JP5212807B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, and the like, and a developing device employed therein.

  Conventionally, a one-component developing device has been widely used as a developing unit of an image forming apparatus. As a typical configuration of the one-component developing device, a flexible sponge roller is used as a supply member for supplying toner to the toner carrier, and the toner is rubbed by pressing the toner against the toner carrier with the sponge roller. The toner is supplied onto the toner carrier while being charged (see FIG. 10). In addition, a regulating member that regulates the amount of toner carried on the toner carrying member is provided, and the toner is pressed against the toner carrying member by the regulating member, so that the toner layer is uniformly thin while frictionally charging the toner (see FIG. 11). In this way, the charged and thinned toner is transported to a portion facing the latent image carrier by the movement of the surface of the toner carrier and developed.

  In this one-component developing device, a strong stress is applied to the toner by pressing the toner against the toner carrying member at the time of supplying the toner by the supply member and at the time of restriction by the restriction member, and causes toner deterioration over time. Specifically, the toner is made of resin as a base material (binder), and additives such as silica and titanium called fluidized particles are attached around it. However, the additive is buried inside the base material (binder) due to stress. Fluidity decreases. Due to the decrease in fluidity, the toner tends to adhere to the toner carrier and the regulating member. In addition, the toner carrier and the regulating member are subjected to frictional heat generated at the supply unit and the regulating unit, so that the adhering toner is not dissolved and peeled off, so-called toner carrier filming or toner fixing to the regulating member. This occurs. In such a situation, the frictional charging of the toner is hindered over time, a predetermined polarity and charge amount cannot be obtained, and background staining is likely to occur, development efficiency is lowered, and image quality is lowered.

  In particular, in recent years, it has been desired to reduce the energy consumption of the image forming apparatus due to environmental problems, and there is a tendency to lower the melting temperature of the toner so as to reduce the energy at the time of toner fixing with a large amount of energy consumption. Further, in many cases, a wax material is mixed and added to the toner in order to improve releasability at the time of fixing. Changes in the characteristics of these toners also contribute to the above problem.

  In view of this, there has been proposed one that suppresses stress applied to the toner. For example, in Patent Document 1, a supply member is disposed in a non-contact manner with respect to a toner carrier in a toner supply unit, and a precharged toner is electrostatically supplied from the supply member to the toner carrier with a potential difference. In addition, there is a description that the toner is made to be a uniform thin layer while the charging amount of the toner is further stabilized by performing frictional charging by a regulating member.

In addition, a method for charging toner by a method other than frictional charging has been proposed. For example, in Patent Document 2, a conductive toner is used, and a charge is applied to the conductive toner contained in the toner container by applying a voltage to the inner wall of the toner container coated with a conductive paint as a charge applying member. Then, after charging the toner, the toner is supplied by flying to a grounded toner carrier.
JP 2003-084565 A Japanese Patent Laid-Open No. 9-300685

  In the developing device disclosed in Patent Document 1, although the stress in the supply unit can be suppressed, the stress in the regulating unit cannot be suppressed, and it cannot be said that the stress reduction effect is sufficient. In addition, in the device that charges the toner by applying a charge to the toner using the charge applying member of Patent Document 2, the effect of suppressing the stress is great, but the toner is charged by charging the bulk toner contained in the container. Therefore, it is difficult to obtain a sufficient and stable toner charge amount as compared with conventional frictional charging.

  The present invention has been made in view of the above problems, and the object of the present invention is to use the one-component development method to stably deteriorate the toner over time by charging the toner stably while suppressing the stress applied to the toner. It is an object of the present invention to provide a developing device and an image forming apparatus capable of suppressing the above and obtaining a high-quality image over time.

In order to achieve the above object, the invention according to claim 1 provides a toner carrier that carries toner and conveys it to a developing region that is a portion facing the latent image carrier, and supplies the toner to the surface of the toner carrier. In a developing device comprising: a toner supply unit; and a toner charging member that is disposed upstream of the development region and downstream of the toner supply unit with respect to the toner transport direction of the toner carrier, and charges the toner. A toner fluidizing unit configured to fluidize the toner contained in the apparatus ; and the toner supply unit receives the toner fluidized by the toner fluidizing unit and drops and guides the toner onto the surface of the toner carrier. a plate-like member which is arranged with the toner carrying member with a predetermined gap therebetween so, the fluidized for toner supplied without pressing against the toner bearing member, the upper Symbol toner charging member Charged the toner by charge injection to the toner layer in contact with at least a portion of the toner layer surface on the toner carrying member, current to the toner carrying member through the toner layer from said toner charging member Adjusting the resistance value of the toner layer so as to flow, or selecting the resistance value of the toner carrier so that current flows from the toner charging member through the toner layer to the toner carrier, and the toner charging member The volume resistance is 10 ⁶ [Ω · cm] or more .
Also, the invention of claim 2 is the developing device according to claim 1, said toner binder resin, a pigment resin and around the toner base particles formed by the kneading of the charge control agent, inorganic materials The relationship between the volume resistivity RMO of the base particle powder and the volume resistivity RT of the toner with the additive is RMO> RT. It is characterized by being.
According to a third aspect of the present invention, in the developing device of the second aspect, a plurality of low resistance regions are provided on the surface of the toner base particles so that a sufficient current flows through the toner layer. The distance between the two is selected.
According to a fourth aspect of the present invention, there is provided a latent image carrier that carries an electrostatic latent image, an electrostatic latent image forming unit that forms an electrostatic latent image on the latent image carrier, and the latent image carrier. In the image forming apparatus including the developing unit for developing the electrostatic latent image, the developing unit according to claim 1 is employed as the developing unit.

  In the present invention, the toner supply means is arranged with a predetermined gap with the toner carrier, and the toner is brought into contact with the surface of the toner carrier without being pressed to supply the toner so that frictional charging does not occur. The toner that is not frictionally charged and supplied to the toner carrier does not have an electrostatic binding force caused by the toner carrier, and therefore adheres to the surface of the toner carrier and the surface of the toner carrier. The toner is carried on the toner carrier by the van der Waals force between the toner and other toner. At this time, the amount of toner that can be carried by the toner carrier is smaller than that carrying the charged toner because there is no electrostatic binding force between the toner and the toner carrier, and the toner is thin on the toner carrier. It becomes a layer state. Then, the toner is charged by injecting charge from a toner charging member that contacts at least a part of the surface of the substantially uncharged toner layer on the toner carrier. Here, since the toner layer on the toner carrying member is a thin layer, uniform charging can be performed as compared with the case where the toner layer is a thick layer or the toner is a lump. That is, in the conventional developing device, the toner charged by the supply unit is carried on the toner carrying member in a thick layer state, the regulating member is pressed by the regulating member to regulate the toner carrying amount, and the toner is thinned and conveyed to the developing region. . On the other hand, in the present invention, the toner is charged by injecting the toner in the thin layer with the toner charging member from the toner charging member by supporting the toner in the thin layer without friction charging at the supply unit. And conveyed to the development area. When injecting the charge, the toner charging member comes into contact with the surface of the toner layer on the toner carrying member, so that a slight stress is applied to the toner layer. It is much smaller than the stress when making it happen. As described above, the toner deterioration over time can be suppressed by stably charging the toner by a method other than frictional charging while suppressing the stress.

  As described above, according to the present invention, by one-component development system, the toner is stably charged while suppressing the stress applied to the toner, thereby suppressing the deterioration of the toner with the lapse of time and obtaining a high-quality image even with the lapse of time. There is an excellent effect of being able to.

  Hereinafter, an embodiment of an image forming method to which the present invention is applied will be described. In the image forming method according to the present invention, a one-component developing device for contact or non-contact development is used. For example, a contact developing device using an aluminum sleeve, a contact developing device using a conductive rubber belt, or a non-contact using a developing sleeve in which a conductive resin layer containing carbon black, metal filler, etc. is formed on the surface of an aluminum base tube. A developing device or the like.

  The one-component developing device according to the present embodiment uses a relatively low-resistance toner, and charges the toner by charge injection without applying stress due to frictional charging. FIG. 1 is a schematic configuration diagram of a one-component developing apparatus according to the present embodiment. In the developing device 2, a toner carrying sleeve 3 that is rotatable as a toner carrying member is disposed so as to face the photosensitive member 1 that is a latent image carrying member. The developing device 2 includes a hopper portion 4 that accommodates the toner 12 and a sleeve accommodating portion 11 that is disposed obliquely below the hopper portion 4 and accommodates the toner carrying sleeve 3.

  The hopper section 4 is provided with an agitator 5 with blades around the rotation axis, and agitates the toner 12 accommodated therein. By this agitation, the toner 12 is released even when it is initially in an aggregated state, and the distance between the toners is increased. As a result, the fluidity of the toner 12 is high and the fluidized state is easy to move. Since the toner 12 that has been fluidized and stirred by the hopper 4 has a low adhesion force between the toners, the toner 12 falls from the hopper 4 and flows out to the vicinity of the toner carrying sleeve 3 of the sleeve accommodating portion 11. The hopper unit 4 contains 100 to 150 [g] of toner.

  The sleeve accommodating portion 11 is provided with a plate-like toner supply member 6 as toner supply means for supplying toner to the surface of the toner carrying sleeve 3. The plate-like toner supply member 6 is disposed so as to face the toner carrying sleeve 3 with a predetermined gap so as to guide the toner flowing in from the hopper portion 4 and to contact the toner carrying sleeve 3 without pressing it. Has been. The distance L1 between the toner supply member 6 and the toner carrying sleeve 3 is preferably about 0.5 [mm] to 1.5 [mm]. Further, a toner charging member 8 is disposed so as to face the surface of the toner carrying sleeve 3 downstream of the toner supply member 6 and upstream of the developing region facing the photoreceptor 1 with respect to the rotation direction of the toner carrying sleeve 3. A negative voltage that is the charging polarity of the toner is applied from the power source 13. The distance L2 between the toner charging member 8 and the toner carrying sleeve 3 is preferably about 0.1 [mm] to 0.3 [mm].

The toner flowing from the hopper 4 is guided by the toner supply member 6 and comes into contact with the surface of the toner carrying sleeve 3 without being pressed. Thus, since the toner is not pressed against the toner carrying sleeve 3, frictional charging does not occur, and the toner is almost uncharged. The substantially uncharged toner is carried on the surface of the toner carrying sleeve 3 by surface adhesion to the toner carrying sleeve 3 or van der Waals force between the toner particles. In other words, the conventional developing device supplies toner while pressing the toner against the toner carrying sleeve 3 by a toner supply member and frictionally charges the toner, or supplies charged toner electrostatically. In such a conventional developing device, since the charged toner is carried on the toner carrying sleeve 3 with a force including an electrostatic restraining force, the carrying amount increases and the layer thickness becomes thick. On the other hand, in the developing device 2 of the present embodiment, the toner that is almost uncharged is carried with a force that does not include the electrostatic restraining force from the toner carrying sleeve 3, so that the toner is smaller than the conventional developing device. The layer becomes a thin layer. At this time, the measured charge amount on the toner carrying sleeve 3 is substantially 0 [μC / g] by the suction method.

Furthermore, since the toner is in a fluidized state, the probability of contact with the toner carrying sleeve 3 increases. Further, since the relationship of the adhesion force of the toner to the toner carrier> the adhesion force between the toners is established, the toner layer is not a thick layer, specifically, a thin layer of 1 to 3 layers.

  The toner carried in a thin layer state on the toner carrying sleeve 3 in this way is conveyed to the toner charging member 8 by the rotation of the toner carrying sleeve 3. FIG. 2 is an explanatory diagram of toner charging by the toner charging member 8. The toner layer is sandwiched between the toner carrying sleeve 3 and the toner charging member 8, and at least a part of the surface of the toner layer comes into contact with the toner charging member 8 to which a negative charge is applied and the toner charging member 8. It is charged by more charge injection. For example, when a voltage of −1000 [V] is applied to the toner charging member 8, a toner potential of −335 V and a toner charge amount of about −9 [μC / g] are obtained. FIG. 3 shows the relationship between the applied voltage and the toner layer potential. Note that the range in FIG. 3 is predicted to move depending on the toner particle size.

Further, as shown in FIG. 4, a high resistance member 10 is disposed inside the toner carrying sleeve 3 facing the toner charging member 8, and a positive voltage is applied to the high resistance member 10 from the power source 14, thereby facing the toner charging member 8. A negative charge may be applied to the toner on the toner carrying sleeve 3. The thickness of the high resistance member is suitably in the range of 50 [μm] to 200 [μm].

  Here, the toner layer resistance will be described in detail. In order to charge the toner as described above, it is necessary to flow a sufficient current through the toner layer to inject the charge, and then hold the charge. In order to control the toner layer resistance, it is necessary to manage the characteristics of the toner itself and the state of the toner thin layer on the toner carrying sleeve during charge injection.

First, it is necessary to adjust the toner layer resistance so that a sufficient current flows from the toner charging member 8 through the toner layer to the toner carrying sleeve 3 so that a sufficient charge is injected into the toner. In the toner used in this embodiment, 1 part by weight of a metal material having a low resistance characteristic is mixed in the toner base, and 5 parts by weight of a low resistance additive is mixed on the surface. The volume average particle diameter of the toner was 6 [μm], and the layer thickness was about 9 [μm] of 1.5 layers. At this time, the filling state is a level at which two layers are sufficiently filled, and a voltage is applied to the toner charging member 8 while applying a slight pressure. As described above, when -1000 [V] was applied, the toner layer potential was -355 [V] and the flowing current was about 110 [μA]. At this time, the volume resistivity of the toner layer was 10 ^ ¹² [Ω · cm]. Here, the contact pressure of the toner charging member 8 is 2 [gf / mm] in terms of linear pressure. However, by increasing this, the packing density is further increased and the toner layer resistance is reduced. This shows the same tendency even when the toner particle diameter is changed, and the toner layer resistance can be appropriately adjusted. FIG. 5 shows the toner layer resistance (provided that the thickness is 9 [μm]) due to the contact pressure of the toner charging member 8. As the toner particle size increases, the voids increase and the toner layer resistance increases.

At this time, the resistance of the toner charging member 8 is set to 10 ⁶ [Ω · cm] or more. This is to prevent the current flowing from the toner charging member 8 through the toner layer to the toner carrying sleeve 3 from becoming too large. Specifically, in order to prevent the current output of the power source connected to the toner charging member 8 from exceeding 1 [mA], the power consumption of the apparatus itself is limited and charging is performed with a necessary and sufficient current. Aim.

  The toner charged by the toner charging member 8 is conveyed to the development area by the rotation of the toner carrying sleeve 3. An electrostatic latent image corresponding to a negative-positive process is formed on the photoreceptor 1 by a known charging and exposure process (not shown). In the developing area, a developing electric field is formed between the toner carrying sleeve 3 and the photoreceptor 1, and the toner on the toner carrying sleeve 3 moves to the image portion of the electrostatic latent image on the photoreceptor 1.

  Here, in the conventional one-component contact development method, the contact pressure is increased because the state of formation of the electric field changes due to the presence of a so-called air gap in the toner layer. Also, a contact pressure is applied to return the toner adhering to the background area of the photoreceptor 1 to the toner carrying sleeve 3 to obtain a so-called scavenging effect. In the developing device 2 of the present embodiment, the contact pressure between the photoreceptor 1 and the toner carrying sleeve 3 is set to 4 [gf / mm], and normal contact development is performed. On the other hand, if the contact pressure is less than 0.5 [gf / mm], the air gap becomes too large, and a portion where the developing electric field does not sufficiently act is formed. On the other hand, if it exceeds 10 [gf / mm], it deviates from the condition of normal contact development, and the developing ability is lowered.

  The toner image developed on the photoreceptor 1 is then subjected to a transfer and fixing process to form an image. A collection bias for collecting the toner on the toner carrying sleeve 3 is applied to the downstream portion of the developing region, and a collection roller 9 as a collection member that rotates in the same speed and in the same direction as the toner carrying sleeve 3 is in contact. Yes. The undeveloped toner is collected by the collection roller 9 and returned to the hopper unit 4 as appropriate.

FIG. 6 shows experimental results comparing the toner additive burial rank over time between the developing device 2 of the present embodiment and a conventional developing device that charges toner by frictional charging. In the developing device 2 of the present embodiment, the additive burying rank is maintained at 4 even when 100 [k sheets (thousand sheets)] is exceeded, whereas in the conventional developing device, the rank is 20 [k sheets]. 3 and ranks 1 at 40 [k]. As a result, the mechanical stress can be suppressed by supplying the toner to the toner carrying sleeve 3 and the charge of the toner by applying the charge without using the conventional triboelectric charge. The image quality can be maintained without doing so.

Next, the toner carrying sleeve 3 employed in the developing device 2 shown in FIG. 1 will be described. In FIG. 1, a rigid drum-shaped photoconductor 1 based on an aluminum tube is used as the photoconductor 1. Therefore, the toner carrying sleeve 3 is made of an elastic rubber material. The hardness is in the range of 10 to 70 ° (JIS-A).

  The toner carrying sleeve 3 is obtained by applying a surface coat layer to a base layer made of a rubber material. Examples of the rubber material for the base layer include silicon, butadiene, NBR, hydrin, and EPDM. Further, in order to further reduce the hardness of the toner carrying sleeve 3, an endless belt using rubber or a thin metal plate can be used.

Examples of the material for the surface coat layer include a material containing a resin such as silicon, acrylic, and polyurethane, and rubber. Another example of the material is a material containing fluorine. A so-called Teflon (registered trademark) material containing fluorine has a low surface energy and excellent releasability, and therefore toner filming with time is extremely difficult to occur. Also, as general resin materials that can be used for the material of the surface coat layer, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene / hexafluoropropylene polymer (FEP) ), Polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) Etc. In order to obtain conductivity, a conductive material such as carbon black is often contained in this. In order to coat the toner carrier more uniformly, another resin may be mixed.

The electric resistance sets the volume resistivity of the bulk including the surface coat layer, and adjusts and adjusts the resistance of the base layer so that it can be set to 10 ² to 10 ⁶ [Ω · cm]. Since the volume resistivity of the base layer used in this embodiment is 10 ¹ to 10 ⁵ [Ω · cm], the volume resistivity of the surface layer may be set slightly higher.

  The diameter of the toner carrying sleeve 3 is preferably 10 to 30 [mm]. In the present embodiment, one having a diameter of 16 [mm] is used. Further, the surface of the toner carrying sleeve 3 was appropriately changed to have a roughness Rz (10-point average roughness) of 1 to 4 [μm]. The range of the surface roughness Rz is 13 to 80% with respect to the volume average particle diameter of the toner 10 and is a range in which the toner 12 is conveyed without being buried in the surface of the toner carrying sleeve 3.

Further, the toner used in the present embodiment is advantageous in that the volume average particle diameter is 4 to 8 [μm] in order to realize a high-quality image. The weight average particle diameter of the toner is 3 to 8 [μm], more preferably 5 to 7 [μm]. If the weight average particle diameter is less than 3 [μm], problems such as contamination in the machine due to toner scattering during long-term use, image density reduction in a low-humidity environment, poor photoconductor cleaning, etc. are likely to occur, and there are concerns about the effects on the human body. The When the weight average particle size exceeds 8 [μm], the resolution of fine spots of 100 [μm] or less is not sufficient, and the image quality tends to be inferior due to many scattering to non-image areas.

Details of the toner are shown below. As resins, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene acrylic resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, polyethylene resin, silicon resin, butyral resin, terpene There are resins, polyol resins and the like. Examples of vinyl resins include styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and homopolymers thereof: styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer. Polymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic copolymer Acid methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl ethyl acetate Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Styrene copolymers such as copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate and the like.

The polyester resin is composed of a dihydric alcohol as shown in the following group A and a dibasic acid salt as shown in the group B, and further a trihydric or higher alcohol as shown in the group C or Carboxylic acid may be added as a third component. Group A: ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4 butanediol, neopentyl glycol, 1,4 butenediol, 1,4-bis (hydroxymethyl) cyclohexane Bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene (2,2) -2,2′-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -2,2′-bis (4 -Hydroxyphenyl) propane and the like.
Group B: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, linolenic acid, or These acid anhydrides or esters of lower alcohols.
Group C: Trivalent or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid. As the polyol resin, an alkylene oxide adduct of an epoxy resin and a dihydric phenol, or a compound having one active hydrogen in the molecule that reacts with the glycidyl ether and the epoxy group, and an active hydrogen that reacts with the epoxy resin in the molecule. There are those obtained by reacting two or more compounds.

Moreover, the following are used as a pigment. Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. . Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.

Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC. Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake. These can use 1 type (s) or 2 or more types. Especially for color toners, uniform dispersion of good pigments is essential. Instead of putting pigments directly into a large amount of resin, a master batch in which pigments are once dispersed at a high concentration is prepared and diluted. The method of throwing in is used. In this case, a solvent is generally used to help dispersibility. However, there is a problem such as the environment, and in this embodiment, water is used for dispersion. When water is used, temperature control is important so that residual moisture in the masterbatch does not become a problem.

Further, a release agent can be internally added to the toner in the present invention to prevent offset at the time of fixing. Release agents include natural waxes such as candelilla wax, carnauba wax, rice wax, montan wax and derivatives thereof, paraffin wax and derivatives thereof, polyolefin wax and derivatives thereof, sazol wax, low molecular weight polyethylene, and low molecular weight polypropylene. And alkyl phosphate esters. The melting point of these release agents is preferably 65 to 90 ° C. When the temperature is lower than this range, blocking during storage of the toner is likely to occur, and when the temperature is higher than this range, an offset is likely to occur in a region where the fixing roller temperature is low.

Additives may be added for the purpose of improving the dispersibility of a release agent or the like. As additives, styrene acrylic resin, polyethylene resin, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, butyral resin, terpene resin, There is a polyol resin or the like, and a mixture of two or more of these resins may be used. As the resin, crystalline polyester may be used. It is an aliphatic polyester having crystallinity, having a sharp molecular weight distribution, and increasing the absolute amount of its low molecular weight as much as possible. This resin undergoes a crystal transition at the glass transition temperature (Tg), and at the same time, the melt viscosity suddenly decreases from the solid state and exhibits a fixing function to paper. By using this crystalline polyester resin, low-temperature fixing can be achieved without excessively reducing the Tg and molecular weight of the resin. Therefore, there is no decrease in storage stability associated with a decrease in Tg. Also, there is no excessively high gloss and offset resistance deterioration due to the low molecular weight. Therefore, the introduction of the crystalline polyester resin is very effective for improving the low-temperature fixability of the toner.

Further, as described above, the toner according to the exemplary embodiment attaches or fixes an inorganic fine powder to the toner surface as a fluidity improver. The average particle size of the inorganic fine powder is suitably 10 to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs. As the inorganic fine powder of the present invention, Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, Zr, etc. And oxides and composite oxides. Of these, fine particles of silicon dioxide (silica), titanium dioxide (titania), and alumina are preferably used. Furthermore, it is effective to perform a surface modification treatment with a hydrophobizing agent or the like. Typical examples of the hydrophobizing agent include the following. Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, Chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexaphenyldisilazane, hexatolyldisilazane, etc.

The inorganic fine powder is preferably used in an amount of 0.1 to 3% by weight based on the toner. If it is less than 0.1% by weight, the effect of improving the toner aggregation is poor, and if it exceeds 3% by weight, there is a tendency to cause problems such as toner scattering between fine wires, contamination in the machine, scratches or abrasion of the photoreceptor. is there. In addition, a charge control agent may be attached or fixed to the surface of at least a powder composed of a resin and a pigment so that the powder surface shape has a small period and a large period. The average particle size is optimally as small as 10 to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs.

In addition, the toner of the present exemplary embodiment includes other additives such as a lubricant powder such as Teflon powder, zinc stearate powder, and polyvinylidene fluoride powder within a range that does not substantially adversely affect the toner; or cerium oxide powder, carbonized carbon Abrasives such as silicon powder and strontium titanate powder can also be used in small amounts as developability improvers. In addition, this evaluation method can also be used for toners and capsule toners produced by a spray-drying method produced without using a kneading step or a pulverizing step.

The toner resistance is adjusted by the inclusion and dispersion of a conductive material. In the case of carbon materials, acetyl black, oil furnace black, thermal black, carbon fiber, graphite and the like can be raised. In the metal system, there are metal powders such as tin oxide (SnO2), zinc oxide (ZnO), Cu, and Ni. The resistance can be adjusted by appropriately dispersing this in a toner base material (binder) resin. In addition, since the above-mentioned material has a powder layer resistance of 10 ³ [Ω · cm] or less, the volume specific resistance RMO in the powder of the base particles and the volume specific resistance as the toner to which the additive is attached are usually obtained. The relationship of RT is RMO> RT. As described above, since the toner has high resistance as the base particles, the electric charge is easily held, and the corresponding region of the image forming speed can be widened. In addition, since the charge can be held until the next transfer step, good transfer performance can be obtained.

Next, toner resistance measurement will be described. FIG. 7 is an explanatory diagram of a toner resistance measurement method. As shown in FIG. 7, the resistance of the toner is obtained by obtaining the resistance from the current value when the toner is sandwiched between the brass electrodes 30 and 31, and obtaining the volume specific resistance as a powder from the thickness and area. It is. At this time, the powder to be measured is placed on the lower electrode 30. Then, the filling rate is increased as much as possible by applying vibrations such as tapping. Then, the upper electrode 31 is placed, a weight of 500 [g] (not shown) is placed on the upper electrode 31, a voltage of 100 [V] is applied to the upper and lower electrodes 30, 31, and the current flowing at that time is measured with an ammeter. The toner used in the present embodiment is prepared by adding about 30 parts of carbon black to a polyester binder resin and dispersing it. The particle diameter is a volume average particle diameter of 6 [μm]. The measured value in a laboratory environment at 22.5 ° C. and 65% was 1 × 10 ¹² [Ω · cm]. As a result of measurement with varying resistance, some particles with a particle size of 25 [μm] were included, but charge injection was performed in the so-called low resistance region of 10 ⁷ [Ω · cm] or less. When the amount of electric charge was measured, the electric charge was not able to be hold | maintained only by particle | grains. In addition, charge injection could not be performed in a higher resistance region than 10 ¹² [Ω · cm]. From this result, the range of the volume resistivity R of the toner powder that can be used when this measurement is used is considered to be 10 ⁸ ≦ R ≦ 10 ¹² [Ω · cm].

Further, as described above, the toner is obtained by kneading a pigment, a charge control agent, or the like into a material mainly composed of a resin serving as a base (binder), and adhering the above-described additive thereto. However, a low resistance region having almost no thickness may be formed on the base surface layer. FIG. 8 is a conceptual diagram of toner in which a low resistance region is formed. Specifically, in the case of a toner particle size of 6 [μm], the diameter of the low resistance region is set to a maximum of about 1 [μm], and the interval is set to be about the same as the diameter of the low resistance region. In FIG. 9, the diameter of the low resistance region is 0.5 [μm] and 0.25 [μm], and the gaps are 1 [μm] and 1.5 [μm], respectively. The result of measuring the toner layer resistance at a toner layer thickness of 9 [μm] with the contact pressure set to 2 [gf / mm] is shown. As described above, the range of the volume specific resistance R of the usable toner powder can be obtained by changing the diameter and gap of the low resistance region. Thereby, the charge injection efficiency is improved and a good charge amount can be obtained.

  As described above, in the present embodiment, the toner carrying sleeve 3 is used as the toner carrying member, but a belt shape may be used. In addition, the contact development method in which the toner carrier and the latent image carrier are developed in contact with each other has been described, but the non-contact development method in which the toner carrier and the latent image carrier are developed in a non-contact manner is also described. Good. In the present embodiment, the best mode for carrying out the present invention has been described. However, it is easy for those skilled in the art to make other embodiments by changing or modifying the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The above description is an example of the best mode of the present invention, and does not limit the scope of the claims.

As described above, according to the present embodiment, the toner supply member 6 is disposed with a predetermined gap from the toner carrying sleeve 3, and the toner is supplied without being pressed against the surface of the toner carrying sleeve 3. In this way, it is supplied in an almost uncharged state. The almost uncharged toner is carried on the toner carrying sleeve 3 in a thin layer state by the adhesion force on the surface of the toner carrying sleeve and the van der Waals force of the toner adhering to the surface of the toner carrying sleeve and the other toner. Then, the toner charging member 8 is charged by injecting a charge into the substantially uncharged thin toner layer on the toner carrying member 3. At this time, since the toner layer is a thin layer, uniform charging can be performed as compared with the case where the toner layer is thick or the toner is in a lump shape. When the charge injection is performed, the toner charging member 8 is brought into contact with the surface of the toner layer on the toner carrying sleeve 3, so that a slight stress is applied to the toner layer, but the toner is placed on the toner carrying sleeve 3 by the regulating member. This is much smaller than the stress at the time of pressing and frictional charging. As described above, the toner deterioration over time can be suppressed by stably charging the toner by a method other than frictional charging while suppressing the stress.
Further, by supplying the toner to the toner carrying sleeve 3 in a fluidized state, the probability of contact with the surface of the toner carrying sleeve 3 increases. Further, since the relationship of the adhesion force of the toner to the toner carrier> the adhesion force between the toners is established, the toner layer does not become a thick layer, and it becomes easier to form a thin layer.
Further, by using the plate-like toner supply member 6 as the toner supply means, it is possible to supply toner without pressing as compared with the case of using a rotating member.
Further, by adjusting the resistance value of the toner layer so that a current flows from the toner charging member 8 to the toner carrying sleeve 3 through the toner layer, the charge injection efficiency can be improved and good chargeability can be obtained. .
Further, by selecting the resistance value of the toner carrier so that a current flows from the toner charging member 8 to the toner carrying sleeve 3 through the toner layer, a sufficient current can be passed through the toner layer. Therefore, sufficient charge can be supplied to the toner, and good chargeability can be obtained.
Further, since the volume resistance of the toner charging member 8 is 10 ⁶ [Ω · cm] or more, the amount of current to flow can be suppressed to the minimum necessary, and the power consumption can be reduced.
In addition, the relationship between the volume specific resistance RMO in the powder of the base particles of the toner and the volume specific resistance RT as the toner to which the additive is attached satisfies RMO> RT. As a result, the toner tends to retain electric charge because the base particles have high resistance. Therefore, the area corresponding to the image forming speed can be expanded.
In addition, multiple low-resistance regions are provided on the surface of the toner base particles, and the area of the low-resistance region and the distance between the regions are selected so that sufficient current flows in the toner layer. Chargeability is obtained.

1 is a schematic configuration diagram of a developing device according to an embodiment. FIG. 6 is an explanatory diagram of toner charging by a toner charging member. 6 is a graph showing the relationship between the voltage applied to the toner charging member and the toner layer potential. The schematic block diagram of the image development apparatus which concerns on the modification of an electric charge injection. 6 is a graph showing the toner layer resistance due to the contact pressure of the toner charging member. The graph which shows the additive embedding rank of the toner of time. Explanatory drawing of the toner resistance measuring method. FIG. 3 is a conceptual diagram of toner in which a low resistance region is formed. 6 is a graph showing toner layer resistance when the diameter and gap of a low resistance region on the toner surface are changed. Explanatory drawing of the toner supply part in the conventional one-component developing device. Explanatory drawing of the toner control part in the conventional one-component developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing device 3 Toner carrying sleeve 4 Hopper part 5 Agitator 6 Toner supply member 8 Toner charging member 9 Collection roller
DESCRIPTION OF SYMBOLS 10 High resistance body 11 Sleeve accommodating part 12 Toner 13 Power supply 14 Power supply 15 Insulating layer 30 Lower electrode 31 Upper electrode 40 Toner carrier 41 Supply roller 42 Control blade

Claims (4)

A toner carrying member that carries toner and transports it to a developing region that is opposite to the latent image carrying member; a toner supply unit that supplies toner to the surface of the toner carrying member; and a toner carrying direction of the toner carrier. In a developing device including a toner charging member that is disposed upstream of the developing region and downstream of the toner supply unit and charges the toner,
Comprising toner fluidizing means for fluidizing toner contained in the apparatus;
The toner supply means is a plate-like member arranged with a predetermined gap from the toner carrier so as to receive the toner fluidized by the toner fluidization means and fall and guide it to the surface of the toner carrier. a member, a fluidized for toner supplied without pressing against the toner bearing member,
Upper Symbol toner charging member is the toner charged by charge injection to the toner layer in contact with at least a portion of the toner layer surface on the toner bearing member,
The resistance value of the toner layer is adjusted so that current flows from the toner charging member to the toner carrier through the toner layer, or current is supplied from the toner charging member to the toner carrier through the toner layer. Select the resistance value of the toner carrier to flow,
A developing device, wherein the toner charging member has a volume resistance of 10 ⁶ [Ω · cm] or more . The developing device 請 Motomeko 1, the toner binder resin, a pigment resin and around the toner base particles formed by the kneading of the charge control agent, the additive consists of particles of an inorganic material A developing device characterized in that a relationship between a volume specific resistance RMO of a base particle powder and a volume specific resistance RT as a toner to which an additive is attached satisfies RMO> RT. 3. The developing device according to claim 2 , wherein a plurality of low resistance regions are provided on the surface of the toner base particles, and an area of the low resistance region and a distance between the regions are selected so that a sufficient current flows in the toner layer. A developing device. A latent image carrier that carries an electrostatic latent image, an electrostatic latent image forming unit that forms an electrostatic latent image on the latent image carrier, and a development that develops the electrostatic latent image on the latent image carrier An image forming apparatus comprising:
An image forming apparatus employing the developing device according to claim 1 as the developing means.

Images