U.S. patent application number 12/975623 was filed with the patent office on 2011-04-21 for dispersant having multifunctional head and phosphor paste composition comprising the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Jae Young CHOI, Seong Jae CHOI, Bum Jae LEE, Jung Hwan LEE, Sangkyu LEE, Ungyu PAIK, Hyeon Jin SHIN, Seon Mi YOON.
Application Number | 20110089376 12/975623 |
Document ID | / |
Family ID | 39772429 |
Filed Date | 2011-04-21 |
United States Patent
Application |
20110089376 |
Kind Code |
A1 |
YOON; Seon Mi ; et
al. |
April 21, 2011 |
DISPERSANT HAVING MULTIFUNCTIONAL HEAD AND PHOSPHOR PASTE
COMPOSITION COMPRISING THE SAME
Abstract
Disclosed is a dispersant having a multifunctional head, and a
phosphor paste composition comprising the dispersant. The
dispersant has a multifunctional head that comprises an acidic
group, a basic group and an aromatic group, thereby enhancing an
affinity for the surface of phosphor particles and improving
dispersibility.
Inventors: |
YOON; Seon Mi; (Yongin-si,
KR) ; SHIN; Hyeon Jin; (Suwon-si, KR) ; CHOI;
Jae Young; (Suwon-si, KR) ; CHOI; Seong Jae;
(Seoul, KR) ; LEE; Bum Jae; (Daejeon, KR) ;
PAIK; Ungyu; (Seoul, KR) ; LEE; Sangkyu;
(Seoul, KR) ; LEE; Jung Hwan; (Gyeongsangbuk-do,
KR) |
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
39772429 |
Appl. No.: |
12/975623 |
Filed: |
December 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11852734 |
Sep 10, 2007 |
|
|
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12975623 |
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Current U.S.
Class: |
252/301.36 ;
528/332; 528/366 |
Current CPC
Class: |
C08F 265/00 20130101;
C08L 51/003 20130101; C09K 11/08 20130101; C08L 53/00 20130101;
C08L 53/00 20130101; C08K 5/0041 20130101; C08L 2666/02 20130101;
C08F 265/04 20130101; C08L 51/003 20130101; C08F 20/10 20130101;
C08L 33/14 20130101; C09K 11/02 20130101; C08L 2666/02
20130101 |
Class at
Publication: |
252/301.36 ;
528/332; 528/366 |
International
Class: |
C09K 11/02 20060101
C09K011/02; C08G 69/26 20060101 C08G069/26; C08G 63/02 20060101
C08G063/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2007 |
KR |
10-2007-0027591 |
Claims
1. A dispersant having a multifunctional head represented by
Formula 1 or 2: ##STR00009## wherein A is an aromatic group, B is
an acidic group and C is a basic group; a, b and c are
independently an integer from 0 to about 10 with the proviso that
two or more of a, b and c are not simultaneously zero; n is an
integer of about 1 to about 15; and D is hydrogen, alkyl, polyester
or polyether; ##STR00010## wherein A is an aromatic group, B is an
acidic group and C is a basic group; a, b and c are independently
an integer from 0 to about 10 with the proviso that two or more of
a, b and c are not simultaneously zero; n is an integer of about 1
to about 15; and D is hydrogen, alkyl, polyester or polyether.
2. The dispersant according to claim 1, wherein in Formula 1 and 2,
A is selected from the group consisting of benzene and a
heterocyclic compound substituted with nitrogen (N), sulfur (S) or
oxygen (O), B is selected from the group consisting of carboxyl
(COOH) and phosphoryl (POOH) groups, and C is selected from the
group consisting of aliphatic amine (--NR.sub.2) wherein R is H,
CH.sub.3, CH.sub.2CH.sub.3, (CH.sub.2).sub.2CH.sub.3, or
(CH.sub.2).sub.3CH.sub.3 and aromatic amine (--XNR.sub.2) wherein X
is benzene and R is H, CH.sub.3, CH.sub.2CH.sub.3,
(CH.sub.2).sub.2CH.sub.3, or (CH.sub.2).sub.3CH.sub.3.
3. The dispersant according to claim 1, wherein the dispersant of
Formula 1 is represented by Formula 3 below: ##STR00011## wherein
a, b and c are independently an integer from 0 to about 10 with the
proviso that two or more of a, b and c are not simultaneously zero,
and n is an integer of about 1 to about 15.
4. The dispersant according to claim 1, wherein the dispersant of
Formula 2 is represented by Formula 4 below: ##STR00012## wherein
a, b and c are independently an integer from 0 to about 10 with the
proviso that two or more of a, b and c are not simultaneously zero,
and n is an integer of about 1 to about 15.
5. The dispersant according to claim 1, wherein the dispersant has
a molecular weight of 1,000 to 20,000 grams per mole.
6. A fluorescent film for a display device produced from a phosphor
paste composition, the phosphor paste composition comprising: a
dispersant represented by Formula 1 or 2 below; a binder solution
of an organic binder in a solvent; and a phosphor ##STR00013##
wherein A is an aromatic group, B is an acidic group and C is a
basic group, a, b and c are independently an integer from 0 to
about 10 with the proviso that two or more of a, b and c are not
simultaneously zero, n is an integer of about 1 to about 15, and D
is hydrogen, alkyl, polyester or polyether; ##STR00014## wherein A
is an aromatic group, B is an acidic group and C is a basic group,
a, b and c are independently an integer from 0 to about 10 with the
proviso that two or more of a, b and c are not simultaneously zero,
and n is an integer of about 1 to about 15.
7. A display device comprising the fluorescent film according to
claim 6.
8. The display device according to claim 7, wherein the display
device is a cathodoluminescent display, a liquid crystal display,
an electroluminescence display, a field emission display, or a
vacuum fluorescent display.
9. An article comprising the fluorescent film according to claim
6.
10. The article according to claim 9, wherein the article is an
exterior decoration or keypad of cellular phone.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/852,734 filed on Sep. 10, 2007, the content of which in
its entirety is herein incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] This non-provisional application claims priority under 35
U.S.C. .sctn.119(a) to Korean Patent Application No.
10-2007-0027591 filed on Mar. 21, 2007, the entire contents of
which are hereby incorporated by reference.
Field of the Invention
[0003] The present invention relates to a dispersant having a
multifunctional head and a phosphor paste composition comprising
the dispersant. More specifically, the present invention relates to
a dispersant having a multifunctional head that comprises an acidic
group, a basic group and an aromatic group, thereby enhancing an
affinity for the surfaces of a variety of phosphor particles and
thus improving dispersibility.
Description of the Related Art
[0004] In recent years, a variety of display devices have been
developed and widely used as substitutes for cathode ray tubes
(CRTs). Such display devices include flat panel displays (FPDs),
such as, for example, liquid crystal displays (LCDs), plasma
display panels (PDPs), electro-luminescent displays (ELDs), field
emission displays (FEDs), and vacuum fluorescent displays (VFDs).
Such display devices can be used for exterior decorations or
display parts of electronic appliances, e.g., exterior decorations
or keypads of cellular phones.
[0005] It is desirable for such display devices to include a
fluorescent screen. The luminescent properties of the display
devices can be varied depending upon the physical properties. In
other words, although a phosphor inherently has a high luminance,
unless a fluorescent film made of the phosphor is suitably formed,
the display device including the fluorescent film cannot exhibit
high luminance.
[0006] A fluorescent film is generally produced by homogeneously
applying a phosphor paste composition to a supporting substrate,
followed by drying the phosphor paste composition. In general,
phosphor paste compositions comprise a solvent, a binder and a
phosphor and selectively comprise a dispersant for improving
dispersibility of the phosphor.
[0007] The dispersant improves dispersibility of the phosphor,
which leads to a lower viscosity. Thus by improving dispersibility,
it is possible to increase the amount of the phosphor present in a
given fluorescent film and to thereby increase the packing density
of the phosphor in a fluorescent film. Thus the efficiency of
fluorescence can be increased over a comparative film having an
equivalent thickness, but having a lower packing density. Using a
dispersant also permits an increase in the stability of a paste
that can be used in a printing process.
[0008] Dispersants that are surfactants include a head and a tail.
The head must have an affinity for a dispersoid to be dispersed in
the dispersion media. The tail must have an affinity for a
dispersion media capable of dispersing the dispersoid. In addition,
it is desirable to use a dispersant capable of keeping adjacent
phosphor particles apart from each other. In other words, it is
desirable for the dispersant to prevent the phosphor particles from
agglomerating with one another.
[0009] Commercially available dispersants for a phosphor have a
monofunctional head generally comprise either an acidic group, or a
basic or aromatic groups, and thus can disperse only specific
phosphors having an affinity for selected functional group that are
attracted to either the acidic group or the basic or the aromatic
groups.
[0010] Accordingly, to improve the luminescent properties of
display devices, there is an increasing demand to develop a novel
dispersant for a phosphor that is capable of being applied to a
variety of phosphors, e.g., organic phosphors, and exhibits
superior dispersibility.
SUMMARY OF THE INVENTION
[0011] In one embodiment, it is desirable for a dispersant for a
phosphor having a multifunctional head to have an enhanced affinity
for the surface of the phosphor particles and thus improve
dispersability. The multifunctional head comprises an acidic group,
a basic group and an aromatic group.
[0012] The dispersant is capable of dispersing a variety of
phosphors, is homogenous and exhibits superior dispersive
capabilities For phosphors over other commercially available
phosphors that do not have the multifunctional head.
[0013] A high luminance fluorescent film made using the dispersant
can also be easily processed.
[0014] In another embodiment, a display device can be manufactured,
wherein the display device comprises the fluorescent film that
comprises the dispersant.
[0015] In another embodiment, there is provided a phosphor paste
composition comprising the dispersant, a phosphor, and a binder
solution comprising a solvent and an organic binder.
[0016] In yet another embodiment, the phosphor paste composition
comprises a binder solution comprising a solvent and an organic
binder, and a phosphor.
[0017] The phosphor paste composition may comprise about 30 to
about 70% by weight of the phosphor, about 0.1 to about 10% by
weight of the dispersant with respect to the phosphor powder, and
the balance of the binder solution.
[0018] The phosphor paste may be used in the manufacture of
fluorescent films that may be used in display devices, such as
cathodoluminescent displays, liquid crystal displays,
electroluminescence displays, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The aforementioned features and other advantages will be
more clearly understood from the following detailed description
taken in conjunction with the accompanying drawings, in which:
[0020] FIG. 1 is a .sup.1H-NMR spectrum of a dispersant synthesized
in Synthesis Example 1 according to one embodiment;
[0021] FIG. 2 is a .sup.1H-NMR spectrum of a dispersant synthesized
in Synthesis Example 2 according to another embodiment;
[0022] FIG. 3a is a graph showing a comparison in the luminescent
properties of fluorescent films produced from phosphor paste
compositions prepared by mixing a polyester binder with a
dispersant according to one embodiment of the present invention,
and FIG. 3b is a graph showing a comparison in the luminescent
properties of fluorescent films produced from phosphor paste
compositions prepared by mixing a polyacrylate binder with a
dispersant according to one embodiment; and
[0023] FIG. 4a is a graph showing a comparison in the luminescent
properties of fluorescent films produced from phosphor paste
compositions prepared by mixing a polyester binder with a
dispersant according to one embodiment, and FIG. 4b is a graph
showing a comparison in the luminescent properties of fluorescent
films produced from phosphor paste compositions prepared by mixing
a polyacrylate binder with a dispersant according to one
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The aforementioned embodiments will now be described in
greater detail with reference to the accompanying drawings.
[0025] As noted above, the dispersant comprises a multi head
structure comprises an acidic group, a basic group and an aromatic
group.
[0026] In one embodiment, the dispersant is represented by Formula
1 or 2:
##STR00001##
wherein A is an aromatic group, B is an acidic group and C is a
basic group; a, b and c are independently an integer from 0 to
about 10 with the proviso that two or more of a, b and c are not
simultaneously zero; n is an integer of 1 to about 15; and D is
hydrogen, alkyl, polyester or polyether; and
##STR00002##
wherein A is an aromatic group, B is an acidic group and C is a
basic group; a, b and c are independently an integer of 0 to about
10 with the proviso that two or more of a, b and c are not
simultaneously zero; and n is an integer of 1 to about 15; and D is
hydrogen, alkyl, polyester or polyether.
[0027] In the dispersant of Formula 1 or 2, A is benzene, or a
heterocyclic compound substituted with nitrogen (N), sulfur (S) or
oxygen (O); B is selected from carboxyl (--COOH) and phosphoryl
(POOH) groups; and C is selected from aliphatic amine (--NR.sub.2)
wherein R is H, CH.sub.3, CH.sub.2CH.sub.3,
(CH.sub.2).sub.2CH.sub.3, or (CH.sub.2).sub.3CH.sub.3, and aromatic
amine (--XNR.sub.2) wherein X is benzene, and R is H, CH.sub.3,
CH.sub.2CH.sub.3, (CH.sub.2).sub.2CH.sub.3, or
(CH.sub.2).sub.3CH.sub.3.
[0028] As can be seen from Formulas 1 and 2, the dispersant
comprises an acidic, basic and aromatic functional groups whose
ratios can be regulated to a desired level, thereby improving the
affinity between one of the groups and the surface of phosphor
particles. In other words, a specific functional group included in
the head of the dispersant can have an affinity for the surface of
phosphor particles that have chemical properties similar to the
specific functional group. Generally, the surface of the phosphor
particles does not have a single property, but a plurality of
properties one of which may be compatible with one of the
properties of one of the functional groups disposed upon the head
of the dispersant.
[0029] Since the dispersant described above has a head comprising
multiple functional group, the probability of it adhering to the
surface of phosphor particles is improved. More specifically, a
larger fraction of the dispersant can adhere to the surface of
phosphor particles. In addition, the adhesive forces between the
dispersant and the phosphor is improved. As a result, there can be
improved dispersibility for a phosphor powder within a phosphor
paste composition when the dispersant is used in the
composition.
[0030] In the case where a dispersant is used for a phosphor powder
having large differences in acidity of various phosphor particles,
it is desirable to use a dispersant that comprises a block
copolymer.
[0031] The dispersant can be applied to a variety of phosphors,
e.g., organic and inorganic phosphors, by controlling the ratio of
the functional groups.
[0032] The dispersant according to one embodiment preferably has a
molecular weight of about 1,000 to about 20,000.
[0033] The dispersant can be prepared by copolymerizing at least
two monomers in the presence of a catalyst. The monomer is selected
from benzyl methacrylate, trimethylsilyl methacrylate,
(diethylamino)ethyl methacrylate, glycidyl methacrylate, or the
like, or a combination comprising at least one of the foregoing
monomers. During the copolymerization, the structure (e.g., random
or block) of the dispersant may be varied depending on the amount
and addition type of each functional group.
[0034] More specifically, examples of preferred dispersants that
can be represented by Formula 1 include a compound represented by
Formula 3 below:
##STR00003##
wherein a, b and c are independently an integer from 0 to about 10
with the proviso that two or more of a, b and c are not
simultaneously zero; and n is an integer of about 1 to about
15.
[0035] Examples of preferred dispersants that can be represented by
Formula 2 include a compound represented by Formula 4 below:
##STR00004##
wherein a, b and c are independently an integer from 0 to about 10
with the proviso that two or more of a, b and c are not
simultaneously zero; and n is an integer of about 1 to about
15.
[0036] In yet another embodiment, a phosphor paste composition
comprises a binder solution and a phosphor, in addition to the
dispersant.
[0037] The binder solution comprises an organic binder and a
solvent. The organic binder is used to modify the viscosity of the
phosphor paste composition. The organic binder is generally
dissolved in the solvent, and prevents damage to the fluorescent
film by changing the energy of attraction between the phosphors and
the substrate, or between adjacent phosphor particles after the
phosphor paste composition is dried. Examples of organic binder
resins that can be used are acrylic polymers, styrenic polymers,
cellulosic polymers, methacrylate ester polymers, styrene-acrylate
ester copolymers, polyvinylbutyrals, polyvinyl alcohols,
polyalkylene oxides, polypropylene carbonates,
polymethylmethacrylates, polyesters, or the like, or a combination
comprising at least one of the foregoing polymers. The organic
binder is determined depending on the kind of an electronic
application and the type of coating process.
[0038] Taking into consideration the kinds of the phosphor and the
organic binder and the desired physical properties of the phosphor
paste composition, the solvent used to prepare the binder solution
can be selected from commercially available solvents and mixtures
thereof. There is no particular restriction as to the kind of
solvents that can be used in the phosphor paste composition, but it
is desirable to use solvents that are volatilized at 150.degree. C.
or higher.
[0039] Examples of solvents that can be used are aromatic
hydrocarbon compounds, e.g., toluene and xylene; ether compounds,
e.g., tetrahydrofuran and 1,2-butoxyethane; ketone compounds, e.g.,
acetone, methyl ethyl ketone and cyclohexanone; ester compounds,
e.g., ethyl acetate, butyl acetate and butyl carbitol acetate
(BCA); and alcohol compounds, e.g., isopropyl alcohol, diethylene
glycol monobutyl ether, terpineol, 2-phenoxyethanol, or the like,
or a combination comprising at least one of the foregoing
solvents.
[0040] The binder solution includes about 1.5 to about 30% by
weight of the organic binder and the remainder of a mixed solvent.
When the organic binder is used in an amount less than 1.5% by
weight, there may disadvantageously occur deterioration in the
quality (e.g., binding force) of a fluorescent film, after the
phosphor paste composition is dried. Meanwhile, when the organic
binder is used in an amount exceeding 30% by weight, there may
disadvantageously occur a reduction in the amount of the phosphor
used.
[0041] The phosphor used in the phosphor paste composition of is
not specially restricted so long as it is used to prepare
conventional phosphor paste compositions. Particularly, there is no
restriction as to the kind and composition of the phosphor used.
Since the phosphor paste composition is mainly used to form
fluorescent films for display devices, such as cathodoluminescent
displays, liquid crystal displays and electroluminescence displays,
as well as for exterior decoration and display parts of electronic
appliances, e.g., keypads of cellular phones, the kind and
composition of the phosphor may be suitably selected according to
the kind of excitation sources used to form the display devices and
to excite the fluorescent films formed from the phosphor paste
composition.
[0042] Specifically, commercially available red, green and blue
phosphors in the form of oxide solid solutions may be used. Sulfide
and organic phosphors may be used as the suitable phosphors. The
type of phosphors depends upon the kind of excitation sources used
in the display devices.
[0043] The phosphor paste composition may further comprise at least
one additive selected from plasticizers, leveling agents,
lubricants, antifoamers and the like, so long as the physical
properties of the composition do not deteriorate.
[0044] The phosphor paste composition may comprise about 30 to
about 70% by weight of the phosphor, the phosphor being in the form
of a powder; with about 0.1 to about 10% by weight of the
dispersant; the weight of the dispersant being based upon the
weight of the phosphor powder, with the balance being the binder
solution.
[0045] When the dispersant is used in amounts of less than 0.1% by
weight, the amount of the phosphor used is has to be increased in
order to produce the same amount of luminance. The result is that
the viscosity of the phosphor paste composition is increased and
processing becomes difficult. Meanwhile, when the content of the
dispersant exceeds 10% by weight, the contents of the other
components has to be reduced in order to generate the same amount
of luminance and there is a risk that the physical properties of
the phosphor paste composition may be deteriorated.
[0046] By using the dispersant the content of the phosphor can be
increased to about 40 to about 70% by weight, based upon the weight
of the paste composition. Further, the increased content of the
phosphor in the phosphor paste composition contributes to an
improvement in the luminance of a fluorescent film formed from the
paste composition.
[0047] The phosphor paste composition can be prepared by adding the
dispersant to the binder solution and adding the phosphor powder
thereto. Specifically, the phosphor paste composition can be
prepared in accordance with the following procedure. First, an
organic binder, such as polyester, is dissolved in cyclohexanone as
a solvent. Then, to the solution are added a vehicle (the vehicle
being another solution in which the binder is melted), followed by
the addition of a phosphor. The resulting mixture is homogeneously
dispersed using a mill, such as a 3-roll mill, to prepare the final
phosphor paste composition.
[0048] In one embodiment, a fluorescent film can be produced from
the phosphor paste composition. The fluorescent film is produced by
applying the phosphor paste composition to a support, such as glass
or transparent plastic, to form a particular pattern thereon and
firing the coated support by drying and baking.
[0049] The fluorescent film can be produced by known techniques,
including but not limited to pattern screen printing, gravure roll
coating, ink jet, and the like.
[0050] The fluorescent film produced from the phosphor paste
composition enables an increase in the packing density of the
phosphor, an improvement in the luminance, and a relatively limited
increase in the viscosity of the composition despite the increased
loading amount of phosphors, thus leading to an improvement in the
processability of the fluorescent film.
[0051] The fluorescent film of the present invention can be used
for the fabrication of a variety of display devices, including
cathodoluminescent displays, liquid crystal displays,
electroluminescence displays, field emission displays and vacuum
fluorescent displays. In addition, the fluorescent film can be used
as a display material for exterior decoration of electronic
appliances, e.g., keypads of cellular phones. Display devices
comprising the fluorescent film exhibit improved luminescent
properties and uniform physical properties.
[0052] Hereinafter, the invention will be explained in more detail
with reference to the following examples. However, these examples
are given for the purpose of illustration and are not to be
construed as limiting the scope of the invention.
EXAMPLES
Synthesis Example 1
[0053] The dispersant represented by the following Formula 5 can be
synthesized by the following reaction scheme 1:
##STR00005##
i) Formation of Random Copolymer as Backbone
[0054] Methyl dimethylketene methyltrimethylsilyl acetal (1.74
grams (g), 10 mmol) as an initiator,
tetrabutylammonium-chlorobenzoate (0.4 g, 0.1 mmol) as a catalyst
and acetonitrile (3 ml) were placed in a round-bottom flask under
an argon atmosphere at room temperature, and stirred using a
magnetic bar for two hours. To the reaction solution was slowly
added a solution of benzyl methacrylate (BMA, 6.16 g, 0.035 mmol),
trimethylsilyl methacrylate (TMSMA, 2.37 g, 0.015 mol) and glycidyl
methacrylate (GMA, 0.71 g, 0.005 mol) as monomers in
tetrahydrofuran (THF, 10 ml). After stirring for 4 hours, the
copolymerization was completed to yield a random copolymer compound
1 as a backbone having (BMA:TMSMA:GMA=7:3:1 (w/w/w), with an
estimated molecular weight of 2,500 grams/mole).
ii) Introduction Carboxyl Group into Trimethylsilyl
Methacrylate
[0055] To substitute the silyl group of trimethylsilyl methacrylate
in the backbone 1 with a carboxyl group, to the TFT solution was
added methanol and refluxed for 6 hours. The solvent was removed
under a reduced pressure. The residue was dried in a vacuum oven
for 24 hours to yield a compound 2 in the form of solid powder,
where a carboxyl group is introduced into the trimethylsilyl
methacrylate.
iii) Introduction Amine Group into Glycidyl Methacrylate
[0056] To substitute the glycidyl group of glycidyl methacrylate in
the backbone 2 with an amine group, the compound 2 (2 g) was
dissolved in glyme (0.5 mL). To the solution was added diethyl
amine and stirred with silica gel under a nitrogen atmosphere at
room temperature for 3 hours. The reaction mixture was precipitated
in ethyl ether. The precipitate was filtered to remove the silica
gel. The residue was dried in a vacuum oven for 24 hours to yield a
compound 3 (a dispersant represented by Formula 5 below) as a solid
powder.
##STR00006##
[0057] The .sup.1H-NMR spectrum of the dispersant of Formula 5 thus
synthesized was shown in FIG. 1.
Synthesis Example 2
[0058] The dispersant represented by the following Formula 6 can be
synthesized by the following reaction scheme 2:
##STR00007##
i) Formation of Random Copolymer as Backbone
[0059] Methyl dimethylketene methyltrimethylsilyl acetal (1.74 g,
10 mmol) as an initiator, tetrabutylammonium-chlorobenzoate (0.4 g,
0.1 mmol) as a catalyst and acetonitrile (3 ml) were placed in a
round-bottom flask under an argon atmosphere at room temperature,
and stirred using a magnetic bar for two hours. To the reaction
solution was slowly added a solution of benzyl methacrylate (BMA,
6.16 g, 0.035 mmol), trimethylsilyl methacrylate (TMSMA, 2.37 g,
0.015 mol) and (diethylamino)ethyl methacrylate (DEAEMA, 0.92 g,
0.005 mol) as monomers in tetrahydrofuran (THF, 10 ml). After
stirring for 4 hours, the copolymerization was completed to yield a
random copolymer compound 4 as a backbone having
(BMA:TMSMA:DEAEMA=7:3:1 (w/w/w), and an estimated molecular weight
of 2,500 g/mole).
[0060] ii) Introduction Carboxyl Group into Trimethylsilyl
Methacrylate
[0061] To substitute the silyl group of trimethylsilyl methacrylate
in the backbone 4 with a carboxyl group, to the TFT solution was
added methanol and refluxed for 6 hours. The solvent was removed
under a reduced pressure. The residue was dried in a vacuum oven
for 24 hours to yield a compound 5 (a dispersant represented by
Formula 6 below) as a solid powder.
##STR00008##
[0062] The .sup.1H-NMR spectrum of the dispersant of Formula 6 thus
synthesized was shown in FIG. 2.
Example 1
[0063] A commercially available organic red phosphor powder
(PKS.sub.--225, UkSeung Chemical Co., Ltd., Korea) was used as a
phosphor. Polyester was used as an organic binder. 45% polyester
binder in cyclohexanone (TEIKOKU INS INK 000 series) was used as a
binder solution. To the binder solution was added the phosphor
powder (2 g) and a solution (0.333 g) of a 30% dispersant in
cyclohexanone. The dispersant was prepared in accordance with the
Synthesis Examples while the ratio of an aromatic, acidic and basic
group was adjusted to 9:1:1. The mixture was milled to prepare a
phosphor paste composition.
[0064] The phosphor paste composition was coated onto a
polyethylene terephthalate (PET) transparent film using a doctor
blade. The coating was dried on a hot plate at 100.degree. C. for
10 min to produce a fluorescent film with a thickness of 35
.mu.m.
Example 2
[0065] A fluorescent film was produced in the same manner as in
Example 1, except that a dispersant, where the ratio of an
aromatic, acidic and basic group is 7:3:1, was used.
Example 3
[0066] A fluorescent film was produced in the same manner as in
Example 1, except that a dispersant, where the ratio of an
aromatic, acidic and basic group is 5:5:1, was used.
Example 4
[0067] A fluorescent film was produced in the same manner as in
Example 1, except that a dispersant, where the ratio of an
aromatic, acidic and basic group is 7:3:3, was used.
Example 5
[0068] A fluorescent film was produced in the same manner as in
Example 1, except that a dispersant where the ratio of an aromatic,
acidic and basic group is 7:3:1 was used, and the basic group was
bonded to a block type copolymer. The block type copolymer was
synthesized under the same reaction conditions in accordance with
the same functionalization method as a random type copolymer,
except that the addition of monomers was performed not
simultaneously but separately.
[0069] Each type of the dispersant used in Examples 1 to 5 is
summarized in the Table 1 below:
TABLE-US-00001 TABLE 1 Ratio (Aromatic:Acidic:Basic group, w/w/w)
Binding type of Aromatic group Acidic group Basic group basic group
Ex. 1 9 1 1 Random Ex. 2 7 3 1 Ex. 3 5 5 1 Ex. 4 7 3 3 Ex. 5 7 3 1
Block
Examples 6-10
[0070] Fluorescent films were respectively produced in the same
manner as in Examples 1 to 5, except that a solution (molecular
weight: 30,000) of 37% polyacrylate in PGMEA (propylene glycol
methyl ether acetate) was used as an organic binder solution, and
the thickness of the fluorescent films was 30 .mu.m.
Example 11
[0071] A fluorescent film was produced in the same manner as in
Example 1, except that polyester acrylate (EB657, acid value: 20 mg
KOH/g, base value: 25 mg KOH/g, molecular weight: 1,500, SK CYTEC.
Co., Ltd., Korea) was used as a dispersant.
Example 12
[0072] A fluorescent film was produced in the same manner as in
Example 6, except that polyester acrylate (EB657, acid value: 20 mg
KOH/g, base value: 25 mg KOH/g, molecular weight 1,500 grams per
mole, SK CYTEC. Co., Ltd., Korea) was used as a dispersant.
Comparative Example 1
[0073] A fluorescent film was produced in the same manner as in
Example 1, except that no dispersant was used.
Comparative Example 2
[0074] A fluorescent film was produced in the same manner as in
Example 1, except that dispersant BYK170 containing only acidic
group (BYK chemie, acid value: 11 mgKOH/g) was used as a
dispersant.
Comparative Example 3
[0075] A fluorescent film was produced in the same manner as in
Example 1, except that dispersant BYK161 containing only basic
groups (BYK chemie, amine value: 11 mgKOH/g) was used as a
dispersant.
Comparative Examples 4-6
[0076] Fluorescent films were respectively produced in the same
manner as in Comparative Examples 1 to 3, except that a solution
(molecular weight 30,000 grams/mole) of 37% polyacrylate in PAMEA
was used as an organic binder solution, and the thickness of the
fluorescent films was 30 .mu.m.
Experimental Example
Evaluation of the Luminescent Properties of Fluorescent Films
[0077] To evaluate the luminescent properties of the florescent
films produced in Examples 1 to 12 and Comparative Examples 1 to 6,
the luminescence intensity of each florescent film was measured on
a UV luminescent device at a wavelength of 400 nm. At this time,
the luminescence intensity was measured using an Ocean Optics USB
100 detector.
[0078] The results are shown in FIGS. 3a and 3b, and FIGS. 4a and
4b.
[0079] As shown in FIGS. 3a and 3b, and FIGS. 4a and 4b, when
compared under the same conditions of thickness and wavelength
(i.e., 400 nm), the luminescence intensity of the florescent films
(Examples 1 to 12) produced using dispersants having a
multifunctional head structure was increased, respectively, when
compared with the florescent films (Comparative Examples 1 to 6)
produced using conventional dispersants or without using any
dispersant. The graphs shown in FIGS. 4a and 4b demonstrate, when
compared using the same binder, that the luminescence intensity of
the florescent films produced using the dispersant comprising both
acidic and basic groups was increased, as compared to that of the
florescent films produced using the dispersant containing either
acidic or basic groups. As shown in FIGS. 3a and 3b, when the
florescent films comprise a polyester-based binder, the
dispersants, where aromatic, acidic and basic groups are
respectively used in a ratio of are respectively 7:3:1, 7:3:3, and
5:5:1, are effective in exhibiting high luminescence intensity.
When the florescent films comprise a polyacrylate-based binder, the
dispersants, where aromatic, acidic and basic groups are
respectively used in a ratio of 9:1:1, 7:3:3, and 5:5:1, are
effective in exhibiting high luminescence intensity. These results
show that the phosphor paste compositions comprising the
dispersants of the present invention exhibit improved luminescence
intensity as compared to conventional phosphor paste
compositions.
[0080] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications and variations are
possible, without departing from the scope and spirit of the
invention as disclosed in the appended claims. Accordingly, such
modifications and variations are intended to come within the scope
of the appended claims.
[0081] As apparent from the above description, the novel dispersant
has advantages that it can improve the dispersibility of a phosphor
paste composition when it is used to prepare the phosphor paste
composition, and be applied to a variety of phosphors.
[0082] Since the phosphor paste composition comprising the
dispersant improves dispersibility and limits an increase in
viscosity, it permits the use of a larger amount of a phosphor,
thus enabling the formation of uniform fluorescent films having
improved luminescent properties. Display devices, such as LCDs,
having high luminance and excellent processability can be
fabricated.
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