JP4761422B2 - Surface light source device and light guide used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source unit of high quality which eliminates unevenness of luminance regularity accompanying the use of a small number of spot primary light sources without deteriorating the traveling-direction distribution of projection light. SOLUTION: The unit has an LED 2, a plate type light guide 2 having a light incidence end surface 41 and a roughened light projection surface 43, and a light deflecting element 6. On a light guide reverse surface 44, a plurality of parallel lens arrays which extend in the direction of directivity in the light projection surface 43 of light guide incident light are formed and its top surface is of 10 to 50 deg. in mean tilt angle and 5 to 30 deg. in the maximum value of the absolute value of the difference between the absolute value (a) of the tilt angle of a tangent at each point of a sectional shape and the mean tilt angle (b). The number of fine areas in a range of &plusmn;5 deg. from the angle where the maximum frequency is shown in the frequency distribution of the absolute value of the tilt angle of a tangent at each fine area of the sectional shape is <=40% of the number of all fine areas. On a light deflecting element incidence surface 61, a plurality of prism arrays 61a are formed in parallel to the light guide light incidence end surface 41.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an edge light type surface light source device, and more particularly to a surface light source device intended for downsizing and power consumption reduction. The surface light source device of the present invention is suitably applied to a backlight of a relatively small liquid crystal display device used as a display panel of a portable electronic device such as a mobile phone or an indicator of various devices.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, liquid crystal display devices have been widely used as monitors for portable notebook computers or the like, as display units for liquid crystal televisions and video-integrated liquid crystal televisions, and in various other fields. The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, an edge light type is often used from the viewpoint of making the liquid crystal display device compact. Conventionally, as a backlight, at least one end face of a rectangular plate-shaped light guide is used as a light incident end face, and a linear or rod-shaped primary light source such as a straight tube fluorescent lamp is arranged along the light incident end face. The light emitted from the primary light source is introduced from the light incident end surface of the light guide into the light guide and is emitted from the light exit surface which is one of the two main surfaces of the light guide. Is widely used.
[0003]
In such a backlight, a sufficient amount of light does not reach the corners of the light guide near the both ends of the linear or bar-shaped primary light source and the area near the side end face adjacent to the light incident end face of the light guide. There is a problem that the luminance of these portions and regions is likely to decrease.
[0004]
By the way, in recent years, liquid crystal display devices having relatively small screen dimensions such as portable electronic devices such as mobile phones and portable game machines or indicators of various electric devices and electronic devices have been required to be reduced in size and to reduce power consumption. Yes. Therefore, in order to reduce power consumption, a light emitting diode (LED) that is a point light source is used as a primary light source of a backlight. As a backlight using an LED as a primary light source, for example, as described in JP-A-7-270624, a plurality of LEDs are used in order to perform the same function as that using a linear primary light source. They are arranged one-dimensionally along the light incident end face of the light guide. As described above, by using the primary light source having a one-dimensional array of a plurality of LEDs, it is possible to obtain a required light amount and uniformity of luminance distribution over the entire screen.
[0005]
However, in the case of a small-sized liquid crystal display device, further reduction in power consumption is required, and in order to meet this demand, it is necessary to reduce the number of LEDs used. However, if the number of LEDs is reduced, the distance between the light emitting points becomes longer, so that the area of the light guide close to the area between the adjacent light emitting points is enlarged and emitted from the light guide area in a required direction. The light intensity decreases. This results in non-uniform luminance distribution in the observation direction on the light emitting surface of the surface light source device (that is, non-uniform luminance uniformity).
[0006]
In Japanese Patent Publication No. 7-27137, a light guide having a rough light exit surface is used, and a prism sheet in which a large number of prism rows are arranged is arranged on the light guide so that the prism surface faces the light guide. A method of narrowing the distribution of emitted light has been proposed in order to reduce the power consumption of the backlight and to reduce the luminance as much as possible. However, in such a backlight, although high luminance can be obtained with low power consumption, the non-uniformity of the luminance distribution of light emitted from the light guide is easily visible through the prism sheet.
[0007]
The cause of the non-uniformity of the brightness distribution is that light emitted from individual LEDs arranged on the light incident end face of the light guide has directivity, and is further guided by refraction when entering the light guide. This is because the light incident on the body has a relatively narrow spread. As shown in FIG. 24, a dark portion is generated in the light guide region corresponding to the outside of the LEDs at both ends in the arrangement of the plurality of LEDs, and the liquid crystal The corner of the effective light emitting area corresponding to the display screen of the display device becomes dark. In particular, in order to reduce power consumption, when the number of LEDs to be used is reduced or the LEDs are installed close to the light guide, the occurrence of dark portions becomes significant. Thus, in a conventional backlight using a point light source as a primary light source, it has been difficult to achieve both reduction in power consumption and maintenance of uniformity of luminance distribution.
[0008]
  Furthermore, in a backlight that uses a linear light source such as a cold cathode tube as a primary light source, as a method of eliminating dark areas in the vicinity of the incident surface, for example,Japanese Patent Laid-Open No. 9-160035Has proposed a method of roughening the light incident end face of the light guide, but in a backlight using a point light source such as an LED as a primary light source, such a method is sufficiently dark as described above. The part could not be resolved.
[0009]
On the other hand, Japanese Utility Model Laid-Open No. 5-6401, Japanese Patent Laid-Open No. 8-179322, and the like disclose that light emitted from a light guide is parallel to a light incident surface in a backlight using a linear light source such as a cold cathode tube. For the purpose of focusing in the direction, there has been proposed one in which a large number of prism rows extending along a direction substantially perpendicular to the light incident end face are formed in parallel on the light exit surface of the light guide or the opposite surface. However, in a backlight using a point light source, when a light guide having a lens array composed of such prism arrays is used, light incident on the light guide can be expanded to some extent within the surface of the light guide. However, in the lens array, light is spread with anisotropy in a specific direction, so that there is a problem that a portion having a nonuniform luminance distribution occurs as shown in FIG.
[0010]
An object of the present invention is to degrade the distribution of the traveling direction of the emitted light due to the nonuniformity of the luminance uniformity due to the use of a small number of point-like primary light sources for reducing the power consumption of the surface light source device as described above. The object is to provide a high-quality surface light source device.
[0011]
[Means for Solving the Problems]
According to the present invention, the object as described above is achieved.
A plate-shaped light guide that guides light emitted from a point-like primary light source and has a light incident end surface on which light emitted from the primary light source is incident and a light exit surface from which light is guided. And
One of the light exit surface and the back surface on the opposite side extends substantially along the direction of directivity of light incident on the light guide from the primary light source in a plane along the light exit surface; A plurality of lens rows arranged in parallel with each other are formed, and the cross-sectional shape of the lens row perpendicular to the extending direction of the lens row has an average inclination angle of 10 to 10 with respect to the lens row forming plane of the light guide. The absolute value of the difference between the absolute value (a) of the tangential line at each point of the cross-sectional shape with respect to the lens array forming plane (a) and the average inclination angle (b) | (a) − ( b) The maximum value of | is in the range of 5 to 30 °, and ± from the angle indicating the maximum power in the frequency distribution of the absolute value of the angle formed between the tangent line in each minute region of the cross-sectional shape and the lens array forming plane. Divide the number of microregions within a range of 5 ° with respect to the total number of microregions. A surface light source device for the light guide, wherein the but 50% or less,
Is provided.
[0012]
In one aspect of the present invention, the spread angle of light incident on the light guide from the primary light source is 90 ° or more, and the average inclination angle of the cross-sectional shape is 12.5 to 30 °. In one aspect of the present invention, the spread angle of light incident on the light guide from the primary light source is 70 to 90 °, and the average inclination angle of the cross-sectional shape is 11 to 20 ° or 25 to 35 °. . In one aspect of the present invention, the spread angle of light incident on the light guide from the primary light source is 70 ° or less, and the average inclination angle of the cross-sectional shape is 10 to 17 ° or 27.5 to 50 °. is there.
[0013]
In one aspect of the present invention, the cross-sectional shape includes an outwardly convex curve. In one aspect of the invention, the cross-sectional shape comprises an outwardly concave curve. In one aspect of the present invention, the cross-sectional shape includes a curve having an outwardly convex portion and an outwardly concave portion.
[0014]
In one aspect of the present invention, the light incident end face is formed at one end edge of the light guide, and the lens array extends along a direction orthogonal to the end edge. In one aspect of the present invention, the light incident end surface is formed at one corner of the light guide, and the lens array extends along a direction connecting the corner and the corner of the diagonal position. Yes. In one aspect of the present invention, the light incident end surface is formed at one corner of the light guide, and is along a direction that forms substantially the same angle with respect to both of two edges adjacent to the corner. The lens array extends.
[0015]
Furthermore, according to the present invention, the object as described above is achieved.
A plate-shaped light guide that guides light emitted from a point-like primary light source and has a light incident end surface on which light emitted from the primary light source is incident and a light exit surface from which light is guided. And
The light incident end surface is made of an anisotropic rough surface, and the anisotropic rough surface has an average inclination angle in a direction along the light emission surface larger than an average inclination angle in a direction orthogonal to the light emission surface. A light guide for a surface light source device,
Is provided.
[0016]
In one aspect of the present invention, the anisotropic rough surface has an average inclination angle in a direction along the light emission surface of 3 to 60 °, and an average inclination angle in a direction orthogonal to the light emission surface. Is 5 ° or less. In one aspect of the present invention, the anisotropic rough surface has a length of a region having an inclination angle of 8 ° or more measured in a direction orthogonal to the light emitting surface is 5% or less of the total measurement length.
[0017]
Furthermore, according to the present invention, the object as described above is achieved.
A plate-shaped light guide that guides light emitted from a point-like primary light source and has a light incident end surface on which light emitted from the primary light source is incident and a light exit surface from which light is guided. And
A plurality of the light incident end surfaces arranged on the same plane and separated in a direction along the light emitting surface, and a portion corresponding to an edge between adjacent ones of the light incident end surfaces is the same A surface light source device characterized by projecting outward from a plane to form a projecting portion, wherein a portion of the end edge adjacent to the light incident end surface is inclined with respect to the same plane. Light guide,
Is provided.
[0018]
In one aspect of the present invention, a portion of the edge of the protruding portion adjacent to the light incident end surface is inclined by 5 to 60 ° with respect to the same plane.
[0019]
In one aspect of the present invention as described above, a light emitting mechanism is provided on one of the light emitting surface and the back surface on the opposite side. In one aspect of the present invention as described above, the light emitting mechanism includes a rough surface or a plurality of lenses extending in a direction substantially parallel to the incident end edge on which the light incident end surface is formed and parallel to each other. Consists of columns. In one aspect of the present invention as described above, the average inclination angle of the light emitting mechanism is 0.5 to 7 °.
[0020]
Furthermore, according to the present invention, the object as described above is achieved.
A light guide for a surface light source device as described above, the primary light source disposed adjacent to the light incident end surface of the light guide, and a light output surface of the light guide. At least one light deflection element, and the light deflection element has a light incident surface located opposite to the light exit surface of the light guide and a light exit surface on the opposite side. The light incident surface of the light deflecting element adjacent to the light guide includes a plurality of prism rows extending in a direction substantially parallel to the incident edge where the light incident end surface of the light guide is formed and parallel to each other. A surface light source device,
Is provided.
[0021]
In one aspect of the present invention, the primary light source is a point light source. In one aspect of the invention, the primary light source is an LED. In one aspect of the present invention, the primary light source is disposed at a distance of 0.2 mm or less with respect to the light incident end face.
[0022]
In one aspect of the present invention, each of the plurality of prism rows on the light incident surface of the light deflection element includes two prism surfaces, and light incident from one of the prism surfaces is transmitted to the prism surface. One of them is totally reflected.
[0023]
In one aspect of the present invention, a light reflecting element is disposed facing the back surface of the light guide.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 is an exploded perspective view showing one embodiment of a surface light source device according to the present invention. As shown in FIG. 1, the surface light source device of the present embodiment includes an LED 2 as a point-like primary light source, and light emitted from the LED is incident from the light incident end surface to be guided from the light emitting surface. A rectangular plate-shaped light guide 4 in the XY plane to be emitted, and a light deflection element 6 and a light reflection element 8 disposed adjacent to the light guide are provided. The light guide 4 has two upper and lower main surfaces and four end edges connecting the outer peripheral edges of the main surfaces.
[0026]
The LED 2 is disposed adjacent to one of a pair of end edges of the light guide 4 that are substantially parallel to each other (an end edge on the near side in FIG. 1: an incident end edge) and at the center in the X direction. In the present invention, it is preferable that the number of point light sources such as LEDs as the primary light source is as small as possible from the viewpoint of low power consumption. Can also be arranged.
[0027]
A light incident end face 41 corresponding to the position where the LED 2 is disposed is formed at the incident end edge of the light guide 4. The light incident end surface 41 formed on the light guide 4 may be formed by notching the incident end edge in a concave shape so as to have a concave cylindrical surface shape or the like. It is preferable that the LED light emitting surface and the light incident end surface have shapes that are opposite to each other and that are opposite to each other (including the case where both are flat surfaces).
[0028]
One main surface (upper surface in the drawing) of the light guide 4 is a light emitting surface 43. On this light emitting surface 43, the directivity for emitting the light guided in the light guide 4 in the direction inclined with respect to the light emitting surface 43 (that is, the direction inclined with respect to the XY plane). A light emission mechanism is provided. The directional light emitting mechanism is composed of, for example, a rough surface (mat surface). The directional light emitting mechanism emits directional light in a distribution in the YZ plane including both the normal direction (Z direction) of the light emitting surface 43 and the Y direction orthogonal to the incident edge. The angle between the direction of the peak of the emitted light distribution and the light emitting surface 43 is, for example, 10 to 40 °, and the half width of the emitted light distribution is, for example, 10 to 40 °.
[0029]
The other main surface (lower surface: back surface in the figure) of the light guide 4 is a lens array forming surface 44. As shown in FIG. 2, the lens array forming surface 44 has a directivity direction of light emitted from the LED 2 and incident on the light guide 4 (the light L having the maximum intensity in the light intensity distribution).₀ The lens rows 44a extend in a direction substantially along the direction of the lens rows and are arranged in parallel to each other (in FIG. 2, ridge lines of the lens rows 44a are shown). For example, when the direction of directivity of the light incident on the light guide 4 is substantially the Y direction, the direction of the lens array 44a can be the Y direction as shown in FIG. In the present invention, the direction of the lens array 44a may be deviated from the directivity direction of the light incident on the light guide 2 as long as the effect of spreading the light is not significantly impaired. In this case, the direction of the lens array 44a is preferably within a range of 20 ° with respect to the directionality of the light incident on the light guide, and more preferably within a range of 10 °. In addition, as shown in FIG. 19, the direction of the lens array 44a is locally changed from the direction of the directivity of the light incident on the light guide 4 particularly in a region close to the edge on the light incident end face 41 side. In this case, the area of the region whose direction is changed is preferably 30% or less. By forming the lens array 44a in such a direction, the light incident on the light guide 4 is spread in the XY plane, and a dark portion is hardly generated.
[0030]
The arrangement pitch P1 of the lens rows 44a is preferably in the range of 10 to 100 μm, more preferably 10 to 80 μm, and still more preferably 20 to 70 μm. In the present invention, the pitch of the lens rows 44a may be the same for all lens rows 44a within the above range, may be partially different, or may be gradually changed. .
[0031]
In the present invention, it is necessary to optimize the shape of the lens array 44a in order to suppress the appearance of bright and dark patterns (brightness unevenness) without impairing the brightness of the surface light source device. In order to suppress the appearance of a bright and dark pattern, the cross-sectional shape of the lens array 44a (the cross-sectional shape orthogonal to the extending direction of the lens array 44a) needs to be curved so that light does not concentrate at a specific angle. In order to suppress the decrease in the light intensity, it is necessary to suppress the spread of light by the lens array 44a as much as possible within a range where no bright and dark pattern is produced. The average inclination angle of the lens array 44a (the cross section orthogonal to the extending direction of the lens array 44a) It is necessary to optimize the average inclination angle) according to the spread angle of light. That is, in order to suppress the appearance of a bright and dark pattern without impairing the luminance of the surface light source device, it is necessary to optimize the average inclination angle and the curved surface shape of the lens array 44a.
[0032]
In the present invention, the light divergence angle means that a point light source is turned on and light guide light on an arc having a radius of 5 mm centered on the position where the maximum intensity light from this point light source enters the light guide. An angular range in which a luminance value of 50% or more of the maximum luminance value is obtained when the luminance distribution on the exit surface is measured. As shown in FIG. 20, the spread angle of light required to suppress the expression of a bright and dark pattern in the effective light emitting region is the distance between the primary light source such as an LED and the light incident end face of the light guide. It depends on the distance between the primary light sources. In order to suppress the appearance of a bright and dark pattern without impairing the luminance of the surface light source device, the light spread angle is set as small as possible so that the bright and dark pattern does not appear, and the cross-sectional shape of the lens array 44a is changed according to the light spread angle. It is necessary to set the average inclination angle.
[0033]
That is, when it is necessary to set the light spreading angle in the light guide to 90 ° or more, the average inclination angle of the lens array 44a is preferably in the range of 12.5 to 30 °, more preferably. Is in the range of 15-28 °. When it is necessary to set the light spreading angle in the light guide to 70 to 90 °, the average inclination angle of the lens array 44a is preferably in the range of 11 to 20 ° or 25 to 35 °. More preferably, it is in the range of 11.5 to 17.5 ° or 25 to 30 °. In addition, when it is necessary to set the light spreading angle in the light guide to 70 ° or less, the average inclination angle of the lens array 44a is in the range of 10 to 17 ° or 27.5 to 50 °. Is more preferable, and the range of 11 to 15 ° or 27.5 to 32.5 ° is more preferable. This is because the average inclination angle of the lens array 44a is in the above range according to the required light spread angle, thereby suppressing the occurrence of bright and dark patterns without causing a significant decrease in luminance as a surface light source device. Because it can. In general, the average inclination angle of the lens array 44a is in the range of 10 to 50 °.
[0034]
In order to suppress the appearance of a bright and dark pattern, it is necessary to make the cross-sectional shape of the lens array 44a curved so that the light does not concentrate at a specific angle. In particular, the inclination of the lens array 44a is not biased to a specific angle. It is preferable that they are distributed with a width.
[0035]
3 to 5 show typical examples of the cross-sectional shape of the lens array 44a formed on the light emitting surface of the light guide according to the present invention or the back surface on the opposite side. In FIG. 3, CF indicates the XZ cross-sectional shape of the surface of the lens array 44a. The cross-sectional shape CF corresponds to a shape obtained by adding the corrected shape CF1 to the basic shape CF0. Here, the basic shape CF0 is composed of two sides sandwiching the apex angle of a triangular shape having an apex angle θ of 80 to 160 °. The angles α and α ′ formed by the two sides with respect to the triangular base are preferably 10 to 50 °, and α = α ′. The corrected shape CF1 has zero correction amounts at both ends with respect to each of the two sides of the basic shape, and the inclination angle β is 30 ° or less in all portions. In the example of FIG. 3, the modified shape CF1 is formed of a curve that protrudes outward.
[0036]
4 and 5 are explanatory views similar to FIG. 3 for showing still another example of the cross-sectional shape of the surface of the lens array 44a. In the example of FIG. 4, the modified shape CF <b> 1 is a curved curve that is concave outward. In the example of FIG. 5, the modified shape CF <b> 1 is formed by a curve having an outwardly convex part and an outwardly concave part. In any case, the corrected shape CF1 has an inclination angle β of 30 ° or less in all parts. In any case, the basic shape CF0 is the same as that in FIG.
[0037]
By making the apex angle θ in the above range, the light emitted from the light guide 4 can be condensed well in a plane substantially perpendicular to the Y direction, and the luminance in the required direction can be sufficiently improved. Can do.
[0038]
6 to 9 are schematic diagrams illustrating examples of the shape of the lens array 44a in a cross section orthogonal to the Y direction. The example of FIG. 6 corresponds to FIG. 3 described above. Here, the sectional shape of the lens array 44a includes outwardly convex curves CV1 and CV2. The example of FIG. 7 corresponds to FIG. 4 described above. Here, the cross-sectional shape of the lens array 44a includes outwardly concave curves CC1 and CC2. The example of FIG. 8 corresponds to FIG. 5 described above, in which the cross-sectional shape of the lens array 44a includes curves CX1 and CX2 each having an outwardly convex portion CV and an outwardly concave portion CC. . In the example of FIG. 9, the sectional shape of the lens array 44a includes polygonal lines K1 and K2. In these figures, SS is the bottom of the cross-sectional shape of the lens array 44a, and corresponds to a virtual plane that typically approximates the light guide surface on which the lens array 44a is formed.
[0039]
In FIG. 10, the distribution in the XY plane of the light emitted from the light emitting part of the LED 2 is indicated by M. Here, the Y direction is an angle of 0. Thus, the light emitted from the light emitting part of the LED 2 is incident on the light incident end face 41 of the light guide 4 with directivity (with an angular distribution in intensity) in the XY plane. In the case shown in FIG. 10, since the directivity of the light emission of the LED 2 is substantially coincident with the Y direction, it hardly receives a refraction action when entering the light guide 4, so the extending direction of the lens array 44a is , Along the direction of light emission directivity of the LED 2, that is, the maximum intensity light L of the light emitted from the light emitting portion of the LED 2₀ Is consistent with the direction.
[0040]
As described above, the XZ cross-sectional shape CF of each surface of the lens array 44a is obtained by adding the corrected shape CF1 to the basic shape CF0, and the corrected shape CF1 is provided on each of two sides of the basic shape. On the other hand, since the correction amount at both ends is zero and the inclination angle β is 30 ° or less in all portions, the light emitted from the LED 2 and incident into the light guide 4 from the light incident end face 41 is used. The distribution in the XY plane can be made wider than M as indicated by N in FIG. Thereby, light of a required intensity can be guided to a wide area of the light emitting surface 43, and the luminance uniformity can be improved. Then, by making the apex angle θ of the basic shape CF0 of the XZ cross-sectional shape CF of the surface of the lens array 44a within the above range, the effect by adding the corrected shape of the lens array forming surface as described above is maintained, and the X direction The emitted light collected on the plane parallel to the light can be emitted, and as a surface light source device, the light can be concentrated and emitted in the direction within the required visual field range to improve the luminance.
[0041]
In the present invention, by making the cross-sectional shape of the lens array 44a specific, the occurrence of a non-uniform portion of the luminance distribution is suppressed.
[0042]
That is, the lens array cross-sectional shape including curves and broken lines as shown in FIGS. 3 to 9 is set such that the average inclination angle with respect to the lens array forming surface 44 is 10 to 50 °. The average inclination angle θa can be obtained as described later in accordance with ISO 4287 / 1-1984.
[0043]
In this specification, when taking a surface such as the lens array forming surface 44 and the light emitting surface 43 as a reference for an angle or direction such as an average inclination angle, a lens array structure or a rough surface structure formed on them. A plane (for example, a plane corresponding to the base SS shown in FIGS. 6 to 9 or a tangential plane in contact with the lens array forming surface 44 in parallel with these) is used.
[0044]
Further, the cross-sectional shape of the lens array 44a is defined as “(a)” as an absolute value of an angle formed between the tangent line at each point and the lens array formation surface of the light guide, and the average inclination angle of the lens array 44a is “( b) ", it is necessary that the absolute value of these differences | (a)-(b) | be in the range of 5 to 30 °, and | (a)-(b) | The maximum value of is preferably in the range of 7 to 25 °, more preferably in the range of 10 to 20 °. By increasing this value, the range of bright portions in FIGS. If this value exceeds 30 °, the action of spreading the light by the lens array 44a is reduced, and the expression of a dark part particularly in the effective light emitting region as shown in FIG. 24 cannot be sufficiently suppressed. This is because if it is less than 0 °, the effect of spreading the light by the lens array 44a is insufficient, and the expression of the light and dark pattern as shown in FIG. 23 cannot be suppressed.
[0045]
Thus, by setting the maximum value of | (a) − (b) | in the cross-sectional shape of the lens array 44a, the XY plane of the light emitted from the LED 2 and incident into the light guide 4 from the light incident end surface 41 The distribution within can be made wider than M, as indicated by N in FIG. Thereby, light of a required intensity can be guided to a wide area of the light emitting surface 43, and the luminance uniformity can be improved. Then, by setting the average inclination angle (b) of the lens array cross-sectional shape within the range of 10 to 50 °, the maximum value range of | (a) − (b) | in the lens array shape as described above is specified. While maintaining the effect, it is possible to emit the emitted light collected on the surface parallel to the X direction, and as a surface light source device, concentrate the light in the direction within the required visual field range to improve the brightness. Can do.
[0046]
Further, the frequency distribution of the absolute value of the angle formed by the tangent line in each minute region obtained by dividing the cross-sectional shape of the lens array 44a at a minute constant interval (for example, 1 μm interval) and the light exit surface of the light guide. Is obtained, it is preferable that the total sum of the number of minute regions (corresponding to the length) within a range of ± 5 ° from the angle indicating the maximum power is 50% or less of the entire lens array 44a, and more preferably. Is 40% or less of the entire lens array 44a. This is because the effect of suppressing the expression of a bright and dark pattern is increased because the inclination of the lens array 44a is distributed with a width without being biased to a specific angle. For example, in a shape in which only the apex of the lens array having a triangular cross section is curved, a specific direction is likely to be bright, and a light and dark pattern is likely to appear.
[0047]
The light deflection element 6 is disposed on the light emitting surface 43 of the light guide 4. The two main surfaces of the light deflecting element 6 are respectively positioned parallel to the XY plane as a whole. One of the two main surfaces (the main surface located on the light output surface 43 side of the light guide) is a light incident surface 61, and the other is a light output surface 62. The light exit surface 62 is a flat surface parallel to the light exit surface 43 of the light guide 4. The light incident surface 61 is a prism row forming surface in which a large number of prism rows 61a are arranged in parallel to each other.
[0048]
The prism rows 61 a on the light incident surface 61 extend in a direction substantially orthogonal to the direction of directivity of light from the LED 2 incident on the light guide 4 and are formed in parallel to each other. In the present embodiment, the prism row 61a extends in the X direction. The prism row 61a is not limited to a linear shape, and may be a curved shape surrounding the LED 2. The arrangement pitch P2 of the prism rows 61a is preferably in the range of 10 to 100 μm, more preferably 10 to 80 μm, and still more preferably 20 to 70 μm. The apex angle of the prism row 61a is preferably in the range of 50 to 80 °, and more preferably in the range of 50 to 70 °.
[0049]
FIG. 11 shows a state of light deflection by the light deflection element 6. This figure shows the traveling direction of the peak outgoing light (light corresponding to the peak of the outgoing light distribution) from the light guide 4 in the YZ plane. The light emitted obliquely from the light emitting surface 43 of the light guide 4 is incident on the first surface of the prism row 61a, is totally reflected by the second surface, and is emitted in the direction of the normal line of the light emitting surface 62. Further, in the XZ plane, the luminance in the normal direction of the light exit surface 62 can be sufficiently improved by the action of the lens array 44a as described above.
[0050]
In the present invention, the light deflection element 6 has a function of deflecting (deflection) the emitted light from the light guide 4 in a target direction, and a large number of lens units are arranged in parallel on at least one surface. Although a lens sheet having a formed lens surface can be used, it is particularly preferable to use a lens sheet in the case of the light guide 4 that emits light with high directivity as in the present invention. Various lens shapes are used depending on the purpose, and examples thereof include a prism shape, a lenticular lens shape, a fly-eye lens shape, and a wave shape. Among them, a prism sheet in which a large number of prism rows having a substantially triangular cross section are arranged is particularly preferable.
[0051]
As the light reflecting element 8, for example, a plastic sheet having a metal vapor deposition reflecting layer on the surface can be used. In the present invention, it is also possible to use a light reflecting layer or the like formed by metal deposition or the like on the main surface 44 opposite to the light emitting surface of the light guide 4 instead of the reflecting sheet as the light reflecting element 8. . In addition, it is preferable to attach a reflecting member also to the four side end surfaces (except the light incident end surface 41) of the light guide 4.
[0052]
The light guide 4 and the light deflection element 6 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, vinyl chloride resins, and cyclic polyolefin resins. In particular, methacrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and molding processability. Such a methacrylic resin is a resin mainly composed of methyl methacrylate, and preferably has a methyl methacrylate content of 80% by weight or more. When forming the rough surface structure of the light guide 4 and the light polarizing element 6 and the surface structure such as a prism array, the transparent synthetic resin plate is formed by hot pressing using a mold member having a desired surface structure. Alternatively, the shape may be imparted simultaneously with molding by screen printing, extrusion molding, injection molding, or the like. The structural surface can also be formed using heat or a photocurable resin. Furthermore, on a transparent substrate such as a polyester film, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylamide resin, or other transparent substrate or rough surface structure made of an active energy ray curable resin. Moreover, a lens array arrangement structure may be formed on the surface, or such a sheet may be bonded and integrated on a separate transparent base material by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylic acid esters, allyl compounds, (meth) acrylic acid metal salts, and the like can be used.
[0053]
In the present invention, as the light emitting mechanism of the light guide 4, in addition to the above rough surface, as shown in FIG. 12, a large number of lens rows such as prism rows, lenticular lens rows, or V-shaped grooves are guided. It is possible to use ones that extend in a direction (X direction) substantially orthogonal to the direction of the directivity of light from the LED 2 incident on the light body 4 and are parallel to each other. In this case, the lens array is not limited to a linear shape, and may be a curved shape surrounding the LED 2. The prism row 43a used for this purpose has an arrangement pitch P3 of preferably 10 to 100 μm, more preferably 10 to 80 μm, still more preferably 20 to 70 μm, and an apex angle of preferably 130 to 179 °, and more. Preferably it is the range of 140-179 degrees.
[0054]
This light emitting mechanism can also be provided so that the emission rate has a non-uniform distribution within the light emitting surface 43 of the light guide 4. For example, when a rough surface is used as the light emitting mechanism, a non-uniform distribution of the emission rate is obtained by performing a roughening process so that the distribution of the surface roughness in the light emitting surface 43 is non-uniform. Can be formed.
[0055]
In the present invention, it is preferable that the light emitting mechanism is formed on the light emitting surface 43 of the light guide 4 as described above, and the main surface (back surface) on the opposite side is the lens array forming surface 44 of the lens array 44a. However, in the present invention, the light emitting surface may be a lens array forming surface, and the light emitting mechanism may be formed on the opposite main surface.
[0056]
The rough surface as the light emitting mechanism and the lens array forming surface have an average inclination angle θa according to ISO 4287 / 1-1984 in the range of 0.5 to 25 °. It is preferable from the point of aiming. The average inclination angle θa is more preferably in the range of 0.5 to 20 °, particularly preferably in the range of 0.5 to 7 °. The average inclination angle θa is preferably set in an optimum range by a ratio (L / t) between the thickness (t) of the light guide 4 and the length (L) in the direction in which the incident light propagates. That is, when using a light guide 4 having an L / t of about 100 to 200, the average inclination angle θa is preferably 0.5 to 8 °, more preferably 0.5 to 6 °. It is a range, More preferably, it is the range of 0.5-4 degrees. Moreover, when using the thing with L / t of about 50-100 as the light guide 4, it is preferable that the average inclination | tilt angle (theta) a shall be 0.8-15 degrees, More preferably, it is 0.5-10 degrees. It is a range, More preferably, it is the range of 1-6 degrees. Furthermore, when the light guide 4 having a L / t of about 50 or less is used, the average inclination angle θa is preferably set to 1.5 to 25 °, more preferably in the range of 2 to 20 °. .
[0057]
The lens array 44a formed on the lens array formation surface 44 of the light guide 4 and the rough surface as the light emitting mechanism or the average inclination angle θa of the lens array are in accordance with ISO 4287 / 1-1984, a stylus type surface roughness meter. Is used to measure the rough surface shape, and the coordinate in the measurement direction is x, and the obtained gradient function f (x) can be used to obtain the following equation (1) and equation (2). Here, L is the measurement length, and Δa is the tangent of the average inclination angle θa.
[0058]
Δa = (1 / L) ∫₀ ^L| (D / dx) f (x) | dx (1)
θa = tan^-1(Δa) (2)
Further, the light guide 4 preferably has a light emission rate in the range of 0.5 to 5%, more preferably in the range of 1 to 3%. This is because when the light emission rate is smaller than 0.5%, the amount of light emitted from the light guide 4 tends to be small and sufficient luminance cannot be obtained. When the light emission rate is larger than 5%, a large amount of light is emitted in the vicinity of the light source 2. This is because light in the Y direction in the light exit surface 43 is remarkably attenuated and the brightness uniformity on the light exit surface 43 tends to decrease. Thus, by setting the light emission rate of the light guide 4 to 0.5 to 5%, the angle of the peak light emitted from the light emission surface is in the range of 50 to 80 ° with respect to the normal of the light emission surface. , Can emit light having a high directivity from the light guide 4 such that the half-value width of the emitted light distribution in a plane that includes the Y direction and is perpendicular to the light emitting surface 43 is 10 to 40 °. The emission direction can be efficiently deflected by the light deflecting element 6, and a surface light source device having high luminance can be provided.
[0059]
In the present invention, the light emission rate from the light guide 4 is defined as follows. The light intensity (I of the outgoing light on the light incident end face 41 side of the light outgoing face 43₀ ) And the intensity (I) of the emitted light at a position L from the end surface, when the thickness (dimension in the Z direction) of the light guide 4 is t, the relationship is as shown in the following equation (3). Satisfied.
[0060]
I = I₀ ・ Α (1-α)^{L / t}   (3)
Here, the constant α is the light output rate, and the ratio of light output from the light guide 4 per unit length in the Y direction on the light output surface 43 (the length corresponding to the light guide thickness t) ( %). The light emission rate α can be obtained from the gradient by plotting the logarithm of the light intensity of light emitted from the light emission surface 43 on the vertical axis and (L / t) on the horizontal axis.
[0061]
By disposing a liquid crystal display element on the light emitting surface (the light exit surface 62 of the light polarizing element 6) of the surface light source device including the LED 2, the light guide 4, the light deflecting element 6, and the light reflecting element 8 as described above, liquid crystal is provided. A display device is configured. The liquid crystal display device is observed by an observer through the liquid crystal display element from above in FIG. Further, in the present invention, a sufficiently collimated narrow distribution of light can be incident on the liquid crystal display element from the surface light source device, so that there is no gradation inversion in the liquid crystal display element and the brightness and hue uniformity. Can be obtained, and light irradiation concentrated in a desired direction can be obtained, and the utilization efficiency of the light emission amount of the primary light source for the illumination in this direction can be enhanced.
[0062]
13 and 14 are plan views showing a light guide for a surface light source device according to the present invention together with LEDs. In these drawings, members or portions having the same functions as those in FIGS. 1 to 12 are denoted by the same reference numerals.
[0063]
In these embodiments, the LED 2 as a point-like primary light source is disposed adjacent to the light incident end face 41 formed in the notch at the corner of the light guide 4. In the embodiment of FIG. 13, the maximum intensity light L emitted from the LED 2₀ Advances in parallel with a diagonal line connecting the corner portion where the notch portion of the light guide 4 is formed and the corner portion of the diagonal position. Further, in the embodiment of FIG. 14, the maximum intensity light L emitted from the LED 2.₀ Advances along a direction that forms substantially the same angle φ with respect to both of the two edges adjacent to the corner where the notch of the light guide 4 is formed. In either case, the lens array 44a on the back surface 44 of the light guide has the maximum intensity light L.₀ It extends in a direction parallel to the traveling direction. The cross-sectional shape CF of the lens array 44a is the same as that of the above embodiment. Also in this embodiment, the same operation effect as the above-mentioned embodiment is produced.
[0064]
FIG. 15 is a partially exploded perspective view showing a part of a light guide for a surface light source device according to the present invention together with LEDs. In these drawings, members or portions having the same functions as those in FIGS. 1 to 14 are denoted by the same reference numerals.
[0065]
In the present embodiment, the light incident end face 41 is made of an anisotropic rough surface. This anisotropic rough surface has an average inclination angle θa in the X direction along the light emitting surface 43 larger than an average inclination angle θa in the Z direction orthogonal to the light emitting surface 43. By setting it as such a rough surface, the distribution in the XY plane of the light emitted from the LED 2 and incident from the light incident end surface 41 into the light guide 4 can be expanded. Thereby, excessive light emission from the light guide 4 in the vicinity of the light incident end face based on excessively widening the distribution in the YZ plane is prevented, and the required area can be efficiently obtained in a wide area of the light emission surface 43. Intense light can be guided and it can contribute to improvement of luminance uniformity.
[0066]
The anisotropic rough surface of the light incident end surface 41 preferably has an average inclination angle in the X direction along the light emitting surface 43 of 3 to 60 °, more preferably 5 to 45 °. When the average inclination angle is less than 3 °, the above-described effects tend to be small, and when the average inclination angle exceeds 60 °, bright lines tend to appear. Further, in order to obtain the above-described effects, it is preferable that the average inclination angle in the Z direction orthogonal to the light emitting surface 43 is 5 ° or less. Further, the anisotropic rough surface of the light incident end face 41 has a length of a region having an inclination angle of 8 ° or more when measured in a direction orthogonal to the light emitting surface 43 is 5% or less of the total measurement length. preferable. If the length of the region with an inclination angle of 8 ° or more exceeds 5% of the total measurement length, the number of rays that enter the light exit surface 43 at a critical angle or less increases when entering the light guide. In the vicinity, the proportion of light rays emitted from the light exit surface 43 increases, and bright lines tend to appear.
[0067]
The distance between the primary light source such as the LED 2 and the light incident end face 41 is preferably 0.2 mm or less. When the distance between the primary light source and the light incident end face exceeds 0.2 mm, the luminance tends to decrease.
[0068]
FIG. 16 is a partial plan view showing a light guide for a surface light source device according to the present invention together with LEDs. In these drawings, members or portions having the same functions as those in FIGS. 1 to 15 are denoted by the same reference numerals.
[0069]
In the present embodiment, a plurality of light incident end faces 41 are provided on the same plane S that are separated from each other in the X direction along the light emitting face 43, and an edge between adjacent ones of the light incident end faces is provided. Are projected outward from the same plane S to form a projection 46, in which the portion adjacent to each light incident end face 41 is inclined with respect to the same plane S by an angle ω. ing. With such a structure, light leaking laterally from the case of the LED 2 can be introduced into the light guide 4 from the end edge, and the light utilization efficiency can be increased. In order to enhance such an effect, the angle ω is preferably 5 to 60 °.
[0070]
FIG. 17 is a perspective view showing still another embodiment of the surface light source device according to the present invention. In the figure, members or parts having the same functions as those in FIGS.
[0071]
In the present embodiment, the reflective sheet 10 having light diffusibility is provided so as to cover the end face portion of the laminated body of the light deflecting element 6, the light guide 4 and the light reflecting element 8 in the region other than the effective light emitting region F and the LED 2. It is attached. Thereby, the light emitted from the end surface portion of the laminated body and the light leaking from the case of the LED 2 can be diffused and reflected well in the XY plane and re-entered to the light guide 4, and the light guide light is emitted. Light having a required intensity can be guided to a wide area of the surface 43, which can contribute to an improvement in luminance uniformity.
[0072]
FIG. 18 is a sectional view showing still another embodiment of the surface light source device according to the present invention. In the figure, members or parts having the same functions as those in FIGS. 1 to 17 are denoted by the same reference numerals.
[0073]
In the present embodiment, a reflective sheet 10 having a light diffusibility is attached so as to cover the end surface portion of the laminated body of the light guide 4 and the light reflecting element 8 in the region other than the effective light emitting region F and the LED 2. On top of this, the light deflection element 6 is arranged. Also by this, the effect similar to embodiment of FIG. 17 can be acquired. However, this embodiment has a low diffusion function in the XY plane as compared with the embodiment of FIG. 17, but can obtain high luminance.
[0074]
In some of the above embodiments, a plurality of point light sources such as LEDs are used. In this case, the plurality of point light sources has the maximum intensity light L of the light emitted from them.₀ It is preferable to arrange so that the directions are parallel to each other.
[0075]
【Example】
Examples of the present invention and comparative examples are shown below. In Examples and Comparative Examples, measurement of average inclination angle, measurement of inclination angle in a micro area (tangential inclination angle), measurement of spread angle, and measurement of luminance unevenness for evaluation of uniformity of luminance distribution It was performed as follows.
[0076]
Average tilt angle measurement
Using a stylus type surface roughness meter (Surfcom 570A type, manufactured by Tokyo Seiki Co., Ltd.), a 1 μm R, 55 ° conical diamond needle (010-2528) was used as the stylus at a driving speed of 0.03 mm / sec. The measurement length was 2 mm. After correcting the slope of the average line of the extracted curve, the center line average value of the curve obtained by differentiating the curve according to the above formulas (1) and (2) was obtained.
[0077]
Measurement of tilt angle in micro area
The extracted curve was divided into minute measurement areas of 1 μm, and the inclination angle (corresponding to the tangential inclination angle) of the lens array cross-sectional shape in each measurement area was obtained. Based on this value, a frequency distribution of the inclination angle was obtained. The frequency distribution was obtained every other degree.
[0078]
Measurement of divergence angle
One LED as a point-like primary light source is turned on, and the luminance of the light guide light exit surface is measured on an arc having a radius of 5 mm with the light incident from the LED as the center, and the maximum luminance value of 50 is measured. An angle range in which a luminance value of% or more was obtained was obtained.
[0079]
Measurement of uneven brightness
Luminance measurement is performed at each 1 mm interval along the length direction in a region of 4 mm to 4.5 mm width 0.5 mm from the edge on the light incident end face side of the light emitting surface of the surface light source device. The ratio (minimum value / maximum value) between the minimum value and the maximum value of the luminance values obtained was determined.
[0080]
[Example 1]
Using a glass bead (FGB-400 manufactured by Fuji Seisakusho Co., Ltd.) with a particle size of 53 μm or less from the stainless steel plate to the spray nozzle on the surface of a stainless steel plate with an effective area of 34 mm × 48 mm and a thickness of 3 mm. And the spraying pressure is 3.0 kgf / cm² The entire surface was blasted to roughen the surface. Thus, a first mold having a rough shape transfer surface was obtained.
[0081]
On the other hand, a lens pattern in which a lens array with a pitch of 50 μm was arranged in parallel to a side with a length of 48 mm on a surface of a brass plate having a mirror-finished effective area of 34 mm × 48 mm and a thickness of 3 mm was formed by cutting. As a result, a second mold having a lens pattern shape transfer surface (concave curved surface) was obtained. FIG. 22 shows the measurement result of the cross-sectional shape of the shape transfer surface of the mold.
[0082]
A wedge shape that is injection molded using the first and second molds described above, is a rectangle with a short side of 34 mm and a long side of 48 mm, and the thickness varies from 1 mm to 0.7 mm along the long side. A transparent acrylic resin plate having one surface made of a rough surface and the other surface made of a lens surface was prepared as a light guide. The average inclination angle on the rough surface side of the obtained light guide was 3.4 °.
[0083]
In addition, the average inclination angle of the cross-sectional shape of the lens surface of the obtained light guide is 16 °, and the absolute value of the inclination angle with respect to the lens array formation plane of the minute region is 31 ° maximum and 0 ° minimum. Therefore, the maximum value of the difference from the average inclination angle was 16 °. When the frequency distribution of the tilt angle in the minute region was determined every 1 °, the tilt angle with the largest frequency was 6 °. The number of micro regions where the inclination angle takes a value of 1 ° to 11 ° was 34% of the number of all micro regions.
[0084]
The light incident end face of the obtained light guide was roughened in a direction perpendicular to the light exit face using # 2000 sandpaper. The roughened light incident end face had an average inclination angle in the direction along the light emission surface of 15 ° and an average inclination angle in the direction perpendicular to the light emission surface of 5 °.
[0085]
Three LEDs (NSCA 215biR manufactured by Nichia Corporation) were arranged at an interval of 9.0 mm so as to face the end surface on the short side with a thickness of 1 mm of the light guide. A light scattering reflection sheet (SU-119 manufactured by Enomoto Electric Manufacturing Co., Ltd.) is disposed on the lens array forming surface side of the light guide, and a large number of prism arrays with an apex angle of 65 ° and a pitch of 50 μm are formed in parallel on the rough surface side. The prism sheet (M165 manufactured by Mitsubishi Rayon Co., Ltd.) was placed so that the prism forming surfaces face each other, and a surface light source device as shown in FIG. 21 was produced. In other words, the rough surface of the light guide was used as the light exit surface. The spread angle of the obtained surface light source device was 110 °. The effective light emission area F of the surface light source device is as illustrated.
[0086]
When the luminance unevenness in the 0.5 mm width region in the vicinity of the light incident end surface of the effective light emitting region F of the obtained surface light source device was measured, the ratio (minimum value / maximum value) between the minimum value and the maximum value of the luminance was The luminance unevenness in the effective light emission region F was not observed.
[0087]
[Comparative Example 1]
Using a glass bead (FGB-400 manufactured by Fuji Seisakusho Co., Ltd.) with a particle size of 53 μm or less from the stainless steel plate to the spray nozzle on the surface of a stainless steel plate with an effective area of 34 mm × 48 mm and a thickness of 3 mm. And the spraying pressure is 3.0 kgf / cm² The entire surface was blasted. Next, an acrylic resin shielding plate is placed 40 mm away from the surface of the stainless steel plate so as to cover a portion other than the width of 4 mm in the vicinity of one short side end face of the stainless steel plate. Using a glass bead (FGB-400 manufactured by Fuji Seisakusho Co., Ltd.) with a particle size of 53 μm or less for the uncovered area, the distance from the stainless steel plate to the spray nozzle is 40 cm, and the spray pressure is 5.0 kgf / cm.² The blasting process was performed in a strip shape having a width of 4 mm. Thus, a first mold having a rough shape transfer surface was obtained.
[0088]
On the other hand, on a surface of a brass plate having an effective area of 34 mm × 48 mm and a thickness of 3 mm that is mirror-finished, a prism array with a pitch of 50 μm having a substantially isosceles triangular cross section with a top angle of 130 ° and a curved surface with a curvature radius of 5 μm. A prism pattern connected in parallel with a side having a length of 48 mm was formed by cutting. As a result, a second mold having a prism pattern shape transfer surface was obtained.
[0089]
A wedge having a rectangular shape with a short side of 34 mm and a long side of 48 mm, the thickness of which varies from 1 mm to 0.7 mm along the long side by injection molding using the first mold and the second mold described above. A transparent acrylic resin plate having a shape and having one surface made of a rough surface and the other surface made of a prism surface was used as a light guide. At the time of injection molding, the side on which the rough surface mold was blasted into a strip shape was made thicker. The average inclination angle on the rough surface side of the obtained light guide is 5.0 ° in the 4 mm strip region from the thick end surface, and gradually changes in the approximately 1 mm region adjacent to the strip region, In other regions, it was 3.4 °.
[0090]
Further, the average inclination angle of the lens array forming surface of the light guide is 22 °, and the maximum absolute value of the angle formed by the tangent line in the minute region of the cross-sectional shape of the lens array and the prism array forming surface of the light guide Was 27 °, the minimum value was 6 °, and the maximum difference from the average inclination angle was 16 °. Further, when the frequency distribution of the inclination angle in the minute region is obtained at intervals of 1 °, the inclination angle at which the frequency is maximum is 25 °, and the number of minute regions in which the inclination angle takes a value of 20 ° to 30 ° is It was 79% of the total. The average inclination angle of the plane portion excluding the curved portion at the top of the prism row of the light guide is 25 °, and is formed by the tangent line in the minute region of the cross-sectional shape of the lens row and the lens row formation surface of the light guide. The maximum value of the difference from the absolute value of the corner was 19 °.
[0091]
Using the obtained light guide, a surface light source device as shown in FIG. 21 was produced in the same manner as in Example 1.
[0092]
When the luminance unevenness in the 0.5 mm width region in the vicinity of the light incident end surface of the effective light emitting region F of the obtained surface light source device was measured, the ratio (minimum value / maximum value) between the minimum value and the maximum value of the luminance was The luminance unevenness was observed in the effective light emission region F.
[0093]
【The invention's effect】
As described above, according to the present invention, the luminance uniformity due to the use of a small number of point-like primary light sources for reducing the power consumption of the surface light source device is deteriorated, and the traveling direction distribution of the emitted light is deteriorated. Therefore, it is possible to provide a high-quality surface light source device.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a surface light source device according to the present invention.
FIG. 2 is a bottom view showing a light guide according to the present invention together with a primary light source.
FIG. 3 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 4 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 5 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 6 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 7 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 8 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 9 is a schematic diagram showing a cross-sectional shape of a lens array of a light guide according to the present invention.
FIG. 10 is a diagram showing an emitted light intensity distribution of an LED and an intensity distribution in the light guide.
FIG. 11 is a diagram showing a state of light deflection by the light deflection element.
FIG. 12 is a plan view showing a light guide according to the present invention together with a primary light source.
FIG. 13 is a bottom view showing a light guide according to the present invention together with a primary light source.
FIG. 14 is a bottom view showing a light guide according to the present invention together with a primary light source.
FIG. 15 is a partially exploded perspective view showing a light guide according to the present invention together with a primary light source.
FIG. 16 is a partial plan view showing a light guide according to the present invention together with a primary light source.
FIG. 17 is a perspective view showing a surface light source device according to the present invention.
FIG. 18 is a cross-sectional view showing a surface light source device according to the present invention.
FIG. 19 is a bottom view showing a light guide according to the present invention together with a primary light source.
FIG. 20 is a plan view showing a light guide according to the present invention together with a primary light source.
FIG. 21 is a schematic diagram showing dimensions of a surface light source device used in Examples.
FIG. 22 is a diagram showing a measurement result of a cross-sectional shape of a shape transfer surface of a mold used in an example.
FIG. 23 is a schematic diagram for explaining the occurrence of uneven luminance distribution in the surface light source device.
FIG. 24 is a schematic diagram for explaining the occurrence of uneven luminance distribution in the surface light source device.
[Explanation of symbols]
2 LED
4 Light guide
41 Light incident end face
43 Light exit surface
43a prism row
44 Lens array forming surface
44a Lens array
46 Protrusion
6 Light deflection elements
61 Light entrance
61a prism row
62 Light-emitting surface
8 Light reflecting elements
10 Light-diffusing reflective sheet
Cross-sectional shape of CF lens array surface
CF0 basic shape
CF1 modified shape
CV1, CV2 outwardly convex curve
CC1, CC2 Curves concave outward
CX1, CX2 Curve having outwardly convex parts and outwardly concave parts
K1, K2 polyline
SS bottom
F Effective light emission area

Claims (13)

A plate-shaped light guide that guides light emitted from a point-like primary light source and has a light incident end surface on which light emitted from the primary light source is incident and a light exit surface from which light is guided. And
One of the light exit surface and the back surface on the opposite side extends substantially along the direction of directivity of light incident on the light guide from the primary light source in a plane along the light exit surface; A plurality of lens rows arranged in parallel with each other are formed, and the cross-sectional shape of the lens row perpendicular to the extending direction of the lens row has an average inclination angle of 10 to 10 with respect to the lens row forming plane of the light guide. The absolute value of the difference between the absolute value (a) of the tangential line at each point of the cross-sectional shape with respect to the lens array forming plane (a) and the average inclination angle (b) | (a) − ( b) The maximum value of the | Divide the number of microregions within a range of 5 ° with respect to the total number of microregions. A surface light source device for the light guide, wherein the but 50% or less.   The spread angle of light incident on the light guide from the primary light source is 90 ° or more, and the average inclination angle of the cross-sectional shape is 12.5 to 30 °. A light guide for a surface light source device.   The spread angle of light incident on the light guide from the primary light source is 70 to 90 °, and the average inclination angle of the cross-sectional shape is 11 to 20 ° or 25 to 35 °. 2. A light guide for a surface light source device according to 1.   The spread angle of light incident on the light guide from the primary light source is 70 ° or less, and the average inclination angle of the cross-sectional shape is 10 to 17 ° or 27.5 to 50 °. Item 2. A light guide for a surface light source device according to Item 1.   The light guide for a surface light source device according to claim 1, wherein the cross-sectional shape includes at least one of a convex curve and a concave curve.   The light incident end surface is made of an anisotropic rough surface, and the anisotropic rough surface has an average inclination angle in a direction along the light emission surface larger than an average inclination angle in a direction orthogonal to the light emission surface. The light guide for a surface light source device according to claim 1, wherein:   The anisotropic rough surface has an average inclination angle in a direction along the light emission surface of 3 to 60 ° and an average inclination angle in a direction orthogonal to the light emission surface of 5 ° or less. The light guide for a surface light source device according to claim 6, wherein   The length of a region having an inclination angle of 8 ° or more when the anisotropic rough surface is measured in a direction orthogonal to the light emitting surface is 5% or less of the total measurement length. The light guide body for surface light source devices in any one of -7.   A plurality of the light incident end surfaces arranged on the same plane and separated in a direction along the light emitting surface, and a portion corresponding to an edge between adjacent ones of the light incident end surfaces is the same The protrusion is formed outwardly from a plane to form a protrusion, and a portion of the protrusion adjacent to the light incident end surface is inclined with respect to the same plane. 2. A light guide for a surface light source device according to 1. 10. The light guide for a surface light source device according to claim 9 , wherein a portion adjacent to the light incident end surface of the end edge of the projecting portion is inclined by 5 to 60 ° with respect to the same plane. body. The light guide for a surface light source device according to any one of claims 1 to 10 , wherein a light emitting mechanism is provided on one of the light emitting surface and the back surface on the opposite side. The light guide for a surface light source device according to any one of claims 1 to 11, the primary light source disposed adjacent to the light incident end surface of the light guide, and a light exit surface of the light guide At least one light deflection element disposed adjacent to the light entrance surface, the light deflection element being disposed opposite the light exit surface of the light guide and the light exit surface on the opposite side. The light incident surface of the light deflection element adjacent to the light guide extends in a direction substantially parallel to the incident end edge of the light incident end surface of the light guide and is parallel to each other. A surface light source device comprising a plurality of prism rows. The surface light source device according to claim 12 , wherein the primary light source is a point light source.

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