JP2003177430A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can stably display high-grade images without depending upon observation directions in reflected display and transmitted display. <P>SOLUTION: The liquid crystal display device has a liquid crystal display panel 10 holding a liquid crystal layer 300 between a pair of substrates 100 and 200 and a back light unit 400 for illuminating the panel 10 from the back. One pixel region P has a reflecting section PR for making display by reflecting external light and a transmitting section PT for making display by allowing the transmission of the back light emitted from the unit 400. The orientation mode of the liquid crystal molecules included in the layer 300 in the reflecting section PR is a HAN type. The orientation mode of the liquid crystal molecules included in the layer 300 in the transmitting section PT is a bend type. <P>COPYRIGHT: (C)2003,JPO

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 liquid crystal molecules 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 conventional transflective liquid crystal display device, the alignment modes of the liquid crystal molecules of the liquid crystal layer in the reflection part and the transmission part are the same. For example, the alignment mode of the liquid crystal molecules in the reflection part and the transmission part is TN (Twist Nematic).
Mold orientation or homogeneous orientation.

In these alignment modes, the phase difference given to the light by the liquid crystal layer differs depending on the incident angle of the light incident on the liquid crystal layer. For example, in the case of homogeneous alignment, the optical path length of light incident on the liquid crystal layer from the normal direction of the substrate is shorter than the optical path length of light incident on the liquid crystal layer at an incident angle inclined by a predetermined angle with respect to the normal line of the substrate. . For this reason, when it is optimized to give a predetermined phase difference to light incident from the normal direction of the substrate, it is not possible to give a predetermined phase difference to light incident at an inclined incident angle.

[0007]

In such a semi-transmissive liquid crystal display device, the phase difference given by the liquid crystal layer differs depending on the incident angle of the light incident on the liquid crystal layer. Therefore, when observed in a direction other than the specific observation direction, there is a problem that the contrast ratio is lowered and gradation inversion occurs. That is, the conventional transflective liquid crystal display device has a problem in that it cannot stably display a high-quality image regardless of the viewing direction.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object thereof is a liquid crystal display device capable of stably displaying a high-quality image regardless of the viewing direction. To provide.

[0009]

A liquid crystal display device according to an aspect of the present invention is a liquid crystal display panel in which a liquid crystal layer is sandwiched between a first substrate and a second substrate, and a backlight for illuminating the liquid crystal display panel from the back side. In a liquid crystal display device including a light unit, one pixel region includes a reflection portion that reflects external light for display, and a transmission portion that transmits backlight light emitted from the backlight unit for display. And the alignment mode of the liquid crystal molecules included in the liquid crystal layer is HAN (Hybrid Align) in the reflective portion.
ment Nematic) type and the alignment mode of the liquid crystal molecules included in the liquid crystal layer is b in the transmissive portion.
It is characterized by being of the end type.

According to the liquid crystal display device having the above-described configuration, the alignment mode of the liquid crystal molecules contained in the liquid crystal layer is the HAN type in the reflection part in one pixel region, and the alignment mode of the liquid crystal molecules is in the transmission part. The mode is bend type.

The liquid crystal molecules aligned in the bend type alignment mode have the first liquid crystal layer centered on the substantially central portion in the thickness direction of the liquid crystal layer.
It is distributed so as to have mirror symmetry on the substrate side and the second substrate side. Due to this feature, when the backlight light emitted from the backlight unit enters the liquid crystal layer, the phase difference given to the backlight light by the liquid crystal layer becomes substantially constant regardless of the incident angle of the backlight light.

Further, the liquid crystal molecules aligned in the HAN type alignment mode are distributed so as to correspond to the case where the bend type alignment mode is halved at the center of the liquid crystal layer. From this feature, the external light incident on the liquid crystal layer is reflected by the reflector,
When the liquid crystal layer is passed through twice, substantially the above-mentioned ben is obtained.
It is equivalent to passing through the liquid crystal layer in the d-type alignment mode. In addition, the thickness of the liquid crystal layer of the HAN-type alignment mode in the reflection portion is about 1/2 of the thickness of the liquid crystal layer of the bend-type alignment mode in the transmission portion, and external light is the liquid crystal layer of the reflection portion. Pass twice. Therefore, as in the case of the above-described backlight light, when the external light is incident on the liquid crystal layer, the phase difference given to the external light by the liquid crystal layer is substantially constant regardless of the incident angle of the external light.

That is, the liquid crystal layer can give a substantially constant phase difference to the backlight light passing through the transmitting portion and the external light passing through the reflecting portion. For this reason,
The transmissive part and the reflective part can match the gradation display, and can suppress the deterioration of the contrast ratio and the gradation reversal depending on the viewing direction, and stably display a high-quality image in a wide visual field range. It becomes possible to do.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A liquid crystal display device according to an embodiment 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 liquid crystal molecules and is disposed between 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 sealing material 106 that bonds the array substrate 100 and the counter substrate 200, and is arranged in a plurality of matrices. It has a pixel area. The peripheral area 104 outside the sealing material 106 has various wiring patterns drawn from the inside of the display area 102.

The array substrate 100 is arranged in a matrix in a display area 102 on a transparent insulating substrate, for example, a glass substrate 101 having a thickness of 0.7 mm, as shown in FIGS. n pixel electrodes 151, m scanning lines Y1 to Ym formed along the row direction of these pixel electrodes 151, and n signal lines X1 to Xn formed along the column direction of these pixel electrodes 151. , M × n pixel electrodes 151 corresponding to the scanning lines Y1 to Ym and the signal line X1.
˜Xn, m × n thin film transistors or TFs arranged as non-linear switching elements near the intersection
T121, m auxiliary capacitance lines 52 arranged in parallel to the m scanning lines Y1 to Ym, the scanning line driving circuit 18 driving the scanning lines Y1 to Ym, and the signal line driving circuit driving the signal lines X1 to Xn. 19 and so on.

The scanning line driving circuit 18 sequentially supplies the scanning voltage to the scanning lines Y1 to Ym in the horizontal scanning period, and the signal line driving circuit 19 supplies the pixel signal voltage to the signal lines X1 to Xn in each horizontal scanning period. 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 151 formed of an alloy such as Cu or Ag-Ru-Au or a metal reflective film such as silver or aluminum.
R and. The transmissive part PT includes a transmissive electrode 151T formed of a transparent conductive member such as indium-tin-oxide, that is, ITO.

Reflective electrode 151R and transmissive 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 transmissive electrode 151T made of ITO is arranged in the transmissive 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 through 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. The bump 161 is arranged so as to cover, for example, the source electrode 127S and the drain electrode 127D of the TFT 121. This bump 1
A reflective electrode 151R made of aluminum is arranged on the surface 61. The reflective electrode 151R is
It is electrically connected to the source electrode 127S through a contact hole 128 penetrating the bump 161.

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 are covered with an alignment film 141 for aligning liquid crystal molecules included in the liquid crystal layer 300 interposed between the transparent substrate 151T and the reflective electrode 151R. ing.

In the reflection part PR, the alignment film 141 is arranged so that liquid crystal molecules near the array substrate 100 are applied with no voltage.
It is oriented substantially perpendicular to the array substrate 100. That is, the alignment film 141 has a tilt angle of liquid crystal molecules near the array substrate 100 (liquid crystal molecules located on the surface of the alignment film) of 7 degrees.
Orientation is performed so as to be about 0 ° to 90 °.

Further, in the transmissive part PT, the alignment film 141
Aligns the liquid crystal molecules near the array substrate 100 substantially parallel to the array substrate 100 in the absence of applied voltage.
That is, the alignment film 141 is aligned so that the tilt angle of the liquid crystal molecules near the array substrate 100 (the liquid crystal molecules located on the surface of the alignment film) is about 1 ° to 50 °.

The alignment film 141 as described above is formed, for example, as follows. That is, first, the alignment film material is applied to the surfaces of the transmissive electrode 151T and the reflective electrode 151R. Then, a rubbing process is performed through a mask having a predetermined pattern so as to selectively cover only the reflection part PR of each pixel region P and expose the transmission part PT. As a result, only the alignment film material on the transmissive electrode 151T is rubbed, and the alignment material on the reflective electrode 151R is not rubbed. As a result, an alignment film 141 is formed in which the liquid crystal molecules on the transmissive part PT are aligned substantially parallel to the substrate and the liquid crystal molecules on the reflective part PR are aligned substantially perpendicular to the substrate.

As another method of forming the alignment film 141 as described above, the following method may be mentioned. For example, a photo-alignment film material applied on the surfaces of the transmissive electrode 151T and the reflective electrode 151R is provided with a photomask having a predetermined pattern that exposes the transmissive part PT of each pixel region P,
There is a method of irradiating only the alignment film material on the transmission electrode 151T with polarized ultraviolet rays. In addition to this, the transparent electrode 15
After the rubbing treatment is performed on the entire alignment film material applied to the surfaces of the 1T and the reflective electrode 151R, the reflective electrode 151R is formed on the reflective electrode 151R through a mask having a predetermined pattern that exposes the reflective portion PR of each pixel region P. There is a method of applying the vertical alignment film material only to the above.

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

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. The surface of the counter electrode 204 has the liquid crystal layer 3 interposed between the counter electrode 204 and the array substrate 100.
Alignment film 20 for aligning liquid crystal molecules contained in
Covered by 5.

The alignment film 205 is arranged so that liquid crystal molecules near the array substrate 100 in the reflection part PR and the transmission part PT are
It is oriented substantially parallel to the counter substrate 200 when no voltage is applied. That is, the alignment film 205 is formed on the counter substrate 2
Liquid crystal molecules near 00 (liquid crystal molecules located on the alignment film surface)
The tilt angle is about 1 ° to 50 °. Such an alignment film 205 is provided in the array substrate 1 described above.
The alignment film 141 formed on the transmission part PT on the 00 side is formed by the same method.

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 arranged 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. For these circularly polarizing plates 183 and 211, optimum directions are selected according to the display mode of the liquid crystal display device and the like.

The circularly polarizing plates 181 and 211 are formed, for example, by laminating one polarizing plate and two retardation plates. The material of the retardation plate is polycarbonate or a norbornane resin represented by Arton. These pair of circularly polarizing plates 181 and 211
Sets the axial angle of the polarizing plate, the axial angle of each of the two phase difference plates, and the phase difference value so that a phase difference of λ / 4 is given to all the wavelengths of the emitted light.

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 made 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.

The ribs 44 are provided in the lamp housing groove 440.
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.

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 300 containing liquid crystal molecules, that is, the gap of a predetermined width formed between the array substrate 100 and the counter substrate 200 is defined by the wiring patterns of the signal lines X and the scanning lines Y, the TFTs 121, the pixels. It is secured by the electrodes 151 and spacers arranged in the non-pixel region such as the peripheral frame portion.

In the example shown in FIG. 4, the liquid crystal layer 300 has a thickness of about 6 μm in the transmissive portion PT of the pixel region P. The reflective electrode 151R is provided on the reflective portion PR of the pixel region P.
And a bump 161 having a thickness of about 1 to 6 μm is disposed under the reflective electrode 151R. This bump 1
61 has a thickness of, for example, approximately ½ of the thickness HT of the liquid crystal layer 300 in the transmissive portion PT, and has a thickness of approximately 3 μm in this embodiment. Therefore, the reflection part P
The thickness HR of the liquid crystal layer 300 at R is approximately 1/2 of the thickness HT of the liquid crystal layer 300 at the transmissive portion PT (HT
≈2 × HR), about 3 μm.

That is, the counter substrate 200 has the liquid crystal layer 30.
While the surface facing 0 is substantially flat, the array substrate 100 has the bumps 161 protruding from the transmissive part PT in the reflective part PR, so that the liquid crystal layer 30 is provided.
The one-way optical path length of the light passing through 0 corresponds to twice the reflection portion PR in the transmission portion PT.

Therefore, at the transmissive portion PT, the backlight light emitted from the backlight unit 30 has a thickness HT.
The liquid crystal layer 300 is passed once. On the other hand, in the reflection part PR, the external light incident from the counter substrate 200 side passes through the liquid crystal layer 300 having the thickness HR, is then reflected by the reflective electrode 151R, and again passes through the liquid crystal layer 300 having the thickness HR. After passing, it is emitted from the counter substrate 200.

Therefore, the backlight light passing through the liquid crystal layer 300 of the transmissive part PT and the liquid crystal layer 300 of the reflective part PR.
The optical path lengths of the external light passing through are substantially equal. For this reason,
The phase difference given to the backlight light and the external light by the liquid crystal layer 300 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.

By the way, according to the liquid crystal display device having the above-described structure, the alignment film 141 on the array substrate 100 side and the alignment film 205 on the counter substrate 200 side each have a predetermined liquid crystal molecule in the transmissive portion PT and the reflective portion PR. It is formed so as to be oriented in the direction of. That is, the alignment films 141 and 205 have the alignment mode H of the liquid crystal molecules included in the liquid crystal layer 300 in the reflection portion PR in the one pixel region P.
AN (Hybrid Alignment Nemat)
ic) type, and in the transmissive part PT, the alignment mode of liquid crystal molecules is formed to be bend type.

The liquid crystal molecules aligned in the bend type alignment mode have alignment films 141 and 2 as shown in FIG.
05, the liquid crystal layer 300B is distributed so as to have mirror symmetry on the array substrate side and the counter substrate side about the center in the thickness direction. That is, in the central portion of the liquid crystal layer 300B, the liquid crystal molecules are aligned substantially perpendicular to the substrate. On the array substrate side of the liquid crystal layer 300B, liquid crystal molecules are aligned substantially parallel to the substrate. Further, on the counter substrate side of the liquid crystal layer 300B, the liquid crystal molecules are aligned substantially parallel to the substrate. However, the liquid crystal layer 300
The liquid crystal molecules on the array substrate side of B are oriented so as to be symmetrical with the liquid crystal molecules on the opposite substrate side.

Due to this feature, when the backlight light emitted from the backlight unit enters the liquid crystal layer 300B, the liquid crystal layer 300 does not depend on the incident angle of the backlight light.
The phase difference that B gives to the backlight light becomes substantially constant.

Further, as shown in FIG. 7B, the liquid crystal molecules aligned in the HAN type alignment mode have the bend type alignment mode in the liquid crystal layer 300 by the alignment films 141 and 205.
It is distributed so as to correspond to the case where the central portion of B is halved. That is, on the array substrate side of the liquid crystal layer 300H, the liquid crystal molecules are aligned substantially perpendicular to the substrate. On the opposite substrate side of the liquid crystal layer 300H, the liquid crystal molecules are aligned substantially parallel to the substrate.

From this feature, when the external light incident on the liquid crystal layer 300H is reflected by the reflective electrode and is passed through the liquid crystal layer 300 twice, it is substantially passed through the bend type alignment mode liquid crystal layer 300B described above. Is equivalent to Moreover,
HAN-type alignment mode liquid crystal layer 300 in the reflection part PR
The thickness of H is approximately ½ of the thickness of the bend type alignment mode liquid crystal layer 300B in the transmissive portion, and external light passes through the liquid crystal layer 300H in the reflective portion twice. Therefore, as in the case of the above-described backlight light, when the external light enters the liquid crystal layer 300H, regardless of the incident angle of the external light,
The phase difference given to the external light by the liquid crystal layer 300H becomes substantially constant.

That is, the liquid crystal layers 300B and 300H
Makes it possible to give a substantially constant phase difference to the backlight light passing through the transmissive portion PT and the external light passing through the reflective portion PR. Therefore, the transmissive part PT and the reflective part PR can match the gradation display, and can suppress the reduction of the contrast ratio and the gradation reversal depending on the observation direction, and a high-quality image in a wide visual field range. Can be displayed stably.

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 reflection part 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, the alignment film material is applied on the transparent electrode 151T and the reflective electrode 151R, and the rubbing treatment is selectively performed by the above-described method, whereby the alignment film 141 is formed.
To form. 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.

Subsequently, 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, a liquid crystal composition containing no 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. The injected liquid crystal composition constitutes the liquid crystal layer 300 sandwiched by the alignment film 141 on the array substrate 100 side and the alignment film 205 on the counter substrate 200 side, and in the transmissive part, the bend type alignment mode is set, and the reflective part is formed. In PR, it becomes a HAN type orientation mode.

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.

In the liquid crystal display device configured as described above, in the reflective portion PR, the liquid crystal layer 30 is provided from the counter substrate 200 side.
External light reflected on the counter substrate 200 side after entering 0 causes a phase difference of λ / 4 in one way. Reflective electrode 151R
The reflected light reflected by (2) causes a phase difference of λ / 2 in a reciprocating manner 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 is transmitted to the counter substrate 200 side has a phase difference of λ / 2 before being transmitted to the counter substrate 200 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 circularly polarizing 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, part of the external light incident from the counter substrate 200 side passes through the circularly polarizing plate 211,
The glass substrate 2 on the counter substrate 200 side is converted into left circularly polarized light.
The light enters from 01 to the liquid crystal layer 300. This left circularly polarized light is H
By passing through the liquid crystal layer 300 of the AN type alignment mode, a phase delay of λ / 4 is generated, reflected by the reflective electrode 151R, and passed through the liquid crystal layer 300 again,
Further, a phase delay of λ / 4 is generated. This causes a total phase delay of λ / 2.

The reflected light reflected and given the phase difference of λ / 4 is converted into right circularly polarized light and passes through the glass substrate 201 on the counter substrate 200 side. This right circularly polarized light is the circularly polarizing plate 21.
By passing through the retardation plate included in No. 1, it is converted into linearly polarized light. The polarization direction of this linearly polarized light is 2
11 is parallel to the polarization direction of the deflector. 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 included in the circular polarization 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. This left-handed circularly polarized light passes through the liquid crystal layer 300 in a state where the liquid crystal molecules are raised up and down once, and thereby the liquid crystal layer 3
Counter substrate 200 without being subjected to phase modulation by 00
It passes through the glass substrate 201 on the side. 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 transmission part 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.

In other words, 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 causes a phase delay of λ / 2 by passing through the liquid crystal layer 300 of bend type alignment mode.

Λ / 2 is transmitted toward the counter substrate 200 side.
The backlight light having the phase difference of 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 part PT operates as follows.

That is, similarly to when the voltage is turned off, a part of the backlight light incident from the array substrate 100 side is converted into left circular polarized light by passing through the circular polarizing 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 liquid crystal display device according to this embodiment is provided with the reflection part PR and the transmission part PT in one pixel region P, and in the bright place, the reflection part PR selectively selects outside light. The backlight unit 400 functions as a reflection type liquid crystal display device that reflects an image to display an image in a dark place.
By functioning as a transmissive liquid crystal display device that selectively transmits the backlight light emitted from the device to display an image, power consumption is higher than that when a backlight unit is always driven as a transmissive liquid crystal display device. Can be significantly reduced.

Further, in this semi-transmissive liquid crystal display device, the liquid crystal layer 300 is set to the HAN type alignment mode in the reflection part PR, and the liquid crystal layer 300 is set to the bend type alignment mode in the transmission part PT. This makes it possible to stably display a high-quality image in reflective display and transmissive display regardless of the viewing direction.

The present invention is not limited to the above-mentioned embodiment, but can be variously modified.

[0091]

As described above, according to the present invention, in reflective display and transmissive display, a liquid crystal display device capable of stably displaying a high-quality image regardless of the viewing direction is provided. can do.

[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 (a) is a diagram for explaining a bend type alignment mode, and FIG. 7 (b) is a diagram for explaining a HAN type alignment mode.

[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 P ... Pixel area PR ... Reflector PT ... Transparent part

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H042 DA02 DA04 DA07 DA12 DA22                       DE00                 2H088 GA02 HA02 HA03 HA04 HA08                       HA12 HA21 HA23 JA03 KA14                       LA02 LA04 MA04 MA07                 2H090 HA15 HC05 HC16 HD11 JA02                       JB02 KA03 LA10 LA11 LA15                       LA16 LA20 MA03 MA11 MA15                       MA17 MB01 MB12                 2H091 FA14Z FA21Z FA23Z FA32Z                       FA41Z FD11 GA06 HA05                       KA05 LA19                 2H092 HA04 HA05 JA24 JB56 KB04                       KB23 KB25 NA01 PA02 PA12                       PA13 QA05

Claims (7)

[Claims] 1. A liquid crystal display device comprising a liquid crystal display panel in which a liquid crystal layer is sandwiched between a first substrate and a second substrate, and a backlight unit for illuminating the liquid crystal display panel from the back side. The area is a reflection portion that reflects external light to display,
A transmissive part that transmits the backlight emitted from the backlight unit to perform display, and in the reflective part, an alignment mode of liquid crystal molecules included in the liquid crystal layer is a HAN type, and the transmissive part 2. The liquid crystal display device according to, wherein the alignment mode of liquid crystal molecules included in the liquid crystal layer is bend type. 2. The first substrate arranged on the side of the backlight unit, in the vicinity of the substrate, aligns liquid crystal molecules in the reflecting portion substantially perpendicularly to the substrate in a state where no voltage is applied, and The liquid crystal display device according to claim 1, further comprising an alignment film that aligns liquid crystal molecules in the transmissive portion substantially parallel to the substrate. 3. The alignment film of the first substrate has a tilt angle of liquid crystal molecules of 70 ° to 90 ° in the reflecting portion and a tilt angle of liquid crystal molecules of 1 in the transmitting portion.
The liquid crystal display device according to claim 2, wherein the liquid crystal display device has an angle of 50 to 50 degrees. 4. The second substrate, in the vicinity of the substrate,
The liquid crystal display device according to claim 1, further comprising an alignment film that aligns liquid crystal molecules in the reflective portion and the transmissive portion substantially parallel to a substrate in a state where no voltage is applied. 5. The optical path length of external light passing through the liquid crystal layer in the reflecting portion is substantially equal to the optical path length of backlight light passing through the liquid crystal layer in the transmitting portion. 1. The liquid crystal display device according to 1. 6. The thickness of the liquid crystal layer in the reflective portion is
The liquid crystal display device according to claim 1, wherein the thickness of the liquid crystal layer in the transmissive portion is approximately ½. 7. The liquid crystal display device according to claim 1, wherein the reflecting portion includes a bump having a thickness that is approximately ½ of a thickness of the liquid crystal layer in the transmitting portion.