JP2013152316A - Concentration detection device and image forming device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentration detection device capable of accurately measuring concentration of a resin component dissolved in a liquid developer and to provide an image forming device equipped with the same.SOLUTION: A QCM sensor 60 having a quartz oscillator is immersed in a liquid developer LD stored in a concentration detection tank 691. A housing 65 in which a circuit unit 64 is housed is arranged and installed at the upper side of the QCM sensor 60. Height D1 of the liquid developer positioned at the upper side of a sensor electrode 61 is held at a fixed level with a bottom surface part of the housing 651. As a result, the oscillation frequency of the quartz oscillator in the sensor electrode 61 is suppressed from being fluctuated by the depth of the QCM sensor 60 in the liquid developer.

Description

  The present invention relates to a concentration detection device that detects the concentration of a resin component dissolved in a liquid developer, and an image forming apparatus including the same.

  As an image forming apparatus, a wet type apparatus that forms a toner image using a liquid developer is known. In the liquid developer, toner as a solid content is dispersed in a dielectric liquid serving as a carrier liquid. The wet image forming apparatus includes a photosensitive drum on which a toner image is formed, a developing device that supplies a liquid developer to the photosensitive drum and forms a toner image on the photosensitive drum, and a toner on the photosensitive drum. A transfer unit that transfers the image onto the sheet; and a fixing unit that fixes the toner image on the sheet onto the sheet.

  In order to form a good toner image on a sheet, it is necessary to properly adjust the toner concentration of the liquid developer before the developing device supplies the liquid developer to the photosensitive drum. For this reason, an apparatus for detecting the toner concentration of a liquid developer is known for the purpose of determining whether or not the toner concentration is properly adjusted (Patent Document 1).

  The density detection apparatus of Patent Document 1 utilizes the specific gravity of a liquid developer, and a comparison container enclosing a liquid developer for density comparison is immersed in the liquid developer to be measured. Then, the toner concentration of the liquid developer is detected based on the change in the position of the comparison container due to the buoyancy caused by the specific gravity difference.

  On the other hand, techniques for measuring the concentration of microorganisms in a microorganism suspension using a QCM sensor equipped with a crystal resonator are known (Patent Documents 2 to 5).

  In this technique, an antibody is immobilized on a crystal resonator, and a weight change occurs on the surface of the crystal resonator electrode by binding the antibody and a microorganism. The change in the oscillation frequency of the quartz crystal resonator accompanying the change in weight is measured, and the concentration of microorganisms is calculated.

JP 2007-310122 A JP 62-64934 A Japanese Unexamined Patent Publication No. Sho 63-11835 JP-A-62-288546 JP-A-62-288547

  In recent years, as a liquid developer for an image forming apparatus, as described above, a toner as a solid content is dispersed in a dielectric liquid serving as a carrier liquid, and a resin component is dissolved in the carrier liquid. Exists. The resin component has a function of precipitating on the sheet in the fixing step of image formation and protecting the surface.

  In a liquid developer in which such a resin component is dissolved, the specific gravity of the carrier liquid as a solvent and the specific gravity of the dissolved resin are often approximated. For this reason, it is difficult to detect the concentration of the dissolved resin in an apparatus using the specific gravity of the liquid developer, such as the concentration detection apparatus of Patent Document 1.

  Also, as disclosed in Patent Documents 2 to 5, an apparatus for detecting a microbial concentration using a crystal resonator is known. However, a dissolved resin concentration in a liquid developer is detected using a crystal resonator. As for the technology to do, it was unclear whether or not its detailed application was possible.

  The present invention has been made in view of the above problems, and provides a concentration detection apparatus capable of accurately measuring the concentration of a resin component dissolved in a liquid developer, and an image forming apparatus including the same. For the purpose.

  The concentration detection apparatus according to an aspect of the present invention is a storage container that stores a liquid developer containing a dissolved resin component, and is immersed in the liquid developer in the storage container, and the dissolved in the liquid developer A sensor unit including a crystal resonator that oscillates a vibration frequency according to the concentration of the resin component, an oscillation circuit that is connected to the sensor unit and oscillates the crystal resonator, and is immersed in the liquid developer in the storage container A regulating member that covers the upper part of the sensor unit and that is maintained at a constant distance in the depth direction from the sensor unit, and the vibration frequency at which the quartz crystal oscillator oscillates in the liquid developer. And a concentration calculation unit for calculating the concentration of the dissolved resin component.

  According to this configuration, the liquid developer is stored in the storage container, and the sensor unit including the crystal resonator is immersed in the liquid developer. The quartz oscillator oscillates at a vibration frequency corresponding to the concentration of the dissolved resin component in the liquid developer. The concentration calculation unit calculates the concentration of the dissolved resin component in the liquid developer from the vibration frequency. When the sensor unit is immersed in the liquid developer, the vibration frequency at which the crystal resonator oscillates may vary depending on the liquid height of the liquid developer located above the sensor unit. Even in such a case, according to the above configuration, the regulating member that is immersed in the liquid developer, covers the upper portion of the sensor unit, and the distance in the depth direction from the sensor unit is kept constant. Arranged. For this reason, the height of the liquid developer located above the sensor unit is kept constant. As a result, the concentration of the dissolved resin component in the liquid developer is accurately measured.

  In the above-described configuration, the semiconductor device further includes a housing that houses the oscillation circuit therein and includes a bottom portion that is immersed in the liquid developer, and the sensor portion is disposed so as to protrude downward from the bottom portion of the housing. Preferably, the oscillation circuit is connected to the sensor portion via the bottom portion, and the restriction member is the bottom portion of the housing.

  According to this configuration, the oscillation circuit is accommodated in the housing, and the liquid developer is prevented from adhering to the oscillation circuit. Further, the sensor unit is disposed so as to protrude downward from the bottom of the housing. For this reason, the bottom part of a housing has a function as a control member. Therefore, the concentration of the dissolved resin component in the liquid developer can be accurately measured with a simple configuration of the housing. Further, the oscillation circuit can be brought as close to the sensor unit as possible through the bottom of the housing. As a result, electrical noise is prevented from interposing between the sensor unit and the oscillation circuit.

  In the above configuration, the apparatus further includes a liquid temperature detection unit that detects a liquid temperature of the liquid developer in the storage container, and the concentration calculation unit is configured to respond to the liquid temperature of the liquid developer detected by the liquid detection unit. It is preferable to correct the vibration frequency or the concentration of the dissolved resin component calculated from the vibration frequency.

  According to this configuration, even when the liquid temperature of the liquid developer containing the dissolved resin component is changed and the viscosity of the liquid developer is changed, the fluctuation due to the liquid temperature among the vibration frequencies of the crystal resonator is changed. Minutes can be corrected. As a result, the concentration of the dissolved resin component in the liquid developer is accurately detected without being affected by the liquid temperature of the liquid developer.

  In the above configuration, the sensor unit is disposed so as to sandwich the crystal resonator from both sides, and a first electrode and a second electrode for applying a voltage to the crystal resonator, and the first electrode or the second electrode. It is preferable to have a surface regulating member that protects one of the electrodes from the liquid developer.

  According to this configuration, the sensor unit is disposed so as to sandwich the crystal resonator from both sides, and has the first electrode and the second electrode that apply a voltage to the crystal resonator. The sensor unit includes a surface regulating member that protects one of the first electrode and the second electrode from the liquid developer. For this reason, current is prevented from flowing from the first electrode to the second electrode via the liquid developer, and a circuit including the crystal unit is prevented from being short-circuited. In particular, this effect is exhibited when moisture is contained in the carrier liquid of the liquid developer LD.

  Said structure WHEREIN: It is preferable to have a shield member which is arrange | positioned at the said housing and interrupts | blocks the exterior of the said housing and the interior space of the said housing electrically.

  According to this configuration, the oscillation circuit accommodated in the housing is prevented from receiving electrical noise from the surroundings.

  In the above configuration, it is preferable that the bottom portion of the housing is formed of a circular flat plate disposed horizontally, and the sensor portion is disposed immediately below the center portion of the bottom portion.

  According to this structure, the bottom part of a housing consists of a circular flat plate arrange | positioned horizontally. In addition, the sensor portion is disposed immediately below the center portion of the bottom portion of the housing. For this reason, the depth at which the sensor unit is immersed in the liquid developer can be made as shallow as possible. In addition, since the sensor unit is disposed corresponding to the central portion of the bottom of the housing, the liquid height of the liquid developer around the sensor unit can be stably maintained.

  Said structure WHEREIN: It is preferable that the said bottom part consists of a flat plate and inclines with respect to a horizontal direction.

  According to this configuration, the bottom portion of the housing that covers the upper portion of the sensor portion in the liquid developer and that has a constant distance in the depth direction from the sensor portion as the regulating member is Inclined. For this reason, even if air bubbles are generated in the liquid developer, the air bubbles are allowed to escape along the slope without staying at the bottom of the housing. Therefore, the bubbles are prevented from affecting the oscillation of the crystal resonator.

  An image forming apparatus according to another aspect of the present invention stores an image carrier on which a toner image is formed and a liquid developer containing the toner and having a resin component dissolved therein. 2. A developing device that supplies the toner to the liquid developer, a developer adjusting unit that adjusts the concentrations of the toner and the resin component in the liquid developer, and a concentration of the resin component in the liquid developer. Or a concentration detection device according to any one of items 1 to 6.

  According to this configuration, in the density detection device, the height of the liquid developer positioned above the sensor unit is kept constant. Therefore, the concentration of the dissolved resin component in the liquid developer is detected with high accuracy. As a result, the concentration adjusting unit appropriately adjusts the concentration of the dissolved resin component in the liquid developer, thereby enabling stable image formation.

  According to the present invention, it is possible to provide a density detection apparatus capable of accurately measuring the density of a resin component dissolved in a liquid developer, and an image forming apparatus including the density detection apparatus.

It is sectional drawing and the block diagram of the density | concentration detection apparatus which concern on embodiment of this invention. It is a partial sectional view of a concentration detection apparatus according to an embodiment of the present invention. It is (a) top view and (b) side view of the QCM sensor which concerns on embodiment of this invention. It is the figure which showed the relationship between the melted resin density | concentration and output frequency of the density | concentration detection apparatus which concerns on embodiment of this invention. It is the figure which showed transition of the output frequency of the density | concentration detection apparatus which concerns on embodiment of this invention. FIG. 4 is a diagram illustrating a relationship between a liquid temperature and a viscosity of a liquid developer according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a relationship between a liquid temperature of a liquid developer and an output frequency in the concentration detection apparatus according to the embodiment of the present invention. It is the figure which showed the temperature dependence of the oscillation circuit with which the density | concentration detection apparatus which concerns on embodiment of this invention is provided. 1 is an overall schematic cross-sectional view of a color printer according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the color printer excluding a liquid developer circulating device. It is sectional drawing which expands and shows one of the image formation parts. It is a block diagram of a liquid developer circulation device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a combination of a cross-sectional view and an electrical block diagram of a concentration detection apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a QCM (Quarts Crystal Microbalance) sensor of the concentration detector. FIG. 3 is a (a) plan view and (b) side view of the QCM sensor.

  Referring to FIG. 1, a dissolved resin concentration detection device 280 (concentration detection device) includes a detection device main body 280A, a power source 693, and a measurement unit 280B.

  The detection device main body 280A is a device main body that measures the concentration of the resin component dissolved in the liquid developer LD (hereinafter, dissolved resin concentration CR). The detection device main body 280A includes a QCM sensor 60, a circuit unit 64, a housing 65, a concentration detection tank 691, and a liquid temperature sensor 692.

  The QCM sensor 60 includes a crystal resonator 611 (FIG. 3) inside, and oscillates a vibration frequency corresponding to the dissolved resin concentration CR of the liquid developer LD. The QCM sensor 60 is immersed in the liquid developer LD to be measured. The QCM sensor 60 includes a sensor electrode 61 and a pedestal portion 62. The sensor electrode 61 includes a crystal resonator 611 therein and has a disk shape when viewed from the front. The pedestal 62 is immersed in the liquid developer LD above the sensor electrode 61. The pedestal portion 62 has a disk shape in plan view and includes two through holes (not shown). The pedestal 62 has a function of fixing the first lead 63a and the second lead 63b disposed between the sensor electrode 61 and the circuit unit 64 through the hole. The QCM sensor 60 is disposed below the bottom surface portion 651 of the housing 65 described later so as to protrude from the housing 65.

  With reference to FIG. 3, the sensor electrode 61 of the QCM sensor 60 has a three-layer structure in a side view, and includes a crystal resonator 611, a first electrode portion 612, and a second electrode portion 613. The first electrode portion 612 and the second electrode portion 613 are disposed so as to sandwich the crystal resonator 611 from both sides. By forming a closed circuit using the crystal unit 611 as a part of the circuit, a predetermined voltage is applied to both sides of the crystal unit 611. Then, the crystal resonator 611 oscillates at different vibration frequencies according to the dissolved resin concentration CR in the surrounding liquid developer LD. The relationship between the dissolved resin concentration CR in the liquid developer LD and the vibration frequency will be described in detail later.

  One surface regulating member 612A (surface regulating member) is disposed on one surface of the first electrode portion 612 and the second electrode portion 613 sandwiching the crystal resonator 611. In the present embodiment, the single-side regulating member 612A is disposed on the surface of the first electrode 612. The single-side regulating member 612A is disposed so as to cover the surface of the first electrode 612, and is formed by an oil-resistant insulating seal or coating. As a result, the liquid developer LD adheres only to the surface of the second electrode portion 613, and the surface of the first electrode 612 is protected from the liquid developer LD. As a result, a current flows between the first electrode portion 612 and the second electrode portion 613 via the liquid developer LD, thereby preventing a short circuit.

  The circuit unit 64 includes an oscillation circuit 641 that is disposed above the QCM sensor 60 and includes an interface circuit therein. The oscillation circuit 641 is disposed on a wiring board as small as possible so as not to be affected by external electrical noise. The circuit unit 64 includes a connector 642. The circuit unit 64 is electrically connected to the QCM sensor 60 by the first lead portion 63a and the second lead portion 63b (FIG. 2). Further, the circuit unit 64 is electrically connected to the power source 693 by the first wiring portion 694. Further, the circuit unit 64 is electrically connected to a frequency meter 696 described later by the second wiring portion 695. An oscillation circuit 641 in the circuit unit 64 is a circuit for causing the crystal resonator 611 to oscillate. In the present embodiment, a multivibrator oscillation circuit is employed as the oscillation circuit 641. A predetermined drive voltage is supplied from the power source 693 to the circuit unit 64 via the first wiring portion 694. The circuit unit 64 outputs the vibration frequency of the crystal resonator 611 of the QCM sensor 60 to the frequency meter 696 of the measurement unit 280B through the second wiring unit 695 as a clock signal.

  The housing 65 is a substantially cylindrical housing and houses the circuit unit 64 therein. The housing 65 includes a bottom surface portion 651 made of a circular flat plate arranged horizontally. A circular opening (not shown) is formed at the center of the bottom surface 651 of the housing 65. The QCM sensor 60 is inserted through the opening through the internal space of the housing 65. Thereby, the QCM sensor 60 is disposed outside the housing 65 and the circuit unit 64 is accommodated inside the housing 65. The QCM sensor 60 is disposed immediately below the center portion of the bottom surface portion 651 of the housing 65. A seal member (not shown) is disposed in the opening to prevent the liquid developer LD from entering the housing 65. A shield 66 is provided on the inner wall of the housing 65 to protect the circuit unit 64 from surrounding electrical noise. With the housing 65 accommodating the circuit unit 64 therein, the bottom surface portion 651 of the housing 65 is immersed in the liquid developer LD. Thereby, even when the QCM sensor 60 is immersed in the liquid developer LD, the circuit unit 64 can be disposed as close to the QCM sensor 60 as possible. As a result, the lengths of the first lead portion 63a and the second lead portion 63b can be shortened, and electrical noise is caused between the QCM sensor 60 and the oscillation circuit 641 in the circuit unit 64. Deterred.

  The density detection tank 691 stores the liquid developer LD to be measured inside. The QCM sensor 60 is immersed in the liquid developer LD stored in the concentration detection tank 691.

  The liquid temperature sensor 692 measures the liquid temperature of the liquid developer LD stored in the concentration detection tank 691. The liquid temperature sensor 692 employs various temperature measuring means such as a thermocouple and a platinum resistance thermometer. The liquid temperature T of the liquid developer LD measured by the liquid temperature sensor 692 is used by the concentration calculation unit 698 in the measurement unit 280B to calculate the dissolved resin concentration CR.

  The power source 693 supplies a predetermined drive voltage to the QCM sensor 60. The power source 693 includes a stabilized power circuit (not shown).

  The measuring unit 280B obtains the dissolved resin concentration CR in the liquid developer LD based on the vibration frequency oscillated from the QCM sensor 60. The measurement unit 280B includes a frequency meter 696, a storage unit 697, and a concentration calculation unit 698. The measurement unit 280B includes a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a control program, a RAM (Random Access Memory) that is used as a work area of the CPU, and the like. The measurement unit 280B functions to include a frequency meter 696, a storage unit 697, and a concentration calculation unit 698 by the CPU executing a control program stored in the ROM.

  The frequency meter 696 cuts noise from the clock signal output from the circuit unit 64 according to the vibration of the crystal resonator 611 and calculates the output frequency F of the crystal resonator 611. The output frequency F is used by the concentration calculation unit 698 to calculate the dissolved resin concentration CR. Various arithmetic units may be used instead of the frequency meter 696. Finally, the oscillation frequency of the QCM sensor 60 may be analyzed based on the clock signal output from the circuit unit 64 so that the dissolved resin concentration CR is calculated on the PPM order.

  The storage unit 697 stores various storage information for the calculation of the dissolved resin concentration CR by the concentration calculation unit 698. The storage unit 697 stores a temperature correction value Vt and a converted concentration value Vd described later.

  The concentration calculation unit 698 uses the output frequency F calculated from the frequency meter 696, the temperature correction value Vt stored in the storage unit 697, the converted concentration value Vd, and the liquid temperature T measured by the liquid temperature sensor 692. The dissolved resin concentration CR is calculated.

<Detection of dissolved resin concentration CR>
In the present embodiment, a liquid developer LD is used as a measurement target of the dissolved resin concentration detection device 280. The liquid developer LD includes an electrically insulating carrier liquid C and colored particles P dispersed in the carrier liquid C. Further, the liquid developer LD contains a resin material R. When used in the image forming apparatus, the concentration of the colored particles P and the concentration of the resin material R in the liquid developer LD are controlled. The components of the liquid developer LD used in this embodiment will be described in detail later.

  The colored particles P in the liquid developer LD are not dissolved in the carrier liquid C. For this reason, the concentration of the colored particles P is measured as the solid content concentration Ds dispersed in the carrier liquid C. The solid content concentration Ds is measured by a known concentration measurement technique based on the specific gravity of the liquid or an improved measurement technique thereof. On the other hand, the resin material R in the liquid developer LD is dissolved in the carrier liquid C. Therefore, the concentration of the resin material R in the liquid developer LD is measured as a dissolved resin concentration CR. The specific gravity of the carrier liquid C and the specific gravity of the dissolved resin material R are approximate. For this reason, even if the dissolved resin concentration CR in the liquid developer LD changes, the overall specific gravity of the liquid developer LD hardly changes. Therefore, it becomes difficult to employ the above-described density measurement technique based on the specific gravity of the liquid for measuring the dissolved resin concentration CR in the liquid developer LD.

  Further, the liquid developer LD in which the resin material R is dissolved is colorless or white light and nonpolar. Furthermore, the liquid developer LD in which the resin material R is dissolved has a feature of high viscosity. For this reason, the rotating body is immersed in the liquid developer LD, and the dissolved resin concentration CR in the liquid developer LD is changed using the fact that the torque of the rotating body changes according to the change in the viscosity of the liquid developer LD. A measurement technique can be considered. However, the viscosity of the liquid developer LD varies greatly depending on the dissolved resin concentration CR.

  Table 1 shows the viscosity of the liquid developer LD corresponding to each dissolved resin concentration CR when the dissolved resin concentration CR of the liquid developer LD is changed in advance. Thus, the viscosity of the liquid developer LD varies greatly depending on the dissolved resin concentration CR. For measuring the viscosity of the liquid developer LD, a rotational viscometer based on “JIS-Z8803 Liquid Viscosity—Measurement Method” was used.

  Since there is such a change in the viscosity of the liquid developer LD, in the concentration region where the viscosity is high (torque is large), even if the concentration is detected with the desired accuracy, in the concentration region where the viscosity is low (torque is small). The concentration is not detected with the desired accuracy. Further, in the region where the viscosity is extremely high (the torque is extremely large), the rotational speed of the rotating body is remarkably lowered, and the accuracy of density detection is lowered. Furthermore, if the torque of the rotating body increases too much, the rotation of the rotating body stops, making it difficult to detect the density.

  In the dissolved resin concentration detection device 280 according to the present embodiment, unlike the concentration detection device in which the rotating body rotates, the liquid developer LD does not have a mechanical action, and thus the viscosity of the liquid developer LD. It becomes possible to cope with the change of. As described below, the dissolved resin concentration detection device 280 according to this embodiment is also characterized in that it uses a change in the viscosity of the liquid developer LD. Hereinafter, measurement of the dissolved resin concentration CR by the dissolved resin concentration detection device 280 according to the present embodiment will be described in detail.

  FIG. 4 is a diagram showing the relationship between the dissolved resin concentration CR of the dissolved resin concentration detection device 280 and the output frequency F of the frequency meter 696 according to the present embodiment. FIG. 5 is a diagram showing the relationship between the output frequency F of the frequency meter 696 and the immersion depth D3 of the QCM sensor 60 in the dissolved resin concentration detection device 280. FIG. 6 is a graph showing the relationship between the liquid temperature T of the liquid developer LD and the viscosity η of the liquid developer LD. FIG. 7 is a diagram showing the relationship between the liquid temperature T of the liquid developer LD and the output frequency F of the frequency meter 696 in the dissolved resin concentration detection device 280. Further, FIG. 8 is a diagram showing the temperature dependence of the oscillation circuit 641 provided in the dissolved resin concentration detection device 280.

  FIG. 4 shows the output frequency F detected by the frequency meter 696 when various conditions of the detection device main body 280A are made constant and the dissolved resin concentration CR of the liquid developer LD is changed in advance. Thus, it can be seen that the output frequency F of the crystal resonator 611 in the QCM sensor 60 changes according to the dissolved resin concentration CR of the liquid developer LD. As described above, this is because the viscosity of the liquid developer LD varies depending on the dissolved resin concentration CR. A certain correlation exists between the dissolved resin concentration CR and the output frequency F. Therefore, the dissolved resin concentration CR in the liquid developer LD can be detected using the output frequency F of the crystal resonator 611.

  On the other hand, the present inventor has found that the output frequency F of the crystal resonator 611 is affected by the depth of the crystal resonator 611 immersed in the liquid developer LD. FIG. 5 shows a state of the output frequency F when the depth D3 (d in FIG. 5) of the sensor electrode 61 of the QCM sensor 60 is changed in the liquid developer LD having a predetermined dissolved resin concentration CR. The depth D3 of the sensor electrode 61 is shown in FIG. 5 that the output frequency F of the crystal unit 611 changes according to the depth D3 in which the sensor electrode 61 is immersed even at the same dissolved resin concentration CR. The change in the output frequency F is affected by the height of the liquid developer LD covering the upper side of the sensor electrode 61. This is because if the liquid height above the sensor electrode 61 increases, a large amount of vibration energy of the crystal resonator 611 is required.

  Further, FIG. 6 shows a change in the viscosity η when the liquid temperature T of the liquid developer LD having a predetermined dissolved resin concentration CR is changed by a heater or a cooling device (not shown). Thus, when the liquid temperature T of the liquid developer LD changes, the fluidity of the resin material R in the carrier liquid C changes, and the viscosity η of the liquid developer LD changes. As shown in FIG. 7, even if the liquid developer LD has the same dissolved resin concentration CR due to the influence of the viscosity η of the liquid developer LD, when the liquid temperature T changes, the output of the crystal unit 611 is output. The frequency F changes. Note that the change in the output frequency F may include the temperature dependence of the oscillation circuit 641 in the circuit unit 64. However, as shown in FIG. 8, it was found that the output frequency F detected by the frequency meter 696 hardly changes even when the temperature of the oscillation circuit 641 itself is changed. Therefore, it can be understood that the change in the output frequency F accompanying the change in the liquid temperature T is due to the change in the viscosity η of the liquid developer LD.

  In the present embodiment, based on the above-described problem when the dissolved resin concentration CR in the liquid developer LD is measured using the vibration action of the crystal resonator 611, in the present embodiment, the concentration calculation of the QCM sensor 60 and the concentration calculation unit 698 is performed. Features in the method.

  As described above, the QCM sensor 60 is immersed in the liquid developer LD in the concentration detection tank 691 (FIG. 1). At this time, the bottom surface portion 651 of the housing 65 is disposed immediately above the QCM sensor 60. The pedestal portion 62 of the QCM sensor 60 is disposed so as to contact the bottom surface portion 651. That is, the bottom surface portion 651 covers the upper side of the QCM sensor 60 in the liquid developer LD, and the distance in the depth direction from the QCM sensor 60 is kept constant. Thereby, the distance D1 in the vertical direction between the sensor electrode 61 and the bottom surface portion 651 of the QCM sensor 60 is always kept constant. For this reason, the liquid height of the liquid developer LD covering the upper side of the QCM sensor 60 is always kept constant. As a result, it is possible to suppress fluctuations in the output frequency F due to the immersion depth of the sensor electrode 61. In order to further avoid the influence of the liquid developer existing above the QCM sensor 60, the depth D1 with respect to the bottom surface portion 651 of the immersed QCM sensor 60 in FIG. 1 is preferably 6 mm or more. . Further, regarding the area of the bottom surface portion 651 that covers the QCM sensor 60, it is preferable that the diameter of the bottom surface portion 651 is 34 mm or more. Thereby, the upper part of the QCM sensor 60 is sufficiently covered by the bottom surface part 651.

  The concentration calculation unit 698 converts the output frequency F detected by the frequency meter 696 into a dissolved resin concentration CR. At this time, the concentration calculation unit 698 corrects the fluctuation amount of the dissolved resin concentration CR caused by the liquid temperature of the liquid developer LD. First, the liquid temperature T of the liquid developer LD detected by the liquid temperature sensor 692 is stored in the storage unit 697. On the other hand, the temperature correction value Vt is stored in the storage unit 697 in advance. The temperature correction value Vt is a correction value calculated based on FIG. 7, and is used to convert the output frequency F at the liquid temperature T to the conversion frequency FC at the reference liquid temperature 25 degrees. The concentration calculation unit 698 derives a conversion frequency FC from the detected liquid temperature T and output frequency F.

  The storage unit 697 stores a density conversion value Vd in advance. The concentration conversion value Vd is used to convert the conversion frequency FC (the output frequency F in FIG. 4) into the dissolved resin concentration CR based on the calibration curve of FIG. For this reason, in this embodiment, the density | concentration conversion value Vd is stored for every predetermined frequency. The concentration calculation unit 698 derives the dissolved resin concentration CR of the liquid developer LD from the converted frequency FC based on the concentration converted value Vd.

  As described above, in the present embodiment, after correcting the influence of the immersion depth D3 (D1) of the QCM sensor 60 immersed in the liquid developer LD and the influence of the liquid temperature T of the liquid developer LD, the liquid It becomes possible to detect the dissolved resin concentration CR of the developer LD.

<Embodiment as Image Forming Apparatus>
Next, an image forming apparatus incorporating the dissolved resin concentration detection device 280 according to the above embodiment will be described. FIG. 9 is a schematic configuration diagram of a color printer 1 (image forming apparatus) in which a dissolved resin concentration detection device 280 is incorporated. FIG. 10 is a schematic cross-sectional view of the color printer 1 excluding the liquid developer circulating device. 11 is an enlarged cross-sectional view of one of the image forming units. Although the image forming apparatus shown in FIGS. 9 to 11 is a color printer, it is a copier, a facsimile machine, a multifunction peripheral (MFP) including these functions, and other devices capable of forming an image on a sheet. It can also be a device.

  As shown in FIG. 9, the color printer 1 is arranged in an upper main body 1A in which various units and parts for image formation are stored, and a lower part of the upper main body 1A, and a liquid developer circulation for each color. It is comprised from the lower main-body part 1B in which apparatus LY, LM, LC, LB is accommodated. Here, the piping connecting the upper main body 1A and the lower main body 1B is not shown.

  As shown in FIG. 10, the upper main body 1 </ b> A is formed by a tandem image forming unit 2 that forms a toner image based on image data, a paper storage unit 3 that stores paper, and an image forming unit 2. A secondary transfer unit 4 that transfers the toner image onto the paper, a fixing unit 5 that fixes the transferred toner image on the paper, a discharge unit 6 that discharges the fixed paper, and a paper storage unit 3. And a paper transport unit 7 for transporting paper from the discharge unit 6 to the discharge unit 6.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22 for the intermediate transfer belt 21, and an image forming unit corresponding to each of yellow (Y), magenta (M), cyan (C), and black (Bk). FY, FM, FC, and FB.

  The intermediate transfer belt 21 is a belt-like member that is conductive and wider than the maximum length of paper in the direction perpendicular to the usable paper transport direction, and is an endless belt-like member. In FIG. 10, it is circulated and driven clockwise. In the circulation driving of the intermediate transfer belt 21, the surface facing outward is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

  The image forming units FY, FM, FC, and FB are arranged in parallel in the vicinity of the intermediate transfer belt 21 and between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but the order of arrangement is preferable in consideration of the influence on the completed image caused by the color mixture of each color.

  The image forming units FY, FM, FC, and FB include a photosensitive drum 10, a charger 11, an LED exposure device 12, a developing device 14, a primary transfer roller 20, a cleaning device 26, and a charge removal device 13. And a carrier liquid removing roller 30. Of the image forming units, the image forming unit FB located closest to the secondary transfer unit 4 is not provided with the carrier liquid removal roller 30, but the other configurations are the same.

  In addition, liquid developer circulating devices LY, LM, LC, and LB are provided corresponding to the image forming units FY, FM, FC, and FB, respectively, and supply and recovery of the liquid developer LD of each color are performed. The liquid developer circulating devices LY, LM, LC, and LB will be described in detail later.

  The photoconductor drum 10 is a cylindrical member, and carries a toner image including toner charged (charged positively in the present embodiment) on the surface thereof. The photosensitive drum 10 is rotated counterclockwise in FIGS. 9 and 10. The charger 11 uniformly charges the surface of the photosensitive drum 10. The LED exposure device 12 has a light source such as an LED, and irradiates light onto the surface of the uniformly charged photoreceptor drum 10 according to image data input from an external device. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10.

  The developing device 14 holds the liquid developer LD including the toner and the liquid carrier so as to face the electrostatic latent image on the surface of the photosensitive drum 10, thereby attaching the toner to the electrostatic latent image. Thereby, the electrostatic latent image is developed as a toner image.

  Referring to FIG. 11, the developing device 14 includes a developing container 140, a developing roller 141, a supply roller 142, a support roller 143, a supply roller blade 144, a development cleaning blade 145, a developer recovery device 146, and a development roller charger 147. Including.

  The developing container 140 is supplied with a liquid developer LD composed of toner particles and a liquid carrier. The liquid developer LD is supplied from the supply nozzle 278 into the developing container 140 in a state where the density adjustment between the toner and the carrier is performed in advance. The liquid developer LD is supplied toward the nip portion between the supply roller 142 and the support roller 143, and the excess part falls below the support roller 143 and is stored at the bottom of the developing container 140. The stored liquid developer LD is collected by the liquid developer circulating device through the pipe 82 (see FIG. 12).

  The support roller 143 is disposed substantially at the center of the developing container 140 and is brought into contact with the supply roller 142 from below to form a nip portion. The supply roller 142 is arranged not diagonally above the support roller 143 but obliquely above in a direction away from the supply nozzle 278. A groove for holding the liquid developer LD is provided on the peripheral surface of the supply roller 142. As shown by a dotted arrow in FIG. 11, the support roller 143 rotates counterclockwise, and the supply roller 142 rotates clockwise.

  The liquid developer LD supplied from the supply nozzle 278 is temporarily retained on the upstream side in the rotation direction of the nip portion. The liquid developer LD is carried upward while being held in the groove of the supply roller 142 as the rollers 142 and 143 rotate. The supply roller blade 144 is pressed against the peripheral surface of the supply roller 142 so that the amount of the liquid developer LD held by the supply roller 142 becomes a predetermined amount. Regulates liquid developer LD. The excess liquid developer LD scraped off by the supply roller blade 144 is received at the bottom of the developing container 140.

  The developing roller 141 is disposed in the upper opening of the developing container 140 so as to be in contact with the supply roller 142. The developing roller 141 is rotated in the same direction as the supply roller 142 (the surface of the developing roller 141 moves in the opposite direction to the surface of the supply roller 142 in the nip portion where the developing roller 141 and the supply roller 142 abut). The liquid developer LD held on the peripheral surface of the supply roller 142 is delivered to the peripheral surface of the developing roller 141. Since the layer thickness of the liquid developer on the supply roller 142 is regulated to a predetermined value, the layer thickness of the liquid developer layer formed on the surface of the developing roller 141 is also maintained at the predetermined value.

  The developing roller charger 147 applies a charging potential having the same polarity as the toner charging polarity on the surface of the developing roller 141. For this reason, the toner in the developer layer carried on the developing roller 141 is moved to the surface side of the developing roller 141, and the development efficiency is improved. The developing roller charger 147 is a peripheral surface of the developing roller 141 on the developing roller 141 on the downstream side in the rotation direction with respect to the contact portion with the supply roller 142 and on the upstream side with respect to the contact portion with the photosensitive drum 10. It arrange | positions so that it may oppose.

  The developing roller 141 is in contact with the photosensitive drum 10. A toner image corresponding to the image data is formed on the surface of the photosensitive drum 10 by the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 141.

  The development cleaning blade 145 is disposed so as to contact the downstream side in the rotation direction with respect to the contact portion of the development roller 141 with the photosensitive drum 10, and the development cleaning blade 145 is on the surface of the development roller 141 that has completed the development operation on the photosensitive drum 10. The liquid developer LD is removed.

  The developer recovery device 146 recovers the liquid developer removed by the development cleaning blade 145 and sends the liquid developer LD to the pipe 81 of the liquid developer circulation device. The liquid developer LD flows down along the surface of the development cleaning blade 145. However, since the viscosity of the liquid developer LD is high, the developer recovery device 146 has a delivery roller (not shown) that assists in feeding the liquid developer LD. Is provided.

  The primary transfer roller 20 is disposed on the back surface of the intermediate transfer belt 21 so as to face the photosensitive drum 10. A voltage having a polarity opposite to that of the toner in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 from a power source (not shown). The primary transfer roller 20 applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21 at a position in contact with the intermediate transfer belt 21. Since the intermediate transfer belt 21 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt 21 and its periphery. The intermediate transfer belt 21 functions as an image carrier that carries a toner image and conveys it to a sheet.

  The cleaning device 26 cleans the liquid developer LD remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21. The cleaning device 26 includes a residual developer conveying screw 261 and a cleaning blade 262. The residual developer conveying screw 261 is a member for conveying the residual developer scraped by the cleaning blade 262 and stored in the cleaning device 26 to the outside of the cleaning device, and is disposed in the cleaning device 26. Yes.

  The cleaning blade 262 is a member for scraping off the liquid developer LD remaining on the surface of the photosensitive drum 10 and is a plate-like member extending in the rotation axis direction of the photosensitive drum 10. The end of the cleaning blade 262 is in sliding contact with the surface of the photosensitive drum 10, and scrapes off the liquid developer LD remaining on the photosensitive drum 10 as the photosensitive drum 10 rotates.

  The static eliminator 13 has a light source for static elimination, and removes the liquid developer LD by the cleaning blade 262 and removes the surface of the photosensitive drum 10 with light from the light source in preparation for image formation in the next round.

  The carrier liquid removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photosensitive drum 10 around a rotational axis parallel to the rotational axis of the photosensitive drum 10. The carrier liquid removing roller 30 is disposed on the side where the secondary transfer unit 4 is disposed with respect to the position where the photosensitive drum 10 and the intermediate transfer belt 21 are in contact with each other, and the carrier liquid is removed from the surface of the intermediate transfer belt 21. Remove.

  Returning to FIG. 10, the paper storage unit 3 is a part for storing a paper for fixing a toner image, and is disposed below the upper main body 1 </ b> A. The paper storage unit 3 has a paper feed cassette that stores paper.

  The secondary transfer unit 4 transfers the toner image formed on the intermediate transfer belt 21 to a sheet. The secondary transfer unit 4 includes a support roller 41 that supports the intermediate transfer belt 21 and a secondary transfer roller 42 that is disposed to face the support roller.

  The fixing unit 5 fixes the toner image on the paper. The fixing unit 5 is disposed on the upper side of the secondary transfer unit 4. The fixing unit 5 includes a heating roller 51 and a pressure roller 52 disposed so as to face the heating roller 51.

  The discharge unit 6 discharges the sheet on which the toner image is fixed by the fixing unit 5. The discharge unit 6 is disposed at the top of the color printer 1. The paper transport unit 7 includes a plurality of transport roller pairs, and transports the paper from the paper storage unit 3 to the secondary transfer unit 4, the fixing unit 5, and the discharge unit 6.

  FIG. 12 is a block diagram showing an outline of the entire liquid developer circulating device LY. The other liquid developer circulating devices LM, LC, LB have the same configuration. This liquid developer circulation device LY supplies the residual developer (mixture of toner and carrier liquid) scraped from the surface of the developing roller 141 by the developing cleaning blade 145 after supplying the liquid developer LD to the photosensitive drum 10. It is a device for circulation and reuse.

  The liquid developer circulation device LY includes a residual developer tank 271, a developer container 272, a solid concentration detector 273, a carrier tank 274, a toner tank 275, a varnish tank 279, a stirring device 276, a developer reserve tank 277, and liquid development. An agent supply device 278, a dissolved resin concentration detection device 280, a liquid developer separation device 28, a plurality of pumps P1 to P15, and a control unit 550 are provided.

  The residual developer tank 271 is a tank that is connected to the developing device 14 via the first pipe 81 and the second pipe 82 and can store the liquid developer LD collected from the developing device 14 side. A first pump P1 and a fifth pump P5 are attached in the middle of the first pipe 81 and the second pipe 82, respectively.

  The liquid developer scraped from the surface of the developing roller 141 by the developing cleaning blade 145 after supplying the toner to the photosensitive drum 10 is sent to the residual developer tank 271 through the first pipe 81 by driving the first pump P1. It is done. Further, in the developing container 140, the liquid developer LD stored in the developing container 140 without being supplied from the supply roller 142 to the developing roller 141 passes through the second pipe 82 by the driving of the fifth pump P5, and remains in the developing process. Sent to the agent tank 271.

  The developer container 272 is connected to the residual developer tank 271. The developer container 272 adjusts the toner concentration to an appropriate range by adding a developer having a higher toner concentration than the developer used in the developing device 14 or a carrier liquid to the residual developer. The liquid developer LD having the adjusted toner density is supplied to the developing device 14. The developer container 272 is connected to the residual developer tank 271 via the third pipe 83. A second pump P2 is attached to the third pipe 83. The liquid developer LD in the residual developer tank 271 is sent to the developer container 272 through the third pipe 83 by driving the second pump P2.

  The solid content concentration detection device 273 detects the toner concentration of the liquid developer LD in the developer container 272. The solid content concentration detection device 273 is connected to an annular fourth pipe 84 connected to the developer container 272. A fourth pump P4 is attached to the annular fourth pipe 84. The liquid developer LD in the developer container 272 is guided from the inlet end of the fourth pipe 84 to the solid concentration detector 273 by the driving of the fourth pump P4, and then developed from the outlet end of the fourth pipe 84. It is returned to the agent storage container 272.

  The dissolved resin concentration detector 280 detects the dissolved resin concentration CR in the liquid developer LD in the developer container 272. A dissolved resin concentration detector 280 is connected to an annular twelfth pipe 892 connected to the developer container 272. A fifteenth pump P15 is attached to the annular twelfth pipe 892. The liquid developer LD in the developer container 272 is guided from the inlet end of the twelfth pipe 892 to the dissolved resin concentration detection device 280 by driving of the fifteenth pump P15, and then the developer from the outlet end of the twelfth pipe 892. Returned to the storage container 272. The dissolved resin concentration detection device 280 according to the embodiment of the present invention is applied to the dissolved resin concentration detection device 280. That is, the annular twelfth pipe 892 is connected to the concentration detection tank 691 (FIG. 2) of the dissolved resin concentration detection device 280.

  The carrier tank 274 stores a carrier liquid. When the solid concentration detector 273 determines that the toner concentration in the developer container 272 is higher than the appropriate range, the carrier liquid is supplied from the carrier tank 274 into the developer container 272, and the container 272 The toner concentration of the liquid developer inside is lowered. The carrier tank 274 and the developer container 272 are connected by a fifth pipe 85, and the supply of the carrier liquid is executed by driving a third pump P3 provided in the middle of the fifth pipe 85.

  The toner tank 275 stores a liquid developer LD having a toner concentration higher than that of the developer used in the developing device 14. When the solid concentration detector 273 determines that the toner concentration in the developer container 272 is lower than the appropriate range, the liquid developer LD having a high toner concentration from the toner tank 275 to the developer container 272. And the toner concentration of the liquid developer LD in the container 272 is increased. The toner tank 275 and the developer container 272 are connected by a sixth pipe 86, and the supply of the liquid developer LD is executed by driving an eighth pump P8 provided in the middle of the sixth pipe 86. .

  The varnish tank 279 stores a liquid developer LD having a dissolved resin concentration CR higher than that of the liquid developer LD used in the developing device 14. When the dissolved resin concentration detection device 280 determines that the dissolved resin concentration CR in the developer container 272 is lower than the appropriate range, the liquid having a high dissolved resin concentration CR from the varnish tank 279 to the developer container 272. Developer LD is supplied. As a result, the dissolved resin concentration CR of the liquid developer LD in the developer container 272 is increased. The varnish tank 279 and the developer container 272 are connected by an eleventh pipe 891, and the supply of the liquid developer LD is executed by driving a thirteenth pump P13 provided in the middle of the eleventh pipe 891.

  The stirring device 276 is a member for stirring the liquid developer in the developer container 272. The purpose of this stirring is to allow the toner or carrier liquid introduced into the developer container 272 for density adjustment to be uniformly mixed with the existing liquid developer in the developer container 272. This is to redisperse the toner that may aggregate in the liquid developer LD accommodated in the developer accommodating container 272. The stirring device 276 includes a rotating shaft and a stirring blade attached to the tip of the rotating shaft. A liquid level detecting member 276a is coaxially assembled to the rotating shaft. The liquid level detection member 276a is driven by a motor (not shown), and the amount of liquid developer is detected based on a change in the load of the motor when the liquid level detection member 276a contacts the liquid level of the liquid developer LD. Is done.

  The developer reserve tank 277 is a tank that stores the liquid developer LD to be replenished to the developing device 14. The developer reserve tank 277 is connected to the developer container 272 by a seventh pipe 871. The developer reserve tank 277 is supplied with the liquid developer LD from the developer container 272 by driving a sixth pump P6 provided in the middle of the seventh pipe 871. Further, the developer reserve tank 277 is connected by a carrier tank 274 and a first direct connection pipe 910, and by a toner tank 275 and a second direct connection pipe 920, respectively. Further, the developer reserve tank 277 is connected to the varnish tank 279 through a third direct connection pipe line 930. An eleventh pump P11, a twelfth pump P12, and a fourteenth pump P14 are arranged in the first, second, and third direct connection pipes 910, 920, and 930, respectively, and carrier, toner, and dissolved resin are directly supplied from each tank. The developer can be supplied to the developer reserve tank 277. The carrier, toner, and dissolved resin supply systems from the first, second, and third direct connection pipes 910, 920, and 930 are known at the start of use of the color printer 1 in which no recovered liquid developer has been generated. This is utilized when the liquid developer LD is promptly generated according to the blending ratio.

  The supply nozzle 278 supplies the liquid developer LD stored in the developer reserve tank 277 to the developing device 14 (developing container 140). The supply nozzle 278 and the developer reserve tank 277 are connected by an eighth pipe 872. The supply of the liquid developer LD is executed by driving a seventh pump P7 attached to the eighth pipe 872.

  Further, the liquid developer circulation device LY includes a direct connection conduit 910 extending from the carrier tank 274 to the developer reserve tank 277 and a direct connection conduit 920 extending from the toner tank 275 to the developer reserve tank 277. These direct connection pipes 910 and 920 are used to supply a predetermined amount of carrier and toner to the developer reserve tank 277 before the liquid developer LD is circulated. This makes it possible to start the development process quickly.

  Although not shown, the residual developer tank 271, the carrier tank 274, the toner tank 275, the developer reserve tank 277, and the varnish tank 279 are provided at appropriate positions for detecting the liquid level in these tanks. A liquid level detection device is provided.

  The liquid developer separating device 28 separates the toner from the residual developer collected by the cleaning device 26 and the carrier liquid C in which the resin material R is dissolved, and separately extracts the toner and the carrier liquid C. The cleaning device 26 and the liquid developer separating device 28 are connected by a ninth pipe 881. A ninth pump P9 is attached to the ninth pipe 881. The residual developer in the cleaning device 26 is sent to the liquid developer separating device 28 by driving the ninth pump P9. Further, the liquid developer separating device 28 and the carrier tank 274 are connected by a tenth pipe 882. A tenth pump P10 is attached to the tenth pipe 882. The carrier liquid C extracted by the liquid developer separating device 28 is sent to the carrier tank 274 by driving the tenth pump P10.

  The control unit 550 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores each control program, and a RAM (Random Access Memory) that temporarily stores data such as arithmetic processing and control processing. Etc. The controller 550 controls driving of the first to twelfth pumps P1 to P15, driving of a motor that operates the liquid level detection member 276a, and the like.

  Next, the operation of the color printer 1 will be described. Upon receiving an image formation instruction from a personal computer (not shown) connected to the color printer 1, the color printer 1 converts toner images of each color corresponding to the image data received with the creation instruction into image forming units FY, FM, FC, It is formed using FB. Specifically, an electrostatic latent image based on image data is formed on the photosensitive drum 10, and toner is supplied to the electrostatic latent image from the developing device 14. The images formed by the image forming units FY, FM, FC, and FB in this way are transferred to the intermediate transfer belt 21 and are superimposed on the intermediate transfer belt 21 to form a color toner image.

  In synchronization with the formation of the color toner image, the paper stored in the paper storage unit 3 is taken out from the paper storage unit 3 one by one by a paper feeding device (not shown), and is transported along the paper transport unit 7. . Then, the sheet is fed into the secondary transfer unit 4, and the color toner image on the intermediate transfer belt 21 is secondarily transferred to the sheet at the secondary transfer unit 4.

  The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 5 and the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged outside the color printer 1 by the discharge unit 6. The toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by the cleaning unit 22 of the intermediate transfer belt 21.

  The liquid developer LD remaining on the developing roller 141 without being supplied to the photosensitive drum 10 during the image forming operation is scraped off by the developing cleaning blade 145 and is collected in the residual developer tank 271 through the first pipe 81. The Further, the liquid developer LD recovered in the developing container 140 without being supplied from the supply roller 142 to the developing roller 141 is also recovered in the residual developer tank 271 through the second pipe 82. Further, the carrier liquid extracted by the liquid developer separating device 28 from the residual developer recovered by the cleaning device 26 is recovered to the carrier tank 274. In order to execute such liquid circulation, the first, fifth, ninth, and tenth pumps P1, P5, P9, and P10 are driven and controlled by the control unit 550.

  When the liquid developer amount in the developer container 272 is exhausted, the control unit 550 drives the second pump P2. The controller 550 causes the residual developer tank 271 to supply the residual developer to the developer storage container 272. When the developer container 272 is filled with the residual developer, the solid concentration detector 273 detects the toner concentration of the liquid developer LD. In accordance with the detection result, the control unit 550 drives the third pump P3 or the eighth pump P8 to supply a necessary amount of carrier liquid or high-concentration liquid developer to the developer container 272. Thereafter, the toner concentration of the liquid developer LD is detected again by the solid content concentration detection device 273. If the toner concentration is within an appropriate range, the liquid developer LD is supplied to the developer reserve tank 277 as necessary. Similarly, after the dissolved resin concentration CR of the liquid developer LD in the developer container 272 is measured by the dissolved resin concentration detection device 280, a necessary amount of the resin component R is adjusted by the control unit 550. The

  Inside the liquid developer separating device 28, the carrier liquid and the toner particles are separated. That is, the collected liquid developer is introduced into the liquid tank 510 through the ninth pipe 881. The carrier liquid separated by the carrier liquid recovery roller 540 is sent to the carrier tank 274 through the tenth pipe 882. On the other hand, the toner recovered from the toner recovery roller 530 is guided to a waste tank. According to the color printer 1 provided with such a liquid developer separation device 28, the separation speed between the toner and the carrier liquid can be increased, so that it is possible to cope with high-speed printing processing.

<About liquid developer>
Next, the liquid developer LD used as a measurement target of the dissolved resin concentration detection device 280 in the above embodiment will be described. As described above, the liquid developer LD includes the electrically insulating carrier liquid C and the colored particles P dispersed in the carrier liquid C. Further, the liquid developer LD contains a resin material R. When used in the image forming apparatus, the liquid developer LD preferably has a viscosity of 30 to 400 mPa · s at a measurement temperature of 25 ° C. More preferably, the viscosity (measurement temperature 25 ° C.) of the liquid developer is 40 to 300 mPa · s, and more preferably 50 to 250 mPa · s.

<Carrier liquid>
The electrically insulating carrier liquid C that plays the role of a liquid carrier enhances the electrical insulation of the liquid developer LD. As the electrically insulating carrier liquid C, for example, an electrically insulating organic solvent having a volume resistance at 25 ° C. of 1012 Ω · cm or more (in other words, conductivity of 1.0 pS / cm or less) is preferable. Further, in addition to the above physical properties, those capable of dissolving a resin material R described later (a resin material R having a relatively high solubility) are preferably used.

  Further, the viscosity, type, and blending amount of the carrier liquid C are appropriately adjusted and selected so that the overall viscosity (measurement temperature 25 ° C.) of the liquid developer LD is 30 to 400 mPa · s. The viscosity of the liquid developer LD also depends on the combination of the organic solvent used as the carrier liquid C and the resin material R described later. Therefore, the type and blending amount of the organic solvent are appropriately determined according to the desired viscosity of the liquid developer LD and the type of the selected resin material R.

  Examples of such an electrically insulating organic solvent include aliphatic hydrocarbons and vegetable oils that are liquid at room temperature.

  As the aliphatic hydrocarbon, for example, liquid n-paraffinic hydrocarbon, iso-paraffinic hydrocarbon, halogenated aliphatic hydrocarbon, branched aliphatic hydrocarbon or a mixture thereof is preferable. For example, n-hexane, n-heptane, n-octane, nonane, decane, dodecane, hexadecane, heptadecane, cyclohexane, perchloroethylene, and trichloroethane are used as the aliphatic hydrocarbon. From the viewpoint of environmental measures (measures against VOC), non-volatile organic solvents and organic solvents with relatively low volatility (for example, those having a boiling point of 200 ° C. or higher) are preferable. Liquid paraffin containing a relatively large amount of hydrogen is preferably used.

  In the above embodiment, as long as the resin material R is dissolved in the carrier liquid C, only the carrier liquid C having a relatively high solubility of the resin material R (good solvent for the resin material R) may be used, or A resin material R having a relatively low solubility (a poor solvent for the resin material R) may be mixed and used.

  The content of the oils in the carrier liquid C depends on the type and content of the resin material R contained in the liquid developer LD. Examples of suitable oil content include 70 to 95% by mass. If it is less than 70 mass%, it will be difficult to dissolve the resin material R well in the carrier liquid C.

  In the embodiment described above, the conductivity of the liquid developer LD is preferably 200 pS / cm or less, for example. The carrier liquid C is an insulating solution by itself, but the liquid developer LD has a predetermined electrical conductivity by dispersing pigments and dispersants that are colored particles. Therefore, liquid development can be achieved by mixing aliphatic hydrocarbons having high electrical resistance with a solution obtained by dissolving resin material R in oils such as tall oil fatty acid (hereinafter referred to as “resin solution”). It is preferable that the electrical conductivity of the agent LD is adjusted to 200 pS / cm or less, for example.

<Colored particles>
In the above embodiment, the pigment itself is used for the colored particles P as the toner. The colored particles P used in the image forming unit FM described above have a magenta hue. The colored particles P used in the image forming unit FC described above have a cyan hue. The colored particles P used in the above-described image forming unit FY have a yellow hue. The colored particles P used in the above-described image forming unit FB have a black hue.

  As a pigment in said embodiment, a conventionally well-known organic pigment and an inorganic pigment are used, for example, without specifically limiting.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. . Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B. Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include C.I. I. Pigment Blue 15: 3, cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorinated product, first sky blue, and indanthrene blue BC. Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.

  The content of the pigment in the liquid developer LD is preferably 1 to 30% by mass. More preferably, it is 3 mass% or more, More preferably, it is 5 mass% or more. Moreover, More preferably, it is 20 mass% or less, More preferably, it is 10 mass% or less.

  The average particle diameter of the pigment in the liquid developer LD, that is, the volume-based median diameter (D50) is preferably 0.1 to 1.0 μm. A pigment having an average particle size of less than 0.1 μm causes, for example, a reduction in image density. A pigment having an average particle diameter exceeding 1.0 μm causes, for example, a decrease in fixability. Here, the volume-based median diameter (D50) is generally that the cumulative curve is 50% when the cumulative curve is obtained with the total volume of a group of particles whose particle size distribution is required as 100%. The particle diameter of

<Polymer compound (resin material)>
The resin material R contained in the liquid developer LD according to the above embodiment is an organic polymer compound. As the organic polymer compound having solubility in the carrier liquid C, a material capable of increasing the viscosity of the liquid developer and suppressing the occurrence of bleeding in image formation is selected. Examples of the organic polymer compound include cyclic olefin copolymer, styrene elastomer, cellulose ether, and polyvinyl butyral. Preferably, a styrene elastomer is used as the organic polymer compound. As the resin material R, a single type of organic polymer compound may be used, or a plurality of types of organic polymer compounds may be used.

  In the liquid developer LD according to the above embodiment, the organic polymer compound is dissolved in the carrier liquid C. The organic polymer compound dissolved in the carrier liquid C may be in a gel state. Depending on the type and molecular weight of the organic polymer compound, a gel-like organic polymer compound entangled with each other in the carrier liquid C can be obtained. Gel-like organic polymer compounds have relatively low fluidity. For example, when the concentration of the organic polymer compound is high, when the affinity between the organic polymer compound and the carrier liquid C is low, or when the temperature is low, a gel-like organic polymer compound is easily obtained. On the other hand, the organic polymer compound with little entanglement in the carrier liquid C becomes a solution having relatively high fluidity.

  The content of the organic polymer compound in the liquid developer LD is appropriately determined according to the type of the organic polymer compound. The content of the organic polymer compound is preferably 1 to 10% by mass, for example.

  If the content of the organic polymer compound is less than 1% by mass, sufficient viscosity in the liquid developer LD cannot be obtained, and there is a possibility that the occurrence of bleeding in image formation cannot be sufficiently suppressed. On the other hand, when the content of the organic polymer compound exceeds 10% by mass, the amount of the coating with the organic polymer compound remaining on the surface of the sheet S is excessively increased, and the drying property of the coating is excessively lowered. As a result, the adhesiveness (tackiness) of the film may be excessively increased, and the scratch resistance of the image may be excessively decreased.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, For example, the following modified embodiment can be taken.

  (1) In the above embodiment, in the dissolved resin concentration detection device 280, the bottom surface portion 651 of the flat housing 65 has been described as being disposed horizontally, but the present invention is not limited to this. For example, the bottom surface portion 651 may be a surface slightly inclined with respect to a horizontal plane at a predetermined angle in advance. In this case, even if bubbles are generated in the liquid developer LD, the bubbles do not stay at the bottom 651 of the housing 65 and escape along the slope of the bottom 651. Therefore, the bubbles are prevented from affecting the oscillation of the crystal resonator 611.

  (2) In the above-described embodiment, the bottom surface portion 651 of the housing 65 has been described as the restricting member that covers the top of the QCM sensor 60 and keeps the immersion depth of the QCM sensor 60 constant. It is not limited. For example, a configuration in which a member different from the housing 65 (bottom surface portion 651) is disposed above the QCM sensor 60 so as to cover the QCM sensor 60 may be employed.

  (3) In the above embodiment, the solid content concentration detection device 273 and the dissolved resin concentration detection device 280 measure the concentration of the liquid developer LD in the developer container 272 via different annular pipes. Explained as a thing. However, the present invention is not limited to this, and the solid content concentration detection device 273 and the dissolved resin concentration detection device 280 measure the liquid developer LD collected from the developer storage container 272 through the same pipe, It may be an embodiment in which the solid content concentration and dissolved resin concentration are detected.

1 Color printer (image forming device)
280 Dissolved resin concentration detector (concentration detector)
280A Detection device body 280B Measurement unit 60 QCM sensor (sensor unit)
61 sensor electrode 611 crystal resonator 612 first electrode portion (first electrode)
613 Second electrode portion (second electrode)
62 Base 63a First lead 63b Second lead 64 Circuit unit 641 Oscillator circuit 65 Housing 651 Bottom (bottom)
66 Shield (Shield member)
691 Concentration detection tank (storage container)
692 Liquid temperature sensor (liquid temperature detection means)
693 Power supply 694 First wiring unit 695 Second wiring unit 696 Frequency meter 697 Storage unit 698 Concentration calculation unit

Claims (8)

A storage container for storing a liquid developer containing a dissolved resin component;
A sensor unit including a crystal resonator that immerses in the liquid developer in the storage container and oscillates a vibration frequency according to the concentration of the dissolved resin component in the liquid developer;
An oscillation circuit connected to the sensor unit and oscillating the crystal resonator;
A regulating member that is immersed in the liquid developer in the storage container, covers an upper portion of the sensor unit, and a distance in the depth direction from the sensor unit is held constant;
A concentration calculator that calculates the concentration of the dissolved resin component in the liquid developer from the vibration frequency at which the crystal resonator oscillates;
A concentration detection apparatus comprising: The housing further includes a housing that houses the oscillation circuit and is immersed in the liquid developer,
The sensor portion is disposed so as to protrude downward from the bottom portion of the housing,
The oscillation circuit is connected to the sensor unit via the bottom,
The concentration detection apparatus according to claim 1, wherein the restriction member is the bottom portion of the housing. A liquid temperature detecting means for detecting a liquid temperature of the liquid developer in the storage container;
The concentration calculation unit corrects the vibration frequency or the concentration of the dissolved resin component calculated from the vibration frequency in accordance with the liquid temperature of the liquid developer detected by the liquid temperature detection unit. The concentration detection apparatus according to claim 1 or 2. The sensor unit is
A first electrode and a second electrode which are disposed so as to sandwich the crystal resonator from both sides and apply a voltage to the crystal resonator;
4. The concentration detection apparatus according to claim 1, further comprising a surface regulating member that protects one of the first electrode and the second electrode from the liquid developer. 5.   The concentration detection apparatus according to claim 2, further comprising a shield member that is disposed in the housing and electrically shields an outside of the housing and an internal space of the housing. The bottom of the housing is a circular flat plate disposed horizontally,
The concentration detection apparatus according to claim 2, wherein the sensor unit is disposed immediately below the center of the bottom.   The concentration detection apparatus according to claim 2, wherein the bottom portion is formed of a flat plate and is inclined with respect to a horizontal direction. An image carrier on which a toner image is formed;
A developing device that contains the toner, stores a liquid developer in which a resin component is dissolved, and supplies the toner to the image carrier;
A developer adjusting unit that adjusts the concentrations of the toner and the resin component in the liquid developer;
The concentration detector according to any one of claims 1 to 7, which detects the concentration of the resin component in the liquid developer.
An image forming apparatus comprising:

Images