(19) United States
`(19) United States
`(12) Patent Application Publication
`(10) Pub. No.: US 2001/0038369 Al
`(12) Patent Application Publication (10) Pub. No.: US 2001/0038369 A1
`Nov. 8, 2001
`Adachi et ai.
`(43) Pub. Date:
`Adachi et al.
`(43) Pub. Date:
`NOV. 8, 2001
`
`111111
`
`11111111111111111111111111111111111111111111111111111111111111
`US 20010038369Al
`US 20010038369A1
`
`(54) LIQUID CRYSTAL DISPLAY DEVICE
`(54) LIQUID CRYSTAL DISPLAY DEVICE
`
`Inventors: Takako Adachi, Nara (lP); Makoto
`(76) Inventors: Takako Adachi, Nara (JP); Makoto
`(76)
`Shiomi, Nara (JP)
`Shiomi, Nara (JP)
`
`(lP) ...................................... 2001-032773
`Feb. 8, 2001
`Feb. 8, 2001 (JP) .................................... .. 2001-032773
`(lP) ........................................ 2001038246
`Feb. 15, 2001
`Feb. 15, 2001 (JP) ...................................... .. 2001038246
`
`Publication Classi?cation
`Publication Classification
`
`Correspondence Address:
`Correspondence Address:
`David G. Conlin, Esq.
`David G. Conlin, Esq.
`Dike, Bronstein, Roberts & Cushman IP Group
`Dike, Bronstein, Roberts & Cushman IP Group
`Edwards & Angel], LLP
`Edwards & Angell, LLP
`130 Water Street
`130 W t
`St
`t
`Bostona REA (33:09 (Us)
`Boston, MA 02109 (US)
`’
`(21) APPL NO:
`(21) Appl. No.:
`
`(22) Filed;
`(22) Filed:
`
`09/820 021
`09/820,021
`’
`Man 28, 2001
`Mar. 28, 2001
`
`(30)
`(30)
`
`Foreign Application Priority Data
`Foreign Application Priority Data
`
`(lP) ...................................... 2000-091832
`Mar. 29, 2000
`Mar. 29, 2000 (JP) .................................... .. 2000-091832
`(lP) ...................................... 2000-096765
`Mar. 31, 2000
`Mar. 31, 2000 (JP) .................................... .. 2000-096765
`
`Int. CI? ....................................................... G09G 3/36
`(51)
`(51) Int. Cl.7 ..................................................... .. G09G 3/36
`(52) U.S. CI.
`................................................................ 345/87
`(52) US. Cl. .............................................................. .. 345/87
`
`ABSTRACT
`(57)
`ABSTRACT
`(57)
`Aliquid crystal (LC) display device includes a LC panel and
`A liquid crystal (LC) display device includes a LC panel and
`a driving circuit. The LC panel exhibits, in its voltage(cid:173)
`a driving circuit. The LC panel exhibits, in its voltage
`transmittance characteristics, an extreme transmittance at a
`transmittance characteristics, an extreme transmittance at a
`voltage equal to or lower than a lowest gray-level voltage.
`voltage equal to or loWer than a loWest gray-level voltage.
`The driving circuit supplies to the LC panel a predetermined
`The driving circuit supplies to the LC panel a predetermined
`driving voltage overshooting a gray-level voltage corre
`driving voltage overshooting a gray-level voltage corre(cid:173)
`sponding to an input image signal of a current vertical
`sponding to an input image signal of a current vertical
`period, according to a combination of an input image signal
`period, according to a combination of an input image signal
`of an immediately preceding vertical period and the input
`of an immediately preceding vertical period and the input
`image signal of the current vertical period.
`image signal of the current vertical period.
`
`EMBODIMEfl:T
`EMBODIMENT
`
`--, )
`1
`I
`//
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`/ COMPARATIVE
`/
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`EXAMPLE =i!===r===t---I;-----t----:--
`EXAMPLE
`I
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`
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`
`SHARP EXHIBIT 1004
`
`Page 1 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 1 of 22
`Nov. 8, 2001 Sheet 1 0f 22
`Patent Application Publication
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
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`Page 2 of 44
`
`

`

`Nov. 8, 2001 Sheet 2 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 2 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 2A
`FIG. 2A
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`c
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`APPLIED VOLTAGE (v)
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`APPLIED VOLTAGE
`(V)
`APPLIED VOLTAGE (V)
`
`Page 3 of 44
`
`

`

`Nov. 8, 2001 Sheet 3 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 3 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 3
`FIG. 3
`
`0
`
`APPLIED VOLTAGE
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`
`Page 4 of 44
`
`

`

`Nov. 8, 2001 Sheet 4 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 4 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 4
`FIG. 4
`
`10
`10
`~ ___________ ~A~ __________ _
`)L
`K
`14 ~ 15
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`13
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`> +
`
`INPUT S
`INPUT S O I
`
`11
`11
`
`Page 5 of 44
`
`

`

`Nov. 8, 2001 Sheet 5 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 5 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG.5A
`FIG. 5A
`
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`APPLIED VOLTAGE
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`
`Page 6 of 44
`
`

`

`Nov. 8, 2001 Sheet 6 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 6 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 5C
`FIG. 5C
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`
`Page 7 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 7 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 7 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 6
`FIG. 6
`
`
`
`@525: 2,672”;
`
`TIME
`TIME
`
`1 FIELD (1/2 FIELD OF FIG. 5B)
`1 FIELD (1/2 FIELD OF FIG. 5B)
`
`Page 8 of 44
`
`

`

`Nov. 8, 2001 Sheet 8 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 8 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 7
`FIG. 7
`
`Z ABSORPTIONAXIS
`A
`
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`
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`
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`
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`ABSORPTION AXIS Z
`A
`
`25
`
`Page 9 of 44
`
`

`

`Nov. 8, 2001 Sheet 9 0f 22
`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 9 of 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 8
`FIG. 8
`
`y
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`y
`
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`
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`
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`(INCLINATION ANGLE = 0 DEGREE)
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`(IN—PLANE RETARDATION : 0)
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`
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`SMALL
`
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`IN~PLANE RETARDATION
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`INCL INAT ION ANGLE
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`
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`
`Page 10 of 44
`
`

`

`Patent Application Publication
`Patent Application Publication Nov. 8,2001 Sheet 10 of 22
`Nov. 8, 2001 Sheet 10 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 9
`FIG. 9
`
`d=O f-l m
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`Page 11 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 11 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 11 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 10
`FIG. 10
`
`/30
`
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`Page 12 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 12 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 12 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 11
`FIG. 11
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`Page 13 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 13 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 13 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 12
`FIG. 12
`
`15
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`Page 14 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 14 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 14 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`"..-...
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`
`Page 15 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 15 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 15 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 14
`FIG. 14
`
`120
`120
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`50. 1
`
`66.8
`66. 8
`
`TIME (msec)
`TIME (Insec)
`
`Page 16 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 16 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 16 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 15
`FIG. 15
`
`1.1
`1
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`
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`4
`
`Cs/Clc
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`
`--+- 48~63
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`---- 16~63
`--* 0~63
`-.- 16~48
`-B- 32~48
`-ts:- 16~32
`-.- 0~48
`-e- 0~32
`-*- 0~16
`
`Page 17 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 17 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 17 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 16
`FIG. 16
`
`JI\
`
`- VO---+V28
`- VO---+V44
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`o
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`50.1
`50. 1
`
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`TIME (msec)
`
`,
`-"
`
`Page 18 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 18 of 22
`Nov. 8, 2001 Sheet 18 0f 22
`Patent Application Publication
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 17
`FIG. 17
`
`POLARIZATION AXIS‘
`POLARIZATION AXIS~ ~
`TRANSMISSION AXIS
`109
`TRANSMISSION AXIS
`109
`
`/100
`
`a
`
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`
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`100b
`lOlb
`lOlb
`
`102
`
`110
`
`104
`
`Page 19 of 44
`
`

`

`Patent Application Publication Nov. 8, 2001 Sheet 19 of 22
`Patent Application Publication
`Nov. 8, 2001 Sheet 19 0f 22
`
`US 2001/0038369 Al
`US 2001/0038369 A1
`
`FIG. 18A
`FIG. 18A
`
`~ ,
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`\
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`"-
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`CONVENTIONAL
`CONVENTIONAL
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`PRESENT INVENTION
`PRESENT INVENTION
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`TIME (msec)
`TIME (msec)
`
`FIG. 18B
`FIG. 1813
`
`INPUT IMAGE SIGNAL
`INPUT IMAGE SIGNAL
`
`OVERSHOOT
`OVERSHOOT
`GRAY-LEVEL VOLTAGE
`GRAY-LEVEL VOLTAGE
`
`- - - - - - - - -
`
`_ _ _ _ _ _ _ _ _ _ _
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`
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`
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`:>
`
`Page 20 of 44
`
`

`

`Patent Application Publication Nov. 8, 2001 Sheet 20 of 22
`
`US 2001/0038369 Al
`
`FIG. 19A
`
`/ A
`203
`
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`UV
`
`Page 21 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 21 of 22
`
`US 2001/0038369 Al
`
`FIG. 20
`
`./ ----
`
`./
`
`/
`
`/
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`
`PRESENT INVENTION
`
`0
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`
`Page 22 of 44
`
`

`

`Patent Application Publication Nov. 8,2001 Sheet 22 of 22
`
`US 2001/0038369 Al
`
`FIG. 21
`
`Sc (t)
`
`:---67-i
`I
`POLARITY
`INPUT
`S (t) 0-----*-------;;-;:;----i,-__ +l---I-----'-~Il\TVERSION
`I
`I ,
`
`I
`
`1
`
`LIQUID
`CRYSTAL
`DISPLAY
`SECTION
`
`65
`
`64
`
`1
`66
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`
`Sd(t)
`
`}
`63
`
`61
`
`FIG. 22
`
`INPUT IMAGE SIGNAL
`S (t)
`
`~--t--- t
`
`TIME-AXIS INPUT CHANGE
`Sd (t)
`
`1 - - - t
`
`HIGH-BAND CORRECTION SIGNAL
`Sc(t)
`
`OPTICAL RESPONSE
`I (t)
`
`Page 23 of 44
`
`

`

`US 2001/0038369 Al
`
`Nov. 8,2001
`
`1
`
`LIQUID CRYSTAL DISPLAY DEVICE
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1. Field of the Invention
`
`[0002] The present invention generally relates to a liquid
`crystal display device (LCD). More particularly, the present
`invention relates to an LCD preferably used for moving
`picture display.
`
`[0003] 2. Description of the Background Art
`
`[0004] The LCDs are used for, e.g., personal computers,
`word processors, amusement equipments, television sets,
`and the like. Improvement in response characteristics of the
`LCDs has been studied for high-quality moving picture
`display.
`
`Japanese Laid-Open Publication No. 4-288589 dis(cid:173)
`[0005]
`closes an LCD having an increased response speed for
`intermediate-gray-scale display in order to reduce a residual
`image. In this LCD, an input image signal having its
`high-band components pre-enhanced is supplied to a liquid
`crystal display section so that the rise and fall speeds of the
`response are increased. Note that the "response speed" in the
`LCDs (liquid crystal panels) corresponds to an inverse
`number of the time required for the liquid crystal layer to
`reach an alignment state corresponding to the applied volt(cid:173)
`age (i.e., response time). The structure of a driving circuit of
`this LCD will be described with reference to FIG. 21.
`
`[0006] The driving circuit of the aforementioned LCD
`includes an image storage circuit 61 for retaining at least one
`field image of an input image signal Set), and a time-axis
`filter circuit 63 for detecting a variation in level of each
`picture element in the time-axis direction, based on the
`image signal retained in the storage circuit 61 and the input
`image signal Set), and filtering the input image signal Set) for
`high-band enhancement in the time-axis direction. The input
`image signal Set) is a video signal decomposed into R (Red),
`G (Green) and B (Blue) signals. Since the R, G and B signals
`are subjected to the same processing, only one channel is
`shown herein.
`
`[0007] The input image signal Set) is retained in the image
`storage circuit 61 for storing an image signal of at least one
`field. A difference circuit 62 calculates the difference
`between respective picture-element signals of the input
`image signal Set) and the image signal stored in the image
`storage circuit 61. Thus, the difference circuit 62 serves as
`a level variation detection circuit for detecting a variation in
`signal level during a single field. A difference signal Sd(t) in
`the time-axis direction from the difference circuit 62 is input
`together with the input image signal S( t) into the time-axis
`filter circuit 63.
`
`[0008] The time-axis filter circuit 63 is formed from a
`weighting circuit 66 for weighting the difference signal Sd( t)
`with a weight coefficient a corresponding to the response
`speed, and an adder 67 for adding the weighted difference
`signal and the input image signal Set) together. The time-axis
`filter circuit 63 is an adaptive filter circuit whose filter
`characteristics can be varied according to the output of the
`level variation detection circuit and the input level of each
`picture element of the input image signal. This time-axis
`filter circuit 63 enhances the input image signal Set) in its
`high band in the time-axis direction.
`
`[0009] The high-band enhanced signal thus obtained is
`converted into an alternating current (AC) signal by a
`polarity inversion circuit 64, and this AC signal is supplied
`to a liquid crystal display section 65. The liquid crystal
`display section 65 is an active-matrix liquid crystal display
`section including display electrodes (also referred to as
`picture-element electrodes) at the respective intersections of
`a plurality of data signal lines and a plurality of scanning
`signal lines crossing the same.
`
`[0010] FIG. 22 is a signal waveform chart illustrating how
`the response characteristics are improved with this driving
`circuit. For simplicity of the description, it is herein assumed
`that the input image signal Set) changes with a cycle period
`of one field, and the figure shows the case where the signal
`level rapidly changes in two fields. In this case, as shown in
`the figure, a change in the input image signal S( t) in the
`time-axis direction, i.e., the difference signal Sd(t), becomes
`positive for one field in response to the input image signal
`Set) changing to positive, and becomes negative for one field
`in response to the input image signal Set) changing to
`negative.
`
`[0011] Basically, high-band enhancement can be achieved
`by adding the difference signal Sd(t) to the input image
`signal Set). Actually, the relation between the respective
`degrees of change in the input image signal Set) and in the
`transmittance depends on the response speed of the liquid
`crystal layer. Therefore, the weight coefficient a is deter(cid:173)
`mined so as to make correction within the range that does
`not cause any overshoot. As a result, a high-band enhanced
`high-band correction signal Sc(t) as shown in FIG. 22 is
`input to the liquid crystal display section, whereby optical
`response characteristics I(t) are improved as shown by the
`solid line over a conventional example shown by the dashed
`line.
`
`In the case where the driving circuit as disclosed in
`[0012]
`the aforementioned publication is applied to a current LCD,
`response characteristics at a rise (a change to the display
`state corresponding to an increase in voltage applied to the
`liquid crystal layer) can be improved. However, the effect of
`improving the response characteristics at a fall (a change to
`the display state corresponding to a decrease in voltage
`applied to the liquid crystal layer) is relatively poor. In the
`LCD, a fall indicates a relaxation phenomenon that the
`liquid crystal molecules are restored from the orientation
`state corresponding to a first voltage toward that correspond(cid:173)
`ing to a second voltage that is lower than the first voltage.
`The time required for the liquid crystal molecules to reach
`the orientation state corresponding to the second voltage
`(fall response time) mainly depends on the restoring force
`acting between the liquid crystal molecules. Accordingly, in
`the case where the voltage applied to the liquid crystal layer
`reduces from the first voltage to the second voltage, the fall
`response speed (or fall response time) of the liquid crystal
`layer generally does not so much depend on the magnitude
`of the second voltage (the difference from the first voltage).
`Therefore, the effect of increasing the fall response speed is
`poor even if the input image signal Set) is emphasized.
`
`It is now assumed that the lowest gray-level volt(cid:173)
`[0013]
`age (the lowest value of the gray-level voltage) is set to the
`value corresponding to the maximum transmittance in the
`LCD having such voltage-transmittance (V-T) characteris(cid:173)
`tics as shown in FIG. 20 of the aforementioned Japanese
`
`Page 24 of 44
`
`

`

`US 2001/0038369 Al
`
`Nov. 8,2001
`
`2
`
`Laid-Open Publication No. 4-288589 (corresponding to the
`V-T curve of 260-nm retardation in FIG. SA of the present
`application). Particularly in this case, the fall response speed
`cannot be increased even if an overshoot voltage (a voltage
`lower than the lowest gray-level voltage) is applied. The
`reason for this is as follows: the orientation state of the liquid
`crystal molecules is substantially the same within a voltage
`region corresponding to the maximum transmittance (a fiat
`region of the V-T curve). Therefore, the restoring force
`acting between the liquid crystal molecules is substantially
`the same whatever voltage within this region is applied.
`
`[0014] As described above, the terms "rise" and "fall" as
`used in the specification correspond to a change in display
`state (or orientation state of the liquid crystal layer) accord(cid:173)
`ing to an "increase" and "decrease" in voltage applied to the
`liquid crystal layer, respectively. A "rise", which is a change
`with an increase in applied voltage, corresponds to a "reduc(cid:173)
`tion in brightness" in the normally white mode (hereinafter,
`referred to as "NW mode") and to an "increase in bright(cid:173)
`ness" in the normally black mode (hereinafter, referred to as
`"NB mode"). A "fall", which is a change with a decrease in
`applied voltage, corresponds to an "increase in brightness"
`in the NW mode and to a "reduction in brightness" in the NB
`mode. In other words, a "fall" is associated with the relax(cid:173)
`ation phenomenon of the orientation of the liquid crystal
`layer (liquid crystal molecules).
`
`[0015] Moreover, the driving method disclosed in the
`aforementioned Japanese Laid-Open Publication No.
`4-288589 has a problem that the input image signal Set)
`capable of being subjected to effective high-band enhance(cid:173)
`ment is limited. More specifically, the high-band correction
`signal Sc(t) cannot exceed a high-band limit signal (which is
`herein defined as a signal having the highest voltage among
`the input image signals s( t) that are input to the liquid crystal
`display section). Therefore, the input image signal can be
`subjected to high-band enhancement if the high-band cor(cid:173)
`rection signal Sc(t)~the high-band limit signal. However, if
`the high-band correction signal Sc(t»the high-band limit
`signal, a correction signal enough to cause a sufficient
`change in transmittance cannot be input to the liquid crystal
`display section. Accordingly, the response speed is increased
`at an intermediate gray level, but the effect of improving the
`optical response characteristics is reduced at a higher band
`level (as the voltage applied to the liquid crystal display
`section is increased).
`
`[0016] The present invention is made in view of the
`aforementioned problems, and it is an object of the present
`invention to provide an LCD with improved fall response
`characteristics. It is another object of the present invention
`to provide an LCD with improved response characteristics at
`least at a high-band level.
`
`SUMMARY OF THE INVENTION
`
`[0017] A liquid crystal display device according to a first
`aspect of the present invention includes: a liquid crystal
`panel including a liquid crystal layer and an electrode for
`applying a voltage to the liquid crystal layer; and a driving
`circuit for supplying a driving voltage to the liquid crystal
`panel, wherein the liquid crystal panel exhibits, in its volt(cid:173)
`age-transmittance characteristics, an extreme transmittance
`at a voltage equal to or lower than a lowest gray-level
`voltage, and the driving circuit supplies to the liquid crystal
`
`panel a predetermined driving voltage overshooting a gray(cid:173)
`level voltage corresponding to an input image signal of a
`current vertical period, according to a combination of an
`input image signal of an immediately preceding vertical
`period and the input image signal of the current vertical
`period. Thus, the object of the present invention, i.e.,
`improved fall response characteristics, is achieved.
`
`[0018] Preferably, a difference in retardation of the liquid
`crystal panel between a state where a voltage is not applied
`and a state where a highest gray-level voltage is applied is
`300 nm or more.
`
`[0019] Preferably, the liquid crystal panel is a transmis(cid:173)
`sion-type liquid crystal panel, and the extreme transmittance
`provides a maximum transmittance.
`
`[0020] A single vertical period of the input image signal
`may correspond to a single frame, at least two fields of the
`driving voltage may correspond to a single frame of the
`input image signal, and the driving circuit may supply, at
`least in a first field of the driving voltage, a driving voltage
`overshooting a gray-level voltage corresponding to an input
`image signal of a current field to the liquid crystal panel.
`
`[0021] Preferably, the liquid crystal layer is a homoge(cid:173)
`neous-orientation liquid crystal layer.
`
`[0022] The liquid crystal panel may further include a
`phase compensator, three principal refractive indices na, nb
`and nc of an index ellipsoid of the phase compensator may
`have a relation of na=nb>nc, and the phase compensator
`may be arranged so as to cancel at least a part of retardation
`of the liquid crystal layer.
`
`[0023] A liquid crystal display device according to a
`second aspect of the present invention includes: a liquid
`crystal panel including a plurality of picture-element capaci(cid:173)
`tors arranged in a matrix, and thin film transistors respec(cid:173)
`tively electrically connected to the plurality of picture(cid:173)
`element capacitors; and a driving circuit for supplying a
`driving voltage to the liquid crystal panel, wherein the liquid
`crystal display device updates display every vertical period
`by rendering the plurality of picture-element capacitors in a
`charged state corresponding to the input image signal, each
`of the plurality of picture-element capacitors includes a
`liquid crystal capacitor formed from a corresponding pic(cid:173)
`ture-element electrode, a counter electrode and a liquid
`crystal layer provided between the picture-element electrode
`and the counter electrode, and a storage capacitor electri(cid:173)
`cally connected in parallel with the liquid crystal capacitor,
`a capacitance ratio of the storage capacitor to the liquid
`crystal capacitor being 1 or more, and the picture-element
`capacitor retains 90% or more of a charging voltage over a
`single vertical period, when at least a highest gray-level
`voltage is applied. Thus, the object of the present invention,
`i.e., improved response characteristics at least at a high-band
`level, is achieved.
`
`[0024] Preferably, the driving circuit supplies to the liquid
`crystal panel a predetermined driving voltage overshooting
`a gray-level voltage corresponding to an input image signal
`of a current vertical period, according to a combination of an
`input image signal of an immediately preceding vertical
`period and the input image signal of the current vertical
`period.
`
`[0025] For the input image signal of every gray level, the
`driving circuit may supply to the liquid crystal panel the
`
`Page 25 of 44
`
`

`

`US 2001/0038369 Al
`
`Nov. 8,2001
`
`3
`
`driving voltage overshooting the gray-level voltage corre(cid:173)
`sponding to the input image signal of the current vertical
`period.
`
`[0026] The liquid crystal layer of the liquid crystal panel
`may include a nematic liquid crystal material having a
`positive dielectric anisotropy,
`the
`liquid crystal layer
`included in each of the plurality of picture-element capaci(cid:173)
`tors may include first and second regions having different
`orientation directions, and the liquid crystal panel may
`further include a pair of polarizers arranged so as to orthogo(cid:173)
`nally cross each other with the liquid crystal layer interposed
`therebetween, and a phase compensator for compensating
`for a refractive index anisotropy of the liquid crystal layer in
`a black display state.
`
`[0027] Alternatively, the liquid crystal layer may be a
`homogeneous-orientation liquid crystal layer.
`
`[0028] Preferably, the liquid crystal panel further includes
`a phase compensator, three principal refractive indices na,
`nb and nc of an index ellipsoid of the phase compensator
`have a relation of na=nb>nc, and the phase compensator is
`arranged so as to cancel at least a part of retardation of the
`liquid crystal layer.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0029] FIG. 1 is a graph showing V-T curves of a liquid
`crystal panel that includes a parallel-orientation liquid crys(cid:173)
`tal layer including a liquid crystal material with a positive
`refractive index anisotropy (lm=n//-n~>O).
`
`[0030] FIG. 2A is a graph showing a voltage-retardation
`curve of a liquid crystal panel having a retardation of 260
`nm.
`
`[0031] FIG. 2B is a graph showing a voltage-retardation
`curve of a liquid crystal panel having a retardation of 300
`nm.
`
`[0032] FIG. 3 is a schematic diagram showing the relation
`between a V-T curve, dedicated overshoot-driving voltage
`Vos and gray-level voltage Vg in a liquid crystal panel
`included in an LCD according to an embodiment of the
`present invention.
`
`[0033] FIG. 4 is a schematic diagram showing the struc(cid:173)
`ture of a driving circuit 10 included in the LCD according to
`the embodiment of the present invention.
`
`[0034] FIG. SA is a graph showing the respective V-T
`curves of the LCD according to the embodiment of the
`present invention (liquid crystal panel with 320-nm retar(cid:173)
`dation) and an LCD of a comparative example (liquid crystal
`panel with 260-nm retardation