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Development of MCPOLYCA Reflector for LED Lighting

1.

INTRODUCTION

The Micro Cellular Plastic (MCP) is a foam with 0.1 to 10
μm of micro cells diameter and closed cells with cell den915
3
sity is between 10 to 10 cells / cm . The foam has beendeveloped by professor Suh and others at MIT in USA.
Initially this material has received a lot of attention as thecell has been very fine and the material weight has been
reduced without decreasing mechanical characteristics(specific strength). Furukawa Electric started the development in 1990 and found out a superior optical performance. And then, polyethylene terephthalate resin (PET)based super micro foamed optical reflector (MCPET) waslaunched in the market, a first in the world.
Since the MCPET performance is characterized by lightreflection and easy workability (bending, punching andcutting), the MCPET has widely utilized applications suchas sign boards for advertising, facade boards for convenient stores and destination boards in railway stations
etc. which offers brightness and energy saving. In addition, from 2009 due to increasing awareness of energy
saving, the MCPET has been adopted as a reflector of fluorescent lighting for renovation application of office lighting, and has contributed to energy savings of office byreducing the number of fluorescent lamps (from 2 to 1).
(Figure 1)

Figure 1

reFbo Light (from Daiwa House
Industry catalogue).

On the other hand, the MCPET is a crystalline plastic
and has a problem in thermo formability (forming condition range is narrow). Therefore, the development of theforming required application was difficult. Thus, we developed the polycarbonate resin based super micro foamed
optical reflector (MCPOLYCA), by applying MCP manufacturing technology that can be applied to a variety of plastics. Non-crystalline MCPOLYCA is excellent in thermo
formability, and expansion to Down light module for LED
lighting is expected.
Overview of the MCPOLYCA and possible application toLED lighting are explained in this report.

2.

CHARACTERISTICS OF THE MCPOLYCA

Figure 2 shows a cross sectional SEM photograph of theMCPOLYCA sheet. Generally, inorganic materials areadded to solids (injection molded products) and films toincrease light scattering. But, the MCPOLYCA contains
only micro foams (hollow) in the order of few μm. By controlling dimension and quantity of this micro foam, a highlight reflective performance, which is not available in othermaterial, is obtained.

Figure 2

SEM photograph of the MCPOLYCA.

Table 1 show physical properties of the MCPOLYCA incomparison with the MCPET (RB grade) which is in salefor lighting and sign board application from Furukawa
Electric. The MCPET shows some better mechanicalcharacteristics than the MCPOLYCA, but the MCPOLYCA
shows higher performances than the MCPET in diffuse
reflectivity and thermal properties (thermal dimensionalchange rate, heat distortion temperature).
The excellent diffuse reflectivity is caused by embossed
shapes given to the surface of the sheet. In case of theMCPOLYCA, the embossed shapes are easily given in
manufacturing process, and remain without loosing theshape after forming. This is the feature of the MCPOLYCA.
Heat distortion temperature was measured by thermomechanical analysis method (TMA method). The MCPET,
which is a crystalline plastic, gradually starts softening at
higher than glass-transition temperature of 75℃ andshows the behavior of a significant softening at higher
than 200℃. On the other hand, because of the non-crystalline plastic feature, the MCPOLYCA starts softening atFurukawa Review, No. 4220129Development of MCPOLYCA Reflector for LED Lighting

glass transition temperature of approximately 140℃ without showing two steps of softening behavior. Judging
from this behavior, the MCPOLYCA has higher applicability than the MCPET as a reflector material for LED lightingthat requires 100℃ to 120℃ of heat resistance.
The MCPET (RB grade) has obtained UL94-HBF for fireretardancy. In-house test result confirmed that theMCPOLYCA had equivalent level of UL94-HBF toUL-94-V2. Fire retardancy is dependent on sheet density
and thickness, and designing is required in accordancewith the customer requirements. In addition, development
is going on in consideration of future launching ofUL94-V0 grade products.
Table 1

 roperties of the MCPOLYCA and the MCPET (RBPgrade).

ItemDirection Unit MCPOLYCAMCPET(RB)

mm

1.0

1.0%

9999%

989621201818451235068627664991519Thickness
1Total reflectivity*

1Diffuse reflectivity*
Tensile strength
Elongation
Tearing strength
Bending strength
Flexural modulus

MDTD
MDTD
MDTD
MDTD
MDTD

Thermal dimensional change rate

MD

(100℃, 22h)

TD

Heat distortion temperature(TMA method)MD

Glass-transition temperature
Fire retardancy

TD

MPa%
MPa
MPa
MPa%℃
℃

1414754

1156

698

882

0.23

0.37

0.18

0.24

14375 (202)14475 (201)145

UL94 HBF～V2 *Metallic mold transfer

Vacuum and pressurized air forming
Pressurized air

Vacuuming

Trimming

Figure 3CutCooling, mold release

Vacuum and pressurized air forming process.

Figure 3 shows vacuum and pressurized air forming
process. Depending on forming shape vacuum forming
method can be used, but by using pressurized air method in combination, products can be formed with better
shape transferability. Figure 4 shows a photograph of acup shape formed product. Edge part shape is preciselycreated.
In case of the MCPET, certain duration of heat set isnecessary for shape stabilization at the same time as theforming. This time is not required for the MCPOLYCA andthe cycle time can be shortened.

Figure 475２Vacuum and pressurized air
forming sample of MCPOLYCA.

HBF*1 : Reflectivity is the relative value against BaSO4 white plate at 550 nm*2 : Fire retardancy of MCPOLYCA is the in-house evaluated value.

3.

Sheet heating

FORMABILITY OF THE MCPOLYCA

The MCPET is necessary to be formed by match-moldforming method using two types of male and female
metallic mold. The MCPOLYCA can be formed by vacuum
forming method or vacuum and pressurized air forming
method using one kind of metallic mold (male or female).

4.

APLICATION TO LED DOWN LIGHT MODULE

Left side photograph of Figure 5 shows LED Down light
module, which applies an MCPOLYCA, manufactured by
A. Die processed goods of the MCPET are placed at thebottom surface of the module (die cutting in accordancewith the placement of LED chip) and side (cylindricalshaped). This has a structure to emit uniform white lightas LED light (blue) diffusely reflects at the yellow diffuser
panel and repeat multiple reflections within the module.
However, this structure has separated reflectors at thebottom and the side, and then from the assembling cost
reduction point of view a formed product which integrates
bottom and side reflectors is required. Right side photograph of Figure 5 shows LED Down light module manufactured by B. By aggregating LED chips to the center
part of the base (modularization of the light source),
inverted truncated cone formed product is possible to be

Furukawa Review, No. 42201210

Development of MCPOLYCA Reflector for LED Lighting

applied. Presently formed MCPET products are applied,
but in accordance with modularization of light source heatincrease becomes an issue, in parallel with the increaseof the light amount. And then we expect that the demands
for the MCPOLYCA with high heat resistant feature willincrease.

Figure 5

Applications to LED Down light modules.

Down light module shown in Figure 5, which utilizes
multiple LED light reflection by placing reflectors at aperture, is suitable for the MCPOLYCA application. Recently
LED light source becomes possible to adjust the lightemission to wide angle, by combining with the condenser
lens. For this to happen, the reflector is essential, and theexpansion into straight fluorescent type lighting and ceiling type lighting is expected.

5.

CONCLUSIONIn addition to the recent enhancement of energy saving
awareness, as a consequence of the drastic change inpower condition caused by catastrophe in 2011, thereplacement of the traditional lighting to LED lighting israpidly growing. One of the merits of LED lighting is theadvantage of flexibility in designing to the traditional lighting. The MCPOLYCA can be easily formed by vacuum
forming method or vacuum pressurized air forming method. Then metallic mold cost becomes lower than metalreflector and injection forming reflector. We think, thismeets the needs of the lighting equipment of high-mix
low-volume production because of the diversification ofthe lighting design. The MCP manufacturing technology
developed by Furukawa Electric is not limited only to theMCPET and the MCPOLYCA, but also applied to the Poly
Ethylene Naphthalate (PEN), the Poly Phenylene Sulfide(PPS), the Poly Ether Sulfone (PES) and a variety of highperformance plastics. Furthermore, by taking advantageof not only light reflection feature but also light weight andhigh rigidity, this product is in sales as a material ofspeaker cone of mobile phones. We thrive to keep introducing MCP products meeting with customers needs.
For more information, please contact:
Sales Engineering Division
MC Products Division, Sales Department
Industrial Products Division
TEL: +81-463-24-8327 FAX: +81-463-24-8567
E-mail address: mc@furukawa.co.jp

Furukawa Review, No. 42201211