JP6136201B2 - Light guide, lighting device, display device - Google Patents

Description

  The present invention relates to a light guide, a lighting device including the light guide, and a display device.

  In recent flat panel displays and the like typified by a liquid crystal television, a direct type illumination device and an edge light illumination device are mainly used. In the direct type illumination device, a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are regularly arranged as light sources on the back surface of the panel. Between the image display element such as a liquid crystal panel and the light source, a diffuser plate having a strong light scattering property is used so that a cold cathode tube or LED as a light source is not visually recognized.

  On the other hand, in an edge light type illumination device, a plurality of cold-cathode tubes and LEDs are arranged on an end face (incident surface) of a translucent plate called a light guide plate. In general, a light deflection element that efficiently guides light incident from the end face of the light guide plate to the exit surface on the surface (light deflection surface) opposite to the exit surface of the light guide plate (surface facing the image display element). Is formed. At present, the light deflection element formed on the light deflection surface is generally one in which white ink is printed in a linear or dot shape (for example, Patent Literature 1 and Patent Literature 2).

  Since the light guide plate has a light source disposed on the end face of the transparent plate, the amount of light guiding the region near the light source is large, and the amount of light guiding the region away from the light source is relatively small. Accordingly, the light deflecting elements are designed so that light is emitted uniformly from the exit surface of the light guide plate by disposing the light deflecting elements closer to the light source and closer to the light source. Patent Document 2 discloses a method of arranging light deflection elements at a fixed pitch while changing the size of the light deflection elements, or a method of changing the arrangement pitch without changing the size of the light deflection elements. Have been described. Most of the light guide plates produced by the current printing method employ a method of arranging them at a constant pitch while changing the size of the light deflection element. However, the light incident on the white dots is diffusely reflected almost uncontrollably, so the emission efficiency is low. Also, light absorption by white ink cannot be ignored.

  Therefore, recently, a method of forming a microlens on the light deflection surface of a light guide plate by an ink jet method, a method of forming a light deflection element by a laser ablation method, and the like have been proposed. Unlike white ink, light absorption hardly occurs because it uses reflection, refraction, and transmission due to the difference in refractive index between the resin of the light guide plate and air. Therefore, it is possible to obtain a light guide plate having a higher light emission efficiency than that of white ink.

  However, the formation of the light deflection element by the ink jet method or the laser ablation method is formed in a separate process after the light guide plate is formed into a flat plate, as in the case of printing with white ink, so the number of manufacturing steps is not reduced. Rather, there is a problem that the tact time is longer than the white ink printing process and the initial cost of the equipment is high, resulting in high costs.

  Therefore, a method has been proposed in which the light guide plate is formed by injection molding or extrusion molding, and the light deflection element is directly shaped during injection molding or extrusion molding (for example, Patent Document 3). Since the light deflection element is formed simultaneously with the formation of the light guide plate, the number of processes is reduced, and the cost can be reduced.

  By the way, the emission light peak from the light guide plate is generally not a front direction but an oblique direction. This is because the light guide plate receives light from the side end surface and guides the light inside the light guide plate, so that light inclined in the light guide direction with respect to the front direction is easily emitted. Conventionally, in general, by arranging 2 to 4 optical sheets such as a diffusion sheet and a prism sheet in addition to the light guide plate, the optical sheet collects and diffuses the light emitted from the light guide plate, and the light intensity peak The inclination of was suppressed.

JP-A-1-241590 Japanese Patent Laid-Open No. 3-6525 JP 2000-89033 A

  However, the use of a plurality of optical sheets increases the light loss accordingly. This is because interface reflection between the optical sheet and air, reflected light due to the lens structure of the lens sheet, and the like increase. Furthermore, even when the backlight is assembled, it is a very troublesome operation to arrange a plurality of optical sheets without causing wrinkles or deflection. Also, a design that takes into account the occurrence of wrinkles and deflection due to thermal deformation, warpage, etc. of each optical sheet when the TV is turned on is required.

  The present invention has been made to solve such problems of the prior art, controls the direction of light emitted from the light guide, and emits it in the front direction without using a condensing lens sheet or the like. It is an object of the present invention to provide a light guide that can be used, a lighting device including the light guide, and a display device using the lighting device.

In order to solve the above-described problem, one aspect of the present invention is a light-transmitting light guide, and the light guide includes a first main surface and a second main surface facing the first main surface. And four side end surfaces connecting the first main surface and the second main surface, and at least one of the four side end surfaces is an incident surface on which light is incident, and the first main surface is incident on the first main surface. A concave light deflection element is formed for deflecting light incident from the surface and guided through the light guide body toward the second main surface side, and the light deflection element extends perpendicularly to the first main surface and one of the incident surfaces. Two contours extending from the top including the portion farthest from the first main surface to the first main surface in a cross-sectional shape when cut by a plane parallel to the direction (Y direction) orthogonal to the direction (X direction) Of the lines, the first function A (y) representing the height from the first main surface of the contour line closer to the incident surface satisfies the expression (1). Further, in the cross-sectional shape when the light deflection element is cut along a plane perpendicular to the first main surface and parallel to the X direction, the contour line is a curved shape whose inclination changes continuously. In addition, an optical path control element is formed on the second main surface and extends in the Y direction and is arranged in the X direction, and regulates the optical path of light guided through the light guide body.

... (Formula 1)

  Here, n represents the refractive index of the light guide, and the first function A (y) is the incident surface from the point that the contour line closer to the incident surface is connected to the first main surface. The height of the contour line from the first main surface at the position of the distance y in the direction away from the first position.

  The first function A (y) is preferably represented by a linear function of the distance y.

  Alternatively, the first function A (y) is represented by a polynomial function of the second or higher order of the distance y, and the fluctuation range of dA (y) / dy that is the differential value of the first function A (y) is the absolute value of the differential value. It is preferable that it is below the average value.

  Moreover, it is preferable that a top part forms a ridgeline.

  Further, in the cross-sectional shape, it is preferable that the top portion is a straight line or a round shape, and the width of the top portion is within 30% of the width of the light deflection element in the Y direction.

  Further, the differential value dB (2) of the second function B (y) representing the height from the first main surface at the position of the distance y of the contour of the two contours that is farther from the incident surface. The average value of the absolute value of y) / dy is preferably equal to or smaller than the average value of the absolute value of the differential value dA (y) / dy of the first function A (y).

  Moreover, it is preferable that the light deflection element has a dot shape that is independently arranged in the first main surface.

  Further, the maximum angle formed between the tangent of the cross-sectional shape when the light deflection element is cut by a plane perpendicular to the first main surface and parallel to the X direction and the first main surface is θd, and the optical path control element is the first main surface. When the maximum angle between the tangent to the first main surface and the tangent of the cross-sectional shape when cut by a plane perpendicular to the plane and parallel to the X direction is θL, and the refractive index of the light guide is n, the maximum angle θL is (Formula 2) is preferably satisfied.

... (Formula 2)

  Another aspect of the present invention includes the light guide described above, a reflection sheet disposed at a position facing the first main surface, and a light source disposed facing the incident surface. It is a lighting device.

  Moreover, it is preferable to provide a diffusible optical sheet on the second main surface side.

  Still another aspect of the present invention is a display device including an image display element that defines a display image in accordance with transmission / shielding in pixel units and the above-described illumination device.

  ADVANTAGE OF THE INVENTION According to this invention, even if it does not arrange | position a condensing optical sheet, a high-intensity light guide, an illuminating device provided with this light guide, and a display apparatus using this illuminating device can be provided.

Schematic cross-sectional view of a lighting device according to an embodiment of the present invention (A) The perspective view of the light guide of embodiment of this invention, (b) (c) The figure seen from the side end surface of the light guide of embodiment of this invention Sectional drawing of the light deflection | deviation element of the light guide of embodiment of this invention The side view which shows the propagation of the light inside the light guide of embodiment of this invention Sectional drawing of the light deflection | deviation element of the light guide of embodiment of this invention Sectional drawing of the light deflection | deviation element of the light guide of embodiment of this invention (A) Top view showing light propagation inside the light guide without the optical path control element, (b) Side view showing light propagation inside the light guide without the optical path control element (A) The figure which shows the surface luminance distribution of a light guide without an optical path control element, (b) The figure which shows the surface luminance distribution of embodiment of this invention (A) Top view showing light propagation inside light guide of embodiment of the present invention, (b) Side view showing light propagation inside light guide of embodiment of the present invention Sectional drawing of the optical path control element and light deflection | deviation element of the light guide of embodiment of this invention Sectional drawing of the optical path control element and light deflection | deviation element of the light guide of embodiment of this invention Schematic cross-sectional view of a display device according to an embodiment of the present invention The top view and sectional drawing of the light guide of the Example of this invention

(Embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the illuminating device 3 in the present embodiment, and the reduced view of each part does not match the actual one. The illumination device 3 includes at least a light guide 7 and a light source 6. Further, it may include a reflective plate (reflective sheet) 5 and at least one transmissive optical sheet 8.

  An example of the light source 6 is a point light source. Examples of the point light source include an LED (light emitting diode), and examples of the LED include a white LED and an RGB-LED composed of red, green, and blue chips that are the three primary colors of light. A plurality of these point light sources are arranged as the light source 6 in the extending direction (X direction) of at least one end surface 7L (incident surface) among the four side end surfaces of the light guide 7. In FIG. 1, an example in which the light source 6 is arranged on one incident surface 7 </ b> L of the light guide 7 is shown, but the present invention is not limited to this, and the light source 6 may be arranged on two opposing end surfaces. Alternatively, the light source 6 may be a fluorescent tube represented by a CCFL (cold cathode tube) or a surface light source. The shape of the light guide 7 may be a wedge shape or the like instead of the flat plate shape as shown in FIG.

  The surface on the observer side F of the light guide 7 is the exit surface 7b which is the second main surface. A light deflection surface 7a, which is a first main surface, is formed on the surface opposite to the emission surface 7b, and the light deflection surface 7a includes a flat surface and a light deflection element 18. The light deflection element 18 deflects the angle of the light guided inside the light guide 7 to the angle emitted from the emission surface 7b. Examples of the light deflection element 18 include dot-shaped structures such as a concave microlens shape and a pyramid shape that are discretely arranged on a plane. By arranging the light deflection elements 18 in the form of dots in the first main surface, it is possible to control the arrangement of the light deflection elements 18 so as to obtain a desired luminance distribution while suppressing the visibility of the light deflection elements 18. Is possible.

  The flat surface of the light deflection surface 7a may be provided with unevenness (not shown) sufficiently finer than that of the light deflection element 18. The height of the fine irregularities is desirably 1/10 or less of the height of the light deflection element 18. This is because if the height of the light deflection element 18 exceeds 1/10, the surface luminance uniformity of the light guide 7 may be reduced. The fine irregularities are desirably in the form of dots that are discretely arranged on the flat surface of the light deflection surface 7a. The shape may be indefinite. When the light deflection elements 18 are arranged at intervals, when the light guide 7 is observed from the observer side F, each of the light deflection elements 18 may be visually recognized. This is because light whose light guide angle is deflected by the light deflection element 18 out of the light guided inside the light guide body 7 is emitted from the emission surface 7b, so that the observer observes the light deflection element 18 shining. This is because the flat surface is observed darkly. By arranging a plurality of fine irregularities between the light deflecting elements 18, a flat portion where the light deflecting elements 18 are not disposed is shined and observed, so that each of the light deflecting elements 18 can be prevented from being visually recognized. I can do it.

  The fine unevenness may be a streaky unevenness. The direction in which the fine irregularities extend is preferably a direction (Y direction) substantially orthogonal to the X direction. This is to assist the function of the optical path control element 19 formed on the exit surface 7b of the light guide 7 to be described later.

  Further, the fine irregularities are streaky irregularities, and the extending direction thereof may be the X direction. This is because, when the fine unevenness extends in the X direction, the light guide that cannot be deflected by only the light deflection element 18 can be deflected and emitted, so that the emission efficiency of the light guide 7 is improved.

  On the other hand, an optical path control element 19 is formed on the exit surface 7 b of the light guide 7. The optical path control element 19 controls the light guiding of the light incident on the light guide 7 through the incident surface 7L from the light source 6 and the light emitted from the exit surface 7b, and the luminance uniformity of the light guide 7 is increased. In addition, high brightness can be realized. The optical path control element 19 has a prism shape or a lenticular lens shape extending in one direction, and the extending direction is a direction (Y direction) substantially orthogonal to the X direction. Here, the substantially orthogonal direction indicates a range of ± 10 degrees with respect to 90 degrees (orthogonal). That is, it substantially coincides with the optical axis direction of the light source 6. There may be a case where the angle is inclined in order to suppress an angle shift caused by the manufacturing method of the light guide 7 or moire suppression when a plate or sheet having a regular structure is disposed on the exit surface 7 b side of the light guide 7. At this time, if it is within a range of ± 10 degrees with respect to the X direction, the characteristics of the lighting device 3 of the present invention described later will not be greatly impaired.

  The illuminating device 3 of this embodiment may be provided with the reflection sheet 5 on the light deflection surface 7a side of the light guide 7 according to the purpose of use. The light guided from the light source 6 through the light incident surface 7L through the light guide 7 is deflected by the light deflection element 18 formed on the light deflection surface 7a and emitted from the emission surface 7b. The light deflecting element 18 refracts and transmits without being reflected. Therefore, since the reflection sheet 5 is provided on the light deflection surface 7a side, the effect of allowing the light emitted from the light deflection surface 7a to enter the light guide 7 again can be obtained. Can be increased. Although the reflection sheet 5 is not specifically limited, For example, a general white reflector and a specular reflector are mentioned. Alternatively, a structural reflector provided with a prism shape may be used.

  Furthermore, the illuminating device 3 of the present embodiment may include one or more transmissive optical sheets 8 on the exit surface 7 b side of the light guide 7. The transmissive optical sheet 8 is desirably a diffusive optical sheet such as a diffusion sheet, a diffusion plate, or a microlens sheet. Further, it may have a function of separating polarized light.

  Hereinafter, the light guide 7 constituting the illumination device 3 of the present embodiment will be described in more detail. FIG. 2 is a perspective view and a side view of the light guide 7. A light deflection element 18 having a concave shape is formed on the light deflection surface 7 a of the light guide 7. The shape of the light deflecting element 18 may be a polygonal prism shape typified by a perfect circular or elliptical microlens shape or a pyramid shape.

  The shape of the light deflection element 18 will be described in more detail with reference to FIG. FIG. 3 is a sectional view of the light deflection element 18 in the Y direction. The cross section of the light deflection element 18 has a top T that is farthest from the light deflection surface 7a and two contour lines that extend from the top T to the light deflection surface 7a. The contour line closer to the light source 6 is the contour line A, and the other is the contour line B. The first function A (y) sets the point where the contour line A and the light deflection surface 7a are connected to 0, and the position of the distance y from there to the point Dy where the contour line B and the light deflection surface 7a connect. Represents the height of the contour line A from the light deflection surface 7a. On the other hand, the second function B (y) similarly represents the height of the contour line B from the light deflection surface 7a at the position of the distance y. At this time, it is desirable to satisfy the following (Formula 1) for the first function A (y).

... (Formula 1)

  Here, n is the refractive index of the light guide 7.

  When the first function A (y) representing the shape of the contour line A satisfies (Equation 1) at all positions, the peak of the emitted light from the light guide 7 is efficiently directed in the front direction of the exit surface 7b. Can be directed. When the first function A (y) does not satisfy (Equation 1) and the angle component of the contour line A is small, the peak of light emitted from the light guide 7 is generated in an oblique direction rather than in the front direction. In order to obtain a high-luminance illumination device, it is necessary to dispose a condensing optical sheet represented by a prism sheet. On the other hand, when the first function A (y) does not satisfy (Equation 1) and the angle component of the contour line A is large, the peak of light emitted from the light guide 7 is not in the front direction but in an oblique direction. Further, the light that is refracted and transmitted without being reflected by the contour line A increases, and the emission efficiency of the illumination device 3 decreases.

  (Equation 1) of this embodiment will be described in detail below with reference to the drawings. The left side of (Equation 1) represents the total reflection angle at the interface with air in the light guide 7 having a refractive index n. That is, the angle component of the contour line A necessary for total reflection when light parallel to the light deflection surface 7a is incident on the contour line A of the light deflection element 18 is shown. However, as shown in FIG. 4, light that is parallel to the light deflection surface 7 a hardly enters the other light deflection elements 18 except for the light deflection element 18 that is actually arranged closest to the incident surface 7 </ b> L. This is because each light deflecting element 18 becomes a shadow of the light deflecting element 18 disposed on the incident surface 7L side from these. Accordingly, when the angle parallel to the light deflection surface 7a is 0 degree, the light k1 is incident on the contour line A with a depression angle of 0 degree or more. There is also light k2 that is reflected by the flat portion of the light deflection surface 7a and travels toward the contour line A, but it is a very small amount of light, and its influence is slight compared to the light k1.

The maximum angle of the light k1 toward the contour line A at an angle of 0 ° or more is equal to the above-described total reflection angle represented by the left side of (Expression 1). Therefore, the condition for totally reflecting the light incident on the contour line A at the maximum angle is the right side of (Equation 1). Actually, the amount of light guided through the light guide 7 at the maximum angle is small. From the light source 6, light having a substantially Lambertian distribution is incident from the incident surface 7 </ b> L. However, as the angle increases, more light is reflected without being transmitted due to Fresnel reflection between the air and the light guide 7. Further, most of the light having a large light guide angle is deflected by the light deflection element 18 in the vicinity of the incident surface 7L and is emitted in the vicinity of the incident surface 7L. Therefore, the right side of (Formula 1) is more preferably 1.5 × sin ⁻¹ (1 / n). Further, as described above, since there is almost no light incident on the contour line A at an angle parallel to the light deflection surface 7a, the left side of (Equation 1) is more preferably 1.1 × sin ⁻¹ (1 / n). is there.

  By setting the shape of the contour line A, which is a surface for directly deflecting the light from the light source, in this way, the light guide 7 that strongly emits the light guided inside the light guide in the front direction is obtained. I can do it.

  Returning to the description of the shape of the light deflection element 18 illustrated in FIG. 3, the first function A (y) is a linear function, and the differential value dA (y) / of the first function A (y) at any position. dy is a constant value. Therefore, it is desirable that the contour line A (y) satisfies (Equation 1) because the peak position of the light emitted from the light guide 7 can be easily controlled in the front direction, that is, the observer side F.

  On the other hand, for the second function B (y) representing the shape of the contour line B, the average absolute value of the differential value dB (y) / dy is the differential value dA (y) / of the first function A (y). It is desirable to be equal to or smaller than the average value of absolute values of dy. The reason will be described. A part of the light incident on the light guide 7 from the light source 6 through the incident surface 7L is deflected by total reflection at the interface between the contour line A of the light deflection element 18 and the air, and from the exit surface 7b. It is ejected to the observer side F. Other light is refracted and transmitted at the interface between the contour line A of the light deflection element 18 and air. At this time, part of the light travels toward the contour line B, is refracted and transmitted at the interface between the air and the contour line B, and reenters the light guide 7. The other light travels toward the reflection sheet 5, is diffusely reflected by the reflection sheet 5, and reenters the light guide 7 from the light deflection surface 7a. At this time, the contour line B out of the light refracted and transmitted from the contour line A increases as the average value of the absolute values of the differential values dB (y) / dy of the second function B (y) representing the shape of the contour line B increases. The light re-incident on the light guide 7 through the light increases, and conversely, the smaller the differential value dB (y) / dy of the second function B (y), Light that is diffusely reflected by the reflection sheet 5 and re-enters the light guide 7 from the light deflection surface 7a increases.

  The outline A of the light deflection element 18 constituting the light guide 7 is emitted from the exit surface 7b by deflecting the light incident on the light guide 7 from the entrance surface 7L, and the peak of the exit light distribution is the front surface. It almost coincides with the direction. Therefore, when the light guide 7 is observed from the observer side F, there arises a problem that the light deflection element 18 is easily visually recognized. That is, each of the light deflection elements 18 is visually recognized as a point light source with strong directivity.

  Therefore, the inventors, when observing the light guide 7 from the observer side F by re-entering the light deflecting surface 7a after the light refracted and transmitted from the contour line A is once diffusely reflected by the reflection sheet, It has been found that the visibility of each of the light deflection elements 18 decreases as a result of the peripheral portion of the light deflection elements 18 being emitted and visually recognized.

  That is, the light guide 7 uses the average value of the differential values dB (y) / dy of the second function B (y) representing the shape of the contour line B as the first function A ( Of the light that is refracted and transmitted from the contour line A by being equal to or smaller than the average value of the differential value dA (y) / dy of y), it is diffusely reflected by the reflection sheet 5 and passes through the light deflection surface 7a. Thus, the light re-entering the light guide 7 can be increased, and the visibility of the light deflection element 18 can be suppressed.

  In addition, when the incident surfaces of the light guide are two side end surfaces facing each other, it is desirable that the contour line B has the same shape as the contour line A in order to deflect incident light from a light source at a distance. On the other hand, when the incident surface of the light guide is one side end surface, it is the contour line A that directly deflects the incident light from the light source. Of the light incident on the contour line A, the light refracted and transmitted without reflecting is incident on the contour line B. In this case, as described above, the average value of the absolute values of the differential value dB (y) / dy of the second function B (y) is greater than the differential value dA (y) / dy of the first function A (y). By setting it to be small, the amount of light that is refracted and transmitted without being reflected out of the light incident on the contour A can be reduced to re-enter the light guide via the contour B.

  FIG. 5 is a cross-sectional view in the Y direction of a light deflection element 18 according to another embodiment. The light deflection element 18 has two contour lines, a contour line A and a contour line B, which extend from the light deflection surface 7a to the light deflection surface 7a. It is represented by a first function A (y) and a second function B (y). Although both the first function A (y) and the second function B (y) of the contour line shown in FIG. 3 are linear functions, the first function of the contour line shown in FIG. The function A (y) and the second function B (y) are polynomial functions including quadratic or higher. At this time, it is desirable that the first function A (y) representing the shape of the contour line A satisfies (Equation 1) at all positions. The light guided inside the light guide 7 is not only light parallel to the Y direction, but also a lot of oblique light guided while being reflected by the light deflection surface 7a and the exit surface 7b of the light guide 7. Therefore, by making the shape of the contour line A a curved surface represented by a polynomial function, light at a plurality of angles can be efficiently deflected and emitted in the front direction. Furthermore, by increasing the amount of light emitted in directions other than the front direction, adjustment can be made so that the light emitted from the illumination device 3 does not become excessively peaky.

  Since the light guided inside the light guide is incident on the light deflection element at any angle, the contour A may have a curved shape having a plurality of angle components. It is also effective when the light emitted from the light guide is desired to be emitted not only in the front direction but also in a certain angle range. However, the shape of the contour line A for efficiently deflecting the emitted light toward the front direction is defined by the above (Formula 1), and when the angle component exceeds the range of the (Formula 1), This is undesirable because the function of deflecting in the direction is reduced. Therefore, the fluctuation range of dA (y) / dy that is the differential value of the first function A (y) is set to a range that is equal to or less than the average value of the absolute values of the differential values, and the fluctuation is suppressed (formula 1). It is preferable not to exceed the range.

  FIG. 6 is a cross-sectional view in the Y direction of a light deflection element 18 according to another embodiment. The light deflection element 18 has a top T of the round farthest from the light deflection surface 7a and two contour lines from the top T to the light deflection surface 7a, contour A and contour B, respectively. The shape is represented by a first function A (y) and a second function B (y). As shown in FIG. 3 and FIG. 5, when the curvature changes discontinuously at the top T and the top T forms a ridge line, the light distribution of the light emitted from the light guide 7 is a peaky characteristic in the front direction. It is easy to become. Moreover, it becomes possible to inject | emit the light which guides the inside of a light guide efficiently by the outline A which reaches a ridgeline to a front direction. As described above, the contour A and the contour B are polynomial functions including quadratic or higher to increase the emission light in directions other than the front direction, and the peaky emission light characteristics are prepared. The same effect can be obtained. Furthermore, when the top portion T is a ridge line, defects tend to occur in the mold that forms the light deflection element 18, and problems such as scratches, chipping, and abrasion due to contact occur. The occurrence of problems can be suppressed. Furthermore, rounding the top is also effective when the light emitted from the light guide is emitted not only in the front direction but also in a certain angle range. Or it is good also considering the top part T as a linear shape.

  By the way, the width Ty of the top part T of the round is desirably within 30% with respect to the width Dy of the light deflection element 18 in the Y direction. Since the area of the round top T is out of the range of (Equation 1) described above, the amount of light deflected in the front direction when the width of the round top T exceeds 30% of the width Dy of the light deflection element 18. This is because the brightness decreases.

  The cross-sectional shape in the Y direction of the light deflection element 18 shown in FIGS. 3, 5, and 6 is a partial example, and is not limited thereto. For example, the first function A (y) representing the contour A may be a linear function, and the second function B (y) representing the contour B may be a polynomial function including quadratic or higher, or vice versa. .

  On the other hand, an optical path control element 19 is formed on the exit surface 7b of the light guide. The optical path control elements 19 have a prism shape or a lenticular lens shape extending in the Y direction, and are arranged at a constant pitch in the X direction. At this time, the optical path control elements 19 may be arranged with a gap. FIG. 2 illustrates a case where the shape of the optical path control element 19 is a lenticular lens. The optical path control element 19 controls the path of light guided through the light guide 7 and the emission direction of light emitted from the emission surface 7b. The conventional problems and the solving means according to the present invention in the case where the light deflection element density D in the X direction of the light guide 7 is constant will be described below.

  FIG. 7 illustrates the behavior of light guided through the light guide 7 without the optical path control element 19. FIG. 7A is a view seen from the exit surface 7b side, and FIG. 7B is a view seen from the entrance surface 7L. Here, the case where one light source 6 is arranged on the incident surface 7 </ b> L of the light guide 7 is simply illustrated.

  When there is no optical path control element 19, the light emitted from the light source 6 enters the light guide 7 through the incident surface 7L, and guides the light guide 7 while spreading in the fan shape. Here, FIG. 8A is a diagram showing the surface luminance distribution of the light guide 7 without the optical path control element 19, and as an example, two long sides of the light guide 7 are used as the incident surface 7L. The light guide 7 without the optical path control element 19 generates a triangular dark portion G shown in the figure. As shown in FIG. 7A, the light incident on the light guide 7 from the light source 6 spreads in a fan shape and is guided. This is due to light leakage from the side end face of the short side where 6 is not disposed. Therefore, in the prior art, when designing the arrangement of the light deflection elements 18, it is difficult to make the light deflection element density D in the X direction constant. There was a problem of not becoming.

  FIG. 9 illustrates the behavior of light guided inside the light guide 7 having the optical path control element 19. FIG. 9A is a view seen from the exit surface 7b side, and FIG. 9B is a view seen from the entrance surface 7L.

  The light incident from the light source 6 has its reflection angle deflected by the inclined surface of the optical path control element 19 and is guided in the Y direction without spreading in a fan shape. FIG. 8B is a diagram showing the surface luminance distribution of the light guide 7 having the optical path control element 19. Since the light incident from the light source 6 does not spread in a fan shape and is guided in the Y direction, the dark portion G as shown in FIG. 8A does not occur. Further, there is almost no leakage light from the end surface on the short side where the light source 6 is not disposed, and the highly efficient lighting device 3 can be obtained.

  As described above, the function of controlling the path of the light guided inside the light guide 7 suppresses the generation of the dark part G described above and improves the luminance uniformity. The illumination device 3 using the light guide 7 can be applied to a backlight of a liquid crystal display, for example, a scanning backlight in a 3D display. In addition, since the light emitting area of the lighting device 3 can be controlled by turning on and off the light source 6, it is possible to contribute to power saving of the liquid crystal display by local dimming.

  The optical path control element 19 may extend in the Y direction and be arranged in the X direction, and may be a prism lens having a triangular cross section, a polygonal prism lens, or a shape having a rounded tip. When the optical path control element 19 has such a prism lens shape, the light emitted from the exit surface 7b is collected, and the high-luminance illumination device 3 can be obtained.

  The cross-sectional shape of the optical path control element 19 is desirably a spherical or aspherical curved lenticular lens. This is because the light emitted from the exit surface 7b is collected by the curved lenticular lens and not only the high-luminance illumination device 3 can be obtained, but also light source unevenness that occurs in the vicinity of the entrance surface 7L can be suppressed. . That is, a plurality of light sources 6 are arranged at regular intervals on the incident surface 7L of the light guide 7, but light source unevenness due to the arrangement intervals of the light sources 6 occurs in the vicinity of the incident surface 7L. The tangential angle of the cross-sectional contour of the curved lenticular lens that is spherical or aspherical is configured at various angles with respect to the surface of the light guide 7. Therefore, the light guide internally reflected by the curved lenticular lens is reflected at various angles, so that light source unevenness can be suppressed.

  Further, the optical path control element 19 has a function of reducing the visibility of the light deflection element 18. When the illumination device 3 of the present embodiment is applied as a backlight for a display, it is not desirable that the light deflection element 18 is visually recognized in a dot shape. When the optical path control element 19 is a prism lens, the image of the light deflection element 18 is split. For example, when the optical path control element 19 is a triangular prism lens, the image of one light deflection element 18 is split into two images. Therefore, the visibility of the light deflection element 18 can be easily reduced. On the other hand, when the optical path control element 19 is a curved lenticular lens, the image of the light deflection element 18 that is dot-like is linearized, so that the visibility of the light deflection element 18 can be easily reduced.

  The optical path control elements 19 extend in the Y direction and are arranged at constant intervals or random intervals in the X direction. At this time, there may be a flat gap between the optical path control elements 19. If the gap is 10% or less of the pitch at which the optical path control elements 19 are arranged, the dark portion G suppressing function or the light emitting surface area controlling function and the visibility reduction of the light deflection elements 18 are not affected. More desirably, the gap is 5% or less of the pitch at which the optical path control elements 19 are arranged. By providing such a gap, it is possible to extend the life of the molding die for the light guide 7 and to suppress the occurrence of molding defects.

  So far, the Y-direction cross-sectional shape of the light deflection element 18 and the optical path control element 19 have been described. Next, the interaction between the X-direction cross-sectional shape of the light deflection element 18 and the X-direction cross-sectional shape of the optical path control element 19 will be described. The new features of will be described below.

  The optical path control element 19 is defined as θd, which is the maximum angle between the tangential line of the cross-sectional shape when the dot-shaped light deflection element 18 is cut by a plane perpendicular to the light deflection surface 7a and parallel to the X direction, and the light deflection surface 7a. When the maximum angle formed between the tangent to the cross-sectional shape and the exit surface 7b when it is cut by a plane perpendicular to the exit surface 7b and parallel to the X direction is θL, and the refractive index of the light guide 7 is n, the maximum By satisfying the range of the following (Equation 2), the angle θL efficiently emits the light incident on the light guide 7 from the exit surface 7b, improves luminance uniformity, and improves light utilization efficiency. I can do it.

... (Formula 2)

  Light incident on the light guide 7 from the light source 6 guides the inside of the light guide 7 through a three-dimensional optical path. When the extending direction of the incident surface 7L is the X direction, the direction orthogonal to the incident surface 7L is the Y direction, and the normal direction of the light deflection surface 7a of the light guide 7, that is, the thickness direction of the light guide 7 is the Z direction. When the light guided through the light guide 7 in the XY plane is viewed, the emission efficiency and the emission angle are determined by the cross-sectional shape of the light deflection element 18 in the XY plane. On the other hand, when the light guided through the light guide 7 in the XZ plane is viewed, light whose optical path is deflected by the cross-sectional shape of the light deflection element 18 in the XZ plane is an optical path control element formed on the exit surface 7b. 19 is further deflected. That is, in order to efficiently emit the light incident on the light guide 7 from the exit surface 7b, not only the cross-sectional shape of the light deflection element 18 in the XY plane but also the cross-sectional shape of the light deflection element 18 in the XZ plane and the optical path. It is necessary to consider the interaction with the cross-sectional shape of the control element 19 in the XZ plane.

  FIG. 10 is a sectional view showing the relationship between the maximum tangent angle θd of the light deflection element 18 and the maximum tangent angle θL of the optical path control element 19 in the XZ plane. The light k incident on the light deflection element 18 is reflected by the maximum tangent angle θd, and the light k incident on the optical path control element 19 is refracted and emitted by the maximum tangent angle θL. Consider a case where the light ray k enters the light deflection element 18 at an angle α with respect to the X direction. At this time, in order to reflect the light ray k, the total reflection condition based on the refractive index difference between the light deflecting element 18 and air is expressed by the following (Equation 3), and the behavior of the light ray k satisfying the total reflection condition will be described.

... (Formula 3)

  The light beam k reflected by the light deflecting element 18 and whose path has been changed to the exit surface 7b side is refracted and transmitted by the light path control element 19. At this time, the angle θa formed between the light beam k emitted from the light guide 7 and the Z axis is made smaller than the angle θp formed between the light beam k and the Z axis inside the light guide 7, that is, the optical path control element 19. In order to collect light in the Z direction, the maximum tangent angle θL of the optical path control element 19 must satisfy the following (Equation 4).

... (Formula 4)

  Considering the case where α is the largest angle, the following (Formula 5) is obtained.

... (Formula 5)

  By forming the optical path control element 19 that satisfies this (Equation 5), the light beam k reflected by the optical deflection element 18 is condensed and emitted in the Z direction by the optical path control element 19. The brightness is improved.

  Most preferably, the angle θa between the light beam k refracted and emitted by the optical path control element 19 and the Z axis is 0 degree. Therefore, it is desirable to satisfy the following (Formula 6).

... (Formula 6)

  The numerical expression of (Expression 6) excluding ± α in the right expression is an expression in which the angle θa formed between the light beam k refracted and emitted by the optical path control element 19 and the Z axis is 0 degree. Here, the incident angle α of the light ray k is a maximum value. However, since the incident angle α of the light beam k reflected by the light deflection element 18 is in the range of the angle represented by (Equation 2) from 0 degrees or more, the maximum tangent angle θL of the optical path control element 19 is ± α from the optimum angle. It is desirable to set between.

  On the other hand, when the maximum tangent angle θL of the optical path control element 19 is too large, the light beam k incident on the optical path control element 19 causes total reflection at the interface between the optical path control element 19 and air, which is not desirable. Here, when considering the case where the incident angle α of the light ray k is 0 degree, it is desirable that the maximum tangent angle θL of the optical path control element 19 satisfies the following (Expression 7).

... (Formula 7)

  When the maximum tangent angle θL of the optical path control element 19 does not satisfy (Equation 4), the light beam k incident on the maximum tangent angle θL of the optical path control element 19 is not transmitted and is reflected, which is not desirable. Even when the incident angle α of the light ray k is the maximum angle obtained by (Expression 1), it is preferable that total reflection does not occur at the interface between the optical path control element 19 and air, and the following (Expression 8) is satisfied. Is more desirable.

... (Formula 8)

  Here, a method of calculating the maximum tangent angle θL of the optical path control element 19 and the maximum tangent angle θd of the light deflection element 18 will be described. When the optical path control element 19 has a curved lenticular lens shape as shown in FIG. 11, the maximum tangential angle becomes a valley of the adjacent optical path control element 19, and the tangential angle decreases from there toward the top of the curved lenticular lens. . That is, since the tangent angle continuously changes on the contour of the curved lenticular lens, it is difficult to discuss the maximum tangent angle at one point in the valley of the adjacent optical path control element 19. Therefore, the definition of the maximum tangent angle θL is defined as follows. That is, when the pitch of the curved lenticular lens is PL, a point between the valleys of the adjacent optical path control elements 19 and a point on the cross-sectional contour of the optical path control element 19 at a position away from that by PL × 1/10 in the X direction. It is defined as the angle of the line connecting The same applies to the maximum tangent angle θd of the light deflection element 18. When the width of the light deflection element 18 in the X direction is Pd, a contact point with the light deflection surface 7a, and a point on the cross-sectional contour of the light deflection element 18 at a position away from it by Pd × 1/10 in the X direction It is defined as the angle of the line connecting.

  The light guide 7 according to the present invention is an acrylic resin represented by PMMA (polymethyl methacrylate), or PET (polyethylene terephthalate), PC (polycarbonate), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer). The light deflection element 18 and the optical path control element are formed by a transparent resin such as AS (acrylonitrile styrene copolymer) and the like by an extrusion molding method, an injection molding method, or a heat press molding method well known in the art. 19 is integrally formed. Or after shaping | molding the flat light guide 7 with the manufacturing method mentioned above, you may form the light deflection | deviation element 18 and the optical path control element 19 using a printing method, UV curable resin, a radiation curable resin.

  In the light guide 7 of the present invention, it is preferable that the light deflection element 18 and the optical path control element 19 are integrally formed by using an extrusion molding method among the manufacturing methods described above. This is because the number of steps for producing the light guide 7 is reduced, and because it is formed by roll-to-roll, mass productivity is high. Since the light deflection element 18 formed in the light guide 7 of the present invention has a one-dimensional sparse / dense pattern, the width direction of the roll mold and the one-dimensional sparse / dense direction preferably match, The light guide 7 can be formed seamlessly by arranging the winding directions at substantially constant intervals.

  FIG. 12 is a schematic cross-sectional view of the display device 1 using the illumination device 3 and the image display element 2 in the present embodiment, and the reduced view of each part does not match the actual one. Examples of the transmissive optical sheet 8 constituting the display device 1 include a diffusion sheet in which diffusion beads are coated on a transparent substrate. The diffusion sheet suppresses the light deflection element 18 formed on the light deflection surface 7a of the light guide 7 and suppresses the visibility, and at the same time, the diffusion beads exhibit the same effect as the microlens so that the light from the light guide 7 It has a function of collecting the emitted light to the observer side F. Alternatively, the transmissive optical sheet 8 may be a microlens sheet in which microlenses having a substantially hemispherical shape with higher light collecting properties are regularly or irregularly arranged. Alternatively, it may be a diffusion plate (sheet) in which a diffusion filler is dispersed in a transparent substrate, and this diffusion plate (sheet) may have a polarization separation function.

  The image display element 2 is preferably an element that displays an image by transmitting / blocking light in pixel units. If an image is displayed by transmitting / blocking light in pixel units, the illumination device 3 of the present invention effectively uses light with improved luminance to the viewer side F, and has high image quality. An image can be displayed.

  The image display element 2 is preferably a liquid crystal display element. A liquid crystal display element is a typical element that transmits / shields light in pixel units and displays an image, and can improve image quality and reduce manufacturing cost compared to other display elements. Can do.

  The light guide 7, the lighting device 3, and the display device 1 of the present invention have been described above, but the lighting device 3 of the present invention is not applied only to the display device 1. That is, the illumination device 3 having a function of efficiently condensing light emitted from the light source 6 can be used for, for example, an illumination device.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited only to a following example.

(Outline of light guide)
The light guide 7 in the present embodiment will be described. A curved lenticular lens (optical path control element) 19 having a height of about 50 μm and a width of about 150 μm is formed on the light exit surface 7 b of the light guide 7. The curved lenticular lenses 19 extend in the Y direction and are arranged without gaps in the X direction. The maximum tangent angle θL in the cross section in the X direction is about 58 degrees.

  On the other hand, the light deflecting surface 7a of the light guide 7 has a concave asymmetrical elliptical microdot (light deflecting element) 18 whose bottom surface is an asymmetrical ellipse as shown in FIG. Are arranged discretely in accordance with. The major axis of the elliptical microdot is about 200 μm, the minor axis is about 60 μm, and the lens height (depth because it is concave) is about 20 μm. The light guide 7 has a thickness of 3 mm and a size of 32 inches, the incident surface 7L has one long side of the four side end surfaces, and is made by extrusion molding using PMMA (polymethyl methacrylate). did.

(Shape of light deflection element)
Next, the asymmetric elliptical microdots 18 formed on the light guide 7 of this embodiment will be described in detail. The major axis of the elliptical microdot 18 is substantially coincident with the X direction, and the minor axis is substantially coincident with the Y direction. Therefore, the shape of the cross section in the Y direction, that is, the short-axis cross section of the elliptical microdot 18 is a plane orthogonal to the optical axis of the light source 6. The contour line on the left side is the contour line A, and the contour line on the right side is the contour line B, both of which have a linear function shape. The light guide 7 in this embodiment is molded using PMMA, and the refractive index of PMMA is about 1.49. Therefore, the total reflection angle at the interface with air is about 43 degrees. According to (Equation 1), the inclination angle of the contour line A is preferably 43 degrees or more and 86 degrees or less, but as described above, it is further preferably in the range of 47 degrees or more and 65 degrees or less. In this embodiment, the angle formed between the contour line A and the light deflection surface 7a is 52 degrees, and the angle formed between the contour line B and the light deflection surface 7a is 28 degrees. The top portion T has a round shape, and its width is 15% with respect to the width Dy in the Y direction of the asymmetric elliptical microdot 18.

(Shape of light deflection element and shape of optical path control element)
Next, the shape of the asymmetric elliptical microdot 18 in the X-direction cross section and the shape of the curved lenticular lens 19 that is the optical path control element 19 will be described. As described above, it is desirable that the maximum tangent angle θd in the X-direction section of the asymmetric elliptical microdot 18 and the maximum tangent angle θL in the X-direction section of the curved lenticular lens 19 satisfy (Equation 2). The shape of the asymmetric elliptical microdot 18 in the cross section in the X direction in this example was a spherical shape having a maximum tangent angle θd of 25 degrees. As described above, since the maximum tangent angle θL of the curved lenticular lens 19 in this embodiment is about 58 degrees, it is desirable that the maximum tangent angle θd in the X-direction cross section of the elliptical microdot 18 is about 38 degrees or less.

(Optical evaluation of light guide)
The light guide 7 produced by determining the shape of the light deflection element 18 and the shape of the optical path control element 19 as described above was subjected to optical evaluation using a liquid crystal TV. A structure is the liquid crystal display element 2, the diffusion sheet 8a, the light guide 7, and the reflection sheet 5 in order from the observer side F. A plurality of light sources 6 are arranged with one long side of the four side end surfaces of the light guide 7 as the incident surface 7L. In Comparative Example 1, a commonly used printed light guide plate was prepared. The exit surface of the printed light guide plate is flat, and the light deflection surface is printed with white ink dots. The structure of the comparative example 1 is the liquid crystal display element 2, the upper diffusion sheet, the prism sheet, the diffusion sheet 8a, the printing light guide plate, and the reflection sheet 5 in order from the observer side. That is, in the liquid crystal display device 1 in the present embodiment, the optical sheet is only the diffusion sheet 8a, while in the liquid crystal display device 1 provided with the printing light guide plate which is the comparative example 1, a prism sheet is provided as a light collecting sheet. For optical evaluation, a spectral radiance meter SR-UL2 (manufactured by TOPCON) was used to measure the screen center luminance.

  Compared with the case where the printed light guide plate of Comparative Example 1 is arranged, the liquid crystal TV in which the light guide body 7 in this example is arranged has an improved screen center luminance of 10%. Moreover, the asymmetrical elliptical microdot 18 was not visually recognized from the screen by placing one diffusion sheet 8a. That is, without using a prism sheet which is a condensing sheet, the optical sheet has only one diffusion sheet 8a, and is 10 from Comparative Example 1 in which three sheets of the diffusion sheet 8a, the prism sheet, and the upper diffusion sheet are arranged. % Brightness improvement was obtained. Thus, by providing the diffusible optical sheet on the second main surface side, the luminance uniformity is further improved, and the visibility of the light deflection element can be suppressed.

  As mentioned above, although the light guide 7, the illuminating device 3, and the display apparatus 1 of this invention were demonstrated in detail based on the Example, the illuminating device 3 and the display apparatus 1 of this invention are not limited to this. Although the case where the illuminating device 3 of this invention is used as a backlight of the display apparatus 1 was demonstrated, it is not limited to this. For example, the lighting device 3 of the present invention can be applied as a lighting fixture.

  As described above, the light guide according to the present invention has a luminance peak in the front direction and high luminance uniformity over the entire surface, so that a lighting device with high luminance and high luminance uniformity can be obtained. Furthermore, by providing a reflection sheet that reflects and reuses light leaking from the first main surface, it is possible to obtain a lighting device with higher brightness. As described above, according to the present invention, it is possible to realize an edge light type illumination device including a light guide body that reduces the number of components and achieves high efficiency and high brightness as compared with the related art, and a display device including the same.

  The present invention is useful for a light guide, a lighting device including the light guide, a display device, and the like.

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Image display element 3 Illumination apparatus 5 Reflection sheet 6 Light source 7 Light guide body 7L End surface 7a Light deflection surface 7b Light emission surface 8 Optical sheet 8a Diffusion sheet 18 Light deflection element 19 Optical path control element

Claims (11)

A translucent light guide,
The light guide has a first main surface, a second main surface facing the first main surface, and four side end surfaces connecting the first main surface and the second main surface, At least one of the four side end surfaces is an incident surface on which light is incident,
The first main surface is formed with a concave light deflection element that deflects light incident from the incident surface and guided through the light guide body toward the second main surface,
In the cross-sectional shape when the light deflection element is cut along a plane perpendicular to the first main surface and parallel to a direction (Y direction) orthogonal to one extending direction (X direction) of the incident surface, Of the two contour lines from the top including the portion farthest from one main surface to the first main surface, the height of the contour line closer to the incident surface from the first main surface the first function a (y) is less than the (equation 1) representing,
In the cross-sectional shape when the light deflection element is cut by a plane perpendicular to the first main surface and parallel to the X direction, the contour line is a curved shape whose inclination changes continuously,
The second main surface is formed with an optical path control element that extends in the Y direction and is arranged in the X direction and that regulates an optical path of light guided through the light guide body. , Light guide.
Here, n represents the refractive index of the light guide, and the first function A (y) is the incident surface from the point that the contour line closer to the incident surface is connected to the first main surface. The height of the contour line from the first main surface at the position of the distance y in the direction away from the first position.   The light guide according to claim 1, wherein the first function A (y) is expressed by a linear function of the distance y.   The first function A (y) is expressed by a second-order or higher-order polynomial function of the distance y, and the fluctuation range of dA (y) / dy that is a differential value of the first function A (y) is the differential value. The light guide according to claim 1, wherein the light guide is equal to or less than an average value of absolute values of the light guides.   The light guide according to claim 1, wherein the top portion forms a ridge line. In the cross-sectional shape, the top is a straight line or a round shape,
The light guide according to any one of claims 1 to 3, wherein in the Y direction, the width of the top is within 30% of the width of the light deflection element.   Of the two contour lines, the differential value of the second function B (y) representing the height from the first main surface at the position of the distance y of the contour line that is farther from the incident surface. The average value of absolute values of dB (y) / dy is equal to or smaller than the average value of absolute values of differential values dA (y) / dy of the first function A (y). Item 6. The light guide according to any one of Items 1 to 5.   The light guide according to claim 1, wherein the light deflection element has a dot shape that is independently arranged in the first main surface. Θd is a maximum angle formed by a tangent of a cross-sectional shape when the light deflection element is cut by a plane perpendicular to the first main surface and parallel to the X direction, and the first main surface;
A maximum angle formed between a tangent of a cross-sectional shape when the optical path control element is cut by a plane perpendicular to the first main surface and parallel to the X direction, and the first main surface is θL,
When the refractive index of the light guide is n,
The maximum angle θL is characterized by satisfying the equation (2), a light guide body according to any one of claims 1 to 7.
The light guide according to any one of claims 1 to 8 ,
A reflective sheet disposed at a position facing the first main surface;
An illumination device comprising: a light source disposed to face the incident surface. The illumination device according to claim 9 , further comprising a diffusive optical sheet on the second main surface side. An image display element that defines a display image according to transmission / shading in pixel units;
Characterized in that it comprises a lighting device according to claim 9 or claim 10, a display device.