JP2003195275A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partial transmission type liquid crystal display device highly efficiently utilizing back light. <P>SOLUTION: A transmission display part arrayed in a grid shape more closely in a scanning line direction and a columnar prism-like microlens parallel to the scanning line direction are combined. Converging efficiency of the back light is improved and bright display of high color purity is obtained under the light environment of a wide range from a dark place to a place under direct sunlight. <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 a liquid crystal display device which exhibits a high contrast ratio display in a wide range of light environments from a dark room to direct sunlight.

[0002]

2. Description of the Related Art A reflection type liquid crystal display device uses a reflection plate to reflect light incident from the surroundings for display. Since the contrast ratio is constant regardless of the ambient brightness, it can be used in a relatively bright environment from direct sunlight to indoors.
By combining the reflective liquid crystal display device with an auxiliary light source, the usage environment can be extended to a dark environment such as a dark room.

A partially transmissive liquid crystal display device using a backlight as an auxiliary light source and having both a reflective electrode and a transparent electrode in one pixel performs display by transmitting backlight light from the transparent electrode portion in a dark place. . A reflective liquid crystal display device using a front light as an auxiliary light source performs display by reflecting the front light light at a reflective electrode portion in a dark place.

Among these, in a partially transmissive liquid crystal display device using a backlight as an auxiliary light source, it is not possible to simultaneously increase the aperture ratio of the reflective display portion and the transmissive display portion, so that both the reflective display and the transmissive display have low brightness. was there. On the other hand, JP-A-11-109417 and JP-A-2000-15
4181 attempts to improve the brightness of transmissive display by condensing the light of the backlight on the transmissive display section using a collimating backlight and a microlens.

[0005]

Since each microlens is very small and a large number of microlenses exist close to other microlenses, it is difficult to control the shape of each lens.
If the shape of the microlens is inappropriate, the light from the backlight cannot be sufficiently condensed on the transmissive display unit. The distribution and shape of the microlenses must be determined in consideration of the collimating property of the backlight and the distribution of the transmissive display portion. The distribution of the transmissive display portion also affects the pixel structure. Further, if the transmissive display section does not have high transmissive efficiency, high-luminance transmissive display cannot be obtained.

As described above, in order to improve the brightness of the partially transmissive transmissive display, not only the condensing efficiency of the microlenses but also the pixel design of the partially transmissive liquid crystal display device, the collimating property of the backlight, and further, The entire design including the display mode is required. However, since such an entire design has not been conventionally made, the light collection efficiency of the microlens is low and the transmissive display brightness of the partial transmission type is low. Therefore, the conventional partially transmissive liquid crystal display device cannot display a good visibility in a wide range of environments.

The problem to be solved by the present invention is to improve the light-collecting efficiency of a microlens placed in a partially transmissive liquid crystal display device with a backlight.

[0008]

First, the features of the arrangement and shape of the transmissive display portions in the partial transmissive liquid crystal display device will be described. The transmissive display portion is in a grid shape parallel to the scanning wiring and the signal wiring, and the grid spacing in the signal line direction is three times the grid spacing in the scanning wiring direction. That is, each pixel is arranged in a grid to clearly display the vertical and horizontal lines,
Since the R, G, and B color filters are used together, each pixel has a ratio of the length in the scanning line direction to the length in the signal line direction of about 1:
It becomes a rectangular shape of 3. If the position occupied by the transmissive display section in each pixel is fixed, the transmissive display section is also arranged in a grid pattern, and the grid spacing in the signal line direction is 3 of the grid spacing in the scanning wiring direction.
Double.

Further, the shape of the transmissive display portion is a square shape, a rectangular shape whose aspect ratio is close to 1, or a polygonal shape similar thereto. Since this is within a rectangular pixel having a long side to short side ratio of about 3: 1, the transmissive display portions of each pixel are arranged closer to each other in the scanning line direction.

The reason why the shape of the transmissive display portion is a square shape, a rectangular shape whose aspect ratio is close to 1, or a polygonal shape similar to this is as follows. A rubbing method is generally used as the alignment method of the liquid crystal layer, but if there is a step between the transmissive display section and the reflective display section, there is a possibility that alignment failure occurs near the boundary line between the transmissive display section and the reflective display section. In order to reduce the alignment defect and to reduce the alignment defect by shortening the length in the vicinity of the boundary line between the transmissive display part and the reflective display part, a plurality of transmissive display parts are not arranged in each pixel. To do. The transparent display has a square shape or a rectangular shape with an aspect ratio close to 1.
Alternatively, a polygonal shape having an aspect ratio close to 1 is used.

Further, the step is formed between the transmissive display portion and the reflective display portion for the following reason. In the reflective display unit, light incident from the outside is reflected by the reflective electrode for display, so that the light passes through the liquid crystal layer before and after reflection. That is, in the reflective display section, light passes through the liquid crystal layer twice. In the transmissive display unit, since display is performed by using the backlight light arranged behind the liquid crystal display device, the light passes through the liquid crystal layer once. Since the number of times of passing through the liquid crystal layer is different as described above, there is a difference in optical path length between the reflective display section and the transmissive display section, and the optical path length of the transmissive display section is half that of the reflective display section. In this case, the display efficiency of the transmissive display unit is reduced. By forming a step between the reflective display portion and the transmissive display portion and making the liquid crystal layer thickness of the transmissive display portion thicker than that of the reflective display portion, the difference in optical path length between the two can be reduced.
The display efficiency of the transmissive display unit can be improved.

Next, the optimum shape of the microlens to be combined therewith will be described. If the shape of the microlens is simpler, its shape can be easily controlled and the backlight light can be condensed on the transmissive display portion at a higher rate. Further, the transmissive display unit and the microlens must be aligned with each other so that the transmissive display unit is sufficiently close to the focal point of the microlens. It will be easier.

Considering that the transmissive display portions are distributed in a grid pattern and are arranged closer to each other in the scanning line direction as described above, the microlenses have a cylindrical prism shape,
The arrangement direction may be parallel to the scanning line. The shape is simpler and easier to control than the case where the microlenses are made to have a convex shape so as to correspond to the individual transmissive display portions one-to-one, and the alignment with respect to the transmissive display portions is facilitated. Also,
Even when the pixel size is reduced and a large-capacity, high-definition display is performed, the shape control and alignment of the microlens are easier.

Since the microlens focuses only the light incident on itself, if the width of the microlens is made wider than at least the width of the transmissive display portion in the signal wiring direction, the effect of focusing can be obtained. Further, if the cross-sectional shape of the microlens is a curved surface such as a quadric surface, a higher light condensing effect can be obtained even when combined with a backlight having an angular distribution for light emission. Since the shape of the microlens is sufficiently large with respect to the wavelength of visible light, the ray tracing method is effective for obtaining the optimum value of the cross-sectional shape of the microlens and the ratio of height to width.

If the collimating property of the backlight is good, the effect of collecting the backlight light by the microlens is improved. A cold cathode tube or an electroluminescence light source is used as a light source of the backlight. In particular, since the electroluminescent light source has a minute light emitting portion, it is possible to make the surface light source highly collimating by the refraction effect, the scattering effect and the interference effect of the light guide plate.

At this time, if the collimating property of the light source is improved beyond a certain level, the entire surface of the liquid crystal display device cannot be seen uniformly. This is because the angle with respect to the viewing direction of the viewer is different at both ends of the liquid crystal display device, and the angles of the viewing direction at both ends are not included in the angle distribution of the light source light. By arranging a diffusion plate between the backlight and the microlens to diffuse the backlight light, it is possible to achieve both in-plane uniformity of light source intensity and collimation.

As the display mode, a single polarizing plate type display mode capable of displaying a high contrast ratio with a low driving voltage is used. The single polarizing plate type has a structure in which a reflecting plate (reflective electrode) is placed close to the liquid crystal layer when placed in the reflective display section, and one polarizing plate and at least one retardation layer are laminated on the upper surface of the liquid crystal layer. In addition to this, in the transmissive display portion, one polarizing plate and at least one retardation are provided on the lower surface of the liquid crystal layer.

The display mode is the reflectance when a voltage is applied,
It is classified into a normally closed type and a normally open type based on the change in transmittance. In the normally closed type, reflectance and transmittance increase with voltage application, and in the normally open type, reflectance and transmittance decrease with voltage application.

In order to make the single-polarizing plate type display mode normally open, a voltage is applied and the phase difference is substantially zero.
Dark display must be realized by using the liquid crystal layer in the closed state. For that purpose, both the upper phase plate polarizing plate and the lower phase plate polarizing plate must be a quarter wavelength plate. Due to such restrictions, the normally open type transmissive display has a drawback that the transmissive efficiency is low. No matter how the parameters such as the twist angle of the liquid crystal layer, the retardation, and the retardation ratio of the reflective display section and the transmissive display section are changed, only about half the transmission efficiency due to the absorption of the polarizing plate can be obtained. I can't.

Since the normally closed type does not have the restrictions of the polarizing plate and the phase plate unlike the normally open type, the parameters of the polarizing plate, the phase plate and the liquid crystal layer, and further the retardation of the reflective display part and the transmissive display part are set. By optimizing, the transmission efficiency almost equal to the upper limit of the transmission efficiency due to the absorption of the polarizing plate can be obtained.

As described above, the transmissive display portions arranged in a lattice shape closer to each other in the scanning line direction, the cylindrical prism-shaped microlenses arranged in parallel to the scanning line direction and at the same pitch as the pixels, and the electroluminescence light source are provided. By combining the collimating backlight used and the normally closed single polarizing plate type display mode, the transmissive display brightness of the partial transmissive liquid crystal display device can be improved.

According to another embodiment of the present invention, in a liquid crystal display device in which a display section is composed of a plurality of pixels, and a light transmission section and a light reflection section are provided in each pixel of the plurality of pixels, The transmissive part is arranged at almost the same position of each pixel, and a cylindrical prism-shaped microlens is arranged in the direction in which the scanning wiring is arranged, corresponding to the position along the light transmissive part arranged in each pixel. That is.

Further, the microlens is arranged so that the light condensed by the microlens is collected in the light transmitting portion.

Further, this microlens is arranged such that the apex position of the cylindrical prism shape is substantially along the position of the light transmitting portion.

Further, a light source is arranged on the side on which the microlens is arranged, and the microlens condenses the light of the light source on the light transmitting portion.

Further, the pixel is formed corresponding to a region surrounded by a plurality of signal wirings and scanning wirings arranged so as to intersect with the plurality of signal wirings, and the cylindrical prism-shaped microlens scans. The wiring is arranged in the direction in which it is arranged.

Further, the signal wiring and the scanning wiring are arranged on a transparent substrate, and the liquid crystal layer is sandwiched between this transparent substrate and another transparent substrate.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in more detail with reference to specific examples.

(Embodiment 1) FIG. 1 is a sectional view of a liquid crystal display element, a microlens and a backlight of a liquid crystal display device of the present invention.
Shown in. A liquid crystal display element, a microlens, and a backlight are sequentially stacked. Of these, micro lens 3
5 and the arrangement relationship between the reflective display section 38 and the transmissive display section 39 in each pixel are shown in FIG. The microlens 35 has a cylindrical prism shape and is parallel to the short side direction of the pixel, that is, the scanning wiring direction 53. Pixel spacing in the signal wiring direction 54 is 0.24 mm
On the other hand, the width of the microlens is 0.22 mm. The outer size of the reflective electrode is 0.234 mm × 0.074
mm, while the size of the transmissive display is 0.09 mm ×
It is 0.06 mm, and it is distributed almost in the center of the pixel. In the signal line direction, the transmissive display parts are distributed with a spacing of 0.15 mm, while in the scanning line direction, they are distributed with a spacing of 0.03 mm, which results in a closer grid distribution in the scanning line direction. Has become. The cross section of the microlens is a substantially quadric surface, and the center 52 of the microlens coincides with the center 51 of the transmissive display section when viewed in the normal direction.

A second substrate, a lower phase plate, a lower polarizing plate, and a microlens substrate are present between the microlens and the transmissive display portion, and their thicknesses are about 0.5 mm and 0, respectively. Since they are 0.1 mm, 0.15 mm and 0.35 mm, there is a space of about 1 mm between the microlens and the transmissive display. The refractive index of the second substrate, lower phase plate, lower polarizing plate, microlens substrate, and microlens is 1.
It is in the range of 5 to 1.6. In consideration of the distance between the microlens and the transmissive display portion and the refractive index, the cross section of the microlens is a substantially quadric surface, and the height-width ratio is 0.2. As a result, when light with particularly good collimating properties enters from the normal direction, the light is condensed by the microlens on the transmissive display unit.

The liquid crystal display element is mainly composed of a first substrate 11, a liquid crystal layer 10 and a second substrate 12, and the first substrate and the second substrate sandwich the liquid crystal layer. The first substrate has a color filter 13, a flattening layer 15, a common electrode 16, and a first alignment film 17 on the side close to the liquid crystal layer. The thin film transistor 19 and the second alignment film 24 are provided on the side of the second substrate which is close to the liquid crystal layer. The thin film transistor is an inverted stagger type, and includes a scanning wiring, a signal wiring, a reflective electrode 23, and a transparent electrode 25.
It is connected to the. The scanning wiring and the signal wiring are insulated by the first insulating layer 20, and the transparent electrode and the reflective electrode are insulated by the second insulating layer 21. The reflective electrode and the thin film transistor are connected by a through hole 27. A third insulating layer is provided on the upper surface of the reflective electrode, and a second alignment film is provided on the upper surface of the third insulating layer, which is close to the liquid crystal layer and defines the alignment direction.

In one pixel, the portion where the reflective electrode is arranged is the reflective display portion, and the portion where the transparent electrode is arranged is the transmissive display portion. The transparent electrode is placed below the reflective electrode, and the thickness of the liquid crystal layer in the transmissive display part is about 1.5 than that of the reflective display part.
μm thicker. As a result, the liquid crystal layer thickness of the transmissive display portion is 5.3 μm, the liquid crystal layer thickness of the reflective display portion is 3.8 μm, and the ratio of the two is approximately 1.4. By setting the ratio of the liquid crystal layer thickness of the transmissive display part to the liquid crystal layer thickness of the reflective display part to about 1.4, the optical path difference between the two is compensated, and both the reflective display part and the transmissive display part are caused by the absorption of the polarizing plate. A reflection efficiency and a transmission efficiency close to the upper limit can be obtained.

The first substrate is made of borosilicate glass and has a thickness of 0.5 mm. Color filters are red, green,
The blue-colored portions are repeatedly arranged in a stripe pattern, and the unevenness caused by the color filter is flattened by the resin flattening layer. Common electrode is Indium Tin Oxide
It is made of (ITO). The first alignment film was a polyimide-based polymer film and was subjected to alignment treatment by a rubbing method.

The second substrate, like the first substrate, is made of borosilicate glass and has a thickness of 0.5 mm. The second alignment film is the same polyimide polymer film as the first alignment film, and was subjected to the alignment treatment by the rubbing method. The signal wiring and the scanning wiring are made of chrome.

The twist angle of the liquid crystal layer is set to 50 degrees, which makes it easy to obtain an uncolored bright display when driven with a relatively low voltage of about 3V. The liquid crystal layer thickness in the reflective display is 3.
The birefringence of the liquid crystal material was adjusted to 0.072 to 8 μm. An NRZ phase plate manufactured by Nitto Denko is used for the upper phase plate 31, and an SEG1425DUHCARS manufactured by Nitto Denko is also used for the upper polarization plate 32.
Was used. A NAF phase plate manufactured by Nitto Denko Corporation was used as the lower phase plate 33, and the retardation was set to 200 nm and the slow axis azimuth angle was set to 120 degrees. Similarly, SEG1425DUHCARS manufactured by Nitto Denko Corp. was used as the upper polarizing plate 34, and its absorption axis azimuth was set to 90 degrees. As a result, both reflective display and transmissive display are normally closed type. Figure 3 shows the applied voltage dependence of reflective display and transmissive display. Both are normally closed types in which reflective display and transmissive display increase with applied voltage.

Here, the azimuth angle is counterclockwise when the liquid crystal display device is observed from the normal direction of the upper substrate side and the twist angle of the liquid crystal layer is Φ, the orientation processing direction of the lower substrate is 0.5Φ degree. Defined around. A high resistance fluorine-based liquid crystal material was used for the liquid crystal layer. True spherical polymer beads having a diameter of 3.9 μm were dispersed at a rate of about 100 particles per 1 mm ² to make the liquid crystal layer thickness in the reflective display area substantially uniform.

The microlens was prepared as follows. By forming a photosensitive resist film on a transparent substrate, stacking a photomask on it, and performing pattern exposure,
The resist film was left so as to be arranged in stripes. Next, this was heated to soften the resist film so that its cross-sectional shape was convex and the bottom surface was enlarged so as to be closer to each other. As described above, a microlens having a structure in which cylindrical prism-shaped projections were arranged in parallel was prepared.

Alternatively, a metal film is formed on this, the surface is hardened, a pressing die is produced using this, and further, the resin film on the substrate is processed by using this pressing die. Microlenses may be made. In addition to this, a metal substrate may be used as a pressing die and a plastic substrate may be pressed.

The backlight 36 has a structure in which two white electroluminescent light sources are provided at the apex of a light guide having a substantially rectangular shape, and the electroluminescent light sources mainly emit light in a diagonal direction. This is reflected to the liquid crystal display element side by utilizing the interference effect of the minute projections on the bottom surface of the light guide. The light emitted from the backlight has high collimating property, but the uniformity of the in-plane luminance distribution is low. The in-plane brightness distribution is made more uniform by passing through the diffusion film. FIG. 4 shows the angle dependence of the emission intensity at the time of passing through the diffusion film. Here, the horizontal axis of FIG. 4 is a polar angle with the normal direction being 0 degree. The full width at half maximum of the emission intensity is about 20 degrees, which shows good collimating properties.

When the transmissive display brightness of the partially transmissive liquid crystal display device manufactured as described above was measured, it was 72 cd / m.
^{Was 2} . When the transmissive display luminance was measured without the microlens, it was 47 cd / m ² . From the above, an effect of improving the brightness by about 1.5 times as compared with the case where the microlens is removed is obtained.

(Embodiment 2) FIG. 5 shows a cross section of a liquid crystal display device of this embodiment. In the liquid crystal display device of Example 1, the microlens is arranged below the lower phase plate and the lower polarizing plate.
In this embodiment, it is arranged above the lower phase plate and directly attached to the second substrate. The lower phase plate and the lower polarizing plate were separately attached on the substrate.

As a result, the lower substrate and the microlens substrate are interposed between the microlens and the transparent electrode. The distance between the microlens and the transparent electrode is about 0.
It was shortened to 85 mm, but the change in the spacing is small enough,
The ratio of the height to the width of the microlens is 0.1 as in the first embodiment.
It was set to 2.

When the transmissive display luminance was measured, it was 65 cd / m.
² and 43 cd / m without the microlens
^{Was 2} . Compared to the case without the micro lens, about 1.
A brightness of 5 times was obtained.

Example 3 In the liquid crystal display device of Example 2, microlenses were directly formed on the second substrate.
FIG. 10 shows a sectional view of the liquid crystal display device of the present invention in this case.

As a result, only the second substrate was interposed between the microlens and the transparent electrode, so that the distance between them was about 0.5 mm. Since the distance between the microlens and the transparent electrode has become smaller, the focal length of the microlens must be reduced accordingly. Since the angle at which light is refracted must be increased, the height-to-width ratio of the microlenses must be increased. Therefore,
The ratio of height to width of the microlens was set to 0.3. Transmissive display luminance was 80 cd / m ^2, when excluding the microlens was 48 cd / m ^2. The brightness was about 1.7 times that obtained when the microlens was removed.

(Embodiment 4) In the construction of Embodiment 3, only the lower substrate is interposed between the microlens and the transparent electrode, and the refractive index of the microlens and the lower substrate are both 1. It is 5 to 1.6. In this configuration, the range of parameters that can improve the brightness was calculated using the ray tracing method. Specifically, it is assumed that the microlens is regarded as an aggregate of minute planes, and the light of the backlight is incident on any of the minute planes with a similar angle distribution, and geometrical refraction and reflection occur. . By changing the height-width ratio of the microlens and the distance between the microlens and the transparent electrode,
A combination of parameters that can obtain the effect of improving the transmittance was obtained.

At this time, FIG. 6 shows a combination of parameters with which the effect of improving the brightness is obtained as compared with the case where the microlens is not used. If x is the distance between the microlens and the transparent electrode, and the unit is mm, and y is the ratio of the height and width of the microlens, the combination of parameters that has the effect of improving the brightness is (x, y) = (1.8 , 0.1), (1.5, 0.
2), (0.65, 0.5), (0.1, 0.5), (0.
1, 0.2), (0.35, 0.1) are distributed in a polygon having vertices.

FIG. 7 shows a combination of parameters with which the effect of improving the brightness by 1.25 times or more as compared with the case where no microlens is used is obtained. (X, y) = (1.
5, 0.1), (1.3, 0.2), (0.55, 0.
5), (0.1, 0.5), (0.3, 0.2), (0.
It is distributed in a polygon with the vertices at 9, 0.1).

FIG. 8 shows a combination of parameters with which the effect of improving the brightness by 1.5 times or more as compared with the case where no microlens is used is obtained. (X, y) = (1.15,0.
17), (0.45, 0.5), (0.15, 0.5), (0.
3, 0.3), (0.5, 0.2), and (0.7, 0.17) are distributed in a polygon having vertices. In Example 1, (x, y) = (1.0, 0.2), in Example 2, (x, y) = (0.85, 0.2), and in Example 3, (x , Y) = (0.5, 0.3), both of which are distributed within the range shown in FIG.

From the above, the combination of the distance (mm) between the microlens array and the transparent electrode and the ratio of the height and width of the microlens is (1.8, 0.1), (1.5, 0.2), ( 0.6
5, 0.5), (0.1, 0.5), (0.1, 0.2),
When selected within a polygon having (0.35, 0.1) as a vertex, an effect of improving the brightness can be obtained, and preferably (1.5, 0.1).
1), (1.3, 0.2), (0.55, 0.5), (0.
1,0.5), (0.3, 0.2), (0.9, 0.1) If you select within a polygon with vertices, you can get the effect of 1.25 times more brightness improvement. More preferably (1.1, 0.1
7), (0.45, 0.5), (0.15, 0.5),
(0.3, 0.3), (0.5, 0.2), (0.7, 0.1)
By selecting within a polygon with 7) as the apex, an effect of improving the brightness by 1.5 times or more can be obtained.

Example 5 In the liquid crystal display device of Example 1, backlights having different collimating properties were produced by changing the diffusivity of the diffusing film. When the full width at half maximum in the polar angle dependence of the emission intensity is defined as the collimating property, the collimating property of the backlight of Example 1 is 20 degrees.
In addition, the collimating property is 14 degrees, 32 degrees, 40 degrees, 5
A backlight of 5 degrees was obtained. Further, when the diffusion film was removed, a backlight having a collimating property of 10 degrees was obtained.

FIG. 9 shows the effect of improving the brightness as compared with the case where the microlens is removed. The vertical axis of FIG. 9 represents the effect of improving the brightness as compared with the case where the microlens is removed. When the collimating properties are 55 degrees and 40 degrees, the effect of improving the brightness is hardly seen, but it can be seen that the effect of improving the brightness increases as the collimating property of the backlight improves. From FIG. 9, when the collimating property exceeds 35 degrees, the effect of improving the brightness can be obtained.

If the collimating property of the backlight is improved, the effect of improving the brightness is increased, but on the other hand, the in-plane uniformity of the brightness is deteriorated. For example, a liquid crystal display device for a mobile phone has a width of about 3 cm, and when it is observed at a distance of 30 cm, the angle connecting both ends is about 5 degrees. Therefore, the full width at half maximum in the polar angle dependence of the emission intensity needs to be at least 5 degrees.

From the above, the collimating property is 5 degrees or more, 35
When the degree is less than or equal to the degree, the effect of improving the brightness can be obtained, and the in-plane uniformity of the brightness which is practically sufficient can be obtained.

(Example 6) In the liquid crystal display device of Example 1, a diffusion adhesive 30 was newly arranged between the first substrate and the upper phase plate except the concavo-convex forming layer. The diffusion adhesive is an adhesive containing a large number of fine particles, and diffusion occurs because the refractive index of the fine particles is different from that of the adhesive. Even if the reflection electrode becomes a mirror surface by removing the concavo-convex forming layer, since the reflected light is diffused by the diffusion adhesive, a reflective display with a quality similar to paper can be obtained. Even with such a simpler configuration, almost the same effect of improving the brightness as in the first embodiment can be obtained.

According to these examples, since the liquid crystal display device of the present invention can obtain highly efficient reflective display and transmissive display,
If this is mounted on a portable information device or the like, an effect of further improving the display characteristics under a wide range of light environments ranging from a dark place to direct sunlight can be obtained. For example, display brightness can be improved in a wide range of lighting environments. If a color filter with high color purity is installed, it is possible to expand the color reproduction range while maintaining the same display brightness as before. As described above, a liquid crystal display device that provides a display with good visibility in a wide range of environments is realized.

[0057]

According to the present invention, it is possible to provide a partially transmissive liquid crystal display device with a backlight capable of improving the light-collecting efficiency of the microlenses.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a liquid crystal display device of Example 1.

FIG. 2 is a perspective view showing a distribution of a transmissive display section and microlenses in Example 1.

FIG. 3 is a diagram showing applied voltage dependence of reflectance and transmittance in Example 1.

FIG. 4 is a diagram showing the angle dependence of the emission intensity of the backlight of Example 1.

FIG. 5 is a cross-sectional view showing a configuration of a liquid crystal display device of Example 2.

FIG. 6 is a diagram showing a combination of the distance between the microlens and the transparent electrode, which has the effect of improving the brightness as compared with the case where the microlens is not used, and the ratio of the height and the width of the microlens.

FIG. 7: Compared to the case without using a microlens, 1.
It is a figure which shows the combination of the space | interval of the microlens and the transparent electrode with which the effect of 25 times the brightness improvement was acquired, and the ratio of the height and width of the microlens.

[Fig. 8] Compared to the case without using a microlens, 1.
It is a figure which shows the combination of the space | interval of the microlens and the transparent electrode with which the effect of the brightness improvement of 5 times was acquired, and the ratio of the height and width of the microlens.

FIG. 9 is a diagram showing the dependence of the effect of improving the brightness on the collimating property of the backlight.

FIG. 10 is a cross-sectional view showing a configuration of a liquid crystal display device of Example 3.

FIG. 11 is a cross-sectional view showing a configuration of a liquid crystal display device of Example 6.

[Explanation of symbols]

10 ... Liquid crystal layer, 11 ... First substrate, 12 ... Second substrate,
13 ... Color filter, 15 ... Flattening layer, 16 ... Common electrode, 17 ... First alignment film, 19 ... Thin film transistor, 2
0 ... First insulating layer, 21 ... Second insulating layer, 22 ... Concavo-convex forming layer, 23 ... Reflective electrode, 24 ... Second alignment film, 25 ... Transparent electrode, 27 ... Through hole, 30 ... Diffusion adhesive material , 31
... upper phase plate, 32 ... upper polarizing plate, 33 ... lower phase plate,
34 ... Lower polarizing plate, 35 ... Microlens, 36 ... Backlight, 37 ... Prism sheet, 38 ... Reflective display section,
39 ... Transmissive display part, 40 ... Diffusion film, 41 ... Microlens substrate, 51 ... Center of transmissive display part, 52 ... Center of microlens, 53 ... Scanning wiring direction, 54 ... Signal wiring direction.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G02F 1/1343 G02F 1/1343 (72) Inventor Ikuo Hiyama 7-1, 1-1 Mikamachi, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory F-term (reference) 2H091 FA08X FA08Z FA11Z FA14Y FA28Z FA29Z FA32Z FA43Z FA44Z FB02 FC22 FC26 FD13 GA03 LA16 LA17 2H092 GA17 HA03 HA05 JA24 NA01 PA07

Claims (14)

[Claims] 1. A first substrate, a second substrate, a liquid crystal layer,
A driving unit, the first substrate and the second substrate sandwich a liquid crystal layer and are connected to the driving unit, the first substrate has a common electrode, and the second substrate has a plurality of signals. Wiring and scanning wiring are provided, active elements are provided at the intersections of signal wiring and scanning wiring on the second substrate, transparent electrodes and reflection electrodes are connected to each active element on the second substrate, and each pixel is transparent. A liquid crystal display device that includes a display unit and a reflective display unit and is distributed in a grid pattern, including a microlens and a backlight behind, and each microlens is in the shape of a cylindrical prism and is distributed parallel to the scanning wiring. Each microlens is a liquid crystal display device that collects backlight light on the transmissive display part of each pixel. 2. The liquid crystal display device according to claim 1, wherein the transmissive display portions in each pixel are distributed in a grid pattern, and are distributed on the center line of the microlenses. 3. The liquid crystal display device according to claim 1, wherein the width of the microlens is wider than that of the transmissive display portion and is equal to or narrower than the pixel spacing in the signal line direction. 4. The light intensity of the backlight has an angle dependence, its maximum is in the vicinity of the normal direction, and the full width at half maximum of the emission intensity is 5 degrees or more and 35 degrees or less. 1. Liquid crystal display device. 5. The distance between the microlens and the transparent electrode is in mm.
, And the combination of the height and width of the microlens is (x, y), (x, y) is (1.8, 0.1),
(1.5, 0.2), (0.65, 0.5), (0.1, 0.
5. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in a polygon having vertices 5), (0.1, 0.2) and (0.35, 0.1). 6. The distance between the microlens and the transparent electrode is in mm
, And the combination of the ratio of the height and width of the microlens is (x, y), (x, y) is (1.5, 0.1),
(1.3, 0.2), (0.55, 0.5), (0.1, 0.
The liquid crystal display device according to claim 5, wherein the liquid crystal display device is in a polygon having vertices 5), (0.3, 0.2), and (0.9, 0.1). 7. The unit between the microlens and the transparent electrode is mm.
And the combination of the height and width ratio of the microlens is (x, y), (1.1, 0.17), (0.45,
0.5), (0.15, 0.5), (0.3, 0.3), (0.
5. The liquid crystal display device according to claim 6, wherein the liquid crystal display device is in a polygon having vertices of (5, 0.2) and (0.7, 0.17). 8. The liquid crystal display device according to claim 1, wherein the reflective display portion and the transmissive display portion exhibit a normally black type applied voltage characteristic in which reflectance and transmittance increase with applied voltage. 9. A liquid crystal display device, wherein a display portion is composed of a plurality of pixels, and a light transmitting portion and a light reflecting portion are provided in each pixel of the plurality of pixels. In the liquid crystal display device, the light transmitting portion of each pixel is located at substantially the same position of each pixel. Are arranged in the position corresponding to the position along the light transmission part arranged in each pixel,
A liquid crystal display device characterized in that a cylindrical prism-shaped microlens is arranged in a direction in which a scanning wiring is arranged. 10. The liquid crystal display device according to claim 9, wherein the microlens is arranged so that the light condensed by the microlens is collected in the light transmitting portion. 11. The liquid crystal display device according to claim 9, wherein the microlenses are arranged such that the apex positions of cylindrical prisms are substantially along the positions of the light transmitting portions. 12. A light source is arranged on the side where the microlens is arranged, and the microlens collects the light of the light source on the light transmitting portion.
The liquid crystal display device according to any one of 1. 13. The pixel is configured to correspond to a region surrounded by a plurality of signal wirings and a scanning wiring arranged so as to intersect the plurality of signal wirings, and the cylindrical prism-shaped microlens includes: 13. The liquid crystal display device according to claim 9, wherein the scanning wiring is arranged in a direction in which the scanning wiring is arranged. 14. The signal line and the scanning line are arranged on a transparent substrate, and a liquid crystal layer is sandwiched between the transparent substrate and another transparent substrate.
Liquid crystal display device.