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Development of the MCPET Reflector for Edge-light LCD TV

1.

INTRODUCTION

Micro Cellular Plastic (MCP) is the foam with 0.1 to 10 μm
9of micro cells and closed cells whose cell density is 10 to15
310 cells / cm . The foam has been developed by professor Suh and others at MIT in USA. Initially this material
has received a lot of attention as the cells have been veryfine and the material weight has been reduced withoutloosing mechanical characteristics (relative mechanicalstrength). Furukawa Electric Co., Ltd. (FEC) started basic
research in 1990 and developed the superior optical performance. And then, MCPET optical reflector waslaunched to the market, a first in the world.
Liquid crystal panel
Variouskinds ofoptical ﬁlms

Diﬀuser panel
MCPET reﬂector
CCFL (cold cathode ﬂuorescent lamp)
Figure 1

In 1997, starting by its adoption to the sign boards of theunderground railway stations, MCPET has been widely
utilized such as sign boards in department stores, convenient stores and lighting equipments etc.. In 2001,
MCPET was adopted to the optical reflector of Direct type
LCD TV for the first time. In 2002, utilizing the superior
bendability, MCPET with mountain folded between CCFL
lamps was adopted. Refer to Figure 1 and Figure 2.
After that, according to the expansion of larger, thinnerand energy saving type of LCD TV, light source position ofback light has been modified from direct type to edge
light type, placed at both lateral edge, using light guideplate. And light source itself has been changed to lower
power consumption Light Emissive Diode (LED). Refer toTable 1.
Table 1Feature of various systems for back light unit.
CCFLDirect typeLEDDirect type

LEDEdge light type

Brightness○◎○

Energy saving

×○◎Thinner××◎○×○Cost◎: Very good○: Good

×: No good

Structure of direct type liquid crystal
display (LCD) TV.

LCD TV with edge light type LED light source, especiallylarger than 40 inches type, has superior feature in energysaving, also in adaptability to thinner type. Furthermore,
screen brightness and cost performance are maintained
at better level than conventional products. So, change toedge light type LCD TV is definitely expanding. Edge lighttype LCD TV already had 38% of market share by the endof 2011. It is expected that the market share will reach to
80% in 2014. (surveyed by NPD Japan LTD.)

Figure 2

Mountain folded MCPET reflector(inside back light).

Furukawa Review, No. 41

201211

Development of the MCPET Reflector for Edge-light LCD TV（1）R grade (1.0 mm thickness)（2）G grade (0.8 mm thickness)（3）H grade (0.7 mm thickness)（4）P grade (0.5 mm thickness)of reflection sheet are increasing. FEC has been developing the reflectors that meet the demands. The thicknessof the first developed R grade product was 1.0 mm. The
newest P grade product succeeded to reduce the thickness almost by half to 0.5 mm. Generally, if only the sheet
thickness is reduced without changing the cell structure(the cell diameter), the reflection reduction problem
occurs as the light reflective surface is simply reduced.
FEC has reduced the cell diameter, simultaneously thethickness was reduced by using the original material
technology, and were able to increase the reflective surface. Thus, not reducing but increasing reflectivity, thethinner sheet was successfully developed. Refer to Table
2.

Table 2Figure 3Optical properties for each grade.

R gradeSEM photos for each grade.

LED light sources

G gradeH gradeP gradeThickness (mm)1.00.80.7

0.5

Total reflectivity (%)

99.4

99.5

100.9

100.8

Diffuse reflectivity (%)

96.0

96.7

96.9

97.3

※Total reflectivity is Barium sulfate white board relative value at 550 nm.

Figure 3
Figure 4Lamp reﬂector

Light source position.
Light source position.

Light source (LED)
Chassis
MCPET

Light guide plate

Optical ﬁlm

2.2 Sheet Stiffness and Heat Resistance
Initially, light sources were placed at 4 points aroundedge light type TV screen. Refer to Figure 4. After that,the positions evolved to both top and bottom ends orboth right and left ends of the screen. Refer to Figure 5.
But, in these days, according to the progressing cost
reduction of light sources, the construction is changing to
1 end of the screen. Because of this change to one lightsource, light has to be guided for longer distance andthus requires a higher power light source. Due to thehigher power, higher heat is generated and higher heat
resistance is required for materials. MCPET is the material
that meets to this requirement.
Table 3 shows the differences in characteristics compared with the product of other manufacturers. MCPET isa foam product, so density is lower (lighter weight) thanthe other company products and yet it has excellent
rigidity and heat resistance.

Liquid crystal panel
Table 3

Stiffness and heat resistance of MCPET.

MCPET
P gradeLight source (LED)

Figure5 4Structureof edge
light
type
LCD
TV.
FigureStructureof Edge
type
LCD
TV.

2.

FEATURES OF MCPET REFLECTOR

Film A(Laminated)

Film B

Thickness (mm)0.500.50

0.35

Density (g/cm )

30.45

0.75

1.15

Stiffness (Bending strength)◎○×

Heat resistance (60℃)○××◎: Very good○: Good

×: No good

2.1 Cell Structure and Optical Characteristics
Cross section SEM photographs of various grade ofMCPET are shown in Figure 3. According to the expansion of thinner type of LCD TV, demands for thinner type

Furukawa Review, No. 41

2012

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Development of the MCPET Reflector for Edge-light LCD TV

3.

CONCLUSION

The internal structure of LCD TV is evolving day by day.
Accordingly, requirements to reflectors are changing inwide varieties. MCPET is the material that can meet thewide variety of requirements. At this moment, after 20
years of the first development, cell miniaturization andperipheral developments are proceeding.
Usage of MCPET is not limited to the reflector for LCD
TV. Since the very beginning, MCPET has been used in
the field of lighting equipments. In these few years,according to the expanding usage of LED, high diffuse
reflectivity of MCPET attracts attention for its ability to diffuse a linear light source. And implementation in themoldings for LED down light modules and others areincreasing. MCPET can be formed to various shapes bythermo molding.
Furthermore, the MCPET manufacturing technology
can be applied not only to Polyethylene Terephthalate(PET) resin but to Polycarbonate resin, Polyphenylene
Sulfide (PPS) resin and a wide variety of engineering
plastics resins. Then, this technology can be developedto many other usages.
In the near future the structure of TV itself will bechanged significantly. FEC will keep making proposals onsolution for a wide variety of requirements helped by ouroverall strength in material technology.
For more information, please contact:
Sales Department
MC Products Division
Industrial Products Division
Energy and Industrial Products Company
TEL: +81-463-24-8327 FAX: +81-463-24-8567

Furukawa Review, No. 41

201213