JP2018084745A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology that achieves appropriate glossiness with a simple configuration.SOLUTION: An image forming apparatus comprises: developing parts for colored toner that form colored toner images; a developing part for transparent toner that forms a transparent toner image; an intermediate transfer part; a fixing part; a reflected light quantity detection sensor that detects quantity of light reflected on the toner images formed on the intermediate transfer part; and a control part. The transparent toner contains a second transparent toner, and a first transparent toner that has transmittance before fixing smaller than that of the second transparent toner and glossiness after fixing higher than that of the second transparent toner. The transparent developer is a two-component developer containing a carrier, and a mixed transparent toner that is a mixture of the first transparent toner and second transparent toner. The control part measures the quantity of light reflected on the transparent toner image formed on the intermediate transfer part with the reflected light quantity detection sensor, and adjusts a mixture ratio of the first transparent toner and second transparent toner contained in the transparent developer on the basis of the measured quantity of reflected light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly to a technique using a transparent toner.

  Along with the recent improvement in image quality, color images particularly used for photographs and the like are required to have higher color developability and glossiness, and improvement in the glossiness of fixed images is desired. In response to the demand for high-quality image formation such as photographic images, it is known that a clearer high-gloss image can be provided by imparting gloss to the surface of a print medium. Specifically, for example, a method of fixing transparent toner on the entire surface of a print medium has been proposed (Patent Document 1). On the other hand, print target images include not only photographic images but also character images, and it is desirable to change the glossiness according to the print target images. Specifically, for example, high gloss is desirable for photographic images, and low gloss processing is preferable for character images.

  Furthermore, control of glossiness (gross) is also required in recent electrophotographic processes. In response to such a request, for example, Patent Document 2 uses a developing unit that performs development using gloss toner having high glossiness and a developing unit that performs development using mat toner having low glossiness. An image forming apparatus is proposed.

JP-A-4-204670 JP 2013-109276 A

  However, the technique of Patent Document 2 requires six developing units, and there is a problem that the image forming apparatus becomes large. Further, the image formation by the six times of toner development also has a problem that image disturbance is likely to occur due to the multilayered toner image.

  The present invention has been made in view of such a situation, and an object thereof is to provide a technique for realizing an appropriate glossiness with a simple configuration.

  The present invention provides an image forming apparatus that forms an image on a print medium using colored toner and transparent toner. The image forming apparatus includes a colored toner photosensitive drum, and performs color development using a colored developer containing the colored toner to form a colored toner image on the colored toner photosensitive drum. For transparent toner having a developing unit for transparent toner and a photosensitive drum for transparent toner, and performing toner development using a transparent developer containing the transparent toner to form a transparent toner image on the photosensitive drum for transparent toner The transparent toner image is primarily transferred from the developing portion and the transparent toner developing portion, and the colored toner image is primarily transferred and superimposed on the transparent toner image from the colored toner developing portion to form a composite toner image. An intermediate transfer portion for secondary transfer of the formed synthetic toner image onto the printing medium, and pressurizing and heating the synthetic toner image secondarily transferred onto the printing medium. Fix Controls a fixing unit, a reflected light amount detection sensor for detecting a reflected light amount of a toner image formed on the intermediate transfer unit, the colored toner developing unit, the transparent toner developing unit, and the reflected light amount detection sensor. A control unit that performs the transparent toner, the second transparent toner, the transmittance before the fixing is smaller than that of the second transparent toner, and the gloss after the fixing is higher than that of the second transparent toner. The transparent developer is a two-component developer including a mixed transparent toner, which is a mixture of the first transparent toner and the second transparent toner, and a carrier. The control unit measures the reflected light amount of the transparent toner image formed on the intermediate transfer unit by the reflected light amount detection sensor, and the first developer included in the transparent developer based on the measured reflected light amount. Clear toner and front Adjusting the mixing ratio of the second transparent toner.

  The present invention provides an image forming method for forming an image on a print medium using a color toner and a transparent toner. In the image forming method, the color toner development is performed such that the color toner image is formed on the photosensitive drum for colored toner by performing toner development using the photosensitive drum for colored toner and a colored developer containing the colored toner. A transparent toner developing step of forming a transparent toner image on the photosensitive drum for transparent toner by performing toner development using a photosensitive drum for transparent toner and a transparent developer containing the transparent toner; The transparent toner image is primarily transferred in the transparent toner developing step, and the colored toner image is primarily transferred to be superimposed on the transparent toner image in the colored toner developing step to form a composite toner image. An intermediate transfer step for secondary transfer of the composite toner image onto the print medium, and fixing for fixing the composite toner image secondarily transferred onto the print medium by pressurizing and heating it. And controlling the reflected light amount detecting step for detecting the reflected light amount of the toner image formed in the intermediate transfer step, the colored toner developing step, the transparent toner developing step, and the reflected light amount detecting step. A control step, wherein the transparent toner has a second transparent toner, and the transmittance before the fixing is smaller than that of the second transparent toner, and the glossiness after the fixing is higher than that of the second transparent toner. The transparent developer is a two-component developer including a mixed transparent toner that is a mixture of the first transparent toner and the second transparent toner, and a carrier. The control step measures the reflected light amount of the transparent toner image formed in the intermediate transfer step in the reflected light amount detection step, and the first transparent contained in the transparent developer based on the measured reflected light amount. With toner Comprising the step of adjusting the serial mixing ratio of the second transparent toner.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which implement | achieves appropriate glossiness with a simple structure can be provided.

2 is a block diagram illustrating a functional configuration of the image forming apparatus 1 according to an embodiment of the present disclosure. 1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus 1 according to an embodiment. 2 is a side cross-sectional view illustrating a structure of a developing unit 100 according to an embodiment. FIG. FIG. 6 is a diagram illustrating a developing bias potential for forming a transparent toner patch in the image forming apparatus 1 according to an embodiment. 5 is a flowchart showing the content of a transparent toner mixture ratio adjustment process of the image forming apparatus 1 according to an embodiment. FIG. 6 is a diagram illustrating a relationship between a reflectance of a transparent toner patch and a duty ratio in the image forming apparatus 1 according to an embodiment.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in the following order with reference to the drawings.

  FIG. 1 is a block diagram showing a functional configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 includes a control unit 10, an image forming unit 20, a storage unit 40, an image reading unit 50, and a fixing unit 80. The image reading unit 50 reads an image from a document and generates an image data ID that is digital data.

  The image forming unit 20 includes a color conversion processing unit 21, a halftone processing unit 22, a calibration density sensor 28, an exposure unit 29, and a photosensitive drum (image carrier) 30c for colored toner which is an amorphous silicon photoconductor. To 30 k, a transparent toner photosensitive drum 30 t that is an amorphous silicon photosensitive member, a colored toner developing unit 100 c to 100 k, and a colored toner supplying unit 200 c that supplies colored toner to each of the colored toner developing units 100 c to 100 k. -200k, a single transparent toner developing unit 100t, two transparent toner supply units 200tg, 200tm for supplying transparent toner to the single transparent toner developing unit 100t, and charging units 25c-25t ing.

  The photosensitive drums 30c to 30t include four colored toner photosensitive drums 30c, 30m, 30y, and 30k, and one transparent toner photosensitive drum 30t. The developing units 100c to 100t include four colored toner developing units 100c, 100m, 100y, and 100k, and one transparent toner developing unit 100t. The charging units 25c to 25t include four colored toner charging units 25c, 25m, 25y, and 25k, and one transparent toner charging unit 25t.

  The colored toner photosensitive drums 30c to 30k, the colored toner developing units 100c to 100k, and the colored toner charging units 25c to 25k are colored toners using colored developers including colored toners of cyan, magenta, yellow, and black. Development can be performed. On the other hand, the transparent toner photosensitive drum 30t, the transparent toner developing unit 100t, and the transparent toner charging unit 25t can perform transparent toner development using a transparent developer containing transparent toner.

  The transparent toner is configured as a mixture (also referred to as a mixed transparent toner) of two types of toners having different characteristics, that is, a gloss toner having a relatively high glossiness and a matte toner having a relatively low glossiness. The gloss toner is supplied from the transparent toner supply unit 200tg containing the gloss toner to the transparent toner developing unit 100t. The matte toner is supplied from the transparent toner supply unit 200tm that contains the matte toner to the transparent toner developing unit 100t. The transparent toner supply unit 200tg and the transparent toner supply unit 200tm can independently control the gloss toner supply amount and the matte toner supply amount. The gloss toner is also called a first transparent toner. The matte toner is also called a second transparent toner. The transparent toner supply unit 200tg is also called a first transparent toner supply unit. The transparent toner supply unit 200tm is also called a second transparent toner supply unit.

  In the present embodiment, a mixing ratio of two types of toners is set based on a preset glossiness. The mixing ratio can be set in a plurality of settings including, for example, a high gloss mode for photographic images and a low gloss mode for character images. The high gloss mode is a mode having a relatively high gloss toner mixing ratio. The low glossiness mode is a mode in which the mixing ratio of the matte toner is relatively high.

  Gross toner is composed of low melting point transparent toner particles using crystalline polyester resin or the like. The matte toner is composed of high melting point transparent toner particles using an amorphous resin or the like. The low melting point transparent toner particles contain a resin having a lower melting point than the resin contained in the high melting point transparent toner particles. For example, various polyester resins can be used as the resin. In the present embodiment, a polyester resin having a melting point of 95 ° C. is used for the low melting point transparent toner particles. A polyester resin having a melting point of 105 ° C. is used for the high melting point transparent toner particles. The difference between the melting point of the high melting point transparent toner and the low melting point transparent toner is preferably 5 ° C to 15 ° C.

  Since the gloss toner is composed of low melting point transparent toner particles, a relatively large amount of the toner is melted by heating / pressurizing process in the fixing process to generate high gloss. On the other hand, the matte toner is composed of transparent toner particles having a high melting point, so that the toner is relatively less melted and less glossy by the heating / pressurizing process in the fixing process.

  Further, the inventor of the present application prior to the fixing step, the transparent toner image using gloss toner (low melting point transparent toner particles) is white, and the transparent toner image using mat toner (high melting point transparent toner particles) is transparent. And found the feature of being optically distinguishable.

  The color conversion processing unit 21 color-converts the image data ID, which is RGB data, into CMYK data. The halftone processing unit 22 performs halftone processing on the CMYK data to generate CMYK halftone data. The halftone processing unit 22 further generates halftone data for transparent toner such that the dots of the transparent toner have a preset dot density.

  The control unit 10 includes main storage means such as RAM and ROM, and control means such as MPU (Micro Processing Unit) and CPU (Central Processing Unit). The control unit 10 also has controller functions related to various I / O, USB (Universal Serial Bus), bus, and other hardware interfaces, and controls the entire image forming apparatus 1.

  The storage unit 40 is a storage device including a hard disk drive or a flash memory that is a non-temporary recording medium, and stores a control program and data for processing executed by the control unit 10.

  In the present embodiment, the storage unit 40 further stores calibration data CD for forming CMYK gradation calibration adjustment patches and CMYK half patches. The half patch is a patch having a dot area ratio of less than 100% and expressing a solid image (solid density image). The storage unit 40 further includes mixture ratio adjustment data AD for forming a transparent toner mixture ratio adjustment patch and detecting the amount of reflected light.

  FIG. 2 is a cross-sectional view illustrating the overall configuration of the image forming apparatus 1 according to the embodiment. The image forming apparatus 1 of the present embodiment is a tandem type color printer. The image forming apparatus 1 includes, in its housing 70, colored toner photoconductor drums (image carriers) 30m, 30c, 30y, and 30k corresponding to the colors magenta, cyan, yellow, and black, and transparent toner. The photosensitive drum 30t is arranged in a row. Colored toner developing units 100m, 100c, 100y, and 100k are disposed adjacent to the colored toner photosensitive drums 30m, 30c, 30y, and 30k, respectively. A transparent toner developing unit 100t is disposed adjacent to the transparent toner photosensitive drum 30t.

  The colored toner photoreceptor drums 30c to 30k and the transparent toner photoreceptor drum 30t are irradiated (exposed) with laser light Lm, Lc, Ly, Lk, and Lt for each color from the exposure unit 29. By this irradiation, electrostatic latent images are formed on the color toner photosensitive drums 30c to 30k and the transparent toner photosensitive drum 30t. The colored toner developing units 100m, 100c, 100y, and 100k attach the toner to the electrostatic latent images formed on the surfaces of the colored toner photosensitive drums 30m, 30c, 30y, and 30k while stirring the colored toner.

  The developing unit 100t for transparent toner stirs the gloss toner and the matte toner to obtain a transparent toner mixed at a predetermined ratio, while applying toner to the electrostatic latent image formed on the surface of the transparent toner photosensitive drum 30t. Adhere. As a result, the development process is completed, and a colored toner image of each color is formed on the surface of the colored toner photoconductor drums 30c to 30k, and a transparent toner image is formed on the surface of the transparent toner photoconductor drum 30t.

  The image forming apparatus 1 has an endless intermediate transfer belt 27. The intermediate transfer belt 27 is stretched around the tension roller 24, the driving roller 26a, and the driven roller 26b. The intermediate transfer belt 27 is driven to circulate by the rotation of the driving roller 26a.

  For example, a transparent toner image, which is a toner image of a transparent toner on the photosensitive drum for transparent toner 30t, sandwiches the intermediate transfer belt 27 between the photosensitive drum for transparent toner 30t and the primary transfer roller 23t, and the intermediate transfer belt 27 is driven to circulate. As a result, primary transfer is performed on the intermediate transfer belt 27. This also applies to cyan, yellow, magenta and black colored toners. A primary transfer is performed on the surface of the intermediate transfer belt 27 so as to overlap each other at a predetermined timing, so that a full color toner image is formed on the transparent toner image. A full-color toner image is also called a colored toner image.

  The transparent toner image and the full color toner image formed on the transparent toner image are collectively referred to as a synthetic toner image. Thereafter, the composite toner image is secondarily transferred to the printing paper P supplied from the paper feed cassette 60. As a result, on the printing paper P, a transparent toner image is formed on the upper side of the full-color toner image (opposite side of the printing paper P). The fixing unit 80 can fix the transparent toner image and the full color toner image on the printing paper P as a printing medium by the fixing roller pair 81.

  FIG. 3 is a side sectional view showing the structure of the developing unit 100 according to the embodiment of the present invention. In the present embodiment, the developing unit 100 is used as a transparent toner developing unit 100t and colored toner developing units 100c to 100k. The developing unit 100 includes two agitating and conveying members 141 and 142, a magnetic roller 143, a developing roller (developer carrying member) 144, a developing container 145, a regulating blade 146, and a developing bias potential applying unit 150. I have. The development bias potential application unit 150 is controlled by the control unit 10.

  The developing container 145 constitutes the outline of the developing unit 100. A partition portion 145 b is provided at the lower portion of the developing container 145. The partition unit 145b partitions the inside of the developing container 145 into a first transfer chamber 145a and a second transfer chamber 145c. The first transfer chamber 145a and the second transfer chamber 145c extend in a columnar shape in a direction perpendicular to FIG. 3, and contain a two-component developer (also simply referred to as a developer) made of a magnetic carrier and transparent toner.

  The developing container 145 further holds a magnetic roller 143 and a developing roller 144. An opening 147 is formed in the developing container 145 to expose the developing roller 144 toward the transparent toner photosensitive drum 30t.

  The two agitating and conveying members 141 and 142 are cyclically moved while stirring the developer inside the first conveying chamber 145a and the second conveying chamber 145c, respectively. The agitating / conveying members 141 and 142 agitate the developer for a time set in advance as the time necessary for mixing, thereby generating a transparent toner as a mixture of gloss toner and mat toner in the magnetic carrier. Can be charged with polarity.

  The stirring and conveying member 142 supplies the charged developer to the magnetic roller 143 as a magnetic brush. The magnetic roller 143 includes a nonmagnetic rotating sleeve 143a and a fixed magnet body 143b fixed inside the rotating sleeve 143a. The magnetic roller 143 and the developing roller 144 are opposed to each other with a predetermined clearance. The restriction blade 146 can adjust the magnetic brush to a predetermined height.

  The developing roller 144 includes a rotatable nonmagnetic developing sleeve 144a and a developing roller side magnetic pole 144b fixed inside the developing sleeve 144a. A magnetic roller potential Vmag is applied to the magnetic roller 143. A developing bias potential Vslv is applied to the developing roller 144 by the developing bias potential applying unit 150. The development bias potential application unit 150 includes an AC application unit 151 that applies an AC bias potential, and a DC application unit 152 that is connected in series to the AC application unit 151 and applies a DC bias potential.

  FIG. 4 is a diagram illustrating a developing bias potential for forming a transparent toner patch in the image forming apparatus 1 according to the embodiment. The developing bias potential applying unit 150 applies an AC bias potential in which a DC bias potential of 20 to 80 V as the developing bias potential Vslv and a rectangular wave potential of a peak-to-peak value of 1600 V having a frequency of 2.7 kHz are superimposed on the developing roller 144. Has been. A DC bias potential of 300 V is applied to the magnetic roller 143 as a magnetic roller potential Vmag during development, and a DC bias potential of −300 V is applied during non-development.

  As a result, during development, the potential difference between the magnetic roller potential Vmag and the development bias potential Vslv (the potential state in which toner is supplied to the developing roller 144) increases, and the amount of toner supplied to the developing roller 144 increases. At the time of non-development, the potential difference between the developing bias potential Vslv and the magnetic roller potential Vmag (the potential state in which toner is collected from the developing roller 144) increases, and the amount of toner collected from the developing roller 144 increases.

  Further, by adjusting the magnetic roller potential Vmag applied to the magnetic roller 143 during development and non-development, the toner layer formation potential difference ΔV during development between the development bias potential Vslv and the magnetic roller potential Vmag is changed. Can do. As a result, a thin toner layer (also simply referred to as a toner layer) having a thickness corresponding to the toner layer formation potential difference ΔV between the development bias potential Vslv and the magnetic roller potential Vmag is formed on the development roller 144.

  Amorphous silicon photoconductors have a characteristic that the relative permittivity is about three times higher than that of organic photoconductors (OPC), and the amount of toner that can be held by the photoconductor is larger than the development contrast potential. For this reason, the amorphous silicon photoconductor can hold more toner than the solid density normally used. Therefore, when the amorphous silicon photoconductor is used in a saturated state, the amorphous silicon photoconductor is held exceeding the amount necessary for the solid density. Therefore, in this embodiment, the amorphous silicon photoconductor is used in a non-saturated state even with a solid density, and almost all of the toner formed on the developing roller 144 is developed on the photoconductor, and the solid density is reached by completing the development. Is used to be determined. The present invention is not limited to an amorphous silicon photoconductor, but can be applied to other photoconductors.

  The developing roller 144 attaches the transparent toner to the transparent toner photosensitive drum 30t through a facing portion (developing nip) having a predetermined clearance between the developing roller 144 and the transparent toner photosensitive drum 30t, thereby transparentizing the transparent toner image. It is formed on the surface of the toner photosensitive drum 30t. The transparent toner image is formed based on the potential difference between the electrostatic latent image potential on the surface of the transparent toner photosensitive drum 30t and the developing bias potential Vslv applied to the developing roller 144.

  The development bias potential Vslv is a rectangular wave having a development bias duty ratio (= T1 / (T1 + T2) × 100) in pulse width modulation, and enables development on the photosensitive drum 30t for transparent toner. In the transparent toner photosensitive drum 30 t, the surface potential is set to 20 V, and a developing electric field is formed between the developing roller 144 and the surface potential. In this developing electric field, the transparent toner particles are accelerated in the direction of the photosensitive drum 30t for the transparent toner at the time T1 when the developing bias potential Vslv is VH, and at the time T2 when the developing bias potential Vslv is VL, the transparent toner particles are Accelerated in the direction of the developing roller 144. The development amount on the photosensitive drum 30t for the transparent toner becomes apparent as the integration of these accelerations twice.

  In this embodiment, the transparent toner development ratio, which is the ratio between the development amount of gloss toner and the development amount of matte toner, can be adjusted by changing the development bias duty ratio of the development bias potential Vslv. This is because the low-melting-point transparent toner particles of the gloss toner are formed so as to have the following physical characteristics as compared with the high-melting-point transparent toner particles of the matte toner. The development bias duty ratio is also simply called a duty ratio.

(1) Matte toner volume average particle diameter (d50)> Gloss toner volume average particle diameter (d50)
(2) Average circularity of matte toner> Average circularity of gloss toner (3) 0.2 <Mat toner volume average particle size−Gloss toner volume average particle size <1.0

  The toner particles having a small volume average particle diameter are unlikely to fly from the developing sleeve 144a to the photosensitive drum 30t for transparent toner due to the influence of van der Waals force or the like. Therefore, the low melting point transparent toner particles of the gloss toner are less likely to fly than the high melting point transparent toner particles of the matte toner. On the other hand, toner particles having a low average circularity have a strong adhesion to the developing sleeve 144a and are difficult to fly to the photosensitive drum 30t for transparent toner. Therefore, the low melting point transparent toner particles of the gloss toner are less likely to fly than the high melting point transparent toner particles of the matte toner.

  According to the experiments of the present inventor, when the duty ratio of the developing bias potential Vslv is low, the low melting point transparent toner particles of the gloss toner are hardly developed, and only the high melting point transparent toner particles of the mat toner are developed. I found. Further, when the duty ratio of the developing bias potential Vslv is increased, the developing amount of the low melting point transparent toner particles of the gloss toner increases rapidly as compared with the increase of the developing amount of the high melting point transparent toner particles of the mat toner. I found it.

  The inventor of the present application has found 0.2 <mat toner volume average particle size−gross toner volume average particle size <1.0 as a preferable range of the volume average particle size of the mat toner and the volume average particle size of the gloss toner. In this range, the image forming apparatus 1 can effectively adjust the transparent toner development ratio, which is the ratio between the development amount of the gloss toner and the development amount of the matte toner, using the duty ratio of the development bias potential Vslv.

  As described above, the image forming apparatus 1 according to the present embodiment can adjust the transparent toner development ratio, which is the ratio between the development amount of the gloss toner and the development amount of the matte toner, by the duty ratio of the development bias potential. However, the control of the transparent toner developing ratio by the duty ratio of the developing bias potential Vslv means that the mixing ratio of the gloss toner and the matte toner that are stirred inside the transparent toner developing unit 100t can be changed.

  Furthermore, the control of the transparent toner developing ratio by the duty ratio of the developing bias potential Vslv is performed by a reference mixing ratio (described later), which is a mixing ratio in which the mixing ratio of the gloss toner and the matte toner in the transparent toner developing unit 100t is set in advance. It is assumed that there is. Therefore, the image forming apparatus 1 according to the present embodiment requests that the mixing ratio of the transparent toner in the transparent toner developing unit 100t is within an allowable error range with respect to the reference mixing ratio.

  FIG. 5 is a flowchart showing the content of the transparent toner mixing ratio adjustment process of the image forming apparatus 1 according to the embodiment. In the transparent toner mixture ratio adjustment process, the transparent toner mixture ratio is measured, and at least one of the gloss toner and the matte toner is removed from the transparent toner supply unit 200tg and the transparent toner supply unit 200tm so as to be within a preset range. It is a process to supply.

  In step S10, the control unit 10 executes an adjustment data reading process. In the adjustment data reading process, the control unit 10 reads the mixing ratio adjustment data AD from the storage unit 40. The mixing ratio adjustment data AD includes a duty ratio for forming the transparent toner mixing ratio adjustment patch for the high glossiness mode and a duty ratio for forming the transparent toner mixing ratio adjustment patch for the low glossiness mode. And a table of reference mixing ratios corresponding to the plurality of duty ratios.

  In step S20, the image forming apparatus 1 executes an adjustment patch forming process. In the adjustment patch forming process, the control unit 10 causes the image forming unit 20 to form an adjustment patch using data read from the mixing ratio adjustment data AD. The adjustment patch is formed on the intermediate transfer belt 27.

  In step S <b> 30, the control unit 10 measures the reflected light amount of the calibration patch for the transparent toner by using the calibration density sensor 28. The calibration concentration sensor 28 emits infrared light from, for example, an LED (not shown), passes through a polarizing filter that transmits only P waves, irradiates the patches with infrared P waves, and is detected by a light receiving element. The density is detected based on the ratio of the P wave and S wave of the reflected light. However, regarding the transparent toner, the calibration density sensor 28 is not used as a density sensor but as a reflected light quantity detection sensor for detecting the reflected light quantity.

  FIG. 6 is a diagram illustrating a relationship between the reflectance of the transparent toner patch and the duty ratio in the image forming apparatus 1 according to the embodiment. In FIG. 6, the developing bias duty ratio is normalized and shown on the horizontal axis, and the P-wave reflectance is normalized and shown on the vertical axis. FIG. 6A shows a gloss toner line TG indicating the relationship between the duty ratio and the P wave reflectance when a transparent toner patch is formed using a transparent toner containing only a gloss toner, and a transparent toner containing only a mat toner. The matte toner line TM showing the relationship between the duty ratio and the P-wave reflectivity when a transparent toner patch is formed using the.

  The matte toner is transparent before the heating action in the fixing process to the printing paper P by the fixing unit 80. Therefore, the transparent toner patch using the matte toner has a low P-wave reflectivity as a whole, and shows a low reflectivity even when the duty ratio is high. On the other hand, the gloss toner forms a white transparent toner patch having a low transmittance by irregular reflection before the fixing process to the printing paper P by the fixing unit 80.

  However, the gloss toner becomes transparent due to its high transmittance due to the heating action in the fixing process. Therefore, both the matte toner and the gloss toner are different only in gloss after fixing, and both can form a transparent layer. As a result, the image forming apparatus 1 can control the glossiness of the printed material while allowing the full color toner image to pass through without being impaired by adjusting the mixing ratio of the transparent toner as the mixture of the gloss toner and the matte toner. it can.

  The calibration density sensor 28 includes a regular reflection method for detecting regular reflection light from the patch and a diffuse reflection method for detecting diffuse reflection light from the patch. In the present embodiment, since the detection of the mixing ratio of the gloss toner and the matte toner in the transparent toner patch is required, the diffuse reflection method is preferable from the viewpoint of effectively detecting the diffuse reflection of the gloss toner.

  FIG. 6B shows the relationship between the duty ratio and the P wave reflectance when a transparent toner patch is formed using a transparent toner as a mixture of gloss toner and matte toner. Curve R shows the relationship between the duty ratio assumed at the reference mixing ratio, which is the reference mixing ratio, and the P-wave reflectivity. A curve L1 shows the relationship between the duty ratio assumed when the gloss toner mixing ratio is excessively high and the P-wave reflectance. A curve L2 shows the relationship between the duty ratio assumed when the mat toner mixing ratio is excessively high and the P-wave reflectance. Curves Rw1 and Rw2 indicate the allowable error range from the reference mixture ratio.

  In step S40, the control unit 10 determines whether or not the measured value of the transparent toner patch is within the reference value range. Specifically, the control unit 10 determines whether or not the measurement value is within a range surrounded by the two curves Rw1 and Rw2, that is, whether or not the measurement value is within an allowable error range. The control unit 10 ends the process if it is within the allowable error range, and proceeds to step S50 if it is not within the allowable error range. Specifically, when the measured value by the calibration concentration sensor 28 is the measured value P2, the process is terminated, and when the measured value is the measured value P1 or the measured value P3, the process proceeds to step S50.

  In step S50, the control unit 10 executes a toner supply amount calculation process. In the toner supply amount calculation process, the control unit 10 calculates the toner supply amount such that the mixture ratio is sufficiently close to the reference mixture ratio based on the deviations d1 and d3 from the reference mixture ratio (see FIG. 6B). To do. Specifically, when the measurement value is the measurement value P1, the control unit 10 calculates the toner supply amount of the matte toner based on the deviation d1, and when the measurement value is the measurement value P3. Since the ratio of the matte toner is excessive, the toner supply amount of the gloss toner is calculated based on the deviation d3.

  In step S60, the control unit 10 executes a toner supply process. In the toner supply process, the control unit 10 controls the transparent toner supply unit 200tg or the transparent toner supply unit 200tm to supply gloss toner or matte toner to the transparent toner developing unit 100t by the calculated toner supply amount. That is, the control unit 10 can adjust the mixing ratio of the transparent toner by supplying the gloss toner and the mat toner in different amounts (for example, supplying only the gloss toner).

  As described above, according to the image forming apparatus 1 according to the embodiment, it is possible to detect the P-wave reflectance of the transparent patch before the fixing process and measure the mixing ratio of the gloss toner and the matte toner. Thereby, the image forming apparatus 1 can appropriately adjust the mixing ratio of the transparent toner as the mixture of the gloss toner and the matte toner. Accordingly, an appropriate glossiness can be realized with a simple configuration by manipulating the duty ratio and adjusting the mixing ratio.

  The present invention can be implemented not only in the above embodiment but also in the following modifications.

  Modification 1: In the above-described embodiment, the mixing ratio of the transparent toner is adjusted by supplying the gloss toner or the matte toner from the transparent toner supply unit to the transparent toner developing unit. However, the present invention is not limited to this. The developing step may be performed with a low duty ratio of the developing bias potential Vslv to adjust the mixing ratio of the transparent toner by forcibly discharging the mat toner, or the gloss toner may be discharged while forcibly discharging the mat toner. You may make it supply.

  Modification 2: In the above embodiment, the intermediate transfer belt method is adopted, but the invention is not limited to this, and for example, a transfer drum method can also be adopted. The image forming apparatus of the present invention may be any apparatus that has an intermediate transfer unit that can measure the amount of reflected light of the transparent patch before the fixing process.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Control part 20 Image forming part 21 Color conversion process part 22 Halftone process part 27 Intermediate transfer belt 28 Density sensor 29 for calibration Exposure parts 30c-30k Photosensitive drum 30t for colored toners Photosensitive drum 40 for transparent toners Storage unit 50 Image reading unit 60 Paper feed cassette 70 Housings 100c to 100k Color toner development unit 100t Transparent toner development unit 200tg, 200tm Transparent toner supply unit 150 Development bias potential application unit

Claims (10)

An image forming apparatus that forms an image on a print medium using colored toner and transparent toner,
A colored toner developing unit that has a colored toner photosensitive drum and performs toner development using a colored developer containing the colored toner to form a colored toner image on the colored toner photosensitive drum;
A transparent toner developing unit having a transparent toner photosensitive drum, and performing toner development using a transparent developer containing the transparent toner to form a transparent toner image on the transparent toner photosensitive drum;
The transparent toner image is primarily transferred from the transparent toner developing portion, and the colored toner image is primarily transferred and superimposed on the transparent toner image from the colored toner developing portion to form a composite toner image, and the formation An intermediate transfer portion for secondary transfer of the synthesized toner image onto the print medium;
A fixing unit that pressurizes and heats the synthetic toner image secondarily transferred onto the print medium and fixes the image on the print medium;
A reflected light amount detection sensor for detecting the reflected light amount of the toner image formed on the intermediate transfer unit;
A control unit for controlling the colored toner developing unit, the transparent toner developing unit, and the reflected light amount detection sensor;
With
The transparent toner includes a second transparent toner and a first transparent toner having a transmittance before fixing that is smaller than that of the second transparent toner and a glossiness after fixing that is higher than that of the second transparent toner. Toner and
The transparent developer is a two-component developer including a mixed transparent toner that is a mixture of the first transparent toner and the second transparent toner, and a carrier.
The control unit measures the reflected light amount of the transparent toner image formed on the intermediate transfer unit by the reflected light amount detection sensor, and the first transparent contained in the transparent developer based on the measured reflected light amount. An image forming apparatus for adjusting a mixing ratio of toner and the second transparent toner. The image forming apparatus according to claim 1,
The first transparent toner includes low melting point transparent toner particles,
The image forming apparatus, wherein the second transparent toner includes high melting point transparent toner particles having a melting point higher than that of the low melting point transparent toner particles. The image forming apparatus according to claim 1, wherein
The first transparent toner is made of a crystalline resin,
The image forming apparatus, wherein the second transparent toner is made of an amorphous resin. The image forming apparatus according to claim 1, further comprising:
A first transparent toner supply unit that contains the first transparent toner and supplies the first transparent toner to the transparent toner developing unit;
A second transparent toner supply section that contains the second transparent toner and supplies the second transparent toner to the transparent toner developing section;
With
The control unit controls the first transparent toner supply unit and the second transparent toner supply unit to supply the first transparent toner and the second transparent toner in different amounts. An image forming apparatus that adjusts the mixing ratio. The image forming apparatus according to any one of claims 1 to 4, wherein
The developing unit for transparent toner has a developing roller for developing the transparent toner on the photosensitive drum for transparent toner, and a bias potential applying unit for applying a developing bias potential of pulse width modulation to the developing roller,
The control unit adjusts a transparent toner development ratio, which is a ratio of a development amount of the first transparent toner and a development amount of the second transparent toner, by changing a duty ratio of the development bias potential.
The first transparent toner has physical characteristics such that when the duty ratio is low, the transparent toner development ratio is smaller than when the duty ratio is high compared to the second transparent toner. Image forming apparatus. The image forming apparatus according to claim 5, wherein
The control unit controls the bias potential applying unit to apply a preset developing bias potential with a low duty ratio and discharge the second transparent toner onto the transparent toner photosensitive drum. An image forming apparatus that adjusts a mixing ratio of the first transparent toner and the second transparent toner. The image forming apparatus according to claim 5, wherein:
The image forming apparatus, wherein the physical characteristic is a volume average particle diameter. The image forming apparatus according to any one of claims 5 to 7,
The image forming apparatus, wherein the physical characteristic is an average circularity. The image forming apparatus according to any one of claims 5 to 8,
The physical property is that the difference between the volume average particle diameter of the first transparent toner and the volume average particle diameter of the second transparent toner is greater than 0.2 and less than 1.0. An image forming method for forming an image on a print medium using colored toner and transparent toner,
A colored toner developing step for forming a colored toner image on the photosensitive drum for colored toner by performing toner development using a photosensitive drum for colored toner and a colored developer containing the colored toner;
A transparent toner developing step of performing toner development using a transparent toner photosensitive drum and a transparent developer containing the transparent toner to form a transparent toner image on the transparent toner photosensitive drum;
The transparent toner image is primarily transferred in the transparent toner developing step, and the colored toner image is primarily transferred to be superimposed on the transparent toner image in the colored toner developing step to form a composite toner image. An intermediate transfer step for secondary transfer of the composite toner image onto the print medium;
A fixing step of pressurizing and heating the synthetic toner image secondarily transferred onto the print medium and fixing it on the print medium;
A reflected light amount detection step for detecting the reflected light amount of the toner image formed in the intermediate transfer step;
A control step for controlling the color toner development step, the transparent toner development step, and the reflected light amount detection step;
With
The transparent toner includes a second transparent toner and a first transparent toner having a transmittance before fixing that is smaller than that of the second transparent toner and a glossiness after fixing that is higher than that of the second transparent toner. Toner and
The transparent developer is a two-component developer including a mixed transparent toner that is a mixture of the first transparent toner and the second transparent toner, and a carrier.
The control step measures the reflected light amount of the transparent toner image formed in the intermediate transfer step in the reflected light amount detection step, and the first transparent contained in the transparent developer based on the measured reflected light amount. An image forming method including a step of adjusting a mixing ratio of toner and the second transparent toner.