siox barrier films for flexible display siox barrier films ...€¦ · siox barrier films for...

AIMCAL 2005 Fall Technical Conference

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SiOx Barrier Films for Flexible Display SiOx Barrier Films for Flexible Display

T. Komori, H. Kobayashi, and H. UyamaTechnical Research Institute, TOPPAN PRINTING CO., LTD.


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OutlineOutline

■ Introduction ■ Introduction

■ SiOx Deposition by PECVD ■ SiOx Deposition by PECVD

■ Application to Flexible Displays■ Application to Flexible Displays

□ Color Filter□ Color Filter

□ OLED□ OLED

□ Ca test□ Ca test


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High insulation

High gas barrier

Low refractive index

Food packages

Electrical devices

Optical devices

PropertiesProperties

High transparency

Applications Applications

SiOx Barrier CoatingSiOx Barrier Coating


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SiOx film

Thermal evaporation

LPCVD

High speed deposition for packaging barrier.

The Methods to Obtain SiOx FilmThe Methods to Obtain SiOx Film

PVD

CVD

Optical coating

Sputtering

Ion plating

Insulation layer

Optical coating

High barrier film

Plasma enhanced CVD


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10－ 3 g/m2/day

10－ 2 g/m2/day

10－ 1 g/m2/day

100 g/m2/day

101 g/m2/day

Polymer substrate

Packaging barrier

LCD Color filter

OLEDUnder 10－ 5 g/m2/day

Electronic PaperElectronic Paper

Water Vapor Transmission Rate (WVTR)Water Vapor Transmission Rate (WVTR)

MOCON detection limit


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High density

Low stress

Composition Reduce impurities and micro defects

Avoid crack and delaminating

Defect less Smooth surface

More dense layer

No defects

To Obtain SiOx Barrier FilmTo Obtain SiOx Barrier Film

Surface morphology of substrate, etc

Barrier propertyDifficulty


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Color Filter

O2： 0.5〔 cm3/m2/day〕

H2O： 0.1〔 g/m2/day〕

> 85%

Ra < 5 nm

OLED

O2： 0.001〔 cm3/m2/day〕

H2O： 10-5〔 g/m2/day〕

> 200゜ C For Color Filter process

Must maintain physical and optical properties after photolithographic processing

Barrier property

Transparency

Chemical proof

Surface morphology

Heat resistant ofthe substrate

> 100゜ C Depending on type of OLED

Ra < 10 nm without any spiky defects

> 85%

Requirements for Display FilmsRequirements for Display Films


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Plastic Substrates for DisplayPlastic Substrates for Display

Typical properties of glass and plastic films

PET = Polyethylene terephthalatePC = PolycarbonatePES = Polyether sulfoneCOP = cyclic-olefin polymer

Glass PET PC PES COPWVTR (g/m2/day @ 100µm) - 4.6 4 124 0.4

Tg　(°C) 660 69 155 223 163Water absorption (%) - 0.7 0.3 1.4 0.01Transmittance (%) 93 87 90 89 91

Refractive index (@550nm) 1.54 1.66 1.58 1.65 1.53Haze (%) <0.5 0.6 0.8 <0.1 <0.1

Relative density 2.52 1.40 1.99 1.37 1.01Tensile strength (Mpa) - 190 85 80 75Tensile elongation (%) - 180 230 23 5

Coefficient ofthermal expansion (/°C)

5x10-6 2x10-5 7x10-5 6x10-5 6x10-5


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Roll-to-roll PECVD

SiOx

HMDSO+O2

Method：

Barrier：

Source material：

■ SiOx deposition process using PECVD

SiOx Deposition by PECVD SiOx Deposition by PECVD

CH3

CH3

H3C Si

CH3

CH3

CH3SiO

HMDSO (Hexamethyldisiloxane)

Winding Room

Deposition Room

HMDSO

RF Source

Electrode

O2

MFCMFC

HMDSO Inlet

Pumping

PumpingSubstrate

Main Roll

Winding roll

rewinding roll

Winding Room

Deposition Room

HMDSO

RF Source

Electrode

O2

MFCMFC

HMDSO Inlet

Pumping

PumpingSubstrate

Main Roll

Winding roll

rewinding roll

PET (175μm)

PES (200μm)

COP (100μm)

Substrate：


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Low transparency

Low density

Increase of dangling bonds

Using HMDSO PrecursorUsing HMDSO PrecursorProblem of PECVD ProcessProblem of PECVD Process

Must be deposited at low temperature <50゜ C

Precursor including methyl-group

Carbon incorporation causes deterioration of SiOx film properties


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Transmittance of SiOx Deposited by PECVDTransmittance of SiOx Deposited by PECVD

Light transmittance of the SiOx deposited film is as same as that of the substrate.

50

60

70

80

90

100

350 450 550 650 750

wavelength (nm)

T%

PES PES/SiOx(100nm)


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400100016002200280034004000

Wavenumber (cm-1

)

T [a

.u.]

Si-CH3Si-O-Si

Si-CH3CH3

(a)

(b)

(c)

FT-IR Spectra of SiOx FilmsFT-IR Spectra of SiOx Films

0.1

0.2

0.4

HMDSO/O2 flow ratio

Rf power 0.5kW

The absorptions from carbon incorporation were not indicated.


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1.450

1.455

1.460

1.465

1.470

1.475

1.480

1.485

1.490

1.495

0 0.1 0.2 0.3 0.4 0.5

HMDSO/O2 flow ratio

Refractive index

Refractive Index of SiOx FilmsRefractive Index of SiOx Films

Stoichiometric SiO2

0.5kW

1.0kW

SiOx film with O-rich or low density or

Incorporation of Si-OH or Si-C

SiOx film with Si-rich

λ =628.8


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1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

0 0.1 0.2 0.3 0.4 0.5

HMDSO/O2 flow ratio

Density [g/cm3]

Stoichiometric SiO2

Density of SiOx FilmsDensity of SiOx Films

0.5kW

1.0kW

XRR = X-Ray Refractivity

32.2g/cm »

The density of thermally oxidated SiO2


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MOCON PERMATRAN 3/33（ 40℃ -90%Rh）

Detection limit ofMOCON

Barrier Properties of SiOx FilmsBarrier Properties of SiOx Films

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

0 20 40 60 80 100 120

SiOx thickness　(nm)

WVTR　(g/m2/day)

PET PES COP

WVTR of the barrier film deposited only 60nm SiOx reached detection limit of MOCON.


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1. UV ozone cleaning

2. Color resist coating

3. Drying under reduced pressure

4. UV exposure

5. Development

6. Cleaning, drying

7. Thermal curing (180゜ C-60min)

Color Filter process = Photolithographic processing

This process was repeated 3 times for color filter fabrication.

Fabrication of Color FilterFabrication of Color Filter

Chemical resistance(e.g. alkali, acid and solvent)

Heat resistance


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Fabrication of Film color filter on Barrier Film（ Substrate： PES）

< 0.01g/m2/dayBarrier film*


< 0.01g/m2/day

Barrier film* / color filter


Fabrication of Color Filter on Barrier FilmFabrication of Color Filter on Barrier Film

Degradation of WVTR was not observed before and after color filter process.

* Both side SiOx coating.


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Glass substrate

Anode (ITO)

Hole transport Layer

Light emitting layer (Polymer type)

CaAg

Adhesive agent

Encapsulation film

Encapsulation Test Using Barrier FilmEncapsulation Test Using Barrier Film

OLED structure which uses a barrier film for encapsulation .

OLED test piece for estimation of WVTR


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Estimation method of WVTR

60℃ 90%RH.

46 hours

Barrier filmWVTR=0.03g/m2/day

Encapsulation Test Using Barrier FilmEncapsulation Test Using Barrier Film

The ratio of dark spot (DS) is observed for 500 hours under 60゜ C 90%RH.environment

Dark spot


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Observation of Dark SpotObservation of Dark Spot

Conditions: 60℃ 90%RH

Time [H] Initial 112 160 328 424 520

Reference

Sample A

Sample B

Barrier film delaminated fromthe OLED

(glass)


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0.00

0.20

0.40

0.60

0.80

1.00

0 100 200 300 400 500 600 700

Time [H]

Area ratio of DS [%]


Encapsulation Test Using Barrier FilmsEncapsulation Test Using Barrier Films

Sample A maintains low area ratio of DS for 500h, comparable to that of glass encapsulation.

Sample B, DS growth was observed and the barrier film was delaminated.

Reference (glass)

Sample A

Sample B


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Water though the barrier film reacts with Ca layer immediately.

Ca test piece

Ca Test for Estimation of WVTRCa Test for Estimation of WVTR

Ca corrosion area was measured by optical micro scope.

Ca 100nm

Barrier film

Glass

Adhesive agent

Ca corrosion


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Appearance of After 196 Hours Test PieceAppearance of After 196 Hours Test Piece

a) 60nm SiOx b) Thicker SiOx

c) Both side SiOx

A certain thickness was required to obtain defect-free barrier film.



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SummarySummary

■ A study of the SiOx coated film by plasma enhanced CVD for display has been presented.

■ Optimizing deposition conditions, WVTR became MOCON detection limit by minimal thickness. The SiOx film obtained on optimized condition approached density 2.2 g/cm3 and refractive index 1.465.

■ Degradation of barrier property was not seen before and after color filter process. These results represent that the SiOx film has resistance against chemicals.

■ From encapsulation test and Ca test, the SiOx barrier film was estimated suitable for OLED.


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Flexible OLED Flexible OLED

The OLED display was fabricated on plastic substrate with SiOx barrier layer.

Uniform luminescence and good flexibility were obtained.

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