JP3268319B2 - Liquid crystal display - Google Patents

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 having a transmission type liquid crystal display with low power consumption,
The present invention relates to a liquid crystal display device suitable for effectively condensing incident light on pixel electrodes even if the incident light is scattered light.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device having a transmission type liquid crystal display of a low power consumption type such as a portable personal computer, a word processor, a liquid crystal television, etc., as shown in FIG. Are not used, and those using a microlens on the light source side as shown in FIG. 7 and 8 show a part of a cross section of the liquid crystal display device.

In FIG. 7, reference numeral 1a denotes a transparent substrate on the light source side A, and 1b denotes a transparent substrate on the display screen side B which is disposed relatively to the transparent substrate 1a. 2
Is a liquid crystal layer formed by filling liquid crystal between the opposing transparent substrates 1a and 1b, and 3a is a pixel electrode arranged in a matrix on the surface of the transparent substrate 1A on the liquid crystal layer 2 side. By applying a voltage to a specific electrode, the light transmittance of the liquid crystal at that location is changed, and an image is displayed by the illumination light 4 from behind, that is, a set of transmitted light points of the backlight. Reference numeral 3b denotes a common electrode, 5 denotes the same surface as the pixel electrode 3a, portions other than the pixel electrode 3a through which light does not transmit, such as wiring and elements, 6 denotes a deflecting plate, and 7 denotes an alignment film. When the illuminating light 4 is incident on the transparent substrate 1a, of the incident light, only the light that has passed through the pixel electrode 3a on the transparent substrate 1a contributes to image formation, and the wiring and elements 5 other than the pixel electrode 3a The light applied to the portion through which light does not pass is reflected and does not contribute to image formation.

The configuration shown in FIG. 7 has a problem that the incident light is not effectively used and the screen becomes dark.
The problem that the aperture ratio is reduced becomes more prominent because the area ratio of a portion of the liquid crystal display device 5 that does not transmit light, such as wirings and elements 5, increases with color and higher definition. In order to solve this problem, a method of increasing the power consumption of the illumination light source and brightening the screen has been adopted so far. However, as a display device in a portable small electronic device or the like, the power consumption is minimized. There is a need for a method of solving this problem without increasing the power consumption of the illumination light source. As shown in FIG. 8, a microlens array 8 is formed near the light source side surface of the transparent substrate 1a, It has been proposed to condense light on the pixel electrode 3a to improve the apparent aperture ratio and brighten the screen display (for example, JP-A-60-165623, JP-A-2-18).
16, JP-A-2-89025, JP-A-2-25190
2, JP-A-2-257119). In this case, the microlens is formed by a general technique such as photolithography, lift-off, metal mask, or ion implantation. In FIG. 8, the same components as those in FIG. 7 indicate the same components.

[0005]

As described above, when the microlens array 8 is formed on the light source side A of the transparent substrate 1a in order to improve the apparent aperture ratio, the light incident on the microlens array 8 is increased. Are all light beams perpendicular to the transparent substrate 1a, almost all incident light is condensed on the corresponding pixel electrode 3a as shown in FIG. A liquid crystal display device having a brighter screen than that of the liquid crystal display device can be obtained. However, actually, the incident light on the transparent substrate 1a is often incident not only when the incident angle is vertical but also obliquely. In particular, when a not-shown reflector or scattering plate is provided between the transparent substrate 1a and the light source so that the brightness of the entire screen is uniform, the incident light on the transparent substrate 1a is scattered light from various directions. . Therefore, in this case, as shown in FIG. 9B, one focus is not determined for one microlens, so that no light is collected. This is because when the microlens array 8 is formed near the surface on the light source side A of the transparent substrate 1a, the thickness dimension of the transparent substrate 1a is 500 to
1000 μm is the pitch 50-100 between each pixel electrode 3a
Therefore, the ratio d / x of the distance d between the microlens array 8 and the pixel electrode 3a to the pitch x between the lenses of the microlens array 8 becomes a value exceeding 5, and the scattered light This is because the incident light cannot be effectively focused on the pixel electrode 3a. in this way,
Pixel electrode 3a to be focused and microlens array 8
Is greater than the pitch x between the microlenses, each microlens and the pixel electrode 3a have a one-to-one correspondence.
However, there is a problem that incident light composed of scattered light cannot be effectively focused on the pixel electrode 3a.

The present invention has been made in view of the above-mentioned problems of the prior art,
It is an object of the present invention to provide a liquid crystal display device having a microlens array capable of effectively condensing incident light on a pixel electrode with a simple configuration even if the incident light is scattered light.

[0007]

To achieve the above object, the present invention provides a light source, a pair of opposing transparent substrates on the light source side and the display screen side, and irradiating the transparent substrate with light emitted from the light source. A microlens array formed at a constant pitch between lenses for condensing and passing, and a liquid crystal layer is interposed between the transparent substrates and formed in a matrix to receive light passing through the microlens array. A liquid crystal display device comprising a pixel electrode, and controlling the amount of light passing through the liquid crystal layer by changing the voltage applied to the pixel electrode to display an image. A distance d between the formed microlens array and the pixel electrode, and a pitch x between lenses of the microlens array.
Is set to be 5 or less.

Further, a light source, a pair of opposing transparent substrates on the light source side and the display screen side, and a micro-pitch formed at a constant pitch between lenses for condensing and passing the irradiation light of the light source on the transparent substrate. A lens array, and a pixel electrode interposed between the transparent substrates and arranged in a matrix so as to receive light passing through the microlens array while interposing a liquid crystal layer, and applying a voltage to the pixel electrode. In a liquid crystal display device that performs image display by controlling the amount of light passing through the liquid crystal layer by changing, the microlens array is formed on the surface of the transparent substrate on the light source side on the liquid crystal layer side,
Forming a transparent intermediate layer between the formed microlens array and the pixel electrode that can be set to any distance between the microlens array and the pixel electrode, the microlens array including the thickness of the transparent intermediate layer and the pixel electrode, And the ratio d / x between the distance d between them and the pitch x between the lenses of the microlens array is 5 or less.

It is preferable that the ratio d / x between the distance d between the microlens array and the pixel electrode and the pitch x between the lenses of the microlens array is 1 or more and 3 or less.

[0010]

With the above arrangement, not only the case where vertical light is incident on the transparent substrate as incident light, but also
Even when scattered light having various incident angles is incident, it is confirmed by an experiment described later that most of the light passing through each microlens is effectively condensed on the corresponding pixel electrode. It was confirmed that illuminance at least twice or more was obtained on the pixel electrode as compared with the case where the microlens array was formed near the light source side surface of the transparent substrate.

In the same experiment, the ratio d / x of the distance d between the microlens array and the pixel electrode to the pitch x between the lenses of the microlens array (hereinafter, simply referred to as the aspect ratio d / x) is calculated. The preferred value depends on the incident angle distribution of the light source light and the characteristics of the microlens used, but is preferably 1 or more and 3 or less, while the aspect ratio is 5 or less.
It is also confirmed that, when the value exceeds, the obliquely incident light reaches portions other than the corresponding pixel electrodes, and as a result, the microlens array does not work effectively.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a view showing a part of a cross section of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is a cross sectional view of an experimental microlens array substrate corresponding to the configuration of FIG. 1, and FIG. FIG. 4 is a graph showing the relationship between the aspect ratio d / x and the amount of light transmitted through the pixel electrode, and FIG. 5 is a diagram showing the optical path of incident light in FIG. FIG. 6 is a view showing an example, and FIG. 6 is a view showing a part of a cross section of a liquid crystal display device according to a second embodiment of the present invention. In the drawing, the same reference numerals as those in FIGS. 7 to 9 indicate the same components.

In FIG. 1, a microlens array 8 is formed on the surface of the transparent substrate 1a on the liquid crystal layer 2 side. The method of forming the microlens is the same as the conventional method. 9
In order to make it possible to set the distance between the microlens array 8 and the pixel electrode 3a at an arbitrary distance, and to smooth the surface on which the pixel electrode 3a and the wiring for the drive circuit are formed, they can be easily formed. This is a transparent intermediate layer provided between the microlens array 8 and the pixel electrode 3a. In the present embodiment, the transparent intermediate layer 9 is made of a thermosetting resin having a high light transmittance. The resin is applied on the microlens 8 and then cured to a desired thickness (in the case of the present embodiment, D), which is the same as the distance between the microlens array 8 and the pixel electrode 3a. In order to secure the thickness d, the step of applying and curing the resin may be repeated a plurality of times. After forming the transparent intermediate layer 9 having a desired thickness d and a smooth surface, a pixel electrode 3a, wiring for a driving circuit, and the like are formed on the surface of the transparent intermediate layer 9 on the liquid crystal layer 2 side. In this embodiment, the thickness of the transparent substrate 1a is 700 μm, the thickness d of the transparent intermediate layer 9 is 100 μm, the pitch x between the lenses of the microlens array 8 is 80 μm, and the aspect ratio d / x = 1.25. Is set.

The embodiment shown in FIG. 1 is described below with reference to FIGS.
Are set based on experiments described with reference to FIG. The purpose of the experiment was to obtain the relationship between the aspect ratio d / x and the amount of transmission through the pixel electrode 3a, and microlens array substrates having different aspect ratios d / x were prototyped. The microlens array substrate shown in FIG. 2 is a simplified version of the liquid crystal display device shown in FIG. 1, and transmits light having the same pitch y as the lens pitch x instead of the pixel electrodes 3 a and the wirings and elements 5. An opening 3a 'and a light-shielding portion 5' that does not transmit light are provided, and the transparent substrate 1b, the liquid crystal layer 2, the common electrode 3b, the deflecting plate 6, and the alignment film 7 are omitted.
In such a configuration, the thickness of the transparent substrate 1a is set to 700 μm.
m, the thickness d of the transparent intermediate layer 9 was set to 100 μm, and the pitch x between the microlenses was changed to 20, 50, 100, and 200 μm to produce four types of prototypes.

On the other hand, the microlens array substrate shown in FIG. 3 is a simplified version of the liquid crystal display device shown in FIG. 8 of the prior art, and, like FIG. Instead, an opening 3a 'through which light is transmitted and a light shielding portion 5' through which light is not transmitted are provided, and the transparent substrate 1b, the liquid crystal layer 2, the common electrode 3b, the deflecting plate 6, and the alignment film 7 are omitted.
The thickness of the transparent substrate 1a corresponding to the distance d between the microlens array 8 and the pixel electrode 3a is set to 800 μm, and the microlens pitch x =
One type provided with a microlens array 8 of 80 μm was prototyped.

The above five prototype aspect ratios d / x
Correspond to 5, 2, 1, 0.5 and 10, respectively. The area of the opening 3a 'corresponding to the pixel electrode 3a is fixed to 1/5 of the area of the microlens array 8, and the characteristics of the microlens array 8, such as the shape and the refractive index, are different from those of the microlens array 8. The light transmittance is set to be maximum according to the value of the interval pitch x.

FIG. 4 shows that the above-mentioned five types of microlens array substrates are irradiated with light from a fluorescent lamp scattered by a reflector, a scattering plate, etc., and the intensity of the transmitted light transmitted through the opening 3a 'is measured. 4 is a graph in which the light intensity when the aspect ratio d / x = 10 is plotted as 1. From this graph, when the aspect ratio d / x is 5 or less, the transmission amount is about twice or more as compared with the case of the related art in which the microlens array 8 is formed on the light source side A of the transparent substrate 1a. In addition, it can be seen that when the aspect ratio d / x is 1 or more and 3 or less, the transmission amount is 5 times or more as compared with the conventional case. However, the graph shown in FIG. 4 is an example when the above-described light source is used, and in the case of a scattered light source having another angular distribution, it is considered that the graph naturally has a slightly different value quantitatively. It can be easily estimated that the change in the transmission amount ratio with respect to the aspect ratio d / x is qualitatively the same regardless of the scattered light source having any angle distribution. As a result, by setting the aspect ratio d / x to 5 or less, incident light can be efficiently condensed on the pixel electrode 3a, and a liquid crystal display device having a screen that is at least twice as bright as the conventional one can be obtained. It becomes possible.

FIG. 5 shows an example of the optical path of the incident light in FIG. 1, and FIG. 5A shows a case where the incident light is perpendicular to the transparent substrate 1a. At this time, the incident light is collected by the microlens array 8, and most of the light passes through the pixel electrode 3a.
FIG. 5B shows a case where the incident light is scattered light. Since the aspect ratio d / x is set to 1.25 as described above, the value of the transmission amount ratio is large as shown in FIG. Most of the incident light is supplied to the pixel electrode 3 by the microlens array 8.
The light is effectively condensed on a, and is less likely to be reflected by wirings, elements, and the like 5. As described above, according to the present embodiment, the brightness of the liquid crystal screen is greatly improved as compared with the case where the microlens array 8 is not used, despite the simple configuration described above. At least 2 times more than when formed on the light source side A surface of the transparent substrate 1a.
It became possible to improve more than twice.

FIG. 6 shows a second embodiment of the present invention. In this embodiment, the pixel electrode 3a is provided on the surface of the transparent substrate 1b on the display screen side B on the liquid crystal layer 2 side, and the pixel electrode 3a and the transparent substrate 1a are provided.
The distance d from the microlens array 8 provided on the liquid crystal layer 2 side is set to 100 μm. This distance d is ensured by forming a transparent intermediate layer 9 with a transparent film interposed between the liquid crystal layer 2 and the transparent substrate 1a forming the microlens array 8. The pitch x between the lenses of the microlens array 8 is set to 50 μm, and the aspect ratio d / x is set to 2. According to the present embodiment,
Even when the incident light is scattered light as in the first embodiment, since the aspect ratio d / x is set to 2, the value of the transmission amount ratio is large as shown in FIG. Is effectively condensed on the pixel electrode 3a by the microlens array 8, and reflected by the wirings, elements, and the like 5 is significantly reduced. Therefore, the brightness of the liquid crystal screen can be improved at least five times or more than that of the related art without increasing the power consumption of the backlight with the simple configuration described above.

[0020]

As described above, according to the present invention, the microlens array in the liquid crystal display device is formed on the surface of the transparent substrate on the light source side on the liquid crystal layer side, and the size of the aspect ratio d / x is 5 or less. Thus, even if the incident light is scattered light, the incident light can be effectively focused on the pixel electrode with a simple configuration, and the amount of light transmitted through the pixel electrode can be reduced by the micro lens array. Is more than doubled as compared with the conventional configuration provided on the light source side surface of the transparent substrate on the light source side, so that a bright screen can be obtained without increasing the power consumption of the backlight.

[Brief description of the drawings]

FIG. 1 is a diagram showing a part of a cross section of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of an experimental microlens array substrate corresponding to the configuration of FIG.

FIG. 3 is a sectional view of an experimental microlens array substrate corresponding to the configuration of FIG. 8;

FIG. 4 is a graph showing a relationship between an aspect ratio d / x and an amount of light transmitted through a pixel electrode.

FIG. 5 is a diagram showing an example of an optical path of incident light in FIG.

FIG. 6 is a diagram showing a part of a cross section of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view of a conventional liquid crystal display device without using microlenses.

FIG. 8 is a cross-sectional view of a liquid crystal display device using a conventional microlens.

FIG. 9 is a diagram illustrating an example of an optical path of incident light in a conventional liquid crystal display device.

[Explanation of symbols]

1a, 1b: transparent substrate, 2: liquid crystal layer, 3a: pixel electrode,
3b: common electrode, 4: illumination light, 5: wiring, element, etc., 6 ...
Deflector, 7 ... Orientation film, 8 ... Micro lens array, 9 ...
Transparent intermediate layer, A: light source side, B: display screen side.

──────────────────────────────────────────────────続 き Continued on the front page (72) Munehisa Kishimoto 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Within Hitachi, Ltd. Production Engineering Laboratory (56) References JP-A-3-248125 (JP, A) 62-203126 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G09F 9/00-9/46

Claims (4)

(57) [Claims] 1. A light source, a pair of opposing transparent substrates on the light source side and the display screen side, and a micro-pitch formed at a constant pitch between lenses for condensing and passing irradiation light of the light source on the transparent substrate. A lens array, and a pixel electrode interposed between the transparent substrates and having a liquid crystal layer interposed therebetween and arranged in a matrix so as to receive light transmitted through the microlens array. In a liquid crystal display device for displaying an image by changing the amount of light passing through the liquid crystal layer, the microlens array is formed on a liquid crystal layer side surface of the transparent substrate on the light source side, and the formed microlens array is formed. And a distance d between the pixel electrodes and a pitch x between lenses of the microlens array.
The liquid crystal display device has a ratio d / x of 5 or less. 2. A light source, a pair of opposing transparent substrates on the light source side and the display screen side, and a micro-pitch formed at a constant pitch between lenses for condensing and passing irradiation light of the light source on the transparent substrate. A lens array, and a pixel electrode interposed between the transparent substrates and arranged in a matrix so as to receive light passing through the microlens array while interposing a liquid crystal layer, and applying a voltage to the pixel electrode. In a liquid crystal display device for displaying an image by changing the amount of light passing through the liquid crystal layer, the microlens array is formed on a liquid crystal layer side surface of the transparent substrate on the light source side, and the formed microlens array is formed. Forming a transparent intermediate layer between the pixel electrode and the pixel electrode, wherein the transparent intermediate layer can be set at an arbitrary distance between the two and the pixel electrode. A ratio d / x between a distance d of the lens and a pitch x between lenses of the microlens array is 5 or less. 3. The ratio d / x of a distance d between the microlens array and the pixel electrode to a pitch x between lenses of the microlens array is 1 or more and 3 or less.
Or the liquid crystal display device according to 2. 4. A first substrate having a plurality of pixel electrodes,
A second lens having a microlens array including a plurality of lenses;
Filling between the second substrate and the first substrate and the second substrate
A liquid crystal layer, the microlens array and the pixel
The distance d between the microlens array and the distance d
Formed so that the ratio d / x to the pitch x between the lenses is 5 or less.
A liquid crystal display device characterized in that: