2282
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`IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 46, NO. 12, DECEMBER 1999
`
`Low-Temperature Polysilicon Thin-Film
`Transistor Driving with Integrated Driver for
`High-Resolution Light Emitting Polymer Display
`
`Mutsumi Kimura, Ichio Yudasaka, Sadao Kanbe, Hidekazu Kobayashi, Hiroshi Kiguchi,
`Shun-ichi Seki, Satoru Miyashita, Tatsuya Shimoda, Tokuro Ozawa, Kiyofumi Kitawada,
`Takashi Nakazawa, Wakao Miyazawa, and Hiroyuki Ohshima
`
`Abstract—A high-resolution low-temperature polysilicon thin-
`film transistor driven light emitting polymer display (LT p-Si TFT
`LEPD) with integrated drivers has been developed. We adopted
`conductance control of the TFT and optimized design and voltage
`in order to achieve good gray scale and simple pixel circuit. A
`p-channel TFT is used in order to guarantee reliability in dc
`bias. An inter-layer reduces parasitic capacitance of bus lines.
`Because of the combination of the LT p-Si TFT and LEP, the
`display is thin, compact, and lightweight, as well as having low
`power consumption, wide viewing angle, and fast response.
`
`I. INTRODUCTION
`
`method cannot drive the LEP, either [9], because the high-
`resolution display demands high voltage in the short scanning
`period in order to achieve the required average brightness, and
`this high voltage results in a lower power efficiency of the light
`emitting. Accordingly, instead of the static or passive matrix
`driving method, an active matrix driving method is better for
`high-resolution display as the pixels may be driven close to
`their best power efficiency point.
`Since the LEPD is not a cell structure, i.e., liquid layer
`and two sandwiching substrates, it does not need the second
`substrate. Moreover, the LEPD does not need a backlight, light
`guide, polarizer, diffuser, etc., which are used in the LCD.
`Therefore, the display consists of one substrate, peripheral
`drivers, and many contacts between them. The next target is to
`eliminate the peripheral drivers and contacts. If the peripheral
`drivers are replaced by monolithic drivers integrated on the
`substrate, not only can the peripheral drivers be eliminated,
`but the number of contacts can also be decreased. The display
`is dramatically reduced to only one substrate. As a result, the
`display will be exceedingly thin, compact, lightweight, and
`inexpensive.
`Because of the advantage of the wide viewing angle, the
`LEPD is suitable for direct view applications. Most applica-
`tions such as these are large size displays. In the case of the
`current LEPD structure, since the polymers and cathode metal
`are serially stacked on the substrate and light emits through
`the substrate, the substrate must be transparent. Therefore, for
`the device to drive the LEPD, the capability of fabrication on
`a large transparent, i.e., glass or plastic, substrate is needed.
`In conclusion, in order to drive the high-resolution LEPD,
`the active matrix device is needed and it must have enough
`performance to compose integrated drivers and have the ca-
`pability to be fabricated on the large transparent substrate,
`simultaneously. Only the LT p-Si TFT can satisfy these
`demands.
`Therefore, the objective of our development in this paper
`is to confirm how the LT p-Si TFT is suitable to drive
`the high-resolution LEPD. A high-resolution LT p-Si TFT
`LEPD with integrated drivers is designed, fabricated, and
`evaluated [10]. We adopted conductance control of the TFT
`and optimized design and voltage in order to achieve good
`gray scale and simple pixel circuit. A p-channel TFT is used in
`order to guarantee reliability in dc bias. An inter-layer reduces
`0018–9383/99$10.00 ª
`
`LOW-TEMPERATURE polysilicon thin-film transistors
`
`(LT p-Si TFT’s) have been utilized to drive liquid
`crystal displays (LCD’s) [1]–[3]. There are many candidates
`for active matrix devices, i.e., single-crystal Si MOS FET,
`amorphous Si TFT, high-temperature p-Si TFT, LT p-Si TFT,
`other semiconductor devices, etc. Among the candidates, only
`the LT p-Si TFT has performance high enough to compose
`integrated driver circuits and the capability of being fabricated
`on a large transparent substrate simultaneously. Additionally,
`it has already been reported that the LT p-Si TFT can also be
`fabricated on a plastic substrate [4]. These advantages of the
`LT p-Si TFT allow the present great successes to come true in
`LCD’s, not only in research and development, but also in the
`market. However, the LT p-Si TFT is not only for LCD’s. The
`LT p-Si TFT’s have great potential even for other displays
`which have integrated driver circuits and are large sizes [5].
`On the other hand, light emitting polymers (LEP’s) [6]–[8]
`promise to achieve thin, compact, lightweight, and inexpen-
`sive displays. Moreover,
`the display can have low power
`consumption, wide viewing angle, and fast response. Until
`now, for LEP displays (LEPD’s), mainly static and passive
`matrix driving methods have been utilized. However, for high-
`resolution displays consisting of many pixels, needless to say,
`the static method cannot drive the LEP. The passive matrix
`
`Manuscript received October 1, 1998; revised June 1, 1999. The review of
`this paper was arranged by Editor J. Hynecek.
`M. Kimura,
`I. Yudasaka, S. Kanbe, H. Kobayashi, H. Kiguchi, S.
`Seki, S. Miyashita, and T. Shimoda are with Base Technology Research
`Center, Seiko Epson Corporation, Owa Suwa 392-8502, Japan (e-mail:
`kimura.mutsumi@exc.epson.co.jp).
`T. Ozawa, K. Kitawada, T. Nakazawa, W. Miyazawa, and H. Ohshima are
`with L Project, Seiko Epson Corporation, Owa Suwa 392-8502, Japan.
`Publisher Item Identifier S 0018-9383(99)09015-2.
`
`1999 IEEE
`
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`KIMURA et al.: HIGH-RESOLUTION LIGHT EMITTING POLYMER DISPLAY
`
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`
`Fig. 1. Cross-sectional view of the LT p-Si TFT LEPD. LT p-Si TFT’s are
`fabricated the same as the TFT-LCD. Light comes through the glass substrate.
`Since the TFT-LEPD needs only some thin films on one substrate, very thin,
`compact, lightweight, and inexpensive displays can be achieved. The function
`of the inter-layer is to distance the cathode and to reduce parasitic capacitance
`of bus lines.
`
`parasitic capacitance of bus lines. The display is thin, compact,
`lightweight, low power consumption, wide viewing angle, and
`fast response.
`
`II. STRUCTURE
`A cross-sectional view of the TFT-LEPD is shown in
`Fig. 1. First, on a glass substrate, LT p-Si TFT’s, bus lines,
`and pixel electrode are fabricated the same as they are in
`the TFT-LCD [1], [2]. A 50-nm a-Si is formed by LPCVD
`of Si H at 425 C. It
`is crystallized by multiple irradi-
`ation of 245 mJ/cm KrF excimer laser. Phosphorous ions
`for n-channel TFT’s and boron ions for p-channel TFT’s
`are implemented with a dose of the 10
`cm order at an
`energy of several ten keV. These impurities are activated at
`300 C–400 C for 4 h. The TFT characteristics are shown
`in Fig. 2. Mobility for n-channel TFT and p-channel TFT is
`120 cm /V s and 40 cm /V s, respectively. In the case of
`the LCD, the ITO pixel electrode is used in order to apply
`voltage to the liquid crystal. On the other hand, in the case
`of the LEPD, the ITO pixel electrode is used as an anode in
`order to supply current to the LEP.
`Next, an adhesive layer,
`inter-layer are fabricated. The
`function of the SiO adhesion layer is to improve adhesion
`between ITO and polyimide. The function of the polyimide
`inter-layer will be written in the following section. After the
`fabrication of the both layers, O plasma surface operation is
`done in order to improve the wettability of the surface of the
`polyimide and ITO.
`After that, LEP layer consisting of a conductive polymer and
`a light emission layer, and a cathode metal are fabricated in
`succession [8]. First, polyethylene dioxythiophene/polystylene
`sulphonate (PEDOT/PSS) are dispersed in water and spin-
`coated. Since the surface of the substrate is wettable by O
`plasma operation mentioned above, the spin-coated layer can
`be very uniform. Then, the spin-coated layer is baked in order
`to remove solvent and make a thin film. Next, precursor of poly
`(p-phenylene vinylene) (PPV) is deposited by spin-coating
`with a water/methanol mixture as solvent. Thermal conversion
`forms the precursor to the conjugated polymer, PPV. The
`
`(a)
`
`(b)
`
`Fig. 2. TFT characteristics. (a) Transfer characteristics and (b) output char-
`acteristics are shown. Mobility for n- and p-channel TFT is 120 cm2/V s
`and 40 cm2/V s, respectively. A TFT model is extracted from these char-
`acteristics.
`
`PEDOT/PSS and PPV are used as a conductive polymer and
`a light emission layer, respectively. After that, the aluminum
`with lithium is sputtered and used as a cathode for the LEPD.
`Finally, a wire to supply current to the cathode is attached
`by pasting. The whole cathode is encapsulated by epoxy resin
`in order to avoid the degradation of the LEP and the cathode.
`A flexible tape is heat-sealed to the contacts on the substrate.
`In the case of the TFT-LCD, an alignment layer, liquid
`crystal, and opposite substrate are needed on the TFT array
`substrate. On the opposite substrate, a black matrix, align-
`ment layer, and opposite electrode are necessary. Moreover,
`a backlight, light guide, polarizer, diffuser, and other optical
`parts must be attached. On the other hand, in the case of
`the TFT-LEPD, whose structure is mentioned above, only
`some thin films on one substrate are needed. Therefore, very
`thin, compact, lightweight, and inexpensive displays can be
`achieved.
`
`III. NOVEL TECHNOLOGIES
`
`A. Conductance Control
`We utilized conductance dependence of the driving TFT
`in order to control gray scale. A pixel equivalent circuit is
`shown in Fig. 3. A pixel is composed of two kinds of TFT,
`i.e., a switching and driving TFT, a storage capacitor, and
`an LEP diode. Actually, the switching TFT consists of three
`TFT’s connected in series in order to decrease off current and
`reduce degradation caused by high electric fields around the
`drain edges of their channels [11]. The driving TFT consists of
`three TFT’s connected in parallel in order to be cooled easily
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`IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 46, NO. 12, DECEMBER 1999
`
`Fig. 3. Pixel circuit of the TFT-LEPD. A pixel is composed of a switching
`and driving TFT, a storage capacitor, and an LEP diode. Conductance
`dependence of the driving TFT is used in order to control gray scale. By
`this method, the pixel circuit can be simple.
`
`and reduce degradation caused by self-heating [12], [13]. The
`scan and signal drivers are integrated around the image area
`on the substrate and their workings are the same as those used
`in TFT-LCD’s.
`i.e., for transferring each
`The mechanism for scanning,
`signal voltage to the corresponding storage capacitor, is similar
`to that used in TFT-LCD’s. The only difference is that the
`signal voltage stored in the capacitor does not have to be
`ac, but can be dc, because the LEP diode is driven by dc
`current and the driving TFT should control the LEP diode by
`dc voltage. Therefore, it is possible to reduce the amplitude of
`the signal voltage and scan voltage.
`The signal voltage stored in the capacitor is also applied to
`the gate terminal of the driving TFT. The gate voltage controls
`conductance of the driving TFT and anode voltage depends on
`the relationship between the resistance of the driving TFT and
`LEP diode. That is, by varying signal voltage, current through
`the LEP from the supply line via the anode to the cathode and
`light emission can be modulated.
`In the bright state, since the resistance of the driving TFT
`is negligible compared to that of the LEP diode, there is
`little voltage drop and wasted power consumption in the
`driving TFT. The power reduction in the bright state is very
`meaningful because the current is larger than other states.
`There are only two TFT’s in a pixel. This structure is
`conventional for current consuming devices, such as the LEP
`diode, and there are some disadvantages, for example, nonuni-
`formity caused by variation of the characteristic between the
`driving TFT’s. However, we chose this structure because the
`simplicity is very practical when we avoid the yield rate
`problem in mass production.
`Next, the design and voltage were optimized. The driving
`TFT cannot work in the saturation region for all the gate
`voltages even if its design parameter is varied. There are two
`reasons. The first reason is low drain voltage. In order to
`reduce the power consumed in the driving TFT in the bright
`state, the resistance of the driving TFT should be negligible
`
`Fig. 4. Operation point analysis of the driving TFT and LEP diode. Hori-
`zontal and vertical axis are voltage of the terminal between the driving TFT
`and the LEP diode and current through the driving TFT and the LEP diode.
`The characteristics of the driving TFT corresponding to each gate voltage and
`the characteristic of the LEP diode are overlapped. The cross points of the
`characteristics mean operational points of the pixel equivalent circuit.
`
`compared to the resistance of the LEP diode. This means that
`the voltage drop between the drain and the source terminal, i.e.,
`drain voltage, is rather small. In addition, since the efficiency
`of the light emission from the LEP becomes very high and
`its threshold voltage becomes very low, recently, only about
`5 V must be applied to the LEP diode for sufficient light
`emission. The second reason is that, as shown in Fig. 2, the
`LT p-Si TFT has no saturation region defined clearly, i.e., a
`flat characteristic which is independent of the drain voltage,
`because of many defects in the channel [14].
`If a TFT worked in the saturation region, it would be easy to
`calculate the current because the current would mainly depend
`only on the gate voltage. However, since the TFT works in
`the nonsaturation region, it is very difficult to calculate the
`current by analytical calculation. The reason is as follows.
`The current depends on not only the gate voltage but also the
`drain voltage. The drain voltage is decided by the relationship
`of the resistance between the driving TFT and the LEP diode.
`This relationship is not decided until the current is decided
`because both the TFT and the LEP diode are nonlinear electric
`devices for applied voltages. Because of such a complicated
`mechanism, operational point analysis or circuit simulation by
`a computer is needed to perform the design.
`Fig. 4 shows operational point analysis of the pixel equiva-
`lent circuit to achieve gray scale. The horizontal axis is voltage
`of the terminal between the driving TFT and the LEP diode,
`which is drain voltage of the driving TFT and anode voltage
`of the LEP diode, simultaneously. The vertical axis is drain
`current of the driving TFT, which is same as the current
`through the LEP diode. The characteristics of the driving
`TFT corresponding to each gate voltage, which is the signal
`voltage stored in the storage capacitor, are overlapped. The
`characteristic of the LEP diode is also overlapped. The cross
`points of the characteristics of the driving TFT and the LEP
`diode mean operational points of the pixel equivalent circuit
`for each gate voltage.
`Circuit simulation with a TFT and LEP model [15] was
`done in order to design the driving TFT and LEP diode
`circuit including gray scale. These models are extracted from
`the measured data. Fig. 5 shows a simulated current–voltage
`
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`KIMURA et al.: HIGH-RESOLUTION LIGHT EMITTING POLYMER DISPLAY
`
`2285
`
`Fig. 5. Simulated current–voltage (I V ) characteristic of the driving TFT
`and LEP diode. Horizontal and vertical axis are signal voltage and current
`through the LEP diode, respectively. Gray scale can be acquired by optimizing
`all the design parameters. Signal voltage can be adjusted within a range of
`less than 5 V.
`
`TABLE I
`SPECIFICATIONS AND DESIGN PARAMETERS OF THE TFT-LEPD. DESIGN
`PARAMETERS WERE OPTIMIZED BY CIRCUIT SIMULATIONS. A HIGH-RESOLUTION
`LT p-Si TFT LEPD WITH INTEGRATED DRIVERS HAS BEEN FABRICATED
`
`(a)
`
`(b)
`
`) characteristic of the equivalent circuit consisting of
`(
`the driving TFT and LEP diode. The horizontal axis is signal
`voltage, which is applied to the gate terminal of the driving
`TFT. The vertical axis is current through the driving TFT and
`LEP diode. Gray scale from the bright state via the halftone
`state to the dark state can be acquired.
`By such analyses and simulations, for the given area of the
`LEP, the design of the driving TFT, i.e., width and length, is
`optimized. Signal voltage can be adjusted within a range of
`less than 5 V, which may achieve very low power consumed
`in video signal circuit in the peripheral controller. After that,
`the entire design of the TFT-LEPD, i.e., the switching TFT,
`storage capacitor, etc., is decided. All the optimized design
`parameters and specifications of the TFT-LEPD are shown in
`Table I.
`
`B. P-Channel TFT for Reliability in DC
`In order to ensure the reliability of the driving TFT even
`when dc voltage is applied, a p-channel TFT is used. Fig. 6
`shows a comparison of the reliability by measurement between
`an n-channel and p-channel TFT. Initial transfer characteristics
`and those after dc stress, i.e., gate voltage 20 V, drain voltage
`0 V, temperature 70 C, bias time 600 h, are overlaid. In this
`stress condition, gate voltage and temperature is higher than
`real working conditions in the TFT-LEPD. This was done to
`accelerate testing. It is clear that the p-channel TFT is much
`more reliable in dc bias than the n-channel TFT. The reason
`
`Fig. 6. Comparison of reliability between an (a) n-channel and (b) p-channel
`TFT. Initial transfer characteristics and those after dc stress, i.e., Vg 20 V,
`Vd 0 V, temperature 70 C, bias time 600 h, are overlaid. The TFT’s have
`W/L of 100/12 m. It is clear that the p-channel TFT is much more reliable
`in dc bias. Thus, a p-channel TFT is used for the driving TFT.
`
`is not understandable now but we will research this important
`phenomena from now on.
`
`C. Inter-Layer to Reduce Parasitic Capacitance
`As we can see in Fig. 1, an inter-layer made of insulator
`covers all areas except for the light emission area in the anode.
`The function of the inter-layer is to exist on the signal lines,
`to distance the cathode, and to reduce parasitic capacitance of
`the signal lines. The thickness of the inter-layer was decided
`to be 1.0 m, while that of SiO adhesive layer, which exists
`between the inter-layer and the anode, is 0.1 m. From these
`values, capacitance between the signal line and cathode is
`3.1 pF. By adding other capacitance, total capacitance of the
`signal line is 10.5 pF. Resistance of the signal line itself is
`330
`and the equivalent resistance of an LT p-Si TFT analog
`switch on the edge of the signal line is on the order of 1 k
`at most. Therefore, the time constant of the signal line is on
`the order of 10 ns. This panel is designed for the point-at-time
`driving scheme [16], which means that during application of
`scan voltage, each signal voltage is applied sequentially. The
`selecting time for one signal line is 240 ns. Since the time
`constant is enough smaller than the selecting time, correct
`signal can be applied to the signal line.
`
`D. Others
`the conductive layer and the light
`i.e.,
`The LEP layer,
`emitting layer, is not patterned. However, crosstalk of light
`emission between pixels does not occur. The reason is as
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`IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 46, NO. 12, DECEMBER 1999
`
`Fig. 7. View overlooking the TFT-LEPD. Because of no backlight, light
`guide, polarizer, diffuser, peripheral drivers, etc., the TFT-LEPD can be
`lightweight, thin, and compact.
`
`Fig. 9. Display image of the TFT-LEPD. Green monochrome display image
`is acquired. Neither nonuniformity nor crosstalk occurs.
`
`Fig. 8. Photographs of pixels and electroluminescence from the pixels. Since
`the light emission area ratio is at most 12%, reflection from cathode metal
`is reduced and contrast can be improved if the rest of the pixel is covered
`with a light shield layer.
`
`Fig. 10. Measured and simulated gray scale. Brightness is normalized by the
`maximum value. The measured gray scale is similar to the simulated one. It
`is found that good gray scale from the bright state via the halftone state to
`the dark state can be acquired.
`
`follows. Since the electric resistivity of the conductive layer
`is about 1 k
`cm and its thickness is very thin (10 nm), its
`sheet resistance is
`/sq and its resistance between
`pixels is
`. The resistance is much higher than the
`LEP diode resistance, the order of
`. Moreover, the
`electric resistivity of the light emitting layer between pixels
`is still higher than that of the conductive layer. As a result,
`the LEP diode can be supposed to be electrically separated
`between each pixel.
`
`IV. RESULTS
`A high-resolution LT p-Si TFT LEPD with a scan and signal
`integrated driver has been fabricated. The specifications have
`already been shown in Table I. A view overlooking the TFT-
`LEPD is shown in Fig. 7. No backlight, light guide, polarizer,
`diffuser, and peripheral drivers are needed. The number of
`contacts between the peripheral controller and the panel is
`reduced to only 27. Twenty-six of the contacts are through
`a flexible tape and one contact is through a wire pasted on
`the cathode. Consequently, the TFT-LEPD can be exceedingly
`lightweight, thin, and compact, as shown in Table I. Here, the
`second glass substrate is used only for encapsulation of the
`LEP and supporter, which can be eliminated easily in the near
`future.
`
`Photographs of pixels and electroluminescence from the
`pixels are shown in Fig. 8. The light emission area ratio, i.e.,
`the ratio between light emission area and whole area in a pixel,
`is at most 12%. In spite of the small ratio, there is no serious
`problem because all light comes from the light emission area,
`no light loss occurs, and power is not wasted. On the contrary,
`the small ratio can reduce reflection from cathode metal. If
`the rest of the pixel is covered with a light shield layer, all
`reflection from the display can be reduced and contrast can
`be improved.
`A display image of the TFT-LEPD is shown in Fig. 9. Here,
`a green monochrome display is acquired. Neither nonunifor-
`mity caused by the parasitic capacitance of the bus lines nor
`crosstalk between pixels occurs. Measured and simulated gray
`scale is shown in Fig. 10. Here, brightness is normalized by
`the maximum value. The measured gray scale is similar to the
`simulated one. It is found that good gray scale from the bright
`state via the halftone state to the dark state can be acquired.
`The achieved power consumption with the voltage and
`current are listed in Table II. The power consumed in the
`integrated driver is 20 mW. In order to achieve brightness
`of 100 Cd/m from the whole panel, only 5 V is needed to
`be applied to the driving TFT and LEP, which leads to less
`than the current of 20 mA through the LEP and the power
`consumption of 100 mW. Therefore, total power consumption
`of the TFT-OELD is 120 mW at most. When the displayed
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`TABLE II
`VOLTAGE, CURRENT AND POWER OF THE TFT-LEPD. TOTAL
`POWER CONSUMPTION OF THE TFT-OELD IS COMPARABLE WITH
`THAT OF THE TFT-LCD. CURRENT DENSITY OF THE LEP IS
`18 mA/cm2 AND EFFICIENCY OF THE LEP IS ABOUT 3 Lm/W
`
`image is darker or smaller, the power consumption is still less.
`It is comparable with or smaller than that of the TFT-LCD.
`
`V. CONCLUSION
`A high-resolution LT p-Si TFT LEPD with a complete set
`of the integrated drivers has been developed and published for
`the first time in the world. We adopted conductance control of
`the TFT and optimized design and voltage in order to achieve
`good gray scale and simple pixel circuit. A p-channel TFT
`is used in order to guarantee reliability in dc bias. An inter-
`layer reduces parasitic capacitance of bus lines, and so on.
`Because of the combination of the LT p-Si TFT and LEP, the
`display is thin, compact and light weight. Additionally, the
`display has low power consumption, wide viewing angle, and
`fast response, which are achieved only from the nature of the
`LEP. The image is uniform and crosstalk does not occur.
`The fabrication processes of the TFT are the same as those
`for the LCD except for some additions and LEP processes.
`Therefore, if the TFT-LEPD proves to be superior to the TFT-
`LCD for some applications, present LT p-Si TFT fabrication
`lines for the LCD’s can be easily changed to those for the
`LEPD.
`
`ACKNOWLEDGMENT
`The authors wish to thank Dr. R. H. Friend, Dr. J. H.
`Burroughes, Dr. C. R. Towns, Dr. K. Heeks, Dr. J. C. Carter,
`and Dr. I. Grizzi of Cambridge Display Technology Ltd., for
`fruitful collaboration of the TFT-LEPD and fabrication of the
`LEP.
`
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`
`Mutsumi Kimura was born in Japan on October
`5, 1966. He received the B.S. and M.S. degrees in
`physical engineering from Kyoto University, Japan,
`in 1989 and 1991, respectively.
`He joined Matsushita Electric Industrial Co., Ltd.,
`Moriguchi Osaka, in 1991. In 1995, he joined Seiko
`Epson Corporation, Owa Suwa, Japan, where he has
`been working on TFT simulator development and
`TFT-LEPD development at the Base Technology
`Research Center.
`
`Ichio Yudasaka was born in Nagano, Japan, on March 22, 1948. He received
`the B.S. degree in atomic nuclear engineering from Tohoku University, Japan,
`in 1971.
`He joined Hitachi Co., Ltd., Hitachi, Japan, in 1971. In 1979, he joined
`Seiko Epson Corporation, Owa Suwa, Japan, where he has been working on
`R&D of p-Si TFT at the Base Technology Research Center.
`
`Sadao Kanbe was born in Gunma, Japan, in May 1947. He received the B.S.
`degree in chemical engineering from Tokyo Institute of Technology, Japan,
`in 1971.
`In 1972, he joined Seiko Epson Corporation, Owa Suwa, Japan, where he
`has been working on R&D of materials for display.
`
`Hidekazu Kobayashi was born in Nagano, Japan, on November 8, 1960.
`He received the B.S. and M.S. degrees in synthetic chemistry from Kyoto
`University, Japan, in 1983 and 1985, respectively.
`In 1985, he joined Seiko Epson Corporation, Owa Suwa, Japan, where,
`until 1997, he was working on liquid crystal development. He is currently
`working on OELD development at the Base Technology Research Center.
`
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`
`Hiroshi Kiguchi was born in Nagano, Japan, on January 7, 1966. He received
`the B.S. degree in chemistry from Shizuoka University, Japan, in 1989.
`In 1989, he joined Seiko Epson Corporation, Owa Suwa, Japan, where he
`has been working on development of ink-jet technologies for industry at the
`Base Technology Research Center.
`
`Tokuro Ozawa was born in Yamanashi, Japan, on December 13, 1966. He
`received the B.S. degree in image science from Chiba University, Japan, in
`1990.
`In 1990, he joined Seiko Epson Corporation, Owa Suwa, Japan, where he
`has been working on the design of TFT-LCD at L Project.
`
`Shun-ichi Seki was born in Nagano, Japan, on June 6, 1968. He received
`the B.S. and M.S. degrees in physics from Science University of Tokyo,
`Japan, in 1992 and 1994, respectively.
`He had been working on pie-conjugated pigment and photosensitive proteins
`in halobacteria at the Institute of Physical and Chemical Research, Riken,
`Tsukuba, Japan. In 1997, he joined Seiko Epson Corporation, Owa Suwa,
`Japan, where he has been working on development of ink-jet technologies for
`LEP at the Base Technology Research Center.
`
`Satoru Miyashita was born in Nagano, Japan, on September 1, 1958.
`He received the B.S. degree in applied chemical engineering from Keio
`University, Japan, in 1981.
`In 1982, he joined Seiko Epson Corporation, Owa Suwa, Japan, where
`he has been working on functional materials research and novel process
`development. He is a Research Manager at the Base Technology Research
`Center.
`
`Kiyofumi Kitawada was born in Nagano, Japan, on July 15, 1964. He
`received the B.S. and M.S. degrees in plasma physics from Kanazawa
`University, Japan, in 1991.
`In 1991, he joined Seiko Epson Corporation, Owa Suwa, Japan, where he
`has been working on R&D of polysilicon TFT technologies at L Project.
`
`Takashi Nakazawa received the B.S. degree from Nihon University, Japan,
`in 1981.
`In 1981, he joined Seiko Epson Corporation, Owa Suwa, Japan, where he
`has been working on R&D of polysilicon TFT technologies, and is a Manager
`of L Project.
`
`Wakao Miyazawa was born in Nagano, Japan, on August 22, 1951.
`In 1970, he joined Seiko Epson Corporation, Owa Suwa, Japan, where he
`has been working on R&D of polysilicon TFT technologies, and is a Manager
`of L Project.
`
`Tatsuya Shimoda was born in Tokyo, Japan, in 1952. He rece