JP2012227062A - Lighting unit and display device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an effect given to luminance unevenness of difference of sizes of an optical structure while removing luminance unevenness, and further to improve a volume of light emitted from a light guide plate.SOLUTION: In the lighting unit provided with a light source 8 and a light guide body 9, the light guide body 9 includes an incident surface 12 with light emitted from the light source 8 incident into, an emission surface 13 nearly crossing the incident surface and emitting the incident light to a side of an observer, and a light reflecting surface 14 facing to the emission surface 13 and guiding light which is not directly emitted among the incident light to the emission surface. A lens 16 with a pitch changed by a distance from the light source 8 is formed on the light reflecting surface 14, and irregularities 17 with an aspect ratio of a height up to a top part to a width comparatively smaller than that of the lens are formed without any gap.

Description

  The present invention relates to an illumination unit mainly used for illumination optical path control and a display device including the illumination unit.

  A flat panel display typified by a liquid crystal display device (LCD) is widely used in which a lighting device necessary for recognizing provided information is incorporated. The luminance of the liquid crystal display device, the viewing angle distribution of the luminance, and the spatial distribution are greatly affected by the performance of the lighting device. Therefore, increasing the luminance of the lighting device and making the luminance space distribution uniform leads directly to increasing the luminance of the liquid crystal display device and making the luminance space distribution uniform.

  Illumination devices used in the liquid crystal display device mainly include a direct method and an edge light method. The direct type illumination device can be provided with a large number of light sources, and thus is applied to a large-sized (mainly 20 inches or more) liquid crystal display device. On the other hand, the edge light method is not applicable to a large display device because the arrangement position of the light source is limited, and is mainly applied to a small display device such as a notebook personal computer, a liquid crystal monitor, or a portable information terminal.

Recently, however, LED (Light Emitting Diode Light-Emitting Diode) instead of cold-cathode tubes has begun to be used as the light source for lighting devices. The device has begun to be used in medium-sized or large-sized liquid crystal display devices of 20 inches or more.
In general, in the edge light system, a light source is disposed on an end face of a light-transmitting plate called a light guide plate, and light is emitted from the entire surface substantially orthogonal to the light source. Therefore, it becomes difficult to uniformly brighten the entire display screen, that is, eliminate luminance unevenness as the liquid crystal display device becomes larger. Further, since the light source is disposed only on the end face of the light guide plate, there is a limit to the number of installed light sources. Therefore, it becomes difficult to improve the luminance as the liquid crystal display device becomes larger.

  As a method for uniformly brightening the entire screen, it is conceivable to provide an optical structure whose density or size is changed depending on the location on the surface facing the exit surface of the light guide plate, as in Patent Document 1. As the optical structure, for example, white diffuse reflection dots are printed and arranged, or as another example, a prism-shaped structure or the like is formed. Between structures such as white diffuse reflection dots and prism shapes, there is a flat surface with no shape.

  However, depending on the manufacturing method, it is often difficult to manufacture a flat surface between structures. If even a slight scratch or streak enters, not only will there be a problem in appearance, but the scratch or streak will function as a light extraction structure. In a light guide plate in which light enters from the end face and is repeatedly reflected and emitted, slight scratches and streaks are also greatly affected. Furthermore, even if a flat surface is formed, there is a problem that an optical structure must be added with a desired size from the surface. This is because, as described above, in the light guide plate, since the light is repeatedly reflected and emitted, only a slight difference in size greatly affects the optical characteristics, particularly the luminance unevenness.

Japanese Patent No. 4203240

  Therefore, the present invention prevents the influence of scratches and streaks on the flat surface, eliminates uneven brightness, reduces the effect of the difference in the size of the optical structure on the uneven brightness, and is emitted from the light guide plate. The purpose is to improve the amount of light.

In order to achieve the above object, the present invention employs the following configuration.
That is, the illumination unit according to claim 1 includes a light source and a light guide, and the light guide has an incident surface on which light emitted from the light source is incident and an incident light that is substantially orthogonal to the incident surface. An illumination surface that emits light toward the observer side, and a light reflecting surface that faces the emission surface and guides light that is not directly emitted out of the incident light to the emission surface. A plurality of lenses are formed on the reflecting surface by changing the pitch according to the distance from the light source, and an aspect ratio that is a ratio of the height to the top with respect to the width is between the lenses. The illumination unit is characterized in that small irregularities are shaped without gaps compared to the above.
Here, the aspect ratio of the lens is the ratio of the lens width to the top of the lens, and the aspect ratio of the unevenness refers to the ratio of the height to the top of the unevenness to the unevenness width.

  With the above configuration, since the flat surface is eliminated from the light reflecting surface of the light guide, it is possible to prevent the effect of scratches and streaks on the flat surface. In addition, since the effect of the difference in lens size on the luminance unevenness is proportional to the amount of light extracted by the lens, increasing the amount of light extracted by the unevenness between the lenses can reduce the effect of the difference in lens size. it can. Further, by forming irregularities between the lenses (forming, the same applies hereinafter), it is possible to extract light that could not be extracted so far, so that the emission efficiency can be increased.

  The illumination unit according to claim 2, wherein a value when the distance from the light source to the position of the light guide that is farthest from the light source is expressed in mm is x, and the thickness of the light guide is mm. 2. The illumination unit according to claim 1, wherein an aspect ratio AP of the unevenness is in a range of the following [Equation 1], where d is a value expressed in units.

When the aspect ratio of the unevenness is equal to or less than the right side of [Equation 1], the entire screen can be brightened uniformly. In the case of exceeding the right side, there arises a problem that it becomes too bright in an area close to the light source. Moreover, the effect of this invention can be exhibited because it is more than the left side of [Equation 1]. If it is less than the left side, the effect of the present invention cannot be obtained sufficiently.
The illumination unit according to claim 3 is the illumination unit according to claim 1 or 2, wherein the lens has a dot shape in which at least a part of a cross-section has a curved shape.
Thereby, the pitch with respect to the direction orthogonal to the arrangement direction of a light source can be made small, and it can be made difficult to observe the fine contrast which is seen when a light-guide plate is observed from an observer direction.

The illumination unit according to claim 4, wherein the pitch of the lenses with respect to the arrangement direction of the light sources is generally larger as the distance from the light source is closer.
Accordingly, it is possible to make it difficult to observe a fine contrast between light and darkness as compared with the illumination unit according to claim 3. This is because the pitch with respect to the direction orthogonal to the arrangement direction of the light sources can be further reduced.

5. The illumination unit according to claim 5, wherein the light sources are arranged in a straight line, and the unevenness has a cylindrical shape extending in an arrangement direction of the light sources. It is an illumination unit given in any 1 paragraph. Here, although there are linear and dotted light sources, the linear light sources are arranged linearly along the incident surface of the light guide, and many of the linear light sources are linear along the incident surface. Accordingly, it is possible to easily manufacture the unevenness, and to reduce manufacturing time and loss.

6. The illumination unit according to claim 6, wherein the unevenness coincides with a top portion of the lens.
Thereby, the unevenness between the lenses can be shaped, for example, by cutting with the same cutting tool, and it is not necessary to replace the cutting tool in the manufacturing process. For this reason, it is possible to simplify the process and reduce factors that change the lens size.
The lighting unit according to claim 7 is the lighting unit according to any one of claims 1 to 6, wherein the pitch of the unevenness changes randomly.
Thereby, it is possible to prevent generation of moire that may occur when the pitch of the unevenness is regular.

The lighting unit according to any one of claims 1 to 7, wherein the lens has an aspect ratio of 0.1 or more and 0.5 or less. is there.
Thereby, it is possible to make the luminance uniform and to prevent the lens pitch from becoming too large with respect to the direction orthogonal to the arrangement direction of the light sources. If the aspect ratio of the lens is less than 0.1, it is impossible to maintain the brightness to make the brightness uniform in the region farthest from the light source, and if it exceeds 0.5, the lens pitch becomes too large, and fine brightness and darkness are reduced. The difference will be observed.

9. The illumination unit according to claim 9, wherein a lenticular lens extending in a direction orthogonal to the arrangement direction of the light sources is arranged on the exit surface of the light guide plate. It is an illumination unit of any one of these.
Thereby, the light which spreads in the arrangement direction of the light source can be confined. In application, it is possible to perform local dimming in which a part is brightened or darkened. In addition, it is possible to scan by changing the brightness in order.

The illumination unit according to claim 10, wherein an optical sheet having a diffusing function is disposed on a viewer direction side facing the exit surface. It is a lighting unit as described in.
This can make it difficult to observe fine contrasts.
The illumination unit according to claim 11 further includes a reflection sheet on the side opposite to the optical sheet of the light guide to reflect light emitted from the reflection surface side and guide the light again to the light guide. The lighting unit according to claim 1, wherein the lighting unit is a lighting unit.
Thereby, the light emitted from the surface opposite to the light emitting surface of the light guide plate can be effectively used, and the luminance can be increased.

A lighting unit according to a twelfth aspect is a display device comprising the lighting unit according to any one of the first to eleventh aspects and an image display element that defines a display image.
The lighting unit according to claim 13 is the display device according to claim 12, wherein the image display element displays an image by transmission / shielding in pixel units.
Thereby, the display apparatus reflecting the effect of the above-mentioned illumination unit can be obtained.

  According to the illumination unit and the display device using the shaped light guide plate according to the present invention, the flat surface is eliminated from the light reflecting surface, and the unevenness is intentionally shaped, thereby preventing the influence of scratches and lines on the flat surface. Can do. In addition, since the light can be extracted by the unevenness, even if the size of the lens whose pitch changes is changed in manufacturing, the influence on the optical characteristics can be reduced. Furthermore, the amount of light emitted from the light guide plate can be improved by forming a concavo-convex shape in a portion that has been flat. Accordingly, it is possible to provide an illumination unit having high emission efficiency and a display device using the illumination unit, in which the luminance unevenness does not change greatly even if there is a manufacturing error while eliminating the luminance unevenness.

It is principal part sectional drawing which shows an example of a display apparatus in a separated state. It is the figure which showed a part of sectional drawing of an example of the illumination unit by embodiment of this invention. It is a perspective view of the light guide plate of an example of an embodiment of the invention. It is the figure which showed a part of sectional drawing of the light-guide plate of an example of embodiment of this invention. It is a perspective view of an example of the illumination unit by embodiment of this invention. It is the figure which showed an example of the shape of a lens and an unevenness | corrugation. It is the figure which showed the brightness nonuniformity at the time of forming only unevenness. It is a figure showing the relationship between the aspect-ratio of an unevenness | corrugation, and the maximum value of front luminance. It is a figure showing the relationship between the thickness of a light-guide plate, and the maximum value of front luminance. It is the figure which showed a part of sectional drawing of an example of the illumination unit by embodiment of this invention. It is the figure which showed a part of sectional drawing of an example of the illumination unit by embodiment of this invention. It is the figure which showed a part of sectional drawing of the light-guide plate of an example of embodiment of this invention. It is the figure which showed a part of sectional drawing of an example of the illumination unit by embodiment of this invention.

Below, the illumination unit by embodiment of this invention and the display apparatus provided with this illumination unit are demonstrated. FIGS. 1 to 13 are schematic diagrams, and the size and shape of each part are exaggerated as appropriate for easy understanding.
A display device 1 shown in FIG. 1 includes an image display panel 2 and an illumination unit 3 arranged facing the light incident side of the image display panel 2.

The image display panel 2 arranged closest to the observer side F includes two polarizing plates (polarizing films) 4 and 5 and an image display element 6 sandwiched therebetween. The image display panel 2 is composed of, for example, a liquid crystal display panel. In that case, the image display element 6 is configured by filling a liquid crystal layer between two glass substrates.
The image display panel 2 is preferably an element that displays an image by transmitting / blocking light in pixel units. If the image is displayed by transmitting / blocking light in pixel units, the illumination unit 3 can provide the display device 1 that reflects the effect of the present invention as it is.

The liquid crystal display element selected as the image display element 6 is a typical element that transmits and blocks light in pixel units and displays an image, and can improve image quality compared to other display elements. .
The illumination unit 3 is an edge light type illumination device, and is disposed facing the light incident side of the image display panel 2. The light source 8 and the light guide plate 9 (on the light guide in the present invention) along the light optical path. Corresponding). In addition, the optical sheet 10 may be disposed in the viewer direction of the light guide plate 9, and the reflection sheet 11 may be provided on the back side of the light guide plate 9. The optical sheet 10 and the reflection sheet 11 are included to constitute a sheeted illumination unit 3 ′.

  Examples of the light source 8 include a linear light source and a point light source. Examples of the linear light source include fluorescent tubes such as CCFL, HCFL, and EEFL. Examples of the point light source include an LED, and examples of the LED include a white LED and an RGB-LED. Although FIG. 1 shows an example in which the light source 8 is disposed on one end face of the light guide plate 9, the present invention is not limited to this, and the light source 8 can also be adopted when disposed on two opposing end faces. At this time, the shape of the light guide plate 9 may be a flat plate shape as shown in FIG. 1 or a wedge shape.

A light reflecting surface 14 is formed on the surface of the light guide plate 9 facing the exit surface 13 disposed on the observer side F. The light reflection surface 14 is a surface for reflecting light that is not directly emitted from the emission surface 13 out of incident light from the light source 8 in various directions in the light guide plate 9 and is directed toward the emission surface 13 side. The surface 14 is provided with a plurality of optical structures 15 for reflecting incident light.
As the optical structure 15, a lens 16 whose shape is changed in pitch with respect to a direction orthogonal to the arrangement direction of the light sources 8 depending on the distance from the light source 8 is formed in FIGS. Concavities and convexities 17 having a small aspect (AP) ratio, which is a ratio of the height H to the top of the lens with respect to the width W, compared to the lens 16 are formed without a gap. A sectional view and a perspective view of the light guide plate 9 are shown in FIGS. 3 and 4, the exit surface 13 is drawn on the lower side so that the lens 16 and the unevenness 17 can be easily seen.

  The light guide plate 9 is molded on a light-transmitting substrate using UV or radiation curable resin, or PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer). Can be formed by an extrusion molding method, an injection molding method, or a hot press molding method well known in the art.

  That is, a mold to be a plate is produced and molded. It is difficult to produce a flat surface in a mold, and it is often necessary to polish after cutting. However, in the present invention, since the flat surface is eliminated by the unevenness 17 existing without a gap between the lenses 16 without forming a flat surface, it is possible to save the trouble of forming the flat surface in the mold. In addition, the effects of scratches and streaks can be prevented.

  In addition, the lens 16 is manufactured after or before the unevenness 17 is formed on the mold. At this time, it is difficult to keep the size of the lens 16 constant, and a deviation of about several um occurs. It often ends up. Therefore, it is desirable that the influence of the difference in the lens 16 size on the luminance unevenness is small. Here, the luminance unevenness represents a spatial distribution of luminance when the light guide plate 9 is observed from the observer direction F. The reason why the luminance unevenness changes due to the change in the size of the lens 16 is that the amount of light extracted depends on the size of the lens 16. Therefore, the variation in luminance unevenness can be reduced by reducing the amount of light extracted by the lens 16 in the first place. In the present invention, light can be extracted by the unevenness 17. Accordingly, the amount of light extracted by the lens 16 can be reduced, and the change in luminance unevenness can be reduced. In addition, since the unevenness | corrugation 17 is arranged without the space | interval, it can be cut extra in manufacture and it is not difficult to keep size constant.

Furthermore, by forming the unevenness 17 between the lenses 16, it becomes possible to extract the light that has been reflected on the flat surface and could not be extracted so far, so that the emission efficiency can be increased. Thereby, the emitted light quantity of the light source 8 can be suppressed, and the power consumption can also be reduced.
In FIG. 3, both the lens 16 and the concavo-convex 17 are illustrated as a lenticular lens shape extending in one direction. However, the shape is not limited to this shape, and as shown in FIGS. 6 (a) to (h), A spherical dot shape or a triangular dot shape may be used. Moreover, the prism shape extended in one direction may be sufficient. Their cross-sectional shape may be a straight line, a curved line, or a shape including both a straight line and a curved line.
In particular, it is more preferable that the aspect ratio (AP) ratio of the unevenness 17 is in the range of the following [Equation 1].

  Here, x and d are as follows. That is, the value when the distance from the light source 8 to the position of the light guide 9 farthest from the light source 8 is expressed in mm, and the value when the thickness of the light guide 9 is expressed in mm. Let d. FIG. 5 shows the lengths indicated by x and d. In FIG. 5, the lens 16 and the unevenness 17 are omitted and not shown for simplification. Moreover, although the example which has arrange | positioned the light source 8 to one end surface of the light-guide plate 9 is shown, when arrange | positioning to two opposing end surfaces, the distance x is the center position of the light guide 9 from the light source 8. Represents the distance to.

  When the aspect ratio (AP) ratio of the unevenness 17 is equal to or less than the right side of [Equation 1], the entire screen can be brightened uniformly. In the case of exceeding the right side, there arises a problem that it becomes too bright in an area close to the light source. Moreover, the effect of this invention can be exhibited because it is more than the left side of [Equation 1]. If it is less than the left side, the effect of the present invention cannot be obtained sufficiently.

Hereinafter, the derivation of the equation will be described.
FIG. 7 shows a graph in which the luminance unevenness when only the irregularities 17 are shaped as the optical structure 15 is plotted against the distance from the light source 8. This is a simulation result when the distance x from the light source 8 to the position of the light guide 9 farthest from the light source 8 is 310 mm and the thickness d of the light guide plate 9 is 4 mm. It can be confirmed that the closer to the light source 8, the higher the luminance, and the higher the aspect ratio (AP) ratio of the unevenness 17, the higher the luminance. The rhombus plots in FIG. 8 are obtained by plotting the peak values of each graph with respect to the aspect (AP) ratio of the unevenness 17. The gray solid line in FIG. 8 is a function of y = 5600000 × (AP) ² and can be confirmed to be consistent with the rhombus plot.

In this model, as a result of simulation using various combinations of the lens 16 and the unevenness 17, it was found that the luminance can be improved to about 9500 when the luminance is emitted almost uniformly, that is, when the luminance unevenness is eliminated. did. A value of 9500 could be obtained when about 90% of the light incident on the light guide plate 9 was available.
That is, if the peak value exceeds 9500 in the model having only the unevenness 17, the luminance unevenness cannot be eliminated. As the distance x increases, the luminance value 9500 decreases in inverse proportion to the distance x.

であれば、本発明の効果を得つつ、輝度むらをなくすことができる。
一方、図８を見てわかるように、アスペクト（ＡＰ）比が小さくなると、急激に輝度ピーク値は小さくなってしまい、本発明の効果を得ることができなくなってしまう。９５００の１／１０である９５０程度以下に輝度値がなってしまうと、本発明の効果は得にくいといえる。

If so, luminance unevenness can be eliminated while obtaining the effects of the present invention.
On the other hand, as can be seen from FIG. 8, when the aspect (AP) ratio is decreased, the luminance peak value is rapidly decreased, and the effect of the present invention cannot be obtained. If the luminance value falls below about 950, which is 1/10 of 9500, it can be said that the effect of the present invention is difficult to obtain.

であることが良いといえる。

It can be said that it is good.

  Moreover, the result of changing the thickness d of the light guide plate 9 is shown in FIG. As can be seen from FIG. 9, the reciprocal of the light guide plate 9 thickness d is proportional to the luminance peak value. The gray solid line is a function of y = (14500 / d + 2000). When d = 4 mm described above, y≈5600, so when considering the light guide plate 9 thickness d,

を満たすことが望ましいということになる。これを計算すると、前記［数１］が得られる。

It is desirable to satisfy. When this is calculated, the above [Equation 1] is obtained.

  The lens 16 and the concavo-convex 17 may have any shape such as a lenticular lens shape or a dot shape extending in one direction as described above. In particular, the lens 16 is at least partially curved in cross section. The dot shape (for example, the shape as shown in FIGS. 6A, 6 </ b> E, and 6 </ b> G), and the unevenness 17 is desirably a cylindrical shape extending in the arrangement direction of the light sources 8.

  The reason why the lens 16 is preferably in a dot shape is that local luminance unevenness of light emitted from the light guide plate 9 can be reduced. Here, the local luminance unevenness is brightened by the light extracted by the lens 16 where the lens 16 is present, and light is extracted where the lens 16 is not present (that is, where the unevenness 17 is present). This is uneven brightness caused by the fact that the amount of light is small and dark.

  The closer to the light source 8, the greater the amount of light that is being guided, so the amount of light that can be extracted by one lens 16 is greater. Therefore, the distance (pitch P) between the lenses 16 needs to be increased. For this reason, local luminance unevenness increases. However, by forming the lens 16 in a dot shape, the distance (pitch P) between the lenses 16 with respect to a direction orthogonal to the arrangement direction of the light sources 8 can be reduced, and luminance unevenness can be reduced, compared with a lenticular lens shape. be able to.

  In addition, by making the dot shape of the lens 16 curved, the light reflected by the lens 16 can be spread in various directions without being reflected only in a specific direction. In this way, the light distribution of the light emitted from the light guide plate 9 can be widened to some extent, and the viewing angle distribution can be prevented from becoming extremely uneven. However, for example, as shown in FIGS. 6 (a), 6 (e), and 6 (g), it is not necessary that all of the cross sections are curved, and a linear portion may be included in a part thereof, or a linear shape may be included. There is no problem even if the shape has a curve in part. Further, by forming the concavo-convex 17 into a lenticular lens shape, manufacturing can be facilitated, and manufacturing time and loss can be reduced.

Here, the shape of the lenticular lens is not limited to that having a semicircular cross section, but as shown in FIGS. 6B, 6D, 6F, and 6H. May be a curved line, a straight line, or a form including both a straight line and a curved line. However, at this time, the extending direction of the projections and depressions 17 must match the arrangement direction of the light sources 8. This is because if the directions are not matched, the above-described light extraction effect due to the unevenness 17 cannot be obtained sufficiently.
Furthermore, by providing a distance (pitch P) between the lenses 16 with respect to the arrangement direction of the light sources 8, the distance (pitch P) between the lenses 16 can be reduced by a corresponding amount in a direction orthogonal to the arrangement direction of the light sources 8. . This is because the light extraction amount is determined by the density of the lens 16. Thereby, it is possible to further reduce local luminance unevenness.

  FIG. 10 is a schematic diagram of the arrangement of the lenses 16 that eliminates luminance unevenness by keeping the distance (pitch P) of the lenses 16 with respect to the arrangement direction of the light sources 8 constant. On the other hand, FIG. 11 is an arrangement schematic diagram in the case where the distance (pitch P) between the lenses 16 with respect to the arrangement direction is increased as the distance from the light source 8 increases. Although the density of the lens 16 is the same in FIGS. 10 and 11, it can be seen that FIG. 11 is arranged more uniformly and local uneven brightness is less likely to occur. In FIGS. 10 and 11, the unevenness 17 is omitted and not shown for simplification. Moreover, in order to make the lens 16 and the unevenness | corrugation 17 easy to see, the emission surface 13 is drawn on the lower side.

It is even better if the irregularities 17 coincide with the top portion of the lens 16. Thereby, the unevenness 17 between the lens 16 and the lens 16 can be shaped by, for example, cutting with the same tool, and it is not necessary to replace the tool in the manufacturing process. For this reason, it is possible to simplify the process and reduce factors that change the lens size. This is because it is possible to eliminate the positional deviation that occurs when changing the cutting tool. FIG. 12 shows a state in which the unevenness 17 coincides with the top portion of the lens 16. In order to make the lens 16 and the unevenness 17 easy to see, the exit surface 13 is drawn on the lower side.
It is even better if the pitch of the irregularities 17 changes randomly. This is because moire that may occur when the pitch of the unevenness 17 is regular can be prevented.

  The aspect ratio (AP) of the lens 16 is more preferably 0.1 or more and 0.5 or less. When the aspect ratio (AP) of the lens 16 is less than 0.1, it is impossible to maintain the brightness to the extent that the luminance is uniform in the region farthest from the light source 8, and when it exceeds 0.5, the pitch P of the lens 16 is set. This is because it becomes too large and local luminance unevenness is easily observed. Therefore, it is desirable that the luminance is uniform and that the pitch P of the lenses 16 is prevented from becoming too large, and is within a range of 0.1 to 0.5. It is not always necessary to have a relationship with the aspect (AP) ratio of the unevenness 17, but there is no problem as long as it is within a range of about 3 to 30 times the aspect (AP) ratio of the unevenness 17.

  As shown in FIG. 13, it is more preferable that lenticular lenses 18 extending in a direction perpendicular to the arrangement direction of the light sources 8 are arranged on the exit surface 13 of the light guide plate 8. Thereby, it is possible to prevent the light incident on the light guide plate 9 from spreading in the arrangement direction of the light sources 8. That is, light can be confined to some extent. In application, it is possible to perform local dimming in which a part is brightened or darkened. In addition, by using this, it is possible to perform scanning in which brightness is changed in order. In some cases, the luminance can be improved.

  It is more preferable that the optical sheet 10 having a diffusing function is disposed on the viewer direction F side facing the emission surface 13. This is because the above-described local luminance unevenness can be made more difficult to observe. Examples of the optical sheet 10 having a diffusion function include a microlens sheet, a diffusion sheet having an uneven surface, and a diffusion sheet in which fine particles having different refractive indexes are mixed. Moreover, there is no problem even if a plurality of optical sheets 10 are arranged. A condensing sheet such as a prism sheet or a lenticular lens sheet, a polarization separation sheet, or the like may be disposed.

On the opposite side of the light guide plate 8 from the optical sheet 10, it is preferable to further include a reflection sheet 11 that reflects the light emitted from the reflection surface 14 side and guides it to the light guide 8 again. Thereby, it is possible to effectively use the light emitted from the surface facing the emission surface 13 of the light guide plate 8 and to increase the luminance.
In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the meaning, it can change suitably. For example, although not mentioned in the present specification, it goes without saying that the effect of the present invention can be obtained even if a light capturing structure is formed on the incident surface 12 or a random structure is formed. Yes.

The lighting unit 3 and the display device 1 including the lighting unit 3 according to the embodiment of the present invention have been described above. However, the lighting unit 3 is not applied only to the display device 1. Examples of the present invention will be described in detail below, but it goes without saying that the present invention is not limited to the following examples.
The lighting unit 3 model was assembled and simulated as follows using lighting design analysis software LightTools manufactured by Optical Research Associates.

  The light guide plate 9 was made of acrylic. A white LED was disposed as a light source 8 on one side of the light guide plate 9. The reflecting surface 14 of the light guide plate 9 is formed with a lens 16 and irregularities 17 as an optical structure 15. The aspect ratio (AP) of the lens 16 was 0.2. The aspect ratio (AP) ratio of the unevenness 17 was set to six types of 0, 0.01, 0.02, 0.03, 0.04, and 0.05. Here, an aspect (AP) ratio of 0 indicates that there is no unevenness 17 and the surface is flat. The thickness d of the light guide plate 9 was 2 mm and 4 mm. The distance x from the light source 9 to the position farthest from the light source 8 was set to three types: 300 mm, 400 mm, and 500 mm. A reflective sheet 11 is disposed at a position facing the reflective surface 14 of the light guide plate 9. A microlens sheet was disposed as the optical sheet 10 at a position facing the exit surface 13 of the light guide plate 9.

In the above model, a total of 36 types of simulations were performed, including combinations of 6 types of aspect ratio (AP) ratio of the unevenness 17, 2 types of light guide plate thickness d, and 3 types of distance. It should be noted that the arrangement of the lens 16 is optimized in each model so as to eliminate luminance unevenness as much as possible.
Three evaluation items were evaluated: luminance unevenness, luminance, and size shift effect. As for the luminance unevenness, whether or not the luminance unevenness disappeared within the error range of the simulation when the arrangement of the lenses 16 was optimized was evaluated as “◯”, and the one not disappeared as “X”. As compared with the case where the aspect ratio was 0, the luminance was evaluated as “◯” when the front luminance at the center of the screen was high, and “×” when the luminance was less than the same. The size shift effect is a result of verifying the change rate of the luminance unevenness when it is shifted from the design value in the manufacturing process. The change rate is smaller than the case where the aspect ratio is 0, and the larger change rate is ×. It was. Furthermore, as a comprehensive evaluation, all three evaluation items were evaluated as “good”, and at least one evaluation item was evaluated as “poor”. Table 1 summarizes the evaluation results.

When Table 1 is confirmed, with respect to the luminance unevenness, the case where the aspect ratio is large, the light guide plate thickness is small, and the distance x is large is marked with x. Regarding the luminance, the aspect ratio is small, the thickness of the light guide plate is large, and the distance x is small is marked with x. Regarding the influence of the size shift, all of those having the unevenness 17 were “good”.
Table 2 shows values of the left side and the right side of [Equation 1] when the light guide plate thickness d and the distance x are determined. Comparing the overall evaluation in Table 1 with Table 2, it was confirmed that the aspect ratio within the range of the left side to the right side of [Equation 1] is ◯ as the overall evaluation.

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Image display panel 3 Illumination unit 4, 5 Polarizing plate 6 Image display element 8 Light source 9 Light guide plate 12 Incident surface 13 Ejection surface 14 Reflective surface 15 Optical structure 16 Lens 17 Concavity and convexity 10 Optical sheet 11 Reflective sheet 18 One direction Lenticular lens d extending to the light guide plate thickness x The distance from the light source 8 of the light guide 9 to the position farthest from the light source 8

Claims (13)

A light source and a light guide, wherein the light guide is incident on which light emitted from the light source is incident; an emission surface that is substantially orthogonal to the incident surface and emits incident light toward the viewer; An illumination unit having a light reflecting surface that faces the exit surface and guides light that is not directly emitted from the incident light to the exit surface;
A plurality of lenses are formed on the light reflecting surface by changing the pitch according to the distance from the light source, and an aspect ratio that is a ratio of the height to the top with respect to the width is between the lenses. An illumination unit characterized in that small irregularities compared to the lens are formed without a gap. The value when the distance from the light source to the position of the light guide farthest from the light source is expressed in mm, x, and the value when the thickness of the light guide is expressed in mm is d. The illumination unit according to claim 1, wherein the aspect ratio AP of the unevenness is within the range of the following [Equation 1].

  The illumination unit according to claim 1, wherein the lens has a dot shape in which at least a part of a cross section has a curved shape.   The lighting unit according to claim 3, wherein the pitch of the lenses with respect to the arrangement direction of the light sources generally increases as the distance from the light sources decreases.   5. The illumination unit according to claim 1, wherein the light sources are arranged in a straight line, and the unevenness has a cylindrical shape extending in an arrangement direction of the light sources.   The illumination unit according to claim 1, wherein the uneven shape coincides with a top portion of the lens shape.   The lighting unit according to any one of claims 1 to 6, wherein the pitch of the unevenness changes at random.   The lighting unit according to claim 1, wherein an aspect ratio of the lens is 0.1 or more and 0.5 or less.   The illumination unit according to any one of claims 1 to 8, wherein a lenticular lens extending in a direction orthogonal to an arrangement direction of the light sources is arranged on the emission surface of the light guide plate. .   The illumination unit according to any one of claims 1 to 9, wherein an optical sheet having a diffusion function is disposed on a viewer direction side facing the emission surface.   The light guide is further provided with a reflection sheet that reflects light emitted from the reflection surface side and guides it to the light guide again on the side opposite to the optical sheet. The lighting unit according to any one of the above. The lighting unit according to any one of claims 1 to 11,
An image display element for defining a display image;
A display device comprising: The display device according to claim 12, wherein the image display element displays an image by transmission / shading in pixel units.

Images