JP2009271346A - Optical unit, backlight device, liquid crystal module, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical unit capable of suppressing deterioration of luminance and reducing luminance unevenness without increasing the number of light sources. <P>SOLUTION: The optical unit 5 for use in a backlight device 1 of a liquid crystal display including a plurality of optical members comprises a light-collecting and -diffusing means 6 having a protruding prism having a saw-teeth like section on one surface thereof, a first light-collecting and -diffusing means 7 having a plurality of hemisphere- or semi-oval-like microlenses on one surface thereof, a light collecting means 8 having a protruding prism having a saw-teeth like section on one surface thereof, and a second light-collecting and -diffusing means 9 having a plurality of hemisphere- or semi-oval-like microlenses 12 on one surface thereof, provided in this order on the optical path of light emitted from a light source 3. Each surface is provided on a light-emitting side of the optical unit, the light distribution half value angle of the first light-collecting and -diffusing means 7 is 2-15°, and the light distribution half value angle α of the second light-collecting and -diffusing means 9 is 8-25°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical unit, a backlight device, a liquid crystal module, and a liquid crystal display that can reduce the occurrence of luminance unevenness in a measurement area.

In recent years, liquid crystal displays have rapidly penetrated the market. Recently, the screen has become larger with the progress of technology.
Furthermore, since the installation property of the liquid crystal display is improved, the demand for thinning is increasing.

With an increase in the size of the display screen, luminance unevenness of the display screen is conspicuous, and improvement is desired.
As a main cause of occurrence of luminance unevenness in the display screen, there is a luminance distribution of illumination light of a backlight device that illuminates a liquid crystal display panel constituting the liquid crystal display.
Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for improving a backlight device in order to reduce the luminance unevenness of such a large-screen liquid crystal display.

Patent Document 1 generally describes as follows.
The backlight device is installed directly below the back surface of the liquid crystal display panel in order to supply illumination light to the liquid crystal display panel.
As shown in FIG. 18, the backlight device 101 described in Patent Document 1 includes a linear light source 102, a reflecting plate 103, and an optical unit 104, and the light source 102 is on one surface side of the reflecting plate 103. Is installed.
Further, in the optical unit 104, a diffusion plate 105, a first diffusion sheet 106, a condensing sheet 107, and a second diffusion sheet 108 are sequentially installed from the side close to the linear light source 102.

The first and second diffusing sheets 106 and 108 are provided with a light diffusing surface in which light diffusing particles are coated on the light emitting surface side of a light-transmitting sheet-like substrate.
The condensing sheet 107 is configured by a prism sheet in which a large number of prism portions having a condensing function are continuously arranged on the light emitting surface side of a translucent sheet-like base material.

  After the light emitted from the linear light source 102 is diffused by the diffusion plate 105 and the first diffusion sheet 106, the scattered light is diffracted by the light collecting sheet 107 so as to approach the direction orthogonal to the light collecting sheet 107, It is collected and emitted. Thereby, the brightness | luminance of a predetermined viewing angle direction is improved. Further, the second diffusion sheet 108 diffuses incident light and reduces luminance unevenness.

JP 2008-46601 A

By the way, in order to reduce the thickness of the liquid crystal display, it is necessary to shorten the distance from the center of the linear light source 102 to the diffusion plate 105 (H, hereinafter referred to as an optical unit distance).
However, in this conventional configuration, the optical unit distance H is about 15 mm. However, when the optical unit distance H is shortened, the luminance difference between the portion directly above the linear light source 102 and the other portion becomes large. Periodic luminance unevenness of illumination light emitted from the backlight device 101 occurs in the plane of the liquid crystal panel.

As a countermeasure, it is possible to reduce luminance unevenness by adding a plurality of optical sheets to the optical unit 104. However, adding a plurality of optical sheets causes an increase in cost and a decrease in luminance. .
Further, as another countermeasure, it is possible to reduce luminance unevenness while suppressing a decrease in luminance by increasing the number of linear light sources 102.
However, increasing the number of the linear light sources 102 leads to an increase in the number of circuit components and the like of the inverter board (not shown) of the driving unit of the liquid crystal panel in addition to the linear light sources 102. Will increase.
Further, in the countermeasure against luminance unevenness by adding the optical sheet and increasing the number of the linear light sources 102, the illumination light emitted from the backlight device 101 is in a direction orthogonal to the backlight device 101. Although the brightness unevenness is improved for the emitted illumination light, it cannot be said that the brightness unevenness is sufficiently improved for the illumination light emitted obliquely.
Further, in order to sufficiently improve the luminance unevenness with respect to the illumination light emitted in the oblique direction, it is necessary to add an additional optical sheet or increase the number of linear light sources 102. An increase in the number of the linear light sources 102 that causes a decrease in luminance causes an increase in cost and power consumption due to an increase in the number of parts of the circuit, which is not practical.

Therefore, an object of the present invention is to reduce luminance unevenness without reducing luminance even when a display screen of a liquid crystal display is enlarged.
Further, even when the distance between the linear light source 102 and the optical unit 104 is reduced and the liquid crystal display is thinned, the decrease in luminance is suppressed without increasing the number of the linear light sources 102, and luminance unevenness is reduced. The purpose is to reduce.
It is another object of the present invention to reduce luminance unevenness not only in a direction orthogonal to the backlight device 101 but also in illumination light emitted in an oblique direction.

In order to achieve the above object, the present invention has the following configurations 1) to 6).
1) In the optical unit 5 that is used in the backlight device 1 of the liquid crystal display and is composed of a plurality of optical members and transmits light from the light source 3 included in the backlight device 1, on the optical path of the light emitted from the light source 3, Scattering and condensing means 6 having a function to scatter incident light and having a saw-toothed cross-section prism on one surface, and a plurality of microlenses having a substantially hemispherical shape or a substantially semi-elliptical shape on one surface. Condensing / diffusing means 7, condensing means 8 having a sawtooth-shaped protrusion prism on one surface, and second condensing / diffusing means having a plurality of microlenses 12 that are substantially hemispherical or substantially semi-elliptical on one surface. 9 are sequentially arranged in this order, and each one surface is set as the light emission side of the optical unit, and the light distribution half-value angle of the first condensing diffusion means 7 is 2 degrees to 15 degrees. And the light distribution half-value angle α of the second light condensing and diffusing means 9 The optical unit 5 is characterized in that the angle is 8 degrees to 25 degrees.
2) In the optical unit 5 described in 1), the light emitted from the light source 3 is separated into two kinds of linearly polarized light on the optical path after passing through the second condensing and diffusing means 9. The optical unit 5 is provided with polarization separating means 16 that transmits the separated light in one linear polarization state and reflects the light in the other linear polarization state.
3) The optical unit 5 according to any one of 1) to 3), the light source 3, and the reflecting plate 4 disposed at a position facing the optical unit 5 with the light source 3 interposed therebetween. The backlight device 1 characterized by the above.
4) A liquid crystal module comprising: the backlight device 1 according to 3); and a liquid crystal panel 23 disposed at a position facing the light source 3 in the backlight device 1 with the optical unit 5 interposed therebetween. 19.
5) A liquid crystal display 20 comprising the liquid crystal module 19 according to 4) and a liquid crystal driving circuit for driving the liquid crystal module 19.

According to the present invention, even when the display screen of the liquid crystal display is enlarged, luminance unevenness can be reduced without lowering the luminance.
In addition, even when the distance between the linear light source and the optical unit is reduced and the liquid crystal display is thinned, the reduction in luminance is suppressed and the luminance unevenness is reduced without increasing the number of linear light sources. Can do.
Further, it is possible to reduce luminance unevenness not only in a direction orthogonal to the backlight device but also in illumination light emitted in an oblique direction.
In addition, since the number of linear light sources is not increased, there is no increase in the number of inverter board circuits in the drive unit, and an increase in cost and power consumption can be suppressed as much as possible.

Embodiments of an optical unit and a backlight device using the same according to the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a backlight device according to the present invention. FIG. 2 is a sectional view showing an example of the optical unit of the first aspect according to the present invention. FIG. 3 is a partial plan view and a partial cross-sectional view showing an embodiment of a diffusion plate with a prism according to the present invention. FIG. 4 is a partial plan view and a partial cross-sectional view showing an embodiment of an optical sheet with a microlens according to the present invention. FIG. 5 is a partial plan view and a partial cross-sectional view showing an example of another embodiment of the optical sheet with a microlens according to the present invention. FIG. 6 is a partial plan view and a partial cross-sectional view showing an example of still another embodiment of the optical sheet with microlenses according to the present invention. FIG. 7 is a schematic diagram showing a method for measuring the half-value distribution angle of the optical sheet with microlenses according to the present invention, and a diagram showing the measurement results. FIG. 8 is a partial plan view and a partial cross-sectional view showing an embodiment of the light collecting sheet with prism according to the present invention. FIG. 9 is a sectional view showing an example of the optical unit of the second mode according to the present invention. FIG. 10 is a partial sectional view showing an embodiment of the backlight device according to the present invention. FIG. 11 is a schematic view showing a method for evaluating the optical characteristics of the backlight device according to the present invention. FIG. 12 shows evaluation results of luminance unevenness by visual observation of the backlight device according to the present invention. FIG. 13 shows measurement results of luminance unevenness by the two-dimensional color luminance meter of the backlight device according to the present invention. FIG. 14 is a schematic diagram for explaining the occurrence of uneven brightness in the backlight device according to the present invention. FIG. 15 is a graph showing the angle dependence of the luminance unevenness of the backlight device according to the present invention. FIG. 16 is a perspective developed view showing a liquid crystal module according to the present invention. FIG. 17 is a perspective view showing a liquid crystal display according to the present invention.
Note that components having common functions are denoted by the same reference symbols throughout the drawings, and repeated descriptions of components once described are omitted.
Furthermore, sectional views, schematic views, and the like are schematic views, and ratios of dimensions and the like are exaggerated.

  First, as shown in FIG. 1, the backlight device 1 irradiates the liquid crystal display panel 2 with illumination light. Of the illumination light emitted from the light source 3 and the light source 3, the opposite direction to the liquid crystal display panel 2. A reflection plate 4 that reflects the light emitted to the liquid crystal display panel 2 and a plurality of plates that are disposed between the light source 3 and the liquid crystal display panel 2 and have a role of improving the display characteristics of the liquid crystal display panel 2 And an optical unit 5 made of a sheet-like or sheet-like optical member.

(Optical unit of the first form)
Next, reduction in luminance unevenness in the display area of the liquid crystal display panel 2 by the optical unit 5a according to the first embodiment of the present invention will be described with reference to FIGS. The brightness unevenness is in-plane unevenness of illumination light irradiated in the display area of the liquid crystal display panel 2.
As shown in FIG. 2, the optical unit 5a of the first embodiment is disposed between the light source 3 and the liquid crystal display panel 2 with a predetermined distance H (optical unit distance) from the light source 3. A diffusion plate 6 with prism and a first optical sheet 7 with a microlens that form a prism on the exit surface of illumination light from the side 3, and a condensing sheet 8 with prism that has a prism formed on one surface having a condensing function And the second optical sheet 9 with microlenses are arranged in this order.

As shown in FIG. 3, the diffusion plate 6 with a prism has a structure in which a prism is integrally formed on an illumination light exit surface of a sheet-like base material.
The diffusion plate 6 with a prism is molded using a material in which a light diffusing agent is dispersed in a transparent resin, or a mixture of two or more kinds of resins that are difficult to mix.
The transmittance and haze can be easily adjusted by changing the dispersion amount of the light diffusing agent or the mixing ratio of the resin.
Thereby, the diffusion plate 6 with a prism can improve the luminance distribution by scattering the light emitted from the light source 3 and the light reflected by the reflection plate 4.

The prism portion 10 formed on the sheet-like base material portion of the diffusion plate 6 with the prism includes a plurality of prisms having a plurality of protrusions that are parallel and equally spaced on the light emission surface. It has a shape.
In the prism, triangles are connected in a cross section obtained by cutting the diffusion plate 6 with a prism in a direction perpendicular to the longitudinal direction, and a V-shaped groove is formed by connecting the base angles of the triangles between the cross sections of the triangles. .
The light incident on the diffusion plate 6 with the prism is diffracted and condensed by the prism so that the direction of the emitted light approaches the direction orthogonal to the incident surface of the diffusion plate 6 with the prism.
The material forming the diffusion plate 6 with prism is made of a material having high transmittance because it is necessary to transmit the incident light beam.
Furthermore, it is desirable that the sheet-like base material 11 and the prism 12 are formed of the same material, and the reflection due to the difference in refractive index at the interface can be eliminated.

When the illumination light emitted from the light source 3 enters the diffusion plate 6 with prism, the illumination light is scattered inside the diffusion plate 6 with prism and reaches the prism unit 10.
In the prism unit 10, the illumination light having a predetermined angle is diffracted so as to approach a direction orthogonal to the incident surface of the diffusion plate 6 with prism, and is condensed and emitted from the prism unit 10. Illumination light incident at other angles is reflected a plurality of times by the prism unit 10, enters the substrate unit, is scattered again, and exits in the direction of the light source 3.
Therefore, the illumination light emitted in the direction of the liquid crystal display panel 2 from the diffusion plate 6 with prism is reduced in luminance unevenness and emitted when compared with the illumination light incident on the diffusion plate 6 with prism from the light source 3. Is closer to the direction orthogonal to the liquid crystal display panel 2.

As shown in FIG. 4, in the first and second optical sheets 7 and 9 with microlenses, a large number of microlenses 12 are two-dimensionally arranged on the side where the light on the sheet-like substrate 11 is emitted. .
The shape of the microlens 12 is a substantially hemispherical or substantially semi-ellipsoidal protrusion. Since both the sheet-like base material 11 and the microlens 12 need to transmit incident light, they are made of a material having a high transmittance. Furthermore, in order to control light distribution, a diffusing agent may be added as necessary.
In addition, it is desirable to use a material that can form the sheet-like base material 11 and the microlens 12 from the same material and can eliminate reflection due to a refractive index difference at the interface.
The optical sheets 7 and 9 with the first and second microlenses have optical functions such as condensing, refraction in the normal direction side, and diffusion by the plurality of microlenses 12 on the surface.
The microlenses 12 are densely arranged on the surface of the sheet-like base material 11. In order to make the best use of the condensing and diffusing effects of the microlenses 12, it is desirable to arrange the microlenses 12 on the sheet-like substrate 11 without any gaps.
As an example of a suitable arrangement, there is an arrangement in which the lines connecting the vertices of the microlenses 12 form a regular triangular lattice pattern, as shown in FIG.

As a more preferable example, as shown in FIG. 4, the substrate 11 of the microlens 12 when viewed from the light emission side.
There is an arrangement in which the diameter of the surface in contact with each of the microlenses 12 is changed.
In this case, a line connecting the vertices of each microlens 12 forms a random lattice pattern. According to this random pattern, it is possible to reduce the occurrence of moiré when the first and second optical sheets 7 and 9 with microlenses are superimposed on other optical members.
The arrangement of the microlenses 12 of the first and second optical sheets 7 and 9 with microlenses is not necessarily the same.

  Furthermore, as a more preferable example, as shown in FIG. 6, the microlens 12 is finely filled on the sheet-like base material 11, and the arrangement of the microlenses 12 having no flat portion on the light emission surface is used. When viewed from the exit surface, the tangent lines of the microlenses form a regular hexagonal lattice pattern. In this structure, there is no flat part, and the sheet-like base material 11 cannot be seen from the light exit surface.

The condensing characteristics of the optical sheets 7 and 9 with microlenses greatly influence the luminance characteristics and luminance unevenness characteristics of the liquid crystal display.
FIG. 7A shows a method for measuring the light condensing characteristics (light distribution characteristics) of the optical sheets 7 and 9 with microlenses.
The light distribution characteristics are measured by allowing parallel light to enter the optical sheets 7 and 9 with microlenses from a direction orthogonal to the surface of the optical sheets 7 and 9 with microlenses on the sheet-like base material 11 side, The goniophotometer 13 performs the light emitted from
The measurement of the luminous intensity I (θ) at each angle is performed at each position where the goniophotometer 13 is inclined from the position where the position orthogonal to the surface of the microlens 12 is 0 degree.
The goniophotometer 13 is an instrument that sets the incident angle of light incident on a measurement object to an arbitrary angle, automatically changes the light receiving angle, and analyzes the intensity distribution state of reflected light and transmitted light. Yes, the measurement of luminous intensity I (θ) in this example was performed using a variable angle photometer (GC5000L) manufactured by Nippon Denshoku Industries Co., Ltd.

FIG. 7B shows the measurement results of the light collection characteristics (light distribution characteristics) of the optical sheets 7 and 9 with microlenses.
The X axis in FIG. 7B is the light distribution angle of the goniophotometer 13, and the Y axis is the luminous intensity I (θ).
The θ-I (θ) curve connecting the luminous intensity I (θ) at each angle has a substantially normal distribution, and the angle of the light distribution angle at which the luminous intensity I (θ) is maximum is approximately 0 degrees. The angle at which the half value of the maximum value I (0) of the light intensity I (θ) of this curve is set as the light distribution half value angle α.

Next, as shown in FIG. 8, the light collecting sheet 8 with the prism includes a plurality of prisms 15 having a plurality of protrusions that are parallel and equally spaced on the light emission surface of the sheet-like base material 14. The cross section of 15 has a sawtooth shape.
The prism 15 has triangles in a cross section obtained by cutting the condensing sheet 8 with a prism in a direction perpendicular to the longitudinal direction, and the base angle of each triangle is connected between the cross sections of each triangle to form a V-shaped groove. ing.
The light incident on the condensing sheet 8 with the prism is diffracted and condensed by the prism 15 so that the direction of the emitted light approaches the direction orthogonal to the condensing sheet 8 with the prism.

The material for forming the condensing sheet 8 with the prism is formed of a material having a high transmittance because it is necessary to transmit the incident light rays as in the optical sheets 7 and 9 with the microlens.
Furthermore, it is desirable that the sheet-like base material 14 and the prism 15 be formed from the same material and the reflection due to the difference in refractive index at the interface can be eliminated.

Next, the optical path when the illumination light emitted from the light source 3 passes through the optical unit 5a of the first embodiment will be described.
The light source 3 used in the backlight device 1 as shown in FIG. 1 is generally a plurality of linear light sources 3, the difference depending on the position of the linear light source 3 and the direct light and the reflected light reflected by the reflector 4. Due to the difference in brightness, luminance unevenness and incident angle distribution are generated on the incident surface of the optical unit 5a of the first embodiment.

  The first embodiment having the diffusion plate 6 with prism, the optical sheet 7 with the first microlens, the condensing sheet 8 with the prism, and the second optical sheet 9 with the microlens configured as described above. The optical unit 5a transmits and collects light of a predetermined angle in the direction of the liquid crystal display panel 2 among the illumination light having the luminance unevenness and the incident angle distribution incident on the diffusion plate 6 with the prism from the light source 3, and otherwise. Is reflected a plurality of times within the diffusion plate 6 with prism and is reflected in the direction of the light source 3.

The light emitted from the diffusion plate 6 with prism in the direction of the liquid crystal display panel 2 is incident on the first optical sheet 7 with microlens, is transmitted in the direction of the liquid crystal display panel 2 and is emitted as condensed illumination light. Next, the light enters the light collecting sheet 8 with the prism, is diffracted so as to approach a direction orthogonal to the incident surface of the light collecting sheet 8 with the prism, and is condensed and emitted. The light emitted from the light collecting sheet 8 with the prism enters the second optical sheet 9 with the microlens, is transmitted in the direction of the liquid crystal display panel 2, and is emitted as the condensed illumination light.
Thereby, the luminance unevenness of the illumination light emitted from the second optical sheet 9 with microlenses is reduced.

Therefore, in the configuration of the optical unit 5a of the first embodiment, the illumination light with a wide incident angle is uniformly liquid crystal display by the condensing action of the two prisms 12 and 14 of the diffusion plate 6 with prism and the condensing sheet 8 with prism. The light can be emitted in the direction of the panel 2.
Therefore, conventionally, the optical unit 5a cannot be brought close to the linear light source 3 in terms of luminance unevenness, but the optical unit 5a is brought closer to the linear light source 3 by using the optical unit 5a of the first embodiment. Thus, the backlight device 1 and the liquid crystal display can be thinned.

(Optical unit of the second form)
Next, the optical unit 5b of the 2nd form is demonstrated using FIG.
As shown in FIG. 9, in the optical unit 5b of the second form, a polarization separation sheet 16 is disposed on the liquid crystal display panel 2 side of the second optical sheet with microlenses 9 of the optical unit 5a of the first form. This is the structure.

Since the optical unit 5a of the first embodiment includes the diffusion plate 13 and the plurality of prisms 7 and 13, the front luminance and the angle dependency of luminance may be reduced as compared with the conventional configuration.
Therefore, the polarization separation sheet 16 is added to the optical unit 5a of the first embodiment for the purpose of improving the luminance of the illumination light reaching the liquid crystal display panel 2 display unit.

  Here, the polarization separation sheet 16 selectively reflects the polarization component absorbed by the polarizing film located on the light source side of the liquid crystal display panel 2 in the incident illumination light using the light interference characteristic. By reusing, the luminance is improved without depending on the viewing angle.

Illumination light emitted from the second optical sheet with microlenses 9 is incident on the polarization separation sheet 16, and P-polarized component light that can be used in the liquid crystal display panel 2 among the incident light is transmitted and supplied to the liquid crystal display panel 2. The S-polarized component that is not used in the liquid crystal display panel 2 is reflected and returned to the direction of the light source 3.
The light reflected in the direction of the light source 3 is incident on the polarization separation sheet 16 again after the polarization direction is disturbed by scattering and reflection by the reflection plate 4, and the light of the P polarization component is supplied to the liquid crystal display panel 2.
Thus, the utilization factor of light is improved by reusing the reflected light.
The illumination light emitted from the polarization separation sheet 16 is a P-polarized component, and almost all light can be used in the liquid crystal display panel 2, so that the luminance in the display area of the liquid crystal display panel 2 is improved.

Hereinafter, an embodiment of the present invention will be described with reference to the backlight device 1 using the structure of the second optical unit 5b.
FIG. 10 is a partial cross-sectional view of the backlight device 1 using the second optical unit 5b.

  The backlight device 1 shown in FIG. 10 has a rectangular planar shape, a plurality of linear light sources 3, an optical unit 5b that improves characteristics such as luminance unevenness of illumination light emitted from the light sources, and emits light sources. The reflection plate 4 reflects the light emitted in the opposite direction to the optical unit 5b in the direction of the optical unit 5b, and the sheet metal 17 that fixes and holds the light source 3, the reflection plate 4, and the optical unit 5b.

Here, a plurality of cold cathode tubes, which are small fluorescent tubes having a small diameter of about 3 mm, were used as the light source 3.
The interval L between the light sources 3 was 24 mm, and the optical unit distance H, which is the distance from the center of the light source 3 to the surface closest to the light source of the optical unit 5b, was 5 mm.
Further, the reflecting plate 4 has a white surface, a surface facing the light source 3 is a flat surface, and is fixed to the sheet metal 17. The side surface of the reflection plate 4 is inclined so that the side of the optical unit 5b spreads in order to guide the light emitted from the light source 3 in the side surface direction toward the optical unit 5b.

  Furthermore, the optical unit 5b includes a diffusion plate 6 with a prism, a first optical sheet 7 with a microlens, a condensing sheet 8 with a prism, a second optical sheet 9 with a microlens, and a polarization from the side closer to the light source 3. The separation sheets 16 are disposed so as to be sequentially stacked in this order.

As the diffusion plate 6 with a prism, a plate having a thickness of 2 mm, a prism apex angle of 100 degrees, and a prism pitch of 70 μm was used.
As the first and second optical sheets 7 and 9 with microlenses, a structure having a plurality of lens diameters as shown in FIG. 4 and a thickness of 200 μm was used.
Here, by changing the lens diameter of the optical sheets 7 and 9 with the first and second microlenses between 40 and 80 μm and the lens height between 20 and 40 μm, the first and second microlenses are changed. The light distribution half-value angles α of the optical sheets 7 and 9 with lenses were prepared between 1 degree and 30 degrees.
Further, the diffusion plate 6 with prism is arranged so that the longitudinal direction of the prism is parallel to the longitudinal direction of the linear light source 3.

As the condensing sheet 8 with prism, a sheet having a thickness of 280 μm, a prism apex angle of 90 degrees, and a prism pitch of 50 μm was used.
As the polarization separation sheet 16, a sheet having a thickness of 400 μm and transmitting the P-polarized component of the incident light and reflecting the S-polarized component was used.
Further, the condensing sheet 8 with the prism was disposed so that the longitudinal direction of the prism was parallel to the longitudinal direction of the linear light source 3.

  As the first optical sheet 7 with a microlens, a light distribution half-value angle α adjusted between 1 degree and 20 degrees is selected, and as the second optical sheet 9 with a microlens, the light distribution half-value angle α is from 2 degrees. The second optical unit 5b is configured together with the diffusion plate 6 with prism, the condensing sheet 8 with prism, and the polarization separation sheet 16 by selecting the one adjusted between 30 degrees, and the backlight device 1 Install to.

FIGS. 11 to 13 show an evaluation method and an evaluation result of the angle dependency of the luminance unevenness of the backlight device 1 formed as described above.
The angle dependency of the luminance unevenness depending on the backlight device 1 does not affect the cut surface in the long side direction of the backlight device 1 (direction parallel to the line light source), and thus the cut surface in the short side direction (line light source). Measurement was performed only in the direction orthogonal to
In addition, the angle dependency of luminance unevenness and the angle dependency of luminance were evaluated by visual observation and the measurement method shown in FIG.

FIG. 11 shows a method for measuring the angle dependency of luminance unevenness, and a two-dimensional color luminance meter 18 is installed at a position facing the light source 3 of the optical unit 5b of the backlight device 1 at a distance from the opposite surface.
Assuming that the position where the two-dimensional color luminance meter 18 is orthogonal to the light exit surface of the backlight device 1 is 0 degree, the measurement of unevenness in the light exit surface of the backlight device 1 with brightness is the 0 degree position and the position. To the position where the two-dimensional color luminance meter 18 is inclined 45 degrees in the short side direction of the backlight device 1.
The two-dimensional color luminance meter 18 is a device that collectively performs luminance unevenness measurement and chromaticity unevenness measurement for various FPDs and backlights on a measurement target surface in a two-dimensional manner. The luminance unevenness of the backlight device 1 was measured using ProMetric 1400 manufactured by Radiant Imaging.

In FIG. 12, the visual evaluation result of the brightness nonuniformity of the backlight apparatus 1 in the 0 degree position is shown.
In FIG. 12, the degree of luminance unevenness when the first half-angle angle of light distribution of the optical sheet 7 with microlenses is 20 degrees and the half-value angle of light distribution of the second optical sheet 9 with microlenses is 8 degrees. Is a combination state in which the luminance unevenness decreases as “b”, “c”, “d”, and “e”.
As shown in FIG. 12, the luminance unevenness varies depending on the combination of the light distribution half-value angle α of the first optical sheet with microlenses 7 and the light distribution half-value angle α of the second optical sheet with microlenses 9. I understand.
In particular, a state where the degree of luminance unevenness was “d” was a good display state with little luminance unevenness. Further, when the degree of luminance unevenness is “e”, the luminance unevenness cannot be recognized.
Moreover, although the evaluation was performed at a position inclined at 45 degrees, the evaluation results were the same.

  Further, FIG. 13 shows the luminance unevenness value Im measured by the method shown in FIG. 11 using the two-dimensional color luminance meter 18 at the 0 degree position. This is because of the difference in the combination of the light distribution half-value angle α of the optical sheet 7 with the first microlens and the light distribution half-value angle α of the second optical sheet 9 with the microlens among the sheets constituting the optical unit 5b. Is the luminance unevenness value Im of the backlight device 1.

A method of calculating the luminance unevenness value Im from the measurement result of the luminance unevenness is as follows.
As shown in FIG. 11, in a plane perpendicular to each line direction of the linear light source 3, when the interval between the linear light sources 3 is L, an area (5L) corresponding to five linear light sources 3 is represented by n. Divide equally and measure each luminance I (k) to obtain an average luminance Iave. Is obtained from equation (1). Here, n corresponds to the number of pixels in one line in the sensor unit of the two-dimensional color luminance meter 18 corresponding to the 5 L region of the linear light source 3. That is, the number of divisions of the 5 L region of the linear light source 3 matches the number of corresponding pixels, and k is in the range of 1 to n.
The luminance distribution I (k) of the region (k = 1 to n) corresponding to the five linear light sources 3 is measured, and the average luminance Iave. Is obtained from equation (1). Next, the luminance of each position and the average luminance Iave. The dispersion luminance Iv, which is the average of the absolute values of the differences, is obtained from the equation (2), and the luminance unevenness value Im is obtained from the equation (3).
In actual measurement, since the region 5L corresponding to the five linear light sources 3 is measured by 330 pixels, the measurement is performed by dividing 5L into 330 equal parts.

From FIG. 12 and FIG. 13, it was found that when the luminance unevenness value Im is an area of 0.6 or less, the result of visual observation of the luminance unevenness is “d”, which is a favorable result with little luminance unevenness.
Further, the combination of the light distribution half-value angle α of the first microlens-equipped optical sheet 7 and the light distribution half-value angle α of the second microlens-equipped optical sheet 9 is the first microlens-equipped optical sheet 7. The light distribution half-value angle α was in the range of 2 to 15 degrees, and the light distribution half-value angle α of the second optical lens-attached optical sheet 9 was in the range of 8 to 25 degrees.

Furthermore, when the luminance unevenness value Im is in the region of 0.5 or less, the result of visual observation of the luminance unevenness is “e”, which indicates that the luminance unevenness cannot be recognized and is in an optimum state.
Further, the combination of the light distribution half-value angle α of the first microlens-equipped optical sheet 7 and the light distribution half-value angle α of the second microlens-equipped optical sheet 9 is the first microlens-equipped optical sheet 7. The light distribution half-value angle α was in the range of 2 to 15 degrees, and the light distribution half-value angle α of the second optical lens-attached optical sheet 9 was in the range of 10 to 20 degrees.

Again, luminance unevenness reduction will be described with reference to FIG.
FIG. 14A is a schematic diagram illustrating a state of typical luminance unevenness in the backlight device 1 with bad luminance unevenness at 0 degrees (luminance unevenness value Im> 0.6). FIG. 14B is a schematic diagram showing a typical luminance unevenness state in the backlight device 1 with good luminance unevenness at 0 degrees (luminance unevenness value Im <0.6).

The result of the backlight device 1 with poor luminance unevenness is that the combination of the light distribution half-value angles α of the optical sheet 7 with the first microlens and the optical sheet 9 with the second microlens of the optical unit 5b is not optimal. Luminance unevenness (Kmax−Kmin), which is the difference between the maximum amount (Kmax) of the emitted light emitted from the apparatus 1 and the minimum amount (Kmin) of the luminance, is large.
Further, the maximum amount of luminance (Kmax) of the irradiation light is a position directly above the linear light source 3, and the minimum amount of luminance (Kmin) is 12 mm (L) which is an intermediate position between the linear light source 3 and the linear light source 3. / 2).
On the other hand, in the backlight device 1 with good luminance unevenness, it can be seen that the luminance unevenness (Kmax−Kmin) is reduced as compared with the backlight device 1 with poor luminance unevenness.

As shown in the schematic diagrams of FIGS. 14A and 14B, in the combination of the light distribution half-value angles α of the first optical sheet 7 with a microlens and the second optical sheet 9 with a microlens of the present invention, The luminance distribution directly above the linear light source 3 is reduced as compared with a combination having poor luminance unevenness due to the influence of reflection, scattering and the like.
This is because the amount of light emitted from the illumination light from the linear light source 3 immediately above the linear light source 3 without being refracted by the optical unit 5b is reduced. On the other hand, the utilization factor (emitted light / incident light) of the light refracted by the optical unit 5 b in the illumination light from the linear light source 3 increases as it approaches the intermediate position of each linear light source 3.
Therefore, the unevenness of brightness of the illumination light emitted from the backlight device 1 reduces in-plane variation.

Next, the angle dependence of luminance unevenness will be described with reference to FIG.
FIG. 15A shows an example in which the angle of the two-dimensional color luminance meter 18 is set to 0 using the backlight device 1 (optical unit distance H = 5 mm) with good luminance unevenness (luminance unevenness value Im <0.6) of the present invention. It is a figure which shows the luminance distribution at the time of setting it to 45 degree | times.
The X axis in FIG. 15A indicates the position of the cut surface (the direction orthogonal to the line light source) in the short side direction of the backlight device 1, and S <b> 1 indicates that the two-dimensional color luminance meter 18 faces the backlight device 1. This corresponds to the position of the light source 3a in FIG. S2, S3, S4 and S5 correspond to 3b, 3c, 3d and 3e in FIG. 11, respectively.
The Y axis in FIG. 15 a) shows the luminance measured with the two-dimensional color luminance meter 18.

For comparison, FIG. 15B shows the measurement results of the angle dependence of the luminance unevenness of the backlight device 1 (the optical unit distance H is 5 mm) with poor luminance unevenness (luminance unevenness value Im> 0.6).
According to FIG. 15B, in the backlight device 1 with poor luminance unevenness, the luminance unevenness of the illumination light emitted from the backlight device 1 is measured at 45 degrees as in the case of the measurement result at 0 degrees. However, since the optical unit distance H is short, it turns out that it is in a bad state.
On the other hand, according to FIG. 15A, it can be seen that the luminance unevenness is reduced in the measurement result at 45 degrees as in the case of the measurement result at 0 degrees.

Furthermore, the liquid crystal module 19 and the liquid crystal display 20 using the backlight device 1 of the present invention will be described.
FIG. 16 is a perspective developed view showing a liquid crystal module 19 using the optical unit 5b of the present invention.
As shown in FIG. 16, the liquid crystal module 19 includes a backlight assembly 21 having a light source 3, a reflector 4 and a sheet metal 17, an optical unit 5b formed on the backlight assembly 21, and a panel for fixing the optical unit 5b. A chassis 22, a liquid crystal panel 23, and a bezel 24 for fixing the liquid crystal panel 23 are provided, and these are assembled by sequentially assembling them.

Further, as shown in FIG. 16, the optical unit 5b includes a diffusion plate 6 with a prism, an optical sheet 7 with a first microlens, a condensing sheet 8 with a prism, and a second microlens from the backlight assembly 21 side. The attached optical sheet 9 and the polarization separation sheet 16 are sequentially stacked.
The configuration of the optical unit 5b is an example, and the optical unit 5 can also be used in the configuration of the optical unit 5a of the first embodiment.

FIG. 17 is a perspective view of a liquid crystal display 20 using the backlight device 1 of the present invention.
The liquid crystal display 20 has an electric circuit such as a driving circuit for the liquid crystal panel 23 and an input / output terminal attached to the liquid crystal module 19 and is incorporated in a housing.

As described above, according to the present invention, even when the display screen of the liquid crystal display 20 is enlarged, luminance unevenness can be reduced without lowering the luminance.
In addition, even when the distance between the linear light source 3 and the optical unit 5 is reduced to 5 mm and the liquid crystal display 20 is thinned, the decrease in luminance is suppressed without increasing the number of the linear light sources 3, Brightness unevenness could be reduced.
Moreover, the luminance unevenness was able to be reduced not only in the direction orthogonal to the backlight device 1 but also in illumination light emitted in an oblique direction.
Further, since the number of the linear light sources 3 is not increased, there is no increase in the number of inverter board circuits in the drive unit, and an increase in cost and power consumption can be suppressed as much as possible.

It is sectional drawing which shows the Example of the backlight apparatus which concerns on this invention. It is sectional drawing which shows the Example of the optical unit of the 1st form which concerns on this invention. It is the fragmentary top view and fragmentary sectional view which show the Example of the diffusion plate with a prism which concerns on this invention. It is the fragmentary top view and fragmentary sectional view which show the Example of the optical sheet with a microlens which concerns on this invention. It is the fragmentary top view and fragmentary sectional view which show the Example of another form of the optical sheet with a microlens which concerns on this invention. It is the fragmentary top view and fragmentary sectional view which show the Example of another form of the optical sheet with a microlens which concerns on this invention. It is the schematic which shows the measuring method of the light distribution half value angle of the optical sheet with a microlens which concerns on this invention, and a figure which shows the measurement result. It is the partial top view and partial sectional view which show the Example of the condensing sheet | seat with a prism which concerns on this invention. It is sectional drawing which shows the Example of the optical unit of the 2nd form which concerns on this invention. It is a fragmentary sectional view which shows the Example of the backlight apparatus which concerns on this invention. It is the schematic which shows the evaluation method of the optical characteristic of the backlight apparatus which concerns on this invention. It is an evaluation result of the brightness nonuniformity by visual observation of the backlight device concerning the present invention. It is a measurement result of the brightness nonuniformity by the 2-dimensional color luminance meter of the backlight apparatus which concerns on this invention. It is the schematic explaining generation | occurrence | production of the brightness nonuniformity of the backlight apparatus which concerns on this invention. It is a graph which shows the angle dependence of the brightness nonuniformity of the backlight apparatus which concerns on this invention. It is a perspective development view showing a liquid crystal module concerning the present invention. It is a perspective view which shows the liquid crystal display which concerns on this invention. It is sectional drawing which shows the conventional backlight apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Backlight apparatus, 2 ... Liquid crystal display panel, 3 ... Light source, 4 ... Reflecting plate, 5 ... Optical unit, 5a ... Optical unit of 1st form, 5b ... Optical unit of 2nd form, 6 ... With prism Diffusion plate, 7 ... Optical sheet with first microlens, 8 ... Condensing sheet with prism, 9 ... Optical sheet with second microlens, 10 ... Prism section, 11 ... Sheet-like substrate, 12 ... Microlens , 13 ... Variable angle photometer, 14 ... Sheet-like substrate, 15 ... Prism, 16 ... Polarized light separating sheet, 17 ... Sheet metal, 18 ... Two-dimensional color luminance meter, 19 ... Liquid crystal module, 20 ... Liquid crystal display, 21 ... Backlight assembly, 22 ... Panel chassis, 23 ... Liquid crystal panel, 24 ... Bezel

Claims (5)

In an optical unit that is used in a backlight device of a liquid crystal display and includes a plurality of optical members, and transmits light from a light source that the backlight device has,
On the optical path of the light emitted from the light source,
Scattering and condensing means having a function of scattering incident light and having a ridged prism having a sawtooth cross section on one surface;
A first condensing and diffusing means having a plurality of microlenses that are substantially hemispherical or substantially semi-ellipsoidal on one surface;
Condensing means having a ridged prism with a sawtooth cross section on one side;
A second light condensing and diffusing means having a plurality of substantially hemispherical or semi-ellipsoidal microlenses on one surface;
Are arranged sequentially in this order,
Each said one surface is made into the light emission side of the said optical unit, the light distribution half value angle of the said 1st condensing diffusion means is 2-15 degrees, and the said 2nd condensing diffusion means A light distribution half-value angle α is 8 degrees to 25 degrees. The optical unit according to claim 1, wherein
On the optical path after the light emitted from the light source passes through the second condensing and diffusing means, the incident light is separated into two types of linearly polarized light, and the separated light of one linearly polarized state is separated. An optical unit comprising: a polarization separating unit that transmits and reflects light in the other linearly polarized state. The optical unit according to claim 1 or 2,
The light source;
A reflector disposed at a position facing the optical unit across the light source;
A backlight device comprising: The backlight device according to claim 3,
A liquid crystal module comprising: a liquid crystal panel disposed at a position facing the light source in the backlight device across the optical unit. A liquid crystal module according to claim 4,
A liquid crystal driving circuit for driving the liquid crystal module;
A liquid crystal display comprising:

Images