JPH11212293A - Nonmagnetic one-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonmagnetic one-component developer which is few in a change in the surface state of toner particles even after repeatedly copying, can maintain the characteristics of the toner and is excellent in durability, particularly in the stability of electrification. SOLUTION: This developer is a nonmagnetic one-component developer made by containing negative charge type toner particles contg. at least a resin binder and a colorant, small particle diameter inorg. fine particles having 1-70 nm average primary particle diameter and fine strontium titanate particles having 100-500 nm average primary particle diameter. The content of the inorg. fine particles is 0.3-3.0 wt.% based on the amt. of the toner particles and the content of the fine strontium titanate particles is 0.3-3.0 wt.% based on the amt. of the toner particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing an electric latent image in electrophotography and electrostatic printing, and more particularly to a non-magnetic one-component developer.

[0002]

2. Description of the Related Art In general, a two-component developing system and a one-component developing system are known as a developing device, but a one-component developing system is often adopted from the viewpoint of preventing a reduction in charging performance and miniaturizing an image forming apparatus. Have been.

The one-component developing system includes a magnetic one-component system and a non-magnetic one-component system. In the magnetic one-component developing system, it is usually necessary to add black magnetic powder to the toner. In this case, a non-magnetic one-component developing system is preferable. In the non-magnetic one-component developing method, the developer regulating member is disposed so as to abut against the developer carrier, and the non-magnetic one-component developer is passed through the gap between the developer carrier and the developer regulating member. In this way, a thin toner layer is formed on the carrier, charged, transported to the developing area as it is, and the electrostatic latent image formed on the electrostatic latent image carrier is developed.

In general, inorganic particles such as silica and titania are added (externally added) to a toner as a fluidizing agent in order to improve fluidity. For example, JP-A-7-439
No. 30, there is reported a technique in which a fluidizing agent having a particle size of 0.05 μm (50 nm) or less is externally added to toner particles in a one-component developing system. However, in the one-component developing method, as described above, the toner particles are charged by passing through the gap (regulating portion) between the developer carrying member and the developer regulating member, so that a large stress is applied to the toner at that time. For this reason, the fluidizing agent externally added to the toner is embedded in the toner particles, so that the fluidity cannot be secured for repeated use. Also, with repeated use, the surface condition of the toner changes as the fluidizing agent is embedded in the toner surface, and stable toner characteristics,
In particular, there is a problem that it is difficult to maintain chargeability. Further, there is a problem that the toner component adheres to the developer carrying member and the developer regulating member due to the influence of the stress at the time of charging, thereby deteriorating the charging stability.

[0005]

An object of the present invention is to provide a non-magnetic mono-component which has a small change in the surface state of toner particles even after repeated copying, maintains toner characteristics, and has excellent durability, especially excellent charging stability. It is intended to provide a developer.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to negatively charged toner particles containing at least a binder resin and a colorant, inorganic fine particles having an average primary particle size of 1 to 70 nm, and an average primary particle size of 100 nm to 500 nm. A non-magnetic one-component developer containing strontium titanate fine particles, wherein the content of the small-sized inorganic fine particles is 0.3 to 3.0% by weight with respect to the toner particles; Is 0.3 to 3 with respect to the toner particles.
The present invention relates to a non-magnetic one-component developer characterized by being 0% by weight.

In this specification, the average primary particle size of the inorganic fine particles is determined by a scanning electron microscope (JSM-840A; manufactured by JEOL Ltd.).
And the average of the major axis of the fine particles was shown.

In the present invention, a small amount of the inorganic fine particles having a specific particle size and the strontium titanate fine particles having a specific particle size are externally added to a conventional toner particle by a specific amount, so that the surface of the toner particle can be obtained even by repeated copying. It has become possible to provide a non-magnetic one-component developer which does not easily change its state and can maintain the toner characteristics, and has excellent durability, particularly excellent charging stability.

The inorganic fine particles having a small particle diameter contained in the developer of the present invention have an average primary particle diameter of 1 to 70 nm, preferably 5 to 60 nm.
nm inorganic fine particles. By uniformly covering the toner particles by incorporating the fine particles, uniform desired toner fluidity can be obtained. If the average primary particle size is less than 1 nm, the stability of toner charging due to long-term use and the stability of toner charging against environmental changes become insufficient, and if it exceeds 70 nm, the dispersibility of the inorganic fine particles in the toner particles is significantly reduced. In addition, the fluidity and chargeability of the toner become non-uniform, and a good copied image cannot be obtained.

As the material used for the small-diameter inorganic fine particles, various materials conventionally used as a fluidizing agent can be used. Examples thereof include silica, alumina, titania (titanium dioxide), and tin oxide. , Magnesium oxide,
Zinc oxide or the like can be used alone or in combination of two or more. Preferred small-particle inorganic fine particles are silica and titania.

The inorganic fine particles having a small particle diameter are 0.3 to 3.0% by weight, preferably 0.5 to 2.0% by weight, based on the toner particles.
It is desirable to contain 5% by weight, more preferably 1.0 to 2.5% by weight. If the amount is less than 0.3% by weight, the desired fluidity cannot be imparted, and the durability deteriorates.
White streaks and image unevenness are likely to occur in the copied image. On the other hand, if the content is more than 3.0% by weight, contamination in the apparatus occurs, the amount of poorly charged toner increases, fogging occurs in a copied image, and the cost is disadvantageous.

In the present invention, the inorganic fine particles having a small particle diameter are preferably surface-treated with a hydrophobizing agent. This is because the environmental stability of the toner, in particular, the change in toner charge due to the influence of humidity is suppressed. The degree of hydrophobicity is 30-80%,
Preferably, it is 40-80%. If the degree of hydrophobicity is lower than 30%, the environmental resistance tends to deteriorate,
If the content exceeds 80%, it is difficult to obtain a stable product in the production.

As the hydrophobizing agent, a silane coupling agent, a titanate coupling agent, a silicone oil,
Conventionally used hydrophobizing agents such as silicone varnish can be used, preferably a silane coupling agent,
A silicon-based oil, more preferably, a silane-based coupling agent is used. Examples of the silane coupling agent include trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane,
Methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyl Trimethoxysilane, n-
Octyltrimethoxysilane, n-octadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane and the like can be used.

As the silicone oil, for example, dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane and the like can be used. The hydrophobizing agent may be used in an amount sufficient to achieve the above-mentioned degree of hydrophobization, and may be treated by a conventional method.

In the present invention, the inorganic fine particles may be surface-treated using a fluorine-based silane coupling agent or a fluorine-based silicone oil in combination. This is because, since the toner is negatively charged, it is effective to improve the negatively charged toner and prevent image fog. Normally, the chargeability of the toner is controlled by including a charge control agent in the toner particles. However, in the one-component developing system according to the present invention, the developer carrier and the developer regulating member Since the toner is charged by frictional charging when the toner passes through the gap between the press contact portions, the chargeability of the toner particles is important for the chargeability of the toner particles. Therefore, when controlling the chargeability, it is more effective to adjust the chargeability of the external additive of the toner than to adjust the content of the charge control agent.

As the fluorinated silane coupling agent,
For example, the following compounds can be used alone or as a mixture, but are not limited thereto. _{· CF 3 (CH 2) 2} SiCl 3 · CF 3 (CF 2) 5 SiCl 3 · CF 3 (CF 2) 5 (CH 2) 2 SiCl 3 · CF 3 (CF 2) 7 (CH 2) 2 SiCl 3 _{· CF 3 (CF 2) 7} CH 2 CH 2 Si (OCH 3) 3 · CF 3 (CF 2) 7 (CH 2) 2 Si (CH 3) Cl 2 · CF 3 (CH 2) 2 Si (OCH 3 _{) 3 · CF 3 (CH 2} ) 2 Si (CH 3) (OCH 3) 2 · CF 3 (CF 2) 3 (CH 2) 2 Si (OCH 3) 3 · CF 3 (CF 2) 5 (CH 2 ) ₂ Si (OCH ₃ ) ₃ · CF ₃ (CF ₂ ) ₆ CONH (CH ₂ ) ₂ Si (OC ₂ H ₅ ) ₃ · CF ₃ (CF ₂ ) ₆ COO (CH ₂ ) ₂ Si (OCH ₃ ) ₃・ CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (OCH ₃ ) ₃・ CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₂ Si (CH ₃ ) (OCH ₃ ) ₂・ CF ₃ (CF ₂ ) ₇ NH (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ .CF ₃ (CF ₂ ) ₈ (CH ₂ ) ₂ Si (OCH ₃ ) ₃

The fluorine-based silane coupling agent is used in an amount of 1 to 20 parts by weight, preferably 2 to 100 parts by weight of the inorganic fine particles.
It is preferable to use １５15 parts by weight.

In order to treat the inorganic fine particles with the surface treating agent (fluorine-based coupling agent or fluorine-based silicone oil, hydrophobizing agent), for example, the surface-treating agent is diluted with a solvent, and the inorganic fine particles are diluted with the diluted solution. After adding and mixing the liquid, heating and drying the mixture, a dry method of crushing, dispersing the inorganic fine particles in an aqueous system, forming a slurry, adding a surface treating agent, mixing and heating and drying the mixture. After that, it can be carried out by a wet method of crushing or the like. In particular, after performing the hydrophobic treatment in an aqueous system from the viewpoint of the uniformity of the surface treatment of the hydrophobic agent with respect to the inorganic fine particles, the anti-aggregation property of the inorganic fine particles, and the like, the fluorinated coupling agent or the fluoric silicone oil is used by a dry method. Surface treatment is preferred.

In the present invention, a mixture of two or more kinds of inorganic fine particles having an average primary particle size different within the above range may be used as the small-diameter inorganic fine particles. Hereinafter, a case where the inorganic fine particles having a smaller particle diameter are referred to as first inorganic fine particles, the inorganic fine particles having a larger particle diameter are referred to as second inorganic fine particles, and these two types of inorganic fine particles are used as the above-described inorganic fine particles having a small particle diameter will be described.

In the present invention, when a mixture of the first inorganic fine particles and the second inorganic fine particles is used as the small inorganic fine particles, one of the inorganic fine particles is preferably made of silica, more preferably the other inorganic fine particles. The fine particles are composed of titania. By using two kinds of inorganic fine particles of silica and titania, environmental resistance and chargeability are improved, and these effects become remarkable especially when a full-color developer is prepared.

The first inorganic fine particles have an average primary particle size of 1 to 40.
nm, preferably 5 to 35 nm, more preferably 5 to 3 nm.
Desirably, it is 0 nm. By including inorganic fine particles having such a particle size, desired toner fluidity can be more easily obtained. If the average primary particle size is less than 1 nm, the stability of toner charging due to long-term use and the stability of toner charging with respect to environmental changes will be insufficient, and if it exceeds 40 nm, it will be difficult to obtain the effect of improving fluidity.

The second inorganic fine particles have an average primary particle size of 40 to 7
It is desirable that the average particle diameter of the first inorganic fine particles is 0 nm, preferably 40 to 60 nm, which is 10 nm or more.
The decrease in the fluidity of the toner due to repeated copying, which has conventionally been a problem, is thought to be due to the fact that small inorganic fine particles such as the first inorganic fine particles are embedded in the toner particles. , The embedding can be relaxed and desired fluidity can be secured. When the average primary particle diameter is less than 40 nm, the effect of relaxing the embedding of the first inorganic fine particles in the toner particles is liable to be remarkably reduced. When the average primary particle diameter exceeds 70 nm, the dispersibility of the inorganic fine particles in the toner particles is significantly reduced. The properties and charging properties become non-uniform, and good copied images cannot be obtained.

The contents of the first inorganic fine particles and the second inorganic fine particles are set so that the total content of the first inorganic fine particles and the second inorganic fine particles is the above-mentioned content of the small inorganic fine particles. 0.1 to 2.0% by weight, preferably 0.3 to 1.5% by weight, and the second inorganic fine particles 0.1 to 2.5% by weight with respect to the toner particles.
Preferably, the content is 0.3 to 2.0% by weight. The content of the first inorganic fine particles is 0.1% by weight.
If the amount is less than the desired value, the desired fluidity is not easily provided, and white streaks are easily generated in the copied image. If the amount is more than 2.0% by weight, contamination in the apparatus occurs, and the amount of poorly charged toner increases, causing fog on the copied image. It is easy and disadvantageous in terms of cost. When the content of the second inorganic fine particles is less than 0.1% by weight, the effect of reducing the embedding of the first inorganic fine particles is difficult to be obtained, and when the content is more than 2.5% by weight, contamination in the machine or occurrence of poorly charged toner increases. As a result, fogging tends to occur in the copied image, and the cost tends to be disadvantageous.

The strontium titanate fine particles contained in the developer of the present invention have an average primary particle size of 100 to 500 n.
m, preferably 150 to 400 nm. By containing the fine particles, the fixation of the toner component at the regulating portion (the contact portion between the developer regulating member and the developer carrying member) is removed by the polishing action of the fine particles (hereinafter, referred to as a refresh effect). It is possible to avoid uneven charging of the toner and unevenness of the formed toner thin layer due to accumulation of toner particles and the like on the developer carrier, which has been a problem in the related art, and it is possible to provide a good copied image. Further, since the fine particles are weakly positively charged, the fine particles are effectively attached to the negatively chargeable toner particles, and have a particularly large effect on the toner charging stability. Further, by the external addition of the fine particles, the photosensitive member is appropriately polished, and the effect as a cleaning improver can be expected.

Further, since the strontium titanate fine particles have a relatively large particle size, the probability of contact between the toner particles is reduced, and the strontium titanate fine particles are regulated by a developer regulating member at the time of development, and are subjected to external stirring and the like in a developing device. Since the stress is diffused, the surface of the toner particles is less likely to be directly affected by external stress. Further, the strontium titanate fine particles have a function of enhancing the function of alleviating embedding of the small-sized inorganic fine particles.

If the average primary particle size is less than 100 nm, a refreshing effect of the developer regulating member cannot be expected, and fogging or the like is likely to occur with respect to chargeability due to an increase in the reverse charge component. Further, the probability of contact between toner particles increases, and external stress directly affects the surface of the toner particles, so that the above function cannot be exhibited. 5
If it exceeds 00 nm, it becomes difficult to adhere to toner particles,
Since most of the strontium titanate fine particles are desorbed and clogged on the developer regulating member, problems such as poor charging, poor thin layer formation, and in-machine contamination occur.

In the present invention, the strontium titanate fine particles may be surface-treated with the above-mentioned hydrophobizing agent in the same manner as the small-diameter inorganic fine particles from the viewpoint of cohesiveness and dispersibility.

The content of the strontium titanate fine particles is 0.3 to 3.0% by weight based on the toner particles.
Preferably, the content is 0.4 to 2.0% by weight. If the amount is less than 0.3% by weight, the refreshing effect of the developer carrier cannot be obtained, and the function of alleviating the embedding of the inorganic fine particles into the toner particles cannot be exerted. On the other hand, if the content is more than 3.0% by weight, the developer regulating member is clogged by the strontium titanate fine particles detached from the toner particles, causing problems such as poor charging, poor thin layer formation, and in-machine contamination.

The above-mentioned inorganic fine particles having a small particle size and strontium titanate fine particles are externally added to negatively charged toner particles obtained by a known method. The negatively charged toner particles used in the present invention contain at least a binder resin and a colorant.

As the binder resin used in the present invention, a resin capable of making the obtained toner particles negatively charged is used. In this case, a resin that can be controlled to be negatively charged by internally adding a charge control agent described later may be used. Further, in order to improve the dispersibility of the colorant in the binder resin, 1.0 to 30.0 KOH mg /
g, preferably a resin having an acid value of 1.0 to 25.0 KOH mg / g, more preferably 2.0 to 20.0 KOH mg / g. This has an acid value of 1.0 KOH
When the amount is smaller than mg / g, the effect of improving the dispersibility is reduced, and 3
This is because if the amount exceeds 0.0 KOH mg / g, the change in the charge amount due to environmental fluctuations increases.

The kind of the resin is not limited as long as it is such a binder resin. For example, a styrene resin, an acrylic resin, a styrene-acryl resin, a polyamide resin,
Polyester-based resins, polyurethane-based resins, epoxy-based resins and other known resins can be used alone or in combination, and a suitable resin may be appropriately selected and used according to the use. For example, a polyester resin is used when preparing a negatively chargeable toner without using a charge control agent, and a polyester resin or styrene-acryl is used when preparing a negatively chargeable toner using a negative charge control agent. It is preferable to use a polyester resin when preparing a full-color toner and a polyester resin or a styrene-acrylic resin when preparing a black toner.

In the present invention, a preferred polyester resin comprises a bisphenol A alkylene oxide adduct as an alcohol component as a main component, and a phthalic dicarboxylic acid or a phthalic dicarboxylic acid and an aliphatic dicarboxylic acid as an acid component. It is synthesized by a polycondensation reaction.

As the bisphenol A alkylene oxide adduct, bisphenol A propylene oxide adduct and bisphenol A ethylene oxide adduct are suitable, and it is preferable to use a mixture of these.

The following diols or polyhydric alcohols may be used as the alcohol component together with the bisphenol A alkylene oxide adduct. Such alcohol components include, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2
Diols such as propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, didiol Pentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, Trimethylolpropane, 1,3,
5-trihydroxymethylbenzene and the like.

Examples of the phthalic dicarboxylic acids include phthalic dicarboxylic acids such as terephthalic acid and isophthalic acid;
The acid anhydride or the lower alkyl ester thereof can be used.

The aliphatic dicarboxylic acids usable together with the phthalic dicarboxylic acids include aliphatic dicarboxylic acids such as fumaric acid, maleic acid, succinic acid, alkyl or alkenyl succinic acids having 4 to 18 carbon atoms, and acids thereof. Examples thereof include anhydrides and lower alkyl esters thereof.

In order to adjust the acid value of the resin, a small amount of a polycarboxylic acid such as trimellitic acid may be used as long as the transparency of the toner is not impaired. Examples of such a polyvalent carboxylic acid component include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid,
1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2 , 4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane,
Examples thereof include 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, anhydrides thereof, and lower alkyl esters.

When the negatively charged toner particles of the present invention are used as a full-color toner, a binder resin having a glass transition point of 55 to 75 ° C., preferably 58 to 7 ° C.
0 ° C, softening point 95-120 ° C, preferably 100-1
At 18 ° C., the number average molecular weight is 2500 to 6000, preferably 3000 to 5500, and the weight average molecular weight / number average molecular weight is 2 to 8, preferably 3 to 7. When the glass transition point is low, the heat resistance of the toner is reduced, and when the glass transition point is high, the light transmittance and the color mixing are reduced. When the softening point is low, a high-temperature offset is likely to occur during fixing, and when the softening point is high, the fixing strength is reduced. When the number average molecular weight is small, the toner is easily peeled off when the image is bent, and when the number average molecular weight is large, the fixing strength is reduced. When the weight-average molecular weight / number-average molecular weight is small, high-temperature offset is likely to occur, and when it is large, the light transmittance is reduced.

As the colorant, various known colorants such as cyan, magenta, yellow, and black can be used, and the amount of the colorant can be the same as that of the conventional colorant. Usually, the colorant is added in an amount of about 1 to 15 parts by weight based on 100 parts by weight of the binder resin.

The negatively charged toner particles of the present invention may contain desired additives such as a charge control agent and an anti-offset agent in addition to the above-mentioned colorants.

As the charge control agent, a zinc salicylate complex or the like and other known negative charge control agents can be used, and the type thereof may be selected according to the purpose of use. For full-color copying, it is preferable to use a colorless, white or pale yellow charge control agent. There is no particular limitation for black copy. The amount of the charge control agent may be appropriately set according to the purpose of use, but is usually 0.1 to 10 parts by weight, preferably 0.5 to 5.0 parts by weight based on 100 parts by weight of the binder resin. Used in the range.

The offset preventing agent is not particularly limited. For example, polyethylene wax, oxidized polyethylene wax, polypropylene wax,
Oxidized polypropylene wax, carnauba wax, sasol wax, rice wax, candelilla wax, jojoba oil wax, beeswax, and the like can be used. This not only improves the offset resistance, but also reduces the problem of toner sticking to the developer regulating member and the developer carrier in the non-magnetic one-component developing device. It is particularly preferable to use a wax having an acid value of 0.5 to 30 KOH mg / g from the viewpoint of dispersibility in a binder resin having the above acid value. The amount of the wax to be added is preferably 0.5 to 5 parts by weight, more preferably 1 to 4 parts by weight, based on 100 parts by weight of the binder resin. This is because if the amount is less than 0.5 part by weight, the effect of the addition is insufficient, and if it is more than 5 parts by weight, light transmittance and color reproducibility are reduced.

The toner particles according to the present invention are prepared by using the binder resin and the colorant described above and other desired additives, and kneading and pulverizing methods, suspension polymerization methods, emulsion polymerization methods, emulsion dispersion granulation methods, and encapsulation. It can be produced by other known methods such as a method. Among these production methods, it is preferable to produce by a kneading / pulverization method from the viewpoint of production cost and production stability.

The kneading and pulverizing method includes a step of mixing toner components such as a resin and a colorant with a mixer such as a Henschel mixer, a step of melting and kneading the mixture, a step of cooling the kneaded product and coarsely pulverizing the mixture. Toner particles are produced by a step of finely pulverizing the coarsely pulverized particles and a step of classifying the obtained finely pulverized particles. The volume average particle diameter of the toner particles of the present invention is preferably adjusted to 4 to 10 μm, more preferably 6 to 9 μm, from the viewpoint of high definition reproducibility of an image. The volume average particle diameter of the toner particles is a value measured with a Coulter Multisizer (manufactured by Coulter Counter Co.) at an aperture diameter of 100 μm.

The obtained toner particles are mixed with the above-mentioned small-sized inorganic fine particles and strontium titanate fine particles using a mixer such as a Henschel mixer to prepare a non-magnetic one-component developer.

The non-magnetic one-component developer of the present invention thus obtained comprises a colorant, a binder resin, a charge control agent,
By appropriately selecting a wax or the like, it can be used as a full color developer or a black developer, but in the present invention, it is effective to use a full color developer. For this reason, the developer of the present invention can be used in any developing device as long as it is a developing device employing a one-component developing method, but is particularly preferably used in a full-color image forming apparatus. Hereinafter, an example of a full-color image forming apparatus will be described with reference to FIG.

In FIG. 1, a full-color laser beam printer is generally driven to rotate in a direction indicated by an arrow a, a photosensitive drum 10, a laser scanning optical system 20, a full-color developing device 30, and a direction driven by an arrow b. It comprises an endless intermediate transfer belt 40 and a paper feed unit 60. Around the photosensitive drum 10, a photosensitive drum 10
A charging brush 11 for charging the surface of the photosensitive drum to a predetermined potential and a cleaner 12 having a cleaner blade 12a for removing toner remaining on the photosensitive drum 10 are provided.

The laser scanning optical system 20 is a well-known type having a built-in laser diode, polygon mirror, and fθ optical element, and its control unit includes C (cyan), M (magenta), Y
(Yellow) and Bk (black) print data are transferred from the host computer. The laser scanning optical system 20 sequentially outputs print data for each color as a laser beam, and scans and exposes the photosensitive drum 10. This allows
An electrostatic latent image for each color is sequentially formed on the photosensitive drum 10.

The full-color developing device 30 includes C, M, Y, B
The four color developing units 31C, 31M, 31Y, and 31Bk each containing a one-component developer composed of k non-magnetic toners are integrated, and can be rotated clockwise about a support shaft 81 as a fulcrum. Each developing device includes a developing sleeve (developer carrying member) 32, a toner regulating blade (developer regulating member) 34
It has. The toner conveyed by the rotation of the developing sleeve 32 is charged by passing through a pressure contact portion (a regulating portion) between the blade 34 and the developing sleeve 32.

The intermediate transfer belt 40 includes support rollers 41, 4
2 and endlessly stretched over the tension rollers 43 and 44, and are driven to rotate in the direction of arrow b in synchronization with the photosensitive drum 10. A projection (not shown) is provided on a side portion of the intermediate transfer belt 40. By detecting the projection by the microswitch 45, image forming processes such as exposure, development, and transfer are controlled. The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 46 and is in contact with the photosensitive drum 10. The contact portion is a primary transfer portion T _1. The intermediate transfer belt 40 is in contact with a rotatable secondary transfer roller 47 at a portion supported by the support roller 42. The contact portion is a secondary transfer portion T _2.

Further, a cleaner 50 is provided in a space between the developing device 30 and the intermediate transfer belt 40. The cleaner 50 has a blade 51 for removing residual toner on the intermediate transfer belt 40. The blade 51 and the secondary transfer roller 47 can contact and separate from the intermediate transfer belt 40.

The paper supply unit 60 includes a paper supply tray 61 that can be opened to the front side of the image forming apparatus main body 1, a paper supply roller 62,
And a timing roller 63. The recording sheets S are stacked on a paper feed tray 61, fed one by one to the right in the drawing by the rotation of a paper feed roller 62, and synchronized with an image formed on the intermediate transfer belt 40 by a timing roller 63. To the secondary transfer section. The horizontal conveyance path 65 for the recording sheet is constituted by an air suction belt 66 and the like including the paper feeding section, and a vertical conveyance path 71 provided with conveyance rollers 72, 73, 74 from the fixing device 70 is provided. The recording sheet S is discharged from the vertical conveyance path 71 to the upper surface of the main body 1 of the image forming apparatus.

Here, the printing operation of the full-color printer will be described. When the printing operation is started, the photosensitive drum 10 and the intermediate transfer belt 40 are driven to rotate at the same peripheral speed, and the photosensitive drum 10 is charged to a predetermined potential by the charging brush 11.

Subsequently, exposure of the cyan image is performed by the laser scanning optical system 20, and an electrostatic latent image of the cyan image is formed on the photosensitive drum 10. This electrostatic latent image is immediately developed by the developing device 31C, and the toner image is transferred onto the intermediate transfer belt 40 in the primary transfer section. Immediately after the end of the primary transfer, the developing device 31M is switched to the developing section D, and then exposure, development, and primary transfer of the magenta image are performed. Further, switching to the developing device 31Y, exposure, development, and primary transfer of the yellow image are performed. Further, switching to the developing device 31Bk, exposure of a black image, development, and primary transfer are performed, and a toner image is superimposed on the intermediate transfer belt 40 for each primary transfer.

When the final primary transfer is completed, the recording sheet S is sent to the secondary transfer section, and the full-color toner image formed on the intermediate transfer belt 40 is transferred onto the recording sheet S. When the secondary transfer is completed, the recording sheet S is conveyed to the belt-type contact heat fixing device 70, where the full-color toner image is fixed on the recording sheet S, and
Is discharged to the upper surface of the The present invention is described in more detail by the following examples.

[0056]

EXAMPLES In this example, the polyester resins A to A used
The method for producing C is described below. (Production of polyester resin A (for color toner)) Polyoxypropylene (2,2) -2,2- was placed in a glass four-necked flask equipped with a thermometer, a stirrer, a falling condenser and a nitrogen inlet tube. Bis (4-hydroxyphenyl) propane, polyoxyethylene (2,2) -2,2-
Bis (4-hydroxyphenyl) propane and terephthalic acid were charged in a molar ratio of 5: 5: 7.5. After further adding a polymerization initiator (dibutyltin oxide), these were reacted with stirring in a mantle heater under a nitrogen atmosphere at 220 ° C. to obtain a number average molecular weight (Mn) of 4800.
Weight average molecular weight / number average molecular weight 4.5, softening point 108
° C, glass transition point 66 ° C, acid value (AV) 4.2 KOHm
g / g of polyester resin A was obtained.

(Production of Polyester Resin B (for Black Toner)) Polyoxypropylene (2,2) -2 was placed in a glass four-necked flask equipped with a thermometer, a stirrer, a falling condenser and a nitrogen inlet tube. , 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,2)-
2,2-bis (4-hydroxyphenyl) propane, isododecenyl succinic anhydride, terephthalic acid and fumaric acid were charged in a weight ratio of 82: 77: 16: 32: 30. After further adding a polymerization initiator (dibutyltin oxide), these were added in a mantle heater under a nitrogen atmosphere.
The mixture was reacted at 220 ° C. with stirring to obtain a polyester resin B having a softening point of 110 ° C., a glass transition point of 60 ° C., and an acid value of 17.5 KOH mg / g.

(Production of Polyester Resin C (for Black Toner)) Styrene and 2-ethylhexyl acrylate were adjusted to a weight ratio of 17: 3.2 and placed in a dropping funnel together with digmyl peroxide as a polymerization initiator. on the other hand,
In a glass four-necked flask equipped with a thermometer, a stirrer, a falling condenser and a nitrogen inlet tube, polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene ( 2,2) -2,2
-Bis (4-hydroxyphenyl) propane, isododecenyl succinic anhydride, terephthalic acid, 1,2,4-anhydride
Benzene tricarboxylic acid and acrylic acid are added in a weight ratio of 4
It was adjusted to 2: 11: 11: 11: 8: 1 and charged with a polymerization initiator (dibutyltin oxide). While stirring these at 135 ° C. in a mantle heater under a nitrogen atmosphere under a nitrogen atmosphere, styrene or the like was dropped from the dropping funnel, and the temperature was raised and reacted at 230 ° C .; 24.5 KOH mg / g of polyester resin C was obtained.

The molecular weight was determined by gel permeation chromatography (807-IT; manufactured by JASCO Corporation).
And using tetrahydrofuran as a carrier solvent, the molecular weight was determined in terms of polystyrene.

For the softening point, use a flow tester (CF
T-500; manufactured by Shimadzu Corporation) using a 1.0 mm × 1.0 mm die for 1.0 g of the sample at a rate of temperature increase of 3.0 ° C./min. The measurement was performed under the conditions of a load of 30 kg and the temperature at which the sample flowed out by half was defined as the softening point.

The glass transition point was measured by a differential scanning calorimeter (DSC-
200; manufactured by Seiko Denshi Co., Ltd.)
0 mg was measured, and alumina was used as a reference, and the shoulder value of the main endothermic peak in the range of 30 to 80 ° C. was taken as the glass transition point.

The acid value was represented by the number of mg of potassium hydroxide required to dissolve the weighed sample in an appropriate solvent and neutralize the acidic group using an indicator such as phenolphthalein.

In this example, the following inorganic fine particles were used as the inorganic fine particles. Inorganic fine particles A (hydrophobic silica, 55% hydrophobicity, average primary particle size 7 nm, TS500; manufactured by Cabosil Co., Ltd.) Inorganic fine particles B (hydrophobic silica, 48% hydrophobicity, average primary particle size 15 nm, R974; Nippon Aerosil Inorganic fine particles C (hydrophobic silica, hydrophobicity 55%, average primary particle size 50 nm, R809; manufactured by Nippon Aerosil Co., Ltd.)

Inorganic fine particles D (hydrophobic titanium dioxide, rutile-type titanium dioxide (MT-150W; manufactured by Teica) having a hydrophobicity of 55% and an average primary particle size of 15 nm, surface-treated with n-hexyltrimethoxysilane) Inorganic fine particles E (hydrophobic titanium dioxide, hydrophobicity 60%,
Anatase type titanium dioxide having an average primary particle size of 20 nm
-Those treated with hexyltrimethoxysilane) Inorganic fine particles F (hydrophobic titanium dioxide, hydrophobicity 57%,
Anatase type titanium dioxide having an average primary particle size of 50 nm
-What is surface-treated with hexyltrimethoxysilane) Inorganic fine particles G (hydrophobic titanium dioxide, hydrophobicity 50%,
Inorganic fine particles F are further subjected to a fluorine-based silane coupling agent (surface-treated with CF ₃ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ )

Inorganic fine particles a (strontium titanate,
Average primary particle size 250 nm) inorganic fine particles b (strontium titanate, average primary particle size 1000 nm) inorganic fine particles c (hydrophobic titanium dioxide, degree of hydrophobicity 49%,
Rutile-type titanium dioxide having an average primary particle size of 250 nm (KR
-380; manufactured by Titanium Industry Co., Ltd.) with surface treatment with silicone oil)

The degree of hydrophobicity was determined by adding 50 ml of pure water to a 200 ml beaker, adding 0.2 g of a sample, and adding methanol dehydrated with anhydrous sodium sulfate from a burette while stirring the beaker. Using the point almost disappeared as the end point, the degree of hydrophobicity was calculated from the required amount of methanol by the following formula: [Methanol use amount / (50 + methanol use amount)] × 100.

A method for producing a melt-blended polypropylene wax used as a wax in the present example is described below. (Production of melt-blended polypropylene wax) Acid value 0
KOH mg / g non-oxidized polypropylene wax (Viscol 550P; manufactured by Sanyo Chemical Industries, Ltd.) and acid value 52
KOH mg / g oxidized polypropylene wax (UMEX 1010; manufactured by Sanyo Chemical Industries, Ltd.) in a weight ratio of 92:
8, melt-kneaded, cooled and pulverized to obtain an acid value of 4.0 KOH mg / g and a melt viscosity at 160 ° C of 20.
A melt-blended polypropylene wax having a softening point of 5 ° C. and a melting point of 150 ° C. was obtained.

Example 1 A polyester resin A and a cyan pigment (CI Pigment Blue 15-3) were charged and kneaded in a pressure kneader at a weight ratio of 7: 3. After cooling the obtained kneaded material, it was pulverized with a feather mill to obtain a pigment master batch.

Polyester resin A93 parts by weight, pigment master batch 10 parts by weight, polypropylene wax (Viscol TS200; manufactured by Sanyo Chemical Industries, Ltd .; acid value: 3.
2 parts by weight of 5KOH mg / g) and 1.5 parts by weight of a zinc salicylate complex (E84; manufactured by Orient Chemical Industries) are sufficiently mixed by a ball mill, and the mixture is subjected to a twin-screw extruder (PC).
M-30; Ikegai Iron Works Co., Ltd.)
Then, it was coarsely pulverized with a feather mill. This coarsely pulverized product was finely pulverized with a jet mill and classified into fine powder to obtain toner particles having a volume average particle size of 8.0 μm.

To 100 parts by weight of the obtained toner particles, 0.5 parts by weight of inorganic fine particles A, 1.0 part by weight of inorganic fine particles F and 1.0 part by weight of inorganic fine particles a were added and mixed by a ball mill to obtain a developer. Was.

Examples 2 to 9 and Comparative Examples 1 to 6 Developers were obtained in the same manner as in Example 1 except that the inorganic fine particles shown in Table 1 or Table 2 were used in the amounts indicated.

Example 10 A developer was obtained in the same manner as in Example 1 except that toner particles having a volume average particle diameter of 6.1 μm were prepared and used.

Example 11 40 parts by weight of a polyester resin B, 60 parts by weight of a polyester resin C, polyethylene wax (800P; manufactured by Mitsui Petrochemical Industries, Ltd .; melt viscosity at 160 ° C. 5400)
cps; softening point 140 ° C.) 1 part by weight, melt-blended polypropylene wax 3 parts by weight, acidic carbon black (Mogal L; manufactured by Cabot Corporation; pH 2.5; average primary particle size 24 nm) 8 parts by weight and zinc salicylate complex (E
84; Orient Chemical Industries Co., Ltd.) 2.5 parts by weight were sufficiently mixed with a Henschel mixer, and the mixture was melt-kneaded with a twin-screw extruder (PCM-30; manufactured by Ikegai Iron Works), cooled, and then hammer milled. And coarsely pulverized. This coarsely pulverized product was finely pulverized by a jet pulverizer and classified into fine powder to obtain toner particles having a volume average particle size of 8.2 μm.

To 100 parts by weight of the obtained toner particles, 0.5 parts by weight of the inorganic fine particles A, 0.5 parts by weight of the inorganic fine particles G and 1.0 part by weight of the inorganic fine particles a were added and mixed by a ball mill to obtain a developer. Was.

Examples 12 and 13 A developer was obtained in the same manner as in Example 11 except that the inorganic fine particles shown in Table 1 were used in the amounts indicated.

Evaluation The developer thus obtained was mounted on an electrophotographic printer (SP1000; manufactured by Minolta) equipped with a non-magnetic one-component developing device in which the pressing force of the regulating blade was variably modified, and the temperature was adjusted to room temperature. At normal humidity (25 ° C., 45%), a character pattern with a B / W ratio of 5% was set to be imaged, and “white streaks” and “charge amount” described in detail below were evaluated. These evaluations were made on the copied images at the initial stage (after 10 copies) and after 3000 copies.

(White Streaks) An A4-size halftone image was copied, and the occurrence of white streaks on the copied image was observed, and the occurrence of streaks on the layer was observed for a thin layer of toner formed on the developing sleeve. And evaluated according to the following ranking. ；: No streaks were generated on the thin toner layer formed on the sleeve, and no white streaks were generated on the image; △: Although some streaks were generated on the thin toner layer, No white streaks occurred on the image, and there was no problem in practical use. ×: Streaks occurred in the thin toner layer, and white streaks occurred on the image.

(Charge amount) As described above, after the white stripes were evaluated at the initial stage (after copying 10 sheets) and after 3000 sheets were copied, one sheet was passed in white development (blank mode), and The charge amount was measured by a toner suction method. The stability of the charge amount is excellent when the absolute value of the difference between the charge amounts at the initial stage and after 3000 copies is 5 μC / g or less.

The above evaluation results are shown in Tables 1 and 2 below together with the processing conditions in the above Examples and Comparative Examples.
Indicated by

[0080]

[Table 1]

[0081]

[Table 2]

From these results, it was clarified that the developer of the present invention did not generate white stripes in the copied image and was excellent in chargeability. It can be seen that the developer of the present invention has excellent durability and fluidity. In Comparative Example 1, 1
Streaks begin to appear in the thin toner layer after about 500 sheets,
At 2,000 sheets, the toner charge became so severe that the toner was spilled, and the measurement of the toner charge amount after copying 3,000 sheets was stopped. In Comparative Example 2, a decrease in the charge amount was observed after 3000 copies, and no refresh effect of the sleeve was observed. In addition, a white powder lump adhered to the regulating blade corresponding to the portion where the streak occurred. In Comparative Example 3, a thin toner layer was not formed on the sleeve from the beginning.
Subsequent copying was stopped. In Comparative Example 4, there was no problem of white stripes or the like, but because the fluidity of the toner was too high, slippage occurred in the regulating portion, and the rise of the toner charge was poor, the initial charge amount was low, and after 3000 copies, Showed a large increase in the charge amount. In Comparative Examples 5 and 6, the initial and 30
The change in charge amount after copying 00 sheets was large, and no refresh effect of the sleeve was observed.

[0083]

According to the present invention, it is possible to provide a non-magnetic one-component developer excellent in fluidity, chargeability and durability, in which white stripes are not generated in a copied image even by repeated copying.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a full-color image forming apparatus.

[Explanation of symbols]

10: Photoconductor drum, 11: Charging brush, 12: Cleaner, 20: Laser scanning optical system, 30: Full color developing device, 32: Developer carrier (sleeve), 33: Support shaft,
34: developer regulating member (blade), 40: intermediate transfer belt, 41: support roller, 42: support roller, 43: tension roller, 44: tension roller, 46: primary transfer roller, 47: secondary transfer roller, 60: paper feed unit, 6
1: paper feed tray, 62: paper feed roller, 63: timing roller, 66: air suction belt, 70: fixing device, 71: vertical transport path.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Anno 2-3-113 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Tsutsui Main Tax Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Osaka Metropolitan Building Minolta Co., Ltd. (72) Inventor Minoru Nakamura 2-3-13 Azuchicho, Chuo-ku, Osaka City, Osaka

Claims (1)

[Claims] 1. Negatively charged toner particles containing at least a binder resin and a colorant, having an average primary particle size of 1 to 70.
Inorganic fine particles having a small particle diameter of 100 nm and an average primary particle diameter of 100 n
A non-magnetic one-component developer containing fine particles of strontium titanate having a particle size of m to 500 nm.
A non-magnetic one-component developer, wherein the content of the strontium titanate fine particles is 0.3 to 3.0% by weight with respect to the toner particles.