JP2001154181A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission and reflection type liquid crystal display device with improved display brightness in a transmission mode. SOLUTION: The liquid crystal display device can display both in a transmission mode and in a reflection mode, and is equipped with a liquid crystal display panel 100 having a liquid crystal layer 23 provided between a first substrate 10 and a second substrate 11, and an illumination device 50 disposed in the first substrate 10 side of the liquid crystal display panel. The liquid crystal display panel 100 has a reflection region to reflect the incident light from the liquid crystal layer 23 side and a transmission region to transmit the incident light from the illumination device 50 side in each pixel region. A collimating element 52 and a light-condensing element 54 are further disposed in this order from the illumination device 50 side between the liquid crystal layer 23 side of the first substrate 10 and the illuminating device 50. The spread angle of the diffused light emitted from the illumination device 50 is decreased by the collimating element 52, and the diffused light with a decreased spread angle is condensed to the transmission region of the liquid crystal panel by the condensing element 54.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art In recent years, liquid crystal display devices have been characterized by their thinness and low power consumption, and have been used in OA devices such as word processors and personal computers, portable information devices such as electronic notebooks, and camera-type devices equipped with a liquid crystal monitor. Widely used for VTRs and the like.

[0002] These liquid crystal display devices are roughly classified into a reflection type and a transmission type. Liquid crystal display devices include CRTs (CRTs) and
Rather than self-luminous display devices such as EL (electroluminescence), the transmissive type displays using the light of a lighting device (so-called backlight) placed behind the liquid crystal display panel, and the reflective type displays the surroundings. Display is performed using light.

A transmissive liquid crystal display device performs display using light from a backlight, and thus has the advantage that it is less affected by ambient brightness and can display a bright image with a high contrast ratio. However, there is a problem that power consumption is large because of the backlight. Approx. 50% of power consumption of normal transmissive liquid crystal display
The above is consumed by the backlight. Also, in a very bright use environment (for example, outdoors in fine weather), there is a problem that the visibility is reduced.

On the other hand, a reflection type liquid crystal display device does not have a backlight, and thus has an advantage that power consumption is extremely small. However, display brightness and contrast ratio are large depending on the use environment such as ambient brightness. It has the problem of being influenced. In particular, there is a disadvantage that visibility is extremely reduced in a dark use environment.

Therefore, as a liquid crystal display device which can solve such a problem, a liquid crystal display device having a function of displaying in both a reflection type and a transmission type mode is disclosed in, for example, Japanese Patent Application Laid-Open No.
No. 109417.

This transflective liquid crystal display device has, in one picture element area, a reflection picture element electrode for reflecting ambient light and a transmission picture element electrode for transmitting light from a backlight. In addition, switching between display in the transmission mode and display in the reflection mode, or display in both display modes, can be performed according to the use environment (brightness of the surroundings).
Therefore, the transflective liquid crystal display device is characterized by the low power consumption characteristic of the reflective liquid crystal display device and the display of a bright and high contrast ratio which is less affected by the ambient brightness of the transmissive liquid crystal display device. Can be performed. Further, the disadvantage of the transmissive liquid crystal display device that visibility is reduced in a very bright use environment (for example, outdoors in fine weather) is also suppressed.

[0007]

In the above-mentioned transflective liquid crystal display device, since the reflection area is formed in the picture element area, the amount of light from the backlight passing through the transmission area is reduced. There is a problem that the display brightness in the mode is lower than that of the conventional transmissive liquid crystal display device. On the other hand, when the area of the reflection region is reduced, the display luminance in the reflection mode is reduced. Therefore, in order to increase the amount of light from the backlight passing through the transmissive area while securing the area of the reflective area, a transflective liquid crystal display in which a microlens sheet is arranged between the liquid crystal display panel and the backlight. An apparatus is disclosed in Japanese Patent Application Laid-Open No. H11-109417. In this dual-purpose liquid crystal display device, the individual microlenses included in the microlens sheet are:
It is provided corresponding to the picture element region of the liquid crystal display panel, and is arranged so as to collect light from the backlight in the transmission region.

However, even in the dual-purpose liquid crystal display device provided with the microlens sheet disclosed in the above publication, the display luminance in the transmission mode may not be sufficiently improved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a transflective liquid crystal display device having improved display luminance in a transmissive mode.

[0010]

A liquid crystal display device according to the present invention comprises: a liquid crystal display panel having first and second substrates; and a liquid crystal layer provided between the first and second substrates.
An illumination device provided on the first substrate side of the liquid crystal display panel, wherein the liquid crystal display panel has a plurality of picture element regions, and the first substrate corresponds to each of the plurality of picture element regions. A liquid crystal display device having a reflection region for reflecting light incident from the liquid crystal layer side and a transmission region for transmitting light incident from the illumination device side, and capable of displaying in a transmission mode and a reflection mode. And further comprising a collimating element and a condensing element in order from the lighting device side between the liquid crystal layer side surface of the first substrate and the lighting device, wherein the collimating element emits light from the lighting device. And the condensing element has a configuration in which the condensing element condenses the diffused light having the narrowed spread angle in the transmission region, whereby the object is achieved. .

The light-collecting element may be a microlens array including microlenses provided for each of the plurality of picture element regions, or may be a prism sheet.

It is preferable that the reflection region has a function of diffusing and reflecting light incident from the lighting device side.

Another liquid crystal display device according to the present invention is a liquid crystal display panel having first and second substrates, a liquid crystal layer provided between the first substrate and the second substrate, and the liquid crystal display panel. And a lighting device provided on the first substrate side, wherein the liquid crystal display panel has a plurality of picture element regions, and the first substrate is formed corresponding to each of the plurality of picture element regions. A liquid crystal display device having a reflection region for reflecting light incident from the liquid crystal layer side and a transmission region for transmitting light incident from the illumination device side, and capable of displaying in a transmission mode and a reflection mode, The reflection area has a configuration having a function of diffusing and reflecting light incident from the lighting device side, thereby achieving the above object.

The operation of the present invention will be described below.

The present invention relates to the above-mentioned JP-A-11-109417.
In the transmission / reflection type liquid crystal display device provided with the microlens sheet disclosed in Japanese Patent Laid-Open Publication No. H10-115, the present invention has been made based on the following findings obtained by elucidating the cause of insufficient improvement in display luminance in the transmission mode.

Since the light emitted from the illumination device (backlight) used in the liquid crystal display device is diffused light, it is substantially parallel to the optical axis of the microlens in the conventional transmission / reflection type liquid crystal display device. The amount of light incident on is small. Therefore, the amount of light condensed on the transmission region by the microlens is small, and as a result, the effect of improving the display brightness in the transmission mode is small.

Therefore, in the liquid crystal display device of the present invention, a collimating element for reducing the spread angle of the diffused light emitted from the illuminating device, that is, a light beam close to a parallel light is provided, and the microlens is arranged with respect to its optical axis. To increase the amount of light incident parallel. Therefore, the amount of light condensed on the transmission region by the microlens increases, and as a result, the display brightness in the transmission mode is improved.

The reflection region of another liquid crystal display device of the present invention diffusely reflects light incident from the lighting device side. Part of the light diffusely reflected by the reflection region passes through the transmission region and can contribute to display in the transmission mode. As a result, display luminance in the transmission mode is improved.

Of course, by imparting a function of diffusing and reflecting light incident from the illumination device side to the reflection region of the transflective liquid crystal display device having the light-collecting element or the collimating element and the light-collecting element. By increasing the amount of light passing through the transmission region, the display brightness in the transmission mode can be further improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. First, the structure and function of a transflective liquid crystal display panel and a lighting device used in the transflective liquid crystal display device of the present invention will be described.

(Transmissive / Reflective Liquid Crystal Display Panel) The T of the liquid crystal display panel used in the transmissive / reflective liquid crystal display device according to the present invention (hereinafter, referred to as “dual-use liquid crystal display device”).
FIG. 1 is a plan view of the FT substrate 100A, and FIG.
FIG. 2 is a partial cross-sectional view of the liquid crystal display panel 100 having A. FIG. 2 corresponds to a cross-sectional view taken along line II-II ′ of FIG.

In the drawings, components having substantially the same function are denoted by the same reference numerals for simplicity.

As shown in FIG. 1, the TFT substrate 100A
Is a thin film transistor (TF) on a glass substrate 10.
T) 5, and a plurality of scanning lines (gate bus lines) 1 and signal lines (source bus lines) 2. A transparent electrode 1 made of, for example, ITO (indium tin oxide) is provided in a region surrounded by each scanning line 1 and each signal line 2.
3 and a reflective electrode 15 made of, for example, Al. The transparent electrode 13 and the reflective electrode 15 constitute a picture element electrode 4. Each of the plurality of picture element regions arranged in a matrix of the liquid crystal display panel 100 is defined by the picture element electrodes 4. Further, the transparent electrode 13 is
The reflection region 15 defines the transmission region on the TFT substrate 100A, and the reflection electrode 15 defines the reflection region on the TFT substrate 100A. The TFT 5 is arranged near a region where the scanning line 1 and the signal line 2 intersect. The scanning line 1 is connected to the gate electrode 6 and the signal line 2 is connected to the source electrode 7.

Referring to FIG. 2, the liquid crystal display panel 10
The structure of the picture element region of 0 will be described.

The liquid crystal display panel 100 includes a TFT substrate 10
0A, a color filter substrate (counter substrate) 100B, and a liquid crystal layer 23 provided between the substrates 100A and 100B.
4 wavelength plates 19 and 21 and a pair of polarizing plates 20 and 2
2 are arranged. The polarizing plates 20 and 22 are arranged in a parallel Nicol state. As the liquid crystal layer 23, a liquid crystal layer in which a liquid crystal material having a positive dielectric anisotropy is parallel-aligned when no voltage is applied is used. Note that an alignment film (not shown) is formed on the surface of the TFT substrate 100A and the color filter substrate 100B on the liquid crystal layer 23 side as necessary.

On the glass substrate 10 of the TFT substrate 100A, a gate insulating film 12 covering the scanning lines 1 (see FIG. 1) and the gate electrode 6 is formed. Semiconductor layer 5a is formed on gate insulating film 12 located on gate electrode 6, and semiconductor layer 5a is connected to source electrode 7 and drain electrode 8 via semiconductor contact layers 7a and 8a, respectively. Is formed. The drain electrode 8 of the TFT 5 is electrically connected to the transparent electrode 13,
Further, the contact hole 9 formed in the resin layer 14 is electrically connected to the reflection electrode 15. The transparent electrode 13 is formed on the gate insulating film 12 near the center of a region surrounded by the scanning lines 1 and the signal lines 2.

On the glass substrate 10, a resin layer 14 having an opening 14a exposing the transparent electrode 13 is formed so as to cover almost the entire surface of the glass substrate 10. Opening 1
The reflection electrode 15 is formed on the resin layer 14 around 4a. The surface of the resin layer 14 on which the reflective electrode 15 is formed has a continuous wavy uneven shape, the reflective electrode 15 has a shape along this surface shape, and the reflective electrode 15 has an appropriate diffuse reflection characteristic. Have. The resin layer 14 having a continuous wavy uneven surface can be formed using, for example, a photosensitive resin (OFPR-800 manufactured by Tokyo Ohka Co., Ltd.).

A color filter layer 16 and a black matrix 17 are formed on the glass substrate 11 of the color filter substrate 100B, and a counter electrode (transparent electrode) 18 is formed on the surface on the liquid crystal layer 23 side. Counter electrode 18
Is formed using, for example, ITO.

The liquid crystal display panel used in the transmission / reflection type liquid crystal display device according to the present invention is not limited to the above-mentioned example, and a known transmission / reflection type liquid crystal display panel can be widely used. However, a liquid crystal display panel having a structure in which the transmission region is formed near the center of the picture element region and the reflection region is formed around the transmission region is preferable. By adopting a structure in which the reflection area is arranged in the peripheral part of the picture element area, it is possible to make a configuration in which a scanning line or a signal line partially overlaps with the reflection area, and the area of the reflection area can be made relatively large. it can. Further, by arranging the transmission area near the center of the picture element area, light can be more efficiently condensed on the transmission area using a collimating element and a condensing element described later.

The display principle of the transflective liquid crystal display device 100 will be briefly described with reference to FIG.

(Reflection Mode) Light (ambient light) incident on the liquid crystal display panel 100 from the display surface (upper side in FIG. 2) is
By passing through the polarizing plate 22, the light is converted into linearly polarized light having a polarization direction parallel to the polarizing axis (transmission axis) of the polarizing plate 22. This linearly polarized light has a polarization axis of the polarizing plate 22 and a slow axis of four.
The light enters the quarter-wave plate 21 arranged at an angle of 5 degrees and becomes circularly polarized light after passing through the quarter-wave plate 21.
When a voltage is applied to the liquid crystal layer 23 between the reflective electrode 15 and the counter electrode 18, the liquid crystal molecules exhibiting positive dielectric anisotropy are oriented in a direction substantially perpendicular to the substrate surface. The liquid crystal layer 23 in such an alignment state has a very small refractive index anisotropy with respect to a light beam incident from the normal direction of the substrate, and the phase difference caused by the light beam passing through the liquid crystal layer 23 is almost zero. is there. Therefore, the circularly polarized light that has entered the liquid crystal layer 23 passes through the liquid crystal layer 23 as it is and is reflected by the reflective electrode 15. The reflected circularly polarized light passes through the liquid crystal layer 23 again while maintaining the circularly polarized light, and enters the quarter-wave plate 21 again. Circularly polarized light becomes linearly polarized light by passing through the quarter-wave plate 21. Since the polarization direction of this linearly polarized light is orthogonal to the polarization axis direction of the polarizing plate 22, it is absorbed by the polarizing plate 22, and the reflected light is It does not pass through the polarizing plate 22. Therefore, when a voltage is applied to the liquid crystal layer 23 between the reflective electrode 15 and the counter electrode 18, black display is performed.

Conversely, when no voltage is applied to the liquid crystal layer 23 between the reflection electrode 15 and the counter electrode 18, the liquid crystal layer 2
The liquid crystal molecules of No. 3 remain aligned in the direction horizontal to the substrate surface. Therefore, the circularly polarized light that has entered the liquid crystal layer 23 becomes elliptically polarized light due to the birefringence of the liquid crystal layer 23 and is reflected by the reflective electrode 15. The reflected elliptically polarized light becomes elliptically polarized light whose polarization axis direction is further changed while passing through the liquid crystal layer 23 again, and even after passing through the quarter-wave plate 21, the polarization direction orthogonal to the polarization axis of the polarizing plate 22. And linearly polarized light having Therefore, the elliptically polarized light (partly) transmits through the polarizing plate 22. Here, the phase difference of the liquid crystal layer 23 (thickness dr) is /.
If the gap dr between the reflective electrode 15 and the counter electrode 18 is adjusted so as to satisfy the wavelength condition, the total phase difference of the quarter-wave plate 21 and the liquid crystal layer 23 (each time the phase difference is twice) Since the phase difference with respect to the passing light) is one wavelength condition (an integer multiple of the wavelength), when the light reaches the polarizing plate 22,
The polarization direction of the linearly polarized light is parallel to the polarization axis of the polarizing plate 22. Therefore, when the liquid crystal layer 23 satisfies this condition, the amount of light transmitted through the polarizing plate 22 becomes maximum. That is, the display luminance in the white display state is maximized.

Also, by controlling the magnitude of the voltage applied between the reflective electrode 15 and the counter electrode 18 and changing the (apparent) birefringence of the liquid crystal layer 23,
Since the amount of light reflected by the light passing through the polarizing plate 22 is adjusted, gradation display is possible.

(Transmission Mode) Light emitted from an illuminating device (not shown) provided on the back surface (the lower part in FIG. 2) of the liquid crystal display panel 100 passes through the polarizing plate 20, and The light is linearly polarized light having a polarization direction parallel to the polarization axis (transmission axis). This linearly polarized light is
1 / arranged so that the polarization axis and slow axis of
After entering the four-wavelength plate 19 and passing through the quarter-wavelength plate 19, the light becomes circularly polarized light. When a voltage is applied to the liquid crystal layer 23 between the transparent electrode 13 and the counter electrode 18, the liquid crystal molecules exhibiting positive dielectric anisotropy are oriented in a direction substantially perpendicular to the substrate surface. The liquid crystal layer 23 in such an alignment state has a very small refractive index anisotropy with respect to a light beam incident from the normal direction of the substrate, and the phase difference caused by the light beam passing through the liquid crystal layer 23 is almost zero. is there. Therefore, the liquid crystal layer 23
The circularly polarized light incident on the liquid crystal layer 23 passes through the liquid crystal layer 23 as it is, and is incident on the quarter-wave plate 21. The circularly polarized light incident on the quarter-wave plate 21 becomes linearly polarized light having a polarization direction orthogonal to the polarization axis of the polarizing plate 22, is absorbed by the polarizing plate 22, and does not pass through the polarizing plate 22. Therefore, when a voltage is applied to the liquid crystal layer 23 between the transparent electrode 13 and the counter electrode 18, black display is performed.

Conversely, when no voltage is applied to the liquid crystal layer 23 between the transparent electrode 13 and the counter electrode 18, the liquid crystal layer 2
The liquid crystal molecules of No. 3 remain aligned in the direction horizontal to the substrate surface. Accordingly, the circularly polarized light incident on the liquid crystal layer 23 becomes elliptically polarized light due to the birefringence of the liquid crystal layer 23, and becomes a quarter-wave plate 21.
, The light does not follow linearly polarized light having a polarization direction orthogonal to the polarization axis of the polarizing plate 22. Therefore, the elliptically polarized light (partly) transmits through the polarizing plate 22. Here, the liquid crystal layer 2
The gap dt between the transparent electrode 13 and the counter electrode 18 is set so that the phase difference of 3 (thickness dt) becomes a half wavelength condition.
Is adjusted, the total phase difference of the quarter-wave plate 21 and the liquid crystal layer 23 is one wavelength condition (an integer multiple of the wavelength).
Therefore, when the light reaches the polarizing plate 22, the polarization direction of the linearly polarized light becomes parallel to the polarization axis of the polarizing plate 22. Therefore,
When the liquid crystal layer 23 satisfies this condition, the amount of light transmitted through the polarizing plate 22 becomes maximum. That is, the display luminance in the white display state is maximized.

Further, by controlling the magnitude of the voltage applied between the transparent electrode 13 and the counter electrode 18 and changing the (apparent) birefringence of the liquid crystal layer 23, the amount of light passing through the polarizing plate 22 is controlled. Is adjusted, so that gradation display is possible.

As described above, when the liquid crystal material has a positive dielectric anisotropy, a so-called normally white mode display, in which white (bright) is displayed when no voltage is applied and black (dark) is displayed when a voltage is applied. Is performed. Of course, the liquid crystal display panel used in the dual-purpose liquid crystal display device of the present invention is not limited to the above example, and the arrangement of the polarizing plate and the phase difference plate (1/4 wavelength plate) can be changed. A liquid crystal display panel of another known liquid crystal mode such as a normally black mode using a liquid crystal material having a negative dielectric anisotropy and a vertical alignment film in a configuration, or a mode not using a polarizing plate such as a guest host mode. Can be used.

(Illumination Device) An example of an illumination device (backlight device) used in the dual-purpose liquid crystal display device according to the present invention is schematically shown in FIGS.

The lighting device shown in FIG. 3 is a direct type backlight device 30. The backlight device 30 includes a diffusion plate 32 and a fluorescent tube 34 and a reflection plate 36 on the back surface of the diffusion plate 32.

The light emitted from the fluorescent tube 34 is directly
Alternatively, the light is reflected by a reflection plate 36 provided on the back surface of the fluorescent tube 34 and enters the diffusion plate 32. The light transmitted through the diffusion plate 32 becomes substantially uniform diffused light having omnidirectional components,
The light is emitted from the upper surface 32s of the diffusion plate 32. The backlight device 30 is arranged such that the upper surface 32s of the diffusion plate 32 is close to the rear surface of the TFT substrate 100A of the liquid crystal display panel.

The lighting device shown in FIG. 4 is an edge light type backlight device 40. Backlight device 4
0 denotes a diffusion plate 42 and a fluorescent tube 4 on the back of the diffusion plate 42.
4, a reflection plate 46 and a light guide plate 48 are provided.

The fluorescent tube 44 is arranged near the side surface 48t of the light guide plate 48 made of a highly transparent material such as an acrylic resin, and surrounds the back surface of the light guide plate 48 and the fluorescent tube 44. Reflection plate 46 is provided as described above.
The light emitted from the fluorescent tube 44 is directly or reflected by the reflection plate 46, and all enters the light guide plate 48. The light incident on the light guide plate 48 is repeatedly reflected on the upper surface 48 s and the lower surface (the side of the reflection plate 46) of the light guide plate 48, and the incident angle on the upper surface 48 s of the light guide plate 48 is smaller than the critical angle of total reflection. At this time, the light exits from the upper surface 48 s of the light guide plate 48 and enters the diffusion plate 42. The light transmitted through the diffuser 42 becomes substantially uniform diffused light having omnidirectional components.
Is emitted from the upper surface 42s. Backlight device 40
Is that the upper surface 42s of the diffusion plate 42 is a TFT of a liquid crystal display panel.
It is arranged so as to be close to the back surface of the substrate 100A.

(Embodiment 1) FIG. 5A is a schematic sectional view of a dual-use liquid crystal display device 200 according to Embodiment 1 of the present invention.

The dual-purpose liquid crystal display device 200 shown in FIG. 5A
Is a dual-purpose liquid crystal display panel 10 shown in FIGS.
0 and the back of the liquid crystal display panel 100 (TFT substrate 100
A) and the liquid crystal display panel 1
00 and the lighting device 50 in order from the lighting device 50 side,
It has a collimating element 52 and a light collecting element 54. As the illumination device 50, a known backlight device that emits diffused light, such as the backlight device 30 or 40 described above, can be preferably used.

The collimating element 52 collimates the light (arrow in the figure) emitted from the upper surface of the backlight device 50 in a direction parallel to the normal to the substrate surface of the liquid crystal display panel 100.

As the collimating element 52, for example, FIG.
As shown in B (a), an element in which two BEFII 90/50 films (manufactured by 3M) 52a are orthogonally arranged can be used. BEFII 90/50 film 52a
As shown in FIG. 5B (b), has a polyester film layer 52b and an acrylic resin layer 52c formed on the polyester film layer 52b and having a triangular wave-shaped convex portion on the surface. By arranging the ridges of the triangular wave-shaped projections so that the directions in which the ridges extend are orthogonal to each other, the spread angle of the diffused light incident from the back surface (the polyester film layer side) of the BEFII 90/50 film 52a (the substrate surface normal to the liquid crystal panel). Can be narrowed, ie, collimated.
For example, as shown in FIG. 5C, the diffused light emitted from the backlight 50 has a substantially uniform intensity over an angle range of ± 60 ° (broken line in FIG. 5C).
By arranging the collimating element 52 in which the BEFII 90/50 films 52a are orthogonally arranged, ± 2
It is possible to increase the intensity of the diffused light within the angle range of 5 °, particularly within the angle range of ± 10 ° (solid line in FIG. 5C).

As the light-collecting element 54, a microlens array 54 having a plurality of microlenses 54a arranged so as to correspond to the respective picture element regions of the liquid crystal display panel 100 is used here. The cross section of the microlens array 54 has substantially the same shape in a direction orthogonal to the direction shown in FIG. 5A. Each micro lens 54a is arranged so as to have an optical axis in a direction parallel to the substrate normal of the liquid crystal display panel 100.

The micro lens array 54 can be formed by a known method. For example, (1) a method of press-molding a synthetic resin, and (2) a photosensitive resin layer is patterned into a flat plate shape corresponding to a microlens using a photolithography process, and then the flat resin layer is heated to a softening point or higher. A method of forming by heating and thermally sagging the edge of the flat resin layer; (3) forming a refractive index distribution by ion diffusion on a glass substrate;
A method of forming a refractive index distribution type micro lens, (4) a method of sandwiching a polymerizable liquid crystal material between a pair of circular electrodes, and polymerizing and curing the liquid crystal material while applying a voltage, and the like. be able to. Micro lens array 5
The liquid crystal panel 4 and the liquid crystal panel 100 can be bonded to each other using, for example, an ultraviolet curable resin having high transparency and a refractive index close to the refractive index of the substrate of the liquid crystal panel 100.

The light emitted from the backlight device 50
The spread angle of the diffused light having substantially uniform intensity components in all directions is narrowed by the collimating element 52. That is, the component of the diffused light parallel to the direction normal to the substrate of the liquid crystal display panel 100 increases (in some cases, "directivity in the direction normal to the substrate is improved"). Since the microlens 54a of the microlens array 554 has an optical axis in a direction parallel to the substrate normal, light rays incident parallel to the substrate normal are converged at the focal point.

When the angular range (± 90 °) of the diffused light emitted from the backlight device 50 is narrowed to ± 10 ° by the collimating element 52 (that is, the angular range of the ray incident on the microlens 54a ±±). θ = ± 10 °
), The thickness D of the substrate 10 is 0.5 mm,
When the refractive index is 1.52, the spot diameter S of the light beam on the transparent electrode 13 is approximately 60 μm from the following equation. Note that the focal point of the microlens is set so as to be located in the transmission area.

S = (2D / n) tan θ = (0.5 / 1.52) tan10 ° ８0.058 mm The width of the transparent electrode 13 of the dual-purpose liquid crystal display device 200 according to the present embodiment (for the scanning line or the signal line) (Parallel direction) is 50μ
When the above configuration is adopted, most of the light emitted from the backlight device 50 can be focused on the transparent electrode (transmission region) 13.
Therefore, light that should be shielded by the region other than the transparent electrode 13 and the black matrix 17 can be focused on the transparent electrode 13 and the color filter 16, so that the efficiency of use of light from the backlight device is improved and the contrast ratio is improved. Is done.

When the area of the reflective electrode 15 in the picture element region is increased, the area of the transparent electrode 13 is inevitably reduced and the transmittance (display luminance in the transmission mode) is reduced. Since the spot diameter S can be further reduced by reducing the area, the area of the reflective electrode 15 can be increased without lowering the transmittance, and the reflectance (display luminance in the reflection mode) can be improved. Therefore, the balance between the display brightness in the transmission mode and the display brightness in the reflection mode can be optimized over a wider range than before, as required, for example, in the application of the liquid crystal display device.

In the above example, the microlens array 54 is disposed between the collimating element 52 and the polarizing plate 20. However, the microlens array 54 may be provided on the collimating element 52 side with respect to the transparent electrode 13; Between the plate 19, the quarter-wave plate 19 and the glass substrate 10, or the glass substrate 1
Alternatively, a microlens array may be directly built in the zero.

FIG. 6 is a schematic sectional view of another dual-purpose liquid crystal display device 300 according to the present embodiment. The dual-purpose liquid crystal display device 300 is different from the dual-purpose liquid crystal display device 200 shown in FIG. 5A in that the dual-purpose liquid crystal display device 300 has a dual-purpose liquid crystal display panel 300 ′ in the guest-host mode.

The liquid crystal layer 2 of the dual-purpose liquid crystal display panel 300 '
Reference numeral 3 denotes a guest-host liquid crystal layer containing a liquid crystal material exhibiting a positive dielectric anisotropy and a dichroic dye, and being aligned in parallel when no voltage is applied. Liquid crystal display panel 3 using guest host liquid crystal layer
00 'does not require a quarter wave plate (19 and 21 in Fig. 5A).

The dual-purpose liquid crystal display device 300 also has a lighting device 5 between the liquid crystal display panel 300 ′ and the lighting device 50.
The collimating element 52 and the condensing element 54 are arranged in this order from the 0 side.
, The dual-purpose liquid crystal display device 20 described above.
Similarly to the case of 0, the use efficiency of light from the lighting device 50 is high.

(Embodiment 2) FIG. 7 is a schematic sectional view of a dual-purpose liquid crystal display device 400 according to Embodiment 2 of the present invention.

The dual-purpose liquid crystal display device 400 shown in FIG.
Is a dual-purpose liquid crystal display panel 10 shown in FIGS.
0 and the back of the liquid crystal display panel 100 (TFT substrate 100
A) and the liquid crystal display panel 1
00 and the lighting device 50 in order from the lighting device 50 side,
It has a collimating element 52 and a condensing element 74. The dual-purpose liquid crystal display device 400 differs from the dual-purpose liquid crystal display device 200 of Embodiment 1 shown in FIG. 5A in that a prism sheet 74 is used instead of the light-collecting element (microlens array) 54.

The condensing element 74 is a prism sheet 74 formed in a mountain-cut shape, and is integrally formed with a plurality of triangular prisms 74a extending in the extending direction of the signal line. In addition, a plurality of triangular prisms 74a
Are arranged so as to correspond one-to-one with the picture element regions along the scanning line direction. FIG. 7 corresponds to a cross-sectional view along the scanning line direction.

The prism sheet 74 is arranged such that the ridge of the triangular prism 74a is located on the liquid crystal display panel 100 side. The diffused light emitted from the illumination device 50 and narrowed by the collimating element 52 enters from the bottom side of the triangular prism 74a and exits from the side surface (upper surface) of the triangular prism 74a. At this time, the light beam is refracted in the direction of the ridge, and is converged toward the center of the width of the picture element region along the scanning line direction. As described above, the triangular prism 74a functions to condense the diffused light incident from the bottom in a linear shape parallel to the ridge of the triangular prism 74a (that is, in this case, parallel to the signal line direction). Since the ridge of the triangular prism 74a is disposed so as to correspond to the center of the transparent electrode 13, the amount of light passing through the transparent electrode 13 increases. Therefore, even if a prism sheet is used as the light condensing element, the utilization efficiency of light from the backlight device is improved, and the contrast ratio is improved. The light-collecting power (angle of refraction) of the triangular prism 74a can be adjusted by controlling the apex angle α of the triangular prism 74a.

The positional relationship between the prism sheet 74 and the liquid crystal panel 100 will be described with reference to FIG. FIG. 8 is a schematic perspective view showing an arrangement relationship between the TFT substrate 100A of the liquid crystal display panel 100 and the prism sheet 74.

As shown in FIG. 8, the prism sheet 74
Each of the plurality of triangular prisms 74a is a picture element electrode composed of a transparent electrode 13 and a reflective electrode 15 in a direction parallel to the signal line extension direction (y direction) and in a scanning line extension direction (x direction). 4 are arranged. Of course, the relationship between the x direction and the y direction may be reversed. When this prism sheet 74 is used, the alignment between the liquid crystal display panel 100 and the prism sheet 74 becomes x
The alignment may be performed with high accuracy only in one of the directions (the x direction in the illustrated example). Therefore,
Compared with a microlens array in which microlenses corresponding to the respective pixel electrodes 4 are two-dimensionally arranged (for example, see FIG. 5A), an advantage that alignment is relatively simple is obtained. Further, even if a lenticular lens (not shown) is used instead of the prism sheet 74, the effect of improving the use efficiency of light from the illumination device and the effect of simplifying the alignment can be obtained. The prism sheet 74 and the lenticular lens in place of the prism sheet 74 can be manufactured by a known method using a transparent substance such as glass or a transparent synthetic resin. For example, it can be manufactured by a method of pressing between molds having an uneven surface, a method of extruding while forming with an embossing roll, and a method of machining the surface.

FIG. 9 is a schematic sectional view of another dual-purpose liquid crystal display device 500 according to the present embodiment. The dual-use liquid crystal display device 500 differs from the guest-host mode dual-use liquid crystal display device 300 shown in FIG. 6 in that a prism sheet 74 is provided instead of the light-collecting element 54.

The dual-purpose liquid crystal display device 500 also has a lighting device 5 between the liquid crystal display panel 300 ′ and the lighting device 50.
Since the collimating element 52 and the prism sheet 74 are provided in order from the 0 side, the use efficiency of the light from the lighting device 50 is high as in the above-described dual-purpose liquid crystal display device 400.

(Embodiment 3) FIG. 10 is a schematic sectional view of a dual-use liquid crystal display device 600 according to Embodiment 3 of the present invention. FIG. 10 is an enlarged view of one picture element area.
Particularly, the reflection area is shown in an enlarged manner.

The dual-purpose liquid crystal display device 600 shown in FIG.
The liquid crystal display panel 600 ′ of the TFT substrate 600
A diffusion layer 85 having a function of diffusing and reflecting (or scattering) light from the backlight device 50 is formed in the reflection region A. The diffusion layer 85 has a surface 85s with a fine unevenness.
To diffusely reflect (or scatter) the light from the backlight device 50. LCD panel 60
Other configurations of 0 'are substantially the same as those of the liquid crystal display panel 100 shown in FIGS. For comparison, the liquid crystal display device 70 having the liquid crystal display panel 100
FIG. 11 shows a partially enlarged cross-sectional view of a portion No. 0.

The function of the diffusion layer 85 will be described with reference to FIGS.

The light from the backlight device 50 incident on the liquid crystal display panel 600 ′ is converted into linearly polarized light by the polarizing plate 20, and turned into clockwise circularly polarized light by the quarter-wave plate 19.
As shown in FIG. 11, when the diffusion layer 85 is not formed, the light reflected on the back surface of the reflective electrode 15 becomes counterclockwise circularly polarized light, passes through the quarter-wave plate 19 again, and is polarized. It becomes linearly polarized light having a polarization direction perpendicular to the polarization axis direction of the plate 20. Since this linearly polarized light is absorbed by the polarizing plate 20, it does not contribute to display. On the other hand, FIG.
As shown in the figure, when the diffusion layer 85 is formed in the reflection region, the clockwise circularly polarized light toward the reflection electrode 15 passes through the diffusion layer 85 and is reflected on the back surface of the reflection electrode 15,
The light passes through the diffusion layer 85 again and returns to the backlight device 50 side. Since the polarization state of the circularly polarized light is disturbed by the finely uneven surface 85s of the diffusion layer 85, the quarter-wave plate 19
Even if it passes through, it is not converted into linearly polarized light but becomes elliptically polarized light,
It is not completely absorbed by the polarizing plate 20. The light that has passed through the polarizing plate 20 is reflected by a backlight device (a diffusion plate surface or a reflector of the backlight device) 50, and again reflected on the liquid crystal display panel 6.
00 ′. As a result, part of the light that has entered the reflective electrode 15 from the backlight device 50 side and has not contributed to the display can contribute to the display in the transmission mode. Therefore, the dual-purpose liquid crystal display device 6
00 has a high light use efficiency from the lighting device 50.

The diffusion layer 85 is formed by, for example, patterning the surface of an insulating film made of silicon oxide or the like into fine irregularities by using an etching method. The degree of the unevenness is appropriately set so as to disturb the polarization direction of the light incident on the diffusion layer 85. TFT substrate 60
The configuration for imparting the function of diffusing and reflecting (or scattering) the light from the backlight device 50 to the reflection region of 0A is not limited to the illustrated configuration. As long as it is between the plates 19, it may be placed anywhere. For example, the gate insulating film 12 in a portion other than the transmission region
Can be patterned into fine irregularities to function as a diffusion layer. Further, for example, a filler is dispersed in a matrix resin forming the resin layer 14 so that the resin layer 1
The same effect can be obtained even if the diffuse reflection characteristics (or scattering characteristics) are given to 4 itself. As the filler dispersed in the matrix resin, a material having a refractive index different from that of the matrix resin can be widely used. A liquid crystal material may be dispersed.

In the above-described dual-use liquid layer display device of the present embodiment, the configuration for imparting the function of diffusing and reflecting (or scattering) the light from the backlight device 50 to the reflection region is as follows.
It can be combined with the dual-use liquid crystal display device of the first and second embodiments.

[0071]

According to the present invention, a transflective liquid crystal display device having improved display luminance in the transmissive mode is provided. According to the present invention, the use efficiency of light from the backlight is improved, so that not only the display brightness and the contrast ratio in the transmission mode are improved, but also the display brightness and the contrast ratio in the reflection mode are improved by increasing the area of the reflection region. You can also. Alternatively, lower power consumption can be achieved by reducing the output of the backlight device.

[Brief description of the drawings]

FIG. 1 is a plan view of a TFT substrate 100A of a liquid crystal display panel used in a transflective liquid crystal display device according to the present invention.

FIG. 2 is a schematic partial sectional view of a liquid crystal display panel 100 having the TFT substrate 100A shown in FIG.

FIG. 3 is a diagram schematically showing an example of an illumination device (backlight device) used in a dual-use liquid crystal display device according to the present invention.

FIG. 4 is a diagram schematically showing another example of a lighting device (backlight device) used in the dual-purpose liquid crystal display device according to the present invention.

FIG. 5A is a schematic sectional view of a dual-use liquid crystal display device 200 according to a first embodiment of the present invention.

FIG. 5B is a diagram schematically illustrating an example of a collimating element 52 used in the dual-use liquid crystal display device according to the embodiment of the present invention, and FIG. 5A is a cross-sectional view illustrating an arrangement of two BEFII 90/50 films 52a. (B) is BEFII
It is a perspective view of 90/50 film 52a.

5C is a graph showing the spread angle of the diffused light narrowed by the collimating element 52 shown in FIG. 5B. The horizontal axis represents the spread angle of the diffused light, and the vertical axis represents the luminance.

FIG. 6 is a schematic sectional view of another dual-purpose liquid crystal display device 300 according to the first embodiment.

FIG. 7 is a schematic sectional view of a dual-purpose liquid crystal display device 400 according to a second embodiment of the present invention.

8 shows a TFT substrate 100A and a prism sheet 7 of a liquid crystal display panel 100 in a dual-use liquid crystal display device 400. FIG.
FIG. 4 is a schematic perspective view showing an arrangement relationship with the fourth embodiment.

FIG. 9 is a schematic sectional view of another dual-purpose liquid crystal display device 500 according to the second embodiment.

FIG. 10 is a schematic partial enlarged sectional view of a dual-use liquid crystal display device 600 according to a third embodiment of the present invention.

FIG. 11 is a schematic partial enlarged sectional view of a liquid crystal display device 700 having the liquid crystal display panel 100.

[Explanation of symbols]

 Reference Signs List 1 scanning line (gate bus line) 2 signal line (source bus line) 4 picture element electrode 5 thin film transistor (TFT) 5a semiconductor layer 6 gate electrode 7 source electrode 7a, 8a semiconductor contact layer 8 drain electrode 9 contact hole 10 glass substrate 11 Glass substrate 12 Gate insulating film 13 Transparent electrode 14 Resin layer 14a Opening 15 Reflective electrode 16 Color filter layer 17 Black matrix 18 Counter electrode 19, 21 Quarter wave plate 20, 22, Polarizer 23 Liquid crystal layer 30, 40 Backlight device (Illumination device) 32, 42 Diffusion plate 32s, 42s Upper surface of diffusion plate 34, 44 Fluorescent tube 36, 46 Reflector 48 Light guide plate 48s Upper surface 48s of light guide plate 50 Illumination device 52 Collimating element 52a BEFII 90/50 film (manufactured by 3M) ) 52b polyester Film layer 52c Acrylic resin layer 54 Light collecting element (microlens array) 54a Microlens 74 Prism sheet 74a Prism 85 Diffusion layer 85s Surface of diffusion layer 100, 300 ', 600' Liquid crystal display panel 100A, 600A TFT substrate 100B Color filter Substrate (counter substrate) 200, 300, 400 Transflective liquid crystal display device 500, 600, 700 Transflective liquid crystal display device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yozo Narutaki 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2H091 FA08X FA08Z FA11X FA11Z FA16Y FA29Z FA32Y FD06 GA03 LA16 LA30 5G435 AA00 AA02 AA03 BB12 BB15 BB16 CC09 EE27 EE33 FF03 FF05 FF06 FF07 FF08 FF13 GG01 GG02 GG03 GG12 GG24 HH12 HH14 LL03 LL07 LL08 LL12 LL14

Claims (5)

[Claims] 1. A liquid crystal display panel having first and second substrates, a liquid crystal layer provided between the first substrate and the second substrate, and a liquid crystal display panel provided on the first substrate side of the liquid crystal display panel. The liquid crystal display panel has a plurality of picture element regions,
The substrate is formed corresponding to each of the plurality of picture element regions, has a reflection region that reflects light incident from the liquid crystal layer side, and a transmission region that transmits light incident from the lighting device side, A liquid crystal display device capable of displaying in a transmission mode and a reflection mode, wherein a collimating element and a condensing element are arranged between the liquid crystal layer side surface of the first substrate and the lighting device in order from the lighting device side. Further, the collimating element narrows the spread angle of the diffused light emitted from the illumination device, and the condensing element collects the diffused light having the narrowed spread angle in the transmission region. Display device. 2. The liquid crystal display device according to claim 1, wherein the light-collecting element is a microlens array including a microlens provided for each of the plurality of picture element regions. 3. The liquid crystal display device according to claim 1, wherein the light-collecting element is a prism sheet. 4. The liquid crystal display device according to claim 1, wherein the reflection region has a function of diffusing and reflecting light incident from the illumination device side. 5. A liquid crystal display panel having first and second substrates, a liquid crystal layer provided between the first and second substrates, and a liquid crystal display panel provided on the first substrate side of the liquid crystal display panel. The liquid crystal display panel has a plurality of picture element regions,
The substrate is formed corresponding to each of the plurality of picture element regions, has a reflection region that reflects light incident from the liquid crystal layer side, and a transmission region that transmits light incident from the lighting device side, A liquid crystal display device capable of displaying in a transmission mode and a reflection mode, wherein the reflection region has a function of diffusing and reflecting light incident from the lighting device side.