P-136 / T. Matsuyama

P-136: Novel In-cell Retarder of Alkali Development TypeTakanori Matsuyama, Takeshi Kobayashi, Kouki Tsubaki,Toshihisa Watanabe, and Yoshihiro Mori
Specialty Chemicals Division, Osaka Organic Chemical Ind. Ltd.
18-8, Katayama-Cho, Kashiwara City, Osaka 582-0020, JapanAbstract
A patterned retarder is important in LCDs and 3D displays. As
for the patterning method of retarder, developing in Alkaliaqueous solution was very difficult. We have developed thepatterned retarder consisting of UV-curable liquid crystal
materials of the new type that developing is possible in Alkaliaqueous solution.

1)

Coating of UV-curable liquid crystal materials
UV-curable LC (RO-001)
Alignment layer
Substrate2)

1.

Introduction

Retarder films are very important to make high performanceliquid crystal displays (LCDs). Recently, a lot of efforts havebeen made to put retarders in LCDs (VA LCDs, IPS LCDs), andmake it possible to replace the external retarder with in-cellretarder. Furthermore patterning of in-cell retarder makes it toimprove brightness and contrast ratio of LCD panels [1-8].
In addition, patterning of retarder can apply to micro-retarder for
3D displays.
The patterned retarder can be obtained by in-situ photopolymerization of UV-curable liquid crystal materials through a
photo mask then developing of non-polymerized region by using
the solvent.
An organic solvent is the most effective to a solvent of thedevelopment process, and development by using Alkali aqueous
solution was very difficult. However from the viewpoint ofenvironment and safety, the Alkali aqueous solution which seems
to be used in color filter process is an ideal.
We have developed the retarder consisting of UV-curable liquid
crystal materials (RO-001) of the new type that the developing
was possible in alkali aqueous solution. In this paper, we willshow the properties of patterned retarder by using Alkalidevelopment.

2.

Results

2.1.

Processes of patterned retarder

Figure 1 presents process to make the retarder. The detailed
process was prepared by the following procedures.
1)
2)
3)
4)
5)

UV irradiation through a photo mask

UV-curable liquid crystal materials (RO-001) were coatedwith spin coater.
The coated substrate was dried on a hot plate.
After dried, the obtained layer was cooled to roomtemperature, and exposed UV-light with photo mask in air.
Non-polymerization region is developed by using an Alkaliaqueous solution (NaHCO3aq).
The obtained patterned layer was heated high temperature(Post bake).

UV-light
Photo mask3)

Developing of non-polymerized region by Alkali solution

Figure 1. Preparation processes of the Patterned retarder.

2.2.

Properties of retarder materials

Table 1 shows the properties of the retarder of Alkali
development type that we developed. The development of thealkali development type of Positive C-plates, Negative C-plates
and O-plates in addition to positive A-plates retarder is also
possible.
Figure 2 shows the value of spin speed against retardation.
Retardation such as quarter wave or half wave can be adjusted bycontrol of spin speed.
Table 1. Properties of the UV-curable LC materials.
Name

RO-001

Clearing point

90 ℃⊿n (Re/d 550nm)

0.12

Firm optical geometries

Homogeneous

Solvent

Cyclopentanone

Remarks

Alkali development typeRetardation ( nm )P-136 / T. Matsuyama
400

2.4.

350

We measured thermal stability of retarder made of RO-001 at
high temperature.
Figure 5 plots retardation normalized by initial value against
heating time at 230℃. In the results, we confirmed high thermal
stability > 95% after 120 minutes.
In addition to thermal stability, we measured transmittance ofretarder made of RO-001 at high temperature.
Figure 6 plots transmittance against heating time at 230℃. In theresults, we confirmed high transmittance > 95% after minutes(Film thickness is ca. 2.5 μm).
In these results, it is possible enough to use retarder of RO-001 as
in-cell retarder.

3002502001501005000200400600

80010001200

1400

Spin speed ( rpm )Thermal stability of retarder

Figure 2. Dependence of spin speed on retardation of theretarder.
100Photolithography properties of retarder

Tharmal stability ( % )2.3.

We confirmed whether patterning of retarder was possible withNaHCO3 aqueous solution as an alkali developer. The concentrationof NaHCO3 aqueous solution is 0.1 %.
Figure 3 shows residual thickness ratio against expose dose. In low
expose dose, the film thickness is maintained > 90%, and even if thedeveloping time is changed, the tendency is similar.
Figure 4 shows Retardation against expose dose in quarter wavefilm. It saturates it with a low expose dose as well as residual
thickness ratio, and the influence on Retardation by the change inthe developing time is not seen. In these results, we confirmed thatpatterning of retarder was possible with NaHCO3 aqueous solution.

95908580
020406080

100120

Heating time at 230 ℃ ( min )Figure 5. Thermal stability of the retarder at 230 ℃.
908070100

Developing time 20sec

60

Developing time 120sec

504004080

120

160200Expose dose ( mJ/cm2 )Ttransmittance ( % )Residual thickness ratio ( % )100

Figure 3. Dependence of residual thickness ratio on Expose
dose in change of developing time.

95
908580020406080

100120

Heating time at 230 ℃ ( min )160

Retardation (nm)150

Figure 6. Transmittance (400 nm) of the retarder at 230℃.

140130120
Developing time 20sec

110

2.5.

Developing time 120sec

100

90
80

050

100

150

200

Expose dose (mJ/cm2)

Figure 4. Dependence of retardation on expose dose inchange of developing time.

Patterned of RO-001 retarder

Figure 7 shows example of Polarizing microscopic photograph ofpatterned retarder with various width of pattern (Line / Space = 1 /1). The resolution of the pattern is about 15μm. It is thought that
resolution improves further when processes condition and modify
materials are optimized.
Figure 8 shows example of SEM image of patterned retarder. In
the results, we confirmed that patterning shape of retarder, andpatterning was possible with Alkali aqueous solution.

P-136 / T. Matsuyama
3.

Conclusions

We have developed the retarder consisting of UV-curable liquid
crystal materials of the new type that the developing is possible inAlkali aqueous solution.
The photolithography properties of the retarder were goods, and it
was able to be confirmed that the value of thermal stability andtransmittance were also high.
The Patterned retarder that we developed can apply to in-cell
retarder for transflective LCDs, and to micro-retarder for 3D
displays.

PRA

4.
[1]

[2]
Figure 7. Polarizing microscopic photograph of thePatterned retarder prepared by Alkali development
under crossed polarizers.

[3]
[4]

[5]

[6]

Glass substrate

10μm

[7]

[8]
Figure 8. SEM image of cross sectional shapeof patterned retarder.

References
C. Doornkamp, B. M. I. Zande et al, “Next generation
mobile LCDs with in-cell retarders,” IDW’03, pp.685-688(2003).
O. Ito, S. Hirota, J. Tanno, M. Morimoto et al, “A New
Transflective IPS-LCD with High Contrast Ratio and Wide
Viewing Angle Performance,” IDW’06, pp.635-638 (2006).
K. J. Kim, H. Y. Lee, S. R. Roh et al, “New Strcture of IPS
Mode with In-cell Retarder for TV application,” SID’06
DIGEST, pp.1158-161 (2006).
N. Koma, M. Mitsui, Y. Tanaka and K. Endo, “A
Transflective In-Plane-Switiching LCD with a HigherOptical-Performance Reflective Area,” SID’07 DIGEST,
pp.1240-1243 (2007).
Y. Kuwana, H. Hasebe, O. Yamazaki, K.T akeuchi, H.
Takatsu, V. Chigrinov and H. S. Kwok, “Optimization of
Photo-alignment Layer for In-cell Retarder,” IDW’07,
pp.1673-1676 (2007).
I. Amimori, S. Suzuki, H. Kaneiwa, M. Nakajima, K. Ito, H.
Yoshino, and W. Kaneko, “In-Cell Viewing Angle
Compensation Using Pixelated Biaxial Retarders for VALCDs with No Color Shift,” IDW’08, pp.735-738 (2008).
P. -C.Y eh, Y. -S. Jeng, C. -J. Hu, and W. -M. Huang, “AWide Viewing Angle Advanced MVA LCD with In CellRetarder,” IDW’08, pp.411-412 (2008).
G. Fukunaga, T. Taguchi, S. Akao, and M. Aimatsu, “Incell retarder on Color filter for Transflective VA-LCDs,”
IDW’08, pp.115-116 (2008).