Patent Grant
8243236
This application is the U.S. national phase of International Application No. PCT/JP2007/067511, filed 7 Sep. 2007, which designated the U.S. and claims priority to Japanese Patent Application No. 2006-284206, filed 18 Oct. 2006, the entire contents of each of which are hereby incorporated by reference.
The present invention relates to a reflection-type or transflective-type liquid crystal display device capable of performing display by utilizing reflected light.
Liquid crystal display devices include the transmission-type liquid crystal display device which utilizes backlight from behind the display panel as a light source for displaying, the reflection-type liquid crystal display device which utilizes reflected light of external light, and the transflective-type liquid crystal display device which utilizes both external light and backlight as light sources. The reflection-type liquid crystal display device and the transflective-type liquid crystal display device are characterized in that they have smaller power consumptions than that of the transmission-type liquid crystal display device, and their displayed images are easy to see in a bright place. The transflective-type liquid crystal display device is characterized in that the display is easier to see than that of the reflection-type liquid crystal display device, even in a dark place.
As show in
In the aforementioned active matrix substrate 100, portions of the reflective layer 110 are formed so as to reach the insulative substrate 101 in portions where a gate layer 102 and the like are not formed (i.e., portions between the islands, hereinafter referred to as “gap portions”). Therefore, in the gap portions, the surface of a reflection surface 112 is recessed in the direction of the insulative substrate 101, thus forming deep dents (or recesses).
In the reflection-type or transflective-type liquid crystal display device, in order to perform bright display by utilizing reflected light, it is necessary to allow incident light entering from various directions to be reflected by the reflection surface more uniformly and efficiently over the entire display surface. For this purpose, it is better if the reflection surface is not completely planar but has moderate recesses/protrusions.
However, since the reflection surface 112 of the aforementioned active matrix substrate 100 has deep dents, light is unlikely to reach the reflection surface located on the bottoms of the dents, and even if at all light reaches there, the reflected light thereof is unlikely to be reflected toward the liquid crystal panel. Therefore, the aforementioned conventional liquid crystal display device has a problem in that the reflected light is not effectively used for displaying. Furthermore, there is also a problem in that, since many portions of the reflection surface 110 have a large angle relative to the display surface of the liquid crystal display device, the reflected light from those portions is not effectively utilized for displaying.
Na×sin α=Nb×sin β
b) is a diagram showing a relationship between incident light and reflected light when incident light perpendicularly entering the display surface of an LCD is reflected from a reflection surface which is tilted by θ with respect to the display surface (or the substrate). As shown in the figure, the incident light perpendicularly entering the display surface is reflected from the reflection surface which is tilted by angle θ with respect to the display surface, and goes out in a direction of an outgoing angle φ.
According to Snell's Law, results of calculating the outgoing angle φ according to Snell's Law with respect to each angle θ of the reflection surface are shown in Table 1.
The values in this Table are calculated by assuming that air has a refractive index of 1.0 and the glass substrate and the liquid crystal layer have a refractive index of 1.5. As shown in Table 1, when the angle θ of the reflection surface exceeds 20 degrees, the outgoing angle φ becomes very large (i.e., 90-φ becomes very small), so that most of the outgoing light does not reach the user. Therefore, even if recesses/protrusions are provided on the reflection surface of the reflective layer, it is necessary to ensure that the angle θ is 20 degrees or less in greater portions of the reflection surface in order to effectively use the reflected light.
Since the reflection surface 112 of the aforementioned active matrix substrate 100 has many portions in which the angle with respect to the display surface is greater than 20 degrees, reflected light is not very effectively used for displaying. In order to solve this problem, it might be possible to form an insulating layer under the reflective layer 110 so as to cover the metal layer 108, thus smoothing the reflection surface. However, this requires a step of forming an insulating layer, a step of forming contact holes for connecting the reflective layer 110 to the drains of TFTs in the insulating layer are needed, etc., thus resulting in a problem of an increase in the material and the number of steps.
In the manufacture of the conventional active matrix substrate 100, the gate layer 102, the gate insulating layer 104, a semiconductor layer 106 and the metal layer 108 are formed concurrently with and under the same conditions as the gate of the TFT, the insulating layer, the semiconductor layer and the source/drain electrode, respectively, and are thereafter etched together, and it is thus difficult to control the slope tilt, etc., of each layer. Therefore, it is difficult to give an intended tilt to the surface of the reflective layer so as to improve the reflection efficiency. Furthermore, if the width of the island-like multilayer structure is relatively large, there is formed a flat reflective layer 110 without recesses/protrusions on the multilayer structure, thereby lowering the efficiency in utilizing the reflected light.
The present invention has been made in view of the above problems, and an objective thereof is to provide a reflection-type liquid crystal display device and a transflective-type liquid crystal display device having a high image quality and including a reflection region having a high reflectivity.
A liquid crystal display device of the present invention is a liquid crystal display device comprising a reflection region for reflecting incident light toward a display surface, wherein the reflection region includes a metal layer, an insulating layer formed on the metal layer, a semiconductor layer formed on the insulating layer, and a reflective layer formed on the semiconductor layer; a plurality of recesses are formed in at least one of the metal layer, the insulating layer and the semiconductor layer; a plurality of dents are formed in the reflective layer in the reflection region according to the plurality of recesses; and a shortest distance between edge portions of at least two of the plurality of recesses is 4 μm or less.
In one embodiment, the shortest distance between edge portions of at least two recesses is 1 μm or more. In one embodiment, a maximum width of at least one of the plurality of recesses is 15 μm or less. In one embodiment, the maximum width of at least one recess is 2 μm or more. In one embodiment, a shortest distance between an edge portion of any one of the plurality of recesses and an edge portion of another recess located closest thereto is 4 μm or less.
Another liquid crystal display device of the present invention is a liquid crystal display device comprising a reflection region for reflecting incident light toward a display surface, wherein the reflection region includes a metal layer, an insulating layer formed on the metal layer, a semiconductor layer formed on the insulating layer, and a reflective layer formed on the semiconductor layer; a plurality of protrusions are formed in at least one of the metal layer, the insulating layer and the semiconductor layer; a plurality of projections are formed in the reflective layer in the reflection region according to the plurality of protrusions; and a maximum width of at least one of the plurality of protrusions is 5 μm or less.
In one embodiment, the maximum width of at least one protrusion is 2 μm or more. In one embodiment, a shortest distance between edge portions of at least two of the plurality of protrusions is 15 μm or less. In one embodiment, the shortest distance between edge portions of at least two protrusions is 3 μm or more. In one embodiment, a shortest distance between an edge portion of any one of the plurality of protrusions and an edge portion of another protrusion located closest thereto is 15 μm or less.
A method for manufacturing a liquid crystal display device of the present invention is a method for manufacturing a liquid crystal display device having a reflection region for reflecting incident light toward a display surface, comprising: a step of forming a metal layer on a substrate; a step of forming an insulating layer on the metal layer; step of forming a semiconductor layer on the insulating layer; and a step of forming a reflective layer on the semiconductor layer, wherein a plurality of recesses are formed in at least one of the metal layer, the insulating layer and the semiconductor layer; in the step of forming a reflective layer, a plurality of dents are formed in the reflective layer in the reflection region according to the plurality of recesses; and a shortest distance between edge portions of at least two of the plurality of recesses is 4 μm or less.
In one embodiment, the shortest distance between edge portions of at least two recesses is 1 μm or more. In one embodiment, a maximum width of at least one of the plurality of recesses is 15 μm or less. In one embodiment, the maximum width of at least one recess is 2 μm or more. In one embodiment, a shortest distance between an edge portion of any one of the plurality of recesses and an edge portion of another recess located closest thereto is 4 μm or less.
In one embodiment, in the step of forming a metal layer, photolithography technique is used to form the plurality of recesses in the metal layer and form at least one of a gate bus line and a storage capacitor line; and a thickness of a resist film used for forming the plurality of recesses is smaller than that of a resist film used for forming at least one of the gate bus line and the storage capacitor line.
Another method for manufacturing a liquid crystal display device of the present invention is a method for manufacturing a liquid crystal display device having a reflection region for reflecting incident light toward a display surface, comprising: a step of forming a metal layer on a substrate; a step of forming an insulating layer on the metal layer; a step of forming a semiconductor layer on the insulating layer; and a step of forming a reflective layer on the semiconductor layer, wherein a plurality of protrusions are formed in at least one of the metal layer, the insulating layer and the semiconductor layer; in the step of forming a reflective layer, a plurality of projections are formed in the reflective layer in the reflection region according to the plurality of protrusions; and a maximum width of at least one of the plurality of protrusions is 5 μm or less.
In one embodiment, the maximum width of at least one protrusion is 2 μm or more. In one embodiment, a shortest distance between edge portions of at least two of the plurality of protrusions is 15 μm or less. In one embodiment, the shortest distance between edge portions of at least two protrusions is 3 μm or more. In one embodiment, a shortest distance between an edge portion of any one of the plurality of protrusions and an edge portion of another protrusion located closest thereto is 15 μm or less.
In one embodiment, in the step of forming a metal layer, photolithography technique is used to form the plurality of protrusions in the metal layer and form at least one of a gate bus line and a storage capacitor line; and a thickness of a resist film used for forming the plurality of protrusions is smaller than that of a resist film used for forming at least one of the gate bus line and the storage capacitor line.
Another liquid crystal display device of the present invention is a liquid crystal display device comprising a reflection region for reflecting incident light toward a display surface, wherein the reflection region includes a metal layer, an insulating layer formed on the metal layer, a reflective layer formed on the insulating layer; a plurality of recesses are formed in at least one of the metal layer and the insulating layer; a plurality of dents are formed in the reflective layer in the reflection region according to the plurality of recesses; and a shortest distance between edge portions of at least two of the plurality of recesses is 4 μm or less.
Another liquid crystal display device of the present invention is a liquid crystal display device comprising a reflection region for reflecting incident light toward a display surface, wherein the reflection region includes a metal layer, an insulating layer formed on the metal layer, a reflective layer formed on the insulating layer; a plurality of protrusions are formed in at least one of the metal layer and the insulating layer; a plurality of projections are formed in the reflective layer in the reflection region according to the plurality of protrusions; and a maximum width of at least one of the plurality of protrusions is 5 μm or less.
Another method for manufacturing a liquid crystal display device of the present invention is a method for manufacturing a liquid crystal display device having a reflection region for reflecting incident light toward a display surface, comprising: a step of forming a metal layer on a substrate; a step of forming an insulating layer on the metal layer; and a step of forming a reflective layer on the insulating layer, wherein a plurality of recesses are formed in at least one of the metal layer and the insulating layer; in the step of forming a reflective layer, a plurality of dents are formed in the reflective layer in the reflection region according to the plurality of recesses; and a shortest distance between edge portions of at least two of the plurality of recesses is 4 μm or less.
Another method for manufacturing a liquid crystal display device of the present invention is a method for manufacturing a liquid crystal display device having a reflection region for reflecting incident light toward a display surface, comprising: a step of forming a metal layer on a substrate; a step of forming an insulating layer on the metal layer; and a step of forming a reflective layer on the insulating layer, wherein a plurality of protrusions are formed in at least one of the metal layer and the insulating layer; in the step of forming a reflective layer, a plurality of projections are formed in the reflective layer in the reflection region according to the plurality of protrusions; and a maximum width of at least one of the plurality of protrusions is 5 μm or less.
According to the present invention, it is possible to provide a reflection-type liquid crystal display device and a transflective-type liquid crystal display device having a high image quality and including a reflection region having a high reflectivity.
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Hereinafter, with reference to the drawing, a first embodiment of the liquid crystal display device according to the present invention will be described.
The TFT substrate 12 comprises a transparent substrate 22, an interlayer insulating layer 26, and a pixel electrode 28, and includes reflection sections 30 and TFT sections 32. Gate lines (scanning lines), source lines (signal lines), and Cs lines (storage capacitor electrode lines), etc., are formed on the TFT substrate 12, which will be described later.
The counter substrate 14 is a color filter substrate (CF substrate), for example, and includes a counter electrode 34, a color filter layer (CF layer) 36, and a transparent substrate 38. The upper face of the transparent substrate 38 serves as a display surface 40 of the liquid crystal display device. Note that although the TFT substrate 12 and the counter substrate 14 each have an alignment film and a polarizer, they are omitted from the figure.
In the liquid crystal display device 10, a region where a reflection section 30 is formed is referred to as a reflection region 42, whereas a region where a TFT section 32 is formed is referred to as a TFT region 44. In the reflection region 42, light entering from the display surface 40 is reflected by the reflection section 30, and travels through the liquid crystal layer 18 and the counter substrate 14 so as to go out from the display surface 40. The liquid crystal display device 10 further has transmission regions 46 which are formed in regions other than the reflection regions 42 and the TFT regions 44. In the transmission regions 46, light which is emitted from a light source in the display device 10 travels through the TFT substrate 12, the liquid crystal layer 18, and the counter substrate 14 so as to go out from the display surface 40.
Note that, as shown in
a) is a plan view of a portion of a pixel region of the liquid crystal display device 10, as seen from above the display surface 40. As shown in the figure, a plurality of pixels 50 (rectangular portions denoted by bold lines) are provided in a matrix shape on the liquid crystal display device 10. The aforementioned reflection section 30 and TFT section 32 are formed in each pixel 50.
In the border of the pixel 50, source lines 52 extend along the column direction (the vertical direction in the figure), and gate lines (gate metal layers) 54 extend along the row direction (the horizontal direction in the figure). In the central portion of the pixel 50, a Cs line (Cs metal layer) 56 extends along the row direction. In the interlayer insulating layer 26 of the reflection section 30, a contact hole 58 for connecting the pixel electrode 28 and the drain electrode of the TFT is formed. The Cs line 56, paired with the pixel electrode, forms a storage capacitor.
b) is a plan view schematically showing the construction of the reflection section 30 above the Cs line 56. The contact hole 58 shown in
Although only eight recesses 48 are shown in the figure for a better understanding of the construction, the number of the recesses 48 is not limited to eight, but there may be more recesses 48. The recesses 48 do not have to be arranged regularly in the vertical and horizontal direction as shown in the figure, but may be arranged randomly or with irregular spacing. According to the present embodiment, many recesses 48 can be formed as closely together as possible by a method to be described later.
Next, referring to
a) shows a cross section of the reflection section 30 (a cross section of a portion shown by arrow C in
The Cs metal layer 56 in the reflection section 30 includes recesses (or openings) 57 formed therein as-shown in the figure, and protrusions 69 of the Cs metal layer 56 are formed between the recesses 57. The recesses 48 of the reflective layer 63 are formed according to the shape of the recesses 57 of the Cs metal layer 56. The semiconductor layer 62 may possibly be absent in the reflection section 30.
b) is a cross-sectional view showing the construction of the gate metal layer (metal layer) 54, the gate insulating layer 61, the semiconductor layer 62, and the reflective layer 63 in the TFT section 32. The gate metal layer 54 in the TFT section 32 is formed concurrently with and from the same member as the Cs metal layer 56 of the reflection section 30. Similarly, gate insulating layer 61, the semiconductor layer 62, and the reflective layer 63 of the TFT section 32 are formed concurrently with and from the same members as the gate insulating layer 61, the semiconductor layer 62, and the reflective layer 63 of the reflection section 30, respectively.
In
In order to improve the reflection efficiency, it is preferred that the interval a between any two recesses 57 adjacent to each other is within the aforementioned predetermined range. Nevertheless, the present invention is not limited to this, and the reflection efficiency can also be improved by setting the interval a between a recess 57 and another recess 57 located closest thereto to a value within the predetermined range. The reflection efficiency can also be improved by setting the interval a between a recess and another recess located closest thereto to a value within the predetermined range for 50% or more of the recesses 57 formed in the reflection section 30. The reflection efficiency can also be improved by setting the interval a between at least two recesses 57 in the reflection section 30 to a value within the predetermined range.
In order to improve the reflection efficiency, it is preferred that the width b of all the recesses 57 is within the aforementioned predetermined range. Nevertheless, the present invention is not limited to this, and the reflection efficiency can also be improved by setting the width b within the predetermined range for 50% or more of the recesses 57 formed in the reflection section 30. The reflection efficiency can also be improved by setting the width b to a value within the predetermined range for at least one recess 57 in the reflection section 30.
In the conventional liquid crystal display device shown in
According to the present embodiment, the recesses 48 (dents) of the reflective layer 63 are formed according to the controlled shape of the Cs metal layer 56, and it is therefore possible to easily form relatively shallow dents in the reflective layer. Therefore, the reflection efficiency at the surface of the reflective layer is improved. Since the shape, the depth, the slope tilt angle, etc., of the recesses 48 can easily be adjusted, the recesses 48 of the reflective layer 63 can easily be formed with a slope tilt angle of 20 degrees or less. Therefore, it is possible to increase the area of the effective reflection surface without increasing the manufacturing cost.
According to the present embodiment, the interval between the recesses 57 in the Cs metal layer 56 can be set to be as small as practically possible. The width of the recesses 57 themselves can also be made as small as possible. Then, more recesses 57 of the Cs metal layer 56 can be arranged in the reflection section 30, thus forming more recesses 48 in the reflective layer 63. This increases the area of the surface where the tilt is 20 degrees or less on the surface of the reflective layer 63, thereby improving the reflection efficiency. Furthermore, since it is possible to reduce the area of the flat portion of the surface of the reflective layer 63, it is possible to further improve the reflection efficiency.
Next, a method for manufacturing the TFT substrate 12 according to the present embodiment will be described.
As shown in
Thereafter, a resist film is formed on the thin metal film, and after forming a resist pattern through an exposure and development step, a dry or wet etching is performed to form the gate metal layer 54 (including the gate electrode and the gate line). The gate metal layer 54 has a thickness of 200 to 500 nm, for example.
Thus, the gate metal layer 54 which is formed by photolithography technique serves as a gate electrode of the TFT. Note that, in this step, the gate lines (gate metal layer) 54 shown in
Next, as shown in
Next, on the gate insulating layer 61, an amorphous silicon (a-Si) (Si(i) film) film and an n+a-Si film (Si (n+) film) obtained by doping amorphous silicon with phosphorus (P). The thickness of the a-Si film is 30 to 300 nm, for example, and the thickness of the n+a-Si film is 20 to 100 nm, for example. Thereafter, these films are shaped by photolithography technique, whereby the semiconductor layer 62 is formed. In this step, the semiconductor layer 62 of the reflection section 30 shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, by using
As shown in
Next, as shown in
Next, As shown in
Next, as shown in
Next, as shown in
Next, using
a) is a diagram showing the shape of a photoresist 99 used when forming the gate line 54, showing the cross-sectional shape at the position shown by arrow B in
As described above, when forming the Cs metal layer 56, the gate electrode and the gate line 54 in the TFT section 32 are also formed concurrently and from the same metal by photolithography technique. While a photoresist having a height x is used as shown in
Thus, since the thickness of the resist film used in the formation of the recesses 57 is thinner than that of the resist film used in the formation of the gate line 54, a gentle slope is formed at the edge portion of the recess 57 in the film-shaping process by etching, whereas a steep slope is formed at the edge portion of the gate line 54. As shown in
Using such a method, it is readily possible, by the same photolithography step, to form the recess 57 with a gentle slope of 20° or less, for example, and to shape the gate line 54 and the Cs line 56 with a high process precision. Moreover, since it is possible to easily control the size, shape and slope tilt of the recesses 57 and the interval between the recesses 57, it is possible to obtain intended recesses 57 without increasing the number of steps. Thus, it is possible to efficiently manufacture a liquid crystal display device having a high reflectivity in which the reflective layer 63 has many surfaces where the tilt is 20° or less.
Next, using
(a) to (e) of
Although the recesses 57 are described as being formed in the Cs metal layer (metal layer) 56 in the embodiment above, the recesses 57 may be formed in the gate insulating layer 61 or the semiconductor layer 62 in the reflection section 30, or may be formed in two or all of these layers. Furthermore, the recesses 57 may be provided in one or two of these layers, with protrusions as will be described in Embodiment 2 being formed in one or two other layers thereof. The semiconductor layer 62 may be absent in the reflection section 30. The recesses 57 may be formed by the aforementioned photolithography technique, or the like, during the formation of the layers. The embodiments of the present invention are deemed to encompass these examples.
Next, using
A plurality of protrusions 169 are formed in the Cs metal layer 56 in the reflection section 30 as shown in the figure, and a recess 157 of the Cs metal layer 56 is formed between two protrusions 169. The protrusion 48′ of the reflective layer 63 is formed according to the shape of the protrusion 169 of the Cs metal layer 56.
In
In order to improve the reflection efficiency, it is preferred that the interval d between any two protrusions 169 adjacent to each other is within the aforementioned predetermined range. Nevertheless, the present invention is not limited to this, and the reflection efficiency can also be improved by setting the interval d between a protrusion 169 and another protrusion 169 located closest thereto to a value within the predetermined range. The reflection efficiency can also be improved by setting the interval d between a protrusion and another protrusion located closest thereto to a value within the aforementioned predetermined range for 50% or more of the protrusions 169 formed in the reflection section 30. The reflection efficiency can also be improved by setting the interval d between at least two protrusions 169 in the reflection section 30 to a value within the predetermined range.
In order to improve the reflection efficiency, it is preferred that the width c of all the protrusions 169 is within the aforementioned predetermined range. Nevertheless, the present invention is not limited to this, and the reflection efficiency can also be improved by setting the width c within the aforementioned predetermined range for 50% or more of the protrusions 169 formed in the reflection section 30. The reflection efficiency can also be improved by setting the width c to a value within the predetermined range for at least one protrusion 169 in the reflection section 30.
The aforementioned Cs metal layer 56 can be formed by a method similar to that described in Embodiment 1. Note however that when shaping the Cs metal layer 56, a mask having a pattern obtained by inverting the pattern used in Embodiment 1 is used as a resist mask. Therefore, the recesses 57 are formed by a so-called “negative-type pattern” in Embodiment 1, whereas the protrusions 169 are formed by a “positive-type pattern” in Embodiment 2.
Next, using
(a) to (f) of
According to the present embodiment, the protrusions 48′ (projections) of the reflective layer 63 are formed according to the controlled shape of the Cs metal layer 56, and it is therefore possible to easily form relatively low projections on the reflective layer. Therefore, the reflection efficiency at the surface of the reflective layer is improved. Since the shape, the height, the slope tilt angle, etc., of the protrusions 48′ can easily be adjusted, it is easy to form many slopes where the tilt angle is 20 degrees or less on the surface of the reflective layer 63. Therefore, it is possible to increase the area of the effective reflection surface without increasing the manufacturing cost.
According to the present embodiment, the width and the interval of the protrusion 169 in the Cs metal layer 56 can be set to be as small as practically possible. Then, more protrusions 169 of the Cs metal layer 56 can be arranged in the reflection section 30, thus forming more protrusions 48′ in the reflective layer 63. This increases the area of the surface where the tilt is 20 degrees or less on the surface of the reflective layer 63, thereby improving the reflection efficiency. Furthermore, since it is possible to reduce the area of the flat portion of the surface of the reflective layer 63, it is possible to further improve the reflection efficiency.
Although the protrusions 169 are described as being formed in the Cs metal layer (metal layer) 56 in the embodiment above, such protrusions may be formed in the gate insulating layer 61 or the semiconductor layer 62 in the reflection section 30, or may be formed in two or all of these layers.
Furthermore, the protrusions 169 may be provided in one or two of these layers, with recesses as described in Embodiment 1 being formed in one or two other layers thereof. The semiconductor layer 62 may be absent in the reflection section 30. The protrusions 169 may be formed by the aforementioned photolithography technique, or the like, during the formation of the layers. The embodiments of the present invention are deemed to encompass these examples.
Next, a third embodiment of the liquid crystal display device of the present invention will be described. The third embodiment is directed to the liquid crystal display device 10 shown in
A plurality of recesses (or openings) 57′ are formed in the Cs metal layer 56 in the reflection section 30 as shown in the figure, and a protruding portion 89 of the Cs metal layer 56 is formed between the recesses 57′. A slope 67 of the protruding portion 89 is formed with a step, and the slope 67 includes an upper slope 85, a flat portion 86 and a lower slope 87. The flat portion 86 is formed generally parallel to the substrate surface. A portion of the protruding portion 89 that is above a plane that includes the flat portion 86 is referred to as an upper portion 69′, and a portion below the plane is referred to as a lower portion 70. The recesses 48 of the reflective layer 63 are formed according to the shape of the recesses 57′ of the Cs metal layer 56.
A reflection section 30′ may be manufactured by a method similar to that described above using
According to the present embodiment, there is obtained an advantage as follows, in addition to those described in Embodiments 1 and 2.
As seen in a cross-sectional shape, each recess 48 includes eight corner portions (portions shown by dotted lines in the figure). In the conventional liquid crystal display device, each recess includes only four corner portions as shown in
As can be seen from
Although the protruding portion 89 of the Cs metal layer 56 has a two-tiered structure including the upper portion 69′ and the lower portion 70 in the present embodiment, the protruding portion 89 may be formed with three or more tiers of steps. In this case, a recess is further formed inside the recess 92 formed in the reflective layer 63, and it is therefore possible to obtain an even higher reflection efficiency.
In the embodiment above, the recess 91 and the recess 92 formed on the surface of the reflective layer 63 are assumed to be formed concentrically as viewed in a direction vertical to the substrate. Nevertheless, the present invention is not limited to this, and the recess 91 and the recess 92 may be arranged so that their centers are not aligned with each other. The periphery of the recess 91 and that of the recess 92 may partially overlap each other. Also in these cases, many recesses/protrusions with steps are formed on the surface of the reflective layer 63, whereby it is possible to widen the effective reflection surface.
Hereinafter, with reference to the drawing, a fourth embodiment of the liquid crystal display device according to the present invention will be described. Like elements to those of Embodiments 1 to 3 will be denoted by like reference numerals and will not be described below.
As shown in the figure, in the present embodiment, the interlayer insulating layer is not formed, and therefore the pixel electrode 28 is formed upon the reflective layer 63 in the reflection section 30 and in the TFT section 32, via an insulating film not shown. The structure and the manufacturing method for the reflection section 30 and the TFT section 32 are the same as in Embodiment 1 except that the interlayer insulating layer 26 is eliminated. The pixel layout and wiring structure in the liquid crystal display device are also similar to what is shown in
Also with this construction, as in Embodiments 1 to 3, the effective reflection surfaces of the reflective layer 63 are expanded in area, so that more light can be reflected toward the display surface 40.
Although the recesses 57 of the Cs metal layer 56 are formed in a circular shape in the embodiment above, the recesses 57 may be formed in any of various shapes, including elliptic shapes, polygonal shapes such as triangles and quadrangles, with sawtoothed edges, or combinations thereof.
The liquid crystal display device of the present invention encompasses display apparatuses, television sets, mobile phones, etc., in which a liquid crystal panel is utilized. Moreover, although the present embodiments illustrate transflective-type liquid crystal display devices as examples, a reflection-type liquid crystal display device having a similar configuration to the aforementioned reflection section would also be encompassed as one configuration of the present invention.
Moreover, since the liquid crystal display device according to the present invention is formed by the above-described manufacturing methods, it can be manufactured with the same materials and steps as those for a transmission-type liquid crystal display device. Therefore, at low cost, a liquid crystal display device having a high reflection efficiency can be provided.
According to the present invention, type and reflection-type liquid crystal display devices having a high image quality can be provided at low cost. Liquid crystal display devices according to the present invention can be suitably used for transflective-type and reflection-type liquid crystal display devices which perform display by utilizing reflected light, e.g., mobile phones, onboard display device such as car navigation systems, display devices of ATMs and vending machines, etc., portable display devices, laptop PCs, and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-284206 | Oct 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/067511 | 9/7/2007 | WO | 00 | 4/17/2009 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/047517 | 4/24/2008 | WO | A |
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