Date Visited: October 8, 1991

Report Author: W. Doane

ATTENDEES

JTEC:

Credelle
Doane
Slusarczuk
Tannas

HOST:

Dr. Haruyoshi Takatsu

Toru Fujisawa

Masao Aizawa

Hiroshi Ogawa

Sadao Takehara

Maeda Ryugo

Presentation by Dr. Takatsu (See attached outline "Liquid Crystal Display with High Information Content")

• LC research started in 1963.
• They now have a joint venture with Hoffman LaRoche called RODIC. This company is the supplier of LC materials.
• STN materials--Important feature is voltage: hold ratio versus UV exposure and temperature.
• Typical response time is 200 msec.
• Important to have high pre-tilt angle and stable angle ~5-10 degrees.

Have studied molecular anchoring for different compounds on same surface.
Comment that higher tilt angle usually means weaker W₀.
Can get normal anchoring for some materials, i.e.,

One comment and overhead by Takatsu indicated that they mix high pre-tilt material ( alignment) with others of low tilt to increase the pre-tilt angle. Alignment layer materials are obtained from JSR and Nissan Chem. They have a cooperative research arrangement with Nissan Chem involving alignment layers; they purchase alignment layers from Nissan Chem and JSR.

• Image sticking--for three possible causes of image sticking. They found a material that avoids image sticking but don't understand it.
• Uniformity of display. Controlled by cell thickness and stability of the pre-tilt angle. They believe that the "rainbow" effect observed upon filling is due to alignment layer (but may be due to material separation).

AM TN LCDs

not high enough. Need pure materials, high ~10(superscript 13)-10(superscript 14)cm. Use fluorinated compounds to reduce ion solubility. These materials give ~8. One problem is they see field induced disclinations around electrodes. They have a ternary mixture that gives V(subscript 90) = 1.5 V at 90 degrees centigrade. It is difficult to control slope of a transmission curve.

MIM LCDs

Second minima are used to give high contrast. Fluorinated tolans are used to give high . CC (useful for PDLCs as well). Requirements for MIM and PDLC are about the same.

FLCs

There are problems with temperature range, filling and response addressing time. Spacers on substrate (1.5 plus/minus 0.05 microns) are formed from resist.

Tilt angle of S(subscript C) can decrease with time to reduce contrast.

They work with a nonprofit group (National Research Lab, Sagamichuhu Central Research Lab) for synthesis and research of chiral additives (dopants).

Their material has two branched chiral groups and they use dopants to reduce pitch.

For TV the response time is ~ 20 micro sec (1000 lines, line-at-a-time addressing). Fabrication and surface stabilization are problems.

Dainippon Ink (DIC) makes FLC material (see attachment). The material needs to be cooled slowly from S(subscript A) to maintain surface alignment.

They don't see any application for anti ferroelectric compounds.

ECB-LCDs

Cell thickness problems--there are not many choices of materials, reducing effort on ECB.

Their comment on Stanley's prototype: visibility poor and slow response time; small after-image that lasts ~2 seconds; transmission efficiency too poor for laptop computers.

VIDEO AND LUNCH

DIC does not make color filters, but is researching dyes and pigments in a joint project with the display industry.

Competition:

• PDLC--Asahi, NEG
• LCs--Chisso Petrochemicals

200 people are at Sukera, expanding to 400-600. Centralizing meetings are held twice a year.

PDLC

DIC interacts with many companies in this area; this is a strong component of the company. They cooperate with 24 companies on PDLC materials.

They have a prototype CdSe AM PDLC display (we did not see it working). They are working with Ghent on CdSe.

Their PDLC material contains approx. 80% LC, 20% polymer. Their PDLC characteristics are obtained with d = 8 microns and the use of fluorinated LCs V(subscript 90 ~) 4V. Their material needs edge seal--large "14" shutter showed fill hole on corner. Polymer material is filled, then cured. They feel PDLC is good for both direct view and projection.

GENERAL QUESTIONS BY TEAM

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They are doing little or no work on polymer LCs.

When volume of LC gets >/approx. 1 ton they will have EPA problems and need special permission from Japanese government. They are studying LC polymers for high-strength fibers only and studying FLC for opto-electronics and printers.

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Liquid Crystal Displays with High Information Contents

(adapted from an origianl handout provided by Dainippon Ink & Chemical, Inc.

Haruyoshi TAKATSU
Dainippon Ink & Chemicals

1. STN-LCDs

• Contrast
  • Large K33/ K11 (bend/splay)
  • Small
  • Large twist angle 220 ~ 260 degrees

    Alkenyls
    e.g.

• Response
  • Cell thickness d 4 to 6 microns
  • Low viscosity
  • Small twist angle
  • Small K33/ K11
    • Phenyl bicyclohexanes e.g.
    • Pyrimidines
      
• Wide domain-free d/p - region
  • High pretilt angle 5 to 10 degrees
  • Stable pretilt angle
    HT (High Tilt) series LCs a certain group

    
    Concentration in PC11 Mixture (%)

• Image sticking
  Polarity of alignment layer and LCs

  Composition of LCs, functional groups of LCs
• Uniformity of display
  • Homogeneity of the cell thickness
  • Stable pretilt angle
  • Chromato-like-phenomena at filling
  • Experimental selection of components

2. Active-matrix-addressed TN-LCDs

2.1 TFT-TN-LCDs

• Flicker of Display
  • High voltage holding ratio >98%
  • High resistivity 10(superscript 13) to 10(superscript 14) cm
• Stability for heat and light
  Fluorinated LCs
  
• Wide viewing angle
  • = 0.4 ~ 0.5 micron d = 4 ~ 6 microns
  • low 0.08 ~ 0.1
• Reverse pretilt
  High pretilt 2 ~ 3 degrees
• Low driving voltage

2.2 MIM-TN-LCDs

• Similar requirements to TFT
• Contrast
  • = 0.9 ~ 1.0 microns d = 5 ~ 6 microns
  • High 0.15 ~ 0.18
    Fluorinated Tolans

3. FLC Displays

• Cell spacing ~2 microns
• Bistability at operating state
• Response time
  • Slow for making image
  • Pixel ~ 50 micro sec -------> 10 ~ 20 micro sec
    
    

4. ECB-LCDs

• Pretilt angle 0.5 ~ 1.0 degrees
• Response thin cell ~5 microns
• Contrast cell spacing
  large ; large ; negative ; large K33/K11
  
  

5. PDLC (Active-matrix-addressed)

NCAP PDLC PN-LCD Ch/P gel

• Contrast
• Driving voltage
• Voltage holding ratio
• Temperature dependence of electro-optical properties

  
  

REFERENCES

1. Handout sheet
2. Brochure on DIC Central Research Laboratories
3. Annual Report, 1990, Dainippon Ink and Chemicals, Incorporated