JP2010181689A - Image forming apparatus - Google Patents

Abstract

The present invention provides an image forming apparatus capable of improving the image quality by paying attention to the thermal characteristics of a release agent that is most easily melted among the components contained in toner used in the image forming apparatus.
An image forming apparatus includes a photosensitive drum carrying a toner image formed by toner containing wax, a developing roller carrying toner, and a toner layer thickness on the developing roller. And a fixing unit 6 for fixing the toner image on the paper. The linear velocity of the outermost periphery of the developing roller 24 is 200 to 300 mm / sec. The linear pressure of the developing blade 25 against the developing roller 24 is 35 to 65 gf / cm. The melting point of the wax is 60-80 ° C. Thereby, development filming does not occur, and it is possible to ensure low-temperature fixability of the toner.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as an electrophotographic color electrophotographic printer using a developer containing a release agent.

  Conventionally, as described in, for example, Patent Document 1 below, the developer carrying member of the layer regulating member having a linear velocity at the outermost periphery of the developer carrying member of 250 mm / sec or less, preferably 200 to 250 mm / sec. In an image forming apparatus such as an electrophotographic color electrophotographic printer using a developer containing a release agent having a linear pressure of 34 to 68 gf / cm, the glass transition point Tg is 45 to 77 ° C. When using a certain developer, a developer having a softening temperature Ts of 58 to 98 ° C., an outflow start temperature Tfb of 78 to 138 ° C., and a melting temperature Tm of 105 to 189 ° C., which is the thermal characteristic value of the developer, is used. In addition, development filming does not occur, the fixing property is good, and an offset which causes a problem in use does not occur, and good printing can be obtained.

JP 2007-41557 A

  However, in the conventional image forming apparatus, development filming occurs even when a developer whose softening temperature Ts, outflow start temperature Tfb, and melting temperature Tm, which are thermal characteristics of the developer, are in the same range as the above-described conventional example, is used. However, there is a problem that the fixing property is poor and a high quality image may not be obtained.

  In order to solve such problems, the present invention focuses on the thermal characteristics of the release agent that is most easily melted among the components contained in the developer. When a wax is used as a release agent, in the pulverized toner that is a developer, the wax is exposed on the toner surface, so that the fixing property and filming property of the toner are greatly influenced by the thermal properties of the wax.

  Accordingly, an object of the present invention is to provide an image forming apparatus that solves the conventional problems by paying attention to the thermal characteristics of such wax.

  The image forming apparatus of the present invention includes an image carrier that carries a developer image formed by a developer containing a release agent, and the developer on an electrostatic latent image formed on the image carrier. A developer carrying member that forms the developer image by attaching the developer, a layer regulating member that is pressed against the developer carrying member and regulates the layer thickness of the developer carried on the developer carrying member, and a recording A fixing unit that fixes the developer image transferred onto the medium to the recording medium.

  The linear velocity at the outermost periphery of the developer carrier is 200 to 300 mm / sec, the linear pressure of the layer regulating member against the developer carrier is 35 to 65 gf / cm, The mold release agent contained has a melting point of 60 to 80 ° C.

  According to the image forming apparatus of the present invention, the linear velocity of the outermost periphery of the developer carrier is 200 to 300 mm / sec, the linear pressure of the layer regulating member to the developer carrier is 35 to 65 gf / cm, and the developer Since the melting point of the release agent contained in the toner is 60 to 80 ° C., development filming does not occur, and the low-temperature fixability of the developer containing the release agent can be ensured. . Thereby, the image quality can be improved.

FIG. 1 is a configuration diagram showing an outline of an image forming apparatus in Embodiment 1 of the present invention. FIG. 2 is an enlarged view of the developing unit in FIG. FIG. 3A is a diagram illustrating a type of toner containing a wax in which the melting point and the addition amount are changed according to the first exemplary embodiment. FIG. 3B is a diagram illustrating the types of toners containing waxes having different melting points and addition amounts in Example 1. FIG. 4A is a diagram illustrating a fixing evaluation result of the toner of FIG. FIG. 4B is a diagram illustrating the result of fixing evaluation of the toner in FIG. FIG. 5 is a graph obtained by graphing FIG. 4 from the melting point and the addition amount of the wax. FIG. 6 is a diagram showing the evaluation results of the developing roller filming when the linear pressure of the developing blade in FIG. 2 is 35 gf / cm. FIG. 7 is a diagram showing the evaluation results of the developing roller filming when the linear pressure of the developing blade in FIG. 2 is 45 gf / cm. FIG. 8 is a diagram showing the evaluation results of developing roller filming when the linear pressure of the developing blade in FIG. 2 is 55 gf / cm. FIG. 9 is a diagram showing evaluation results of the developing roller filming when the linear pressure of the developing blade in FIG. 2 is 65 gf / cm. FIG. 10 is a diagram showing the evaluation results of the developing roller filming when the linear pressure of the developing blade in FIG. 2 is 75 gf / cm. FIG. 11 is a graph obtained by graphing FIG. 6 from the melting point and the addition amount of the wax. FIG. 12 is a graph obtained by graphing FIG. 7 from the melting point and the addition amount of wax. FIG. 13 is a graph of FIG. 8 based on the melting point and addition amount of wax. FIG. 14 is a graph obtained by graphing FIG. 9 from the melting point and the addition amount of wax. FIG. 15 is a graph of FIG. 10 based on the melting point and addition amount of wax. FIG. 16 is a diagram illustrating evaluation results of developing roller filming when the linear pressure between the photosensitive drum and the developing roller in Example 2 of the present invention is 20 gf / cm. FIG. 17 is a diagram illustrating evaluation results of developing roller filming when the linear pressure between the photosensitive drum and the developing roller in Example 2 is set to 30 gf / cm. FIG. 18 is a diagram showing the evaluation results of developing roller filming when the linear pressure between the photosensitive drum and the developing roller in Example 2 is 40 gf / cm. FIG. 19 is a graph of FIG. 16 based on the melting point and addition amount of wax. FIG. 20 is a graph of FIG. 17 based on the melting point and addition amount of wax. FIG. 21 is a graph of FIG. 18 based on the melting point and addition amount of wax.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Image Forming Apparatus of Example 1)
FIG. 1 is a configuration diagram showing an outline of an image forming apparatus in Embodiment 1 of the present invention.

  The image forming apparatus 1 is, for example, an electrophotographic color electrophotographic printer, and a developer using toner that is a developer of each color of black (A), yellow (B), magenta (C), and cyan (D). Each developing unit 2 (= 2A, 2B, 2C, 2D) for forming a toner image as an image, each color toner cartridge 3 (= 3A, 3B, 3C, 3D) containing each developer, and a recording medium ( For example, a transfer unit 4 to a sheet) 50, a paper feed cassette 5 that stores and supplies the sheet 50, and a fixing unit 6 that is a fixing unit that fixes a toner image on a recording medium are provided.

  The paper feed cassette 5 is disposed in the lower part of the image forming apparatus main body 1. The paper feed cassette 5 includes a pair of paper feed rollers 51 a and 51 b and transport rollers 52 a and 52 b for transporting the paper 50 fed from the paper feed cassette 5 to the transfer unit 4.

  The transfer unit 4 includes a transfer belt 41 which is a conveying member and a first transfer member. The transfer belt 41 is interlocked with a belt motor (not shown) that is a belt conveyance drive unit.

  Each image forming unit of the image forming apparatus 1 includes each developing unit 2 and a transfer unit 4. Each image forming unit forms an image of each color of black (A), yellow (B), magenta (C), and cyan (D).

  Further, by using the double-sided printing unit 7 for the paper 50, the paper 50 that has undergone the development processes of toner image formation, transfer, fixing, and image formation is reversed, and the above development process is performed on the back surface of the paper on which the image is formed. Do it again. As a result, images are formed on both sides of the paper 50.

  The transfer unit 4 is a transfer belt 41 stretched between the driving roller 42 and the belt idle roller 43, and each image carrier of each developing unit 2 (see FIG. 2) with the transfer belt 41 interposed therebetween. Each transfer roller 44 (= 44A, 44B, 44C, 44D), which is a second transfer member, is provided to face the photosensitive drum 21 (= 21A, 21B, 21C, 21D). The belt idle roller 43 applies tension to the transfer belt 41 so that the transfer belt 41 does not slack.

  Each transfer roller 44 transfers a toner image, which is a developer image of each color, formed on each photosensitive drum 21 to each sheet 50 in each developing unit 2. As a result, a color toner image is formed on the paper 50.

  The color toner image formed on the paper 50 is fixed on the paper by the fixing unit 6. As a result, a color image is formed on the paper 50. The fixing unit 6 includes discharge conveyance rollers 61 a and 61 b that discharge the sheet 50 on which an image is formed to the outside of the image forming apparatus main body 1.

  A fixing member and a pressure member are arranged in the fixing unit 6. The fixing member includes a fixing roller 62 that can be rotated by a fixing motor that is a fixing driving unit. The pressure member includes a pressure roller 63 that can be rotated together with the fixing roller 62. The toner, which is a developer, is melted on the paper 50 by the heat generated from the heater 64 that is a heating member disposed in the fixing roller 62.

  The fixing roller 62 is formed by coating an elastic body such as silicone rubber on a core metal such as iron or aluminum. The surface of the elastic body is coated with a fluorine resin. This prevents toner from adhering to the fixing roller 62. The pressure roller 63 is made of aluminum sheet metal, silicone rubber, or resin. The outer periphery of the pressure roller 63 is covered with an endless polyimide belt and is in pressure contact with the fixing roller 62.

  Opposed to the fixing roller 62, a fixing thermist 65 that is a temperature detection unit in the fixing unit 6 is disposed. A halogen lamp (not shown) is selectively energized based on the surface temperature of the fixing roller 62 detected by the fixing thermistor 65. As a result, the surface temperature of the fixing roller 62 is controlled and maintained at a predetermined temperature.

  Note that reference numeral 15 in FIG. 1 denotes a recording medium conveyance roller. 19a and 19b are movable recording medium travel guides. The transfer unit 4 includes a waste developer tank 45 and a transfer belt cleaning blade 46.

FIG. 2 is an enlarged view of each developing unit 2 shown in FIG.
Each developing unit 2 includes an image carrier, a charging roller, a toner collecting device, a developer carrier having an outermost linear velocity of 200 to 300 mm / sec, a layer regulating member, and a developer supply member. And a sealing member and a stirring bar.

  For example, the image carrier is composed of photosensitive drums 21 (= 21A, 21B, 21C, 21D) that can rotate at a predetermined speed. The charging roller includes each charging roller 22 (= 22A, 22B, 22C, 22D) provided in contact with the peripheral surface of each photosensitive drum 21. The toner collecting device includes cleaning blades 23 (= 23A, 23B, 23C, and 23D) that collect toner remaining on the photosensitive drums 21 after transfer onto the paper 50. The developer carrying member is in contact with each photosensitive drum 21 and rotates together with each photosensitive drum 21, and each developing roller 24 (development is performed by attaching toner to the electrostatic latent image formed on each photosensitive drum 21. = 24A, 24B, 24C, 24D).

  The layer restricting member is composed of developing blades 25 (= 25A, 25B, 25C, 25D) that are pressed against the developing rollers 24, restrict the toner layer thickness, and are charged to a predetermined polarity. The developer supply member contacts each developing roller 24, rotates opposite to each developing roller 24, and supplies each toner supplying roller 26 (supplied with toner 30 'in each developing unit 2 to each developing roller 24 side). = 26A, 26B, 26C, 26D). The seal member is composed of each seal member 27 (= 27A, 27B, 27C, 27D) that prevents the toner from leaking to the outside of each developing unit 2. Further, the stirring bar is a member (not shown) that stirs the toner 30 ′ in each developing unit 2.

  Each toner cartridge 3 is detachably mounted above each developing unit 2. Each toner cartridge 3 has a supply port 31 for supplying toner 30 accommodated therein to the developing unit 2. Each toner cartridge 3 has each stirring bar 32 (= 32A, 32B, 32C, 32D) that stirs the toner 30.

  An electrostatic latent image and a visible image are formed on each photosensitive drum 21. Each charging roller 22 includes a metal shaft and semiconductive epichlorohydrin rubber. Each cleaning blade 23 is made of urethane rubber. Each developing roller 24 is made of a charging member to which a predetermined voltage can be applied.

  Each developing roller 24 is composed of an elastic layer formed of urethane rubber around the core metal, and a surface layer formed of isocyanate on the surface of the elastic layer.

  Each developing blade 25 is formed by bending a stainless steel (SUS304B-TA) plate having a thickness of 0.08 mm with a bending radius of 0.275 mm and bending the short side when viewed from the rotation direction of each developing roller 24 to the upstream side. The developing rollers 24 are pressed against each other so that the side is on the downstream side and is bent with a predetermined linear pressure.

  Each toner supply roller 26 is a sponge roller, and has silicone foam rubber made of open cells having a cell diameter of 300 to 500 μm around the core metal.

  The toner is a non-magnetic one-component pulverized toner that is negatively charged, and has an average particle diameter of 6 μm. Further, each developing roller 24 and each toner supply roller 26 are applied with DC voltages of 170 V and 300 V during a printing operation from a power source not shown in FIG. The members and the configuration of each developing unit 2 are all the same as those described above.

(Example of production method of toner as developer)
100 parts by weight of an amorphous polyester resin as a binder resin, 0.2 parts by weight of a salicylic acid complex (Bontron E-84 manufactured by Orient Chemical Co., Ltd.) as a charge control agent, and MOGUL-L (as a colorant) 4.0 parts by weight (manufactured by Cabot Corporation) and 1.8 parts by weight of wax (melting point 46 ° C.) as a release agent are stirred and mixed using a mixer (Henschel mixer manufactured by Mitsui Miike Chemical Co., Ltd.). A mixture was obtained. This mixture was kneaded while applying a temperature of 100 ° C. with a twin screw extruder, and then cooled to obtain a kneaded product.

  In addition, paraffin wax was used as the wax. However, the wax only needs to have a predetermined melting point, and the material is not particularly limited.

  Next, this kneaded material is coarsely pulverized by a cutter mill having a screen having a diameter of 2 mm, and then pulverized using an impact plate type pulverizer (a dispersion separator manufactured by Nippon Pneumatic Industry Co., Ltd.). A toner was obtained. Further, the pulverized toner was classified using an air classifier to obtain a toner base having an average particle size of 6 μm.

  Next, as an external addition step, 100 parts by weight of the obtained toner base of the obtained powder was crushed (separated inorganic fine particles aggregated by a high-speed stirrer such as the Henschel mixer) hydrophobic silica R972 (Nippon Aerosil) Co., Ltd., average primary particle size 16 nm) 2.5 parts by weight and hydrophobic silica RY-50 (Nihon Aerosil Co., Ltd., average primary particle size 40 nm) 2 parts by weight crushed by the same crushing method The toner was stirred for 2 minutes at a rotation speed of 3200 (rotation / min) with the Henschel mixer having a capacity of 10 liters to prepare a toner. The produced toner was designated as developer A-1.

  Further, by the same method and blending as described above, the melting point and addition amount of the wax are changed, and Developers A-2 to 9, Developers B-1 to 9, Developers C-1 to 9, Developer D-1 To 9, Developers E-1 to 9, Developers F-1 to 9, Developers G-1 to 9, Developers H-1 to 9, and Developers 1 to 9 were produced.

  FIGS. 3A and 3B are diagrams illustrating the types of toners containing the wax having the melting point and the addition amount changed in Example 1 used in the image forming apparatus 1 of FIG.

(Operation of Image Forming Apparatus of Example 1)
In the image forming apparatus of FIG. 1, when a print signal is sent from an interface (not shown), the heater 64 in the fixing unit 6 starts heating. At the same time, the fixing roller 62 and the pressure roller 63 that rotates with the fixing roller 62 start to rotate. When the thermistor 65 detects that the surface temperature of the fixing roller 62 has reached the set temperature, a signal is sent from a main control unit (not shown) to the mechanism control unit, and paper feeding is started.

  Further, the temperature control unit sends a signal to the heater control unit to control on / off of the energization of the heater 64 so as to keep the set temperature constant. A target toner image is formed on the paper 50 through toner formation by each developing unit 2 and transfer by the transfer unit 4.

  The sheet 50 on which the toner image is formed is conveyed in the arrow direction H and advances between the fixing roller 62 and the pressure roller 63. The heat of the fixing roller 62 melts the toner image on the paper 50, and the toner image melted on the paper 50 is pressed at the pressure contact portion between the fixing roller 62 and the pressure roller 63, so that the toner image is applied to the paper 50. It is fixed.

  At this time, if the amount of heat applied to the toner is too small, the toner is peeled off from the paper 50 (hereinafter, this state is referred to as “unfixed”). On the other hand, if it is too large, the toner adheres to the fixing roller 62, and the fixing roller 62 goes around and adheres to the paper 50 (hereinafter referred to as "high temperature offset").

(Evaluation of toner by the image forming apparatus of Example 1)
Toner (for example, developer A-1 to 9, developer B-1 to 9, developer C-1 to 9, developer D-1 to 9, developer E-1 to 9, developer F-1 to 9, the developer G-1 to 9, the developer H-1 to 9, the developer I-1 to 9), and the linear pressure of each developing blade 25 against each developing roller 24 is changed. The toner fixing evaluation (1) by the apparatus 1 and the developing roller filming evaluation (2) will be described.

  The evaluation paper 50 was A4 size Xerox P paper, the linear velocity of the outermost periphery of the developing roller 24 was 200 mm / sec, and the linear velocity of the outermost periphery of the fixing roller 62 was 160 mm / sec. The reason why the peripheral speeds of the developing rollers 24 and the fixing rollers 62 are different is that each developing roller 24 has a peripheral speed difference with respect to each photosensitive drum 21.

  In Example 1, the linear velocity of the developing roller was 200 mm / sec, but the result was the same if it was in the range of 200 to 300 mm / sec. It should be noted that when the linear velocity is less than 200 mm / sec, the printing speed is low, and thus the high-speed printing requirement cannot be satisfied. On the other hand, when the linear velocity is higher than 300 mm / sec, the fixability is deteriorated and the toner tends to be unfixed, and development roller filming is likely to occur.

(1) Toner fixing evaluation The toner fixing evaluation is 0.45 mg / cm ² of toner adhesion on the paper 50, height = 40 mm at the upper end of the paper 50 when viewed from the printing direction, and width = whole printable range. This was done by developing and fixing the printed pattern at 100% duty.

  To determine whether toner has not been fixed, the surface of the fixing roller is fixed at 170 ° C., and a tape (mending tape manufactured by Sumitomo 3M Limited) is applied to the center of the obtained printing portion. -It was performed by reciprocating after reciprocating. At this time, the weight does not apply any force from the top other than its own weight, and the moving speed guideline of the weight is 10 mm / sec. The density measurement of the tape peeling part and the tape non-peeling part was performed using an X-RITE spectral densitometer (manufactured by X-Rite). Those with a density difference of less than 10% were marked with O, and those with a density difference of 10% or more were marked with x.

  The high temperature offset of the toner was evaluated by fixing the surface of the fixing roller at a temperature of 195 ° C., and visually evaluating the obtained paper. The case where the toner is not attached to the fixing roller 62 is indicated by O, and the case where the toner is attached is indicated by ×.

  4A and 4B are the toners (developers A-1 to 9, developer B-1 to 9, developer C-1 to 9) used in the image forming apparatus 1 shown in FIG. Developer D-1-9, Developer E-1-9, Developer F-1-9, Developer G-1-9, Developer H-1-9, Developer I-1-9) It is a figure which shows a fixing evaluation result.

  In the “Overall” column in FIGS. 4A and 4B, the evaluation result of both the unfixed and the high temperature offset is x, the evaluation result of only the unfixed evaluation is O, the high temperature offset evaluation When only the result was O, O, and when both evaluation results of unfixed and high temperature offset were O, ◎ was given.

  FIG. 5 is a graph showing the fixing evaluation result of FIG. 4 while paying attention to the melting point and the addition amount of the wax added to the toner.

  The meaning of each notation (x, o, O, ◎) in FIG. 5 is the same as in FIG. From the graphed fixing evaluation results, the toner non-fixing evaluation results were improved by increasing the addition amount of the low melting point wax. Moreover, the evaluation result of high temperature offset became favorable by increasing the addition amount of the high melting point wax. It can also be seen that the overall fixability is improved by increasing the amount of wax added.

(2) Development roller filming evaluation As shown in FIG. 4, toners having good overall fixability, specifically, developers B-9, C-3 to 9, D-3 to 9, Development roller filming evaluation was performed using E-3-9, F-3-9, G-3-9, and H-3-9.

  The developing roller filming evaluation was performed by the image forming apparatus 1 in FIG. 1 in which the linear pressure of the developing blade 25 against the developing roller 24 was changed. After printing 4000 sheets at 5% duty (printing the area ratio 100% when printing all over a single A4 sheet as “100% duty”), a 100% duty image was printed and evaluated. O, (triangle | delta), and x were attached | subjected on the following three-stage evaluation criteria.

  O: No dot printing missing on the image, and no wax adhering to the toner on the developing roller surface.

  Δ: Although there is no dot-like printing omission on the image, the wax adhering to the toner was also observed on the surface of the developing roller (less than 0.5 mm).

×: Dot-like printing missing on the image.
Note that Δ is a case where filming appears on the developing roller but filming is small, so that no print omission due to filming occurs on the printed image.

  This dot-like print omission is caused by the fact that the wax added to the toner adheres to the surface of the developing roller (filming), and no toner layer is formed at that location.

  When the linear pressure of the developing blade 25 against the developing roller 24 is 25 gf / cm, the linear pressure is too low, so that the toner layer cannot be stably formed on the developing roller. Therefore, development roller filming evaluation was not performed.

  FIG. 6 is a diagram showing evaluation results of developing roller filming when the linear pressure of the developing blade 25 in FIG. 2 on the developing roller 24 is 35 gf / cm.

  Similarly, FIGS. 7 to 10 show the developing roller filming when the linear pressure of the developing blade 25 in FIG. 2 against the developing roller 24 is 45 gf / cm, 55 gf / cm, 65 gf / cm, and 75 gf / cm, respectively. It is a figure which shows an evaluation result.

  FIGS. 11 to 15 are graphs showing the evaluation results of the developing roller filming of FIGS. 6 to 10 while paying attention to the melting point and the addition amount of the wax added to the toner.

  From the graphed evaluation results, the development result of the developing roller filming deteriorates as the amount of added wax increases, and the evaluation result of the developing roller filming deteriorates as the wax having a low melting point is added. I understand that.

  Further, focusing on the linear pressure of the developing blade 25 against the developing roller 24, it can be seen that the higher the linear pressure of the developing blade 25, the worse the evaluation result of the developing roller filming.

  From the evaluation results of the toner fixing property and the developing roller filming as described above, the amount of wax added to the toner is 2.6 to 4.2 parts by weight, the melting point of the wax is 60 to 80 ° C., and the development in the developing unit is performed. When the linear pressure of the blade 25 against the developing roller 24 satisfies the conditions of 35 to 65 gf / cm, the fixing property and the developing roller filming are good.

  Note that the above evaluation was performed using a 5% duty print pattern. Also, in the evaluation using the 50% duty and 100% duty printing patterns, no printing failure occurred under the conditions of Example 1, and good evaluation results were obtained.

(Modification of Example 1)
The first embodiment has been described based on a color electrophotographic printer including toner cartridges for each color. However, a printer having a single color toner cartridge may be used.

(Effect of Example 1)
According to the first embodiment, the amount of wax added to the toner is 2.6 to 4.2 parts by weight, the melting point of the wax is 60 to 80 ° C., and each developing roller 24 of each developing blade 25 in each developing unit 2. When the linear pressure against the condition satisfies 35 to 65 gf / cm, the toner fixing property and the developing roller filming are good.

(Comparative example of Example 1)
The conventional developer used in the image forming apparatus 1 does not take into consideration the thermal characteristics of the release agent that is a component of the developer. Therefore, when a conventional developer, particularly a pulverized toner is used, a high quality image may not be obtained due to development filming.

  However, in the first embodiment, a toner containing a release agent that limits the numerical values of the linear velocity of the developing roller 24 and the linear pressure of the developing blade 25, which are constituent parts of the developing unit 2, and the numerical value of the melting point is used. did. Thereby, development filming does not occur and printing with good fixability can be obtained.

(Configuration and operation of embodiment 2)
In the image forming apparatus 1 according to the second embodiment of the present invention, the configuration and operation of the developing unit 2 in which the linear pressure between each photosensitive drum 21 and each developing roller 24 in each developing unit 2 shown in FIG. Unlike Example 1, other configurations and operations are the same as those of Example 1. In Example 2, the developing roller linear velocity was 200 mm / sec. However, the results were the same when the linear velocity was 200 to 300 mm / sec.

(Evaluation of Example 2)
In each developing unit 2 of the second embodiment, the developing roller filming evaluation is performed with the linear pressure between each photosensitive drum 21 and each developing roller 24 being 10 gf / cm, 20 gf / cm, 30 gf / cm, and 40 gf / cm. went. In each developing unit 2 of Example 1, the developing roller filming evaluation was performed with the linear pressure between each photosensitive drum 21 and each developing roller 24 being 45 gf / cm.

  The linear pressure of each developing blade 25 against each developing roller 24 was set to 65 gf / cm. As for the toner, developer B-9, C-3 to 9, D-3 to 9, E-3 to 9, F-3 to 9, G- 3-9 and H-3-9 were used.

  Unless otherwise specified, the developing roller filming evaluation method and the evaluation result display method of the second embodiment are the same as those of the first embodiment.

  When the linear pressure between each photosensitive drum 21 and each developing roller 24 is 10 gf / cm, the linear pressure is too low, so that the toner layer cannot be stably developed on the photosensitive drum. Therefore, evaluation of developing roller filming was not performed.

  FIG. 16 is a diagram showing the evaluation results of developing roller filming when the linear pressure between each photosensitive drum 21 and each developing roller 24 in Example 2 of the present invention is 20 gf / cm. Similarly, FIG. 17 and FIG. 18 show the evaluation of developing roller filming when the linear pressure between each photosensitive drum 21 and each developing roller 24 is 30 gf / cm and 40 gf / cm in the second embodiment. It is a figure which shows a result.

  Further, FIGS. 19 to 21 are graphs regarding the evaluation results of the developing roller filming of FIGS. 16 to 18 while paying attention to the melting point and the addition amount of the wax added to the toner.

  From the graphed evaluation results, when the linear pressure of each developing blade 25 against each developing roller 24 is 65 gf / cm, the developing roller fill decreases as the linear pressure between each photosensitive drum 21 and each developing roller 24 decreases. The good range of evaluation results for Ming is expanding.

  Further, when the linear pressures of the developing blades 25 with respect to the developing rollers 24 were set to 35 gf / cm, 45 gf / cm, and 55 gf / cm, equivalent results were obtained. However, in the case of 75 gf / cm, the evaluation result (see FIGS. 10 and 15) of the developing roller filming of Example 1 was the same.

  From the above evaluation results, the linear pressure between each photosensitive drum 21 and each developing roller 24 is 20 to 40 gf / cm, the amount of wax added to the toner is 2.6 to 4.6 parts by weight, and the melting point of the wax is 54. When the condition of -80 ° C. and the linear pressure of the developing blade against the developing roller of 35 to 65 gf / cm is satisfied, the toner fixing property and the developing roller filming are good.

  Note that the above evaluation was performed using a 5% duty print pattern. Further, even in the evaluation with the 50% duty print pattern, the print defect did not occur under the conditions of Example 2, and a good evaluation result was obtained. However, in the evaluation with a 100% duty print pattern, after 3500 prints, several prints in which a faint image was seen were seen.

  Next, among the toners having good toner fixability and developing roller filming as defined in Example 1 and Example 2, the toner containing the most wax with the lowest melting point (specifically, In Example 1, the developer D-7 was extracted, and in Example 2, the developer C-8) was extracted, and an evaluation of a good fixing temperature range was performed.

  As an evaluation method, the same fixing unit 6 as in Example 1 was used. The linear velocity of the outermost periphery of the fixing roller 62 was fixed at 160 mm / sec, and the unfixed and high temperature offset of each toner was evaluated while changing the temperature of the surface of the fixing roller. When both evaluation results were good, the temperature was determined as a good fixing temperature.

  The upper limit of the surface temperature of the fixing roller is set to 195 ° C. in the specification of the fixing unit 6. The evaluation was performed by decreasing the temperature by 5 ° C. until unfixed by both toners of developer D-7 and developer C-8 occurred. Other conditions not specifically mentioned are the same as those in the first embodiment.

  From the above evaluation results, the fixing favorable temperature range of developer D-7 (good range toner of Example 1) was 130 ° C. to 195 ° C., whereas developer C-8 (good range of Example 2). In the toner, the temperature was 110 ° C. to 195 ° C. That is, with the toner of the image agent C-8, an expansion of the fixing favorable temperature range of 20 ° C. was observed.

  As described above, by setting the linear pressure between each photosensitive drum 21 and each developing roller 24 to 20 to 40 gf / cm, it is possible to use toner excellent in low-temperature fixing. Enlargement is possible.

(Effect of Example 2)
According to Example 2, the linear pressure between each photosensitive drum 21 and each developing roller 24 is 20 to 40 gf / cm, the amount of wax added to the toner is 2.6 to 4.6 parts by weight, and the melting point of the wax. Is 54 to 80 ° C. and the linear pressure of each developing blade 25 in each developing unit 2 against each developing roller 24 satisfies the conditions of 35 to 65 gf / cm, the toner fixing property and the developing roller filming are good. The fixing temperature range can be expanded.

(Other variations of Examples 1 and 2)
In the first and second embodiments, the paper 50 is used as the recording medium, but the present invention can also be applied to recording media other than paper. In the first and second embodiments, the image forming apparatus 1 has been described as a color electrophotographic printer. However, the present invention relates to an image forming apparatus such as a facsimile machine, a copying machine, and a multifunction peripheral (MFP) having them in combination. It can also be applied to.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Developing unit 3 Toner cartridge 4 Transfer unit 5 Paper feed cassette 6 Fixing unit 21 Photosensitive drum 22 Charging roller 23 Cleaning blade 24 Developing roller 25 Developing blade 62 Fixing roller 63 Pressure roller 64 Heater 65 Fixing thermistor

Claims (7)

An image carrier that carries a developer image formed by a developer containing a release agent;
A developer carrier that forms the developer image by attaching the developer to an electrostatic latent image formed on the image carrier;
A layer regulating member that is in pressure contact with the developer carrying member and regulates the layer thickness of the developer carried on the developer carrying member;
A fixing unit for fixing the developer image transferred on the recording medium to the recording medium,
The linear velocity of the outermost periphery of the developer carrier is 200 to 300 mm / sec,
The linear pressure on the developer carrying member of the layer regulating member is 35 to 65 gf / cm,
The image forming apparatus according to claim 1, wherein a melting point of the release agent contained in the developer is 60 to 80 ° C. The developer is a pulverized toner,
The image forming apparatus according to claim 1, wherein the release agent is a wax.   The image forming apparatus according to claim 2, wherein the content of the wax is 2.6 to 4.2 parts by weight with respect to 100 parts by weight of the binder resin. An image carrier that carries a developer image formed by a developer containing a release agent;
A developer carrier that forms the developer image by attaching the developer to an electrostatic latent image formed on the image carrier;
A layer regulating member that is in pressure contact with the developer carrying member and regulates the layer thickness of the developer carried on the developer carrying member;
A fixing unit for fixing the developer image transferred on the recording medium to the recording medium,
The linear velocity of the outermost periphery of the developer carrier is 200 to 300 mm / sec,
The linear pressure on the developer carrying member of the layer regulating member is 35 to 65 gf / cm,
The melting point of the release agent contained in the developer is 54 to 80 ° C.,
An image forming apparatus, wherein a linear pressure between the image carrier and the developer carrier is 20 to 40 gf / cm. The developer is a pulverized toner,
The image forming apparatus according to claim 4, wherein the release agent is a wax.   The image forming apparatus according to claim 5, wherein the content of the wax is 2.6 to 4.6 parts by weight with respect to 100 parts by weight of the binder resin. The fixing unit is
A fixing roller rotatable by a fixing driving unit;
A pressure roller that is in pressure contact with the fixing roller and can be rotated together with the fixing roller;
A heater provided in the fixing roller;
A thermistor for fixing provided opposite to the fixing roller and capable of controlling the surface temperature of the fixing roller;
The image forming apparatus according to claim 1, wherein the image forming apparatus is configured by a fixing unit.

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