JP7031166B2 - Microchannel device and image forming device - Google Patents

Description

The present disclosure relates to microchannel devices and image forming devices.

In recent years, a microchip including a flow path physically processed by microfabrication technology has been proposed as a device for analytical technology in the fields of chemistry, biotechnology, or medical treatment (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2005-007529 Japanese Unexamined Patent Publication No. 2005-000744

However, the prior art as described in Patent Documents 1 and 2 requires a microchip in which a highly accurate flow path pattern having a size of several hundred μm is physically processed. Therefore, not only the processing time requires a very long time, but also the change of the flow path pattern for each chip is costly. Therefore, the prior art as described above may not be able to provide a microchannel device capable of forming a channel pattern at low cost and quickly.

The present disclosure has been made in view of such a situation, and is intended to enable the formation of a flow path pattern at low cost and quickly.

The microchannel device according to the first aspect of the present disclosure is a microchannel device containing a substrate, in which a layer is formed on the substrate, and a fluid is formed on the surface of the layer. The first region including the flow path and the second region adjacent to the first region are formed flush with each other, and the contact angle between the first region and the fluid is set to θa. The contact angle between the second region and the fluid is θa', and the whole boundary condition equation is satisfied. The whole boundary condition equation is expressed by θa'−θa> 45 °. The first region and the second region are formed in a repeating pattern in the traveling direction of the fluid, and the ratio of the first region is formed so as to increase in the traveling direction of the fluid .

Further, θa, which is the contact angle between the first region and the fluid, satisfies the first boundary condition equation, and the first boundary condition equation is expressed by θa <90 °. There, θa', which is the contact angle between the second region and the fluid, satisfies the second boundary condition equation, and the second boundary condition equation is expressed by θa'> 90 °. It is preferable that it is a thing.

Further, it is preferable that the contact angle between the surface of the layer and the fluid increases as the distance from the center of the flow path increases along the vertical cross section of the flow path.

Further, it is preferable that the contact angle between the surface of the layer and the fluid becomes smaller as the flow path is downstream along the traveling direction of the fluid flowing through the flow path.

Further, the layer is preferably a thin film of a photocatalyst formed on the surface of the base material.

Further, it is preferable that the thin film contains metal nanoparticles.

Further, it is preferable that the metal nanoparticles include gold nanoparticles.

Further, it is preferable that the metal nanoparticles include aluminum nanoparticles.

Further, the image forming apparatus according to the second aspect of the present disclosure is an image forming apparatus including an exposure apparatus, and the exposure apparatus is capable of irradiating irradiation light with the irradiation light described above. The flow path formed in the flow path device is formed.

According to the first and second aspects of the present disclosure, the flow path pattern is formed at low cost and quickly.

It is a schematic diagram of the microchannel device 1 which concerns on Embodiment 1 to which this disclosure is applied. It is sectional drawing of the micro flow path device 1 which concerns on Embodiment 1. FIG. It is a figure explaining the contact angle θ between the surface of the layer 5 and the liquid which concerns on Embodiment 1. FIG. It is a figure which shows an example of the driving force of the fluid F flowing through the flow path caused by the difference in the wettability of the surface of the layer 5 which concerns on Embodiment 1. FIG. It is a figure which shows an example of the driving force of the fluid F generated by the difference of contact angles θ1 and θ2 between the surface of the layer 5 which concerns on Embodiment 1 and the fluid F flowing through a flow path. It is a figure which shows an example of the pattern of the 1st region K and the 2nd region J which concerns on Embodiment 1. FIG. It is a figure which shows another example of the pattern of the 1st region K and the 2nd region J which concerns on Embodiment 1. FIG. It is a figure which shows still another example of the pattern of the 1st region K and the 2nd region J which concerns on Embodiment 1. FIG. It is an example of the cross-sectional view of the microchannel device 1 containing the metal nanoparticles 9 according to the first embodiment. It is a figure which shows the structural example of the image forming apparatus 50 which concerns on Embodiment 2 to which this disclosure is applied.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the following embodiments. It should be noted that, as used in the description of embodiments of the present disclosure, "consisting", "consisting", "including", "containing", "having", "providing" or any other of them. Synonyms are intended to include non-exclusive inclusion relationships. For example, a process, method, article or appliance that includes an enumeration of elements is not required to be limited to those elements alone, but other elements that are not explicitly enumerated or should be inherent. It may be included in such a process, method, article or appliance. Moreover, unless explicitly stated, "or" is comprehensive and not an exclusive sum. For example, "condition A or B" is satisfied in any case where A exists and B does not exist, A does not exist and B exists, and both A and B exist. Is.

Embodiment 1.
FIG. 1 is a schematic diagram of a microchannel device 1 according to the first embodiment to which the present disclosure is applied. FIG. 2 is a cross-sectional view of the microchannel device 1 according to the first embodiment. As shown in FIGS. 1 and 2, the microchannel device 1 includes a base material 3, and a layer 5 is formed on the base material 3. The base material 3 is not particularly limited, and for example, glass, metal, resin, ceramics, or the like can be used. The surface of layer 5 includes a first region K and a second region J. The first region K includes a flow path through which the fluid F flows. The second region J is adjacent to the first region K. As shown in FIG. 2, which is a cross-sectional view taken along the line AA of FIG. 1, the first region K and the second region J are formed flush with each other.

FIG. 3 is a diagram illustrating a contact angle θ between the surface of the layer 5 and the liquid according to the first embodiment. As shown in FIG. 3, wetting is a phenomenon in which the interface between the vapor as a gas and the layer 5 as a solid is replaced with the interface between the liquid and the layer 5 as a solid, and the contact angle θ is. When it is small, it indicates a state in which it is easy to get wet, and when the contact angle θ is large, it indicates a state in which it is difficult to get wet. In order to form a flow path by the first region K and the second region J, the contact angle θa between the first region K and the fluid F and the contact angle between the second region J and the fluid F It is preferable to make a difference with θa'. For example, if the difference between the contact angle θa and the contact angle θa'is small, the first region K and the second region J show substantially the same wettability. In this case, the boundary as a flow path becomes ambiguous. Further, when the difference between the contact angle θa and the contact angle θa'is large and the contact angle θa is smaller than the contact angle θa', the liquid stays on the side where it is easy to get wet, so that the first region including the flow path is included. The fluid F stays in K. Therefore, in order to form the flow path in the first region K, it is preferable that the difference between the contact angle θa and the contact angle θa'is large, and the contact angle θa is smaller than the contact angle θa'.

Specifically, by utilizing the wettability between the base material 3 and the liquid, that is, hydrophilicity and hydrophobicity, the function as a flow path is exhibited without providing a physical boundary. More specifically, when the base material 3 is not specially surface-processed, when a droplet of the aqueous solution is dropped, the contact angle θ becomes about 55 ° or more due to the surface tension of the liquid and the surface energy of the base material 3. Stable in the state of droplets. On the other hand, the surface energy of the base material 3 is reduced by subjecting a part of the surface of the base material 3 to hydrophilicity, and the contact angle θ when the liquid flows without resistance is 10 ° or less. Therefore, as a result of diligent studies by the present inventors, the first region K including the flow path has a contact angle θa of 10 ° or less, and the second region J not including the flow path has a contact angle θa. We have obtained the finding that if'is about 55 ° or more, the liquid can flow in the first region K without leaking to the second region J, and the present disclosure is applied based on that finding. The microchannel device 1 according to the first embodiment was completed.

That is, the contact angle θa and the contact angle θa ′ satisfy the overall boundary condition equation, and the overall boundary condition equation is expressed by the contact angle θa ′ − contact angle θa> 45 °. Further, the contact angle θa satisfies the first boundary condition expression, and the first boundary condition expression is expressed by the contact angle θa <90 °. The contact angle θa'satisfies the second boundary condition expression, and the second boundary condition expression is expressed by the contact angle θa'> 90 °. Specifically, wetting can be classified into three types using the contact angle θ. The contact angle θ represents the angle formed by the tangent line of the liquid and the solid surface when the liquid is dropped on the solid surface such as the base material 3. When the contact angle θ ≈ 0 °, it is called extended wetting, and represents a state in which the liquid spreads forever on the solid surface. When the contact angle θ = 0 ° to 90 °, it is called immersion wetting, and represents a state in which the spread of the liquid becomes stable somewhere where 0 ° <contact angle θ ≦ 90 °. When the contact angle θ> 90 °, it is called adherent wetting and represents a state in which wetting does not progress. Therefore, since the first region K includes the flow path, it is required that the liquid is wetted. Therefore, it is desirable that the contact angle θa ≈ 0 ° or 0 ° <contact angle θa ≦ 90 °. On the other hand, since the second region J is outside the flow path and is required to stop the progress of wetting from the first region K, it is desirable that the contact angle θa'> 90 °. Therefore, by dividing the contact angle θ at the boundary of 90 ° in the first region K and the second region J, it is possible to clearly separate the progress characteristics of wetting.

FIG. 4 is a diagram showing an example of the driving force of the fluid F flowing through the flow path caused by the difference in the wettability of the surface of the layer 5 according to the first embodiment. FIG. 5 is a diagram showing an example of the driving force of the fluid F generated by the difference in the contact angles θ1 and θ2 between the surface of the layer 5 and the fluid F flowing through the flow path according to the first embodiment. Along the vertical cross section of the flow path, the contact angle θ between the surface of the layer 5 and the fluid F increases as the distance from the center C of the flow path increases. On the other hand, as the flow path is on the downstream side along the traveling direction of the fluid F flowing through the flow path, the contact angle θ between the surface of the layer 5 and the fluid F becomes smaller. That is, when there is a wetting slope as shown in FIG. 4, the contact angle θ of the dropped liquid differs depending on the location, and as shown in FIG. 5, the contact angle θ1 and the contact angle θ2 are the contact angle θ1. > The contact angle θ2. Therefore, since the driving force acts toward the contact angle θ2, the droplet moves to the side of the contact angle θ2.

The slope of wettability does not have to be continuous. It suffices if the average value of wettability per unit area decreases monotonically. For example, the hydrophilic region and the hydrophobic region may be realized in a coarse and dense repeating pattern by utilizing the first region K and the second region J. FIG. 6 is a diagram showing an example of a pattern of the first region K and the second region J according to the first embodiment. FIG. 7 is a diagram showing another example of the pattern of the first region K and the second region J according to the first embodiment. FIG. 8 is a diagram showing still another example of the patterns of the first region K and the second region J according to the first embodiment. In one example of FIG. 6, the driving force is expressed in the fluid F by forming the ratio of the region of the contact angle θa in a divergent manner according to the traveling direction of the fluid F. In the examples of FIGS. 7 and 8, the driving force is expressed in the fluid F by forming the ratio of the region of the contact angle θa so as to increase according to the traveling direction of the fluid F.

FIG. 9 is an example of a cross-sectional view of the microchannel device 1 containing the metal nanoparticles 9 according to the first embodiment. As shown in FIG. 9, the layer 5 is a thin film of a photocatalyst formed on the surface of the base material 3 and contains metal nanoparticles 9. The metal nanoparticles 9 include nanoparticles of gold or nanoparticles such as aluminum. The flow path is formed by irradiating a thin film of a photocatalyst with ultraviolet light. The thin film of the photocatalyst is not particularly limited, and for example, titanium oxide, nitrogen-doped titanium oxide, carbon-doped titanium oxide, sulfur dome titanium oxide, zinc oxide, or the like can be used. In particular, titanium oxide is desirable from the viewpoint of improving catalyst efficiency such as cost, handleability, and safety. The thin film of the photocatalyst is formed by sputtering, vapor deposition, or the like, and exhibits hydrophobicity in the film-formed state, and exhibits a catalytic effect by irradiating with ultraviolet light and exhibits superhydrophilicity. There are various irradiation methods for ultraviolet light, such as irradiation with a UV laser and irradiation with a UV lamp by creating a mask pattern.

The photocatalyst exhibits its catalytic function when irradiated with ultraviolet light, but its utilization efficiency is low with respect to the irradiated light as it is. Therefore, the photocatalyst contains the metal nanoparticles 9. The metal nanoparticles 9 are not particularly limited, but from the viewpoint of more effectively using plasmon light, it is desirable to include nanoparticles of a substance that causes plasmon. It is desirable that the metal nanoparticles 9 contain silver, gold, copper, or aluminum, or any alloy containing these, and in particular, gold nanoparticles or aluminum nanoparticles are desirable. The particle size of the aluminum nanoparticles is preferably 100 nm or less in consideration of the absorption efficiency of plasmon light. Further, as shown in FIG. 9, it is desirable that the metal nanoparticles 9 are deposited on the layer 5 which is a thin film of the photocatalyst. With such a configuration, the plasmon light generated in the vicinity of the metal nanoparticles 9 included in the irradiation region irradiated with ultraviolet light acts on the photocatalyst, and a part of the layer 5 changes to hydrophilicity. On the other hand, in order to maintain the hydrophobic state in the non-irradiated region not irradiated with ultraviolet light, the irradiated region of ultraviolet light is formed as the first region K, and the non-irradiated region of ultraviolet light is formed as the second region J. Ru.

Next, a conventional example will be specifically described. In recent years, microchips in which minute flow paths, valves, pumps, etc. are integrated on a silicon or glass substrate have been actively studied as research applied to analytical techniques in the fields of chemistry, biotechnology, and medical care. In addition, the microchip market is expanding and growing at an annual rate of 20%, and is expected to be applied to in vitro diagnosis, drug research, drug delivery, etc. in addition to analytical applications. Conventionally, a microchip having a flow path formed by injection molding, lithography, or the like has been provided. In the prior art, there is one formed by creating a specific mold and transferring it to the base material 3 for forming a flow path. In such a prior art, it makes sense to first create a flow path pattern mold and then generate a large number of microchips of the same specifications to duplicate it. However, since the mold of the flow path pattern is transferred, it is costly to change the flow path pattern individually, and since there are many manufacturing processes, it takes a very long time to complete the microchip. Is required.

In addition, some are formed by mechanical cutting to form a flow path, and some are formed by an etching process by photolithography using a mask. In such a conventional technique, it is possible to form a flow path pattern individually, but since the cutting process is machining that requires extremely high accuracy, large equipment is required and a microchip is required. It takes several days just to create one. Further, even in the case of lithography, the capital investment is enormous, and the etching processing process after exposing the flow path pattern requires an enormous amount of time. In short, the prior art is costly and time consuming.

The biggest factor that causes such a thing is that in the prior art, a microchip is formed by physically processing a highly accurate flow path pattern having a size of several hundred μm. Since it is premised on a physically high-precision flow path pattern, there are restrictions on the processing method, and further, it is not possible to change the flow path pattern for each processing time or chip. In particular, since it is necessary to perform various analyzes in in vitro diagnosis or research and development, there is a demand for prompt acquisition after appropriately optimizing the flow path pattern. The current situation is that conventional technology cannot fully meet such demands.

Therefore, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the space between the first region K and the second region J is formed flush with each other, so that microfabrication by cutting can be performed. It has not been. Further, since the difference in contact angle θ between the first region K and the second region J is 45 ° or more, the surface energy of the first region K is lower than that of the second region J. On the surface, the fluid F flows into the first region K and does not flow into the second region J. Therefore, a flow in which the fluid F flows only on a surface having a different contact angle θ such that the difference between the first region K and the second region J is 45 ° or more without microfabrication by cutting. A road pattern is formed. Therefore, the flow path pattern can be formed quickly and at low cost.

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, since the contact angle θa between the first region K and the fluid F is less than 90 °, the first region K is expanded wetting or immersion. It is in a wet state. Therefore, in the first region K, wetting by the liquid progresses. On the other hand, since the contact angle θa'between the second region J and the fluid F exceeds 90 °, the second region J is in a wet state. Therefore, since the wetting by the liquid does not proceed in the second region J, the progress of the wetting by the liquid from the first region K can be stopped. Therefore, by dividing the contact angle θ between the first region K and the second region J with 90 ° as a boundary, the progress characteristics of liquid wetting can be clearly separated.

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the liquid will move from a region where it is difficult to get wet to a region where it is easy to get wet, that is, from a region where the contact angle θ is large to a region where the contact angle θ is small. It has the property of Therefore, if the contact angle θ between the surface of the layer 5 and the fluid F increases as the distance from the center C of the flow path increases along the vertical cross section of the flow path, the flow path is set in the cross section direction of the flow path. A force acting toward the central axis of the traveling fluid F in the traveling direction becomes possible. Therefore, it is possible to prevent the fluid F from leaking out of the flow path.

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the liquid will move from a region where it is difficult to get wet to a region where it is easy to get wet, that is, from a region where the contact angle θ is large to a region where the contact angle θ is small. It has the property of Therefore, if the contact angle θ between the surface of the layer 5 and the fluid F becomes smaller as the flow path is downstream along the traveling direction of the fluid F flowing through the flow path, the fluid is dropped into the flow path. A driving force is generated for the fluid F from the upstream side to the downstream side. Therefore, since the liquid can be conveyed without applying pressure to the liquid on the flow path from the outside, the configuration of a drive source such as a pump can be simplified.

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the layer 5 is a thin film of a photocatalyst formed on the surface of the base material 3. The flow path is formed by irradiating a thin film of a photocatalyst with ultraviolet light. The thin film of the photocatalyst exhibits a catalytic effect when irradiated with ultraviolet light and becomes superhydrophilic. Therefore, if the thin film of the photocatalyst is formed on the surface of the base material 3, the irradiated portion changes to hydrophilicity only by irradiating the portion formed as the flow path with ultraviolet light, and the portion can function as a channel. ..

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the thin film contains metal nanoparticles 9. That is, by coexisting the metal nanoparticles 9 and the photocatalyst, the plasmon resonance that occurs in a part of the metal nanoparticles 9 can dramatically improve the efficiency of light utilization in the photocatalyst.

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the metal nanoparticles 9 include gold nanoparticles. Since the gold nanoparticles act as co-catalysts, the activity efficiency of the photocatalyst can be increased. Therefore, the exposure time can be shortened and the optical system can be made compact.

Further, in the microchannel device 1 according to the first embodiment to which the present disclosure is applied, the metal nanoparticles 9 include aluminum nanoparticles. Aluminum nanoparticles are substances that cause plasmon resonance in the ultraviolet region. When the aluminum nanoparticles are irradiated with ultraviolet light, plasmon resonance occurs, so that the ultraviolet light irradiated in the vicinity of the aluminum nanoparticles remains as an electric field. Such an electric field acts on the photocatalyst. Therefore, the activity efficiency of the photocatalyst can be increased. Therefore, the exposure time can be shortened and the optical system can be made compact.

Embodiment 2.
In the second embodiment, the image forming apparatus 50 forming the flow path will be described. FIG. 10 is a diagram showing a configuration example of the image forming apparatus 50 according to the second embodiment to which the present disclosure is applied. As shown in FIG. 10, the image forming apparatus 50 includes a reading unit 511 and an image forming apparatus main body 519. The reading unit 511 includes an ADF 511A and a document reading unit 511B. The ADF511A includes a document tray 513, a paper passing path 515, a paper ejection tray 517, a close contact type image sensor 521, a density reference member 523, and the like. The density reference member 523 is used at the time of shading correction of ADF511A. The document reading unit 511B includes a document lighting unit 525, a reflection mirror 526, a condenser lens 527, a sensor 528, a platen glass 529, and the like. The reading unit 511 separates and feeds the documents set in the document tray 513 one by one, conveys them in the sub-scanning direction along the paper passing path 515 in which the close contact type image sensor 521 is arranged, and discharges the paper. The paper is discharged to the tray 517. The document illumination unit 525 includes a lamp 525A and a mirror 525B. While the document is conveyed in the sub-scanning direction along the paper path 515, the line-by-line reading operation in the main scanning direction is repeatedly executed by the document illumination unit 525, the reflection mirror 526, the condenser lens 527, and the sensor 528. ..

The image forming apparatus main body 519 includes an image forming unit 541, a fixing unit 543, a paper feeding unit 545, and the like. The image forming unit 541 includes an exposure device 551, a developing device 555, a photosensitive drum 555, and a transfer belt 557. The image forming unit 541 supplies toners of different colors to the photosensitive drum 555 by the exposure apparatus 551 and develops them based on the image data of the original document read by the reading unit 511. The image forming unit 541 transfers the toner image developed on the photosensitive drum 555 by the transfer belt 557 to the paper supplied from the paper feeding unit 545. The image forming unit 541 melts the toner of the toner image transferred to the paper at the fixing unit 543, so that the color image is fixed on the paper.

That is, the image forming apparatus 50 includes the exposure apparatus 551, and the exposure apparatus 551 can irradiate the irradiation light freely. Therefore, the exposure apparatus 551 forms a flow path formed in the micro flow path device 1 by the irradiation light. Specifically, since the exposure apparatus 551 can form the irradiation region in the hydrophilic region by irradiating the thin film of the photocatalyst with the irradiation light, the hydrophilic region and the hydrophobic region can be formed on the layer 5. Moreover, since the exposure apparatus 551 can appropriately control the irradiation position of the irradiation light, an arbitrary flow path pattern can be formed on the surface of the layer 5. Therefore, the image forming apparatus 50 can form the flow path pattern at low cost and quickly.

Although the microchannel device 1 to which the present disclosure is applied has been described above based on the embodiment, the present disclosure is not limited to this, and changes may be made without departing from the gist of the present disclosure. ..

For example, in the present embodiment, an example in which the upper layer 5 is in an open state has been described, but the present invention is not particularly limited to this. For example, a frame along the edge of the layer 5 may be placed on the layer 5, and a member functioning as a lid may be placed on the frame to prevent foreign matter from entering the flow path.

1 Microchannel device, 3 base material, 5 layers, 9 metal nanoparticles 50 image forming device 511 reading unit, 511A ADF, 511B document reading unit, 513 document tray 515 paper passing path, 517 paper ejection tray, 219 image forming device Main body 521 Adhesion type image sensor, 523 Concentration standard member 525 Original lighting unit, 525A lamp, 525B mirror, 526 Reflection mirror 527 Condensing lens, 528 sensor, 259 Platen glass 541 Image forming unit, 543 Fixing unit, 545 Paper feed unit 551 Exposure device, 555 developing device, 555 photosensitive drum, 557 transfer belt K 1st region, J 2nd region, F fluid, C center θ, θa, θa', θ1, θ2 Contact angle

Claims (9)

A microchannel device containing a substrate,
A layer is formed on the base material, and the layer is formed.
The surface of the layer is
A first region including a flow path through which a fluid flows and a second region adjacent to the first region are formed flush with each other.
The contact angle between the first region and the fluid is θa, the contact angle between the second region and the fluid is θa', and the whole boundary condition equation is satisfied.
The whole boundary condition expression is
Represented by θa'-θa> 45 ° ,
The first region and the second region are repeatedly patterned in the traveling direction of the fluid, and the ratio of the first region is formed so as to increase in the traveling direction of the fluid.
Micro flow path device. Θa, which is the contact angle between the first region and the fluid, satisfies the first boundary condition equation.
The first boundary condition expression is
It is expressed by θa <90 ° and is expressed by θa <90 °.
Θa', which is the contact angle between the second region and the fluid, satisfies the second boundary condition equation.
The second boundary condition expression is
It is represented by θa'> 90 °,
The microchannel device according to claim 1. Along the vertical cross section of the flow path, the contact angle between the surface of the layer and the fluid increases as the distance from the center of the flow path increases.
The microchannel device according to claim 1 or 2. The contact angle between the surface of the layer and the fluid becomes smaller as the flow path is downstream along the traveling direction of the fluid flowing through the flow path.
The microchannel device according to any one of claims 1 to 3. The layer is
A thin film of photocatalyst formed on the surface of the substrate.
The microchannel device according to any one of claims 1 to 4. The thin film is
Contains metal nanoparticles,
The microchannel device according to claim 5. The metal nanoparticles are
Contains gold nanoparticles,
The microchannel device according to claim 6. The metal nanoparticles are
Contains aluminum nanoparticles,
The microchannel device according to claim 6. An image forming apparatus equipped with an exposure apparatus, which is an image forming apparatus.
The exposure apparatus is
The flow path is freely irradiated with the irradiation light, and the irradiation light forms the flow path formed in the micro flow path device according to any one of claims 5 to 8.
Image forming device.

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