(12) United States Patent
`Tagusa
`
`US006226061Bl
`(10) Patent NO.: US 6,226,061 B1
`(45) Date of Patent:
`May 1,2001
`
`(54) LIQUID CRYSTAL DISPLAY DEVICE
`HAVING PHASE DIFFERENT PLATES
`
`(75)
`
`Inventor: Yasunobu Tagusa, Ikoma (JP)
`
`(73) Assignee: Sharp Kabushiki Kaisha, Osaka (JP)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 091047,115
`Mar. 24, 1998
`
`(22) Filed:
`
`Foreign Application Priority Data
`(30)
`(JP) ................................................... 9-072257
`Mar. 25, 1997
`(JP) ................................................. 10-033444
`Feb. 17, 1998
`(51) Int. CL7 ....................... G02F 111333; G02F 111347;
`G02F 111343
`(52) U.S. C1. ............................ 349184; 3491141; 3491169;
`3491188; 349175
`(58) Field of Search ................................ 349184, 75, 141,
`3491169, 181, 188, 117, 120
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`* 511993 Wada ..................................... 359163
`411996 Yamahara et al. ..................... 359173
`* 1211996 Ito et al. .............................. 3491118
`611997 den Boer et al. ...................... 257159
`* 411998 Moriwaki et al. ................... 3491117
`* 611998 Nakamura ............................ 3491117
`* 811998 Nakamura .............................. 349196
`* 911998 Mori et al. ........................... 3491118
`* 411999 VanderPloeg et al. .............. 3491120
`* 1111999 Winker et al. ....................... 3491120
`812000 Shimada et al. ....................... 349139
`
`FOREIGN PATENT DOCUMENTS
`1211997 (EP) .
`111980 (JP) .
`1011983 (JP) .
`811993 (JP) .
`1111993 (JP) .
`
`0 851 269 A1
`55-600
`58-172685
`5-210099
`5-313159
`
`6-230422
`6-242437
`7-64096
`
`811994 (JP) .
`911994 (JP) .
`311995 (JP) .
`
`OTHER PUBLICATIONS
`
`"Challenge to Super-Resolution in CRT By Displaying One
`Pixel With Plural Pixel Regions" (Nikkei Microdevices,
`published on Jul. 1, 1997, pp. 108-110).
`Radler et al, "Cylotene Advanced Electronics Resins for
`High Aperture AMLCD Applications". SID 96 Applications
`Digest pp. 33-36, 1996.*
`
`* cited by examiner
`
`Primary Examinerxenneth Parker
`Assistant E x a m i n e r 4 i k e Qi
`(74) Attorney, Agent, o r F i r m 4 a v i d G. Conlin; Steven M.
`Jensen; Dike, Bronstein, Roberts and Cushman, LLP
`
`(57)
`
`ABSTRACT
`Aliquid crystal display (LCD) device is composed of (1) an
`LCD element having (i) a glass substrate on which a flat
`portion including pixel electrodes and a flat portion includ-
`ing switching elements, wires, and the like are laminated
`with interlayer insulating films therebetween, each interlayer
`insulating film being an organic film with an optical trans-
`mittance of not less than 95 percent with respect to light with
`a peak wavelength and (ii) a liquid crystal layer made of
`liquid crystal whose refractive index anisotropy An(450)
`with respect to light with a wavelength of 450 nm and whose
`refractive index anisotropy An(650) with respect to light
`with a wavelength of 650 nm satisfy a condition that a
`difference An(450)-An(650) between them is set so as to be
`in a range of 0 to 0.01, and (2) a phase difference plate whose
`refractive index anisotropy is negative (na=nc>nb) and
`whose index ellipsoids are inclined substantially throughout
`the phase difference plate. By thus arranging the LCD
`device, phase differences depending on viewing angles
`which tend to occur to the LCD element are eliminated
`whereby the viewing angle dependence of the LCD device
`is suppressed, while the structure of the pixel substrate is
`improved, and as a result, reversal influences to a display
`screen are avoided.
`
`14 Claims, 14 Drawing Sheets
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`Sheet 1 of 14
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`F I G. 1 (a)
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`F I G.1 (b)
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`Sheet 3 of 14
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`T OP ( ANTI-VIEWING ANGLE
`I DIRECTION )
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`RIGHT
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`BOT T 0 M (NORMAL VIEWING ANGLE
`DIRECTION)
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`FI G. 7 (a)
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`WAVELENGTH ( nm )
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`FIG.8 (a)
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`FIG. 9
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`FIG.10 (a)
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`FIG. 14
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`US 6,226,061 B1
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`2
`other words, the liquid crystal layer is provided between the
`pixel electrodes 51 on the active matrix substrate and the
`counter electrodes provided on the counter substrate,
`thereby constituting a liquid crystal capacitor. The additional
`s capacitors 55 are connected in parallel with the liquid crystal
`capacitor,
`
`in
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`20
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`45
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`1
`LIQUID CRYSTAL DISPLAY DEVICE
`HAVING PHASE DIFFERENT PLATES
`
`FIELD OF THE INVENTION
`
`The present invention relates to a liquid crystal display
`device. More specifically, the present invention relates to a
`liquid crystal display device equipped with switching ele-
`merits such as thin film transistors (hereinafter referred to as
`TFTs) which improve visibility properties and display prop-
`erties of a display screen and make a display not inferior to
`a display of a CRT (cathode-ray tube) display device.
`
`BACKGROUND OF THE INVENTION
`
`each TFT 52 in
`as
`62 is formed On a transparent
`12' a gate
`substrate 61, and a gate insulating film 63 is formed so as to
`cover the gate electrode 62. On the gate electrode 62, a
`semiconductor film 64 is provided with the gate insulating
`film 63 interlaminated therebetween. On a center portion of
`the semiconductor film 64, there is provided a channel
`protective layer 65. On source section sides of the channel
`Conventionally, a liquid crystal display (LCD) device 1s protective layer 65 and the semiconductor thin film 64, a
`using a nematic-type liquid crystal display element has been
`source electrode 66a composed of a microcrystal n+-silicon
`widely used as a digit-segment-type liquid crystal display
`layer is formed, while on drain section sides of the same, a
`device for use in a watch or a electric calculator. Recently it
`drain electrode 66b composed of a microcrystal n+-silicon
`has come to be used as a display device for use in a word
`layer is formed.
`Processor, a computer, a navigation system, or the like.
`The source electrode 66a is connected with a metal layer
`Among such LCD devices, in particular, an active matrix
`67a serving as a source wire, while the drain electrode 66b
`LCD device wherein active elements such as TFTs are used
`is connected with a metal layer 67b serving as a drain wire.
`as switching elements and pixels are arranged in a matrix
`A surface of the TFT 52 is covered with an interlayer
`form is widely used and known. The LCD device has
`insulating film 68, and a transparent conductive film serving
`advantages such as having a drastically reduced thickness 25 as the pixel electrode 51 is formed thereon. The pixel
`electrode 51 is connected with the metal layer 67b as the
`(depth), consuming less power, and being easily modified to
`drain wire of the TFT 52 through a contact hole 69. Further,
`a full-color display device, as compared with the CRT
`on the pixel electrode 51, an alignment film (not shown) for
`display device. Therefore, the demand for the LCD device is
`increasing in various fields such as those of personal
`aligning the liquid crystal is uniformly provided substan-
`computers, various monitors, potable TVs, and cameras. 30 tially throughout a whole display region including marginal
`However, since such a conventional LCD device is inferior
`portions.
`As described above, the interlayer insulating film 68 is
`to the CRT display device in a viewing angle range,
`luminance, color reproduction, and the like, improvement is
`provided between the scanning lines 53 and the signal lines
`35 54 on one hand and the transparent conductive films serving
`eagerly desired in respect to these aspects.
`as the pixel electrodes 51 on the other hand. Therefore, the
`The active matrix LCD device has a transparent active
`matrix substrate, on which a plurality of pixel electrodes 51
`pixel electrodes 51 can be laminated on the scanning lines 53
`and the signal lines 54 with the interlayer insulating film 68
`for applying voltages to a liquid crystal layer are arranged in
`a matrix form as shown in FIG. 11. As active elements which
`interlaminated therebetween. Such arrangement is disclosed
`are switching means for selectively driving the pixel elec- 40 by, for example, the Japanese Publication for Laid-Open
`trodes 51, thin-film transistors (TFTs) 52 are formed on the
`Patent Application No.58-17268511983 (Tokukaisho
`substrate and are connected with the pixel electrodes 51.
`58-172685). With the arrangement, a pixel aperture ratio of
`Further, in the case where the color display is conducted,
`the LCD device is enhanced, and disclination of the liquid
`color filter layers of red, green, blue, and other colors are
`crystal is suppressed by shielding an electric field due to
`signals conducted through the signal lines 54 with the use of
`provided, though not shown, on the active matrix substrate
`or a counter substrate, in addition to the foregoing arrange-
`the interlayer insulating film 68.
`ment.
`As the interlayer insulating film 68, an inorganic thin film
`Gate electrodes of the TFTs 52 are connected with scan-
`made of SIN or the like has conventionally been used. The
`ning lines 53, while source electrodes of the TFTs 52 are
`SIN film is formed by, for example, the CVD (chemical
`connected with signal lines 54. The scanning lines 53 and the
`vapor deposition) method to a thickness of about 500 nm.
`signal lines 54 are provided so as to run beside the pixel
`Here, liquid crystal molecules used as the liquid crystal
`electrodes 51 arranged in matrix and orthogonally cross each
`layer have a refractive index anisotropy An, and the liquid
`other. The TFTs 52 are driven in response to input of gate
`crystal molecules are aligned with an inclination with
`signals through the scanning lines 53. Upon the driving of
`respect to the active matrix substrate and the counter sub-
`the TFTs 52, data signals (display signals) are supplied to the 55 strate sandwiching the liquid crystal molecules. Therefore, a
`pixel electrodes 51 through the signals lines 54 and the TFTs
`contrast of a displayed image alters depending on a viewing
`52.
`direction or a viewing angle of an observer, whereby aggra-
`Furthermore, drain electrodes of the TFTs 52 are con-
`vating the viewing angle dependence.
`nected with the pixel electrodes 51 and additional capacitors
`Regarding the foregoing problem, a liquid crystal display
`55. Counter electrodes provided vis-a-vis the additional 60 method for an LCD device of the twisted-nematic
`capacitors 55 with an insulating layer therebetween are
`(hereinafter referred to as TN) type, which is particularly
`connected with common lines 56. The additional capacitors
`often used among the LCD devices of the nematic type, is
`55 are intended to hold voltages to be applied to the liquid
`explained as follows. As shown in FIG. 13, when a voltage
`crystal layer.
`for a half-tone display is applied to an LCD element 7 1 of
`In the active matrix LCD device, the liquid crystal layer 65 the TN type, each liquid crystal molecule 72 slightly raises
`an end thereof. Here, a linearly polarized light 75 running in
`is provided between the active matrix substrate and the
`a normal direction of surfaces of substrates 73 and 74, and
`counter substrate vis-a-vis to the active matrix substrate. In
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`linearly polarized lights 76 and 77 running in a direction
`Japanese Publication for Laid-Open Patent Application
`inclining with respect to the normal direction cross the liquid
`No.5-31315911993 (Tokukaihei 5-313159)): the LCD
`crystal molecules 72 at different angles. Since the liquid
`device has (i) an LCD element which is arranged so that a
`crystal molecules 72 have the refractive index anisotropy An
`retardation An.d which is a product of a refractive index
`as described above, an ordinary light and an extraordinary 5 anisotropy An of a liquid-crystalline material of the liquid
`light occur when the linearly polarized lights 753 76, and 77
`crystal layer and a thickness d of the liquid crystal layer is
`directed in the respective directions pass through the liquid
`in a range between 200 nm to 500 nm and (ii) a phase
`72. he linearly polarized lights 75, 76,
`difference plate provided between the LCD element and a
`and 77 are
`polarized lights in
`polarizing plate, the phase difference plate being arranged so
`accordance with phase differences between the
`lo that a main refractive index direction of its index ellipsoid is
`light and the extraordinary light, respectively, thereby caus-
`parallel with a normal direction of a surface of the phase
`ing the viewing angle dependence.
`difference plate.
`Inside the liquid crystal layer, among the liquid crystal
`This arrangement is characterized in that the properties of
`molecules 72, those around a mid point between the sub-
`the phase difference plate and the LCD
`are
`strates 73 and 74, those near the substrate 73, and those near
`that a mbbing
`as described above but
`the substrate 74 have different tilt angles. Besides, those near l5 Set "Ot
`direction of an alignment film constituting the LCD element,
`the substrate 73 are twisted with respect to those near the
`a 'low axis direction of the phase difference plate, and a
`substrate 74 through an angle of 90" a round an axis directed
`transmission axis of the polarizing plate are parallel, thereby
`in the normal direction, For these reasons, when passing
`through the liquid crystal layer, the linearly polarized lights
`ensuring further
`of the viewing
`d e ~ e n -
`75, 76, and 77 are affected by various birefringence effects 20
`Even in the case where such a phase difference plate is
`depending on the directions and angles thereof, thereby
`used, reversal which occurs when viewed in the normal
`exhibiting complicated viewing angle dependence.
`viewing angle direction is still recognized in a narrow angle
`phenomena of the viewing angle dependence,
`the following phenomena occurs, in the case where an LCD 25 range.
`Furthermore, to use another arrangement wherein a main
`device is disposed so that better visibility is obtained when
`refractive index direction of the index ellipsoid is inclined
`viewed \in a direction inclined toward a top side\ of the
`with respect to the normal direction of the surface of the
`screen, as shown in FIG, 14: (1) as the viewing direction is
`phase difference plate has been also proposed (see the
`inclined from the normal direction of the screen to a normal
`Japanese Publication for Laid-Open Patent Application
`viewing angle direction which is a direction inclined to a
`bottom side of the display screen, the display becomes 30 No.6-7511611994 (Tokukaihei 6-75116)). In this
`discolored (hereinafter referred to as discoloring) when the
`arrangement, either of phase difference plates of the follow-
`ing two types is used.
`viewing angle exceeds a certain degree, or black and white
`reverse (hereinafter referred to as reversal); and (2) as the
`One is arranged so that among three main refractive
`viewing direction is inclined to an anti-viewing angle direc- 35 Fdexes of the index ellipsoid, the smallest main refractive
`tion which is a direction inclined to a top side of the screen,
`index has a direction parallel with the surface of the phase
`the contrast drastically deteriorates.
`difference plate, and one of the rest two main refractive
`On top of that, the aforementioned LCD device has a
`indexes is inclined at an angle 0 with respect to the surface
`drawback in that the angle of visibility narrows as the
`while the other is inclined at an angle 0 with respect to a
`display screen expands. In viewing a large LCD screen at a 40 normal direction of the surface of the phase difference plate,
`where 0 satisfies 20°50570 ".
`short distance from the front, colors displayed in an upper
`part and in a lower part sometimes differ due to an influence
`The other is arranged so that: (1) the phase difference
`of the viewing angle dependence. This is because an angle
`plate does not have a refractive index anisotropy around its
`surface; (2) a main refractive index nb in a normal direction
`of vision for viewing the whole screen becomes greater,
`whereby viewing an edge portion of the large screen 45 of the surface of the phase difference plate and main
`becomes identical to viewing a smaller LCD screen in a
`refractive indexes na and nc parallel with the surface of the
`direction further inclined.
`phase difference plate satisfy na=nc>nb, that is, the phase
`To suppress the viewing angle dependence, to insert a
`difference plate is negatively uniaxial; and (3) the index
`ellipsoid is inclined by rotating the main refraction index nb
`phase difference plate (phase difference film) as an optical
`element having an optical anisotropy between the LCD
`direction in a clockwise direction or in an anti-clockwise
`element and one polarizing plate has been proposed (see, for
`direction around an axis which is either of the directions of
`example, the Japanese Publication for Laid-Open Patent
`the main refractive indexes na or nc so that the index
`Application No.55-60011980 (Tokukaisho 55-600)).
`ellipsoid shifts from a state of being parallel with the normal
`According to this method, light converted from the lin-
`direction of the phase difference plate surface to a state of
`early polarized light to the elliptically polarized light as 5s being inclined to the same.
`described above is caused to pass through the phase different
`Regarding the foregoing two types of phase difference
`plates, the former may be uniaxial or biaxial. As to the latter,
`plate(s) provided on one side or both the sides of the liquid
`crystal layer, so as to be again converted to linearly polarized
`instead of using a single phase difference plate, a combina-
`light, whereby a phase difference between ordinary light and
`tion of two phase difference plates whose main refractive
`extraordinary light occurring to the viewing angle is 60 index nb directions resulting on the inclination described
`compensated, and suppression of the viewing angle depen-
`above have an angle of 90" therebetween may be used.
`dence is enabled. Therefore, to conduct this method, it is
`In the LCD device thus arranged so as to have at least one
`necessary to adjust not only properties of the phase differ-
`such phase difference plate between the LCD element and
`ence plate but also those of the liquid crystal layer, i.e., the
`the polarizing plate, the viewing angle dependence is sup-
`LCD element.
`65 pressed to some extent. As shown in FIG. 15 which illus-
`Then, to further suppress the viewing angle dependence,
`trates an example of this, improvement regarding the con-
`an LCD device arranged as follows is proposed (see the
`trast and the suppression of reversal is achieved in this case,
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`signal lines 54 on one hand and the pixel electrodes 51 on
`as compared with the case of FIG. 14: the contrast is
`the other hand increases, thereby impairing the display
`improved substantially in all directions, and reversal in the
`quality.
`normal viewing angle direction is also further suppressed,
`More specifically, since an inorganic film such as an SIN
`not occurring till the viewing angle exceeds about 350.
`another means to suppress the viewing angle 5 film has a high dielectric constant such as 8 and such a film
`is formed by the CVD method or the like, it has to be formed
`dependence, an arrangement wherein regions differing in the
`thin to 500 nm or less with a view to reducing defects caused
`tilt angle and the alignment are formed in one pixel electrode
`region has been also proposed (see the Japanese Publications
`by
`forming
`forming time (reflected in
`and
`costs). For these reasons, the electric capacity between the
`for Laid-Open Patent Applications No,5-21009911993
`scanning lines 53 and the signal lines 54 on one hand and the
`(Tokukaihei 5-210099) and No.7-6409611995 (Tokukaihei lo pixel electrodes 51 on the other hand drastically increases,
`7-64096)). With this arrangement, the viewing angle depen-
`Therefore, the following problems (1) and (2) arise.
`dence can be suppressed to some extent.
`(1) In the case of an arrangement wherein the signal lines
`Furthermore, a new-type LCD device which
`a
`54 and the pixel electrodes 51 are laminated, the signal
`so-called IPS (in-~lane switching) scheme has been devel-
`transmittance (leakage of signals) increases due to an
`as an LCD device
`a new arrangement, and mass-
`increase in the electric capacity between the signal lines 54
`production of the same has been promoted (see Nikkei
`and the pixel electrodes 51. This causes the signal voltages
`Microdevices, July 1997, ~~.108-110). This is the display
`held by the pixel electrodes 51 during a signal holding time
`scheme which provides the most excellent viewing angle
`to fluctuate depending on potentials of the data signals on the
`properties among various display schemes now being sub-
`signal lines 54. This further causes effective values of the
`ject to practical application, and this is actually installed in 20 voltages (effective voltages) to alter upon application of
`monitors of computers and the like.
`voltages by the pixel electrodes 51 on the liquid crystal,
`However, in the case of the aforementioned arrangement
`thereby particularly causing vertical cross-talk to pixels
`disclosed by Tokukaisho 58-172685 wherein SIN,, SiO,,
`neighboring in vertical directions in display actually
`TaO,, or the like is deposited by the CVD method or the
`obtained.
`sputtering method SO as to form a transparent insulating film 25 A driving method of an LCD device wherein each signal
`which is served as the interlayer insulating film 68, as shown
`line 54 is supplied with a set of data signals corresponding
`in FIG. 12, a surface of the interlayer insulating film 68
`to the signal line 54 with the polarity thereof alternately
`becomes uneven due to unevenness of the surfaces of the
`inverted has been proposed, for example, in the Japanese
`metal layers 67a and 67b, the channel protective layer 65, 30 Publication for Laid-Open Patent Application No.6-2304221
`and the like thereunder. Therefore, in the case where the
`1994 (Tokukaihei 6-230422) so as to reduce the influence of
`pixel electrodes 51 are formed on the interlayer insulating
`electric capacity between the signal lines 54 and the pixel
`electrodes 51 onto the displayed images, This driving
`film 68, further greater level differences occur in accordance
`with level differences of various films underneath, whereby
`method is capable of rendering great effects to an LCD
`defects in liquid crystal molecule alignment (disclination) 35 device wherein neighboring pixels have close correlation
`occur.
`concerning display, as in a monochromatic LCD device.
`Furthermore, in the case where, to flatten a surface on
`However, in an LCD device wherein pixel electrodes are
`which a pixel section is formed, an organic film is formed by
`arranged in a vertical stripe form, as in a usual notebook-
`applying polyimide or the like conventionally available in
`type personal computer, neighboring pixels connected with
`the market, a step for forming contact holes for electrically 40 one signal line 54 have different colors to display. In the case
`connecting the pixel electrodes 51 with the drain electrodes
`of color display in particular, for example, in one pixel
`region shaped in a square, three pixel electrodes 51 corre-
`66b has to be added to the manufacturing process. More
`sponding to three colors of red (R), green (G), and blue (B)
`concretely, a step of conducting photo-patterning with
`respect to the organic film made of polyimide or the like by
`respectively are arranged in this order in a rectangular shape
`using a mask, then, forming contact holes by etching, and 45 which is long in a vertical direction (this arrangement of the
`pixel electrodes 51 is hereinafter referred to as a vertical
`finally, peeling off a photoresist which is no longer necessary
`has to be added.
`stripe arrangement).
`Besides, if such organic film conventionally sold in the
`In the case of a usual color display device having pixel
`market is applied to the LCD device arranged as described
`electrodes arranged in such a vertical stripe form, a sufficient
`above, the resin appears discolored after the interlayer
`effect of suppressing vertical cross-talk cannot be achieved
`insulating film 68 is formed.
`by the aforementioned driving method wherein the polarity
`is alternately inverted for each signal line 54.
`For these reasons, such arrangement does not render the
`LCD device high translucency, transparency, and color
`(2) In the case where the scanning lines 53 and the pixel
`reproductivity.
`electrodes 51 are laminated, the electric capacity between
`A photosensitive polyimide film may be used as the 5s the scanning lines 53 and the pixel electrodes 51 becomes
`interlayer insulating film 68 to cut the etching and peeling
`greater. Therefore, a drawback in that a field-through of a
`write voltage applied to the pixel electrodes 51 becomes
`step, but if a conventional material is used, it appears more
`discolored, resulting in further deterioration of the display
`greater arises from a switching signal for controlling the
`TFTs 52.
`quality. For this reason, this arrangement cannot be applied
`to an LCD device required of high translucency and trans- 60 Note that it is possible to suppress the increase in the
`parency.
`electric capacity by forming the inorganic film to not less
`Furthermore, in the case where, as in the aforementioned
`than 500 nm in film thickness. However, as the inorganic
`arrangement, the pixel electrodes 51 are allowed to be
`thin film is formed thicker, a time consumed for this step in
`laminated above the scanning lines 53 and the signal lines 54
`the manufacturing process increases thereby raising the
`by forming the interlayer insulating film 68 therebetween so 65 costs, while cracks tend to occur due to a film formation
`that the aperture ratio of the LCD device is improved,
`residual stress thereby causing an increase in defects and
`electric capacity between the scanning lines 53 and the
`deterioration of reliability.
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`7
`the case where a liquid crystal panel with a low pixel
`Besides, with the arrangement disclosed in Tokukaihei
`aperture ratio is further used, the number of light sources for
`5-313159, it is possible to suppress the viewing angle
`a backlight has to be increased. Therefore, sometimes the
`dependence of the display screen in a specific direction, but
`liquid crystal has a great temperature rise, thereby becoming
`the arrangement is not sufficient to suppress the viewing
`5 unusable, or requiring an extra cooling unit.
`angle dependence in all directions.
`SUMMARY OF THE INVENTION
`Furthermore, the arrangement disclosed by Tokukaihei
`6-75116 is insufficient as well to solve the reversal,
`The present invention is to solve the aforementioned
`particularly, the reversal which occurs when viewed in the
`problems of the conventional cases, and the first object of
`normal viewing angle direction. In the arrangement dis-
`the present invention is to provide an LCD device wherein,
`closed in Tokukaihei 6-75116, as described above, condi- 10 by providing flat pixel electrodes and wires so as to overlap
`tions of the phase difference plate are set so that the index
`each other, (1) the aperture ratio is raised, (2) disclination of
`ellipsoid is inclined. On the other hand, in an embodiment,
`liquid crystal is suppressed, and (3) influences on the display
`used is an LCD element whose liquid-crystalline material
`of cross-talk and the like that tend to be caused by capacity
`has an refractive index anisotropy An of 0.08 and whose
`components between the wires and the pixel electrodes are
`liquid crystal layer has a thickness d of 4.5 pm, i.e., whose 15 further reduced, so that excellent display is obtained. BY
`liquid crystal layer has a retardation An.d of 360 nm.
`thus arranging the LCD device, it comes to feature 6 )
`However, nothing more than the above is mentioned about
`of the lowering of the contrast, the discoloring,
`S ~ P P ~ ~ S S ~ O ~
`depending On a
`which tend
`what type of an LCD element and what type of a polarizing
`and the
`Occur
`viewing angle, (ii) high luminance, low Power consumption,
`plate should be used so that the phase difference plate is
`20 high precision, and high color reproductivity, and (iii) high-
`provided therebetween.
`quality images with vivid colors, particularly white and red
`As for the arrangement wherein the viewing angle depen-
`colors not inferior to those of the CRT display device, which
`dence is suppressed by providing the phase difference plate
`are reproduced in a wide viewing angle range of not less
`between the LCD element and the polarizing plate, it is
`than 70".
`necessary to set properties of not only the phase difference
`TO achieve the foregoing first object, a first LCD device
`plate but also the LCD element. l-herefore, regarding this 25
`of the present invention is characterized in comprising (1) an
`arrangement, in what range the value of An,d of the LCD
`at least a
`substrate, a pixel
`LCD
`element combined with the phase difference plate should be
`substrate, and a liquid
`layer, wherein (i) the
`in order to most
`conduct compensation of the
`substrate has a common electrode, the pixel substrate or the
`phase difference is unclear, As a result, there is a drawback
`in that the arrangement is still insufficient to suppress the 30 counter substrate having a plurality of color filters, (ii) the
`pixel substrate has scanning lines, signal lines, switching
`viewing angle dependence of the LCD device with the use
`elements each being provided in the vicinity of each point of
`of the phase difference plate.
`intersection of the scanning lines and the signal lines, and
`Furthermore, in an arrangement disclosed in the Japanese
`pixel electrodes each being connected with each switching
`Publication for Laid-Open Patent Application No.8-502061 35 element, each switching element having a gate electrode
`1996 (Tokukaihei 8-50206) which is improved as compared
`connected with the scanning line, a source electrode con-
`with
`5-313159,
`the viewing
`properties are
`nected with the signal line, and a drain electrode connected
`considerably improved in all directions as compared with
`with the pixel electrode, each scanning line, signal line and
`the conventional phase difference plate, whereas it is diffi-
`switching element being covered with an interlayer insulat-
`cult to say that the problem of the gradation reversal which 40 ing film being composed of an organic film whose optical
`occurs when viewed in the normal viewing angle direction
`transmittance is not less than about 95 percent with respect
`is sufficiently solved.
`to light which is emitted from a light source and has a peak
`with an arrangement
`in the
`wavelength in the vicinity of a wavelength band of colors of
`for Laid-O~en Patent
`No.7-64096/
`the color filters, each pixel electrode being provided on each
`1995 (Tokukaihei 7-64096), which features
`45 interlayer insulating film, and (iii) the liquid crystal layer is
`the viewing
`properties are
`provided between the counter substrate and the pixel
`upward and
`thereby
`substrate, and is made of liquid crystal whose refractive
`the
`index anisotropy An(450) with respect to light with a wave-
`reversal when viewed in the normal viewing angle direction.
`On the other hand, there is still a drawback in that the
`length of 450 nm and whose refractive index anisotropy
`viewing angle properties rightward and lef