JPH03290670A - Toner and image forming method - Google Patents

Abstract

PURPOSE:To improve resolution and cleanability by specifying the volume average grain size and volume shape coefft. of the toner, making wax coexist in an aq. medium, adding an inorg. oxide at a specific ratio to the toner and providing specific two blades. CONSTITUTION:The toner consists of the colored particles obtd. by making at least a polymerizable monomer, coloring agents and the wax for the purpose of improving a fixing characteristic coexist in the aq. medium and subjecting the medium to granulation and polymn. The volume average grain size of the toner is specified to 2 to 8mum and the volume shape factor thereof to 0.6 to 2.00, by which the images having the high resolution and high image quality are obtd. and the cleanability is improved. The cleanability is further improved if the inorg. oxide is added at 0.5 to 5wt.% ratio. The images are formed by using this toner and by the image forming device provided with the two blades made of urethane which rubs and cleans the surface of an image carrier formed by using an org. compd. semiconductor as a photosensitive body.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a toner and an image forming method used for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc. [Prior Art] In an example of electrophotography, an electrostatic charge image is formed on an image carrier by charging and exposure, and this electrostatic charge image is developed with a developer containing toner to form a toner image. This toner image is then transferred to a transfer material and fused to form a visible image.

On the other hand, toner remaining on the image carrier without being transferred to the transfer material is preferably cleaned by a cleaning member such as a blade that is placed in pressure contact with the surface of the image carrier.

A so-called pulverization method is known as a method for producing toner constituting a developer. This pulverization method is a method in which a colorant and other additives used as necessary are added to a thermoplastic resin as a binder, the mixture is melted and kneaded, and then pulverized and classified to produce a toner.

However, the toner obtained by the pulverization method generally has a wide particle size distribution, and therefore has the disadvantage that the triboelectric charging properties of the toner are uneven and fogging is likely to occur. Furthermore, due to production efficiency issues, it is difficult to obtain toner with a small volume average particle size of 2 to 8 μm, and therefore, there is a problem that the demand for high image quality cannot be met.

Under these circumstances, in recent years, the application of granulation polymerization has been considered. This granulation polymerization method is a method of producing toner by granulation polymerization of a composition containing a polymerizable monomer for forming a resin as a binder and additives such as a colorant. Yes (Japanese Patent Application Laid-open No. 110945-1
Publication No. 10951, JP 61255353-255
Publication No. 357, JP-A-58-50544-50545
Publications, etc.).

According to the 20 granulation polymerization method, it is possible to produce a toner having a small volume average particle size of 2 to 8 μm, and the toner has the advantage of having a narrow particle size distribution. Moreover, since expensive equipment such as a jet crusher is not required, it is also possible to reduce production costs.

[Problem to be solved by the invention]

However, in the toner obtained by the granulation polymerization method, surface tension acts during the polymerization process, so the sphericity of the particles becomes high. There is a problem that cleaning becomes difficult due to the

This problem becomes particularly noticeable when the image carrier is a photoreceptor using an organic compound semiconductor.

That is, if the pressing force of the blade against the surface of the photoreceptor is increased in order to prevent cleaning failures, the photoreceptor is likely to be damaged and its service life will be shortened. On the other hand, if the pressing force of the blade against the photoreceptor is reduced, residual toner will not be scraped off sufficiently, resulting in image defects due to poor cleaning.

An object of the present invention is to provide a toner and an image forming method that can stably form high-resolution, high-quality images many times without causing cleaning failures.

[Means to solve the problem]

In order to achieve the above object, the inventor of the present invention has conducted intensive research and found that the volumetric shape coefficient of toner particles is a factor that greatly affects cleaning performance, and by defining this volumetric shape coefficient within a specific range, The cleaning properties of toner obtained through granulation polymerization are also significantly improved;
Furthermore, the present invention was completed based on the discovery that the cleaning performance can be further improved by using an image forming apparatus equipped with two blades made of urethane rubber that rub and clean the surface of the image carrier.

That is, the toner of the present invention is a toner made of colored particles obtained by granulation polymerization in the presence of at least a polymerizable monomer and a colorant in an aqueous medium, and has a volume average particle diameter of 2 to 2. 8 μm and a volume shape factor of 0.60 to 2.
00 is adopted.

In the above toner, it is preferable that wax is further present in the aqueous medium.

It is preferable that an inorganic oxide is further added to the above toner in a proportion of 0.5 to 5% by weight.

The image forming method of the present invention employs a configuration in which an image is formed using the above toner by an image forming apparatus equipped with two blades made of urethane rubber that rub and clean the surface of an image carrier.

It is preferable that the image carrier is a photoreceptor using an organic compound semiconductor.

[Effect]

With a toner having a volume average particle diameter of 2 to 8 μm, a high-quality image with high resolution can be obtained.

However, since the toner obtained by the granulation polymerization method has high sphericity, cleaning defects may occur, but in the present invention, the toner has a volume shape coefficient of 0.60 to 2.0.
Since it is 0, cleaning performance is greatly improved.

Further, when wax is further present in the aqueous medium, the fixing properties of the toner are improved.

Furthermore, when a predetermined proportion of an inorganic oxide is added and mixed into the toner from the outside, the cleaning performance is further improved.

According to an image forming apparatus equipped with two blades made of urethane rubber, toner remaining on the surface of the image carrier is cleaned twice, further improving cleaning performance.

[Specific explanation of configuration]

Hereinafter, the configuration of the present invention will be specifically explained.

The toner of the present invention comprises colored particles obtained by granulation polymerization in the presence of at least a polymerizable monomer, a colorant, and optionally a wax in an aqueous medium;
The volume average particle size is 2 to 8 μm, and the volume shape factor is 0.60.
~2.00.

In addition, 0.5 to 5% by weight of an inorganic oxide is added to the colored particles.
The toner may be constituted by adding and mixing them at a ratio of .

Here, the volume average particle diameter is a value measured by a laser beam scattering method using a laser diffraction particle size distribution analyzer "rHELOs" (sold by JEOL Ltd.).

Further, the volume shape coefficient is a coefficient that relates the particle diameter and the volume of the particle, and is φ defined by the following equation.

V=φ9·D, 3 v: Average value of the body size of one particle φV: Average value of the volume shape coefficient and the two particle diameters. However, ■ is determined by measuring the particles with a Coulter counter. Moreover, it is determined by the above-mentioned "HEL○S".

For example, in the case of a sphere, φ7=π/ 6 =0.523, and in the case of a cube, φ9=1 (assuming that one side of the cube is 0.523).

If the volumetric shape coefficient of the toner is in the range of 0.60 to 2.00, the toner has a small diameter obtained by granulation polymerization, but its cleaning properties are significantly improved. On the other hand, when the volume shape factor is less than 0.60, poor cleaning tends to occur.On the other hand, when it exceeds 2.00, manufacturing becomes difficult and the surface area becomes too large, making it difficult for external additives to be effective. It is difficult to use and is highly dependent on the environment.

If the volume average particle diameter of the toner is in the range of 2 to 8 μm, it is possible to form an image with high resolution and high quality. On the other hand, when the volume average particle diameter is less than 2 μm, image density tends to decrease and toner scattering tends to occur. On the other hand, when the volume average particle diameter exceeds 8 μm, resolution tends to decrease.

In the present invention, in order to set the volume shape coefficient of the toner in the range of 0.60 to 2.00 as described above, the following method can be adopted.

(1) A method of associating primary particles to form secondary particles and giving them irregular shapes during granulation polymerization.

(2) A method in which, during granulation polymerization, a monomer that reacts preferentially with a functional group exposed on the surface of particles that serve as a nucleus for polymerization is dropped to give the particles a different shape.

(3) By performing granulation polymerization using polymerizable monomers that will yield two or more types of polymers that are incompatible with each other, polymer particles consisting of the two types of polymers are produced, and then one of the polymers is A method in which polymer particles are made into irregular shapes by performing post-treatment to dissolve the polymer.

The polymerizable monomer used in the toner of the present invention is used to form a resin as a binder of the toner. As such resin, styrene/acrylic resin is preferable.

Polymerizable monomers for obtaining styrene/acrylic resin include styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methylstyrene,
-ethylstyrene, 2,4 dimethylstyrene, pn-
butylstyrene, pt-butylstyrene, p-n
-hequinrustyrene, p-n-octylstyrene, p-
n-7nylstyrene, p-n-decylstyrene, p-n
- Styrenic monomers such as dodecylstyrene, p-methkinstyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, metinope acrylate, ethyl acrylate, acrylic@n-butyl, acrylate Butinope acrylate Propinope acrylate n-octyl acrylate, dodenyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearinopea acrylate 2-chloroethyl acrylate, pheninope acrylate α-chloromethyl acrylate, methacrylic acid metinobe ethyl methacrylate, propinope methacrylate n-butinope methacrylate inbutinope methacrylate n-octinope methacrylate dodecyl methacrylate, lauryl methacrylate,
α of 2-ethylhexynope methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.
Examples include acrylic monomers such as methylene aliphatic monocarboxylic acid esters, acrylonitrinopemethacrylonitrile, acrylic acid or methacrylic acid derivatives such as acrylamide.

These monomers may be used in combination as appropriate.

When producing styrene/acrylic resin by granulation polymerization in an aqueous medium using the above polymerizable monomers, the polymerization initiator is 0.5 to 10% by weight based on the polymerizable monomers. It may be used within the range of As such a polymerization initiator, a peroxide initiator, an azo initiator, etc. can be used.

Coloring agents to be present in the aqueous medium together with the above polymerizable monomers include carbon black, nigrosine dye, aniline blue, calco oil blue chrome yellow, ultramarine blue, DuPont oil red, Orient oil red #330, quinoline yellow. , methylene blue chloride, phthalocyanine blue, malachite green offsalate, lamp black, rose bengal, oil black, azo oil black and the like. The surface of these colorants may be treated with a silane coupling agent or grafted.

Other toner components, such as wax, may be present in the aqueous medium, if necessary.

Examples of the wax include low molecular weight polyolefin waxes such as polyethylene and polypropylene, paraffin waxes, fatty acid ester waxes, fatty acid amide waxes, and the like.

As the granulation polymerization method, a suspension polymerization method can be preferably used. In this suspension polymerization method, the polymerization composition is dispersed and suspended in an aqueous medium as dispersed particles of a predetermined particle size by mechanical stirring, and polymerization is performed, but as the polymerization progresses, the stickiness of the dispersed particles increases. Therefore, the dispersed particles tend to coalesce excessively and become large in diameter. Therefore, it is preferable to use a suspension stabilizer to prevent excessive coalescence of dispersed particles.

Such suspension stabilizers include water-soluble polymer substances such as gelatin, starch, and polyvinyl alcohol, poorly water-soluble salts such as barium sulfate, barium sulfate, barium carbonate, calcium carbonate, and calcium phosphate, and these poorly water-soluble salts. It is possible to use combinations of surfactants such as sodium dodecylbenzenesulfonate and sodium dodecyl sulfate, inorganic polymer substances such as talc, clay, silicic acid, and diatomaceous earth, and poorly water-soluble inorganic compounds such as metal oxides. can.

In addition, ionic substances such as nitrogen-containing polymerizable monomers, poorly water-soluble amines, and other cationic or anionic substances are present in the aqueous medium, and when dispersed in the aqueous medium, When the particles are charged with either positive or negative polarity, an ionic dispersant that is charged with the opposite polarity when dispersed in an aqueous medium, such as negatively charged colloidal silica, positively charged colloidal silica, etc. Chargeable aluminum oxide or the like can be effectively used as a suspension stabilizer.

Next, an example of manufacturing the toner of the present invention by applying the suspension polymerization method will be described.

First, a polymerizable monomer, wax, polymerization initiator, etc. are thoroughly mixed using a Santo Starr or the like to prepare a polymerization composition. This polymerization composition is added to an aqueous medium containing a suspension stabilizer, suspended and dispersed using a high-speed stirrer such as a homojetter, and maintained at a predetermined temperature condition to form the first suspension dispersion. Prepare.

On the other hand, a second suspension dispersion liquid is prepared by suspending and dispersing a coloring agent such as carbon black into a polymerization composition similar to that described above dispersed in an aqueous medium.

This second suspension and dispersion is gradually dropped into the first suspension and dispersion, and a certain amount of a coloring agent such as carbon black is used as a core, and a polymerizable monomer is added to the functional group on the surface. The polymerization reaction is carried out while preferentially precipitating and growing the body.

The polymer particles thus obtained are colored particles containing a coloring agent therein, and their surfaces are appropriately shaped. The degree of deformation depends on the temperature during manufacturing,
It can be controlled by adjusting conditions such as stirring and the type and amount of wax, colorant, polymerization initiator, etc., so the volume shape factor can be easily defined in the range of 60 to 2.00. can.

In addition, the particle size of the polymer particles can be determined depending on the suspension and dispersion state of the polymerization composition, so by adjusting the dispersion conditions, colored particles with a volume average particle size of 2 to 8 μm can be easily obtained. Can be done.

In the present invention, the toner may be composed only of the colored particles obtained as described above, or the toner may be formed by adding and mixing an inorganic oxide to the colored particles at a ratio of 0.5 to 5% by weight. It is preferable to configure. By adding this inorganic oxide, the cleaning properties of the toner can be further improved. As such inorganic oxides, fine particles of phosphoric acid, aluminum oxide, titanium oxide, etc. can be used.

Further, the toner may be constituted by further adding and mixing other external additives to the colored particles. Other external additives include carbide particles, nitride particles, silicone resin particles, acrylic resin particles, fatty acids such as stearic acid, fatty acid metal salts, and the like.

In the image forming method of the present invention, an image is formed using the above-mentioned small-diameter toner by an image forming apparatus equipped with two blades made of urethane rubber that rub and clean the surface of the image carrier.

The cleaning process is a process of scraping and removing toner that inevitably remains on the image carrier after the toner image on the image carrier is transferred to a transfer paper.

In the present invention, this cleaning step is performed using two urethane rubber blades.

In a preferred embodiment, one blade is
One blade is a counter type as shown in Figure 1(a), and the other blade is a trail type as shown in Figure 1(b).
It is best to use these together. In this case, the shortcomings of each method are mutually covered, and the cleaning performance for small-diameter toner is significantly improved.

In FIG. 1, l is a blade, 2 is an image carrier,
θ is the contact angle.

To explain in detail, a single counter type blade has the drawback that if the contact pressure is small, it tends to rub against the belly, and if the contact pressure is large, it tends to vibrate. Further, with only a trail type blade, there is a drawback that if the contact pressure is small, small-diameter toner easily slips through, and if it is large, it deforms and small-diameter toner easily slips through.

Therefore, if a counter-type blade and a trail-type blade are used together as mentioned above, the drawbacks of each blade will be compensated for, and cleaning performance will be improved with a suitable contact pressure that will not damage the surface of the image carrier. You can improve your performance.

The contact pressure of the blade against the image carrier is preferably in the range of 15 to 30 g/cm for a counter type blade, and in the range of 10 to 25 g/cm for a trail type blade.

In a further preferred embodiment, the first step shown in FIG. 1 (
The blades were spaced apart along the rotational direction of the image carrier so that cleaning was performed with the trail type blade shown in b), and then cleaning was performed with the counter one type blade shown in FIG. 1(a). It is best to place them in order.

With this arrangement, toner can be effectively prevented from being caught between the blade and the image carrier.

The image carrier used in the present invention is preferably a photoreceptor (hereinafter abbreviated as 1 organic photoreceptor) using an organic compound semiconductor.

An organic photoreceptor is usually constructed by laminating an organic photosensitive layer on a conductive support, in which an organic compound semiconductor exhibiting photoconductivity is dispersed in a binder resin.

The organic photosensitive layer preferably has a laminated structure including a carrier generation layer and a carrier transport layer.

The carrier generation layer is a layer containing a carrier generation substance that absorbs visible light and generates charged carriers. Further, the carrier transport layer is a layer containing a carrier transport substance that transports either or both of positive and negative carriers generated in the carrier generation layer. According to such a functionally separated photosensitive layer, the selection range of materials that can be used for the construction of the photosensitive layer is wide, and it becomes possible to independently select a material or material system that optimally performs each function.

Examples of the above carrier-generating substances include anthanthrone pigments, perylene derivatives, phthalocyanine pigments,
Bisazo pigments, indigoid dyes, etc. can be used.

As the above-mentioned carrier transport substance, for example, carbazole derivatives, oxadiazole derivatives, triarylamine derivatives, polyarylalkane derivatives, hydrazone derivatives, pyrazoline derivatives, stilbene derivatives, styryltriarylamine derivatives, etc. can be used.

Binder resins used in the photosensitive layer include polycarbonate, vinyl acetate resin, epoxy resin, polyurethane resin, polyester resin, polyurethane resin, methacrylic resin, acrylic resin, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride- Examples include vinyl acetate-maleic anhydride copolymer.

The conductive support constituting the organic photoreceptor includes metal plates or drums made of aluminum, nickel, copper, zinc, palladium, silver, indium, tin, platinum, gold, stainless steel, steel, brass, alloys, etc., and paper. Alternatively, use a conductive treated sheet obtained by laminating a conductive material such as aluminum, palladium, gold, alloy, indium oxide, etc. on the surface of an insulating sheet such as plastic by coating, vapor deposition, lamination, etc. be able to.

〔Example〕

Examples of the present invention will be described below along with comparative examples, but the embodiments of the present invention are not limited to these Examples. In addition, in the following, "part" represents 1 part by weight.

<Example 1> Styrene 80 parts Lauryl methacrylate 20 parts Polyolefin wax 5 parts Paraffin wax
5 parts 2.2° -Azobisisobutyronitrile 2 or more parts of the materials were thoroughly mixed using a Santo Starr to prepare a polymerization composition. This polymerization composition was added to an aqueous medium containing a suspension stabilizer, suspended and dispersed using a homojetter, and maintained at a temperature of 40 to 50°C to prepare a first suspension dispersion. .

On the other hand, a second suspension dispersion was prepared by suspending and dispersing 112 parts of the same polymerization composition as above and 10 parts of carbon black in an aqueous medium containing a suspension stabilizer using a homojetter. This 20th turbid dispersion is gradually dropped into the 10th turbid dispersion to cause the polymerizable monomer to preferentially precipitate and grow on the functional groups on the surface of a certain amount of carbon black. The polymerization reaction was carried out for 30 hours.

Thereafter, the reaction solution was filtered to collect solid matter, which was washed and dried to produce colored particles. The volume average particle diameter of these colored particles is 5 μm, and the volume shape coefficient is 1.2.
It was 3.

Next, an inorganic oxide consisting of silicon oxide was externally added and mixed to the colored particles at a ratio of 0.6% by weight to produce a toner.

A developer having a toner concentration of 5% by weight was prepared by mixing the above toner and a silicone resin coated carrier.

Using the above developer, an electrophotographic copying machine manufactured by Konica R
A live photo test was conducted using a modified U-BIX 1515J machine, and the resolution and cleaning performance were evaluated.

The resolution was determined by the number of fine lines per 1+nm that could be clearly identified by visual inspection.

Cleanability was determined based on the presence or absence of image defects due to poor cleaning.

The cleaning device of this modified machine has a trail-type urethane rubber blade shown in FIG. 1(b) and a counter-type cleaning device shown in FIG. 1(a) in order on the surface of the image carrier along its rotation direction. The blades made of urethane rubber are arranged in contact with each other, and the contact pressure is 17 g/cm for the trail type blade on the upstream side and 20 g/cm for the counter type blade on the downstream side.

The image carrier is a rotating drum-shaped photoreceptor made of an organic compound semiconductor.

<Example 2> A toner consisting of colored particles with a volume average particle diameter of 5 μm and a volume shape factor of 1.23 was produced in the same manner as in Example 1 except that the polyolefin wax was changed to 10 parts and the paraffin wax was omitted. was manufactured.

Using this toner, a photographic test was conducted and evaluated in the same manner as in Example 1.

<Example 3> Styrene 80 parts Dimethylaminoethyl acrylate 20 parts Polyolefin wax 20 parts Paraffin wax
5 parts benzoyl peroxide
Colored particles having a volume average particle diameter of 5 μm and a volume shape factor of 1.23 were produced in the same manner as in Example 1 using 5 parts or more of the material.

Next, an inorganic oxide consisting of silicon oxide was externally added and mixed to the colored particles in a proportion of 0.8% by weight to produce a toner.

A developer having a toner concentration of 5% by weight was prepared by mixing the above toner and a fluororesin coated carrier.

Using the above-mentioned developer, an actual photographic test was conducted and evaluated in the same manner as in Example 1.

<Example 4> In the same manner as in Example 1 except that the carbon black was changed to copper phthalocyanine, the volume average particle size was 5 μm.
, colored particles with a volume shape factor of 1.23 were produced.

Next, an inorganic oxide consisting of silicon oxide was externally added and mixed to the colored particles in a proportion of 0.6% by weight to produce a toner.

Using this toner, a photographic test was conducted and evaluated in the same manner as in Example 1.

<Comparative Example 1> In the same manner as in Example 2, a comparative toner consisting of colored particles having a volume average particle diameter of 9 μm and a volume shape coefficient of 0.55 was produced.

Using this comparative toner, a photographic test was conducted and evaluated in the same manner as in Example 1.

Evaluations of the above Examples and Comparative Examples are shown in Table 1 below.

As is clear from Table 1, according to the embodiments of the present invention:
It is clear that images with high resolution and no image defects due to poor cleaning can be stably formed many times.

On the other hand, in Comparative Example 1, the resolution was low due to the large volume average particle diameter of the toner, and image defects due to poor cleaning occurred early due to the high sphericity. It is clear that it is inferior to the example.

〔Effect of the invention〕

According to the toner of the present invention, since the toner has a small diameter and a volumetric shape factor within a specific range, it is possible to improve resolution and cleanability.

Further, when wax is further present in the aqueous medium, the effect of improving the fixing properties of the toner is synergized.

Further, when an inorganic oxide is further added to the toner at a ratio of 0.5 to 5% by weight, the cleaning properties of the toner are further improved.

According to the image forming method of the present invention, since an image is formed using two blades made of urethane rubber, good leaning can be achieved without increasing the contact pressure of each blade against the image carrier. Therefore, even when using a photoreceptor using an organic compound semiconductor whose surface is particularly susceptible to damage, sufficient cleaning can be performed without causing damage.

[Brief explanation of the drawing]

FIG. 1(a) is an explanatory diagram showing a counter-type blade, and FIG. 1(a) is an explanatory diagram showing a trail-type blade. 1...Blade 2...Image carrier θ...Contact angle diagram (0) (b) e:sd' e≦cr

Claims (5)

[Claims] (1) A toner consisting of colored particles obtained by granulation polymerization in the presence of at least a polymerizable monomer and a colorant in an aqueous medium, with a volume average particle diameter of 2 to 8 μm and a volume shape coefficient. is 0.60
~2.00. (2) The toner according to claim 1, further comprising wax in the aqueous medium. (3) A toner comprising the toner according to claim 1 or 2 further mixed with an inorganic oxide in a proportion of 0.5 to 5% by weight. (4) Forming a surface image using the toner according to claim 1 or 3 using an image forming apparatus equipped with two urethane rubber blades that rub and clean the surface of an image carrier. Characteristic image forming method. (5) An image forming method, wherein the image carrier according to claim 4 is a photoreceptor using an organic compound semiconductor.