JP4473035B2 - Illumination device and display device including the same - Google Patents

Description

  The present invention relates to a display device used in a watch, a mobile phone, an audio, an electronic device, and the like, and a lighting device used in the display device.

  2. Description of the Related Art In recent years, a liquid crystal display element is often used because a display element used in a mobile device, particularly a mobile phone, is required to be small and light. However, since the liquid crystal display element is a light receiving type, there is a problem in visibility in a dark place. Therefore, an illuminating device is often installed on the front surface or the back surface of the liquid crystal display element. In order to realize this thin and light weight, a sidelight type lighting device in which an LED as a light source is arranged on the side surface of a light guide plate is often used (see, for example, Patent Document 1).

Further, in such a liquid crystal display device, a columnar lens sheet having a columnar structure including a columnar central region having a higher refractive index than the surrounding region is arranged in a plane and has a function of guiding light in the thickness direction. It is disclosed that a light guide sheet is used (see, for example, Patent Document 2).
Patent No. 3301752 (page 3, Fig. 1) Japanese Unexamined Patent Publication No. 2000-35576 (page 3-5, FIG. 7)

  However, in the conventional sidelight type illumination device, if the thickness of the light guide plate is made thinner than the size of the LED light source, the light from the LED light source cannot be efficiently guided to the inside of the light guide plate. Had the problem of not being able to.

  Further, in the conventional configuration using the columnar lens sheet disclosed in Patent Document 2, since the diffusion layer is used in the gap between the backlight light guide plate and the columnar lens sheet, the diffusion layer serves as a light guide for the backlight. This has an effect on the characteristics, and there is a problem that it is impossible to perform illumination that is uniform and has high luminance and excellent viewing angle characteristics.

  The illuminating device of the present invention includes a light guide plate having a transparent wedge-shaped light incident portion and a thin light illuminating portion that are sequentially thinned stepwise from the light source side. A light reflecting layer is formed on the three side surfaces of the wedge-shaped light incident portion except for the light source side end surface, and at least one surface of the light illuminating portion of the light guide plate has a columnar structure having a columnar structure having a predetermined inclination angle. The lens sheet is bonded. With such a configuration, even if the light illumination part of the light guide plate is thinned to about 1 mm, the light from the light source can be efficiently introduced into the light guide plate, and the above-described problems can be solved.

  ADVANTAGE OF THE INVENTION According to this invention, the thin and lightweight illuminating device which has favorable brightness | luminance and brightness distribution can be provided. Therefore, not only the display quality of the liquid crystal display device using the same is improved, but also the liquid crystal display device can be reduced in thickness and weight.

  The illuminating device of the present invention includes a light source, a light guide having an illumination surface that irradiates the irradiated body with illumination light, a light incident surface on which light from the light source enters, and a light transmission unit that transmits light to the light guide. Provided on the opposite side of the light incident body and the light irradiation portion of the light guide plate, and includes a directional scattering layer that scatters light incident at a specific angle range and transmits light incident at other angles, The central angle of the specific angle range is inclined to the side where the light source is disposed with respect to a reference line perpendicular to the illumination surface of the light guide plate. Further, a second directional scattering layer that scatters light incident at a second specific angle range and transmits light incident at other angles is provided on the light illumination surface of the light guide plate, The central angle of the specific angle range is inclined to the opposite side of the side where the light source is disposed with respect to a reference line perpendicular to the illumination surface of the light guide plate. Here, the light incident body and the light guide body may be formed integrally or individually.

  Furthermore, the thickness of the light incident member is configured so as to be gradually reduced from the light incident surface side toward the light transmission unit side. Here, the light incident body is configured to be thin in steps from the light incident surface side. Further, the stepped step portion formed in the light incident body is formed substantially vertically. The light guide has an incident surface for receiving light from the light transmitting part of the light incident member and an end surface opposite to the incident surface, and the end surface is a plane parallel to the incident surface. Is inclined at a predetermined angle with reference to.

  The display device of the present invention includes the illumination device having any one of the above-described configurations and a non-self-luminous display element provided on the light irradiation surface side of the illumination device.

  The illumination device of the present invention will be described below with reference to the drawings. Hereinafter, an example in which a columnar lens sheet is used as the directional scattering layer will be described. The columnar lens sheet is a structure in which a plurality of columnar structures in which a region having a higher refractive index than the surrounding region is continuously formed in the thickness direction are arranged in the plane, and has a function of guiding light in the thickness direction. ing. Moreover, the wedge-shaped light incident part 2 as a light incident body is formed integrally with the light guide. FIG. 1 schematically shows a cross-sectional view of the configuration of the illumination device of the present invention. As shown in the figure, the illumination device of the present invention includes an LED light source 1 as a light source, a light guide plate having a wedge-shaped light incident portion 2 and a light illumination portion 3, and a columnar lens sheet 6. The light emitted from the LED light source 1 is narrowed down by the wedge-shaped light incident part 2, guided in the light illumination part 3 of the light guide plate and the inside of the columnar lens sheet 6, and the light of the light guide plate which is the light irradiation surface of the illumination device. The object to be illuminated (not shown) is uniformly irradiated in a planar shape from the upper surface side of the illumination unit 3. By using a liquid crystal panel as the object to be illuminated, a thin liquid crystal display device with uniform brightness and brightness can be obtained.

  Although only one is drawn in FIG. 1, a plurality of LED light sources 1 such as 3 to 5 are usually used. Although not shown, the light incident surface that is the light source side end surface of the wedge-shaped light incident portion 2 facing the LED light source 1 has an in-plane direction inside the wedge-shaped light incident portion 2 of the light emitted from the LED light source 1. A small prism is formed to control the spread angle. This microprism has a vertical ridgeline in the plane of FIG. 1, and the spread angle of light inside the wedge-shaped light incident portion 2 can be controlled by the apex angle and height of the microprism. Although not clearly shown in the drawing, the light incident surface of the light guide plate facing the light incident surface on which the plurality of light sources are arranged, that is, the side of the light guide plate facing the light incident end surface from the light source 1 of the light illumination unit 3. The end surface of the LED has a taper on the LED light source side with respect to a plane parallel to the light incident surface. The taper angle is suitably 3 to 7 degrees.

  In this embodiment, the wedge-shaped light incident portion 2 has a plurality of steps in a step shape, and is gradually thinner from the light source side toward the illumination portion 3 of the light guide plate. These step portions are formed with a substantially vertical angle. In order to make the figure easy to see, the figure shows a case where the number of stages is three, but in reality, about 20 to 100 stages are formed. Further, a light reflection layer 5 is formed on the surface of the wedge-shaped light incident portion 2 except for the light source side end surface. This light reflecting layer is formed by laminating Al, Ag, or a compound of Ag and Pd with a film thickness of 100 nm or more, preferably about 1 μm. The light reflecting layer can be easily formed by a vapor phase growth method such as vacuum deposition or a method in which electroless plating and electrolytic plating are combined. The light guide plate having the wedge-shaped light incident portion 2 is made of a transparent polymer such as acrylic resin, polycarbonate resin, polyethylene resin, or cycloolefin resin. A columnar lens sheet 6 is bonded to the back surface of the light illumination unit 3 of the light guide plate using a bonding agent. As a method for joining the columnar lens sheets, an acrylic adhesive or an epoxy adhesive may be used, or a normal pressure-sensitive adhesive may be used. A light reflection layer 4 is formed on three side surfaces of the light guide plate except the light source side in the light illumination unit 3 and the columnar lens sheet 6. This light reflecting layer is formed by laminating Al, Ag, or a compound of Ag and Pd with a film thickness of 100 nm or more, preferably about 1 μm. The light reflecting layer can be easily formed by a vapor phase growth method such as vacuum deposition or a method in which electroless plating and electrolytic plating are combined.

  FIG. 2 schematically shows a cross-section of another configuration relating to the illumination device of the present invention. The configuration shown in FIG. 2 is different from the configuration shown in FIG. 1 in that the second columnar lens sheet 7 is bonded to the light irradiation surface of the light illumination unit 3 of the light guide plate by a bonding agent. Although it is not clear in the drawing, the columnar lens that constitutes the second columnar lens sheet 7 is inclined to the side opposite to the side where the LED light source is disposed with reference to a vertical line standing on the surface of the second columnar lens sheet 7. Oriented. The inclination angle is smaller than the inclination angle of the columnar lens sheet 6 and is about 0 to 30 degrees. Next, the operation of the columnar lens sheet 6 and the second columnar lens sheet 7 used in FIGS. 1 and 2 will be described. The columnar lens sheet 6 and the second columnar lens sheet 7 have a function of guiding light in the thickness direction by arranging a plurality of fine columnar structures in a plane. This columnar structure has a function as a columnar lens. That is, a graded index columnar lens whose refractive index continuously increases toward the center, or a step index having a two-layer structure in which the refractive index of the central portion is higher than the refractive index of the outer peripheral region surrounding it. It has a film structure in which a plurality of mold columnar lenses are arranged in a plane.

  In both the graded index columnar lens and the step index columnar lens, the direction of the optical axis of the columnar lens constituting them is referred to as the orientation direction of the columnar lens. The columnar lens sheet 6 used in the best mode is formed so that the orientation direction of the columnar lens is inclined toward the side where the LED light source 1 is disposed with reference to the direction of the perpendicular line standing on the surface of the columnar lens sheet 6. When the angle formed by the orientation direction with respect to the direction of the vertical line standing on the surface of the columnar lens sheet 6 is called an inclination angle, the inclination angle is in the range of about 30 to 60 degrees.

  The columnar lens sheet 6 is manufactured by, for example, irradiating a liquid reaction layer composed of two or more kinds of photopolymerizable compounds having different refractive indexes with ultraviolet rays through a gradation-processed photomask, thereby obtaining a light irradiation intensity. The refractive index distribution is controlled by the difference in the photopolymerization rate of the photopolymerizable compound. The control of the tilt angle can be easily realized by controlling the direction of the irradiated ultraviolet rays.

  Next, the behavior of light in the columnar lens sheet will be described. FIG. 6 is a schematic diagram showing the behavior of light when a step index type columnar lens sheet is used. In the drawing, one of optical paths of light incident on the second columnar lens sheet 7 from the inside of the light illumination part 3 of the light guide plate is indicated by 22. The light guided through the light illuminating unit 3 of the light guide plate passes through the bonding agent 9 and then enters the second columnar lens sheet 7 with various incident angles. However, most of the incident light is incident on the light guide plate. The incident angle is larger than the critical angle. In other words, the incident angle of light on the second columnar lens sheet 7 is almost larger than 43 degrees.

  In the step index type columnar lens, the high refractive index region 10 and the low refractive index region 11 are formed with a clear boundary. The light incident on the high refractive index region 14 from the light illumination unit 3 of the light guide plate through the bonding agent 9 enters the boundary surface with the low refractive index region 15, but the orientation direction of the columnar lens is opposite to the light source side. Therefore, the incident angle to the boundary surface is larger than the critical angle, and the light is totally reflected. This light is repeatedly totally reflected at the boundary surface between the high refractive index region 10 and the low refractive index region 11 and guided upward, and is emitted from the upper surface of the second columnar lens sheet 7. The incident angle to the upper surface of the second columnar lens sheet 7 is emitted to the outside because the light is reflected by the boundary surface in the columnar lens and has a value smaller than the critical angle.

  At this time, the light emission direction from the second columnar lens sheet 7 is determined by the layer thickness of the second columnar lens sheet 7 and the incident angle and position of the light incident on the high refractive index region 10. This light is emitted in the same way as light is scattered and emitted. And it is radiate | emitted so that the bias | inclination of a scattering direction may become large, so that the layer thickness of the 2nd columnar lens sheet 7 becomes thick. Further, the larger the refractive index difference between the high refractive index region 10 and the low refractive index region 11, the larger the scattering angle. Furthermore, the haze value increases as the layer thickness of the second columnar lens sheet 7 increases, as the cylindrical radius decreases, and as the number density of columnar lenses in the sheet plane increases.

  Next, the behavior of light incident on the columnar lens sheet 6 from the inside of the light illumination unit 3 of the light guide plate is shown in FIG. In this case, since the columnar lens is inclined opposite to the light source side, the light incident on the boundary surface between the high refractive index region 10 and the low refractive index region 11 as indicated by the optical path 23 in the figure. Is smaller than the incident angle of FIG. As a result, the light passes through the boundary surface, enters the low refractive index region 11, is totally reflected on the surface of the columnar lens sheet 6, and returns to the light illumination unit 3 of the light guide plate again.

  At this time, the direction of the light returning from the columnar lens sheet 6 to the bonding agent 9 varies depending on the incident angle and the incident position of the light on the reflecting surface. That is, the light is scattered and emitted. When the incident angle of the light indicated by the optical path 23 is further increased, the light is not scattered at all by the columnar lens sheet and acts in the same manner as a normal transparent sheet.

  As described above, whether the light is scattered from the surface of the columnar lens sheet, is totally reflected and scattered and emitted into the light guide plate, or is reflected linearly depends on the inclination angle of the columnar lens. In general, in a columnar lens sheet, light incident on the sheet in a certain angle range is guided through the columnar lens and scattered and emitted from the surface, and light incident at an angle other than the angle range is substantially linear in the columnar lens sheet. Transmits and is not scattered. The incident angle of the scattered and emitted light is referred to as the scattering incident angle, and the incident angle of the linearly transmitted light is referred to as the linear transmission angle. Of course, if the reflection angle of the return light reflected by the surface of the columnar lens sheet is within the range of the scattering incident angle of the columnar lens sheet, the light is scattered and emitted into the light guide plate, but within the range of the linear transmission angle. If there is, it returns straight to the inside of the light guide plate without being scattered.

  Next, the behavior of light in the columnar lens sheet by the graded index columnar lens will be described. A graded index columnar lens has a high refractive index region with a distribution that maximizes the refractive index near the central axis of the columnar lens, and has a distribution that minimizes the refractive index at the outermost periphery around it. Although it is covered with the low-refractive index region, it does not have a clear boundary surface between the high-refractive index region and the low-refractive index region like the step index type columnar lens.

  Light incident on the inside of the graded index columnar lens bends the optical path toward a higher refractive index. Therefore, the optical path in this columnar lens shows a smooth curve. However, in this case as well, as in the case of the step index type columnar lens, there are a scattering incident angle and a linear transmission angle. That is, the light incident at the scattering incident angle is guided through the columnar lens and scattered and emitted from the surface of the columnar lens sheet, but the light incident at the linear transmission angle travels almost straight and is totally reflected by the surface of the columnar lens sheet. Return to the light guide plate again. At this time, if the return light is within the range of the scattering incident angle of the columnar lens sheet, the light is scattered and emitted into the light guide plate, but if it is within the range of the linear transmission angle, the light guide plate is linearly received without being scattered. Go back inside.

  At this time, as in the case of the step index type columnar lens sheet, the light emission direction from the columnar lens sheet is determined by the layer thickness of the columnar lens sheet, the incident angle of light to the columnar lens, and the incident position. And it is radiate | emitted so that the bias | inclination of a scattering direction may become large, so that the layer thickness of a columnar lens sheet | seat becomes thick. Further, the scattering angle increases as the amount of change in the refractive index formed by the high refractive index region and the low refractive index region increases. Furthermore, the haze value increases as the layer thickness of the columnar lens sheet increases, as the column radius decreases, and as the number density of columnar lenses in the sheet plane increases.

  Regardless of the step index type columnar lens sheet or the graded index type columnar lens sheet, the scattering incident angle is 45 by adjusting the refractive index difference or the refractive index change amount between the high refractive index region and the low refractive index region. It can be set to an arbitrary angle of about the degree or less. Here, most of the light propagating through the light illuminating unit 3 of the light guide plate is inclined with an incident angle to the surface of the light guide plate of about 43 degrees or more so that the light is efficiently totally reflected and propagated inside. It is at an angle. Further, the incident angle of the guided light in the light guide plate has a larger component having an angle inclined toward the LED light source. On the other hand, the columnar lens sheet only scatters specific light incident at a scattering incident angle, and linearly transmits light incident at other incident angles in the same manner as for a normal transparent sheet. To do.

  In the illuminating device of the present invention, the columnar lens constituting the columnar lens sheet 6 is inclined to the LED light source side, and the second columnar lens sheet 7 is inclined to the opposite side to the LED light source side, thereby allowing the inside of the light guide plate The light propagating in is efficiently scattered by the columnar lens sheet. Specifically, the inclination angle of the columnar lens is inclined about 30 to 60 degrees toward the LED light source side with respect to the normal line standing on the emission surface of the columnar lens sheet 6. The inclination angle of the columnar lens is inclined about 0 to 30 degrees on the opposite side to the LED light source with respect to the normal line standing on the emission surface of the second columnar lens sheet 7.

  The light incident on the columnar lens sheet 6 from the LED light source side has an optical path similar to the optical path 23 in FIG. Therefore, the light incident on the columnar lens sheet 6 from the LED light source side is reflected on the surface of the columnar lens sheet 6 and is emitted from the columnar lens sheet 6 to the light guide plate side. At this time, since the tilt angle of the columnar lens is 30 to 60 degrees and the scattering incident angle can be 10 to 45 degrees, by using the first columnar lens sheet having an appropriate tilt angle and scattering incident angle. The reflected light from the back surface can be scattered and emitted to the light guide plate side at a rate of 0 to 100%. Since the incident angle of the incident light of the scattered light on the irradiation surface of the light guide plate is -15 to 45 degrees, most of the light can be emitted from the irradiation surface of the light guide plate according to Snell's law.

  Further, the light incident on the second columnar lens sheet 7 from the LED light source side is the same as the optical path 22 in FIG. At this time, the incident angle of the light directly propagating from the LED light source through the light guide plate is about 43 degrees or more, while the inclination angle of the columnar lens constituting the second columnar lens sheet 7 is 0 to 30 degrees. is there. Therefore, even if the inclination angle of the second columnar lens sheet 7 is set to be as large as 30 degrees and the scattering incident angle is set to 45 degrees, about 30% of the light is totally reflected on the surface and returns to the light guide plate side. On the other hand, as described above, the light reflected and scattered and emitted from the back surface of the columnar lens sheet 6 enters the second columnar lens sheet 7 within an incident angle range of about -15 to 45 degrees. Therefore, if the inclination angle and the scattering incident angle of the columnar lens sheet 6 and the second columnar lens sheet 7 are appropriately selected, this scattered light can be scattered and emitted from the second columnar lens sheet 7 by almost 100%.

  In the illumination device of the present invention, a columnar lens sheet having a columnar lens with a lens diameter of 1 μm to 250 μm and a lens height (columnar lens sheet layer thickness) of 10 μm to 200 μm can be used. However, considering the production yield, light utilization efficiency, ease of handling, etc., the lens diameter is preferably 5 μm to 100 μm, and the lens height is preferably 20 μm to 80 μm. In addition, a columnar lens having a refractive index difference of 0.01 to 0.05 can be used. Furthermore, the inclination angle of the columnar lens can be 10 to 60 degrees.

  As described above, the illumination device of the present invention can efficiently emit light from the LED light source without forming a fine reflection structure such as a prism on the front or back surface of the light guide plate by using the columnar lens sheet having the inclination angle. Light can be emitted from the irradiation surface side. Therefore, manufacture becomes easy and a product can be made at low cost.

  Next, the filling density of the columnar lenses constituting the columnar lens sheet 6 and the second columnar lens sheet 7 will be described. As described above, in order to efficiently scatter and emit the light propagating through the light guide plate, the columnar lens sheet used in the present invention uniformly arranges the packing density of the columnar lenses constituting the columnar lens sheet in the sheet. The luminance on the LED light source side becomes too large, and the luminance distribution is deteriorated.

  Using such a feature of the columnar lens sheet, in the lighting device of the present invention, the columnar lens filling density on the far side is larger than the columnar lens filling density on the side closer to the LED light source of the light guide plate. A columnar lens sheet was used. By doing in this way, the to-be-illuminated body can be irradiated with light from the LED light source more uniformly than when a columnar lens sheet having a uniform columnar lens filling density is used. When the second columnar lens sheet 7 is used, since the relationship with the columnar lens sheet 6 is complicated, the filling density of the columnar lenses constituting the columnar lens sheet 6 is changed to configure the second columnar lens sheet 7. The filling density of the columnar lenses should be uniform.

  FIG. 9 shows a configuration example in which the columnar lens filling density of the columnar lens sheet 6 is changed. As shown in the drawing, it is a plan view of the illumination device of the present invention as viewed from the columnar lens sheet 6 side, and three LED light sources 1a, 1b, 1c are arranged on the light incident side end face of the light guide plate. A plurality of columnar lenses 14 are filled in the columnar lens sheet 6 and arranged. By arranging the lens diameter of the columnar lens on the LED light source side so as to decrease as the distance from the LED light source increases, the filling density of the columnar lens is changed. The columnar lens diameter is distributed in a size of about 5 μm to 100 μm, and the values are based on the size of the light guide plate or the refractive index of the light guide plate not shown. The optimum value varies depending on the layer thickness and refractive index of the columnar lens. Further, the arrangement in the surface of the columnar lens sheet 6 is an arrangement from which periodicity is removed in order to prevent the generation of moire fringes.

  FIG. 10 shows another configuration example in which the columnar lens filling density of the columnar lens sheet is changed. In this structure, it arranges so that the packing density may change by changing the column density in which the columnar lenses are arranged as the distance from the LED light sources 1a, 1b, and 1c increases. Specifically, the columnar lenses are arranged in units of columns arranged in a line in the arrangement direction of the LED light sources, and the column density is sparse on the side close to the LED light sources and becomes denser as the distance from the LED light sources is increased. In the present embodiment, the distance between the columns is arranged so as to become a quadratic function as the distance from the LED light source increases.

  In addition to the method shown in FIG. 10, the packing density is changed by keeping the column spacing of the columnar lenses constant, and the arrangement density of the columnar lenses in the column becomes sparser as the column gets closer to the LED light source. Alternatively, this and the method shown in FIG. 9 may be used in combination.

  In the configuration shown in FIG. 10, all the columnar lenses in the row have the same diameter and the same refractive index difference. However, in order to adjust the luminance distribution in the LED light sources 1a, 1b, and 1c, the columnar lens diameter may be changed within the column so that the filling density of the columnar lenses in the region with low light intensity within the column is increased. Good. By doing in this way, not only the luminance distribution in the whole lighting device can be improved, but also the occurrence of moire fringes in the LED light source direction can be prevented.

  FIG. 11 shows the light transmission characteristics of the columnar lens sheet used in the present invention. In FIG. 11, the horizontal axis represents the incident angle of light to the columnar lens sheet, and the vertical axis represents the light transmission intensity for each incident angle. In the drawing, the characteristic of the columnar lens sheet when the inclination angle is 0 degree is represented by a curve 24, and the characteristic of the columnar lens sheet when the inclination angle is α degrees is represented by a curve 25. However, the measurement atmosphere is in the air, and the case where the columnar lens sheet alone is evaluated is shown.

  In the case of the characteristic curve 24, it can be seen that the light intensity of the columnar lens sheet is almost zero at an angle ± β. When the incident angle is in the range of -β to β, light is scattered and transmitted, and when the absolute value of the incident angle is β or more, the light is transmitted without being scattered. That is, β is the scattering incident angle.

  On the other hand, the characteristic curve 25 when the inclination angle of the columnar lens is inclined by α degrees is shifted to a position where the scattering incident angle is shifted by α degrees as compared with the case where the inclination angle is 0 degrees. At that time, the range of the scattering incident angle hardly changes and only shifts within the range of α−β to α + β. Therefore, in the characteristic curve 25 of FIG. 11, light incident at an angle α is scattered during transmission, but light incident at an angle −α is transmitted linearly without being scattered. That is, when this columnar lens sheet is joined to the light guide plate, the light incident at an angle of −α is totally reflected on the exit surface of the columnar lens sheet and returns to the light guide plate again.

  In FIG. 11, consider the case of the characteristic curve 24 having an inclination angle of 0 degrees. At this time, the illumination light incident at an angle of β to −β from the light guide plate propagates through the columnar lens and is scattered and irradiated from the surface. If γ is larger than β but smaller than the critical angle, light incident at an incident angle γ receives Fresnel reflection on the surface of the columnar lens sheet, and part of the light is not scattered from the surface. Irradiated. However, if γ is an angle larger than β and the critical angle, the light incident at the incident angle γ is totally reflected by the exit surface of the columnar lens sheet and returns to the inside of the light guide plate again, so that it does not contribute to illumination. In addition, since most of the light propagating through the light guide plate is incident on the columnar lens sheet with a large incident angle of about 43 degrees or more, in order to use this efficiently, the columnar lens sheet is inclined according to the viewing angle characteristics. An angle must be given and a scattering incident angle matched to that must be used.

  Next, consider the case of the characteristic curve 25 using a columnar lens sheet whose inclination angle is inclined by α. First, light incident from the light guide plate within an incident angle range of incident angles α−β to α + β is scattered and emitted. In addition, the light incident from the light guide plate in the other incident angle range is reflected on the surface of the columnar lens sheet and returns to the inside of the light guide plate in the same manner as in the case of the inclination angle of 0 degree. The value of β can be controlled to an arbitrary value of about 10 to 45 degrees by adjusting the layer thickness of the columnar lens array sheet, the aperture of the columnar lens, or the difference in refractive index of the columnar lens.

  Moreover, the value of the inclination angle α can be set to an arbitrary angle of about 0 to 70 degrees by inclining the light irradiation angle at the time of manufacture. Therefore, when illumination light having an incident angle of about 43 degrees is incident from the light guide plate, the value of α is set to 35 to 70 degrees, so that the light guided through the light guide plate is removed from the surface of the columnar lens sheet. Can be emitted. However, if the value of α is too large, the inclination of the emitted light becomes too large. For example, when the illumination device of the present invention is applied to a liquid crystal display device, the visibility deteriorates. It is desirable to make it about.

  Since the light guide plate 3 is thinly formed with a thickness of about 1 mm, the number of times the light guided inside is reflected by the inner surface of the light guide plate is smaller than that of a normal light guide plate having a thickness of about 5 to 10 mm. Therefore, the formation density of the columnar lenses constituting the columnar lens sheet may be about 1/10 to 1/5 that of a normal light guide plate. This also significantly improves the luminance distribution of the illumination light as compared to an illumination device having a normal light guide plate thickness.

  FIG. 3 schematically shows another cross-sectional configuration example relating to the thin illumination device of the present invention. Here, the light reflection layer 8 is formed on the surface of the columnar lens sheet 6. In this way, by forming the light reflecting layer 8 on the surface of the columnar lens sheet 6, light that is about to escape from the back surface of the columnar lens sheet is efficiently irradiated with light, that is, the surface side of the light illumination unit 3 of the light guide plate, That is, it can be returned to the light irradiation surface. Such light is caused by light components scattered and emitted from the columnar lens sheet.

  FIG. 4 schematically shows a cross-sectional view of a configuration example having a wedge-shaped light incident portion of another shape. The wedge-shaped light incident portion 2 shown in FIG. 4 has a step formed only on the upper surface, and has a wedge shape that becomes narrower as the distance from the light incident end increases. There is no restriction on the height of each step, but it is desirable to make the step height as low as possible. Specifically, the height of each step can be arbitrarily set in the range of 50 to 1000 μm. With this structure, the length of the wedge-shaped light incident portion 2 is longer than that shown in FIGS. 1 and 2, but the bottom surface of the light guide plate including the wedge-shaped light incident portion 2 is made flat. Therefore, it has an advantage that the lighting arrangement is easy.

  FIG. 5 shows the behavior of light inside the wedge-shaped light incident portion 2 shown in FIG. FIG. 5 shows an example of the optical path 20 and 21 in the wedge-shaped light incident part 2. In FIG. 5, the light emitted from the light source enters the wedge-shaped light incident portion 2 from the light incident end face of the wedge-shaped light incident portion 2. First, the light indicated by the optical path 20 is reflected by the light reflecting layer 4 formed on the upper surface of the light incident portion and directly enters the light illumination portion 3 of the light guide plate from the wedge-shaped light incident portion 2. On the other hand, the light indicated by the optical path 21 is reflected by the light reflecting layer 4 formed in the step part and once returns to the light incident end face side, but is reflected again by the light incident end face and enters the light illumination part 3 of the light guide plate. . As shown here, the wedge-shaped light incident part 2 used in the present invention is formed of a vertical stepped part, so that the side surface of the wedge-shaped light incident part 2 can be The angle of incidence on the upper and lower surfaces does not change. That is, it is possible to guide to the light illumination unit 3 of the light guide plate without substantially changing the emission angle from the light source 1.

  If a wedge-shaped light incident portion having a normal smooth taper or a wedge-shaped light incident portion having a stepped portion having a taper is used, the light reflected by the taper is consequently larger than the emission angle from the light source. Since it is equivalent to light having a large emission angle and enters the light illumination part 3 of the light guide plate and immediately leaks to the outside, the formation of the fine reflection structure should have a higher order change. Therefore, it is important that the illumination luminance distribution is not biased toward the light source.

  Regarding the behavior of light inside the light illuminating unit 3 of the light guide plate, as described in the action of the columnar lens sheet, the light repeatedly repeats multiple reflections within the light illuminating unit 3 of the light guide plate, and forms a columnar lens sheet. Light entering the columnar lens sheet is scattered at an incident angle smaller than the scattering incident angle. The scattered light is scattered and emitted from the light irradiation surface with a predetermined scattering angle.

  FIG. 8 schematically shows a cross-sectional configuration of the liquid crystal display device of the present invention. The illumination device used in FIG. 8 has the same configuration as that shown in FIG. 4, and a light reflection layer 8 is formed on the back surface of the columnar lens sheet 6. As the liquid crystal panel 12, either an active matrix type liquid crystal display panel using a TFT element or a passive matrix type liquid crystal panel can be used. A prism sheet 13 is provided in the gap between the liquid crystal panel 12 and the illumination device. This prism sheet is a transparent sheet in which minute prisms having irregularities facing the light illumination unit 3 side of the light guide plate and having ridge lines in a direction perpendicular to the paper surface of FIG. 8 are regularly formed. By disposing the prism sheet 7 between the illuminating device and the liquid crystal panel as described above, the illumination light can be efficiently incident on the surface of the liquid crystal panel 12 to increase the luminance of the liquid crystal display device. be able to. As can be seen from FIG. 8, in the thin illumination device of the present invention, the light illumination portion of the light guide plate can be made thin, and as a result, the liquid crystal display device itself can be thinned.

  Next, an example of an optical path that can be placed in the illumination device of the present invention shown in FIG. 1 will be described. The light emitted from the LED light source 1 is repeatedly reflected in the wedge-shaped light incident portion 2 and then enters the illumination portion 3 of the light guide plate and enters the columnar lens sheet 6. As shown in FIG. 7, since this incident light is incident on the columnar lens sheet 6 at a linear transmission angle, it is reflected on the back surface of the columnar lens sheet 6 as it is. At this time, when light is reflected within the range of the scattering incident angle of the columnar lens sheet, the light is guided in the columnar lens and scattered and emitted from the surface. Of the scattered light returned to the light illuminating unit 3 of the light guide plate, a component having an incident angle on the light illuminating surface of about 43 or less is subjected to Fresnel reflection on the light illuminating surface of the light illuminating unit 3 of the light guide plate. A liquid crystal panel as an object to be irradiated is irradiated from the back side. Of the scattered light, the light reflected and reflected by Fresnel reflection on the light irradiation surface returns again to the inside of the light illumination part 3 of the light guide plate and reaches the back surface of the columnar lens sheet 6. Since the light reaching the back surface of the columnar lens sheet 6 is incident at an angle smaller than the critical angle, a part of the light is transmitted again after receiving Fresnel reflection. If the light reflecting plate is disposed to face the columnar lens sheet 6, the light reflecting plate is reflected by the light reflecting plate and reenters the columnar lens sheet 6 from the back surface. If a light reflection layer is formed on the back surface of the columnar lens sheet 6, the light is reflected as it is by the light reflection layer and reenters the columnar lens sheet 6. The re-incident light is again scattered and emitted by the columnar lens sheet 6 into the light illumination unit 3 of the light guide plate, and a part of the re-incident light irradiates the liquid crystal panel from the back surface.

  On the other hand, the light reflected by the back surface of the columnar lens sheet 6 at an angle equal to or greater than the scattering incident angle passes straight through the columnar lens sheet 6 and returns to the inside of the light illumination unit 3 of the light guide plate. The light that has returned to the inside of the light guide plate repeats total internal reflection a plurality of times and enters the surface facing the light incident surface in the same manner as when guided in a normal flat transparent substrate.

  Since the surface facing the light incident surface has a taper of 3 to 7 degrees, the reflected light is deflected by that amount and returns to the inside of the light illumination unit 3 of the light guide plate. Therefore, the return light enters the irradiation surface of the light illumination unit 3 of the light guide plate at an incident angle larger than the incident light, and is further reflected to return to the columnar lens sheet 6. Since a part of this light is incident at the scattering incident angle of the columnar lens sheet 6, the light transmitted through the columnar lens sheet 6 is scattered and reflected by the back surface of the columnar lens sheet 6. The scattered light passes through the columnar lens sheet 6 and irradiates the liquid crystal panel from the surface of the light illumination unit 3 of the light guide plate. Further, the light incident at the remaining linear transmission angle is reflected on the back surface of the columnar lens sheet 6, then passes through the columnar lens sheet 6, is totally reflected on the inner surface of the light illuminating unit 3 of the light guide plate, and is again on the light guide plate The reflection is repeated inside the light illumination unit 3.

  As a result of the existence of various optical paths inside the light illumination unit 3 of the light guide plate as described above, the illumination device of the present invention shown in FIG. 1 can perform efficient illumination.

  Next, the optical path in the thin illumination device of the present invention having two columnar lens sheets as shown in FIG. 4 will be described. The light path in the illuminating device having the configuration of FIG. 4 is different from the optical path in the illuminating device having the configuration of FIG. 1 in that light incident on the second columnar lens sheet 7 from the columnar lens sheet 6 side is the second columnar lens sheet 7. Is within the range of the scattering incident angle of the liquid crystal panel, the light controlled within the range of the scattering incident angle around the tilt angle from the surface of the second columnar lens sheet 7 is scattered and irradiated. . As a result, this liquid crystal display device can realize image display superior in viewing angle characteristics than the liquid crystal display device shown in FIG.

  In this way, in the case of using one or two columnar lens sheets, the light irradiated from the surface of the columnar lens sheet is diffused and thus becomes more uniform illumination. Due to the regulated directivity, the liquid crystal panel can be irradiated efficiently, and a uniform and bright illumination device with excellent viewing angle characteristics can be obtained.

Specific examples of the present invention will be described below.
(Specific example 1)
The lighting device having the structure shown in FIG. 1 was produced as follows. A wedge-shaped light incident portion 2 having a thickness of 7 mm on the light source side and a width of 35 mm was molded from an acrylic resin. The light illumination part 3 of the light guide plate had a thickness of 1 mm and a length of 40 mm. Aluminum was deposited on the surface of the wedge-shaped light incident portion 2 to a thickness of about 1 μm. The height of each step portion of the wedge-shaped light incident portion was 80 μm, and the number of steps was 37 on each side. On the three side surfaces of the light guide plate except for the upper and lower surfaces of the light illuminating unit 3, an aluminum light reflection layer was formed by vapor deposition of about 1 μm. Three white LED light sources were used as the light source. As the columnar lens sheet, a graded index columnar lens having a scattering incident angle of 30 degrees was used. The columnar lens sheet had a thickness of 70 μm and a columnar lens diameter of 30 μm. As the inclination angles of the columnar lens sheets to be pasted, four types of angles of 0 degrees, 15 degrees, 30 degrees, and 60 degrees were used.

  When the LED light source was turned on, the relationship between the emission angle of light emitted from the produced light guide plate and the luminance was measured and shown in FIG. In FIG. 12, the result of using a columnar lens sheet having a scattering incident angle of 0 degrees is shown as a curve 26, the result of using a columnar lens sheet having a scattering incident angle of 15 degrees is shown as a curve 27, and the scattering incident angle of 30 degrees. The result when the columnar lens sheet is used is shown by a curve 28, and the result when a columnar lens sheet having a scattering incident angle of 60 degrees is used is shown by a curve 29. As can be seen from this result, when a columnar lens sheet having an orientation angle of 0 degrees is used, almost no light is emitted from the sheet surface. Moreover, the maximum value of the light intensity emitted from the sheet surface increases as the orientation angle increases. Furthermore, the amount of emitted light was maximum when the tilt angle was 60 degrees. This is presumably because most of the light incident on the columnar lens sheet has a total reflection angle of about 43 degrees or more. Therefore, all the light incident on the columnar lens sheet having an inclination angle of 0 degrees is larger than the scattering incident angle and is not emitted to the outside. On the other hand, with respect to the columnar lens sheet having a scattering incident angle of 30 degrees or more, since the incident light contains components within the scattering incident angle, the outgoing light to the outside increases.

From this, when using only one columnar lens sheet as shown in FIG. 1, it was confirmed that the inclination angle of the columnar lens sheet should be about 30 to 60 degrees. When the luminance of the thin illuminating device thus manufactured was measured, a value of 1800 to 2300 cd / m 2 was obtained, and performance equivalent to that of a normal sidelight illuminating device was obtained. Moreover, the thickness of the illumination part of the illuminating device can be reduced to 1 mm, which is 1/7 of the conventional thickness.
(Specific example 2)
The lighting device shown in FIG. 4 was produced as follows. The number of stages of the light incident part 2 was 74 with a height of 80 μm. As the light illuminating unit 3 of the light guide plate, the same one as in the first specific example was used. Moreover, the aluminum plate which made the reflective surface the mirror surface as the light reflection plate 6 was used for the back surface of the light-guide plate. Further, three white LED light sources were used as the light source. The taper angle of the end face of the light guide plate on the side opposite to the side where the LED light source is arranged was 3 degrees. As the columnar lens sheet 6 and the second columnar lens sheet 7, those in which graded index columnar lenses having a scattering incident angle of 30 degrees are uniformly arranged are used. The thickness of these columnar lens sheets was 70 μm, and the columnar lens diameter was 30 μm. The columnar lens sheet 6 has an inclination angle of 30 degrees, and the second columnar lens sheet 7 has four inclination angles of 0 degree, 15 degrees, 30 degrees, and 60 degrees.

When the LED light source was turned on, the relationship between the emission angle of light emitted from the produced light guide plate and the luminance was measured and shown in FIG. In FIG. 13, the result when the second columnar lens sheet having a scattering incident angle of 0 degrees is used is shown as a curve 30, and the result when the second columnar lens sheet having a scattering incident angle of 15 degrees is used as a curve 31. A curve 32 shows a result when the second columnar lens sheet having an angle of 30 degrees is used, and a curve 33 shows a result when the second columnar lens sheet having a scattering incident angle of 60 degrees is used. As is clear from FIG. 13, a large luminance is obtained when the inclination angle of the second columnar lens sheet is 15 degrees and 30 degrees. That is, when the inclination angle of the columnar lens sheet 6 is 30 degrees, it can be seen that bright illumination with a scattering angle suitable for the viewing angle characteristic is possible if the inclination angle of the second columnar lens sheet 7 is 0 to 30 degrees. . When the luminance of this thin illuminating device was measured, a luminance of 1800 to 2100 Cd / m 2 was obtained.
(Specific example 3)
A columnar lens sheet 6 having an inclination angle of 60 degrees with the same configuration as that of Example 2 was prepared. The result is shown in FIG. In FIG. 14, the case where the second columnar lens sheet having a scattering incident angle of 0 degrees is used is shown as a curve 34, the case where the second columnar lens sheet having a scattering incident angle of 15 degrees is used as a curve 35, and the scattering incident angle being 30 degrees. A curve 36 shows the case where the second columnar lens sheet is used, and a curve 37 shows the case where the second columnar lens sheet having a scattering incident angle of 60 degrees is used. From FIG. 14, it was found that the luminance was increased when the inclination angle of the second columnar lens sheet was 30 to 60 degrees. However, if the inclination angle of the second columnar lens sheet is larger than 30 degrees, the viewing angle characteristics are deteriorated. Therefore, the inclination angle of the second columnar lens sheet is preferably about 30 degrees.

  From the specific examples 2 and 3 described above, in the illumination device having the configuration shown in FIG. 4, when the inclination angle of the columnar lens sheet 6 is about 30 to 60 degrees, the inclination angle of the second columnar lens sheet 7 is about 0 to 30. It was found that a bright lighting device with excellent viewing angle characteristics can be realized by setting the degree.

It is sectional drawing which shows typically the illuminating device by this invention. It is sectional drawing which shows typically the structure of the illuminating device by this invention. It is sectional drawing which shows typically the structural example of the illuminating device by this invention. It is sectional drawing which shows typically the structural example of the illuminating device by this invention. It is sectional drawing which shows typically an example of the optical path in a wedge-shaped light incident part. It is explanatory drawing which shows an example of the optical path in the columnar lens sheet used by this invention. It is explanatory drawing which shows an example of the optical path in the columnar lens sheet used by this invention. It is sectional drawing which shows typically the liquid crystal display device using the thin illuminating device of this invention. It is a top view which shows typically the columnar lens arrangement | sequence example of the columnar lens sheet | seat used by this invention. It is a top view which shows typically the columnar lens arrangement | sequence example of the columnar lens sheet | seat used by this invention. It is a graph showing the characteristic of the columnar lens sheet used by this invention. It is a graph which shows the luminance characteristic of the illuminating device of this invention. It is a graph which shows the luminance characteristic of the illuminating device of this invention. It is a graph which shows the luminance characteristic of the illuminating device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED light source 2 Wedge-shaped light entrance part 3 Light illumination part of a light-guide plate 4, 5 Light reflection layer 6 Columnar lens sheet 7 Second columnar lens sheet 8 Light reflection layer 9 Bonding agent 10 High refractive index area | region 11 Low refractive index area | region

Claims (10)

A light source;
A light guide having an illumination surface for illuminating the irradiated body with illumination light;
It has a heat transmitting portion for transmitting light to the light guide and the light incident surface on which light enters from the light source, which is formed so that the thickness than the thickness of the light incident surface side the heat transfer optical unit side is thinner Light incident body,
A columnar lens that is provided on the opposite side of the illumination surface of the light guide plate and in which a plurality of columnar lenses in which a region having a higher refractive index than the surrounding region is continuously formed in the thickness direction is arranged in the surface, and guides light in the thickness direction. A lens sheet ,
The columnar lens sheet has a function of scattering light incident at a specific angle range and transmitting light incident at other angles,
The columnar lens is formed to be inclined to the side where the light source is disposed with respect to a reference line perpendicular to the illumination surface of the light guide plate, so that the central angle of the specific angle range is the illumination of the light guide plate. An illumination device, wherein the illumination device is inclined to a side where the light source is disposed with respect to a reference line perpendicular to the surface. The illumination device according to claim 1, wherein the columnar lenses are formed on the columnar lens sheet in an array having no periodicity. On the illumination surface side of the light guide plate , a plurality of columnar lenses in which regions having a higher refractive index than the surrounding region are continuously formed in the thickness direction are arranged in the surface to guide the light in the thickness direction, and the second A second columnar lens sheet having a function of scattering light incident at a specific angle range and transmitting light incident at other angles,
The columnar lens of the second columnar lens sheet is formed to be inclined to the side opposite to the side where the light source is disposed with respect to a reference line perpendicular to the illumination surface of the light guide plate . The center angle of the two specific angle ranges is inclined to the opposite side of the side where the light source is disposed with respect to a reference line perpendicular to the illumination surface of the light guide plate. The lighting device described. 4. The illumination according to claim 3, wherein the columnar lens sheet has a high filling density of the columnar lens in a portion far from the light source, and the filling density of the columnar lens is uniform in the sheet in the second columnar lens sheet. apparatus. The light incident member, either from the entering thickness of the optical body is the light incident surface side of the claims 1-4, characterized in that it is constituted successively thinned substantially vertical stepped toward the heat transfer optical unit side the lighting device according to an item or. The light guide has an incident surface for entering light from a light transmitting portion of the light incident member and an end surface opposite to the incident surface, and the end surface is parallel to the incident surface. the lighting device according to any one of claims 1 to 5, characterized in that such inclined plane on the light source side in 3-7 degree angle as a reference. The illumination device according to claim 1, wherein the light incident body and the light guide body are integrally formed. The columnar lens sheet is attached to the light guide plate with a bonding agent, and a light reflection layer is provided on the back side of the columnar lens sheet. The lighting device described. A display device comprising: the illumination device according to any one of claims 1 to 8 ; and a non-self-luminous display element provided on a light irradiation surface side of the illumination device. The display device according to claim 9, wherein a prism sheet is provided between the illumination device and the display element.

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