, chromium oxide, pigment green B1
Malachite Green Lake, Fananore Yellow Green G. White pigments: zinc white, titanium oxide, antimony white, zinc sulfide.

Constitutional material; Palite powder, barium carbonate, clay, silica, white carbon, talc, aluminum white.

These color pigments may be used alone or in combination of two or more. The amount of color pigment added is 1 to 3 parts per 100 parts by weight of the binder resin in order to obtain a sufficient toner image density.
0 parts by weight is preferred, and 2 to 20 parts by weight is more preferred.

When the above-mentioned toner is a magnetic toner, a magnetic material pigment can be blended together with or in place of the colored pigment.

As the magnetic material pigment, a fine powder of a known magnetic material is used. For example, triiron tetroxide (Fe304), iron sesquioxide CT Fez Os), iron zinc oxide (ZnFe
zOn), iron yttrium oxide (Y.Fe50+z),
Cadmium oxide (Cdz Fes O+z), steel oxide (CuFez Oa), iron lead oxide (PbFe+z0)
．． ．． ), iron manganese oxide (MnFet 04 ), neodymium iron oxide (Nd Fe 03 ), barium iron oxide (B a Fe 12019), magnesium iron oxide (MgFe.O.), lanthanum iron oxide (LaF
Examples include fine powders such as eO:+), iron powder (Fe), cobalt powder (Co), and nickel powder (Ni). The amount of these magnetic material pigments added is 5 to 7 parts per 100 parts by weight of the binder resin.
0 parts by weight is preferred, and 20 to 50 parts by weight is more preferred.

A charge control agent may also be included to control the charge of the toner. Examples of charge control agents include oil-soluble dyes such as nigrosine dye, oil black, and soubiron black; naphthenic acid, salicylic acid, octylic acid, higher fatty acids, and resin acids such as manganese, iron, cobalt, nickel, lead, zinc, and cerium. , metal soaps that are metal salts such as calcium;
Metal-containing ab dyes; pyrimidine compounds; and metal chelates of alkyl salicylic acids are used. Among these, alcohol-soluble ones are particularly preferably used.

These charge control agents are used in an amount of 0 per 100 parts by weight of the binder resin.
．． 1 to 5 parts by weight is preferably used.

Furthermore, the above-mentioned toner can be blended with various compounding agents known per se that are used in this field.

For example, as an anti-offset agent, various waxes such as low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, etc.; olefinic polymers having 4 or more carbon atoms; fatty acid amides; silicone oil, etc. may be used in amounts ranging from 0.5 to 100 parts by weight per 100 parts by weight of the binder resin. It is preferably contained in an amount of 15 parts by weight.

A toner is manufactured using any of the known manufacturing methods using the toner materials as described above. The toner of the present invention may be either a spherical toner obtained by a polymerization method and a spray drying method, or an amorphous toner obtained by a pulverization method, as long as it satisfies the conditions specified in the present invention.

The above conditions mean that if the toner of the present invention and a friction member are appropriately combined, the volume average diameter Dv50 of the toner alone and the equivalent projected area circle diameter D P 97 of the toner when frictionally charged by the friction member. The ratio with 5 satisfies the second condition.

DP 9? ．． When S/DV so≦1.61.6, a large amount of coarse toner particles adhered and aggregated due to reverse polarity charging etc. will be contained, causing image unevenness, toner spots, white spots, etc.

Further, the toner may be surface-treated with a known surface treatment agent such as an inorganic powder such as silica, alumina, titanium oxide, or tin oxide, or a resin powder such as styrene, acrylic, or silicone.

Examples of the friction member used in the present invention include conventionally known various metal and resin doctor blades, conductive metal sleeves, and various carriers.

Examples of carriers include glass beads, oxidized or unoxidized iron powder, uncoated carriers such as ferrite: iron, nickel,
Magnetic materials such as cobalt and ferrite are combined with styrene polymers,
Acrylic polymer, silicone resin, phenolic resin,
Examples include coated carriers coated with one or more resins such as melamine resin, fluororesin, and polyester. Generally, ferrite particles coated with a high-resistance resin are preferably used because they can form a soft magnetic brush.

The ferrite particles are preferably spherical, with a particle size of 20 μm to 150 μm, particularly 50 μm to 120 μm.
It is desirable that it be in the range of m.

As ferrite, iron zinc oxide (ZnFe.04),
Yttrium iron oxide (Y3Fe,0,2), oxidized yttrium
(C di F es O+z), iron copper oxide (C
uFez 04 ), iron lead oxide (P b Fe 12
019), iron manganese oxide (MnFe, 04), neodymium iron oxide (NdFeO, ), barium iron oxide (BaF
e +gO+q), magnesium iron oxide (MgFe
．． 04), ferrite particles containing one or more compounds selected from compounds such as lanthanum iron oxide (LaFeO, ) are used. Especially Cu, Zn, Mg,
A soft ferrite containing one, preferably two or more metal components selected from the group consisting of Mn and Ni, such as copper-zinc-magnesium ferrite, is used.

The toner of the present invention is used in combination with a friction member appropriately selected so that the toner satisfies the conditions of the present invention. When the carrier and developer are used, the toner concentration is between 2 and 1.
0%, preferably 3-8%.

Since the developer of the present invention does not contain coarse toner particles that have adhered and aggregated due to reverse polarity charging, etc., the image density of copies is uniform.

(Experiment example) Hereinafter, the present invention will be specifically explained based on experimental examples.

Hereinafter, parts refer to parts by weight unless otherwise specified.

Preparation of toner A: 100 parts of styrene-acrylic copolymer as a binder resin,
8 parts of carbon black (Printex, manufactured by Degussa) as a coloring agent, 1 part of Bontron S-34 (manufactured by Orient Chemical Co., Ltd.), a metal-containing monoazo dye, as a charge control agent, and low molecular weight polypropylene as an offset inhibitor. Two parts of Viscol 550P (manufactured by Sanyo Chemical Industries, Ltd.) were melt-kneaded, pulverized, and classified to obtain a toner having a certain particle size range.

The volume average diameter of this toner was measured using a Coulter counter and was found to be Dv50=11.2 μm.

Preparation of toner B: 100 parts of styrene-acrylic copolymer as a binder resin,
Carbon black (MA-1 manufactured by Mitsubishi Kakai) was used as a coloring agent.
00) 7 parts, 1.5 parts of Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), which is a metal-containing monoazo dye, as a charge control agent;
Two parts of Viscol 550P (manufactured by Sanyo Chemical Industries, Ltd.), which is a low molecular weight polypropylene, was melt-kneaded as an offset inhibitor, pulverized, and classified to obtain a toner having a certain particle size range. The volume average diameter of this toner was measured using a Coulter counter and was found to be Dv50=9.0 μm.

Experiment: The obtained toners A and B and various ferrite carriers shown in Table 1 were mixed so that the toner concentration was 3% to prepare a developer. Equivalent projected area circle equivalent diameter D of this developer
p9? ．． 5 was determined using an image analysis device.

The values are shown in Table 2. Further, an image development test was conducted using this developer, and unevenness and graininess of solid image areas were evaluated. The results are shown in Table 2.

Table 1 (hereinafter referred to as margins) As is clear from Table 2, if the toner and developer of the present invention are used, solid areas will have high density and excellent uniformity, and halftone areas will also have good images with no density unevenness. can get. It can also be seen that the combination of toner and carrier as a friction member has a great effect on image quality.

(Effects of the Invention) According to the present invention, uniform solid images can be obtained without image unevenness, toner spots, white spots, etc. caused by coarse toner.

Furthermore, high-quality images without density unevenness can be obtained even in halftones.

Further, according to the present invention, the uniformity of an image can be estimated without actually producing the image.

that's all

Claims (1)

[Claims] 1. A toner for developing an electrostatic image using fine toner particles triboelectrically charged by a frictional member, wherein the toner has a volume average diameter Dv_5_0 and when the toner is triboelectrically charged by the frictional member. Equivalent projected area circle equivalent diameter Dp_9_7 of toner
＿． Ratio with _5 Dp_9_7_. A toner having _5/Dv_5_0 of 1.6 or less. 2. A developer for developing an electrostatic image, comprising the toner according to claim 1 and a carrier as a friction member.