JP4913084B2 - Optical sheet and method for manufacturing optical sheet - Google Patents

Description

  The present invention relates to an optical sheet used for a backlight such as a liquid crystal display device and a signboard, and a method for manufacturing the optical sheet.

  As a backlight of a liquid crystal display device, for example, a direct type surface light source composed of a back light source and a diffusion sheet is known.

  In the liquid crystal display device, since the brightness of the front of the observer is important, a lens sheet for improving luminance may be used together with the front surface (outgoing surface side) of the diffusion sheet. As an example, a method using a prism sheet disclosed in Patent Document 1 is known.

  Regarding the viewing angle of the display device, it is generally required that the horizontal direction is wider than the vertical direction. For this reason, by arranging the longitudinal directions of the prisms in the horizontal direction and condensing the vertical viewing angle in the front direction, it is bright when viewed from the front direction and has a wide viewing angle in the horizontal direction.

  As another example, as disclosed in Patent Document 2, a sheet in which a lenticular lens is provided on one side and a reflective stripe layer is provided on a non-light-collecting portion of the lens on the opposite side is known.

  When a plurality of sheets such as a diffusion sheet and a prism sheet are used, there is a problem that handling when assembling the backlight is complicated. In addition, there has been a problem that the sheets are rubbed against each other due to vibration during transportation of the backlight or the liquid crystal display device, resulting in scratches and uneven brightness.

  Therefore, it is conceivable to bond the diffusion sheet and the prism sheet, or the diffusion sheet and the lenticular sheet with the reflective stripe layer. However, since the prism sheet condenses to the front surface using the effect that light is refracted on the incident surface, the effect cannot be exhibited if they are simply bonded together. This will be explained using the figure.

  FIG. 12 shows a state in which light is incident at a large incident angle on the side opposite to the prism surface of the prism sheet 5 that is not bonded, and is refracted and transmitted. Synthetic resin is generally used as the material constituting the prism sheet 5, but its refractive index is about 1.5 to 1.6, so that even when the incident angle is close to π / 2 rad (90 °), it is critical. The prism sheet 5 is advanced with a refraction angle smaller than an angle of about (2π / 360) × 40 rad (40 °). Therefore, the light condensed at a certain angle is incident on the prism surface, and the effect of condensing to the front is exhibited.

  On the other hand, when the diffusion sheet 4 is bonded to the entire incident surface of the prism sheet 5, the difference in refractive index is at most about 0.1 or almost zero. Therefore, as shown in FIG. 13, light of various angles is incident on the prism surface, and the effect of condensing it to the front cannot be exhibited.

Therefore, as disclosed in Patent Document 3, in order to form a gap between the diffusion sheet and the prism sheet, the top of the hemispherical pattern formed on the exit surface of the diffusion sheet is bonded to the entrance surface of the prism sheet. Combined optical sheets are known.
JP 62-144102 A JP 2005-221619 A JP 2008-3233 A

  The optical sheet of Patent Document 2 is not configured to be able to effectively use light incident on the bonded portion.

  An object of this invention is to provide the manufacturing method of an optical sheet and optical sheet with high light utilization efficiency.

The optical sheet according to the present invention is
An optical sheet for backlight arranged in the order of a diffusion sheet and a prism sheet from the light source side,
The prism sheet has a prism arranged in parallel on the exit surface side,
The exit surface of the diffusion sheet and the entrance surface of the prism sheet are bonded via a reflective layer, and the reflective layer is arranged in a stripe shape that intersects the longitudinal direction of the prism. With such a configuration, it is possible to suppress the light incident on the bonded portion from entering the prism at a large incident angle, and thus it can be effectively condensed in the front direction. In addition, it is difficult for a moire failure in which the pitch between the prism and the reflective layer interferes. In addition, handling of the sheet when assembling the backlight is simplified. Further, since the sheets do not rub against each other, they can be prevented from being damaged. In addition, wrinkles do not occur even when the prism sheet is thin.

  The reflective layer described above is preferably formed on the convex portion on the light exit surface side of the diffusion sheet. The reflective layer can be formed by a general method such as roll printing or screen printing. Therefore, it is possible to easily form a reflective layer, and there is little waste associated with production.

  Or it is preferable that the above-mentioned reflection layer is formed in the convex part by the side of the entrance plane of a prism sheet. The reflective layer can be formed by a general method such as roll printing or screen printing. Therefore, it is possible to easily form a reflective layer, and there is little waste associated with production.

  Here, the area ratio of the reflective layer to the prism sheet is preferably 3% or more and 50% or less.

  Further, the angle at which the prism and the reflective layer intersect with each other is (2π / 360) × 3 rad or more (2π / 360) × 15 rad or less, or (2π / 360) × 75 rad or more (2π / 360) × 87 rad or less. It is preferable.

  Moreover, it is preferable that the pitch of the above-mentioned reflection layer is 0.3 mm or more and 5 mm or less.

The method for producing an optical sheet according to the present invention includes:
A method of manufacturing an optical sheet for backlight arranged in the order of a diffusion sheet from a light source side and a prism sheet in which prisms are arranged in parallel on the exit surface side,
When the prism sheet is disposed on the exit surface side of the diffusion sheet, forming a stripe-shaped convex portion intersecting with the longitudinal direction of the prism of the prism sheet on the exit surface of the diffusion sheet;
Forming a reflective layer on the convex part;
Arranging the diffusion sheet and the prism sheet so as to sandwich the reflection layer, and bonding the exit surface of the diffusion sheet and the entrance surface of the prism sheet via the reflection layer;
Have The reflective layer can be formed by a general method such as roll printing or screen printing. Therefore, it is possible to easily form a reflective layer, and there is little waste associated with production.

Moreover, the method for producing an optical sheet according to the present invention includes:
A method of manufacturing an optical sheet for backlight arranged in the order of a diffusion sheet from a light source side and a prism sheet in which prisms are arranged in parallel on the exit surface side,
Forming a stripe-shaped convex portion intersecting with the longitudinal direction of the prism of the prism sheet on the incident surface of the prism sheet;
Forming a reflective layer on the convex part;
Arranging the diffusion sheet and the prism sheet so as to sandwich the reflection layer, and bonding the exit surface of the diffusion sheet and the entrance surface of the prism sheet via the reflection layer;
Have The reflective layer can be formed by a general method such as roll printing or screen printing. Therefore, it is possible to easily form a reflective layer, and there is little waste associated with production.

  The reflective layer described above is preferably formed by roll printing or the like.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of an optical sheet and optical sheet with high light utilization efficiency can be provided.

  Embodiments of an optical sheet and a method for producing the optical sheet according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

<Embodiment 1>
Embodiment 1 of the optical sheet according to the present invention will be described with reference to FIGS. As shown in FIG. 1, the optical sheet 1 is preferably used as an optical sheet for a backlight including a reflector 3 on the back surface of the light source 2, and is arranged in the order of the diffusion sheet 4 and the prism sheet 5 from the light source 2 side. Has been.

  In the optical sheet 1, as shown in FIG. 2, the prism 6 is arranged in parallel on the emission surface side of the prism sheet 5. The exit surface side of the diffusion sheet 4 and the entrance surface side of the prism sheet 5 are bonded together via a reflective layer 7, and the reflective layer 7 is arranged in a stripe shape intersecting the longitudinal direction of the prism 6. FIG. 1 is for explaining the arrangement of each layer and sheet on the light source side and the observer side, but does not explain how the prism 6 and the reflective layer 7 intersect.

  In the optical sheet 1 having such a configuration, light emitted from the light source 2 enters the diffusion sheet 4 and is diffused by the diffusion sheet 4, and the in-plane luminance is made uniform. Of the light diffused by the diffusing sheet 4, components incident on portions other than the reflective layer 7 (hereinafter sometimes referred to as openings) 8 are condensed in the front direction as shown in FIG. 1. .

  On the other hand, of the light diffused by the diffusion sheet 4, consider the component incident on the reflective layer 7. Incident light is reflected by the reflective layer 7 toward the diffusion sheet 4, then reflected by the diffusion sheet 4 and the reflection plate 3 on the back side of the light source 2, and travels toward the prism sheet 5 again. A part of the light enters the opening 8 and is condensed and emitted in the front direction as described above. In this specification, once reflected by the reflective layer 7 and then incident on the opening 8 is called light reuse. Thus, the light incident on the reflective layer 7 is repeatedly reflected and reused, so that the light utilization efficiency is high.

  As described above, the reflective layer 7 is formed on the adhesive portion, and light incident on the adhesive portion can be prevented from entering the prism 6 at a large incident angle, so that the light is effectively condensed in the front direction. be able to.

  In addition, the optical sheet 1 is arranged in a stripe shape in which the reflective layer 7 intersects with the longitudinal direction of the prism 6, so that it is difficult for a moiré failure in which the pitch between the prism 6 and the reflective layer 7 interferes.

  Further, since the diffusion sheet 4 and the prism sheet 5 are bonded together, handling of the sheet when assembling the backlight is simplified. Further, since the sheets do not rub against each other, they can be prevented from being damaged. In addition, even when the prism sheet 5 is thin, wrinkles do not occur.

Below, the structure of the optical sheet 1 shown in FIG. 2 is demonstrated in detail.
As the diffusion sheet 4, for example, a light diffusing synthetic resinous sheet mixed with a light diffusing agent can be used. Preferably, the diffusing sheet 4 has a multilayer structure, and the exit surface side is a layer having a relatively small diffusing force, and the incident surface side is a layer having a relatively large diffusing force.

For example, as shown in FIG. 3, an optical sheet having a configuration in which the diffusion sheet 4 includes a diffusion layer 4a containing a diffusing agent on the incident surface side and a transparent layer 4b not containing the diffusing agent on the output surface side is considered. .
The light incident on the reflective layer 7 once travels toward the diffusion sheet 4, then passes through the transparent layer 4 b and is diffusely reflected toward the exit surface in the diffusion sheet 4, so that it is separated from the reflective layer 7 in the prism array direction. The probability of reflection at the position increases. Therefore, the probability of reusing light with a small number of reflections increases, and the components that are repeatedly reflected between the reflective layer 7 and the diffusion sheet 4 can be reduced, so that the light utilization efficiency is increased.

  Note that the thickness of the layer having a small diffusing power is preferably 0.5 to 10 times the stripe pitch of the reflective layer 7. If the thickness of the layer having a low diffusing power is smaller than 0.5 times the stripe pitch of the reflective layer 7, the effect of providing a layer having a low diffusing power may not be sufficiently exhibited. Even if the thickness of the layer with low diffusive power is larger than 10 times the stripe pitch of the reflective layer 7, the effect of providing the layer with low diffusive power does not remarkably increase, but rather the thinning and weight reduction of the backlight are hindered. Become.

  Another configuration of the diffusion sheet 4 may include a diffusion layer containing a high concentration diffusing agent on the incident surface side and a diffusion layer containing a low concentration diffusing agent on the exit surface side. Also, a diffusion layer containing a diffusing agent having a large refractive index difference from the base material is provided on the incident surface side, and a diffusing layer containing a diffusing agent having a small refractive index difference from the base material is provided on the exit surface side. good. Further, it may be provided with a diffusion layer whose diffusing agent concentration changes stepwise or continuously from the vicinity of the incident surface to the vicinity of the emission surface.

  The incident surface of the diffusion sheet 4 may be flat, or a fine uneven shape or a lens array may be formed. When the light source 2 is a linear light source or a light source in which point light sources are arranged in a line, a lens array substantially parallel to the longitudinal direction of the arrangement of the linear light sources or point light sources is provided on the incident surface of the diffusion sheet 4. It is preferable. This is because the in-plane luminance is made uniform.

  The prism sheet 5 can be manufactured by a known manufacturing method. For example, an extrusion method or a transfer method using an ultraviolet curable resin. The sectional shape of the prism 6 may be a triangular prism shape as shown in FIG. 1 or the like, a parabola, a hyperbola, a polygonal line, or a combination thereof.

  The thickness of the prism sheet 5 is not particularly limited, but is preferably 0.2 mm or more in consideration of sheet handling. On the other hand, if it is thicker than 0.5 mm, it is not preferable because the backlight is thin and light.

  Incidentally, the surface of the prism sheet 5 may be provided with a diffusion layer (not shown) to the extent that it does not adversely affect the luminance improvement in the front direction in order to prevent scratches and moire. Moreover, in order to adjust the viewing angle characteristics, fine surface irregularities may be provided on the surface of the prism sheet 5. Further, a material having a refractive index different from that of the prism 6 may be laminated on the surface of the prism sheet 5, and a lens array may be formed. When the longitudinal direction of the prism of the prism sheet 5 intersects the longitudinal direction of the lens row, the viewing angle characteristics in the horizontal and vertical directions can be adjusted.

  As the material of the reflective layer 7, for example, a material composed of a binder component made of resin or the like and a general white pigment such as titanium oxide can be used, and an adhesive between the diffusion sheet 4 and the prism sheet 5 can be used. As the base material binder of the white pigment, a thermosetting resin, a solvent drying adhesive, an ultraviolet curable resin, or the like can be used.

  The area ratio of the reflective layer 7 to the prism sheet 5 is preferably in the range of 3% to 50%. When the area ratio of the reflective layer 7 to the prism sheet 5 is larger than 50%, the ratio of repeating reflection and diffusion between the reflective layer 7 and the diffusion sheet 4 and the reflection plate 3 increases, and light is absorbed by absorption by the reflector. Use efficiency may be reduced. On the other hand, when the area ratio of the reflective layer 7 to the prism sheet 5 is smaller than 3%, there is a possibility that a problem in durability may occur such that the adhesive area is too small and the sheet is easily peeled off. The area ratio of the reflective layer 7 to the prism sheet 5 is more preferably in the range of 5% to 25%.

  The angle θ (FIG. 7) at which the prism 6 and the reflective layer 7 intersect is preferably (2π / 360) × 3 rad (3 °) or more. If the angle θ is smaller than (2π / 360) × 3 rad, the moire elimination effect may be insufficient. On the other hand, the angle θ may be π / 2 rad (90 °), that is, the prism 6 and the reflective layer 7 may be orthogonal to each other. If the angle θ is π / 2 rad, moire due to interference with the vertical pitch of the pixels can be effectively avoided, but moire due to interference with the horizontal pitch of the pixels may occur. In that case, the angle θ is preferably (2π / 360) × 87 rad (87 °) or less.

  In addition, as will be described in detail later, in the case where the reflective layer 7 is formed on the convex portions of the diffusion sheet 4 or the prism sheet 5, a case where a strip-shaped convex portion is formed in the longitudinal direction of the sheet using a roll mold is considered. Then, if they intersect at a relatively large angle, it may be difficult to manufacture the mold. Further, considering the case of cutting the sheet obliquely, the size of the sheet is limited, or a portion that cannot be effectively used is generated at the end in the width direction of the sheet, which is not efficient. Therefore, the angle at which the prism 6 and the reflective layer 7 intersect is (2π / 360) × 3 rad or more (2π / 360) × 15 rad (15 °) or less, or (2π / 360) × 75 rad (75 °) or more (2π / 360) × 87 rad or less is preferable.

  The pitch P of the reflective layer 7 is preferably 0.3 mm or greater and 5 mm or less. If the pitch P is larger than 5 mm, the shadow of the reflective layer 7 may be visually recognized. Even if the pitch P is smaller than 0.3 mm, the degree to which the shadow of the reflective layer 7 becomes difficult to be visually recognized is no longer improved, but rather the formation of the reflective layer 7 may be difficult.

<Embodiment 2>
In Embodiment 1 described above, the exit surface of the diffusion sheet 4 and the entrance surface of the prism sheet 5 are formed to be flat. However, like the optical sheet 100 shown in FIG. Alternatively, the reflective layer 7 may be formed on the convex portion 9.

  The height H1 of the convex portion 9 is preferably 5 μm or more so that the reflective layer 7 can be easily formed. The shape of the convex portion 9 can be arbitrarily selected such that the cross section thereof is a quadrangle, a triangle, a semicircle, or the like.

The optical sheet 100 having such a configuration can be manufactured by using the manufacturing method of the present invention.
That is, when the prism sheet 5 is first arranged on the exit surface side of the diffusion sheet 4, stripe-shaped convex portions 9 that intersect the longitudinal direction of the prism 6 of the prism sheet 5 are formed on the exit surface of the diffusion sheet 4. Rather than forming a prism sheet on one side and a double-sided shaped prism sheet with projections on the other side using a roll mold, the prism is on one side and the other side is flat as in Embodiment 3 described later Manufacture is easier if the prism sheet and the diffusion sheet having a convex portion on one side and a flat sheet on the other side are separately molded.

  Next, the reflective layer 7 is formed on the convex portion 9. At this time, the reflective layer 7 can be formed by a general method such as roll printing or screen printing. Therefore, the reflective layer 7 can be easily formed, and the waste associated with the production is small.

  The prism sheet 5 is disposed on the reflective layer 7, and the exit surface of the diffusion sheet 4 and the entrance surface of the prism sheet 5 are bonded together via the reflective layer 7. The completed optical sheet 100 can be configured to have high light utilization efficiency and less likely to cause moire failure, similar to the optical sheet 1 of the first embodiment. In addition, handling is simple, and each sheet can be prevented from coming into contact and being damaged.

  The incident surface of the diffusion sheet 4 may be formed flat, or a fine uneven shape or a lens array may be formed. When the light source 2 is a linear light source or a light source in which point light sources are arranged in a line, a lens array substantially parallel to the longitudinal direction of the arrangement of the linear light sources or the point light sources is provided on the incident surface of the diffusion sheet 4. It is preferable to form. This is because the in-plane luminance is made uniform.

  In this case, the convex portion 9 is formed on the exit surface of the diffusion sheet 4 and the lens array is provided on the entrance surface, as described above, “a prism sheet on one side and a prism sheet with the other surface flat and a convex sheet on one side. It seems to be contradictory to the description that “the molding of the diffusion sheet separately forming the part is easier to manufacture”, but this is not necessarily the case. When a lens sheet is manufactured, molding unevenness is actually generated, resulting in luminance unevenness. However, in general, the lens sheet on the viewer side is most conspicuous in the backlight. Therefore, if the convex portion 9 and the luminance uniforming lens array are formed on both sides of the diffusion sheet relatively far from the observer side, the prism sheet on the most observer side can be flattened on one side. The molding accuracy of the lens array can be improved.

<Embodiment 3>
In Embodiment 1 described above, the exit surface of the diffusion sheet 4 and the entrance surface of the prism sheet 5 are formed flat, but the convex portion 10 is formed on the entrance surface of the prism sheet 5 as in the optical sheet 200 shown in FIG. Alternatively, the reflective layer 7 may be formed on the convex portion 10.

  The height H2 of the convex portion 10 is preferably 10 μm or more, more preferably 20 μm or more so that the reflective layer 7 can be easily formed. The shape of the convex portion 10 can be arbitrarily selected such that the cross section thereof is a quadrangle, a triangle, or a semicircle.

The optical sheet 200 having such a configuration can be manufactured by using the manufacturing method of the present invention.
That is, first, the stripe-shaped convex portion 10 that intersects the longitudinal direction of the prism 6 of the prism sheet 5 is formed on the incident surface of the prism sheet 5. Next, the reflective layer 7 is formed on the convex portion 10. At this time, the reflective layer 7 can be formed by a general method such as roll printing or screen printing. Therefore, the reflective layer 7 can be easily formed, and the waste associated with the production is small.

  The diffusion sheet 4 and the prism sheet 5 are disposed so as to sandwich the reflection layer 7, and the emission surface of the diffusion sheet 4 and the incident surface of the prism sheet 5 are bonded together via the reflection layer 7. The completed optical sheet 200 can be configured to have high light utilization efficiency and less likely to cause moire failure, as with the optical sheet 1 of the first embodiment. In addition, handling is simple, and each sheet can be prevented from coming into contact and being damaged.

  In addition, although the optical sheet of the said Embodiments 1-3 was set as the structure which bonded the prism sheet 5 to the diffusion sheet 4, the prism sheet 5 was once bonded to another translucent sheet | seat, and it was further made into the diffusion sheet. The effect of reusing light is exhibited in the same manner even when bonded to 4.

<Example 1>
Example 1 of a backlight using the optical sheet of the present invention will be described with reference to FIGS. FIG. 6 is for explaining the arrangement of each layer and sheet on the light source side and the observer side, but does not explain how the prism 6 and the reflective layer 7 intersect.

A prism sheet 5, a diffusion sheet 4, and a linear light source 2 are arranged from the observer side.
The prism sheet 5 has a prism 6 formed on the exit surface, and the entrance surface is flat. The apex angle of the prism 6 is π / 2 rad, the pitch is 150 μm, and the sheet thickness is 250 μm.

  The diffusion sheet 4 has a lenticular lens 11 formed on the incident surface and a stripe-shaped convex portion 12 formed on the output surface. The lenticular lens 11 has a substantially semicircular cross section and a pitch of 300 μm. The convex part 12 has a trapezoidal cross section, an upper side of 75 μm, a lower side of 100 μm, a height of 40 μm, and a pitch of 400 μm. The sheet thickness is 2 mm from the top of the lenticular lens 11 to the top of the convex portion 12. Further, the diffusion sheet 4 has a multi-layer structure in which the emission surface side is a transparent layer 4b and the incident surface side is a light diffusing agent-containing layer 4a, and the thickness of the transparent layer 4b including the convex portion 12 is 700 μm.

  The prism sheet 5 and the diffusion sheet 4 are bonded together only by the convex portions 12 of the diffusion sheet 4, and the adhesion width is 40 μm (adhesion layer area ratio = 10%). The adhesive contains a light diffusing agent in urethane-based ultraviolet curable resin, and also serves as the reflective layer 7.

  The arrangement of the backlight frame, the linear light source 2, the prism longitudinal direction, and the like will be described with reference to FIG. FIG. 7 is a schematic view of the backlight as viewed from the observer side, and only a part of the sheet is shown for explanation.

  The backlight is a rectangle that is long in the horizontal direction, and the longitudinal direction of the linear light source 2 is arranged in the horizontal direction. The longitudinal direction of the reflective layer 7 and the longitudinal direction of the lenticular lens 11 of the diffusion sheet 4 intersect with the horizontal direction at an angle θ = (2π / 360) × 5 rad (5 °). The longitudinal direction of the prism 6 is arranged in the horizontal direction. A calculation example of the viewing angle characteristic is shown in FIG.

Calculation method and conditions Program name: Optical Research Associates Light Tools Ver 6.0.0
-Refractive index: 1.549
-Light transmittance of the reflective layer: 10% (reflectance 90%)
-Reuse efficiency of light reflected by the reflective layer: 96%
・ Integral calculation method: piecewise quadrature method (2π / 360) × 5 rad steps ・ Diffusion characteristics of incident light on prism sheet: Lambert distribution

<Example 2>
Viewing angle characteristics were calculated in the same manner as in Example 1 except that the adhesive width was 120 μm (adhesive layer area ratio = 30%). The result is shown in FIG.

<Comparative Example 1>
The viewing angle characteristics were calculated in the same manner as in Example 1 except that the adhesive layer was not provided with a reflective layer and was transparent (that is, the light transmittance of the reflective layer was 100% and the reflectance was 0%). The result is shown in FIG.

<Comparative example 2>
Viewing angle characteristics were calculated in the same manner as in Comparative Example 1 except that the adhesive width was 120 μm (adhesive layer area ratio = 30%). The result is shown in FIG.

実施例は同じ接着層面積比率である比較例より正面輝度が高くなっていることが分かる。 Table 1 summarizes the viewing angle characteristics of the examples and comparative examples.

It can be seen that the front luminance of the example is higher than that of the comparative example having the same adhesive layer area ratio.

  As described above, since the optical sheet of the present invention has a reflective layer at the bonded portion, the light incident on the bonded portion can be reused, and the front luminance can be increased. And since it is the structure of 1 sheet bonded together, it is excellent in handleability. Further, the occurrence of moire can be prevented by intersecting the longitudinal direction of the reflective layer 7 and the longitudinal direction of the lenticular lens 11 with the longitudinal direction of the prism, the horizontal direction of the screen, and the vertical direction.

  Furthermore, since the angle at which the lenticular lens 11 intersects the linear light source 2 is small, light can be diffused and uneven brightness can be reduced.

  In addition, by making the longitudinal direction of the reflective layer 7 coincide with the longitudinal direction of the lenticular lens 11, continuous molding such as extrusion molding becomes easy. And since the reflective layer 7 is formed in the convex part 12, the reflective layer 7 can be continuously formed by roll printing etc.

It is the side view which showed roughly the backlight using the optical sheet which concerns on this invention. 3 is a structural diagram illustrating an optical sheet according to Embodiment 1. FIG. It is the side view which showed the optical sheet of the structure by which the diffusion sheet was provided with the diffusion layer which contains the diffusing agent in the incident surface side, and was equipped with the transparent layer which does not contain a diffusing agent in the output surface side. 6 is a structural diagram illustrating an optical sheet according to Embodiment 2. FIG. 6 is a structural diagram illustrating an optical sheet according to Embodiment 3. FIG. It is the perspective view which showed schematically the Example of the backlight using the optical sheet which concerns on this invention. It is the schematic which showed the backlight from the observer side. FIG. 3 is a diagram showing viewing angle characteristics of the backlight of Example 1. FIG. 6 is a view showing viewing angle characteristics of the backlight of Example 2. 6 is a view showing viewing angle characteristics of a backlight of Comparative Example 1. FIG. FIG. 6 is a view showing viewing angle characteristics of a backlight of Comparative Example 2. It is the figure which showed progress of the light of the prism sheet which has not bonded the diffusion sheet. It is the figure which showed advancing of the light of the optical sheet which bonded the diffusion sheet to the whole entrance plane of a prism sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical sheet 2 Light source 3 Reflector 4 Diffusion sheet 5 Prism sheet 6 Prism 7 Reflective layer 9 Convex part 10 of diffusion sheet Convex part 12 of diffusion sheet Optical part 200 Optical sheet 200 Optical sheet

Claims (9)

An optical sheet for backlight arranged in the order of a diffusion sheet and a prism sheet from the light source side,
The prism sheet has a prism arranged in parallel on the exit surface side,
An optical sheet in which the exit surface of the diffusion sheet and the entrance surface of the prism sheet are bonded via a reflective layer, and the reflective layer is arranged in a stripe shape intersecting the longitudinal direction of the prism.   The optical sheet according to claim 1, wherein the reflective layer is formed on a convex portion on an emission surface side of the diffusion sheet.   The optical sheet according to claim 1, wherein the reflective layer is formed on a convex portion on an incident surface side of the prism sheet.   4. The optical sheet according to claim 1, wherein an area ratio of the reflective layer to the prism sheet is 3% or more and 50% or less. 5.   The angle at which the prism and the reflective layer intersect is (2π / 360) × 3 rad or more (2π / 360) × 15 rad or less, or (2π / 360) × 75 rad or more (2π / 360) × 87 rad or less. The optical sheet according to claim 1, which is characterized.   The optical sheet according to any one of claims 1 to 5, wherein a pitch of the reflective layer is 0.3 mm or more and 5 mm or less. A method of manufacturing an optical sheet for backlight arranged in the order of a diffusion sheet from a light source side and a prism sheet in which prisms are arranged in parallel on the exit surface side,
When the prism sheet is disposed on the exit surface side of the diffusion sheet, forming a stripe-shaped convex portion intersecting with the longitudinal direction of the prism of the prism sheet on the exit surface of the diffusion sheet;
Forming a reflective layer on the convex part;
Arranging the diffusion sheet and the prism sheet so as to sandwich the reflection layer, and bonding the exit surface of the diffusion sheet and the entrance surface of the prism sheet via the reflection layer;
The manufacturing method of the optical sheet which has this. A method of manufacturing an optical sheet for backlight arranged in the order of a diffusion sheet from a light source side and a prism sheet in which prisms are arranged in parallel on the exit surface side,
Forming a stripe-shaped convex portion intersecting with the longitudinal direction of the prism of the prism sheet on the incident surface of the prism sheet;
Forming a reflective layer on the convex part;
Arranging the diffusion sheet and the prism sheet so as to sandwich the reflection layer, and bonding the exit surface of the diffusion sheet and the entrance surface of the prism sheet via the reflection layer;
The manufacturing method of the optical sheet which has this.   The method for manufacturing an optical sheet according to claim 7, wherein the reflective layer is formed by roll printing or the like.

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