JP2010101978A - Developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exhibit good fixability even when a developer has a smaller particle size, by configuring the developer to have a capsule structure in which a core material has a glass transition temperature of 57 to 61 [°C] and a shell material has a glass transition temperature of 75 to 95 [°C]. <P>SOLUTION: The developer has a capsule structure comprising a core material covered with a shell material, and is deposited on an electrostatic latent image on an image carrier to form a developer image, the developer image then to be transferred onto a medium and fixed to the medium by heat and pressure added by a heating member and a pressurizing member. The developer has an average particle size of 3.0 to 5.0 [μm]; the core material has a glass transition temperature of 57 to 61 [°C]; and the shell material has a glass transition temperature of 75 to 95 [°C]. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developer and an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic printer, copying machine, facsimile machine, etc., the surface of a photosensitive drum is uniformly charged by a charging device, and the charged photosensitive drum surface is exposed by an exposure device. An image is formed, and a developing device attaches toner to the electrostatic latent image and develops it to form a toner image.

By the way, in order to perform image formation at high speed, capsule toner is used as toner. The capsule toner includes a core material and a shell material that covers the surface of the core material. As the shell material, a material having a glass transition temperature higher than that of the core material is used in order to increase the storage stability at a high temperature. For example, a shell material having a glass transition temperature of 75 to 100 [° C.] is used (see, for example, Patent Document 1).
JP-A-11-202547

  However, in the conventional image forming apparatus, there has been a problem that the storage stability cannot be secured or the fixing property is deteriorated as the toner particle size is reduced.

  The present invention solves the above-mentioned conventional problems, and a developer having a capsule structure in which the glass transition temperature of the core material is 57 to 61 [° C.] and the glass transition temperature of the shell material is 75 to 95 [° C.] Thus, it is an object of the present invention to provide a developer and an image forming apparatus that can exhibit good fixability even when the particle size of the developer is reduced.

  Therefore, the developer of the present invention has a capsule structure in which a core material is covered with a shell material, and adheres to an electrostatic latent image on an image carrier to form a developer image, and the developer image is a medium. Is a developer that is fixed to the medium by heat and pressure applied from a heating member and a pressure member, and has an average particle size of 3.0 to 5.0 [μm], and the core material is The glass transition temperature is 57 to 61 [° C.], and the shell material has a glass transition temperature of 75 to 95 [° C.].

  According to the present invention, the developer has a capsule structure in which the glass transition temperature of the core material is 57 to 61 [° C.] and the glass transition temperature of the shell material is 75 to 95 [° C.]. Thereby, good fixability can be exhibited even if the particle size is reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

  In the figure, reference numeral 10 denotes an image forming apparatus, for example, an electrophotographic printer, a facsimile machine, a copier, a printer, a multifunction machine having a function of a facsimile machine and a copier (MFP: Multi Function Printer), etc. Any type of image forming apparatus may be used. In the present embodiment, the case where the image forming apparatus 10 is a so-called tandem color electrophotographic printer will be described.

  In the image forming apparatus 10, developing devices 11a, 11b, 11c, and 11d corresponding to four colors of C (cyan), M (magenta), Y (yellow), and K (black) are printed as media. Along the conveyance path of the paper 24, they are arranged in order in the conveyance direction (left direction in the figure). The developing devices 11a, 11b, 11c, and 11d have the same configuration, and the color of toner 36 that will be described later stored as a developer is different. The developing devices 11a, 11b, 11c, and 11d will be described as the developing device 11 when they are described in an integrated manner. Each developing device 11 is mounted in the image forming apparatus 10 as an independent detachable image forming unit, and forms an image on the printing paper 24 conveyed along the conveyance path.

  Here, reference numeral 23 denotes a paper feed cassette that accommodates the print paper 24, reference numeral 12 denotes a paper feed roller that feeds the print paper 24 from the paper feed cassette 23, and 13 is fed from the paper feed cassette 23. 14a and 14b are conveying rollers for conveying the printing paper 24, 15 is a transfer belt as a conveying unit, and 17 is rotated by a driving means (not shown). Thus, the drive roller drives the transfer belt 15.

  Reference numeral 21 denotes a transfer belt cleaning unit for removing unnecessary toner 36 and foreign matters adhering to the surface of the transfer belt 15. The belt cleaning blade and the belt cleaning blade are removed from the surface of the transfer belt 15. A waste developer tank for storing and collecting unnecessary toner 36 and foreign matters is provided.

  Reference numeral 25 denotes a fixing device as a fixing unit for fixing the toner image transferred onto the printing paper 24 to the printing paper 24 by heat and pressure. The fixing device 25 includes a heating roller 18 as a heating member and a pressure member. A pressure roller 19 is provided.

  Reference numerals 16a, 16b, 16c and 16d are arranged to face toner powder images of cyan, magenta, yellow and black, that is, developing devices 11a, 11b, 11c and 11d for forming toner images. It is a transfer roller, which is a roller in which a metal shaft is covered with a urethane sponge layer. Note that when the transfer rollers 16a, 16b, 16c, and 16d are described in an integrated manner, the transfer rollers 16 are described.

  Further, reference numeral 22 denotes a paper discharge guide, which guides the print paper 24 on which the toner image is fixed and discharged, and sends it out of the image forming apparatus 10.

  Next, the configuration of the developing device 11 and the fixing device 25 will be described in detail.

  FIG. 2 is a diagram showing the configuration of the developing device and the fixing device in the first embodiment of the present invention.

  In the developing device 11, the developing device 11a corresponding to cyan is adjacent to the fixing device 25 on the most downstream side in the transport direction of the printing paper 24, but as described above, the other developing devices 11b, 11c, and 11d. In this example, the developing device 11 will be described as a representative.

  As shown in the figure, the developing device 11 includes a developing unit 26a that forms a toner image on a printing paper 24, and a toner cartridge 26b that supplies toner 36 to the developing unit 26a.

  The developing unit 26a selectively exposes the photosensitive drum 31 as an image carrier, a charging roller 32 as a charging device for charging the surface of the photosensitive drum 31, and the surface of the charged photosensitive drum 31. An LED (Light Emitting Diode) head 33 as an exposure device that forms an electrostatic latent image, a developing roller 34 as a developer carrying member, and a toner supply as a developer supplying member that supplies toner 36 to the developing roller 34 A roller 35, a developing blade 37 as a thin layer forming means for thinning the toner 36 on the developing roller 34, and a cleaning blade as a developer collecting device for collecting the toner 36 remaining on the surface of the photosensitive drum 31. 38 and a toner containing portion 39 for containing the toner 36.

  The developing roller 34, the toner supply roller 35, and the developing blade 37 are disposed in a toner accommodating portion 39.

  Then, the photosensitive drum 31, the charging roller 32, the developing roller 34, the toner supply roller 35, the transfer roller 16a, and the drive roller 17 rotate in the directions indicated by arrows a to e in the drawing. The toner image formed on the surface is transferred onto the printing paper 24 conveyed by the transfer belt 15.

  In addition to the heating roller 18 and the pressure roller 19, the fixing device 25 opposes the heating roller 18 disposed above the heating roller 18 and the heating roller 18 above the heating roller 18. A fixing thermistor 28 is provided as a fixing temperature detector arranged as described above.

  The heating roller 18 includes a hollow cylindrical cored bar made of iron, aluminum, etc., an elastic body made of silicone rubber or the like coated on the cored bar, and a fluorine-based coating coated on the surface of the elastic body. Provide resin. The fluororesin prevents the toner 36 from adhering.

  The pressure roller 19 includes a cored bar made of iron, aluminum, etc., an elastic body made of silicone rubber or the like coated on the cored bar, a fluorine-based resin coated on the surface of the elastic body, and the fluorine An endless polyimide belt covering the outer periphery of the system resin is provided and is in pressure contact with the heating roller 18.

  Next, the toner 36 will be described in detail.

  FIG. 3 is a diagram showing an endothermic curve of the developer according to the first embodiment of the present invention.

  The toner 36 as a developer in the present embodiment is a toner particle (base toner) that can be formed by mixing and aggregating a styrene acrylic copolymer resin, a colorant, and a wax produced by an emulsion polymerization method. It is obtained by adding silica and titanium oxide fine powder and mixing with a mixer.

  In the emulsion polymerization method, primary particles of a polymer which is a binder resin of the toner 36 are prepared in an aqueous solvent, and a colorant emulsified with an emulsifier (surfactant) in the same solvent as the primary particles is mixed. If necessary, wax, a charge control agent, etc. are mixed and agglomerated to form toner particles in the solvent, and the toner particles are removed from the solvent, washed and dried to remove unnecessary solvent components and auxiliary agents. In this method, the product components are removed to obtain toner particles.

  In the present embodiment, only the glass transition temperatures of the core material and the shell material are changed in order to obtain the toners 36 having different storability and fixability. The toner 36 in the present embodiment is a so-called capsule toner and has a capsule structure in which a core material is covered with a shell material. Here, a copolymer of n-butyl acrylate and styrene is used for the core material, and a methacrylic acid-n-butyl and styrene having a glass transition temperature higher than that of the acrylic acid-n-butyl is used for the shell material. And a copolymer was used. And each glass transition temperature of a core material and a shell material was adjusted by changing the composition ratio with respect to styrene of acrylic acid-n-butyl and methacrylic acid-n-butyl. In addition, when the composition ratio with respect to styrene of acrylic acid-n-butyl and methacrylic acid-n-butyl is made high, a glass transition temperature will fall.

  The toner 36 used in the present embodiment has an average particle diameter of 5.0 [μm] when the D50 value obtained by measuring the particle size distribution is taken as the average particle diameter. Specifically, a Coulter Multisizer 3 (manufactured by Beckman Coulter, Inc.) was used, and the count diameter was measured at 3000 [μm], and the volume average particle diameter of the toner 36 at that time was defined as the average particle diameter.

  In the present embodiment, the endothermic peak temperature measured using a differential scanning calorimeter (DSC: manufactured by ParkinElmer) was used as an index of the glass transition temperature of the core material and the shell material. In this case, the toner 36 was heated from 20 [° C.] to 200 [° C.] at a temperature rising rate of 10 [° C./min], and the amount of heat used when the temperature rose at each temperature was measured.

  The endothermic peak temperature refers to the temperature at the apex of the endothermic peak due to glass transition. The figure shows an example of an endothermic curve obtained by measuring the toner 36 used in the present embodiment using DSC. Whether each of the two peaks in the curve shown in the figure is due to the shell material or the core material is determined by the height of the peak. In the case of the toner 36, it has been found that the peak of the shell material is higher.

  Next, the operation of the image forming apparatus having the above configuration will be described.

  In the image forming process, the photosensitive drum 31 is rotated at a constant peripheral speed in a direction indicated by an arrow a in FIG. The surface of the photosensitive drum 31 is uniformly charged by applying a DC high voltage from a high voltage power supply for a charging roller (not shown) to the charging roller 32 that contacts the surface of the photosensitive drum 31 and rotates counterclockwise.

  Further, the LED head 33 disposed facing the photosensitive drum 31 selectively irradiates light onto the surface of the photosensitive drum 31 that rotates in response to the image signal. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31. A laser exposure apparatus or the like can be used instead of the LED head 33.

  Further, the toner 36 is supplied from the toner cartridge 26 b to the developing unit 26 a, and the toner storage unit 39 is filled with the toner 36. Then, a DC high voltage is applied from a high voltage power supply for a toner supply roller (not shown) to the toner supply roller 35 disposed in the toner container 39, and the toner supply roller 35 is indicated by an arrow c in FIG. The toner 36 is supplied to the developing roller 34 by being rotated in the direction of rotation.

  The developing roller 34 adsorbs the toner 36 and rotates in the direction indicated by the arrow b in FIG. The developing blade 37 abuts the surface of the developing roller 34 on the downstream side in the rotational direction with respect to the position where the developing roller 34 and the toner supply roller 35 abut, whereby a thin layer of toner 36 having a uniform thickness is formed on the developing roller 34. Formed on the surface.

  Since a bias voltage is applied between the conductive support of the photosensitive drum 31 and the developing roller 34 by a high voltage power supply for a toner carrier (not shown), there is no photosensitive between the developing roller 34 and the photosensitive drum 31. Electric lines of force corresponding to the electrostatic latent image formed on the surface of the drum 31 are generated. Therefore, the toner 36 on the developing roller 34 adheres to the electrostatic latent image on the surface of the photosensitive drum 31 by the action of electrostatic force, and a toner image is formed.

  On the other hand, the printing paper 24 accommodated in the paper feed cassette 23 is sent out by the paper feed roller 12 and sent along the paper feed guide 13 to the nip portions of the transport rollers 14a and 14b in the stopped state. Then, the skew of the printing paper 24 is corrected at the nip portion.

  After the skew of the printing paper 24 is corrected, when the conveying rollers 14a and 14b are driven to rotate, the printing paper 24 sandwiched between the conveying rollers 14a and 14b is rotated in the direction indicated by the arrow e in FIG. It is sent to a transfer belt 15 driven by a roller 17. When the printing paper 24 reaches the position of the developing device 11, it is formed on the surface of the photosensitive drum 31 by the transfer roller 16 to which a DC high voltage is applied via the transfer belt 15 by a transfer roller high voltage power source (not shown). The transferred toner image is transferred to the printing paper 24.

  Note that some toner 36 may remain on the surface of the photosensitive drum 31 after the toner image is transferred. However, the remaining toner 36 is removed by the cleaning blade 38 that contacts the surface of the photosensitive drum 31.

  Subsequently, the printing paper 24 onto which the toner image has been transferred is sent to the fixing device 25 and is conveyed while being sandwiched between the heating roller 18 and the pressure roller 19. At this time, the heat of the heating roller 18 melts the toner 36, the toner 36 melted by the pressurizing action of the pressure roller 19 penetrates between the fibers of the printing paper 24, and the toner image is fixed on the printing paper 24. The printing paper 24 on which the toner image is fixed proceeds along the paper discharge guide 22 and is discharged to the outside of the image forming apparatus 10.

  Next, an experimental example in the present embodiment will be described. First, the evaluation of the storage stability of the toner 36 will be described.

  FIG. 4 is a diagram showing the evaluation test results of the storage stability of the toner in the first embodiment of the present invention.

  Generally, when the amount of heat given to the toner 36 when the printing paper 24 passes through the fixing device 25 is too large, the toner 36 adheres to the heating roller 18, and further, the toner 36 attached to the heating roller 18 heats up. A phenomenon (high temperature offset) occurs in which the roller 18 adheres to the printing paper 24 after one rotation. Further, when the amount of heat given to the toner 36 when the printing paper 24 passes through the fixing device 25 is too small, the toner 36 is not fixed and peels off from the printing paper 24 (unfixed). ) Will occur.

  Therefore, the inventor of the present invention, as shown in FIG. 4, the core material having an endothermic peak temperature (T1) as the glass transition temperature of 45, 55, 65 and 75 [° C.], and the glass transition temperature as The toner 36 having a capsule structure combined with a shell material having an endothermic peak temperature (T2) of 65, 75, 85, 95, and 105 [° C.] was subjected to a storage stability evaluation test (where T1 <T2).

  Here, an evaluation test method will be described.

  First, a metal cylinder having a diameter of 30 [mm] and a height of 80 [mm] is set on a glass plate, and 10 [g] of toner 36 is put into the cylinder. A weight of 20 [g] is placed thereon and left in an environment maintained at an air temperature of 50 [° C.] and a humidity of 55 [%] for 48 hours.

  Thereafter, the weight and the cylinder are removed, and the weight is increased on the toner 36 in increments of 10 [g], and the load at which the toner 36 collapses is confirmed.

  And when it collapses with a load of 30 [g] or less, it is evaluated that the storage stability is good (◯), and when it collapses with a load of 40 [g] or more, the storage stability is poor (x). It was evaluated.

  Thereby, the result as shown in FIG. 4 was able to be obtained. FIG. 4 shows that the storage stability of the toner 36 depends on the endothermic peak of the shell material, and if the endothermic peak of the shell material is 75 [° C.] or more, the storage stability is good.

  Next, evaluation of the low-temperature fixability of the toner 36 will be described.

  FIG. 5 is a diagram for explaining a fixing evaluation test method according to the first embodiment of the present invention. FIG. 6 is a diagram for explaining a first method of fixing strength evaluation test according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining the second method of the fixing strength evaluation test in the first embodiment of the present invention, and FIG. 8 shows the result of the toner fixing property evaluation test in the first embodiment of the present invention. FIG. 1 and FIG. 9 are second diagrams showing results of evaluation tests of toner fixability in the first embodiment of the present invention, and FIG. 10 is toner fixability in the first embodiment of the present invention. FIG. 11 is a fourth diagram showing the results of evaluation tests for toner fixability in the first embodiment of the present invention.

  Here, as shown in FIGS. 8 to 11, the inventor of the present invention has a core material having endothermic peak temperatures (T1) of 55, 57, 59, 61, 63 and 65 [° C.], and an endothermic peak temperature. The toner 36 having a capsule structure in which (T2) is 75, 85, 95, and 105 [° C.] combined with a shell material was subjected to an evaluation test for low temperature fixability. Regarding the low temperature fixability evaluation test, two types of evaluation tests, a fixing evaluation test and a fixing strength evaluation test, were performed. When both evaluation results were satisfactory, the low temperature fixability was evaluated as good.

  First, a tape peeling (peeling) peeling evaluation test as a fixing evaluation test will be described.

  As shown in FIG. 5, the front end in the printing direction of the printing paper 24, that is, the entire printable range in the width direction and 40 [mm] from the upper end is set as a printing portion, and toner having a density of 100% is set in the printing portion. The image is transferred, and the toner image is fixed by the fixing device 25.

  After fixing the toner image, a tape (mending tape manufactured by Sumitomo 3M) is attached to the upper end of the printing surface of the printing paper 24 (the surface to which the toner image is transferred) in the width direction. The tape is peeled after one reciprocation with a weight of 500 g. At this time, the weight is moved at a speed of 10 mm / sec so that no vertical force other than its own weight is applied to the weight.

  In this case, the density of the toner image at the place where the tape was affixed was measured using an X-rite spectral densitometer (manufactured by X-Rite) before and after peeling the tape. And when the density | concentration after peeling of a tape fell below 90 [%] of the density | concentration before peeling of a tape, it evaluated that low-temperature fixability was unsatisfactory.

  This tape peeling evaluation test evaluates the ease with which the toner 36 is melted by the fixing device 25.

  Next, the fixing strength evaluation test will be described.

  First, as in the case of the tape peeling evaluation test, as shown in FIG. 5, the front end of the printing paper 24 in the printing direction, that is, the entire printable range in the width direction and 40 [mm] from the upper end is set as the printing portion. Then, the toner image is transferred to the printing portion, and the toner image is fixed by the fixing device 25. However, the density of the toner image is set to 300 [%].

  Subsequently, as shown in FIG. 6, the printing paper 24 is folded in two along the center line in the width direction so that the printing surface is inside. At this time, the printed portion is not creased. Then, a crease is made by reciprocating a 500 g weight on the printed portion. The weight is moved at a speed of 10 [mm / sec] so that no vertical force other than its own weight is applied to the weight.

  Thereafter, as shown in FIG. 7, the crease of the printing paper 24 is opened, a weight of 500 g is placed on the nonwoven fabric (BEMCOT, manufactured by Asahi Kasei Co., Ltd.), and the printed part is reciprocated twice. At this time, the weight is moved at a speed of 10 mm / sec so that no vertical force other than its own weight is applied to the weight.

  When the fixing strength is weak, as shown in FIG. 7, the toner 36 on the fold of the printed portion is peeled off from the surface of the printing paper 24 in a streak manner by reciprocating the nonwoven fabric on which the weight is placed. When the width of the stripe was 2 mm or more, it was evaluated that the low-temperature fixability was poor due to insufficient fixing strength.

  In addition, those having both good evaluation by the tape peeling evaluation test and evaluation by the fixing strength evaluation test were evaluated as having good low-temperature fixability.

  By evaluating in this way, the adhesive strength between the printing paper 24 and the toner 36 can be evaluated.

  In the tape peeling evaluation test and the fixing strength evaluation test, that is, the low temperature fixability evaluation test, the speed of the printing paper 24 on the transfer belt 15 is 230 [mm / sec], and the heating roller 18 in the fixing device 25 is used. And the pressure roller 19, ie, the nip (NIP) width was 9.1 [mm], and the surface temperature of the heating roller 18 was 145 [° C.].

  Next, evaluation of the high temperature offset property of the toner 36 will be described.

  The inventor of the present invention, the toner 36 subject to the low temperature fixability evaluation test, that is, the core material having an endothermic peak temperature (T1) of 55, 57, 59, 61, 63 and 65 [° C.] The toner 36 having a capsule structure combined with a shell material having endothermic peak temperatures (T2) of 75, 85, 95, and 105 [° C.] was subjected to a high temperature offset evaluation test.

  First, as in the case of the tape peeling evaluation test, as shown in FIG. 5, the front end of the printing paper 24 in the printing direction, that is, the entire printable range in the width direction and 40 [mm] from the upper end is set as the printing portion. Then, a toner image having a density of 100% is transferred to the printed portion, and the toner image is fixed by the fixing device 25.

  Subsequently, a portion of the printing surface of the printing paper 24 that is separated from the printing portion by a distance corresponding to one circumference of the outer periphery of the heating roller 18 is visually confirmed, and evaluation is performed based on whether toner 36 is attached or not. .

  Then, when the surface temperature of the heating roller 18 is 195 [° C.] and the toner 36 does not adhere, the high temperature offset property is evaluated as good. The outer periphery of the heating roller 18 was 86 [mm].

  As described above, by performing the tape peeling evaluation test, the fixing strength evaluation test, and the high temperature offset property evaluation test, results as shown in FIGS. 8 shows the results when a shell material having an endothermic peak temperature (T2) of 75 [° C.] is used, and FIG. 9 shows the results when a shell material having an endothermic peak temperature (T2) of 85 [° C.] is used. FIG. 10 shows the results when a shell material having an endothermic peak temperature (T2) of 95 [° C.] is used, and FIG. 11 shows the results when a shell material having an endothermic peak temperature (T2) of 105 [° C.] is used. Is the result of the case.

  As shown in FIG. 11, it is understood that the low-temperature fixability of the toner 36 is lost when a shell material having an endothermic peak temperature (T2) of 105 ° C. or higher is used.

  Further, as shown in FIG. 8, when a shell material having an endothermic peak temperature (T2) of 75 [° C.] is used, the endothermic peak temperature (T1) is in a range of 57 [° C.] or more and 61 [° C.] or less. It can be seen that when a certain core material is used, the low-temperature fixability of the toner 36 is good.

  Further, as shown in FIG. 9, even when a shell material having an endothermic peak temperature (T2) of 85 [° C.] is used, the endothermic peak temperature (T1) is in a range of 57 [° C.] or more and 61 [° C.] or less. It can be seen that the low-temperature fixability of the toner 36 is good when the core material is used.

  Furthermore, as shown in FIG. 10, even when a shell material having an endothermic peak temperature (T2) of 95 [° C.] is used, the endothermic peak temperature (T1) is in a range of 57 [° C.] or more and 61 [° C.] or less. It can be seen that the low-temperature fixability of the toner 36 is good when the core material is used.

  In the present exemplary embodiment, the case where the storability, the low-temperature fixing property, and the high-temperature offset property of the toner 36 having an average particle diameter of 5.0 [μm] is evaluated has been described. Similar evaluation results could be obtained when the particle size was in the range of 3.0 to 5.0 [μm].

  In the present embodiment, the toner 36 having an average particle size of less than 3.0 [μm] was not evaluated. This is because if the average particle size of the toner 36 becomes small, it becomes difficult to clean the transfer residual toner remaining on the photosensitive drum 31 after the transfer, a cleaning failure occurs, or the toner 36 leaks from the toner cartridge 26b or the developing device 11. It is because it becomes easy to scatter.

  In the present embodiment, the toner 36 having an average particle size larger than 5.0 [μm] was not evaluated. This is because when the average particle size of the toner 36 is large, the dot formation defect by the toner 36 with respect to the dots of the electrostatic latent image formed on the surface of the photosensitive drum 31 (deterioration of dot reproducibility, dot toner omission, dot diameter variation). This is because it is difficult to obtain a high-quality toner image.

  Thus, in this embodiment, the shell material having an endothermic peak temperature of 75 to 95 [° C.] and the core material having an endothermic peak temperature of 57 to 61 [° C.] are provided, and the average particle size is 3.0. Toner 36 having a capsule structure of ˜5.0 [μm] is used. As a result, it is possible to obtain the image forming apparatus 10 that has both good storage stability and low-temperature fixability and does not cause high-temperature offset.

  Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 12 is a first diagram showing the results of evaluation tests for low-temperature fixability of toner in the second embodiment of the present invention, and FIG. 13 is an evaluation test for low-temperature fixability of toner in the second embodiment of the present invention. It is a 2nd figure which shows a result.

  In the first embodiment, the low temperature fixability evaluation test was performed with the nip (NIP) width between the heating roller 18 and the pressure roller 19 in the fixing device 25 fixed at 9.1 [mm]. However, when the nip width between the heating roller 18 and the pressure roller 19 is increased, the low-temperature fixability is improved. If the nip width between the heating roller 18 and the pressure roller 19 is increased, a high temperature offset tends to occur.

  Therefore, in the present embodiment, the heating roller 18 and the toner 36 using the shell material and the core material, which are evaluated to be good in both the low temperature fixing property and the high temperature offset property in the first embodiment, Evaluation of low-temperature fixability and high-temperature offset property with the nip width with the pressure roller 19 changed to five values of 8.5, 9.1, 10.5, 11.8 and 12.5 [mm]. In addition, the present inventors have found a combination of a shell material and a core material in which both the low temperature fixing property and the high temperature offset property are good and the nip width between the heating roller 18 and the pressure roller 19.

  In the evaluation test, the nip width between the heating roller 18 and the pressure roller 19 was changed by changing the pressure roller 19 to have a different diameter. The toner 36 to be evaluated uses a shell material with endothermic peak temperatures (T2) of 75 and 95 [° C.] and a core material with endothermic peak temperatures (T1) of 57, 59 and 61 [° C.]. Toner 36 is obtained. Further, the speed of the printing paper 24 on the transfer belt 15 and the surface temperature of the heating roller 18 were set to 230 [mm / sec] and 145 [° C.] as in the first embodiment.

  As for the low temperature fixability evaluation test, two types of evaluation tests, a tape peeling evaluation test and a fixing strength evaluation test, are performed in the same manner as in the first embodiment, and both evaluation results are satisfactory. In addition, it was evaluated that the low-temperature fixability was good. As a result, the results shown in FIGS. 12 and 13 were obtained. FIG. 12 shows the results when a shell material having an endothermic peak temperature (T2) of 75 [° C.] is used, and FIG. 13 shows the results when a shell material having an endothermic peak temperature (T2) of 95 [° C.] is used. It is a result.

  As shown in FIGS. 12 and 13, the low temperature fixability changed the nip width between the heating roller 18 and the pressure roller 19 rather than the influence of using the shell material and the core material having different peak temperatures. It can be seen that it is strongly influenced by It can be seen that the low-temperature fixability is good when the nip width between the heating roller 18 and the pressure roller 19 is 9.1 [mm] or more regardless of the type of the shell material and the core material.

  Next, evaluation of the high temperature offset property of the toner 36 will be described.

  FIG. 14 is a first diagram illustrating the evaluation test result of the high temperature offset property of the toner according to the second embodiment of the present invention, and FIG. 15 is the evaluation test of the high temperature offset property of the toner according to the second embodiment of the present invention. It is a 2nd figure which shows a result.

  The high temperature offset evaluation test in the present embodiment is performed in the same manner as in the first embodiment, and the toner 36 does not adhere under the condition that the surface temperature of the heating roller 18 is 195 [° C.]. In addition, the high temperature offset property was evaluated as good. As a result, the results as shown in FIGS. 14 and 15 were obtained. 14 shows the results when a shell material having an endothermic peak temperature (T2) of 75 [° C.] is used, and FIG. 15 shows the results when a shell material having an endothermic peak temperature (T2) of 95 [° C.] is used. It is a result.

  As shown in FIGS. 14 and 15, the high temperature offset property is similar to the low temperature fixability as compared with the effect of using the shell material and the core material having different peak temperatures. It can be seen that it is strongly influenced by changing the nip width. And it turns out that high temperature offset property is favorable when the nip width | variety of the heating roller 18 and the pressure roller 19 is 11.8 [mm] or less irrespective of the kind of shell material and core material.

  Thus, in the present embodiment, the toner 36 including the shell material having an endothermic peak temperature of 75 to 95 [° C.] and the core material having an endothermic peak temperature of 57 to 61 [° C.] is used. Further, the nip (NIP) width between the heating roller 18 and the pressure roller 19 in the fixing device 25 is set to 9.1 or more and 11.8 [mm] or less. As a result, it is possible to obtain the image forming apparatus 10 having both the low-temperature fixability and the high-temperature offset property.

  In the first and second embodiments, the example in which the image forming apparatus 10 is a printer has been described. However, the present invention can also be applied to an MFP, a facsimile machine, and a copying apparatus.

  The present invention is not limited to the above-described embodiment, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a diagram illustrating a configuration of a developing device and a fixing device according to a first embodiment of the present invention. It is a figure which shows the endothermic curve of the developer in the 1st Embodiment of this invention. It is a figure which shows the evaluation test result of the storage stability of the toner in the 1st Embodiment of this invention. It is a figure explaining the method of the fixing evaluation test in the 1st Embodiment of this invention. It is a figure explaining the 1st method of the fixing strength evaluation test in the 1st embodiment of the present invention. It is a figure explaining the 2nd method of the fixing strength evaluation test in the 1st Embodiment of this invention. FIG. 6 is a first diagram illustrating a toner fixing property evaluation test result according to the first exemplary embodiment of the present invention. FIG. 6 is a second diagram showing the results of an evaluation test of toner fixability in the first embodiment of the present invention. FIG. 6 is a third diagram showing the results of an evaluation test of toner fixability in the first embodiment of the present invention. FIG. 10 is a fourth diagram showing the results of a toner fixing property evaluation test in the first embodiment of the present invention. FIG. 6 is a first diagram illustrating a test result of low-temperature fixability of a toner according to a second embodiment of the present invention. FIG. 10 is a second diagram showing the evaluation test result of the low-temperature fixability of the toner in the second embodiment of the present invention. FIG. 10 is a first diagram illustrating the evaluation test result of the high-temperature offset property of the toner according to the second embodiment of the present invention. FIG. 10 is a second diagram showing the evaluation test result of the high temperature offset property of the toner in the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11a, 11b, 11c, 11d Developing device 15 Transfer belt 18 Heating roller 19 Pressure roller 24 Printing paper 25 Fixing device 36 Toner

Claims (4)

It has a capsule structure in which a core material is covered with a shell material, and adheres to an electrostatic latent image on an image carrier to form a developer image. The developer image is transferred to a medium, and is heated from a heating member and a pressure member. A developer fixed to the medium by applied heat and pressure,
The average particle size is 3.0 to 5.0 [μm], the core material has a glass transition temperature of 57 to 61 [° C.], and the shell material has a glass transition temperature of 75 to 95 [° C.]. A developer characterized by that. The conveyance speed of the medium is 230 [mm / sec], and
The developer according to claim 1, wherein a contact distance between the heating member and the pressure member is 9.1 to 11.8 [mm]. An image forming unit for forming a developer image by attaching a developer having a capsule structure in which a core material is covered with a shell material to an electrostatic latent image on an image carrier, and transferring the developer image to a medium;
A transport unit for transporting the medium;
An image forming apparatus including a heating member and a pressure member, and having a fixing unit that fixes the developer image on a medium by heat and pressure,
The developer has an average particle size of 3.0 to 5.0 [μm], the core material has a glass transition temperature of 57 to 61 [° C.], and the shell material has a glass transition temperature of 75 to 95 [° C.]. ° C.]. The conveyance speed of the medium by the conveyance unit is 230 [mm / sec], and
The image forming apparatus according to claim 3, wherein a contact distance between the heating member and the pressure member is 9.1 to 11.8 [mm].

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