JP2001305306A - Collimating plate, lighting system and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collimating plate having superior collimating performance, a lighting system which emits collimated light having high luminance and high directivity and a liquid crystal display having a wide angle of a visual field. SOLUTION: The collimating plate has a lens substrate, plural microlenses arranged on one face of the lens substrate, circular light incident parts each having its center on the optical axis of the corresponding microlens, a light shielding layer formed on the other face of the lens substrate so as to cover the face except the light incident parts and, optionally, a diffuse reflection layer formed nearer the light incident face than the light shielding layer so as to cover the face except the light incident parts. The refractive index n of the lens substrate, the thickness t of the substrate, the diameter R of the light incident parts and the size Sr of the microlenses satisfy the expression Sr>=2t×tanθ+R (where θ=sin-1(1/n)).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of widening the viewing angle in a liquid crystal display device, and more particularly, to high collimation performance for realizing a wide viewing angle in a liquid crystal display.
Or a collimating plate with excellent light collimating performance,
The present invention relates to a lighting device using the collimating plate and a liquid crystal display device using the lighting device.

[0002]

2. Description of the Related Art In recent years, the use and frequency of a liquid crystal display (LCD) as a display of a word processor or a computer have been greatly increased. In addition, the use of LCDs is being considered as a monitor for medical diagnostic devices such as an ultrasonic diagnostic device, a CT diagnostic device, and an MRI diagnostic device, in which a CRT (Cathode Ray Tube) has conventionally been mainstream.

[0003] LCDs have numerous advantages, such as being easy to miniaturize, thin and lightweight. On the other hand, the viewing angle characteristics are poor (the viewing angle is narrow), that is, the contrast of the image is sharply reduced depending on the viewing direction and the angle, and the inversion of the gradation occurs, so that the appearance of the image is different. Therefore, there is a problem that the image cannot be properly observed depending on the position of the observer or the like.

In particular, in the above-mentioned medical applications, diagnosis is performed based on the density of the image, so that an image having a high contrast ratio is required. This may cause discrepancies in the diagnostic results. Therefore, in particular, in the case of a medical diagnostic image observed by a diagnostician such as a plurality of doctors, a display image having a high contrast ratio over a wide viewing angle is required. Further, in a medical monitor, a display image is usually a monochrome image, and thus the image contrast greatly depends on the viewing angle, which is more problematic.

As a method for widening the viewing angle of an LCD, collimated light (parallel light) is used as a backlight (collimated backlight), and light carrying an image passing through a liquid crystal display panel is diffused by a light diffusion plate. Known methods are disclosed in Japanese Patent Publication No. 7-7162,
No. 5099).

In this method, as the collimated light with high luminance and high directivity (small divergence angle) is used, L
It is possible to increase the viewing angle of a CD. Therefore, the collimating plate that converts the diffused light into the collimated light is required to be able to sufficiently condense the incident diffused light and to be able to use the light emitted from the light source with high efficiency.

Also, light (stray light) improperly emitted without passing through a predetermined optical path of the collimating plate causes display unevenness and image blur. In particular, in the above-mentioned medical use, display unevenness and image blurring can be a cause of erroneous diagnosis, and are therefore an important problem. That is, an optical collimator used for an LCD is required to have excellent collimating performance and to have less stray light, and a conventional collimating plate has not always obtained sufficient performance.

Further, a collimating plate used for an LCD for the purpose of widening the viewing angle can sufficiently collect incident diffused light and emit collimated light having high directivity and high brightness. There is a demand and it is desired to realize a collimating plate having better collimating performance, but it has not been realized yet.

[0009]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a collimating plate having excellent collimating performance capable of emitting collimated light with high luminance and high directivity, and a light use efficiency using the collimating plate. Lighting equipment that can emit collimated light with high brightness, high directivity,
Another object of the present invention is to provide a liquid crystal display device that can display an image with high contrast over a wide viewing angle using the lighting device.

A second object of the present invention is that, in addition to the first object, a collimating plate with less stray light, an illuminating device using the collimating plate, and display unevenness and image blur using the illuminating device. It is an object of the present invention to provide a liquid crystal display device capable of displaying an image having no image.

[0011]

In order to achieve the above first and second objects, a first aspect of the present invention provides a lens substrate and a plurality of microlenses arranged on one surface of the lens substrate. And a circular light incident portion having a center on the optical axis of the micro lens and set on the opposite surface to the micro lens, and the micro lens of the lens substrate so as to cover other than the light incident portion. A light-shielding layer formed on the opposite side, wherein the refractive index of the lens substrate is n, the thickness of the lens substrate is t, the diameter of the light incident portion is R, and the size of the microlens is Sr. And a collimating plate satisfying the following expression [1]. Sr ≧ 2t × tan θ + R (where θ = sin ⁻¹ (1 / n)) [1]

Here, in this collimating plate, it is preferable that the microlenses are circular when viewed from the optical axis direction, and are arranged in a close-packed manner, or when viewed from the optical axis direction. It is preferably hexagonal and arranged densely in hexagons.

In order to achieve the first and second objects, a second aspect of the present invention provides a lens substrate, a plurality of microlenses arranged on one surface of the lens substrate, and a microlens. A rectangular light incident portion having a center on the optical axis of the lens and set on the opposite surface to the micro lens, and formed on the opposite side of the lens substrate to the micro lens so as to cover other than the light incident portion. Wherein the refractive index of the lens substrate is n, the thickness of the lens substrate is t,
The length of one side of the light incident portion is A, the length of the other side of the light incident portion is B, the size of the micro lens in the side direction of the length A is Sa, and the side direction of the length B is When the size of the microlens is set to Sb, the following formulas [2] and [3] are satisfied. Sa ≧ 2t × tan θ + A [2] Sb ≧ 2t × tan θ + B (where θ = sin ⁻¹ (1 / n)) [3]

Here, in this collimating plate, the microlenses are preferably square when viewed from the optical axis direction, and are arranged in a square dense shape, or rectangular when viewed from the optical axis direction. And it is preferable that they are arranged densely in a rectangular shape.

Further, in order to achieve the first object,
According to a third aspect of the present invention, there is provided a lens substrate, a plurality of microlenses arranged on one surface of the lens substrate, and an optical axis of the microlens set on an opposite surface to the microlens of the lens substrate. And a light-shielding layer formed on the lens substrate on a side opposite to the microlenses so as to cover portions other than the light incident portions, and the shape of the microlens is represented by the following formula [4]. Part of the elliptical sphere shown,
The eccentricity ε of the ellipsoidal sphere is represented by the following equation [5], and the ellipsoidal sphere has a collimator plate whose focal point farther from the light emitting side coincides with the light incident part. To provide. x ² / a ² + y ² / a ² + z ² / c ² = 1 Equation [4] ε = (c ² −a ² ) ^1/2 / c = 1 / n Equation [5] (Equation [4] and In [5], x and y indicate the direction of the lens substrate surface, z indicates the direction of the optical axis, and n indicates the refractive index of the material forming the microlens.

Here, in this collimating plate, the microlenses are preferably circular when viewed from the optical axis direction, and are arranged in a close-packed manner, or when viewed from the optical axis direction. It is preferably hexagonal and densely arranged in hexagons.

Further, in the above-mentioned collimating plate according to the first, second and third aspects of the present invention, the diffusion formed on the light incident surface side of the light shielding layer so as to cover portions other than the light incident portion. It is preferable to have a reflective layer.

In the collimating plate according to each of the embodiments of the present invention, the refractive index of the lens substrate is 1.4 to
It is preferably 2.

In order to achieve the first and second objects, a fourth aspect of the present invention is directed to a light source, a lamp housing having an inner wall for housing the light source covered with a diffuse reflection layer, and a light source. An object of the present invention is to provide a lighting device having the collimating plate according to each aspect of the invention.

In order to achieve the first and second objects, a fifth aspect of the present invention is directed to a collimating plate according to each aspect of the present invention, and the collimating plate is provided for each of the light incident portions. And a plurality of light sources. In this lighting device, it is preferable that the light emission size of the light source is smaller than the size of the light incident portion, and the light source is an LED or an organic EL.
It is preferably an element.

In order to achieve the first and second objects, a sixth aspect of the present invention provides a liquid crystal display panel comprising:
It is another object of the present invention to provide a liquid crystal display device comprising: the lighting device according to each of the above aspects of the present invention, in which light is incident on the liquid crystal display panel. In this liquid crystal display device, it is preferable that the liquid crystal display device has a light diffusion plate for diffusing light carrying an image passing through the liquid crystal display panel.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A collimating plate, a lighting device and a liquid crystal display device according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 conceptually shows an embodiment of the liquid crystal display device according to the sixth aspect of the present invention. A liquid crystal display device (hereinafter, referred to as a display device) 10 shown in FIG. 1 is a so-called liquid crystal display (hereinafter, referred to as an LCD) that uses a liquid crystal display panel 12 as an image display means. Collimated light (parallel light) is applied to the liquid crystal display panel 12
Backlight unit 14 for inputting light, and liquid crystal display panel 12
And a light diffusion plate 16 for diffusing light carrying an image passing through the light diffusion plate 16.

In the illustrated example, a driver (not shown) for driving the liquid crystal display panel 12 is connected thereto. Further, the display device 10 of the present invention has an opening for image observation, and accommodates members such as the backlight unit 14, the liquid crystal display panel 12, the light diffusing plate 16, and the driver in a predetermined position. Known L, such as
Various members of the CD are arranged as needed.

The display device 10 is a transmissive LCD. In the display device 10, a normal transmissive LC is used.
Similarly to D, the collimated light (collimated backlight) emitted from the backlight unit 14 is incident on the liquid crystal display panel 12 driven according to the display image and passes therethrough to become light carrying an image. The light is diffused by the light diffusion plate 16 to display an image.

The backlight unit 14 includes the liquid crystal display panel 1
2 emits collimated light as a backlight for observing the displayed image.
, A (lamp) housing 20 and a light source 22. Here, the backlight unit 14 is the fourth unit of the present invention.
The lighting device according to the above aspect, therefore, the collimating plate 18
Is a collimating plate of the present invention.

The housing 20 is a rectangular housing that is open on one side. In the backlight unit 14 according to the lighting device of the fourth aspect of the present invention, light is reflected on the inner wall surface of the housing 20 by diffusing incident light.
A diffuse reflection layer 20a is formed. With such a configuration, the light emitted from the light source 22 is reflected by the inner wall surface of the housing 20 without being absorbed, and
Since the light can be incident on the collimating plate 18, high-luminance collimated light can be emitted. There is no particular limitation on the diffusion reflection layer 20a, and a coating material in which fine particles of a light diffusion material such as alumina (Al ₂ O ₃ ) or titanium oxide (TiO ₂ ) are dispersed is prepared and applied to the inner surface of the housing 20 to be formed. Various known materials such as a diffuse reflection layer can be used.

The light source 22 is housed in the housing 20. As the light source 22, any known light source used for a so-called transmissive LCD can be used as long as it has a sufficient amount of light.

The collimating plate 18 condenses light emitted from the light source 22 and light reflected on the inner wall surface of the housing 20 and emits the light as collimated light. The collimating plate 18 is arranged so as to close the opening of the housing 20. Is done.

FIGS. 2A and 3 show the collimating plate 1.
8 is schematically shown. As shown in both figures, the collimating plate 18 is a microlens array (hereinafter, referred to as a lens array) in which a large number of hemispherical microlenses 26a are two-dimensionally arranged on one surface of a plate-shaped lens substrate 24. Do) 2
6. The lens array 26 of the lens substrate 24
On the other side, that is, on the other surface, each micro lens 2
A circular light incident part 28 is set so that the center of the optical axis 6a coincides with the center (on-axis), and a light shielding layer 30 is formed so as to entirely cover the part other than the light incident part 28. Further, a diffusion reflection layer 32 that reflects light by diffusion is formed on the light incident surface so as to cover the entire surface except for the light incident portion 28.

The collimating plate 18 is used for the lens array 2
It is fixed to the housing 20 with the 6 side facing the liquid crystal panel 12. The light emitted from the housing 20 is shown in FIG.
As shown in (2), the light enters the lens substrate 24 from the light incident part 28, passes through, enters each micro lens 26a, is refracted and condensed, and is emitted as collimated light.

Further, since the light has a diffuse reflection layer 32, light incident on portions other than the light incident portion 28 is reflected without being absorbed, and is returned into the housing 20.
Is reflected by the diffuse reflection layer 20a of the
, The light use efficiency is high, and high-luminance collimated light can be emitted. Further, even if the light passes through the diffuse reflection layer 32, the light is shielded by the light shielding layer 30, so that the light does not become stray light that causes a decrease in directivity of the collimated light.

In such a collimating plate 18, the material of the lens substrate 24 and the lens array 26 is not particularly limited, and various materials used for the lens, such as glass and various optical resins, can be used. It should be noted that the lens substrate 24 and the lens array 26 may be integrally formed or fixed by combining separate members. Also,
The refractive index of the lens substrate 24 is not particularly limited, but is preferably 1.4 to 2 in terms of collimating performance and the like.

In the present invention (including an embodiment in which the light incident portion is rectangular as described later), the micro lens 26a
The shape is not limited to a hemisphere, but is a shape obtained by cutting a sphere on a plane that does not pass through the center (small side of the crown) or a shape obtained by cutting an ellipsoid (spheroid) on a plane perpendicular to the long axis (small side)
Can also be suitably used. In the present invention (same as above), the shape of the light exit surface of the micro lens 26a (= the shape of the boundary surface with the lens substrate 24), that is, the shape of the micro lens 26a when viewed from the optical axis direction is The shape is not limited to a circle, and various shapes such as a rectangle and a hexagon can be used.

The diffuse reflection layer 32 and the light shielding layer 30 are not particularly limited, and various known ones can be used. As an example, the diffuse reflection layer 32 is exemplified by the inner wall surface of the housing 20, and the light shielding layer 30 is exemplified by a paint containing chrome (Cr) or carbon black used for the BM of the liquid crystal panel 12. Is done.

The method of forming the diffuse reflection layer 32 and the light-shielding layer 30 is not particularly limited, either. The above-mentioned paint is prepared and applied according to the material or the like, a thin film forming technique such as vapor deposition, printing, or the like. May be created by a known method. In the case where these layers are formed by coating or forming a thin film, the light incident portion 28 may be formed using a known method, for example, a mask manufactured by a known method. In addition, the mask may be manufactured by self-alignment using a photoresist or the like using the microlens 26a.

The thicknesses of the diffuse reflection layer 32 and the light-shielding layer 30 are not particularly limited, and may be any thickness that can exhibit the necessary reflection performance and light-shielding performance according to the material of the formation. Here, if both layers are too thick, the angle of the light that can be incident on the light incident portion 28 becomes narrow, and the efficiency is reduced.

In the example shown in FIGS. 2A and 2B, the surface of the lens substrate 24 opposite to the lens array 26 is a flat surface, and the light incident portion 28 is set on this surface. Is not limited to this, and as shown in FIG. 4, the convex portion 24a is formed on the surface of the lens substrate 24 opposite to the lens array 26.
And the end face of the convex portion 24a may be used as the light incident portion 28. Such a convex portion 24a may be manufactured by a known molding method.

Here, in the collimator plate 18 of the present invention, as shown in FIGS. 2A, 2B and 3, the refractive index of the lens substrate 24 is n, and the thickness of the lens substrate 24 (light T is the length from the surface of the incident part 28 to the micro lens 26a, R is the diameter of the light incident part 28, and the micro lens 2
When the size of 6a is Sr (in the illustrated example, the diameter of the corresponding sphere because the microlens 26a is hemispherical), the following equation [1] Sr ≧ 2t × tan θ + R (where θ = sin ⁻¹⁾ (1 / n)) [1] is satisfied.

As shown in FIG. 2B, light incident on the lens substrate 24 at a certain incident angle φ ₁ is refracted, travels at an angle θ ₁ with respect to the optical axis, and enters the micro lens 26a. The light is refracted and emitted as collimated light. Here, the light incident portion 28 is set so that the center coincides with the optical axis corresponding to each micro lens 26a. Therefore, FIG.
As shown by a dotted line in (B), when light incident from a certain light incident part 28 enters an uncorresponding microlens 26a, this becomes stray light (leakage light), which reduces the collimating performance and reduces the liquid crystal. This causes image display unevenness and image blur.

The maximum incident angle φ of light is 90 °, and light incident at this angle travels at the largest angle θ. Angle θ at which light incident on a medium at an incident angle of 90 ° travels
Is, according to Snell's law, "θ = sin ^-1 (1 /
n) "(n is the refractive index of the medium). For example, if the material for forming the lens substrate 24 is acrylic, the refractive index n
Is 1.49, the angle θ is 42.16 °.

That is, as shown in FIG.
Of the lens substrate 24 having a thickness t
Is incident on the microlens array 26 at a maximum of “t tan θ + R / 2” with respect to the optical axis of the corresponding microlens 26a. Therefore, the size Sr of the micro lens 26a is set to “2t × tan θ + R”
In this case, the light incident from the light incident portion 28 must be
The light enters the corresponding micro lens 26a.

Therefore, the collimating plate of the present invention eliminates the stray light incident on the incompatible micro lens 26a,
A decrease in the directivity and efficiency of the collimated light due to this is prevented, and a component that was conventionally stray light can be emitted as collimated light, so that extremely high collimating performance can be exhibited. Also, as described above, the provision of the diffuse reflection layer 32 on the light incident surface allows emission of high-luminance collimated light with high light use efficiency.

The larger the projected area of the light incident on the microlens 26a, the more efficiently the collimated light can be emitted. Therefore, the size Sr is “2t × tan θ +
It is most preferable to make the same as "R", but a slight margin is required to reliably prevent stray light. Therefore, by setting the size Sr to be substantially the same, which is slightly larger than “2t × tan θ + R”, it is possible to use the micro lens 26a to the maximum and to emit the collimated light very efficiently, which is preferable.

For example, the lens array 26 and the lens substrate 2
4 are integrally molded, the forming material is acrylic (n = 1.49), and the thickness t of the lens substrate 24 is 300 μm.
m, when the diameter R of the light incident portion 28 is 50 μm, the size Sr of the microlens 26a may be 593.2 μm or more. For example, by setting the size Sr to 600 μm, collimated light is efficiently emitted. be able to. Alternatively, conversely, the size S of the micro lens 26a
r, the thickness of the lens substrate 24 and the light incident portion 28
May be selected or adjusted.

In this embodiment (an embodiment in which the light incident portion 28 is circular), the shape of the light exit surface of the micro lens 26a (the shape of the micro lens when viewed from the optical axis direction) is circular as shown in the illustrated example. As shown schematically in FIG. 2A and FIG. 5, the microlenses 26a are arranged so as to be arranged on one surface of the lens substrate 24 at the highest density, that is, to be closest-packed. Is preferred. As a result, the area where the collimated light cannot be emitted is
Only the gap between the microlenses 26a shown in black in FIG. 5 is present, and therefore, the emission area ratio of the collimated light to the lens substrate 24 is 90.7% (= π / (2 × [3
^1/2 ])), and a more efficient collimating plate can be obtained.

Alternatively, in this embodiment, as described above, the shape of the light emitting surface is hexagonal, and as shown schematically in FIGS. 6A and 6B, the hexagonal dense (honeycomb-like) micro It is also preferable to dispose the lens 26a.
As a result, the area where the collimated light cannot be emitted is as shown in FIG.
(B), there is only a region other than the circle inscribed in the hexagon shown in black, so that the emission area ratio of the collimated light with respect to the lens substrate 24 is 90.7% at maximum (= 3 ^1/2).
π / 6), and a more efficient collimating plate can be obtained.

In this embodiment, the micro lens 2
When the shape of the light emitting surface of the micro lens 26a is circular, the size Sr of the micro lens 26a is its diameter. When the shape of the light emitting surface of the micro lens 26a is other than circular, the size of the micro lens 26a is Sr is the diameter of a circle inscribed in the shape of the light exit surface.

In the example described above, the light incident portion 28 is circular, but the collimating plate according to the second embodiment of the present invention has a rectangular light incident portion. In this collimating plate, the length of one side of the rectangular light incidence portion is A, the length of the other side of the rectangular light incidence portion is B, and the length of the side corresponding to the length A of the microlens is The size is Sa, the size in the direction corresponding to the side of the length B of the microlens is Sb,
Otherwise, when the same as the above embodiment, the following formula [2]
And [3] Sa ≧ 2t × tan θ + A [2] Sb ≧ 2t × tan θ + B (where θ = sin ⁻¹ (1 / n)) [3]

Also in this embodiment, the rectangular light incident portion
The center (the intersection of the diagonal lines of the rectangle) is set to coincide with the optical axis of the microlens. Furthermore, the sizes Sa and Sb of the microlenses are the same as the direction of the light incident portion (the direction of rotation about the optical axis) and the ratio of the two adjacent sides is the same. It is the length of each side of the rectangle inscribed in the shape. That is, if the light incident portion is square, the length of the side of the square inscribed in the shape of the light exit surface of the microlens and in the same direction as the light incident portion is obtained. In addition, if the light incident portion is rectangular, the rectangular side inscribed in the shape of the light exit surface of the microlens in the same direction as the light incident portion and having the same ratio of the long side to the short side as the light incident portion is used. Length.

As in the above-described embodiment, according to the collimating plate of the present invention, stray light incident on an uncorresponding microlens is eliminated, and a decrease in the directivity and efficiency of the collimated light caused by this is prevented. Demonstrates very high collimation performance. Further, by having the diffuse reflection layer 32 on the light incident surface, high-luminance collimated light can be emitted with good efficiency.

The collimating plate has basically the same configuration as the above-described collimating plate having the circular light incident portion except that the shape of the light incident portion is rectangular. Mainly do the different things.

FIG. 7 schematically shows an example having a square light incident portion 34. In this example, the micro lens 3
Reference numeral 6 denotes a spherical crown shape obtained by cutting the sphere at a plane that does not pass through the center. The shape of the light emitting surface (the shape of the microlens when viewed from the optical axis direction) is the same as the direction of the light incident part 34. Is a square.

Here, in this collimating plate, both sides of the light incident portion 34 are equal in length, A = B, and therefore the size of the microlens is also Sa = Sb. That is, in this example, the expression “Sa ≧ 2t × tan θ + A”
Should be satisfied. In addition, the size Sa is set to “2t × tan θ”.
+ A ", which is preferably substantially the same.
This is the same as the previous embodiment.

In a collimator plate having a square light incident portion 34, the shape of the light exit surface of the microlens 36 is a square in the same direction as the light incident portion 34, as shown in FIG. It is preferable to dispose the micro lens 36 in the above. Thereby, the emission area ratio of the collimated light to the lens substrate 24 can be made close to 100% at the maximum, and a highly efficient collimating plate can be obtained.

FIG. 9 schematically shows an example having a rectangular light incident portion. In this example, the micro lens 39
Is a crown shape obtained by cutting the sphere on a surface that does not pass through the center. The shape of the light emitting surface (the shape of the microlens when viewed from the optical axis direction) is determined by the ratio of the long side to the short side and The direction is the same rectangle as the light incident part 38. Further, for example, the length of the long side of the rectangle is A, the length of the short side is B (A ≠ B), and the size of the light incident portion 38 of the micro lens 39 in the long side direction is S.
a, the size in the short side direction is Sb, and the above two equations are satisfied. Further, the sizes Sa and Sb are set to “Sa ≧ 2t”.
Similarly, it is preferable that they are substantially the same, which is slightly larger than “× tan θ + A, Sb ≧ 2t × tan θ + B”.

In the collimator plate in which the light incident portion 38 is rectangular, the shape of the light emitting surface is rectangular as shown in FIG. 8 with the same ratio of the long side and the short side as the light incident portion 38 and the same direction. Therefore, it is preferable to dispose the microlenses 39 in a rectangular shape. Thereby, the emission area ratio of the collimated light to the lens substrate 24 can be made close to 100% at the maximum, and a highly efficient collimating plate can be obtained.

Here, in the display device 10 of the present invention, the collimating plate of the third embodiment of the present invention can be used instead of the collimating plate 18. In FIG. 10A,
FIG. 6 schematically shows a collimating plate 19 according to a third embodiment of the present invention. The collimating plate 19 of the third embodiment of the present invention shown in FIG. 10A and the collimating plate 18 of the first embodiment of the present invention shown in FIG. Except that the shape of the microlenses 26a is hemispherical, whereas the shape of the microlenses 26b of the microlens array 26 of the collimating plate 19 is semispherical, the same components are included. ,
The same reference numerals are given and the detailed description is omitted.

As shown in FIG. 10 (A), the collimating plate 19 is, like the collimating plate 18, a micro-lens 26b two-dimensionally arranged on one surface of a plate-shaped lens substrate 24. It has an array 26. In the illustrated example, the micro lens 26 b
At the center of one axis, it has the shape of a semi-elliptical sphere cut in a plane perpendicular to this axis. This micro lens 26
The shape of b will be described later in detail.

The collimating plate 19 is a collimating plate 1
Similarly to 8, the lens array 26 is fixed to the housing 20 with the liquid crystal panel 12 facing the liquid crystal panel 12. As shown in FIG. 10A, the light emitted from the housing 20 enters the lens substrate 24 from the light incident part 28, passes through, enters the microlenses 26b, and is refracted and condensed. , And are emitted as collimated light. The operation will be described later in detail.

In such a collimating plate 19,
Similarly to the collimating plate 18, the lens substrate 24 and the lens array 26 may be integrally formed or fixed by combining and separating them. However, in terms of collimating performance and the like, both have the same refractive index. It is preferred that

In the example shown in FIGS. 10A and 10B, the surface of the lens substrate 24 opposite to the lens array 26 is a flat surface, and the light incident portion 28 is set on this surface. Is not limited to this, as shown in FIG.
The convex portion 2 is formed on the surface of the lens substrate 24 opposite to the lens array 26.
4a may be provided, and the end face of the convex portion 24a may be used as the light incident portion 28. Such a convex portion 24a may be manufactured by a known molding method.

Here, in the collimating plate 19 of the present invention, as shown in FIGS. 10A and 10B, the direction of the substrate surface of the lens substrate 24 is the x-axis and the y-axis, and the optical axis of the microlens 26b. When the direction (= normal direction of the lens substrate 24) is the z-axis, the shape of the microlens 26b is a part of an elliptical sphere in which the optical axis and the z-axis represented by the following equation [4] match, Further, assuming that the refractive index of the material forming the microlens 26b is n, the eccentricity ε of this elliptical sphere
Is represented by the following formula [5], and x ² / a ² + y ² / a ² + z ² / c ² = 1 formula [4] ε = (c ² −a ² ) ^1/2 / c = 1 / n Formula [5] Further, in this elliptical sphere, the focal point F on the far side (light incident side) from the side from which light is emitted coincides with the light incident portion 28, that is,
This focal point F coincides with the surface 24s of the lens substrate 24 on the side opposite to the microlenses 26b.

As is well known, the shape of an elliptical sphere (elliptical surface) is represented by the general formula: x ² / a ² + y ² / b ² + z ² / c ² = 1. The eccentricity of the ellipse is represented by the general formula ε = (a ² −b ² ) ^1/2 / a.

Accordingly, the eccentricity ε _xz and the focal position f _xz of the ellipsoidal sphere on the _xz plane are expressed as follows: ε _xz = (c ² −a ² ) ^1/2 / _{cf xz} = c × ε _xz Similarly, the eccentricity ε _yz and the focal position f _{yz in the yz} plane are represented by ε _yz = (c ² −b ² ) ^1/2 / c f _yz = c × ε _yz .

Here, in the case of a lens having an elliptical spherical shape, when the eccentricity ε is the reciprocal of the refractive index n of the lens-forming material, as shown by an arrow k in FIG. The light parallel to the optical axis converges on the focal point F farther from the light incident side. Therefore, as shown by an arrow m in FIG. 10B, the diffused light that has entered the focal point F is emitted from the lens as light parallel to the optical axis, that is, collimated light.

In the elliptical sphere, “ε _xz =
If “ε _yz ”, the focal position f _{xz in the xz} direction matches the focal position f _{yz in the yz} direction. Therefore, x
The length a in the axial direction and the length b in the y-axis direction are equal, that is, a = b, that is, the shape of the elliptical sphere is changed so that the diameters in the x-axis direction and the y-axis direction are 2a and the diameters in the z-axis direction. X ² / a ² + y ² / a ² + z ² / c ² =
1 ”, and the eccentricity ε of the elliptical sphere is set to“ ε = (c
² −a ² ) ^1/2 / c = 1 / n ”, the light incident on the lens and parallel to the optical axis is focused on the focal point F far from the incident side.
Conversely, the diffused light incident on the focal point F is collected and emitted as collimated light.

The collimating plate of this embodiment is based on the above findings. The shape of the plurality of microlenses 26b arranged on one surface of the lens substrate 24 is a part of an elliptical sphere satisfying the above conditions, Part 28 (micro lens 2
By making the lens substrate surface 24s) opposite to the side 6b coincide with the focal point F farther from the light emitting side, the diffused light can be condensed well and collimated light with high directivity can be emitted. it can. Further, by having the diffuse reflection layer 32 on the light incident surface, it is possible to emit high-luminance collimated light with high light use efficiency, and by having the light shielding layer 30,
As described above, generation of stray light can be prevented.

Such a collimating plate of the present invention uses, for example, a = [(n ² -1) ^1/2 / n] × cf = c / n derived from the above equation. Molding may be performed. For example, the lens array 26 (microlens 26b) and the lens substrate 24 are integrally formed, and the material for forming the same is acrylic (n).
= 1.49), and c of the micro lens 26b is 10
When it is 0 μm, a is 74.1 μm and f is 67.
The lens array 26 and the lens substrate 2 have a thickness of 1 μm.
4 may be formed.

The microlens 26b is not limited to a semi-elliptical spherical shape as shown in the figure as long as the microlens 26b satisfies the above conditions. Cut shapes (smaller sides) are also suitably available. Further, the shape of the light exit surface (boundary surface with the lens substrate 24) of the microlens 26b, that is, the shape of the microlens 26b when viewed from the optical axis direction is not limited to a circle, but may be a rectangle, a hexagon, or the like. Various shapes are available.

Here, in the present invention, FIG.
As shown in FIG. 5 and FIG. 5, the shape of the light exit surface of the microlens 26b is circular, and the microlenses 26b are arranged on one surface of the lens substrate 24 at the highest density, that is, the microlenses 26b are closely packed. 26b is preferably arranged. As a result, the area where the collimated light cannot be emitted is the micro lens 26 shown in black in FIG.
b, so that the emission area ratio of the collimated light to the lens substrate 24 is 90.7% at maximum (= π / π
(2 × [3 ^1/2 ])), and a more efficient collimating plate can be obtained.

Alternatively, as schematically shown in FIGS. 12 (A) and 12 (B), it is preferable that the shape of the light emitting surface is hexagonal and the microlenses 26b are arranged in a hexagonal close-packed (honeycomb) shape. As a result, the area where the collimated light cannot be emitted is only the area outside the circle inscribed in the hexagon shown in black in FIG.
The maximum emission area ratio of the collimated light to the lens substrate 24 can be 90.7% (= 31 ^/ 2π / 6),
A more efficient collimating plate can be obtained.

The shape of the light incident portion 28 is not limited to a circle whose center in the illustrated example coincides with the optical axis (z-axis) of the microlens 26b. Shape. There is no particular limitation on the size of the light incident portion 28, but a smaller size is advantageous in collimating performance, and a larger size is more advantageous in light use efficiency. Therefore, the size of the light incident portion 28 may be appropriately determined according to the use and size of the collimating plate, the size of the microlens, the required collimating performance, the brightness of the collimated light, and the like.

As described above, in the display device 10,
The fourth aspect of the present invention utilizing the collimating plate of each aspect of the present invention.
The collimated light (collimated backlight) emitted from the backlight unit 14 according to the illumination device of the above aspect enters the liquid crystal display panel 12 (hereinafter, referred to as the display panel 12).

In the display device 10 of the present invention, the display panel 12 is a known liquid crystal display panel used for various LCDs. As an example, a display panel having a liquid crystal layer filled with liquid crystal between two glass substrates and having a polarizing plate disposed on the opposite sides of the liquid crystal layers of both glass substrates is exemplified. Further, between the glass substrate and the polarizing plate, various optical compensation films such as a phase compensation film may be arranged as necessary.

Therefore, the display panel 12 may be color or monochrome, and may include a type of liquid crystal, a liquid crystal cell, and a TFT (Thin).
There is no particular limitation on a driving means (switching element) such as a film transistor, a black matrix (BM), or the like. The operation modes are also TN (Twisted Nematic) mode, STN (Super Twisted Nematic) mode, ECB (El
ectrically Controlled Birefringence) mode, IP
S (In-Plane Switching) mode, MVA (Multidomain V
All modes of operation, such as an Alignment mode, are available.

Light incident on and passing through the liquid crystal panel 12 becomes light for carrying an image, is diffused by the light diffusion plate 16, and is observed by an observer. A collimated backlight is used, that is, a collimated light is used as a backlight, and light carrying an image passing through the liquid crystal panel 12 is transmitted to the light diffusing plate 16.
As described above, it is possible to widen the viewing angle of the LCD by diffusing the light.

In the display device 10 of the present invention, the light diffusing plate 16 is not particularly limited, and various known light diffusing plates (light diffusing sheets) can be used.
JP-A-7-5306 discloses a light diffusion plate having a transparent electron conductive layer between the transparent support and the light diffusion layer
And a light diffusion plate having a layer of a cross-linked body of an ion conductive resin having a cationic quaternary ammonium base in a side chain between a transparent support and a light diffusion layer disclosed in Japanese Patent Application Laid-Open Publication No. H11-15064. .

In the display device 10 of the illustrated example, as a preferred embodiment, the light diffusing plate 16 schematically shown in FIG.
Is used. The light diffusing plate 16 includes two hemispherical microlenses 42 a on one surface of a plate-shaped lens substrate 40.
A plurality of dimensionally arranged microlens arrays 42 are formed, and the other surface of the lens substrate 40 opposite to the lens array 42 is provided with the entire surface except for the light emitting portion 44 set on the optical axis of each microlens 42a. A light-shielding layer 46 is formed so as to cover the surface, and an anti-reflection (AR) layer 48 is similarly formed on the observation surface side of the light-shielding layer 46. FIG. 2 (A),
As is apparent from FIG. 13B and FIG. 13, the light diffusing plate 16 has basically the same configuration as the above-described collimating plate 18 except that an anti-reflection layer 48 is formed in place of the diffusion reflecting layer 32. It has.

The light diffusing plate 16 is arranged with the lens array 42 side facing the liquid crystal panel 12. In the light diffusion plate 16, the light carrying the image (collimated light), which has passed through the liquid crystal panel 12, is incident on the microlens 42 a and is refracted, contrary to the operation of the collimator plate 18. The light is diffused and emitted from the light emitting section 44 as diffused light. On the other hand, the light (stray light) incident on portions other than the light emitting portion 44 is shielded by the light shielding layer 46, and thus does not hinder observation. In a preferred embodiment, since the antireflection layer 48 is formed on the observation surface side, good image observation is possible. The antireflection layer 48 is not particularly limited, and various known ones can be used.

As a preferred example other than the light diffusion plate 16 in the illustrated example, instead of the hemispherical micro lens 42a,
There is also exemplified a light diffusion plate in which a number of beads are fixed to the support sheet by using light-transmitting spheres (beads) such that a part of the beads is in contact with the transparent support sheet.

Here, in the present invention, in the display device 10 shown in FIG.
Instead of the backlight unit 14 according to the lighting device of the fourth aspect of the present invention using 8 or 19, the backlight units 15a and 15b according to the lighting device of the fifth aspect of the present invention can also be used. .

FIGS. 14 and 15 schematically show backlight units 15a and 15b according to a lighting device of a fifth embodiment of the present invention. Backlight parts 15a and 15 according to a lighting device according to a fifth embodiment of the present invention shown in FIGS.
b, the diffuse reflection layer 32 is removed from the collimator plate 18 of the first and second embodiments of the present invention shown in FIG. 2A and the collimator plate 19 of the third embodiment shown in FIG. 10A, respectively. In the collimator plates 18a and 19a, a light source 23 smaller than the size of the concave opening 29, such as a point light source, is disposed for each opening 29 forming a light incident portion 28 formed of a concave portion surrounded by the light shielding layer 30. . For this reason,
The collimating plates 18a and 19a used for the backlight portions 15a and 15b of this embodiment are respectively shown in FIG.
The collimator plate 18 shown in FIG. 10A and the collimator plate 19 shown in FIG. 10A have the same configuration except that they do not have the diffuse reflection layer 32. Have the same reference numerals and their description is omitted.

The light source 23 is preferably smaller than the size of the concave opening 29 and can be inserted into the concave opening 29. The light emission size of the light source 23 is
9 (light incident portion 28). Examples of such a light source 23 include an LED and an organic EL element. By doing so, the emitted light (light source light) from the light source 23 can be efficiently incident only on the light incident portion 28 of the lens substrate 24 of the collimating plates 18a and 19a, and the collimated light can be further efficiently used. Can be generated and emitted.

In this case, the light emitted from the light source 23 is
Since there is little or no leakage from the opening 29, like the backlight unit 14 shown in FIG.
In order to prevent the light emitted from the light source 23 from leaking and to increase the utilization efficiency of the light source light, the collimator plates 18a and 19a
It is not necessary to attach the housing to the lens substrate 24 side, but a plate (not shown) for disposing the small light source 23 corresponding to the plurality of concave openings 29 is provided on the collimating plate 1.
8a or 19a may be attached to the lens substrate 24 side.
By doing so, it is possible to generate and emit collimated light with even higher utilization efficiency. At this time, the surface of the plate (not shown) on the light source 23 side may be a diffuse reflection surface.

As described above, in the collimator plates 18a and 19a used for the backlight portions 15a and 15b of this embodiment, the light source 2 is provided for each opening 29.
The arrangement of 3 is for the purpose of improving the efficiency. The light emitting size of the light source 23 is preferably smaller than the opening size of the opening 29 for the efficiency. This is because most of the light emitted from the light source 23 enters the lens array 26. Therefore, as shown in the illustrated example, the light emission size of the light source
9, the collimator plates 18a and 19a
It is not necessary to provide a diffuse reflection layer as in the above. In addition, since the diffuse reflection layer of the collimator plate has little relation to the collimation performance, the collimation performance is not impaired even if the diffusion reflection layer is not provided.

In the backlight portions 15a and 15b of the present embodiment, when the light source whose light emission size is larger than the opening size of the opening 29 of the collimating plate is used as the small light source 23, the effect of the diffuse reflection layer is recognized. So that the collimator plates 18a and 19a without the diffuse reflection layer
Instead of the collimating plate 18 shown in FIG. 2A and the collimating plate 1 shown in FIG.
9 is preferably used. In particular, as shown in FIG. 1, when combined with a lamp housing, the collimator plates 18 and 19 having a diffuse reflection layer are in a preferred form for improving light use efficiency, that is, for achieving higher luminance.

The first and second embodiments of the present invention shown in FIG.
In the collimator plate 18 of the third embodiment and the collimator plate 19 of the third embodiment shown in FIG. 11, or in a collimator plate (not shown) in which the diffuse reflection layer 32 is removed therefrom, the light shielding layer 30 and the diffuse reflection layer 32 Or a light source 23, preferably in the vicinity of a light incident part 28 formed on a convex part 24a of the lens substrate 24 surrounded by only the light shielding layer 30;
By arranging the light source 23 having a size equal to or smaller than the size of the light incident portion 28, the collimated light is generated and emitted with even higher utilization efficiency as in the backlight portions 15a and 15b shown in FIGS. be able to. At this time, the light source 23 is particularly preferably a light source that emits light having high directivity, and a plate or housing (not shown) for arranging the plurality of small light sources 23 is attached to the collimator plates 18 and 19 on the lens substrate 24 side. good. Also in this case, when the light emission size of the light source 23 is smaller than the size of the light incident portion 28 of the collimator plate, a collimator plate without a diffuse reflection layer may be used. Can use collimator plates (18 and 19) without a diffuse reflection layer.

Although the collimating plate, the lighting device and the liquid crystal display device of the present invention have been described in detail with reference to various embodiments, the present invention is not limited to the above embodiments.
Of course, various improvements and changes may be made without departing from the spirit of the present invention.

[0090]

As described in detail above, the collimating plates according to the first and second embodiments of the present invention have excellent collimating performance that can emit collimated light with high luminance and high directivity with little stray light. Is a collimating plate having Further, the lighting device of the present invention using this collimating plate has high light use efficiency, and can emit collimated light with high luminance and high directivity. Furthermore, the liquid crystal display device of the present invention using this lighting device has no display unevenness or image blur,
In addition, a high-contrast image can be displayed over a wide viewing angle.

As described in detail above, the collimating plate according to the third embodiment of the present invention is a collimating plate having high collimating performance and capable of emitting collimated light with high luminance and high directivity. Further, the lighting device of the present invention using this collimating plate has high light use efficiency, and can emit collimated light with high luminance and high directivity. Further, the liquid crystal display device of the present invention using this lighting device can display a high-contrast image over a wide viewing angle without display unevenness or image blur.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view of one embodiment of a liquid crystal display device of the present invention.

FIG. 2A is a conceptual cross-sectional view of an embodiment of the collimator plate of the present invention, and FIG. 2B is a conceptual cross-sectional view for explaining the collimator plate of the present invention.

FIG. 3 is a conceptual perspective view for explaining a collimating plate of the present invention.

FIG. 4 is a conceptual cross-sectional view of another embodiment of the collimating plate of the present invention.

FIG. 5 is a schematic plan view of one embodiment of a microlens array used for the collimator plate of the present invention.

FIG. 6A is a schematic perspective view of another embodiment of the microlens array used for the collimating plate of the present invention,
(B) is a schematic plan view thereof.

FIG. 7 is a conceptual perspective view for explaining an example of the second embodiment of the collimating plate of the present invention.

FIG. 8 is a schematic perspective view of one embodiment of a microlens array used for the collimator plate shown in FIG.

FIG. 9 is a conceptual perspective view for explaining another example of the second embodiment of the collimating plate of the present invention.

FIG. 10A is a conceptual cross-sectional view of one embodiment of the collimating plate according to the third aspect of the present invention, and FIG. 10B is a conceptual perspective view for explaining the collimating plate of the present invention. is there.

FIG. 11 is a conceptual diagram of another embodiment of the collimating plate of the present invention.

FIG. 12A is a schematic perspective view of another example of the microlens array used for the collimator plate of the present invention,
(B) is a figure which shows the plane typically.

13 is a conceptual cross-sectional view of one embodiment of a light diffusion plate of the liquid crystal display device shown in FIG.

FIG. 14 is a conceptual cross-sectional view of one embodiment of a lighting device according to another aspect of the present invention.

FIG. 15 is a conceptual cross-sectional view of another embodiment of a lighting device according to another aspect of the present invention.

[Explanation of symbols]

 Reference Signs List 10 liquid crystal display device 12 (liquid crystal) display panel 14, 15 backlight unit 16 light diffusion plate 18, 19 collimation plate 20 housing 20a, 32 diffuse reflection layer 22, 23 light source 24, 40 lens substrate 24a convex portion 26 (micro) lens Array 26a, 26b, 36, 39 Microlens 28, 34, 38 Light incident part 29 Opening 30, 46 Light shielding layer 48 Antireflection layer

Claims (14)

[Claims] 1. A lens substrate, a plurality of microlenses disposed on one surface of the lens substrate, and a circular shape having a center on an optical axis of the microlens and set on a surface opposite to the microlens. A light incident portion, and a light shielding layer formed on the lens substrate on a side opposite to the microlenses so as to cover portions other than the light incident portion, wherein the refractive index of the lens substrate is n, and the thickness of the lens substrate is n. A collimator plate that satisfies the following formula [1], where t is t, the diameter of the light incident portion is R, and the size of the microlens is Sr. Sr ≧ 2t × tan θ + R (where θ = sin ⁻¹ (1 / n)) [1] 2. The microlenses are circular when viewed from the optical axis direction and are arranged in a close-packed manner, or are hexagonal when viewed from the optical axis direction and are arranged in a hexagonal close-packed manner. The collimating plate according to claim 1, wherein 3. A lens substrate, a plurality of microlenses disposed on one surface of the lens substrate, and a rectangular shape having a center on the optical axis of the microlens and set on a surface opposite to the microlens. A light incident portion, and a light shielding layer formed on the lens substrate on a side opposite to the microlenses so as to cover portions other than the light incident portion, wherein the refractive index of the lens substrate is n, and the thickness of the lens substrate is n. T, the length of one side of the light incident portion is A, the length of the other side of the light incident portion is B, the size of the micro lens in the side direction of the length A is Sa, and the length is A collimating plate characterized by satisfying the following expressions [2] and [3] when the size of the micro lens in the side direction of B is Sb. Sa ≧ 2t × tan θ + A [2] Sb ≧ 2t × tan θ + B (where θ = sin ⁻¹ (1 / n)) [3] 4. The microlenses are square when viewed from the optical axis direction and are arranged in a square-dense manner, or are microscopic when viewed from the optical axis direction and are arranged in a rectangular and densely-spaced manner. The collimating plate according to claim 3, wherein 5. A lens substrate, a plurality of microlenses disposed on one surface of the lens substrate, and a light incident portion which is set on the surface of the lens substrate opposite to the microlens and includes an optical axis of the microlens. And a light-shielding layer formed on the lens substrate on a side opposite to the microlenses so as to cover portions other than the light incident portion, and the shape of the microlenses is an elliptical sphere represented by the following formula [4]. And the eccentricity ε of the ellipsoidal sphere is represented by the following equation [5], and the ellipsoidal sphere is characterized in that the focal point farther from the side from which light is emitted coincides with the light incident part. Collimating plate. x ² / a ² + y ² / a ² + z ² / c ² = 1 Equation [4] ε = (c ² −a ² ) ^1/2 / c = 1 / n Equation [5] (Equation [4] and In [5], x and y indicate the direction of the lens substrate surface, z indicates the direction of the optical axis, and n indicates the refractive index of the material forming the microlens. 6. The microlenses are circular when viewed from the optical axis direction and are arranged in a close-packed manner, or are hexagonal when viewed from the optical axis direction and are arranged in a hexagonal close-packed manner. The collimating plate according to claim 5, wherein: 7. The collimating plate according to claim 1, further comprising: a diffuse reflection layer formed on a light incident surface side of the light shielding layer so as to cover a portion other than the light incident portion. A collimating plate comprising: 8. The collimating plate according to claim 1, wherein said lens substrate has a refractive index of 1.4 to 2. 9. An illuminating device comprising: a light source; a lamp housing in which an inner wall for accommodating the light source is covered with a diffuse reflection layer; and the collimating plate according to claim 1. 10. An illuminating device comprising: the collimating plate according to claim 1; and a plurality of light sources arranged for each light incident portion of the collimating plate. 11. The lighting device according to claim 10, wherein a light emission size of the light source is smaller than a size of the light incident part. 12. The lighting device according to claim 10, wherein the light source is an LED or an organic EL element. 13. A liquid crystal display device comprising: a liquid crystal display panel; and the illuminating device according to claim 9, wherein light is incident on the liquid crystal display panel. 14. The liquid crystal display device according to claim 13, further comprising a light diffusing plate for diffusing light carrying an image passing through said liquid crystal display panel.