JP2003075825A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can stably display an image of high picture quality by reflection and transmission. SOLUTION: The liquid crystal display device is equipped with a liquid crystal display panel 10 which has a liquid crystal layer 300 sandwiched between a couple of substrates 100 and 200 and a back light unit 10 which lights up the liquid crystal display panel 10 from behind. One pixel area P has a reflection part PR which reflects external light to display a screen picture and a transmission part PT which transmits back-light light emitted by the back light unit 300 to display a screen picture. The 1st direction where the intensity of the reflected light reflected by the reflection part PR becomes maximum is nearly the same as the 2nd direction where the intensity of the back-light light transmitted by the transmission part PT becomes maximum, and the 1st and 2nd directions are slanted at a specific angle θ to the normal direction O of the liquid crystal display panel 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to displaying an image by transmitting external light in a pixel region to display an image and by transmitting backlight light. And a transflective liquid crystal display device having a transmissive portion.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device has a switching element arranged near an intersection of a scanning line and a signal line arranged orthogonally to each other and a pixel electrode electrically connected to the switching element. The liquid crystal display panel includes an array substrate, a counter substrate having a counter electrode, and a liquid crystal layer containing a liquid crystal composition sandwiched between the array substrate and the counter substrate.

A semi-transmissive liquid crystal display device is provided with a reflection portion having a reflection electrode and a transmission portion having a transmission electrode in one pixel area. The reflective electrode and the transmissive electrode are pixel electrodes connected to the switching element, and are simultaneously driven by the same drive voltage.

Such a semi-transmissive liquid crystal display device functions as a transmissive liquid crystal display device in which a backlight is turned on in a dark place and an image is displayed by utilizing a transmissive portion in a pixel area. In some cases, there is an advantage that power consumption can be significantly reduced by functioning as a reflective liquid crystal display device that displays an image by reflecting external light using a reflection portion in a pixel region.

In the reflective display using external light as a light source, the reflected light reflected in a direction deviated from the regular reflection direction of the light source by several degrees to several tens of degrees due to the balance between the difficulty of seeing due to the reflection of the light source and the brightness of the display. The maximum intensity is within the range of good visibility. The direction in which the intensity of the reflected light is maximized within the range of good visibility is the optimum viewing direction of the reflective display. Usually the outside light is
Since the light is incident from a direction inclined by about 10 ° to 40 ° from the normal line direction of the liquid crystal display panel surface, the optimum viewing direction of the reflective display is opposite to the incident direction of external light, and 5 ° from the normal direction.
The direction is inclined by about 45 °.

On the other hand, in the transmissive display using the backlight light as a light source, the intensity of the backlight light emitted from the backlight becomes maximum in the direction normal to the surface of the liquid crystal display panel, and the optimum viewing direction of the transmissive display is obtained. Becomes

[0007]

In such a semi-transmissive liquid crystal display device, the optimum viewing direction for reflective display and the optimum viewing direction for transmissive display are different. Therefore, there is a problem that the utilization efficiency of the light source is low. Further, in the liquid crystal display panel, there is a problem in that the optimum optical design of the reflecting portion and the transmitting portion is different.

Therefore, in the reflective display and the transmissive display, there arises a problem that a high quality image cannot be stably displayed.

The present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal display device capable of stably displaying a high quality image in reflective display and transmissive display. Especially.

[0010]

In order to solve the above problems and achieve the object, a first aspect of the present invention is to illuminate a liquid crystal display panel in which a liquid crystal layer is sandwiched between a pair of substrates and the liquid crystal display panel from the back side. In a liquid crystal display device including a backlight unit, one pixel region has a reflection portion that reflects external light for display, and a transmission unit that transmits backlight light emitted from the backlight unit and performs display. Department,
The first direction in which the intensity of the reflected light reflected by the reflecting portion is maximum within a range with good visibility is a second direction in which the intensity of the backlight light transmitted by the transmitting portion is maximum. The first direction and the second direction are substantially the same, and are inclined by a predetermined angle with respect to the normal direction of the liquid crystal display panel.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a liquid crystal display device of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a liquid crystal display device according to an embodiment of the present invention is an active matrix type transflective color liquid crystal display device, and includes a liquid crystal display panel 10 and a backlight unit 400. Is equipped with.

As shown in FIGS. 1 and 2, the liquid crystal display panel 10 includes an array substrate 100 serving as a first substrate, a counter substrate 200 serving as a second substrate facing the array substrate 100, and an array substrate. The liquid crystal layer 300 includes a liquid crystal composition and is disposed between the liquid crystal composition 100 and the counter substrate 200. In such a liquid crystal display panel 10, a display area 102 for displaying an image is formed in a region surrounded by a sealant 106 that bonds the array substrate 100 and the counter substrate 200, and has a plurality of pixel regions. . A peripheral area 104 having various wiring patterns drawn out from the display area 102 is formed outside the sealing material 106.

The display area 102 of the array substrate 100 is
As shown in FIGS. 2 to 4, m × n pixel electrodes 151 arranged in a matrix on a transparent insulating substrate, for example, a glass substrate 101 having a thickness of 0.7 mm, and a row of these pixel electrodes 151. M scanning lines Y1 formed along the direction
To Ym, n signal lines X1 to Xn formed along the column direction of these pixel electrodes 151, m × n pixel electrodes 15
1 corresponding to the scanning lines Y1 to Ym and the signal lines X1 to Xn
M thin film transistors or TFTs 12 arranged as non-linear switching elements near the intersection of
1, m auxiliary capacitance lines 52 arranged in parallel to the m scanning lines Y1 to Ym, a scanning line driving circuit 18 driving the scanning lines Y1 to Ym, and signal line driving driving these signal lines X1 to Xn It has a circuit 19 and the like.

The scanning line driving circuit 18 sequentially supplies the scanning voltage to the scanning lines Y1 to Ym in the horizontal scanning cycle, and the signal line driving circuit 19 supplies the pixel signal voltage to the signal lines X1 to Xn in each horizontal scanning cycle. To do.

In this embodiment, as shown in FIGS. 3 and 4, the pixel region P substantially corresponds to a region defined by the scanning lines Y and the signal lines X provided on the array substrate 100. The one pixel region P includes a reflection part PR that displays an image by selectively reflecting external light, and a transmission part PT that displays an image by selectively transmitting backlight light from the backlight unit 400. have.

The reflecting portion PR includes a bump 161 formed of, for example, an acrylic resin resist, and the bump 16.
1 provided on top of Ag-Pa-Cu or Ag-Ru-
A reflective electrode 151R formed by a silver alloy such as Cu or Ag-Ru-Au or a metal reflective film such as aluminum.
It has and. The transparent portion PT is made of indium tin.
The transparent electrode 151T is made of a transparent conductive material such as oxide, that is, ITO.

Reflecting electrode 151R and transmitting electrode 151T
Function as the pixel electrode 151 electrically connected to the source electrode of the TFT 121.

As shown in FIG. 5, the TFT 121 is, for example, a top gate type, and has a semiconductor film 122 made of a polysilicon film formed on the glass substrate 101. The semiconductor film 122 has an active region 122A, and an impurity-doped source region 122S and a drain region 122D. The surfaces of the semiconductor film 122 and the glass substrate 101 are a silicon oxide film, that is, S
It is covered with a gate insulating film 123 formed by iO _2.

The active region 12 is formed on the gate insulating film 123.
A gate electrode 124 protruding from the scanning line Y is arranged directly above 2A. The gate electrode 124 and the gate insulating film 123 are made of a silicon oxide film, that is, SiO 2.
It is covered with an interlayer insulating film 125 formed by ₂ . The scanning line Y including the gate electrode 124 is formed of, for example, aluminum.

A transparent electrode 151T made of ITO is arranged in the transparent portion PT on the interlayer insulating film 125.

The source electrode 127S of the TFT 121 is in contact with the source region 122S of the semiconductor film 122 via a contact hole 126S penetrating the gate insulating film 123 and the interlayer insulating film 125. This source electrode 1
27S is electrically connected to the transparent electrode 151T.

The drain electrode 127D of the TFT 121 is
The drain region 122D of the semiconductor film 122 is contacted through a contact hole 126D penetrating the gate insulating film 123 and the interlayer insulating film 125. The drain electrode 127D is formed in the same step as the signal line X and forms a part of the signal line X. The signal line X including the source electrode 127S and the drain electrode 127D is formed of, for example, a molybdenum / aluminum / molybdenum laminate.

The reflective portion PR on the interlayer insulating film 125 is provided with bumps 161 made of resin having a predetermined thickness. This bump 161 is a TFT
121 source electrode 127S and drain electrode 127D
It is also arranged so that it also covers. A reflective electrode 151R made of aluminum is formed on the bump 161.
Are arranged. The reflective electrode 151R is the bump 1
It is electrically connected to the source electrode 127S through a contact hole 128 penetrating 61.

In the example shown in FIGS. 3 and 4, the TFT 12
1 is a bump 16 near the intersection of the signal line X and the scanning line Y
It is arranged in the lower layer of 1. The TFT 12 is provided on the transmissive electrode 151T and the reflective electrode 151R as the pixel electrode 151.
The same drive signal is supplied from one source electrode 127S.

As shown in FIG. 4, the surfaces of the transmissive electrode 151T and the reflective electrode 151R have an alignment film 1 for aligning the liquid crystal composition 300 interposed between the transparent substrate 151T and the reflective electrode 151R.
It is covered by 41.

As shown in FIG. 2, each TFT 121 is driven by the signal line driving circuit 19 when the corresponding scanning line is driven by the scanning line driving circuit 18 to select the pixel electrode 151 of the corresponding row. The potentials of the signal lines X1 to Xn are applied to the pixel electrodes 151 of these corresponding rows.

The display area 102 of the counter substrate 200 is, as shown in FIGS. 2 and 4, a transparent insulating substrate, for example, a color filter CF provided on a glass substrate 201 having a thickness of 0.7 mm, and the color filter CF. The counter electrode 204 is provided on the color filter CF.

The color filter CF is provided for each pixel area in order to realize color display. In this embodiment, for example, color filters CF colored in red, green, and blue are provided in the red pixel area, the green pixel area, and the blue pixel area, respectively. These color filters CF are formed of, for example, a resin in which pigments of respective color components are dispersed.

The counter electrode 204 is a transparent conductive member such as ITO that forms a potential difference with the pixel electrode 151.
Is formed by. Further, the surface of the counter electrode 204 is covered with an alignment film 205 for aligning the liquid crystal composition 300 interposed between the counter electrode 204 and the array substrate 100.

The counter electrode 204 is composed of a plurality of pixel electrodes 151.
Is set to the reference potential. An electrode transfer material arranged around the substrate, that is, a silver paste as a transfer, is provided to supply a voltage from the array substrate 100 to the counter substrate 200, and the counter electrode 204 drives the counter electrode connected through the transfer. Driven by the circuit 20.

As shown in FIG. 2, the liquid crystal capacitance CL is formed by the liquid crystal layer 300 sandwiched between the pixel electrode 151 and the counter electrode 204. The auxiliary capacitance CS, which is electrically parallel to the liquid crystal capacitance CL, is formed by a pair of electrodes arranged to face each other on the array substrate 100 with an insulating layer interposed therebetween.
In other words, the auxiliary capacitance CS is arranged so as to face each other with the insulating layer interposed therebetween, and has the same potential as the pixel electrode 151.
1 and the auxiliary capacitance line 52 set to a predetermined potential.

As shown in FIG. 4, a circularly polarizing plate 181 is provided on the outer surface of the glass substrate 101 of the array substrate 100. A circular polarization plate 211 is provided on the outer surface of the glass substrate 201 of the counter substrate 200. Circularly polarizing plate 183
For 211 and 211, the optimum direction is selected according to the display mode of the liquid crystal display device, the twist angle of the liquid crystal composition, and the like.

The circularly polarizing plates 181 and 211 are formed by laminating one polarizing plate and two retardation plates. The material of the retardation plate is polycarbonate or norbornane resin represented by Arton.
The pair of circularly polarizing plates 181 and 211 form a predetermined angle with respect to the normal direction of the liquid crystal display panel surface, that is, 5 °.
In order to give a phase difference of λ / 4 to the light emitted along the direction inclined by the range of 45 ° or more, the axis angle of the polarizing plate, the axis angle of each of the two phase difference plates, and the phase difference value To set.

The backlight unit 400 shown in FIG.
Are arranged on the back surface of the array substrate 100 in the liquid crystal display panel 10. This backlight unit 400
Is a rectangular plate-shaped holding frame 424, a light guide 426, a plurality of sheet members, for example, three optical sheets 428, 4
30, 432, an elongated tubular cold cathode ray tube 4 as a light source
33 or an LED, a protective cover 434 and the like.

The holding frame 424 is made of, for example, a synthetic resin and has a rectangular accommodating recess 436. The optical sheet 428 is a reflective sheet made of, for example, a milky white polyimide resin, and the holding frame 424.
Is formed in a rectangular shape having substantially the same size as the storage recess 436 of FIG.

The light guide 426 is formed of, for example, acrylic resin, and has a storage recess 436 of the holding frame 424.
It is formed in a rectangular shape having substantially the same size as. The light guide 426 has a thick portion 426a on one side thereof, a thin portion 426b on a side facing the thick portion 426a, and has a wedge-shaped cross section. One side surface 426d of the thick portion 426a of the light guide 426 is a cold cathode ray tube or L
It is arranged so as to face the light source 433 of the ED and serves as an incident surface on which the light emitted from the light source 433 enters. The above-mentioned reflection sheet 428 is provided on the back surface 426e side of the light guide 426. The main plane 4 facing one main surface of the light guide 426, that is, the back surface 426e provided with the reflection sheet 428.
26c is an emission surface from which the light incident from the incidence surface 426d is emitted.

The optical sheet 430 is, for example, a diffusion sheet, and is formed in a rectangular shape having substantially the same size as the storage recess 436. The optical sheet 430 is used for the light guide 42.
6 is laminated on the emission surface 426c. The optical sheet 432 is a prism sheet and is formed in a rectangular shape having substantially the same size as the storage recess 436. The optical sheet 432 is laminated on the diffusion sheet 430.

In the vicinity of the side wall 424a of the holding frame 424, an elongated lamp accommodating groove 440 extending over the entire length in the width direction is formed. A rib 441 having substantially the same height as the side wall 424a is provided upright in the central portion in the longitudinal direction inside the lamp housing groove 440. This rib 441 is
Along the longitudinal direction of the lamp housing groove 440 and the side wall 4
It extends at a predetermined distance from the inner surface of 24a.

In the lamp housing groove 440, the rib 44 is formed.
The cold cathode ray tube 433 is housed in the region of the first storage recess 436 side. That is, the cold cathode ray tube 433 is integrally assembled with the reflector 448 in a state where both ends thereof are supported by the holder 442 in a predetermined positional relationship. The reflector 448 has a substantially U-shaped cross section, and is arranged to surround a peripheral surface of the cold cathode ray tube 432 other than the peripheral surface facing the light guide 426. The cold cathode ray tube 433 is arranged at a predetermined position facing the thick portion 426a of the light guide 426.

From the pair of holders 442, the cold cathode ray tube 4 is
Connection cables 444a and 444b for supplying voltage to 33
Have been derived respectively. The connection cable 444a is
In the lamp housing groove 440, the rib 441 and the side wall 42 are formed.
4a, and is routed to the other holder 442 side through the area between the other side and 4a, and is led out to the outside together with the other connection cable 444b. Two connection cables 4 pulled out
44a and 444b are connected to a lamp drive circuit.

The backlight unit 4 having such a structure
In 00, at least one of the guide pattern shape on the back surface of the light guide body 426 and the condensing direction of the prism sheet 432 is the direction in which the intensity of the backlight light emitted from the backlight unit 400 is the maximum (second The direction is adjusted to be a direction inclined by 5 ° or more and 45 ° or less from the normal direction of the liquid crystal display panel surface.

An example for realizing this will be described. As shown in FIG. 8, when the emission angle with respect to the normal line of the emitted light emitted from the light guide plate 426 is α and the apex angle of the prism 432 a forming the prism sheet 432 is β, the light is emitted from the prism sheet 432. The emission angle θ with respect to the normal line of the emitted light is θ = β−α.

Here, α is 60 °, and θ is 5 ° to 4
To make it 5 °, β may be set to 65 ° to 105 °. In this case, the backlight unit 400 and the liquid crystal display panel 10 are combined as shown in FIG. That is, the light source 43 of the backlight unit 400
3 is arranged on the side opposite to the direction inclined from the normal line of the emitted light. That is, when the liquid crystal display panel 10 and the backlight unit 400 are stacked, the light source 433 is arranged above the liquid crystal display panel 10. Then, the emitted light is emitted at an angle of 5 ° to 45 ° downward.

As shown in FIG. 4, the liquid crystal display panel 10
Is the backlight unit 40 configured as described above.
The optical sheet 432 is disposed so as to overlap with the optical sheet 0, and is adjacent to the optical sheet 432. During operation of the liquid crystal display device, a part of the light emitted from the cold cathode ray tube 433 directly enters the light guide body 426 through the incident surface 426d of the light guide body 426, and the remaining light is reflected by the reflector 448. Then, the light enters the inside of the light guide 426 through the incident surface 426d. The incident light propagates through the inside of the light guide 426,
The light is emitted from the light emitting surface 426c toward the diffusion sheet 430.

The light leaked from the light guide 426 to the reflection sheet 428 side is reflected by the reflection sheet 428 and is incident on the light guide 426 again. Emitting surface 426c of light guide 426
Light emitted from the liquid crystal display panel 10 is diffused by the diffusion sheet 430 and is diffused by the prism sheet 432.
Be guided to the entire surface of.

The thickness of the liquid crystal layer in which the liquid crystal composition 300 is sandwiched, that is, the gap of a predetermined width formed between the array substrate 100 and the counter substrate 200 is defined by a wiring pattern such as the signal line X and the scanning line Y. TFT 121, pixel electrode 15
1. It is secured by the spacers arranged in the non-pixel area such as the peripheral frame portion.

In the example shown in FIG. 4, the thickness of this liquid crystal layer is about 5 μm in the transmissive portion PT of the pixel region P. In the reflection part PR of the pixel region P, the reflection electrodes 151R,
And a thickness of about 1 to 5 μm under the reflective electrode 151R,
In this embodiment, since the bumps 161 having a thickness of about 2.5 μm are provided, the thickness of the liquid crystal layer in the reflective portion PR is about 2.5 μm, unlike the thickness of the liquid crystal layer in the transmissive portion PT. .

That is, the counter substrate 200 has the liquid crystal layer 30.
While the surface facing the 0 is substantially flat, the array substrate 100 has the bumps 161 protruding from the transmissive portion PT in the reflective portion PR, so that the one-way position of light passing through the liquid crystal layer is increased. The phase difference in the transmissive part PT is equivalent to twice that in the reflective part PR.

In the transparent portion PT, the backlight unit 3
The light emitted from 0 passes through the liquid crystal layer 300 once, whereas in the reflection part PR, the light incident from the counter substrate 200 side passes through the liquid crystal layer 300 and then the reflection electrode 151.
The light is reflected by R, passes through the liquid crystal layer 300 again, and then is emitted from the counter substrate 200. Therefore, the phase difference between the light passing through the liquid crystal layer of the transmission part PT and the light passing through the liquid crystal layer of the reflection part PT becomes substantially equal.

As described above, in the transmissive part PT, the backlight light is transmitted through the liquid crystal layer 300 only once, whereas in the reflective part PR, the external light from the counter substrate 200 side is the liquid crystal layer 3.
00 is passed twice, it is preferable that the thickness of the liquid crystal layer 300 of the reflection part PR is about ½ of the thickness of the transmission part PT.

Next, a method of manufacturing this liquid crystal display device will be described.

That is, the film formation and patterning of the metal film and the insulating film are repeated on the glass substrate 101 to form various wirings such as the scanning line Y and the signal line X, and the TFT 121 and the like.

Subsequently, in the transparent portion PT, the glass substrate 10
An ITO thin film is formed on the entire surface of No. 1 by a sputtering method and then patterned to form a transparent electrode 151.
Form T. This transparent electrode 151T is
Is electrically connected to the source electrode 127S of.

On the other hand, in the reflecting portion PR, the glass substrate 101
A transparent UV-curable acrylic resin resist is applied to the entire upper surface by a spinner and dried. Then, the acrylic resin resist is applied to a 36-th photomask having a predetermined pattern corresponding to the reflection part PR of each pixel region P.
After exposure with a wavelength of 5 nm and an exposure dose of 100 mJ / cm ² , the film is developed with a predetermined developing solution for 70 seconds. Then, by firing, the bumps 16 having a film thickness of 2.5 μm are formed.
1 is formed.

Subsequently, an aluminum thin film is formed on the bump 161 by a sputtering method and then patterned to form a reflection electrode 151R. At this time, the reflective electrode 151R is removed from the TFT 12 through the contact hole 128 formed in the bump 161.
The first source electrode 127S is electrically connected.

Subsequently, an alignment film material is applied on the transparent electrode 151T and the reflective electrode 151R, and a rubbing treatment is performed to form an alignment film 141. As a result, the array substrate 100 is formed.

On the other hand, a glass substrate 201 having a thickness of 0.7 mm
The counter electrode 204 and the alignment film 205 are respectively formed thereon, and the counter substrate 200 is formed.

Subsequently, the sealing material 106 is provided along the periphery of the alignment film 205 of the counter substrate 200 except for the liquid crystal injection port 32.
To print. Further, an electrode transfer material for supplying a voltage from the array substrate 100 side to the counter electrode 204 on the counter substrate 200 side is formed on the electrode transfer electrode around the sealing material 106.

Next, the array substrate 100 and the counter substrate 200 are arranged so that the alignment films 141 and 205 face each other, and the sealing material 106 is cured by heating to bond the two substrates. At this time, a predetermined gap is formed between the array substrate 100 and the counter substrate 200.

Subsequently, the liquid crystal composition 300 containing a chiral agent is injected from the liquid crystal injection port 32 between the array substrate 100 and the counter substrate 200, and the liquid crystal injection port 32 is sealed with the ultraviolet curable resin 33. . Injected liquid crystal composition 300
Is the alignment film 141 on the array substrate 100 side and the counter substrate 2
A liquid crystal layer of twist alignment or homogeneous alignment is formed by the alignment film 205 on the 00 side.

Subsequently, the array substrate 100 and the counter substrate 2
Circularly polarizing plates 181 and 211 are arranged on the outer surface of 00, respectively. Thereby, the liquid crystal display panel 10 is manufactured.

As described above, the thickness of the liquid crystal layer 300 is
The reflection part PR and the transmission part PT of the pixel region P are different. Further, the direction (first direction: optimum observation direction) of the reflected light reflected by the reflecting portion PR (the intensity is maximum within a range where visibility is good) is the intensity of the backlight light transmitted by the transmitting portion PT. Is substantially the same as the maximum direction (second direction: optimum observation direction), and these first and second directions are at a predetermined angle θ with respect to the normal direction O of the liquid crystal display panel surface. That is, it is inclined by an angle in the range of 5 ° to 45 °.

In the reflection part PR, the external light reflected in the first direction after entering the liquid crystal layer 300 from the counter substrate 200 side has a one-way phase difference of λ / 4, and is reflected by the reflection electrode 151R. The light reciprocally causes a phase difference of λ / 2 before being emitted to the counter substrate 200 side. In the transmissive portion PT, the backlight light that is incident on the liquid crystal layer 300 from the array substrate 100 side and then is transmitted in the second direction is transmitted to the counter substrate 2.
A phase difference of λ / 2 is generated before the light is transmitted to the 00 side.

Circular polarizing plates 181 and 211 are arranged on the outer surfaces of the array substrate 100 and the counter substrate 200.
Circularly polarized light generated by passing through the circular deflection plate is converted into forward or reverse circularly polarized light by turning on / off the voltage to the liquid crystal layer 300. As a result, when passing through the circularly polarizing plate again, light passing / non-passing is selected. Using this principle, an image is displayed mainly in a dark place by selectively transmitting backlight light. Also, mainly in a bright place, an image is displayed by selectively reflecting external light.

The operation of such a transflective liquid crystal display device will be described in more detail.

First, the light passing through the liquid crystal layer 300 in the reflection part PR operates as follows in a state where no potential difference is generated in the liquid crystal layer 300, that is, when the voltage is OFF.

That is, a part of the external light entering from the counter substrate 200 side is converted into left circularly polarized light by passing through the circularly polarizing plate 211, and the glass substrate 201 on the counter substrate 200 side causes the liquid crystal layer 300 to pass. Incident on. The left-handed circularly polarized light is a liquid crystal layer 30 containing a homogeneously aligned liquid crystal composition.
Passing 0 causes a phase delay of λ / 4, is reflected by the reflective electrode 151R, and passes through the liquid crystal layer 300 again, causing a further phase delay of λ / 4. This causes a total phase delay of λ / 2.

The reflected light reflected in the first direction and given a phase difference of λ / 4 is converted into right circularly polarized light, and the counter substrate 200
It passes through the glass substrate 201 on the side. The right circularly polarized light is converted into linearly polarized light by passing through the phase difference plate included in the circularly polarizing plate 211. The polarization direction of this linearly polarized light is parallel to the polarization direction of the polarizing plate included in the circularly polarizing plate 211. Therefore, the linearly polarized light converted by the retardation plate passes through the polarizing plate and performs bright display of a single color corresponding to the color of the color filter CF.

On the other hand, in the state where the potential difference is generated in the liquid crystal layer 300, that is, when the voltage is ON, the light passing through the liquid crystal layer 300 in the reflecting portion PR operates as follows.

That is, as in the case where the voltage is turned off, a part of the external light incident from the counter substrate 200 side is reflected by the circularly polarizing plate 2.
After passing through 11, the light is converted into left-handed circularly polarized light and enters the liquid crystal layer 300 from the glass substrate 201 on the counter substrate 200 side. The left-handed circularly polarized light passes through the liquid crystal layer 300 containing the liquid crystal composition in a state where the liquid crystal molecules are raised up and down, and passes through the glass substrate 201 on the counter substrate 200 side without being subjected to the phase modulation by the liquid crystal layer 300. To do.
This left circularly polarized light is converted into linearly polarized light by passing through a retardation plate included in the circularly polarizing plate 211. The polarization direction of this linearly polarized light is orthogonal to the polarization direction of the polarizing plate. Therefore, the linearly polarized light converted by the retardation plate cannot pass through the polarizing plate and dark display, that is, black display is performed.

On the other hand, the light passing through the liquid crystal layer 300 in the transmissive portion PT operates as follows in the state where no potential difference is generated in the liquid crystal layer 300, that is, when the voltage is OFF.

That is, a part of the backlight light emitted from the backlight unit 400 is a circularly polarizing plate 181.
Is converted into left-handed circularly polarized light and enters the liquid crystal layer 300 from the array substrate 100 side. This left-handed circularly polarized light is a liquid crystal layer 3 containing a homogeneously aligned liquid crystal composition.
Passing 00 causes a phase delay of λ / 2.

The backlight light transmitted in the second direction and given a phase difference of λ / 2 is converted into right circularly polarized light and passes through the glass substrate 201 on the counter substrate 200 side. The right circularly polarized light is converted into linearly polarized light by passing through the phase difference plate included in the circularly polarizing plate 211. The polarization direction of this linearly polarized light is parallel to the polarization direction of the polarizing plate included in the circularly polarizing plate 211. Therefore, the linearly polarized light converted by the retardation plate passes through the polarizing plate and performs bright display of a single color corresponding to the color of the color filter CF.

On the other hand, when a potential difference is generated in the liquid crystal layer 300, that is, when the voltage is ON, the light passing through the liquid crystal layer 300 in the transmissive portion PT operates as follows.

That is, as in the case where the voltage is turned off, a part of the backlight light incident from the array substrate 100 side is converted into left circularly polarized light by passing through the circular polarization plate 181, and the array substrate 100 side. Is incident on the liquid crystal layer 300. This left-handed circularly polarized light passes through the liquid crystal layer 300 containing the liquid crystal composition in which liquid crystal molecules are raised,
It passes through the glass substrate 201 on the side of the counter substrate 200 without being subjected to the phase modulation by the liquid crystal layer 300. This left circularly polarized light is converted into linearly polarized light by passing through the retardation plate 209 included in the circularly polarizing plate 211. The polarization direction of this linearly polarized light is orthogonal to the polarization direction of the polarizing plate. Therefore, the linearly polarized light converted by the retardation plate cannot pass through the polarizing plate and dark display, that is, black display is performed.

As described above, the transflective liquid crystal display device is provided with the reflection portion PR and the transmission portion PT in one pixel region P, and in the bright place, the reflection portion PR selectively reflects the outside light to form an image. Functioning as a reflective liquid crystal display device that displays
The backlight unit 30 is turned on, and the transmissive portion PT functions as a transmissive liquid crystal display device that selectively transmits the backlight light emitted from the backlight unit 30 to display an image. Compared to the case where a backlight unit is driven as a display device, power consumption can be significantly reduced.

Further, in the above-mentioned semi-transmissive liquid crystal display device, the reflection portion PR is formed in the first state in the liquid crystal layer 300 in the ON state.
A phase difference of λ / 4 is given to the external light reflected along the direction, and λ / 2 is given to the backlight light passing through the transmissive part PT in the liquid crystal layer 300 in the ON state along the second direction.
So as to give a phase difference of
The thickness of the liquid crystal layer 300, the thickness of the bump 161 and the like are set.

The first direction is the direction in which the intensity of the reflected light reflected by the reflecting portion is maximum within the range of good visibility, and the second direction is the backlight light transmitted by the transmitting portion. This is the direction in which the strength of is maximum. The first direction and the second direction are substantially the same direction and are inclined by a predetermined angle with respect to the normal direction of the liquid crystal display panel, that is, an angle within the range of 5 ° or more and 45 ° or less.

As described above, since the optimum viewing direction in the transmissive display substantially coincides with the optimum viewing direction in the reflective display, it is possible to improve the utilization efficiency of the light source. Can be displayed.

In the above-described first embodiment, the case where the thickness of the liquid crystal layer in the transmissive portion is larger than the thickness of the liquid crystal layer in the reflective portion has been described, but the counter substrate passes through the transmissive portion and the reflective portion. The configuration is not limited to this as long as the phase difference of λ / 2 can be given to the light emitted from the side.

Next, a second embodiment of the present invention will be described. The same components as those in the above-described embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The difference between the second embodiment and the first embodiment is the vertical relationship between the bump 172 and the reflective electrode 151R, as shown in FIG. That is, the reflection part PR
The reflective electrode 151R is disposed on the glass substrate in the same layer as the transmissive electrode 151T in the transmissive portion PT.
The bumps 172 provided to control the thickness of the liquid crystal layer in the reflective portion PR are substantially transparent and are disposed on the reflective electrode 151R.

In the second embodiment, a color filter is used instead of the bump 172, and the counter substrate 20 is used.
The color filter layer on the 0 side may be omitted.

Also in the above-described second embodiment, when the voltage is turned on / off, the same operation as in the above-described first embodiment can be performed and the same effect can be obtained.

As described above, according to the liquid crystal display device of the present invention, the reflection portion that can function as a reflection type liquid crystal display device by utilizing external light is provided in one pixel region, and the backlight disposed on the back surface. And a transmissive part that can function as a transmissive liquid crystal display device using the backlight light from the unit,
It is possible to reduce power consumption when using in a bright place and a dark place.

Further, with respect to light emitted from the counter substrate side after passing through the liquid crystal layers of the transmission part and the reflection part, respectively,
By controlling the thickness of the liquid crystal layer so that a phase delay of / 2 can be given, the brightness can be improved and the deterioration of the contrast can be prevented, so that a high-quality image can be displayed. .

[0088]

As described above, according to the present invention, it is possible to provide a liquid crystal display device capable of stably displaying a high-quality image in reflective display and transmissive display.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing an example of a liquid crystal display panel applied to a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of the liquid crystal display panel shown in FIG.

3 is a plan view schematically showing one pixel region of the liquid crystal display panel shown in FIG.

FIG. 4 is a cross-sectional view schematically showing a cross section of the one pixel region shown in FIG. 3 taken along the line AB.

5 is a sectional view schematically showing a configuration of a thin film transistor in the liquid crystal display panel shown in FIG.

6 is an exploded view schematically showing the structure of a backlight unit applied to the liquid crystal display panel shown in FIG.

FIG. 7 is a cross-sectional view schematically showing a cross section when one pixel region is cut in a liquid crystal display device according to another embodiment of the present invention.

FIG. 8 is a diagram for explaining the relationship between the prism shape of the prism sheet applied to the liquid crystal display device according to the embodiment of the present invention and the direction of emitted light.

9 is a diagram for explaining the relationship between the position of a light source and the direction of emitted light when the prism sheet shown in FIG. 8 is applied.

[Explanation of symbols]

10 ... Liquid crystal display panel 100 ... Array substrate 121 ... Thin film transistor 151 ... Pixel electrode 151R ... Reflective electrode 151T ... Transparent electrode 161 ... Bump 200 ... Counter substrate 204 ... Counter electrode 300 ... Liquid crystal composition 400 ... Backlight unit 426 ... Light guide 433 ... Light source P ... Pixel area PR ... Reflector PT ... Transparent part

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H091 FA07Z FA23Z FA41Z FA42Z                       FA45Z FB02 FB08 GA03                       GA07 GA13 KA10 LA16 LA17                 5C094 AA03 BA03 BA43 CA19 CA24                       EA04 EA05 EA06 EA07 EB02                       EB05

Claims (6)

[Claims] 1. A liquid crystal display device comprising: a liquid crystal display panel having a liquid crystal layer sandwiched between a pair of substrates; and a backlight unit for illuminating the liquid crystal display panel from the back surface. A reflective part that reflects and displays
A first direction in which the intensity of the reflected light reflected by the reflecting section is maximized, and the transmitting section transmits the backlight emitted from the backlight unit to perform display. Is substantially the same as the second direction in which the intensity of the back light is maximized, and the first direction and the second direction are inclined at a predetermined angle with respect to the normal direction of the liquid crystal display panel. A liquid crystal display device characterized in that 2. The liquid crystal display panel is provided with circularly polarizing plates on an incident surface side and an emitting surface side of a backlight, respectively, and the pair of circularly polarizing plates emit the backlight along the second direction. The liquid crystal display device according to claim 1, wherein a phase difference of λ / 4 is given to the light. 3. The liquid crystal according to claim 1, wherein the liquid crystal layer imparts a phase difference of λ / 4 to the reflected light reflected in the first direction after entering the reflecting portion. Display device. 4. The liquid crystal layer has a wavelength of λ / with respect to backlight light transmitted in the second direction after being incident on the transmission portion.
The liquid crystal display device according to claim 1, wherein a phase difference of 2 is provided. 5. The liquid crystal display device according to claim 1, wherein the predetermined angle is within a range of 5 ° or more and 45 ° or less. 6. The backlight unit includes a light source, a light guide body having a guide pattern for guiding the light generated from the light source to the liquid crystal display panel, and between the light guide body and the liquid crystal display panel. And an optical sheet that imparts predetermined optical characteristics to the light emitted from the light guide, and at least one of the guide pattern and the optical sheet is incident on the liquid crystal display panel in the second direction. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a function of maximizing the intensity of the backlight light.