JP2010082579A - Method and apparatus for applying microparticles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for applying microparticles capable of keeping the number of spacers contained in individual spacer sections formed by dripping a coating liquid onto a substrate in a liquid crystal display and subsequently drying the dripped liquid, substantially constant and uniform. <P>SOLUTION: The method of applying microparticles includes a process of supplying a dispersion comprising a solvent and microparticles dispersed therein at least one of a plurality of nozzles 7 attached to an applicator head 6 and dripping the dispersion onto an object to be treated from the nozzle(s) 7 in question by applying a prescribed driving voltage to a piezoelectric device 7d that regulates the amount of droplets to be ejected from the nozzles 7, and a process of drying the solvent to agglomerate and array a plurality of microparticles on the object. The driving voltage to be applied to the piezoelectric device 7d is determined from the rate of change in the number of the microparticles on the object and the measured value of the number of the microparticles thereon, with the former obtained beforehand by dripping the dispersion onto the object while changing the driving voltage applied to the piezoelectric device 7d and the latter measured upon dripping the dispersion onto the object by applying a prescribed driving voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fine particle coating method and a fine particle coating apparatus, and more particularly to an ink jet type that can be used to form a spacer portion that maintains a cell gap in a liquid crystal display device.

  In recent years, for example, a liquid crystal display device using an active matrix liquid crystal panel has been used as a display means for devices such as personal computers and portable information terminals. In this liquid crystal display device, a color filter and a liquid crystal driving side substrate are opposed to each other to provide a gap (cell gap) of about 1 to 10 μm, and the gap is filled with liquid crystal and the periphery thereof is sealed with a sealing material. Yes. In order to obtain such a liquid crystal display device with good display quality, it is necessary to maintain the cell gap constant and uniform.

  As a method for maintaining a constant and uniform cell gap, an inkjet coating apparatus is used, and a plurality of dispersion liquids in which granular (spherical) or rod-shaped spacers are dispersed in a solvent are ejected to a predetermined position on a substrate. For example, Patent Document 1 discloses the formation of a spacer portion made of an aggregate of spacers. In Patent Document 1, for example, a dispersion liquid is dropped onto a portion where a light-shielding film provided so as to surround pixels on a substrate intersects in a T shape or a cross shape, or the dispersion liquid is simultaneously ejected from a plurality of coating heads. It has also been proposed to improve productivity.

  As the coating head used in the above-described ink jet type coating apparatus, one having a plurality of nozzles provided with piezoelectric elements (piezo elements) in the coating liquid passage is easy to adjust the droplet discharge amount. Generally used. Prior to the discharge of droplets from each nozzle of the coating head, the size (droplet discharge amount) of the droplets discharged (dropped) from the nozzles is proportional to the dropping speed of the coating liquid, Focusing on the fact that the dropping speed of the coating liquid from the nozzle is proportional to the drive pulse voltage applied to the piezoelectric element, so that the dropping speed of the coating liquid from each nozzle is within the desired specified speed range. The drive pulse voltage and pulse width (drive voltage application time) to the piezoelectric element are adjusted every time.

However, even if the droplet discharge amount is adjusted as described above, since the number of spacers included in each droplet varies, the number of spacers included in each formed spacer portion varies. There is a problem that it is difficult to form the height of the portion uniformly.
JP-A-11-24083

  In view of the above points, the present invention provides a fine particle coating capable of making the number of spacers included in each spacer portion formed by dropping and drying droplets on a processing object to be substantially constant and uniform. It is an object of the present invention to provide a method and a fine particle coating apparatus.

  In order to solve the above-described problems, the present invention provides a piezoelectric element that supplies a dispersion liquid in which fine particles are dispersed in a solvent to at least one nozzle of a coating head, and adjusts a droplet discharge amount from the nozzle. In the fine particle coating method, the method comprising: applying a predetermined driving voltage to dripping a dispersion liquid onto a processing object from a nozzle; and drying the solvent to aggregate and arrange a plurality of fine particles. When the rate of change in the number of fine particles on the object to be treated when the dispersion liquid is dropped by changing the driving voltage is acquired in advance, and the dispersion liquid is dripped onto the object to be treated at a predetermined driving voltage. The number of fine particles is measured, and the drive voltage to be applied to the piezoelectric element is determined from the measured value and the rate of change.

  According to the present invention, after the dispersion liquid is dropped from a nozzle of the coating head onto a predetermined position on the object to be coated, the number of fine particles at the position is measured. And based on this measured value and the rate of change of the number of fine particles with respect to the drive voltage acquired in advance, the drive voltage to the piezoelectric element for adjusting the droplet discharge amount is changed. The number can be made substantially constant and uniform.

  As described above, in the present invention, if the fine particles are spacers for forming a spacer portion that maintains a cell gap in a liquid crystal display device, the number of spacers included in each spacer portion is made substantially constant and uniform. Therefore, a liquid crystal display device with high display quality can be manufactured with high productivity.

  In order to solve the above problems, the present invention is directed to a stage that is movable in a single axis direction while holding a processing target, and a direction perpendicular to the X axis direction, where the moving direction of the stage is an X axis direction. A coating head having at least one nozzle provided in the Y-axis direction, and applying a predetermined driving voltage to the piezoelectric element while relatively moving the coating head and the object to be processed to remove particles from the nozzle. In the fine particle coating apparatus for applying the dispersion liquid dispersed on the object to be treated by dropping, a measuring means for actually measuring the number of fine particles when the dispersion liquid is applied onto the object by being dropped from the nozzle, A rate of change of the number of fine particles on the object to be processed according to a change in the drive voltage is stored, and a control unit for controlling the drive voltage to be applied to each nozzle from the actual measurement value and the rate of change in the measurement unit is further provided. And features.

  In the following, referring to the drawings, the object to be processed is provided with a light shielding film P so as to surround a pixel G on a substrate W such as glass for color filter, and the light shielding film P is T-shaped or cross-shaped. An embodiment in which the fine particle coating method and the fine particle coating apparatus of the present invention are applied to the formation of a spacer portion SP made of an aggregate of a plurality of (2 to 15) spacers at portions intersecting in a shape will be described.

  As shown in FIGS. 1 and 2, the fine particle coating apparatus M of the present embodiment is of an ink jet type and includes a platform 1. A rectangular parallelepiped base plate 2 is disposed on the platform 1, and a horizontal axis 1 is placed on the base plate 2 along a guide rail 4 on which a stage 3 for attracting and holding the substrate W is fixed to the upper surface of the base plate 2. It is supported so as to be movable in the (X-axis direction). The stage 3 is reciprocated in the X-axis direction via a feed screw mechanism by a motor (not shown). In this embodiment, when forming the spacer portion SP, the substrate W moves from the left side to the right side in FIG. 1, and the substrate W is placed on the stage 3 by the substrate transfer means R on the upstream side of the frame described later. It can be positioned and arranged.

  On the base plate 2, a gate-shaped frame 5 that is long in the horizontal direction (Y-axis direction) orthogonal to the X-axis direction is disposed so as to straddle the movement path of the stage 3. An ink jet type coating head 6 is provided on the frame 5 so as to reciprocate along the Y-axis direction by a driving means (not shown). The coating head 6 has a plurality of nozzles 7 arranged in a row at a predetermined interval in the Y-axis direction. In this case, the interval between the nozzles 7 is set to coincide with the interval between the intersecting portions of the light shielding film P. In order to finely adjust the interval, an axis line in the Z-axis direction orthogonal to the X-axis direction is set. It is preferable to employ a configuration in which a rotation mechanism (not shown) that rotates the coating head 6 around is provided.

  As shown in FIG. 3, each nozzle 7 has the same structure, and is a known one provided with a coating liquid passage 7a and a nozzle head 7c communicating with the lower end of the coating liquid passage 7a via a chamber 7b. Yes, a piezoelectric element 7d (for example, a piezo element) provided in the chamber 7b is appropriately driven by applying a driving voltage in a pulse form by a voltage control circuit (not shown) to discharge and drop a dispersion liquid described later from the nozzle head 7c. It is configured as follows.

  Here, there is no restriction | limiting in particular as a coating liquid used for spacer part SP formation in manufacture of a liquid crystal display device, A well-known thing can be used, for example, the spacer which has a predetermined particle diameter is disperse | distributed in a solvent. The dispersion liquid is used. As the spacer S, a known one having a spherical or rod shape made of glass, alumina, plastic or the like and having a particle diameter of about 1 μm to 10 μm is used. The solvent is not particularly limited as long as it is a liquid at room temperature and can disperse the spacer S. However, water or a hydrophilic solvent is used so that it can be stably discharged from the coating head 6. It is preferable to use an organic solvent.

  The solvent preferably contains a hydrophilic organic solvent having a boiling point (under 1 atm) of 100 ° or less so that the solvent volatilizes at a low temperature after the dispersion is applied on the substrate W. Examples of such hydrophilic organic solvents include lower monoalcohols such as ethanol, n-propanol and 2-propanol, and acetone. These may be used alone or in combination of two or more.

  Such a dispersion liquid is accommodated in the coating liquid storage part 8 which leads to the coating liquid passage 7b of the nozzle 7 via the pipe 7e. The coating liquid storage unit 8 includes an agitation tank 8c and an ultrasonic treatment tank 8d that are isolated from each other and enable transfer of the dispersion liquid between both tanks via a pipe 8b provided with a fluid pump 8a. It is a well-known thing. Then, while stirring the spacer S in the solvent in the stirring tank 8c and degassing in the ultrasonic processing tank 8d, vibration is applied by ultrasonic waves to prevent the spacer S from aggregating in the dispersion. Thus, the dispersion liquid in which the spacers S are uniformly dispersed is always supplied to each nozzle 7. In addition, after applying the dispersion liquid to a predetermined position of the substrate W, for example, a resistance heating type heater is attached to the stage 3 to forcibly evaporate the solvent and dry, thereby adopting a configuration capable of heating the substrate W. Also good.

  The fine particle coating apparatus M has a known control means C equipped with a microcomputer, a sequencer, etc., and controls the droplet discharge amount by suction holding of the substrate W, movement of the stage 3, and control of the driving voltage to the piezoelectric element 7d. General control is now possible. Further, a CCD camera 9 is provided on the downstream side in the movement direction of the substrate W. The CCD camera 9 is hung on a support plate (not shown) that is movable in the Y-axis direction, captures the application position of the substrate W coated with the dispersion liquid, and does not show the captured image. After being analyzed by the image analysis device, the image data is transmitted to the control means C. In this case, the CCD camera and the image analysis apparatus constitute the measuring means of the present embodiment.

  The formation of the spacer portion SP by the fine particle coating method of the present invention will be described below. First, prior to the application of the dispersion liquid to the glass substrate W by the nozzles 7 of the coating heads 6, meniscuses that can discharge the coating liquid from the nozzles 7 are formed, and then the preparation for discharging is performed by a known method. Is called. For example, the coating device M is provided with a stroboscopic light emitting device and an observation device such as a CCD camera for detecting the position of the liquid droplet ejected from the nozzle head 7c. The velocity and the flying angle of the droplet with respect to the extended line from the nozzle head 7c are detected. Then, the drive voltage or the pulse width (drive voltage application time) to be applied is adjusted by the control means C via the voltage control circuit so that the ejection speed and the flight angle are included in the predetermined range. The drop rate of droplets from each nozzle 7 is adjusted (preparation for discharge).

  This preparation for discharge is performed by a known method. For example, the coating device M is provided with a stroboscopic light emitting device and an observation device such as a CCD camera for detecting the position of the liquid droplet ejected from the nozzle head 7c. The velocity and the flying angle of the droplet with respect to the extended line from the nozzle head 7c are detected. Then, the drive voltage or the pulse width (drive voltage application time) to be applied is adjusted by the control means C via the voltage control circuit so that the discharge speed and the flying angle are included in the predetermined range.

  Next, a dummy substrate (not shown) is used, and at least one nozzle 7 has a constant pulse width and the number of spacers S forming the spacer portion SP when the drive voltage applied to the piezoelectric element 7d is changed. Get the rate of change. That is, the dispersion liquid is dropped one by one while shifting the dropping position on the dummy substrate and increasing the driving voltage stepwise while keeping the pulse width constant by the voltage control circuit. At this time, it is preferable to apply a plurality of droplets (preferably 100 points or more) dispersion liquid for each driving voltage.

  Then, after the substrate W is naturally dried or heat-dried and aggregated, the number of the spacers S at each application position is measured by a measuring unit. That is, at each application position, the position where the dispersion liquid is applied is picked up by the CCD camera 9, the picked-up image is analyzed by a known image analysis device (not shown), and the image data is transmitted to the control means C. . Thereby, the number of spacers S with respect to the drive voltage is measured, and based on this, the rate of change of the number of spacers is calculated, and the rate of change is stored in the control means C.

  In addition, in FIG. 4, as an example when the change rate of the number of spacers is acquired, the nozzle diameter is 27 μm, the spacer is manufactured by Sekisui Chemical Co., Ltd., the average particle diameter is 3.6 μm, the solvent is isopropyl alcohol, ethylene glycol The result of measuring the number of spacers S with respect to the driving voltage is shown using a dispersion liquid in which the above spacer is dispersed (concentration 1.8 wt%), and the rate of change is calculated therefrom. Is done. Such a change rate acquisition operation may be appropriately performed, for example, after maintenance of the coating head 6 is performed. The number of spacers S is appropriately set according to the type of the liquid crystal display device, and the target number can be input to the control means.

  Next, the drive voltage applied to the piezoelectric element 7d of each nozzle 7 is individually set. First, a light shielding film P provided so as to surround the pixel G on the substrate W is used, and an aggregate of a set target number of spacers is formed at a portion where the light shielding film intersects in a T shape or a cross shape. A spacer portion SP is formed.

  That is, the substrate W used for mutually adjusting the number of the spacers S is positioned and arranged on the stage and then held by suction. In this state, the stage 3 is moved along the X-axis direction, and the coating head 6 is scanned and moved in synchronism with the movement of the stage 3 while applying a drop of the dispersion liquid to each of the intersections. I will do it. When the substrate W is naturally dried or heat-dried and aggregated, the spacer portion SP is formed at the above position.

  At this time, the number of the spacers S that form the spacer portion SP at each application position is measured by the measuring means located on the downstream side of the application head 6. That is, at each application position, the position where the dispersion liquid is applied is picked up by the CCD camera 9, the picked-up image is analyzed by a known image analysis device (not shown), and the image data is transmitted to the control means C. . When image data is input to the control means C, an optimum driving voltage to be applied to each coating head is determined from the actual measurement value and the rate of change, thereby preparing for the formation of the spacer portion on the glass substrate for mass production. Ends.

  That is, if the actually measured number of spacers is Nc, the target number of spacers is Nr, the current drive voltage is Vc (V), and the drive voltage to be corrected is Vr (V), then ΔN = Nc−Nr (Equation 1 ), ΔV = Vc−Vr (Equation 2), and this ΔN / ΔV coincides with the rate of change of the number of spacers with respect to the drive voltage acquired in advance.

  Here, if the rate of change ΔN / ΔV = 1.7 (see FIG. 4) is described as an example, if Nc is 13, Nr is 11 and Vc is 14, ΔN = 2 from equation (1). If this is substituted into the equation (3), ΔV becomes 1.2V. As a result, Vc is found to be 12.8 V from this value and equation (2). In this way, the drive pulse voltage is determined for each nozzle 7.

  A dummy substrate can be used in preparation for forming the spacer portion, and the actual number of spacers S is measured for all the nozzles 7. In this case, the number of the spacers S is measured by the measurement means by discharging the dispersion liquid a plurality of times (preferably 100 points or more) to one nozzle 7, and the average value is used as the actually measured number of spacers. Is good.

  Then, in the same procedure as described above, the glass substrate W, which is a product, is sucked and held on the stage 3 and moved in the X-axis direction, and the coating head 6 is operated in synchronism, so that one drop of dispersion liquid is applied to each of the intersections. When the substrate is dropped and applied, and the substrate is naturally dried or heated to be agglomerated, spacer portions SP having a uniform and uniform number of spacers S are formed at various portions of the substrate (see FIG. 5).

  As described above, according to the present embodiment, after the dispersion liquid is dropped and applied from the nozzles 7 of the coating head 6 to a predetermined position on the glass substrate W, the number of the spacers S at the position is actually measured. Since the driving voltage is changed for each nozzle 7 on the basis of the value and the rate of change, the number of spacers S can be made substantially constant and uniform, and when forming the spacer portion SP that maintains the cell gap in the liquid crystal display device. The number of spacers S included in each spacer portion SP can be made substantially uniform, and a liquid crystal display device with high display quality can be manufactured with high productivity.

  In the above embodiment, the drive voltage change rate is acquired in advance. However, the present invention is not limited to this, and the pulse width (drive voltage application time) is maintained while maintaining the drive voltage at a constant value. ) May be changed stepwise to obtain the rate of change of the number of spacers, and the pulse width may be adjusted to make the number of spacers uniform. In addition, the measuring means has been described by taking as an example one provided with a CCD camera in order to actually measure the number of spacers forming the spacer portion, but there is no particular limitation as long as the number of the spacers can be actually measured.

  In Example 1, the ink head type fine particle coating apparatus M shown in FIG. 1 is used, and a substrate having a size of 370 × 470 mm and provided with a light shielding film P so as to surround 64 columns of pixels is used. A spacer portion made of an aggregate of spacers was formed at a portion where the light shielding film intersected in a T shape or a cross shape. In this case, the number of nozzles of one coating head 6 of the fine particle coating apparatus M was 64, and the nozzle diameter of each nozzle was 27 μm. Further, as the spacer, an average particle size of 3.6 μm manufactured by Sekisui Chemical Co., Ltd., a mixed liquid of isopropyl alcohol, ethylene glycol or the like as a solvent was used, and a dispersion liquid in which the spacer was dispersed was used (concentration: 1. 8% by weight).

  Then, the droplet discharge speed is set to 4 m / s, the volume of the discharged droplet is set to 15 pl, and the dispersion liquid is dropped onto the substrate from the nozzles 7 of the coating head 6 and applied. The number was measured and adjusted by changing the drive voltage for each nozzle 7 based on the measured value and the rate of change.

  FIG. 6 shows the result of measuring the average value and standard deviation value of the number of spacers of 100 droplets per row (this Example 1) applied without adjusting the drive voltage of each nozzle. It is a table | surface shown with (comparative example 1). According to this, it was confirmed that the variation in the number of nozzles in Example 1 was smaller than that in Comparative Example 1.

The side view which shows the inkjet type fine particle coating device of this invention. The top view explaining application | coating of the spacer dispersion liquid using the fine particle coating device of FIG. The figure which illustrates the structure of a nozzle typically. The graph which shows the relationship between the drive voltage to a piezoelectric element, and the measured value of the number of spacers. The elements on larger scale explaining spacer part formation to a board | substrate. 2 is a table showing experimental results for showing the effects of the present invention as Example 1. FIG.

Explanation of symbols

M Inkjet coating device
3 stages
6 Application head
7 Nozzles
7d Piezoelectric element
9 CCD camera (measuring means)
G pixel
P light shielding film
S spacer (fine particles)
SP spacer
W substrate (object to be processed)

Claims (3)

A dispersion liquid in which fine particles are dispersed in a solvent is supplied to at least one nozzle of a coating head, and a predetermined driving voltage is applied to a piezoelectric element that adjusts a droplet discharge amount from the nozzle, thereby processing the nozzle. In a fine particle coating method comprising a step of dripping a dispersion liquid on an object and a step of aggregating and arranging a plurality of fine particles by drying the solvent,
The rate of change of the number of fine particles on the object to be processed when the dispersion liquid is dropped by changing the driving voltage to the piezoelectric element is acquired in advance, and the dispersion liquid is applied on the object to be processed at a predetermined driving voltage. A method for applying fine particles, comprising: actually measuring the number of fine particles when droplets are dropped, and determining a drive voltage to be applied to the piezoelectric element from the measured value and the rate of change.   2. The fine particle coating method according to claim 1, wherein the fine particles are spacers for forming a spacer portion for maintaining a cell gap in a liquid crystal display device. A stage that is movable in one axial direction while holding the object to be processed, and at least one nozzle provided in the Y-axis direction orthogonal to the X-axis direction, where the moving direction of the stage is the X-axis direction. A dispersion liquid in which fine particles are dispersed in a solvent from a nozzle by applying a predetermined driving voltage to the piezoelectric element while relatively moving the coating head and the processing object. In the fine particle coating device for coating,
Measuring means for actually measuring the number of fine particles when the dispersion liquid is dropped onto the object to be treated and applied from the nozzle, and the rate of change of the number of particles on the object to be treated according to the change in drive voltage is stored, A fine particle coating apparatus further comprising control means for controlling a driving voltage to be applied to each nozzle from an actual measurement value and a change rate of the measuring means.

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