U.S. patent application number 13/377537 was filed with the patent office on 2013-02-21 for base film of modified polyvinyl alcohol and its preparation method and polarizer.
The applicant listed for this patent is Hui Fang Duan, Hongqing Huang, Junjie Huang, Quan Liu, Jungmao Tsai, Rui Xu, Weiwei Zhang. Invention is credited to Hui Fang Duan, Hongqing Huang, Junjie Huang, Quan Liu, Jungmao Tsai, Rui Xu, Weiwei Zhang.
Application Number | 20130045390 13/377537 |
Document ID | / |
Family ID | 47712868 |
Filed Date | 2013-02-21 |
United States Patent
Application |
20130045390 |
Kind Code |
A1 |
Xu; Rui ; et al. |
February 21, 2013 |
Base Film of Modified Polyvinyl Alcohol and Its Preparation Method
and Polarizer
Abstract
The present invention provides a base film of modified polyvinyl
alcohol as well as a method for preparing the base film of modified
polyvinyl alcohol and a polarizer made from the base film. The
method includes steps of: (1) executing surface graft modification
of nano-silicon dioxides with fluorinated silane to obtain modified
nano-silicon dioxide powders; (2) adding the modified nano-silicon
dioxide powders obtained from the step (1) to an aqueous solution
of polyvinyl alcohol polymers, in order to prepare a composite
solution of polyvinyl alcohol polymers; and (3) pouring the
composite solution of polyvinyl alcohol polymers prepared from the
step (2) onto a surface of a casting substrate to obtain a base
film of modified polyvinyl alcohol (PVA). The present invention
enhances the heat and humidity resistances and the stability of the
PVA base film, and improves its mechanical performance and
sticking-resistance.
Inventors: |
Xu; Rui; (Shenzhen City,
CN) ; Zhang; Weiwei; (Shenzhen City, CN) ;
Huang; Hongqing; (Shenzhen City, CN) ; Huang;
Junjie; (Shenzhen City, CN) ; Liu; Quan;
(Shenzhen City, CN) ; Tsai; Jungmao; (Shenzhen
City, CN) ; Duan; Hui Fang; (Shenzhen City,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Xu; Rui
Zhang; Weiwei
Huang; Hongqing
Huang; Junjie
Liu; Quan
Tsai; Jungmao
Duan; Hui Fang |
Shenzhen City
Shenzhen City
Shenzhen City
Shenzhen City
Shenzhen City
Shenzhen City
Shenzhen City |
|
CN
CN
CN
CN
CN
CN
CN |
|
|
Family ID: |
47712868 |
Appl. No.: |
13/377537 |
Filed: |
October 9, 2011 |
PCT Filed: |
October 9, 2011 |
PCT NO: |
PCT/CN2011/080581 |
371 Date: |
December 9, 2011 |
Current U.S.
Class: |
428/447 ;
524/263; 977/773 |
Current CPC
Class: |
C08K 9/06 20130101; C08J
5/18 20130101; C08J 2329/04 20130101; C09D 129/04 20130101; G02B
5/305 20130101; B05D 3/007 20130101; G02B 1/08 20130101; B82Y 30/00
20130101; B05D 5/06 20130101; Y10T 428/31663 20150401; G02B 1/14
20150115; C09C 1/3081 20130101; C01P 2004/64 20130101 |
Class at
Publication: |
428/447 ;
524/263; 977/773 |
International
Class: |
B32B 9/04 20060101
B32B009/04; C09D 129/04 20060101 C09D129/04; C08K 5/5415 20060101
C08K005/5415 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 2011 |
CN |
201110234045.1 |
Claims
1. A preparation method for a base film of modified polyvinyl
alcohol, wherein comprising preparation steps of: (1) executing
surface graft modification of nano-silicon dioxides with
fluorinated silane to obtain modified nano-silicon dioxide powders;
(2) adding the modified nano-silicon dioxide powders obtained from
the step (1) and an anionic carboxylate fluorocarbonic surfactant
to an aqueous solution of polyvinyl alcohol polymers, in order to
prepare a composite solution of polyvinyl alcohol polymers; and (3)
pouring the composite solution of polyvinyl alcohol polymers
prepared from the step (2) onto a surface of a casting substrate,
in order to obtain a base film of modified polyvinyl alcohol;
wherein the fluorinated silane in the step (1) are selected from
one or any mixture of dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,
tetramethyl-(perfluoro-hexyl-ethyl)propyl-trimethoxy-silane and
tridecafluoro-octyl-trimethoxy-silane, and the weight of the added
fluorinated silane is 33% to 40% of that of the nano-silicon
dioxide; and wherein a molecular formula of the anionic carboxylate
fluorocarbonic surfactant in the step (2) is RF--CH.sub.2--COOH,
wherein R represents a carbon chain of C.sub.6 to C.sub.10, and the
weight of the added modified silicon dioxide powders is 4% to 8% of
that of the polyvinyl alcohol polymer.
2. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 1, wherein the particle diameter of the
nano-silicon dioxides in the step (1) is between 35 and 45 nm.
3. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 1, wherein the weight of the surfactant
added in the step (2) is 0.2% to 0.3% of that of the polyvinyl
alcohol polymer.
4. A preparation method for a base film of modified polyvinyl
alcohol, wherein comprising preparation steps of: (1) executing
surface graft modification of nano-silicon dioxides with
fluorinated silane to obtain modified nano-silicon dioxide powders;
(2) adding the modified nano-silicon dioxide powders obtained from
the step (1) to an aqueous solution of polyvinyl alcohol polymers,
in order to prepare a composite solution of polyvinyl alcohol
polymers; and (3) pouring the composite solution of polyvinyl
alcohol polymers prepared from the step (2) onto a surface of a
casting substrate, in order to obtain a base film of modified
polyvinyl alcohol.
5. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 4, wherein the fluorinated silane in
the step (1) are selected from one or the mixture of
dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,
tetramethyl-(perfluoro-hexyl-ethyl)propyl-trimethoxy-silane and
tridecafluoro-octyl-trimethoxy-silane.
6. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 4, wherein the particle diameter of the
nano-silicon dioxides in the step (1) is between 35 and 45 nm.
7. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 4, wherein the weight of the
fluorinated silane added in the step (1) is 33% to 40% of that of
the nano-silicon dioxide.
8. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 4, wherein the weight of the modified
silicon dioxide powder added in the step (2) is 4% to 8% of that of
the polyvinyl alcohol polymer.
9. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 4, wherein an anionic carboxylate
fluorocarbonic surfactant is further added in the step (2), and the
molecular formula thereof is RF--CH.sub.2--COOH, wherein R
represents a carbon chain of C.sub.6 to C.sub.10.
10. The preparation method for a base film of modified polyvinyl
alcohol as claimed in claim 9, wherein the weight of the surfactant
added in the step (2) is 0.2% to 0.3% of that of the polyvinyl
alcohol polymer.
11. A base film of modified polyvinyl alcohol, wherein the base
film of modified polyvinyl alcohol comprises polyvinyl alcohol
polymers, nano-silicon dioxide groups and fluorinated silane
groups, the base film of modified polyvinyl alcohol has the
following general formula: ##STR00002## wherein A group is the
fluorinated silane group; and B group is the nano-silicon dioxide
group; wherein the fluorinated silane group is selected from one or
any mixture of dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,
tetramethyl-(perfluoro-hexyl-ethyl)propyl-trimethoxy-silane and
tridecafluoro-octyl-trimethoxy-silane.
12. The base film of modified polyvinyl alcohol as claimed in claim
11, wherein iodine molecules are bonded in the polyvinyl alcohol
polymers, wherein the nano-silicon dioxide group connected with the
fluorinated silane groups is coated on the polyvinyl alcohol
polymers and the iodine molecules.
13. The base film of modified polyvinyl alcohol as claimed in claim
11, wherein the base film of modified polyvinyl alcohol and a
protection film adhered on one surface or two surfaces of the base
film of modified polyvinyl alcohol commonly form a polarizer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The present invention relates to a base film, of polyvinyl
alcohol and more particularly to a base film of modified polyvinyl
alcohol as well as its preparation method and a polarizer prepared
from the base film of modified polyvinyl alcohol.
[0003] 2. Related Art
[0004] Polarizer is one of the essential important components in a
liquid crystal display (LCD), and its function is to convert
natural light into polarized light, in order to cooperate with
liquid crystal molecules twisted to control light passing and
presentation of color signals. An existing polarizer used in a LCD
is mostly made of a highly oriented high polymer such as a base
film of polyvinyl alcohol (PVA) as its substrate, dyed with various
types of dichroic dyes, extended under a certain humidity and
temperature, and then a layer of triacetate cellulose (TAC) film
with high light transmission rate, excellent waterproof
characteristic and a certain degree of mechanical strength is
composited on each of two sides of the PVA base film, so as to
prepare the polarizer. In comparing to polarizers dyed with organic
dichroic dyes, iodine polarizers have become the mainstream
polarizers for LCDs because of their polarization characteristic of
wider range of wavelengths, higher light transmission rates and
better price-performance ratios. Nevertheless, iodine polarizers
are comparatively less resistant to heat and water. As liquid
crystal displays are commonly applied to many products, higher
durability for polarizers is also demanded. Therefore, modification
of PVA base films for development of polarizers with excellent
optical and durability performances for LCDs is a technical
difficulty encountered currently.
[0005] Firstly, a PVA base film is swelled, soaked and dyed in
iodine, and extended uniaxially; then a layer of triacetate
cellulose (TAC) film is composited on each of two sides of the PVA
base film, so as to prepare an iodine polarizer. PVA is a linear
high molecular polymer with a plurality of --OH groups of strong
polarity evenly distributed in a long molecular chain as shown in
FIG. 1, therefore it has relatively strong hydrophilic property,
and is less water resistant and less stable. Furthermore, iodine
molecular structure is easily damaged under high temperatures and
humidity, so that iodine polarizers are less humidity and heat
resistant with poor mechanical performance. Generally, they may
only meet testing conditions of 80.degree. C..times.500 hrs or
60.degree. C..times.90% RH.times.500 hrs, and may easily become
warped and peeled off, resulting in limiting their application
range.
[0006] Referring to FIG. 1 which shows a diagram of a molecular
structure of a PVA base film of an existing iodine polarizer,
wherein a TAC protection film of the iodine polarizer is not shown.
A plurality of OH groups with strong polarity and hydrophilic
property is evenly distributed on a surface of a polyvinyl alcohol
polymer 3 of the PVA base film. And a structure of iodine molecules
2 may be easily damaged under high temperatures and humidity.
Therefore, the PVA base film of the iodine polarizer is relatively
less stable under high temperatures and humidity.
[0007] In order to improve the heat and humidity resistances of the
PVA base film of the iodine polarizer, the PVA base film needed to
be modified or cross-linked. Currently, a method for improving the
heat and humidity resistances of the PVA base film is to add a
second constituent which is a material to be cross-linked with the
hydrophilic --OH groups in PVA. For example, both China patents
published No. 1979231A and 101281267A employ dicarboxylic acids and
boric acids to have the PVA base film cross-linked. Nevertheless,
boric acids increase the toughness of the PVA base film which will
limit its extension percentage during a stretching process. Others
use vacuum coating or ion sputtering method to have silicon
dioxides (SiO.sub.2) plated on the PVA base film in order to
improve its heat and humidity resistances, but costs for both
coating methods of silicon dioxide film are relatively high, and a
problem with compatibility between silicon dioxides and the PVA
base film also arises.
[0008] Therefore, a new PVA base film is required in the hope that
it features relatively higher heat and humidity resistances,
stability and mechanical performance, and at the same time with
lower defective percentage of polarizers and have anti-glare
function.
SUMMARY OF THE INVENTION
[0009] A first object of the present invention is to provide a
method for preparing a base film of modified polyvinyl alcohol.
[0010] To achieve the above object, the present invention provides
a method for preparing a base film of modified polyvinyl alcohol,
comprising preparation steps of:
[0011] (1) executing surface graft modification of nano-silicon
dioxides with fluorinated silane to obtain modified nano-silicon
dioxide powders;
[0012] (2) adding the modified nano-silicon dioxide powders
obtained from the step (1) and an anionic carboxylate
fluorocarbonic surfactant to an aqueous solution of polyvinyl
alcohol polymers, in order to prepare a composite solution of
polyvinyl alcohol polymers; and
[0013] (3) pouring the composite solution of polyvinyl alcohol
polymers prepared from the step (2) onto a surface of a casting
substrate, in order to obtain a base film of modified polyvinyl
alcohol; wherein the fluorinated silane in the step (1) are
selected from one or any mixture of
dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,
tetramethyl-(perfluoro-hexyl-ethyl)propyl-trimethoxy-silane and
tridecafluoro-octyl-trimethoxy-silane, and the weight of the added
fluorinated silane is 33% to 40% of that of the nano-silicon
dioxide; and
[0014] wherein a molecular formula of the anionic carboxylate
fluorocarbonic surfactant in the step (2) is RF--CH.sub.2--COOH,
wherein R represents a carbon chain of C.sub.6 to C.sub.10, and the
weight of the added modified silicon dioxide powders is 4% to 8% of
that of the polyvinyl alcohol polymer.
[0015] In an embodiment of the present invention, particle diameter
of the nano-silicon dioxides in the step (1) is between 35 and 45
nm.
[0016] In an embodiment of the present invention, the weight of the
surfactant added in the step (2) is 0.2% to 0.3% of that of the
polyvinyl alcohol polymer.
[0017] A first object of the present invention, the present
invention further provides a method for preparing a base film of
modified polyvinyl alcohol, comprising preparation steps of:
[0018] (1) executing surface graft modification of nano-silicon
dioxides with fluorinated silane to obtain modified nano-silicon
dioxide powders;
[0019] (2) adding the modified nano-silicon dioxide powders
obtained from the step (1) to an aqueous solution of polyvinyl
alcohol polymers, in order to have a composite solution of
polyvinyl alcohol polymers prepared; and
[0020] (3) pouring the composite solution of polyvinyl alcohol
polymers prepared from the step (2) onto a surface of a casting
substrate, and then vacuum drying it to a constant weight to obtain
a base film of modified polyvinyl alcohol (PVA).
[0021] In an embodiment of the present invention, specific steps of
the method for preparing a base film of modified polyvinyl alcohol
include:
[0022] (1) executing surface graft modification of nano-silicon
dioxides with fluorinated silane: adding dried nano-silicon dioxide
particles, anhydrous ethanol, deionized water, ammonia and
fluorinated silane into a round-bottom flask in turn; after
ultrasonic dispersion and then stirring in high speed; executing
filtration and deposition, washing with anhydrous ethanol
repeatedly; then extracting with toluene to remove unreacted
fluorinated silane; finally vacuum drying to a constant weight, and
grinding to obtain modified nano-silicon dioxide powders;
[0023] (2) adding the modified silicon dioxide powders obtained
from the step (1) and a surfactant to an aqueous solution of
polyvinyl alcohol polymers, and dispersing by ultrasonic at room
temperature; and then stirring in high speed, in order to prepare a
composite solution of polyvinyl alcohol polymers;
[0024] (3) pouring the composite solution of polyvinyl alcohol
polymers prepared from the step (2) onto a surface of a cast
substrate, and vacuum drying under 80.degree. C..about.90.degree.
C. to a constant weight, so as to obtain a base film of modified
polyvinyl alcohol (PVA).
[0025] In an embodiment of the present invention, the fluorinated
silane in the step (1) are selected from one or any mixture of
dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,
tetramethyl-(perfluoro-hexyl-ethyl)propyl-trimethoxy-silane and
tridecafluoro-octyl-trimethoxy-silane.
[0026] In an embodiment of the present invention, the purity
specification of nano-silicon dioxides in the step (1) is
analytical degree pure reagent, and particle diameter thereof is
between 35 and 45 nm.
[0027] In an embodiment of the present invention, the weight of the
fluorinated silane added in the step (1) is 33% to 40% of that of
the nano-silicon dioxide.
[0028] In an embodiment of the present invention, the degree of
polymerization of the polyvinyl alcohol polymer in the step (2) is
4000 and its degree of alcoholysis is 98%.
[0029] In an embodiment of the present invention, the weight of the
modified silicon dioxide powder added in the step (2) is 4% to 8%
of that of the polyvinyl alcohol polymer.
[0030] In an embodiment of the present invention, an anionic
carboxylate fluorocarbonic surfactant is further added in the step
(2), and a molecular formula thereof is RF--CH.sub.2--COOH, wherein
R represents a carbon chain of C.sub.6 to C.sub.10.
[0031] In an embodiment of the present invention, the weight of the
surfactant added in the step (2) is 0.2% to 0.3% of that of the
polyvinyl alcohol polymer.
[0032] A second object of the present invention is to provide a
base film of modified polyvinyl alcohol prepared from the
abovementioned preparation method.
[0033] In order to achieve the abovementioned object, the present
invention discloses a technical solution, as follows:
[0034] A base film of modified polyvinyl alcohol, the base film of
modified polyvinyl alcohol comprises polyvinyl alcohol polymers,
nano-silicon dioxide groups and fluorinated silane groups, the base
film of modified polyvinyl alcohol has a general formula shown as
below:
##STR00001##
[0035] wherein:
[0036] (A) groups represent the fluorinated silane groups, the
fluorinated silane groups are selected from one or any mixture of
dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,tetramethyl-(perfluoro-
-hexyl-ethyl)propyl-tri methoxy-silane and
tridecafluoro-octyl-trimethoxy-silane; and
[0037] (B) group represents nano-silicon dioxide group.
[0038] In an embodiment of the present invention, by dyeing with an
iodine solution, iodine molecules are bonded in the polyvinyl
alcohol polymers, wherein the nano-silicon dioxide group connected
with the fluorinated silane groups is coated on and outside the
polyvinyl alcohol polymers and the iodine molecules.
[0039] A third object of the present invention is to provide a
polarizer made of the abovementioned base film of modified
polyvinyl alcohol.
[0040] In order to achieve the abovementioned object, the present
invention discloses technical plans as follow: a polarizer,
comprising: the abovementioned base film of modified polyvinyl
alcohol; and a protection film adhered on one surface or two
surfaces of the polarizing film, the protection film for example is
a triacetate cellulose (TAC) film. The base film of modified
polyvinyl alcohol and the protection film adhered on one surface or
two surfaces of the base film of modified polyvinyl alcohol
commonly form a polarizer of the base film of modified polyvinyl
alcohol.
[0041] The present invention has the following positive
effects:
[0042] 1) Heat and humidity resistances as well as stability of the
base film of modified polyvinyl alcohol (PVA) are enhanced:
[0043] Low surface energy fluorinated groups migrate and aggregate
toward a surface of the PVA base film, so that the PVA base film
will feature excellent water, oil and corrosion resistances.
Furthermore, the bond energy of C--F bonds is strong, and the bonds
are very closely arranged on an outer layer of a carbon skeleton,
so that fluoride polymers have excellent stability against
heat.
[0044] 2) Mechanical performance of the PVA base film is
enhanced:
[0045] Nano-silicon dioxide has high rigidity, and has
characteristics of high strength, high toughness, and high
stability under high temperatures, and a 3-dimensional network is
formed when combined with a high polymer chain of PVA, so that the
mechanical strength, elasticity and abrasion resistance of the PVA
base film are substantially enhanced. On the other hand, easily
damaged iodine molecules are protected when they are coated with
nano-silicon dioxides grafted with long-chain fluorinated silicon
groups, so as to enhance the mechanical stability of the PVA
polarizing film.
[0046] 3) Defective percentage of polarizers is reduced:
[0047] The acting force between polymer molecules of C--F bonds of
fluorinated materials is weak and therefore has excellent
sticking-resistance and surface self-cleaning performance. During
later-staged adhering process of the PVA base film and other
membrane layers, it can effectively prevent foreign substances from
entering, as a result, the defective percentage of polarizers can
be reduced.
[0048] 4) Anti-Glare function is obtained:
[0049] In existing processes, in order that the PVA base film is
protected because of its hydrophilic property, a protective film of
triacetate cellulose (TAC) with high light transmission rate,
excellent waterproof characteristic and a certain degree of
mechanical strength is composited on each of two sides of the PVA
base film. However, the size of this type of protective film can
easily be changed under high temperatures and humidity, and thus
its mechanical performance is weakened and its protective
performance is also affected. The present invention can
substantially enhance the heat and humidity resistances as well as
the mechanical strength of the PVA base film, even that the TAC
film can be omitted (i.e. the PVA base film can be directly used as
a polarizer). Furthermore, a certain degree of roughness can be
formed on the surface of the PVA base film by controlling the sizes
of nano-silicon dioxides, and thus images are diffused and
reflected by the concave and convex shapes thereof, in order to
prevent the light from being overly-concentrated to cause
discomfort in viewing, as a result, an anti-glare function is
achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 is an illustration of a molecular structure of a PVA
base film of an existing iodine polarizer; and
[0051] FIG. 2 is an illustration of a molecular structure of a PVA
base film of a polarizer of a preferred embodiment of the present
invention.
[0052] Wherein: numeral 1 is nano-silicon dioxide group, numeral 2
is iodine molecule, numeral 3 is polyvinyl alcohol (PVA) polymer,
and numeral 4 is fluorinated silane group.
DETAILED DESCRIPTION OF THE INVENTION
[0053] The structure and the technical means adopted by the present
invention to achieve the above and other objects can be best
understood by referring to the following detailed description of
the preferred embodiment and the accompanying drawings, but should
not be construed as limitations thereof.
[0054] According to a preferred embodiment of the present
invention, the present invention provides a base film of modified
polyvinyl alcohol (PVA) and its preparation method, wherein its
specific preparation steps include:
[0055] (1) Surface graft modification of nano-silicon dioxides
using fluorinated silane: 6 g of dried nano-silicon dioxide
particles, 120 ml of anhydrous ethanol, 6.5 g of deionized water,
3.4 g of ammonia of 25% weight percentage and 2.0.about.2.4 g of
dodecafluoro-heptyl-propyl-trimethoxy-silane are added in a
round-bottom flask in turn; after 1 hour of ultrasonic dispersion
and then stirring in high speed for 5 hours under 40.degree. C.,
processing with filtration and deposition, washing with anhydrous
ethanol repeatedly; then extracting with toluene for 16 hours to
remove unreacted dodecafluoro-heptyl-propyl-trimethoxy-silane;
vacuum drying to a constant weight, and grinding to obtain white
modified nano-silicon dioxide powders, wherein condensation
polymerization occurred between hydroxyl groups (--OH) generated by
hydrolysis of --OCH.sub.3 groups which are connected to Si in
dodecafluoro-heptyl-propyl-trimethoxy-silane, and hydroxyl groups
(--OH) on the surfaces of the nano-silicon dioxide particles, thus
Si--O--Si bonds are formed. In the Si--O--Si bonds, the binding
force between Si and O is stronger than that between silicon and
oxygen in the connection of Si and --OH, therefore fluorinated
silane can be reacted with nano-silicon dioxide particles.
[0056] (2) The modified nano-silicon dioxide powders obtained from
the step (1) and an anionic carboxylate fluorocarbonic surfactant
(RF--CH.sub.2--COOH) are added to an aqueous solution of polyvinyl
alcohol (PVA) polymers, and dispersed by ultrasonic at room
temperature for 1 hour; then stirring in high speed for 5 hours
under 40.degree. C., in order to prepare a composite solution of
polyvinyl alcohol (PVA) polymers. Steric hindering effect between
particles is enhanced by the modified nano-silicon dioxides which
thus can be evenly distributed in a system; on the other hand,
there are still some --OH on the surface of the hydrolytic
fluorinated silane and the surface of the modified nano-silicon
dioxides, which can be further cross-linked and condensed with the
--OH in the long molecular chain of PVA.
[0057] (3) The composite solution of polyvinyl alcohol polymers
prepared from the step (2) is poured on a surface of a casting
substrate, and vacuum drying under 80.degree. C..about.90.degree.
C. is kept until a constant weight is reached, so as to obtain a
base film of modified polyvinyl alcohol (PVA).
[0058] Wherein, the fluorinated silane is selected from
dodecafluoro-heptyl-propyl-trimethoxy-silane, but not limited
thereto, the fluorinated silane may be selected from one or any
mixture of dodecafluoro-heptyl-propyl-trimethoxy-silane,
dodecafluoro-heptyl-propyl-methyl-dimethoxy-silane,
tetramethyl-(perfluoro-hexyl-ethyl)propyl-trimethoxy-silane and
tridecafluoro-octyl-trimethoxy-silane.
[0059] Wherein, the purity specification of nano-silicon dioxides
is analytical degree pure reagent, and the particle diameter is
between 35 and 45 nm; the degree of polymerization of polyvinyl
alcohol polymer is 4000 and its degree of alcoholysis is 98%.
[0060] Wherein, the weight of the fluorinated silane is 33% to 40%
of that of the nano-silicon dioxide.
[0061] The weight of the modified silicon dioxide powder added in
the step (2) is 4% to 8% of that of the polyvinyl alcohol polymer;
the molecular formula of the anionic carboxylate fluorocarbonic
surfactant added in the step (2) is RF--CH.sub.2--COOH, wherein R
represents a carbon chain of C.sub.6 to C.sub.10. The weight of the
added surfactant is 0.2% to 0.3% of that of the polyvinyl alcohol
polymer.
[0062] The obtained modified PVA base film is used as a substrate
material. After being dyed in iodine and stretched uniaxially as
conventionally used in prior arts, a modified PVA base film of a
polarizer is prepared as shown in a molecular structure in FIG. 2,
and it comprises polyvinyl alcohol (PVA) polymers 3, iodine
molecules 2, a nano-silicon dioxide group 1 and fluorinated silane
groups 4.
[0063] More specifically, as shown in FIG. 2, wherein the
nano-silicon dioxide group 1 is grafted and modified by
dodecafluoro-heptyl-propyl-trimethoxy-silane; after treated with a
certain dispersing means, the grafted and modified nano-silicon
dioxide group 1 is evenly dispersed in the PVA base film and
combined with a high polymer chain of the polyvinyl alcohol (PVA)
polymers 3 to form a three-dimensional network structure, and
organic and inorganic nano-composite materials are obtained. The
organic and inorganic nano-composite materials are incorporated
with the excellent characteristics of the PVA base film and nano
materials. Fluorinated materials are materials with the lowest
surface energy discovered so far, low surface energy fluorinated
groups migrate and aggregate towards a surface of the PVA base
film, with only a very little amount, the surface of the PVA base
film will feature excellent hydrophobic, oleophobic,
sticking-resistant and self-cleaning performances. Furthermore,
rigid nano-silicon dioxides allow the PVA base film to have
excellent capabilities of heat resistance and mechanical stability.
Better compatibility of organic and inorganic can be achieved from
organic and inorganic nano-composite materials prepared from
silicon dioxides modified by organic fluorinated silane.
[0064] More specifically, in the present invention, during a
heating process, low surface energy fluorinated groups migrate and
aggregate towards a surface of the PVA base film, so that the PVA
base film will feature excellent water, oil and corrosion
resistances. Furthermore, the bond energy of C--F bonds is strong,
and the bonds are very closely arranged on an outer layer of a
carbon skeleton, so that fluoride polymers have excellent stability
against heat.
[0065] The nano-silicon dioxide group has high rigidity, and has
characteristics of high strength, high toughness, and high
stability under high temperatures, and a 3-dimensional network is
formed when combined with a high polymer chain of PVA, so that the
mechanical strength, elasticity and abrasion resistance of the PVA
base film are substantially enhanced. On the other hand, easily
damaged iodine molecules are protected when they are coated with
nano-silicon dioxides grafted with long-chain fluorinated silicon
groups, which enhances the mechanical strength and stability of the
PVA base film.
[0066] The acting force between the polymer molecules of C--F bonds
of fluorinated materials is weak and therefore has excellent
sticking-resistance and surface self-cleaning performance. During
later-staged adhering process of the PVA base film and other
membrane (e.g. TAC film) layers, it may effectively prevent foreign
substances from entering, as a result, the defective percentage of
polarizers can be reduced.
[0067] A certain degree of roughness can be formed on the surface
of the polarizer by controlling the sizes of nano-silicon dioxides,
and thus images are diffused and reflected by the concave and
convex shapes, in order to prevent the light from being
overly-concentrated to cause discomfort in viewing, as a result, an
anti-glare function is achieved.
[0068] The present invention has been described with a preferred
embodiment thereof and it is understood that many changes and
modifications to the described embodiment can be carried out
without departing from the scope and the spirit of the invention
that is intended to be limited only by the appended claims.
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