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					 Introduction to Thermal
and Photocurable Polymers
                      Prof. Myong-Hoon Lee

   SPLEO (Synthetic Polymer Laboratory for Electronics and Optics)
                Chonbuk National University

What is cure?
     Conversion of a fluid or resinous polymer composition into a hard, tough, adherent and solid film
      by intermolecular interaction

Types of Cure
    1. Auto-oxidation
              usually at ambient temperature
              drying of alkyd or oleoresinous binders
              takes long reaction time
    2. Chemical cure
              chemical reaction between two components at ambient temperature
              epoxies, urethanes, and etc.
    3. Thermal cure
              crosslinking between components by thermal heating
              usually involves chemical cure reaction (mostly by ionic mechanism)
              amino resins (P/F, U/F, M/F), epoxies
    4. Radiation cure
              requires photoactive (photosensitive) compounds
              mostly by free-radical mechanism generated by photochemical reaction
              photodimerization, dichromate crosslinking, photocurable resin, and
               photopolymerization of side chain
              e-beam, UV (g-line @436nm, i-line @365nm, KrF @248nm, ArF @193nm, F2
               @157nm, Ar2 @126nm), g-ray, etc.


  Curing of oil by oxygen                          CH2 O CO (CH2)7CH=CH(CH2)7CH3               (oleic)
       crosslinking of double bond in fatty acid   CH O CO (CH2)7CH=CHCH2CH=CH(CH2)4CH3        (linoleic)
       conjugated or non-conjugated double bonds   CH2   O CO (CH2)7CH=CH CH=CH CH=CH(CH2)3CH3 (eleostearic)

       eg) painting oils, alkyds, etc.                             fat (oil)


                                                     CH2 OH         HO CO (CH2)7CH=CH(CH2)7CH3
                                                     CH OH      +   HO CO (CH2)7CH=CHCH2CH=CH(CH2)4CH3
                                                     CH2 OH         HO CO (CH2)7CH=CH CH=CH CH=CH(CH2)3CH3
                                                     glycerol              fatty acid

           CH2 CH=CH CH=CH CH2 CH2                    CH2 CH=CH CH CH CH2 CH2

                          CH2 CH=CH CH CH CH2 CH2
                          CH2 CH=CH CH CH CH2 CH2

Chemical Cure

  Crosslinking via reactive functional groups at room temperature
       room temperature reaction
       generally two component system
       epoxies, urethanes

                                 structure of epoxy resins

                           epoxy curing                              ③

                                                  ②                  ④
Thermocurable Resins

  Crosslinking via reactive functional groups at high temperature
       one pack system (with two components) possible
       low storage stability
       crosslinking between components by thermal heating
       usually involves chemical cure reaction (mostly by ionic mechanism)
       amino resins (P/F, U/F, M/F), epoxies, urethanes

M/F Resins
                                CH2OR           CH2OH HO                                                    CH2OR           CH2O              R
                                N       N       N                    R                                      N       N       N
                 OH HOCH2                         CH2OR                                        R    OCH2                        CH2OR
                                                                          150 oC
    R                               N       N                                                                   N       N
                                                                          - H2O

methylol reaction                       N                                                                           N
                             ROCH2          CH2OH HO                                                    ROCH2           CH2O              R

                 M/F (melamine/formaldehyde) resin                                                    crosslinked structure

                                                                                                           NHCH2O C4H9
U/F Resins                                                                                            O C
                                                                                   NHCH2O C4H9             NHCH2O
        O             H                             NHCH2OH
                                                              n-C4H9OH                                              NHCH2O C4H9
  H2N C NH2       +       C O                   O C                             O C
                      H                                                            NHCH2OH                      O C
                                                                                                                        O C
   O C
                          crosslinked structure
        180 oC
        - H2O

                                    OH                               OH                                O            R
P/F Resins                                      H                         CH2
                                                                                           150 oC
                                            +       C O
                                                H                                          - H2O

                                                                     CH2OH HO                          CH2O                 R
                                                                  novolac                           crosslinked structure
Epoxy Resins

        O                       CH3                                      CH3                         O
     CH2 CH CH2 O               C            O CH2 CH CH2 O              C            O CH2 CH CH2
                                CH3                    OH                CH3

    Mol. wt. diversity
           340 (n = 0) ~ 700 : liquid
           ~ 8000 (n = 26) : solid
    Crosslinking by reactive epoxide ring and/or hyrdoxyl groups
           with other -OH, -COOH, -NH2
    Excellent thermal and chemical stability
           C-C or C-O-C linkage only
           no phenolic -OH (good color)
    Excellent adhesion
           many -OH groups (H-bonding)
    Various structures available
                      CH2                          O
                                                   C       CH2                 CH3               O
                        CH2                            O
                                         O                           O   CH2 C C O R CH2 CH CH2


              epoxy novolac                  cycloaliphatic epoxy              epoxy acrylates

Crosslinking of Epoxy Resins
   Epoxide ring-opening by hydroxyl groups
         internal -OH groups
         produces -OH groups          OH
                                             O                                 O                                                             OH
                                           CH2 CH CH2                    CH2 CH CH2                         CH2 CH CH2                    CH2 CH CH2
                                                                                                               OH              OH

   Epoxide ring-opening by amine groups
         external curing agents (aliphatic & aromatic)
         DETA (diethylenetriamine), TETA (triethylenetetramine), DADM (4,4'-diaminodiphenylmethane), etc.
         room temp. ~ 130 oC                       H2N CH2CH2 NH CH2CH2 NH2
                                                                                                   H2N                   CH2        CH2
                                                        H2N CH2CH2 NH CH2CH2 NH CH2CH2 NH2

   Epoxide ring-opening by acid (anhydride) groups
         external curing agents
         longer cure time and higher temperature
                               O                              O                          O

                                                                  OR   epoxide               OR        OH
                               O   + HOR                          OH                         O         CH
                                                                                                 CH2        CH2
                               O                              O                          O

   Polyaddition by catalysts (cationic)
         catalyzed by lewis acids (BF3 etherate)
         often mixed with other reactions
                                                                                  O                               OH
                               O                         OH                 CH2 CH CH2                      CH2 CH CH2
                                      cat. H+
                         CH2 CH CH2                 CH2 CH CH2 cat                                    O
                                                                                                  CH2 CH CH2 cat

Photocrosslinkable Polymers

         photodimerization
         dichromate crosslinking
         photopolymerization of side chain
         photocurable resin

                         g - line
                                                         i - line

    i - line


                                              E - beam

Photocrosslinkable Polymers

(1) Photodimerization
     • [2+2] cycloaddition of p-bonds
     • eg. poly(vinyl cinnamate)

                   CH2 CH                    CH2 CH                           CH2 CH
                        OH                        O                               O
                                                  C O                             C O
               Poly(vinyl alcohol)
                                                  CH                       HC     CH
                                                                           HC     CH

                                                                         O C
                                        poly(vinyl cinnamate)               CH CH2

                                                                     (cyclobutane) structure

     • Known as Kodak Photoresist (KPR) in 1954
     • Many other structures including epoxy cinnamate, maleimides, 2,5-distyrylpyrazine, thymine, etc.

(2) Dichromate crosslinking
    • oldest photoresist before KPR
    • PVA (or gelatine) + dichromate

                                              h                                 CH2
                 CH2 CH
                             +   [Cr2O7]2-                   C O
                                                                    Cr(III)    O C

(3) Photopolymerization of side chains
    • Acryl side chains
    • Can also be used in photocurable resin as a reactive binder

                                                               COOR           COOH     O
          COOR      COOH     O C CH CH2                                                C O
                                                                                       CH CH2

(4) Photocurable resin
    • UV-curing resins
    • Major ingradient:
          multifunctional monomer (MM) - reactive diluent
          reactive prepolymer (binder)
          photoinitiator (PI)
          solvent, additives, etc.

         MM                                                   binder
                               O CH2 CF2 CF3                                     O                   CH3                      O
                H2C C                    n
                                                                       CH2 C C O CH2CH2CH2           Si    O       CH2CH2CH2 O C C CH2
                          R     n=1~6
                                R = H or CH3                                 R                       CH3                          R
                  O                                   O
                                                                                                   R = H or CH3
                          O CH2 CF2 CH2 O
              H2C C                n                  C CH2
                      R   n=1~6                   R
                          R = H or CH3

                                    O                           PI                           O CH2CH3         CH3
                                        C CH2                            O       N             C          N
                              CH2                                                                             CH3
                                    R                                                          CH2
               HO CH2 C CH2 O                                           max= 313, 365 nm
                                              C CH2
                                    O                                                   Irgacure-369
                                        C CH2

                    General Properties of UV Curable Resins

                   Advantages                                       Problems

• low temperature cure
     - low thermal stress
• fast cure                                      • comparably high price
      - high throughput and wide applicability   • skin sensitive
• high solid content                             • not applicable to colored product
     - environmentally safe
                                                 • only applicable to planar surfaces
• easy operation
• energy saving

Components of UV Curable Resin

                                    Prepolymer (binder)
                   Main resin
                                    Monomer (multifunctional)



                                    Anti-misting agent
                                    Leveling agent
                                    Flow controller

Components of UV Curable Resin

       Binder Resin     Photoinitiator

                                                            Cured Polymer

      Multifunctional       Additives
      Monomer (MM)

             Increased glass transition temperature (Tg)
             Improved mechanical strength
             Becomes insoluble
             Better adhesion
             Selective Image: Patternable

Binder Resins (Reactive Oligomer)
    Generally produces crosslinking with multifunctional monomers with its acryl functional group
    Imparts final film properties (hardness, adhesion, electrical properties, chemical resistance)

Type of Reactive Oligomers
      Polyester-Acrylate
            good reactivity and anearobic
            most widely used
            low viscosity
            easy to handle
            good pigment dispersion

      Epoxy-Acrylate
           hard and flexible
           stable to oxygen
           good cure property
           widely used in ink, varnish, and adhesives
           usually mixed with other resins

      Urethane-Acrylate
            good cure property (even with O2)
            tough, hard and chemical resistant
            expensive
            slow cure rate
            good pigment wetting
            easily degraded by heat or light
            very high viscosity due to hydrogen bonding
                     Comparison of Reactive Oligomers

              Type                    Advantages                  Disadvantages

                           cheap
Polyester-Acrylate                                        low chemical resistance
                           balanced properties

                             good cure properties
                             flexible and durable        relativley expensive
                             good chemical resistance    high viscosity
                             balanced properties

                           good cure properties
                                                          high viscosity
Epoxy-Acrylate             good chemical resistance
                                                          poor weatherability
                           excellent adhesion

Cure Rate and Oligomer Characteristics

    Factors affecting cure rate
         molecular weight
         number of functional groups
         viscosity
         monomer fraction

                 slow                      Cure rate       fast

                 low                    Molecular weight   high

                 low                       Viscosity       high

                small                     Functionality    large

                 low                    Monomer fraction   high

Multifunctional Monomer
    Role
         reactive diluent
         diluent for oligomers imparting coating ability                              O
         polymerizes by itself and crosslinks with oligomers                               O CH2 CF2 CF3
                                                                             H2C C
                                                                                       R     n=1~6
    Requirements                                                                            R = H or CH3

         low viscosity                                                        O                                   O
         good properties after cure                                                   O CH2 CF2 CH2 O
         highly reactive (acrylate>methacrylate>vinyl)                    H2C C                                   C CH2
                                                                                   R   n=1~6                   R
         low toxicity and low smell                                                   R = H or CH3
         curable under O2 atmosphere
         good compatability with oligomers and initiators                                       O
         low volatility                                                                    O
         multifunctionality increases film properties                                     CH2
                                                                                                     C CH2
    Reactivity                                                             HO CH2 C CH2 O
                                                                                                           C CH2
         acryl group has higher reactivity than methacryl groups                                      R
         multifunctional monomer shows faster cure kinetics than                          CH2
           monofunctional monomers                                                          O
                                                                                                     C CH2
         ether type monomer shows faster cure rate
         cure is inhibited by O2
         to reduce inhibition by O2, monomers containing alkyl,
           unsaturated fatty acids, tetrahydrofurfuryl, and benzyl ether
           groups are helpful
                Monomer Functionality and Resin Properties

                                     Reactivity   Viscosity   Adhesion   Toxicity

      Monofunctional Monomer           slow         low         good      high
       Bifunctional Monomer              ↕           ↕            ↕        ↕
      Multifunctional Monomer           fast        high        poor      low

                 low m.w. monomer      slow         low         good      high
  for same
                         ↕               ↕           ↕            ↕        ↕
                 high m.w. monomer      fast        high        poor      low

                   Acryl Monomer        fast        low         poor      high
  for same
                                         ↕           ↕            ↕        ↕
                 Methacryl Monomer     slow         high        good      low

Types of Photoinitiator

                          PI Type                                                   PII Type

Intramolecular Photocleavage Type                          Intermolecular Hydrogen Abstraction Type
→ formation of radical by decomposition of triplet state   → formation of radicals by coupling of triplet state
    photoinitiator                                         photoinitiator and hydrogen donor molecule (amines) with
                                                           complex formation and abstracting hydrogen
Energy = 71~73 kcal/mol
→ enough for further reaction                              Energy = 69 kcal/mol
                                                           → marginal for further reaction

 <Merits >                                                 <Merits>
 ① not affected by solution viscosity                      ① no oxygen inhibition when enough amine is present

 <Demerits>                                                <Demerits>
 ① affected by oxygen                                      ① slow polymerization rate
                                                           ② yellowing of film
                                                           ③ sometimes low storage stability
                                                           ④ affected by viscosity
                                                                 (for high viscosity, slower rate due to slow diffusion)

1. Chloroacetophenone

                          Merits                 Demerits

           high reactivity           HCl produced by Cl radical
           good storage stability     → may have corrosion problem

2. Diethoxy Acetophenone (DEAP)


                  Norish II-type

                             Merits                                    Demerits
       stable than benzoin ether due to a-H
       higher efficiency and low concentration       slow reaction rate due to absence of a-
       no yellowing                                   phenyl group
       liquid - better compatibility with acrylic    bad smell
        polymers and monomers

3. Hydroxy Acetophenone
  (1) 1-phenyl-2-hydroxy-2-methyl propane-1-one (Darocure 1173, HMPP)

                               Merits                                       Demerits

                                                           the higher m.w. substituent, the slower
             high reactivity due to high photon
                                                            reaction rate in
              efficiency and reactive radical formation
             no yellowing

  (2) 1-hydroxy cyclrohexyl phenyl ketone (Irgacure 184, HCPK)

                no yellowing, thus can be used in clear coating
                compared to Irgacure-651, faster polymerization rate and shorter
                induction period under N2

4. α-Amino Acetophenone (Irgacure-907)

                           Merits                       Demerits

       low oxygen inhibition due to decomposition by
        Norrish I type and radical formation by H-
       when mixed with thioxanthanes (ITX), low
        yellowing and high sensitivity possible

5. Benzoin Ether

             Norrish I type

             different cure rate and pot life depending on R
             a-decomposition is possible because triplet state energy of benzyl ether (73 kcal/mol) is larger than
              a-dissociation energy (63 kcal/mol)

                              Merits                                                   Demerits

                                                                 unstable in the presence of monomer
                                                                 storage stability in the dark is poor resulting in
     no loss of photodecomposition activity
                                                                  gelation of monomer
     efficient due to high decomposition rate (> 1010sec-1)
                                                                 can be stabilized with substituting benzyl hydrogen
                                                                  with alkyl groups

6. Benzyl Dimethyl Ketal (Irgacure-651)

                                Merits                                                Demerits

          good reactivity and high cure rate because both of    yellowing problem
           radicals produced can initiate polymerization
          good storage stability
          applicable to various systems including styrene,
           unsaturated polyesters, acrylates

7. Benzophenone
                    PII type

                                electron transfer                      triplet exciplex

                               hydrogen transfer                           ketyl radical

                          Merits                                              Demerits

      hydrogen abstraction efficiency depends on R
                                                         slow cure rate due to low diffusion rate for high
      requires hydrogen donor such as alcohol (-OH),
                                                          viscosity solution
       ether (R-CH-OR), amine (R2CH-NR1), thiol (RSH)

8. Thioxanthone

                             Merits                           Demerits

       low coloration (cf. Michelars Ketone)
       efficient for thick or white coating containing
       strong absorption at near UV to visible
       efficient when mixed with PI type initiator such as
        α-Amino Ketone, IC-907

9. 2-ETAQ (2-EthylAnthraquinone)

                          Merits                        Demerits

        not affected by O2         can not be used alone
        good for MMA polymers      should be mixed with PI type initiators

Application of Photocurable Resins

   Coatings Industry
        acrylic- and epoxy-based resins
        flat surfaces (wood, metal, plastic)
        suitable for plastic hard coatings due to low temperature process (eg. mobile phone)

   Photoresists
        negative-type photoresist
               butyl rubber + diazide
               for posi-type PR, DNQ-ballast type dissolution inhibitors + novolac system is used

   LCD film materials
       color filter (C/F)
              acryl-based photopolymers + RGB pigments
       black matrix (Resin B/M)
              acryl-based photopolymers + carbon black
       overcoat (O/C)
              acryl-based photopolymers + RGB pigments

   Nanoimprinting
        S-FIL technology (세부과제명: 유기 박막의 나노 패터닝 공정 기술, LG Electronics Co.)
             Siloxane-based acrylate
             Si is used for etch barrier property for RIE

                                 국제 반도체 Roadmap(ITRS)

                                            Near-term Years                       Long-term Years

                                   1999      2001      2003      2005      2008         2011        2014

    1/2pitch          DRAM         180       150       120       100        70           50         35
      (nm)            MPU          230       180       145       115        80           55         40

  Generation        Introduc.       1G       2G         4G        8G         -          64G          -
   (DRAM)           Production     256M     (512M)      1G        2G         -          16G          -

DRAM Chip size      Introduc.      400       438       480       526       603          691         792
   (mm2)            Production     132       145       159       194       199          229         262

Frequency (MHz) On-chip, clock     1,250    1,767     2,490     3,500     6,000        10,000    13,500

 ILD Effective        DRAM          4.1      4.1      3.0-4.1   2.5-3.0   2.5-3.0      2.0-2.5   2.0-2.3
Dielectric const.     MPU         3.5-4.0   2.7-3.5   2.2-2.7   1.6-2.2    1.5          <1.5        <1.5

S-FIL (Step & Flash Imprint Lithography) Process

  Quartz template
  Release layer

  Transfer layer

  Substrate (Si)

                     Orient substrate and template         Photopolymer dispensed into capillary

                     UV illumination                       Separate template from substrate

                     Break-thru with F2 gas for residue    O2 RIE

                     Stripping of photopolymer layer       High resolution and high aspect ratio pattern

 S-FIL Process

 Step and Flash Imprint Lithography (S-FIL) is an attractive method for printing sub-100 nm geometries.

 Relative to other imprinting processes S-FIL has the advantage that the template is transparent(quartz), the
  imprint process is performed at low pressures and room temperature, which minimizes magnification and
  distortion errors.

 S-FIL is a next generation lithography technique in which etch barrier monomer is compressed between a
  lower plate consisting of substrate and transfer layer, and a patterned template above. The monomer is then
  polymerized by shining UV light through the quartz template, as shown in the figure above.

 Our task is to synthesize and characterize functional polydimethylsiloxane for use as etch barrier layer

 A successful etch barrier requires several distinct characteristics :
   1) the etch barrier fluid must wet the template well to facilitate filling the topography
   2) it must release from the template readily after exposure
   3) it must polymerize rapidly
   4) it can resist the O2 reactive ion etch (RIE)

Requirements of Photopolymer (Etch Barrier)

      Adhesion
            good adhesion to transfer layer
            low surface energy
      Wettability and viscosity - filling in the capillary
            low surface energy and low viscosity for fast capillary filling
            model by Washburn equation
            viscosity is proportional to oligomer concentration and molecular weight
      Photopolymerization kinetics
            should be fast for high productivity                                       PDMS + Acryl
            rate is also proportional to oligomer concentration and molecular weight
            depending on the monomer structure and polymerization conditions              Based
      Mechanical Strength                                                              Photopolymer
            depending on the degree of polymerization                                    Systems!
      Shrinkage
            generally unignorable for acrylate systems
      Etch selectivity
            High Si contents
            Based on PDMS + photoacrylate system
      Release Property
            high surface energy
            should be traded off with wettability

Functions of Components in Photopolymer System

      Acrylate monomers
            low viscosity
            selections from various monomers for good adhesion and mechanical properties
            fast photopolymerization kinetics
            cheap
      PDMS monomers
            high etch resistance (with high Si content)
            inclusion by photo-crosslinking
      Photoinitiator
            produces radical by UV for initiation of polymerization
            sensitivity of UV wavelength varies with structure
            affecting kinetics most significantly
      Multi-finctional Monomers (if required)
            imparts high mechanical properties
      Oligomer (if required)
            for faster curing
            increases viscosity
      Additives (if required)
            release agent - controls release propery
            adhesion promoter - increases adhesion
            levelling or planarization agents - improves thin film quality
            anti-foaming agent or defoamer - improves thin film quality

Change of Conversion with Different Exposure Time

                                                                        Exposure time(s)   Conversion(%)

                                                                                0                 0
                                                                               30               71.5
  Conversion (%)

                   0.6                                                         60               77.7

                   0.4                                                         120              81.1

                                                                               240              91.7
                                                                               360              97.9
                   0.0                                                         480              1.00

                         0       200      400       600    800   1000          720              98.0
                                       Exposure Time (s)                       960              98.5

                             Monomer Photopolymerization Rates

FT-IR Spectra with Different Exposure Time

                                                      0s                                             0s
                                                      30s                                            30s
                                                      60s                                            60s
                                                      120s                                           120s
                                                      240s                                           240s
                                                      360s                                           360s
                                                      480s                                           480s
                                                      720s                                           720s
                                                      960s                                           960s

      3000   2500     2000   1500        1000   500          0        1640             1620              1600
                    wavenumber(cm )
                                    -1                                       wavenumber(cm )

                       -CH3 peak                                 -C=C- peak decrease at 1634 cm-1 with
                       -C=C- peak (1634 cm-1)                        respect to the irradiation time

Surface Hardness
measured by Shore A & D hardness tester





                         75                                                     ShoreA

                              0         100       200       300      400       500       600
                                                   Exposure Time (s)
                                   Sample was measured after irradiation of 30, 60, 120, 240,
                                    360, 480, and 600 sec with ca. 120 mW/cm2, respectively

Contact Angle of Photopolymer
with Different Composition of F-based Surfactant

                                 0 wt.%            0.5 wt.%   1.0 wt.%   1.5 wt.%

C3H8O3-droplet on surface

H2O-droplet on surface

CH2I2-droplet on surface

Surface Energy of Photopolymer
with Different Composition of F-based Surfactant

   From the harmonic-mean method of Wu, the surface energies can be calculated as following formula:
            gl(1+cos)=4[(gld gsd)∕(gld+ gsd)+(glp gsp)∕(glp+ gsp)] , gs= gsd+ gsp
            H2O:      gld=22.1mN∕m glp=50.7mN∕m
            CH2I2:     gld=44.1mN∕m glp=6.7mN∕m
            C3H8O3 : gld=34.0mN∕m glp=30.0mN∕m

                                      Contact angles                            Contact angles   Surface energies
                                                          Contact angles
          Sample#       F (wt%)        with C3H8O3                               with CH2I2
                                                         with H2O (degree)                           (mN/m)
                                         (degree)                                 (degree)
              1            0.0            59.007               53.930                37.252           58.43

              2            0.5            74.255               68.948                50.323           54.11

              3            1.0            74.657               74.375                59.123            44.2

              4            1.5            82.159               80.481                68.784            39.3

           Measured by EEO300 contact analyzer

Synthesis of Siloxane Monomer
tetramethyldisiloxane-1,3-bismethylmethacrylate (Si2MMA)

                                                                                   b               d
            CH3   CH3                    CH3                                   a   CH3     c           CH3   CH3       CH3
    Cl   CH2 Si O Si CH2 Cl       +   CH2 C C OH                               CH2 C C O CH2 Si O Si CH2 O C C CH2
                                                          xylene, reflux
            CH3   CH3                        O                                         O               CH3   CH3   O

                                                                                               b.p.: 127o/3mmHg
                                                                                                   yield: 45%


                                                      c                    b

                              6         5         4            3           2           1           0
                                            Chemical Shift (ppm, CDCl3)

                                               1H-NMR Spectrum of Si2MMA
What-to-Do List

        Synthesis of siloxane monomers
             various acrylates and methacrylates containing dimethylsiloxane
             monomers and oligomers to be purchased

        Photopolymer resin formulation
             various acrylate and methacrylate monomers - MMA, MA, AA, EA, BA, HEMA, etc.
             various photoinitiators
             various siloxane monomers and oligomers
             additives - planarization, release, anti-foaming, etc.
             photocuring conditions - time, temperature, exposure dose, film thickness, etc.

        Characterization and evaluation of photopolymer
             chemical - cure kinetics, viscosity, etch selectivity, etc.
             physical and mechanical - adhesion, hardness, tensile, surface energy, shrinkage etc.

        Modification and improvement of photopolymer characteristics
        Application to real systems and feed-back

Researches at SPLEO
        Photosensitive Polyimides (KRF)
             Synthesis and characterization of PIAE containing photocleavable 2-nitrobenzyl ester
             Positive patterning with 10 mm resolution
        New Fabrication Method of Polymer Waveguide (MOCIE)
             Photosensitive polyimides containing cinnamyl and chalcone groups
             Photo-induced refractive index change
             Simple fabrication process without etching process
             Zero birefringence (Dn < 0.00002)
             Low-loss (< 0.3@1.3mm)
        Polyimide Nanofoam from Grafted PI (KOSEF)
             Homogeneous distribution of 20 ~ 40 nm pore in PI matrix
             Low-k material and membranes
        Polymer Electrolyte Membranes for m-Fuel Cell (ERC)
             Proton exchange membrane based on PI
        Polymer Materials for TFT-LCD (SPLEO)
             Resin black matrix (B/M), overcoat (O/C), alignment layer (A/L)
            Photoalignment materials based on PI
        Other Syntheses for Electronic and Optical Applications
            Photochromic polymers
            Anionic polymerization
            Conducting polymers based on PAn, and PPy


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