Source: http://www.google.com/patents/US7442566?dq=5,758,352
Timestamp: 2015-03-30 10:55:01
Document Index: 396554122

Matched Legal Cases: ['arts 260', 'arts 260', 'arts 260', 'arts 260', 'arts 260', 'arts 260', 'arts 260', 'arts 260']

Patent US7442566 - Liquid crystal display device and manufacturing method for the same - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsOn a glass substrate, gate bus lines, data bus lines, and TFTs are formed. Then, on the substrate, an insulating film, covering the gate bus lines, data bus lines and TFTs, is formed, and a positive type photoresist film is further formed thereon. Next, through exposure and development processes, the...http://www.google.com/patents/US7442566?utm_source=gb-gplus-sharePatent US7442566 - Liquid crystal display device and manufacturing method for the sameAdvanced Patent SearchPublication numberUS7442566 B2Publication typeGrantApplication numberUS 11/499,952Publication dateOct 28, 2008Filing dateAug 7, 2006Priority dateNov 6, 2002Fee statusPaidAlso published asUS7209107, US7768606, US7889296, US20040090410, US20060270085, US20070146589, US20070146594Publication number11499952, 499952, US 7442566 B2, US 7442566B2, US-B2-7442566, US7442566 B2, US7442566B2InventorsKatsufumi Ohmuro, Norio Sugiura, Kunihiro Tashiro, Yoshio KoikeOriginal AssigneeSharp Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (24), Referenced by (2), Classifications (20), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetLiquid crystal display device and manufacturing method for the same
US 7442566 B2Abstract
forming on a first substrate gate bus lines supplied with scanning signals, data bus lines supplied with display signals, thin-film transistors having gate electrodes connected to the gate bus lines and drain electrodes connected to the data bus lines;
forming a photoresist film on upper part of the gate bus lines, the data bus lines, and the thin-film transistors;
dividing the photoresist film for each picture element and exposing and developing photoresist to form opening parts at positions corresponding to source electrodes of the thin-film transistors;
changing inner stresses in a thickness direction of the photoresist film;
subjecting the photoresist film to heat treatment to form wrinkle-form surface ruggedness;
forming on the photoresist film reflection electrodes electrically connected to the source electrodes of the thin-film transistors via the opening parts; and
arranging opposingly the first substrate and a second substrate provided with an electrode made of a transparent conductive film, and enclosing liquid crystal therebetween.
2. The manufacturing method for the liquid crystal display device according to claim 1, wherein the reflection electrodes are formed at positions overlapping with the gate bus lines, the data bus lines, and the thin-film transistors.
3. The manufacturing method for the liquid crystal display device according to claim 1, wherein in the step of exposing and developing, a slit is formed so as to further dividing the resist film of one picture element into a plurality of regions, and in the step of forming the reflection electrodes, a part corresponding to the slit is opened to serve as a light transmission region.
4. The manufacturing method for the liquid crystal display device according to claim 1, wherein a structure for multi-domain is formed at least on one of the substrates. Description
This is a divisional of application Ser. No. 10/701,305, now U.S. Pat. No. 7,209,107, filed Nov. 4, 2003 now U.S. Pat. No. 7,209,107.
The transflective type liquid crystal display device that improves the transmission characteristics without decreasing the reflection characteristics, is proposed in Japanese Patent Laid-Open No. 2003-202594 filed by the present applicant. This transflective type liquid crystal display device will be explained with reference to FIGS. 2 to 5. FIG. 2 shows a structure of the TFT substrates of the transflective type liquid crystal display device, and FIG. 3 shows a sectional structure of the transflective type liquid crystal device taken along the line I-I of FIG. 2. As shown in FIGS. 2 and 3, reflection electrodes 110 are formed so as to cover gate bus lines 104, data bus lines 106, and TFTs 108. The regions where the reflection electrodes 110 are formed serve as reflection regions R and R′. The regions surrounding the reflection electrodes 110 serve as transmission regions T and T′. The liquid crystal in the transmission regions T and T′ are driven similarly to the liquid crystal in the reflection regions R and R′ by an oblique electric field between the reflection electrodes 110 and a common electrode 130.
As described above, according to the transflective type liquid crystal display devices as shown in FIGS. 2 to 5, the transmission characteristics can be enhanced without decreasing the reflection characteristics. At the same time, the manufacturing process can be simplified and the manufacturing costs can be reduced. However, this transflective type liquid crystal display device still has such problems as will be described below. FIG. 6 shows a schematic sectional structure of three picture elements of the liquid crystal display device taken along the line II-II of FIG. 4. As shown in FIG. 6, a light beam t of the transmission light emitted from a backlight unit (not shown) to be emitted to a display screen side, and a light beam r of the reflection light incident from the display screen side and reflected by the reflection electrode 110 to be emitted to the display screen side, pass along different light paths. That is, the light beam t of the transmission light is transmitted through the CF layer R only once. On the other hand, the light beam r of the reflection light is transmitted through the CF layer R twice. Therefore, there arises a problem that color purity is made to be different between the transmission mode display and the reflection mode display, thereby degrading display quality.
An object of the present invention is to provide a liquid crystal display device of those with high resolution excellent in reflection characteristics compared with a conventional one, and a manufacturing method for the same.
Note that in order to obtain good reflection characteristics, a flattened area where the average angle of the surface of the reflection electrode is 5□<or less is preferably set to 50% or more. In addition, when the resist film is divided by the slit into the plurality of regions, the length of the short side of each divided region is preferably set to 5 μm or more in order to obtain surface ruggedness of a uniform pattern on the resist film.
FIG. 8 is a schematic sectional view taken along the line III-III of FIG. 7.
FIG. 7 is a plan view showing a liquid crystal display device of a first embodiment of the present invention, and FIG. 8 is a schematic sectional view taken along the line III-III of FIG. 7. Note that this embodiment shows an example in which the present invention is applied to a transflective type liquid crystal display device using a VA (vertically aligned) type liquid crystal.
As shown in FIG. 8, the liquid crystal display device of this embodiment is constituted including a TFT substrate 10 and a counter substrate 30, and a vertically aligned nematic liquid crystal 40. The TFT substrate 10 and the counter substrate 30 face each other, and the vertically aligned nematic liquid crystal 40 is enclosed between these substrates. Polarizing plates (linear polarizing plate or circular polarizing plate having the linear polarized light+f�/4 phase difference combined) 38 and 39 are arranged under the TFT substrate 10 and on the counter substrate 30, respectively. In addition, a light source (backlight: not shown) is disposed below the TFT substrate 10.
Note that the rugged pattern formed on the resist film also relates to the film thickness of the resist film. In addition, in order to efficiently reflect the light incident from the upside of the liquid crystal display device in the direction of a normal line of a panel surface, a flattened area (area where the average angle of inclination is) 5 degrees or less in a surface of the reflection electrode is preferably set to 50% or more.
Next, as shown in FIG. 9I, the positive type photoresist film 19 is formed on the entire upper surface of the glass substrate 11, which is then subjected to exposure and development processes to form opening parts where the contact holes 18 a and 18 b are exposed and to divide the resist film 19 for each picture element. Subsequently, post-baking at a temperature of 130 to 145� C., the surface layer of the resist film 19 is further irradiated with a UV ray (ultraviolet ray) to crosslink the polymers in the surface layer. Next when baking at a temperature of 200� C. or more, since thermal deformation characteristics (coefficient of thermal expansion or of thermal shrinkage) between the surface layer (crosslinked part) and the deep part thereof (not crosslinked part) of the resist film 19 are different, fine wrinkle-form ruggedness is generated, as shown in FIG. 9J, on the surface of the resist film 19. In this case, as described before, the resist film 19 is divided into small regions for each picture element in this embodiment, and therefore the rugged pattern formed on the resist film 19 is uniform.
FIG. 10 is a view showing relations of transmissive aperture ratio and effective reflection area ratio to resolution, between the conventional transflective type liquid crystal display device shown in FIG. 1 and the transflective type liquid crystal display device of this embodiment, with the resolution (ppi) as the abscissa and with transmissive aperture ratio (left axis) and effective reflection area ratio (right axis) as the ordinate. Herein, in the conventional liquid crystal display device, the transmissive aperture ratio is fixed to be 14% regardless of the resolution. In addition, an inter-picture element interval is set to 8 f�m, a width of the data bus lines is set to 5 f�m, a width of the storage capacitor bus lines is set to 12 f�m, and a width of the gate bus lines is set to 10 f�m.
FIG. 11 shows microscopic images obtained by checking a reflection state and a transmission state at displaying when applied voltages are 0 V and 2.3 V, in the liquid crystal display device manufactured according to this embodiment. Herein, the resolution of this liquid crystal display device corresponds to 180 ppi, and a cell gap is 3 μm, and an n-type nematic liquid crystal is enclosed between the TFT substrate and the counter substrate after the vertical alignment of these substrates is subjected to rubbing treatment. A design values of a photomask used for manufacturing the liquid crystal display device is also shown in FIG. 11. Moreover, FIG. 12 shows an AFM (Atomic Force Microscope) image of the reflection electrodes of the liquid crystal display device. It is found from FIG. 11 that good characteristics can be obtained in any case of using the liquid crystal display device as a reflection type liquid crystal display device and as a transmission type liquid crystal display device.
As described before, a rugged pattern formed on the resist film is determined depending on the size of the resist film. Like this embodiment, by providing the slits 52 on the reflection electrode 51 and the resist film thereunder, a desired rugged pattern can be formed on the reflection electrode 51 even when the reflection electrode 51 is large in size. In addition, slit 52 portions serve as transmission regions, thereby heightening the transmissive aperture ratio. Slits 53 or 54 having the shapes as shown in FIGS. 13B and 13C, respectively, may also be formed according to a desired rugged pattern. In order to surely form ruggedness of a uniform pattern, any short side of the regions divided by the slits 52, 53 and 54 is preferably 5 f�m.
FIG. 14 is a view showing relations of transmissive aperture ratio and effective reflection area ratio to resolution, between the conventional transflective type liquid crystal display device shown in FIG. 1 and the transflective type liquid crystal display device of this embodiment, with the resolution (ppi) as the abscissa and with transmissive aperture ratio (left axis) and effective reflection area ratio (right axis) as the ordinate. Herein, in the conventional liquid crystal display device, the transmissive aperture ratio is fixed to be 14% regardless of the resolution. In addition, an inter-pixel interval is set to 8 f�m, a width of the data bus lines is set to 5 f�m, a width of the storage capacitor bus lines is set to 12 f�m, and a width of the gate bus lines is set to 10 f�m.
In this embodiment, as shown in FIG. 16A, a reflection electrode 61 is provided with slits 62, and slit 62 portions serve as transmission regions. Slits 63 and 64 in the shapes as shown in FIGS. 16B and 16C, respectively, may also be provided. However, the shapes of the slits are preferably common to each picture element. Moreover, any short side of the regions divided by the slits is preferably 5 μm or more.
On the surface opposite to the element forming surface of the TFT substrate 202, a polarizing plate 287 is stuck. On the other surface of the polarizing plate 287 on the opposite side to the TFT substrate 202, for example, a backlight unit 288 including a linear primary light source and a surface light guide plate, is disposed. Meanwhile, on the other surface of the counter substrate 204 on the opposite side to the resin CF layer forming surface, a polarizing plate 286 is stuck. A linearly polarizing plate or the combination of a linearly polarizing plate and a �-wavelength plate is used for the light polarizing plates 286 and 287.
Next, a liquid crystal display device according to example 1 of this embodiment will be explained by use of FIGS. 24A and 24B. FIG. 24A shows a structure of the liquid crystal display device according to example 1, and FIG. 24B shows an outline sectional structure of the liquid crystal display device taken along the line IV-IV of FIG. 24A. As shown in FIGS. 24A and 24B, on the TFT substrate 202 of the liquid crystal display device, a plurality of gate bus lines 212 extending in right and left directions of FIG. 24A in parallel with each other, are formed. In addition, on the TFT substrate 202, a plurality of data bus lines 214, intersecting the gate bus lines 212 via an insulating film (not shown), and extending in the vertical direction of FIG. 24A in parallel with each other, are formed. In the vicinity of each intersection position of the gate bus line 212 and the data bus line 214, a TFT 220 is formed. The TFT 220 has a working semiconductor film (not shown) made of a-Si (amorphous silicon) for example. On the working semiconductor film, a channel protection film (not shown) is formed. On the channel protection film, a drain electrode 221 led out from the adjacent data bus line 214, and a source electrode 222 are formed so as to face each other interposing a predetermined gap therebetween. In this structure, the gate bus lines 212 directly under the channel protection film is adapted to function as a gate electrode of the TFT 220.
FIG. 25 is an x-y chromaticity chart of the liquid crystal display device of this example 1. A solid line a in the chart shows a color reproducing range (an ideal value) in the reflection mode of the liquid crystal display device in which the area ratio of the region of the reflection regions where the CF layers are formed to the entire reflection regions is 90%. Similarly, a solid line b shows a color reproducing range of the liquid crystal display device having the above-described area ratio of 80% in the reflection mode, a solid line c shows a color reproducing range of the liquid crystal display device having the area ratio of 70% in the reflection mode, and a solid line d shows a color reproducing range of the liquid crystal display device having the above-described area ratio of 50% in the reflection mode. A broken line e shows a color reproducing range (an ideal value) of a conventional reflection type liquid crystal display device in which CF layers having the film thickness of 0.75 μm are used. As shown in FIG. 25, according to example 1, by setting the above-described area ratio to 70% to 90%, a reflection mode display, in which the color reproducing range is wider than that of the conventional reflection type liquid crystal display device, can be obtained. In addition, since the CF layers for an LCD monitor are used in example 1, the same color reproducing range as that of the LCD monitor can be obtained in the transmission mode.
Next, a liquid crystal display device according to example 2 of this embodiment will be explained by use of FIGS. 26A and 26B. FIG. 26A shows a structure of the liquid crystal display device according to this example, and FIG. 26B shows an outline sectional structure of the liquid crystal display device taken along the line V-V of FIG. 26A. As shown in FIGS. 26A and 26B, the reflection electrodes 216 are formed so as to cover the data bus lines 214, the TFTs 220 for driving the adjacent picture elements located on the lower side in FIG. 26A, and the gate bus lines 212. The regions where the reflection electrodes 216 are formed serve as reflection regions. The regions between the adjacent reflection electrodes 216 are used as transmission regions. The liquid crystal 206 in the transmission regions is driven similarly to the liquid crystal 206 in the reflection regions, by an oblique electric field between the reflection electrodes 216 and a common electrode (not shown). In part of the reflection regions and in the transmission regions on the counter substrate 204, any one of the CF layers R, G and B is formed for each picture element. In the example 2 also, the effects similar to those in example 1 can be obtained. In addition, by applying example 2 to the structure of the conventional liquid crystal display device shown in FIGS. 2 and 3, the liquid crystal display device with good display quality can be obtained.
Next, a liquid crystal display device according to example 3 of this embodiment will be explained by use of FIGS. 27A and 27B. FIG. 27A shows a structure of the liquid crystal display device according to example 3, and FIG. 27B shows an outline sectional structure of the liquid crystal display device taken along the line VI-VI of FIG. 27A. As shown in FIGS. 27A and 27B, in the reflection electrodes 216, opening parts 260 a to 260 c opened in various shapes are formed. For example, in the reflection electrode 216 for the left picture element of three picture elements shown in FIG. 27A, a plurality of diamond-shaped opening parts 260 a are formed. Moreover, a plurality of rectangular opening parts 260 b having long sides almost in parallel to the extending direction of the gate bus lines 212, are formed in the reflection electrode 216 for the middle picture element of the three picture elements. In the reflection electrode 216 for the right picture element, a plurality of rectangular opening parts 260 c having long sides almost in parallel to the extending direction of the data bus lines 214, are formed. The regions where the reflection electrodes 216 are formed serve as reflection regions, and the regions where the opening parts 260 a to 260 c are formed serve as transmission regions. The liquid crystal 206 in the transmission regions is driven similarly to the liquid crystal 206 in the reflection regions, by an oblique electric field between the reflection electrodes 216 and a common electrode (not shown).
Next, a liquid crystal display device according to example 4 of this embodiment will be explained by use of FIGS. 28A and 28B. FIG. 28A shows a structure of the liquid crystal display device according to example 4, and FIG. 28B shows an outline sectional structure of the liquid crystal display device taken along the line VII-VII of FIG. 28A. As shown in FIGS. 28A and 28B, the reflection electrodes 216 are formed so as to cover the gate bus lines 212, the data bus lines 214, and the TFTs 220. In the reflection electrodes 216, a plurality of opening parts 260 opened in a nearly elliptical shape are formed. The regions where the opening parts 260 are formed serve as transmission regions T1. The regions where the reflection electrodes 216 are formed serve as reflection regions. Moreover, the regions where the opening parts 260 are formed and the regions between the adjacent reflection electrodes 216 serve as transmission regions. The liquid crystal 206 in the transmission regions is driven similarly to the liquid crystal 206 in the reflection regions, by an oblique electric field between the reflection electrodes 216 and a common electrode (not shown).
The present invention is applicable to a MVA (Multi-domain Vertical Alignment) type liquid crystal display. In this case, a slit functions as a structure for a multi-domain. When voltage is impressed, the liquid crystal molecules of the both side of a slit incline in the different direction. Thereby, a multi-domain is attained. It is not necessary to rubbing, which can simplify the fabrication process.
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