JP6907799B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus.

In an image forming apparatus, particularly when forming a full-color image, it is required to impart a desired glossiness to a recording medium. Techniques for controlling glossiness are disclosed below (for example, JP-A-2009-8709 (Patent Document 1), JP-A-2007-4034 (Patent Document 2), JP-A-2007-286510 (Patent Document 1). Document 3)).

Japanese Unexamined Patent Publication No. 2009-8709 JP-A-2007-4034 JP-A-2007-286510

In the case of double-sided printing, there is a problem that a gloss difference occurs on the front and back sides of the recording medium. The difference in gloss between the front and back of the recording medium deteriorates the image quality, and it is required to suppress the difference in gloss between the front and back of the recording medium.

An object of the present invention is to provide an image forming apparatus capable of suppressing a difference in gloss between the front and back surfaces of a recording medium during double-sided printing.

The present inventors have an image forming apparatus including a first fixing portion for fixing a toner image and a second fixing portion for imparting unevenness to a recording medium on which the toner image is fixed to control glossiness. It was confirmed that there was a difference in gloss between the front and back of the recording medium during double-sided printing.

As the present inventors proceed with their research, the surface (first surface) of the recording medium to which the unevenness has already been imparted passes through the second fixing portion again during double-sided printing, so that the unevenness is leveled. It was found that a gloss difference occurs on the front and back of the recording medium.

Therefore, the present inventors have further studied so that the difference in gloss between the front and back surfaces can be suppressed even in an image forming apparatus provided with a second fixing portion, and have completed the present invention.

This image forming apparatus includes a first fixing portion and a second fixing portion. The first fixing portion fixes the toner image on the recording medium. The second fixing portion is arranged on the downstream side in the transport direction of the recording medium with respect to the first fixing portion. The first fixing portion includes a heating portion and a first opposed roller. The heating unit has a heat source. The first opposed roller forms the first nip portion facing the heating portion. The second fixing portion includes a roughness roller and a second opposed roller. The second opposed roller forms a second nip portion facing the roughness roller. The recording medium has a first main surface in contact with the heating portion and a second main surface in contact with the first opposed roller. The roughness roller has a larger surface roughness than the second opposed roller. The roughness roller imparts unevenness to the toner image fixed on the first main surface. The image forming apparatus further includes a first cooling unit, a second cooling unit, and a control unit. The first cooling unit cools the first opposed roller. The second cooling section cools the second main surface side of the recording medium between the time when the recording medium passes through the first fixing section and the time when the recording medium rushes into the second fixing section. The control unit controls the operation of the first cooling unit and the second cooling unit. When the softening temperature of the toner is Tm and the temperature of the toner image fixed on the first main surface immediately before the recording medium enters the second nip portion is T1, T1> Tm is satisfied. The temperature of the toner image fixed on the second main surface immediately after the recording medium passes through the first nip portion is set to T3, and the toner fixed on the second main surface immediately before the recording medium enters the second nip portion. When the temperature of the image is T2, the control unit controls the first cooling unit and the second cooling unit so that T2 <Tm and T3 <Tm.

According to the above-mentioned image forming control device, it is possible to suppress the difference in gloss between the front and back surfaces of the recording medium in double-sided printing.

In the above image forming control device, the first cooling unit and the second cooling unit are fans. As a result, the manufacturing cost can be suppressed.

In the above image forming control device, when the temperature of the toner image fixed on the second main surface immediately after the recording medium passes through the second nip portion is T4, the control unit is set to T4 <Tm. It controls the first cooling unit and the second cooling unit.

According to the above-mentioned image forming control device, it is possible to reliably suppress the difference in gloss between the front and back surfaces of the recording medium in double-sided printing.

In the above image forming control device, when the temperature of the toner image fixed on the second main surface immediately before the recording medium rushes into the first nip portion is T5, T5 <Tm is satisfied.

According to the above-mentioned image forming control device, it is possible to more reliably suppress the difference in gloss between the front and back surfaces of the recording medium in double-sided printing.

In the above-mentioned image forming control device, the image forming device further includes a third cooling unit for cooling the second opposed roller. As a result, T2 <Tm and T3 <Tm can be more reliably set.

In the above image forming control device, the control unit operates the first cooling unit and the second cooling unit when a predetermined number or more of recording media are continuously printed. As a result, power consumption can be suppressed.

In the above image forming control device, no heat source is provided in the second fixing portion. Thereby, Tm> T2 and Tm> T3 can be surely satisfied.

In the above image forming control device, the time from when the recording medium passes through the first nip portion to when it enters the second nip portion is 0.5 seconds or less. As a result, T1> Tm can be surely satisfied.

In the image forming control device described above, the control unit activates the first cooling unit and the second cooling unit when either T2 or T3 exceeds Tm. As a result, power consumption can be suppressed.

In the above image forming control device, the control unit can adjust the pressing force of the second opposed roller on the roughness roller. As a result, it is possible to suppress the occurrence of a gloss difference on the front and back surfaces of the recording medium.

In the above image forming control device, the control unit operates the first cooling unit and the second cooling unit only when printing on the second surface of the recording medium in double-sided printing. As a result, T1> Tm can be surely set.

In the above image forming control device, the control unit operates the first cooling unit and the second cooling unit from the time of printing on the first surface of the recording medium in double-sided printing. Thereby, Tm> T2 and Tm> T3 can be surely satisfied.

According to this image forming apparatus, it is possible to realize an image forming apparatus capable of suppressing the difference in gloss between the front and back surfaces of a recording medium during double-sided printing.

It is the schematic of the image forming apparatus of Embodiment 1. FIG. It is the schematic which shows the fixing device of Embodiment 1. FIG. It is a partially enlarged view of the roughness roller which gives unevenness to the toner image fixed on the 1st main surface. It is a block diagram which shows the structure of the fixing device. It is a partially enlarged view of the first side of the recording medium in double-sided printing passing through the first nip part. It is a figure which shows the toner image which made the unevenness by the roughness roller in the 2nd nip part. It is a figure which shows the mode that the recording medium in double-sided printing passes through a 2nd fixing part again. It is a figure which shows the recording medium of FIG. 7 after passing through a 2nd fixing part. It is the schematic of the fixing device for demonstrating the effect of suppressing the difference in gloss. It is a graph which shows the change of the temperature of the toner image on the 1st main surface and the temperature of the toner image on a 2nd main surface when the 1st cooling part and the 2nd cooling part are not operated. It is a graph which shows the change of the temperature of the toner image on the 1st main surface and the temperature of the toner image on a 2nd main surface when only the 1st cooling part is operated. It is a graph which shows the change of the temperature of the toner image on the 1st main surface and the temperature of the toner image on a 2nd main surface when the 1st cooling part and the 2nd cooling part are operated. It is a flowchart in the gloss difference suppression control of Embodiment 1. It is a flowchart in the gloss difference suppression control of Embodiment 2. It is a flowchart in the gloss difference suppression control of Embodiment 3. It is the schematic which shows the fixing device of Embodiment 4. It is the schematic which shows the fixing device of Embodiment 5. It is a table which shows the evaluation result in each Example and each comparative example.

Hereinafter, the image forming apparatus according to each embodiment will be described with reference to the drawings. In each of the following embodiments, the same or substantially the same configuration is designated by the same reference numerals, and duplicate description will not be repeated. The configurations of the embodiments described below may be selectively combined as appropriate.

(Embodiment 1)
<Image forming device 1501>
Examples of the image forming method include a direct transfer method and an intermediate transfer method. In the direct transfer method, the image is formed by going through a step of directly transferring the toner image formed on the photoconductor to the recording medium and a step of heating and fixing the toner image transferred on the recording medium.

In the intermediate transfer method, a step of transferring the toner image formed on the photoconductor to the intermediate transfer belt (primary transfer) and a step of transferring the toner image transferred on the intermediate transfer belt to a recording medium (secondary transfer). The image is formed by going through the steps of heating and fixing the toner image transferred onto the recording medium.

FIG. 1 is a schematic view of the image forming apparatus 1501 of the first embodiment. The image forming apparatus 1501 of the first embodiment employs an intermediate transfer method. The image forming apparatus 1501 includes an intermediate transfer belt 1502 as a belt member in a substantially central portion inside the image forming apparatus 1501.

Below the lower horizontal portion of the intermediate transfer belt 1502, an image forming unit 1506Y corresponding to yellow (Y), an image forming unit 1506M corresponding to magenta (M), an image forming unit 1506C corresponding to cyan (C), and Image forming units 1506K corresponding to black (K) are arranged side by side along the intermediate transfer belt 1502.

The image forming unit 1506Y has a photoconductor drum 1507Y. The image forming unit 1506M has a photoconductor drum 1507M. The image forming unit 1506C has a photoconductor drum 1507C. The image forming unit 1506K has a photoconductor drum 1507K.

A charger 1508, a print head portion 1509, a developing device 1510, and a primary transfer roller 1511Y are arranged in order around the photoconductor drum 1507Y along the rotation direction of the photoconductor drum 1507Y. The arrangement around the photoconductor drum 1507M, the photoconductor drum 1507C, and the photoconductor drum 1507K is the same as the arrangement around the photoconductor drum 1507Y.

The primary transfer roller 1511Y faces the photoconductor drum 1507Y with the intermediate transfer belt 1502 interposed therebetween. The primary transfer roller 1511M, the primary transfer roller 1511C, and the primary transfer roller 1511K are also arranged in the same manner as the primary transfer roller 1511Y.

The secondary transfer roller 1503 is pressure-welded to the portion of the intermediate transfer belt 1502 supported by the intermediate transfer belt drive roller 1505, and the nip portion between the secondary transfer roller 1503 and the intermediate transfer belt 1502 is the secondary transfer region. It is 1530. The fixing device 1 is arranged at a position downstream of the transport path 1541 on the wake side of the secondary transfer region 1530.

A paper cassette 1517 is detachably arranged at the lower part of the image forming apparatus 1501. The paper P loaded and stored inside the paper feed cassette 1517 is sent out one by one from the uppermost one to the transport path 1540 by the rotation of the paper feed roller 1518.

An image density (AIDC) sensor 1519 that also serves as a resist sensor is installed between the image forming unit 1506K on the most downstream side of the intermediate transfer belt 1502 and the secondary transfer region 1530.

(Approximate operation of image forming apparatus 1501)
Next, the schematic operation of the image forming apparatus 1501 having the above configuration will be described. An image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the image forming device 1501. The image signal processing unit to which the image signal is input creates a digital image signal in which the image signal is color-converted into yellow, cyan, magenta, and black.

The printhead portion 1509 of the image forming unit 1506Y emits light based on a digital image signal to expose the photoconductor drum 1507Y. The image forming unit 1506M, the image forming unit 1506C, and the image forming unit 1506K are also exposed with the same configuration as the above image forming unit 1506Y.

The electrostatic latent image formed on the photoconductor drum 1507Y is developed by the developer 1510 to become a yellow toner image. The yellow toner image is first transferred onto the intermediate transfer belt 1502 by the action of the primary transfer roller 1511Y.

Similar to the photoconductor drum 1507Y, the electrostatic latent image formed on the photoconductor drum 1507M becomes a magenta toner image. The electrostatic latent image formed on the photoconductor drum 1507C becomes a cyan toner image. The electrostatic latent image formed on the photoconductor drum 1507K becomes a black toner image.

The magenta toner image is first transferred onto the intermediate transfer belt 1502 by the action of the primary transfer roller 1511M. The cyan toner image is primarily transferred onto the intermediate transfer belt 1502 by the action of the primary transfer roller 1511C. The black toner image is first transferred onto the intermediate transfer belt 1502 by the action of the primary transfer roller 1511K.

The toner images of each color (yellow, magenta, cyan, black) are sequentially superposed on the intermediate transfer belt 1502 rotating in the direction of arrow A and primary transfer is performed.

The toner image formed on the intermediate transfer belt 1502 reaches the secondary transfer region 1530 as the intermediate transfer belt 1502 moves. In the secondary transfer region 1530, the superimposed color toner images are collectively secondary transferred to the paper P by the action of the secondary transfer roller 1503.

The toner image secondarily transferred to the paper P reaches the fixing device 1. In this fixing device 1, the toner image is fixed on the paper P. Details of the fixing device 1 will be described later.

After the paper P has passed through the fixing device 1, it is conveyed to the paper ejection roller 1514, and in the case of single-sided printing, the paper is ejected to the paper ejection tray 1513. In the case of double-sided printing, it is conveyed along the reversal path (arrow B in FIG. 1). The paper P is secondarily transferred to the surface (second surface) opposite to the surface (first surface) on which the toner image is already fixed by the same procedure as the first surface, passes through the fixing device 1 again, and is transferred to the second surface. The toner image is fixed.

(toner)
The toner of the first embodiment contains at least a binder resin and a wax in the toner matrix particles. Next, the binder resin will be described. The binder resin is, for example, a styrene resin, an acrylic resin, a styrene-acrylic resin, a polyester resin, a silicone resin, an olefin resin, an amide resin, an epoxy resin, or the like.

The binder resin preferably contains a styrene-acrylic resin from the viewpoint of toner particle size, shape controllability, and chargeability. Examples of the polymerizable monomer for obtaining a styrene-acrylic resin include styrene-based monomers such as styrene, methylstyrene, methoxystyrene, butylstyrene, phenylstyrene, and chlorostyrene; methyl (meth) acrylate. , Ethyl (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate, and other (meth) acrylate-based monomers; carboxylic acid-based monomers such as acrylic acid, methacrylic acid, and fumaric acid are used. It is preferable to do so. One of these types may be used, or two or more types may be used in combination.

The glass transition point (Tg) of the binder resin is preferably 30 to 50 ° C, more preferably 35 to 48 ° C. When the glass transition point of the binder resin is within the above range, both low-temperature fixability and heat-resistant storage property can be obtained at the same time.

The glass transition point of the binder resin is measured using "Diamond DSC" (manufactured by PerkinElmer). As a measurement procedure, 3.0 mg of a sample (binding resin) is sealed in an aluminum pan and set in a holder. The reference uses an empty aluminum pan.

The measurement conditions are a measurement temperature of 0 ° C. to 200 ° C., a temperature rise rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min under temperature control of heating-cooling-heating, based on the data of the second heating. The analysis is performed, and an extension of the baseline before the rise of the first heat absorption peak and a tangent line showing the maximum slope between the rise of the first peak and the peak peak are drawn, and the intersection is shown as the glass transition point. ..

Next, wax will be described. Waxes are polyolefin waxes such as polyethylene wax and polypropylene wax, branched chain hydrocarbon waxes such as microcrysterin wax, long chain hydrocarbon waxes such as paraffin wax and sazole wax, and dialkylketone waxes such as distearyl ketone. , Carnauba wax, Montan wax, Bechenic acid behenate, Trimethylol propantribehenate, Pentaerythritol tetrabehenate, Pentaerythritol diacetate dibehenate, Glycerin tribehenate, 1,18-Octadecanediol distearate, It is preferable to use an ester wax such as tristearyl trimellitic acid or distealyl maleate, or an amide wax such as ethylenediamine behenylamide or tristealyl amide trimellitic acid. Among these, it is preferable to use a branched chain hydrocarbon wax such as microcrystalline wax from the viewpoint of suppressing uneven gloss.

The melting point of the wax contained in the toner is preferably 70 to 100 ° C, more preferably 70 to 85 ° C. The melting point of the wax indicates the temperature of the peak top of the endothermic peak, and the differential scanning calorimetry using the differential scanning calorimeter "DSC-7" (manufactured by PerkinElmer) and the thermal analyzer controller "TAC7 / DX" (manufactured by PerkinElmer). DSC is measured by analysis.

Specifically, 4.5 mg of a sample (wax) is sealed in an aluminum pan (KITNO.0219-0041), set in the sample holder of "DSC-7", and elevated at a measurement temperature of 0 to 200 ° C. The temperature of heating-cooling-heating is controlled under the measurement conditions of a temperature rate of 10 ° C./min and a temperature lowering rate of 10 ° C./min, and the analysis is performed based on the data of the second heating.

An empty aluminum pan is used to measure the reference. The wax content is preferably 1 to 30 parts by mass, and more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the binder resin. When the wax content is within the above range, fixing separability can be obtained.

Next, the colorant contained in the toner particles will be described. As the colorant, generally known dyes and pigments can be used. For example, as a colorant for obtaining black toner, various known colorants such as carbon black such as furnace black and channel black, magnetic substances such as magnetite and ferrite, dyes, and inorganic pigments containing non-magnetic iron oxide are used. It can be used arbitrarily.

As the colorant for obtaining the color toner, known dyes, organic pigments and the like can be arbitrarily used. Specifically, examples of the organic pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 166, 177, 178, 222, 238 , 269, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment Orange 31, 43, C.I. I. Pigment Blue 15; 3, 60, 76 and the like can be mentioned, and examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 68, 11, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. There are Solvent Blue 25, 36, 69, 70, 93, 95 and so on.

The colorant for obtaining the toner of each color may be used alone or in combination of two or more for each color. The content ratio of the colorant is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin.

When the toner particles contain a charge control agent, a known positive charge control agent or negative charge control agent can be used. Examples of the positive charge control agent include niglosin dyes such as "niglosin base EX" (manufactured by Orient Chemical Industries, Ltd.), "quaternary ammonium salt P-51" (manufactured by Orient Chemical Industries, Ltd.), and "copy charge PX VP435". (Manufactured by Hext Japan Co., Ltd.), quaternary ammonium salts, alkoxylated amines, alkylamides, molybdic acid chelating pigments, and imidazole compounds such as "PLZ1001" (manufactured by Shikoku Kasei Kogyo Co., Ltd.).

Examples of the negative charge control agent include "Bontron S-22" (manufactured by Orient Chemical Industry Co., Ltd.), "Bontron S-34" (manufactured by Orient Chemical Industry Co., Ltd.), and "Bontron E-81" (manufactured by Orient Chemical Industry Co., Ltd.). ), "Bontron E-84" (manufactured by Orient Chemical Industry Co., Ltd.), "Spiron Black TRH" (manufactured by Hodoya Chemical Industry Co., Ltd.) and other metal complexes, thioindigo pigments, "Copy Charge NX VP434" (manufactured by Hext Japan Co., Ltd.) Quaternary ammonium salts such as "Bontron E-89" (manufactured by Orient Chemical Co., Ltd.), calixarene compounds such as "LR147" (manufactured by Nippon Carlit), magnesium fluoride, carbon fluoride Fluorine compounds such as, etc. can be mentioned.

Metal complexes used as negative charge control agents include oxycarboxylic acid metal complexes, dicarboxylic acid metal complexes, amino acid metal complexes, diketone metal complexes, diamine metal complexes, and azo group-containing benzene-benzene derivatives, in addition to those shown above. Some have various structures such as a skeleton metal body and an azo group-containing benzene-naphthalene derivative skeleton metal complex.

The content of the charge control agent is preferably 0.01 to 30 parts by mass, and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

The toner can be used as it is in the image forming apparatus 1501 of the first embodiment. However, in order to improve the fluidity, chargeability, cleanability and the like, a toner to which an external additive is added may be used.

Examples of the external additive include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, and strontium titanate and zinc titanate. There are inorganic fine particles such as inorganic tanoic acid compound fine particles such as.

From the viewpoint of heat-resistant storage and environmental stability, these inorganic fine particles are preferably surface-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil, or the like.

The inorganic fine particles constituting the external additive preferably have an average primary particle size of 30 nm or less. Since the external additive composed of inorganic fine particles has the above particle size, the toner is less likely to release the external additive when forming an image. The amount of the external additive added is 0.05 to 5% by mass, preferably 0.1 to 3% by mass in the toner.

The toner used in the image forming apparatus 1501 of the first embodiment can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer.

When the toner is used as a two-component developer, the carrier is a conventionally known material such as a ferromagnetic metal such as iron, a ferromagnetic metal and an alloy such as aluminum and lead, and a compound of a ferromagnetic metal such as ferrite and magnetite. Magnetic particles made of the above can be used, and ferrite particles are particularly preferable.

As the carrier, a coat carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a binder type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like can also be used.

Examples of the coating resin constituting the coat carrier include an olefin resin, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, and a fluororesin. As the resin constituting the resin-dispersed carrier, for example, a styrene-acrylic resin, a polyester resin, a fluororesin, a phenol resin, or the like can be used.

When the toner of the first embodiment is used as a two-component developer, a charge control agent, an adhesion improver, a primer treatment agent, a resistance control agent and the like are further added to the toner and the carrier, if necessary. It is also possible to form a two-component developer.

The toner particles of the first embodiment preferably have an average particle size of, for example, 3 to 9 μm in terms of volume-based median diameter, and more preferably 3 to 8 μm. This particle size can be controlled by, for example, the concentration of the agglutinating agent used, the amount of the organic solvent added, the fusion time, and the composition of the polymer in the case of producing by adopting the emulsion aggregation method described later.

When the volume-based median diameter is in the above range, the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved. The volume-based median diameter of toner particles is measured and calculated using a measuring device that connects a computer system equipped with data processing software "Software V 3.51" to "Multisizer 3" (manufactured by Beckman Coulter). Is to be done.

Specifically, 0.02 g of a sample (toner particles) is 20 mL of a surfactant solution (for the purpose of dispersing toner particles, for example, a neutral detergent containing a surfactant component diluted 10-fold with pure water). After adding to the solution) and acclimatizing, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion, and this toner particle dispersion contains "ISOTONII" (manufactured by Beckman Coulter) in the sample stand. Inject into the beaker with a pipette until the indicated concentration of the measuring device reaches 8%.

By setting this concentration range, reproducible measured values can be obtained. Then, in the measuring device, the number of measured particles is 25,000, the aperture diameter is set to 50 μm, the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256, and the volume integration fraction is 50 from the largest. % Is the volume-based median diameter.

From the viewpoint of improving the transfer efficiency, the toner particles of the first embodiment preferably have an average circularity of 0.930 to 1.000, more preferably 0.950 to 0.995. The average circularity of the toner particles is measured using "FPIA-2100" (manufactured by Sysmex Corporation).

Specifically, the sample (toner particles) is blended with an aqueous solution containing a surfactant, ultrasonically dispersed for 1 minute to disperse the particles, and then measured under the measurement conditions HPF by "FPIA-2100" (manufactured by Sysmex). In the (high magnification imaging) mode, shooting was performed at an appropriate density of 3,000 to 10,000 HPF detections, the circularity of each toner particle was calculated according to the following formula (T), and the circularity of each toner particle was calculated. Calculated by adding degrees and dividing by the total number of toner particles.

Circularity = (perimeter of a circle having the same projected area as the particle image) / (perimeter of the projected particle image) ... (T)
The viscoelastic property of the toner is measured in the following manner using, for example, a viscoelasticity measuring device (rheometer) "RDA-II type" (manufactured by Leometrics). A parallel plate having a diameter of 10 mm is used as the measuring jig. The measurement sample is used by molding the toner into a columnar sample having a diameter of about 10 mm and a height of 1.5 to 2.0 mm after heating and melting. The measurement frequency is 6.28 radians / second. For the measurement distortion setting, the initial value is set to 0.1%, and measurement is performed in the automatic measurement mode. The sample elongation correction is adjusted in the automatic measurement mode.

(Fixing device 1)
FIG. 2 is a schematic view showing the fixing device 1 of the first embodiment. The fixing device 1 has a first fixing portion 50 for fixing the toner image 301 to the recording medium 302, and a second fixing portion 50 arranged on the downstream side of the recording medium 302 in the transport direction DR1 with respect to the first fixing portion 50. A unit 400 is provided.

(First fixing portion 50)
The first fixing portion 50 includes a heating portion 100 and a first opposed roller 200. The first opposed roller 200 forms the first nip portion N1 facing the heating portion 100. The heating unit 100 includes a heat source 104, a heat transfer roller 103, a heat transfer belt 105, and a heating roller 102.

The heat source 104 is, for example, a glass tube heater having a filament. The heat source 104 is arranged inside the cylindrical heat transfer roller 103, and transfers heat to the heat transfer roller 103. The heat transfer roller 103 transfers heat to the heat transfer belt 105 in contact with the heat transfer roller 103. The heat transfer belt 105 transfers heat to the recording medium 302 while conveying the recording medium 302 passing through the first nip portion N1, and fixes the toner image 301 on the recording medium 302.

The set temperature of the heat source 104 is 80 ° C. or higher and 250 ° C. or lower. The temperature of the heat transfer belt 105 is monitored by a temperature sensor (not shown) installed on the surface of the heat transfer belt 105, fed back to a temperature control circuit (not shown), and controlled to a predetermined temperature.

The heat transfer belt 105 is stretched on the heating roller 102 and the heat transfer roller 103. The heat transfer belt 105 has a base made of metal, resin, or the like and a rubber layer that covers the base, and generally has a release layer on the surface of the heat transfer belt 105.

When a resin is used as the substrate of the heat transfer belt 105, a resin having high heat resistance such as polyimide is preferable. The rubber layer is preferably silicone rubber or fluororubber having high heat resistance. The thickness of the rubber layer is about 0.1 mm or more and about 5 mm or less, and the hardness of the rubber layer is about 5 degrees or more and about 50 degrees or less. As the release layer, a fluororesin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and polytetrafluoroethylene (PTFE) is used.

The metal heating roller 102 has an elastic layer 106 on the outer peripheral surface. For the elastic layer 106, heat-resistant rubber (for example, silicone rubber, fluororubber, etc.) is used. The hardness of the elastic layer 106 is about 5 degrees or more and 50 degrees or less. The thickness of the elastic layer 106 in the radial direction is about 1 mm or more and 50 mm or less. In order to improve the releasability, the surface of the elastic layer 106 may be coated with a fluorine-based resin or the like.

The first opposed roller 200 has a metal substrate 202 and an elastic layer 201 covering the substrate 202. The elastic layer 201 is a rubber having high heat resistance such as silicone type and fluorine type. The thickness of the elastic layer 201 in the radial direction is about 0.1 mm or more and 20 mm or less. The hardness of the elastic layer 201 is about 5 to 50 degrees.

It is preferable to provide a release layer on the surface of the elastic layer 201. In order to heat the first opposed roller 200 quickly, a heat source (heater or the like) may be installed in the first opposed roller 200.

The recording medium 302 has a first main surface 302a and a second main surface 302b. The first main surface 302a comes into contact with the heating unit 100 when the recording medium 302 passes through the first fixing unit 50. The second main surface 302b comes into contact with the first opposed roller 200 when the recording medium 302 passes through the first fixing portion 50.

The first main surface 302a is a surface facing the heating unit 100 side with respect to the transport direction DR1. The second main surface 302b is a surface facing the first facing roller 200 side with respect to the transport direction DR1.

When printing the second side of double-sided printing, the front and back sides of the recording medium 302 are reversed, but even in this case, the heating unit 100 side is the first main surface 302a and the first opposing roller 200 side is the second main surface 302b. .. The toner image 301b is already fixed on the first surface (second main surface 302b side) of the recording medium 302 in double-sided printing. The toner image 301a is fixed on the second surface (first main surface 302a) of the recording medium 302 in double-sided printing.

(Second fixing part 400)
In the first fixing portion 50, the recording medium 302 in which the toner image 301a is fixed on the first main surface 302a is conveyed to the second fixing portion 400. The toner image 301a is because it is heated by the heating unit 100 in the first fixing portion 50, the toner softening temperature Tm [° C.] (storage modulus G '= 1 × 10 ⁶ toner temperature in [Pa]) or more temperature Is transported to the second fixing portion 400 while maintaining the above.

The second fixing portion 400 includes a roughness roller 401 and a second opposed roller 402. The second opposed roller 402 forms the second nip portion N2 facing the roughness roller 401. It is preferable not to provide a heat source in the second fixing portion 400.

The second opposed roller 402 has a metal cylindrical base and rubber covering the base. The rubber is a rubber having high heat resistance such as silicone type and fluorine type. The thickness in the radial direction is about 0.1 mm to 20 mm, and the hardness is about 5 to 50 degrees. It is preferable to provide a release layer on the surface. The second opposed roller 402 presses the roughness roller 401. The pressing force of the second opposing roller 402 on the roughness roller 401 can be adjusted by the pressing force adjusting unit 410.

FIG. 3 is a partially enlarged view of the roughness roller 401 that imparts unevenness to the toner image 301a fixed on the first main surface 302a. The roughness roller 401 has a larger surface roughness than the second opposed roller 402. The surface roughness Rz of the roughness roller 401 is preferably 0.5 or more and 20 μm or less, and more preferably 1 or more and 5 μm or less.

In order to improve the followability of the roughness roller 401 to the recording medium 302, it is preferable that the surface of the roughness roller 401 is coated with rubber. Further, it is more preferable that the rubber is coated with a resin. The resin is preferably a resin having high releasability such as PFA.

When the temperature of the toner image 301a is Tm or higher, the toner is melted, so that the toner image 301a is easily deformed. The recording medium 302 passes between the second opposed roller 402 and the roughness roller 401 while the toner image 301a is easily deformed. The recording medium 302 is pressed by the second opposed roller 402, so that the recording medium 302 is pressed against the roughness roller 401. As a result, the toner image 301a is provided with irregularities.

By imparting unevenness to the toner image 301a, the glossiness of the recording medium 302 is reduced. Therefore, the glossiness of the recording medium 302 is controlled.

(Cooling part)
As shown in FIG. 2, the image forming apparatus 1501 further includes a first cooling unit 501 and a second cooling unit 502. The first cooling unit 501 and the second cooling unit 502 are, for example, fans, respectively, and are composed of a blower device that outputs (blows) air α. Instead of air, it may be, for example, an inert gas.

Adjust the cooling function by lowering the temperature of the air or changing the strength of the air. By using a cooling mechanism using a fan, the fixing device 1 can be configured in a simple manner, and the manufacturing cost can be suppressed.

The first cooling unit 501 blows air α to cool the first opposed roller 200 from the surface. The second cooling unit 502 sends air α to the second main surface 302b side of the recording medium 302 between the time when the recording medium 302 passes through the first fixing unit 50 and the time when the recording medium 302 rushes into the second fixing unit 400. The recording medium 302 is cooled by blowing air from the second main surface 302b side.

In the case of double-sided printing, the toner image 301b is already fixed on the second main surface 302b side, and the second cooling unit 502 blows air α toward the second main surface 302b to blow the toner image 301b. To cool.

(Temperature detector)
As shown in FIG. 2, the image forming apparatus 1501 includes a first temperature detection unit 601, a second temperature detection unit 602, a third temperature detection unit 603, a fourth temperature detection unit 604, and a second. The temperature detection unit 605 of 5 is further provided. The temperature detectors are non-contact thermometers. Each temperature detection unit can measure the temperature on the first main surface 302a side or the temperature on the second main surface 302b side of the recording medium 302.

The first temperature detection unit 601 measures the temperature T1 of the toner image 301a fixed on the first main surface 302a immediately before the recording medium 302 rushes into the second nip portion N2. T1 satisfies T1> Tm in relation to the toner softening temperature Tm.

The length between the first fixing portion 50 and the second fixing portion 400 in the transport direction DR1 is, for example, 150 mm. T1> Tm can be maintained by appropriately setting the length and the set temperature of the heater, and controlling the first cooling unit 501 and the second cooling unit 502.

By keeping T1> Tm, the toner image 301a is in a state of being easily deformed, so that the toner image 301a can be provided with irregularities in the second fixing portion 400. Therefore, the glossiness of the recording medium 302 can be controlled.

The fifth temperature detection unit 605 measures the temperature T5 of the toner image 301b fixed on the second main surface 302b immediately before the recording medium 302 rushes into the first nip portion N1 during double-sided printing. The third temperature detection unit 603 measures the temperature T3 of the toner image 301b fixed on the second main surface 302b immediately after the recording medium 302 passes through the first nip portion N1 during double-sided printing.

The second temperature detection unit 602 measures the temperature T2 of the toner image 301b fixed on the second main surface 302b immediately before the recording medium 302 rushes into the second nip portion N2 during double-sided printing. The fourth temperature detection unit 604 measures the temperature T4 of the toner image 301b fixed on the second main surface 302b immediately after the recording medium 302 passes through the second nip portion N2 during double-sided printing.

Immediately before entering the first nip portion N1 or the second nip portion N2, for example, when the transport speed of the recording medium 302 is 300 mm / sec, the entry into the first nip portion N1 or the second nip portion N2. It is a position 0.05 s before, that is, a position 15 mm before the first nip portion N1 or the second nip portion N2.

Immediately after passing through the first nip portion N1 or the second nip portion N2, for example, if the transport speed of the recording medium 302 is 300 mm / sec, it passes through the first nip portion N1 or the second nip portion N2. The position after 0.05 s, that is, the position 15 mm after the first nip portion N1 or the second nip portion N2.

(Control unit 700)
As shown in FIG. 1, the image forming apparatus 1501 further includes a control unit 700 and an image forming control unit 650. The control unit 700 controls the operation of the first cooling unit 501 and the second cooling unit 502.

FIG. 4 is a block diagram showing the configuration of the fixing device 1. The first temperature detection unit 601 detects the temperature T1. The second temperature detection unit 602 detects the temperature T2. The third temperature detection unit 603 detects the temperature T3. The fourth temperature detection unit 604 detects the temperature T4. The fifth temperature detection unit 605 detects the temperature T5.

The first temperature detection unit 601 inputs the detected temperature data T1 to the control unit 700. The second temperature detection unit 602 inputs the detected temperature data T2 to the control unit 700. The third temperature detection unit 603 inputs the detected temperature data T3 to the control unit 700. The fourth temperature detection unit 604 inputs the detected temperature data T4 to the control unit 700. The fifth temperature detection unit 605 inputs the detected temperature data T5 to the control unit 700.

The image formation control unit 650 receives data related to image formation, and inputs the data to the control unit 700. The data related to image formation is, for example, whether or not there is a recording medium 302 for double-sided printing, the number of prints of the recording medium 302 for continuous printing, and the like. The memory 93 stores data on the number of continuous prints, data on the toner softening temperature Tm, and the like.

The control unit 700 receives the temperature data T1 from the first temperature detection unit 601. The control unit 700 receives the temperature data T2 from the second temperature detection unit 602. The control unit 700 receives the temperature data T3 from the third temperature detection unit 603. The control unit 700 receives the temperature data T4 from the fourth temperature detection unit 604. The control unit 700 receives the temperature data T5 from the fifth temperature detection unit 605. The control unit 700 receives data related to image formation from the image formation control unit 650.

The control unit 700 and the first cooling unit 501 are based on the temperature data T1, T2, T3, T4, and T5, the data related to image formation from the image formation control unit 650, and the data stored in the memory 93. A control signal for operating the second cooling unit 502 and the second opposing roller 402 is output.

<Mechanism of gloss difference generation>
When gloss control is performed on both sides of the recording medium 302 in double-sided printing, a gloss difference may occur on both sides of the recording medium 302. Hereinafter, the mechanism of gloss difference generation will be described.

FIG. 5 is a partially enlarged view of the first surface of the recording medium 302 in double-sided printing that passes through the first nip portion N1. The toner image 301a is pressed and heated by the heat transfer belt 105. Since the surface is fixed by the heat transfer belt 105 having a smooth surface, the surface of the toner image 301a becomes smooth, and the first surface of the recording medium 302 becomes highly glossy.

FIG. 6 is a diagram showing a toner image 301a in which irregularities are imparted by a roughness roller 401 in the second nip portion N2. The recording medium 302 that has passed through the first nip portion N1 rushes into the second nip portion N2. The toner image 301a on the first main surface 302a is deformed by being pressed by the roughness roller 401 to give unevenness. The glossiness of the recording medium 302 is reduced due to the unevenness.

In the case of double-sided printing, the uneven recording medium 302 is conveyed to the fixing device 1 again along the inversion path shown in FIG. 1 (arrow B). The front and back sides of the recording medium 302 are reversed, and the recording medium 302 passes through the first fixing section 50 and the second fixing section 400 again.

FIG. 7 is a diagram showing how the recording medium 302 in double-sided printing passes through the second fixing portion 400 again. FIG. 8 is a diagram showing a recording medium 302 of FIG. 7 after passing through the second fixing portion 400.

In the second fixing portion 400, the toner image 301a fixed on the first main surface 302a corresponding to the second surface in double-sided printing is given unevenness by the roughness roller 401, and at the same time, the unevenness is already given. The toner image 301b on the two main surfaces 302b (first surface) is pressed by the second opposing roller 402.

When the temperature of the toner image 301b on the second main surface 302b exceeds Tm, the toner image 301b is easily deformed. Therefore, when the recording medium 302 passes through the second fixing portion 400 again, the unevenness of the toner image 301b already applied is smoothed by the second opposed roller 402 whose surface roughness is smaller than that of the roughness roller 401. Will be.

As a result, as shown in FIG. 8, the glossiness of the first surface (second main surface 302b side) becomes large, and between the first surface and the second surface (first main surface 302a side) to which the unevenness is newly added. Gloss difference will occur.

In particular, when continuous printing is performed, heat is transferred from the recording medium 302 that continuously passes through the second nip portion N2 to the second opposing roller 402, and the temperature of the second opposing roller 402 increases.

As a result, the temperature of the toner image 301b on the second main surface 302b that passes through the second fixing portion 400 tends to increase, so that a gloss difference tends to occur on the front and back surfaces of the recording medium 302.

The same can be considered not only when the temperature of the second opposing roller 402 is high, but also when the temperature of the first opposing roller 200 is high. That is, in double-sided printing, when the recording medium 302 passes through the first fixing portion 50 again, the toner image 301b is deformed in a state where the temperature of the toner image 301b on the second main surface 302b exceeds Tm. Cheap.

Therefore, when the recording medium 302 passes through the first fixing portion 50 again, the unevenness of the toner image 301b already applied is smoothed by the first opposed roller 200 whose surface roughness is smaller than that of the roughness roller 401. Will be. As a result, a gloss difference is generated between the first surface and the second surface.

<Effect of suppressing gloss difference by cooling>
FIG. 9 is a schematic view of the fixing device 1 for explaining the effect of suppressing the difference in gloss. The nip width region of the first nip portion N1 in the transport direction DR1 is R1, and the nip width region of the second nip portion N2 in the transport direction DR1 is R3. The region between the first fixing portion 50 and the second fixing portion 400 in the transport direction DR1 is defined as R2.

FIG. 10 shows changes in the temperature of the toner image 301a on the first main surface 302a and the temperature of the toner image 301b on the second main surface 302b when the first cooling unit 501 and the second cooling unit 502 are not operated. It is a graph which shows. The horizontal axis of FIG. 10 indicates the transport time of the recording medium 302. The vertical axis of FIG. 10 shows the temperatures of the toner images 301a and 301b.

The solid line graph A in FIG. 10 is the temperature of the toner image 301a. The dotted line graph B in FIG. 10 is the temperature of the toner image 301b. R1, R2, and R3 in FIG. 10 correspond to R1, R2, and R3 in FIG. In FIG. 10, the toner softening temperature Tm is shown.

When the recording medium 302 passes through the first fixing portion 50 in the region R1, the temperature of the toner image 301a that receives heat directly from the heating portion 100 rises significantly between the regions R1. Also in the toner image 301b on the second main surface 302b, heat is transferred from the heating unit 100 to the second main surface 302b, and the temperature of the toner image 301b rises between the regions R1.

At this time, the temperature T3 of the toner image 301b immediately after the recording medium 302 passes through the first nip portion N1 (t3 in FIG. 10) is T3> Tm in relation to the toner softening temperature Tm. The fact that T3> Tm means that the toner image 301b may be easily deformed in the nip width region R1 of the first nip portion N1, and has already been imparted by the first opposed roller 200. The unevenness of the toner image 301b may be leveled.

In the region R2, the heat of the toner image 301a on the first main surface 302a is transferred to the toner image 301b on the second main surface 302b, and the temperature of the toner image 301a gradually decreases. On the other hand, the temperature of the toner image 301b rises accordingly.

As a result, the relationship between the temperatures T2 and Tm of the toner image 301b before entering the second fixing portion 400 (t2 in FIG. 10) is T2> Tm. When T2> Tm, the toner image 301b that has already been fixed is easily deformed in front of the second nip portion N2, and the unevenness is leveled by the second opposed roller 402.

FIG. 11 is a graph showing changes in the temperature of the toner image 301a on the first main surface 302a and the temperature of the toner image 301b on the second main surface 302b when only the first cooling unit 501 is operated. The explanations of the solid line graph A, the dotted line graph B, and the like in FIG. 11 are the same as those in FIG.

In the region R1, heat is transferred from the heating unit 100 to the toner image 301b as in FIG. 10, but since the first opposing roller 200 is cooled by the first cooling unit 501, the temperature of the toner image 301b is shown in FIG. It rises more slowly than in the case. As a result, T3 <Tm.

The fact that T3 <Tm means that the toner image 301b is not easily deformed in the nip width region R1, and even if the second main surface 302b is pressed by the first opposing roller 200, the toner image 301b The unevenness already given to the toner is not leveled.

In the region R2, the temperature of the toner image 301a decreases and the temperature of the toner image 301b increases as in the case shown in FIG. The relationship between the temperature T2 and Tm of the toner image 301b before entering the second fixing portion 400 (t2 in FIG. 10) is T2> Tm.

When T2> Tm, the toner image 301b that has already been fixed is easily deformed in front of the second nip portion N2, and the unevenness is leveled by the second opposed roller 402.

FIG. 12 shows changes in the temperature of the toner image 301a on the first main surface 302a and the temperature of the toner image 301b on the second main surface 302b when the first cooling unit 501 and the second cooling unit 502 are operated. It is a graph which shows. The explanations of the solid line graph A, the dotted line graph B, and the like in FIG. 12 are the same as those in FIG. 10, and will be omitted.

In the region R1, the temperature of the toner image 301 on the second main surface 302b gradually rises because the first opposed roller 200 is cooled by the first cooling unit 501 as in FIG. 11. As a result, T3 <Tm.

In the region R2, the temperature of the toner image 301a decreases and the temperature of the toner image 301b increases as in the case shown in FIG. 11, but the second cooling unit 502 operates to cool the second main surface 302b side. Therefore, the temperature rise of the toner image 301b is slower than that in the case of FIG. As a result, T2 <Tm.

When T3 <Tm and T2 <Tm, the unevenness of the toner image 301b is not leveled by the first opposing roller 200 and the second opposing roller 402, so that the difference in gloss between the front and back surfaces of the recording medium 302 is suppressed. To be done.

The first cooling unit 501 so that the relationship between the temperature T5 of the toner image 301b fixed on the second main surface 302b immediately before the recording medium 302 enters the first nip portion N1 and Tm is T5 <Tm. And it is preferable that the second cooling unit 502 is controlled.

By satisfying T5 <Tm, it is possible to reliably suppress the unevenness of the toner image 301b from being leveled by the first opposed roller 200.

The first cooling unit 501 so that the relationship between the temperature T4 of the toner image 301b fixed on the second main surface 302b immediately after the recording medium 302 passes through the second nip portion N2 and Tm is T4 <Tm. And it is more preferable that the second cooling unit 502 is controlled.

By satisfying T4 <Tm, it is possible to reliably suppress the unevenness of the toner image 301b from being leveled by the second opposed roller 402. Therefore, it is possible to reliably suppress the difference in gloss between the front and back surfaces of the recording medium 302 in double-sided printing.

(Gloss difference suppression control flow by cooling)
As described above, by operating the first cooling unit 501 and the second cooling unit 502 during double-sided printing, T2 <Tm and T3 <Tm can be set, and the gloss difference between the front and back surfaces of the recording medium 302. Can be suppressed. The control method for suppressing the gloss difference will be described below.

FIG. 13 is a flowchart of the gloss difference suppression control according to the first embodiment. In the gloss difference suppression control of the first embodiment, first, in step S101, the control unit 700 receives data on the number of continuous prints from the image formation control unit 650 and data on a predetermined number of sheets stored in the memory 93 (for example, 20 sheets). ), It is determined whether or not a predetermined number or more of recording media 302 are continuously printed.

When the control unit 700 determines that a predetermined number or more of the recording media 302 are not continuously printed (NO in step S101), the control is terminated (finished). When the control unit 700 determines that a predetermined number or more of the recording media 302 are continuously printed (YES in step S101), the process proceeds to step S102.

In step S102, the control unit 700 determines, based on the data from the image formation control unit 650, whether or not there is a double-sided printing of the recording media 302 after the predetermined number of sheets. When the control unit 700 determines that there is no recording medium 302 for double-sided printing after the predetermined number of sheets (NO in step S102), the control ends (end). If the control unit 700 determines that there is a double-sided printing recording medium 302 after the predetermined number of sheets (YES in step S102), the process proceeds to step S103.

In step S103, the control unit 700 determines whether or not a predetermined number of printing media 302 has been printed based on a predetermined number of data stored in the memory 93. The determination in step S103 is repeated until a predetermined number of recording media 302 are printed. When the control unit 700 determines that the recording medium 302 has printed a predetermined number of sheets (YES in step S103), the process proceeds to step S104.

After a predetermined number of recording media 302 are printed, in step S104, it is determined whether or not the recording medium 302 to be printed next is double-sided printing based on the print data by the image formation control unit 650. The determination in step S104 is repeated until the recording medium 302 for double-sided printing is printed. If it is determined that double-sided printing is performed on the recording medium 302 (YES in step S104), the process proceeds to step S105.

In step S105, it is determined whether or not to print on the second surface of the recording medium 302. The determination in step S105 is repeated until printing is performed on the second surface of the recording medium 302.

When printing is performed on the second surface of the recording medium 302 (YES in step S105), in step S106, the control unit 700 operates the first cooling unit 501 and the second cooling unit 502.

By operating the first cooling unit 501 and the second cooling unit 502, T2 <Tm and T3 <Tm can be satisfied as described with reference to FIGS. 9 to 12. Thereby, in the case of double-sided printing, it is possible to suppress the difference in gloss between the front and back surfaces of the recording medium 302.

In the case of continuous printing, heat is transferred from the recording medium 302 to the first opposing roller 200 and the second opposing roller 402, and the temperature rises. Therefore, the difference in gloss between the front and back surfaces of the recording medium 302 during double-sided printing is particularly large. It is more likely to occur.

By configuring the first cooling unit 501 and the second cooling unit 502 to operate only when double-sided printing is performed after continuous printing of a predetermined number of sheets or more, power consumption can be suppressed.

Further, by operating the first cooling unit 501 and the second cooling unit 502 only when printing on the second surface of the recording medium 302 in double-sided printing, when printing on the first surface in double-sided printing, the second surface is printed. Since the main surface 302b side is not cooled, T1> Tm can be reliably set.

Next, in step S107, the control unit 700 determines whether or not the recording medium 302 for double-sided printing still remains based on the data of the recording medium 302 for continuous printing from the image formation control unit 650.

If the recording medium 302 for double-sided printing still remains (YES in step S107), the process returns to step S104 again. If the recording medium 302 for double-sided printing does not remain, the control is terminated (finished).

(Embodiment 2)
FIG. 14 is a flowchart of the gloss difference suppression control according to the second embodiment. Unlike the gloss difference suppression control of the second embodiment, there is no step S105, and the control unit 700 operates the first cooling unit 501 and the second cooling unit 502 from the time of printing on the first surface of the recording medium 302 in double-sided printing. Let me. Thereby, T2 <Tm and T3 <Tm can be surely satisfied. Therefore, in the case of double-sided printing, the difference in gloss between the front and back surfaces of the recording medium 302 can be reliably suppressed.

(Embodiment 3)
FIG. 15 is a flowchart of the gloss difference suppression control according to the third embodiment. In the gloss difference suppression control of the third embodiment, first, in step S201, the control unit 700 determines whether or not there is a recording medium 302 to be printed on both sides based on the data related to printing from the image formation control unit 650. ..

When the control unit 700 determines that there is no recording medium 302 for double-sided printing (NO in step S201), the control ends (end). When the control unit 700 determines that there is a recording medium 302 for double-sided printing (YES in step S201), the process proceeds to step S202.

In step S202, it is determined whether or not the recording medium 302 is double-sided printing. The determination in step S202 is repeated until the double-sided printing recording medium 302 is printed. Based on the print data by the image formation control unit 650, it is determined whether or not the recording medium 302 is double-sided printing.

When the recording medium 302 is printed on both sides (YES in step S202), in step S203, based on the data of T5 from the fifth temperature detection unit 605 and the data of the toner softening temperature Tm stored in the memory 93. , T5> Tm is determined. If T5> Tm is not satisfied (NO in step S203), the process proceeds to step S204.

In step S204, it is determined whether or not T3> Tm is satisfied based on the data of T3 from the third temperature detection unit 603 and the data of the toner softening temperature Tm stored in the memory 93. If T3> Tm is not satisfied (NO in step S204), the process proceeds to step S205.

In step S205, it is determined whether or not T2> Tm is satisfied based on the data of T2 from the second temperature detection unit 602 and the data of the toner softening temperature Tm stored in the memory 93. If T2> Tm is not satisfied (NO in step S205), the process proceeds to step S206.

In step S206, it is determined whether or not T4> Tm is satisfied based on the data of T4 from the fourth temperature detection unit 604 and the data of the toner softening temperature Tm stored in the memory 93. If T4> Tm is not satisfied (NO in step S206), the process ends (end).

If YES in step S203, step S204, step S205, and step S206, respectively, the control unit 700 operates the first cooling unit 501 and the second cooling unit 502.

When any of T2, T3, T4, and T5 exceeds Tm, the first cooling unit 501 and the second cooling unit 502 are operated to perform double-sided printing on the recording medium 302 or then double-sided printing. It is possible to suppress the difference in gloss between the front and back surfaces of the recording medium 302. By operating the first cooling unit 501 and the second cooling unit 502 when the gloss difference begins to occur, power consumption can be suppressed.

For example, the second cooling unit 502 may be operated when T2 = Tm-5 ° C., and the first cooling unit 501 may be operated when T3 = Tm-5 ° C. By controlling in this way, it is possible to prevent the occurrence of a gloss difference between the front and back surfaces of the recording medium 302 in advance.

(Embodiment 4)
FIG. 16 is a schematic view showing the fixing device 1 of the fourth embodiment. The fixing device 1 of the fourth embodiment further includes a third cooling unit 506. When operating the first cooling unit 501 and the second cooling unit 502, the third cooling unit 506 may be operated together with the first cooling unit 501 and the second cooling unit 502.

The third cooling unit 506 is, for example, a fan, and is composed of a blower that outputs (blows) air α. Adjust the cooling function by lowering the temperature of the air or changing the strength of the air. The third cooling unit 506 blows air α to cool the second opposed roller 402 from the surface.

By further providing the third cooling unit 506, T2 <Tm and T3 <Tm can be reliably satisfied, so that the gloss difference between the front and back surfaces of the recording medium can be more reliably suppressed in the case of double-sided printing. ..

(Embodiment 5)
FIG. 17 is a schematic view showing the fixing device 1 of the fifth embodiment. The second cooling unit 502 of the fifth embodiment has a heat pipe 503, a cooling belt 504, and a cooling roller 505. The cooling roller 505 stretches the cooling belt 504.

The heat pipe 503 cools the cooling belt 504. The cooling belt 504 conveys the recording medium 302 between the first fixing portion 50 and the second fixing portion 400. The cooling belt 504 cools the recording medium 302 at the same time while conveying it.

Hereinafter, examples will be described. Image forming devices with different cooling functions and types of cooling units are prepared as examples and comparative examples, and high-quality paper (Konica Minolta CF paper) is used for each image forming device to reduce gloss by a roughness roller. The effect and the difference in gloss on both sides of the recording medium were evaluated.

<Implementation conditions>
(Toner manufacturing method)
[Production Example 1 of Resin Dispersion Liquid]
85 parts by mass of terephthalic acid, 6 parts by mass of trimellitic acid, and 250 parts by mass of bisphenol A propylene oxide adduct were placed in a reaction vessel equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas introduction tube, and the inside of the reaction vessel was dried. After replacement with nitrogen gas, 0.1 part by mass of titanium tetrabutoxide was added, and a stirring reaction was carried out at about 180 ° C. for 8 hours under a nitrogen gas stream.

Further, 0.2 parts by mass of titanium tetrabutoxide was added to raise the temperature to about 220 ° C., and the stirring reaction was carried out for 6 hours. Then, the inside of the reaction vessel was reduced to 10 mmHg, and the reaction was carried out under reduced pressure to obtain a polyester resin [ A1] was obtained.

The glass transition point (Tg) of the polyester resin [A1] was 59 ° C., and the weight average molecular weight (Mw) was 9,000. 200 parts by mass of amorphous polyester resin [A1] is dissolved in 200 parts by mass of ethyl acetate, and while stirring this solution, the concentration of sodium polyoxyethylene lauryl ether sulfate in 800 parts by mass of ion-exchanged water becomes 1% by mass. The dissolved aqueous solution was slowly added dropwise.

After removing ethyl acetate from this solution under reduced pressure, the pH was adjusted to 8.5 with ammonia. Then, the solid content concentration was adjusted to 20% by mass. As a result, a dispersion liquid of the fine particles of the amorphous polyester resin [A1] in which the fine particles of the polyester resin [A1] were dispersed in the aqueous medium was prepared.

[Production Example 2 of Resin Dispersion Liquid]
After 315 parts by mass of dodecane diic acid and 220 parts by mass of 1,6-hexanediol were placed in a reaction vessel equipped with a stirrer, a thermometer, a cooling tube and a nitrogen gas introduction tube, the inside of the reaction vessel was replaced with dry nitrogen gas. , 0.1 part by mass of titanium tetrabutoxide was added, and a stirring reaction was carried out at about 180 ° C. for 8 hours under a nitrogen gas stream.

Further, 0.2 part by mass of titanium tetrabutoxide was added, the temperature was raised to about 220 ° C., and the stirring reaction was carried out for 6 hours. Then, the inside of the reaction vessel was reduced to 10 mmHg, and the reaction was carried out under reduced pressure to obtain the polyester resin [B1]. Obtained.

The melting point (Tm) of the polyester resin [B1] was 72 ° C., and the weight average molecular weight (Mw) was 14,000.

[Example of adjusting wax dispersion]
200 parts by mass of Fischer-Tropsch wax "FNP-0090" (manufactured by Nippon Seiro Co., Ltd., melting point 89 ° C.) was heated to 95 ° C. and melted. This was further added to an aqueous surfactant solution dissolved in 800 parts by mass of ion-exchanged water so that sodium alkyldiphenyl ether disulfonate had a concentration of 3% by mass, and then dispersion treatment was performed using an ultrasonic homogenizer.

The solid content concentration was adjusted to 20% by mass. As a result, a wax dispersion liquid in which fine particles of wax were dispersed in an aqueous medium was prepared.

[Toner manufacturing example 1]
300 parts by mass of polyester resin [A1] dispersion, 100 parts by mass of polyester resin [B1] dispersion, 77.3 parts by mass of wax dispersion, 41.3 parts by mass of colorant dispersion, 225 parts by mass of ion-exchanged water and polyoxy. 2.5 parts by mass of ethylene lauryl ether sodium sulfate was put into a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, and 0.1 N hydrochloric acid was added while stirring to adjust the pH to 2.5.

Next, 0.3 parts by mass of a polyaluminum chloride aqueous solution (10% aqueous solution in terms of AlCl3) was added dropwise over 10 minutes, and then the internal temperature was raised to 60 ° C. with stirring. Further gradually raise the temperature to 75 ° C., maintain the internal temperature at 75 ° C., measure with a Coulter counter, and when the average particle size reaches the 6 μm level, 3-hydroxy-2,2'-iminodicosuccinic acid 4 When 2 parts by mass of an aqueous sodium solution (40% aqueous solution) was added to stop the particle size growth, the internal temperature was raised to 85 ° C., and the shape coefficient reached 0.96 using "FPIA-2000", the temperature was 10 ° C. It was cooled to room temperature at a rate of / min. The reaction solution was repeatedly filtered and washed, and then dried to obtain toner particles [1].

In the obtained toner particles [1], hydrophobic silica (number average primary particle diameter = 12 nm, degree of hydrophobicity = 68) 1% by mass and hydrophobic titanium oxide (number average primary particle diameter = 20 nm, degree of hydrophobicity = 63) ) 1% by mass was added, mixed with a "Henschel mixer" (manufactured by Mitsui Miike Kakoki Co., Ltd.), and then coarse particles were removed using a sieve with a 45 μm opening to obtain a toner [1]. .. The volume-based median diameter of the toner [1] was 6.10 μm, and the average circularity was 0.965.

(First fixing portion 50 and second fixing portion 400)
A heater was used as a heat source. The heat transfer belt had a silicone rubber layer on a polyimide substrate, and the surface was coated with PFA. The thickness of the silicone rubber layer was 220 μm, the rubber hardness was 20 °, the thickness of the PFA layer was 30 μm, and the MD-1 hardness (typeC) of the heat transfer belt was 85 °. The peripheral length of the heat transfer belt was 120 mm.

The outer diameter of the heating roller was 60 mm. The hardness of the elastic layer of the heating roller was 10 degrees, and the thickness of the elastic layer in the radial direction was 20 mm.

The outer diameter of the first opposed roller was 60 mm. The radial thickness of the elastic layer of the first opposed roller was 5 mm. The hardness of the elastic layer was 10 degrees. The rubber was coated with silicone rubber and the surface was coated with PFA resin. The set temperature was 80 ° C. and the set load was 2000 N.

The outer diameter of the roughness roller was 30 mm. The thickness of the rubber layer of the roughness roller was 10 mm, and the rubber hardness was 10 °. The rubber was silicone rubber, and the surface was coated with PFA resin. The surface PFA was blasted to give a roughness of Rz = 3 μm.

The outer diameter of the second opposed roller was 30 mm. The thickness of the rubber layer of the second opposing roller was 2 mm. The rubber hardness was 10 °. The rubber was silicone rubber, and the surface was coated with PFA resin.

The amount of toner adhered was 8 g / m ² . The toner softening temperature was Tm = 70 ° C. As the toner, the toner [1] obtained by the production method described above was used.

(Cooling part)
Except for the image forming apparatus in Example 2, the fixing apparatus of the first embodiment was used. The first cooling unit, the second cooling unit, and the third cooling unit were fans, and the temperature of the air was room temperature.

As the image forming apparatus 1501 in the second embodiment, the fixing apparatus 1 of the fifth embodiment was used. The first cooling unit 501 and the third cooling unit 506 were fans, and the temperature of the air was room temperature. The second cooling unit 502 cooled the recording medium 302 while conveying the recording medium 302 by the cooling belt 504 cooled to the heat pipe 503.

(T1 to T4)
The transport speed of the recording medium was 300 mm / sec. T1 was the temperature of the toner image fixed on the first main surface at a position 0.05 s before the recording medium rushed into the second nip portion (a position 15 mm before the second nip portion). T2 was the temperature of the toner image fixed on the second main surface at a position 0.05 s before the recording medium rushed into the second nip portion (a position 15 mm before the second nip portion).

T3 is the temperature of the toner image fixed on the second main surface at the position 0.05 s after the recording medium passes through the first nip portion (the position 15 mm after the first nip portion). T4 is the temperature of the toner image fixed on the second main surface at the position 0.05 s after the recording medium passes through the second nip portion (the position 15 mm after the second nip portion).

<Example 1>
After 100 sheets were continuously printed, double-sided printing was performed. The set temperature of the heater in the first fixing portion 50 was set to 180 ° C. The first cooling unit 501 and the second cooling unit 502 were operated. No heat source was provided in the second fixing portion 400. The pressing force at the second fixing portion 400 was 100 kPa. The distance between the first fixing portion 50 and the second fixing portion 400 was 150 mm.

<Example 2>
Unlike the first embodiment, a heat pipe 503, a cooling belt 504, and a cooling roller 505 were used for the second cooling unit 502. The temperature of the cooling belt 504 was 20 ° C. Other conditions were the same as in Example 1.

<Example 3>
Unlike the first embodiment, the set temperature of the heater in the first fixing unit 50 was set to 200 ° C., and the third cooling unit 506 was operated in addition to the first cooling unit 501 and the second cooling unit 502. Other conditions are the same as in Example 1.

<Comparative example 1>
Unlike the third embodiment, the first cooling unit, the second cooling unit, and the third cooling unit were not operated. Other conditions were the same as in Example 3.

<Comparative example 2>
Unlike Comparative Example 1, only the first cooling unit was operated. Other conditions were the same as in Comparative Example 1.

<Comparative example 3>
Unlike Example 3, double-sided printing was performed from the beginning. The first cooling unit and the second cooling unit were operated. The distance between the first fixing portion and the second fixing portion was 300 mm. Other conditions were the same as in Example 3.

<Evaluation method of glossiness>
The glossiness of the recording medium was measured using a glossiness meter (GMX-203, manufactured by Murakami Color Co., Ltd., measurement angle 75 °). The roughness roller exerts a gloss reducing effect, and when the glossiness is less than 40, it is evaluated as "good", when it is 40 or more and less than 50, it is evaluated as "OK", and when it is 50 or more, it is evaluated as "impossible". Those with "OK" or higher are considered to have exhibited the effect of reducing the gloss of the roughness roller.

In double-sided printing, the case where the difference in glossiness between the front and back surfaces of the recording medium was less than 5 was evaluated as "good", 5 or more and less than 10 was evaluated as "possible", and 10 or more was evaluated as "impossible". Those with "OK" or higher are considered to have the effect of suppressing the difference in gloss.

<Evaluation result>
FIG. 18 is a table showing the evaluation results in each Example and each Comparative Example. In Examples 1 to 3, since T1> Tm, the toner image 301 before entering the second nip portion N2 is in a state of being easily deformed. Therefore, the roughness roller 401 tends to give unevenness to the toner image 301, and the evaluation result of the glossiness reducing effect is “good”.

Further, in Examples 1 to 3, at least the first cooling unit 501 and the second cooling unit 502 are operating, so that Tm> T2, Tm> T3, and Tm> T4 are satisfied. As a result, during double-sided printing, the unevenness of the toner image 301b that has already been imparted is not smoothed by the first opposing roller 200 and the second opposing roller 402, and the difference in gloss between the front and back surfaces of the recording medium is increased. The result did not occur.

Comparing Comparative Example 1 and Example 3, since Comparative Example 1 did not operate the first cooling unit, the second cooling unit, and the third cooling unit, T3> Tm and T2> Tm. There was a difference in gloss on the front and back of the recording medium, and it became "impossible". Even when only the first cooling unit is operated as in Comparative Example 2, T3 <Tm is satisfied, but since T2> Tm and T4> Tm, a gloss difference occurs on both sides, which is "impossible". It became.

In the case of double-sided printing without continuous printing as in Comparative Example 3, when the first cooling unit and the second cooling unit are operated, Tm> T2, Tm> T3, and Tm> T4 are satisfied, and both sides are satisfied. The result was that there was no difference in gloss.

However, when double-sided printing is performed before continuous printing, the heated portion is not yet sufficiently heated, and in Comparative Example 3, the distance between the first fixing portion and the second fixing portion is the third embodiment. Since it is twice as large as (300 mm), it is cooled during the time (1 sec) of being conveyed between the first fixing portion and the second fixing portion, and T1 <Tm, which is the effect of reducing the glossiness by the roughness roller. The evaluation result of was "impossible".

In order to impart unevenness by the roughness roller 401, it is necessary to satisfy T1> Tm in relation to the toner softening temperature Tm. In particular, when the heat source is not provided in the second fixing portion 400, the recording medium 302 is cooled while passing between the first fixing portion 50 and the second fixing portion 400, and does not satisfy T1> Tm. There is.

From the results of Example 3 and Comparative Example 3, the time from when the recording medium 302 passes through the first nip portion N1 to when it enters the second nip portion N2 is 0.5 seconds (= 150 [mm] / It is preferably 300 [mm / sec]) or less. T1> Tm can be satisfied by appropriately setting the time from when the recording medium passes through the first nip portion to when it enters the second nip portion.

As a result, the toner image 301a can be reliably provided with irregularities in the second fixing portion 400. Therefore, the glossiness of the recording medium 302 can be controlled.

Since the second fixing portion 400 is not provided with a heat source, the temperature of the toner image 301b on the second main surface 302b is less likely to rise when printing the second side in double-sided printing. Therefore, Tm> T2 and Tm> T3 can be reliably satisfied. Therefore, the difference in gloss between the front and back surfaces of the recording medium 302 is suppressed.

On the other hand, a heat source may be provided in the second fixing portion 400 as needed. As a result, T1> Tm can be reliably satisfied, and unevenness can be reliably imparted by the toner image 301a.

In the first to fifth embodiments, the pressing force of the second opposed roller 402 on the roughness roller 401 can be adjusted by the pressing force adjusting unit 410. When printing on the second side of the recording medium 302 in double-sided printing, by reducing the pressing force of the second opposed roller 402 on the roughness roller 401, it is possible to suppress the occurrence of a gloss difference between the front and back surfaces of the recording medium 302. You can also do it.

Although the image forming apparatus 1501 that employs the intermediate transfer method has been described in the first to fifth embodiments, it can also be applied to an image forming apparatus that employs the direct transfer method.

It should be considered that the embodiments and examples disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 fixing device, 50 first fixing part, 100 heating roller, 104 heat source (heater), 200 first opposed roller, 301a, 301b toner image, 302 recording medium, 302a first main surface, 302b second main surface, 400 2nd fixing part, 401 Roughness roller, 402 2nd opposed roller, 501 1st cooling part, 502 2nd cooling part, 506 3rd cooling part, 601 1st temperature detecting part, 602th 2 temperature detection unit, 603 third temperature detection unit, 604 fourth temperature detection unit, 605 fifth temperature detection unit, 700 control unit, 1501 image forming apparatus, N1 first nip unit, N2 second Nip part, c transport path.

Claims (12)

The first fixing part that fixes the toner image on the recording medium,
A second fixing portion arranged on the downstream side of the recording medium in the transport direction with respect to the first fixing portion,
The first fixing portion includes a heating portion having a heat source and a first opposing roller that faces the heating portion and forms a first nip portion.
The second fixing portion includes a roughness roller and a second opposing roller that faces the roughness roller and forms a second nip portion.
The recording medium has a first main surface in contact with the heating portion and a second main surface in contact with the first opposed roller.
The roughness roller has a larger surface roughness than the second opposed roller, and imparts unevenness to the toner image fixed on the first main surface.
A first cooling unit that cools the first opposed roller, and
A second cooling unit that cools the second main surface side of the recording medium between the time when the recording medium passes through the first fixing portion and the time when the recording medium enters the second fixing portion.
A control unit that controls the operation of the first cooling unit and the second cooling unit is provided.
When the softening temperature of the toner is Tm and the temperature of the toner image fixed on the first main surface immediately before the recording medium rushes into the second nip portion is T1, T1> Tm is satisfied.
The temperature of the toner image fixed on the second main surface immediately after the recording medium passes through the first nip portion is set to T3, and the temperature of the second main immediately before the recording medium enters the second nip portion. When the temperature of the toner image fixed on the surface is T2, the control unit controls the first cooling unit and the second cooling unit so that T2 <Tm and T3 <Tm. Device. The image forming apparatus according to claim 1, wherein the first cooling unit and the second cooling unit are fans. When the temperature of the toner image fixed on the second main surface immediately after the recording medium passes through the second nip portion is T4, the control unit has the first control unit so that T4 <Tm. The image forming apparatus according to claim 1 or 2, which controls the cooling unit and the second cooling unit. Any one of claims 1 to 3, where T5 <Tm is satisfied, where T5 is the temperature of the toner image fixed on the second main surface immediately before the recording medium rushes into the first nip portion. The image forming apparatus according to item 1. The image forming apparatus according to any one of claims 1 to 4, further comprising a third cooling unit for cooling the second opposed roller. The control unit operates the first cooling unit and the second cooling unit when a predetermined number or more of recording media are continuously printed, according to any one of claims 1 to 5. Image forming device. The image forming apparatus according to any one of claims 1 to 6, wherein no heat source is provided in the second fixing portion. The method according to any one of claims 1 to 7, wherein the time from when the recording medium passes through the first nip portion to when the recording medium enters the second nip portion is 0.5 seconds or less. Image forming device. The control unit operates any one of claims 1 to 8 when either the T2 or the T3 exceeds the Tm to operate the first cooling unit and the second cooling unit. The image forming apparatus according to. The image forming apparatus according to any one of claims 1 to 9, wherein the control unit can adjust the pressing force of the second opposed roller onto the roughness roller. The control unit operates the first cooling unit and the second cooling unit only when printing on the second surface of the recording medium in double-sided printing, according to any one of claims 1 to 10. Image forming device. The one according to any one of claims 1 to 10, wherein the control unit operates the first cooling unit and the second cooling unit from the time of printing on the first surface of the recording medium in double-sided printing. Image forming device.

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