(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0197664 A1
`Koyama
`(43) Pub. Date:
`Oct. 23, 2003
`
`US 2003O197664A1
`
`(54) ELECTRO-OPTICAL DEVICE
`(75) Inventor: Jun Koyama, Kanagawa (JP)
`
`Correspondence Address:
`Edward D. Manzo
`Cook, Alex, McFarron, Manzo, Cummings &
`Mehler, Ltd.
`200 West Adams St., Ste. 2850
`Chicago, IL 60606 (US)
`
`: S
`73) AS
`(73)
`Signee
`
`Laborat
`ductor E
`y uctor Illnergy Laboratory
`
`es
`
`(21) Appl. No.:
`
`(22) Filed:
`
`10/435,968
`9
`May 12, 2003
`
`Related U.S. Application Data
`(63) Continuation of application No. 09/692,713, filed on
`Oct. 19, 2000, now Pat. No. 6,587,086.
`
`Foreign Application Priority Data
`(30)
`Oct. 26, 1999 (JP).
`... 11-304679
`Nov. 29, 1999 (JP)........................................... 11-337OO3
`Publication Classification
`
`(51) Int. Cl. ................................................... G09G 3/30
`(52) U.S. Cl. ................................................................ 345/76
`
`(57)
`
`ABSTRACT
`
`An electro-optical device for performing time division gra
`p
`p
`9.
`gray
`Scale display and which is capable of arbitrarily Setting the
`amount of time during which light is emitted by EL elements
`is provided. From among in Sustain periods TS1, ..., TSn, the
`brightness of light emitted by the EL elements during at least
`one Sustain period is set to be always lower than the
`brightness of light emitted by the EL elements during the
`other Sustain periods, and the Sustain periods are extended
`by the amount that the brightness has dropped. In accor
`dance with the above Structure, the Sustain periods can be
`extended by lowering the Setting of the brightness of light
`emitted by the EL elements.
`
`
`
`1508
`
`1500
`
`r
`
`is
`
`is
`
`some s - - - . .
`
`.
`
`.
`
`.
`
`Petitioner Samsung Ex. 1011 - Page 1 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 1 of 22
`
`US 2003/0197664 A1
`
`
`
`1500
`
`Petitioner Samsung Ex. 1011 - Page 2 of 50
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`

`

`Patent Application Publication
`
`Oct. 23, 2003 Sheet 2 of 22
`
`US 2003/0197664 A1
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`Petitioner Samsung Ex. 1011 - Page 3 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 3 of 22
`
`US 2003/0197664 A1
`
`drain current(ld)
`
`
`
`Fig.3A
`
`gate voltage(Vg)
`
`drain current(ld)
`
`Fig.3B
`
`sub-threshold region
`
`s
`
`With
`
`gate Voltage(Vg)
`
`Petitioner Samsung Ex. 1011 - Page 4 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 4 of 22
`Video
`Signals
`
`CKSP
`
`US 2003/0197664 A1
`
`time partitioning
`gradation data signal
`generator circuit 114
`
`
`
`
`
`Digital Data
`Signals
`
`
`
`
`
`Latch
`Signals
`
`source signal side driver circuit 102
`
`shift register 102a
`
`latch(A)102b
`
`latch(B) 102c
`
`
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`
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`pixel portion 101
`
`107
`
`104
`
`Petitioner Samsung Ex. 1011 - Page 5 of 50
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`

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`Patent Application Publication
`
`Oct. 23, 2003 Sheet 5 of 22
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`US 2003/0197664 A1
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`
`
`Petitioner Samsung Ex. 1011 - Page 6 of 50
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`

`

`Patent Application Publication
`
`Oct. 23, 2003 Sheet 6 of 22
`
`US 2003/0197664 A1
`
`
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`
`Petitioner Samsung Ex. 1011 - Page 7 of 50
`
`

`

`Patent Application Publication
`
`Oct. 23, 2003 Sheet 7 of 22
`
`US 2003/0197664 A1
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`
`
`Petitioner Samsung Ex. 1011 - Page 8 of 50
`
`

`

`Patent Application Publication
`
`Oct. 23, 2003 Sheet 8 of 22
`
`US 2003/0197664 A1
`
`
`
`
`
`Petitioner Samsung Ex. 1011 - Page 9 of 50
`
`

`

`Patent Application Publication
`
`Oct. 23, 2003 Sheet 9 of 22
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`US 2003/0197664 A1
`
`
`
`
`
`Petitioner Samsung Ex. 1011 - Page 10 of 50
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`

`

`Patent Application Publication
`
`Oct. 23, 2003 Sheet 10 of 22
`
`US 2003/0197664 A1
`
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`Petitioner Samsung Ex. 1011 - Page 11 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 11 of 22 US 2003/0197664 A1
`2214 2203
`2205 2204
`
`
`
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`2201:glass substrae 2202: pixel portion 2203;gate signal side driving circuit
`2204:source signal side driving circuit 2205:switching TFT
`2206:gate wiring line 2207:source wiring line 2208:El driver TFT
`2209:Current-feed line 221 1:EL element 2212:FPC
`2213-2215.input-output wiring lines 2216:capacitor
`
`225
`
`Fig.11
`
`Petitioner Samsung Ex. 1011 - Page 12 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 12 of 22 US 2003/0197664 A1
`
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`Fig.12B
`
`Petitioner Samsung Ex. 1011 - Page 13 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 13 of 22 US 2003/0197664A1
`
`
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`Petitioner Samsung Ex. 1011 - Page 14 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003. Sheet 14 of 22 US 2003/0197664 A1
`
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`
`Petitioner Samsung Ex. 1011 - Page 15 of 50
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`

`

`Patent Application Publication Oct. 23, 2003 Sheet 15 of 22 US 2003/0197664 A1
`
`1291 1202
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`Petitioner Samsung Ex. 1011 - Page 16 of 50
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`

`

`Patent Application Publication Oct. 23, 2003 Sheet 16 of 22 US 2003/0197664A1
`
`120 1 a
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`
`Petitioner Samsung Ex. 1011 - Page 17 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 17 of 22 US 2003/0197664 A1
`
`
`
`2106 image reception portion
`
`2104 operation
`Switch
`
`2101 main body
`
`2103 voice inputting portion
`
`2105 battery
`
`2404 display device(a)
`
`2401 main body
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`2402 recording
`medium
`
`2405 display device(b)
`Fig.17D
`
`display device
`2306
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`head fixation band
`2303
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`display monitor
`2304
`
`optical systern
`2305
`main body 2301
`
`signal cable 2302
`Fig.17C
`
`250 main body 2505 display portion
`
`2502 camera portion
`
`
`
`2504 operation switch
`
`Fig.17E
`
`Petitioner Samsung Ex. 1011 - Page 18 of 50
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`

`

`Patent Application Publication Oct. 23, 2003 Sheet 18 of 22 US 2003/0197664 A1
`
`
`
`1800
`
`Petitioner Samsung Ex. 1011 - Page 19 of 50
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`

`

`Patent Application Publication Oct. 23, 2003 Sheet 19 of 22
`
`US 2003/0197664 A1
`
`
`
`
`
`po?ued euuel?
`
`Petitioner Samsung Ex. 1011 - Page 20 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 20 of 22 US 2003/0197664 A1
`
`
`
`(1111)
`(1110)
`
`(O100)
`
`(0000)
`
`(1110) (1111)
`(1000)
`(0000) (OOO1)
`pre-Compensation video signal
`
`Fig.20
`
`Petitioner Samsung Ex. 1011 - Page 21 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 21 of 22 US 2003/0197664 A1
`
`9.
`
`in 1 C
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`non-volatile memory
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`non-volatile memory
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`non-volatile memory
`
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`non-volatile memory
`
`
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`SO
`
`Petitioner Samsung Ex. 1011 - Page 22 of 50
`
`

`

`Patent Application Publication Oct. 23, 2003 Sheet 22 of 22 US 2003/0197664 A1
`pre-compensation video signal
`post-compensation video signal
`
`in 1 in2 in3 in4
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`Fig.22
`
`Petitioner Samsung Ex. 1011 - Page 23 of 50
`
`

`

`US 2003/O197664 A1
`
`Oct. 23, 2003
`
`ELECTRO-OPTICAL DEVICE
`
`BACKGROUND OF THE INVENTION
`0001) 1. Field of the Invention
`0002 The present invention relates to an EL (electro
`luminescence) display (an electro-optical device) formed by
`preparing an EL element on a Substrate. More particularly,
`the invention relates to an EL display using a Semiconductor
`element (an element using a semiconductor thin film).
`Furthermore, the present invention relates to an electronic
`equipment in which the EL display is used in a display
`portion thereof.
`0003 2. Description of the Related Art
`0004.
`In recent years, technology for forming a TFT on a
`Substrate has been largely improved, and an application
`development of the TFT to an active matrix type display
`device has been carried out. In particular, the TFT using a
`polysilicon film has a higher electric field effect mobility
`than the TFT using a conventional amorphous Silicon film,
`and therefore, the TFT may be operated at a high speed.
`Thus, the pixel control which has been conducted at a driver
`circuit outside of the Substrate may be conducted at the
`driver circuit which is formed on the same Substrate as the
`pixel.
`0005 Such an active matrix type display device can, by
`preparing various circuits and elements on the same Sub
`Strate, obtain various advantages Such as a decrease in the
`manufacturing cost, a decrease in the size of the display
`device, an increase in the yield, and a decrease in the
`throughput.
`0006 Further, research on the active matrix type EL
`display having an EL element as a Self-light-emitting device
`is becoming more and more active. The EL display is
`referred to as an organic EL display (OELD) or an organic
`light-emitting diode (OLED).
`0007. The EL display is a self-light-emitting type unlike
`a liquid crystal display device. The EL element is constituted
`in Such a manner that an EL layer is Sandwiched between a
`pair of electrodes. However, the EL layer normally has a
`lamination Structure. Typically, the lamination Structure of a
`"positive hole transport layer/aluminous layer/an electron
`transport layer” proposed by Tang et al. of the Eastman
`Kodak Company can be cited. This structure has a very high
`light-emitting efficiency, and this structure is adopted in
`almost all the EL displayS which are currently Subjected to
`research and development.
`0008. In addition, the structure may be such that on the
`pixel electrode, a positive hole injection layer/a positive hole
`transport layer/aluminous layer/an electron transport layer,
`or a positive hole injection layer/a positive hole transport
`layer/a luminous layer/an electron transport layer/an elec
`tron injection layer may be laminated in order. Phosphores
`cent dye or the like may be doped into the luminous layer.
`0009. In this specification, all the layers provided
`between the pixel electrode and an opposite electrode are
`generally referred to as EL layers. Consequently, the positive
`hole injection layer, the positive hole transport layer, the
`luminous layer, the electron transport layer, the electron
`injection layer and the like are all included in the EL layers.
`
`0010. Then, a predetermined voltage is applied to the EL
`layer having the above Structure from the pair of the elec
`trodes, So that a recombination of carriers is generated in the
`luminous layer and light is emitted. Incidentally, in this
`Specification, the fact that the EL element is emitted is
`described as the fact that the EL element is driven. Further
`more, in this specification, the light-emitting element formed
`of the anode, the EL layer and the cathode is referred to as
`an EL element.
`0011) An analog type driver method (analog drive) can be
`given as a method of driving an EL display. An analog drive
`EL display is explained using FIGS. 18 and 19.
`0012. The structure of a pixel portion of the analog drive
`EL display is shown in FIG. 18. Ygate signal lines (G1 to
`Gy) for inputting gate signals are connected to gate elec
`trodes of Switching TFTs 1801 of pixels. One of a source
`region and a drain region of the Switching TFF 1801 of each
`pixel is connected to X Source Signal lines (also referred to
`as data Signal lines) (S1 to SX) for inputting analog video
`Signals, and the other is connected to the gate electrode of an
`EL driver TIFT 1804 of each pixel and to a capacitor 1808
`of each pixel.
`0013 The source region and the drain region of the EL
`driver TFT 1804 incorporated in each of the pixels is
`connected to the power source Supply lines (V1 to Vx) while
`the other is connected to the EL element 1806. The potential
`of the power source supply lines (V1 to Vx) is referred to as
`the potential of the power Source. Note that, the power
`Source Supply lines (V1 to Vx) is connected to a capacitor
`1808 incorporated in each of the pixels.
`0014. The EL element 1806 comprises an anode, a cath
`ode and an EL layer provided between the anode and the
`cathode. In the case where the anode is connected to the
`Source region or the drain region of the EL driver TFT 1804,
`namely, in the case where the anode is the pixel electrode,
`the cathode which is the opposite electrode is held at a
`constant potential. On the contrary, in the case where the
`cathode is connected to the Source region or the drain region
`of the EL driver TFT 1804, that is, in the case the cathode
`is the pixel electrode, the anode, which is an opposite
`electrode is held at a constant potential.
`0015 The opposite electrodes are normally maintained at
`a constant electric potential, and in the present Specification,
`the electric potential of the opposite electrodes is referred to
`as a Steady-State electric potential. Note that anpower Source
`for imparting the Steady-state electric potential to the oppo
`Site electrodes is referred to as a steady-state power Source.
`The electric potential difference between the steady-state
`electric potential of the opposite electrodes and the power
`Source electric potential of the pixel electrodes is an EL
`driver Voltage, and the EL driver Voltage is applied to the EL
`layers.
`0016 A timing chart for a case of driving the EL display
`by the analog method is shown in FIG. 19. A period during
`which one gate Signal line is Selected is referred to as one
`line period (L). Further, a period until selection of all the
`gate Signal lines (G1 to Gy) is completed corresponds to one
`frame period (F). There are y gate Signal lines for the case
`of the EL display of FIG. 18, and therefore y line periods
`(L1 to Ly) are formed during one frame period.
`0017 Note that 60 or more frame periods are formed
`during one Second in the EL display drive. In other words,
`
`Petitioner Samsung Ex. 1011 - Page 24 of 50
`
`

`

`US 2003/O197664 A1
`
`Oct. 23, 2003
`
`60 or more images are displayed during one Second. If the
`number of images displayed in one Second becomes leSS
`than 60, then problems. Such as image flicker Start to become
`Visually conspicuous.
`0.018. The number of line periods during one frame
`period increases as the number of gradations increases, and
`the driver circuit must operate at a high frequency.
`0019 First, electric power source Supply lines (V1 to Vx)
`are maintained in an off-power Source electric potential.
`Note that the off-power Source electric potential in an analog
`driver method is in a range in which the EL elements do not
`emit light and is the same Strength as the Steady-state electric
`potential. Note also that the difference between the off
`power Source electric potential and the Steady-State electric
`potential is referred to as an off EL driver Voltage. Ideally,
`it is preferable that the off EL driver voltage be 0 V, but it
`is acceptable provided that it is such that EL elements 1806
`do not emit light.
`0020 Agate signal is input to the gate signal line G1 in
`the first line period (L1). An analog video signal is then input
`to the Source signal lines (S1 to SX) in order. A Switching
`TFT (1.1) is therefore in an On state (on), and consequently
`the analog video signal input to the Source Signal line S1 is
`input to the gate electrode of an EL driver TFT (1,1), through
`the Switching TFF (1,1).
`0021. The electric potential of the power source Supply
`line V1 then changes from the off-power source electric
`potential to a Saturation power Source electric potential. Note
`that, throughout this specification, Saturation power Source
`electric potential refers to an electric potential having an
`electric potential difference with the Steady-state electric
`potential to the extent that the EL element emits light. Note
`also that this electric potential difference is referred to as a
`Saturation power Source Voltage.
`0022. When the analog video signal is input to the gate
`electrode of the EL driver TFT and one of the source region
`and the drain region is maintained at the Saturation power
`Source electric potential, the other becomes the on-power
`Source electric potential. Note that the difference between
`the on EL driver electric potential and the Steady-state
`electric potential is referred to as an on EL driver Voltage.
`Further, the on EL driver voltage and the off EL driver
`Voltage are generically referred to as an EL driver Voltage
`throughout this specification.
`0023 The on driver voltage is then applied to the EL
`element, and the pixel performs display. The amount of
`electric current flowing in channel forming regions of the EL
`driver TFTs is controlled by the voltage size of the analog
`Video signal input to the gate electrodes of the EL driver
`TFTS. The size of the on EL driver electric potential is
`therefore controlled by the analog video Signal applied to the
`gate electrode of the EL driver TFT (1,1). Consequently, the
`size of the on EL driver voltage applied to the EL element
`is also controlled by the analog video Signal applied to the
`gate electrode of the EL driver TFT (1,1).
`0024. Next, the analog video signal is similarly applied to
`the Source signal line S2, and a Switching TFT (2,1) turns on.
`The analog video signal input to the Source Signal line S2 is
`therefore input to the gate electrode of the EL driver TFT
`(2,1) through the Switching TFT (2,1).
`
`0.025 The EL driver TFT (2.1) is therefore placed in the
`On State. The electric potential of the power Source Supply
`line V2 then changes from the off-power Source electric
`potential to the Saturation power Source electric potential.
`The on driver Voltage, whose size is controlled by the analog
`video signal input to the gate electrode of the EL driver TFT
`(2,1), is therefore applied to the EL element, and the pixel
`performs display.
`0026. By repeating the above operations and completing
`input of the analog video signal to the Source signal lines (S1
`to SX), the first line period (L1) is completed. The second
`line period (L2) begins next, and the gate signal is input to
`the gate Signal line G2. Then, Similar to the first line period
`(L1), the analog video signal is input to the Source signal
`lines (S1 to SX) in order.
`0027. The analog video signal is input to the source
`signal line S1. A switching TFT (12) turns on, and therefore
`the analog video signal input to the Source Signal line S1 is
`input to the gate electrode of an EL driver TFT (1,2) through
`the Switching TFT (12).
`0028. The EL driver TFT (1,2) therefore turns on. The
`electric potential of the power Source Supply line V1 then
`changes from the off-power Source electric potential to the
`Saturation power Source electric potential. The on driver
`Voltage, whose Size is controlled by the analog video signal
`applied to the gate electrode of the EL driver TFT (1,2), is
`therefore applied to the EL element, and the pixel performs
`display.
`0029. By repeating the above operations and completing
`input of the analog video signal to the Source signal lines (S1
`to SX), the second line period (L2) is completed. The third
`line period (L3) begins next, and the gate signal is input to
`the gate Signal line G3.
`0030 The above operations are then repeated in order,
`the gate signal is completely input to the gate Signal lines
`(G1 to Gy), and all of the line periods (L1 to Ly) are
`completed. When all of the line periods (L1 to Ly) are
`complete, one frame period is complete. All of the pixels
`perform display during one frame period, forming one
`image.
`0031. Thus the amount of light emitted by the EL ele
`ments is controlled in accordance with the analog video
`Signal, and gray Scale display is performed by controlling the
`amount of light emitted. This method is a driver method
`referred to as the analog driver method, and gray Scale
`display is performed by changing the amplitude of the
`Signal.
`0032. A detailed description of the state of controlling the
`amount of electric current Supplied to the EL elements by the
`gate voltage of the EL driver TFTs is made using FIGS. 3A
`and 3B.
`0033 FIG. 3A is a graph showing the transistor charac
`teristics of the EL driver TFTs, and reference numeral 401 is
`referred to as an Id-Vg characteristic (also referred to as an
`Id-Vg curve). Id is a drain current, and Vg is a gate Voltage
`here. The amount of electric current flowing with respect to
`an arbitrary gate Voltage can be found from this graph.
`0034. A region of the Id-Vg characteristic shown by a
`dotted line 402 is usually used in driving the EL elements.
`
`Petitioner Samsung Ex. 1011 - Page 25 of 50
`
`

`

`US 2003/O197664 A1
`
`Oct. 23, 2003
`
`An enlarged diagram of the region enclosed by the dotted
`line 402 is shown in FIG. 3B.
`0035) The shaded region in FIG. 3B is referred to as a
`Sub-threshold region. In practice, this indicates a gate Volt
`age in the vicinity of, or below, the threshold voltage (Vth),
`and in this region, the drain current changes exponentially
`with respect to the changes in the gate Voltage. Electric
`current control is performed in accordance with the gate
`Voltage by using this region.
`0.036 The Switching TFT turns on, and the analog video
`Signal input within the pixel becomes the gate Voltage of the
`EL driver TFT. At this point, the gate voltage and the drain
`current vary linearly in accordance with the Id-Vg charac
`teristic shown in FIG. 3A. In other words, the drain region
`electric potential(the on EL driver electric potential) is
`determined in correspondence with the Voltage of the analog
`video signal input to the gate electrode of the EL driver TFT,
`a predetermined drain current flows in the EL element, and
`the EL element emits light with an emission amount corre
`sponding to the amount of electric current.
`0037. The amount of light emitted by the EL element is
`thus controlled in accordance with the Video signal, and gray
`Scale display is performed by the control of the amount of
`light emitted.
`0.038 However, the above analog drive has a drawback in
`that it is extremely weak with respect to variations in the
`TFT characteristics. For example, Suppose that the Id-Vg
`characteristic of a Switching TFT differs from that of the
`Switching TFT of an adjacent pixel displaying the same
`gradation (a case of an overall positive or negative shift).
`0039. In this case, the drain current of each Switching
`TFTS becomes different on the degree of the variation, and
`a different gate Voltage becomes applied to the EL driver
`TFT of each pixels. In other words, a different electric
`current flows in each of the EL elements, and as a result, the
`amount of light emitted differs, and display of the same
`gradation can not be performed.
`0040. Further, even Supposing that equal gate Voltages
`are applied to the EL driver TFT of each pixels, if there is
`dispersion in the Id-Vg characteristic of the EL driver TFTs,
`then the same drain current cannot be output. In addition, as
`is made clear from FIG. 3A, the region used is one in which
`the drain current changes exponentially with respect to
`changes in the gate Voltage, and therefore even if the Id-Vg
`characteristic deviates by a slight amount, a situation can
`develop in which the amount of electric current output
`differs greatly even with equal gate Voltages. If this occurs,
`then even if the same Voltage signals are input, the amount
`of light emitted by EL elements in adjacent pixels differs
`greatly due to a slight deviation in the Id-Vg characteristic.
`0041. In practice, there is a multiplier effect between the
`variations in the Switching TFTs and the EL driver TFTs, and
`therefore it becomes conditionally more difficult. The analog
`drive is thus extremely Sensitive with respect to dispersion
`in TFT characteristics, and this disturbs the multi-coloriza
`tion of conventional active matrix EL display devices.
`
`SUMMARY OF THE INVENTION
`0042. The present invention has been made in view of the
`above problems, and an object of the present invention is to
`
`provide an active matrix type EL display device capable of
`performing clear multi-gray Scale display. In addition, an
`object of the present invention is to provide a high perfor
`mance electronic device in which this type of active matrix
`EL display device is loaded as a display.
`0043. The applicant of the present invention considers
`that the above analog driver problems arise from the fact that
`the amount of electric current flowing in the EL elements is
`controlled by using the Sub-threshold region, in which the
`impact of dispersion in the Id-Vg characteristic is easily felt
`because the drain current changes exponentially with respect
`to changes in the gate Voltage.
`0044 Namely, when there are variations in the Id-Vg
`characteristic, there is exponential change in the drain cur
`rent with respect to changes in the gate Voltage in the
`Sub-threshold region, and therefore differing electric cur
`rents (drain currents) are output even if equal gate voltages
`are applied. As a result, a defect develops in which desired
`gradations are not obtained.
`004.5 The applicant of the present invention therefore
`considers performing control of the amount of light emitted
`by the EL elements by not performing control of the electric
`current using the Sub-threshold region, but mainly perform
`ing control of the amount of time that the EL elements emit
`light. In short, gray Scale display is performed with the
`present invention by controlling the amount of light emitted
`by the EL elements with time. Performing gray Scale display
`by controlling the amount of time which light is emitted by
`the EL elements is referred to as a time partitioning driver
`method (hereafter referred to as a digital drive). Note that
`gray Scale display performed by the time partitioning driver
`method is referred to as time division gray Scale display.
`0046 By employing the above structure, variations in the
`amount of electric current output when equal gate Voltages
`are applied can be Suppressed even if there are Small
`variations in the Id-Vg characteristic of the TFTs. It there
`fore becomes possible to eliminate the Situation of greatly
`differing amounts of light emitted by the EL elements of
`adjacent pixels due to variations in the Id-Vg characteristic,
`even if the same Voltage Signal is input.
`0047 The constitution of the present invention is shown
`below.
`0048. According to the present invention, there is pro
`Vided an electro-optical device comprising a plurality of EL
`elements and a plurality of pixels having the plurality of EL
`elements, wherein gray Scale display is performed by con
`trolling the period during which the EL elements emit light,
`and the brightness of the light emitted by the EL elements,
`during one frame period.
`0049 According to the present invention, there is pro
`Vided an electro-optical device comprising a plurality of EL
`elements and a plurality of pixels having the plurality of EL
`elements, wherein one frame period consists of n Subframe
`periods SF1, SF2, . . . , Sfn, the n subframe periods SF1,
`SF2, ..., SFn have address periods Ta1, Ta2, ..., Tan and
`Sustain periods TS1, TS2, ..., TSn, respectively, digital data
`Signals in the address periods Ta1, Ta2, ..., Tan are input
`to all of the plurality of pixels, the plurality of EL elements
`are Selected to emit light or not to emit light during the
`Sustain periods TS1, TS2, . . . , TSn in accordance with the
`digital data Signals, the brightness of the light emitted by the
`
`Petitioner Samsung Ex. 1011 - Page 26 of 50
`
`

`

`US 2003/O197664 A1
`
`Oct. 23, 2003
`
`EL elements during at least one Sustain period Tsp (where p
`is a natural number greater than or equal to 1, and less than
`or equal to n), among the Sustain periods TS1, Ts2, ... Tsin,
`is 1/m (where m is a positive number) of the brightness of
`the light emitted by the EL elements during an arbitrary
`Sustain period TSq, excepting the Sustain period Tsp, and
`(where q is an arbitrary natural number greater than or equal
`to 1, and less than or equal to n, excepting p), the length of
`the sustain period Tsp is expressed as 2PTxm (where T
`is a positive constant), and the length of the Sustain period
`Tsq is expressed as 2T.
`0050. According to the present invention, it may be
`characterized in that the plurality of EL elements each have
`a first electrode, a Second electrode, and an EL layer formed
`between the first electrode and the second electrode and the
`EL layerS contain a low molecular weight organic material
`or an organic polymer material.
`0051. According to the present invention, there is pro
`Vided an electro-optical device comprising a plurality of EL
`elements and a plurality of pixels having the plurality of EL
`elements, wherein one frame period consists of n Subframe
`periods SF1, SF2, . . . , Sfn, the n subframe periods SF1,
`SF2, ..., SFn have address periods Ta1, Ta2, ..., Tan and
`Sustain periods TS1, TS2, ..., TSn, respectively, digital data
`Signals in the address periods Ta1, Ta2, . . . , Tan are input
`to all of the plurality of pixels, the plurality of EL elements
`are Selected to emit light or not to emit light during the
`Sustain periods TS1, TS2, . . . , TSn in accordance with the
`digital data Signals, the brightness of the light emitted by the
`EL elements during at least one Sustain period Tsp (where p
`is a natural number greater than or equal to 1, and less than
`or equal to n), among the Sustain periods TS1, TS2,..., Tsin,
`is 1/m (where m is a positive number) of the brightness of
`the light emitted by the EL elements during an arbitrary
`Sustain period TSq, excepting the Sustain period Tsp, and
`(where q is an arbitrary natural number greater than or equal
`to 1, and less than or equal to n, excepting p), the length of
`the sustain period Tsp is expressed as 2PTxm (where T is
`a positive constant), the length of the Sustain period Tsq is
`expressed as 2Tm, each the plurality of EL elements
`has a first electrode, a Second electrode, and an EL layer
`formed between the first electrode and the second electrode
`and the brightness of the light emitted by the EL elements is
`controlled by an on EL driver voltage applied between the
`first electrode and the Second electrode.
`0.052 According to the present invention, it may be
`characterized in that the EL layerS contain a low molecular
`weight organic material or an organic polymer material.
`0.053 According to the present invention, it may be
`characterized in that the low molecular weight organic
`material is made from Alq3 (tris-8-quinolinolate aluminum
`complex) or TPD (triphenylamine dielectric).
`0.054 According to the present invention, it may be
`characterized in that the organic polymer material is made
`from PPV (poly-paraphenylene vinylene), PVK (poly-vinyl
`carbazole), or polycarbonate.
`0.055 According to the present invention, one frame
`period may be equal to or less than /60 Second.
`0056 According to the present invention, it may be
`characterized in that the electro-optical device has a memory
`circuit for Storing correction data in order to apply a cor
`
`rection to a display and the digital Video signal corrected by
`the memory circuit is input to a Source Signal Side driver
`circuit.
`0057 The present invention may be a computer, a video
`camera or a DVD player using the electro-optical device.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`In the accompanying drawings:
`0058
`0059 FIG. 1 is a circuit diagram of a pixel portion of an
`EL display of the present invention;
`0060 FIG. 2 is a timing chart of a digital time division
`gray Scale display of the present invention;
`0061
`FIGS. 3A and 3B are graphs showing the transis
`tor characteristics of an EL driver TFT,
`0062 FIGS. 4A and 4B are diagrams showing a circuit
`Structure of an EL display of the present invention;
`0063 FIG. 5 is a schematic diagram of a cross sectional
`Structure of an EL display of the present invention;
`0064 FIG. 6 is a timing chart of a digital time division
`gray Scale display of the present invention;
`0065 FIGS. 7A to 7E are diagrams showing a process of
`manufacturing an EL display of the present invention;
`0066 FIGS. 8A to 8D are diagrams showing the process
`of manufacturing the EL display of the present invention;
`0067 FIGS. 9A to 9D are diagrams showing the proc