U.S. patent application number 11/006597 was filed with the patent office on 2006-05-11 for method for dyeing polarizers.
Invention is credited to Shih-Ming Chen, Yao-Chung Cheng, Jui-Chi Wu.
Application Number | 20060096045 11/006597 |
Document ID | / |
Family ID | 36314777 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060096045 |
Kind Code |
A1 |
Wu; Jui-Chi ; et
al. |
May 11, 2006 |
Method for dyeing polarizers
Abstract
A polarizing substrate is placed into a dyeing tank for dyeing.
A concentration of a dyeing agent in the dyeing tank is less than
800 ppm, and a dyeing period is greater than 200 seconds, so as to
improve the dyeing of the polarizing substrate by lengthening the
dyeing period and reducing the dyeing agent concentration.
Inventors: |
Wu; Jui-Chi; (Ping Chen
City, TW) ; Chen; Shih-Ming; (Ping Chen City, TW)
; Cheng; Yao-Chung; (Ping Chen City, TW) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Family ID: |
36314777 |
Appl. No.: |
11/006597 |
Filed: |
December 8, 2004 |
Current U.S.
Class: |
8/516 |
Current CPC
Class: |
D06P 1/673 20130101;
G02B 5/3033 20130101; D06P 1/34 20130101; D06P 1/0004 20130101 |
Class at
Publication: |
008/516 |
International
Class: |
D06P 3/04 20060101
D06P003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2004 |
TW |
93134019 |
Claims
1. A method for dyeing a polarizing substrate, the method
comprising: dyeing a polarizing substrate in a dyeing tank with a
dyeing agent, wherein a concentration of the dyeing agent is less
than 800 ppm, and a dyeing period is greater than 200 seconds, so
as to improve the dyeing of the polarizing substrate by the long
dyeing period and the dyeing agent with the low concentration.
2. The method of claim 1, wherein the method further comprises:
extending a dyeing path of the polarizing substrate in the dyeing
tank to increase the dyeing period.
3. The method of claim 2, wherein the dyeing path extending
comprises: extending the dyeing path by a plurality of rollers
configured in the dyeing tank.
4. The method of claim 2, wherein the dyeing path extending
comprises: extending the dyeing path by increasing a size of the
dyeing tank.
5. The method of claim 1, wherein the dyeing agent comprises
iodine.
6. The method of claim 1, wherein a material of the polarizing
substrate is polyvinyl alcohol.
Description
RELATED APPLICATIONS
[0001] The present application is based on, and claims priority
from, Taiwan Application Serial Number 93134019, filed on Nov. 8,
2004, the disclosure of which is hereby incorporated by reference
herein in its entirety.
BACKGROUND
[0002] 1. Field of Invention
[0003] The present invention relates to a method for manufacturing
polarizers. More particularly, the present invention relates to a
method for dyeing polarizers.
[0004] 2. Description of Related Art
[0005] Liquid crystal displays (LCD) have many advantages over
conventional types of displays including having high display
quality, having small volume, being lightweight, and having low
driving voltage and low power consumption. Hence, LCDs are widely
used in small portable televisions, mobile telephones, video
recording units, notebook computers, desktop monitors, projector
televisions and so on, and they have gradually replaced the
conventional cathode ray tube (CRT) as a mainstream display
unit.
[0006] Polarizers are main components of a liquid crystal display.
Traditionally, a polarizing substrate is dyed, extended and
corrected first, and then is adhered onto a protection film to form
a polarizer. The polarizing substrate is made of polyvinyl alcohol
(PVA) molecules, which are distributed irregularly at any angle in
the beginning. After extending, PVA molecules are gradually turned
toward the extending direction, and iodine ions adhered on the PAV
molecules are also arranged in the extending direction. Thus, the
polarizer can absorb an amount of light parallel to the extending
direction and only allow an amount of light perpendicular to the
extending direction to pass through.
[0007] FIG. 1 is a schematic view of a conventional dyeing
apparatus for polarizers. As illustrated in FIG. 1, a polarizing
substrate 110 is dyed as mentioned above in a dyeing tank 102. A
common dyeing agent is an iodine solution 112, and the iodine ions
thereof are diffused into the polarizing substrate 110 by soaking
the polarizing substrate 110 in the iodine solution 112. As
production capacity gradually increases, the rolling speed of
polarizers while manufacturing, i.e. the machine speed, also
becomes faster. When the machine speed is fast, the period of the
polarizing substrate 110 soaking in the iodine solution 112 is
short, thus causing insufficient dyeing.
[0008] Therefore, the prior art generally enlarges the size of the
dyeing tank 102 or increases the concentration of the iodine
solution 112 to obtain better dyeing results. However, a larger
dyeing tank or a higher concentrated dyeing agent requires a
greater amount of chemicals and increases manufacturing cost.
Moreover, the dyeing result of a higher concentrated dyeing agent
is hard to control, easily causing uneven dyeing, which decreases
the quality and affects the optical performance of polarizers.
SUMMARY
[0009] It is therefore an aspect of the present invention to
provide a method for dyeing polarizers, of which the dyeing period
is increased and the concentration of the dyeing agent is
decreased, to reduce manufacturing cost and enhance polarizer
quality, especially for a polarizer manufacturing process with high
machine speed.
[0010] In accordance with the foregoing and other aspects of the
present invention, a method for dyeing polarizers is provided. A
polarizing substrate is placed into a dyeing tank for dyeing. A
concentration of a dyeing agent in the dyeing tank is less than 800
ppm, and a dyeing period is greater than 200 seconds, so as to
improve the dyeing of the polarizing substrate by lengthening the
dyeing period and lowering the dyeing agent concentration.
[0011] According to one preferred embodiment of the present
invention, a dyeing path of the polarizing substrate is extended to
increase the dyeing period by use of a plurality of rollers
configured in the dyeing tank or by increasing a size of the dyeing
tank. The dyeing agent comprises iodine, and a material of the
polarizing substrate is polyvinyl alcohol.
[0012] The present invention increases the dyeing period and
decreases the concentration of the dyeing agent of the dyeing
process and thus prevents uneven dyeing and improves the dyeing
quality. Moreover, decreasing the dyeing agent concentration also
reduces the amount of chemicals used and thus decreases
manufacturing cost.
[0013] It is to be understood that both the foregoing general
description and the following detailed description are examples and
are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] These and other features, aspects, and advantages of the
present invention will become better understood with regard to the
following description, appended claims, and accompanying drawings
where:
[0015] FIG. 1 is a schematic view of a conventional dyeing
apparatus for polarizers; and
[0016] FIG. 2 is a schematic view of one preferred embodiment of
the present invention
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0018] The present invention provides a method for dyeing
polarizers, which improves the dyeing by using a long dyeing period
and a dyeing agent with low concentration. The features of the
present invention comprise controlling the dyeing period and the
concentration of the dyeing agent using specific values. More
particularly, the dyeing period is greater than 200 seconds and the
concentration of the dyeing agent is less than 800 ppm, so as to
obtain polarizers with good optical quality.
[0019] According to a preferred embodiment of the present
invention, a dyeing path in the dyeing tank can be extended to
increase the dyeing period. FIG. 2 is a schematic view of one
preferred embodiment of the present invention. As illustrated in
FIG. 2, the preferred embodiment adds rollers 202 in the dyeing
tank 102. The dyeing path in the dyeing tank 102 is extended to
increase the dyeing period of the polarizing substrate 110, such as
a PVA substrate, soaked in the iodine solution 112. Because the
dyeing period is increased to be greater than 200 seconds, the
concentration of the dyeing agent can be decreased to be lower than
800 ppm.
[0020] In the preferred embodiment, the monomer transmittance of
the polarizers can be over 43%; and the degree of polarization of
polarizers can be greater than 99.90% when the dyeing temperature
is between about 30.degree. C. and 50.degree. C., the dyeing time
is greater than 200 seconds, and the concentration of the iodine
solution is less than 800 ppm. The dyeing uniformity of the
polarizer of the preferred embodiment is superior to the polarizer
manufactured at the same dyeing temperature with a dyeing period of
80 seconds and the concentration of the iodine solution greater
than 1200 ppm. Therefore, the preferred embodiment reduces the
amount of chemicals, decreases the manufacturing cost and prevents
uneven dyeing.
[0021] An experiment is used to prove that the preferred embodiment
reduces the amount of chemicals by extending the dyeing path. As in
the foregoing embodiment, the dyeing path is extended by rollers
202 to increase the dyeing period of the polarizing substrate 110.
It is noted that, several dyeing paths with different lengths are
provided by changing the number of the rollers 202 in this
experiment. However, the hues of the obtained polarizers are the
same, and thus the amount of the dyeing agent used for different
dyeing paths are observed. Table 1 lists path lengths, dyeing
periods and amounts of dyeing agents for different dyeing paths,
which are formed by different numbers of rollers, all combinations
of which obtain polarizers with the same hue. TABLE-US-00001 TABLE
1 A comparison of different dyeing paths toobtain polarizers with
the same hue. Roller number 5 3 2 1 Path length (mm) 210 140 130 80
Dyeing period (sec) 225 150 140 80 Iodine stock solution (L) 3 3.6
3.6 4.9
[0022] The dyeing agent used here is an iodine solution diluted
with other solvents and additives. For clarity, the iodine stock
solutions, which are not diluted with other solvents and additives,
for different dyeing paths are listed in Table 1 for easy and clear
comparison. Because the size of the dyeing tank 202 and the volume
of the iodine solution 112 therein are both fixed, the changes of
the iodine stock solutions can be regarded as the changes of the
concentrations of the iodine solutions. As indicated in Table 1,
the preferred embodiment can certainly reduce the amount of dyeing
agent used for dyeing by increasing the dyeing period, without
affecting the desired polarizer hue.
[0023] In addition, besides increasing the number of rollers to
extend the dyeing path in order to increase the dyeing period as
illustrated in the foregoing embodiment, the dyeing period can also
be increased by changing the size and configuration of the rollers,
increasing the size of the dyeing tank, and applying dyeing delay
agents or other dyeing period extending methods known in prior art,
according to other preferred embodiments.
[0024] The present invention increases the dyeing period and
decreases the concentration of the dyeing agent of the dyeing
process, and thus prevents uneven dyeing and improves the dyeing
quality. Moreover, decreasing the dyeing agent concentration also
reduces the amount of chemicals used and thus decreases
manufacturing cost.
[0025] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *