Development of the Flexible Surface Light Source using ...shiko-tec.co.jp/wp/wp-content/uploads/2016/12/IDW... · Shikoh Tech LLC All right reserved. 6 Transmittance of the glass

Shikoh Tech LLC All right reserved. 1

Development of the Flexible Surface

Light Source

using Luminous Array Film Technology

Kenji Awamoto, Hitoshi Hirakawa, Junichiro Takahashi*, Takefumi Hidaka*

and Tsutae Shinoda

Shinoda Plasma Co., Ltd. *Shikoh Tech LLC.

Shikoh Tech LLC All right reserved. 2

Outline

1. Basic structure for Deep UV flexible surface

light source with “Luminous Array Film (LAFi)”

technologies

2. Fabrication process and device configuration

for flexible characteristics

3. Improvement of the UV emission power and

the life time

4. Performance of the UVC surface light source

for a sterilization application

5. Summary

Shikoh Tech LLC All right reserved.

3

Prototype roll-up display by LAFi technology

Prototype 1 x 1-m display in I-Zone,

Display Week 2013 at Vancouver, Canada

Display film:

1024 x 1024 mm,

320 x 320 pixels

Thickness < 1 mm

weight =2 kg

Luminous tubes

1

mm

Films with electrodes

MgO layer

Phosphor Layer

Discharge gas

Basic structure of Luminous Array Film (LAFi) Display Application of LAFi


4

Issues of LAFi structure for DUV light

Cross section of the LAFi for display

Front plastic film Color emission

R G B

Discharge

VUV

1 mm

Front and back plastic film with electrodes and adhesive layer absorb UVB and UVC light

Film material and adhesive material deteriorate by UV light

Glass tube material of the bolo-silicate absorb UVC light

183 280 315 400 (nm)

UV-C UV-B UV-A VUV Visible

Deep UV (DUV)

Transmission Absorption

Glass tube

Plastic film

Adhesive material

Front electrodes

Glass tube

Phosphor layer

Back electrodes

Back plastic film

Adhesive layer

Ne + Xe gas


5

Cross section of the DUV luminous tube and the array structure

AC driving pulse

X

Y

Driving structure

Basic structure for DUV emission

Backside electrodes apply AC electrical field on the discharge gas in

the glass tube, and DUV light emits only to front side

Electrode film and adhesive material are protected by reflecting the

UV light with widely formed phosphor layer in bottom of the tube

AC driving pulse provide a stable and uniform discharge in the tube

DUV emission

Back electrode substrate

Pair electrodes

Electrodes

Phosphor layer

DUV emission

Adhesive layer

Glass tube

Luminous tubes

Discharge

VUV

AC discharge Inverter circuit


6

Transmittance of the glass wall

Absorption of UVC by the glass wall was reduced by ultra thin glass

tube formation technique

Reflection of UVC by the glass wall was very little because of low

dispersion at the no phosphor area of the glass tube

UVC output was achieved with low cost glass material

0

20

40

60

80

100

230 240 250 260 270 280 290 300 310 320 330

Wavelength (nm)

Tra

nsm

itta

nce

(%

)t = 0.07mm

t = 0.1mm

t = 0.2mm

t = 0.5mm

t = 1.1mm

t

Transmission

Reflection

Absorption

Transmittance in DUV by bolo-silicate glass thickness

3.8%

80%


7

Fabrication Process of LAFi

1st step

Glass formation 2nd step

phosphor layer formation

Phosphor

Glass tube

4th step

Aging and selection

3rd step

Exhaust and gass

filling

Ne + Xe Discharge gas

Exhaust 2 mm

40mm - 1 m

Bolo-silicate glass is formed as designed size

Final sealing

Pre-sealing

5th step

Back substrate formation

Last step

Arraying and adhere

Luminous tubes

Luminous tubes

PCB Insulator

Adhesive film

Back substrate

Simple process of the luminous tube without electrode formation

External electrodes


8

Configuration for the bendable array

Selectable substrate; the solid plate or the flexible film

The tube gap, the adhesive and insulation layer is important

PCB with electrodes

Luminous tubes

Gap for flexibility

Adhesive layer

FPC with electrodes

Adhesive layer

Insulating layer

Luminous tubes

8 x 6-cm surface light source

with FPC substrate

Insulating layer


9

UV emissions spectrum by typical three phosphors

Several phosphor materials were tested by making a small

size LAFi light source

Single-band phosphor is expected to focus on a particular

application

UVC broadband light provides a several new applications

0

0.2

0.4

0.6

0.8

1

200 250 300 350 400 450Wavelength (nm)

Re

lative

em

issio

n in

ten

sity Multiband UVA, C phosphor

0

0.2

0.4

0.6

0.8

1

200 250 300 350 400 450Wavelength (nm)

Re

lative

em

issio

n in

ten

sity

UVB Narrow band

UVC Broad band


10

Variation of UV-LAFi

Surface size is designed by the tube length and the tube arrangement

Flexible film substrate is available

Long tube of over 20cm is available

4 x 1-cm

4 x 3.2-cm

8 x 2.2-cm 8 x 6-cm 8 x 12-cm

8 x 6-cm These design flexibilities provides

many advantages for UV applications 10 g


11

Improvement of UV emissions power

Miss-matching of the impedance between the drive circuit output and the gas

space was reduced by optimizing the insulation layer and the inverter circuit

By these optimization, the high UVC emission of 200 mW (4 mW/cm2) was

achieved with 8 x 6-cm surface light source

Electrodes

Top view of the luminous tubes

Side view of the discharge in the luminous tubes

Electrodes

Narrow discharge pass

Strong discharge Strong discharge

Gap

Gap


12

Life test results and life control

The 8 x 6-cm light sources with two types of UV phosphors

were tested in two driving condition

The life time varies according to the phosphor material

The life time is controllable by controlling emission power with pulse duty ratio control technique

0.0

0.2

0.4

0.6

0.8

1.0

1 10 100 1000Relative time

Re

lative

UV

in

ten

sity

Phosphor-1, 75%

Phosphor-1, 100%

Phosphor-2, 75%

Phosphor-2, 100%

Phosphor-1

Phosphor-2

Full duty driving pulse

Driving pulse with 75 % duty ratio

Ta

Tb

Duty ratio

= Ta/Tb

Full duty driving pulse

Driving pulse with 75 % duty ratio

Burst driving


13

Sterilization by UV-LAFi with broad band UVC phosphor

High speed sterilization

99.999% of sterilization rate

within 10 sec

High sterilization efficiency with

UVC broad band phosphor

Irradiation energy for 99.9% inactivation with

254 nm emission by Low-pressure Hg lamp

Name of a bacteria UVC irradiation

for 99.9% inactivation

Bacillus subtilis

(spores, NBRC 3134) 20.3 mJ/cm2

Escherichia coli

(NBRC 3972) 9.8 mJ/cm2

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 10 20 30

Irradiation time (sec.)

Re

sid

ua

l b

acte

ria

ra

tio

Bacillus subtilis（irradiance 2.7mW/cm2）

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0 10 20 30

Irradiation time (sec.)

Re

sid

ua

l b

acte

ria

ra

tio

Escherichia coli （irradiance 2.0mW/cm2）

No irradiation

After 15 sec irradiation

Detection limit

(D = 35 mm Labo-dish)


14

Advantage of UV-LAFi with broadband UVC phosphor

The shape of the emission spectrum of broadband UVC phosphor is

very similar to that of sterilization curve

Diffusion light by surface light source provides a shadow free lighting

0

0.2

0.4

0.6

0.8

1

200 250 300 350 400 450Wavelength (nm)

Re

lative

in

ten

sity

UVC Broad band

Sterilization curve

Surface lighting

Spot or line lighting

Shadow

little shadow


15

Summary

A flexible light source technologies using Luminous Array Film (LAFi) realized a new mercury free flexible surface deep-UV light source.

We developed several wavelength and size of DUV-LAFi and improved emission power to spread there application field.

UVC light source for sterilization provides very high performance against to strong bacteria.

LAFi is the best device for large area surface light source in DUV light applications.

Documents

Development of the Flexible Surface Light Source using ...shiko-tec.co.jp/wp/wp-content/uploads/2016/12/IDW... · Shikoh Tech LLC All right reserved. 6 Transmittance of the glass