Image forming apparatus and image forming method

Abstract

The invention discloses an image forming apparatus and an image forming method. The image forming apparatus includes an electrophotographic photoreceptor, a charging device that charges a surface of the photoreceptor, an electrostatic charge image forming device that forms an electrostatic charge image on the surface of the charged photoreceptor, and a developer that accommodates and supplies an electrostatic charge image developer containing toner and develops the electrostatic charge image formed on the surface of the photoreceptor as a toner image. A primary transfer device for primarily transferring the toner image formed on the surface of the photoreceptor to the surface of the intermediate transfer body; and a secondary transfer device for secondarily transferring the toner image transferred on the surface of the intermediate transfer body to the surface of recording paper. A fixing device that fixes the toner image to the surface of the recording paper; a first heating device that heats the toner image transferred to the surface of the intermediate transfer body before the toner image is secondarily transferred to the surface of the recording paper by the secondary transfer device; and a second heating device that heats the recording sheet before the toner image is secondarily transferred to the surface of the recording sheet by the secondary transfer device.

Description

Technical Field

[0001] The present invention relates to an image forming device and an image forming method. Background Art

[0002] The formation of an image based on electronic photography is carried out, for example, as follows: after charging the surface of a photoreceptor, an electrostatic charge image is formed on the surface of the photoreceptor according to image information, then the electrostatic charge image is developed using a developer containing a colorant to form a colorant image, and the colorant image is transferred and fixed to the surface of a recording medium.

[0003] Here, Japanese Patent Application Laid-Open No. 2002-123114 discloses “an image forming method comprising: a transfer step of transferring a toner image formed on an image carrier to an intermediate transfer body; and a transfer and fixing step of transferring the toner image on the intermediate transfer body to a recording medium and fixing the toner image simultaneously, wherein the toner forming the toner image contains at least a binder resin and a colorant, and the toner has a loss elastic modulus (G") of 1×10 4 Pa, the storage elastic modulus (G') of the toner is 2×10 2 ~6×10 3 Pa, in the transfer and fixing process, the heat-resistant belt is pressed against the fixing roller in such a way that a nip is formed between the fixing roller covered with an elastic body and the heat-resistant belt stretched by a support roller, and at the outlet of the nip, a fixing device is used in which the elastic body of the fixing roller is deformed through the heat-resistant belt by a pressure roller arranged on the inner side of the heat-resistant belt to perform transfer and fixing. ".

[0004] Japanese Patent Application Laid-Open No. 2000-112249 discloses an image forming apparatus comprising: an image carrier having a toner image formed on a surface thereof; a toner image forming unit, the toner image forming unit forming a toner image on the image carrier; an intermediate transfer body, the intermediate transfer body cyclically moving along a path passing through a primary transfer position on the image carrier in contact with or close to the image carrier and a predetermined transfer fixing position, at the primary transfer position, receiving the transfer of the toner image on the image carrier on the surface thereof and conveying the toner image to the transfer fixing position; and a primary transfer unit, the primary transfer unit transferring the toner image on the image carrier to the transfer fixing position at the primary transfer position. The recording body is transferred to the intermediate transfer body; a recording body conveying unit, which conveys the recording body to the transfer fixing position; a transfer fixing unit, which sandwiches the toner image transferred to the intermediate transfer body by the primary transfer unit between the intermediate transfer body and the recording body at the transfer fixing position and heats the toner image while applying pressure, thereby fixing the toner image on the intermediate transfer body to the recording body while transferring; and a heating unit, which is arranged on the moving path of the intermediate transfer body, upstream of the primary transfer position and downstream of the transfer fixing position, and heats the intermediate transfer body at a temperature lower than the heating temperature of the transfer fixing unit. ". Summary of the invention

[0005] The present invention aims to provide an image forming device, the image forming device comprising: an electrophotographic photoreceptor; a charging device, the charging device charging the surface of the electrophotographic photoreceptor; an electrostatic charge image forming device, the electrostatic charge image forming device forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing device, the developing device containing an electrostatic charge image developer containing a toner, supplying the electrostatic charge image developer, and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; an intermediate transfer body, the intermediate transfer body having the toner image transferred to its surface; and a primary transfer device, the primary transfer device transferring the toner image formed on the surface of the electrophotographic photoreceptor to a primary transfer position. The printing press of the printing ink is performed by a first heating device and a second heating device. The printing ink is transferred to the surface of an intermediate transfer body; a secondary transfer device, which secondary transfers the colorant image transferred to the surface of the intermediate transfer body to the surface of a recording paper; and a fixing device, which fixes the colorant image to the surface of the recording paper, wherein, compared with a case where the first heating device and the second heating device are not provided, uneven image density occurring in a high temperature and high humidity environment is suppressed, the first heating device heats the colorant image transferred to the surface of the intermediate transfer body before the secondary transfer device transfers the colorant image to the surface of the recording paper, and the second heating device heats the recording paper before the secondary transfer device transfers the colorant image to the surface of the recording paper.

[0006] According to a first aspect of the present invention, there is provided an image forming device, which comprises: an electrophotographic photosensitive body; a charging device, the charging device charging the surface of the electrophotographic photosensitive body; an electrostatic charge image forming device, the electrostatic charge image forming device forming an electrostatic charge image on the surface of the charged electrophotographic photosensitive body; a developing device, the developing device containing an electrostatic charge image developer containing a colorant, supplying the electrostatic charge image developer, and developing the electrostatic charge image formed on the surface of the electrophotographic photosensitive body as a colorant image; an intermediate transfer body, the intermediate transfer body having the colorant image transferred to its surface; and a primary transfer device, the primary transfer device transferring the colorant image formed on the surface of the electrophotographic photosensitive body to the electrostatic charge image formed on the surface of the electrophotographic photosensitive body. The colorant image is first transferred to the surface of the intermediate transfer body; a secondary transfer device, which secondarily transfers the colorant image transferred on the surface of the intermediate transfer body to the surface of the recording paper; a fixing device, which fixes the colorant image to the surface of the recording paper; a first heating device, which heats the colorant image transferred on the surface of the intermediate transfer body before the secondary transfer device secondly transfers the colorant image to the surface of the recording paper; and a second heating device, which heats the recording paper before the secondary transfer device secondly transfers the colorant image to the surface of the recording paper.

[0007] According to a second aspect of the present invention, in the image forming device based on the first aspect, the first heating device is a device that uses the heat emitted from the fixing device to heat the colorant image, and the second heating device is a device that uses the heat emitted from the fixing device to heat the recording paper.

[0008] According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a heating temperature of the toner image by the first heating device is 40° C. or higher and 70° C. or lower.

[0009] According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, a heating temperature of the recording paper by the second heating device is 40° C. or higher and 70° C. or lower.

[0010] According to the fifth aspect of the present invention, an image forming method is provided, which comprises: a charging process for charging the surface of an electrophotographic photosensitive body; an electrostatic charge image forming process for forming an electrostatic charge image on the surface of the charged electrophotographic photosensitive body; a developing process for supplying an electrostatic charge image developer containing a colorant and developing the electrostatic charge image formed on the surface of the electrophotographic photosensitive body as a colorant image; a primary transfer process for primary transferring the colorant image formed on the surface of the electrophotographic photosensitive body to the surface of an intermediate transfer body; a secondary transfer process for secondary transferring the colorant image transferred on the surface of the intermediate transfer body to the surface of a recording paper; a fixing process for fixing the colorant image to the surface of the recording paper; a first heating process for heating the colorant image transferred on the surface of the intermediate transfer body before the toner image is secondary transferred to the surface of the recording paper; and a second heating process for heating the recording paper before the toner image is secondary transferred to the surface of the recording paper.

[0011] According to a sixth aspect of the present invention, in the image forming method according to the fifth aspect, the toner has toner particles containing a binder resin and resin particles.

[0012] According to a seventh aspect of the present invention, in the image forming method according to the sixth aspect, the content of the resin particles is 2% by mass or more and 30% by mass or less relative to the toner particles.

[0013] According to an eighth aspect of the present invention, in the image forming method according to the sixth or seventh aspect, the resin particles are styrene (meth) acrylic resin particles.

[0014] According to a ninth aspect of the present invention, in the image forming method according to any one of the sixth to eighth aspects, an average primary particle diameter of the resin particles is 20 nm or more and 300 nm or less.

[0015] (Effect)

[0016] According to the first aspect, an image forming device is provided, the image forming device comprising: an electrophotographic photoreceptor; a charging device, the charging device charging the surface of the electrophotographic photoreceptor; an electrostatic charge image forming device, the electrostatic charge image forming device forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing device, the developing device containing an electrostatic charge image developer containing a toner, supplying the electrostatic charge image developer, and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; an intermediate transfer body, the intermediate transfer body having the toner image transferred to its surface; and a primary transfer device, the primary transfer device transferring the toner image formed on the surface of the electrophotographic photoreceptor to the primary transfer body. The first heating device heats the toner image transferred on the surface of the intermediate transfer body before the secondary transfer device transfers the toner image on the surface of the intermediate transfer body to the surface of the recording paper, and the second heating device heats the recording paper before the secondary transfer device transfers the toner image on the surface of the intermediate transfer body to the surface of the recording paper.

[0017] According to the second aspect, there is provided an image forming apparatus that can suppress uneven image density that occurs under a high-temperature and high-humidity environment at low cost, compared to a case where the first heating device and the second heating device do not use heat generated by the fixing device.

[0018] According to the third aspect, there is provided an image forming apparatus that suppresses uneven image density that occurs under a high-temperature and high-humidity environment, compared with a case where the heating temperature of the toner image by the first heating device is lower than 40° C.

[0019] According to the fourth aspect, there is provided an image forming apparatus that suppresses occurrence of uneven image density in a high-temperature and high-humidity environment, compared with a case where the second heating device heats the recording paper at a temperature lower than 40°C.

[0020] According to the fifth aspect, an image forming method is provided, which comprises: a charging process for charging the surface of an electrophotographic photosensitive body; an electrostatic charge image forming process for forming an electrostatic charge image on the surface of the charged electrophotographic photosensitive body; a developing process for supplying an electrostatic charge image developer containing a toner and developing the electrostatic charge image formed on the surface of the electrophotographic photosensitive body as a toner image; a primary transfer process for transferring the toner image formed on the surface of the electrophotographic photosensitive body to the surface of an intermediate transfer body; and a secondary transfer process for transferring the toner image formed on the surface of the intermediate transfer body. The colorant image on the surface of the intermediate transfer body is secondarily transferred to the surface of the recording paper; and a fixing process for fixing the colorant image to the surface of the recording paper, wherein, compared with a case where there are no first heating process and second heating process, uneven image concentration occurring in a high temperature and high humidity environment is suppressed, wherein in the first heating process, the colorant image transferred on the surface of the intermediate transfer body is heated before the colorant image is secondarily transferred to the surface of the recording paper, and in the second heating process, the recording paper is heated before the colorant image is secondarily transferred to the surface of the recording paper.

[0021] According to the sixth, seventh or eighth aspects, an image forming method is provided, the image forming method comprising: a charging process for charging the surface of an electrophotographic photosensitive body; an electrostatic charge image forming process for forming an electrostatic charge image on the surface of the charged electrophotographic photosensitive body; a developing process for supplying an electrostatic charge image developer containing a colorant and developing the electrostatic charge image formed on the surface of the electrophotographic photosensitive body as a colorant image; a primary transfer process for primary transferring the colorant image formed on the surface of the electrophotographic photosensitive body to the surface of an intermediate transfer body; a secondary transfer process for secondary transferring the colorant image transferred on the surface of the intermediate transfer body to the surface of a recording paper; and a fixing process for fixing the colorant image to the recording paper. the surface of the intermediate transfer body, wherein, compared with a case where the first heating step and the second heating step are not provided, even if a toner having toner particles containing a binding resin and resin particles, toner particles in which the content of the resin particles is 2% by mass or more and 30% by mass or less relative to the toner particles, or toner particles in which the resin particles are styrene (meth) acrylic resin particles is applied, uneven image density occurring in a high temperature and high humidity environment is suppressed, wherein in the first heating step, the toner image transferred on the surface of the intermediate transfer body is heated before the toner image is secondarily transferred to the surface of the recording paper medium, and in the second heating step, the recording paper is heated before the toner image is secondarily transferred to the surface of the recording paper medium.

[0022] According to the ninth aspect, there is provided an image forming method in which the occurrence of uneven image density under a high temperature and high humidity environment is suppressed compared with a case where the average primary particle size of the resin particles is less than 20 nm or exceeds 300 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram showing an example of an image forming apparatus according to the present embodiment;

[0024] Figure 2 This is a schematic partial configuration diagram showing another example of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION

[0025] Hereinafter, an embodiment as an example of the present invention will be described in detail.

[0026] <Image Forming Apparatus>

[0027] The image forming apparatus of this embodiment includes:

[0028] Electrophotographic photoreceptor;

[0029] a charging device for charging the surface of the electrophotographic photoreceptor;

[0030] an electrostatic charge image forming device for forming an electrostatic charge image on a surface of a charged electrophotographic photoreceptor;

[0031] a developing device that contains an electrostatic charge image developer containing a toner, supplies the electrostatic charge image developer, and develops the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image;

[0032] an intermediate transfer body having a toner image transferred onto a surface thereof;

[0033] a primary transfer device for primarily transferring a toner image formed on the surface of the electrophotographic photoreceptor to a surface of an intermediate transfer body;

[0034] a secondary transfer device for secondarily transferring the toner image transferred on the surface of the intermediate transfer body to the surface of the recording paper;

[0035] a fixing device that fixes the toner image to the surface of the recording paper;

[0036] a first heating device for heating the toner image transferred onto the surface of the intermediate transfer body before the toner image is secondarily transferred onto the surface of the recording paper by the secondary transfer device; and

[0037] The second heating device heats the recording paper before the toner image is secondarily transferred to the surface of the recording paper by the secondary transfer device.

[0038] In the image forming apparatus of the present embodiment, the image forming method of the present embodiment is implemented, and the image forming method of the present embodiment has the following steps:

[0039] A charging process for charging the surface of the electrophotographic photoreceptor;

[0040] An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor;

[0041] A developing step of supplying an electrostatic charge image developer containing a toner and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image;

[0042] A primary transfer process is to transfer the toner image formed on the surface of the electrophotographic photoreceptor to the surface of the intermediate transfer body;

[0043] A secondary transfer process of secondarily transferring the toner image transferred on the surface of the intermediate transfer body to the surface of the recording paper;

[0044] A fixing process to fix the toner image to the surface of the recording paper;

[0045] a first heating step of heating the toner image transferred onto the surface of the intermediate transfer body before the toner image is secondarily transferred onto the surface of the recording paper; and

[0046] The second heating step heats the recording paper before the toner image is secondarily transferred onto the surface of the recording paper.

[0047] The image forming apparatus of this embodiment suppresses uneven image density that occurs in a high-temperature and high-humidity environment by means of the above-described configuration. The reason for this is presumably as follows.

[0048] In an image forming apparatus using an intermediate transfer method, since a plurality of toner layers are laminated on an intermediate transfer body, a high transfer voltage is applied when performing secondary transfer onto a recording sheet.

[0049] On the other hand, in a high temperature and high humidity environment, the moisture content of the recording paper increases along with the toner, the resistance of the toner and the recording paper decreases, and charges easily flow to the toner and the recording paper. As a result, the charge injection property deteriorates.

[0050] As a result, in a high-temperature and high-humidity environment, the electric field applied to the toner becomes relatively large, and a sufficient transfer voltage is no longer applied to the toner, so that transferability is reduced and image density unevenness occurs.

[0051] Therefore, in the image forming apparatus of this embodiment, the toner image transferred to the surface of the intermediate transfer body is heated by the first heating device before the secondary transfer device transfers the toner image to the surface of the recording paper. In addition, the recording paper is heated by the second heating device before the secondary transfer device transfers the toner image to the surface of the recording paper.

[0052] Thus, before the secondary transfer, the moisture content of the toner and the recording paper is reduced, and the resistance reduction of the toner and the recording paper is suppressed. As a result, the deterioration of the charge injection property is suppressed. Therefore, even in a high temperature and high humidity environment, the charge injection into the toner caused by applying an excessive voltage to the toner is suppressed, and the reduction of the toner charging and the reduction of the transferability associated therewith are suppressed, and the occurrence of uneven image density is suppressed.

[0053] Based on the above, it is inferred that the image forming apparatus according to the present embodiment suppresses uneven image density that occurs under a high-temperature and high-humidity environment.

[0054] The image forming apparatus of the present embodiment employs a known image forming apparatus such as an apparatus including a static eliminator that irradiates a surface of a photoreceptor with static eliminator light to eliminate static electricity after the toner image is transferred and before charging.

[0055] In the image forming apparatus of the present embodiment, at least a portion including the photosensitive body constitutes a unit for the image forming apparatus, and may be a cartridge structure (ie, a process cartridge) that is attachable to and detachable from the image forming apparatus.

[0056] For example, as an image forming apparatus unit, there is a unit including at least a photoreceptor.

[0057] Next, an example of the structure of the image forming apparatus according to the present embodiment will be described in detail.

[0058] An example of the image forming apparatus of the present embodiment is shown below, but the present invention is not limited thereto. In addition, the main parts shown in the figure are described, and the description of other parts is omitted. The arrow UP shown in the figure indicates the vertical upward direction.

[0059] Figure 1 This is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.

[0060] (Main Parts of Image Forming Apparatus)

[0061] like Figure 1 As shown in FIG. 1 , the image forming apparatus 210 includes an image forming apparatus body 211 in which various components are stored. A storage unit 212 for storing recording paper P, an image forming unit 214 for forming an image on the recording paper P, and a conveying unit 216 for conveying the recording paper P from the storage unit 212 to the image forming unit 214 are provided inside the image forming apparatus body 211. In addition, a discharge unit 218 for discharging the recording paper P on which the image is formed by the image forming unit 214 is provided at the top of the image forming apparatus body 211. Furthermore, a control device 220 for controlling the operation of various components of the image forming apparatus 210 is provided inside the image forming apparatus body 211.

[0062] The image forming section 214 includes: image forming units 222Y, 222M, 222C, and 222K (hereinafter referred to as 222Y to 222K), which form colorant images of yellow (Y), magenta (M), cyan (C), and black (K); an intermediate transfer belt 224 (an example of an intermediate transfer body), which transfers the colorant images formed by the image forming units 222Y to 222K; a primary transfer roller 226 (an example of a primary transfer device), which transfers the colorant images formed by the image forming units 222Y to 222K to the intermediate transfer belt 224; and a secondary transfer roller 228 (an example of a secondary transfer device), which transfers the colorant images transferred to the intermediate transfer belt 224 by the primary transfer roller 226 from the intermediate transfer belt 224 to the recording paper P.

[0063] Here, a unit composed of the intermediate transfer belt 224 , the primary transfer roller 226 , and the secondary transfer roller 228 corresponds to an example of a transfer device.

[0064] The image forming unit 214 is not limited to the above-described configuration, and may be any other configuration as long as it can form an image on the recording paper P.

[0065] The image forming units 222Y to 222K are arranged side by side in a state inclined relative to the horizontal direction at the vertical center of the image forming device 210. In addition, the image forming units 222Y to 222K each have a plurality of Figure 1 The photosensitive body 232 (an example of an image holding body) rotates in the clockwise direction in FIG. 2. In addition, since the image forming units 222Y to 222K are configured in the same manner, Figure 1 The reference numerals of the components of the image forming units 222M, 222C, and 222K are omitted.

[0066] Around each photosensitive body 232, there are arranged in sequence from the upstream side in the rotation direction of the photosensitive body 232 a charging device 223 having a charging roller 223A for charging the photosensitive body 232, an exposure device 236 (an example of an electrostatic charge image forming device) for exposing the photosensitive body 232 charged by the charging device 223 to form an electrostatic charge image on the photosensitive body 232, a developing device 238 for developing the electrostatic charge image formed on the photosensitive body 232 by the exposure device 236 to form a colorant image, and a photosensitive body cleaning device 240 for cleaning residual colorant remaining on the photosensitive body 232.

[0067] Here, the photoconductor 232 , the charging device 223 , the exposure device 236 , the developing device 238 , and the photoconductor cleaning device 240 are integrally held by a housing (frame) 222A and formed as a cartridge (process cartridge).

[0068] A self-scanning LED print head is applied to the exposure device 236. Alternatively, the exposure device 236 may be an exposure device of an optical system that exposes the photoreceptor 232 from a light source via a polygon mirror.

[0069] The exposure device 236 forms an electrostatic charge image based on the image signal transmitted from the control device 220. The image signal transmitted from the control device 220 may be, for example, an image signal acquired by the control device 220 from an external device.

[0070] The developing machine 238 includes: a developing roller 238A (an example of a developer retaining body), which retains the developer on the surface, supplies the developer to the photosensitive body 232, and develops the electrostatic charge image formed on the photosensitive body 232 as a colorant image; and a plurality of conveying parts 238B, which convey the developer given to the developing roller 238A while stirring it.

[0071] The photoconductor cleaning device 240 includes a scraper 240A that comes into contact with the photoconductor 232 to clean the residual toner remaining on the photoconductor 232 .

[0072] The intermediate transfer belt 224 is formed in an annular shape and is arranged on the upper side of the image forming units 222Y to 222K. Winding rollers 242, 244, and 328 around which the intermediate transfer belt 224 is wound are provided on the inner circumference of the intermediate transfer belt 224. The intermediate transfer belt 224 is rotated by any one of the winding rollers 242, 244, and 328, and is moved in one direction (for example, Figure 1 In addition, the winding roller 242 serves as an opposing roller opposed to the secondary transfer roller 228.

[0073] The primary transfer roller 226 faces the photoconductor 232 with the intermediate transfer belt 224 interposed therebetween. The area between the primary transfer roller 226 and the photoconductor 232 serves as a first transfer position at which the toner image formed on the photoconductor 232 is transferred onto the intermediate transfer belt 224.

[0074] The secondary transfer roller 228 faces the winding roller 242 across the intermediate transfer belt 224. The area between the secondary transfer roller 228 and the winding roller 242 serves as a second transfer position where the toner image transferred onto the intermediate transfer belt 224 is transferred onto the recording paper P.

[0075] The transport section 216 includes a feed roller 246 for feeding out the recording paper P stored in the storage section 212 , a transport path 248 for feeding out the recording paper P fed out by the feed roller 246 , and a plurality of transport rollers 250 arranged along the transport path 248 and transporting the recording paper P fed out by the feed roller 246 to a second transfer position.

[0076] A fixing device 260 for fixing the toner image formed on the recording paper P by the image forming section 214 to the recording paper P is provided downstream in the transport direction of the second transfer position.

[0077] The fixing device 260 includes a heating roller 264 that heats the image on the recording paper P and a pressure roller 266 that is an example of a pressure member. A heat source 264B is provided inside the heating roller 264 .

[0078] Discharge rollers 252 for discharging the recording paper P with the toner image fixed thereon to the discharge section 218 are provided downstream of the fixing device 260 in the conveying direction.

[0079] (Toner image and recording paper heating device)

[0080] The image forming apparatus 210 includes a first heating roller 270 (an example of a first heating device) for heating the toner image transferred onto the surface of the intermediate transfer belt 224 before the secondary transfer roller 228 transfers the toner image onto the surface of the recording paper P. The first heating roller 270 is provided, for example, in contact with or in non-contact with the inner peripheral surface of the intermediate transfer belt 224 to heat the toner image via the intermediate transfer belt 224. Alternatively, the first heating roller 270 may be provided in non-contact with the outer peripheral surface of the intermediate transfer belt 224 to directly heat the toner image.

[0081] The heating temperature of the toner image by the first heating roller 270 is preferably 40° C. or higher and 70° C. or lower, and more preferably 50° C. or higher and 65° C. or lower.

[0082] By setting the heating temperature of the toner image to the above range, it is possible to suppress the melting of the toner and reduce the water content of the toner. As a result, it is easy to suppress uneven image density.

[0083] On the other hand, the image forming apparatus 210 includes a second heating roller 272 (an example of a second heating device) for heating the recording paper P before the secondary transfer roller 228 transfers the toner image to the surface of the recording paper P. The second heating roller 272 is disposed on the conveying path of the recording paper P in a contact or non-contact manner with both sides or one side of the recording paper P, and directly heats the recording paper P. In addition, Figure 1 In FIG. 2 , a pair of second heating rollers 272 for heating both sides of the recording paper P is shown.

[0084] The heating temperature of the recording paper P by the second heating roller 272 is preferably 40° C. or higher and 70° C. or lower, and more preferably 50° C. or higher and 65° C. or lower.

[0085] By setting the heating temperature of the recording paper P to the above range, it is possible to suppress the fluctuation of the paper due to rapid volatilization of water from the paper and reduce the moisture content of the recording paper P. As a result, it is easy to suppress uneven image density.

[0086] Examples of the first heating roller 270 and the second heating roller 272 include heating rollers each having a built-in heat source such as a halogen lamp or a heating wire.

[0087] In addition, the first heating device and the second heating device are not limited to the first heating roller 270 and the second heating roller 272, and a known heating device such as a planar heater may be applied.

[0088] In addition, it is also preferable that the first heating device is a device that uses the heat generated from the fixing device 260 (specifically, the heating roller 264) to heat the toner image, and the second heating device is a device that uses the heat generated from the fixing device 260 (specifically, the heating roller 264) to heat the recording paper P. Specifically, for example, the following methods can be cited.

[0089] like Figure 2 As shown in the figure, as an example of the first heating device, a first duct 274 is provided for sending the air heated by the fixing device 260 (specifically, the heating roller 264) from the fixing device 260 to the inner peripheral surface of the intermediate transfer belt 224. Inside the first duct 274, an air intake fan 274A is provided on the fixing device 260 side, and an exhaust fan 274B is provided on the intermediate transfer belt 224 side. By driving each fan, the air heated by the fixing device 260 passes through the first duct 274 and is sent to the inner peripheral surface of the intermediate transfer belt 224, and the toner image is heated by the air via the intermediate transfer belt 224.

[0090] On the other hand, as an example of a second heating device, a second duct 276 is provided for sending the air heated by the fixing device 260 (specifically, the heating roller 264) from the fixing device 260 to the conveying path of the recording paper P. Inside the second duct 276, an air intake fan 276A is provided on the fixing device 260 side, and an exhaust fan 276B is provided on the conveying path side of the recording paper P. By driving each fan, the air heated by the fixing device 260 passes through the second duct 276 and is sent to the conveying path of the recording paper P, and the recording paper P passing through the conveying path is heated by the air.

[0091] Here, in the method of heating the colorant image and the recording paper using the heat generated by the fixing device 260, as for adjusting the heating temperature, for example, there are a method of separately providing a duct in the path of each duct to introduce air from outside the fixing device, a method of adjusting the length of the duct, etc.

[0092] Compared with a method of providing a separate heat source such as a heating roller, by heating the toner image and the recording paper using the heat generated by the fixing device 260 , it is possible to suppress uneven image density that occurs in a high-temperature and high-humidity environment at low cost.

[0093] Here, the heating temperature of the toner image and the heating temperature of the recording paper are preferably set to a temperature of 40° C. or higher and 70° C. or lower when the toner image and the recording paper reach the secondary transfer member.

[0094] In addition, a part of the first duct 274 and the second duct 276 may be shared on the fixing device 260 side.

[0095] Here, Figure 2 In the figure, T denotes a toner image, 228 denotes a second transfer roller, 242 denotes a winding roller, 264 denotes a heating roller, and 266 denotes a pressure roller.

[0096] (Operation of Image Forming Apparatus)

[0097] An example of the operation of the image forming apparatus 210 according to the present embodiment will be described. Note that various operations of the image forming apparatus 210 are performed by a control program executed in the control device 220 .

[0098] First, in the image forming apparatus 210 , the recording paper P fed out from the storage portion 212 by the feed roller 246 is fed to the second transfer position by the plurality of transport rollers 250 .

[0099] Here, the recording paper P is heated by the second heating roller 272 before reaching the second transfer position.

[0100] On the other hand, in the image forming units 222Y to 222K, the photoconductor 232 charged by the charging device 223 is exposed by the exposure device 236 to form an electrostatic charge image on the photoconductor 232. The electrostatic charge image is developed by the developing device 238 to form a toner image on the photoconductor 232. The toner images of the respective colors formed by the image forming units 222Y to 222K overlap with the intermediate transfer belt 224 at the first transfer position to form a color image. Then, the color image formed on the intermediate transfer belt 224 is transferred to the recording paper P at the second transfer position.

[0101] Here, the color image (ie, the toner image) formed on the intermediate transfer belt 224 is heated by the first heating roller 270 before reaching the second transfer position.

[0102] The recording paper P with the toner image transferred thereto is conveyed to the fixing device 260, and the transferred toner image is fixed by the fixing device 260. The recording paper P with the toner image fixed thereto is discharged to the discharge section 218 by the discharge roller 252. A series of image forming operations are performed as described above.

[0103] [Electrostatic image developer]

[0104] Next, an electrostatic image developer stored in a developing device in the image forming apparatus according to the present embodiment (hereinafter also referred to as “electrostatic image developer according to the present embodiment”) will be described.

[0105] The electrostatic image developer according to the present embodiment contains at least toner.

[0106] The electrostatic charge image developer of the present embodiment may be a one-component developer containing only a toner, or may be a two-component developer containing a toner and a carrier.

[0107] The toner contains toner particles. The toner may contain toner particles and external additives.

[0108] Next, the toner will be described in detail.

[0109] (Toner particles)

[0110] The toner particles contain, for example, a binder resin, and may contain a colorant, a release agent, resin particles, and other additives.

[0111] In particular, the toner particles may contain a binder resin and resin particles. Toner particles having such a structure are prone to contain water in a high temperature and high humidity environment, and thus image density unevenness is prone to occur.

[0112] However, in the image forming apparatus of the present embodiment, even when toner particles containing a binder resin and resin particles are used, image density unevenness is suppressed.

[0113] -Bonding resin-

[0114] Examples of the binder resin include homopolymers of monomers such as styrenes (e.g., styrene, p-chlorostyrene, α-methylstyrene, etc.), (meth)acrylates (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (e.g., ethylene, propylene, butadiene, etc.), or copolymers of two or more of these monomers.

[0115] As the binder resin, for example, non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, modified rosin, mixtures thereof with the above-mentioned vinyl resins, or graft polymers obtained by polymerizing vinyl monomers in the coexistence of these resins can also be cited.

[0116] These binder resins may be used alone or in combination of two or more.

[0117] As the binder resin, polyester resin is preferable.

[0118] As the polyester resin, for example, a known amorphous polyester resin can be cited. The polyester resin can also be used together with a crystalline polyester resin. Among them, the crystalline polyester resin can be used in a range of 2 mass % to 40 mass % (preferably 2 mass % to 20 mass %) relative to the total binder resin.

[0119] The "crystallinity" of a resin means that it has a clear endothermic peak instead of a step-like change in endothermic value in differential scanning calorimetry (DSC). Specifically, it means that the half-value width of the endothermic peak is within 10°C when measured at a heating rate of 10 (°C / min).

[0120] On the other hand, the "amorphous" nature of a resin means that the half value width exceeds 10°C, the endothermic value shows a step-like change, or a clear endothermic peak is not confirmed.

[0121] Amorphous polyester resin

[0122] Examples of the non-crystalline polyester resin include polycondensates of polycarboxylic acids and polyols. In addition, as the non-crystalline polyester resin, a commercially available product may be used, or a synthesized product may be used.

[0123] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexane dicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, etc.), anhydrous products thereof, or lower (e.g., carbon number of 1 to 5) alkyl esters thereof. Among these, aromatic dicarboxylic acids are preferred as the polycarboxylic acid.

[0124] The polycarboxylic acid may also be used in combination with a trivalent or higher carboxylic acid having a crosslinked structure or a branched structure. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrous forms thereof, or lower (e.g., having a carbon number of 1 or more and 5 or less) alkyl esters thereof.

[0125] The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0126] Examples of the polyol include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among them, the polyol is preferably, for example, an aromatic diol or an alicyclic diol, and more preferably an aromatic diol.

[0127] As the polyol, a trivalent or higher polyol having a cross-linked structure or a branched structure may be used together with a diol. Examples of the trivalent or higher polyol include glycerol, trimethylol propane, and pentaerythritol.

[0128] The polyols may be used alone or in combination of two or more.

[0129] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50° C. or higher and 80° C. or lower, and more preferably 50° C. or higher and 65° C. or lower.

[0130] The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, according to the "extrapolated glass transition start temperature" described in the method for determining the glass transition temperature of JIS K 7121-1987 "Methods for determining transition temperatures of plastics".

[0131] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less.

[0132] The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2,000 or more and 100,000 or less.

[0133] The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.

[0134] In addition, the weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). In the molecular weight measurement based on GPC, GPC HLC-8120GPC manufactured by Tosoh was used as a measuring device, and a chromatographic column TSKgelSuperHM-M (15 cm) manufactured by Tosoh was used and THF solvent was used. The weight average molecular weight and the number average molecular weight were calculated using a molecular weight calibration curve prepared using a monodisperse polystyrene standard sample based on the measurement results.

[0135] The amorphous polyester resin is obtained by a known production method, specifically, for example, by setting the polymerization temperature to 180° C. to 230° C., reducing the pressure in the reaction system as necessary, and reacting while removing water or ethanol generated during condensation.

[0136] In addition, when the monomer of the raw material is insoluble or incompatible at the reaction temperature, a high boiling point solvent may be added as a cosolvent to dissolve it. In this case, the polycondensation reaction is carried out while the cosolvent is removed by distillation. In the case of the presence of monomers with poor compatibility, the monomers with poor compatibility may be pre-condensed with an acid or ethanol to be polycondensed with the monomers, and then polycondensed together with the main component.

[0137] Crystalline polyester resin

[0138] Examples of the crystalline polyester resin include polycondensates of polycarboxylic acids and polyols. In addition, as the crystalline polyester resin, a commercially available product may be used, or a synthesized product may be used.

[0139] Here, in the case of the crystalline polyester resin, a polycondensate of a polymerizable monomer having a linear aliphatic group is preferably used rather than a polymerizable monomer having an aromatic group in order to easily form a crystalline structure.

[0140] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalene-2,6-dicarboxylic acid, etc.), anhydrous products thereof, or lower (e.g., having a carbon number of 1 to 5) alkyl esters thereof.

[0141] The polycarboxylic acid may also be used together with the dicarboxylic acid and a tricarboxylic acid or higher having a cross-linked structure or a branched structure. Examples of the tricarboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), their anhydrates, or their lower (e.g., carbon number of 1 or more and 5 or less) alkyl esters.

[0142] As the polycarboxylic acid, a dicarboxylic acid having a sulfonic acid group or a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids.

[0143] The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0144] Examples of the polyol include aliphatic diols (e.g., linear aliphatic diols having a main chain portion having carbon atoms of 7 or more and 20 or less). Examples of the aliphatic diols include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosandiol. Among them, preferred aliphatic diols include 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

[0145] The polyol may be used together with the diol in a trivalent or higher alcohol having a cross-linked structure or a branched structure. Examples of the trivalent or higher alcohol include glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, and the like.

[0146] The polyols may be used alone or in combination of two or more.

[0147] Here, the content of the aliphatic diol in the polyol can be 80 mol % or more, preferably 90 mol % or more.

[0148] The melting temperature of the crystalline polyester resin is preferably 50° C. or higher and 100° C. or lower, more preferably 55° C. or higher and 90° C. or lower, and further preferably 60° C. or higher and 85° C. or lower.

[0149] The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) according to the “melting peak temperature” described in the method for determining the melting temperature in JIS K7121-1987 “Methods for determining transition temperatures of plastics”.

[0150] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0151] The crystalline polyester resin can be obtained by a known production method, for example, similar to the amorphous polyester resin.

[0152] The content of the binder resin is, for example, preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and further preferably 60% by mass to 85% by mass, based on the entire toner particles.

[0153] -Colorants-

[0154] Examples of the colorant include carbon black, chrome yellow, Hansa yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Vulcan orange, youthful red, fast red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil-soluble red, pyrazolone red, litho red, rhodamine B lake, lake red C, pigment red, Bengal rose red, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, malachite green oxalate and other pigments; and acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, nigrosine-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, thiazole-based and other dyes.

[0155] The coloring agent may be used alone or in combination of two or more.

[0156] The colorant may be a surface-treated colorant as required, or may be used together with a dispersant. In addition, a plurality of colorants may be used together.

[0157] The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the entire toner particles.

[0158] -Release agent-

[0159] Examples of the release agent include hydrocarbon wax, natural wax such as palm wax, rice bran wax, and candelilla wax, synthetic wax such as montan wax or mineral and petroleum wax, and ester wax such as fatty acid ester and montanic acid ester. The release agent is not limited thereto.

[0160] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower.

[0161] The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) according to the “melting peak temperature” described in the method for determining the melting temperature in JIS K7121-1987 “Methods for determining transition temperatures of plastics”.

[0162] The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the entire toner particles.

[0163] -Resin particles-

[0164] Examples of the resin particles include polyolefin resins (polyethylene, polypropylene, etc.), styrene resins (polystyrene, α-polymethylstyrene, etc.), (meth)acrylic resins (polymethyl methacrylate, polyacrylonitrile, etc.), epoxy resins, polyurethane resins, polyurea resins, polyamide resins, polycarbonate resins, polyether resins, polyester resins, and copolymers of these resins.

[0165] As the resin particles, styrene-(meth)acrylic copolymer resin particles are preferred.

[0166] Examples of the styrene-(meth)acrylic copolymer resin particles include resin particles obtained by polymerizing a styrene monomer and a (meth)acrylic monomer by radical polymerization.

[0167] Examples of the styrene monomers include styrene, α-methylstyrene, vinylnaphthalene, or alkyl-substituted styrenes having an alkyl chain such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene, halogen-substituted styrenes such as 2-chlorostyrene, 3-chlorostyrene, and 4-chlorostyrene, and fluorine-substituted styrenes such as 4-fluorostyrene and 2,5-difluorostyrene. Among them, styrene and α-methylstyrene are also preferred as styrene monomers.

[0168] Examples of the (meth)acrylic acid monomer include (meth)acrylic acid, n-methyl (meth)acrylate, n-ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, Amyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, tert-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, cyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, β-carboxyethyl (meth)acrylate, (meth)acrylonitrile, (meth)acrylic acid amide, etc. Among them, as the (meth)acrylic monomer, n-butyl (meth)acrylate and β-carboxyethyl (meth)acrylate are preferred.

[0169] The resin particles are preferably cross-linked resin particles. In the cross-linked resin particles, examples of the cross-linking agent for cross-linking the resin include aromatic polyvinyl compounds such as divinylbenzene and divinylnaphthalene, polyvinyl esters of aromatic polycarboxylic acids such as divinyl phthalate, divinyl isophthalate, divinyl terephthalate, divinyl homophthalate, divinyl trimesic acid, trivinyl trimesic acid, divinyl naphthalene dicarboxylate, and divinyl biphenyl carboxylate, divinyl esters of nitrogen-containing aromatic compounds such as divinyl pyridine dicarboxylate, vinyl esters of unsaturated heterocyclic carboxylic acid compounds such as vinyl furoate, vinyl furancarboxylate, vinyl pyrrole-2-carboxylate, and vinyl thiophenecarboxylate, and linear polyols such as butanediol diacrylate, butanediol methacrylate, hexanediol acrylate, octanediol methacrylate, decanediol acrylate, and dodecanediol methacrylate. (meth)acrylates of branched, substituted polyols such as (meth)acrylates of neopentyl glycol dimethacrylate, 2-hydroxyl, 1,3-diacryloxypropane, etc., polyethylene glycol di(meth)acrylates, polypropylene polyethylene glycol di(meth)acrylates, succinic acid divinyl ester, fumaric acid divinyl ester, maleic acid vinyl ester, maleic acid divinyl ester, dihydroxyacetic acid divinyl ester, itaconic acid vinyl ester, itaconic acid divinyl ester, acetone dicarboxylic acid divinyl ester, n-glutaric acid divinyl ester, 3,3'-thiodipropionic acid divinyl ester, trans-aconitic acid divinyl ester, trans-aconitic acid trivinyl ester, adipate divinyl ester, pimelate divinyl ester, suberate divinyl ester, azelaic acid divinyl ester, sebacate divinyl ester, dodecanedioic acid divinyl ester, tridecanedioic acid divinyl ester and other polyvalent vinyl esters of polyvalent carboxylic acids, etc. The crosslinking agent may be used alone or in combination of two or more.

[0170] Examples of the resin particles that tend to increase the water content of the toner by absorbing moisture under a high-temperature and high-humidity environment include (meth)acrylic resin particles.

[0171] Examples of the (meth)acrylic resin particles include homopolymer resin particles of only a (meth)acrylic monomer and copolymer resin particles of a styrene monomer and a (meth)acrylic monomer.

[0172] Examples of homopolymer resin particles of only a (meth)acrylic monomer include homopolymer particles of monomers such as polymethyl methacrylate and polyethyl acrylate.

[0173] Examples of copolymerized resin particles of a styrene-based monomer and a (meth)acrylic monomer include copolymerized resin particles in which the styrene-based monomer is styrene, the (meth)acrylic monomer is n-butyl acrylate, and the mass ratio of the styrene-based monomer to the (meth)acrylic monomer (styrene-based monomer / (meth)acrylic monomer) is 10 / 90 or more and 70 / 30 or less (preferably 20 / 80 or more and 65 / 35 or less).

[0174] In addition, when the (meth)acrylic resin particles are crosslinked resin particles using a crosslinking agent, the crosslinking agent is preferably a bifunctional alkyl acrylate having an alkylene chain having 6 or more and 12 or less carbon atoms, and the content of the crosslinking agent is, for example, preferably 0.3 or more and 5.0 parts by mass, more preferably 0.5 or more and 2.5 parts by mass, and further preferably 1.0 or more and 2.0 parts by mass, relative to 100 parts by mass of the total of the styrene monomer, the (meth)acrylic monomer and the crosslinking agent.

[0175] Even when toner particles including such resin particles and easily increasing the water content by absorbing moisture under a high-temperature and high-humidity environment are used, the image forming apparatus of the present embodiment can suppress uneven image density.

[0176] The average primary particle size of the resin particles is preferably 20 nm or more and 500 nm or less, more preferably 30 nm or more and 300 nm or less, and further preferably 50 nm or more and 250 nm or less.

[0177] When the average primary particle size of the resin particles is within the above range, the toner particles are prone to having resin particles of an appropriate size that are difficult to aggregate, so that it is difficult to form a conductive path formed by the resin particles, and the uneven image density caused by the moisture absorption of the toner particles in a high temperature and high humidity environment is suppressed.

[0178] The average primary particle size of the resin particles is a value measured using a transmission electron microscope (TEM).

[0179] As the transmission electron microscope, for example, JEM-2100plus manufactured by JEOL Ltd. can be used.

[0180] Specifically, the method for measuring the average primary particle size of the resin particles is as follows.

[0181] The toner particles were sliced ​​into pieces with a thickness of about 0.1 μm using a microtome. A 10,000-fold photograph of the cross section of the toner particles was taken using a transmission electron microscope. The equivalent circle diameters of 100 resin particles dispersed in the toner particles were calculated based on the cross-sectional areas of each particle, and the value obtained by arithmetic averaging of the equivalent circle diameters was set as the average primary particle diameter.

[0182] The content of the resin particles is preferably 2% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 25% by mass or less, and still more preferably 5% by mass or more and 20% by mass or less, based on the toner particles.

[0183] Toner particles containing the resin particles in the above content range are likely to contain water under a high-temperature and high-humidity environment, and thus image density unevenness is less likely to occur.

[0184] However, in the image forming apparatus of the present embodiment, even when toner particles containing a binder resin and resin particles are used, image density unevenness is suppressed.

[0185] -Other additives-

[0186] Examples of other additives include known additives such as magnets, charge control agents, and inorganic powders. These additives are contained in toner particles as internal additives.

[0187] -Characteristics of toner particles, etc.-

[0188] The toner particles may be toner particles of a single-layer structure, or may be toner particles of a so-called core-shell structure consisting of a core portion (core particle) and a coating layer (shell layer) that covers the core portion.

[0189] Here, the toner particles of the core-shell structure may be composed of, for example, a core portion including a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer including a binder resin.

[0190] The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0191] In addition, various average particle diameters and various particle size distribution indices of the toner particles were measured using a Coulter Counter II (manufactured by Beckman Coulter Inc.), and the electrolyte was measured using an ISOTON-II (manufactured by Beckman Coulter Inc.).

[0192] During measurement, 0.5 mg to 50 mg of a measurement sample is added as a dispersant to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate), and this is added to 100 ml to 150 ml of an electrolyte.

[0193] The electrolyte solution in which the sample was suspended was dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with a particle size ranging from 2 μm to 60 μm was measured using a Coulter particle counter II with an aperture of 100 μm. The number of particles sampled was 50,000.

[0194] Relative to the particle size range (pores) divided based on the measured particle size distribution, the cumulative distribution of volume and number is drawn from the small diameter side, and the particle size with a cumulative total of 16% is defined as the volume particle size D16v and the number particle size D16p, the particle size with a cumulative total of 50% is defined as the volume average particle size D50v and the cumulative number average particle size D50p, and the particle size with a cumulative total of 84% is defined as the volume particle size D84v and the number particle size D84p.

[0195] Use them to calculate the volume particle size distribution index (GSDv) as (D84v / D16v) 1 / 2 , the number particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 .

[0196] The average circularity of the toner particles is preferably 0.90 or more and 1.00 or less, and more preferably 0.92 or more and 0.98 or less.

[0197] The average circularity of the toner particles is determined by (equivalent circumference) / (circumference) [(circumference of a circle having the same projected area as the particle image) / (circumference of the particle projected image)]. Specifically, it is a value measured by the following method.

[0198] First, the toner particles to be measured are sampled by suction to form a flat flow, and a particle image is obtained as a still image by instantaneous stroboscopic light emission, and the particle image is analyzed by a flow particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation). Then, the number of samples for obtaining the average circularity is set to 3500.

[0199] When the toner has an external additive, the toner (developer) to be measured is dispersed in water containing a surfactant, and then subjected to ultrasonic treatment to obtain toner particles from which the external additive is removed.

[0200] (External Additives)

[0201] Examples of the external additive include inorganic particles, such as SiO2, TiO2, Al2O3, SrTiO3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, K2O·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4.

[0202] The surface of the inorganic particles as an external additive can be subjected to hydrophobic treatment. The hydrophobic treatment is carried out by, for example, impregnating the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and for example, silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents, etc. can be cited. They can be used alone or in combination of two or more.

[0203] The amount of the hydrophobizing agent is usually, for example, 1 part by mass or more and 10 parts by mass or less relative to 100 parts by mass of the inorganic particles.

[0204] Examples of the external additives include resin particles (polystyrene, polymethyl methacrylate (PMMA), melamine resin and other resin particles), detergent active agents (for example, metal salts of higher fatty acids represented by zinc stearate, and particles of fluorine-based high molecular weight bodies).

[0205] The amount of the external additive added is, for example, preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.01% by mass or more and 6.0% by mass or less, based on the toner particles.

[0206] (Method for producing toner)

[0207] Next, a method for producing the toner according to the present embodiment will be described.

[0208] The toner according to the present embodiment is obtained by manufacturing toner particles and then externally adding an external additive to the toner particles.

[0209] The toner particles may be produced by any of dry methods (e.g., kneading and pulverization methods) and wet methods (e.g., aggregation and coalescence methods, suspension polymerization methods, and dissolution and suspension methods). The method for producing the toner particles is not particularly limited among these methods, and a known method may be used.

[0210] Among them, it is most preferable to obtain toner particles by an aggregation and coalescence method.

[0211] Specifically, for example, when toner particles are produced by an aggregation and coalescence method, the toner particles are produced, for example, through the following steps:

[0212] A step of mixing a first resin particle dispersion in which first resin particles serving as a binder resin are dispersed, a colorant dispersion in which a colorant is dispersed, and a release agent particle dispersion in which particles of a release agent (hereinafter also referred to as "release agent particles") are dispersed, and agglomerating the particles and the colorant in the obtained dispersion to form first aggregated particles (first aggregated particle forming step);

[0213] After obtaining a first agglomerated particle dispersion in which first agglomerated particles are dispersed, a second resin particle serving as a binder resin is added to the first agglomerated particle dispersion to agglomerate the second resin particle on the surface of the first agglomerated particle to form second agglomerated particles (second agglomerated particle forming step); and

[0214] A step of heating the second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and aggregate the second aggregated particles to form toner particles (fusion and aggregation step).

[0215] Furthermore, the present aggregation and coalescence method is described as a method for producing toner particles containing a binder resin, a colorant, and a release agent, but the colorant and the release agent are components contained in the toner particles as necessary.

[0216] The details of each process are described below.

[0217] -Each dispersion preparation step-

[0218] First, each dispersion used in the aggregation and coalescence method is prepared. Specifically, a first resin particle dispersion in which first resin particles serving as a binder resin are dispersed, a colorant dispersion in which a colorant is dispersed, a second resin particle dispersion in which second resin particles serving as a binder resin are dispersed, and a release agent particle dispersion in which release agent particles are dispersed are prepared.

[0219] In addition, in each dispersion liquid preparation step, the first resin particles and the second resin particles are described as “resin particles”.

[0220] Here, the resin particle dispersion is prepared by, for example, dispersing the resin particles in a dispersion medium using a surfactant.

[0221] Examples of the dispersion medium used in the resin particle dispersion include aqueous media.

[0222] Examples of the aqueous medium include water such as distilled water and ion-exchanged water, and ethanol, etc. These may be used alone or in combination of two or more.

[0223] As the surfactant, for example, anionic surfactants such as sulfate ester salts, sulfonates, phosphates, soaps, cationic surfactants such as amine salts, quaternary ammonium salts, polyethylene glycols, alkylphenol ethylene oxide adducts, polyols, and nonionic surfactants, etc., can be cited. Among them, anionic surfactants and cationic surfactants are particularly cited. Nonionic surfactants can also be used in combination with anionic surfactants or cationic surfactants.

[0224] The surfactant may be used alone or in combination of two or more.

[0225] As a method for dispersing the resin particles in the dispersion medium in the resin particle dispersion, for example, a general dispersion method such as a rotary shearing homogenizer, a ball mill with a medium, a sand mill, a dyno mill, etc. can be cited. In addition, depending on the type of the resin particles, for example, a phase inversion emulsification method can be used to disperse the resin particles in the resin particle dispersion.

[0226] The phase inversion emulsification method refers to a method in which a resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) and neutralized, and then an aqueous medium (W phase) is added to convert the resin from W / O to O / W (so-called phase inversion) rather than to a discontinuous phase, so that the resin is dispersed in the aqueous medium in the form of particles.

[0227] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and further preferably 0.1 μm or more and 0.6 μm or less.

[0228] In addition, the volume average particle size of the resin particles is measured by using a particle size distribution obtained by measuring with a laser diffraction particle size distribution measuring device (e.g., LA-700 manufactured by Horiba, Ltd.), and the volume is subtracted from the cumulative distribution from the small particle size side relative to the divided particle size range (channel), and the particle size that is 50% of the total particles is measured as the volume average particle size D50v. In addition, the volume average particle size of particles in other dispersions is also measured in the same manner.

[0229] The content of the resin particles in the resin particle dispersion is, for example, preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

[0230] In addition, for example, a colorant dispersion and a release agent particle dispersion are prepared in the same manner as the resin particle dispersion. That is, the volume average particle size of the particles in the resin particle dispersion, the dispersion medium, the dispersion method, and the content of the particles are the same for the colorant dispersed in the colorant dispersion and the release agent particles dispersed in the release agent particle dispersion.

[0231] -First Agglomerated Particle Formation Step-

[0232] Next, the first resin particle dispersion, the colorant dispersion, and the release agent particle dispersion are mixed.

[0233] Then, in the mixed dispersion, the first resin particles, the colorant, and the release agent particles are heterogeneously aggregated to form first aggregated particles including the first resin particles, the colorant, and the release agent particles.

[0234] Specifically, for example, a coagulant is added to a dispersion obtained by mixing a first resin particle dispersion, a colorant dispersion, and a release agent particle dispersion, and the pH of the mixed dispersion is adjusted to be acidic (for example, a pH of greater than 2 and less than 5). After adding a dispersion stabilizer as needed, the temperature is brought to a range of greater than 20°C and less than 50°C, so that the particles dispersed in the mixed dispersion are aggregated to form first aggregated particles.

[0235] In the first agglomerated particle formation step, for example, the mixed dispersion can be stirred with a rotary shearing homogenizer, and the above-mentioned coagulant can be added at room temperature (for example, 25°C), the pH of the mixed dispersion can be adjusted to acidic (for example, pH is greater than 2 and less than 5), and the above-mentioned heating can be performed after adding a dispersion stabilizer as needed.

[0236] As the coagulant, for example, a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, an inorganic metal salt, a binary or higher metal complex can be cited. In particular, when a metal complex is used as the coagulant, the amount of the surfactant used is reduced and the charging characteristics are improved.

[0237] If necessary, an additive that forms a complex or similar bond with the metal ion of the coagulant may be used. As such an additive, a chelating agent is preferably used.

[0238] Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide.

[0239] As the chelating agent, a water-soluble chelating agent may also be used. Examples of the chelating agent include hydroxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminoacetic acid (IDA), triacetamide (NTA), and ethylenediaminetetraacetic acid (EDTA).

[0240] The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the first resin particles.

[0241] -Second Agglomerated Particle Formation Step-

[0242] Next, after obtaining the first aggregated particle dispersion in which the first aggregated particles are dispersed, the second resin particle dispersion in which the second resin particles are dispersed is added to the first aggregated particle dispersion.

[0243] In addition, the second resin particles may be of the same kind as the first resin particles, or may be of a different kind.

[0244] Then, in the dispersion of the first aggregated particles and the second resin particles, the second resin particles are aggregated on the surface of the first aggregated particles. At this time, a release agent particle dispersion may be added to aggregate the second resin particles and the release agent particles on the surface of the first aggregated particles. Specifically, for example, in the first aggregated particle formation step, when the first aggregated particles reach a target particle size, the second resin particle dispersion is added to the first aggregated particle dispersion, and the second resin particles are heated below the glass transition temperature.

[0245] Then, by adjusting the pH of the dispersion liquid to, for example, a range of about 6.5 or more and 8.5 or less, the continuation of aggregation is stopped.

[0246] Thus, second aggregated particles are obtained in which the second resin particles are attached to the surfaces of the first aggregated particles and aggregated.

[0247] -Fusion and coalescence process-

[0248] Next, the second agglomerated particle dispersion containing the second agglomerated particles is heated, for example, to a temperature above the glass transition temperature of the first and second resin particles (for example, a temperature 10 to 30°C higher than the glass transition temperature of the first and second resin particles) to fuse and aggregate the second agglomerated particles to form colorant particles.

[0249] Through the above steps, toner particles can be obtained.

[0250] In the above-described aggregation and coalescence method, the first aggregated particles may be fused and coalesced to form toner particles without performing the second aggregated particle forming step. Alternatively, the second aggregated particle forming step may be repeated a plurality of times.

[0251] Here, after the fusion and coalescence step is completed, toner particles are obtained in a state where the toner particles formed in the solution are dried through a known washing step, a solid-liquid separation step, and a drying step.

[0252] In the washing process, replacement washing with ion exchange water can be fully implemented from the perspective of chargeability. In addition, there is no particular restriction on the solid-liquid separation process, and suction filtration, filter pressing, etc. can be implemented from the perspective of productivity. In addition, there is no particular restriction on the method in the drying process, and freeze drying, air flow drying, fluidized drying, vibration-type fluidized drying, etc. can be implemented from the perspective of productivity.

[0253] The toner of the present embodiment is produced, for example, by adding an external additive to the obtained dry toner particles and mixing them. The mixing can be performed, for example, by a V mixer, a Henschel mixer, a Lödige mixer, etc. Furthermore, if necessary, a vibration sieving machine, a wind sieving machine, etc. can be used to remove coarse particles of the toner.

[0254] <Electrostatic Image Developer>

[0255] The electrostatic image developer according to the present embodiment contains at least the toner according to the present embodiment.

[0256] The electrostatic charge image developer of the present embodiment may be a one-component developer containing only the toner of the present embodiment, or may be a two-component developer in which the toner and a carrier are mixed.

[0257] The carrier is not particularly limited, and known carriers may be mentioned. Examples of the carrier include a coated carrier in which a coating resin is coated on the surface of a core material composed of magnetic powder, a magnetic powder dispersion type carrier in which magnetic powder is dispersed and blended in a matrix resin, and a resin impregnated type carrier in which porous magnetic powder is impregnated with a resin.

[0258] Furthermore, the magnetic powder dispersed carrier and the resin impregnated carrier may be a carrier in which the constituent particles of the carrier are used as core materials and the core materials are coated with a coating resin.

[0259] Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0260] As the coating resin and the matrix resin, for example, there can be mentioned polyolefin resins such as styrene (meth) acrylic resin, polyethylene resin, and polypropylene resin, polystyrene, (meth) acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone and other polyethylene or polyvinylidene resins, vinyl chloride-vinyl acetate copolymers, straight-chain silicone resins composed of organic siloxane bonds or modified products thereof, fluororesins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene, polyesters, polyurethanes, polycarbonates, amino resins such as urea-formaldehyde resins, epoxy resins, and the like.

[0261] The coating resin and the matrix resin preferably contain a (meth)acrylic resin, more preferably contain 50% by mass or more of the (meth)acrylic resin based on the total mass of the resin, and further preferably contain 80% by mass or more of the (meth)acrylic resin based on the total mass of the resin.

[0262] It is particularly preferred that the coating resin and the matrix resin contain an alicyclic (meth)acrylic resin as the (meth)acrylic resin.

[0263] Furthermore, other additives such as conductive particles may be contained in the coating resin and the matrix resin.

[0264] Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0265] Here, when coating the coating resin to the surface of the core material, the coating layer formed by dissolving various additives in a suitable solvent as required and coating with a solution can be enumerated, etc. As the solvent, there is no particular limitation, and it can be selected by considering the coating resin used, coating suitability, etc.

[0266] Specific resin coating methods include an immersion method in which the core material is immersed in a coating layer forming solution, a spraying method in which the coating layer forming solution is sprayed onto the surface of the core material, a fluidized bed method in which the coating layer forming solution is sprayed in a state where the core material is floated by flowing air, and a kneading coating method in which the core material of the carrier and the coating layer forming solution are mixed in a kneading coater and the solvent is removed.

[0267] The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner:carrier=1:100 to 30:100, more preferably 3:100 to 20:100.

[0268] [Example]

[0269] Hereinafter, the present invention will be described more specifically and in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0270] <Preparation of Amorphous Resin Particle Dispersion Liquid 1>

[0271] Terephthalic acid: 98 parts by mole

[0272] Trimellitic anhydride: 2 molar parts

[0273] Bisphenol A ethylene oxide 2 mole adduct: 20 mole parts

[0274] Bisphenol A propylene oxide 2 mole adduct: 80 mole parts

[0275] The above materials were placed in a reaction vessel equipped with a stirring device, a nitrogen introduction tube, a temperature sensor, and a distillation column, and the temperature was raised to 190°C over 1 hour. 1.2 parts of dibutyltin oxide were added to 100 parts of the above materials. The temperature was raised to 240°C over 6 hours while distilling off the generated water, and the dehydration condensation reaction was continued at 240°C for 3 hours, and then the reactant was cooled.

[0276] The reactants were transferred to Cavitron CD1010 (manufactured by Eurotec) in a molten state at a rate of 100 g per minute. At the same time, a separately prepared 0.37 mass % ammonia water was heated to 120° C. using a heat exchanger and transferred to Cavitron CD1010 at a rate of 0.1 liter per minute. The rotor was rotated at 60 Hz and the pressure was 5 kg / cm2 Cavitron CD1010 was operated under the conditions of , to obtain a resin particle dispersion in which resin particles having a volume average particle size of 160 nm were dispersed. Ion exchange water was added to the resin particle dispersion to adjust the solid content to 20% by mass to prepare an amorphous resin particle dispersion 1.

[0277] <Preparation of Crystalline Resin Particle Dispersion>

[0278] Sebacic acid: 202 parts by mass

[0279] Ethylene glycol: 62 parts by mass

[0280] The above materials were added to a reaction vessel equipped with a stirring device, a nitrogen introduction tube, a temperature sensor and a distillation tower, and the temperature was raised to 160°C over 1 hour, and 0.8 parts by mass of dibutyltin oxide was added. While distilling off the generated water, the temperature was raised to 180°C over 6 hours, and maintained at 180°C for 5 hours for dehydration condensation reaction. After that, the temperature was gradually raised to 230°C under reduced pressure, and maintained at 230°C for 2 hours of stirring. After that, the reactant was cooled. After cooling, solid-liquid separation was performed, and the solid was dried to obtain a crystalline polyester resin.

[0281] Crystalline polyester resin: 100 parts

[0282] Methyl ethyl ketone: 40 parts

[0283] Isopropyl ethanol: 30 parts

[0284] 10% ammonia solution: 6 parts

[0285] The above materials were added to a 3-liter jacketed reaction tank (BJ-30N manufactured by Tokyo Rikakki Co., Ltd.) equipped with a capacitor, a thermometer, a water dripping device, and an anchor wing, and the resin was dissolved while being stirred and mixed at 100 rpm while being maintained at 80°C in a water circulation thermostatic bath. Thereafter, the water circulation thermostatic bath was set to 50°C, and 400 parts of ion exchange water kept at 50°C were dripped at a rate of 7 parts by mass / minute to invert the phase, thereby obtaining an emulsion. 576 parts by mass of the obtained emulsion and 500 parts by mass of ion exchange water were placed in a 2-liter eggplant-shaped bottle, and placed in an evaporator (manufactured by Tokyo Rikakki Co., Ltd.) equipped with a vacuum control unit via a collecting ball. While rotating the eggplant-shaped bottle, it was heated in a water bath at 60°C, and the pressure was reduced to 7 kPa while paying attention to bumping, and the solvent was removed. Thereafter, ion exchange water was added to obtain a crystalline resin particle dispersion having a solid content concentration of 20% by mass.

[0286] [Preparation of styrene (meth) acrylic resin particle dispersion]

[0287] <Preparation of Styrene (Meth) Acrylic Resin Particle Dispersion 1>

[0288] Styrene: 47.9 parts

[0289] n-Butyl acrylate: 51.8 parts

[0290] β-Carboxyethyl acrylate: 0.3 parts

[0291] Anionic surfactant (Dowfax 2A1, manufactured by The Dow Chemical Company): 0.8 parts (filling amount)

[0292] Butanediol diacrylate: 1.65 parts

[0293] The above raw materials were mixed and dissolved, and 60 parts of ion exchange water was added and dispersed and emulsified in a flask to prepare an emulsion.

[0294] Next, 1.3 parts (addition amount) of anionic surfactant (Dowfax 2A1, manufactured by The Dow Chemical Company) was dissolved in 90 parts of ion exchange water, 1 part of the emulsion was added thereto, and 10 parts of ion exchange water in which 5.4 parts of ammonium persulfate was dissolved was further added.

[0295] After that, the remaining emulsion was added over 180 minutes, and after nitrogen substitution in the flask, the solution in the flask was heated to 65° C. in an oil bath while stirring. Emulsion polymerization was continued in this state for 500 minutes to obtain a styrene (meth) acrylic resin particle dispersion 1 having a solid content adjusted to 24.5% by mass.

[0296] <Preparation of Styrene (Meth) Acrylic Resin Particle Dispersions 2 to 5>

[0297] Styrene (meth) acrylic resin particle dispersions 2 to 5 were obtained in the same manner as in the styrene (meth) acrylic resin particle dispersion 1 except that the following production conditions were changed as shown in Table 1.

[0298] Styrene content

[0299] n-Butyl acrylate

[0300] Acrylic acid amount

[0301] ·β-Carboxyethyl Acrylate

[0302] Total amount of anionic surfactant (the ratio of the amount charged to the amount added is the same as that of dispersion 1)

[0303] ·Butanediol diacrylate (crosslinking agent in the table)

[0304] ·Ammonium persulfate amount

[0305] Temperature when heated by oil bath (polymerization temperature in the table)

[0306] · Residual time of emulsion (addition time in the table)

[0307] ·Time for emulsification polymerization to continue after heating (holding time in the table)

[0308] <Preparation of Colorant Dispersion>

[0309] Carbon black (Regal 330 manufactured by Cabot Corporation): 50 parts

[0310] Anionic surfactant NEOGEN RK (Daiichi Kogyo Pharmaceutical): 5 parts

[0311] Ion exchange water: 192.9 parts

[0312] The above components were mixed and treated with ULTMAIZER (manufactured by SUGINO MACHINE CO., LTD.) at 240 MPa for 10 minutes to prepare a colorant dispersion (solid content: 20%).

[0313] <Preparation of Release Agent Dispersion Liquid 1>

[0314] Fischer-Tropsch wax (FNP0090 manufactured by Nippon Seiwa Co., Ltd., melting temperature Tw: 90°C): 50 parts

[0315] Anionic surfactant (NEOGEN RK manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1 part

[0316] Ion exchange water: 200 parts

[0317] The above materials were mixed and heated to 130°C, dispersed using a homogenizer (ULTRA-TURRAX T50 manufactured by IKA), and then dispersed using a Manton-Gaulin high pressure homogenizer (manufactured by Gaulin) to obtain a release agent dispersion (solid content 20% by mass) in which release agent particles were dispersed. The volume average particle size of the release agent particles was 180 nm.

[0318] <Preparation of Toner>

[0319] (Preparation of Toner 1)

[0320] · Amorphous resin particle dispersion 1: 169 parts

[0321] ·Styrene (meth) acrylic resin particle dispersion 1: 33 parts

[0322] Crystalline resin particle dispersion: 53 parts

[0323] Release agent dispersion: 25 parts

[0324] Colorant dispersion: 33 parts

[0325] Anionic surfactant (Dowfax 2A1, manufactured by The Dow Chemical Company): 4.8 parts

[0326] The raw materials adjusted to a liquid temperature of 10° C. were placed in a 3 L cylindrical stainless steel container and dispersed and mixed for 2 minutes while applying a shear force using a homogenizer (ULTRA-TURRAX T50 manufactured by IKA Corporation) at 4000 rpm.

[0327] Next, 1.75 parts of a 10% nitric acid aqueous solution of aluminum sulfate was gradually dropped as a coagulant, and the rotation speed of the homogenizer was set to 10,000 rpm to disperse and mix for 10 minutes to prepare a raw material dispersion.

[0328] After that, the raw material dispersion was transferred to a polymerization reactor equipped with a stirring device using two paddles and a thermometer, and the stirring speed was set to 550 rpm and heating was started with a mantle heater to promote the growth of aggregated particles at 40° C. In addition, at this time, the pH of the raw material dispersion was controlled within the range of 2.2 to 3.5 using 0.3 M nitric acid and 1 M sodium hydroxide aqueous solutions. The above pH range was maintained for 2 hours to form aggregated particles.

[0329] Next, a dispersion obtained by mixing a non-crystalline resin particle dispersion liquid of 1:21 and a styrene (meth) acrylic resin particle dispersion liquid of 1:8 was added and maintained for 60 minutes to allow the resin particles of the binder resin and the styrene (meth) acrylic resin particles to adhere to the surface of the agglomerated particles. The temperature was then raised to 53° C., and then a non-crystalline resin particle dispersion liquid of 1:21 was added and maintained for 60 minutes to allow the resin particles of the binder resin to adhere to the surface of the agglomerated particles.

[0330] Agglomerated particles were adjusted while confirming the size and shape of the particles using an optical microscope and a particle counter 3. Thereafter, the pH was adjusted to 7.8 using a 5% sodium hydroxide aqueous solution and maintained for 15 minutes.

[0331] After that, the pH was raised to 8.0 to fuse the aggregated particles, and the temperature was raised to 85° C. After confirming the fusion of the aggregated particles with an optical microscope, the heating was stopped after 2 hours, and the mixture was cooled at a temperature drop rate of 1.0° C. / min. After that, the mixture was sieved with a 20 μm mesh, repeatedly washed with water, and dried with a vacuum dryer to obtain toner particles 1.

[0332] 100 parts of the obtained toner particles and 0.7 parts of silica particles treated with dimethyl silicone oil (RY200 manufactured by Nippon Aerosil Co., Ltd.) were mixed with a Henschel mixer to obtain Toner 1.

[0333] <Toners 2 to 9>

[0334] Toners 2 to 9 were obtained in the same manner as Toner 1 except that styrene (meth) acrylic resin particle dispersions of the types shown in Table 2 were used instead of styrene (meth) acrylic resin particle dispersion 1 in an amount such that the content of the resin particles (i.e., styrene (meth) acrylic resin particles) relative to the entire toner particles was the value shown in Table 2.

[0335] <Preparation of Developers 1 to 9>

[0336] 8 parts of the toner shown in Table 2 and 100 parts of the following carrier were mixed to obtain developers 1 to 9.

[0337] -Carrier production-

[0338] ·100 parts of ferrite particles (average particle size 35 μm)

[0339] ·Toluene 14 parts

[0340] · 3 parts of styrene / methyl methacrylate copolymer (copolymer ratio 15 / 85)

[0341] ·0.2 parts of carbon black

[0342] The above components except the ferrite particles are dispersed in a sand mill to prepare a dispersion, and the dispersion is put into a vacuum degassing kneader together with the ferrite particles, and dried under reduced pressure while stirring to obtain a carrier.

[0343] <Example 1>

[0344] The developers shown in Table 2 were placed in a developing machine of an image forming apparatus (“Apeos C2570 (Marble 4)” manufactured by Fujifilm Business Innovations Co., Ltd.).

[0345] In this image forming apparatus, the air heated by the fixing device is sent to the inner peripheral surface of the intermediate transfer belt through a duct (length 60 cm) to heat the toner image before secondary transfer (refer to Figure 2 ), and also modified to send the air heated by the fixing device to the conveying path of the recording paper through a duct (length 60cm) to heat the recording paper before the secondary transfer (refer to Figure 2 ). Regarding the heating temperature of the toner image and the recording paper, the temperature of the toner image on the intermediate transfer belt and the recording paper before being conveyed to the fixing device were measured using a non-contact laser sensor. The temperature of the heating roller in the fixing device was set to 175°C.

[0346] <Examples 2 to 19, Comparative Example 1>

[0347] The heating temperatures of the toner image and the recording paper were set as shown in Table 2 by adjusting the duct length, and the image forming apparatus of each example was set.

[0348] However, the image forming apparatus does not heat the toner image and the recording paper in Comparative Example 1. In Table 2, the heating temperature of the toner image and the recording paper is indicated as "20° C."

[0349] <Evaluation>

[0350] (Uneven image density)

[0351] Recording paper (C2 paper manufactured by Fujifilm Business Innovation Co., Ltd.) was left in a normal temperature and normal humidity environment of 22° C. 55% RH and in a high temperature and high humidity environment of 28° C. 85% RH for 72 hours.

[0352] The image forming apparatus was left to stand in a high temperature and high humidity environment of 28° C. and 85% RH for 72 hours.

[0353] Using these papers and image forming devices, five completely black images were output on each paper. The five output images were evaluated according to the following criteria. (G0 to G2 are good)

[0354] A. The 60° glossiness was measured at five locations on each paper that was left in a high-temperature, high-humidity environment of 28°C and 85%RH for 72 hours, and the difference between the maximum and minimum values ​​was defined as ΔGloss.

[0355] B. The image density (SAD) at five locations on each sheet of paper placed in the environments of 22°C 55% RH and 28°C 85% RH is measured, and the average value is defined as SAD. The difference between the SAD in the environment of 22°C 55% RH and the SAD in the environment of 28°C 85% RH is defined as ΔSAD.

[0356] The 60° glossiness was measured using a micro-gloss 60° gloss meter manufactured by TETSUTANI, and the SAD was measured using X-Rite 939 manufactured by X-Rite.

[0357] G0: ΔGloss≤3, ΔSAD<0.1

[0358] G1: 3≤ΔGloss≤5, 0.1≤ΔSAD<0.2

[0359] G2: 0.2≤ΔSAD<0.3

[0360] G3: 0.3≤ΔSAD<0.4

[0361] G4: ΔSAD ≥ 0.4

[0362] [Table 1]

[0363]

[0364] [Table 2]

[0365]

[0366] The above results show that the present embodiment suppresses uneven image density that occurs under a high-temperature and high-humidity environment, as compared to the comparative example.

[0367] (Note) (((1)))

[0369] An image forming device comprising:

[0370] Electrophotographic photoreceptor;

[0371] a charging device for charging the surface of the electrophotographic photoreceptor;

[0372] an electrostatic charge image forming device for forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor;

[0373] a developing device that contains an electrostatic charge image developer containing a toner, supplies the electrostatic charge image developer, and develops the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image;

[0374] an intermediate transfer body having the toner image transferred onto a surface thereof;

[0375] a primary transfer device for primarily transferring the toner image formed on the surface of the electrophotographic photoreceptor to the surface of the intermediate transfer body;

[0376] a secondary transfer device for secondarily transferring the toner image transferred on the surface of the intermediate transfer body to a surface of a recording paper;

[0377] a fixing device that fixes the toner image to a surface of a recording paper;

[0378] a first heating device for heating the toner image transferred onto the surface of the intermediate transfer body before the toner image is secondarily transferred onto the surface of the recording paper by the secondary transfer device; and

[0379] A second heating device heats the recording paper before the secondary transfer device secondarily transfers the toner image onto the surface of the recording paper. (((2)))

[0381] The image forming apparatus according to (((1))), wherein:

[0382] The first heating device is a device for heating the toner image using heat generated by the fixing device.

[0383] The second heating device is a device that heats the recording paper using heat emitted from the fixing device. (((3)))

[0385] The image forming apparatus according to (((1))) or (((2))), wherein:

[0386] The first heating device heats the toner image at a temperature of 40° C. or higher and 70° C. or lower. (((4)))

[0388] The image forming apparatus according to any one of (((1))) to (((3))), wherein:

[0389] The second heating device heats the recording paper at a temperature of 40° C. or higher and 70° C. or lower. (((5)))

[0391] An image forming method comprising:

[0392] A charging process for charging the surface of the electrophotographic photoreceptor;

[0393] An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor;

[0394] A developing step of supplying an electrostatic charge image developer containing a toner and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image;

[0395] a primary transfer step of primarily transferring the toner image formed on the surface of the electrophotographic photoreceptor to the surface of an intermediate transfer body;

[0396] a secondary transfer step of secondarily transferring the toner image transferred on the surface of the intermediate transfer body to the surface of the recording paper;

[0397] A fixing step of fixing the toner image to the surface of the recording paper;

[0398] a first heating step of heating the toner image transferred onto the surface of the intermediate transfer body before secondarily transferring the toner image onto the surface of the recording paper; and

[0399] The second heating step heats the recording paper before the toner image is secondarily transferred onto the surface of the recording paper. (((6)))

[0401] The image forming method according to (((5))), wherein:

[0402] The toner has toner particles including a binder resin and resin particles. (((7)))

[0404] The image forming method according to (((6))), wherein:

[0405] The content of the resin particles is 2% by mass or more and 30% by mass or less based on the toner particles. (((8)))

[0407] The image forming method according to (((6))) or (((7))), wherein:

[0408] The resin particles are styrene (meth) acrylic resin particles. (((9)))

[0410] The image forming method according to any one of (((6))) to (((8))), wherein

[0411] The average primary particle size of the resin particles is 20 nm or more and 300 nm or less.

[0412] According to (((1))), there is provided an image forming device comprising: an electrophotographic photoreceptor; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic charge image forming device for forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing device for accommodating an electrostatic charge image developer containing a toner, supplying the electrostatic charge image developer, and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; an intermediate transfer body having a toner image transferred onto its surface; and a primary transfer device for primary transferring the toner image formed on the surface of the electrophotographic photoreceptor. to the surface of the intermediate transfer body; a secondary transfer device, which secondarily transfers the colorant image transferred on the surface of the intermediate transfer body to the surface of the recording paper; and a fixing device, which fixes the colorant image to the surface of the recording paper, wherein, compared with a case where the first heating device and the second heating device are not provided, image density unevenness occurring in a high temperature and high humidity environment is suppressed, the first heating device heats the colorant image transferred on the surface of the intermediate transfer body before the secondary transfer device secondarily transfers the colorant image to the surface of the recording paper, and the second heating device heats the recording paper before the secondary transfer device secondarily transfers the colorant image to the surface of the recording paper.

[0413] According to (((2))), an image forming apparatus is provided that can suppress uneven image density that occurs under a high-temperature and high-humidity environment at low cost, compared to a case where the first heating device and the second heating device do not utilize heat generated from the fixing device.

[0414] According to (((3))), there is provided an image forming apparatus that suppresses uneven image density that occurs under a high temperature and high humidity environment, compared with a case where the heating temperature of the toner image by the first heating device is lower than 40°C.

[0415] According to (((4))), there is provided an image forming apparatus that suppresses occurrence of uneven image density in a high temperature and high humidity environment, compared with a case where the heating temperature of the recording paper by the second heating device is lower than 40°C.

[0416] According to (((5))), an image forming method is provided, which comprises: a charging step for charging the surface of an electrophotographic photoreceptor; an electrostatic charge image forming step for forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing step for supplying an electrostatic charge image developer containing a toner and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; a primary transfer step for primary transferring the toner image formed on the surface of the electrophotographic photoreceptor to the surface of an intermediate transfer body; and a secondary transfer step for transferring the toner image transferred to the surface of the intermediate transfer body. The colorant image on the surface of the printing body is secondarily transferred to the surface of the recording paper; and a fixing process is performed to fix the colorant image to the surface of the recording paper, wherein, compared with a case where there is no first heating process and a second heating process, the uneven image concentration occurring in a high temperature and high humidity environment is suppressed, wherein in the first heating process, the colorant image transferred on the surface of the intermediate transfer body is heated before the colorant image is secondarily transferred to the surface of the recording paper, and in the second heating process, the recording paper is heated before the colorant image is secondarily transferred to the surface of the recording paper.

[0417] According to (((6))), (((7))) or (((8))), an image forming method is provided, which comprises: a charging step for charging the surface of an electrophotographic photoreceptor; an electrostatic charge image forming step for forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing step for supplying an electrostatic charge image developer containing a toner and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; a primary transfer step for primary transferring the toner image formed on the surface of the electrophotographic photoreceptor to the surface of an intermediate transfer body; a secondary transfer step for secondary transferring the toner image transferred on the surface of the intermediate transfer body to the surface of a recording paper; and a fixing step for fixing the toner image to the surface of the recording paper. The surface of recording paper, wherein, compared with a case where there are no first heating steps and second heating steps, even if a toner having toner particles containing a binding resin and resin particles, toner particles having a resin particle content of 2% to 30% by mass relative to the toner particles, or toner particles having resin particles that are styrene (meth) acrylic resin particles is applied, image density unevenness occurring in a high temperature and high humidity environment is suppressed, wherein in the first heating step, the toner image transferred to the surface of an intermediate transfer body is heated before the toner image is secondarily transferred to the surface of the recording paper, and in the second heating step, the recording paper is heated before the toner image is secondarily transferred to the surface of the recording paper.

[0418] According to (((9))), there is provided an image forming method in which uneven image density is suppressed in a high temperature and high humidity environment compared with a case where the average primary particle size of the resin particles is less than 20 nm or exceeds 300 nm.

Claims

1. An image forming device, characterized in that: have: Electrophotographic photoreceptor; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic charge image forming device for forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing device that contains an electrostatic charge image developer containing a toner, supplies the electrostatic charge image developer, and develops the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; an intermediate transfer body having the toner image transferred onto a surface thereof; a primary transfer device for primarily transferring the toner image formed on the surface of the electrophotographic photoreceptor to the surface of the intermediate transfer body; a secondary transfer device for secondarily transferring the toner image transferred on the surface of the intermediate transfer body to a surface of a recording paper; a fixing device that fixes the toner image to a surface of a recording paper; a first heating device for heating the toner image transferred onto the surface of the intermediate transfer body before the toner image is secondarily transferred onto the surface of the recording paper by the secondary transfer device; as well as A second heating device heats the recording paper before the secondary transfer device secondarily transfers the toner image onto the surface of the recording paper.

2. The image forming apparatus according to claim 1, wherein: The first heating device is a device for heating the toner image using heat generated by the fixing device. The second heating device is a device that heats the recording paper using heat emitted from the fixing device.

3. The image forming apparatus according to claim 1 or 2, wherein: The first heating device heats the toner image at a temperature of 40° C. or higher and 70° C. or lower.

4. The image forming apparatus according to any one of claims 1 to 3, wherein: The second heating device heats the recording paper at a temperature of 40° C. or higher and 70° C. or lower.

5. An image forming method, characterized in that: have: A charging process for charging the surface of the electrophotographic photoreceptor; An electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; A developing step of supplying an electrostatic charge image developer containing a toner and developing the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; a primary transfer step of primarily transferring the toner image formed on the surface of the electrophotographic photoreceptor to the surface of an intermediate transfer body; a secondary transfer step of secondarily transferring the toner image transferred on the surface of the intermediate transfer body to the surface of the recording paper; A fixing step of fixing the toner image to the surface of the recording paper; a first heating step of heating the toner image transferred onto the surface of the intermediate transfer body before secondarily transferring the toner image onto the surface of the recording paper; as well as The second heating step heats the recording paper before the toner image is secondarily transferred onto the surface of the recording paper.

6. The image forming method according to claim 5, wherein: The toner has toner particles including a binder resin and resin particles.

7. The image forming method according to claim 6, wherein: The content of the resin particles is 2% by mass or more and 30% by mass or less based on the toner particles.

8. The image forming method according to claim 6 or 7, wherein: The resin particles are styrene (meth) acrylic resin particles.

9. The image forming method according to any one of claims 6 to 8, wherein: The average primary particle size of the resin particles is 20 nm or more and 300 nm or less.

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