Imaging device

An imaging system includes a heating device, a conveyor belt including a surface layer located on an outer surface of the heating device to receive a printing medium, and a cooling device to cool the surface layer after the conveyor belt passes along the outer surface of the heating device. The surface layer includes a temperature sensitive material to vary an adhesive force of the conveyor belt with respect to the printing medium in response to a change in temperature of the surface layer. The adhesive force increases in response to an increase in temperature of the surface layer.

BACKGROUND

A printing device includes an endless belt which conveys a printing medium, a heating roll which heats the endless belt, and a pressing roll which presses the endless belt against the heating roll. The printing medium which is conveyed onto the endless belt is heated and pressed while passing between the heating roll and the pressing roll.

DETAILED DESCRIPTION

In the following description, with reference to the drawings, the same reference numbers are assigned to the same components or to similar components having the same function, and overlapping description is omitted. In some cases, drawings may be drawn in a simplified or exaggerated manner for the sake of clarity of example.

As illustrated inFIG. 1, an example imaging system1forms a color image by using magenta, yellow, cyan, and black colors. The imaging system1may include an imaging apparatus or a gloss control device. Additionally, the imaging system1may be a printer or a component of an imaging system. For example, the imaging system1may comprise a developing device used in an imaging system or the like. The imaging system1includes, for example, a recording medium conveying device10, a plurality of developing devices20, a transfer device30, a plurality of photosensitive bodies40, a fixing device50, and a gloss control device60. The recording medium conveying device10conveys a printing medium P, such as a sheet. The photosensitive body40forms an electrostatic latent image and the developing device20develops the electrostatic latent image. The transfer device30secondarily transfers a toner image onto the printing medium P. For example, the fixing device50fixes the toner image onto the printing medium P and the gloss control device60controls the gloss of the toner image. In some examples, the fixing device50may be a primary fixing device which performs a first fixing operation of the printing medium P and the gloss control device60may be a secondary fixing device which performs a second fixing operation of the printing medium P.

The example recording medium conveying device10includes a feeding roller11which conveys the printing medium P having an image formed thereon along a conveying route R1. The printing medium P is stacked and accommodated in a cassette C and is picked up and conveyed by the feeding roller11. The feeding roller11is provided, for example, in the vicinity of the outlet of the printing medium P of the cassette C. The recording medium conveying device10allows the printing medium P to reach a secondary transfer region R2through the conveying route R1at a timing in which the toner image transferred onto the printing medium P reaches the secondary transfer region R2.

In some examples, a separate developing device20may be provided for each color. Each developing device20includes a developing roller21which carries toner on the photosensitive body40. In the developing device20, toner and carrier may be adjusted so as to realize a predetermined mixing ratio and the toner is uniformly dispersed by mixing the toner and the carrier. A developing agent is carried on the developing roller21. The developing roller21rotates so that the developing agent is conveyed to a region facing the photosensitive body40. Then, the toner in the developing agent carried on the developing roller21moves to the electrostatic latent image of the photosensitive body40so that the electrostatic latent image is developed.

The transfer device30may convey the toner image formed by the developing device20and the photosensitive body40to the secondary transfer region R2. For example, an image developed on the photosensitive body40is transferred onto the transfer device30. In some examples, the transfer device30includes a transfer belt31, suspension rollers32a,32b,32c, and32d, a primary transfer roller33, and a secondary transfer roller34. The transfer belt31may be suspended by the suspension rollers32a,32b,32c, and32d. Additionally, a separate primary transfer roller33may be provided for each color. Each primary transfer roller33sandwiches the transfer belt31along with each photosensitive body40. The secondary transfer roller34sandwiches the transfer belt31along with the suspension roller32d.

The transfer belt31may include an endless belt which moves in a circulating manner by the suspension rollers32a,32b,32c, and32d. The primary transfer roller33presses the photosensitive body40from the inner peripheral side of the transfer belt31. The secondary transfer roller34presses the suspension roller32dfrom the outer peripheral side of the transfer belt31. In some examples, the photosensitive body40includes a photosensitive drum that is provided for each color. The plurality of photosensitive bodies40are arranged in series along the movement direction of the transfer belt31. A developing device20, an exposure unit41, a charging device42, and a cleaning device43are provided at a facing position of the outer peripheral surface of each photosensitive body40.

The example imaging system1may include a process cartridge2in which the developing device20, the photosensitive body40, the charging device42, and the cleaning device43are integrally provided. Additionally, the imaging system1may include an apparatus body3to and from which the process cartridge2is attached and detached. The process cartridge2is attachable to or detachable from the apparatus body3in such a manner that a door of the apparatus body3is opened and the process cartridge2is inserted into or extracted from the apparatus body3.

In some examples, the charging device42uniformly charges the outer peripheral surface of the photosensitive body40to a predetermined potential. The charging device42may include a charging roller that rotates to follow the rotation of the photosensitive body40. The exposure unit41exposes the outer peripheral surface of the photosensitive body40charged by the charging device42in response to the image formed on the printing medium P. A potential of a portion exposed by the exposure unit41on the outer peripheral surface of the photosensitive body40changes and hence an electrostatic latent image is formed on the outer peripheral surface of the photosensitive body40.

In some examples, toner tanks25are disposed in the plurality of developing devices20so as to face each other. For example, magenta, yellow, cyan, and black toners are accommodated in the respective toner tanks25. Toner is supplied from each toner tank25to each developing device20. Each developing device20develops an electrostatic latent image by the supplied toner and forms a toner image on the outer peripheral surface of the photosensitive body40. The toner image formed on the outer peripheral surface of the photosensitive body40is initially transferred onto the transfer belt31and the toner remaining on the outer peripheral surface of the photosensitive body40after the toner image is transferred is removed by the cleaning device43.

The fixing device50fixes, for example, the toner image secondarily transferred from the transfer belt31onto the printing medium P onto the printing medium P. As an example, the fixing device50includes a heating roller51which heats the printing medium P and fixes the toner image onto the printing medium P and a pressing roller52which presses the heating roller51. One or both of the heating roller51and the pressing roller52may be formed in a cylindrical shape.

A heat source such as a halogen lamp may be provided inside the heating roller51. Furthermore, a heat source such as a halogen lamp may be provided inside the pressing roller52. A nip portion N1which is a fixing region of the printing medium P is provided between the heating roller51and the pressing roller52. When the printing medium P passes through the nip portion N1, the toner image is melted and fixed onto the printing medium P.

In some examples, the gloss control device60allows the image of the printing medium P to be glossy by smoothing the toner of the printing medium P onto which the toner image is melted and fixed by the fixing device50. The gloss control device60improves the glossiness of the image by melting and pressing fine unevenness of the toner formed on the printing medium P and smoothing the toner. An example configuration of the gloss control device60will be described in further detail later. Furthermore, the imaging system1may include discharge rollers45and46which discharge the printing medium P (of which the gloss of the image is controlled by the gloss control device60) to the outside of the imaging system1.

An example imaging method may comprise a printing process using the imaging system1. For example, when an image signal of a target recording image is input to the imaging system1, the printing medium P stacked in the cassette C is picked up by the rotation of the feeding roller11and the printing medium P is conveyed along the conveying route R1. Then, the charging device42uniformly charges the outer peripheral surface of the photosensitive body40to be a predetermined potential based on the image signal. Additionally, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive body40in such a manner that the exposure unit41irradiates a laser beam onto the outer peripheral surface of the photosensitive body40.

Next, the developing device20performs a developing operation by forming a toner image on the photosensitive body40. For example, the toner image is initially transferred from each photosensitive body40onto the transfer belt31in a region in which each photosensitive body40faces the transfer belt31. The toner images respectively formed on the plurality of photosensitive bodies40may be sequentially laminated on the transfer belt31to form one laminated toner image. The laminated toner image is secondarily transferred onto the printing medium P conveyed from the recording medium conveying device10in the secondary transfer region R2in which the suspension roller32dthe secondary transfer roller34face each other.

The printing medium P onto which the laminated toner image is secondarily transferred is conveyed from the secondary transfer region R2to the fixing device50. For example, the fixing device50melts and fixes the laminated toner image onto the printing medium P by allowing the printing medium P to pass through the nip portion N1while applying a heat and a pressure to the printing medium P. Additionally, the printing medium P onto which the laminated toner image is melted and fixed may be conveyed to the gloss control device60. The gloss control device60smoothes the toner by melting and pressing the toner of the laminated toner image again.

The gloss control device60hardens the toner by cooling the printing medium P having the smoothed laminated toner image. Accordingly, the gloss control device60improves the glossiness of the image of the printing medium P so that the image of the printing medium P becomes close to the photo image. As a result, a high quality image may be obtained. The printing medium P having image quality improved by the gloss control device60is discharged to the outside of the imaging system1by, for example, the discharge rollers45and46.

With reference toFIG. 2, an example gloss control device60will be described in more detail.

As illustrated inFIG. 2, the example gloss control device60includes a conveyor belt61, a heating device62and a support roller63which may include rotation bodies suspending the conveyor belt61. Additionally, the gloss control device60may include a cleaner64which cleans the conveyor belt61, a pressing portion65(which may include a rotating body) pressing the printing medium P, and a cooling device66which cools the conveyor belt61. The heating device62may include a roll-shaped heating roller and the heating device62may include a belt-shaped heating belt. In some examples, the conveyor belt61passes along the outer surface of the heating device62and loads the printing medium P thereon. The conveyor belt61conveys the printing medium P. The heating device62, the support roller63and the cooling device66may be provided inside the conveyor belt61. The cleaner64and the pressing portion65may be provided outside the conveyor belt61.

The heating device62heats the conveyor belt61and generates a high temperature region A1inside the imaging system1. Meanwhile, the cooling device66cools the conveyor belt61and generates a low temperature region A2inside the imaging system1. In some examples, the high temperature region A1may be a region including the heating device62and may include the conveyor belt61heated by the heating device62. The low temperature region A2may be a region including the cooling device66and may include, for example, the support roller63, the cleaner64, and the conveyor belt61cooled by the cooling device66.

The heating device62may include a free belt which is operated by the external power of the gloss control device60. Additionally, a nip portion N2which is a fixing region of the printing medium P may be provided between the heating device62and the pressing portion65. A contact pressure is exerted between the heating device62and the pressing portion65. The nip portion N2is formed by the contact pressure. The nip portion N2may include a re-melting portion which re-melts the toner P1of the printing medium P. When the printing medium P passes through the nip portion N2, the toner P1of the printing medium P is smoothed.

In some examples, the support roller63supports the conveyor belt61from the inside of the conveyor belt61and the conveyor belt61moves in a circulating manner along the outer peripheries of the heating device62and the support roller63. The printing medium P is conveyed along the conveyor belt61and passes along the nip portion N2and the cooling device66. Then, the printing medium P is peeled off from the support roller63and is conveyed to the outside of the gloss control device60. The pressing portion65may be formed as a roll-shaped pressing roll or some other shape. In some examples, the surface hardness of the pressing portion65may be equal to between approximately 45 and 80 in ASKER-C hardness. The heating device62may include, for example, a rigid body, and the surface hardness of the heating device62may be equal to or smaller than the surface hardness of the pressing portion65.

In some examples, the cooling device66may include at least one of a heat sink contacting the opposite side of the printing medium P in the conveyor belt61, and a fan blowing air to the conveyor belt61. Further, the cooling device66may include at least one of a Peltier element and a heat pipe. For example, the cooling device66cools and hardens the toner P1of the printing medium P smoothed while passing through the nip portion N2.

The cleaner64may include a blade which contacts the conveyor belt61in the low temperature region A2. A material of the blade of the cleaner64may include a material, such as felt, that is softer than the conveyor belt61. The cleaner64may be disposed to obliquely extend toward the upstream side of the conveyor belt61from a contact portion64awith respect to the conveyor belt61. In some examples, a configuration of the cleaner64may not include the blade with felt. Instead of, or in addition to, the felt, the cleaner64may include a brush contacting the conveyor belt61.

With reference toFIG. 3, an example configuration of the conveyor belt61and the pressing portion65will be described in further detail.FIG. 3is a diagram illustrating an example layer structure of the conveyor belt61and the pressing portion65. The conveyor belt61may include a base layer61aand a surface layer61band a pressing portion65includes a base layer65a, an intermediate layer65b, and a surface layer65c. Additionally, the surface layer61bmay include a smooth surface61con which the printing medium P is loaded and the smooth surface61cof the surface layer61bmay have a high glossiness. The base layer61ais located at the opposite side of the printing medium P when viewed from the surface layer61b. The base layer65a, the intermediate layer65b, and the surface layer65cmay be arranged in this order from the inside to the outside of the pressing portion65in the radial direction.

The surface layer61bof the conveyor belt61may include a layer which conveys the loaded printing medium P. The surface layer61bincludes a temperature sensitive material of which an adhesive force of the conveyor belt61with respect to the printing medium P changes in response to a change in temperature of the surface layer61b. For example, the adhesive force of the surface layer61bincreases in response to an increase in temperature of the surface layer61b. Additionally, the adhesive force of the surface layer61bmay decrease as the temperature of the surface layer61bdecreases. In some examples, the adhesive force of the surface layer61bin the high temperature region A1increases to a degree in which peeling-off of the printing medium P is suppressed. The adhesive force of the surface layer61bin the low temperature region A2decreases to a degree in which the printing medium P may be peeled off.

In the high temperature region A1in which the adhesive force of the surface layer61bis high, the toner P1having unevenness may be more reliably melted and smoothed by controllably transmitting heat to the printing medium P. Further, in the low temperature region A2in which the adhesive force of the surface layer61bis low, the printing medium P may be smoothly peeled off from the support roller63. Since the adhesive force of the surface layer61bof the conveyor belt61located in the low temperature region A2is low, dirt of residual toner may be easily removed from the surface layer61bby the cleaner64located in the low temperature region A2.

FIG. 4is a graph showing an example relationship between the adhesive force and the temperature of the material of the surface layer of the conveyor belt. InFIG. 4, the solid line indicates the adhesive force and the temperature of the surface layer61bof the conveyor belt61. The dashed line indicates a comparative example different from the surface layer61b. In the case of the conveyor belt of the comparative example, the adhesive force decreases as the temperature of the surface layer increases. In the case of the temperature sensitive material of the surface layer61bof the conveyor belt61, the adhesive force is small as it is close to 0, for example, when the temperature is lower than the temperature threshold value T. However, the adhesive force can be increased when the temperature is equal to or higher than the temperature threshold value T.

In some examples, the adhesive force of the surface layer61bof the high temperature region A1is higher than the adhesive force between the base layer65aand the intermediate layer65b, and higher than the adhesive force between the intermediate layer65band the surface layer65cillustrated inFIG. 3. The adhesive force of the surface layer61bwhen the temperature is equal to or higher than the temperature threshold value T is higher than the stiffness of the printing medium P. Accordingly, the printing medium P may continue to adhere to the conveyor belt61in the high temperature region A1of the outlet of the nip portion N2.

The surface layer61bensures the adhesiveness with respect to the printing medium P when the temperature is equal to or higher than the temperature threshold value T, and allows the printing medium P to be separable when the temperature is lower than the temperature threshold value T. For example, the surface layer61bhas high adhesiveness when the temperature is equal to or higher than the temperature threshold value T and has easy peelability when the temperature is lower than the temperature threshold value T. Additionally, the surface layer61bmay be a temperature sensitive adhesive sheet adhering to the base layer61aof the conveyor belt61. The example conveyor belt61includes the surface layer61bof which the adhesiveness is controlled in a plurality of levels by the control of the temperature. In some examples, the temperature threshold value T is equal to between approximately 35° C. and 45° C.

The temperature sensitive material of the surface layer61bmay include side-chain crystalline resin. For example, the temperature sensitive material of the surface layer61bmay include acrylic resin and/or polystearyl acrylate. In some examples, the surface layer61bcauses a phase transition by using the temperature threshold value T as a boundary. When the temperature is equal to or higher than the temperature threshold value T or the temperature is lower than the temperature threshold value T, the adhesive property of the surface layer61bchanges. In some examples, the temperature sensitive material of the surface layer61bis non-crystallized when the temperature becomes equal to or higher than the temperature threshold value T due to the heating, is crystallized when the temperature is lower than the temperature threshold value T due to the cooling, and performs a phase transition by using the temperature threshold value T as a boundary.

The adhesive property of the temperature sensitive material of the surface layer61bmay change in response to a value above or below the temperature threshold value T. In the high temperature region A1in which the temperature is higher than the temperature threshold value T, the printing medium P is not easily peeled off from the surface layer61bsince the adhesiveness of the surface layer61bincreases. Meanwhile, in the low temperature region A2in which the temperature is lower than the temperature threshold value T, the printing medium P is easily peeled off from the surface layer61bsince the adhesiveness of the surface layer61bis low. Thus, when the toner P1of the printing medium P is melted in the nip portion N2and the temperature of the surface layer61bis equal to or higher than the temperature threshold value T, the printing medium P may continue to be adhered to the conveyor belt61due to the high adhesive force of the surface layer61b.

Additionally, the printing medium P may be smoothly peeled off from the conveyor belt61due to the curvature of the conveyor belt61in the support roller63after the printing medium P is cooled so that the temperature becomes lower than the temperature threshold value T. Since the adhesive property of the temperature sensitive material of the surface layer61bchanges due to the temperature difference inside the gloss control device60, the relationship between the temperature difference inside the gloss control device60and the adhesive force of the temperature sensitive material may be effectively used to control the adhesive force.

As described above, in the example gloss control device60and the imaging system1, the separation of the printing medium P due to the surface layer61bhaving a high adhesive force may be suppressed, since the temperature of the surface layer61bin the nip portion N2and the high temperature region A1in the periphery thereof is equal to or higher than the temperature threshold value T. By improving the heat transmission efficiency to the printing medium P in the nip portion N2, a stable image may be obtained while suppressing the unevenness of the toner P1. Further, the stable image may be obtained with suppressed cooling unevenness and the printing medium P may be smoothly peeled off in the low temperature region A2in which the adhesive force is low.

since the adhesive property of the surface layer61bof the conveyor belt61may be selectively controlled in response to a change in temperature, one or more of the systems and method described herein may be used regardless of the type of the printing medium P or the type of toner P1. Thus, the gloss control device60and the imaging system1can be used in a versatile manner, with different types of printing medium and toner. Further, by omitting a component that presses the printing medium against the conveyor belt and/or by omitting other components such as a component used to vacuum the printing medium, as described herein, a reduced size and cost of the gloss control device60and the imaging system1may be achieved.

It is to be understood that not all aspects, advantages and features described herein may necessarily be achieved by, or included in, any one particular example. Indeed, having described and illustrated various examples herein, it should be apparent that other examples may be modified in arrangement and detail is omitted. For example, at least one of the conveyor belt61, the heating device62, and the pressing portion65may not be a rotating body.