Synthesis of new single black pigments based on azo and anthraquinone moieties for LCD black matrix

Article abstract of DOI:10.1080/15421406.2010.495684

Based on azo group and anthraquinone moiety, new black matrix pigment materials AAQ and DAAQ were synthesized for the first time through Suzuki C-N coupling. As a result of verifying UV-visible absorption spectra of the synthesized materials, DAAQ was fou

Full text of DOI:10.1080/15421406.2010.495684

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Synthesis of New Single Black Pigments
Based on Azo and Anthraquinone
Moieties for LCD Black Matrix
Jiyun Jung a , Youngil Park a , Jae-Yun Jaung b & Jongwook Park a
a Department of Chemistry/Display Research Center , The Catholic
University of Korea , Wonmi, Bucheon, Korea
b Department of Fiber and Polymer Engineering , Hanyang
University , Seongdong-gu, Seoul, Korea
Published online: 11 Nov 2010.
To cite this article: Jiyun Jung , Youngil Park , Jae-Yun Jaung & Jongwook Park (2010) Synthesis of
New Single Black Pigments Based on Azo and Anthraquinone Moieties for LCD Black Matrix, Molecular
Crystals and Liquid Crystals, 529:1, 88-94
To link to this article: http://dx.doi.org/10.1080/15421406.2010.495684
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Mol. Cryst. Liq. Cryst., Vol. 529: pp. 88–94, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421406.2010.495684
Synthesis of New Single Black Pigments
Based on Azo and Anthraquinone Moieties
for LCD Black Matrix
JIYUN JUNG,1 YOUNGIL PARK,1 JAE-YUN JAUNG,2
AND JONGWOOK PARK1
1Department of Chemistry=Display Research Center, The Catholic
University of Korea, Wonmi, Bucheon, Korea
2Department of Fiber and Polymer Engineering, Hanyang University,
Seongdong-gu, Seoul, Korea
Based on azo group and anthraquinone moiety, new black matrix pigment materials
AAQ and DAAQ were synthesized for the first time through Suzuki C-N coupling.
As a result of verifying UV-visible absorption spectra of the synthesized materials,
DAAQ was found to absorb the entire visible region in 400 ꢀ 800 nm in solution state
with high extinction coefficient of 8.1 ꢁ 103 L=cm ꢂ mol. Realization of black color
using a single material is expected to be useful for black matrix application. Also
in film state made through spin coating, both AAQ and DAAQ absorbed the entire
visible region.
Keywords Anthraquinone; azo group; black matrix; LCD
Introduction
Liquid crystal display (LCD) has been the spotlight for long time as a flat panel dis-
play. For full color realization of LCD, a color filter (CF) is necessary to change
white back light into red (R), green (G) and blue (B) lights. In such CF a black
matrix (BM) materials are between each R, G, B color pixels for high contrast
[1–3]. BM improves the contrast of red, green and blue lights converted from white
back light through prevention of external incident light. BM is also used to prevent
malfunction of thin film transistor (TFT) by minimizing reflection of light [4,5].
Although Cr=CrOx with sputtering process has been in use as BM, Cr is a heavy
metal element that causes environmental problems itself. And high cost and compli-
cated sputtering process are increasing the necessity of an organic BM [6,7]. Carbon
black can also be candidate as a BM, but high dielectric constant limits future use
because of TFT malfunction and the new organic BM materials have been recently
Address correspondence to Prof. Jongwook Park, Department of Chemistry=Display
Research Center, The Catholic University of Korea, 43-1, Yeokgok, Wonmi, Bucheon
420-743, Korea (ROK). Tel.: (þ82)2-2164-4821; Fax: (þ82)2-2164-4764; E-mail: hahapark@
catholic.ac.kr
88

New Single Black Pigments for LCD Black Matrix
89
Scheme 1. Chemical structures of 4PhNa, AAQ and DAAQ.
highlighted [8]. Therefore, it is important to develop black pigment which is the core
material of organic BM.
In order to make a black pigment used as BM, absorption of external light and
reflection of white back light must be blocked. Ideally, light should be absorbed
throughout the entire visible region overall even between 400ꢀ800 nm as well as high
absorption coefficient are also required. In addition, the pigment must have excellent
thermal stability because it should not change by heat at the highest temperature of
250ꢃC during the LCD manufacturing process [2,9]. Also, red, blue and green mix-
ture method and single BM material method are available for BM. In case of single
organic material method, it is extremely difficult for a material to absorb the entire
spectrum, and single material method is hardly in practical use.
Accordingly in this study, a single black pigment was designed as follows using
representative functional groups of dyes and pigments with high absorption coef-
ficient, azo and anthraquinone groups [10,11]. First, azo pigment called
4-phenylazo-1-naphthylamine (4PhNa) has high extinction coefficient in the blue
region of 440 nm. Anthraquinone has diverse substitution positions and can adjust
absorption spectrum according to substitution position [12]. In particular, positions
1 and 4 of anthraquinone can induce absorption of long wavelength region through
intramolecular hydrogen bonding with the carbonyl group [13]. A new black pig-
ment was designed and synthesized as shown in Scheme 1 through absorption of
440 nm by azo group and long wavelength absorption other than 440 nm by intra-
molecular hydrogen bonding of anthraquinone. Optical characteristics of the synthe-
sized material were measured using UV-visible spectrum, and thermal stability was
also measured with thermo gravimetric analysis (TGA) and differential scanning
calorimetry (DSC).
Experimental
Synthesis
Synthesis of 1-(4-Phenylazo-naphthalen-1-ylamino)-anthraquinone [AAQ].
4-phenylazo-1-naphthylamine (2.5 g, 10.12 mmol), 1-chloroanthraquinone (2.9 g,
12.14 mmol), Pd2(dba)3 (0.28 g, 0.30 mmol), [2.20-bis(diphenylphosphine-1.10-
binaphthyl] (BINAP) (0.75 g, 1.20 mmol), cesium carbonate (9.89 g, 30.35 mmol) and
100 ml toluene were into the 3neck flask. Then the mixture was stirred for 7 h at
100ꢃC under nitrogen. The reaction mixture was quenched with 5 ml water and
extracted with chloroform (CHCl3) and dried over magnesium sulfate anhydrous
(MgSO4). Evaporation of solvent under vacuum resulted in a brown residue, which
was purified by column chromatography using CHCl3 and reprecipitation with
1
methanol. (3.11 g, yield: 67.8%) H NMR (500 MHz, CDCl3) d (ppm): 11.96 (s,1H),

90
J. Jung et al.
9.07–9.06 (d,1H), 8.40–8.39 (d,1H), 8.33–8.31 (d,1H), 8.28–8.26 (d,1H), 8.07–8.06
(d,2H), 7.93–7.92 (d,1H), 7.84–7.79 (m,3H), 7.73 (t,1H), 7.69–7.66 (m,2H), 7.59–7.56
(t,2H) 7.53–7.51 (m,3H) ; FAB-Mass 453 m=z.
2-2. Synthesis of 1,4-Bis-(4-Phenylazo-naphthalen-1-ylamino)-anthraquinone[DAAQ].
4-phenylazo-1-naphthylamine (5.6 g, 22.6 mmol), 1,4-dichloroanthraquinone (2.5 g,
9.0 mmol), Pd2(dba)3 (0.219 g, 0.24 mmol), [2.20-bis(diphenylphosphine-1.10-
binaphthyl] (BINAP) (0.437 g, 0.70 mmol), cesium carbonate (11.58 g, 35.54 mmol)
and 100 ml toluene were into the 3neck flask. Then the mixture was stirred for 24 h
at 110ꢃC under nitrogen. The reaction mixture was quenched with 5 ml water and
extracted with chloroform (CHCl3) and dried over magnesium sulfate anhydrous
(MgSO4). Evaporation of solvent under vacuum resulted in a black residue, which
was purified by column chromatography using tetrahydrofuran (THF) and
reprecipitation with acetone. (0.90 g, yield: 14.4%) 1H NMR (500 MHz,CDCl3)
d (ppm): 12.88 (s,2H), 9.07–9.05 (d,2H), 8.48–8.47 (m,2H), 8.36–8.34 (d,2H),
8.05–8.04 (d,4H), 7.92–7.91 (d,2H), 7.84–7.83 (m,2H), 7.75–7.67 (m,4H), 7.60–7.55
(m,8H), 7.51–7.46 (t,2H); FAB-Mass 698 m=z.
Measurements
1H-NMR spectra were recorded on Bruker, Advance 500 and fast atom bombard-
ment (FAB) mass spectra were recorded by JEOL, JMS-AX505WA, HP5890 series
II. The optical absorption spectra of synthesized materials were obtained by HP 8453
UV-VIS-NIR spectrometer. The melting temperatures (Tm), glass-transition tem-
peratures (Tg) and degradation temperatures (Td) were measured by carrying out dif-
ferential scanning calorimetry (DSC) under a nitrogen atmosphere using a DSC2910
(TA Instruments) operated at heating rates 10ꢃC=min. Thermogravimetric analysis
(TGA) using a SDP-TGA2960 (TA Instruments). The Thermal stability of samples
under a nitrogen atmosphere was determined by measuring their mass losses while
heating at a rate 20ꢃC=min. Td was determined from the 5% degradation points of
weight loss of the compounds.
Results and Discussion
As shown in Scheme 2, 4PhNa and mono-substituted or di-substituted anthraqui-
none with chlorine substituted at position 1 or 1 and 4 were used to synthesize
AAQ and DAAQ in facile one step reaction through Suzuki C-N coupling. The
1
structure of synthesized materials was mainly verified by using H NMR and mass
spectrum. NH-proton shows intramolecular hydrogen bonding with the carbonyl
group of anthraquinone. Therefore, NH2 peak prior to synthesis was 4.59 ppm
and NH-proton peak moved respectively to 11.96 and 12.88 ppm after synthesis in
1H NMR spectroscopy of the synthesized AAQ and DAAQ [14].
UV-visible spectra of synthesized materials in solution state are summarized in
Figure 1 and Table 1. As shown in Figure 1, absorption spectrum of 4PhNa in the
visible region (400ꢀ800 nm) has a peak at 440 nm and the synthesized AAQ and
DAAQ also respectively showed peak spectrum at 428 and 481 nm. Also in case
of 4PhNa, the range of absorption spectrum in the visible region is 400ꢀ550 nm
and 1-chloroanthraquinone and 1,4-dichloroanthraquinone absorb UV wavelength
light under 400 nm. However, AAQ was found to absorb broader range of spectrum

New Single Black Pigments for LCD Black Matrix
91
Scheme 2. Synthetic routes of AAQ and DAAQ.
Figure 1. UV-Visible spectra of 4PhNa (- -), AAQ (-4-) and DAAQ (- -) (1 ꢁ 10ꢄ4 M in
&
ꢃ
THF solution).
Table 1. Optical properties of 4PhNa, AAQ and DAAQ in THF solution (1ꢁ 10ꢄ4 M
concentration)
UV Absorption-
range (nm)
UVmax (nm)
e (L=cm ꢂ mol)
Log e
4PhNa
AAQ
DAAQ
440
428
481
400ꢀ580
503ꢀ624
400ꢀ800
1.9 ꢁ 104
5.9 ꢁ 103
8.1 ꢁ 103
4.29
3.77
3.91

92
J. Jung et al.
&
Figure 2. UV-Visible spectra of AAQ (-4-) and DAAQ (- -) (film on the glass).
including 503 ꢀ 624 nm and DAAQ showed possibility as a BM material with
absorption of the entire visible region between 400ꢀ800 nm. This result can be inter-
preted by that as the number of intramolecular hydrogen bonding between anthra-
quinone carbonyl group and NH-proton increases, absorption spectrum become
wider from 440 nm to longer wavelength [11].
Extinction coefficient value of AAQ and DAAQ was respectively 5.9 ꢁ 103 and
8.1 ꢁ 103 L=cm ꢂ mol. Converted into log, these values were relatively high at 3.77
and 3.91. The two synthesized materials were made into film state by using spin coat-
ing on a glass substrate. As a result of measuring UV-visible spectrum in film state,
as shown by Figure 2, AAQ absorbs the entire visible region, which is broader range
of absorption compared to that in solution state. This result could be due to the
absorption of longer wavelength region by molecular packing and stacking in film
state. DAAQ was also verified to evenly absorb the whole visible region. Therefore,
both AAQ and DAAQ presented possibility as organic black matrix pigments.
Thermal stability of the synthesized materials was measured by TGA and DSC,
and the results are summarized in Table 2. Td of AAQ and DAAQ was 353 and
366ꢃC, respectively. AAQ showed Tm at 267ꢃC. Since this result has higher thermal
stability than the highest temperature (250ꢃC) reached during LCD manufacturing
process, these materials can be candidate for LCD organic BM material [2,8]. An
experiment is currently being conducted on the synthesis which increases the number
Table 2. Thermal property of AAQ and DAAQ
Tg (ꢃC)
Tm (ꢃC)
Td (ꢃC)
AAQ
DAAQ
–
–
267
–
353
366

New Single Black Pigments for LCD Black Matrix
93
of intramolecular hydrogen bonding in a molecule and on dispersion stability of the
synthesized materials for various application.
Conclusions
Black matrix pigments AAQ and DAAQ composed of new single material were
synthesized for the first time through Suzuki C-N coupling based on representative
dye and pigment functional groups, azo group and anthraquinone moiety. As a
result of verifying UV-visible spectrum in solution state, absorption range was
shown as 4PhNa (400ꢀ580 nm), AAQ (503ꢀ624 nm) and DAAQ (400ꢀ800 nm).
This result could be due to the increased number of intramolecular hydrogen bond-
ing between 1,4 substituted NH-proton and carbonyl group in anthraquinone. Parti-
cularly in case of DAAQ, the entire visible region is absorbed with high extinction
coefficient of 8.1 ꢁ 103 L=cm ꢂ mol. As a result of measuring UV-visible spectrum
in film state prepared by spin coating, both AAQ and DAAQ absorbed the entire
visible region.
For thermal stability of synthesized materials, Td of AAQ and DAAQ was
respectively 353 and 366ꢃC. Tm of AAQ was measured at 267ꢃC. Since synthesized
materials have high thermal stability compared to the peak temperature of 250ꢃC
during LCD manufacturing process, they can be used as LCD organic BM pigments.
Acknowledgments
This research was supported by a grant (Catholic Univ.) from the Fundamental
R&D Program for Core Technology of Materials funded by the Ministry of Knowl-
edge Economy (MKE), Republic of Korea. This study was supported by a grant
(Hanyang Univ.) from the Fundamental R&D Program for Core Technology of
Materials funded by the Ministry of Knowledge Economy (MKE), Republic of
Korea. This work was supported by the National Research Foundation of Korea
(NRF) grant funded by the Korea government (No. M2009A010800007). This study
was supported by a grant from the Strategy Project funded by the Ministry of
Knowledge Economy (MKE), Republic of Korea.
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