JP2005227566A - Lighting device and display device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To brighten and uniformize luminance of a surface lighting device using a cylindrical lens sheet and a light guide plate. <P>SOLUTION: A plurality of cylindrical lens sheets are joined to the light emission side of the light guide plate. Respective inclined angles of cylindrical structures of the respective cylindrical lens sheets are set to be smaller in turn from the cylindrical lens sheet close to the light guide plate to the farther one. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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, liquid crystal display elements have been widely used because display elements used in portable devices, particularly mobile phones, are 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 (Light-Emitting-Diode) is arranged as a light source on the side surface of the light guide plate is often used.

For such a liquid crystal display device, a plurality of fine columnar structures are arranged in a plane, and the columnar central region of the columnar structure is formed with a higher refractive index than the outer peripheral region surrounding it, and in the thickness direction. A manufacturing technique of a light guide sheet which is a columnar lens sheet having a function of guiding light and a liquid crystal display device using the same are disclosed (for example, see Patent Document 1).
Japanese Unexamined Patent Publication No. 2000-35576 (page 3-5, FIG. 7)

  In the conventional configuration using the columnar lens sheet disclosed in Patent Document 1, a diffusion layer is used between the light guide plate of the backlight and the columnar lens sheet. However, this diffusion layer has an effect on the light guide characteristics of the backlight, and there is a problem that uniform and high-brightness illumination cannot be performed.

  In the present invention, a plurality of fine columnar structures are arranged in a plane, and the columnar central region of the columnar structure is formed with a higher refractive index than the outer peripheral annular region surrounding it, and has a function of guiding light in the thickness direction. A plurality of the columnar lens sheets are joined to the light irradiation surface side of the light guide plate, and the inclination angle of the alignment direction of the columnar structures is made to decrease sequentially from the light guide plate side. Such a structure makes it possible to easily manufacture a lighting device having good luminance and viewing angle characteristics.

  That is, the illuminating device of the present invention is provided on a flat light guide plate formed of a transparent material, a light source for entering light from a side end surface of the light guide plate, and a light irradiation surface side of the light guide plate, and in a specific angle range. The illumination device includes a lens sheet that scatters incident light and transmits light incident at other angles, and the lens sheet is provided with a plurality of layers, and the lens sheet closer to the light guide plate has a specific angle range. The central angle is a small angle with respect to the light irradiation surface of the light guide plate.

  Alternatively, a flat light guide plate made of a transparent material, a light source arranged on the side end surface of the light guide plate, and a columnar lens in which a region having a higher refractive index than the surrounding region is continuously formed in the thickness direction A plurality of columnar lens sheets arranged in the thickness direction and having a function of guiding light in the thickness direction, and the columnar lens has a side on which a light source is disposed with reference to a direction of a perpendicular line standing on a surface of the columnar lens sheet; The columnar lens sheet is inclined in the opposite direction, and the inclination angle of the columnar lens sheet is smaller as the columnar lens sheet is closer to the light guide plate. Furthermore, the columnar lens sheet includes a first columnar lens sheet disposed above the light guide plate and a second columnar lens sheet laminated on the first columnar lens sheet, and the columnar lens of the first columnar lens sheet is provided. The inclination angle is about 20 to about 45 degrees, and the inclination angle of the columnar lens of the second columnar lens sheet is about 0 to about 25 degrees. Alternatively, the columnar lens sheet includes a first columnar lens sheet disposed above the light guide plate, a second columnar lens sheet stacked on the first columnar lens sheet, and a second columnar lens sheet stacked on the second columnar lens sheet. A third columnar lens sheet is provided, the inclination angle of the columnar lens of the first columnar lens sheet is about 30 to about 50 degrees, and the inclination angle of the columnar lens of the second columnar lens sheet is about 15 to about 35 degrees. The inclination angle of the columnar lens of the columnar lens sheet was about 0 to about 20 degrees.

  Further, a high refractive index layer having a refractive index larger than the refractive index of the light guide plate and substantially equal to the refractive index of the high refractive index region constituting the columnar lens, between the columnar lens sheet closest to the light guide plate and the light guide plate. It was set as the structure which provides. Further, a high refractive index bonding agent is used as the high refractive index layer. Further, the arrangement of the columnar lenses constituting the columnar lens sheet was an aperiodic arrangement.

  The display device of the present invention includes the illumination device having the above-described configuration for illuminating a non-self-luminous display element.

  According to the present invention, it is possible to provide a thin and light illumination device having good luminance and luminance distribution, so that not only the display quality of a liquid crystal display device using the same can be improved, but also the liquid crystal display device can be reduced in thickness and weight. Can also be realized.

  The illumination device of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the configuration of the illumination device of the present invention. A fine reflecting structure 5 is formed on the lower surface of the light guide plate 3, and the first columnar lens sheet 2a and the second columnar lens sheet 2b are disposed on the upper surface of the light guide plate 3 via the first bonding layer 4a and the second bonding layer 4b. Are joined in order. The LED light source 1 is disposed on the side surface of the light guide plate 3, and light emitted from the LED light source is guided through the light guide plate 3 and reaches the irradiation surface of the light guide plate. Since the columnar lens sheet is laminated on the irradiation surface of the light guide plate as described above, the light from the light source is uniformly irradiated onto the illumination target (not shown) from the second columnar lens sheet surface. . By using a non-self-luminous display element such as a liquid crystal display element as the object to be illuminated, a thin liquid crystal display device with uniform brightness and brightness can be obtained.

  Here, the light guide plate 3 is made of a transparent polymer such as acrylic resin, polycarbonate resin, or cycloolefin resin. The fine reflecting structure 5 formed on the lower surface of the light guide plate 3 includes a group of fine prisms having a ridge line in a direction perpendicular to the paper surface of FIG. A triangular prism group or a grain structure can be used. 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, a minute prism for controlling the spread angle of the light emitted from the LED light source 1 inside the light guide plate 3 is formed on the side surface of the light guide plate 3 facing the LED light source 1. . This microprism has a vertical ridgeline on the paper surface in FIG. 1, and the spread angle can be controlled by the apex angle and height of the microprism.

  The first columnar lens sheet 2a and the second columnar lens sheet 2b have a plurality of fine columnar structures arranged in a plane, and the columnar structure has a higher refractive index than the surrounding area. That is, 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 plane. With such a configuration, the columnar lens sheet has a function of guiding light in the thickness direction. Specifically, a graded index columnar lens whose refractive index continuously increases toward the center of the columnar structure, or 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. The film structure has a plurality of step index columnar lenses arranged as shown in FIG. 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 used in the present invention is formed such that the orientation direction of the columnar lens is inclined to the side opposite to 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. The angle formed by the orientation direction with respect to the direction of the perpendicular line standing on the surface of the columnar lens sheet is referred to as an inclination angle.

  The first columnar lens sheet 2a is bonded to the second columnar lens sheet 2b by the second bonding layer 4b. The second columnar lens sheet 2a is joined to the light guide plate 3 by the first joining layer 4a. As these bonding layers, ordinary optical adhesive layers such as epoxy adhesives and acrylic adhesives may be used, but it is easy to use ordinary film adhesives.

  The first columnar lens sheet 2 a and the second columnar lens sheet 2 b used in FIG. 1 have different inclination angles, and the inclination angle of the first columnar lens sheet 2 a joined to the light guide plate 3 is different. Is larger than the second columnar lens sheet. Specifically, the inclination angle of the first columnar lens sheet 2a is 20 to 45 degrees, and the inclination angle of the second columnar lens sheet 2b is 0 to 25 degrees. Thus, by laminating and joining two columnar lens sheets having different inclination angles, the light from the light guide plate 3 can be illuminated more efficiently than when only one columnar lens sheet is used.

  Further, as the bonding layer 4a between the light guide plate 3 and the first columnar lens sheet 2a, a high refractive index bonding layer 6 is used as shown in FIG. Accordingly, light can be efficiently transmitted from the light guide plate 3 to the first columnar lens sheet 2a as compared with a case where a normal bonding layer is used, and as a result, the luminance of the lighting device of the present invention can be improved. it can. In ordinary pressure-sensitive adhesives, the refractive index is lowered by mixing with air or the like, but in the high-refractive index bonding layer 6, a high-refractive-index polymer material or high-refractive-index oxide ultrafine particles are mixed in an adhesive or a pressure-sensitive adhesive. Therefore, a high refractive index can be obtained. At this time, it goes without saying that a high refractive index bonding layer may be used as the bonding layer 4b between the columnar lens sheets.

  FIG. 2 shows an illumination device having a configuration in which three columnar lens sheets are stacked on a light guide plate. Here, the inclination angle of the first columnar lens sheet 2a is 30 to 50 degrees, the inclination angle of the second columnar lens sheet 2b is 15 to 35 degrees, and the inclination angle of the third columnar lens sheet 2c is 0 to 20 degrees. By using three columnar lens sheets in this way, the structure is complicated compared to the case of two columnar lens sheets, but more efficient illumination can be realized.

  In general, in a columnar lens sheet, as will be described later, light incident on the sheet within 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 columnar. It passes through the lens sheet almost linearly 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.

  FIG. 4 shows an illumination device having a configuration in which a high refractive index layer 7 is formed on the light guide plate side surface of the first columnar lens sheet 2a. The refractive index of the high refractive index layer 7 is larger than the refractive index of the light guide plate 3, and is the same as or higher than the refractive index of the high refractive area of the fine columnar lens constituting the first columnar lens sheet. Has a smaller value. The layer thickness of the high refractive index layer 7 is about 1 to 5 μm. As a method for forming the high refractive index layer 7, a material mixture of CeO2 or MgO and SiO2 may be formed by vacuum deposition, or a mixed sol having a adjusted refractive index such as a mixed sol of silica sol and titania sol is applied and baked. May be formed. Thus, the 1st columnar lens sheet 2a in which the high refractive index layer 7 was formed is joined to the light guide plate 3 by the joining layer 4a with the high refractive index layer 7 side facing the irradiation surface of the light guide plate 3.

  This columnar lens sheet is manufactured, for example, by irradiating a liquid reaction layer made of two or more kinds of photopolymerizable compounds having different refractive indexes with an irradiation angle corresponding to an inclination angle through a photomask subjected to gradation processing. Thus, the refractive index distribution is controlled by utilizing the difference in the photopolymerization rate of the photopolymerizable compound depending on the light irradiation intensity.

  Next, the behavior of light in the columnar lens sheet will be described with reference to FIGS. Here, for the sake of simplicity, a case where two columnar lens sheets are used in the same manner as shown in FIG. 3 and the columnar lens sheet and the light guide plate are bonded using the high refractive index bonding layer 6 will be described. In the drawing, one of the optical paths of light incident on these columnar lens sheets from the inside of the light guide plate 3 is indicated by an arrow 12. The light guided in the light guide plate 3 enters the high refractive index bonding layer 6 with various incident angles, but most of the incident light has an incident angle larger than the critical angle of the light guide plate 3. Incident. Since the high refractive index bonding layer 6 has a larger refractive index than the light guide plate 3, the refraction angle to the high refractive index bonding layer 6 is smaller than the incident angle according to Snell's law. In the step index type columnar lens, the high refractive index region 14 and the low refractive index region 15 are formed with a clear boundary. On the other hand, a graded index type columnar lens has a high refractive index region in which the refractive index near the central axis of the columnar lens is maximized, and a distribution in which the refractive index at the outermost periphery is minimized. 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 unlike the step index type columnar lens. Here, in order to simplify the description, a case where a step index type columnar lens sheet is used will be described.

  Here, the refractive index of the high refractive index region 14 which is the central region of the columnar lens is equal to or larger than the refractive index of the high refractive index bonding layer 6. Therefore, the light incident on the high refractive index region 14 of the first columnar lens sheet from the high refractive index bonding layer 6 travels straight as it is, or is further refracted toward the normal side of the light guide plate irradiation surface. The light incident on the high refractive index region 14 is incident on the boundary surface with the low refractive index region 15, but since the incident angle on the boundary surface is larger than the critical angle, all the light is incident on this boundary surface. Reflected. This light is repeatedly totally reflected at the boundary surface between the high refractive index region 14 and the low refractive index region 15 and guided upward, and is emitted from the upper surface of the first columnar lens sheet. The incident angle to the inner upper surface of the first columnar lens sheet is smaller than the critical angle due to light reflected at the boundary surface in the columnar lens, and is thus emitted to the outside of the columnar lens sheet.

  At this time, the light emission direction, that is, the scattering angle, of the light from the first columnar lens sheet 2a is determined by the layer thickness of the first columnar lens sheet 2a on the light guide plate 3 side, the incident angle of light to the high refractive index region 14, and the incident position. .

  The light entering the bonding layer 4 in this way enters the second columnar lens sheet 2b on the exit surface side. In FIG. 5, it is written so as to be incident on the high refractive index region 14 of the second columnar lens sheet 2 b, but when the junction between the columnar lens sheets 2 a and 2 b is shifted, it is incident on the low refractive index region 15. There is also. In either case, when the emission angle of light from the first columnar lens sheet 2a is at the scattering incident angle of the second columnar lens sheet 2b, the light is emitted from the second columnar lens sheet 2b as shown in FIG. The light is scattered and emitted from the surface through the high refractive index region 14. In addition, when the light emission angle from the first columnar lens sheet 2a is within the range of the linear transmission angle of the second columnar lens sheet 2b, the incident angle to the second columnar lens sheet 2b is also a linear transmission angle. It is totally reflected on the surface of the two-column lens sheet 2b and returns to the light guide plate 3 side again.

  Next, FIG. 6 shows a case where light that has entered the high refractive index bonding layer 6 from the inside of the light guide plate 3 at a larger incident angle enters the high refractive index region 14 of the first columnar lens sheet 2a. In this case, as indicated by the optical path 16 in the figure, the incident angle of the light incident on the boundary surface between the high refractive index region 14 and the low refractive index region 15 of the first columnar lens sheet 2a is as shown in FIG. Smaller than the case. As a result, the light passes through the boundary surface, enters the low refractive index region 15, and is emitted almost linearly from the surface of the first columnar lens sheet 2 a into the bonding layer 4. In this case, as shown in FIG. 6, light enters the second columnar lens sheet 2b from the bonding layer 4 at a linear transmission angle, is totally reflected on the surface of the second columnar lens sheet 2b, and returns to the light guide plate 3 side again. . In FIG. 5 and FIG. 6, the columnar lens constituting the first columnar lens sheet 2a is tilted and oriented in the range of an inclination angle of 20 to 45 degrees on the opposite side to the LED light source with respect to the perpendicular standing on the surface. . Further, the scattering incident angle can have a range of 10 to 45 degrees. On the other hand, the light component guided inside the light guide plate 3 is mainly composed of components that are inclined and propagate toward the LED light source at a large incident angle of about 43 degrees or more, which is the critical angle of the light guide plate 3. Even in such a situation, since the columnar lenses constituting the first columnar lens sheet 2a are inclined as described above, the incident angle to at least the first columnar lens sheet 2a is about 43 degrees or more and the inside of the light guide plate 3 A part of the light propagated through can be made incident at a scattering incident angle. Of course, when the tilt angle is as small as 25 degrees, the first columnar lens sheet 2a having a scattering incident angle of 18 degrees or more must be used.

  On the other hand, at this time, the incident angle of the light to the second columnar lens sheet 2b is approximately -20 to 90 degrees. Among these lights, the light incident at the scattering incident angle of the second columnar lens sheet 2b is guided in the second columnar lens sheet 2b having an inclination angle of 0 to 25 degrees and scattered in the direction of the inclination angle. Emitted.

  Note that the light incident on the inside of the graded index columnar lens is not reflected at the boundary between the high refractive index region 14 and the low refractive index region 15, but is more refracted when the light is guided through the columnar lens. The optical path can be bent toward the higher rate. 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 is a scattering emission angle. In other words, light incident at an incident angle smaller than the scattering emission angle is guided through the columnar lens and scattered and emitted from the surface of the columnar lens sheet, but light incident at an incident angle larger than the scattering emission angle travels substantially straight. It is totally reflected on the surface of the columnar lens sheet and returns to the light guide plate 3 again. That is, such an incident angle corresponds to a linear transmission angle.

  Regardless of the step index type columnar lens sheet or the graded index type columnar lens sheet, the scattering emission angle is set to 10 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 45 degrees.

  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.

  Next, in the illumination device shown in FIG. 2, the first columnar lens sheet 3a, the second columnar lens sheet 3b, and the third columnar lens sheet 3c are sequentially bonded to the light guide plate by the bonding layers 4a, 4b, and 4c. . The inclination angles of the columnar lenses constituting these columnar lens sheets are 30 to 50 degrees for the first columnar lens sheet 4a, 15 to 35 degrees for the second columnar lens sheet 2b, and 0 to 25 degrees for the third columnar lens sheet. It has become. Thus, by laminating three columnar lens sheets, the light propagating inside the light guide plate 3 can be efficiently transmitted to the third columnar lens sheet 2c for the same reason as described in FIGS. Irradiation from the surface is possible. In particular, in this case, since the inclination angle of the first columnar lens sheet 2a can be increased as compared with the case of FIG. 1, light having a wider incident angle component propagating through the light guide plate 3 is transmitted to the light guide plate. 3 and the range of the scattering incident angle of each columnar lens sheet can be reduced to about 30 degrees. As a result, the luminance can be improved and the light can be efficiently emitted in the viewing angle direction as compared with the illumination device having the configuration shown in FIG.

  Next, a display device using the illumination device of the present invention will be described. An example of an optical path in a liquid crystal display device using a liquid crystal display element and a lighting device as a non-self-luminous display element will be described with reference to FIG. The liquid crystal display device according to the present invention includes an illumination device including an LED light source 1, a light guide plate 3, a first columnar lens sheet 2a, a second columnar lens sheet 2b, a high refractive index bonding layer 6, a bonding layer 4, and a reflecting plate 11. And the liquid crystal panel 10. Further, a fine reflecting structure 5 is formed on the back surface of the light guide plate 3. In the drawing, the optical paths of light propagating through the interior of the illumination device are indicated by arrows 18 and 19.

  The light emitted from the LED light source 1 enters the light guide plate 3, then passes through the high refractive index bonding layer 6, and sequentially reaches the first columnar lens sheet 2 a, the bonding layer 4, and the second columnar lens sheet 2 b. Incident. At this time, when light is incident on the second columnar lens sheet 2b within the range of the scattering incident angle of the second columnar lens sheet, the light is guided in the second columnar lens sheet 2b as indicated by an arrow 18 and is surfaced. Scattered emission from. Further, as indicated by an arrow 19, when the light is incident at the linear transmission angle of the second columnar lens sheet 2b, the light is totally reflected on the surface of the second columnar lens sheet 2b as it is, and again the bonding layer 4 and the second layered lens sheet 2b. The light passes through the columnar lens sheet 2 a and the high refractive index bonding layer 6 in order and returns to the inside of the light guide plate 3. The light that has returned to the light guide plate 3 is deflected by the fine reflective structure 5 on the back surface, passes through the back surface of the light guide plate 3, is reflected by the reflective plate 11, and returns to the light guide plate 3 again. Since this return light is deflected, when it passes through the high refractive index bonding layer 6 and then enters the first columnar lens sheet 2a again, its incident angle is the linear transmission angle of the first columnar lens sheet 2a. It has become. For this purpose, the light passes through the first columnar lens sheet 2 a in a straight line and then enters the second columnar lens sheet 2 b through the bonding layer 4. Since this light has the scattering incident angle of the second columnar lens sheet 2b, it is guided through the second columnar lens sheet 2b and scattered and emitted from the surface, and the liquid crystal panel 10 is illuminated from the back surface. Here, the case where a fine prism structure formed with an apex angle of about 100 degrees or less or a fine reflection structure protruding in a convex shape from the light guide plate surface has been described. However, when a fine prism structure formed with an apex angle of about 100 degrees or more or a fine reflection structure recessed inward from the surface of the light guide plate, most of the return light is generated by the fine reflection structure 5. Reflected directly to the liquid crystal panel.

  Since the light irradiated from the surface of the second columnar lens sheet 2b is scattered in this way, the liquid crystal panel can be efficiently used for more uniform illumination and directivity regulated by the scattering incident angle. Can be irradiated. Therefore, a bright lighting device having excellent viewing angle characteristics can be obtained.

  Furthermore, if one or two prism sheets having a fine prism structure on one side on the lens sheet side are arranged between the second columnar lens sheet 2b and the liquid crystal panel 10, the directivity of scattered light is further vertical. It becomes possible to convert to a direction, and more efficient illumination becomes possible.

  Next, the filling density of the columnar lenses constituting the columnar lens sheet will be described. As described above, the columnar lens sheet used in the present invention has a uniform packing density of the columnar lenses constituting the columnar lens sheet in order to efficiently scatter and emit light propagating in the light guide plate. The luminance on the LED light source side becomes too large and the luminance distribution becomes worse. 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. The columnar lens sheet obtained as described above was used. In the present invention, since a plurality of columnar lens sheets are used, the portions where the columnar lens sheets are superimposed are joined so that the weight density is substantially the same. 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. At this time, a fine reflecting structure such as a fine prism structure may or may not be formed on the back surface of the light guide plate 3. However, the uniformity of the brightness and the light utilization efficiency are improved when the fine reflective structure is formed on the back surface of the light guide plate 3. The formation density and pitch of the fine reflecting structures are formed by optimizing the columnar lens filling density distribution of the columnar lens sheet.

  FIG. 8 shows an example in which the columnar lens filling density of the columnar lens sheet is changed. This figure is the top view which looked at the illuminating device of this invention from the columnar lens sheet side, and three LED light sources 1a, 1b, and 1c are arrange | positioned at the light-guide plate side surface. A plurality of columnar lenses 12 are filled in the columnar lens sheet 2 and arranged. As shown in the drawing, the filling density of the columnar lenses is changed by arranging the lens diameters of the columnar lenses on the LED light source side so as to decrease as the distance from the LED light source increases. It is exaggerated to make it easy to see the figure, but the columnar lens diameter is distributed in a size of about 5 μm to 200 μm, and its value is the size of the light guide plate, a light guide plate not shown, and high refraction. The optimum value varies depending on the refractive index of the refractive index layer and the thickness and refractive index of the columnar lens. Further, the arrangement in the surface of the columnar lens sheet 2 is an arrangement from which periodicity is removed in order to prevent the generation of moire fringes.

  FIG. 9 illustrates another configuration 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 rows arranged in a row in the arrangement direction of the LED light sources, and the side where the column density is close to the LED light sources is denser and becomes sparse as the distance from the LED light sources is increased. In this best mode, 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. 9, 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. 8 may be used in combination.

  In the configuration shown in FIG. 9, 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. In the case of changing the importance density as shown in FIG. 9, it is necessary to strictly align and join the columnar lenses constituting the plurality of columnar lens sheets so that they overlap each other.

FIG. 10 shows the light transmission characteristics of the columnar lens sheet used in the present invention. In FIG. 10, the horizontal axis represents the incident angle of light to the columnar lens sheet, and the vertical axis represents the light transmission intensity. In the figure, a characteristic curve 20 of a columnar lens sheet having an inclination angle of 0 degrees and a characteristic curve 21 of a columnar lens sheet having an inclination angle of α degrees are shown. However, the measurement atmosphere is in the air, and the case where the columnar lens sheet alone is evaluated is shown. It can be seen from the characteristic curve 20 that the columnar lens sheet has almost zero light intensity 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 21 when the alignment direction of the columnar lens is tilted 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 alignment direction 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 21 shown in FIG. 10, 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 affixed to the light guide plate, the light incident at an angle of -α is totally reflected at the exit surface of the columnar lens sheet and again toward the light guide plate if α is larger than the critical angle. Go back to.

  In FIG. 10, the case of the characteristic curve 20 in which the inclination angle of the columnar lens is 0 degree is considered. 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. However, if γ is larger than β and larger than the critical angle, the light incident at the incident angle γ is totally reflected on the exit surface of the columnar lens sheet and does not return to the inside of the light guide plate and 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 scattering incident angle of the columnar lens sheet is set to 45 degrees. It is desirable that the value is set to a large value, or the minute reflection structure formed on the light guide plate is configured so that the reflected light from it is reflected perpendicularly to the columnar lens sheet.

  Next, consider a characteristic curve 21 using a columnar lens sheet whose orientation direction 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, light incident from the light guide plate in the other incident angle range is totally reflected by the surface of the columnar lens sheet and returns to the inside of the light guide plate again. 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 sheet, the diameter of the columnar lens, or the difference in refractive index of the columnar lens. Further, the value of the orientation direction α can be set to an arbitrary angle of about 0 to 50 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, it can be efficiently emitted from the surface of the columnar lens sheet by setting the value of α to 10 to 50 degrees.

  In the above description, the case where the number of columnar lens sheets joined on the light guide plate is two and three has been described, but it goes without saying that the number may be four or more.

  Examples of the present invention will be specifically described below.

  The lighting device having the configuration shown in FIG. 1 was produced as follows. Two columnar lens sheets were attached to the surface of an acrylic light guide plate having a size of 35 mm × 43 mm × 0.7 mm using a normal adhesive. Three LED light sources were arranged on the side of the light guide plate. As the first columnar lens sheet, a graded index columnar lens having a scattering incident angle of 45 degrees and an inclination angle of 45 degrees was used. A second columnar lens sheet having a scattering incident angle of 45 degrees and an inclination angle of 15 degrees was used. The thickness of these two columnar lens sheets was 70 μm, and the columnar lens diameter was 30 μm. On the other hand, a sample for comparison was prepared by attaching only the same first columnar lens sheet as described above to the same light guide plate as described above.

  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. 11, the result when the comparative sample is used is shown as a curve 23, and the result when the sample of the present invention is used is shown as a curve 22. As can be seen from the results, luminance peaks appear at two locations of 0 ° and 45 ° in the comparative sample, but in the sample of the present invention, there are large luminance peaks at 15 ° and small peaks at 0 ° and 60 °. I understand that. The 0 degree peak appears when the reflected light component of 0 degree from the light guide plate is linearly transmitted, and the 60 degree peak is the linear incident on the second columnar lens sheet of the scattered light from the first columnar lens sheet. The cause is thought to be the light that is horned. In addition, the total light intensity of the sample of the present invention was about 15% greater than that of the comparative sample.

  Thus, since the brightness | luminance was high in the direction of 15 degree | times which is a visual angle direction, the sample of this invention felt brighter than the comparative sample in visual sense.

  A lighting device having the configuration shown in FIG. 2 was produced as follows and used as a sample. Three columnar lens sheets were attached to the surface of an acrylic light guide plate of 35 mm × 43 mm × 0.7 mm using a normal adhesive. Three LED light sources were arranged on the side of the light guide plate. As the first columnar lens sheet, a graded index columnar lens having a scattering incident angle of 30 degrees and an inclination angle of 45 degrees was used. As the second columnar lens sheet, a graded index columnar lens having a scattering incident angle of 30 degrees and an inclination angle of 30 degrees was used. As the third columnar lens sheet, one having a scattering incident angle of 30 degrees and an inclination angle of 15 degrees was used. The thickness of these three columnar lens sheets was 70 μm, and the columnar lens diameter was 30 μm. On the other hand, this sample was compared with the sample produced in Example 1.

  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 the figure, the result when the sample of Example 1 is used is shown as a curve 22, and the result when the sample of this example is used is shown as a curve 24. As can be seen from this result, it can be seen that the luminance peak around 60 degrees that was present in the sample of Example 1 has disappeared in the sample of this example. It can also be seen that the peaks at 0 and 15 degrees are higher. This indicates that light dissipation due to scattering is reduced between the three columnar lens sheets. As a result, the total light intensity of the sample produced in this example was about 8% greater than that of the sample of Example 1.

  Thus, since the sample of this example had high brightness in the direction of the viewing angle of 15 degrees, it felt brighter than the comparative sample.

  In the configuration of Example 1, as shown in FIG. 4, an illumination device in which a high refractive index layer was provided on the surface of the first columnar lens sheet was produced. In this example, a mixture of antimony oxide sol or titanium oxide sol containing silica sol as a main component was applied and baked to form a high refractive index layer having a refractive index of 1.52 and a thickness of 5 μm. As a result, the brightness of the manufactured lighting device was further increased by 5 to 11% compared to Examples 1 and 2 described above.

It is sectional drawing which shows typically the illuminating device by this invention. It is sectional drawing which shows typically an example of the illuminating device by this invention. It is sectional drawing which shows typically an example of the illuminating device by this invention. It is sectional drawing which shows typically an example of the illuminating device 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 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 illuminating device of this invention. It is the typical top view which showed an example of the arrangement | sequence of the columnar lens in the columnar lens sheet surface used by this invention. It is the typical top view which showed an example of the arrangement | sequence of the columnar lens in the columnar lens sheet surface 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED light source 2a 1st columnar lens sheet 2b 2nd columnar lens sheet 2c 3rd columnar lens sheet 3 Light guide plate 4, 4a, 4b, 4c Joining layer 5 Fine reflection structure 6 High refractive index joining layer 7 High refractive index layer 10 Liquid crystal panel 11 Reflector 12 Columnar lens 14 High refractive index region 15 Low refractive index region

Claims (8)

A flat light guide plate formed of a transparent material;
A light source for entering light from a side end surface of the light guide plate;
An illumination device comprising a lens sheet that is provided on the light irradiation surface side of the light guide plate and scatters light incident at a specific angle range and transmits light incident at other angles,
The lens sheet is provided with a plurality of layers, and the lens sheet closer to the light guide plate has a smaller central angle of the specific angle range with respect to the light irradiation surface of the light guide plate. A flat light guide plate formed of a transparent material;
A light source disposed on a side end surface of the light guide plate;
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 are arranged in a plane, and a plurality of columnar lens sheets having a function of guiding light in the thickness direction are provided.
The columnar lens is inclined to the side opposite to the side where the light source is arranged with reference to the direction of the perpendicular line standing on the surface of the columnar lens sheet, and the inclination angle of the columnar lens sheet is closer to the light guide plate. An illumination device characterized in that the columnar lens sheet is smaller.   The columnar lens sheet includes a first columnar lens sheet disposed above the light guide plate and a second columnar lens sheet laminated on the first columnar lens sheet, and the columnar lens sheet has a columnar shape. The lighting device according to claim 2, wherein an inclination angle of the lens is about 20 to about 45 degrees, and an inclination angle of the columnar lens of the second columnar lens sheet is about 0 to about 25 degrees. The columnar lens sheet is stacked on the first columnar lens sheet disposed above the light guide plate, the second columnar lens sheet stacked on the first columnar lens sheet, and the second columnar lens sheet. And a third columnar lens sheet,
The inclination angle of the columnar lens of the first columnar lens sheet is about 30 to about 50 degrees, the inclination angle of the columnar lens of the second columnar lens sheet is about 15 to about 35 degrees, and the third columnar lens sheet The illumination apparatus according to claim 2, wherein an inclination angle of the columnar lens is about 0 to about 20 degrees.   A high refractive index between the columnar lens sheet closest to the light guide plate and the light guide plate, having a refractive index greater than the refractive index of the light guide plate and substantially equal to the refractive index of the high refractive index region constituting the columnar lens. The lighting device according to claim 2, further comprising an index layer.   The lighting device according to claim 5, wherein a high refractive index bonding agent is used as the high refractive index layer.   The illumination device according to any one of claims 2 to 6, wherein the arrangement of the columnar lenses constituting the columnar lens sheet is an aperiodic arrangement.   A display device comprising: a non-self-luminous display element; and the illumination device according to claim 1 provided to illuminate the display element.

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