U.S. patent application number 10/134722 was filed with the patent office on 2003-08-28 for apparatus for dispensing liquid crystal and method for controlling liquid crystal dropping amount.
This patent application is currently assigned to LG. Philips LCD Co., Ltd.. Invention is credited to Kweon, Hyug-Jin, Son, Hae-Joon.
Application Number | 20030161939 10/134722 |
Document ID | / |
Family ID | 27751974 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030161939 |
Kind Code |
A1 |
Kweon, Hyug-Jin ; et
al. |
August 28, 2003 |
APPARATUS FOR DISPENSING LIQUID CRYSTAL AND METHOD FOR CONTROLLING
LIQUID CRYSTAL DROPPING AMOUNT
Abstract
A liquid crystal dispensing apparatus and a method of
controlling a liquid crystal dropping amount are provided to drop
liquid crystal onto a substrate corresponding to at least one unit
panel area. In one aspect, the apparatus uses a liquid crystal
dispensing unit to dispense liquid crystal. The liquid crystal
dispensing unit includes a nozzle having a discharging hole through
which the liquid crystal is dropped onto the substrate, a needle
moveable between a down position in which the needle blocks the
discharging hole and an up position in which the needle is
separated from the discharging hole, a spring member to bias the
needle toward the down position, and a solenoid coil to provide a
magnetic force to move the needle to the up position. The dropping
amount liquid crystal dispensing unit may be electrically
controlled by controlling the solenoid coil or by controlling a gas
pressure used to drive the liquid crystal through the discharging
hole. Variations and errors in the dropping amount may also be
compensated by an automated compensation of the electric power to
the solenoid and/or the gas pressure.
Inventors: |
Kweon, Hyug-Jin; (Gumi,
KR) ; Son, Hae-Joon; (Pusan, KR) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
LG. Philips LCD Co., Ltd.
|
Family ID: |
27751974 |
Appl. No.: |
10/134722 |
Filed: |
April 30, 2002 |
Current U.S.
Class: |
427/8 ; 118/663;
118/695 |
Current CPC
Class: |
B05C 5/0225 20130101;
G02F 1/1341 20130101; G02F 1/13415 20210101 |
Class at
Publication: |
427/8 ; 118/663;
118/695 |
International
Class: |
B05D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2002 |
KR |
10616/2002 |
Claims
What is claimed is:
1. A liquid crystal dispensing apparatus for dropping liquid
crystal onto a substrate corresponding to at least one unit panel
area, the apparatus comprising: a liquid crystal dispensing unit to
dispense liquid crystal, the liquid crystal dispensing unit
including: a nozzle having a discharging hole through which the
liquid crystal is dropped onto the substrate, a needle moveable
between a down position in which the needle blocks the discharging
hole and an up position in which the needle is separated from the
discharging hole, a spring member to bias the needle toward the
down position, and a solenoid coil to provide a magnetic force to
move the needle to the up position; an electric power supply unit
to provide electric power to the solenoid coil to move the needle
to the up position; a gas supply unit to provide a gas pressure to
the liquid crystal dispensing unit to drive the liquid crystal
through the discharging hole when the needle is in the up position;
and a control unit to calculate a dropping amount of the liquid
crystal to be dropped on the substrate and to control the electric
power supply unit and the gas supply unit such that the calculated
dropping amount of the liquid crystal is dispensed onto the
substrate.
2. The apparatus according to claim 1, wherein the control unit
includes: an input unit through which data is input; a dropping
amount calculation unit to calculate the dropping amount of the
liquid crystal and a dropping position of the liquid crystal onto
the substrate according to the input data; at least one of an
electric power control unit control the electric power provided by
the electric power supply unit to the solenoid coil according to
the liquid crystal dropping amount calculated by the dropping
amount calculation unit, and a flow control unit to control the gas
pressure according to the liquid crystal dropping amount calculated
by the dropping amount calculation unit; and a substrate driving
unit to drive one of the substrate and the liquid crystal
dispensing unit with respect to the other so that the nozzle is
positioned above the dropping position calculated by the dropping
amount calculation unit.
3. The apparatus according to claim 2, wherein the input data
includes at least an area of the liquid crystal panel unit, a cell
gap of the liquid crystal unit panel, and characteristic
information of the liquid crystal.
4. The apparatus according to claim 2, wherein the control unit
further includes an output unit to display the input data, the
calculated dropping amount of the liquid crystal, and a dropping
status of the liquid crystal.
5. The apparatus according to claim 2, wherein the dropping amount
calculation unit includes: a total dropping amount calculation unit
to calculate a total amount of the liquid crystal to be dropped
onto the substrate according to the input data; a dropping position
calculation unit to calculate a dropping position of the liquid
crystal according to the total amount of liquid crystal to be
dropped calculated by the total dropping amount calculation unit; a
dropping number calculation unit to calculate a number of drops of
the liquid crystal according to the total dropping amount
calculated by total dropping amount calculation unit; and a single
dropping amount calculation unit to calculate a single drop amount
of the liquid crystal according to the total dropping amount
calculated by the total dropping amount calculation unit.
6. The apparatus according to claim 1, further comprising a
compensating unit to compensate the dropping amount of the liquid
crystal when a measured dropping amount of the liquid crystal being
dropped is different from the calculated dropping amount of the
main control unit.
7. The apparatus according to claim 6, wherein the compensating
unit includes: a dropping amount measuring unit to measure the
measured dropping amount of the liquid crystal; and a compensating
amount calculation unit to compare the measured dropping amount and
the calculated dropping amount, to calculate a compensating amount,
and to drive the at least one of the electric power control unit
and the flow control unit.
8. The apparatus according to claim 7, wherein the compensating
amount calculation unit includes: a dropping amount setting unit in
which the dropping amount calculated in the main control unit is
set; a comparing unit to compare the dropping amount set in the
dropping amount setting unit with the measured dropping amount and
to calculate a difference value; and a compensation calculation
unit to calculate an error value of dispensing characteristic in
order to compensate for the difference value calculated by the
comparing unit.
9. The apparatus according to claim 8, wherein the compensation
calculation unit includes at least one of: a pressure error
calculation unit to calculate an error value of the gas pressure
applied to the liquid crystal in the liquid crystal dispensing unit
according to the difference value calculated in the comparing unit,
to calculate the flow amount of the gas corresponding to the error
value of the gas pressure, and to output the flow amount such that
the gas pressure is compensated; and an electric power error
calculation unit to calculate an error value of the electric power
amount applied to the solenoid coil based on the difference value
calculated in the comparing unit and to output the error value of
the electric power amount such that the electric power provided to
the solenoid coil is compensated.
10. A method of dispensing a liquid crystal onto a substrate having
at least one liquid crystal unit panel area from a liquid crystal
dispenser using a gas pressure to dispense liquid crystal
therefrom, the liquid crystal dispenser including a nozzle having a
discharging opening from which the liquid crystal is dropped, a
needle moveable between a down position to block the discharging
opening and an up position to open the discharging opening, a
spring to bias the needle toward the down position, and a solenoid
coil to provide a magnetic force to open the discharging hole, the
method comprising the steps of: inputting data; calculating a total
dropping amount of the liquid crystal to be dropped onto the
substrate according to the input data; calculating a dropping
position at which liquid crystal is to be dropped onto the
substrate according to the calculated total dropping amount;
calculating a single dropping amount of the liquid crystal
according to the total dropping amount; calculating an amount of
electric power to be supplied to the solenoid coil and a gas
pressure to be applied onto the liquid crystal in the liquid
crystal dispenser according to the calculated single dropping
amount; and applying the calculated amount of the electric power to
the solenoid coil and supplying the calculated gas pressure to the
liquid crystal dispenser.
11. The method according to claim 10, wherein the step of inputting
data includes inputting an area of the liquid crystal unit panel, a
cell gap of the liquid crystal panel, and characteristic
information of the liquid crystal.
12. The method according to claim 10, further comprising a step of
controlling a tension of the spring.
13. The method according to claim 12, wherein the step of
controlling the tension of the spring includes an operator setting
the tension at an initial stage of the liquid crystal dropping.
14. The method according to claim 10, wherein the amount of
electric power corresponding to a single dropping amount of the
liquid crystal is fixed at an initial stage of the liquid crystal
dropping.
15. The method according to claim 10, wherein the step of
compensating the dropping amount of the liquid crystal includes the
steps of: measuring the measured amount the liquid crystal dropped;
and calculating a compensating amount by comparing the measured
dropping amount with the calculated single dropping amount; and
controlling at least one of the electric power applied to the
solenoid coil and the gas pressure according to the calculated
compensating amount.
16. The method according to claim 15, wherein the gas pressure
corresponding to a single dropping amount is fixed at an initial
stage of the liquid crystal dropping.
17. The method according to claim 15, further comprising a step of
compensating the dropping amount of the liquid crystal if a
measured amount of the liquid crystal dropped on the substrate is
different from the calculated single dropping amount.
18. The method according to claim 13, further comprising the step
of displaying the input data, the calculated dropping amount of the
liquid crystal, and a dropping status of the liquid crystal.
19. A liquid crystal dispensing apparatus for dropping liquid
crystal onto a substrate, comprising: a liquid crystal dispensing
unit to dispense liquid crystal; a measuring system to measure an
amount of liquid crystal dispensed from the dispensing unit; and a
controller to receive the measured amount of liquid crystal from
the measuring system, the controller comparing the measured amount
of liquid crystal with a target amount of liquid crystal to be
dispensed and electrically adjusting at least one dispensing
characteristic of the liquid crystal dispensing unit if the
measured amount is different than the target amount.
20. The apparatus according to claim 19, wherein the liquid crystal
dispensing unit includes a nozzle having a discharging opening from
which the liquid crystal is dropped, a needle moveable between a
down position to block the discharging opening and an up position
to open the discharging opening, a spring to bias the needle toward
the down position, and a solenoid coil to provide a magnetic force
to open the discharging hole.
21. The apparatus according to claim 20, wherein a gas pressure is
used to drive the liquid crystal through the discharging opening
when the needle is in the up position.
22. The apparatus according to claim 21, wherein the controller
controls at least one of the gas pressure and the solenoid coil to
adjust the at least one dispensing characteristic of the liquid
crystal dispensing unit.
23. A liquid crystal dispensing apparatus for dropping liquid
crystal onto a substrate corresponding to at least one unit panel
area, the apparatus comprising: a liquid crystal dispensing unit to
dispense liquid crystal, the liquid crystal dispensing unit
including: a nozzle having a discharging hole through which the
liquid crystal is dropped onto the substrate, a needle moveable
between a down position in which the needle blocks the discharging
hole and an up position in which the needle is separated from the
discharging hole, a spring member to bias the needle toward the
down position, and a solenoid coil to provide a magnetic force to
move the needle to the up position; a dropping amount measuring
unit to measure a dropping amount of liquid crystal dropped; a
compensating amount calculation unit to compare the measured
dropping amount with a target dropping amount to calculate a
compensating value; and a compensating control unit to control at
least one of the electric power applied to the solenoid coil and
the gas pressure according to the compensating value.
24. The apparatus according to claim 23, wherein the compensating
control unit includes at least one of: an electric power control
unit to control the electric power applied to the solenoid coil
according to the compensating amount calculated in the compensating
amount calculation unit; and a flow control unit to control a gas
pressure applied to the liquid crystal in the liquid crystal
dispensing unit according to the compensating amount calculated in
the compensating amount calculation unit.
25. The apparatus according to claim 23, wherein the dropping
amount measuring unit includes a gravimeter adjacent to the
substrate.
26. The apparatus according to claim 23, wherein the dropping
amount measuring unit measures the dropping amount by measuring a
total dropping amounts of set number of drops.
27. The apparatus according to claim 23, wherein the compensating
amount calculation unit includes: a dropping amount setting unit in
which the target dropping amount is set; a comparing unit to
compare the dropping amount with the measured dropp ing amount and
to calculate a difference value; and an electric power error
calculation unit to calculate an error value of an electric power
amount applied to the solenoid coil according to the difference
value calculated in the comparing unit and to output the error
value to control the electric power amount applied to the solenoid
coil.
28. The apparatus according to claim 23, wherein the compensating
amount calculation unit includes: a dropping amount setting unit in
which the target dropping amount is set; a comparing unit to
compare the dropping amount with the measured dropping amount and
to calculate a difference value; and a pressure error calculation
unit to calculate an error value of the gas pressure applied to the
liquid crystal in the liquid crystal dispensing unit according to
the difference value calculated in the comparing unit and to output
the error value to control the gas pressure.
29. The apparatus according to claim 23, wherein the compensating
amount calculation unit comprises: a dropping amount setting unit
in which the target dropping amount is set; a comparing unit to
compare the dropping amount with the measured dropping amount and
to calculate a difference value; a pressure error calculation unit
to calculate an error value of the gas pressure applied to the
liquid crystal in the liquid crystal dispensing unit according to
the difference value calculated in the comparing unit and to output
the error value of the gas pressure to control the gas pressure;
and an electric power error calculation unit to calculate an error
value of an electric power amount applied to the solenoid coil
according to the difference value calculated in the comparing unit
and to output the error value of the electric power amount to
control the electric power amount applied to the solenoid coil.
30. A method of dispensing liquid crystal onto a substrate
corresponding to at least one unit panel area, the method
comprising the steps of: filling a liquid crystal dispensing unit
with liquid crystal; dispensing a first quantity of liquid crystal
onto the substrate; conducting an automated compensation of at
least one dispensing characteristic of the liquid crystal
dispensing unit; and dispensing a second quantity of the liquid
crystal onto the substrate, the second quantity being determined
according to the automated compensation.
31. The method according to claim 30, wherein the step of
conducting the automated compensation includes the steps of
dispensing a test quantity of liquid crystal to a measuring system
substantially adjacent to the substrate; measuring the amount of
liquid crystal dispensed in the test quantity; comparing the
measured amount with a target amount; and automatically adjusting
the at least one dispensing characteristic of the liquid crystal
dispensing unit.
32. The method according to claim 31, wherein the liquid crystal
dispensing unit includes at least one of an electrically controlled
valve structure to control the dispensing of the liquid crystal and
an electrically controlled gas supply to apply a gas pressure in
order to drive the dispensing of the liquid crystal when the
electrically controlled valve structure is open, and wherein the
step of automatically adjusting the dispensing characteristics
includes the step of electrically adjusting at least one of the
electrically controlled valve structure and electrically controlled
the gas supply.
33. The method according to claim 32, wherein the electrically
controlled valve structure includes a nozzle having discharging
hole and a needle moveable between a first position to close the
discharging hole and a second position to open the discharging
hole.
34. A method of dispensing a liquid crystal from a liquid crystal
dispenser using a gas pressure to dispense liquid crystal
therefrom, the liquid crystal dispenser including a nozzle having a
discharging opening from which the liquid crystal is dropped, a
needle moveable between a down position to block the discharging
opening and an up position to open the discharging opening, a
spring to bias the needle toward the down position, and a solenoid
coil to provide a magnetic force to open the discharging hole, the
method comprising the steps of: setting a dropping amount of the
liquid crystal to be dropped; measuring an amount of liquid crystal
dropped; calculating a compensating amount by comparing the set
dropping amount with the measured dropping amount; and controlling
at least one of an electric power applied to the solenoid coil and
the gas pressure applied to the liquid crystal according to the
calculated compensating amount.
35. The method according to claim 34, wherein the dropping amount
of the liquid crystal is calculated according to an area of a
liquid crystal unit panel, a cell gap of the liquid crystal unit
panel, and characteristic information of the liquid crystal.
36. The method according to claim 34, wherein the step of measuring
the amount of liquid crystal dropped includes the step of measuring
a weight of the liquid crystal dropped.
37. The method according to claim 34, wherein the step of
calculating the compensating amount includes the steps of:
calculating a difference value by comparing the set dropping amount
with the measured dropping amount; calculating an error value of
the gas pressure applied to the liquid crystal in the liquid
crystal dispensing unit according to the calculated difference
value in the dropping amount; and calculating a gas flow amount
corresponding the calculated error value.
38. The method according to claim 34, wherein the step of
calculating the compensating amount includes the steps of:
calculating a difference value by comparing the set dropping amount
with the measured dropping amount; calculating an error amount of
the electric power applied to the solenoid coil according to the
difference value; and calculating an electric power corresponding
to the calculated error value.
39. The method according to claim 34, wherein the step of
calculating the compensating amount includes the steps of:
calculating a difference value by comparing the set dropping amount
with the measured dropping amount; calculating an error value of
the gas pressure applied to the liquid crystal in the liquid
crystal dispensing unit according to the calculated difference
value in the dropping amount to determine a gas flow amount
corresponding the calculated error value of the gas pressure; and
calculating an error amount of the electric power applied to the
solenoid coil according to the difference value to determine an
electric power corresponding to the calculated error value.
40. The method according to claim 34, further comprising the step
of controlling a tensile force of the spring in accordance with the
calculated compensating amount.
Description
[0001] The present application claims the benefit of Korean Patent
Application No. 10616/2002 filed in Korea on Feb. 27, 2002, which
is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an apparatus and method for
dropping a controlled amount of liquid crystal, and more
particularly, to an apparatus and method for dropping a controlled
amount of liquid crystal such that an exact and optimal amount of
liquid crystal is dispensed onto a substrate for a liquid crystal
unit panel.
[0004] 2. Description of the Related Art
[0005] Recently, various portable electric devices such as mobile
phones, personal digital assistants (PDA), and notebook computers
have been developed, and therefore, the needs for a flat panel
display device used in small, light weight, and power-efficient
devices for such portable devices have correspondingly increased.
To meet such needs, flat panel display device technologies such as
liquid crystal display (LCD) technology, plasma display panel (PDP)
technology, field emission display (FED) technology, and vacuum
fluorescent display (VFD) technology have been actively researched.
Of these flat panel display devices, the LCD is highlighted due to
current mass production, efficient driving schemes, and superior
image quality.
[0006] The LCD is a device for displaying information on a screen
using refractive anisotropy of liquid crystal. As shown in FIG. 1,
the LCD 1 comprises a lower substrate 5, an upper substrate 3, and
a liquid crystal layer 7 formed between the lower substrate 5 and
the upper substrate 3. The lower substrate 5 is a driving device
array substrate. A plurality of pixels (not shown) are formed on
the lower substrate 5, and a driving device such as a thin film
transistor (TFT) is formed on each pixel. The upper substrate 3 is
a color filter substrate, and a color filter layer for reproducing
real color is formed thereon. Further, a pixel electrode and a
common electrode are formed on the lower substrate 5 and the upper
substrate 3, respectively. An alignment layer is formed on the
lower substrate 5 and the upper substrate 3 to align liquid crystal
molecules of the liquid crystal layer 7 uniformly.
[0007] The lower substrate 5 and the upper substrate 3 are attached
by a sealing material 9, and the liquid crystal layer 7 is formed
therebetween. In addition, the liquid crystal molecules are
reoriented by the driving device formed on the lower substrate 5 to
control the amount of light transmitted through the liquid crystal
layer, thereby displaying information.
[0008] Fabrication processes for a LCD device can be divided into a
driving device array substrate process for forming the driving on
the lower substrate 5, a color filter substrate process for forming
the color filter on the upper substrate 3, and a cell process.
These processes will be described with reference to FIG. 2 as
follows.
[0009] At first, a plurality of gate lines and data lines are
arranged on the lower substrate to define a pixel area by the
driving device array process and the thin film transistor connected
to the both gate line and the data line is formed on the each pixel
area (S101). Also, a pixel electrode, which is connected to the
thin film transistor to drive the liquid crystal layer according to
a signal applied through the thin film transistor, is formed by the
driving device array process.
[0010] At the same time, R (Red), G (Green), and B (Blue) color
filter layers for reproducing the color and a common electrode are
formed on the upper substrate 3 by the color filter process
(S104).
[0011] In addition, the alignment layer is formed on the lower
substrate 5 and the upper substrate 3, respectively. Then, the
alignment layer is rubbed to induce a surface anchoring (that is, a
pretilt angle and alignment direction) to the liquid crystal
molecules of the liquid crystal layer between the lower substrate 5
and the upper substrate 3 (S102 and S105). Thereafter, a spacer for
maintaining the cell gap constant and uniform is dispersed on the
lower substrate 5. Then, the sealing material is applied on an
outer portion of the upper substrate 3 to attach the lower
substrate 5 to the upper substrate 3 by compression (S103, S106,
and S107).
[0012] The lower substrate 5 and the upper substrate 3 are made
from a glass substrate of larger area. That is, the large glass
substrate includes a plurality of unit panel areas in which the
driving device such as TFT and the color filter layer are formed
on. To fabricate the individual liquid crystal unit panel, the
assembled glass substrate should be cut into unit panels (S 108).
Thereafter, the liquid crystal is injected into the empty
individual liquid crystal unit panel through a liquid crystal
injection opening (S109). The liquid crystal unit panel filled with
the liquid crystal is completed by sealing the liquid crystal
injection opening, and each liquid crystal unit panel is inspected
(S110).
[0013] As described above, liquid crystal is injected through the
liquid crystal injection opening. At that time, the injection of
the liquid crystal is induced by pressure difference. FIG. 3 shows
a device for injecting the liquid crystal into the liquid crystal
panel. As shown in FIG. 3, a container 12 in which the liquid
crystal is contained is placed in a vacuum chamber 10, and the
liquid crystal panel is located on an upper portion of the
container 12. The vacuum chamber 10 is connected to a vacuum pump
to maintain a vacuum state. Further, a liquid crystal panel moving
device (not shown) is installed in the vacuum chamber 10 to move
the liquid crystal panel from the upper part of the container 12 to
the surface of the liquid crystal to contact an injection opening
16 of the liquid crystal panel 1 with the liquid crystal 14 (this
step is called a liquid crystal dipping injection step).
[0014] When the vacuum in the chamber 10 is released by introducing
nitrogen gas (N.sub.2) into the vacuum chamber 10 so that the
injection opening of the liquid crystal panel 1 contacts the liquid
crystal, liquid crystal 14 is injected into the panel through the
injection opening by the pressure difference between the pressure
in the liquid crystal panel and the pressure of the vacuum chamber.
After the liquid crystal is entirely filled into the panel 1, the
injection opening 16 is sealed by a sealing material to seal the
liquid crystal layer (this step is called a liquid crystal vacuum
injection step).
[0015] However, there are several problems in the liquid crystal
dipping injection/vacuum injection method as follows.
[0016] First, the time needed to inject the liquid crystal into the
panel 1 is increased. Generally, a gap thickness between the
driving device array substrate and the color filter substrate in
the liquid crystal panel is very narrow as order of magnitude of
micrometers, and therefore, a very small amount of liquid crystal
is injected into the liquid crystal panel per unit time. For
example, it takes about 8 hours to inject the liquid crystal
completely in fabrication process of the 15 inches-liquid crystal
panel 15. Thus, the liquid crystal fabrication process time is
increased due to the liquid crystal injection of long time, thereby
reducing fabricating efficiency.
[0017] Second, the liquid crystal consumption is increased in the
above liquid crystal injection method. A small amount of liquid
crystal of the liquid crystal contained in the container 12 is
injected into the liquid crystal panel 1. However, when the liquid
crystal is exposed to atmosphere or to a certain gas, the liquid
crystal is contaminated by reaction with the gas. Therefore, the
remaining liquid crystal should be discarded after the injection
when the liquid crystal 14 contained in the container 12 is
injected into a plurality of liquid crystal panels 1, thereby
increasing the liquid crystal panel fabrication cost.
SUMMARY OF THE INVENTION
[0018] Accordingly, the present invention is directed to an
apparatus for dispensing liquid crystal and a method for
controlling a liquid crystal dropping amount that substantially
obviate one or more of the problems due to limitations and
disadvantages of the related art.
[0019] An object of the present invention is to provide an
apparatus for dropping liquid crystal that dispenses liquid crystal
directly onto a glass substrate of larger area corresponding to at
least one liquid crystal unit panel area.
[0020] Another object of the present invention is to provide an
apparatus for dropping liquid crystal and a method for controlling
a liquid crystal dropping amount such that a precisely controlled
amount of liquid crystal is automatically dropped.
[0021] Still another object of the present invention is to provide
an apparatus and a method for compensating an amount of the liquid
crystal dropped such that an exact and optimal amount of liquid
crystal can be dropped onto a substrate of at least one liquid
crystal unit panel area.
[0022] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0023] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described herein, a liquid crystal dispensing apparatus for
dropping liquid crystal onto a substrate corresponding to at least
one unit panel area comprises a liquid crystal dispensing unit to
dispense liquid crystal, the liquid crystal dispensing unit
including a nozzle having a discharging hole through which the
liquid crystal is dropped onto the substrate, a needle moveable
between a down position in which the needle blocks the discharging
hole and an up position in which the needle is separated from the
discharging hole, a spring member to bias the needle toward the
down position, and a solenoid coil to provide a magnetic force to
move the needle to the up position; an electric power supply unit
to provide electric power to the solenoid coil to move the needle
to the up position; a gas supply unit to provide a gas pressure to
the liquid crystal dispensing unit to drive the liquid crystal
through the discharging hole when the needle is in the up position;
and a control unit to calculate a dropping amount of the liquid
crystal to be dropped on the substrate and to control the electric
power supply unit and the gas supply unit such that the calculated
dropping amount of the liquid crystal is dispensed onto the
substrate.
[0024] In another aspect, a method of dispensing a liquid crystal
onto a substrate having at least one liquid crystal unit panel area
from a liquid crystal dispenser using a gas pressure to dispense
liquid crystal therefrom, the liquid crystal dispenser including a
nozzle having a discharging opening from which the liquid crystal
is dropped, a needle moveable between a down position to block the
discharging opening and an up position to open the discharging
opening, a spring to bias the needle toward the down position, and
a solenoid coil to provide a magnetic force to open the discharging
hole comprises the steps of inputting data; calculating a total
dropping amount of the liquid crystal to be dropped onto the
substrate according to the input data; calculating a dropping
position at which liquid crystal is to be dropped onto the
substrate according to the calculated total dropping amount;
calculating a single dropping amount of the liquid crystal
according to the total dropping amount; calculating an amount of
electric power to be supplied to the solenoid coil and a gas
pressure to be applied onto the liquid crystal in the liquid
crystal dispenser according to the calculated single dropping
amount; and applying the calculated amount of the electric power to
the solenoid coil and supplying the calculated gas pressure to the
liquid crystal dispenser.
[0025] In another aspect, a liquid crystal dispensing apparatus for
dropping liquid crystal onto a substrate comprises a liquid crystal
dispensing unit to dispense liquid crystal; a measuring system to
measure an amount of liquid crystal dispensed from the dispensing
unit; and a controller to receive the measured amount of liquid
crystal from the measuring system, the controller comparing the
measured amount of liquid crystal with a target amount of liquid
crystal to be dispensed and electrically adjusting at least one
dispensing characteristic of the liquid crystal dispensing unit if
the measured amount is different than the target amount.
[0026] In another aspect, a liquid crystal dispensing apparatus for
dropping liquid crystal onto a substrate corresponding to at least
one unit panel area comprises a liquid crystal dispensing unit to
dispense liquid crystal such that the liquid crystal dispensing
unit includes a nozzle having a discharging hole through which the
liquid crystal is dropped onto the substrate, a needle moveable
between a down position in which the needle blocks the discharging
hole and an up position in which the needle is separated from the
discharging hole, a spring member to bias the needle toward the
down position, and a solenoid coil to provide a magnetic force to
move the needle to the up position; a dropping amount measuring
unit to measure a dropping amount of liquid crystal dropped; a
compensating amount calculation unit to compare the measured
dropping amount with a target dropping amount to calculate a
compensating value; and a compensating control unit to control at
least one of the electric power applied to the solenoid coil and
the gas pressure according to the compensating value.
[0027] In another aspect, a method of dispensing liquid crystal
onto a substrate corresponding to at least one unit panel area
comprises the steps of filling a liquid crystal dispensing unit
with liquid crystal; dispensing a first quantity of liquid crystal
onto the substrate; conducting an automated compensation of at
least one dispensing characteristic of the liquid crystal
dispensing unit; and dispensing a second quantity of the liquid
crystal onto the substrate, the second quantity being determined
according to the automated compensation.
[0028] In another aspect, a method of dispensing a liquid crystal
from a liquid crystal dispenser using a gas pressure to dispense
liquid crystal therefrom, the liquid crystal dispenser including a
nozzle having a discharging opening from which the liquid crystal
is dropped, a needle moveable between a down position to block the
discharging opening and an up position to open the discharging
opening, a spring to bias the needle toward the down position, and
a solenoid coil to provide a magnetic force to open the discharging
hole comprises the steps of setting a dropping amount of the liquid
crystal to be dropped; measuring an amount of liquid crystal
dropped; calculating a compensating amount by comparing the set
dropping amount with the measured dropping amount; and controlling
at least one of an electric power applied to the solenoid coil and
the gas pressure applied to the liquid crystal according to the
calculated compensating amount.
[0029] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory, and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention. In the drawings:
[0031] FIG. 1 is a cross-sectional view showing a general LCD;
[0032] FIG. 2 is a flow chart showing a conventional method for
fabricating the LCD;
[0033] FIG. 3 is a view showing liquid crystal injection in the
conventional method for fabricating the LCD;
[0034] FIG. 4 is a view showing an exemplary LCD fabricated using a
method for dropping liquid crystal according to the present
invention;
[0035] FIG. 5 is a flow chart showing an exemplary method for
fabricating the LCD according to the liquid crystal dropping
method;
[0036] FIG. 6 is a view showing basic concept of the liquid crystal
dropping method;
[0037] FIGS. 7A and 7B are cross-sectional views respectively
showing an exemplary apparatus for dropping liquid crystal
according to the present invention in a state in which the liquid
crystal is not dispensed and a state in which the liquid crystal is
dispensed,
[0038] FIG. 7C is an exploded perspective view showing the
apparatus of FIGS. 7A and 7B;
[0039] FIG. 8 is a block diagram showing an exemplary structure of
a main control unit in the apparatus for dropping the liquid
crystal according to the present invention;
[0040] FIG. 9 is a block diagram showing an exemplary structure of
a dropping amount calculation unit shown in FIG. 8;
[0041] FIG. 10 is a block diagram showing an exemplary method for
dropping the liquid crystal according to the present invention;
[0042] FIG. 11 is a block diagram showing an exemplary structure of
the main control unit performing the compensation of single liquid
crystal dropping amount;
[0043] FIG. 12 is a block diagram showing an exemplary structure of
a compensating amount control unit shown in FIG. 11; and
[0044] FIG. 13 is a flow chart showing an exemplary method for
compensating the dropping amount of the liquid crystal according to
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0045] Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings.
[0046] In order to solve the problems of the conventional liquid
crystal injection methods such as a liquid crystal dipping method
or liquid crystal vacuum injection method, a liquid crystal
dropping method has been introduced recently. The liquid crystal
dropping method is a method for forming a liquid crystal layer by
directly dropping the liquid crystal onto the substrates and
spreading the dropped liquid crystal over the entire panel by
pressing together the substrates during the assembling procedure of
the substrates, rather than by injecting the liquid crystal into
the empty unit panel by the pressure difference between the inner
and outer sides of the panel. According to the above liquid crystal
dropping method, the liquid crystal is directly dropped onto the
substrate in a short time period so that the liquid crystal layer
in a LCD of larger area can be formed quickly. In addition, the
liquid crystal consumption can be minimized due to the direct
dropping of the liquid crystal as much as required amount, and
therefore, the fabrication cost can be reduced.
[0047] FIG. 4 is a view showing the basic concept of the liquid
crystal dropping method. As shown, in the liquid crystal dropping
method, the liquid crystal is dropped onto a lower substrate 105
before assembling the lower substrate 105 and an upper substrate
103 having a driving device and a color filter respectively.
Alternatively, the liquid crystal 107 may be dropped onto the
substrate 103 on which the color filter is formed. That is, the
liquid crystal 107 may be dropped either on a TFT (thin film
transistor) substrate or on a CF (color filter) substrate. However,
the substrate on which the liquid crystal 107 is dropped should
preferably be located on lower part when the substrates 105 and 105
are assembled.
[0048] At that time, a sealing material 109 is applied on an outer
part of the upper substrate 103, and therefore, the upper substrate
103 and the lower substrate 105 are attached as the upper substrate
103 and the lower substrate 105 are compressed. At the same time,
the liquid crystal drop 107 is spread out due to the pressure,
thereby forming a liquid crystal layer of uniform thickness between
the upper substrate 103 and the lower substrate 105. That is, with
the liquid crystal dropping method, the liquid crystal 107 is
dropped onto the lower substrate 105 before the panel 101 is
assembled, and subsequently the upper substrate 103 and the lower
substrate 105 are attached by the sealing material 109.
[0049] FIG. 5 shows a method for fabricating the LCD by applying
the above liquid crystal dropping method. As shown, the driving
devices such as the TFT and the color filter layers are formed on
the upper substrate and on the lower substrate with the TFT array
process and the color filter process, respectively (S201 and S204).
The TFT array process and the color filter process are generally
similar to those of the conventional processes shown in FIG. 2.
These processes are proceeded on the glass substrate having a
plurality of the unit panel areas. By applying the liquid crystal
dropping method to the manufacturing of the LCD, a glass substrate
of large area (i.e. having an area of 1000.times.1200 mm.sup.2 or
more) can be used which is much larger than that of the
conventional fabrication method.
[0050] On the lower and upper substrates on which the TFT and the
color filter layer are respectively formed, the aligmnent layers
are formed and rubbed (S202 and S205). The liquid crystal is
dropped onto the liquid crystal unit panel areas of the lower
substrate, and the sealing material is applied onto the outer
portion areas of the liquid crystal unit panel areas on the upper
substrate (S203 and S206).
[0051] Thereafter, the upper and lower substrates are disposed
facing each other and compressed to attach to each other using the
sealing material. By this compression, the liquid crystal drops
spread out on the entire panel evenly (S207). By this process, a
plurality of liquid crystal unit panel areas, on which the liquid
crystal layers are formed, are formed on the assembled large glass
substrates (i.e., the attached lower and upper substrates). Then,
the assembled glass substrates are processed and cut into a
plurality of liquid crystal unit panels (S208). The resultant
liquid crystal unit panels are inspected, thereby finishing the LCD
panel process (S208 and S209).
[0052] The difference between the method for fabricating the LCD by
applying the liquid crystal dispensing method shown in FIG. 5 and
the method for fabricating the LCD by applying the conventional
liquid crystal injection method shown in FIG. 2 will be described
as follows. First, there is the difference between the dropping and
injecting of the liquid crystal as well as the difference in the
fabricating time of a larger area LCD. Moreover, in the injection
method for fabricating the LCD of FIG. 2, the liquid crystal is
injected through an injection opening and then the injection
opening is sealed with a sealing material. However, with the
dropping method of fabricating the LCD of FIG. 5, the liquid
crystal is dropped directly onto the substrate so that the sealing
process of an injection opening is not needed. In addition, in the
injection method of FIG. 2, the panel is contacted with the liquid
crystal contained in the container during the liquid crystal
injection process, thereby contaminating the outer surface of the
panel. Thus, a cleaning process of the substrate is necessary.
However, with the liquid crystal dispensing method of FIG. 5, the
liquid crystal is directly dropped onto the substrate. Therefore,
the panel is not contaminated by the liquid crystal, and the
cleaning process is not needed. Accordingly, the method for
fabricating LCD by the liquid crystal dispensing method is simpler
than that by the liquid injection method, thereby improving
efficiency and yield.
[0053] In the method for fabricating LCD using the liquid crystal
dispensing method, the dropping position of the liquid crystal and
the dropping amount of the liquid crystal should be controlled to
form the liquid crystal layer with a desired thickness. Since the
thickness of the liquid crystal layer is closely related to the
cell gap of the liquid crystal panel, the dropping position and the
dropping amount of the liquid crystal should be carefully
controlled to prevent defect in the resultant liquid crystal panel.
Therefore, the present invention provides a dispensing apparatus
for dropping specific amount of liquid crystal at a predetermined
position.
[0054] FIG. 6 shows a generalized arrangement for dropping the
liquid crystal 107 onto the substrate 105 (glass substrate of
larger area) using the liquid crystal dispensing apparatus 120
according to the present invention. As shown, the liquid crystal
dispensing apparatus 120 is installed above the substrate 105.
Although not shown in FIG. 6, liquid crystal 107 to be dropped onto
the substrate 105 is contained in the liquid crystal dispensing
apparatus 120.
[0055] Generally, the liquid crystal 107 is dropped onto the
substrate 107 as drops. The substrate 105 moves in the x and
y-directions at a predetermined speed while the liquid crystal
dispensing apparatus 120 discharges the liquid crystal 107 at a
predetermined time intervals. Therefore, the liquid crystal 107
dropping onto the substrate 105 is generally arranged along the x
and y directions with predetermined intervals therebetween.
Alternatively, the substrate 105 may be fixed, while the liquid
crystal dispensing apparatus 120 is moved in the x and y directions
to drop the liquid crystal 107 at predetermined time intervals.
However, the liquid crystal drop shape may be trembled by the
movement of the liquid crystal dispensing apparatus 120, so errors
in the dropping position and the dropping amount of the liquid
crystal 107 may occur. Therefore, it is preferable that the liquid
crystal dispensing apparatus 120 be fixed and that the substrate
105 be moved.
[0056] FIG. 7A is cross sectional view showing an exemplary liquid
crystal dispensing apparatus when the liquid crystal is not
dropped, FIG. 7B is a cross-sectional view showing the apparatus
when the liquid crystal is dropped, and FIG. 7C is an exploded
perspective view showing the apparatus. The liquid crystal
dispensing apparatus 120 according to the present invention will be
described in more detail with reference to drawings as follows.
[0057] As shown in FIGS. 7A-7C, a cylindrical liquid crystal
container 124 is enclosed in a case 122 of the liquid crystal
dispensing apparatus 120. The liquid crystal container 124
containing the liquid crystal 107 may be made of polyethylene.
Further, the case 122 is made of a stainless steel to enclose the
liquid crystal container 124 therein. Generally, because
polyethylene has superior plasticity, it can be easily formed in
the desired shape. Since polyethylene does not react with the
liquid crystal 107 when the liquid crystal 107 is contained
therein, polyethylene can be used for the liquid crystal container
124. However, polyethylene has a weak strength so that it can be
easily distorted by external shocks or other stresses. For example,
when polyethylene is used as the liquid crystal container 124, the
container 124 may become distorted so that the liquid crystal 107
cannot be dropped at the exact position. Therefore, the container
124 should be enclosed in the case 122 made of the stainless steel
or other material having greater strength. A gas supply tube 153
connected to an exterior gas supply unit 152 may be formed on an
upper part of the liquid crystal container 124. An inert gas, such
as nitrogen, is provided through the gas supply tube 153 from the
gas supply unit 152 to fill the portion where the liquid crystal is
not contained. Thus, the gas pressure compresses the liquid crystal
107 to be dispensed.
[0058] On the lower portion of the case 122, an opening 123 is
formed. When the liquid crystal container 124 is enclosed in the
case 122, a protrusion 138 formed on a lower end portion of the
liquid crystal container 124 is inserted into the opening 123 so
that the liquid crystal container 124 is connected to the case 122.
Further, the protrusion 138 is connected to a first connecting
portion 141. As shown, a nut (i.e., female threaded portion) is
formed on the protrusion 138, and a bolt (i.e., male threaded
portion) is formed on one side of the first connecting portion 141
so that the protrusion 138 and the first connecting portion 141 are
interconnected by the nut and the bolt. Of course, it should be
recognized that in this description and in the following
description other connection types or configurations may be
used.
[0059] A nut is formed on the other side of the first connecting
portion 141 and a bolt is formed on one side of a second connection
portion 142, so that the first connecting portion 141 and the
second connecting portion 142 are interconnected. A needle sheet
143 is located between the first connecting portion 141 and the
second connecting portion 142. The needle sheet 143 is inserted
into the nut of the first connecting portion 141, and then the
needle sheet 143 is combined between the first connecting portion
141 and the second connecting portion 142 when the bolt of the
second connecting portion 142 is inserted and bolted. A discharging
hole 144 is formed through the needle sheet 143, and the liquid
crystal 107 contained in the liquid crystal container 124 is
discharged through the discharging hole 144 passing through the
second connecting portions 142.
[0060] A nozzle 145 is connected to the second connecting portion
142. The nozzle 145 is used to drop the liquid crystal 107
contained in the liquid crystal container 124 as much as a small
amount. The nozzle 145 comprises a supporting portion 147 including
a bolt connected to the nut at one end of the second connecting
portion 142 to connect the nozzle 145 with the second connecting
portion 142, a discharging opening 146 protruded from the
supporting portion 147 to drop a small amount of liquid crystal
onto the substrate as a drop.
[0061] A discharging tube extended from the discharging hole 144 of
the needle sheet 143 is formed in the supporting portion 147, and
the discharging tube is connected to the discharging opening 146.
Generally, the discharging opening 146 of the nozzle 145 has very
small diameter to finely control the liquid crystal dropping
amount, and the discharging opening 146 protrudes from the
supporting portion 147.
[0062] A needle 136 is inserted into the liquid crystal container
124, and one end part of the needle 136 is contacted with the
needle sheet 143. Preferably, the end part of the needle 136
contacted with the needle sheet 143 is conically formed to be
inserted into the discharging hole 144 of the needle sheet 143,
thereby closing the discharging hole 144.
[0063] Further, a spring 128 is installed on the other end of the
needle 136 located in an upper case 126 of the liquid crystal
dispensing apparatus 120 to bias the needle 136 toward the needle
sheet 143. A magnetic bar 132 and a gap controlling unit 134 are
preferably connected above the needle 136. The magnetic bar 132 is
made of magnetic material such as a ferromagnetic material or a
soft magnetic material, and a solenoid coil 130 of cylindrical
shape is installed on outer side of the magnetic bar 132 to be
surrounded thereof. The solenoid coil 130 is connected to an
electric power supplying unit 150 to supply electric power thereto,
thereby generating a magnetic force on the magnetic bar 132 as the
electric power is applied to the solenoid coil 130.
[0064] The needle 136 and the magnetic bar 132 are separated by a
predetermined interval (x). When the electric power is applied to
the solenoid coil 130 from the electric power supplying unit 150 to
generate the magnetic force on the magnetic bar 132, the needle 136
contacts the magnetic bar 132 as a result of the generated magnetic
force. When the electric power supplying is stopped, the needle 136
is returned to the original position by the elasticity of the
spring 128. By the movement of the needle 136 in up-and-down
directions, the discharging hole 144 formed on the needle sheet 143
is opened or closed. The end of the needle 136 and the needle sheet
143 repeatedly contact each other according to the supplying status
of the electric power to the solenoid coil 130. Thus, the part of
the needle 136 and the needle sheet 143 may be damaged by the
repeated shock caused by the repeated contact. Therefore, it is
desirable that the end part of the needle 136 and the needle sheet
143 are preferably formed by using a material which is strong to
shock, for example, a hard metal to prevent the damage caused by
the shock. Also, the needle 136 should be formed of a magnetic
material in this exemplary configuration to be magnetically
attracted to the magnetic bar 132.
[0065] As shown in FIG. 7B, as the discharging hole 144 of the
needle sheet 143 is opened, the gas (nitrogen gas) supplied to the
liquid crystal container 124 compresses the liquid crystal, thereby
dropping liquid crystal 107 from the nozzle 145. At that time, the
dropping amount of the liquid crystal 107 is dependant upon the
opening time of the discharging hole 144 and the gas pressure
applied onto the liquid crystal 107. The opening time is determined
by the distance (x) between the needle 136 and the magnetic bar
132, the magnetic force of the magnetic bar 132 generated by the
solenoid coil, and the tension of the spring 128 installed on the
needle 136. The magnetic force of the magnetic bar 132 can be
controlled according to the winding number of the solenoid coil 130
installed around the magnetic bar 132 or the magnitude of the
electric power applied to the solenoid coil 130. Here, the distance
x between the needle 136 and the magnetic bar 132 can be controlled
by the gap controlling unit 134 installed on the end part of the
magnetic bar 132.
[0066] The distance x between the needle 136 and the magnetic bar
132 as well as the tension of the spring 128 can be set by the
operator. That is, the operator is able to directly set the
distance x between the needle 136 and the magnetic bar 132 by
operating the gap controlling unit 134, or the operator is able to
set the tension of the spring 128 by operating a spring controlling
means (not shown) to change the length of the spring 128.
[0067] In contrast, the amount of the electric power applied to the
solenoid coil 130 or the amount of the nitrogen gas (N.sub.2)
supplied to the liquid crystal container 124 are controlled by the
main control unit 160 through the power supply unit 150 and a flow
control valve 154 installed on the gas supplying tube 153 supplying
the gas into the liquid crystal container 124, respectively. That
is, the amount of the electric power supply and the flow amount of
the gas are not determined by the direct operation of the operator,
but by the automated control of the main control unit 160. The
amount of electric power supply and the flow amount of the gas are
calculated according to input data.
[0068] As shown in FIG. 8, the main control unit 160 comprises a
data input unit 161 for inputting various data such as the size of
the liquid crystal unit panel to be fabricated, the number of
liquid crystal panel areas included in the substrate, the cell gap
of the liquid crystal panel (i.e., a height of a spacer), and
information of the liquid crystal; a dropping amount calculation
unit 170 for calculating the amount of liquid crystal to be dropped
onto the substrate, the number of liquid crystal drops, a single
drop amount of liquid crystal, and the dropping positions of the
liquid crystal based on the input data and then outputting a
signal; a substrate driving unit 163 for driving the substrate
based on the dropping positions of the liquid crystal calculated by
the dropping amount calculation unit 170; a power control unit 165
for supplying the electric power to the solenoid coil 130 by
controlling the power supplying unit 150 based on the single
dropping amount of the liquid crystal calculated by the dropping
amount calculation unit 170; a flow control unit 167 for supplying
the gas into the liquid crystal container 124 from the gas
supplying unit 154 by controlling the flow control valve 154 based
on the single dropping amount of the liquid crystal calculated by
the dropping amount calculation unit 170; and an output unit 169
for outputting the inputted data, the calculated dropping amount
and dropping positions, and current status of the liquid crystal
dropping.
[0069] The input unit 161 inputs data using a general operating
device such as a keyboard, a mouse, or a touch panel. The data such
as the size of the liquid crystal unit panel to be fabricated, the
size of the substrate, and the cell gap of the liquid crystal panel
is input by the operator. The output unit 169 notifies the operator
of various information. The output unit 169 includes a display
device such as a cathode ray tube (CRT) or LCD and an output device
such as a printer.
[0070] The dropping amount calculation unit 170 calculates the
total dropping amount of liquid crystal to be dropped onto the
substrate having a plurality of liquid crystal unit panel areas, an
amount of each dropping, the dropping positions of each liquid
crystal drop and the dropping amount of the liquid crystal to be
dropped on a particular liquid crystal unit panel area. As shown in
FIG. 9, the dropping amount calculation unit 170 comprises a total
dropping amount calculation unit 171 for calculating the total
amount of the liquid crystal to be dropped on the liquid crystal
unit panel area and the total amount of the liquid crystal to be
dropped on the entire substrate having a plurality of liquid
crystal unit panel areas based on the size of the liquid crystal
unit panel and the cell gap input through the input unit 161; a
dropping times calculation unit 175 for calculating the number of
times the liquid crystal is dropped based on the total dropping
amount data calculated by the total dropping amount calculation
unit 171; a single dropping amount calculation unit 173 for
calculating the single dropping amount of the liquid crystal
dropped on a certain position of the substrate; and a dropping
position calculation unit 177 for calculating the dropping
positions on the substrate.
[0071] The total dropping amount calculation unit 171 calculates
the dropping amount (Q) on the liquid crystal unit panel area
according to the input size (d) of the unit panel and the cell gap
(t) (Q=d x t) and calculates the total dropping amount of liquid
crystal to be dropped on the substrate according to the number of
the unit panel areas formed on the substrate.
[0072] The dropping times calculation unit 175 calculates the
number of times the liquid crystal is dropped within the unit panel
area based on the input total dropping amount, the size of the unit
panel, and characteristics of the liquid crystal and the substrate.
Generally, in the dropping method, the liquid crystal to be dropped
on the substrate spreads out on the substrate by the pressure
generated when the upper and lower substrates are attached. The
spreading of the liquid crystal depends on characteristics of the
liquid crystal such as the viscosity of the liquid crystal and the
structure of the substrate on which the liquid crystal will be
dropped, for example, the distribution of the pattern. Therefore,
the spreading area of the liquid crystal which is dropped once is
determined by these factors. Thus, the number of drops of the
liquid crystal that should be dropped is determined by considering
the above spreading area. Also, the number of drops on the entire
substrate is calculated from the number of drops on the respective
unit panels.
[0073] Further, the single dropping amount calculation unit 173
calculates the single dropping amount of the liquid crystal based
on the inputted total dropping amount. As shown in FIG. 9, the
dropping times calculation unit 175 and the single dropping amount
calculation unit 173 are preferably formed separately to calculate
the dropping times and the single dropping amount based on the
inputted total dropping amount. However, the dropping times
calculation unit 175 and the single dropping amount calculation
unit 173 are related closely to each other, and the dropping times
and the single dropping amount are correlated. In other words, the
single dropping amount should be determined according to the
dropping times.
[0074] The dropping position calculation unit 177 calculates the
positions at which the liquid crystal will be dropped by
calculating the area where the dropped liquid crystal spreads out
based on the dropping amount and the characteristics of the liquid
crystal.
[0075] The dropping times, the single dropping amount, and the
dropping positions calculated as above are input into the substrate
driving unit 163, the power control unit 165, and the flow control
unit 167 of FIG. 8. The power control unit 165 of FIG. 8 calculates
the electric power based on the inputted data (for example,
dropping times and the single dropping amount), and then outputs a
signal to the power supplying unit 150 to supply corresponding
electric power to the solenoid coil 130. The flow control unit 167
calculates the flow amount of the gas based on the inputted data,
and supplies the corresponding nitrogen gas (N.sub.2) by
controlling the flow control valve 154 of FIGS. 7A and 7B. Further,
the substrate driving unit 163 outputs a substrate driving signal
based on the calculated dropping position data to operate a
substrate driving motor (not shown). Therefore, the substrate is
moved to align the liquid crystal dispensing apparatus at the next
dropping position on the substrate.
[0076] On the other hand, the output unit 169 displays the size of
the liquid crystal unit panel, the cell gap, and the characteristic
information of the liquid crystal which are input by the operator
through the input unit 161. The output unit 169 also displays the
dropping number, the single drop amount, and the dropping positions
which are calculated based on the input data, and the present
dropping status such as the times, position, and the amount of the
liquid crystal at present. Thus, the operator can identify the
above information.
[0077] As described above, in the liquid crystal dispensing
apparatus, the dropping positions, the number of drops, and the
single drop amount of the liquid crystal are calculated based on
the data input by the operator, and subsequently, the liquid
crystal is dropped on the substrate automatically. The liquid
crystal dropping method using the above liquid crystal dispensing
apparatus will be described as follows.
[0078] FIG. 10 is a flow chart showing an exemplary liquid crystal
dropping method. As shown, when the operator inputs the size of the
liquid crystal unit panel, cell gap, and the characteristic
information of the liquid crystal through the input unit 161 by
operating the keyboard, the mouse, or the touch panel (S301), the
total dropping amount calculation unit 171 calculates the total
dropping amount of the liquid crystal to be dropped on the
substrate (or each unit panel area) (S302). Thereafter, the
dropping time calculation unit 175, the single dropping amount
calculation unit 173, and the dropping position calculation unit
177 calculate the dropping times, the dropping position, and the
single dropping amount of the liquid crystal based on the
calculated total dropping amount, respectively (S303 and S305).
[0079] The substrate, disposed beneath the liquid crystal
dispensing apparatus 120, is moved along the x and y directions by
a motor. The dropping position calculation unit 177 calculates the
next position where the liquid crystal is dropped based on the
input total dropping amount, the characteristic information of the
liquid crystal, and the substrate information. The dropping
position calculation unit then moves the substrate by operating the
motor so that the liquid crystal dispensing apparatus 120 is
located at the calculated dropping position (S304).
[0080] As described above, the power control unit 165 and the flow
control unit 167 calculate the electric power amount and flow
amount of the gas corresponding to the opening time of the
discharging hole 144 for the single dropping amount based on the
single dropping amount of the liquid crystal in the state that the
liquid crystal dispensing apparatus 120 is located at the dropping
position (S306). Subsequently, electric power is supplied to the
solenoid coil 130 and the nitrogen gas (N.sub.2) is supplied to the
liquid crystal container 124 by controlling the power supply unit
150 and the flow control valve 154 to start the liquid crystal
dropping at the calculated dropping position (S307 and S308).
[0081] As described above, the single dropping amount of the liquid
crystal is determined by the amount of the electric power applied
to the solenoid coil 130 and the amount of nitrogen gas (N.sub.2)
supplied to the liquid crystal container 124 to compress the liquid
crystal. The liquid crystal dropping amount may be controlled by
changing these two elements. Alternatively, the dropping amount may
be controlled by fixing one element and changing another element.
That is, the calculated amount of liquid crystal may be dropped on
the substrate by fixing the flow amount of the nitrogen gas
(N.sub.2) supplied to the liquid crystal container 124 and by
changing the amount of the electric power applied to the solenoid
coil 130. In addition, the calculated amount of the liquid crystal
may be dropped on the substrate by fixing the amount of the
electric power applied to the solenoid coil 130 to be the
calculated amount and by changing the flow amount of the nitrogen
gas (N.sub.2) supplied to the liquid crystal container 124.
[0082] Alternatively, the single drop amount of the liquid crystal
dropped on the dropping position of the substrate can be determined
by controlling the tension of the spring 128 or by controlling the
distance x between the needle 136 and the magnetic bar 132.
However, it is desirable that the tensile force of the spring 128
or the distance x are set in advance because the operator is able
to control these two elements by a simple manual operation.
[0083] When the liquid crystal is dropped on the substrate, the
dropping amount of the liquid crystal is very small amount, for
example, in order of magnitude of milligrams. Therefore, it is very
difficult to drop such fine amounts exactly, and such fine amounts
can be changed easily by various facts. Therefore, in order to drop
exact amount of the liquid crystal on the substrate, the dropping
amount of the liquid crystal should be compensated. This
compensation for the dropping amount of the liquid crystal may be
achieved by a compensating control unit included in the main
control unit 160 of FIG. 7A.
[0084] As shown in FIG. 11, an exemplary compensating control unit
comprises a dropping amount measuring unit 181 for measuring the
amount of dropping liquid crystal and a compensating amount
calculation unit 190 for comparing the measured dropping amount
with the predetermined dropping amount to calculate compensating
amount of the liquid crystal.
[0085] Although not shown, a balance for measuring the precise
weight of the liquid crystal is installed on the liquid crystal
dispensing apparatus (or on an outer part of the liquid crystal
dispensing apparatus) to measure the weight of the liquid crystal
at regular times or occasionally. Generally, the liquid crystal
weighs only a few milligrams. Therefore, it is difficult to weigh a
single liquid crystal drop exactly. Therefore, in the present
invention, the amount of predetermined dropping times, for example,
the liquid crystal amount of 10 drops, 50 drops, or 100 drops are
preferably measured. Thus the single dropping amount of the liquid
crystal can be determined.
[0086] As shown in FIG. 12, the compensating amount calculation
unit 190 comprises a dropping amount setting unit 191 for setting
the dropping amount calculated by the single dropping amount
calculation unit 173 as a present dropping amount; a comparing unit
192 for comparing the set dropping amount with the dropping amount
measured by the dropping amount measuring unit 181 and calculating
a difference value between the amounts; a pressure error
calculation unit 194 for calculating an error value of the pressure
corresponding to the difference value of dropping amount calculated
by the comparing unit 192; and an electric power error calculation
unit 196 for calculating an error value of the electric power
corresponding to the difference value of the dropping amount
calculated in the comparing unit.
[0087] The pressure error calculation unit 194 outputs the error
value of the pressure into the flow control unit 167. Then, the
flow control unit 167 converts the error value into the supplying
amount of the gas to outputs a controlling signal to the flow
control valve 154 so as to increase or decrease the flow amount of
the gas flowed into the liquid crystal container 124.
[0088] Further, the electric power error calculation unit 196
outputs the calculated error value of the electric power into the
power control unit 165. Then, the power control unit 165 converts
the inputted error value into the electric power amount to apply
the increased or decreased electric power into the solenoid coil
130 so as to compensate the dropping amount of the liquid
crystal.
[0089] FIG. 13 is a view showing an exemplary method for
compensating the dropping amount of the liquid crystal. As shown,
after the liquid crystal dropping of the predetermined number of
times is completed, the dropping amount of the liquid crystal is
measured using the balance (S401). Subsequently, the measured
dropping amount is compared to the set dropping amount to determine
whether or not there is an error in the dropping amount (S402 and
S403).
[0090] If there is no error value, it means that the present
dropping amount is same as the set dropping amount and the dropping
process proceed. If there is an error value, the pressure error
calculation unit 194 calculates the pressure of the nitrogen gas
(N.sub.2) corresponding to the error value (S404). Further, the
flow control unit 167 calculates the flow amount of the nitrogen
gas (N.sub.2) which will be supplied to the liquid crystal
container 124 based on the pressure corresponding to the error
value (S405). Then, the flow control valve 154 is operated to
supply the nitrogen gas (N.sub.2) after increasing or decreasing to
the above calculated amount from the originally calculated amount
of the gas to the liquid crystal container 124, thereby
compensating the amount of liquid crystal to be dropped on the
substrate (S406 and S409).
[0091] Alternatively, or in addition, if there is an error in the
dropping amount of the liquid crystal, the electric power error
calculation unit 196 can calculate the electric power amount
corresponding to the error, and applies an increased or decreased
amount of electric power as compared to the calculated amount to
the solenoid coil 130 by controlling the electric power supply unit
150. Accordingly, a compensated amount of liquid crystal can be
dropped on the substrate (S407, S408, and S409).
[0092] The compensating processes described above may be repeated.
For example, whenever a predetermined number of liquid crystal
drops are completed, the compensating processes can be repeated to
always drop the exact amount of the liquid crystal.
[0093] During the compensating process of the liquid crystal
dropping amount, the dropping amount of the liquid crystal can be
compensated by controlling the flow amount of the nitrogen supplied
to the liquid crystal container 124 together with the electric
power applied to the solenoid coil 130 mutually. However, the
dropping amount of the liquid crystal can be compensated by fixing
one element and controlling another element. Further, it is
desirable that the tension of the spring 128 or the distance (x)
are fixed at initially predetermined values.
[0094] As described above, according to the liquid crystal
dispensing apparatus of the present invention, the position and the
amount of liquid crystal dropping on the substrate are calculated
by the inputted size of the unit panel area, the cell gap, and the
characteristic information of the liquid crystal. Therefore, an
exact amount of liquid crystal can always be dropped on the exact
position. Also, according to the present invention, if the amount
of dropping liquid crystal is different from the set dropping
amount, the error can be automatically compensated. Thus, defective
liquid crystal panels caused by errors in the dropping amount of
the liquid crystal can be prevented.
[0095] As described above, according to the present invention
providing the liquid crystal dispensing apparatus, the dropping
amount of the liquid crystal to be dropped on the substrate is
calculated automatically based on the size of the unit panel, the
cell gap, and the characteristic information of the liquid crystal.
Then, the liquid crystal is dropped as the predetermined amount on
the substrate. In addition, if there is an error in the dropping
amount of the liquid crystal after measuring the amount of dropping
liquid crystal, the error value is compensated, thereby always
maintaining an exact amount of the liquid crystal to be dropped on
the substrate. According to the present invention, the dropping
position, dropping times, and the dropping amount of the liquid
crystal are automatically calculated based on the inputted data,
and if there is an error after measuring the dropping amount, the
error is compensated automatically.
[0096] While the above descriptions have been provided for the
liquid crystal dispensing apparatus having a specified structure,
the present invention is not limited to the above structure, but
can be applied to all liquid crystal dispensing apparatus including
the function of automatically calculating the dropping position,
the dropping times, and the dropping amount and the function of
automatic compensating. For example, a liquid crystal dispensing
apparatus having the structure of U.S. patent application entitled
"Liquid Crystal Dispensing Apparatus with Nozzle Protecting Device"
(Attorney Docket No. 041993-5167) filed Apr. 24, 2002 and/or U.S.
patent application entitled "Liquid Crystal Dispensing Apparatus"
(Attorney Docket No. 041993-5169) filed Apr. 24, 2002, which are
both hereby incorporated by reference.
[0097] It will be apparent to those skilled in the art that various
modifications and variations can be made in the apparatus for
dispensing liquid crystal and the method for controlling a liquid
crystal dropping amount of the present invention without departing
from the spirit or scope of the invention. Thus, it is intended
that the present invention cover the modifications and variations
of this invention provided they come within the scope of the
appended claims and their equivalents.
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