The present invention relates to an illumination apparatus, a method for illuminating, and a display apparatus capable of controlling an emerging light angle, and in particular to a thin and highly visible illumination apparatus, a backlight for a display apparatus, and also a display apparatus comprising the illumination apparatus.
Recently, display panels are widely used in large terminals such as televisions, mid-sized terminals such as notebook-sized personal computers and cash dispensers, and also in small sized terminals such as mobile telephones and portable game machines. In particular, display apparatuses using liquid crystal display panels have advantages such as being thin and lightweight with low power consumption, and are mounted in many terminal devices.
Conventionally, a narrow viewing angle was considered to be one disadvantage of liquid crystal display panels; but in-plane switching methods, vertical alignment modes, and the like have become practical; and currently, wide viewing angle displays are possible. Liquid crystal display panels capable of wide viewing angle displays are mounted not only in large terminals such as televisions, but even in portable/small sized terminals (mobile telephones, portable game machines, etc.) used for viewing by multiple persons and information sharing despite compact sizes. On the other hand, display apparatuses with narrow viewing angles are desirable for such portable/small sized terminals and mid-sized terminals (notebook-sized personal computers, cash dispensers, etc.) to provide privacy and confidentiality. Therefore, a display apparatus capable of switching between a narrow viewing angle display and a wide viewing angle display, i.e., a display apparatus capable of switching a viewing angle (viewing angle control), is desirable.
A liquid crystal display apparatus comprising an illumination apparatus according to Patent Literature 1 is an example of a display apparatus capable of a viewing angle control such as that recited above. The conventional viewing angle control liquid crystal display apparatus according to Patent Literature 1 comprises a liquid crystal display device, a scattering control device (scattering control means), and an illumination apparatus; and the scattering control device is arranged between the liquid crystal display device and the illumination apparatus.
In the conventional illumination apparatus according to Patent Literature 1 thus configured, an emerging light angular distribution of light emerging from the irradiation unit 121 is made narrow (highly parallel light) by the sheet with light shielding slits 120, after which the emerging light angular distribution is controlled (controlled into highly parallel emerging light and scattered light) by the scattering control device (scattering control means) 126. In other words, the scattering control device 126 controls the scattering of incident beams according to an existence or absence of an applied electrical potential; and therefore when the scattering control device 126 is in a scattering state, the light emerging from the scattering control device 126 is light of a wide viewing angle; and when the scattering control device 126 is in a transparent state, the light emerging from the scattering control device 126 is light of a narrow viewing angle. According to Patent Literature 1, the illumination apparatus controls the emerging light angular distribution and thereby controls the viewing angle of the liquid crystal display apparatus.
However, in the conventional viewing angle control liquid crystal display apparatus according to Patent Literature 1, as the distance between the liquid crystal display device and the sheet with light shielding slits is small, moiré effects occur due to interference between structural bodies in the liquid crystal display device (such as a black matrix or internal circuitry) and the sheet with light shielding slits; and the visibility markedly declines. Methods for suppressing such moiré effects comprise methods recited in, for example, paragraphs (0024) to (0025) of Patent Literature 2 or FIG. 2 of Patent Literature 2 for inclining a sheet with light shielding slits at a predetermined bias angle. This method suppresses moiré effects by inclining an extension direction of a light shielding material of a sheet with light shielding slits at a predetermined bias angle with respect to a periodic direction of the pixel structure when adhering the sheet with light shielding slits to the liquid crystal display device.
Also, examples of display apparatuses using a beam direction regulator for controlling an emerging light angular distribution such as the sheet with light shielding slits according to Patent Literature 1 comprise a liquid crystal display apparatus according to Patent Literature 3. In this liquid crystal display apparatus, a light control film (light controller) having a reflective processing is arranged between a liquid crystal display unit and a backlight to reflect incident light from a display face side and transmit light from the backlight. By such a configuration, the light from the backlight is used for the display in dark locations; and in bright locations, external light is reflected by the reflective processing of the light control film, and the reflected light is used for the display. Thus, a liquid crystal display apparatus capable of transmitting and reflecting and having highly oriented emerging light (a narrow viewing angle) is realized.
Furthermore, a liquid crystal display apparatus illustrated in FIG. 1 of Patent Literature 4 comprises louvers arranged between a liquid crystal display cell and a light source. Additionally, a liquid crystal display apparatus illustrated in FIG. 4 of Patent Literature 4 comprises louvers arranged on a display face side of a liquid crystal display cell and a reflection plate arranged on an opposing face side thereof. The liquid crystal display apparatus illustrated in FIG. 1 of Patent Literature 4 results in a narrower viewing angle; and the liquid crystal display apparatus illustrated in FIG. 4 of Patent Literature 4 suppresses a diffused reflection of a display apparatus surface of a reflecting liquid crystal display apparatus using external light for the display and improves contrast. Further, technology wherein a reflection plate is arranged on one face of a louver is recited in claim 2 of Patent Literature 4. No detailed description or exemplary embodiment is recited for this claim, but it appears that utilization is possible in a reflecting liquid crystal display apparatus using external light for the display (a modification of the liquid crystal display device illustrated in FIG. 4 of Patent Literature 4).
Patent Literature 1: Japanese Patent No. 3328496
Patent Literature 2: Japanese Patent No. 3675752
Patent Literature 3: Japanese Utility Model Application Laid-Open No. H06-076934
Patent Literature 4: Unexamnined Japanese Patent Application KOKAI Publication No. H01-25123
However, the problems indicated below exist for the conventional art recited above.
In the liquid crystal display apparatus according to Patent Literature 1, the distance between the liquid crystal display device and the sheet with light shielding slits is small as recited above, and therefore moiré effects occur and the visibility markedly declines. Also, according to the method of Patent Literature 2 for inclining the sheet with light shielding slits at a predetermined bias angle, although it is possible to somewhat suppress moiré effects, it is difficult to sufficiently suppress moiré effects. In particular, the interference between structural bodies in the liquid crystal display device and the beam direction regulator becomes more complex in the case where the viewing angle is controlled from multiple directions using a beam direction regulator or the like having a polygon or circular transparent region covered by a light absorption region rather than the viewing angle being controlled in only one direction (only the direction perpendicular to the slits) using the sheet with light shielding slits according to Patent Literature 1; and therefore it is exceedingly difficult to suppress moiré effects by a method for inclining the bias angle. Moreover, according to the liquid crystal display apparatus of Patent Literature 1, an unevenness of the luminance of the liquid crystal display apparatus occurs due to unevenness of the width or spacing of light shielding materials of the sheet with light shielding slits, and unfortunately the display quality declines. Additionally, despite even slightly thinner display apparatuses being desirable for portable terminals, the liquid crystal display apparatus according to Patent Literature 1 comprises additions of scattering control means and a light shielding slit sheet and therefore unfortunately becomes thicker than general liquid crystal display apparatuses.
Also, in the liquid crystal display apparatuses according to Patent Literature 3 and Patent Literature 4, moiré effects occur and the visibility unfortunately declines similarly to the liquid crystal display apparatus according to Patent Literature 1. Further, each of the reflection plates arranged in the liquid crystal display apparatuses according to Patent Literature 3 and Patent Literature 4 reflects external light and is used to realize a reflecting liquid crystal display apparatus; and no description is provided regarding suppression of moiré effects and uneven luminance, thickness reductions of display apparatuses, etc.
The present invention was accomplished in consideration of the relevant problems and is directed to provide an illumination apparatus and a method for illuminating capable of controlling an emerging light angular distribution to suppress moiré effects and uneven luminance, and a display apparatus comprising the illumination apparatus and capable of controlling a viewing angle.
An illumination apparatus according to the present invention comprises: a light source; a light guide plate for emitting incident light from the light source in a direction opposite to an illumination direction; a first beam direction regulator arranged at a side of the light guide plate opposite to the illumination direction for regulating a direction of incident light and emitting the light; a reflecting member arranged at a side of the first beam direction regulator opposite to the illumination direction for reflecting incident light; and a transmittance/scattering switching device arranged at the illumination direction side of the light guide plate and capable of emitting incident light and switching between a state for transmitting and a state for scattering; wherein light from the light source emerges from the light guide plate in a direction opposite to the illumination direction, passes through the first beam direction regulator, and is reflected by the reflecting member; and the reflected light passes through the first beam direction regulator, the light guide plate, and the transmittance/scattering switching device and emerges in the illumination direction.
The first beam direction regulator may comprise a light absorption layer and a transparent layer; and the light absorption layer and the transparent layer may be alternately laminated.
An extension direction of the light absorption layer of the first beam direction regulator may be parallel or perpendicular to a light guiding direction in the light guide plate of incident light from the light source.
Also, an extension direction of the light absorption layer of the first beam direction regulator may be inclined with respect to a light guiding direction in the light guide plate of incident light from the light source or a direction perpendicular thereto.
Additionally, the first beam direction regulator may comprise a plurality of laminated beam direction regulators comprising a light absorption layer and a transparent layer; and extension directions of light absorption layers of the beam direction regulators may be mutually different.
Furthermore, the first beam direction regulator may have a light absorption layer and a transparent layer; and a cross-sectional shape of the transparent layer in a plane perpendicular to the irradiation direction may be any of a polygon, a circle, or an ellipse.
A configuration may comprise a second beam direction regulator between the light guide plate and the transmittance/scattering switching device.
Each of the first and the second beam direction regulators may comprise a beam direction regulator having an alternately laminated light absorption layer and transparent layer.
A configuration is possible wherein an extension direction of the light absorption layer of one of the first or the second beam direction regulator is parallel or inclined with respect to a light guiding direction in the light guide plate of incident light from the light source, and an extension direction of the light absorption layer of the other of the first or the second beam direction regulator is parallel or inclined with respect to a direction perpendicular to a light guiding direction in the light guide plate of incident light from the light source.
A configuration may comprise a third beam direction regulator proximal to a light incident face of the light guide plate wherein light enters from the light source.
A configuration is possible wherein the third beam direction regulator is a beam direction regulator wherein a light absorption layer and a transparent layer are alternately laminated, and the light absorption layer extends parallel to a thickness direction of the light guide plate.
A reflection face of the reflecting member may be inclined with respect to a plane of the first beam direction regulator opposing the reflection face.
The first beam direction regulator and the reflecting member may be combined.
A configuration may comprise a prism sheet or a spherical/aspherical lens sheet between the light guide plate and the transmittance/scattering switching device.
A configuration may comprise either or both of a light concentrator and a diffuser.
A method for illuminating according to the present invention may be characterized by: causing light from a light source to emerge from a light guide plate in a direction opposite to a predetermined illumination direction; receiving light from the light guide plate, regulating a direction of the light by a first beam direction regulator, and emitting the light; reflecting light from the first beam direction regulator by a reflecting member and transmitting the light through the first beam direction regulator and the light guide plate; and causing light emerging from the light guide plate to emerge from a transmittance/scattering switching device, and switching between a state for transmitting and a state for scattering light.
A display apparatus according to the present invention comprises the illumination apparatus and a display panel. Furthermore, the display panel may be, for example, a liquid crystal display panel.
According to the invention related to claim 1, transmittance/scattering is controlled by a transmittance/scattering switching device, thereby controlling an emerging light angular distribution from an illumination apparatus. Then, a first beam direction regulator is arranged behind a light guide plate with respect to an illumination direction, and therefore a large distance exists between a display panel such as a liquid crystal display panel arranged at a front of the light guide plate, i.e., illumination direction side of the illumination apparatus of the present invention, and a first beam direction regulator; and moiré effects due to an interference between the display panel and the first beam direction regulator can be suppressed. Furthermore, a large distance exists between the first beam direction regulator and a light emergence face of the transmittance/scattering switching device, and therefore light emerging from the first beam direction regulator widens and uneven luminance can be suppressed. Also, by reflecting light transmitted through the first beam direction regulator by a reflecting member and once again transmitting the light through the first beam direction regulator, even in the case where the thickness of the first beam direction regulator is half the thickness of a beam direction regulator of a conventional illumination apparatus, it is possible to produce a maximum light emergence angle from the first beam direction regulator identical to a maximum light emergence angle from the beam direction regulator of the conventional illumination apparatus. Thus, the emerging light angle can be controlled using half of the thickness of a conventional beam direction regulator, and therefore a thickness reduction of the illumination apparatus is possible.
Also, according to the invention related to claim 13, a reflecting member and a first beam direction regulator are combined, thereby improving the control precision of the emerging light angular distribution and improving the light utilization efficiency of the illumination apparatus.
Additionally, according to the invention related to claim 16, moiré effects and uneven luminance can be suppressed by comprising an illumination apparatus of the present invention; and a thin display apparatus capable of controlling a viewing angle can be provided.
1: Illumination apparatus
2: Light source
3: Light guide plate
4: Transmittance/scattering switching device
5, 15: Beam direction regulator
6: Reflection plate
7: Illumination direction
8: Light absorption layer
9: Transparent layer
10: Light guiding direction of light in the light guide plate
11: Second beam direction regulator
12: Light absorption layer of the first beam direction regulator
13: Light absorption layer of the second beam direction regulator
14: Third beam direction regulator
16: Liquid crystal display panel
17: Protective layer
18: Light emerging from the light guide plate toward the beam direction regulator
19: Prism sheet
20: Extension direction of the light absorption layer
21: Light absorption layer of the third beam direction regulator
22: Mixing region
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. First, an illumination apparatus according to a first exemplary embodiment of the present invention will be described.
As illustrated in
According to the first exemplary embodiment, the beam direction regulator 5 is arranged such that the extension direction of the light absorption layers 8 is parallel to the light guiding direction 10 of the light in the light guide plate, but the beam direction regulator 5 also may be arranged such that the extension direction of the light absorption layers 8 and the light guiding direction 10 of the light in the light guide plate are perpendicular. In such a case, the angle regulation direction of the emerging light is orthogonal to that of this exemplary embodiment.
A transparent polymer material such as polyethylene, polypropylene, or polysilicon (silicone rubber), etc. may be used as the transparent layer 9 of the beam direction regulator 5; and the light absorption layer 8 may comprise a mixture such as carbon black or a pigment mixed into the polymer material. Then, the beam direction regulator 5 of this exemplary embodiment can be made by alternately laminating these transparent layers and light absorption layers. Also, the construction is possible by a method for using a die or the like to form a pattern for the transparent layer or the light absorption layer, after which the light absorption layer material or the transparent layer material is filled into a recessed portion. A beam direction regulator having a transparent layer with a planar shape of a polygon, a circle, or an ellipse also may be made similarly.
The reflection plate 6 of the illumination apparatus 1 of this exemplary embodiment may be formed, for example, of Al (aluminum) material. In
Next, the light guide plate 3 of the illumination apparatus 1 of this exemplary embodiment will be described. The light guide plate 3 may be made using, for example, a transparent material such as a resin (acrylic resin, etc.) or glass; and in the case of a resin, the construction is possible by a method such as injection molding, hot pressing, milling, etc. An existing light guide plate for a backlight/frontlight and the like used in portable/small terminals may be used as the light guide plate 3 of this exemplary embodiment, and one example thereof is illustrated in
Also, a liquid crystal device capable of controlling a transmittance/scattering ability such as a polymer dispersed liquid crystal (PNLC) device and the like may be used as the transmittance/scattering switching device 4 of this exemplary embodiment. In particular, a PNLC device is favorable because the degree of the transmittance/scattering can be changed by an electrical potential applied between substrates. Additionally, it is possible to use a cold cathode fluorescent tube, an LED (Light Emitting Diode), or the like as the light source 2 of this exemplary embodiment.
Next, an operation of this exemplary embodiment will be described using
Referencing
As illustrated in
On the other hand, in
Also, for the conventional illumination apparatus, in the case where light from a backlight or a light source is used for the display, a thickness D1 of the beam direction regulator 5 is determined as follows. As illustrated in
Here, the angle a is an inclination angle from a direction perpendicular to the upper face or the lower face of the beam direction regulator 5. The thickness D1 of the beam direction regulator 5 is determined by formula 2 recited below from a geometric relation to the angle θ1.
Conversely, a thickness D2 of the beam direction regulator 5 according to this exemplary embodiment is determined as follows. As illustrated in
It is obvious from formulae 2 and 3 that for the same maximum emergence angle a, the thickness D2 of the beam direction regulator of this exemplary embodiment is half of the thickness D1 of the conventional beam direction regulator. Thus, the beam regulator of this exemplary embodiment can realize the same maximum emergence angle with half the thickness of the beam direction regulator used in the conventional illumination apparatus, and therefore a thickness reduction of the entire illumination apparatus is possible.
A protective layer 17 may be arranged on the beam direction regulator 5 as illustrated in
Also, for some existing light guide plates, a maximum luminance direction (emerging light angular distribution) of the emerging light 18 from the light guide plate toward the beam direction regulator is inclined (inclination angle β) with respect to a direction perpendicular to the light guiding direction 10 of the light in the light guide plate as illustrated in
In such a case, emerging light in a direction perpendicular to the light guiding direction of the light guide plate can be obtained by arranging a new beam direction regulator between the light guide plate and the transmittance/scattering switching device.
Also, in an illumination apparatus combining a light guide plate 3 and a beam direction regulator 5 wherein the light absorption layers extend in a direction perpendicular to the light guiding direction of the light guide plate 3 (restricting the emerging light angular distribution in a direction parallel to the light guiding direction) as in
Moreover, similar to the beam direction regulator wherein the light absorption layers extend parallel to the light guiding direction of the light in the light guide plate, emerging light in a direction perpendicular to the light guiding direction of the light in the light guide plate can be obtained by arranging the beam direction regulator 15 in the illumination direction 7 (referring to
Next, effects of this exemplary embodiment will be described. In an illumination apparatus 1 of this exemplary embodiment, an emerging light angular distribution from the illumination apparatus 1 can be controlled by a control of transmittance/scattering by the transmittance/scattering switching device 4. Furthermore, the beam direction regulator 5 is behind the light guide plate 3 with respect to the illumination direction 7, and therefore distances to a liquid crystal display panel, a cover for illumination having a lens sheet and structural bodies (lenses, slits, etc.), and the like arranged in the illumination direction 7 increases; and moiré effects due to interference between these and the beam direction regulator 5 can be suppressed. Moreover, according to this exemplary embodiment, a thickness reduction of the illumination apparatus is possible. Also, the distance increases between the beam direction regulator 5 and the emergence face of the transmittance/scattering switching device 4, i.e., the final emergence face, and therefore the light emerging from the beam direction regulator 5 widens, and uneven luminance can be suppressed. Additionally, consolidating the reflection plate 6 and the beam direction regulator 5 improves the precision of the emerging light angular distribution control and also improves the light utilization efficiency of the illumination apparatus.
As illustrated in
Also, a beam direction regulator wherein a plurality of laminated beam direction regulators having mutually different directions of extension of the light absorption layers 8 can be used as the beam direction regulator 5. Furthermore, a beam direction regulator 5 may be used wherein a cross-sectional shape in a plane parallel to the light emergence face of the transparent layer of the beam direction regulator is any of a polygon, a circle, or an ellipse. Viewing angle control can be performed from multiple directions by using such a beam direction regulator 5.
The illumination apparatus of this exemplary embodiment may comprise either or both of a light concentrator and a diffuser, thereby enabling an adjustment of the emerging light angular distribution, uniformity, etc.
Next, an illumination apparatus according to a second exemplary embodiment of the present invention will be described.
According to this exemplary embodiment, an angular distribution of light emerging from the light guide plate 3 in the illumination direction 7 can be regulated by the second beam direction regulator 11. In other words, a viewing angle control can be performed from multiple directions by changing the extension directions of the light absorption layers of the first beam direction regulator 5 and the second beam direction regulator 11 with respect to each other. For example, as illustrated in
Next, an illumination apparatus according to a third exemplary embodiment of the present invention will be described.
Also,
Next, an illumination apparatus according to a fourth exemplary embodiment of the present invention will be described. The illumination apparatus of this exemplary embodiment is characterized in that a portion or the entirety of the reflection face of the reflection plate is inclined with respect to the plane of the beam direction regulator arranged opposite to the reflection plate. In other words, the reflection plate according to this exemplary embodiment has a reflection face inclined between the light absorption layers of the beam direction regulator or a reflection face inclined along the light absorption layers.
For example, in the case of a beam direction regulator wherein the extension direction of the light absorption layer is parallel to the light guiding direction of the light in the light guide plate, a reflection plate 6 having centrally symmetric inclined faces between the light absorption layers 8 may be used as illustrated in
Also, as illustrated in
Next, a display apparatus according to a fifth exemplary embodiment of the present invention will be described. The display apparatus of this exemplary embodiment is a display apparatus comprising an illumination apparatus according to the present invention recited above. Such a display apparatus comprises, for example, a liquid crystal display apparatus having an illumination apparatus of the present invention and a liquid crystal display panel. Such a liquid crystal display apparatus is capable of viewing angle control, enables the suppression of moiré effects/uneven luminance, and also enables the realization of a thin display apparatus.
Hereinafter, examples of the present invention will be described in comparison to a comparison example outside of the range of the present invention.
As a conventional beam direction regulator, a beam direction regulator having a transparent layer width L2=0.085 mm, a transparent layer refractive index n=1.60, a light absorption layer width L3=0.015 mm, and a thickness D1=0.258 mm was made and combined with a backlight and a PNLC device to make a conventional illumination apparatus (referring to
A beam direction regulator having a transparent layer width L2=0.085 mm, a transparent layer refractive index n=1.60, a light absorption layer width L3=0.015 mm, and a thickness D2=0.129 mm wherein an Al reflection plate was vapor-deposited on one face and the light absorption layers extended parallel to the light guiding direction of the light guide plate was made. The beam direction regulator, a line light source, a light guide plate, and a PNLC device were combined to make an illumination apparatus of the present invention as illustrated in
The beam direction regulator of example 1, a light guide plate as illustrated in FIG. 25A (emerging light inclination in the light guiding direction: β=about 43°), a beam direction regulator having a prism face with an apical angle of 50° (
The beam direction regulator of comparison example 1 (second beam direction regulator) was arranged between the beam direction regulator and the PNLC device of the illumination apparatus of example 2 such that the light absorption layers extended perpendicular to the light guiding direction of the light guide plate to make an illumination apparatus (
A beam direction regulator having a transparent layer width L2=0.085 mm, a transparent layer refractive index n=1.60, a light absorption layer width L3=0.015 mm, and a thickness D2=0.066 mm wherein an Al reflection plate was vapor-deposited on one face and the light absorption layers extended perpendicular to the light guiding direction of the light guide plate was made. This beam direction regulator; the line light source, the light guide plate, and the PNLC device of example 2; and a beam direction regulator having a prism face as illustrated in
The present invention can be favorably used as an illumination (backlight) of a liquid crystal display apparatus, as interior lighting, etc.
Number | Date | Country | Kind |
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2006 170740 | Jun 2006 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/062230 | 6/18/2007 | WO | 00 | 12/18/2008 |