JP2009157029A - Lens sheet, backlight using lens sheet, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens sheet which is high in front luminance, and wide in visual field angle in a prescribed direction. <P>SOLUTION: The lens sheet 15 includes a columnar lens layer 22 formed on a surface 211 of a base film 21, a prism layer 23 formed on a surface 212 of a base film 21, and a packed layer 24 formed on the prism layer 23. The columnar lens layer 22 includes a plurality of columnar lenses 221. Each of the columnar lenses 221 consists of a plurality of microlens sections connected in a row. The prism layer 23 includes a plurality of prisms parallel to the columnar lenses 221. The refractive index of the prism layer 23 is lower than the refractive index of the base film 21 and the packed layer 24. The lens sheet 15 condenses light stepwise as the light progresses to the packed layer 24, the prism layer 23, the base film 21, and the columnar lenses 221, and improves the front luminance. Also, the width in the luminance visual field angle characteristics in the longitudinal direction of the columnar lenses 221 can be maintained wide. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lens sheet, a backlight using the lens sheet, and a liquid crystal display device. More specifically, the present invention relates to a lens sheet having a condensing function, a backlight using the lens sheet, and a liquid crystal display device.

  A liquid crystal display device is required to have high front luminance. Therefore, the backlight used for the liquid crystal display device includes a lens sheet that improves the front luminance. As disclosed in Japanese Patent No. 3262230 (Patent Document 1), a prism sheet is generally used as a lens sheet.

  Although the prism sheet improves the front luminance, the luminance viewing angle characteristics have the problems shown in the following (1) and (2).

  (1) In the luminance viewing angle characteristics of the prism sheet, not only a luminance peak occurs in the front, but also a luminance peak (side lobe) occurs in a direction oblique to the front. The solid line in FIG. 30 shows the luminance viewing angle characteristics in the vertical direction of a prism sheet in which prisms having a cross-sectional shape with an apex angle of 90 degrees are arranged in parallel in the vertical direction of the display screen. The horizontal axis represents the viewing angle (deg), and the vertical axis represents the luminance at each viewing angle. Referring to FIG. 30, in the luminance viewing angle characteristic in the vertical direction of the conventional prism sheet, the first peak is shown at 0 deg of the viewing angle, and the second peak (so-called side lobe) is around the viewing angle ± 80 deg. Indicates. Such a side lobe gives the user a strange feeling when viewing the display screen.

  (2) A broken line in FIG. 30 indicates luminance viewing angle characteristics in the left-right direction of the prism sheet (that is, the longitudinal direction of the prism). In the luminance angle distribution in the left-right direction, when the viewing angle is within a range of ± 40 deg, the luminance does not change much even if the viewing angle increases. However, when the viewing angle exceeds the range of ± 40 deg, the luminance rapidly decreases as the viewing angle increases. If the distribution is a natural distribution in which the viewing angle is 0 deg as a peak and the luminance gradually decreases as the viewing angle increases, the user does not feel uncomfortable even if the angle at which the user views the display screen is changed. However, in the display screen showing the luminance angle distribution in the left-right direction as shown in FIG. 30, the luminance changes rapidly in the vicinity of the viewing angle ± 40 deg. Therefore, the user who views the display screen near the viewing angle of ± 40 deg is uncomfortable.

  A microlens array sheet is also known as a lens sheet that replaces the prism sheet. The microlens array sheet includes a plurality of microlenses arranged in a lattice arrangement or a staggered arrangement at equal intervals. Since each microlens is hemispherical, it collects light in all directions equally and increases the front luminance. In addition, the side lobe unlike the prism sheet does not occur, and the viewing angle characteristic of the luminance has a natural distribution in which the luminance gradually decreases with increasing viewing angle with the viewing angle of 0 deg as a peak.

  However, the luminance viewing angle characteristics of the microlens array sheet have the same width in both the vertical direction and the horizontal direction, and the width is narrow. In short, when the microlens array sheet is used, the viewing angle becomes narrow. In general, since the user has more opportunities to see the display from the left and right oblique directions than the opportunity to see the display from the upper and lower oblique directions, it is particularly preferable that the viewing angle in the left and right direction is wide.

  Japanese Patent No. 3252471 (Patent Document 2) discloses a microlens array sheet that can widen the left and right viewing angles. The microlenses of the microlens array sheet of this document have a semi-ellipsoid shape, and are arranged so that the longitudinal direction of the semi-ellipsoid is parallel to the horizontal direction of the display. If this microlens array sheet is used, the width of the luminance viewing angle characteristic in the left-right direction can be maintained wide, and the viewing angle in the left-right direction is wide. However, since the microlens has an ellipsoidal shape, light in the left-right direction and diagonal direction cannot be collected, and as a result, the front luminance is low.

A lenticular lens sheet in which a plurality of cylindrical lenses are arranged side by side is also known as another lens sheet that can maintain a wide left-right viewing angle and has a natural distribution of luminance viewing angle characteristics. However, the lenticular lens sheet has a low front luminance, similar to the semi-ellipsoidal microlens array sheet.
Japanese Patent No. 3262230 Japanese Patent No. 3252471

  An object of the present invention is to provide a lens sheet having a high front luminance and a wide viewing angle in a predetermined direction.

  Another object of the present invention is to provide a lens sheet that can suppress the occurrence of luminance unevenness.

Means for Solving the Problems and Effects of the Invention

  The lens sheet according to the present invention includes a sheet-like or film-like base material layer, a columnar lens layer including a plurality of columnar lenses, a prism layer, and a filling layer. The base material layer has first and second surfaces. Each of the plurality of columnar lenses includes a plurality of plano-convex lens portions connected in a line, and is arranged in parallel on the first surface. The prism layer includes a plurality of prisms arranged side by side on the second surface. The prism layer further has a lower refractive index than the substrate layer. The filling layer is formed on the prism layer. The filling layer further has a higher refractive index than the prism layer.

  In the lens sheet according to the present invention, incident light rays are condensed stepwise. Since the refractive index of the filling layer is higher than the refractive index of the prism layer, the diffused light incident on the filling layer is refracted on the prism surface and collected on the front surface. Next, since the refractive index of the base material layer is higher than the refractive index of the prism layer, the light beam that has entered the base material layer from the prism layer is refracted on the surface of the base material layer and is collected more in front. Furthermore, the light beam emitted from the base material layer enters the columnar lens, is refracted on the convex surface of the columnar lens, and is collected and emitted to the front. At this time, since the columnar lens includes a plurality of plano-convex lenses connected in one row, it can collect light in almost all directions. Thus, the lens sheet of the present invention can collect incident light rays in a stepwise manner, and can obtain high front luminance. Furthermore, even if the lens sheet according to the present invention includes a plurality of prisms, the occurrence of side lobes can be suppressed.

  Preferably, the columnar lens is parallel to the prism.

  Since the plurality of plano-convex lens portions constituting the columnar lens are connected in the longitudinal direction of the columnar lens, the light collecting ability in the longitudinal direction is lower than the light collecting ability in the width direction. In addition, since the prism of the prism layer is also parallel to the columnar lens, the lens sheet according to the present invention can maintain a wide range of luminance viewing angle characteristics in the longitudinal direction of the columnar lens and the prism. Furthermore, since the columnar lens and the prism are in parallel, the occurrence of uneven brightness can be suppressed.

  Preferably, a gap is formed between adjacent columnar lenses.

  Preferably, adjacent plano-convex lens portions in the same columnar lens are in surface contact with each other. The “surface” here includes a virtual surface.

  In this case, the width of the viewing angle characteristic of luminance in the longitudinal direction of the columnar lens can be maintained wide.

  Preferably, the columnar lens includes a plurality of plano-convex lens portions having different heights.

  In this case, the wet-out phenomenon can be suppressed. Moreover, the occurrence of moire can be suppressed.

  A ridge line of a prism or a valley line formed between adjacent prisms may meander in the width direction of the prism. Further, the arrangement pitch of the prisms may be nonuniform, and the height of the prisms may vary in the longitudinal direction of the prisms.

  Further, the filling layer may include a resin and a plurality of particles dispersed in the resin and having a refractive index different from that of the resin.

  In these cases, the generation of moire can be further suppressed.

  The backlight according to the present invention includes the lens sheet. A liquid crystal display device according to the present invention includes the above-described backlight and a liquid crystal panel laid on the backlight.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Configuration of liquid crystal display device and backlight]
With reference to FIGS. 1 and 2, the liquid crystal display device 1 includes a backlight 10 and a liquid crystal panel 20 laid in front of the backlight 10. The liquid crystal panel 20 includes a plurality of pixels arranged in a matrix. The display screen 29 of the liquid crystal display device 1 has a rectangular shape having long sides in the left-right direction (x direction in the figure) and short sides in the up-down direction (y direction in the figure).

  The backlight 10 is a so-called direct type, and includes a surface light source 11 that emits diffused light, and a sheet-like or film-like lens sheet 15 laid on the surface light source 11.

  The surface light source 11 includes a housing 12, a plurality of fluorescent tubes 13 that are line light sources, and a diffusion plate 14. The housing 12 is a housing having an opening 120 on the front surface, and houses a plurality of fluorescent tubes 13 therein. The inner surface of the housing 12 is covered with a reflective film 121. The reflection film 121 irregularly reflects the light emitted from the fluorescent tube 13 and guides the irregularly reflected light to the opening 120. The reflective film 121 is, for example, Toray Co., Ltd. Lumirror (registered trademark) E60L or E60V. The reflective film 121 preferably has a diffuse reflectance of 95% or more.

  The plurality of fluorescent tubes 13 are arranged in the housing 12 in the vertical direction (y direction in FIG. 1). The fluorescent tube 13 is a linear light source extending in the left-right direction (x direction in FIG. 1), and is, for example, a CCFL (Cold Cathode Fluorescent Lamp) or an EEFL (External Electrode Fluorescent Lamp: external electrode fluorescent tube). A plurality of point light sources such as LEDs (Light Emitting Device) may be housed in the housing 12 together with the fluorescent tube 13. Moreover, a pseudo line light source may be formed by arranging a plurality of housed LEDs in a line.

  The diffusion plate 14 is fitted into the opening 120. The diffusion plate 14 is disposed in parallel with the back surface of the housing 12. When the diffusion plate 14 is fitted into the opening 120, the inside of the housing 12 is sealed. For this reason, it is possible to prevent light emitted from the fluorescent tube 13 from leaking from a portion other than the diffusion plate 14 to improve light utilization efficiency.

  The diffusion plate 14 diffuses the light from the fluorescent tube 13 and the light reflected by the reflection film 121 substantially uniformly and emits the light to the front. The diffusion plate 14 includes a transparent base material and a plurality of fillers (fine particles) dispersed in the base material. The filler dispersed in the substrate has a refractive index different from that of the substrate with respect to light having a wavelength in the visible light region. Therefore, the diffusion plate 14 diffuses the incident light, and the diffused light passes through the diffusion plate 14.

  The base material of the diffusion plate 14 is, for example, glass, polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin. , Polyether sulfonic acid resin, triacetyl cellulose resin and the like.

[Lens sheet]
3 to 5, the lens sheet 15 includes a base film 21 that is a base material layer, a columnar lens layer 22 formed on one surface 211 of the base film 21, and the other of the base film 21. A collimating layer 25 formed on the surface 212. These are integrally formed.

  The base film 21 is transparent with respect to wavelengths in the visible light region. The base film 21 is, for example, glass, polyester resin, polycarbonate resin, polyacrylate resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin, polyether. It is composed of a resin such as a sulfonic acid resin or a triacetyl cellulose resin. Both the surfaces 211 and 212 of the base film 21 are flat. Further, the base film 21 may be a film shape, a sheet shape, or a plate shape.

[Columnar lens layer]
The columnar lens layer 22 is formed on the surface 211. The columnar lens layer 22 includes a plurality of columnar lenses 221.

  The plurality of columnar lenses 221 are transparent to visible light, and are arranged in parallel in the vertical direction (y direction) of the display screen 29. That is, the columnar lens 221 is parallel to the fluorescent tube 13 that is a line light source.

  The columnar lens 221 includes a plurality of microlens portions 222. The micro lens unit 222 is a plano-convex lens, and the plurality of micro lens units 222 are connected in a line in the left-right direction (x direction) of the display screen 29. The adjacent microlens portions 222 in the same columnar lens are in surface contact with each other. The “surface” here includes a virtual surface (hereinafter referred to as a virtual surface). Specifically, as shown in FIGS. 4 and 6, the microlens portions 222 adjacent to each other are connected by a virtual surface 224.

  As shown in FIG. 4, when the microlens portion 222 is viewed from directly above, it is preferable that the periphery of the microlens portion 222 other than the coupling portion 224 is an arc. This is because if the periphery is a circular arc, light in all directions can be easily collected.

  The tops Tc of the micro lens units 222 are staggered. A flat gap 223 is formed between the adjacent columnar lenses 221. The convex surface of the microlens unit 222 may be a spherical surface having a certain curvature as shown in FIGS. 3 to 6, and as shown in FIG. 7, the transverse shape has the end of the long axis LA as the top Tc. It may be an elliptical arc. Further, as shown in FIG. 8, the transverse shape may be an arc shape including an arc 316 including the vertex Tc and a straight line 317 connecting each end point CP of the arc 316 and the edge ED of the lens.

  The columnar lens 221 is made of an ionizing radiation curable resin. The ionizing radiation curable resin is cured by ionizing radiation such as ultraviolet rays and electron beams. The ionizing radiation curable resin is, for example, a polyester acrylate resin, a urethane acrylate resin, a polyether acrylate resin, an epoxy acrylate resin, a polyester methacrylate resin, a urethane methacrylate resin, a polyether methacrylate resin, or an epoxy methacrylate resin. .

  The convex surface of the microlens portion 222 has a curvature. Therefore, the columnar lens layer 22 collects not only light in the vertical direction (y direction) and horizontal direction (x direction) but also light in an oblique direction. In short, the columnar lens layer 22 can collect light in all directions. Therefore, the front brightness is improved.

  Further, the plurality of microlens portions 222 are connected in a line in the left-right direction (x direction) to form the columnar lens 221. Adjacent microlens portions 222 are in surface contact and are joined by a virtual surface 224. Therefore, the convex surface of each microlens portion 222 is wide in the y direction and narrow in the x direction. Therefore, each microlens unit 222 collects light in the vertical direction (y direction) more than light in the horizontal direction (x direction).

[Collimate layer]
Referring to FIGS. 3 and 5 again, the collimating layer 25 includes a filling layer 24 and a prism layer 23. The prism layer 23 includes a plurality of prisms 230 formed on the surface 212 of the base film 21 and arranged in parallel with each other.

  The filling layer 24 is filled on the surface of the prism layer 23 on which the prisms 230 are arranged. A portion of the filling layer 24 filled between the plurality of prisms 230 constitutes a prism 240. Since the prisms 230 are arranged side by side, the plurality of prisms 240 are also arranged side by side. The surface 243 opposite to the surface on which the prisms 240 are arranged is flat. The surface 243 faces the surface light source 11.

  The prisms 230 and 240 are arranged in parallel in the vertical direction of the screen of the liquid crystal display device 1 (y direction in FIG. 1). That is, the columnar lens 221 is parallel to the prisms 230 and 240. Since the columnar lens layer 22 is formed on the collimating layer 25 composed of the prisms 230 and 240, side lobes hardly appear in the luminance viewing angle characteristics. The luminance viewing angle characteristic has a natural distribution in which the luminance decreases as the viewing angle increases with the front as a peak. In addition, the columnar lens 221 and the prisms 230 and 240 are parallel and both extend in the left-right direction (x direction), so that the width of the luminance viewing angle characteristic in the left-right direction is widened. Moreover, since the juxtaposition direction of any lens is the same as the juxtaposition direction of the fluorescent tubes 13, the occurrence of uneven brightness can be suppressed.

  The prism layer 23 and the filling layer 24 are made of resin. More specifically, the prism layer 23 and the filling layer 24 are made of an ionizing radiation curable resin. The filling layer 24 may be made of an ionizing radiation curable resin, or may be made of another resin such as polycarbonate or polystyrene.

The refractive index n23 of the prism layer 23 has the relationship of the following formula (1) with the refractive index n24 of the filling layer 24, and has the relationship of the following formula (2) with the refractive index n21 of the base film 21.
n23 <n24 (1)
n23 <n21 (2)
In short, the refractive index n23 is smaller than the refractive index n24 and the refractive index n21. Since the prism layer 23 is made of resin as described above, its refractive index n23 is larger than the refractive index na of air = 1.0.

  Since the refractive index n24 of the filling layer 24 is larger than the refractive index n23 of the prism layer 23, the collimating layer 25 collimates the light incident on the filling layer 24 to the front and emits it to the base film 21. If the refractive index n24 is increased, the light refraction angle at the lower surface 243 of the filling layer 24 is increased. The light beam collimated by the lower surface 243 reaches the surface of the prism 240 and is collimated further to the front surface. Therefore, the front luminance is further improved when the refractive index n24 is larger. A preferable refractive index n24 of the filling layer 24 is 1.5 <n24 ≦ 1.8. However, even if the refractive index n24 is 1.5 or less, the effect of the present invention can be achieved to some extent as long as it is larger than the refractive index n23.

  The refractive index of the prism layer 23 is smaller than the refractive index of the filling layer 24, but is larger than the refractive index na of air = 1.0. For this reason, the critical angle of light incident on the surface of the prism 240 in the collimating layer 25 is increased. If the critical angle is increased, the ratio of the total reflection of the light incident on the filling layer 24 is reduced, so that the emission of sidelobe light can be suppressed. This point will be described later. A preferable refractive index n23 of the prism layer 23 is 1.3 ≦ n23 ≦ 1.5. However, even if the refractive index n23 is outside the above range, the effects of the present invention can be achieved to some extent if the refractive index n23 satisfies the expressions (1) and (2).

  The refractive index n21 of the base film 21 is larger than the refractive index n23. Therefore, when the light condensed on the front surface by the collimating layer 25 is incident on the surface 212 of the base film 21, it is further collimated on the front surface. Therefore, the base film 21 contributes to the improvement of the front luminance.

  As described above, the lens sheet 15 can improve the front luminance by the columnar lens layer 22, the base film 21, and the collimating layer 25. Furthermore, the lens sheet 15 can suppress the occurrence of side lobes and can have a wide viewing angle in the left-right direction. Further, luminance unevenness is also suppressed. Hereinafter, these effects will be described in detail.

[Suppression of side lobe]
The lens sheet 15 can suppress the occurrence of side lobes in the vertical luminance viewing angle characteristics by the collimating layer 25 and the columnar lens layer 22.
The reason why the collimating layer 25 suppresses the side lobes is not necessarily clear, but it is assumed that the following matters are mainly caused.

  First, a side lobe generation mechanism in a conventional prism sheet will be described. In FIG. 9, among the light beams incident on the prism PL on the conventional prism sheet 100, the light beam R2 is totally reflected by one side surface BP1 of the prism PL and then transmitted through the other side surface BP2 and emitted to the outside. The light ray R2 forms a side lobe.

  Specifically, the light ray R0 emitted in the direction of the angle θ0 from the normal line n0 (front surface of the display screen 29) of the emission surface of the surface light source 11 reaches the side surface BP1 of the prism PL. When the incident angle θi1 of the light ray R0 is larger than the critical angle θc1, the light ray R0 is totally reflected and propagates in the prism PL as the light ray R1. If the incident angle θi2 is smaller than the critical angle θc1 when the light ray R1 reaches the side surface BP2, the light ray R1 is emitted to the outside as sidelobe light R2 having a wide angle with respect to the normal line n0 (front). .

  In contrast, the collimating layer 25 suppresses the generation of sidelobe light. Referring to FIG. 10, the collimating layer 25 includes a prism layer 23 and a filling layer 24 that satisfy the relationship of formula (1), and a prism 240 is filled between the plurality of prisms 230.

  Here, it is assumed that the refractive index n24 of the filling layer 24 is the same as the refractive index n100 of the prism sheet 100. In this case, the relative refractive index when the light beam enters the prism layer 23 from the filling layer 24 is smaller than the relative refractive index when the light beam enters the air from the prism sheet 100. This is because the refractive index n23 of the prism layer 23 made of resin is larger than the refractive index of air (= 1.0).

  Since the relative refractive index is small, the critical angle θc0 on the surfaces 241 and 242 of the prism 240 in the collimating layer 25 is larger than the critical angle θc1 on the surfaces BP1 and BP2 of the prism PL of the prism sheet 100. As a result, on the surface of the prism 240, it is considered that the ratio of the light ray R0 that is totally reflected is reduced, and the emission of the sidelobe light R2 can be suppressed.

  Moreover, it is estimated that the columnar lens layer 22 can suppress the emission of sidelobe light for the following reason. Referring to FIG. 11, light ray R <b> 0 incident at the same angle θ <b> 0 as in FIG. 9 reaches boundary surface BP <b> 3 on the convex surface of columnar lens 221. When the incident angle θi1 of the light ray R0 is larger than the critical angle θc2, the light ray R0 is totally reflected and reaches the boundary surface BP4 on the convex surface. At this time, the incident angle θi2 of the light ray R0 is often larger than the critical angle θc2. Therefore, the light ray R0 is totally reflected again and returns to the surface light source 11. In short, in the columnar lens 221, the light beam that has been totally reflected once is more likely to be totally reflected again and return to the surface light source than to be transmitted and emitted to the outside. Therefore, emission of the side lobe light R2 can be suppressed, and generation of side lobes in the luminance angle distribution can be suppressed.

  For the above estimated reason, the lens sheet 15 suppresses the occurrence of side lobes in the luminance viewing angle characteristics in the vertical direction. As a result, it is possible to obtain a viewing angle characteristic of luminance showing a natural orientation distribution in which the luminance gradually decreases with the viewing angle widening with a viewing angle of 0 deg as a peak.

[Realization of wide viewing angle in the horizontal direction]
The columnar lens 221, the prism 230, and the prism 240 of the lens sheet 15 are all arranged in the same direction as the arrangement direction of the fluorescent tubes 13. Therefore, light in the left-right direction (x direction in the figure) is less likely to be condensed than in the up-down direction (y direction in the figure). As a result, a wide viewing angle can be realized in the luminance angle characteristic in the left-right direction.

  FIG. 12 shows an example of the luminance angle dependency of the lens sheet 15. The horizontal axis in FIG. 12 is the viewing angle. With respect to the viewing angle, the normal direction (front) of the display screen is defined as the 0 deg axis, the tilt angle from the 0 deg axis in the vertical direction is defined as the vertical viewing angle, and the tilt angle from the 0 deg axis in the horizontal direction is defined as the left and right viewing angle. Of the left and right viewing angles, the tilt angle (viewing angle) from the normal to the right is indicated by plus (+), and the tilt angle (viewing angle) from the normal to the left is indicated by minus (−). Similarly, of the vertical viewing angles, the inclination angle (viewing angle) from the normal to the upward direction is indicated by plus (+), and the inclination angle (viewing angle) from the normal to the downward direction is indicated by minus (−). . The vertical axis in FIG. 12 indicates relative luminance. The relative luminance is a luminance ratio at each viewing angle when the front luminance when the liquid crystal panel is directly laid on the surface light source is used as a reference (1.0). The broken line in FIG. 12 indicates the viewing angle characteristic of the luminance in the left-right direction, and the solid line indicates the viewing angle characteristic of the luminance in the vertical direction.

  Referring to FIG. 12, the luminance viewing angle characteristics of lens sheet 15 have a natural distribution in which the viewing angle is 0 deg in both the vertical and horizontal directions, and the luminance gradually decreases as the viewing angle widens.

  Further, the luminance viewing angle characteristic in the left-right direction is wider than that in the up-down direction. More specifically, when used in a liquid crystal display device including a liquid crystal panel, the viewing angle range in which the luminance is ½ or more of the front luminance is 50 degrees (−50 deg to +50 deg) or more. The user of the liquid crystal display device has more opportunities to view the display screen from the left and right diagonal directions than the opportunity to view the display screen from the upper and lower diagonal directions. In the present embodiment, the horizontal direction is a wide viewing angle. Therefore, even if the user looks at the display screen from an oblique direction, it is difficult for the user to feel an extreme change in luminance, and the display screen can be viewed without a sense of incongruity.

[Improve front brightness]
In the lens sheet 15, the light incident from the lower surface is condensed on the front by each of the collimating layer 25, the base film 21, and the columnar lens layer 22. Therefore, the front luminance can be further improved with one sheet.

  The refractive index n24 of the filling layer 24 in the collimating layer 25 is larger than the refractive index n23 of the prism layer 23. Therefore, the collimating layer 25 condenses the diffused light from the surface light source in the front and emits it to the base film 21.

  The refractive index n21 of the base film 21 is larger than the refractive index n23 of the prism layer 23. Therefore, the light beam incident on the base film 21 from the collimating layer 25 is refracted on the lower surface of the base film 21, further condensed on the front surface, and emitted to the columnar lens layer 22.

  The convex surfaces of the plurality of microlens portions 222 in the columnar lens layer 22 have a curvature. Therefore, the columnar lens layer 22 collects not only light in the vertical direction (y direction) and left and right direction (x direction) but also light in the diagonal direction. In short, the columnar lens layer 22 collects light in all directions. Therefore, the columnar lens layer 22 condenses incident light further on the front and emits it to the outside.

  As described above, in the lens sheet 15, each of the collimating layer 25, the base film 21, and the columnar lens layer 22 collimates the incident light beam in the front. Therefore, the front luminance can be further improved with a single lens sheet 15.

[Preventing uneven brightness]
As described above, when the plurality of fluorescent tubes 13 are arranged in the vertical direction, luminance unevenness is likely to occur in the vertical direction. Specifically, the luminance is highest at the portion directly above the fluorescent tube 13, and the luminance is likely to be lowest at the intermediate portion between the adjacent fluorescent tubes 13.
However, in the lens sheet 15 according to the present embodiment, the direction in which the prism 230 and the prism 240 are arranged is the same as the direction in which the plurality of fluorescent tubes 13 in the surface light source 11 are arranged, and the columnar lenses 221 are arranged in parallel. The direction is also the same as the direction in which the fluorescent tubes 13 are juxtaposed. Therefore, the lens sheet 15 collects more light in the vertical direction (y direction in FIG. 1) and emits it to the front. As a result, it is possible to suppress the occurrence of luminance unevenness.

[Other examples of columnar lens layers]
In the above-described embodiment, the top Tc of the microlens portion 222 has a staggered arrangement, but the top Tc may have a lattice arrangement as shown in FIG. However, the staggered arrangement has a higher light collection function because the width of the gap 223 is narrower than the lattice arrangement.

  4 and 13, each microlens portion 222 has the same size, but as shown in FIG. 14, the columnar lens 221 may include a plurality of microlens portions 222 and 227 having different sizes. . Since the microlens portions 222 and 227 have different heights, the lens sheet 15 is difficult to stick to the liquid crystal panel 20. As a result, it is possible to suppress the occurrence of a wet-out phenomenon (screen blur) on the display screen 29 of the liquid crystal panel 20. Moreover, the occurrence of moire can be further suppressed by arranging the microlens portions 222 and 227 at random.

  The plurality of microlens portions having different sizes may have different heights. Therefore, in a plurality of microlenses, as shown in FIG. 14, the radii of curvature may be different from each other, the radii of curvature at the periphery when viewed from directly above are the same, and only the heights are different from each other. Also good.

[Prevention of moire]
When the prism 230, the prism 240, and the columnar lens layer 221 are arranged in the same direction, moiré is likely to occur if the arrangement pitch of these lenses is constant.
Therefore, preferably, the arrangement pitch of the prisms 230 and / or the arrangement pitch of the columnar lenses 221 are made non-uniform. For example, as shown in FIG. 15, a plurality of prisms 230 having the same apex angle are arranged so that the distances Pn and Pn + 1 (n = 1 to 4) between the ridge lines of adjacent prisms 230 are different from each other. If the arrangement pitch of the prisms 230 and / or the columnar lenses 221 is not uniform, the pitch of the columnar lenses 221 and the pitch of the prisms 230 are difficult to synchronize with each other at a constant period, and the occurrence of moire can be suppressed.

  As shown in FIGS. 16 and 17, when the collimating layer 25 is viewed from above, the pitches of the adjacent prisms 240 are the same, but are formed between the ridgelines of the prisms 240, that is, between the adjacent prisms 230. The valley line 400 may be irregularly meandering in the width direction of the prism 230 instead of a straight line. Also in this case, since the pitch of the columnar lenses 221 and the pitch of the prisms 230 are difficult to synchronize with each other at a constant period, the occurrence of moire can be suppressed. In FIG. 16, the valley line 400 meanders, but the ridge line 500 of the prism 230 may meander. 16 and 17, the height of the prism 230 may vary in the longitudinal direction of the prism 230.

  As shown in FIG. 18, the arrangement pitch of the prisms 230 is preferably smaller than the arrangement pitch of the columnar lenses 221. The prism 230 is made of a low refractive index resin, but the low refractive index resin is expensive to manufacture. Therefore, it is preferable that the prism layer 23 is formed with as little resin as possible. If the pitch of the prisms 230 in the prism layer 23 is made smaller than the arrangement pitch of the columnar lenses 221, the period in which the arrangement pitch of the columnar lenses 221 and the prisms 230 is synchronized becomes longer, and the occurrence of moire is suppressed to some extent.

  In addition, particles (fillers) having a refractive index different from the refractive index of the resin constituting the filling layer 24 may be contained in the filling layer 24 that is the lowermost layer of the lens sheet 15. Referring to FIG. 19, the filling layer 24 includes a transparent resin 244 and a plurality of particles (fillers) 245 dispersed in the resin. The filler 245 has a refractive index different from that of the resin.

  The light incident on the inside of the filling layer 24 is diffused to some extent by the filler 245 and emitted to the prism layer 23. Therefore, the occurrence of luminance unevenness and moire can be suppressed.

  The filler 245 may be made of an organic material or an inorganic material. The filler 245 is, for example, calcium carbonate, barium sulfate, titanium oxide, silicone fine particles, acrylic fine particles, styrene fine particles, MS fine particles, glass fine particles, or the like. These may be used alone or in combination. The particle size of the filler 245 is not particularly limited, but if it is excessively large, it is difficult to form the filling layer 24. On the other hand, if it is too small, the diffusion effect is small. A preferable particle size of the filler 245 is 0.5 μm to 10 μm. Further, if the filler 245 is excessively contained, the front luminance of the lens sheet 15 is lowered. Therefore, the preferable filler 245 content is 0.1 to 30 parts by weight with respect to 100 parts by weight of the resin.

  Although the backlight 10 is a direct type in the present embodiment, the above-described effects of the present invention can be achieved to some extent even if the backlight 10 is an edge light type.

[Production method]
As an example of the manufacturing method of the lens sheet 15 described above, a manufacturing method using a roll-to-roll method will be described.

  First, the collimating layer 25 is formed on the surface 212 of the base film 21. A cylindrical first roll having a film-like base film 21 wound on its surface and a prism roll plate 50 having transfer grooves 52 of the prism 230 on its surface are prepared as shown in FIGS. The transverse shape of the transfer groove 52 is the same as the transverse shape of the prism 230, and the transverse shape of the ridge 53 corresponding to the edge (flange portion) of the transfer groove 52 is the same as the transverse shape of the prism 240. . The transfer groove 52 is juxtaposed in the roll axis direction. As shown in FIG. 16, when the ridgeline of the prism 240 is meandered, the transfer groove 52 is not constant in the height of the ridge 53 as shown in FIG. 22, and the pitch P0 is the same as that in FIG. However, it has portions with different depths. That is, the angle (vertical angle) of the valley of the transfer groove 52 is constant, and the depth is changed in the longitudinal direction of the transfer groove 52. In this case, since the ridge line of the prism 240 corresponds to the top of the ridge 53 of the transfer groove 52, the ridge line of the formed prism 240 becomes a wavy curve meandering in the width direction of the prism 240.

  The first roll and the roll plate 50 are arranged so that the axial direction of the first roll is parallel to the axial direction of the roll plate 50. After the arrangement, the surface of the roll plate 50 is filled with an ionizing radiation curable resin having a refractive index n23 lower than the refractive index n21 of the base film 21. The charged ionizing radiation curable resin is transferred onto the base film 21 fed from the first roll while rotating the first roll and the roll plate 50. At this time, the transfer is performed while the base film 21 is sandwiched between the backup roll disposed opposite to the roll plate 50 with the base film 21 interposed therebetween and the roll plate 50. The transferred ionizing radiation curable resin is irradiated with ionizing radiation to cure the ionizing radiation curable resin, thereby forming the prism layer 23.

  After forming the prism layer 23, the filling layer 24 is formed on the prism layer 23. First, a roll plate having a smooth surface is prepared. Next, an ionizing radiation curable resin having a refractive index n24 higher than the refractive index n23 is applied to the roll plate. A roll plate having a surface coated with an ionizing radiation curable resin is pressed against the surface of the prism layer 23 on which the prism 230 is formed to transfer the ionizing radiation curable resin. Then, by irradiating with ionizing radiation, the transferred ionizing radiation curable resin is cured, and the filling layer 24 is formed.

  The filling layer 24 may be manufactured by the following method instead of the above method. First, a paint in which a resin having a refractive index n24 higher than the refractive index n23 of the prism layer 23 is dissolved in a solvent is prepared. Using the gravure coater or the like, the prepared paint is uniformly applied on the prism layer 23. The applied paint is dried to form the filling layer 24.

  Through the above steps, the collimating layer 25 is formed on the surface 212 of the base film 21. The base film 21 on which the collimating layer 25 is formed is arranged in parallel in the axial direction.

  Next, the columnar lens layer 22 is formed on the surface 211 of the base film 21. The roll plate for the columnar lens layer has a transfer groove for the columnar lens 221 on the surface. Each transfer groove extends in the circumferential direction of the roll plate and is arranged in the axial direction. The transverse shape of the transfer groove corresponds to the transverse shape of the columnar lens 221.

  The columnar lens 221 has a shape in which the microlens portions 222 are connected in series. However, the columnar lens 221 has an advantage that bubbles are less likely to remain in the interior as compared with the microlens on the microlens array. The roll plate for the microlens array has a plurality of transfer holes on the surface. The plurality of transfer holes are independent of each other to correspond to the microlens. Therefore, once a bubble enters the ionizing radiation curable resin filled in the transfer hole, the bubble is difficult to escape from the ionizing radiation curable resin. This is because the ionizing radiation curable resin does not flow easily in the transfer hole. However, the transfer groove of the roll plate used in this embodiment is formed by connecting holes corresponding to transfer holes for the microlens array. For this reason, even if bubbles enter the filled ionizing radiation curable resin, the ionizing radiation curable resin easily flows in the transfer groove, so that the bubbles are easily removed. As a result, bubbles can be prevented from remaining in the formed columnar lens 221.

  The feed roll, roll plate, and take-up roll are arranged in this order so that their axial directions are parallel to each other. After the disposition, the transfer groove of the roll plate is filled with ionizing radiation curable resin.

  After filling, the delivery roll is rotated to deliver the base film, and the base film is conveyed from the delivery roll toward the roll plate. Subsequently, the roll plate is rotated to transfer the ionizing radiation curable resin filled in the transfer groove onto the base film. The ionizing radiation curable resin transferred by irradiating with ionizing radiation is cured to form a columnar lens 221 on the base film. The lens sheet 15 is manufactured through the above steps. The manufactured lens sheet 15 is wound up on a winding roll.

  In the manufacturing method described above, the collimating layer 25 is first formed and then the columnar lens layer 22 is formed. However, the columnar lens layer 22 may be formed first, and then the collimating layer 25 may be formed.

  As mentioned above, although the manufacturing method by the roll toe roll system using a roll plate was demonstrated as an example of the manufacturing method, the lens sheet 15 can be manufactured also by another manufacturing method. The collimating layer 25 and the columnar lens layer 22 may be formed using a plate-shaped plate instead of the roll-to-roll method. The columnar lens layer 22 may be formed by an extrusion method, a hot press method, or an injection molding method.

  In the manufacturing method described above, the ionizing radiation curable resin is applied on the roll plate, but the ionizing radiation curable resin may be applied on the base film 21 to form an ionizing radiation curable resin film. In this case, for example, the ionizing radiation curable resin film on the base film 21 is pressed against the roll plate to transfer the columnar lens 221 and the prism 230. Moreover, you may apply | coat ionizing radiation hardening resin to the surface of a roll plate, and the surface of the base film 21, respectively.

  A plurality of lens sheets having different lens shapes were manufactured, and front luminance and viewing angle characteristics of luminance were investigated.

試験番号１のレンズシートは、図３〜５に示すように、複数の柱状レンズを含む柱状レンズ層と、プリズム層と充填層を有した。柱状レンズ内の各マイクロレンズ部は半球状であり、その半径Ｒは１５μｍであった。また、マイクロレンズ部の配列は、図４と同様に千鳥配列であり、マイクロレンズ部の頂上Ｔｃの左右方向（ｘ方向）の配列ピッチＰｘは２５μｍ、上下方向（ｙ方向）の配列ピッチＰｙは３０μｍであった。柱状レンズ層の硬化後の屈折率は１．５６であった。 Lens sheets of test numbers 1 to 6 shown in Table 1 were produced by a roll-to-roll method. A polyethylene terephthalate (PET) film was used as the base film, and an ultraviolet curable resin was used as the ionizing radiation curable resin.

The lens sheet of Test No. 1 had a columnar lens layer including a plurality of columnar lenses, a prism layer, and a filling layer, as shown in FIGS. Each microlens portion in the columnar lens was hemispherical, and its radius R was 15 μm. Further, the arrangement of the microlens portions is a staggered arrangement as in FIG. 4, the arrangement pitch Px in the left-right direction (x direction) of the top Tc of the microlens portion is 25 μm, and the arrangement pitch Py in the up-down direction (y direction) is It was 30 μm. The refractive index after curing of the columnar lens layer was 1.56.

  The apex angle of each prism of the prism layer of test number 1 was 110 degrees, and the distance (arrangement pitch) P230 between vertices of adjacent prisms was 50 μm. The height H230 of each prism was 17.5 μm. The refractive index after curing of the prism layer was 1.49, and the refractive index after curing of the filling layer was 1.56.

  Similarly to Test No. 1, the lens sheet of Test No. 2 also had a columnar lens layer, a prism layer, and a filling layer. However, the columnar lens layer had the shape shown in FIG. 14, and the columnar lens had two types of microlens portions. Each microlens part was hemispherical, and its radius R was 15 μm or 20 μm. The other configuration was the same as that of test number 1.

  Similarly to the test number 1, the lens sheet of the test number 3 also has a columnar lens layer, a prism layer, and a filling layer. However, the apex angle of the prism of the prism layer was 90 degrees. Further, the arrangement pitch P230 and the height H230 were random. The other configuration was the same as that of test number 1.

  The lens sheet of test number 4 had a microlens array layer shown in FIG. 23 instead of the columnar lens layer, as compared with the lens sheet of test number 1. That is, the test number 4 had a prism layer formed on one surface of the base film, a filling layer formed on the prism layer, and a microlens array layer formed on the other surface of the base film. .

  As shown in FIG. 23, the microlens array layer had a plurality of microlenses. Each microlens was a hemisphere, and its radius R was 16.25 μm. Adjacent microlenses were not in contact with each other. The arrangement of the microlenses was a staggered arrangement, and the arrangement pitches Px and Py (see FIG. 23) were both 50 μm. The refractive index of the microlens layer was 1.56. The other configuration was the same as that of test number 1.

  As a lens sheet of test number 5, a microlens array sheet having the shape shown in FIG. 24 was prepared. Each microlens is a semi-ellipsoid and is staggered so that the longitudinal direction thereof is parallel to the left-right direction (x direction). The major axis length was 62 μm and the minor axis length was 28.75 μm. The arrangement pitch Px defined in FIG. 24 was 62.5 μm, and Py was 50 μm. Each microlens was independent of each other.

  For test number 6, a prism sheet having a plurality of prisms arranged in parallel with each other was prepared. The apex angle of each prism was 110 degrees, the arrangement pitch was 50 μm, and the height was 17 μm.

[Investigation method of optical characteristics]
The front luminance and luminance viewing angle characteristics of the manufactured lens sheets of test numbers 1 to 6 were investigated. First, a 32-inch surface light source that accommodates 18 EEFLs arranged in parallel in the vertical direction (y direction) and has a diffusion plate was prepared for each test number. And the lens sheet of each test number was laid in the prepared surface light source, and the backlight of each test number was manufactured. At this time, the lens sheets of Test Nos. 1 to 3 are laid so that the columnar lenses are arranged side by side in the vertical direction (y direction), and the lens sheets of Test No. 4 are arranged in parallel with the prisms of the prism layer in the vertical direction. Laid to be. The microlens array sheet with test number 5 is laid so that the long axis of the microlens is parallel to the longitudinal direction of the EEFL, and the prism sheet with test number 6 is such that the prisms are juxtaposed in the vertical direction. Laid.

  A liquid crystal panel was laid on the manufactured backlight of each test number, and the luminance viewing angle characteristics were investigated. As described above, the viewing angle is the normal direction (front) of the lens sheet as 0 deg axis, the tilt angle from the 0 deg axis to the vertical direction is the vertical viewing angle, and the tilt angle from the 0 deg axis to the horizontal direction is the left viewing angle. did. The luminance at each vertical viewing angle and left and right viewing angle was measured with a luminance meter. The luminance measurement location was at the center of the display screen.

  Further, a liquid crystal panel was laid on a surface light source on which no lens sheet was laid, and the front luminance was measured. The measured front brightness was defined as the reference front brightness.

  The ratio of the front luminance at the viewing angle of 0 deg obtained from the luminance viewing angle characteristics of Test Nos. 1 to 6 to the reference front luminance was calculated and used as the front luminance ratio of each test number.

  Further, a viewing angle range (hereinafter referred to as 1/2 vertical viewing angle) having a luminance of 1/2 or more of the front luminance among the viewing angle characteristics of the luminance in the vertical direction was obtained. In addition, a viewing angle range (hereinafter referred to as ½ left and right viewing angle) having a luminance of 1/2 or more of the front luminance among the viewing angle characteristics of luminance in the left and right directions was obtained.

  Luminance unevenness and moire were evaluated by the following methods. The above-mentioned liquid crystal panel was laid on the backlights of the above test numbers 1 to 6. Then, whether or not luminance unevenness and moire were generated on the display screen of the liquid crystal panel was visually evaluated.

[Investigation result]
The survey results are shown in Table 1. Here, “54” in the 1/2 left / right viewing angle column of test number 1 indicates that the viewing angle range of ½ or more of the front luminance is a range of −54 deg to +54 deg. The same applies to other test numbers. In addition, “◯” marks in the luminance unevenness column and the moire column indicate that no luminance unevenness or moire has occurred, and “x” indicates that luminance unevenness or moire has occurred.

  The luminance viewing angle characteristics of Test No. 1 were as shown in FIG. The viewing angle characteristics of test number 2 were as shown in FIG. 25, and the viewing angle characteristics of test numbers 3 to 6 were as shown in FIGS. The solid line in the figure indicates the viewing angle characteristic in the vertical direction, and the broken line indicates the viewing angle characteristic in the horizontal direction.

  As shown in Table 1, in the lens sheets of test numbers 1 to 3, the front luminance ratio was 1.65 or more, and high front luminance was exhibited. As shown in FIGS. 12, 24, and 25, the luminance viewing angle characteristics have a natural distribution in which the viewing angle is 0 deg as a peak and the luminance gradually decreases as the viewing angle increases. And side lobes did not occur at a viewing angle of 70 degrees or more. Furthermore, the width of the viewing angle characteristic in the left-right direction was wider than that in the up-down direction, and the 1/2 left-right viewing angles were all 50 degrees or more. Moreover, in the lens sheets of test numbers 1 to 3, luminance unevenness and moire did not occur.

  In contrast, in the lens sheet of test number 4, the front luminance ratio was 1.65 or more, but the ½ left-right viewing angle was less than 50 deg. Since each microlens was independent of each other, as a result of equivalently condensing light in all directions, it is considered that the viewing angle in the left-right direction was narrowed to the same extent as in the up-down direction, as shown in FIG. In addition, uneven brightness occurred.

  The microlens array sheet of test number 5 had a front luminance ratio of less than 1.65, although the ½ left-right viewing angle was as large as 80 deg. Since the microlens was a semi-ellipsoid, it is considered that the light collecting function was low. In addition, uneven brightness occurred.

  The lens sheet of test number 6 had a prism apex angle of 110 degrees, and thus no significant side lobe was generated in the luminance viewing angle characteristics. However, as in FIG. 30, the luminance viewing angle characteristics in the left-right direction did not have a natural distribution. Moreover, the front luminance ratio was less than 1.65. Furthermore, luminance unevenness occurred.

  While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

It is a perspective view of the liquid crystal display device provided with the lens sheet by embodiment of this invention. It is sectional drawing in line segment II-II in FIG. It is a perspective view of the lens sheet in FIG. FIG. 4 is a top view of the lens sheet shown in FIG. 3. It is sectional drawing in line segment VV in FIG. It is a longitudinal cross-sectional view of the columnar lens shown in FIG. It is a cross-sectional view of the other columnar lens which has a shape different from the columnar lens shown in FIGS. It is a cross-sectional view of the other columnar lens which has a shape different from the columnar lens shown in FIGS. It is a schematic diagram for demonstrating the locus | trajectory of the light ray which injected into the prism sheet. It is a schematic diagram for demonstrating the locus | trajectory of the light ray which injected into the collimating layer in FIG. It is a schematic diagram for demonstrating the locus | trajectory of the light ray which injected into the columnar lens in FIG. It is a figure which shows the viewing angle characteristic of the brightness | luminance of the lens sheet shown to FIGS. It is a top view of the other lens sheet which has a shape different from FIG. It is a top view of the other lens sheet which has a shape different from FIG.4 and FIG.13. It is sectional drawing of the other lens sheet which has a different cross section from FIG. It is a bottom view of a collimate layer among lens sheets which have a shape different from Drawings 3-5. It is sectional drawing in line segment XVII-XVII in FIG. It is sectional drawing of the other lens sheet which has a shape different from FIGS. It is sectional drawing of the other lens sheet which has a shape different from FIGS. 3-5, FIG. 16, and FIG. It is a perspective view of the roll plate for manufacturing the lens sheet shown in FIG. It is a figure which shows a part of roll plate in FIG. It is a figure which shows a part of roll plate different from FIG. It is a top view of the lens sheet used in the Example. It is a top view of the lens sheet of a shape different from FIG. It is a figure which shows the viewing angle characteristic of the brightness | luminance obtained with the lens sheet used in the Example. It is a figure which shows the viewing angle characteristic of the brightness | luminance obtained with the lens sheet different from FIG. It is a figure which shows the viewing angle characteristic of the brightness | luminance obtained with the lens sheet different from FIG.25 and FIG.26. It is a figure which shows the viewing angle characteristic of the brightness | luminance obtained with the lens sheet different from FIGS. It is a figure which shows the viewing angle characteristic of the brightness | luminance obtained with the lens sheet different from FIGS. It is a figure which shows the viewing angle characteristic of the brightness | luminance obtained with the prism sheet which has a prism whose apex angle is 90 degree | times in a transverse shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Backlight 11 Surface light source 13 Fluorescent tube 15 Lens sheet 21 Base film 22 Columnar lens layer 23 Prism layer 24 Filling layer 25 Collimate layer 221 Columnar lens 222 Microlens part 223 Clearance 224 Virtual surface 230,240 Prism

Claims (11)

A base material layer having a first surface and a second surface opposite to the first surface;
A columnar lens layer each including a plurality of plano-convex lens portions connected in a row and including a plurality of columnar lenses arranged in parallel on the first surface;
A plurality of prisms arranged side by side on the second surface, the prism layer having a lower refractive index than the base material layer;
A lens sheet comprising: a filler layer formed on the prism layer and having a higher refractive index than the prism layer. The lens sheet according to claim 1,
The lens sheet, wherein the columnar lens is parallel to the prism. The lens sheet according to claim 1 or 2,
A lens sheet, wherein a gap is formed between the adjacent columnar lenses. The lens sheet according to any one of claims 1 to 3,
The lens sheet according to claim 1, wherein the plano-convex lens portions adjacent in the same columnar lens are in surface contact with each other. The lens sheet according to any one of claims 1 to 4,
The columnar lens includes a plurality of plano-convex lens portions having different heights. The lens sheet according to any one of claims 1 to 5,
The lens sheet, wherein a ridge line of the prism or a valley line formed between adjacent prisms meanders in the width direction of the prism. The lens sheet according to any one of claims 1 to 6,
The lens sheet, wherein the arrangement pitch of the prisms is not uniform. The lens sheet according to any one of claims 1 to 7,
A lens sheet, wherein the height of the prism varies in the longitudinal direction of the prism. It is a lens sheet given in any 1 paragraph of Claims 1-8,
The packed bed is
Resin,
A lens sheet comprising a plurality of particles dispersed in the resin and having a refractive index different from that of the resin. A surface light source;
A lens sheet laid on the surface light source,
The lens sheet is
A base material layer having a first surface and a second surface opposite to the first surface;
A columnar lens layer each including a plurality of plano-convex lens portions connected in a row and including a plurality of columnar lenses arranged in parallel on the first surface;
A plurality of prisms arranged side by side on the second surface, and a prism layer having a refractive index lower than that of the base member;
And a filling layer formed on the prism layer and having a higher refractive index than the prism layer. A surface light source;
A lens sheet laid on the surface light source;
A liquid crystal panel laid on the lens sheet,
The lens sheet is
A base material layer having a first surface and a second surface opposite to the first surface;
A columnar lens layer each including a plurality of plano-convex lens portions connected in a row and including a plurality of columnar lenses arranged in parallel on the first surface;
A plurality of prisms arranged side by side on the second surface, and a prism layer having a refractive index lower than that of the base member;
A liquid crystal display device comprising: a filler layer formed on the prism layer and having a higher refractive index than the prism layer.

Images