JP2019102372A - Luminaire, backlight device and front light device - Google Patents

Abstract

[Problem] To provide an illumination device that can make the most of the light emitted from a surface light source, illuminate only where it is needed, easily achieve a slim device design, and reduce costs. [Solution] Almost all of the light beam L0 emitted from a surface light source 10 is captured by a focusing optical system 20 consisting of a meniscus lens 21 and a convex lens 22, and is converted into a light beam L1 with an emission angle α of 19° to 30°. This is converted into a light beam L with a spread angle β of 5.0° or less by a collimating optical system 30 consisting of two to four lenses 31, 32, .... This is reflected in an oblique direction by a concave reflecting mirror 15, and further reflected in the thickness direction by a reflective prism sheet 14, and finally emits a parallel light beam Lr. [Selected Figure] Figure 1

Description

  The present invention provides a lighting device that emits parallel light with uniform brightness, a backlight device and a front light device comprising the lighting device, a liquid crystal display equipped with the backlight device, and the front light device The present invention relates to a reflective liquid crystal display provided with

  Lighting is generally defined as "the light emitted from a light source that acts or functions to brighten a specific place substantially uniformly." At present, with the development of blue LED (LED is an abbreviation of light emitting diode) and the drastic improvement of its luminous efficiency, LED has become widely used as a light source of the lighting device, and conventional light bulbs and fluorescent lamps have already been used. It is spreading by the time it goes. However, even with current LED lighting devices, as with conventional light bulbs and fluorescent lamps, the uniformity of illuminance is realized by diffusing the strong light emitted from the light source at a wide angle and combining these diffused lights. Therefore, it has not reached the technology which can brighten only a specific place uniformly. In addition, light emitted to a place other than a specific place is useless energy, and by reducing this useless energy, it is possible to realize a lighting device that can achieve more power saving than the current LED lighting device.

  In the case of illuminating a flat surface, generally, as shown in FIG. 11 (b), a cylindrical illumination means 50 with a reflecting plate 51 (referred to collectively as a fluorescent lamp or a straight tube LED lamp etc.) is of the flat plate 52. In the upper part, the reflector 51 is inclined such that the longitudinal direction of the cylindrical illumination means 50 is parallel to the upper edge of the flat plate surface and the main optical axis (center) of the cylindrical illumination means 50 hits the flat plate surface. A lighting device is used which is adjusted and installed so that the difference in brightness between the upper edge and the lower edge is reduced. However, in the lighting device shown in FIG. 11 (b), the illuminance decreases in inverse proportion to the square of the distance from the lighting device to the flat surface, so the upper edge is bright and the lower edge is dark, and uniformity of luminance can not be realized. .

  On the other hand, as shown in FIG. 11A, the emission intensity is almost equal (for example, within ± 10% of the average value of emission intensity), and the emission direction is within ± 10 ° of the average of angles of the emission direction (for example, the reference direction). And) approximately equal, nearly ideal collimated light illumination means 60 emitting collimated light is installed on the upper edge of the flat plate with the illumination light falling on the upper and lower edges of the flat surface. If used, the illuminance at the upper edge, center and lower edge of the flat surface can be made approximately equal. Furthermore, since there is no useless light to be irradiated to other than the flat surface, the utilization efficiency of the light emitted from the lighting device can be realized almost 100%, and a significant energy saving effect is expected compared to the lighting device of FIG. it can.

  Patent Documents 1 and 2 disclose a lighting device that emits parallel light with uniform brightness as a lighting device that is structurally similar to FIG. 11 (a). The light emitted from the LED chip is passed through a homogenizer such as a rod-like integrator to make a small area surface light source with uniform brightness at the exit, and the surface light source is a lens with a focal length f1 (f1 lens) And a focal length f2 of a spherical reflection mirror (f2 spherical reflection mirror) and a reflection type prism sheet (reflection prism) to expand the surface to a reflection prism surface while maintaining uniform brightness, all of the surface light source expanded to this reflection prism surface The light is emitted with its direction being changed in the normal direction by the reflecting surface of the reflecting prism.

  On the other hand, Patent Document 3 uses a meniscus lens and a convex lens to form a virtual image of a surface light source under specific conditions on both lenses, thereby causing almost all light from the surface light source to be incident, the optical axis position and the optical axis An illumination device is disclosed in which incident light from a position deviated from can be emitted at substantially the same angle, and uniformity of the irradiation light intensity is enhanced, and it is also possible to adjust the irradiation angle of the irradiation light.

JP, 2015-198054, A JP 2017-098084 A Patent No. 5901037

  However, in both of the patent documents 1 and 2, the light emitted from the LED chip is emitted at an emission angle distributed within an angle range of ± 90 ° of the normal direction with respect to the normal direction of the light emission surface Since the light incident surface of a rod-like integrator used as a homogenizer is generally flat, almost all of the light emitted from the LED chip can not be incident. For example, even if the distance between the light emitting surface of the LED chip and the light incident surface of the rod-like integrator is set to almost zero, there is light that is totally reflected by the light incident surface. Can not. For example, the problem that about 70% of the total emitted light from a LED chip can not be used may arise.

  It is also conceivable to use collimated optical system 70 as shown in FIG. 15 instead of the rod-like integrator so that almost all of the light emitted from the LED chip 71 can be used. In FIG. 15, the LED chip 71 is disposed at the focal position of the collimating optical system 70 composed of the meniscus lens 72 and the aspheric lens 74. However, in this configuration, since the meniscus lens 72 and the LED chip 71 are physically separated, light emitted from the LED chip 71 at a large angle will not be incident on the meniscus lens 72.

  In addition, the lighting device of Patent Document 3 can adjust the irradiation angle of the irradiation light, but in order to emit the illumination light as parallel light, five or more expensive aspheric lenses are required separately, which makes cost reduction difficult. It is.

  The present invention has been made in view of the above circumstances, and its object is to improve the utilization efficiency of light while making use of the merits of a lighting device that emits parallel light with uniform brightness. An illumination-type signboard, a poster or a picture illumination, a reflective liquid crystal display with uniform surface brightness, and an illumination type signboard that can reduce power consumption by minimizing the use of a light source and achieve a large observation target surface. When applied to ink displays and general lighting, it is possible to make maximum use of the emitted light of the surface light source, to illuminate only where it is needed, to easily achieve thinning of the device, and to achieve cost reduction. And providing a lighting device.

In order to solve the problems described above and achieve the above object, a lighting device according to the present invention is:
(1) A surface light source having a light exit surface,
A convex lens placed so that the optical axis is aligned immediately after the light emitting surface side of the first lens by taking in substantially all of the light flux emitted from the surface light source with the first lens which is a meniscus lens covering the surface light source A condensing optical system in which the light emission angle α of the light beam emitted from the light emission surface side of the second lens is α = 19 ° to 30 ° on the side where the light beam spreads with respect to the optical axis. System,
The light flux emitted from the light collection optical system at the emission angle with respect to the optical axis is collimated at a spread angle β of not more than 5.0 ° with respect to the light axis, at least two A collimating optical system comprising the following lenses,
It consists of a concave reflecting mirror with a focal length f, which reflects the light beam emitted from the collimating optical system into a parallel light beam,
The reflective optical system satisfying the condition of 0.9 M <f <1.1 M with respect to the distance M from the light emitting surface of the collimating optical system to the reflecting surface of the concave reflecting mirror;
Furthermore, an optical path changing means,
A lighting device provided with
The reflection direction of the light flux reflected from the reflection optical system is inclined with respect to the optical axis of the light flux passing through the light collection optical system and the collimating optical system,
Furthermore, the optical path changing means is formed of a reflective prism sheet that changes the optical path of the light beam reflected from the reflective optical system.
It is characterized by
(2) In the illumination device according to the present invention, in the invention of (1), the first lens and the second lens of the focusing optical system have arcs as lens surfaces on both the light incident surface and the light output surface. It is characterized in that it is a spherical lens consisting of a rotational surface used as a generatrix.
(3) The illumination device according to the present invention is characterized in that, in the invention of the above (1) or (2), the first lens and the second lens of the focusing optical system are integrally molded of resin. Do.
(4) The illumination device according to the present invention is, in the invention according to any one of the above (1) to (3), a lens on the condensing optical system side of 2 or more and 4 or less lenses forming the collimating optical system. The latter is larger in the diameter and the lens diameter on the side of the reflection optical system.
(5) The illumination device according to the present invention is characterized in that in the invention according to any one of the above (1) to (4), the collimating optical system comprises two plano-convex lenses.
(6) The illumination device according to the present invention is characterized in that in the invention according to any one of the above (1) to (5), the collimating optical system is composed of two Fresnel lenses.
(7) In the illumination device according to the present invention, in the invention according to any one of the above (1) to (6), the concave reflection mirror has a light incident surface side whose reflection surface is the lower surface side of the reflection type prism sheet , And inclined at an inclination angle θ of 1.0 ° to 5.0 ° with respect to the thickness direction of the reflective prism sheet.
(8) The illumination device according to the present invention is characterized in that, in the invention according to any one of the above (1) to (7), the width direction center line of the reflection convex portion of the reflection type prism sheet is arc-shaped. .
(9) The illumination device according to the present invention is, in the invention according to any one of the above (1) to (8), an inclination of each reflection surface of the reflection type prism sheet on which the light flux reflected from the concave reflection mirror is reflected. As in the linear Fresnel lens, they have different inclinations.
(10) A backlight device according to the present invention is characterized by comprising the lighting device according to the invention of any one of the above (1) to (9).
(11) A liquid crystal display according to the present invention comprises the backlight device according to the invention of (10) above, and a flat plate-like liquid crystal panel having at least a liquid crystal sandwiched by a plurality of light distribution layers,
A luminous flux emitted from the backlight device may be made incident on the back surface of the liquid crystal panel. Here, the back surface of the liquid crystal panel means the surface of the liquid crystal panel on the side opposite to the viewer side.
(12) A front light device according to the present invention is characterized by comprising the lighting device according to the invention of any of the above (1) to (9).
(13) A reflective liquid crystal display according to the present invention comprises the front light device according to the invention of (12) and a flat plate reflective liquid crystal panel having at least a liquid crystal sandwiched between a plurality of light distribution layers. ,
The luminous flux emitted from the front light device may be made to be incident on the front of the reflective liquid crystal panel. Here, the front of the reflective liquid crystal panel means the surface on the viewer's side of the reflective liquid crystal panel.

  According to the present invention, the light emitted from the surface light source can be used to the maximum, parallel light can be emitted with uniform brightness, and illumination can be performed only at a necessary place, and the thinness of the device can be achieved even if the irradiation target surface is a large screen. It is possible to achieve an excellent effect of realizing a lighting device which can be easily achieved and whose cost can be reduced.

It is a side view showing typically the lighting installation by a 1st embodiment of the present invention. It is a side view which shows typically the form of the condensing optical system by the 2nd Embodiment of this invention. It is a side view which shows typically the form of the condensing optical system by the 3rd Embodiment of this invention. It is a side view which shows typically the form of the collimating optical system by the 4th Embodiment of this invention. It is a side view which shows typically the form of the collimating optical system by the 5th Embodiment of this invention. It is a side view which shows typically the form of the collimating optical system by the 6th Embodiment of this invention. It is a partial YZ sectional view of the reflection type prism sheet in FIG. (A) Bottom view, (b) Side view, and (c) Front view schematically showing the form of a reflective prism sheet according to the eighth embodiment of the present invention. It is a side view which shows typically the arrangement | positioning form of the backlight apparatus by the 10th Embodiment of this invention. It is a side view which shows typically the arrangement | positioning form of the front light apparatus by 12th Embodiment of this invention. It is a schematic diagram which shows the illuminating device which irradiates a flat surface, (a) shows the case where a normal cylindrical illumination means is used, when (b) substantially parallel light illumination means is used. As an example, an illumination device for which a design condition satisfying the limitation conditions of α and β in one example of the first embodiment is obtained by optical simulation is schematically shown, (a) is a side view, (b) is a front view. is there. It is a diagram which shows the one-dimensional intensity distribution of the Y direction of the surface for irradiation in an Example. It is a diagram which shows the one-dimensional intensity distribution of the Z direction of the irradiation object surface in an Example. It is a side view showing typically the lighting installation which installed the LED chip in the front focus position of a collimating optical system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited by the following embodiments. Further, in the drawings, the same or corresponding elements are given the same reference numerals as appropriate, and the redundant description is appropriately omitted. Further, the drawings are schematic, and the relationship between dimensions of each element is a reality. It should be noted that it may be different from In addition, parts having different dimensional relationships and ratios may be included among the drawings.

First Embodiment
First, a lighting apparatus according to the invention of (1) will be described as a first embodiment of the present invention. FIG. 1 is a side view seen from the X direction showing the configuration of the lighting device according to the first embodiment. The direction perpendicular to the XY plane in FIG. 1 is taken as the Z direction.
As shown in FIG. 1, the illumination device 1 according to the first embodiment includes a surface light source 10 having a light emitting surface, for example, an LED chip, a condensing optical system 20, a collimating optical system 30, and concave reflection of a focal distance f. It is configured to have a reflection optical system consisting of a mirror 15 and an optical path changing means consisting of a reflection type prism sheet 14. The normal direction of the light exit surface of the surface light source 10 is taken as the Z direction.

The surface light source 10 is a light emitting body having a light emitting surface, and examples thereof include an LED chip. In addition, if it is a light-emitting body which has a light emission surface, it will not be limited to a LED chip.
The condensing optical system 20 includes a first lens 21 which is a meniscus lens covering the surface light source 10, and a second lens 22 which is a convex lens disposed so that the optical axis coincides immediately after the exit surface side of the first lens 21. And substantially all, for example, 95% or more of the light flux L ₀ emitted from the surface light source 10 is taken in by the first lens 21 and is incident on the second lens 22, and the light exit surface side of the second lens 22 is exit angle alpha of the light beam L ₁ emitted optical axis with respect to (Z-direction), and is configured such that the side extending the light beam becomes α = 19 ° ~30 ° from. Preferably, α is 22 ° to 28 °. In addition, preferably, a light blocking plate (not shown in FIG. 1 and a light blocking plate 25 in FIG. 2 described later) that blocks the incidence of external light to the second lens 22 between the first lens 21 and the second lens 22. ) May be installed.

The collimating optical system 30 has a light beam L ₁ emitted from the condensing optical system 20 at an emission angle α of α = 19 ° to 30 ° by four or less lenses, for example, two lenses 31 and 32 as an optical axis On the other hand, collimation is performed at a spread angle β of not more than β = 5.0 ° on the spread side of the light flux.

  The concave reflecting mirror 15 having the focal length f reflects the light beam L emitted from the collimating optical system 30 so as to be a parallel light beam, which is a light beam having substantially the same emission direction (extension direction) of light rays in the light beam. Here, that the radiation directions of the light rays in the light flux are substantially the same is that the angle between any one light ray in the light flux and each one of all the remaining light rays is 0 ° or more and 10 ° or less Means That is, the parallel luminous flux is a luminous flux in which an angle between any one of a plurality of light rays forming the luminous flux and each one of the remaining ones is 0 ° or more and 10 ° or less.

The focal length f of the concave reflecting mirror 15 satisfies the condition of 0.9 M <f <1.1 M with respect to the distance M from the light emitting surface of the collimating optical system 30 to the reflecting surface of the concave reflecting mirror 15. The reflection direction of the light flux L _R reflected from the concave reflection mirror 15 is inclined at an angle of 2θ with respect to the optical axis of the light flux L which has passed through the condensing optical system 20 and the collimating optical system 30. The angle 2θ is twice the angle θ that the central axis of the concave reflecting mirror 15 makes with the Z direction. That is, it is twice the inclination angle θ with respect to the thickness direction of the reflective prism sheet 14 with respect to the plane normal to the central axis of the concave reflection mirror 15.

The reflection type prism sheet 14 changes the light path of the light flux L _R (also referred to as parallel light flux L _R ) reflected as parallel light from the concave reflection mirror 15 as parallel light in the opposite direction of the Y direction, for example, It emits as Lr.).

FIG. 7 is a partial YZ sectional view of the reflective prism sheet 14. As shown in FIG. 7, it extends parallel to the X direction, that is, in a direction perpendicular to the optical path direction of the parallel light beam L _R viewed from the Y direction, on the reflection prism surface on the irradiation target surface side of the reflection type prism sheet 14 A plurality of reflecting convex portions 14a are provided. Reflecting projection 14a, for example, with YZ section has a height t ₀ triangular width l _0, is provided at a distance l _1. Further, the surface of at least the concave reflection mirror 15 side of the reflection convex portion 14 a is configured by a mirror surface capable of reflecting the parallel light beam L _R. Then, the parallel light flux L _R from the concave reflection mirror 15 is obtained by adjusting the width l ₀ or height t ₀ of the base of the triangular shape in the reflection convex part 14 a or the distance l ₁ between the adjacent reflection convex parts 14 a The surface of the reflective prism sheet 14 between the reflective protrusions 14 a can be prevented from reaching the surface. Therefore, it is possible to make the parallel light beam L _R from the concave reflection mirror 15 reach only the slope formed by the mirror surface of the reflection convex portion 14 a, and to reflect the parallel light beam L _R by this slope. As a result, the light flux reaching the surface of the reflective prism sheet 14 and scattered in a direction different from the desired direction can be minimized, so that the light utilization efficiency can be improved. Furthermore, a part of the light emitted from the collimating optical system 30 is directly incident on the slope of the reflecting convex portion 14 a on the side of the collimating optical system 30 without passing through the concave reflecting mirror 15 and reflected to be parallel light flux (shown It is also possible to emit it as

Further, the parallel light flux L is adjusted by adjusting the shapes of the reflection type prism sheet 14 and the reflection convex portion 14 a and the inclination angle formed with respect to the Z direction according to the optical path of the parallel light flux L _R from the concave reflection mirror 15. It is possible to reflect in a desired direction while maintaining _R at a predetermined in-plane intensity distribution.

  In the present invention, as shown in FIG. 1, cost reduction can be achieved by setting the number of lenses of the collimating optical system 30 to two or more and four or less. If the number of lenses in the collimating optical system 30 is five or more, cost reduction can not be achieved. Further, if the number of lenses of the collimating optical system 30 is one, it is difficult to satisfy β = 5.0 ° or less. Therefore, the number of lenses of the collimating optical system is two to four. Among them, two are preferable because the cost can be reduced most.

In addition, a reflecting surface of the concave reflecting mirror 15 having a focal length f satisfying the condition of 0.9 M <f <1.1 M is provided at the position of the distance M from the light emitting surface of the collimating optical system 30 to the emitting side. Inclining with respect to the XY plane so that the reflection direction of the reflected light flux L _R makes an angle 2θ with the optical axis (Z direction) of the light flux L that has passed through the focusing optical system 20 and the collimating optical system 30 θ), and the collimated luminous flux L _R is changed its optical path by the reflection type prism sheet 14 so as to be collimated luminous flux Lr. By this, even if the number of lenses of the collimating optical system 30 is two or more and four or less, only necessary places can be illuminated, and even if the irradiation target surface is a large screen equivalent to a display screen of 100 inches or more, for example Can be easily achieved.

Then, almost all of the light beam L ₀ emitted from the surface light source 10, such as 95% or more, the emission by the first lens 21 to capture the second lens 22, the emission angle of the light beam L ₁ emitted from the second lens 22 alpha but so that the α = 19 ° ~30 °, set the conditions for the material and dimensions of the first lens 21 and second lens 22, and then a light beam L ₁ is collimated by four or less lens The conditions of the material and dimensions of the lens of the collimating optical system 30 are set so that the spread angle β of the luminous flux L emitted from the collimating optical system 30 to be emitted becomes β = 5.0 ° or less, and from the collimating optical system 30 The incident light beam L is made incident on the reflection surface of the concave reflection mirror 15 so that the emitted light of the surface light source is maximally utilized and the parallel light beam L _R reflected by the concave reflection mirror 15 is reflected by the reflection type prism sheet 14 light The brightness of the irradiation target surface of the parallel luminous flux Lr may be equalized to, for example, 20% or more by the ratio of the luminance of the darkest part to the luminance of the brightest part in the irradiation target surface. it can.

When β is more than 5.0 °, it is difficult to obtain the parallel luminous flux L _R and the parallel luminous flux Lr. Although a surface light source is used in the present invention, it is difficult to set β to 0 ° in the case of a surface light source unlike in the case of a point light source.
Further, in the range where α is less than 19 °, it is difficult to realize by the meniscus lens (first lens 21) and the convex lens (second lens 22), while in the range where α is greater than 30 °, the number of lenses is four. It is difficult to realize β = 5.0 ° or less by the following collimating optical system 30.
Therefore, according to the present invention, it is possible to use the light emitted from the surface light source as much as possible, emit parallel light with uniform brightness, and illuminate only where it is needed, even if the irradiation target surface is a large screen Thus, it is possible to realize a lighting device which can easily achieve the thinning of the device and can reduce the cost.

Second Embodiment
Next, as a second embodiment, a lighting device according to the invention of (2) will be described based on FIG. FIG. 2 shows the illumination device according to the invention of (2), in which the first lens 21 and the second lens 22 of the condensing optical system 20 are shown in FIG. 2 as in the invention of (1). It is shown that both the surface and the light emitting surface are in the form of a spherical lens (spherical lens) composed of a rotational surface having an arc as a generatrix as a lens surface. In the present invention, α = 19 ° to 30 ° can be realized even if spherical lenses which are significantly cheaper than aspheric lenses are available as the first and second lenses of the focusing optical system. According to the embodiment of the present invention, further cost reduction is achieved. In the example of FIG. 2, as a preferred embodiment, a light shielding plate 25 is provided between the first lens 21 and the second lens 22 for blocking the incidence of external light on the second lens 22.

Third Embodiment
Next, as a third embodiment, a lighting device according to the invention of (3) will be described based on FIG. In FIG. 3, in the illumination device according to the invention (3), in the invention (1) or (2), the first lens 21 and the second lens 22 of the focusing optical system 20 are integrally molded of resin (in detail Indicates that a part of the lens interface is integrally formed). Examples of the resin include PMMA (polymethyl methacrylate) and PC (polycarbonate). As described above, the positions of the surface light source 10 and the condensing optical system 20 are integrated by integrally molding the first lens 21 and the second lens 22 of the condensing optical system 20 into two. It can be easily fitted and fixed. In addition, since the number of times of molding when molding the first lens 21 and the second lens 22 can be reduced from two times (in the case of two bodies) to one time (in the case of one body), the manufacturing cost can be further reduced. Can.

Fourth Embodiment
Next, as a fourth embodiment, a lighting device according to the invention of (4) will be described based on FIG. FIG. 4 shows that the illumination device according to the invention of (4) comprises two or more and four or less lenses forming the collimating optical system 30 (the lens 31 and FIG. 4 in any of the inventions of (1) to (3)). A total of two lenses 32 are shown.) The lens diameter (hereinafter referred to as the incident side lens diameter) of these lenses on the condensing optical system 20 side, for example, the lens diameter of the lens 31 and the reflection optical The lens diameter on the system side (concave reflection mirror 15 side, see FIG. 1) (hereinafter referred to as the exit side lens diameter), for example, the lens diameter of the lens 32, the latter is larger. It shows.

  It is difficult to design the lens 31 so that the diameter of the intersection area between the light beam emitted from the lens 31 and the plane orthogonal to the optical axis decreases as the distance from the lens 31 to the light emission side increases. If the lens diameter of the lens is smaller than or equal to the lens diameter of the incident side (the lens diameter of the lens 31), it is difficult to make all light beams emitted from the lens 31 incident on the lens 32. On the other hand, in the fourth embodiment in which the exit side lens diameter (the lens diameter of the lens 32) is larger than the entrance side lens diameter (the lens diameter of the lens 31), all the emitted light flux from the lens 31 is incident on the lens 32 It becomes easy to further improve the utilization efficiency of light.

Fifth Embodiment
Next, as a fifth embodiment, a lighting apparatus according to the invention of (5) will be described based on FIG. In the illumination device according to the invention of (5) in FIG. 5, in the invention of any of (1) to (4), the number of lenses of the collimating optical system 30 is preferably two among two to four. It is shown that the two lenses 31 and 32 are in the form of a plano-convex lens.

The plano-convex lens can be manufactured at low cost as compared with the case where one of the lens surfaces is convex and the other is flat and both lens surfaces are curved. Therefore, according to the fifth embodiment in which the collimating optical system is configured of two plano-convex lenses, cost reduction can be further achieved as compared to the case where the collimating optical system includes a lens having curved surfaces on both sides of the lens.
Sixth Embodiment
Next, as a sixth embodiment, a lighting apparatus according to the invention of (6) will be described based on FIG. In the illumination device according to the invention of (6), as shown in FIG. 6, in the invention of any of (1) to (5), for example, as shown in FIG. Among the two lenses 31, 32, among these lenses 31, 32 are shown to be formed of Fresnel lenses.
A Fresnel lens is a shape in which an original lens without steps on the lens surface is divided into a plurality of lens pieces in a plane orthogonal to the optical axis, and each lens piece is parallelly moved in the optical axis direction of the original lens and arranged on the same plane Since the overlapping portion is fused, the lens thickness can be significantly reduced, for example, to 30% or less of the lens thickness of the prototype lens while providing optical characteristics equivalent to that of the original lens. Weight reduction of the illuminating device which concerns on invention can be achieved.

Seventh Embodiment
Next, as a seventh embodiment, a lighting apparatus according to the invention of (7) will be described based on FIGS. 1 and 7. FIG. 1 shows an illumination device according to the invention of (7), wherein in the invention of any of (1) to (6), the concave reflection mirror 15 has light whose reflection surface is the lower surface side of the reflection type prism sheet 14 It shows that it inclines with respect to the thickness direction (Y direction) of the reflection type prism sheet 14 toward the entrance plane side, and FIG. 7 shows an embodiment in which the inclination angle θ is 1.0 ° to 5.0 °. Is shown. If θ is less than 1.0 °, the reflected light from the concave reflection mirror 15 returns to the collimating optical system 30. On the other hand, if θ exceeds 5.0 °, it becomes necessary to increase the size of the concave reflection mirror 15 as the irradiation target surface becomes larger, which makes it difficult to miniaturize the entire illumination device.

Eighth Embodiment
Next, as an eighth embodiment, a lighting apparatus according to the invention of (8) will be described based on FIG. The illumination device according to the invention of (8) is characterized in that, in the invention of any one of (1) to (7), the width direction center line of the reflection convex portion of the reflection type prism sheet is in an arc shape.
In the eighth embodiment, in place of the reflective prism sheet 14 according to the first to seventh embodiments, the center line in the width direction of the reflective convex portion 14 a of the reflective prism sheet is linear. The reflection type prism sheet 14A has a form in which the widthwise center line 14c of the reflection convex portion 14a of the reflection type prism sheet is arc-shaped. The center of curvature of this arc is located on the side where the parallel light beam L _R from the concave reflection mirror 15 is incident. FIG. 8A is a bottom view, FIG. 8B is a side view, and FIG. 8C is a front view schematically showing the configuration of a reflection type prism sheet 14A according to the eighth embodiment of the present invention. According to this, the parallel light beam L _R incident from the concave reflection mirror 15 to the reflection type prism sheet 14A is reflected by the reflection convex part 14a, but as shown in FIGS. 8 (a) and 8 (b), the width since the reflective protrusion 14a-direction center line 14c is arc-shaped having a focal p, the reflected light beam Lr ₁ in FIG. 8, not the parallel light beam is diffused after condensed into a focus p. In this eighth embodiment, by changing the diffusion angle φ reflected light beam Lr ₁ by changing the radius of curvature of the arcuate widthwise center line 14c, since it easily change the X-direction size of the irradiation region, the Compared with the first to seventh embodiments, application to an irradiation target surface having a larger area is easy even with the same device thickness. However, the light intensity is reduced at the end in the X direction of the irradiation area as compared with the central part in the X direction.

Ninth Embodiment
Next, a lighting apparatus according to the invention of (9) will be described as a ninth embodiment. The illuminating device which concerns on invention of (9) is an invention in any one of (1)-(8) WHEREIN: The inclination of each reflective surface which the light beam reflected from the said concave reflective mirror of the said reflection type prism sheet reflects is made As in the case of a linear Fresnel lens, they have different forms (not shown). According to this, application to arbitrary linear illumination and circular illumination also becomes easy.

Tenth Embodiment
Next, as a tenth embodiment, a backlight device 1B (see FIG. 9) including the illumination device 1 according to the invention of (1) to (9) according to the invention of (10) will be described. For example, as shown in FIG. 9A, in the backlight device 1B, the back surface of the light-transmissive display plate 53 whose surface is the vertical surface, for example, the surface opposite to the viewer side has a rectangular irradiation target As the surface 53BS, the parallel light flux Lr (see FIG. 7) is irradiated from an oblique upper side without excess and deficiency. In this arrangement form, the length in the longitudinal direction (Z direction) of the light emission port of the backlight device 1B is adjusted to the length of, for example, the upper side of the irradiation target surface 53BS, and the longitudinal direction range of the backlight device 1B is the irradiation target The backlight device 1B is disposed, for example, on the upper end side of the irradiation target surface 53BS so as to be parallel to the upper side length range of the surface 53BS and overlap without excess. The angle θ _{1 B, which} is the extra angle of the incident angle of the collimated light beam Lr from the light exit to the illumination target surface 53 BS, is the height H of the illumination target surface 53 BS and the X direction of the light exit The XZ plane of the backlight device 1B was arranged to be inclined from the horizontal surface so as to satisfy the geometrical relationship with the length X _1B : (X _1B / H) = sin θ _1B .

For example _X 1B = 60 mm, when the _{θ 1B = 0.7 ° ~10 °,} H = X 1B / sinθ 1B, more height direction length H of the illuminated target surface 53BS, the irradiation target surface of most current It is about 346 to 4911 mm, including its size, so it can illuminate most current areas of the illuminated surface with uniform brightness without wasting light. In addition, it can be determined by calculating the distribution of the light intensity in the surface to be irradiated by optical simulation as to how wide the range which can be illuminated with uniform brightness in the surface to be irradiated becomes.

Further, for example, as shown in FIG. 9B, the parallel luminous flux is incident on the back surface side of the light-transmissive display plate 53 substantially perpendicularly (for example, incident angle within 0 ° ± 10 °). A prism sheet 54 may be provided as an optical path changing means for changing the optical path of Lr. In addition, the word simply described as "prism sheet" without bearing "reflection type" refers to a refraction type prism sheet.
The example of FIG. 9 shows the case where the backlight device 1B is provided with the reflective prism sheet 14 (see FIG. 7) for emitting the parallel light beam Lr.

Eleventh Embodiment
Next, a liquid crystal display according to the invention of (11) will be described as an eleventh embodiment. The eleventh embodiment comprises the backlight device according to the invention of (10) and a flat plate-like liquid crystal panel having at least a liquid crystal sandwiched between a plurality of light distribution layers, and emitted from the backlight device. It is a form (not shown) which makes a light beam enter with respect to the back surface which is a surface on the opposite side to the observer side of the said liquid crystal panel. In this eleventh embodiment, in the tenth embodiment shown in FIGS. 9A and 9B (for example, any of FIGS. 9A and 9B), the light transmitting display plate 53 is used. Instead, it corresponds to a flat plate-like liquid crystal panel having at least a liquid crystal sandwiched by a plurality of light distribution layers (not shown). The words “liquid crystal display” and “liquid crystal panel” simply without an article are referred to as “transmission type”.
Examples of the flat plate-like liquid crystal panel having at least the liquid crystal sandwiched between the plurality of light distribution layers described in the eleventh embodiment include, for example, a polarizing filter, a glass substrate, and a liquid crystal sandwiched between the light distribution layers. A conventionally known liquid crystal panel (not shown) can be used which is formed of a laminate in which a diffusion plate and the like are laminated.

Twelfth Embodiment
Next, as a twelfth embodiment, a front light apparatus 1F (see FIG. 10) including the illumination apparatus 1 according to the invention of (1) to (9) according to the invention of (12) will be described. For example, as shown in FIG. 10A, in the front light device 1F, the front surface, which is the surface on the viewer side of the light-impermeable display plate 55 having the plate surface as the vertical surface, for example, is rectangular The configuration is such that the collimated light beam Lr (see FIG. 7) is emitted from the obliquely lower side without excess or deficiency. In this arrangement form, the length in the longitudinal direction (Z direction) of the light emission port of the front light device 1F is made equal to the length of the lower side of the irradiation target surface 55FS, for example. The front light device 1F is disposed, for example, on the lower end side of the irradiation target surface 55FS so as to overlap with the lower side length range of the surface 53FS in parallel and without excess and deficiency. Then, the angle θ _{1 F, which} is the extra angle of the incident angle of the collimated light beam Lr from the light emission port to the irradiation target surface 55 FS, is the height direction length H of the irradiation target surface 55 FS and the X direction of the light emission port The XZ plane of the front light device 1F was arranged to be inclined from the horizontal surface so as to satisfy the geometrical relationship with the length X _1F : (X _1F / H) = sin θ _1F .

For example _X 1F = 60 mm, when a _{θ 1F = 0.7 ° ~10 °,} H = X 1F / sinθ 1F, more height direction length H of the illuminated target surface 55FS is irradiated target surface of most current It is about 346 to 4911 mm, including its size, so it can illuminate most current areas of the illuminated surface with uniform brightness without wasting light. In addition, it can be determined by calculating the distribution of the light intensity in the surface to be irradiated by optical simulation as to how wide the range which can be illuminated with uniform brightness in the surface to be irradiated becomes.

Further, for example, as shown in FIG. 10 (b), parallel to the front side of the light impermeable display plate 55, the light is incident almost perpendicularly (for example, incident angle within 0 ° ± 10 °). A prism sheet 54 may be provided as an optical path changing means for changing the optical path of the light flux Lr.
In the example of FIG. 10, the front light device 1F includes the reflective prism sheet 14 (see FIG. 7) for emitting the parallel light flux Lr.

Thirteenth Embodiment
Next, a reflective liquid crystal display according to the invention of (13) will be described as a thirteenth embodiment. The thirteenth embodiment comprises the front light device according to the invention of (12), and a flat plate-like reflective liquid crystal panel having at least a liquid crystal sandwiched by a plurality of light distribution layers, and the light is emitted from the front light device. It is a form (not shown) which makes the light beam made incident into the front which is the surface by the side of the observer of the said reflection type liquid crystal panel. In the thirteenth embodiment (for example, any of FIGS. 10A and 10B), the light-impermeable display plate 55 is replaced with a plurality of light distribution layers in the tenth embodiment (for example, either of FIGS. 10A and 10B). This corresponds to a flat plate-like reflective liquid crystal panel having at least the liquid crystal (not shown).

  Examples of the flat plate-like reflection-type liquid crystal panel having at least the liquid crystal sandwiched by the plurality of light distribution layers described in the thirteenth embodiment include a polarizing filter, a glass substrate, a light distribution layer, liquid crystal, and A conventionally known reflective liquid crystal panel can be used which is formed of a laminate in which a diffusion plate or the like is laminated on a reflection plate whose reflection surface is on the viewer side.

  An embodiment will be described based on FIG. The size of the light emitting surface of the surface light source 10 made of an LED chip was 1.4 mm × 1.4 mm. The focal length f of the concave reflecting mirror and the distance M (see FIG. 1) from the light emitting surface of the collimating optical system to the reflecting surface of the concave reflecting mirror are f = M = 514.5 mm. The collimating optical system 30 has two lenses. Further, the reflection type prism sheet 14 has a form shown in FIG. 7 (the center line in the width direction of the reflection convex portion is linear, and the Z direction arrangement of the reflection concaves is equidistant), and the length in the Z direction is 500 mm. The normal to the center of the light exit surface of the surface light source 10 is taken as the optical axis of the condensing optical system 20 and the collimating optical system 30, and the distance from this optical axis to the reflective prism sheet 14 is 30 mm (FIG. 12). (B). Further, the length of the concave reflecting mirror 15 in the X direction is 70 mm, and the length in the Y direction is 70 mm. The inclination angle θ (see FIG. 1) of the concave reflection mirror 15 was set to θ = 3 °.

In the above embodiment, the condensing optical system 20 takes in 95% or more of the emitted light flux L ₀ (see FIG. 1) from the surface light source 10, and all the light flux satisfying the condition α of 19 ° to 30 °. The light beam L is emitted to the collimating optical system 30 as L ₁ (refer to FIG. 1), and the light beam L satisfying the condition [β = 5.0 ° or less] of the light beam L (refer to FIG. 1) The design conditions of the optical system from the surface light source 10 to the collimating optical system 30 which are sufficient to allow the light to enter the concave reflection mirror 15 are determined by optical simulation as follows.
(A) The distance between the surface light source 10 and the meniscus lens (first lens 21) of the focusing optical system 20 in the optical axis direction is 2.5 mm.
(B) The maximum lens diameter of the focusing optical system 20, which is the lens diameter of the second lens 22 having the larger lens diameter among the two lenses of the focusing optical system 20, is 10 mm. The two lenses 22 had spherical lens surfaces on both the light incident side and the light output side, and the focal lengths of the first lens 21 and the second lens 22 were 16.3 mm and 29.7 mm, respectively.
(C) In the collimating optical system 30, both of the two lenses 31 and 32 arranged in order from the light incident side are plano-convex lenses, the lens surface of the convex side is spherical, and the lens diameter of the lens 31 and focal length are 34 mm. The lens diameter and focal length of the lens 32 are 36 mm and 125.8 mm, respectively.
Distance from the light exit surface of (d) the surface light source 10 to the light exit surface of the lens 32 of the collimating optical system 30 (referred to as _{M 1) was} set to M 1 = 46.8 mm.

Assuming a surface 58 to be irradiated (FIG. 12B) on which the parallel light beam Lr emitted from the reflection type prism sheet 14 of the illumination device 1 of the embodiment is incident at an incident angle = 90 ° −θ ₁ = 82 °. The distribution of the light intensity in the irradiation target surface 58 was obtained by optical simulation in the case where the power of light output from the surface light source 10 was 1 W. 13 shows the distribution of light intensity in the Y direction of the irradiation target surface 58, that is, the Y coordinate value (= the distance in the Y direction from the point C with the point C (FIG. 12B) in the irradiation target surface 58 as the origin. mm] × Y direction conversion coefficient [mm- ¹ ]; Y direction conversion coefficient = 1) shows the relationship between the light intensity. Further, FIG. 14 shows the distribution of light intensity in the Z direction of the irradiation target surface 58, that is, the Z coordinate value (= Z direction from the point C with the point C (FIG. 12B) in the irradiation target surface 58 as the origin. The relationship between the distance [mm] x conversion factor in the Z direction [mm- ¹ ]; conversion factor in the Z direction = 1) and the light intensity is shown. In FIG. 13 and FIG. 14, “(numerical value 1) E− (numerical value 2)” on the vertical axis represents “(numerical value 1) × 10 ^{− (numerical value 2)} ”.

From FIG. 13, the Y coordinate value of the irradiation target surface 58 in the Y direction is about −210 to about 260, and the length in the Y direction is about 470 mm in a wide range of about (4 to 9) × 10 ⁻⁶ W. It can be seen that a sufficient and uniform light intensity (brightness) of cm ⁻² can be obtained. Further, from FIG. 14, the Z coordinate value of the irradiation target surface 58 in the Z direction is about −180 to about 180, and the length in the Z direction is about 360 mm in a wide range of about (4 to 9) × 10 ^−6. It can be seen that a sufficient and uniform light intensity (brightness) of W · cm ⁻² can be obtained.

DESCRIPTION OF SYMBOLS 1 illumination apparatus 1B back light apparatus 1F front light apparatus 10 surface light source 14 and 14A reflective prism sheet 15 concave reflective mirror 20 condensing optical system 21 1st lens (meniscus lens)
22 Second lens (convex lens)
30 Collimated optics 31, 32 lenses (lenses of collimated optics)
53 Light transmitting display plate 53BS Illumination target surface 54 of backlight device 1B Prism sheet 55 Light opaque display plate 55FS Illumination target surface 58 of front light device 1F Irradiation target surface H Irradiation target surface 53BS or irradiation target surface 55FS focal length M collimating optical system of the X-direction length f concave reflecting mirror in the height direction length Lr parallel beam X _1B back X-direction of the light exit opening of the light device 1B length X _1F front light device 1F of the light emitting window Distance M from the light exit surface to the reflecting surface of the concave reflecting mirror
Distance α from the light exit surface of the M ₁ surface light source to the light exit surface of the lens on the light exit side of the collimating optical system α to the light flux spreading side of the light flux emitted from the light exit surface side of the second lens Of the light beam collimated by the collimating optical system with respect to the optical axis, the spread angle θ of the light beam to the spreading side, the inclination angle θ of the concave reflecting mirror _1B illumination of the parallel light beam Lr from the light exit of the backlight device 1B Angle θ ₁ which is a complementary angle of the incident angle to the target surface 53BS Angle θ _{1F which is} a complementary angle of the incident angle to the irradiation target surface 55FS of the parallel beam Lr from the light exit of the front light device 1F

Claims (13)

A surface light source having a light emitting surface;
A convex lens placed so that the optical axis is aligned immediately after the light emitting surface side of the first lens by taking in substantially all of the light flux emitted from the surface light source with the first lens which is a meniscus lens covering the surface light source A condensing optical system in which the light emission angle α of the light beam emitted from the light emission surface side of the second lens is α = 19 ° to 30 ° on the side where the light beam spreads with respect to the optical axis. System,
The light flux emitted from the light collection optical system at the emission angle with respect to the optical axis is collimated at a spread angle β of not more than 5.0 ° with respect to the light axis, at least two A collimating optical system comprising the following lenses,
It consists of a concave reflecting mirror with a focal length f, which reflects the light beam emitted from the collimating optical system into a parallel light beam,
The reflective optical system satisfying the condition of 0.9 M <f <1.1 M with respect to the distance M from the light emitting surface of the collimating optical system to the reflecting surface of the concave reflecting mirror;
Furthermore, an optical path changing means,
A lighting device provided with
The reflection direction of the light flux reflected from the reflection optical system is inclined with respect to the optical axis of the light flux passing through the light collection optical system and the collimating optical system,
Furthermore, the optical path changing means is formed of a reflective prism sheet that changes the optical path of the light beam reflected from the reflective optical system.
A lighting device characterized by   The first lens and the second lens of the light collecting optical system are spherical lenses each having a light incident surface and a light emitting surface as lens surfaces and a rotation surface having an arc as a generatrix. The lighting device according to 1.   The illumination device according to claim 1, wherein the first lens and the second lens of the focusing optical system are integrally molded of a resin.   The latter is larger in the lens diameter on the condensing optical system side and the lens diameter on the reflective optical system side of the two or more and four or less lenses forming the collimating optical system. The lighting device according to any one of Items 1 to 3.   The illumination device according to any one of claims 1 to 4, wherein the collimating optical system comprises two plano-convex lenses.   The said collimating optical system consists of two Fresnel lenses, The illuminating device of any one of the Claims 1-5 characterized by the above-mentioned.   The concave reflection mirror has its reflection surface directed to the light incident surface side which is the lower surface side of the reflection type prism sheet, and the inclination angle θ = 1.0 ° to 5.0 with respect to the thickness direction of the reflection type prism sheet The lighting device according to any one of claims 1 to 6, which is inclined at an angle of °.   The illumination apparatus according to any one of claims 1 to 7, wherein a center line in a width direction of the reflection convex portion of the reflection type prism sheet has an arc shape.   The inclination of each of the reflection surfaces of the reflection-type prism sheet, on which the light flux reflected from the concave reflection mirror is reflected, is different from each other like a linear Fresnel lens. A lighting device according to any one of the preceding claims.   A backlight device comprising the lighting device according to any one of claims 1 to 9. A backlight device according to claim 10, and a flat plate-like liquid crystal panel having at least a liquid crystal sandwiched between a plurality of light distribution layers.
A liquid crystal display characterized in that a light flux emitted from the backlight device is made incident on the back surface of the liquid crystal panel.   A front light device comprising the lighting device according to any one of claims 1 to 9. A front light device according to claim 12, and a flat plate-like reflective liquid crystal panel having at least a liquid crystal sandwiched between a plurality of light distribution layers.
A reflective liquid crystal display characterized in that a light flux emitted from the front light device is made incident on the front of the reflective liquid crystal panel.

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