(12) United States Patent
`Shimoda et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,774,884 B2
`Aug. 10, 2004
`
`US006774884B2
`
`(54) ELECTROPHORETIC DEVICE,
`ELECTRONIC SHEET INCLUDING THE
`SAME, ELECTRONIC BOOK INCLUDING
`THE ELECTRONIC SHEET, AND
`MANUFACTURING METHOD THEREOF
`
`(75) Inventors: Tatsuya Shimoda, SuWa (JP);
`Hideyuki KaWai, SuWa (JP); Satoshi
`Inoue, SuWa (JP)
`
`(73) Assignee: Seiko Epson Corporation (JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC 154(b) by 149 days.
`
`(21) Appl. No.: 09/999,160
`(22) Filed:
`Nov. 30, 2001
`
`(65)
`
`(30)
`
`Prior Publication Data
`
`US 2002/0105600 A1 Aug. 8, 2002
`Foreign Application Priority Data
`
`Dec. 1, 2000
`
`(JP) ..................................... .. 2000-367165
`
`(51) Int. Cl.7 ................................................ .. G09G 3/34
`
`(52) US. Cl. . . . . . . . . . . . . . . . . . .
`
`. . . .. 345/107; 359/296
`
`(58) Field of Search ............................... .. 345/107, 105,
`345/106, 204, 205, 206, 901, 903, 92, 87,
`88,89, 91; 359/296; 430/38; 349/38, 39,
`42
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`6,192,890 B1
`
`2/2001 Levy et al. ............... .. 128/899
`
`6,266,037 B1
`
`*
`
`7/2001 Flasck ............ ..
`
`345/92
`
`*
`
`*
`
`11/2001 Duthaler et a1. ............ .. 445/24
`6,312,304 B1
`4/2002 Jensen et a1. ............. .. 433/136
`6,375,461 B1
`6,473,072 B1 * 10/2002 Comiskey et a1.
`.
`6,518,949 B2 * 2/2003 Drzaic
`2002/0033792 A1 * 3/2002 Inoue .......... ..
`
`.. 345/173
`345/107
`345/107
`
`2002/0123176 A1 * 9/2002 IZumi et al. .............. .. 438/149
`
`2002/0141801 A1 * 10/2002 Shimoda et al. ............ .. 400/76
`
`* cited by examiner
`
`Primary Examiner—Xiao Wu
`(74) Attorney, Agent, or Firm—Harness, Dickey & Pierce,
`PLC
`
`(57)
`
`ABSTRACT
`
`An electrophoretic device including a display region includ
`ing a plurality of pixels, each having an electrophoretic
`dispersion layer, a capacitive element for storing charge for
`maintaining the electrical polarization of the electrophoresis
`dispersion, and an organic transistor for causing the capaci
`tive element to store charge When turned on, Wherein the
`electrophoretic dispersion layer has a electrophoresis dis
`persion. Adriver region for optionally choosing pixels in the
`display region to turn on the transistors of the pixels is
`provided around the display region of the electrophoretic
`device. An electronic sheet is achieved by transmitting
`external signals to the driver region to freely change display
`contents on the display region.
`
`5,956,005 A * 9/1999 Sheridon ................... .. 345/84
`
`16 Claims, 8 Drawing Sheets
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`Aug. 10, 2004
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`Aug. 10, 2004
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`Aug. 10, 2004
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`Aug. 10, 2004
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`Aug. 10, 2004
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`Aug. 10, 2004
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`Aug. 10, 2004
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`US 6,774,884 B2
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`Aug. 10, 2004
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`US 6,774,884 B2
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`US 6,774,884 B2
`
`1
`ELECTROPHORETIC DEVICE,
`ELECTRONIC SHEET INCLUDING THE
`SAME, ELECTRONIC BOOK INCLUDING
`THE ELECTRONIC SHEET, AND
`MANUFACTURING METHOD THEREOF
`
`TECHNICAL FIELD
`
`The present invention relates to an electrophoretic device,
`an electronic sheet including the same, an electronic book
`including the electronic sheet, and a manufacturing method
`thereof. The present invention particularly relates to an
`electrophoretic device for displaying desired information, an
`electronic sheet including the same, an electronic book
`including the electronic sheet, and a manufacturing method
`thereof.
`
`10
`
`15
`
`BACKGROUND ART
`
`In general, When information output from personal com
`puters is displayed, displays such as CRTs (Cathode Ray
`Tube) or liquid crystal displays are used. Information dis
`played on the displays is printed With a printer in some cases.
`When mobile computers are used out of the of?ce, printing
`is not possible. When printers are not at a place Where one
`is visiting, there is no means for printing and that is
`inconvenient.
`Aso-called electronic book having a liquid crystal display
`is disclosed in Japanese Unexamined Patent Application
`Publication No. 5-265961. Although displayed contents on
`the displays are reWritable, carrying is not easy because of
`the thickness and the Weight. In order to use electronic
`sheets such as recording media and electronic books Which
`are electrically Writable, that is, electronic devices Which
`include the recording media and in Which speci?c informa
`tion is recorded, maintaining a display of contents and
`records for a long time is necessary and the excellent
`?exibility is also important.
`
`SUMMARY OF THE INVENTION
`The present invention has been developed to solve the
`above problems of knoWn technology, and it is an object to
`provide an electrophoretic device Which is easy to carry and
`is capable of being printed out of the office, an electronic
`sheet having the same, an electronic book including the
`electronic sheet, and a manufacturing method thereof.
`The electrophoretic device of the present invention
`includes a display region including a plurality of pixels
`having an electrophoretic dispersion layer, a capacitive
`element for maintaining the electrical polariZation of the
`electrophoretic dispersion layer, and an organic transistor
`storing charge in the capacitive element, Wherein the elec
`trophoretic dispersion layer includes an electrophoretic dis
`persion.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a plan vieW shoWing a planar structure of an
`electronic sheet according to an embodiment of the present
`invention.
`FIG. 2 is an illustration shoWing a con?guration of a
`display region shoWn in FIG. 1.
`FIG. 3 is an illustration shoWing an exemplary con?gu
`ration for supplying electricity and transmitting data to an
`electronic sheet.
`FIG. 4 is an illustration shoWing another exemplary
`con?guration for supplying electricity and transmitting data
`to an electronic sheet.
`
`25
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`35
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`2
`FIG. 5 is a sectional vieW shoWing a sectional structure of
`the display region of an electronic sheet according to an
`embodiment of the present invention.
`FIG. 6 includes illustrations shoWing the principles of
`display of an electronic sheet.
`FIG. 7 is a sectional vieW shoWing an exemplary sectional
`structure of an organic transistor.
`FIG. 8 includes illustrations, each having a sectional vieW
`shoWing a manufacturing process of an electronic sheet and
`the steps thereof.
`FIG. 9 includes illustrations shoWing an exemplary use of
`an electronic sheet.
`FIG. 10 includes illustrations shoWing an example of a
`binder-type electronic book.
`
`PREFERRED EMBODIMENTS OF THE
`INVENTION
`An electrophoretic device according to the present
`invention, includes a display region including a plurality of
`pixels, each having an electrophoretic dispersion layer, a
`capacitive element for maintaining the electrical polariZa
`tion of the electrophoretic dispersion layer and an organic
`transistor for causing the capacitive element to store charge,
`Wherein the electrophoretic dispersion layer includes an
`electrophoretic dispersion. Printing out of the of?ce is pos
`sible and carrying is easy due to such a con?guration.
`In a preferred embodiment according to the present
`invention, an electronic sheet including the above electro
`phoretic device is provided, Wherein the electrophoretic
`device is formed on a ?exible substrate. The ?exible elec
`tronic sheet is achieved by forming the display region
`including a electrophoretic dispersion on the ?exible sub
`strate. The organic transistor is de?ned as one having an
`active layer Which is composed of an organic material.
`In a preferred embodiment according to the present
`invention, the electronic sheet further including a driver
`region for controlling the operation of the organic transistors
`is provided. Since the driver region is provided to the
`electronic sheet, it is not necessary to provide an external
`driver circuit.
`In a preferred embodiment according to the present
`invention, the electronic sheet in Which the electrophoretic
`dispersion layer is formed by arranging a plurality of cap
`sules ?lled With the electrophoretic dispersion is provided.
`Since the capsules ?lled With the electrophoretic dispersion
`are used, application of the dispersion is easy.
`In a preferred embodiment according to the present
`invention, the electronic sheet in Which the driver region is
`formed by stripping a thin-?lm formed on a substrate and
`then pasting the thin-?lm onto a surface of another ?exible
`substrate is provided. Since the driver region is formed by
`the above method, the driver region may be easily disposed
`around the display region.
`In a preferred embodiment according to the present
`invention, the electronic sheet further including a contactless
`terminal for inputting external signals transmitted to the
`driver region is provided, Wherein the external signals are
`applied through the contactless terminal. Since contactless
`terminals are used, reliability and durability of the electronic
`sheet are improved due to the non-use of exposed terminals.
`In a preferred embodiment according to the present
`invention, the electronic sheet in Which the contactless
`terminal includes an loop coil and a through hole extending
`through the center of the loop coil is provided, Wherein the
`external signals are input by magnetism applied over the
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`through hole. In such a con?guration, the electronic sheet is
`joined in a binder and receives signals concerning display
`contents in a contactless manner.
`In a preferred embodiment according to the present
`invention, the electronic book including a rod magnet
`extending through the through hole provided in the above
`electronic sheet and a controlling coil Wound around the rod
`magnet is provided, Wherein the external signals are input to
`the electronic sheet by applying magnetism generated by the
`controlling coil. In such a con?guration, signals concerning
`display contents are transmitted to the electronic sheet
`joined in a binder in a contactless manner.
`In a preferred embodiment according to the present
`invention, the electronic book in Which the rod magnet
`freely opens and closes at a dividable intermediate portion
`thereof and the magnetic loop is closed When the rod magnet
`is closed to join the electronic sheet in a state Where the rod
`magnet extends through the through hole is provided. Since
`the closed loop is formed, signals are accurately transmitted
`to the electronic sheet in a binder in a contactless manner.
`In a preferred embodiment according to the present
`invention, the electronic book in Which transmitting and
`receiving the external signals are performed betWeen the
`controlling coil and the loop coil by magnetism is provided.
`Since transmitting and receiving signals betWeen the coils
`are performed, signals are accurately transmitted to the
`electronic sheet in a binder in a contactless manner.
`In a preferred embodiment according to the present
`invention, a method for manufacturing the above electronic
`sheet includes the steps of forming a transistor array includ
`ing the organic transistors on the ?exible substrate, forming
`a partition in the shape of a frame outside the resulting
`transistor array, and forming an electrophoretic dispersion
`layer inside the frame. The electronic sheet is easily manu
`factured by such a method.
`In a preferred embodiment according to the present
`invention, in the method for manufacturing the electronic
`sheet, the electrophoretic dispersion layer is formed by
`arranging a plurality of capsules ?lled With the electro
`phoretic dispersion. Since the electrophoretic dispersion is
`encapsulated in the capsules, application of the dispersion is
`easy.
`In a preferred embodiment according to the present
`invention, the method for manufacturing the electronic sheet
`further includes the steps of forming the driver region as a
`thin-?lm on another substrate, pasting the stripped driver
`region onto a region other than the organic transistor region;
`electrically connecting the organic transistor region and the
`driver region, and forming a partition in the shape of a
`frame. Since the driver region is formed by the above
`method, the driver region is easily disposed around a display
`region.
`In a preferred embodiment according to the present
`invention, a method for manufacturing the electronic sheet
`includes the step of forming the organic transistor by at least
`an ink jet process. Since the organic transistors are formed
`by the ink jet process, the electronic sheet is manufactured
`Without special equipment such as a vacuum chamber.
`With reference to the draWings, embodiments of the
`present invention Will noW be described in detail. In the
`draWings referred to in the folloWing description, the same
`components or parts as those of other draWings are repre
`sented by the same reference numerals.
`FIG. 1 shoWs an electronic sheet according to an embodi
`ment of the present invention. As shoWn in the ?gure, the
`electronic sheet 1 of the embodiment includes a display
`
`10
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`region 100, a scan driver region 13, and a data drive region
`14, Wherein the display region 100 includes an electro
`phoretic dispersion and an organic TFT (thin ?lm transistor)
`formed by arranging organic transistors, and the scan driver
`region 13 having the TFT and the data driver region 14
`having the TFT are provided around the display region 100.
`The scan driver region 13 transmits a scan signal for
`choosing the pixels of the display region 100. The data
`driver region 14 transmits a data signal corresponding to
`data displayed by using the pixels of the display region 100.
`When a driver circuit having the same functions as those of
`the scan driver region 13 and the data driver region 14 is
`provided outside the electronic sheet 1, an electrophoretic
`device Without the scan driver region 13 and the data driver
`region 14 is achieved. As shoWn in FIG. 1, When a driver
`region is provided in the electronic sheet 1, an external
`driver circuit is not necessary.
`The display region 100 includes a plurality of pixels for
`creating a desired display. Each pixel includes an electro
`phoretic dispersion 10, a capacitive element 11 for main
`taining the electric polariZation of the electrophoretic dis
`persion 10, and an organic transistor 12 for sWitching to
`cause the capacitive element 11 to store charge.
`Referring to FIG. 1, the display region 100 also includes
`a scan line 130 for transmitting a scan signal to the gate of
`each organic transistor 12 from the scan driver region 13, a
`data line 140 for transmitting a data signal to the source of
`each organic transistor 12 from the data driver region 14, and
`a ground line 120 for providing a ground potential to one
`electrode of the capacitive element 11. The capacitive ele
`ment 11 has a capacitor C5. Also, the electrophoretic dis
`persion 10 having a capacitor Ce is shoWn in FIG. 1.
`The equivalent circuit of the display region 100 is shoWn
`in FIG. 2. Referring to the ?gure, the ground line 120 shoWn
`in FIG. 1 provides a ground potential to one of the electrodes
`of the capacitive element 11. The other electrode of the
`capacitive element 11 is connected to the drain of the
`transistor 12 and one electrode 10b of the capacitor Ce
`included in the electrophoretic dispersion 10. The other
`electrode 10a of the capacitor Ce included in the electro
`phoretic dispersion 10 is applied With a voltage of a prede
`termined level. As described beloW, changing the direction
`of the voltage applied to the electrophoretic dispersion 10
`realiZes tWo kinds of polariZation in the electrophoretic
`dispersion 10 to create a desired display.
`The organic transistors may be manufactured by a liquid
`phase process or preferably by an ink jet process in some
`cases.
`In such a con?guration, a transistor of the organic tran
`sistors 12 in the display region 100, of Which the gate
`receives a scan signal through the scan line 130, is turned on.
`Charge is stored in the capacitive element 11 through the
`transistor, Which is turned on, in response to a data signal
`received through the data line 140. At this time, the elec
`trophoretic dispersion 10 is electrically polariZed. Even if
`the transistor is then turned off, the polariZation of the
`electrophoretic dispersion 10 is maintained by the charge
`stored in the capacitive element 11. In this instance, the
`polariZation is maintained in a state Where speci?c color
`components gather at the side of either an electrode 10a or
`an electrode 10b in response to the signal level of the data
`signal. Thus, data corresponding to the contents of the
`received data signal is displayed on the display region 100.
`The driver region 13 outputting the scan signal and the
`driver region 14 outputting the data signal require external
`electricity and data. The electricity and the like may be
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`supplied to the scan driver region 13 and the data driver
`region 14 transmitting signals to the display region 100
`through external terminals Which are electrically connected
`as shoWn in FIG. 3, or the electricity and the like may be
`supplied Without contact through contactless external termi
`nals as shoWn in FIG. 4.
`In the con?guration shoWn in FIG. 3, one ends of external
`signal lines 13a and 14a are connected to the scan driver
`region 13 and the data driver region 14, other ends thereof
`are connected to external terminals (not shoWn) provided on
`the surface of the electronic sheet, and electricity and the
`like may be supplied through an external circuit electrically
`connected to the external terminals.
`In the con?guration shoWn in FIG. 4, an integrated circuit
`150 including contactless terminals and the like is provided
`on the surface of the electronic sheet, and electricity and the
`like may be externally supplied to the integrated circuit 150
`in a contactless manner. For example, a method of data
`communication and electrical supply in a contactless IC card
`system disclosed in Japanese Unexamined Patent Applica
`tion Publication No. 2000-242739 may be applicable.
`FIG. 5 shoWs the sectional structure of one pixel of the
`display region 100. The display region of the electronic
`sheet includes a substrate 43, the organic transistor 12
`formed on the substrate 43, an electrode 36 composed of
`ITO (indium tin oxide), a via hole 37 connecting the organic
`transistor 12 With the electrode 36, a resin layer 35 formed
`thereon, an electrophoretic dispersion layer 33, an ITO
`electrode 32 formed thereon, and a PET ?lm 31. When the
`resin layer 35 is composed of a proper material, the resin
`layer 35 functions as a capacitive element. When the resin
`layer 35 does not function as a capacitive element, a
`capacitive element may be provided at a position to be
`electrically connected in parallel or in series to the electro
`phoretic dispersion layer 33.
`Many microcapsules 33a ?lled With the electrophoretic
`dispersion are arranged in the electrophoretic dispersion
`layer 33. Since the electrophoretic dispersion is encapsu
`lated in capsules, application of the dispersion is easy. The
`microcapsule 33a is preferably ?lled With a liquid disperse
`medium and electrophoretic particles dispersed in the liquid
`disperse medium. The liquid disperse medium and the
`electrophoretic particles preferably have different colors
`from each other.
`The electrophoretic dispersion in the microcapsule 33a is
`electrically polariZed in tWo states in response to the direc
`tion of the applied voltage. That Will noW be described With
`reference to FIG. 6. FIG. 6 schematically shoWs the elec
`trical polariZation in a microcapsule. FIG. 6(a) shoWs that an
`electrophoretic dispersion 50 in the microcapsule 33a is
`placed betWeen an electrode 34 and a transparent electrode
`32. The electrophoretic dispersion 50 is composed of the
`liquid disperse medium 6 and the electrophoretic particles 5.
`The liquid disperse medium 6 and the electrophoretic par
`ticles 5 have different colors from each other.
`PoWer sources 9a and 9b for applying voltage in the
`opposite direction to each other are connected through a
`sWitch 8. That is, the electrode 32 is connected to one end
`of each of the poWer sources 9a and 9b, and the electrode 34
`is connected to the other end of each of the poWer sources
`9a and 9b through the sWitch 8. In such a connection, the
`direction of an applied voltage is changed With the sWitch 8.
`Changing the direction of the applied voltage polariZes the
`electrophoretic dispersion, thereby creating a desired dis
`play. As shoWn in FIG. 6(b), When applying a voltage from
`the poWer source 9a, the electrophoretic particles 5 gather at
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`the transparent electrode 32 side close to the observer. In this
`state, the observer sees the color of the electrophoretic
`particles 5. On the other hand, as shoWn in FIG. 6(c), When
`applying a voltage from the poWer source 9b, the electro
`phoretic particles 5 gather at the electrode 34 side far from
`the observer. In this state, the observer sees the color of the
`liquid disperse medium 6.
`As described above, tWo kinds of colors are displayed in
`response to the direction of an applied voltage by electrically
`polariZing the electrophoretic dispersion 50 in the micro
`capsule; hence, the electronic sheet using electrophoretic
`display technology is achieved by providing the con?gura
`tion shoWn in FIG. 6(c) to all pixels.
`Referring to FIG. 5, the organic transistor 12 includes a
`gate 42, an insulating layer 41, a source 39, a drain 40, and
`a semiconductor layer 38.
`The sectional structure of the organic transistor Will noW
`be described With reference to FIG. 7.
`As shoWn in FIG. 7, the organic transistor includes the
`gate 42 formed on the substrate 43, the gate insulating layer
`41 formed on the gate 42, the source 39 and the drain 40
`formed on the gate insulating layer 41 and the substrate 43,
`and the semiconductor layer 38 for providing a channel
`region.
`In this con?guration, the substrate 43 is composed of, for
`example, PET (polyethylene terephthalate) or borosilicate
`glass for a liquid crystal display (for example, glass No.
`7059 manufactured by Corning Inc.). When a glass substrate
`is used, it is soaked in a solution, for example, hexadecane
`containing 2% of organic silane (OST:
`octadecyltrichlorosilane) and then is dried. When a PET
`substrate is used, it is exposed to an OST vapor, for example,
`in an vacuum.
`The semiconductor layer 38 is prepared under the folloW
`ing conditions: for example, a vacuum thermal deposition of
`pentacene, a substrate temperature of 60° C., and a deposi
`tion rate of 0.5 A/s. The pentacene is puri?ed in advance by
`thermal gradient vacuum sublimation. High mobility is
`achieved by a loW substrate temperature, loW deposition
`rate, and high purity.
`The semiconductor layer 38 is composed of, for example,
`pentacene. The gate 42 is composed of, for example, nickel
`by ion beam sputtering. Photolithography may be used for
`the preparation.
`The gate insulating layer 41 is composed of, for example,
`silicon oxide (SiO2) and prepared at a substrate temperature
`of 80° C. to reduce stress. Photolithography may be used for
`the preparation. The source 39 and the drain 40 are com
`posed of, for example, palladium by ion beam sputtering.
`Photolithography may be used for the preparation. The gate
`insulating layer 41 is surface-treated to increase mobility.
`The transistor prepared by the above procedure has the
`folloWing characteristics: gate Width/gate length=240/44
`pM, ?eld effect mobility p eff=1.1 cmZ/Vs, and Vth=2 V in
`the case of using a PET substrate; and gate Width/gate
`length=500/5 pm, ?eld effect mobility p eff=1.7 cm2/Vs,
`Vth=10 V, an S value of 0.9 V/decade, an On/Off ratio of
`103, and a current of 2.5 pA/micron gate Width in case of
`using a glass substrate.
`The organic transistor is described in Gundlach, David J.
`et al., “High-Mobility, LoW Voltage Organic Thin Film
`Transistors”, IEDM99-111, 1999, IEEE.
`Referring to FIGS. 8A to 8G, a process for manufacturing
`the electronic sheet having the display region described
`above Will noW be described. As shoWn in FIG. 8(a), an
`
`Patent Owner’s Exhibit 2002
`IPR2015-00022
`12 of 16
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`

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`US 6,774,884 B2
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`7
`organic TFT array 400 composed of the organic transistors
`described above is ?rst formed on a substrate 43. In the
`?gure, the organic TFT array 400 includes an electrode 401.
`As shoWn in FIG. 8(b), an SUFTLA-TFT 403 is transferred
`to form the same layer as the organic TFT array 400. As
`shoWn in FIG. 8(a), the electrode 401 of the organic TFT
`array 400 and the electrode 402 of the SUFTLA-TFT 403
`are connected With a Wiring 404. The Wiring 404 is formed
`by an ink jet process or photolithography.
`“SUFTLA” is de?ned as a technique that a thin-?lrn
`formed on a substrate is stripped by laser irradiation or the
`like and then is pasted onto another substrate. The driver
`region can be easily disposed around the display region by
`this technique. “SUFTLA-TFT” is de?ned as a thin-?lrn
`transistor prepared by “SUFTLA”. “SUFTLA” is described
`in Utsunorniya, S. “Low Temperature Poly-Si TFTs on
`Plastic Substrate Using Surface Free Technology by Laser
`Ablation/Annealing” SID 00 DIGEST. “SUFTLA” is a
`trademark.
`As shoWn in FIG. 8(a'), a passivation layer 405 is formed.
`The passivation layer 405 is composed of silicon oxide
`(SiO2) or an organic insulator such as polyirnides. Then, as
`shoWn in FIG. 8(6), a resin layer 406 is applied onto the
`frame to form a partition. As shoWn in FIG. 8(1‘), an
`electrophoretic dispersion 407 is used inside the frame
`composed of the resin layer 406. Finally, as shoWn in FIG.
`8(g), an ITO sheet 408 is larninated.
`By the above manufacturing process, the electronic sheet
`having the planar structure shoWn in FIG. 1 is provided.
`Since the organic transistor is used in the above manufac
`turing process, the electronic sheet can be manufactured by
`an ink jet process or the like Without using special equipment
`such as a vacuum chamber. Since special equipment such as
`a vacuum chamber is not used, the manufacturing cost is
`reduced and a loW-cost electronic sheet can be manufac
`tured.
`The electronic sheet as described above preferably has a
`thickness of about 0.1 to 0.2 mm and the electrophoretic
`dispersion layer has a thickness of about 30 to 50 urn.
`Thus, the electronic sheet may be handled as sheet and
`printed contents (displayed contents) thereof may be reWrit
`ten many times Without a printer. In mobile computers, When
`the external terrninals described above or terminals for
`supplying electricity and the like to the integral circuit 150
`is connected to the electronic sheet, contents displayed in the
`electronic sheet may be freely reWritten.
`Although general displays must be reWritten 60 times per
`second, the electronic sheet may be reWritten With a very
`loW frequency (for example, once per minute); hence, the
`electronic sheet is bene?cial since the time for reWriting is
`short. Since the contents may be reWritten many times, the
`electronic sheet of the present invention may be used instead
`of sheet; hence, recycling is stimulated.
`The displayed contents (that is, the polariZation of the
`electrophoretic dispersion) of the electronic sheet are main
`tained by charge stored in the capacitive elernent provided to
`each pixel, as described above. The capacitive element may
`be disposed to be electrically connected in parallel or in
`series to the electrophoretic dispersion layer. The capacitive
`element may be composed of a dielectric material and such
`a con?guration may be effective in maintaining the polar
`iZation of the electrophoretic dispersion for a long time in
`some cases.
`FIG. 9 shoWs an exemplary use of the electronic sheet
`manufactured by the above procedure. As shoWn in FIG.
`9(a), the electronic sheet 1 has a plurality of external
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`terminals 2. These external terminals 2 are electrically
`connected to an external circuit, not shoWn, to provide
`required electricity or data concerning contents to be dis
`played in the display region 100. FIG. 9(a) shoWs the Words,
`“ABCDEFG Corporation”, and ?gures such as a quadrilat
`eral and a circle in the display region 100. As shoWn in FIG.
`9(b), the electronic sheet 1 may be bent. In the con?guration
`shoWn in FIG. 9(b), the external terminals 2 are electrically
`connected to an external circuit, not shoWn, to provide
`required electricity or data concerning contents to be dis
`played in the display regions 100a and 100b.
`Furthermore, the electronic sheet of the present invention
`may be applicable to an electronic book. That is, a binder
`type electronic book is achieved by joining a plurality of the
`electronic sheets 1 in a binder functioning as a cover. FIG.
`10(a) shoWs the binder-type electronic book. The ?gure
`illustrates a plurality of the electronic sheets 1 joined in a
`binder 3. In this case, each joined electronic sheet 1 is
`provided With through holes 30a and 30b, and rod rnagnets
`4a and 4b included in the binder 3 extend through the
`through holes 30a and 30b, respectively. Both ends of each
`of the rod rnagnets 4a and 4b are ?xed to the binder 3, and
`the rod rnagnets may be divided at each intermediate por
`tion. When divided at the intermediate portion, the elec
`tronic sheet 1 is freely joined and separated to and from the
`binder 3. The rod rnagnets 4a and 4b freely open and close
`at each intermediate portion Which may be divided, and a
`magnetic loop may be closed While the electronic sheet 1 is
`joined.
`As shoWn in FIG. 10(b), the binder 3 includes controlling
`coils 3a and 3b corresponding to the rod rnagnets 4a and 4b,
`respectively, an arnpli?er 3c for supplying a current to the
`controlling coils 3a and 3b, and a CPU 3d for controlling the
`arnpli?er 3c.
`As shoWn in FIG. 10(c), the electronic sheet 1 has the
`display region 100 and the through