JP3808598B2 - Surface light source device, polarized light source device, and liquid crystal display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
  The present invention is an optical path control useful for preventing moire and improving visibility in liquid crystal display devices and the like.LayerThe present invention relates to a surface light source device and a polarized light source device that are excellent in uniformity of light emission and effective use efficiency of light.
[0002]
BACKGROUND OF THE INVENTION
While the light transmittance of liquid crystal cells and the like decreases with colorization and high definition, a bright and easy-to-see liquid crystal display device is required. With the provision of light becoming an important issue, the group to which the present inventors belonged previously has periodic fine prism-like irregularities on at least one of the upper and lower surfaces for the purpose of solving the problem. Has been proposed (Japanese Patent Application No. Hei 7-321036).
[0003]
However, as illustrated in FIG. 6, the light guide plate 3 has a drawback in that the light emission inevitably becomes a stripe pattern of the bright portion 38 and the dark portion 39 based on the structure for improving the light utilization efficiency. There is a problem that moire is generated due to interference with pixels such as a liquid crystal cell, the display is glaring and inferior in quality, and the directivity of the emitted light is deviated from the direction advantageous for visual recognition of the liquid crystal display device.
[0004]
The moire problem can be solved by making the period of fine prism-like irregularities on the light guide plate sufficiently smaller than 1/5 of the pixel size. Incidentally, for a pixel size of 100 μm × 300 μm, moire can be solved by setting a period of fine prism-like irregularities of 20 μm or less.
[0005]
However, in the above case, the period of the fine prism-like irregularities is likely to cause interference and diffraction, and there is a drawback that the display quality is lowered due to a decrease in the light output rate and the dispersion of light. As the degree of fineness increases, the height needs to be several μm or less, especially 1 μm or less, which makes it difficult to manufacture the light guide plate and makes it difficult to emit light due to roundness of the prism.
[0006]
On the other hand, in the application of a known method for solving the moire problem by leveling light emission with a diffusion plate, there is a difficulty in reducing the advantages of the light guide plate. In other words, the leveling of the bright and dark stripes through the diffuser plate requires a wide range of diffusibility to eliminate moire due to the Gaussian distribution of the diffusion characteristics, which reduces the directivity of the emitted light. However, the amount of emitted light in the direction advantageous for visual recognition of the liquid crystal display device is reduced, and the amount of light that can be used effectively is reduced, and it is difficult to control the correction of the position and direction of the light emission, and the light utilization efficiency is also improved by backscattering There was a downside.
[0007]
On the other hand, the directivity problem of the emitted light described above is that the maximum intensity direction of the emitted light is not the vertical direction of the emission surface that is most advantageous for visual recognition, but is slightly different in the direction away from the light source than the vertical direction, typically 5-20. It has an angle of degrees, and this direction means that the light transmittance of the liquid crystal cell is low and the display inversion rate is high, so that improvement in the effective utilization efficiency of light and display quality is desired.
[0008]
An optical path control system via a prism sheet has been proposed, but it is difficult to overcome the directivity problem described above with a conventional prism sheet. That is, as shown in FIG. 9, the conventional prism sheet 9 is composed of a groove composed of two inclined surfaces 91 having an inclination angle of about 45 degrees, and the light α emitted from the light guide plate at an angle of 5 to 20 degrees is substantially applied to the two inclined surfaces 91. Incident with the same probability and dispersed in two optical paths (α₁), Large angle outgoing light α_ThreeOr return light α to the light guide plate by total reflection_FourIt becomes.
[0009]
Therefore, the optical path direction β in which most of the emitted light α is excellent in the desired verticality.₂However, the effective utilization efficiency of the light is greatly reduced. The emitted light is β₂Is the incident light β having a large incident angle of about 40 degrees, and therefore, in the conventional prism sheet, near vertical light having an emission angle of about 20 degrees or less from the light guide plate is more vertical. It is difficult to change the optical path in a direction that excels. Further, in an illuminating device described in Japanese Patent Application Laid-Open No. 9-146092, in which a polarization separating unit and an optical path conversion unit are sequentially provided on a wedge-shaped light guide, depending on the arrangement of the polarization separating unit, the optical path disposed thereon The conversion means disturbs the transmitted polarized light and the light use efficiency is lowered, and such an arrangement state is not preferable. Further, the light emitted from the light guide plate is assumed to have a large angular direction, and it is difficult to make the near vertical light more vertical.
[0010]
[Technical Problem of the Invention]
The present invention can prevent the occurrence of moire between pixels when a light guide plate in which emitted light exhibits directivity close to the vertical direction and forms a stripe pattern of bright and dark portions is applied to a liquid crystal cell. An object of the present invention is to form a liquid crystal display device with excellent quality, and to bring the emitted light from the light guide plate close to the vertical direction that is advantageous for visual recognition of the liquid crystal display device.
[0011]
[Means for solving problems]
  The present inventionAt least one of the upper surface, the lower surface facing it, and the upper and lower surfaces of the plate-like object having the light source arrangement side surface between the upper surface and the lower surface periodically has fine prism-like irregularities in the direction along the light source arrangement side surface. On the light exit side of the light guide plate that emits the incident light from the light source arranged in the stripe pattern of the bright part and the dark part from one of the upper and lower surfaces,A streak-like groove composed of a gentle slope with an inclination angle of 5 to 35 degrees and a steep slope of 60 degrees or more with respect to the plane has a period of 10 to 80 μm periodically.LightRoad control layerThe groove of the optical path control layer intersects with the fine prism-like irregularities of the light guide plate at an angle of 5 to 40 degrees, and the gentle slope of the groove is thin in the direction away from the light source. InIt is characterized bySurface light source deviceIs to provide.
[0012]
【The invention's effect】
  Main departureClearlyAccording toOptical path control layerThe groove of the light source subdivides the emission lines based on the light guide plate, shortens the emission interval of the emission lines, and refines the period of the fine prism-like irregularities, and also refracts the emission lines through the gentle slope that forms the grooves. The luminance difference from the dark part is leveled, so that moire due to interference with the pixels of the liquid crystal cell can be reduced, and moire can also be suppressed by spherical waves due to diffraction based on the groove period.
[0013]
Also, most of the directional emission lines emitted from the light guide plate are incident on the gentle slope of the groove, and the optical path of the transmitted light is converted with good directivity in the thickness direction of the gentle slope based on the function of the wedge plate. Therefore, by arranging the optical path control layer so that the gentle slope of the groove is thin in the direction away from the light source, the optical path of the directional emission line emitted from the light guide plate is made closer to the vertical direction through refraction. It is possible to convert with good directivity, prevent deterioration of brightness due to diffusion, and maintain the directivity of the bright line emitted from the light guide plate well without damaging it by diffusion or dispersion, and can change the light path and reduce the light emitted from the light guide plate. It can be used in a low state and in a state of excellent verticality, and is excellent in the effective use efficiency of light.
[0014]
As a result of the above, although the light utilization efficiency is excellent and bright light is provided, the advantages of the light guide plate that has the disadvantage that the directivity of the emission of the striped bright line and the emitted light that cause the moire are shifted are utilized. It is possible to overcome the difficulties, and it is possible to form a backlight system that efficiently provides the light emitted in the direction effective for improving the visibility of liquid crystal display devices, etc., making a liquid crystal display device that is bright, easy to see and has low power consumption Can be formed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
  Of the present inventionSurface light source deviceIsAt least one of the upper surface, the lower surface facing it, and the upper and lower surfaces of the plate-like object having the light source arrangement side surface between the upper surface and the lower surface periodically has fine prism-like irregularities in the direction along the light source arrangement side surface. On the light exit side of the light guide plate that emits the incident light from the light source arranged in the stripe pattern of the bright part and the dark part from one of the upper and lower surfaces,Periodically having a streak-like groove composed of a gentle slope with an inclination angle of 5 to 35 degrees and a steep slope with 60 degrees or more with respect to a plane.An optical path control layer is arranged, the groove of the optical path control layer intersects the fine prism-like irregularities of the light guide plate at an angle of 5 to 40 degrees, and the gentle slope of the groove is thin in the direction away from the light source. In a state to becomeIt consists of things. ThatOptical path control layerExamples are shown in FIGS. 1 is an optical path control layer, 11 is a groove, 12 is a gentle slope, and 13 is a steep slope. Reference numeral 14 is a transparent substrate, and 2 is a diffusion layer. In the present inventionOkeThe optical path control layer can be formed in an appropriate form such as an independent optical path control plate made of a sheet or the like, or a component attachment layer formed directly on an optical component such as a light guide plate.
[0016]
The gentle slope in the optical path control layer is the main part of the optical path change by the wedge plate function, and a structure in which as much as possible, ideally 100% of light is incident on this part, has an effective light utilization efficiency. It is preferable from the viewpoint of improvement. From this point, the inclination angle θ of the gentle slope₁Is 5 to 35 degrees with respect to the plane. If the angle is less than 5 degrees, the effect of changing the optical path is poor, and if it exceeds 35 degrees, the projected area with respect to the plane is reduced when the same period is used, and that of the steep slope becomes relatively large, which increases the incidence efficiency on the gentle slope. Become scarce.
[0017]
The inclination angle of the gentle slope can be appropriately determined in accordance with the angle of light incident on it such as light emitted from the light guide plate in the above range. As shown in FIG. 1, when the incident angle α to the optical path control layer 1 is about 20 degrees or less, especially 5 to 20 degrees, the optical path changeability in the vertical direction (α₁, Α₂The angle of inclination of the gentle slope is preferably 7 to 30 degrees, more preferably 10 to 25 degrees.
[0018]
On the other hand, the steep slope has loss light that cannot effectively use the incident light. Therefore, an inclination angle θ of 60 degrees or more with respect to the plane is used because the incident light is suppressed as much as possible.₂It is said. A preferable inclination angle of the steep slope is 75 to 110 degrees, especially 85 to 90 degrees from the viewpoint of suppression of incident light.
[0019]
The gentle slope and the steep slope do not need to be flat, and may be curved surfaces or the like as long as the inclination angle is maintained, but the grooves formed thereof are periodically formed in a streak shape. The period can be appropriately determined according to the characteristics of incident light for the purpose of controlling the optical path, but is generally 80 μm or less, especially 65 μm or less, especially from the viewpoint of groove formation and bright line segmentation. 10 to 50 μm. Incidentally, when the period is less than 10 μm, it is necessary to make the groove depth 5 μm or less, and the difficulty of high-precision manufacturing increases. The optical path control layer can be thinned by forming a groove shape having a gentle slope periodically through a steep slope.
[0020]
The optical path control layer can be formed by an appropriate method using an appropriate material exhibiting transparency according to the wavelength region of incident light. Incidentally, in the visible light region, for example, a transparent resin or glass represented by an acrylic resin, a polycarbonate resin, an epoxy resin, or the like can be used.
[0021]
A preferable method for manufacturing the optical path control layer from the viewpoint of mass productivity is a method of transferring a shape by pressing a mold or a roll capable of forming a predetermined groove shape against a thermoplastic resin under heating, and forming a predetermined groove shape. Filling or casting a liquid resin that can be polymerized with heat, ultraviolet rays, radiation, etc. into a mold or roll, a method of polymerizing by coating, a method of polymerizing while coating on a transparent substrate, or after coating, heating and melting For example, a method of filling a mold that can be molded into a predetermined groove shape with a thermoplastic resin or a resin fluidized through heat or a solvent by an injection method or the like.
[0022]
In the present invention, as shown in FIG. 2, the optical path control layer may be formed as a laminate of the same or different materials, for example, as shown in FIG. It need not be formed as an integral monolayer of one material. As the transparent substrate, for example, an appropriate material such as a plastic film having a thickness of 30 to 500 μm can be used.
[0023]
The thickness of the optical path control layer can be appropriately determined depending on the purpose of use and the like, but generally it is 1 mm or less, especially 5 to 500 μm, especially 10 to 200 μm for the purpose of thinning. When the optical path control layer is formed as an optical path control plate or the like, a groove shape including a gentle slope and a steep slope may be provided on both the front and back surfaces. Further, the surface on which the groove shape including the gentle slope and the steep slope is provided may have an appropriate surface form such as a flat surface or a surface, and is not particularly limited.
[0024]
  As illustrated in FIG. 2, the optical path control layer 1 has one or both sides as required.ExpandedA scattering layer 2 can also be provided. The diffusion layer is intended to further suppress moire by the diffusion effect obtained by leveling the bright and dark areas as described above. In this case, the diffusion layer has a small diffusion angle, that is, a low diffusivity is used. The fall of property etc. can be controlled.
[0025]
  AboveThe optical path control layer changes the optical path according to the incident angle for various incident light.The present invention uses the optical path control layer.Surface light source deviceFormedThe In FIG.ThatSurface light sourceSetAn example is shown. In this configuration, the optical path control layer 1 is provided on the light emitting side of the light guide plate 3 that emits incident light from the light source 4 arranged on the side surface as a stripe pattern of bright and dark portions from one of the upper and lower surfaces.
[0026]
  As a light guide plate,lightFrom the point of obtaining a bright surface light source with excellent use efficiencyOf plateAt least one of the upper and lower surfaces has fine prism-shaped irregularities in the direction along the side of the light source arrangement.Periodically, preferablyLight guide plate having a period of 50 to 500 μmForYes.
[0027]
The example of the said light-guide plate was shown to Fig.4 (a)-(c). Moreover, the example of the fine prism-shaped unevenness | corrugation was shown to Fig.5 (a)-(c). In FIG. 4, 21 is an upper surface, 22, 26 and 27 are lower surfaces, 23 is a light source arrangement side surface, 24 is a lateral side surface, and 25 is a side end portion facing the light source arrangement side surface 23. In FIG. 5, 28 and 29 are convex portions, 30 is a concave portion, 31, 33 (34) and 37 are downward slopes, and 32, 35 and 36 are upward slopes.
[0028]
  Light guide plate,UpIt consists of a plate-shaped object which has a surface, the lower surface which opposes it, and the light source arrangement side surface between an upper surface and a lower surface. The plate-like object may be the same thick plate or the like, but preferably, as shown in the figure, the thickness of the side end portion 25 facing the light source arrangement side surface 23 is thinner than that of the light source arrangement side surface, especially 50% or less. The thickness of
[0029]
As a result of the thinning of the opposing side end, as shown by the thick arrow shown in FIG. 5 (a), the upward slope of the lower surface until the light incident from the side surface of the light source reaches the opposing side end as the transmission end. And the like. The incident light can be efficiently supplied to the target surface by being reflected from the reflection, and the light guide plate can be reduced in weight. Incidentally, when the lower surface is a straight surface as shown in FIG. 4A, the weight of the light guide plate having a uniform thickness can be about 75%.
[0030]
The fine prism-like unevenness provided on at least one of the upper and lower surfaces of the plate-like object is periodically formed as a convex portion or a concave portion on an inclined surface along the light source arrangement side surface. In addition, a convex part or a recessed part is based on the straight line 20 which connects the intersection with the lower surface of the slope which forms the convex part or the recessed part, whether the intersection (vertex) of a slope protrudes from the said straight line (convex), or is depressed ( Concave).
[0031]
Further, the slope forming the convex portion or the concave portion is composed of a downward slope and an upward slope based on a straight line connecting the intersection and the apex with the lower surface. As a result, in addition to the transmission light that is directly incident on the ascending slope, the transmission light that is incident on the descending slope and incident on the ascending slope via the reflection can be supplied to the exit surface by reflection via the ascending slope. Therefore, the light utilization efficiency can be improved accordingly. The down slope or the up slope is dependent on whether it is a down slope or an up slope in a direction away from the light source.
[0032]
The surface of the light guide plate on which the fine prism-like irregularities are provided is usually an inclined surface as described above, but the inclined shape is arbitrary, such as a linear surface as illustrated in FIG. An appropriate surface shape such as a curved surface as illustrated in FIG. When the surface is not a straight surface, it is preferably within a range of 5 degrees or less from the average inclination angle at all positions on the surface where the fine prism-shaped irregularities are provided, rather than the point of directing the outgoing direction of outgoing light (directivity).
[0033]
The shape of the convex part or the concave part forming the fine prism-like irregularities does not need to be formed as a linear inclined surface as illustrated in FIGS. 5A to 5C, and includes an inclined surface including a refracting surface and a curved surface. It may be formed by. Further, the convex portion or the concave portion need not have the same concave and convex shape or the shape of the entire surface, and the shape and angle gradually change from the light source arrangement side in terms of improving the perpendicularity of the emitted light. The structure is preferable, and in particular, the structure in which the inclination angle of the ascending slope with respect to the light guide plate plane sequentially increases from the light source side is preferable.
[0034]
The period of the convex part or the concave part is related to the interval between the stripe-like bright lines in the emitted light, and the period is 500 μm or less, especially 10 to 400 μm, as described above, from the viewpoint of averaging the brightness of the entire surface, etc. 50-300 micrometers is especially preferable.
[0035]
Further, the above-described downward slope forming the convex portion or the concave portion is inclined by an inclination angle θ with respect to the plane of the light guide plate as illustrated in FIG._ThreeIs preferably 10 degrees or less, more preferably 5 degrees or less, and particularly preferably 2 degrees or less. Note that, as illustrated in FIG. 5B, the downward slope allows the inclination angle to be 0 degree. In the illustrated example, the portion 34 having an inclination angle of 0 degrees is partially provided, but the entire portion between the ascending slopes may be a horizontal plane having an inclination angle of 0 degree through a step portion formed of a vertical surface or the like. Therefore, the downward slope in the present invention includes a horizontal plane having an inclination angle of 0 degree. By setting the range of such an inclination angle, as illustrated by a broken line arrow in FIG. 5A, light transmitted at an angle larger than the inclination angle is incident on the down slope 31 and reflected. Based on the inclination angle of the slope, the light is reflected by the exit surface 21 at a parallel angle, enters the uphill slope 32, is reflected, and exits from the exit surface.
[0036]
As a result, the incident angle of the light incident on the upward slope can be made constant, the variation in the reflection angle can be suppressed, and the emitted light can be made parallel. Therefore, by adjusting the inclination angle of the downward slope and the upward slope forming the convex part or the concave part, it is possible to give the outgoing light directivity, thereby allowing the light to be emitted at an angle close to the vertical direction with respect to the outgoing face. The light can be emitted.
[0037]
On the other hand, the above-described upward slope forming the convex portion or the concave portion has an inclination angle θ with respect to the light guide plate plane as illustrated in FIG._FourIs preferably 30 to 50 degrees, and more preferably 35 to 45 degrees. By setting the range of such an inclination angle, the transmission light incident directly or via the downward slope is nearly perpendicular to the emission surface 21 via the upward slope 32 as illustrated by the broken line arrow in FIG. Light can be efficiently emitted by reflecting at an angle. When the angle of inclination of the ascending slope is out of the above range, the deviation from the vertical direction becomes large, and it is difficult to provide the directivity close to the perpendicular to the outgoing light, and the outgoing efficiency (utilization efficiency) of the transmitted light may be lowered.
[0038]
There is no limitation in particular about the shape of the light source arrangement | positioning side surface in a light-guide plate, You may determine suitably. In general, the surface is perpendicular to the exit surface, but the incident light rate can be improved by a shape corresponding to the outer periphery of the light source such as a curved concave shape. Moreover, it can also be set as the surface structure which has the introducing | transducing part interposed between light sources. The introduction portion can have an appropriate shape depending on the light source and the like.
[0039]
The light guide plate can be formed of an appropriate material exhibiting transparency according to the wavelength region of the light source, and examples of the material and manufacturing method thereof include those exemplified for the optical path control layer described above. Note that the light guide plate may be formed as a laminate of different materials, such as a sheet in which fine prism-like irregularities are bonded to a light guide portion that carries light transmission, and may be integrated with a single material. It does not have to be formed as a single layer. The thickness of the light guide plate can be appropriately determined depending on the size of the light guide plate and the size of the light source depending on the purpose of use. When used for a liquid crystal display device or the like, the general thickness is 20 mm or less, especially 0.1 to 10 mm, particularly 0.5 to 8 mm, based on the side surface of the light source.
[0040]
As shown in FIG. 3, a reflective layer 5, preferably a metal reflective layer, may be provided on the surface of the light guide plate provided with fine prism-like irregularities, as illustrated in FIG. Such a reflective layer is effective in improving the emission efficiency by preventing the generation of leakage light from the surface having the fine prism-like unevenness. In the case of the polarized light source device combined with the polarization separation means, it also functions as a polarization conversion means.
[0041]
When functioning as the polarization conversion means, a reflective layer made of metal is particularly preferable. According to such a metal reflection layer, the polarization characteristics can be efficiently reversed at the time of reflection, and the polarization conversion efficiency is superior to the case of total reflection or diffuse reflection through an interface having a different refractive index. Incidentally, when circularly polarized light is incident on the metal surface substantially perpendicularly, the left and right conversion efficiencies of the circularly polarized light are close to 100%.
[0042]
A metal reflective layer preferable from the viewpoint of polarization conversion efficiency has a metal surface containing at least one of highly reflective metals such as aluminum, silver, gold, copper, or chromium. The metal reflective layer having excellent adhesion to the light guide plate can be formed as a mixed coating layer of metal powder with a binder resin, or an attached layer of a metal thin film by a vapor deposition method or the like. An appropriate coat layer for the purpose of improving reflectivity, preventing oxidation, or the like can be provided on one or both surfaces of the metal reflective layer, if necessary.
[0043]
  The optical path control layer 1 provided on the light emitting side 21 of the light guide plate 3 has a groove of 5 to 40 degrees with respect to the fine prism-like irregularities of the light guide plate in order to prevent the occurrence of moire.Placed in an intersecting state at an angle ofIn particular, it is preferable to be in a state of crossing at an angle of 7 to 30 degrees, particularly 10 to 25 degrees, and it is preferable to use an optical path control layer in which the period of the grooves is smaller than the period of the fine prism-like irregularities of the light guide plate. . When the crossing relationship is vertical or parallel, the effect of eliminating moire is poor, and when it exceeds 40 degrees, the optical path change in the groove direction of the optical path control layer becomes large, and the direction controllability of the emitted light is reduced and directivity is reduced. It may become scarce. On the other hand, if the period of the grooves is larger than the period of the fine prism-like irregularities, the bright lines may not be sufficiently subdivided and the moire prevention effect may be poor.
[0044]
  Further, the optical path control layer is configured to convert the light emitted from the light guide plate based on the wedge plate effect as illustrated in FIG.,Due to the fact that the optical path is changed in the vertical direction with good directivity, the gentle slope in the groove is arranged so as to be thin in the direction away from the light source.Ru. In FIG. 1, the left side of the drawing is the light source side.
[0045]
  As described above, the optical path control layer may be formed directly on the light guide plate, or may be disposed on the light guide plate as an independent object such as an optical path control plate. In the case of an independent object, the present inventionInThere is no front and back in the optical path control layer, and either surface can be on the light guide plate side, so that there is no misplacement between the front and back unlike the conventional prism sheet. However, from the viewpoint of suppressing light incident on the steep slope, it is preferable that the side without the groove is the light guide plate side.
[0046]
As the light source 4 arranged on the side surface of the light guide plate, an appropriate one can be used. For example, a linear light source such as a (cold, hot) cathode tube, a point light source such as a light emitting diode, or a linear or planar shape thereof. An array body or the like can be preferably used. A cold cathode tube is particularly preferable from the viewpoints of low power consumption and durability. When forming the surface light source device, the light source holder 41 that surrounds the light source in order to guide the divergent light from the linear light source to the side surface of the light guide plate, the diffusion layer 2 for obtaining uniform surface light emission, and the leaked light as necessary. A combination in which appropriate auxiliary means such as the reflective layer 5 for prevention are arranged at appropriate positions may be used.
[0047]
As the light source holder, a resin sheet or a metal foil provided with a highly reflective metal thin film is generally used. The arrangement of the diffusion layer is advantageous for forming a surface light source device that is superior in brightness uniformity by preventing the occurrence of unevenness of light and darkness, and is formed as a diffusion layer having a small diffusion angle by a diffusion plate or fine uneven surface. be able to.
[0048]
In addition, about a reflective layer, it can replace with the above-mentioned reflective layer 5, or a reflective sheet can also be provided along the formation surface of the fine prism-shaped unevenness | corrugation of a light-guide plate with the reflective layer. The reflection sheet can conform to the reflection layer described for the light guide plate, and thus a reflection sheet having a metal reflection surface can be preferably used in the polarized light source device.
[0049]
As described above, according to the surface light source device according to the present invention, the light collimated with high accuracy is emitted in a direction excellent in verticality advantageous for visual recognition, and the light from the light source is efficiently used to be excellent in brightness. Various devices such as a polarized light source device and a liquid crystal display device which is bright, easy to see and excellent in low power consumption can be formed, and can be preferably used as a sidelight type backlight.
[0050]
The above-described polarized light source device aims to convert incident light that does not exhibit polarization characteristics into polarized light with high efficiency by using both polarization and separation means by transmission and reflection, and in that case, the surface light source device according to the present invention. Provides high-accuracy collimated outgoing light with excellent verticality, and allows the return light through the polarization separation means to be re-exited with a good degree of direction matching with the initial outgoing light with little change in angle. Make it possible.
[0051]
FIG. 7 illustrates a polarized light source device 7 according to the present invention. This is composed of a polarization separation means 6 by transmission and reflection disposed above the optical path control layer 1 in the surface light source device described above. In the embodiment, as the polarization separating means, a device that transmits predetermined circularly polarized light and reflects non-predetermined circularly polarized light is used, and is disposed immediately above the optical path control layer 1 without a diffusion layer. In FIG. 7, a layer 61 provided on the upper surface of the polarization separating means 6 is a linearly polarized light converting means.
[0052]
According to the above-described apparatus, the light emitted from the optical path control layer 1 enters the polarization separating means 6, and predetermined (tentatively left) circularly polarized light in the left and right is transmitted, and non-predetermined (right) circularly polarized light is reflected. Then, the reflected light reenters the light guide plate through the optical path control layer as return light. The light that re-enters the light guide plate is reflected by the reflective function portion including the reflective layer on the lower surface, is incident again on the polarization separating means, and is separated again into transmitted light and reflected light (returned light). Therefore, the return light as the reflected light is confined between the polarization separation means and the light guide plate until it becomes a predetermined circularly polarized light that can be transmitted through the polarization separation means, and is repeatedly reflected.
[0053]
In the above, the surface light source device according to the present invention provides output light that is parallelized with high accuracy and excellent in perpendicularity, and reaches the light guide plate via a gentle slope that is excellent in reversibility of the optical path control layer. Most of the return light through the means is incident on the descending slope of the light guide plate, reflected without changing the angle greatly based on the gentle inclination angle, and the direction approximated to the initial outgoing light with a small angle change reflection Therefore, the light can be re-emitted with good verticality, and the light having excellent coincidence between the directions of the initial emitted light and the re-emitted light and excellent in polarization characteristics can be obtained in a state of excellent utilization efficiency with little loss.
[0054]
As described above, since the return light that has passed through the polarization separation means is re-emitted through reflection by the down slope of the light guide plate, the light guide plate used for forming the polarized light source device has a projected area of the down slope with respect to the exit surface. Is more than 3 times, especially 5 times or more, especially 10 to 100 times that of the upslope, from the viewpoint of light utilization efficiency.
[0055]
The light guide plate used for forming the polarized light source device is provided with a reflective layer or / and a reflective sheet on the side of the light guide plate that is not the light exit surface in order to efficiently reflect the return light through the polarization separating means through the downward slope. It is preferable to have. When the reflective layer or the like has a metal reflecting surface, the return light is converted into a predetermined polarization state with high efficiency by reflection inversion thereby, and light can be extracted efficiently.
[0056]
As the polarized light separating means, suitable means capable of separating light having different polarization characteristics through transmission and reflection, such as those separated into the left and right circularly polarized light described above, can be used. In the present invention, it is not necessary to have a complete separation function, but it is preferable that the polarization of other states contained in the polarized light separated by transmission or reflection is smaller.
[0057]
Incidentally, examples of the polarization separation means described above include one that selectively separates linearly polarized light or circularly polarized light. A specific example of the material that selectively separates the linearly polarized light is a multilayer film that exhibits anisotropy of reflectance due to birefringence. A specific example of the material that selectively separates the circularly polarized light includes a cholesteric liquid crystal phase. Etc.
[0058]
The polarized light separating means may consist of the above-mentioned multilayer film or a single layer of cholesteric liquid crystal phase, or an appropriate form such as a laminate or a cell in which these are supported or held by a transparent substrate such as a plastic film or a glass plate. It may have. As the cholesteric liquid crystal phase, those composed of a cholesteric liquid crystal polymer are particularly preferable from the viewpoint of handleability.
[0059]
The polarized light separating means, particularly the polarized light separating means comprising a cholesteric liquid crystal phase, may be composed of two or more layers. Superposition is advantageous from the viewpoint of dealing with a wider wavelength range of the separation function and a wavelength shift of obliquely incident light. In that case, superposition is performed with a combination of different center wavelengths of light reflected as non-predetermined circularly polarized light. It is preferable.
[0060]
Incidentally, a cholesteric liquid crystal layer having a central wavelength of selective reflection of 300 to 900 nm is used in a combination of reflecting circularly polarized light in the same polarization direction, and in a combination of different central wavelengths of selective reflection, especially 50 nm or more. By superimposing the six types, it is possible to efficiently form a polarization separation means that can cover a wide wavelength range such as the visible light range.
[0061]
The point of superimposing a combination of those that reflect circularly polarized light of the same polarization direction prevents the polarization state of circularly polarized light reflected by each layer from changing to a different polarization state in each wavelength range, The purpose is to increase the amount of polarized light in a usable state. For superimposing the cholesteric liquid crystal layer, it is particularly advantageous to use a liquid crystal polymer from the viewpoints of production efficiency and thinning.
[0062]
In the present invention, as shown in FIG. 7, when the linearly polarized light converting means 61 is provided above the polarized light separating means 6 for selectively separating the circularly polarized light, the phase of the circularly polarized light emitted from the polarized light separating means is changed. be able to. Accordingly, light having a wavelength corresponding to a quarter wavelength of the phase change is converted into linearly polarized light, and other wavelength light is converted into elliptically polarized light. The converted elliptically polarized light becomes flattened elliptically polarized light as it is closer to the wavelength of the light converted into the linearly polarized light. As a result, light in a state containing a large amount of linearly polarized light components that can pass through the polarizing plate is emitted from the linearly polarized light converting means.
[0063]
As described above, the linearly polarized light converting means arranged as necessary on the polarized light separating means aims to convert the circularly polarized light emitted from the polarized light separating means into a state having a large amount of linearly polarized light components. By converting to a state with a large amount of linearly polarized light components, it is possible to make the light easily transmitted through the polarizing plate. For example, in the case of a liquid crystal display device, the polarizing plate may be an optical element that maintains a display quality by preventing a decrease in polarization characteristics caused by a change in viewing angle with respect to a liquid crystal cell, and may realize a higher degree of polarization. It functions as an optical element that achieves display quality.
[0064]
In other words, in the above, it is possible to achieve display by allowing the outgoing circularly polarized light from the polarization separating means to enter the liquid crystal cell as it is without using the polarizing plate, but the display quality is improved by using the polarizing plate. In some cases, a polarizing plate may be used as necessary. In that case, the higher the transmittance with respect to the polarizing plate, the more advantageous from the point of display brightness, and the higher the transmittance, the higher the linearly polarized component in the polarization direction that coincides with the polarizing axis (transmission axis) of the polarizing plate. Therefore, for this purpose, the output polarized light from the polarization separation means is converted into predetermined linear polarization through the linear polarization conversion means.
[0065]
By the way, when natural light or circularly polarized light is incident on a regular iodine-based polarizing plate, the transmittance is about 43%, but when linearly polarized light is incident with the polarization axis coincident, the transmittance exceeds 80%. Therefore, it is possible to obtain a liquid crystal display having excellent brightness by greatly improving the light use efficiency.
[0066]
As the linearly polarized light converting means, an appropriate one can be used according to the polarization characteristics. In the case of circularly polarized light, a retardation layer capable of changing the phase can be preferably used. As the phase difference layer, the circularly polarized light emitted from the polarization separating means can form a large amount of linearly polarized light corresponding to the phase difference of ¼ wavelength, and light of other wavelengths can be made as much as possible with the linearly polarized light. In other words, those having a major axis direction in a parallel direction and capable of being converted into flat elliptical polarization as close to linear polarization as possible are preferable.
[0067]
By using the retardation layer as described above, it is possible to transmit the polarizing plate by arranging the linearly polarized light direction of the emitted light and the major axis direction of the elliptically polarized light as parallel as possible to the transmission axis of the polarizing plate. Light with a large amount of linearly polarized light components can be obtained. The retardation layer is preferably made of an appropriate material and can give a transparent and uniform retardation, and a retardation plate is generally used.
[0068]
The phase difference imparted by the phase difference layer can be appropriately determined according to the wavelength region of circularly polarized light emitted from the polarization separation means. By the way, in the visible light region, from the point of wavelength range, conversion efficiency, etc., considering that most phase difference plates show wavelength dispersion of positive birefringence than the material properties, those having a small phase difference, In particular, those giving a phase difference of 100 to 200 nm, particularly 100 to 160 nm can be preferably used.
[0069]
The retardation plate can be formed as one layer or two or more overlapping layers. In the case of a retardation film composed of one layer, the smaller the birefringence wavelength dispersion, the more preferable it is that the polarization state can be made uniform for each wavelength. On the other hand, the superposition of the phase difference plate is effective in improving the wavelength characteristics in the wavelength region, and the combination may be appropriately determined according to the wavelength region.
[0070]
When a retardation plate having two or more layers for the visible light region is used, it is possible to obtain light with a large amount of linearly polarized light by including a layer that gives a phase difference of 100 to 200 nm as an odd number of one or more layers as described above. It is more preferable than the point. The layers other than the layer giving a phase difference of 100 to 200 nm are generally preferably formed of a layer giving a phase difference of 200 to 400 nm from the viewpoint of improving the wavelength characteristics, but is not limited thereto.
[0071]
The retardation plate can be obtained as a birefringent sheet obtained by stretching a film made of polycarbonate, polysulfone, polyester, polymethyl methacrylate, polyamide, polyvinyl alcohol, or the like. From the point of maintaining the emission intensity and emission color uniformly over a wide viewing angle, the smaller the phase difference error in the plane of the retardation layer, the better. In particular, the error is preferably ± 10 nm or less.
[0072]
The phase difference and the direction of the optical axis set in the phase difference layer can be appropriately determined according to the vibration direction of the target linearly polarized light. Incidentally, in the case of a retardation layer that gives a retardation of 135 nm, linearly polarized light (wavelength 540 nm) having a vibration direction of +45 degrees or −45 degrees with respect to the optical axis is obtained depending on the direction of circularly polarized light. When the retardation layer is composed of two or more layers, particularly when the outer surface layer is occupied by a layer giving a retardation of 100 to 200 nm, it is preferable to set the arrangement angle based on the layer.
[0073]
As described above, the polarized light source device according to the present invention prevents reflection loss or the like by reusing the reflected light (returned light) by the polarization separating means as the outgoing light by polarization conversion, and uses the outgoing light as a phase difference as necessary. By converting into a light state containing a linearly polarized light component richly through a layer or the like, the light can be easily transmitted through the polarizing plate to prevent absorption loss and to improve the light utilization efficiency.
[0074]
Accordingly, as described above, the surface light source device and the polarized light source device according to the present invention provide light that is excellent in light use efficiency, bright, and excellent in verticality, and can easily be increased in area and the like. It can be preferably applied to various devices as a light system or the like, and a liquid crystal display device or the like that is bright, easy to see, and has low power consumption can be obtained.
[0075]
FIG. 8 illustrates a liquid crystal display device 8 using the polarized light source device 7 according to the present invention in a backlight system. 81 is a lower polarizing plate, 82 is a liquid crystal cell, 83 is an upper polarizing plate, and 84 is a diffusion plate. The lower polarizing plate 81 and the diffusing plate 84 are provided as necessary.
[0076]
In general, a liquid crystal display device is formed by appropriately assembling components such as a liquid crystal cell functioning as a liquid crystal shutter and an accompanying driving device, a polarizing plate, a backlight, and a retardation plate if necessary. The In this invention, there is no limitation in particular except the point which uses the above-mentioned surface light source device or polarized light source device, It can form according to the former. In particular, a direct-view liquid crystal display device can be preferably formed.
[0077]
Accordingly, the liquid crystal cell to be used is not particularly limited, and an appropriate one can be used. In the case of using a polarized light source device, it is advantageously used for display by making light in a polarized state incident on a liquid crystal cell. For example, it can be preferably used for a liquid crystal cell using twisted nematic liquid crystal or super twisted nematic liquid crystal. It can also be used for non-twisted liquid crystals, guest-host liquid crystals in which dichroic dyes are dispersed in liquid crystals, or liquid crystal cells using ferroelectric liquid crystals. There is no particular limitation on the driving method of the liquid crystal.
[0078]
From the point of obtaining a good contrast ratio display due to the incidence of highly linearly polarized light, the polarization degree of the polarizing plate, particularly the polarizing plate on the backlight side, such as an iodine-based or dye-based absorbing linear polarizer, etc. The thing using a high thing is preferable. Further, when forming a liquid crystal display device, for example, a diffusion plate or anti-glare layer provided on the polarizing plate on the viewing side, an antireflection film, a protective layer or protective plate, or a compensation retardation plate provided between the liquid crystal cell and the polarizing plate. These appropriate optical elements can be appropriately arranged.
[0079]
The compensation retardation plate is intended to improve visibility by compensating for the wavelength dependence of birefringence. In this invention, it arrange | positions as needed between the polarizing plate and liquid crystal cell of a visual recognition side or / and a backlight side. As the compensation retardation plate, an appropriate one can be used according to the wavelength region and the like, and it may be formed as one layer or two or more overlapping layers.
[0080]
In the present invention, optical elements or components such as an optical path control plate, a light guide plate, a polarization separation means, a liquid crystal cell, and a polarizing plate forming the surface light source device, the polarized light source device, and the liquid crystal display device described above are wholly or partially. The layers may be integrated and fixed, or may be arranged so as to be easily separated. Various diffusion plates and the like can be arranged on the upper surface of the surface light source device. In the case of a polarized light source device, a diffusion plate and the like that can maintain the polarization characteristics can be arranged on the upper surface.
[0081]
【Example】
Reference example 1
A side-chain cholesteric liquid crystal polymer having an acrylic main chain and a glass transition temperature of 57 ° C. is formed on the polyimide rubbing treated surface of the triacetyl cellulose film by spin coating, heated at 140 ° C. for 30 seconds, and further 120 ° C. The plate was rapidly cooled by heating for 5 minutes to obtain a polarization separation plate exhibiting a specular selective reflection state. This showed good selective reflectivity in the wavelength range of 420 to 505 nm, and 90% or more was selectively reflected in the regular reflection direction in this region.
[0082]
Reference example 2
Using side-chain cholesteric liquid crystal polymers with different glass transition temperatures, good selective reflectivity is exhibited in the wavelength range of 500 to 590 nm or 595 to 705 nm in accordance with Reference Example 1, and 90% or more is regularly reflected in this region. Two kinds of polarization separators selectively reflecting in the direction were obtained.
[0083]
Reference example 3
The three types of polarization separation plates obtained in Reference Example 1 and Reference Example 2 were stacked in the selective reflection wavelength order to obtain a superimposed polarization separation plate. This showed good selective reflectivity in the wavelength range of 420 to 705 nm, and 90% or more was selectively reflected in the regular reflection direction in this region.
[0084]
Reference example 4
Polymethylmethacrylate (PMMA) was melted by heating and poured into a metal mold at 100 ° C. having a predetermined prism structure, allowed to stand for 1 minute, and then slowly cooled to obtain a light guide plate. This light guide plate has a width of 195 mm, a depth of 150 mm, a thickness of 3 mm at the side of the light source arrangement, and a thickness of 1 mm at the opposite end, the emission surface (upper surface) is flat, and the lower surface is flat from the side of the light source arrangement toward the opposite end. The convex surface (FIG. 5a) parallel to the light source arrangement side surface has a 225 μm period on the entire curved surface protruding downward (FIG. 4b) close to, and the inclination angle of the downward slope is about 5 degrees. The inclination angle is about 40 degrees, and the projected area ratio of the down slope / up slope to the exit surface is 8/1.
[0085]
referenceExample5
  Apply PMMA containing about 1% by weight of a reaction initiator to the surface of the mold that has a predetermined groove shape, place a polyester film on it and irradiate a high-pressure mercury lamp to cure the PMMA. It peeled and the optical path control board which has an optical path control layer which consists of a hardened layer of PMMA on the polyester film was obtained. The optical path control layer has a gentle slope with an inclination angle of 10 degrees and a steep slope with 80 degrees at a period of 30 μm.
[0086]
referenceExample6
  referenceExample5In accordance with the above, an optical path control plate having a gentle slope of 20 degrees was obtained.
[0087]
referenceExample7
  referenceExample5According to the above, an optical path control plate having a gentle slope of 35 degrees was obtained.
[0088]
referenceExample8
  referenceExample5In accordance with the above, an optical path control plate having a steep slope of 60 degrees was obtained.
[0089]
referenceExample9
  Other than using a triacetyl cellulose film instead of a polyester filmreferenceExample5An optical path control plate was obtained according to the above.
[0090]
referenceExample 10
  referenceExample5According to the above, an optical path control plate having a gentle slope of 45 degrees was obtained.
[0091]
referenceExample11
  referenceExample5According to the above, an optical path control plate having a steep slope of 45 degrees was obtained.
[0092]
referenceExample12
  referenceExample5In accordance with the above, an optical path control plate having an inclination angle of 45 degrees on a gentle slope and a steep slope was obtained.
[0093]
referenceExample13
  Two glass plates were arranged at a crossing angle of 20 degrees, and PMMA was filled between them to obtain a wedge plate.
[0094]
Example1
  A cold cathode tube having a diameter of 3 mm is arranged on a predetermined side of the light guide plate obtained in Reference Example 4 and surrounded by a light source holder made of a polyester film subjected to silver deposition, and the same material as the light source holder is reflected on the lower surface of the light guide plate. Place the sheet through the silver vapor deposition layer side and place it on the exit surface of the light guide platereferenceExample5The surface light source device was obtained by arranging the optical path control plate obtained in the above with the prism surface facing down and the thick sloped side facing the light source. The optical path control plate was installed so that the groove had an intersection angle of 10 degrees with respect to the light source arrangement side surface (prism direction) of the light guide plate.
[0095]
Example2
  Example except that the optical path control plate is installed so that the groove has an intersection angle of 5 degrees with respect to the light source arrangement side surface of the light guide plate1A surface light source device was obtained according to the above.
[0096]
Example3
  Example except that the optical path control plate is installed so that the groove has an intersection angle of 35 degrees with respect to the light source arrangement side surface of the light guide plate1A surface light source device was obtained according to the above.
[0097]
Example4
  Example except that the optical path control plate is installed so that the groove is parallel to the light source side surface of the light guide plate1A surface light source device was obtained according to the above.
[0098]
Example5
  referenceExample6Other than using the optical path control plate obtained in Example1A surface light source device was obtained according to the above.
[0099]
Example6
  referenceExample7Other than using the optical path control plate obtained in Example1A surface light source device was obtained according to the above.
[0100]
Example7
  referenceExample8Other than using the optical path control plate obtained in Example1A surface light source device was obtained according to the above.
[0101]
Example8
  referenceExample9Other than using the optical path control plate obtained in Example1A surface light source device was obtained according to the above.
[0102]
Comparative example1
  referenceExample 10The optical path control plate obtained in step 1 was used with the prism surface facing up.1A surface light source device was obtained according to the above.
[0103]
Comparative example2
  referenceExample11Other than using the optical path control plate obtained in Example1A surface light source device was obtained according to the above.
[0104]
Comparative example3
  referenceExample12The optical path control plate obtained in step 1 was used with the prism surface facing up.1A surface light source device was obtained according to the above.
[0105]
Comparative example4
  Instead of the optical path control plate,referenceExample13Example using the wedge plate obtained in1A surface light source device was obtained according to the above.
[0106]
Comparative example5
  Example except that no optical path control plate is arranged1A surface light source device was obtained according to the above.
[0107]
Example9
  Example5The polarization separation plate obtained in Reference Example 3 was placed on the optical path control plate of the surface light source device obtained in the above to obtain a polarization light source device.
[0108]
Example 10
  Example8Example using the surface light source device obtained in 1 above9A polarized light source device was obtained according to the above.
[0109]
Comparative example6
  Comparative example3Example using the surface light source device obtained in 1 above9A polarized light source device was obtained according to the above.
[0110]
Comparative example7
  Comparative example5Example using the surface light source device obtained in 1 above9A polarized light source device was obtained according to the above.
[0111]
                               Evaluation test 1
Maximum brightness and direction
  Example1~8Comparative example1~5The light source of the surface light source device obtained in (1) was turned on, and the maximum luminance and its direction in the central part were examined using a luminance meter (Topcon Co., Ltd., BM-7).
[0112]
Moire
  Example1~8Comparative example1~5A white TFT liquid crystal cell was placed on the surface light source device obtained in the above, and the state of occurrence of moire was examined. Evaluation was made on a five-point scale, with 5 being strong and 1 being weak. Further, a surface light source device in which a diffuser plate having a haze of 60% was disposed between the optical path control plate and the light guide plate, and moiré was similarly examined.
[0113]
  Table above results1Indicated.
[Table 1]
         ┏━━━━━┳━━━━┳━━━━┳━━━━━━━━━┓
         ┃ ┃ Maximum brightness ┃ Maximum brightness ┃ Moare ┃
         Cd ┃ (cd / m²) ┃ direction (degree) ┣━━━━┳━━━━┫
         ┃ ┃ ┃ ┃ Diffusion plate No diffusion plate
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples1  ┃ 2240 ６ 6 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples2  ┃ 2250┃ 5 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples3  ┃ 1990 ┃ 9 ┃ 1 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples4  ┃ 2270 ┃ 5 ┃ 4 ┃ 2 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples5  ┃ 2190 ┃ 3 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples6  ┃2040┃-1−１2┃1┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples7  ┃2090┃ 6 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Examples8  ┃ 2290 ┃ 6 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Comparative example1  ┃ 1870 ６５ 65 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Comparative example2  ┃ 1730 ６ 6 ┃ 2 ┃ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Comparative example3  ┃ 1520 ４７ 47 ┃ 2 １ 1 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Comparative example4  ┃ 2310 ４ 4 ┃ 5 ┃ 3 ┃
         ┣━━━━━╋━━━━╋━━━━╋━━━━╋━━━━┫
         ┃ Comparative example5  ┃ 2390 １１ 11 ┃ 5 ┃ 3 ┃
         ┗━━━━━┻━━━━┻━━━━┻━━━━┻━━━━┛
[0114]
(Delete)
[0115]
                             Evaluation test 2
Luminance characteristics
  Example5,8Comparative example3,5A white-state TFT liquid crystal cell was placed on the surface light source device obtained in (1), and the luminance in the front (vertical) direction, the maximum luminance and the direction thereof were examined using a luminance meter.
[0116]
Luminance characteristics
  Example9, 10Comparative example6,7A retardation plate having a retardation of 135 nm was disposed on the polarization light source device obtained in the above, a white-state TFT liquid crystal cell was disposed thereon, and the luminance in the front direction was examined using a luminance meter. The retardation plate was disposed so that the optical axis thereof was 45 degrees with respect to the optical axis of the polarizing plate, and was disposed so that the transmittance was maximized.
[0117]
  The results are shown in Table 2.
【table2]
              ┏━━━━━┳━━━━┳━━━━┳━━━━┓
              ┃ ┃ Front brightness ┃ Maximum brightness ┃ Maximum brightness ┃
              Cd ┃ (cd / m²) ┃ (cd / m²) ┃ direction (degrees) ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Examples5  １０１ 101 １０４ 104 ┃ 3 ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Examples8  ┃ 98 １０８ 108 ┃ 6 ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Examples9  １ 138 ┃ − ┃ − ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              Example 10１４ 147 ┃ − ┃ − ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Comparative example3  １９ 19 ６１ 61 ┃-40 ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Comparative example5  ┃ 79 １０５ 105 ┃ 9 ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Comparative example6  ４２ 42 ┃ − ┃ − ┃
              ┣━━━━━╋━━━━╋━━━━╋━━━━┫
              ┃ Comparative example7  ┃ 142 ┃ − ┃ − ┃
              ┗━━━━━┻━━━━┻━━━━┻━━━━┛
[0118]
(Delete)
[0119]
  table1In the surface light source device of the example, when the optical path control layer is not provided (comparative example)5It can be seen that the optical path is converted in a direction in which most of the light emitted from the light guide plate is more excellent in perpendicularity via the optical path control layer. Comparative example1,3The reason why the prism surface is on the upper side is that if it is on the lower side, the optical path cannot be changed in the vertical direction. Comparative example1-3The large decrease in the maximum brightness at is greatly affected by the light incident on the steep slope.1,3In the comparative example, light incident on a gentle slope returns to the light guide plate side by reflection.2In this case, it is considered that the amount of light incident on the steep slope increases, and the amount of light that can be effectively used is further reduced when the emission angle is taken into account.
[0120]
  Examples3Further, it is understood that the crossing angle between the groove direction and the prism direction is approximately 35 degrees, and if the angle is larger than this, the deviation in the direction toward the steep slope increases, and the directivity decreases, leading to a decrease in the maximum luminance in the vertical direction. . Further table2Thus, it can be seen that the surface light source device and the polarized light source device of the example are superior in front luminance and small in difference from the maximum luminance as compared with the comparative example, and bright display is achieved.
[0121]
  For moiré, compared to the case without an optical path control layer, the embodiment1-3,5-8And comparative examples1-3It can be seen that both are greatly improved by the intervention of the optical path control layer. Examples4It can be seen that when the groove direction and the prism direction are parallel, the effect of subdividing bright lines is poor and the effect of preventing moiré is reduced, but it reaches the practical level with the arrangement of the diffusion plate. But comparative example4It can be seen that this wedge plate has no effectiveness in suppressing moire.
[0122]
  Comprehensive from the above results, the present inventionThenA surface light source device that can efficiently change the light path of the light emitted from the light guide plate in the front direction effective for visual recognition while suppressing deterioration in luminance and directivity through the optical path control layer, and more effective use of light. It can be seen that a polarized light source device with excellent efficiency can be obtained, and a liquid crystal display device with high display quality can be formed which is easy to see with little moire.
[Brief description of the drawings]
FIG. 1 is an explanatory side view of an example of an optical path control layer.
FIG. 2 is an explanatory side view of another optical path control layer example.
FIG. 3 is an explanatory side view of an example of a surface light source device.
FIG. 4 is an explanatory side view of a light guide plate example.
FIG. 5 is an explanatory side view of an example of fine prism-like irregularities.
FIG. 6 is an explanatory diagram of the light emission state.
FIG. 7 is an explanatory side view of an example of a polarized light source device.
FIG. 8 is an explanatory side view of an example of a liquid crystal display device.
FIG. 9 is an explanatory side view of a conventional example.
[Explanation of symbols]
    1: Optical path control layer
        11: Groove
            12: Slope
            13: Steep slope
        14: Transparent substrate
    2: Diffusionlayer
    3: Light guide plate
                    21: Upper surface (outgoing surface)
        22, 26, 27: bottom surface
                    28, 29: Convex part
                          30: recess
                31, 33 (34), 37: Down slope
                        32, 35, 36: Uphill slope
        23: Light source arrangement side
        38: Bright part
        39: Dark area
    4: Light source
    5: Reflective layer
    7: Polarized light source device
        6: Polarization separation means
      61: Linear polarization conversion means
    8: Liquid crystal display device
        81, 83: Polarizing plate
        82: Liquid crystal cell
        84: Diffuser

Claims (11)

At least one of the upper surface, the lower surface facing it, and the upper and lower surfaces of the plate-like object having the light source arrangement side surface between the upper surface and the lower surface periodically has fine prism-like irregularities in the direction along the light source arrangement side surface. On the light exit side of the light guide plate that emits the incident light from the light source arranged in the upper and lower surfaces as a stripe pattern of the bright part and the dark part, a gentle slope with an inclination angle of 5 to 35 degrees and a steep slope with 60 degrees or more with respect to the plane An optical path control layer having periodic streak-like grooves is arranged, the grooves of the optical path control layer intersect with the fine prism-like irregularities of the light guide plate at an angle of 5 to 40 degrees, and the surface light source device according to claim state near Rukoto the gentle slope of the groove is thin in a direction away from the light source. 2. The surface light source device according to claim 1, wherein the optical path control layer has grooves at a period of 10 to 80 [mu] m on at least one surface of a transparent substrate having a thickness of 30 to 500 [mu] m. According to claim 1 or 2, the surface light source device in which the optical path control layer has a diffusion layer on at least one surface. In one of claims 1 to 3, the surface light source device cycle of fine prismatic asperities in the light guide plate is 50 to 500 [mu] m. 5. The surface light source device according to claim 1, wherein an inclination angle of an inclined surface that is inclined upward in a direction away from the light source in the fine prism-shaped unevenness of the light guide plate is 35 to 45 degrees. 6. The surface light source device according to claim 1, wherein an inclination angle of a slope inclined upward in the direction away from the light source in the fine prism-like irregularities of the light guide plate is sequentially increased from the light source side. In one of claims 1 to 6, the inclination angle with respect to the light guide plate plane slopes downwardly inclined in the direction away from the light source in the fine prismatic asperities of the light guide plate is 0-10 degrees, the downlink inclined with respect to emitting surface of the light guide plate A surface light source device in which the projected area of the slope is at least five times that of the upward slope facing it. Polarized light source device characterized by having the polarization separating means on the light emitting side of the surface light source device according to one of claims 1 to 7. 9. The polarized light source device according to claim 8, wherein the polarized light separating means selectively separates circularly polarized light or linearly polarized light. According to claim 8 or 9, the polarization light source having a reflective layer on the side not the light emitting surface of the light guide plate. A liquid crystal display device comprising the liquid crystal cell on the light emitting side of the polarization light source device according to one of the surface light source device or claim 8-1 0 according to one of claims 1 to 7.

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