Property of Cover Glass in Capacitive Touch Screen - Corningmedia.corning.com/flash/displaytechnologies/2008/Display_Taiwan... · • Corning is the world leader in specialty glass

Property of Cover Glass in CapacitiveTouch Screen

2© Corning Incorporated 2008Technical Materials

Corning Incorporated

Founded:1851

Headquarters:Corning, New York

Employees:Approximately 25,000 worldwide

2007 Sales:$5.86 Billion

Fortune 500 Rank:417

• Corning is the world leader in specialty glassand ceramics.

• We create and make keystone componentsthat enable high-technology systems forconsumer electronics, mobile emissionscontrol, telecommunications andlife sciences.

• We succeed through sustained investmentin R&D, over 150 years of materials scienceand process engineering knowledge, and adistinctive collaborative culture.


Corning market segments and additional operations

DisplayTechnologies

Telecom EnvironmentalTechnologies

LifeSciences

SpecialtyMaterials

OtherProducts

& Services

•LCD GlassSubstrates

•LTPS-LCD GlassSubstrates

•Optical Fiber &Cable

•Hardware &Equipment

CoaxialConnectivityProducts

•EmissionsControl Products

– Automotive– Diesel– Stationary

•Cell Culture &Bioprocess

•GeneralLaboratoryProducts

•Advanced Optics &Materials

•Display Optics &Components

•SemiconductorOptics &Components

•Aerospace•Astronomy•Optical Metrology•Ophthalmic•Telecom

Components•Specialty Glass

•Display Futures

•New BusinessDevelopment

•Drug DiscoveryTechnology

•Steuben Glass

•Equity Companies– Dow Corning Corp.– Eurokera, S.N.C– Samsung Corning

Precision GlassCompany, LTD(SCP)

GorillaTM Glass


A culture of innovation

Processes for massproducing thetelevision bulb

19471879

Glass envelope forThomas Edison’slight bulb

1915

Heat-resistantPyrex® glass

First low-lossoptical fiber

1970 1984

AMLCD glass forcomputers andlarge screen TVs

1972

Ceramic substratesfor automotivecatalytic converters

Dow Corningsilicones

1934

Glass ceramics

1952 2006

High-throughputlabel-free screeningplatform fordrug discovery

Fusion drawprocess

1960


Capacitive Touch ScreenStructure


Current Tech

Surface Capacitive is currently the 2nd largest technology

Source: 3M

•How it works– ITO conducts a continuous electrical

current across the sensor– Finger touch alters the capacitance field– The resulting distortion is measured by

circuits at each corner of the screen

•Advantages: durability

•Disadvantages: requires finger touch

•Applications: retail, game/entertainment,industrial/financial


Current Tech

Projected Capacitive becomes more popular due toiPhone, and can be used for both small and large panels

Source: Elo

•How it works– Consists of a sensor grid of micro-fine wires

laminated between two layers of protectiveglass

– Touch location calculated from changingelectrical characteristics of the sensor grid

– Can be installed behind other materials, e.g.vandal-resistant glass

– Finger does not have to be in physicalcontact

•Advantages: durability, environmental tolerance

•Disadvantage: high cost

•Applications: mobile phone, retail


Design Considerationsfor

Cover Glass


Typical glass surface damage from “used”devices

~ 20 micron depth

~ 40 micron depth

Scratch with Lateral Cracks

Scratches

Impacts


Surface damages cause glass failureSummary of Failure Analysis of Broken Devices (Field-returned and drop tested):

• Major cause of fracture – Impact damage– Sharp impacts create flaws that cause failure

• Keys, pens, gravel, etc.

• Second major cause - Scratch-related damage– Fracture initiated from a flaw within the scratch

• Over-stress alone does not cause failure– Strengthened glass deflects substantially before failure

• Devices do not have room for so much deflection– Failure stresses are never reached

Origin

Depth of damage 15 µm

Impact event

Depth of scratch 25-40µm

Scratch event

Impact

Scratch

Other

0

10

20

30

40

50

60

1st Qtr


Design considerations• Define “Design strength”

• Strength of glass decreaseswhen damaged– In-use strength measured by

Abraded Strength– Abrasion per ASTM C158

0

100

200

300

400

500

600

700

Glass and IX Condition

Stre

ngth

, MPa

IG3NS

IG3 Corning18

Corning31

Corning45

Corning57

only enoughspecimens forabrasion at tmeof testing

Unabraded

abraded

• Strength of brittle materialsrepresented by Weibull statistics– Select low (1%?) probability of

failure strength– Apply a factor of safety

Strength, MPa

Failu

re P

roba

bilit

y, %

100 10001

5

10

50

90

99

Soda limeglass

Gorillaglass

• Input requirements from failure-mode analysis


Requirements for glass in mobile devices

1. Tight Strength distributions

2. High retained (abraded) strength

3. Increased resistance to impact damage

4. Greater resistance to scratching


Gorilla™ Glass


What is Corning Gorilla™ Glass?

• Alumino-silicate thin sheet glass– Capable of high strength and reliability when chemically

tempered with an ion-exchange process

• Formed using Corning’s proprietary fusion draw process– Highest quality of as-drawn glass sheets in the world– Thickness 0.7 mm –2.0 mm as drawn

• Corning glass is ideal for display cover windows– Touch screens– Mobile phones– Other mobile electronic devices


Key benefits

• Glass designed for deep, protective, ion-exchange layer

• High strength and reliability

• Ability to sustain impacts without damage

• Retains high strength after use and abuse

• Pristine glass sheet surface

• Scalable sheet sizes for optimal throughput


Gorilla™ Glass combines unique capabilities

Proprietary fusionforming process:superior surface,

scalability,reliability

Innovative glasscompositionoptimized for

chemicaltempering

Gorilla Glass


Fusion-formed for a pristine surface

Roughness Measurement ResultsArea 1 Area 2

RMS 0.29 nm 1.46 nmRa 0.23 nm 1.13 nmZ-Range 4.23 nm 33.7 nm

5 um 5 m

Fusion Lap & polish10 nm


What properties of glass provide these requirements?

• Flaws, damages andscratches on the surfacereduce strength

• Enveloping compression layerof Gorilla™ Glass providestight strength distributions

Flaw populations in the surface

Competition GorillaCross section of a chip

Competition GorillaCross section of a scratch

Competition Gorilla

DOL

DOL


Gorilla™ Glass –ideally suited for protective covers formobile displays

• Highest degree of chemical strengthening

• Tightest strength distribution

• Highly tolerant to in-use damage (high retained strength)

• Highest impact resistance

• Highest resistance to scratch


The ion-exchange process

O2

Si

AlNa: 0.97Å

K:1.33Å

KNO3bath

glass

Glasssurface


What is chemical strengthening?

• Compressive stress and depthof layer (DOL) define thecharacteristics of chemicalstrengthening

• Stress equilibrium will inducea tensile stress in the centerof the sheet

• Overcoming the compressivestress at the crack tip isnecessary to initiate failure

CS

TS

DOL


Gorilla™ Glass has the highest depth of layer (DOL)

• Degree of chemicalstrengthening is thedevelopment of thedesired level ofcompressive stress(CS) over desiredDOL

• Gorilla Glass canachieve DOLgreater than typicaldamages/flawsdepth

• Gorilla glass isdesigned for lowerstress relaxation,higher DOL andhigh CS

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

300.0 400.0 500.0 600.0 700.0 800.0 900.0Compressive stress (MPa)

DO

L ( µ

m)

E

A

I

Gorilla

Compressive Stress (MPa)

Gorilla

DO

L (µ

m)


300

400

500

600

700

800

900

E A I Gorilla

Com

pres

sive

Str

ess

(MPa

) DOL = 15DOL = 25

Gorilla™ Glass has the highest CS at given DOL

• The predicted CS at15 um and 25 umDOL is shown

• At deeper DOL,compressivestresses aresignificantly lowerfor the soda-limeglassesC

ompr

essi

ve S

tress

(MP

a)

Gorilla

Extrapolated





• Highly tolerant to in-use damage




Gorilla™ Glass has tighter strength distribution

A

Gorilla

Strength, MPa

Failu

re P

roba

bilit

y, %

100 10001

5

10

50

90

99

• Gorilla Glassshows thehighest overallstrength

Note: Edge strength is measured using 4-pt bend test









Flaws induced during in-service life

Gorilla™ Soda Lime

• “In Use Flaws”canbe simulated byabrading thesurface

– ASTM C158

• Measure strengthafter increasinglevels of abrasionof glass surface– Ring-on-ring test

method


• “Contact force factor”combines abrasionpressure with gritdiameter

• A deeper DOL protectsthe glass surface fromin-use damage

0

100

200

300

400

500

600

700

0 5 10 15 20Contact Force Factor

Stre

ngth

(MPa

)

GorillaAEI

Gorilla™ Glass retains significant strength after use

Gorilla

Stre

ngth

(MPa

)

Contact Force Factor

Higher “In Use”Strength


High retained strength is directly related to DOL

0

100

200

300

400

500

600

700

Glass and IX Condition

Stre

ngth

, MPa

IG3NS

IG3 Corning18

Corning31

Corning45

Corning57

only enoughspecimens forabrasion at tmeof testing

Unabraded

abraded






• Highest damage resistance



Gorilla™ has increased resistance to impact damage

4500 g load 1500 g load

IOX Gorilla Glass IOX Soda Lime

Vickers indenter: a = 68.00°


Gorilla™ Glass can bear up to 6X more load

Gorilla glass withstands 6X higher loads before radial cracks form- Sharp object impact

0

1000

2000

3000

4000

5000

6000

7000

A I E Gorilla

Crit

ical

Loa

d (g

)

Gorilla

Crit

ical

Loa

d (g

)


Gorilla™ Glass is more resistant to lateral cracking

No lateral cracks were initiated in Gorilla glass for loads up to 6500 grams

Load Required to Initiate Lateral CracksLoad required to initiate lateral cracks

14.81214.2

0

1000

2000

3000

4000

5000

6000

A C E 1317

Cri

tical

Loa

d (g

)

no cracks

I

DOL

Gorilla

Crit

ical

Loa

d (g

)

Load Required to Initiate Lateral Cracks


Gorilla™ Glass is more resistant to chipping

Gorilla glass inhibits formation of chips associated with indentation

Load required to initiate chipping

14.812

14.2

0

1000

2000

3000

4000

5000

6000

A C E 1317

Cri

tical

Loa

d (g

)

no chips

I

Load Required to Initiate Chipping

DOL

Gorilla

Crit

ical

Loa

d (g

)









Gorilla™ Glass shows minimum collateral damageafter scratch event

A20

400

Load

(g)

lateral cracks

scratch groovechipping

I20

400

Load

(g)

chipping scratch groove

Gorilla20

400

Load

(g)

E

Loadchart notto scale


Gorilla™ Glass is designed for mobile devices

Minimum collateralDamage after scratch

event

Highest DamageTolerance

Greatest RetainedStrength

Tightest StrengthDistribution

DeepestDepth of Layer

Maximum SurfaceCompressive Stress

OptimalMobile DevicePerformance

Thank You

Documents

Property of Cover Glass in Capacitive Touch Screen - Corningmedia.corning.com/flash/displaytechnologies/2008/Display_Taiwan... · • Corning is the world leader in specialty glass