LIQUID MATERIAL APPLICATION UNIT, LIQUID MATERIAL APPLICATION DEVICE, AND LIQUID MATERIAL APPLICATION METHOD

A liquid material application unit includes an application needle and an application liquid container. The application liquid container includes a joining section and a needle movement section. The joining section extends in a horizontal direction. The needle movement section extends, in a vertical direction, from the joining section. A protrusion amount by which the application needle is allowed to protrude from a through-hole of the application liquid container in the vertical direction is greater than or equal to 1 mm and less than or equal to 3 mm. A first width of the needle movement section in the horizontal direction is less than or equal to 5 mm. A length of the needle movement section extending from the joining section to the through-hole in the vertical direction is greater than or equal to 5 mm.

TECHNICAL FIELD

The present disclosure relates to a liquid material application unit, a liquid material application device, and a liquid material application method.

BACKGROUND ART

During packaging of electronic components, a liquid material such as a conductive material or an adhesive is applied. The recent trend of downsizing of electronic components has required such a liquid material in a trace amount to be stably applied.

Further, for fixing a component such as a minute optical component using an adhesive, an adhesive composed of a liquid material that is a mixture of two liquids and cured by a chemical reaction is widely used. This is because a single-component moisture-curable adhesive takes time to be cured.

The process of applying the liquid material to an electronic component and the process of applying the liquid material adhesive composed of a mixture of two liquids are preferably performed using, for example, an application needle as disclosed in Japanese Patent Laying-Open No. 2007-268353, In this case, the liquid material in an application liquid container adheres to the application needle in the application liquid container. Subsequently, the application needle protrudes from a through-hole of the application liquid container, and the liquid material adhering to the application needle is transferred to an application object. The use of the application needle allows a fine pattern to be applied to liquid materials over a wide viscosity range.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

For the application of the liquid material using the application needle, it is important to control a so-called protrusion amount, which is a distance by which the application needle protrudes from the application liquid container, That is, when the protrusion amount is excessively large, air bubbles may mix into the liquid material in the application liquid container, or the applied pattern may vary in application diameter. Further, when the protrusion amount is excessively small, the applied pattern may increase in application diameter.

The present disclosure has been made in view of the above-described problems. It is therefore an object of the present disclosure to provide a liquid material application unit, a liquid material application device, and a liquid material application method that can prevent air bubbles from mixing into a liquid material and stably supply a pattern having a minute application diameter.

Solution to Problem

A liquid material application unit according to the present disclosure includes an application needle and an application liquid container. The application needle applies a liquid material. The application liquid container holds therein the liquid material and has a through-hole formed at a bottom portion, the through-hole allowing the application needle to pass through. The application liquid container includes a joining section and a needle movement section. The joining section extends in a horizontal direction intersecting an extending direction of the application needle. The needle movement section extends from the joining section to the through-hole in a vertical direction that coincides with the extending direction of the application needle. A protrusion amount by which the application needle is allowed to protrude from the through-hole of the application liquid container in the vertical direction is greater than or equal to 1 mm and less than or equal to 3 mm. A first width of the needle movement section in the horizontal direction is less than or equal to 5 mm. A length of the needle movement section extending from the joining section to the through-hole in the vertical direction is greater than or equal to 5 mm.

Under a liquid material application method according to the present disclosure, an application liquid container having a through-hole formed at a bottom portion is aligned over an application object of a liquid material with the liquid material held in the application liquid container and a distal end of an application needle immersed in the liquid material. The application liquid container is brought close to the application object. The application needle is moved in an extending direction of the application needle to apply the liquid material to the application object. In the above-described application process, a protrusion amount by which the application needle is allowed to protrude from the through-hole of the application liquid container in the extending direction is greater than or equal to 1 mm and less than or equal to 3 mm. In the above-described approaching process, the application liquid container is placed to be at least partly surrounded by the application object.

Advantageous Effects of Invention

According to the present disclosure, the liquid material application unit, the liquid material application device, and the liquid material application method that can prevent air bubbles from mixing into a liquid material and stably supply a pattern having a minute application diameter can be provided.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present embodiment will be described with reference to the drawings.

FIG.1is a schematic perspective view of a liquid material application device according to the present embodiment. With reference toFIG.1, a liquid material application device200according to the present embodiment includes a base12disposed on a floor surface, an X-axis table 1, a Y-axis table 2, a Z-axis table 3, a liquid material application unit4, an observation optical system6, a CCD camera7connected to observation optical system6, and a controller11.

Y-axis table 2 movable in a Y-axis direction inFIG.1is installed on an upper surface of base12. Specifically, Y-axis table 2 has a guide section installed on a lower surface of Y-axis table 2 and is slidably connected with and along a guide rail installed on the upper surface of base12. Y-axis table 2 further has a ball screw connected to the lower surface of Y-axis table 2. Y-axis table 2 is movable along the guide rail (in the Y-axis direction) by the ball screw operated with a driving member such as a motor. An upper surface portion of Y-axis table 2 serves as a placement surface on which an application object5is placed. Note thatFIG.1illustrates a thin plate substrate as application object5. This is, however, merely an example, and application object5may be, for example, a bottom portion of a groove as described later.

On base12, a gate-shaped structure installed across the guide rail of Y-axis table 2 in an X-axis direction is provided. X-axis table 1 movable in the X-axis direction is placed on the structure. For example, a ball screw makes X-axis table 1 movable in the X-axis direction.

Z-axis table 3 is placed on a movable body of X-axis table 1, and liquid material application unit4and observation optical system6are placed on Z-axis table 3. Liquid material application unit4and observation optical system6are movable in the X direction together with Z-axis table 3. Liquid material application unit4is provided to apply an application liquid to an application surface (upper surface) of application object5using an application needle provided in liquid material application unit4. Observation optical system6is provided to observe an application position of application object5. CCD camera7of observation optical system6converts an observed image into an electrical signal, Z-axis table 3 supports liquid material application unit4and observation optical system6movable in a Z-axis direction.

Controller11includes a control panel8, a monitor9, and a control computer10, and controls X-axis table 1, Y-axis table 2, Z-axis table 3, liquid material application unit4, and observation optical system6. Control panel8is used to input a command to control computer10. Monitor9displays image data obtained by conversion made by CCD camera.7of observation optical system6and data output from control computer10.

When a circuit pattern is drawn on application object5, a drawing start position is determined by moving a drawing position of application object5directly below observation optical system6with X-axis table 1 and Y-axis table 2, and observing and confirming the drawing start position with observation optical system6. Then, the circuit pattern is drawn from the drawing start position thus determined. From the drawing start position, application object5is moved, step-by-step, by X-axis table 1 and Y-axis table 2 so as to make the drawing position immediately below liquid material application unit4. When the movement is completed, liquid material application unit4is driven to perform application. Continuously repeating the above processing makes it possible to draw the circuit pattern.

A relationship between a descent end position of an application needle24and a focus position of observation optical system6is stored in advance, and during drawing, the application is performed after moving application needle24in the Z-axis direction with the Z-axis table to a height at which application needle24comes into contact with application object5with a position where the focus of observation optical system6is on an image as a reference in the Z-axis direction. When an area of the circuit pattern to be drawn is large, and the height of the application position of application object5greatly varies during the drawing, the focus position is checked as needed during the drawing, and the application is performed after the position in the Z-axis direction is corrected. At this time; the focus position may be adjusted by an autofocus method using image processing, or a method by which the height position of the surface of application object5to be applied is constantly detected with a laser sensor or the like, and correction is performed in real time.

Next, liquid material application unit4according to the present embodiment will be described in detail with reference toFIGS.2to7.

FIG.2is a diagram schematically illustrating a configuration of a part of the liquid material application unit according to the present embodiment. With reference toFIG.2, liquid material application unit4according to the present embodiment includes an application liquid container21and application needle24. Application liquid container21holds a liquid material100therein. Application liquid container21has a through-hole22formed at a bottom portion, which is the lowermost portion inFIG.2. Application needle24is disposed in application liquid container21so as to be able to pass through application liquid container21.

Application needle24applies liquid material100held in application liquid container21. InFIG.2, a distal end23, which is the lowermost portion of application needle24, is immersed in liquid material100. When application needle24moves down, at least distal end23passes through through-hole22to protrude from through-hole22. This causes application needle24to apply liquid material100to the application object.

Application liquid container21includes a joining section25and a needle movement section26. As described later, liquid material application unit4includes a drive unit such as a linear motion mechanism and a servomotor. Joining section25is a section where main members of liquid material application unit4such as the linear motion mechanism and application liquid container21are joined together. In the state illustrated inFIG.2where application needle24is allowed to pass through application liquid container21from through-hole22, joining section25extends in a horizontal direction (left-right direction inFIG.2) intersecting an extending direction (vertical direction inFIG.2) of application needle24passing through application liquid container21. On the other hand, needle movement section26is a section extending from joining section25to through-hole22in the vertical direction (Z direction inFIG.1) that coincides with the extending direction of application needle24. In other words, needle movement section26is a section disposed below joining section25and extending in the vertical direction below joining section25inFIG.2. Application needle24moves in the vertical direction inside needle movement section26.

A protrusion amount P by which application needle24is allowed to protrude from through-hole22of application liquid container21in the vertical direction inFIG.2is greater than or equal to 1 mm and less than or equal to 3 mm. That is, when application needle24illustrated inFIG.2moves down for applying liquid material100to application object5, protrusion amount P as the distance by which distal end23protrudes downward from through-hole22is greater than or equal to 1 mm and less than or equal to 3 mm. A state where distal end23protrudes downward from through-hole22is represented by a dotted line inFIG.2, Note that protrusion amount P may be greater than or equal to 1.5 mm and less than or equal to 3 mm, and more preferably greater than or equal to 2 mm and less than or equal to 3 mm. Protrusion amount P is more preferably greater than or equal to 2.5 mm and less than or equal to 3 mm. As an example, protrusion amount P is 3 mm.

A first width W1 of needle movement section26in the left-right direction inFIG.2is less than or equal to 5 mm. That is, for example, when needle movement section26is viewed from above inFIG.2, the maximum width of an outer periphery in the horizontal direction is less than or equal to 5 mm. As an example, W1 is 5 mm. When the lowermost portion of needle movement section in26inFIG.2has a tapered shape, first width W1 indicates the maximum width of an outer periphery, in the horizontal direction, of a region where the maximum width of the outer periphery is substantially uniform in the vertical direction, other than the region having the tapered shape.

A length T of needle movement section26extending from joining section25to through-hole22in the vertical direction inFIG.2is greater than or equal to 5 mm. That is, needle movement section26extends downward from the lowermost portion of joining section25by at least 5 mm. As an example, T is 15 mm.

In liquid material application unit4having the above-described characteristics, first width W1 is less than or equal to five times a second width W2, in the left-right direction inFIG.2, a section of application needle24extending in the vertical direction inFIG.2. Here, the portion of application needle24extending in the vertical direction inFIG.2corresponds to a region where the maximum width of the outer periphery is substantially uniform in the vertical direction, other than a region such as distal end23inFIG.2that is inclined as a result of taper machining or the like. That is, in the region having second width W2 of application needle24, the outer periphery of application needle24extends straight in the vertical direction and has a uniform outer peripheral width. Second width W2 means the maximum width of the outer periphery in the horizontal direction when application needle24is viewed from above inFIG.2, for example. As an example, W1 is 5 mm, and W2 is 1 mm.

As illustrated inFIG.2, application object5preferably has, fir example, a groove shape, a recessed shape, or a container shape having a side surface portion capable of surrounding application needle24when application needle24moves down and a bottom surface portion that is located below the side surface portion and to which liquid material100is applied. A lateral distance D across the processed side surface portion of application object5surrounding application needle24is, for example, greater than or equal to 6.5 mm, and may be 12 mm or 17 mm.

Liquid material100may be a conductive material used for, for example, mounting a crystal oscillator. Alternatively, liquid material100may be a catalytic material that is applied to a so-called micro electro mechanical systems (MEMS) gas sensor. Alternatively, liquid material100may be an adhesive that is applied to a light emitting diode (LED). Liquid material100may be a mixture of two liquids.

Liquid material100may be a liquid having fine particles suspended therein. For example, when liquid material100is an adhesive, reinforcing particles for the adhesive may be contained as fine particles. Liquid material100is not limited to a pure liquid containing no particles, and may be a liquid containing particles. Specifically, liquid material100may be a conductive paste containing metal particles for industrial use. In this case, the fine particles are metal particles. Liquid material100may be an adhesive containing inorganic particles. In this case, the fine particles are inorganic particles.

Note that a good balance between surface tension across the edge of through-hole22and pressure applied by the weight of liquid material100in application liquid container21prevents liquid material100in application liquid container21from leaking out through through-hole22.

FIG.3is a schematic front view of the liquid material application unit according to the present embodiment, illustrating a first example of the configuration of the liquid material application unit.FIG.4is a schematic side view of the liquid material application unit according to the present embodiment, illustrating the first example of the configuration of the liquid material application unit. With reference toFIGS.3and4, liquid material application unit4includes a servomotor120, a motor driver121, an application needle holder102, an application needle holder housing104, an application needle holder fixing section106, and a linear motion mechanism130, in addition to application liquid container21illustrated inFIG.2.

Servomotor120is provided as a drive source for moving application needle24up and down. Application needle holder102holds one application needle24having a tapered tip. Linear motion mechanism130moves application needle holder102up and down in response to rotation of servomotor120. Motor driver121controls the rotation of servomotor120so as to move application needle holder102up and down at an appropriate speed.

Linear motion mechanism130includes an origin sensor118, an eccentric plate116, an eccentric shaft114, a linear guide132, a coupling plate112, a movable section108, a coupling shaft110, and bearings122,124.

Eccentric plate116is rotated by servomotor120and attached to a rotation shaft of servomotor120extending orthogonal to a vertical movement direction of application needle holder102. Eccentric plate116is provided with eccentric shaft114at a position eccentric from the rotation shaft of servomotor120.

Origin sensor118detects an origin defined on eccentric plate116and outputs the origin to motor driver121. This origin is closest to origin sensor118when eccentric plate116coincides with a reference rotation angle.

In movable section108, application needle holder102is attached to application needle holder fixing section106, and one application needle24is held with distal end23facing downward from the lower surface of application needle holder102. Linear guide132supports movable section108to which application needle holder102is fixed movable in the vertical direction.

Coupling plate112couples coupling shaft110provided in movable section108that moves up and down together with application needle holder102and eccentric shaft114with a fixed length.

Movable section108is attracted toward a fixing pin128via a spring126to prevent vibrations from being generated due to looseness of hearings122,124during driving. Applying a preload to bearings122,124to eliminate looseness allows a configuration without spring126.

When servomotor120is driven to rotate eccentric plate116, application needle24reciprocates in the vertical direction in response to the movement of eccentric shaft114in the vertical direction. When eccentric plate116rotates in one direction, coupling shaft110moves up and down by a vertical movement stroke AZ. That is, application needle24moves in the vertical direction in needle movement section26illustrated inFIG.2. This causes distal end23of application needle24to repeatedly apply liquid material100and retract into liquid material100after the application.

FIG.5is a schematic front and side view of the liquid material application unit according to the present embodiment, illustrating a second example of the configuration of the liquid material application unit. That is, (A) ofFIG.5is a schematic front view, and (B) ofFIG.5is a schematic side view. With reference toFIG.5, the second example is basically die same in configuration as the first example illustrated inFIGS.3and4, and thus no detailed description will be given below. Note that, as in the second example illustrated inFIG.5, the extending direction of joining section25of application liquid container21may substantially coincide with the left-right direction in which servomotor120extends. Alternatively, as in the first example illustrated inFIGS.3and4, the extending direction of joining section25of application liquid container21may intersect (for example, substantially orthogonal to) the left-right direction in which servomotor120extends. Note that liquid material application unit4illustrated inFIGS.3to5converts the rotation of servomotor120into a linear motion to move application needle24up and down. The configuration, however, is not limited to such an example. For example, as a mechanism for causing application needle24to linearly, reciprocate illustrated inFIGS.3to5, any one selected from the group consisting of an electric linear motion actuator using a screw, an air cylinder using air pressure, and a solenoid may be used.

FIG.6is a schematic front and side view of the liquid material application unit according to the present embodiment, illustrating a third example of the configuration of the liquid material application unit. That is, (A) ofFIG.6is a schematic front view, and (B) ofFIG.6is a schematic side view.FIG.7is a schematic diagram for describing a cam member of an application mechanism illustrated inFIG.6. With reference toFIGS.6and7, liquid material application unit4of the third example mainly includes servomotor120, a cam143, bearing122, a cam coupling plate145, movable section108, and application needle holder102, in addition to application liquid container21illustrated inFIG.2. Application needle holder102holds application needle24. Servomotor120is installed with its rotation shaft extending in the Z-axis direction illustrated inFIG.1. Cam143is connected to the rotation shaft of servomotor120. Cam143is rotatable about the rotation shaft of servomotor120.

Cam143includes a center section connected to the rotation shaft of servomotor120and a flange section connected to one end of the center section. As illustrated in (A) ofFIG.7, an upper surface (surface adjacent to servomotor120) of the flange section is a cam surface161. Cam surface161is formed in an annular shape along an outer periphery of the center section, and is formed in a slope shape so as to cause a distance from a bottom surface of the flange section to vary. Specifically, as illustrated in (B) ofFIG.7, cam surface161includes an upper end flat region162having the largest distance from the bottom surface of the flange section, a lower end flat region163disposed apart from the upper end flat region162and having the smallest distance from the bottom surface of the flange section, and a slope section connecting upper end flat region162and lower end flat region163. Here, (B) ofFIG.7is a developed view of the flange section including cam surface161disposed to surround the center section as viewed from a side.

Bearing122is disposed in contact with earn surface161of cam143. As illustrated in (A) ofFIG.6, bearing122is disposed adjacent to a specific side (right side of servomotor120) as viewed from cam143and is kept in contact with cam surface161when cam143rotates in response to the rotation of the rotation shaft of servomotor120. Cam coupling plate145is connected to bearing122. Cam coupling plate145has one end connected to bearing122and the other end fixed to movable section108. Application needle holder fixing section106and application needle holder housing104are connected to movable section108. Application needle holder housing104houses application needle holder102.

Application needle holder102includes application needle24. Application needle24is disposed so as to protrude from the lower surface (the lower side remote from the side where servomotor120is located) of application needle holder102.

Application liquid container21is disposed below application needle holder102. Application needle24is held with application needle24put into application liquid container21.

Movable section108is provided with a fixing pin128B. Further, a frame holding servomotor120is provided with a different fixing pin128A. Spring126is installed so as to connect fixing pins128A,128B. Spring126applies, to movable section108, a pulling force toward application liquid container21. Further, the pulling force of spring126acts on bearing122via movable section108and cam coupling plate145. This pulling force of spring126keeps bearing122pressed against earn surface161of cam143.

Further, movable section108, application needle holder fixing section106, and application needle holder housing104are connected to linear guide132installed on the above-described frame. Linear guide132is disposed extending in the Z-axis direction. This makes movable section108, application needle holder fixing section106, and application needle holder housing104movable in the Z-axis direction.

Next, a description will be given of how liquid material application unit4described above operates. In liquid material application unit4described above, servomotor120is driven to rotate the rotation shaft of servomotor120, thereby rotating cam143. This causes cam surface161of cam143to change in height in the Z-axis direction, so that the position, in the Z-axis direction, of bearing122in contact with cam surface161on the right side of cam143illustrated in (A) ofFIG.6also changes in response to the rotation of a drive shaft of servomotor120.

Then, movable section108, application needle holder fixing section106, and application needle holder housing104move in the Z-axis direction in response to the change in position of bearing122in the Z-axis direction. This also causes application needle holder102held in application needle holder housing104to move in the Z-axis direction, thereby allowing a change in the position, in the Z-axis direction, of application needle24installed in application needle holder102.

Next, a liquid material application method using liquid material application unit4according to the present embodiment will be described with reference toFIG.8.

FIG.8is a schematic diagram for describing the liquid material application method using the liquid material application unit according to the present embodiment. Under the liquid material application method illustrated inFIG.8, a process is performed in the order of (A), (B), (C), (D), and (E). With reference toFIG.8, first, as illustrated in (A), liquid material100is held inside application liquid container21of liquid material application unit4having through-hole22formed at the lowermost portion (bottom portion). Application liquid container21illustrated inFIG.8is substantially the same in shape and size as application liquid container21illustrated inFIG.2. At least distal end23of application needle24is immersed in liquid material100. The region of application needle24immersed in liquid material100may include a part of a region located above distal end23illustrated inFIG.8and linearly extending with the uniform outer peripheral width. In this state, application liquid container21is aligned over, in the vertical direction inFIG.8, the bottom surface of application object5such as a groove-shaped member or a recessed member to which liquid material100is applied.

Next, as illustrated in (B), application liquid container21is brought close to application object5. Specifically, application liquid container21moves down. This causes needle movement section26of application liquid container21to be at least partially surrounded by the side surface portion of application object5. In other words, needle movement section26partially enters the recessed portion of application object5so as to overlap the side surface portion of application object5in the horizontal direction. In other words, needle movement section26partially enters the recessed portion of application object5so as to make the side surface portion of application object5and needle movement section26identical in position in the vertical direction to each other.

Next, as illustrated in (C), application needle24is moved in the extending direction of application needle24, that is, in the vertical direction. That is, as illustrated in (C), application needle24is moved down to bring distal end23close to the bottom surface portion of application object5. This causes, as illustrated in (D), liquid material100adhering to, for example, distal end23of application needle24to be applied to the bottom surface portion of application object5or the like. Note that, at this time, application needle24may move down until distal end23comes into contact with application object5as illustrated in (D). Alternatively, application needle24may move down until liquid material100adhering to application needle24comes into contact with application object5without bringing distal end23into contact with application object5. At this time, the protrusion amount by which application needle24is allowed to protrude from through-hole22located at the lowermost portion of application liquid container21in the vertical direction that coincides with the extending direction of application needle24is greater than or equal to 1 mm and less than or equal to 3 mm.

After the application, application needle24moves up as illustrated in (E). This causes distal end23to retract again into application liquid container21. During the application process, it is preferable that the reciprocating motion including the movement (C), (D) of application needle24toward application object5in the extending direction of application needle24and the movement (E) of application needle24away from application object5be repeated nine times or less per second. This allows liquid material100to be suitably applied.

Next, a description will be given, with reference, as needed, toFIGS.9to11, of actions and effects of the present embodiment in comparison with a comparative example.

FIG.9is a schematic diagram for describing a liquid material application method using a liquid material application unit according to the comparative example. InFIG.9, a process is performed in the order of (A), (B), (C), and (D). With reference toFIG.9, an application liquid container21according to the comparative example is, as illustrated in (A), lamer in first width w1 of needle movement section26and shorter in length tin the vertical direction than application liquid container21according to the present embodiment. First width tial is larger than a lateral distance d across the side surface portion of application object5. First width w1 is greater than five times second width w2. This makes application liquid container21according to the comparative example unable to move down to the position where needle movement section26is surrounded by application object5. Therefore, as illustrated in (B), with application liquid container21unchanged in position in the vertical direction, only application needle24moves down to protrude from application liquid container21. Then, liquid material100is applied to application object5as illustrated in (C), and application needle24moves up as illustrated in (D).

Since application liquid container21does not move down as illustrated inFIG.9, it is necessary to increase a protrusion amount p of application needle24as compared with the present embodiment illustrated inFIG.8. An increase in protrusion amount p of application needle24(for example, 15 mm), however, will cause the following problem.

First, when application needle24moves up after the application of liquid material100illustrated in (D) ofFIG.9, air bubbles may mix into liquid material100in application liquid container21. This is because of the following reason. As illustrated in (B), (C) ofFIG.9, liquid material100nonuniformly adheres to the portion of application needle24that is exposed when application needle24moves down. That is, on the outer periphery of application needle24, a region to which liquid material100adheres and a region to which no liquid material100adheres alternately, appear in the extending direction. Such nonuniform adhesion is caused by a gap between application needle24and application liquid container21in a region close to through-hole22when liquid material100is pulled by application needle24when application needle24moves down. When a portion of the side surface of application needle24to which no liquid material100adheres returns into application liquid container21as illustrated in (D) ofFIG.9, air bubbles are likely to mix into liquid material100in application liquid container21. The larger protrusion amount p of application needle24, the larger the number of regions where liquid material100adheres and regions where no liquid material100adheres that alternately appear, Therefore, when protrusion amount p increases, the possibility that air bubbles mix in increases accordingly.

Further, the region where liquid material100nonuniformly adheres causes an increase in variation in application diameter of liquid material100to application object5. Here, the application diameter means the maximum value of the dimension of applied liquid material100as viewed from above (for example, the length of the major axis of an ellipse), in other words, the diameter of a virtual circle circumscribing liquid material100. This may make the planar shape of the pattern formed of liquid material100uneven.

On the other hand, when protrusion amount p inFIG.9is extremely small (for example, less than 1 mm), another problem described below may occur.FIG.10is a schematic diagram illustrating an application process with the application needle protruding by a normal amount.FIG.11is a schematic diagram illustrating an application process with the application needle protruding by an extremely small amount, given for comparison withFIG.10. InFIGS.10and11, the process is performed in the order of (A), (B), and (C), where (A) illustrates a standby state before application, (B) illustrates an application state, and (C) illustrates a retracted state after application. With reference toFIGS.10and11for comparison, in the case ofFIG.11where the protrusion amount of application needle24from through-hole22located at the bottom portion of application liquid container21is small, the application diameter of liquid material100to be transferred to the application object becomes excessively large as compared withFIG.10in which the protrusion amount is nominal. This is because, inFIG.11, distal end23of application needle24reaches application object5immediately after being exposed from through-hole22, so that the amount of liquid material100adhering to distal end23when distal end23is exposed from through-hole22becomes excessively large.

In view of the above-described problem of the comparative example, liquid material application unit4according to the present embodiment includes application needle24and application liquid container21. Application needle24applies liquid material100. Application liquid container21holds therein liquid material100and has through-hole22formed at the bottom portion, the through-hole22allowing application needle24to pass through. Application liquid container21includes joining section25and needle movement section26. Joining section25extends in the horizontal direction intersecting the extending direction of application needle24. Needle movement section26extends from joining section25to through-hole22in the vertical direction that coincides with the extending direction of application needle24. Protrusion amount P by which application needle24is allowed to protrude from through-hole22of application liquid container21in the vertical direction is greater than or equal to 1 mm and less than or equal to 3 mm. First width W1 of needle movement section26in the horizontal direction is less than or equal to 5 mm. The length of needle movement section26extending from joining section25to through-hole22in the vertical direction is greater than or equal to 5 mm.

Liquid material application unit4described above and liquid material application device200including liquid material application unit4can drastically reduce air bubbles mixing into liquid material100in application liquid container21by setting the protrusion amount at a suitable small amount, specifically, less than or equal to 3 mm. The number of regions of the side surface of application needle24where liquid material100adheres and regions where no liquid material100adheres that alternately appear as illustrated in (D) ofFIG.9decreases. This reduces the possibility that air generated by the gap between the regions where no liquid material100adheres and the wall portion of through-hole22is caught in application liquid container21when application needle24moves up. Therefore, the above-described effects can be obtained.

Further, setting the protrusion amount less than or equal to 3 mm, which is suitably short, makes it possible to reduce variations in application diameter of liquid material100and to transfer a pattern having a uniform application diameter. The number of regions of the side surface of application needle24where liquid material100adheres and regions where no liquid material100adheres that alternately appear as illustrated in (D) ofFIG.9decreases. This is because the influence of liquid material100nonuniformly adhering on the transferred pattern of liquid material100is reduced.

Further, setting the protrusion amount less than or equal to 3 mm, which is suitably short, makes it possible to reduce the application time. This is because the time required for application needle24to protrude (move down) and retreat (move up) becomes short due to the small protrusion amount as compared with a case where the protrusion amount is large. This allows even highly volatile liquid material100to be quickly and stably applied.

Further, setting the protrusion amount less than or equal to 3 mm, which is suitably short, makes it possible to reduce a loss of liquid material100. It is difficult to use liquid material100nonuniformly adhering to the side surface of application needle24for subsequent transfer to application object5. Therefore, reducing the protrusion amount and the amount of liquid material100nonuniformly adhering makes it possible to reduce the amount of liquid material100that is not used for transfer.

The effect of suitably reducing the protrusion amount can be obtained by setting the first width of needle movement section26in the horizontal direction less than or equal to 5 mm and setting the length of needle movement section26extending from joining section25in the vertical direction greater than or equal to 5 mm. Accordingly, when application object5has a groove shape or a recessed shape, needle movement section26can be placed to be surrounded by the side surface portion of application object5, and application liquid container21can be brought close to the bottom surface portion of application object5. That is, needle movement section26is at least partly inserted to fit into the side surface portion, such as a groove shape, of application object5. This can make the distance between the bottom surface portion of application object5and the lowermost portion of needle movement section26equal to a length suitable for application. Note that length T of needle movement section26in the vertical direction is more preferably greater than or equal to 5 mm as described above. Length T, however, only needs to be greater than at least a dimension obtained by subtracting protrusion amount P (for example, 3 mm) of application needle24from the depth of the side surface portion of application object5in the vertical direction. Accordingly, the above-described effects can be obtained.

Further, setting the protrusion amount greater than or equal to 1 mm, which is suitably long, makes it possible to reduce the amount of liquid material100adhering to distal end23of application needle24and allows a fine pattern to be applied.

The characteristics such as the shape and size of application liquid container21of liquid material application unit4according to the present embodiment are particularly effective when liquid material100is transferred to the bottom surface portion located at the bottom of the side surface portion of application object5having a groove shape or a recessed shape.

In liquid material application unit4descried above, first width W1 is preferably less than or equal to five times second width W2, in the horizontal direction, the portion of application needle24extending in the vertical direction. Accordingly, the same effects as described above can be obtained.

The liquid material application method according to the present embodiment includes the following processes. Application liquid container21having through-hole22formed at the bottom portion is aligned over application object5of liquid material100with liquid material100held in application liquid container21and distal end23of application needle24immersed in liquid material100. Application liquid container21is brought close to application object5. Application needle24is moved in the extending direction of application needle24to apply liquid material100to application object5. In the above-described application process, protrusion amount P by which application needle24is allowed to protrude from through-hole22of application liquid container21in the extending direction is greater than or equal to 1 mm and less than or equal to 3 mm. In the above-described approaching process, application liquid container21is placed to be at least partly surrounded by application object5. Accordingly, the same effects as described above can be obtained.

For the liquid material application method, liquid material100is preferably a liquid having fine particles suspended therein. Liquid material100containing fine particles has poor elasticity and easily breaks, so that nonuniform adhesion to the side surface of application needle24as illustrated in (B) to (D) ofFIG.9is likely to occur. Liquid material application method according to the present embodiment is particularly effective in a case where such a liquid material100is used can produce the same actions and effect as described above.

For the liquid material application method, the viscosity of the liquid material is preferably less than or equal to 13.10 Pa's. When liquid material100is excessively high in viscosity, it is difficult to separate liquid material100located between application needle24and application object5at the start of ascending after application due to a large amount of liquid material100adhering to distal end23of application needle24. Lowering the viscosity as described above can reduce the possibility of the occurrence of such a problem.

First Working Example

A test to weigh air-bubble mixing ratios with protrusion amount P variously changed was conducted. Examinations were conducted on a case where protrusion amount P of application needle24from application liquid container21was set at 15 mm and a case where protrusion amount P was set at 3 mm. Liquid material100is a polymer solution. As liquid material100, three types of a liquid material having a viscosity of 0.45 Pa·s (denoted as “A”), a liquid material having a viscosity of 1.95 Pa·s (denoted as “B”), and a liquid material having a viscosity of 13.10 Pa·s (denoted as “C”) were used. 48 samples were prepared for each type, and the same test was conducted on each sample.

The following Table 1 shows test results in a case where, as application needle24, an application needle in which distal end23is not tapered, and a cross section intersecting the extending direction has a circular shape with first width W1 equal to 1000 μm (hereinafter, referred to as a “first application needle”) was used.

Further, the following Table 2 shows test results in a case where, as application needle24, an application needle in which a portion other than distal end23has a circular shape with first width W1 equal to 1000 μm as described above, distal end23is tapered, and a cross section of the lowermost portion intersecting the extending direction has a circular shape with an outer peripheral diameter (corresponding to W1 described above) equal to 800 μm (hereinafter, referred to as a “second application needle”) was used.

From Tables 1 and 2, regardless of the type of application needle24, air bubbles mixed in with high probability when protrusion amount P was 15 mm, whereas air bubbles were completely prevented front mixing in when protrusion amount P was 3 mm. The higher the viscosity of liquid material100, the higher the air-bubble mixing ratio when protrusion amount is 15 mm. On the other hand, when protrusion amount was 3 mm, air bubbles did not mix in at all even with the example of 13.10 Pa·s that is the highest viscosity. From this, when the viscosity was less than or equal to 13.10 Pa·s, air bubbles were completely prevented from mixing in with protrusion amount set at 3 mm.

Further, in the above-described tests, examinations were conducted on variations in application diameter of liquid material100.FIG.12is a graph showing test results of variations in application diameter with the protrusion amount set at 3 mm.FIG.13is a graph showing test results of variations in application diameter with the protrusion amount set at 15 mm. In each drawing, “Φ800 μm” indicates results of the second application needle, and “Φ1000 μm” indicates results of the first application needle. Calculation results of the coefficient of variation (3σ/Ave.) obtained fromFIGS.12and13are shown in the following Table 3.

With reference toFIG.12,FIG.13, and Table 3, the following results were obtained. When protrusion amount was 1.5 mm, the coefficient of variation varied among liquid materials100different in viscosity, that is, among A, B, and C, and also varied among liquid materials100the same in viscosity. Further, the absolute value of the coefficient of variation increased when protrusion amount was 15 mm. On the other hand, when protrusion amount was 3 mm, variations in the coefficient of variation were small among liquid materials100different in viscosity, that is, among A, B, and C, and variations were also small among liquid materials100the same in viscosity. Further, variations in the coefficient of variation were small when protrusion amount was 3 mm. There was no clear difference between the case where the first application needle is used and the case where the second application needle is used.

As described above, setting the protrusion amount at 3 mm makes variations in the application diameter small as compared with the case where protrusion amount is 15 mm. This is presumably because setting the protrusion amount at 3 mm makes variations in the application amount of liquid material100adhering to the side surface of application needle24small as compared with the case where protrusion amount is 15 mm, and liquid material100can be stably applied accordingly.

Second Working Example

As described above, reducing protrusion amount P (seeFIG.2) of application needle24from through-hole22of application liquid container21in the application process makes it possible to reduce the number of air bubbles mixing into liquid material100in application liquid container21. This allows a pattern having a minute application diameter to be stably supplied.

However, when the amount of liquid material100in application liquid container21is small, air bubbles may mix into liquid material100in application liquid container21. This is presumably because when application needle24moves up to retract into application liquid container21, the tip of application needle24(the lowermost portion of distal end23) is separated upward from the liquid level of liquid material100in application liquid container21, and the tip of application needle24catches air when application needle24moves down again. This may reduce, even in an early stage of the application process in which the amount of liquid material100in application liquid container21has not been significantly reduced, the use efficiency of liquid material100because air bubbles mixing into liquid material100prevents liquid material100from being sufficiently applied. In the present working example, a result of examining a method for adjusting the configuration of the liquid material application unit against the cause of the mixing of air bubbles will be described. In the following description, the liquid level of liquid material100means, unless otherwise specified, a liquid level (uppermost portion of liquid material100) on the upper side of liquid material100in the vertical direction.

With a liquid material the same in viscosity as liquid material “C” having a viscosity of 13.10 Pa's according to the first working example, whether air bubbles mix in while changing the initial position of application needle24in the vertical direction relative to the position, in the vertical direction, of the liquid level of liquid material100in application liquid container21was examined. The following Table 4 shows examination results. Note that the initial position of application needle24means a first vertical position of application needle24before application needle24starts to move down to perform the application process (initial state).

Table 4 shows that when the tip of application needle24is placed above the liquid level of liquid material100in the initial state, that is, when application needle24is not immersed in liquid material100at all, air bubbles are likely to be generated in liquid material100. It is therefore necessary to set the initial position of application needle24so as to position the tip of application needle24as low as possible relative to the liquid level of liquid material100. In particular, when the amount of liquid material100is small, and the liquid level is lowered, it is important to adjust the initial position of application needle24.

FIG.14is a schematic diagram illustrating the initial position, in the vertical direction, of the application needle in the application liquid container. With reference toFIG.14, application needle24includes distal end23inclined, as illustrated inFIG.14, as a result of taper machining or the like, and a uniform width region24aother than distal end23. Uniform width region24ais a region that is located above distal end23and where the maximum width of the outer periphery is substantially uniform in the vertical direction. The maximum width of the outer periphery of uniform width region24ais W2.

An inner wall21aof application liquid container21has a tapered shape on a lower side in which the dimension of inner wall21ain the left-right direction in the drawing, that is, the area of the cross section in the horizontal direction, is smaller than the dimension on an upper side. The initial position of application needle24is a position, in the vertical direction, of the tip of application needle24relative to a lowermost portion O of through-hole22of application liquid container21, and is denoted as a distance P0. Distance P0is set larger than a length t, in the vertical direction, of through-hole22located at the lower portion of application liquid container21. When application needle24is retracted into application liquid container21, liquid material100flows around and into a region adjacent to the tip of application needle24(a region immediately below the tip of application needle24) in application liquid container21.

When distance P0in the vertical direction between the lowermost portion of through-hole22and the tip of application needle24is small at the initial position of application needle24, it is, however, difficult for liquid material100to flow into the region adjacent to the tip of application needle24, and the time required for the inflow becomes longer. As the time required for the inflow becomes longer, a so-called “application interval” is set longer, and the takt time of the application process of causing application needle24to apply liquid material100becomes longer. Accordingly, the initial position of application needle24, that is, the above-described distance P0, is empirically set larger than length t of through-hole22in the vertical direction. The design criterion for distance P0, however, was not clear. Therefore, in the present working example, a method by which the initial position (distance P0) of application needle24can be made as short as possible by controlling a void ratio at a “gap position”, and the tip of application needle24can be positioned as low as possible relative to the liquid level of liquid material100was examined. Specifically, a method by which the initial position of the lowermost portion of distal end23of application needle24is set at a position where distal end23is placed in liquid material100and is covered with liquid material100was examined. A case where distance P0is smaller than t will be also examined below.

FIG.15is a schematic diagram for describing the gap position. With reference toFIG.15, a gap position P1is a position at which the distance between application needle24and particularly the inner wall of through-hole22of application liquid container21in the left-right direction (horizontal direction) inFIG.15intersecting the extending direction of application needle24is the smallest among the initial positions of application needle24in the vertical direction in the initial state. Here, application needle24located at gap position P1may be distal end23having the outer periphery formed into a tapered shape. Gap position P1is defined in a region of the lowermost portion of through-hole22above a region where a C surface27is formed inFIG.15. Normally, as illustrated inFIG.15, the distance in the left-right direction between the outer periphery of distal end23of application needle24and the wall surface of through-hole22surrounding the outer periphery from the side is smaller than the distance in the left-right direction in the other regions. In this case, gap position P1is located at the uppermost portion of through-hole22. This is because the outer periphery of distal end23of application needle24gradually increases along the tapered shape from the tip, and a tip diameter Td of application needle24at gap position P1is larger than a diameter Pd of the tip of application needle24(note that diameter Td is smaller than a diameter Hd of through-hole22). In the region above through-hole22, the dimension in the left-right direction of inner wall21aof application liquid container21is significantly larger than the dimension in the left-right direction of through-hole22. Therefore, in the region above the through-hole22, the distance between the outer periphery of distal end23and inner wall21aof application liquid container21does not become minimum. Therefore, the position where diameter Td becomes maximum just beside through-hole22is usually the uppermost portion of the through-hole22. Note that, inFIG.15, distal end23is placed at a position of the uppermost portion of through-hole22in the vertical direction, or alternatively, uniform width region24amay be placed at the position.

FIG.16is a schematic cross-sectional view taken along a line XVI-XVI inFIG.15. That is,FIG.16illustrates a cross section at gap position P1in the vertical direction. Thus,FIG.16is a schematic diagram for describing the void ratio. With reference toFIG.16, the void ratio is a ratio of an area of a void region excluding the portion where the application needle (distal end23) is placed to an area of a region surrounded by inner wall21a(through-hole22) of application liquid container21on a plane (paper surface on whichFIG.16is given) in the horizontal direction at gap position P1described above. In other words, the void ratio is a ratio of an area of a region of a void28between the outermost portion of distal end23and the inner wall (through-hole22) to an area of a region inside the portion (through-hole22) inFIG.16corresponding to inner wall21ainFIG.15.

In the present working example, with a liquid material the same in viscosity as liquid material “C” having a viscosity of 13.10 Pa·s, the influence on the application interval when the void ratio is changed was examined. Note that the application interval is a time from immediately after the upward movement of application needle24after application to immediately before application needle24starts to move down to perform application again. The application interval was determined as a time required for comparing the first application diameter of the pattern applied in a first application process and a second application diameter of the pattern applied in a second application process immediately after the first application process and bringing a difference within 5% of the first application diameter.

Normally, when the application interval is shorter than the time during which liquid material100flows into the region adjacent to and immediately below the tip of application needle24in application liquid container21, the application diameter tends to be small. The application interval when the void ratio is 80% was defined as a reference value of 1, and a change in the application interval when the void ratio is changed was calculated. The following Table 5 shows the calculation results. In Table 5, when the rate of change in the application interval with the void ratio of 80% is within 5% (that is, when the application interval is greater than or equal to 0.95 and less than or equal to 1.05), the application interval is described as 1 (no change).

As shown in Table 5, the lower the void ratio, the longer the application interval. In other words, a lower void ratio indicates a lower position of application needle24. This is because, with distal end23located at the same height as the uppermost portion of through-hole22, when application needle24moves down, diameter Td of application needle24at the same height as the uppermost portion of through-hole22becomes larger. Therefore, when the initial position of application needle24is lowered to make the void ratio less than or equal to, for example, 43%, it is possible to reduce the number of air bubbles mixing in as shown in Table 4. This is because when the void ratio is less than or equal to 43%, the tip of application needle24is placed relatively downward in liquid material100at the initial position as compared with the case where the void ratio is 80%, and the application needle is sufficiently immersed in liquid material100accordingly. In this case, however, as shown in Table 5, the longer the application interval, the longer the takt time, which makes the use efficiency of the liquid material lower.

Therefore, from Table 5, application liquid container21is aligned over application object5of liquid material100before the application process (as illustrated in (A) ofFIG.8) so as to bring the application interval as close as possible to the reference value. At this time, it is more preferable that the initial position of application needle24be determined so as to minimize the void ratio within a void ratio range in which the application interval does not change relative to the reference value (even if the application interval changes relative to the reference value, the change falls within 5% of the reference value of the application interval when the void ratio is 80%). Specifically, in the aligning process as illustrated in (A) ofFIG.8, the initial position of application needle24is preferably determined to be a position where the void ratio is greater than or equal to 62% (60%). When the initial position of application needle24is lowered to the position where the void ratio is, for example, 62% (60%), application needle24is located lower than the initial position of application needle24where the void ratio is 80%. It is therefore more preferable that the initial position of application needle24be lowered to the position where the void ration is 62% (60%) because it is possible to reduce the number of air bubbles mixing in as shown in Table 4 and to suppress an increase in the application interval as shown in Table 5. Therefore, when the void ration is 62% (60%), it is possible to suppress the extension of the takt time of the application process while reducing the number of air bubbles mixing in. As described above, the use of the adjustment method by which the application interval is minimized as compared with the known empirical method allows an increase in the use efficiency of liquid material100and can minimize the application interval.

Note that, with application needle24having large tip diameter Pd, and high viscous liquid material100used, when application needle24is placed at the preferable initial position found in the present working example, air bubbles can be prevented, but the application interval may become longer. In this case, design factors such as the internal shape of application liquid container21, diameter Hd of through-hole22of application liquid container21, and the shape of application needle24may be optimized. As a result, the space in the vicinity of the tip of application needle24at the initial position may be designed to be larger to allow liquid material100to flow into the space in the vicinity of the tip of application needle24more easily. This allows an increase in the effect of making the takt time of the application process shorter without mixing air bubbles.

Third Working Example

The second working example shows, with attention paid to gap position P1, a method for preventing an increase in the application interval. However, when the application interval is made shorter, air bubbles may mix into liquid material100in application liquid container21.FIG.17is a schematic diagram illustrating how air bubbles mix in in a manner that depends on the application interval.FIG.17illustrates changes over time in the order of (A), (B), and (C). With reference toFIG.17, when application needle24is retracted into application liquid container21, liquid material100flows into the region adjacent to the tip of application needle24in application liquid container21. When, however, the application interval is short, application needle24enters application liquid container21while the region adjacent to the tip of application needle24is not sufficiently filled with liquid material100. At this time, air in the region adjacent to the tip of application needle24that is not sufficiently filled with liquid material100is caught in liquid material100. When such a problem occurs, it is considered preferable to increase the application interval.

FIG.18is a flowchart of the liquid material application method according to the third working example. With reference toFIG.18, in the present working example, the application process of causing application needle24to apply liquid material100is performed a plurality of times. That is, the application process includes the first application process (S10) of causing application needle24to apply liquid material100, and the second application process (S20) of causing application needle24to apply liquid material100again immediately after the first application process.

Between the first application process (S10) and the second application process (S20), as illustrated in (F) ofFIG.8, application needle24moves up away from application object5(S11). This causes entire application needle24including the tip to be retracted into application liquid container21. Application liquid container21may move up simultaneously with or immediately after the retraction, Immediately, after the retraction, a horizontal movement process of causing application needle24to relatively move in the horizontal direction to a position where liquid material100is to be applied in the second application process (S12). That is, application object5moves on, for example, X-axis table 1 and Y-axis table 2 (seeFIG.1) such that application object5to be applied next by application needle24is located immediately below liquid material application unit4. Alternatively, application needle24may move in a direction along the XV plane to immediately above application object5to be applied next. This aligns application liquid container21over application object5of liquid material100.

Furthermore, a wait process (S13) of causing application needle24to wait in application liquid container21is provided between the first application process (S10) and the second application process (S20). Specifically, a time during which application needle24waits in application liquid container21is a time during which the stage such as X-axis table 1 and application liquid container21do not move, application needle24does not move up or down relative to application liquid container21, and application needle24remains stationary in application liquid container21. In the present working example, for the process (S13), such a wait time of application needle24is provided. Subsequently, application liquid container21is brought close to application object5(S14). That is, for example, as illustrated in (B) ofFIG.8, application liquid container21moves down. Subsequently, application needle24moves down relative to application liquid container21as illustrated in (C) ofFIG.8, and distal end23of application needle24comes into contact with application object5as illustrated in (D) ofFIG.8. The second application process (S20) is performed as illustrated in (C), (D) ofFIG.8.

As described above, in the present working example, the wait process (S13) of causing application needle24to wait in application liquid container21is provided between the first application process (S10) and the second application process (S20) in addition to the processes (S11), (S12), (S14). The process (S13) may be performed temporally before or after the horizontal movement process (S12). The application interval in the present working example is obtained by adding the time of the wait process (S13) of causing application needle24to wait in application liquid container21to the application interval in the second working example. That is, the application interval in the present working example is a time from immediately after the upward movement of application needle24to retract entire application needle24into application liquid container21after the application in the first application process (S10) to immediately before application needle24starts to move down in the second application process (S20) after the horizontal movement process (S12) (including the upward movement of application liquid container21), the wait process (S13), and the downward movement of application liquid container21(S14).

When the distance (pitch) in the horizontal direction between the application position in the first application process (S10) and the application position in the second application process (S20) is short, the adjustment method of the present working example is particularly effective. Further, the adjustment method of the present working example is also particularly effective when the movement time of the stage such as X-axis table 1 and Y-axis table 2 in the horizontal movement process (S12) is short.

Next, experiment details and results of the present working example will be described. Examinations were conducted, using liquid materials the same in viscosity as liquid material “A” having a viscosity of 0.45 Pa·s, liquid material “B” having a viscosity of 1.95 Pa·s, and liquid material “C” having a viscosity of 13.10 Pa·s, on air-bubble mixing ratios with the application interval variously changed. The change in the application interval was adjusted in accordance with the presence or absence of the wait process (S13) of causing application needle24to wait in application liquid container21and the change over time. The following Table 6 shows the test results.

As shown in Table 6, in the case of A that is low in viscosity, air bubbles did not mix in with the short application interval of 1 second (that is, in an example where the wait process (S13) of causing application needle24to wait in application liquid container21is not performed). However, in the case of the short application interval of 1 second, B that is high in viscosity was higher in air-bubble mixing ratio than A. C that is further higher in viscosity was higher air-bubble mixing ratio than B. It can be presumed that, since A was low in viscosity, liquid material100easily flowed, and liquid material100filled the region immediately below the tip of application needle24immediately after application needle24was retracted into application liquid container21, thereby preventing air bubbles from mixing in. Even with B, C that are high in viscosity, however, an increase in the application interval and providing the wait process (S13) made the air-bubble mixing ratio lower. When the application interval was 3 seconds, the air-bubble mixing ratio was 13% with C that is the highest in viscosity, whereas when the application interval was 5 seconds, the air-bubble mixing ratio was 0% even with C. Note that the wait time of application needle24with the application interval of 3 seconds was 2 seconds. The wait time of application needle24with the application interval of 5 seconds was 4 seconds. This shows that higher viscosity requires a longer application interval (wait time of application needle24in the process (S13)) to prevent air bubbles from mixing in.

Note that polymer solutions as liquid material100have complicated flow characteristics depending on types, and have different fluid behavior depending on the presence or absence of thixotropy and stringiness even with the same viscosity. When the application interval is set, it is preferable that the application interval be set on the basis of the test results of Table 6 with due consideration given to the flow characteristics of liquid material100to be used.

The features described in each example included in the embodiment and each working example may be appropriately combined and applied within a range where there is no technical contradiction. For example, the features derived in the second working example and the features derived in the third working example may be combined. The features included in the present embodiment may be applied to each of the first to third working examples.

It should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the above description, and the present invention is intended to include the claims, equivalents of the claims, and all modifications within the scope.

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