JP2010145640A - Lens sheet and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens sheet which improves brightness on an observer side, has a broad omnidirectional visual field and smooth brightness change. <P>SOLUTION: The lens sheet has a light-translucent base material, a first lens array, a second lens array and a third lens array. The first lens array is provided on one side of the light-translucent base material and contains two or more unit lenses which extend along a first direction and further are arranged in parallel with each other. The second lens array is provided at a top of each unit lens of the first lens array and contains two or more unit lenses which extend along a second direction crossing the first direction where the unit lenses of the first lens array extend and further are arranged in parallel with each other. The third lens array is provided on another side of the light-translucent base material and contains two or more unit lenses which extend along a third direction that is different from the first direction where the unit lenses of the first lens array extend and from the second direction where the unit lenses of the second lens array extend and further are arranged in parallel with each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens sheet used for illumination optical path control and a display device using a backlight unit including the lens sheet.

  A recent large-sized liquid crystal television employs a structure in which a direct-type backlight unit in which a plurality of cold-cathode tubes and LEDs (Light Emitting Diodes) are arranged is provided on the back of an image display panel. In this case, a diffuser plate having a strong light scattering property is provided between the image display panel and the light source so that a cold cathode tube or an LED as a light source is not visually recognized.

  Since the diffusion plate diffuses light in all directions by the light diffusion effect, the image display panel is darkened. In addition, the diffusion plate usually needs to have a thickness of about 1 to 5 mm in order to enhance the light scattering property and support the optical film provided on the diffusion plate. To darken.

  2. Description of the Related Art Conventionally, a diffusion plate used in a direct type backlight is intended to reduce luminance unevenness (lamp image) by diffusing light emitted from a cold cathode tube as a light source. Therefore, in general, a single or a plurality of optical films are arranged on the diffusion plate in order to improve the luminance in the viewer side direction.

  As a means for improving the brightness of the liquid crystal display screen, a brightness enhancement film (BEF, registered trademark of 3M USA) is widely used.

  FIG. 14 is a cross-sectional view showing an example of the BEF arrangement, and FIG. 15 is a perspective view of the BEF. As shown in FIGS. 14 and 15, the BEF 185 is an optical film in which unit prisms 187 having a triangular cross section are periodically arranged in one direction on a transparent substrate 186. The unit prism 187 has a size (pitch) set larger than the wavelength of light.

  The BEF 185 collects light from “off-axis” and redirects or “recycles” this light “on-axis” towards the viewer. be able to. That is, the BEF 185 can increase the on-axis luminance by reducing the off-axis luminance when the display is used (observation). Here, “on the axis” means a direction that coincides with the viewing direction F ′ of the viewer, and is generally on the normal direction side with respect to the display screen.

  When a lens sheet represented by BEF185 is used, a diffusion filler is applied on a transparent substrate, and a diffusion film (hereinafter referred to as a lower diffusion film) having both diffusion and condensing functions is used as the diffusion plate and the lens sheet. The diffused light emitted from the diffusion plate can be efficiently collected and the visibility of the light source that cannot be erased only by the diffusion plate can be suppressed.

  Furthermore, when a light diffusion film is disposed between the lens sheet and the liquid crystal panel, side lobes can be reduced and moire interference fringes generated between the regularly arranged lenses and the liquid crystal pixels can be reduced. Can be prevented.

  The adoption of BEF allows display designers to achieve the desired on-axis brightness while reducing power consumption.

  As a patent document disclosing that a brightness control member having a repetitive array structure of prisms represented by BEF is adopted for a display, there are many known as exemplified in Patent Documents 1 to 3. Yes.

  In the optical sheet using the BEF as a brightness control member as described above, the light from the light source is finally emitted from the film at a controlled angle by the refraction action, so that the light in the visual direction of the viewer is reflected. It can be controlled to increase the strength.

  However, when BEF185 is used, the light component due to the reflection / refraction action may be emitted in the lateral direction without proceeding in the viewer's visual direction F '.

  As shown by the broken line B in FIG. 16, the light intensity distribution emitted from the optical sheet using BEF has the light intensity when the angle with respect to the visual direction of the observer, that is, the visual direction F ′ is 0 ° (corresponding to the on-axis direction). Although it is the highest, a small light intensity peak (side lobe) is generated in the vicinity of ± 90 ° with respect to F ′, and the amount of light emitted from the lateral direction is increased. A luminance distribution having such a light intensity peak is not desirable. As shown by the solid line A in FIG. 16, a smooth luminance distribution having no light intensity peak around ± 90 ° is preferable.

  On the other hand, when only the on-axis luminance is excessively improved, the peak width of the luminance distribution curve is remarkably narrowed, resulting in an extreme luminance change. In order to realize a smooth profile, it is necessary to install another diffusion film on the prism sheet, and there is a problem that the number of members increases.

  In addition, such a liquid crystal display device is strongly required as a market need for light weight, low power consumption, high luminance, and thinning. Accordingly, the backlight unit mounted on the liquid crystal display device is also required to be lightweight, low power consumption, and high luminance.

  In particular, in the color liquid crystal display devices that have been remarkably developed in recent years, the panel transmittance of the liquid crystal panel is much lower than that of a monochrome-compatible liquid crystal panel. It is essential to obtain low power consumption of the device itself.

  However, as described above, it is difficult to say that the conventional device sufficiently satisfies the demand for high brightness and low power consumption, and the user has low price, high brightness, high display quality, and low power consumption. The development of a backlight unit and a display device that can realize a liquid crystal display device of this kind is awaited.

  In addition, when a diffusion film is placed on the BEF, the side lobes are reduced and the luminance distribution is smoothed, but the front luminance peak is reduced. For this reason, a diffusion film having a low haze as much as possible is desirable. However, when a low haze diffusion film is used, the luminance distribution changes drastically, and an undesirable phenomenon is observed in which the display suddenly becomes dark when the line of sight is changed obliquely from the front.

On the other hand, there is a demand not only for high front luminance, but also for a wide field of view, for example, a half-value angle of up, down, left, and right is 40 degrees or more. If this demand is to be realized by a combination of BEF and a strong diffusion film, the peak is considerably lowered and the film configuration is increased, so that the cost and optical properties are unsatisfactory.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500

  The present invention efficiently collects diffused light emitted from a diffuser plate, thereby improving the brightness on the viewer side, having a wide vertical and horizontal visual field, and a smooth luminance change, and a back including the same An object of the present invention is to provide a display device using a light unit.

  The invention of claim 1 includes a translucent substrate and a plurality of unit lenses provided on one surface of the translucent substrate, extending along a first direction and arranged in parallel to each other. A first lens array including the first lens array, and a second direction that is provided on a top of each unit lens of the first lens array and that intersects a first direction in which the unit lens of the first lens array extends. And a second lens array including a plurality of unit lenses arranged parallel to each other, and a first direction in which the unit lenses of the first lens array provided on the other surface of the translucent substrate extend. And a third lens array including a plurality of unit lenses that extend along a third direction different from any of the second directions in which the unit lenses of the second lens array extend and are arranged in parallel to each other. Lens sheet characterized by having A.

  According to a second aspect of the present invention, an angle formed between a first direction in which the unit lenses of the first lens array extend and a second direction in which the unit lenses of the second lens array extend is approximately 90 degrees. The angle formed by the third direction in which the unit lenses of the third lens array extend and the first direction or the second direction is approximately 45 degrees. It is a lens sheet.

  A third aspect of the present invention is the lens sheet according to the first aspect, wherein the unit lens of the third lens array has a semi-cylindrical shape.

  According to a fourth aspect of the present invention, the unit lenses of the first lens array have a trapezoidal prism shape, and the unit lenses of the second lens array have a prism shape whose apex angle is in the range of 70 degrees to 110 degrees. The lens sheet according to claim 3.

  According to a fifth aspect of the present invention, in the unit lens of the first lens array, an apex angle formed by extending a side surface of the trapezoidal prism is in a range of 70 degrees to 110 degrees. It is a lens sheet.

  The invention according to claim 6 is the lens sheet according to claim 1, wherein the aspect ratio of the unit lens of the third lens array is 1% or more and 20% or less.

  The invention according to claim 7 is the lens sheet according to claim 1, wherein an area ratio of the third lens array to the translucent substrate is 50% or more and 90% or less.

  The invention according to claim 8 is an image display panel that defines a display image, a light source provided on the back surface of the image display panel, and a diffusion plate that emits diffused light by allowing light emitted from the light source to enter and diffuse. And a backlight unit including the lens sheet according to any one of claims 1 to 7.

  According to the lens sheet of the present invention, the diffused light emitted from the diffuser plate is condensed on the front surface side of the optical film by the two-direction lens, thereby improving the brightness on the viewer side, and the oblique side on the back surface side. By attaching a curved surface pattern, the vertical and horizontal emission distribution from the surface can be made smooth with little change. In addition, the function of integrating the lens sheet and the diffusion plate can be obtained, the number of parts can be reduced, and wrinkles and deflection can be prevented at the same time. Furthermore, a high-performance display device having a backlight unit including the lens sheet can be provided.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view showing an example of a display device having a backlight unit including the lens sheet of the present invention.

  The display device 70 according to the embodiment of the present invention includes an image display panel 35 and a backlight unit 55. In the backlight unit 55 according to the embodiment of the present invention, a plurality of light sources 41 are disposed in a lamp house (reflecting plate) 43, and light incident from the light sources 41 is diffused thereon (observer side direction F). Then, the diffusion plate 25 that emits light and the lens sheet 1 according to the embodiment of the present invention are arranged and configured.

  The light H emitted from the light source 41 is diffused by the diffusion plate 25, condensed by the lens sheet 1 disposed thereon, and the light K emitted from the backlight unit 55 enters the image display panel 35, The light is emitted to the observer side F.

  The light source 41 supplies light to the image display panel 35. As the light source 41, for example, a plurality of linear light sources or point light sources can be used. As the plurality of linear light sources, for example, a plurality of fluorescent lamps, a lamp light source such as a cold cathode tube (CCFL) or EEFL, and a point light source such as an LED can be used.

  The reflector 43 is arranged on the opposite side of the plurality of light sources 41 when viewed from the observer side F, and out of the light emitted from the light sources 41 in all directions, the light emitted in the direction opposite to the observer side F. Is reflected and emitted to the observer side F. As a result, the light H emitted to the observer side F becomes light emitted almost in all directions from the light source 41. By using the reflection plate 43 in this way, the light utilization efficiency can be increased. The reflection plate 43 may be any member that reflects light with high efficiency. For example, a general reflection film, a reflection plate, or the like can be used.

Next, the lens sheet 1 according to the embodiment of the present invention will be described in more detail with reference to the drawings.
FIG. 2 is a perspective view of the lens sheet 1 according to the embodiment of the present invention as viewed obliquely from above. 3A is a cross-sectional view of the lens sheet 1 cut along a direction (second direction) orthogonal to the first direction so that the cross section of the first lens array 3 can be seen, and FIG. It is sectional drawing which cut | disconnected the lens sheet | seat 1 along the direction (1st direction) orthogonal to a 2nd direction so that the cross section of 2 lens array 5 may be seen. FIG. 4A is a plan view of the first lens array 3 and the second lens array 5, and FIG. 4B is a plan view of the third lens array 7. FIG. 5 is a perspective view of the lens sheet 1 as viewed obliquely from below.

  In the lens sheet 1 according to the embodiment of the present invention shown in these drawings, the first lens array 3 has a trapezoidal prism shape, the second lens array 5 has a triangular prism shape, and the third lens array 7 has a semi-cylindrical shape. Yes.

  A first lens array 3 including a plurality of unit lenses extending along the first direction and arranged in parallel to each other is formed on the surface 17b on the viewer side F of the translucent substrate 17. A second lens array 5 including a plurality of unit lenses arranged in parallel to each other along a second direction intersecting the first lens array 3 is formed on the top 3a of each unit lens of the first lens array 3. Has been. The first direction in which the unit lenses of the first lens array 3 extend and the unit lenses of the second lens array 5 extend on the surface 17a opposite to the surface 17b on the viewer side F of the translucent substrate 17. A third lens array 7 is formed that includes a plurality of unit lenses that extend along a third direction different from any of the existing second directions and are arranged in parallel to each other.

  The top 5 a of the second lens array 5 coincides with the top 3 a of the trapezoidal prism that is the first lens array 3. In each lens array, a light collection effect is obtained in the arrangement direction of the unit lenses.

  As shown in FIG. 4A, the unit lens (triangular prism) of the first lens array 3 on the surface side extends in the first direction and the unit lens (triangular prism) of the second lens array 5 extends. The angle formed with the second direction is preferably approximately 90 degrees, for example, 90 degrees ± 15 degrees. By setting this angle to approximately 90 degrees, when the display device is observed from the observer side F, a light collecting effect is obtained in the horizontal direction Ho and the vertical direction Ve.

  As shown in FIGS. 4A, 4B and 5, the third direction in which the unit lenses (semi-cylindrical lenses) of the third lens array 7 on the back surface side extend, and the first lens on the front surface side. The angle between the first direction in which the trapezoidal prisms of the array 3 extend or the second direction in which the triangular prisms of the second lens array 5 extend is preferably approximately 45 degrees, for example, 45 degrees ± 15 degrees. . The third lens array 7 affects the luminance distribution both in the light collection direction by the first lens array 3 and in the light collection direction by the second lens array 5. By setting the above angle to about 45 degrees, when the display device is observed from the observer side F, the effect of a wide viewing angle is obtained in the horizontal direction Ho and the vertical direction Ve.

  The unit lens of the second lens array 5 is preferably a triangular prism. Since the triangular prism has a high light condensing effect on the observer side F, it is advantageous for obtaining a display device 70 with high luminance. In order to obtain a display device 70 with high brightness, it is desirable that the apex angle θ2 of the triangular prism is in the range of 70 ° to 110 °, more preferably 80 ° to 100 °.

  The unit lens of the first lens array 3 is preferably a trapezoidal prism. A second lens array 5 is formed on the top 3a of the trapezoidal prism. The trapezoidal prism has the same inclined surface 3b as the triangular prism, and provides the same effect as the triangular prism. Since the trapezoidal prism also has a high light condensing effect on the viewer side F, it is advantageous to obtain a display device 70 with high brightness. In order to obtain a display device 70 with high brightness, the apex angle θ1 formed by extending the side surface of the trapezoidal prism is desirably in the range of 70 to 110 degrees, more preferably 80 to 100 degrees.

  The unit lens of the third lens array 7 is preferably a semi-cylindrical lens. In order to reduce the influence of the first lens array 3 and the second lens array 5 on the light condensing effect, the aspect ratio ([lens height S] / [lens pitch R] of the semi-cylindrical lens shown in FIG. ) Is preferably in the range of 1% to 20%, more preferably 5% to 15%.

  Since the lens sheet 1 of the present invention has a light collecting function in two directions, the light collecting effect is enhanced. Here, as a conventional optical film having a light collecting function in two or more directions, a polygonal pyramid lens represented by a quadrangular pyramid is known. In order to adjust the light collection rate in two directions with a polygonal pyramid lens, it is necessary to change the apex angle of the polygonal pyramid. Taking a quadrangular pyramid as an example, the configuration with the highest luminance is a quadrangular pyramid with an apex angle of 90 degrees, but when expanding or narrowing the field of view in either direction, the apex angle is increased or decreased. There is a need. However, when the apex angle is changed, there arises a problem that the luminance is lowered.

  On the other hand, in the lens sheet 1 of the present invention, the unit lens of the first lens array 3 is a trapezoid prism, the unit lens of the second lens array 5 is a triangular prism, and the trapezoid prism constituting the first lens array 3. Of the triangular prisms constituting the second lens array 5 coincide with each other. For this reason, by adjusting the width of the top portion 3a of the first lens array 3, the light collection ratio in two directions can be adjusted without largely changing the luminance. That is, the range of the field of view is arbitrarily set according to the application conditions of the lens sheet 1 of the present invention, such as setting the field of view in the Ho direction wide, or setting the fields of view in the two directions of the Ho direction and the Ve direction to the same extent. Can do.

  However, in the lens sheet 1 of the present invention, the range in which the field of view can be adjusted by the two-way condensing ratio by the first lens array 3 and the second lens array 5 is narrow, and the luminance change degree, that is, the luminance gradient is substantially the same. is there. Therefore, by providing the third lens array 7 made of a semi-cylindrical lens extending obliquely on the back surface, the influence on the front surface is reduced and the field of view is widened and the luminance gradient can be reduced.

  Further, since the lens sheet 1 of the present invention has a composite shape of the trapezoidal prism of the first lens array 3 and the triangular prism of the second lens array 5, the side lobe generated by the triangular prism hardly occurs. In addition, since the aspect ratio of the third lens array 7 on the back surface is small, there is almost no influence on the occurrence of side lobes.

  FIG. 6 shows the luminance distribution of the 90 degree triangular prism. Since the triangular prism condenses in the front direction, it has a maximum peak at 0 degrees. However, a side lobe occurs, and a valley Va occurs near 45 degrees. The side lobe is emitted light in a direction unnecessary for the display device 70, but the side lobe itself is not a problem in observing the display device 70, but the valley Va between the main peak of 0 degrees and the side lobe. Low brightness is a problem. This is because when the display device 70 is observed from the angle of the valley Va, the screen becomes dark. Therefore, if the luminance of the valley Va is too low even if the side lobes are reduced, it is not desirable as the display device 70.

  FIG. 7 shows a luminance distribution of an example (A) of the lens sheet of the present invention. Since the lens sheet 1 of FIG. 7 has a composite shape in which the first lens array 3 is a trapezoidal prism and the second lens array 5 is a triangular prism, as shown in FIG. 7, light is emitted at an angle corresponding to the valley Va in FIG. Can be emitted. This is because a luminance distribution characteristic obtained by combining the Ve direction luminance distribution and the Ho direction luminance distribution of the 90 degree triangular prism shown in FIG. 6 is obtained. Further, by adjusting the width of the top portion 3 of the first lens array 3, it is possible to adjust the field of view in the Ve direction to be widened or conversely to widen the field of view in the Ho direction. In FIG. 7, the width of the top 3b of the first lens array 3 is adjusted so that the visual field in the Ve direction and the visual field in the Ho direction are the same.

  FIG. 8 shows the luminance distribution of another example (B) of the lens sheet of the present invention. In the lens sheet of FIG. 8, the first lens array 3 and the second lens array 5 on the surface are the same as in FIG. 7, but the aspect ratio of the third lens array 7 is slightly larger than that in FIG. As shown in FIG. 8, there is a luminance peak in the front direction, the visual field in the Ve direction and the visual field in the Ho direction are the same, and the luminance distribution is ideally smooth. High brightness is obtained in the front direction.

  FIG. 9 shows the luminance distribution of still another example (C) of the lens sheet of the present invention. In the lens sheet of FIG. 9, the width of the top portion 3a of the first lens array 3 on the front surface is adjusted so that the visual field in the Ve direction is wider than the visual field in the Ho direction, and the aspect ratio of the third lens array 7 on the back surface is set. The same as in FIG. FIG. 9 has a luminance peak in the front direction and the visual field in the Ve direction and the visual field in the Ho direction are different, but both luminance distribution shapes are ideally smooth. High brightness is obtained.

  Various widths of the top portion 3 of the first lens array 3 were adjusted so that the field of view in the Ve direction and the field of view in the Ho direction were the same, and various lens sheets were produced in which the aspect ratio of the third lens array 7 was changed. In this measurement, the arrangement direction of the first lens array 3 is the Ve direction, the arrangement direction of the second lens array 5 is the Ho direction, and the arrangement direction of the third lens array 7 is the oblique direction (the first lens array 3 and the third lens array). The display device 70 is arranged so that the angle with the array 5 is approximately 45 degrees. FIG. 10A shows the relationship between the half-value angle in the Ve direction and the Ho direction and the aspect ratio. FIG. 10B shows the relationship between the luminance change amount in the Ve direction and the Ho direction and the aspect ratio. 10A and 10B is the aspect ratio of the third lens array 7 and is the ratio of the height S and the pitch R of the unit lenses constituting the third lens array 7. The half-value angle represents a viewing angle at which the luminance is 50% when the luminance in the 0 degree direction (observer side F) is 100%. The amount of change in luminance is the ratio between the difference in luminance of 30 degrees and 45 degrees and the luminance of 0 degrees.

  Also, various widths of the top portion 3 of the first lens array 3 were adjusted so that the field of view in the Ve direction and the field of view in the Ho direction were different, and various lens sheets were produced in which the aspect ratio of the third lens array 7 was changed. FIG. 11A shows the relationship between the half-value angle in the Ve direction and the Ho direction and the aspect ratio. FIG. 11B shows the relationship between the luminance change amount in the Ve direction and the Ho direction and the aspect ratio.

  When the aspect ratio of the third lens array 7 is increased, both the condensing effect of the first lens array 3 and the condensing effect of the second lens array 5 are weakened, and the half-value angles in the Ve direction and the Ho direction are widened. On the contrary, when the aspect ratio of the third lens array 7 is reduced, both the light collection effect of the first lens array 3 and the light collection effect of the second lens array 5 are strengthened, so that the half-value angles in the Ve direction and the Ho direction are narrow. Become.

  When the aspect ratio of the third lens array 7 is increased, both the light condensing effect of the first lens array 3 and the light condensing effect of the second lens array 5 are weakened, and the luminance change amount in the Ve direction and the Ho direction is decreased. When the aspect ratio is 15% or more, the amount of change in luminance decreases. However, the amount of change in luminance does not change even when the aspect ratio is 20% or more. On the other hand, when the aspect ratio of the third lens array 7 is reduced, the condensing effect of the first lens array 3 and the condensing effect of the second lens array 5 are increased, so that the amount of luminance change in the Ve direction and the Ho direction is increased. When the aspect ratio is less than 5%, the amount of change in luminance is likely to change, so an aspect ratio of 5% or more is effective.

  When the display device 70 of the present invention is used for television, it is desirable that the half-value angle in the Ho direction is wide. This is because the observer observes the television from various positions in the Ho direction.

  When the display device 70 of the present invention is used as an advertising billboard application or the like, it may be desirable that the half-value angle in the Ve direction is wide or the half-value angles in the Ve direction and the Ho direction are wide.

  In the lens sheet 1 of the present invention, the first lens array 3 may be arranged in the Ve direction or in the Ho direction. As described above, by changing the width L of the top portion 3a of the first lens array 3, the half-value angles in the Ve direction, the Ho direction, or both can be controlled. Accordingly, the ratio between the width L of the top 3a of the first lens array 3 and the pitch P of the unit lenses constituting the first lens array 3 can be arbitrarily selected.

  In the lens sheet 1 of the present invention, the direction of the third lens array 7 is oblique to the direction of the first lens array 3 or the direction of the second lens array 5, but the first lens array 3 or the second lens array. The angle formed by 5 may be changed within a range of 45 ° ± 15 °. As described above, by changing the direction of the third lens array 7, the amount of change in luminance can be controlled by the Ve direction, the Ho direction, and the aspect ratio. Therefore, the ratio between the height S of the third lens array 7 and the pitch R of the unit lenses constituting the third lens array 7 can be arbitrarily selected.

  Further, in the lens sheet 1 of the present invention, the relationship between the third lens array 7, the first lens array 3, and the second lens array 5 is not necessary, and the pitch, alignment, and direction that are parameters of the third lens array 7 are not necessary. Can be chosen arbitrarily.

  The unit lenses of the third lens array 7 are oriented obliquely with respect to the direction of the trapezoidal prism of the first lens array 3, and the pitch R of the unit lenses constituting the third lens array 7 and the first lens array 3 are It is desirable that the relationship with the pitch P of the constituent unit lenses is 0.05 ≦ R / P ≦ 0.5. When R is the same as P or larger than P, the direction of light incident on each unit lens of the first lens array 3 or the incident location is too different between the adjacent lenses. As a result, the first lens array 3 is on the observation side F. This causes uneven brightness in the direction, resulting in an undesirable display. Conversely, when R is smaller than P, substantially the same light is incident on each unit lens of the first lens array 3, and a uniform display is obtained. When R is much smaller than P, for example, when R / P <0.05, it is difficult to form the third lens array 7 and there is a possibility that diffraction may appear. Is less desirable.

  As shown in FIGS. 10A and 10B and FIGS. 11A and 11B, the half-value angle and the luminance change amount are affected by the aspect ratio of the third lens array 7. A high front luminance, a wide viewing angle, and a low luminance change amount are desirable, but it is difficult to satisfy all of them. In the case of a liquid crystal television, what is important is a wide viewing angle and a low luminance change amount. Even if the front brightness is high, it is not a desirable display if the field of view is narrow or the brightness changes rapidly depending on the viewing angle. On the other hand, even if the front luminance is a little low, it can be said to be a desirable display when the field of view is wide and the luminance changes smoothly depending on the viewing angle.

  The aspect ratio of the third lens array 7 is preferably 2% or more and 20% or less, more preferably 5% or more and 15% or less. If the aspect ratio is 20% or more, the front luminance continues to decrease, but the change in luminance change becomes dull, and the effect becomes undesirably thin. On the contrary, when the aspect ratio is less than 2%, it is difficult to form the shape, and the effect is small, so there are few merits.

  The relationship between the pitch P of the unit lenses constituting the first lens array 35 and the pitch Q of the unit lenses constituting the second lens array 5 is 0.05 ≦ Q / P ≦ 2.0. desirable. The second lens array 5 of the lens sheet 1 of the present invention is formed on the top 3 a of the first lens array 3. The unit lens of the first lens array 3 is a trapezoidal prism, and the unit lens of the second lens array 5 is a triangular prism. The optimum range of the apex angle is 70 degrees to 110 degrees. When the first lens array 3 is a trapezoidal prism having an apex angle of 70 degrees and the second lens array 5 is a triangular prism having an apex angle of 110 degrees, the pitch Q of the unit lenses constituting the second lens array 5 is the first. When the pitch P of unit lenses constituting the lens array 3 exceeds twice the pitch P (Q / P> 2.0), the units constituting the second lens array 5 are determined by the height of the unit lenses constituting the first lens array 3. The height of the lens becomes higher, and the effect of the first lens array 3 disappears. Therefore, Q / P is desirably 2 or less. When the pitch Q of the unit lenses constituting the second lens array 5 is smaller than the pitch P of the unit lenses constituting the first lens array 3, there is no problem in terms of optical characteristics, but for example the units constituting the second lens array 5 When the lens pitch Q is 20 μm, if Q / P is 0.05, the pitch P of the unit lenses constituting the first lens array 3 is 400 μm. If the pitch P of the unit lenses constituting the first lens array 3 is too large, moire interference fringes are likely to occur between the periodic structure of the image display panel 35 and the periodic structure of the first lens array 3, which is not desirable. On the other hand, if the pitch P of the unit lenses constituting the first lens array 3 is reduced, the pitch R of the unit lenses constituting the second lens array 5 becomes too small. Therefore, it is desirable that Q / P is 0.05 or more.

  The lens sheet 1 of the present invention is manufactured using a mold shown in FIGS. 12 (a) and 12 (b). The surface shape of the lens sheet 1 is formed using a mold 2 as shown in FIG. The back surface shape of the lens sheet 1 is formed using a mold 2a as shown in FIG. A first lens array 3 is formed by the first lens array mold 4 in FIG. 12A, and a second lens array 5 is formed by the second lens array mold 6. Or after forming the 1st lens array 3 on the translucent base material 17, the 2nd lens array 5 can also be formed.

  In the above description, the case where the unit lens of the third lens array 7 of the lens sheet 1 of the present invention is a semi-cylindrical lens extending in one direction has been described. A microlens in which lenses are two-dimensionally arranged can also be used.

  FIG. 13 shows a lens sheet in which the unit lens of the first lens array 3 is a trapezoidal prism, the unit lens of the second lens array 5 is a triangular prism, and the unit lenses of the third lens array 7 are two-dimensionally arranged spherical lenses obliquely downward. It is the perspective view seen from.

  Since the third lens array 7 in FIG. 13 is two-dimensionally arranged, an optical influence is obtained on the visual field in the Ve direction and the visual field in the Ho direction as in the configuration shown in FIG. However, since there are gaps in the two-dimensionally arranged microlenses, the effect differs depending on the area ratio occupied by the planar portion. In order to obtain the same effect, a low aspect ratio is sufficient if the area ratio of the planar portion is small, but on the contrary, a high aspect ratio is required if the area ratio of the planar portion is large. When the aspect ratio is 20%, it is desirable that the area ratio of the planar portion is 50% to 90%.

  As shown in FIG. 1, in the lens sheet 1 of the present invention, light transmitted from a light source 41 through a diffusion plate 25 and a gap (air layer) 100 is incident from an incident surface, and the light is optically transmitted from a surface opposite to the incident surface. Light is emitted as light K having a gain of 1 or more.

  The optical gain is one of the indexes indicating the diffusibility of the optical diffusing member, and is expressed as a ratio to the luminance of the light when the luminance of the diffuser that diffuses completely is 1. When the diffusivity of the diffusing member to be measured is biased depending on the direction, the diffusion characteristic of the diffusing member can be shown by taking out the optical gain for each direction.

  Also, complete diffusion refers to an ideal diffuser that has zero absorption and has a certain intensity in any direction. That is, an optical gain of 1 or more indicates that there is an effect of collecting light in the measurement direction, and that the larger the value, the stronger the light collection effect.

  The diffusion plate 25 is formed by dispersing a light diffusion region in a transparent resin. As the transparent resin, a thermoplastic resin, a thermosetting resin or the like can be used. For example, a polycarbonate resin, an acrylic resin, a fluorine acrylic resin, a silicone acrylic resin, an epoxy acrylate resin, a polystyrene resin, a cycloolefin polymer, Methyl styrene resin, fluorene resin, polyethylene terephthalate (PET), polypropylene, acrylonitrile styrene copolymer, acrylonitrile polystyrene copolymer, and the like can be used.

  The light diffusion region is preferably made of light diffusion particles. This is because suitable diffusion performance can be easily obtained.

  As the light diffusing particles, transparent particles made of an inorganic oxide or a resin can be used. As the transparent particles made of an inorganic oxide, for example, silica, alumina or the like can be used. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, melamine / formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Fluoropolymer particles such as fluoroethylene / hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene / tetrafluoroethylene copolymer), silicone resin particles, and the like can be used.

  Two or more kinds of transparent particles may be used in combination from the transparent particles described above. The size and shape of the transparent particles are not particularly defined.

  In order to give the uneven shape to the diffuser plate 25, while forming the diffuser plate 25 by the coextrusion forming method or the injection molding method, the uneven shape is transferred by applying pressure to the mold for shaping the uneven shape. Can be used.

  It is also possible to mold the entrance surface or exit surface of the diffusion plate 25 using a radiation curable resin such as a UV curable resin. For example, after the diffusion plate 25 is formed as a plate-like member by a co-extrusion method, an uneven shape can be formed on the incident surface or the output surface of the diffusion plate 25 by UV molding.

  The film having the concavo-convex shape may be formed as a separate body, and the film having the concavo-convex shape and the diffusion plate 25 may be bonded to each other through a bonding layer made of an adhesive or an adhesive material.

  When light diffusing particles are used as the light diffusing region, the thickness of the diffusing plate 25 is preferably 0.1 to 5 mm.

  When the thickness of the diffusion plate 25 is 0.1 to 5 mm, optimum diffusion performance and brightness can be obtained. On the other hand, if the thickness is less than 0.1 mm, the diffusion performance is insufficient, and if it exceeds 5 mm, the amount of resin is large, and the luminance is reduced due to absorption.

  When a thermoplastic resin is used as the transparent resin, air bubbles may be used as the light diffusion region.

  The internal surface of the bubble formed inside the thermoplastic resin causes diffused reflection of light, and a light diffusing function equivalent to or higher than that when light diffusing particles are dispersed can be expressed. Therefore, it becomes possible to make the film thickness of the diffusion plate 25 thinner.

Examples of the diffusion plate 25 include white PET and white PP. White PET is obtained by dispersing a resin incompatible with PET, a filler such as titanium oxide (TiO ₂ ), barium sulfate (BaSO ₄ ), and calcium carbonate in PET, and then stretching the PET by a biaxial stretching method. As a result, bubbles are generated around the filler.

  The diffusion plate 25 made of a thermoplastic resin only needs to be at least uniaxially stretched. If it is at least uniaxially stretched, bubbles can be generated around the filler.

  Examples of the thermoplastic resin include polyethylene terephthalate (PET), polyethylene-2, 6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, and spiroglycol copolymer polyester resin. , Polyester resins such as fluorene copolymerized polyester resins, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate, polycarbonate, polystyrene, polyamide, polyether, Polyesteramides, polyetheresters, polyvinyl chloride, cycloolefin polymers, and copolymers comprising these It can be used as mixtures of these resins, not particularly limited.

  When bubbles are used as the light diffusion region, the thickness of the diffusion plate 25 is preferably 25 to 500 μm.

  When the thickness of the diffusing plate 25 is less than 25 μm, it is not preferable because the sheet is insufficiently squeezed and wrinkles are easily generated in the manufacturing process and display. In addition, when the thickness of the diffusion plate 25 exceeds 500 μm, there is no particular problem in optical performance, but the rigidity is increased, so that it is difficult to process into a roll shape and the slit cannot be easily formed. This is not preferable because the advantage of thinness obtained in this manner is reduced.

  The thickness of the lens sheet 1 is determined by the manufacturing process or the required physical characteristics of the lens sheet 1 rather than the influence on the optical characteristics.

  For example, when the first lens array 3 and the second lens array 5 are formed by UV molding, the base material thickness T of the supporting base film is wrinkled when it is 50 μm or less, so it is necessary that 50 μm <T. is there.

  Furthermore, the thickness of the base material varies depending on the size of the backlight unit or display device used. For example, in a display device having a diagonal size of 37 inches or more, the substrate thickness T is desirably 0.05 mm to 3 mm.

  In general, many displays have a periodic pixel structure, and as a result, high-order moire such as moire between the respective periodic structures and secondary moire generated in three or more periodic structures is generated, resulting in a defect that impairs the appearance. . Therefore, the lens direction of the lens sheet 1 may be shifted from the direction of the periodic structure of the image display panel 35 within a range of 30 degrees or less. Thereby, it is possible to prevent moiré that occurs between the horizontal and vertical structures of the periodic pixel structure of the image display panel 35.

  As a method for preventing moire, the first lens array 3, the second lens array 5, and the third lens array 7 may be meandered.

  As another method for preventing moire, the lens pitch of the first lens array 3, the second lens array 5, and the third lens array 7 may be random. In this case, there are a method of randomizing the lens height and pitch, a method of randomizing only the pitch without changing the lens height, and a method of randomizing the shift amount Δ of the prism lens. However, from the viewpoint of unevenness in appearance, a method of randomizing without changing the lens height is desirable. In that case, the random rate (pitch increase / decrease rate with respect to the standard pitch) is preferably 20% or less, and more preferably 10% or less.

  As shown in FIG. 1, the display device 70 according to the embodiment of the present invention includes an image display panel 35 and a backlight unit 55.

  The image display panel 35 includes two polarizing plates (polarizing films) 31 and 33 and a liquid crystal panel 32 sandwiched therebetween. The liquid crystal panel 32 is configured, for example, by filling a liquid crystal layer between two glass substrates.

  The light K emitted from the backlight unit 55 enters the liquid crystal unit 32 via the polarizing filter 33 and is emitted to the viewer side F via the polarizing filter 31.

  The image display panel 35 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 optical sheet 52 improves the luminance toward the viewer side F, reduces the viewing angle dependency of the light intensity, and further reduces the lamp image. An image with high image quality can be displayed by effectively using the reduced light.

  The image display panel 35 is preferably a liquid crystal display element. A liquid crystal display element is a typical element that transmits / shields light in pixel units and displays an image, and can improve image quality and reduce manufacturing cost compared to other display elements. Can do.

  The display device 70 according to the embodiment of the present invention may be provided with a diffusion film, a prism sheet, a polarized light separating / reflecting sheet, or the like. By doing so, the image quality can be further improved.

  Since the display device 70 according to the embodiment of the present invention is configured to use the light K whose light collection / diffusion characteristics are improved by the optical sheet 52, the luminance on the viewer side F is improved, and the distribution of the light intensity in the viewing angle direction is achieved. And an image with a reduced lamp image can be displayed on the image display panel 35.

  The display device 70 according to the embodiment of the present invention is an image display panel 35 that defines a display image according to transmission / light-shielding in pixel units, and light K whose light collection / diffusion characteristics are improved by a backlight unit 55. Therefore, it is possible to improve the luminance on the viewer side F, smooth the distribution of the light intensity in the viewing angle direction, and obtain an image with a reduced lamp image.

  The display device 70 according to the embodiment of the present invention has a configuration in which the image display panel 35 is a liquid crystal display element and uses the light K whose light collection / diffusion characteristics are improved by the backlight unit 55. The luminance of the light can be improved, the distribution of the light intensity in the viewing angle direction can be smoothed, and an image with a reduced lamp image can be obtained.

  So far, the case where the lens sheet 1 of the present invention and the optical sheet 52 using the lens sheet 1 are used in a liquid crystal display device has been described. However, the present invention is not limited to this, and a rear projection screen, a solar cell, an organic or inorganic EL, an illumination device. As long as it performs optical path control, it can be used for any device.

  Hereinafter, the present invention will be described in detail based on examples. In addition, this invention is not limited only to these Examples.

[Example 1]
The lens sheet 1 was produced by extrusion molding using polycarbonate with a substrate 17 having a thickness of 250 μm. The first lens array 3 was a trapezoidal prism having an apex angle of 90 degrees, a lens pitch of 100 μm, and a width L of the apex 3a of 14 μm. The second lens array 5 was a triangular prism having an apex angle of 90 degrees and a lens pitch of 33 μm. The angle formed by the first lens array 3 and the second lens array 5 was 90 degrees. The third lens array 7 was a semi-cylindrical lens having a lens radius of 430 μm and a lens pitch of 40 μm. The angle formed by the third lens array 7 and the first lens array 3 or the second lens array 5 was arranged at 45 degrees.

[Comparative Example 1]
The lens sheet 1 was produced by extrusion molding using polycarbonate with a substrate 17 having a thickness of 250 μm. The first lens array 3 was a trapezoidal prism having an apex angle of 90 degrees, a lens pitch of 100 μm, and a width L of the apex 3a of 14 μm. The second lens array 5 was a triangular prism having an apex angle of 90 degrees and a lens pitch of 33 μm. The angle formed by the first lens array 3 and the second lens array 5 was 90 degrees. The back surface of the substrate 17 was flat.

  The lens sheet 1 produced in Example 1 and the lens sheet produced in Comparative Example 1 were placed in the backlight 55, and the light distribution was measured. In the configuration of the backlight 55, the CCFL 41 is arranged on the observer side F of the reflecting plate 43, and the diffuser plate 25 and the lens sheet 1 are arranged thereon (on the observer side F).

  In the lens sheet of Example 1, the arrangement direction of the first lens array 3 was arranged as the Ve direction. As a result, in the lens sheet of the comparative example, the front luminance is high. However, when the field of view is changed from the front, the luminance in the vertical direction (Ve direction) near 30 degrees rapidly decreases. In the lens sheet of Example 1, it was confirmed that when the field of view was changed from the front, the luminance change was gradual and no sense of incongruity was produced. Moreover, when the half-value angle was compared by changing a visual field from the front to the horizontal direction (Ho direction), it was confirmed that the half-value angle of the practical example 1 was slightly wide.

  As shown in FIG. 9, it was confirmed that the lens sheet 1 of Example 1 has a wide half-value angle and a small amount of change in luminance.

Sectional drawing of the display apparatus which concerns on embodiment of this invention. The perspective view which looked at the lens sheet concerning the embodiment of the present invention from the slanting upper part. Sectional drawing of the lens sheet which concerns on embodiment of this invention. The top view of the lens sheet concerning the embodiment of the present invention. The perspective view which looked at the lens sheet concerning the embodiment of the present invention from the slanting lower part. The figure which shows the luminance distribution of a 90-degree triangular prism. The figure which shows the luminance distribution of the lens sheet which concerns on embodiment of this invention. The figure which shows the luminance distribution of the lens sheet which concerns on embodiment of this invention. The figure which shows the luminance distribution of the lens sheet which concerns on embodiment of this invention. The figure which shows the relationship between the half value angle of the lens sheet which concerns on embodiment of this invention, and an aspect ratio, and the figure which shows the relationship between a luminance variation | change_quantity and an aspect ratio. The figure which shows the relationship between the half value angle of the lens sheet which concerns on embodiment of this invention, and an aspect ratio, and the figure which shows the relationship between a luminance variation | change_quantity and an aspect ratio. The perspective view which looked at the type | mold for producing the lens sheet which concerns on embodiment of this invention from diagonally downward. The perspective view which looked at the lens sheet which concerns on other embodiment of this invention from diagonally downward. Sectional drawing which shows an example of arrangement | positioning of BEF. The perspective view of BEF. The figure which shows the relationship between the light intensity and the angle with respect to a visual field direction.

Explanation of symbols

  A: BEF light intensity distribution, B: Optical film light intensity distribution, H, K: Light, L: Top width of first lens array, P: Pitch of first lens array, Q: Second lens array P, R: Pitch of third lens array, S: Height of third lens array, F, F ′: Observer side, X: Observation direction, Va: Valley of luminance distribution, Ve: Vertical direction of image display device, Ho: Horizontal direction of the image display device, 1 ... lens sheet, 2 ... mold, 2a ... mold, 3 ... first lens array, 3a ... top of the first lens array, 3b ... inclined surface of the first lens array, 4 ... first. DESCRIPTION OF SYMBOLS 1 lens array type, 5 ... 2nd lens array, 5a ... Top part of 2nd lens array, 6 ... 2nd lens array type, 7 ... 3rd lens array, 8 ... 3rd lens array type, 17 ... Translucent base Material, 17a: surface opposite to the observer, 17b: surface on the observer side, 25 Diffuser, 31, 33 ... Polarizing plate, 32 ... Liquid crystal panel, 35 ... Image display panel, 41 ... Light source, 43 ... Reflector (reflective film), 52 ... Optical sheet, 55 ... Backlight unit, 70 ... Display device , 182 ... diffusion film, 184 ... light diffusion film, 185 ... BEF, 186 ... transparent substrate, 187 ... unit prism.

Claims (8)

A translucent substrate;
A first lens array including a plurality of unit lenses provided on one surface of the translucent substrate and extending in the first direction and arranged in parallel to each other; and each of the first lens arrays A plurality of unit lenses provided at the top of the unit lens and extending along a second direction intersecting with a first direction in which the unit lenses of the first lens array extend and arranged in parallel with each other; A two-lens array;
Either the first direction in which the unit lens of the first lens array extends on the other surface of the translucent substrate or the second direction in which the unit lens of the second lens array extends. And a third lens array including a plurality of unit lenses that extend in a third direction different from each other and are arranged in parallel to each other.   The angle formed by the first direction in which the unit lenses of the first lens array extend and the second direction in which the unit lenses of the second lens array extend is approximately 90 degrees, and the third lens array The lens sheet according to claim 1, wherein an angle formed between a third direction in which the unit lens extends and the first direction or the second direction is approximately 45 degrees.   The lens sheet according to claim 1, wherein the unit lens of the third lens array has a semi-cylindrical shape.   The unit lens of the first lens array has a trapezoidal prism shape, and the unit lens of the second lens array has a prism shape with an apex angle in a range of 70 degrees to 110 degrees. Lens sheet.   The lens sheet according to claim 4, wherein the unit lens of the first lens array has an apex angle formed by extending a side surface of the trapezoidal prism in a range of 70 degrees to 110 degrees.   2. The lens sheet according to claim 1, wherein an aspect ratio of a unit lens of the third lens array is 1% or more and 20% or less.   2. The lens sheet according to claim 1, wherein an area ratio of the third lens array to the translucent substrate is 50% or more and 90% or less. An image display panel for defining a display image;
A light source provided on the back of the image display panel;
A diffusion plate that emits diffused light by causing the light emitted from the light source to enter and diffuse;
A display device comprising: a backlight unit including the lens sheet according to claim 1.

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