WO2006051890A1

WO2006051890A1 - Non-magnetic one-component developer

Info

Publication number: WO2006051890A1
Application number: PCT/JP2005/020676
Authority: WO
Inventors: Tetsuo Hasegawa; Toru Nakamura
Original assignee: Ticona Gmbh
Priority date: 2004-11-11
Filing date: 2005-11-04
Publication date: 2006-05-18
Also published as: JP2006138978A; TW200629017A

Abstract

There is provided a developer for developing electrostatic latent images, including a non-crosslinked cyclic olefin polymer resin, which provides stable image quality over reproductions when used in a development system in which a developer-carrying member is brought into contact, or into contact under pressure, with a developer-regulating member. The non-magnetic one-component developer includes a binder, a colorant, and, if necessary, a charge control agent, and a free flow agent, wherein the binder includes a non-crosslinked cyclic olefin polymer resin, and the developer includes an abrasive externally added.

Description

DESCRIPTION

NON-MAGNETIC ONE-COMPONENT DEVELOPER

Field of the Invention

The present invention relates to a developer for developing an electrostatic latent image, in particular, to a developer used in a non-magnetic one-component developing system in which a rotating developer-carrying member is brought into contact, or into contact under pressure, with a fixed developer-regulating member.

Background of the Invention

With the rapid development of office automation in the past ten years or so, output images from copiers or printers having an electrostatic image-developing system are increasingly required to have more clearness, better transparency, and better fixing properties. Further, in recent years, due to the needs for space-saving, or the wide spread of personal computers in homes, demands for small copiers and printers are high. In addition, full-color copiers and printers have also generally been spreading. For these reasons, the demand for developers, which not only satisfy the basic performance related to the image quality, but also are suitable for copiers or printers of such types, has increased.

As such developers, there have been known non-magnetic one-component developers. The developers of this type, in contrast to two component developers which comprise both a carrier and a toner, do not contain a carrier. Therefore, they offer the advantage that no consideration has to be paid to variation of triboelectricity which may occur with a change in the mixing ratio between the carrier and the toner. In addition, they are suitable for small machines because the device for precisely controlling said mixing ratio can be dispensed with. Further, unlike magnetic developers, they do not need black magnetic powder, and thus are suitable for full-color development. There have been proposed several developing processes which use a non-magnetic one-component developer, but, among these processes, use is usually made of a process in which a developer-regulating member is brought into contact, or into contact under pressure, with a rotating developer-carrying rubber member, and a developer is allowed to flow between the two members to form a thin film of the developer on the roll. This thin film of developer is then directly conveyed to the developing area, and applied onto the electrostatic latent image, thereby performing development.

As a system suitable as such a non-magnetic one-component developer, one has been proposed which includes a binder based on a polyolefin resin having a cyclic structure. These resins generally excel in various aspects of developing performance, such as transparency, clearness, and fixing properties, compared with conventional styrene/acrylic resins or polyester resins, and offer great advantages in that they provide images of very high quality. For this, reference should be made to, for example, EP0843223A1 , EP0978766A1 , and WO 98/29783.

Of such polyolefin resins having a cyclic structure, non-crosslinked cyclic olefin polymer resins (hereinafter also referred to as COCs) exhibit very high performance as a binder in toners in such a way that they, when used in developers, provide developers having good low-temperature fixing properties, no occurrence of offset on fixing rollers, high gloss, and high triboelectric stability under various environments, and also stably allowing high-speed printing and high image quality. However, according to experiments which the present inventors carried out, there arose problems in respect to the image quality intactness or stability over reproductions. That is, when developers, which comprise such binders, are applied in the aforementioned developing systems having a developer-carrying member and a developer-regulating member, then the developers were fused onto the regulating member due to an elevation in the friction heat on the interface between said two members and, as a result, "streaks" form over the image; and, therefore, the quality of the initial output image could no longer be reproduced until later. Description of the Invention

Accordingly, an object of the present invention is to provide a developer for developing electrostatic latent images, which comprises a non-crosslinked cyclic olefin polymer resin, and, even when used in said developing system having a developer-carrying member and a developer-regulating member brought into contact, or into contact under pressure, with each other, does not cause the above problems and, thereby, provides long-lasting image quality stability over reproductions.

In order to solve the above-described problems, the present inventors have tried various approaches, such as: 1) shaping the toner in the form of a sphere to increase the apparent strength of the toner; 2) adding a lubricant externally over, or internally into, the toner, thereby making the surface of toner slippery; 3) crosslinking the binder to strengthen the toner; 4) internally adding SiO₂ or TiO₂ as a filler to increase the apparent strength of the toner; 5) reducing the contact pressure between the developer-carrying member and the developer-regulating member; and 6) externally adding an abrasive to the toner. However, for approaches 1)-5), the following drawbacks were observed: for 1), desired effectiveness was only observed until the output of approximate 300 copies and, thereafter, streaks and fogs appeared; for 2), no effectiveness was acknowledged; for 3), certain effectiveness was acknowledged, but there still remained the problem that crosslinked resins of COCs could only be synthesized with difficulty; for 4), no effectiveness was acknowledged; and, for 5), certain effectiveness was acknowledged, but fogs appeared in the initial image. Therefore, it was found that only approach 6), i.e., the external addition of abrasives, eradicated said problems.

Accordingly, the present invention provides a non-magnetic one-component developer comprising a binder, a colorant, and, if necessary, a charge control agent, and a free flow agent, wherein the said binder comprises a non-crosslinked cyclic olefin polymer resin, and the developer also comprises an abrasive externally added. In the following, the constituents of the non-magnetic one-component developer of the present invention will be described one by one. 1) Binder:

The binder used according to the present invention comprises a cyclic olefin polymer. The cyclic olefin polymer is a polymer obtainable by polymerization methods which uses, for example, a metallocene catalyst, a Ziegler catalyst, and a catalyst for metathesis polymerization, that is, a double bond opening and ring opening polymerization reaction. Said cyclic olefin polymer is known per se, and examples of its synthesis are disclosed in, for example, EP0560090A1, EP0501370A1, EP0610851A1, EP203799A1 , EP407870A1, EP283164A1, and EP156464A1.

Preferably, said cyclic olefin polymer is a copolymer of a lower alkene having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms (α-olefin, in its broad sense, non-cyclic olefin), and a cyclic and/or polycyclic compound (cyclic olefin) having 3 to 17 carbon atoms, preferably 5 to 12 carbon atoms and at least one double bond, and is colorless and transparent and has high transparency. Examples of lower alkenes that can constitute said polymer include ethylene, propylene and butylenes. Examples of cyclic olefins include norbornene, tetracyclododecene (TCD), dicyclopentadiene (DCPD), and cyclohexene. Of the above examples, particularly preferably selected are ethylene for the lower alkene, and norbornene for the cyclic olefin.

According to the aforementioned publications, said cyclic olefin polymer can be obtained by polymerizing one or more cyclic olefin monomers, optionally with one non-cyclic olefin monomer, at a temperature of -78 to 150⁰C, preferably 20 to 80⁰C, and at a pressure of 0.01 to 64 bar, in the presence of a catalyst composed of at least one metallocene (for example, those containing zirconium or hafnium) and a co-catalyst, such as an aluminoxane. Other useful polymers can be found in EP317262A, and it is also possible to use a hydrogenated polymer or a copolymer of styrene with dicyclopentadiene, as disclosed therein. Since a metallocene catalyst is activated in the state where it is dissolved in an inert aliphatic or aromatic hydrocarbon, pre-activation and polymerization are conducted by, for example, dissolving a metallocene catalyst in a solvent such as toluene. The important properties of cyclic olefin polymers are their softening point, melting point, viscosity, dielectric properties, anti-offset temperature range, and transparency. These can be advantageously adjusted by suitable selection or use of monomers or comonomers, the ratio of comonomers, molecular weight, molecular weight distribution, hybridization, blending, and additives.

The designed molar ratio of non-cyclic olefin to cyclic olefin introduced to the polymerization reaction can vary within a wide range depending on the desired olefin polymer having a cyclic structure, and is preferably adjusted to 50 : 1 to 1 : 50 and particularly preferably 20 : 1 to 1 : 20.

For example, when two compounds, ethylene for the non-cyclic olefin and norbornene for the cyclic olefin, are introduced as copolymer components and allowed to react, the glass transition temperature (Tg) of the resulting reaction product, an olefin polymer having a cyclic structure (also referred to as "cyclic olefin polymer" hereinafter, for simplicity), is largely affected by the ratio between said two compounds introduced to the reaction, and the Tg tends to increase when the content of norbornene is increased. For example, if the amount of norbornene is 15% or less (85% or more of ethylene), a copolymer having a Tg of -20°C to 65°C can be obtained. On the other hand, if the amount of norbornene is 15% or more, a copolymer having a Tg of more than 65°C to 180⁰C can be obtained. Physical properties, such as number average molecular weight, can be adjusted according to methods known from the literature.

For the cyclic olefin polymer used in the present invention, use is preferably made of those having a number average molecular weight of 100 to 100,000, more preferably 500 to 50,000, and a weight average molecular weight of 200 to 300,000, preferably 3,000 to 200,000, and a glass transition temperature of -20⁰C to 180⁰C, and preferably 40 to 80⁰C. As used herein, the "glass transition temperature (Tg)" means a temperature that corresponds to the midpoint of the transition, which shows the transition heat, measured by differential scanning calorimetry (DSC). The "number average molecular weight (Mn)" and "weight average molecular weight (Mw)" are values measured by gel permeation chromatography (GPC) against a polyethylene or polystyrene standard, and more specifically are values measured under the following conditions.

Column used: JORDI-SAEULE 500x10 LINEAR (JORDI, US) Mobile phase: 1 ,2-dichlorobenzene (135°C), flow rate 0.5 ml/min. Detector: differential refractometer

The cyclic olefin polymer can be modified with an acid and, in this case, the acid value is 5 to 50 mg KOH/g. This modification with an acid will be described in more detail below.

In one embodiment of the present invention, the cyclic olefin polymer is non-modified and has a relatively low molecular weight; specifically, it has a number average molecular weight of 100 to 20,000 and preferably 500 to 7,000, and a weight average molecular weight of 200 to 40,000 and preferably 3,000 to 20,000, and a glass transition temperature of -20⁰C to 65°C, and preferably 40⁰C to 65°C. The corresponding acid-modified product has a number average molecular weight of 100 to 20,000 and preferably 500 to 8,800, and a weight average molecular weight of 300 to 80,000 and preferably 3,000 to 25,000, and a glass transition temperature of -20⁰C to 65°C and preferably 4O⁰C to 65⁰C, and an acid value of 5 to 50. The non-modified cyclic olefin polymer and the acid-modified cyclic olefin polymer may be used independently, or in combination. In the latter case, they can be appropriately combined in the weight ratio range of 95 : 5 to 5 : 95.

In another embodiment of the present invention, the cyclic olefin polymer is non-modified and has a relatively high molecular weight; specifically it has a number average molecular weight of 1 ,000 to 100,000 and preferably 2,000 to 50,000, and a weight average molecular weight of 2,000 to 200,000 and preferably 4,000 to 100,000, and a glass transition temperature of 60 to 18O⁰C and preferably 60⁰C to 8O⁰C. The corresponding acid-modified polymer has a number average molecular weight of 1,000 to 100,000 and preferably 15,000 to 50,000, and a weight average molecular weight of 2,500 to 300,000 and preferably 6,000 to 200,000, and a glass transition temperature of 6O⁰C to 180⁰C and preferably 60⁰C to 80⁰C, and an acid value of 5 to 50. These non-modified cyclic olefin polymer and acid-modified cyclic olefin polymer may also be used independently, or in combination, and, in the latter case, they can be appropriately combined in the weight ratio range of 95 : 5 to 5 : 95.

As mentioned above, through the introduction of carboxyl groups into the cyclic olefin polymer, i.e., acid-modification with carboxylic acids or carboxylic anhydrides, it is possible to improve the compatibility of the cyclic olefin polymer with other resins and improve the dispersibility of pigments in toners. Such introduction of carboxyl groups can also improve the adhesion and, therefore, fixation of toners to substrates, such as paper or films.

For introducing carboxyl groups, a two-step reaction process is advantageous, in which a cyclic olefin polymer is first prepared and, subsequently, carboxyl groups are introduced to the polymer. There are at least two methods for introducing carboxyl groups. One is "melt air oxidation", which is carried out by oxidizing the terminal alkyl groups of the polymer (e.g., methyl groups) to convert them to carboxylic groups. In this method, however, if the polymer is a cyclic olefin polymer synthesized using a metallocene catalyst, it is difficult to introduce many carboxyl groups to the polymer because such a polymer has almost no branches.

Specifically, the introduction of carboxyl groups can be carried out by graft-polymerizing, onto a cyclic olefin polymer, carboxylic acids or carboxylic anhydrides, such as acrylic acid or methacrylic acid, using a peroxide as a initiator, such as t-butanol peroxide, so that a degree of grafting of preferably 1 to 5% by weight and particularly preferably 3 to 5% by weight relative to the olefin polymer is attained. With a degree of grafting of less than 1% by weight, the aforementioned effectiveness, such as compatibility, is not sufficient. On the other hand, if the degree of grafting is more than 5% by weight, intermolecular crosslinking occurs within the olefin polymer and increases the molecular weight of the polymer, resulting in a kneadability and grindability poor for practical use, and also causing strong yellow discoloration and, therefore, a loss of transparency. Therefore, in the latter case, there is a tendency to produce a polymer unsuitable for use in color toners, for which the colorlessness and transparency of the polymer are required. The same improvement can also be achieved by introducing hydroxyl groups or amino groups according to known methods.

The cyclic olefin polymers having the aforementioned properties are also commercially available. Ticona GmbH (DE) manufactures and sells such polymers under the trade name of "Topas TM", "Topas TMG, "Topas TB", and "Topas TBG" (Topas is a registered trademark of the same company).

In one embodiment of the present invention, the polymers described below are used as said cyclic olefin polymers.

• Low-molecular-weight ethylene-norbomene copolymers (e.g. "Topas TM"), or carboxylic acid-modified derivatives thereof (the acid value is about 10 to 20 mg KOH/g, e.g. "Topas TMG"), having: a glass transition temperature (Tg) of 40 to 59°C, a number average molecular weight (Mn) of 500 to 7,000, a weight average molecular weight (Mw) of 3,000 to 20,000, a polydispersity (weight average molecular weight (Mw)/number average molecular weight

(Mn)) of 10 or less, a copolymerization molar ratio of ethylene to norbornene of 85/15 to 95/5.

• High-molecular-weight ethylene-norbomene copolymers (e.g. "Topas TB"), or carboxylic acid-modified derivatives thereof (the acid value is about 10 to 20 mg KOH/g, e.g. "Topas TBG"), having: a glass transition temperature (Tg) of 60 to 80⁰C, a number average molecular weight (Mn) of 2,000 to 50,000, a weight average molecular weight (Mw) of 6,000 to 200,000, a polydispersity (Mw/ Mn) of 4 to 10, a copolymerization molar ratio of ethylene to norbomene of 75/25 to 85/15.

Further, in order to ensure good fixability and to obtain a wide anti-offset temperature range, it has also proven advantageous to combine said low-molecular-weight cyclic olefin polymers and said high-molecular-weight cyclic olefin polymers. Therefore, it is also included in the scope of the present invention to use such a combination of high-molecular-weight and low-molecular-weight polymers.

In one example of such an embodiment, the cyclic olefin polymer used can be composed of a) a low-molecular-weight polymer or polymer fraction having the physical properties described below, and b) a high-molecular-weight polymer or polymer fraction having the physical properties described below. In this case, the cyclic olefin polymer may be a mixture of polymer a) and polymer b); or may be those having one peak in the molecular weight distribution and composed of a polymer fraction having a relatively low number-average molecular weight and a polymer fraction having a relatively high number-average molecular weight; or may be those having two or more peaks in the molecular weight distribution, at least one of which peaks corresponding to a polymer fraction having a relatively low number-average molecular weight and the other peak(s) corresponding to a polymer fraction(s) having a relatively high number-average molecular weight.

Thus, by having the cyclic olefin polymer composed of a) a low-viscosity (low-molecular-weight) polymer or polymer fraction and b) a high-viscosity (high-molecular-weight) polymer or polymer fraction in this way, the anti-offset temperature range expands toward both the higher and lower temperature sides and, as a result, the toner fixability, during high-speed copying and also at a low temperature and pressure, can be simultaneously improved.

In a specific embodiment of the present invention, the polymer or polymer fraction a) (hereinafter referred to as component a)) can have a number average molecular weight {measured by GPC against a polyethylene standard; the same will apply hereinafter} of less than 7,500, preferably 1 ,000 to less than 7,500, and more preferably 2,000 to less than 7,500; a weight average molecular weight of less than 15,000, preferably 1 ,000 to less than 15,000, and more preferably 4,000 to less than 15,000; an intrinsic viscosity (Lv.; measured at 135°C for a solution of 1.Og of the polymer uniformly dissolved in 100ml of decalin) of less than 0.25 dl/g; and a glass transition temperature (Tg) of preferably less than 70⁰C.

The polymer or polymer fraction (b) (hereinafter referred to as component b)) can have a number average molecular weight of 7,500 or more and preferably 7,500 to 50,000; a weight average molecular weight of 15,000 or more and preferably 15,000 to 200,000; an intrinsic viscosity (i.v.) of 0.25 dl/g or more.

The content of component b) is preferably less that 50% by weight of the entire binder, preferably 5 to 35% by weight. Component b) imparts structural viscosity to the toner, thereby providing improvement in the offset-preventing action and in the adhesion to substrates, such as paper and films. If the content of component b) is more than 50% by weight, the uniform kneadability may extremely deteriorate and the toner performance may be impaired. Specifically, it may cause a difficulty in obtaining high quality images, i.e., clear images having high fixing strength and good heat responsibility; or may impair the mechanical grindability and cause a technical difficulty in attaining a particle size necessary for toners.

As used herein, the "polymer or polymer fraction" means, for those cyclic olefin polymers composed of a mixture of components different in their number average molecular weight or in other properties, respective polymer components before being mixed; and, for the other cases, means respective polymer fractions fractionable from a final synthesis product by a suitable means, such as GPC. If these polymer fractions both nearly have monodispersity, the overall polydispersity is about 2.0. The number average molecular weight (Mn) of 7,500 approximately corresponds to the weight average molecular weight (Mw) of 15,000. Low-viscosity component a), of which the cyclic olefin polymer is composed, contributes to the expansion of the anti-offset temperature range toward the lower temperature side. In contrary, high-viscosity component b) contributes to higher-temperature side expansion. To effectively expand the anti-offset temperature range toward the high temperature side, the presence of a high-viscosity component b) having a number-average molecular weight of 20,000 or more is preferable.

The ratio of component a) and component b) in the cyclic olefin polymer is preferably 50% by weight or more of component a) : 50% by weight or less of component b), and particularly preferably 65 to 95% by weight of component a) : 5 to 35% by weight of component b).

The high-viscosity (high-molecular-weight) and low-viscosity (low-molecular-weight) cyclic olefin polymers have a low Mw/Mn of 1.5 to 2.5. The polydispersity Mw/Mn indicates the dispersity of molecular weight distribution, and is determined based on the aforementioned number-average-molecular weight (Mn) and weight-average molecular weight (Mw). Namely, these polymers nearly have monodispersity. Owing to this, it is possible to produce a developer having a fast heat response, thereby providing strong fixation and allowing fixation at a low temperature and pressure. Furthermore, these polymers contribute to other properties of toners, such as storage stability, toner-spent resistance, and electrical stability. The electric stability represents the uniformity of charge distribution and of charging and discharging efficiency. In particular, it is preferable for the low-viscosity polymer or polymer fraction to have, or nearly have, monodispersity because the resulting toner, in this case, has fast heat response as is shown by its quick melting and coagulation behaviors.

Since the cyclic olefin polymers are colorless and transparent and have high transparency, these can keep sufficient transparency even if the three principle colors, pigments, yellow, cyan and magenta, are added thereto (For this reason, these polymers have already been utilized in color toners in the art). In addition, the cyclic olefin polymers have a very low heat of fusion, as is measured using DSC and, therefore, a significant saving of the energy consumption for the fixation of toners can also be expected.

For those cyclic polyolefin resins composed of a low-viscosity polyolefin resin having a number-average molecular weight of less than 7,500 and a high-viscosity polyolefin resin having a number-average molecular weight of more than 25,000, it may be advantageous to add thereto medium-viscosity cyclic olefin polymer resins having a number-average molecular weight of 7,500 to less than 25,000 in order to improve the compatibility of the high-viscosity component with others because it provides a continuous offset-free range.

Namely, the present invention advantageously includes in its scope the embodiments where the binder comprises a cyclic olefin polymer resin and the latter polymer resin is composed of resins or resin fractions having three number-average molecular weight ranges, as measured by GPC, of less than 7,500, of 7,500 to less than 25,000, and of 25,000 or more. The resin fractions, which constitute said respective molecular weight ranges, may be those fractions which are present in different resins each having one or two peaks in their molecular weight distribution and are classifiable to said molecular weight ranges, respectively, or those fractions present in one resin, which have three or more peaks in its molecular weight distribution by, e.g., mixing, so that at least one molecular weight peak appears in the respective molecular weight ranges.

The proportion of the medium-viscosity cyclic polyolefin resin or resin fraction, to be used for improving the compatibility, is preferably 1 parts by weight, and more preferably 5 parts by weight or more, per 100 parts of the entire binder.

According to the present invention, a developer, which uses a binder obtained by mixing said cyclic olefin polymer with other resins and/or waxes, can also achieve high-quality images, that is, images having clearness and good fixing strength. Examples of the other resins include styrene-based polymers, such as polystyrenes and substituted polystyrenes, styrene-acrylic ester copolymers, styrene-methacrylic ester copolymers, and styrene-acrylonitrile copolymers; acrylic resins, such as poly(meth)acrylic resins and poly(meth)acrylic ester resins; polyester resins, and epoxy resins, individually, or a mixture or hybrid polymer of said polymers. Examples of waxes include plant waxes, animal waxes, mineral waxes, and petroleum waxes; specifically, camauba wax, candelilla wax, lanolin, beeswax, montan wax, paraffin waxes, microcrystalline waxes, and the like; higher fatty acid derivatives, for example stearic acid, palmitic acid, oleic acid, lauric acid, and polyhydric alcohol esters, as well as metal salts of higher fatty acids, such as calcium stearate, zinc stearate, lead stearate, and magnesium stearate; and polyolefin waxes, for example polyethylene waxes and polypropylene waxes. The proportions of the cyclic olefin polymer resin and the other resin and/or wax in the binder are, per 100 parts by weight of the entire binder in each case, preferably 1 to 100 parts by weight of the former, more preferably 20 to 90 parts by weight, and particularly preferably 50 to 90 parts by weight; and preferably 99 to 0 parts by weight of the latter, more preferably 80 to 10 parts by weight, and particularly preferably 50 to 10 parts by weight. If the amount of the former, the cyclic olefin polymer resin, is less than 1 part by weight, it may then be difficult to obtain high-quality images.

The binder, which comprises the cyclic olefin copolymer resin, is used in amounts of typically 70 to 98 parts by weight, and preferably 80 to 95 parts by weight, per 100 parts of the entire developer.

2) Abrasive:

The non-magnetic one-component developer according to the present invention comprises, as a further characteristic component, an abrasive, which has been added externally. The abrasive is preferably one or more selected from the group consisting of α-SiC, β-SiC, CeO₂, ZrO₂, B₄C, Si₃N₄, and AI₂O₃. Particularly preferable is α-SiC, β-SiC, or a mixture thereof.

In one particular embodiment of the present invention, an abrasive having the following characteristics is used:

Vickers hardness: 1 ,000 to 3,000 kg/cm², Young's modulus: 1.5 x 10⁶ to 6 x 10⁶ kg/cm²,

Melting point: 1900 to 2500⁰C,

Thermal conductivity (at room temperature): 0.04 to 0.4 cal/cm-sec-°C,

Particle size distribution: 0.01 to 1 μm, preferably 0.03 to 0.5 μm.

If the Vickers hardness is less than 1 ,000 kg/cm², the developer (or abrasive) may have a slight preventing effect against the formation of "streaks" and, thus, may lead to poor image quality intactness over reproductions. If the thermal conductivity is higher than 0.5 cal/cm-sec-°C, the thermal fixation of images may be insufficient. The Vickers hardness can be measured in accordance with the method specified in JIS R1610.

The abrasive is preferably a white or colorless one for use in color non-magnetic one-component developers. However, even if it is lightly brownish, there might arise no problem in the quality of images, since its mixing ratio to toner is low.

The mixing ratio of said abrasive to the developer of the present invention is typically 0.1 to 10 parts by weight per 100 parts of the entire developer, preferably 0.3 to 8 parts by weight. If the amount is less than 0.1 part by weight, the preventing effect against the formation of "streaks" is not enough. If the amount is more than 10 parts by weight, the abrasive may adhere to the images, thereby causing disadvantages, such as poor color quality of color images, or weak image fixation.

3) Colorant:

As colorants used in the non-magnetic one-component developer of the present invention, any dyes or pigments, which are conventionally used in the art, can be used. Examples of such colorants include those conventionally used in toners for monochromatic or full color copiers, such as carbon black, diazo yellow, phthalocyanine blue, quinacridone, carmine 6B, monoazo red, and perilene. The mixing ratio of the colorants to the developer of the present invention is typically 3 to 12 parts by weight per 100 parts of the entire developer, and preferably 5 to 10 parts by weight.

4) Charge Control Agent

The non-magnetic one-component developer according to the present invention may comprise a charge control agent if necessary, specifically if it is necessary to control the electrostatic charge of the developer. Such a charge control agent is known in the art, and any conventionally used one can be used. Examples of such charge control agents include: nigrosine dyes, fatty acid-modified nigrosine dyes, metal-containing nigrosine dyes, metal-containing fatty acid-modified nigrosine dyes, 3,5-di-t-butylsalicylic acid chromium complexes, quaternary ammonium salts, triphenylmethane dyes, and azochromium complexes.

The mixing ratio of the charge control agent to the developer of the present invention is typically 0.5 to 4 parts by weight per 100 parts of the entire developer, preferably 1 to 2 parts by weight.

5) Free Flow Agent

Free flow agents are also additives whose kinds, functions and usage are well known in the art. They can be added and used in accordance with conventional methods. Specific examples of such free flow agents include colloidal silicas (including fumed silicas), aluminum oxides, and titanium oxides. Hydrophobically-treated free flow agents are preferably used.

The mixing ratio of the free flow agent to the developer of the present invention is typically 0.01 to 2.0 parts by weight per 100 parts of the entire developer, preferably 0.1 to 2.0 parts by weight.

6) Other Optional Components

Unlike conventional developers, the non-magnetic one-component developer according to the present invention is characterized essentially in that the binder used comprises the aforementioned cyclic olefin polymer resin, and an abrasive is externally added. Therefore, not only the aforementioned colorants, charge controlling agents, and free flow agent, but also any conventionally and commonly used components can be used in suitable amounts. Examples of such conventional components include lubricants, preferably hydrophobically-treated lubricants, which comprise metal salts of fatty acids, such as barium stearate, calcium stearate, and barium laurate, and functionality-imparting agents.

As the functionality-imparting agent, various polar or nonpolar waxes can be added in order to expand the anti-offset temperature range and, thereby, improve the anti-offset property of the toner. Examples of polar waxes include amide waxes, carnauba wax, higher fatty acids and esters thereof, metallic soaps of higher fatty acids, partially saponified higher fatty acid esters, and higher aliphatic alcohols. Examples of nonpolar waxes include polyolefin waxes and paraffin waxes. At least one wax selected from the above ones can be used as a functionality-imparting agent.

Of the above various waxes, fatty acid amide waxes, oxidized polyethylene waxes, acid-modified polypropylene waxes, and mixtures of oxidized/non-oxidized polyethylene waxes are preferably used from the viewpoint of obtaining a wider anti-offset temperature range.

To improve the toner performance by expanding the anti-offset temperature range, waxes should be preferably used as follows: Preferably, two or more waxes whose melting points (the peak temperature measured by DSC) are in the range of 80 to 140⁰C, but having different melting points within said range, respectively, are used in combination. If the melting point is lower than 80⁰C, the problem of blocking tends to occur in the toner due to the low-melting wax.

On the other hand, the functionality-imparting agent is required to be completely melted at kneading temperatures higher than the softening point of the binder and, therefore, the selection of it is limited by the softening point (typically about 130 to 140⁰C) of the cyclic olefin polymer, which is the main component of the binder. Thus, usually the upper limit of the melting point is preferably 14O⁰C. Specifically, two or more waxes are selected from the fatty acid amide waxes or hydrocarbon waxes described below as examples.

i) Wax Having Polar Groups

Various fatty acid amide waxes, such as arachic acid monoamide (m.p. 11O⁰C), behenic acid monoamide (m.p. 115⁰C), N.N'-dioleylsebacic acid amide (m.p. 115°C), N.N'-dioleyladipic acid amide (m.p. 119°C), and N,N^J-distearylisophthalic acid amide (m.p. 129°C); oxidized olefin waxes, such as oxidized polyethylene waxes (m.p. 116°C); acid-modified polyolefin waxes, such as acid-modified polypropylene waxes (m.p. 138°C); carnauba wax (m.p. 80⁰C), and mixtures of oxidized/non-oxidized polyethylene waxes.

ii) Nonpolar Wax (not having polar groups)

Olefin waxes, a sort of hydrocarbon waxes, such as polyethylene waxes (m.p. 100 to 130⁰C), polypropylene waxes (m.p. 120 to 150⁰C), paraffin waxes (m.p. about 60 to 8O⁰C)₁ sasol wax (solidification point about 98°C), and microcrystalline waxes (m.p. about 80 to 100⁰C). In addition, as a further functionality-imparting agent for preventing offset phenomena, a silicone oil, which provides a releasing effect, can be combined with the aforementioned waxes provided that it does not impair the advantages of the present invention.

In the non-magnetic one-component developer of the present invention, the particle size distribution of the toner base material, before the addition of external additives (such as abrasives, free flow agents, lubricants), is typically 5 to 20 μm and preferably 3 to 10 μm, whereas, as mentioned above, the particle size distribution of the abrasive can be, in one preferred embodiment, 0.05 to 1 μm and preferably 0.03 to 0.5 μm. In this case, it is preferable that the ratio of the particle size distribution of the abrasive to that of the toner base material is 1:100 to 1:10. By using such a ratio, the surfaces of the individual particles of the toner base material are uniformly and perfectly covered by the abrasive material and, therefore, the advantages not only of the maximum abrasion efficiency, but also of non-excessive fixation temperature on substrates, such as paper, can be obtained. Therefore, said embodiment, where the ratio of the particle size distribution to that of the toner base material is within the aforementioned range, is also an advantageous embodiment of the present invention.

The particle size distribution of the toner base material and abrasive of the present invention can be measured by various methods, for example, using Coulter Counter TA-II or Coulter Multisizer (Coulter). Specifically, Coulter Multisizer is used, and an interface (Nikkaki K.K., JP) that outputs population distribution and a personal computer PC9801 (NEC Corp., JP) are connected thereto. As an electrolytic solution, an aqueous 1% NaCI solution is prepared using first class grade sodium chloride. For example, ISOTON R-Il (Coulter Scientific Japan Co., JP) may be used. Measurement is carried out by adding 100 to 150 ml of the above aqueous electrolytic solution, and further adding 2 to 20 mg of a sample to be measured. The electrolytic solution in which the sample has been suspended is subjected to a dispersing treatment for about 1 to about 3 minutes in an ultrasonic dispersion machine. The number of toner particles and abrasive particles is measured by means of the above Coulter Multisizer using a suitable aperture, and the population distribution is calculated based on the measured number of particles.

The non-magnetic one-component developer can be prepared using any methods conventional for this type of developer, without requiring special apparatuses or methods. For example, it can be prepared by mixing the binder of the present invention, colorants, and, optionally, charge-control agents, and, if necessary, other optional internal additives in a twin-roll, three-roll or pressure kneader, or a twin-screw extruder, typically at a temperature of 80 to 18O⁰C for 10 minutes to 2 hours; then, after cooling, coarsely crushing the mixture in a hammer mill or any other suitable means; and, subsequently, finely grinding with a jet mill or any other suitable fine grinders; and classifying the mixture using an air classifier or others, thereby giving a toner base material. The toner base material can be then combined with external additives (e.g., abrasives, free flow agents, lubricants, etc.) in a Henschel mixer, a tumbling mixer, a coffee mill, or the like, to give the inventive non-magnetic one-component developer. The non-magnetic one-component developer according to the present invention is highly suitable for use in non-magnetic one-component developing systems in which a rotating developer-carrying member and a fixed developer-regulating member come into contact, or into contact under pressure, with each other. The use of the non-magnetic one-component developer of the present invention makes it possible to successfully dissolve the problems of non-intact reproductions in such a type of developing system. Further, the external addition of abrasives does not affect the image quality, and it is thus possible to perfectly enjoy those benefits attainable by the use of the cyclic olefin polymer as binder, such as low-temperature fixability, no occurrence of offset on the fixing rollers, high gloss, and stable triboelectricity under different environments.

Accordingly, the present invention provides the aforementioned non-magnetic one-component developer for use in non-magnetic one-component developing systems in which a rotating developer-carrying member and a fixed developer-regulating member come into contact, or into contact under pressure, with each other. The present invention further provides copiers or printers, which are operated with a non-magnetic one-component developing system and have, as construction elements, a rotating developer-carrying member and a fixed developer-regulating member brought into contact, or into contact under pressure, with each other, particularly small and/or color copiers and printers, wherein the developer used for developing electrostatic latent images is the non-magnetic one-component developer of the present invention. Developing systems, copiers and printers of said type are known per se. As the developer-carrying member, those called soft rollers and hard rollers are known, for example. As the developer-regulating member, for example, those made of metals, rubbers or resins and in the form of a blade, a bar or a roller are known. According to the present invention, any types of these members can be used with the inventive developer. In one preferred embodiment of the present invention, a developer-carrying member made of a rubber and a developer-regulating member in the form of a metal blade are used. Various copiers and printers of said type are commercially sold in the market and one example is the color printer CLP-500 from Samsung, which was used in examples described below. The present invention can be put into practice only by replacing the conventional developers used in such known copiers or printers with the developer of the present invention.

Examples

In the following the present invention will be described in more detail based on examples. However, it should be understood that these examples are not intended to limit the present invention. Example 1 Table 1

The components shown in Table 1 were kneaded in a twin-screw extruder (PCM-45, lkegai Chemical Industries, Ltd., JP) at 180⁰C and 60 rpm, crushed in a hummer mill, finely ground in SR-25 (Nisshin Engineering Inc., JP), and classified to obtain a toner base material having a particle size distribution of 5 to 20 μm.

Then, with 100 parts by weight of the above toner were mixed 7 parts of α-SiC (trade name: GC-15R, Yakushima Denko Co., Ltd., JP) having a particle size distribution of 0.05 to 0.5 μm (average particle size of 0.1 μm), a Vickers hardness of 2000 to 3000 kg/mm², a Young's modulus of 4 x 10⁶ to 6 x 10⁶ kg/cm² and a thermal conductivity of 0.16 to 0.4 Cal/cm-sec-°C, and 0.6 part by weight of a hydrophobic silica (trade name: R972, NIPPON AEROSIL, JP) in a coffee mill for 10 seconds, obtaining a non-magnetic one-component developer.

Subsequently, the developer was charged in a CLP-500 Printer (LBP color printer, manufactured by Samsung, KR), and subjected to a test for initial image quality stability over successive reproductions. Example 2

The same procedure as in Example 1 was repeated except that 5 parts by weight of pigment yellow 160 (trade name: Yellow HG, Clariant, DE) was used instead of 6 parts by weight of carbon black, and 3 parts by weight of β-SiC having a particle size distribution of 0.05 to 0.5 μm

(average particle size of 0.2 μm) (trade name: SM-15, from ESK, DE) was used instead of the α-SiC.

Example 3

The same procedure as in Example 2 was repeated except that 5 parts by weight of AI₂O₃ having a particle size distribution of 0.1 to 0.5 μm (average particle size of 0.2 μm) (trade name: Nanofine A, from Hinomoto Kenmazai Co., Ltd., JP) was used instead of the β-SiC.

Example 4

The same procedure as in Example 1 was repeated except that 5 parts by weight of pigment violet 19 (trade name: PV FastRed E5B, Clariant, DE) was used instead of 6 parts by weight of carbon black, and ZrO₂ having a particle size distribution of 0.1 to 0.5 μm (average particle size of 0.3 μm) (trade name: ZrO₂, Yakushima Denko Co., Ltd., JP) was used instead of the α-SiC. The ZrO₂ has a Vickers hardness of 1000 to 1500 kg/mm², a Young's modulus of 3.5 x 10⁶ to 4 x 10⁶ kg/cm², and a thermal conductivity of 0.07 to 0.09 Cal/cm-sec-°C.

Comparative Examples 1 to 4

The respective procedures used in Examples 1-4 were repeated except that no abrasive was used in each case, preparing non-magnetic one-component developers as comparative examples.

The results of the above examples and comparative examples are shown in Table 1 below. Table 2

Dmax: Reflection density of image Dfog: Fog density

The Dmax and Dfog were determined by quantifying the reflection density of the image or non-image area, relative to the blank value zero for the reflection density of a paper surface on which no print has been made. The measurements were carried out using RD-191 (Macbeth, CH).

Claims

1. A non-magnetic one-component developer, comprising a binder, a colorant, and, if necessary, a charge control agent, and a free flow agent, wherein the binder comprises a non-crosslinked cyclic olefin polymer resin, and the developer comprises an abrasive externally added.

2. The non-magnetic one-component developer according to claim 1 , wherein the cyclic olefin polymer resin is an ethylene-norbornene copolymer resin.

3. The non-magnetic one-component developer according to claim 2, wherein the cyclic olefin polymer resin is one or more ethylene-norbornene copolymer resins selected from the group consisting of:

1) an ethylene-norbornene copolymer having a glass transition temperature of 40 to 59⁰C, a number-average molecular weight of 500 to 7,000, a weight-average molecular weight of 3,000 to 20,000, a polydispersity of 10 or less, and a copolymerization molar ratio of ethylene to norbornene of 85/15 to 95/5;

2) an acid-modified derivative of copolymer 1), having an acid value of 10 to 20 mg KOH/g;

3) an ethylene-norbornene copolymer having a glass transition temperature of 60 to 80⁰C, a number average molecular weight of 2,000 to 50,000, a weight average molecular weight of 6,000 to 200,000, a polydispersity of 4 to 10, and a copolymerization molar ratio of ethylene to norbornene of 75/25 to 85/15; and

4) an acid-modified derivative of copolymer 3), having an acid value of 10 to 20 mg KOH/g.

4. The non-magnetic one-component developer according to any one of claims 1 to 3, wherein the abrasive has a Vickers hardness of 1,000 to 3,000 kg/cm², a Young's modulus of 1.5 x 10⁶ to 6 x 10⁶ kg/cm², a melting point of 1900 to 2500⁰C, a thermal conductivity, at room temperature, of 0.04 to 0.4 cal/cm-sec-°C, and a particle size distribution of 0.01 to 1 μm.

5. The non-magnetic one-component developer according to any one of claims 1 to 4, wherein the abrasive comprises one or more selected from the group consisting of α-SiC, β-SiC, CeO₂, ZrO₂, B₄C, Si₃N₄, and AI₂O₃.

6. The non-magnetic one-component developer according to any one of claims 1 to 5, wherein the abrasive comprises α-SiC, β-SiC, or a mixture thereof.

7. The non-magnetic one-component developer according to any one of claims 1 to 6, comprising the abrasive in an amount of 0.1 to 10 parts by weight per 100 parts of the entire developer.

8. The non-magnetic one-component developer according to any one of claims 1 to 7, wherein the particle size distribution of the abrasive is 1/100 to 1/10 times that of a toner base material to which no external additive has been added yet.

9. The non-magnetic one-component developer according to any one of claims 1 to 8, which is used in a non-magnetic one-component development system in which a rotating developer-carrying member is brought into contact, or into contact under pressure, with a fixed developer-regulating member.

10. A copier or printer, operated with a non-magnetic one-component development system and fitted with, as construction elements, a rotating developer-carrying member and a fixed developer-regulating member, which is brought into contact, or into contact under pressure, with the former member, wherein the non-magnetic one-component developer according to any one of claims 1 to 8 is used for developing electrostatic latent images.

11. The copier or printer according to claim 10, which is a color printer or a color copier.