JP2008159295A - Optical sheet and backlight unit using the same, and display device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve highly efficient light extraction from a light source while facilitating manufacturing in an optical sheet and a backlight unit using the same, and a display device and its manufacturing method. <P>SOLUTION: The optical sheet 21 is provided with a base material film 4 made of a light-transmitting film, each reflective layer 6 molded on one face of the base material film 4 by a radiation curing resin, and a plurality of condenser lenses 5 formed on the other face of the base material film 4. The reflective layers 6 form a light shielding pattern that has each opening part 30 at each position facing each of a plurality of condenser lenses 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical sheet, a backlight unit using the same, a display device, and a method for manufacturing the same. For example, the present invention relates to an optical sheet suitable for controlling an illumination optical path to a liquid crystal display element, a backlight unit using the same, a display device, and a manufacturing method thereof.

2. Description of the Related Art Conventionally, for example, a display device represented by a liquid crystal display device (LCD) has a backlight unit disposed on the back side of a liquid crystal display element in which ON / OFF of each pixel is controlled according to an image signal. Light from the unit is used as display light. In such an LCD, the power consumption of the liquid crystal display element is small, but the power consumption of the backlight unit is large. For example, when used in battery-powered devices such as laptop computers and mobile phones, the light of the light source It is demanded to reduce the power consumption of the apparatus by increasing the use efficiency of the apparatus.
Therefore, an optical sheet having a plurality of lenses, prisms, and the like is often disposed between the liquid crystal display element and the backlight unit in order to collect diffused light from the backlight unit to some extent.
For example, Patent Document 1 includes a liquid crystal panel and light source means for irradiating light from the back side to the liquid crystal panel, and the light source means is provided with a lens layer that guides light from the light source to the liquid crystal panel. A liquid crystal display device having a light shielding portion having an opening in the vicinity of the focal plane of the lens layer or a light shielding portion having an opening outside the focal plane of the lens layer in a positional relationship where an image is formed inside the liquid crystal layer by the lens layer is described. .
Patent Document 1 suggests that the light use efficiency can be further improved by using a light shielding portion as a reflective layer.
JP 2000-284268 A (FIGS. 1-3)

However, the above conventional optical sheet has the following problems.
In the technique described in Patent Document 1, a light shielding portion is arranged in the vicinity of the focal position of each lens, that is, on the back side of the lens surface, in a sheet-like lens layer composed of a plurality of lenses. When the position mismatch occurs, moire or luminance unevenness occurs, and the uniformity of display light decreases. For this reason, there is a problem that it is necessary to accurately align the lens and the light-shielding portion that should be arranged to face each other on an appropriate positional relationship on the front and back surfaces.
Patent Document 1 does not describe any manufacturing method and arrangement method of the light-shielding portion, but the reflective layer provided on the light guide plate is “white titanium dioxide (TiO ₂ ) powder in a solution such as a transparent adhesive. The mixed mixture is printed in a predetermined pattern, such as a dot pattern, dried and formed. Therefore, it is conceivable that the light shielding part is also formed by such printing. In this case, since the lens layer molding and printing are separate processes, alignment is difficult, and a complicated lens layer is molded. Since the later dimensions are likely to vary, the pitch from the printing plate tends to shift.
On the other hand, a method in which the lens layer and the light-shielding portion are separately formed and bonded together, or a method in which the lens layer is formed and then a reflective layer is formed by a self-alignment method using a photosensitive resin layer can be considered. It is difficult to maintain the bonding accuracy, and the latter involves an increase in the number of members and processes, which causes an increase in component costs and an increase in manufacturing cost due to a decrease in yield.

  The present invention has been made in view of the above problems, and an optical sheet that can efficiently extract light from a light source and that is easy to manufacture, a backlight unit using the same, a display device, and the same An object is to provide a manufacturing method.

In order to solve the above-mentioned problems, in the invention according to claim 1, in the optical sheet, a base material made of a light-transmitting film and a reflective layer formed on one surface of the base material by a radiation curable resin And a plurality of optical elements formed on the other surface of the base material, and a configuration in which a light-shielding pattern having an optical opening at an opposed position of the plurality of optical elements is formed by the reflective layer. To do.
According to this invention, since the reflective layer for forming the light-shielding pattern having the optical opening is provided on one surface of the optical sheet at the position opposed to the plurality of optical elements formed on the other surface, the light is incident from the light source. Of the diffused light, light incident on the range of the light shielding pattern is reflected by the reflective layer and reused by the light source. Therefore, it is possible to improve the utilization efficiency of the diffuse transmitted light emitted from the optical element.
Moreover, since the reflective layer is formed of a radiation curable resin, the manufacturing becomes easier as compared with the case where a sheet on which the reflective layer is formed is attached or formed by a self-alignment method.

According to a second aspect of the present invention, in the optical sheet of the first aspect, the reflective layer has a thickness of 10 μm or more and 20 μm or less.
According to this invention, it is possible to efficiently form a reflective layer having a good reflectance.
When the reflective layer is thinner than 10 μm, the transmitted light component increases, and thus the reflectance decreases. On the other hand, when the reflective layer is thicker than 20 μm, the radiation hardly penetrates, so that the molding time becomes long, the production efficiency decreases, and the molding shrinkage increases, resulting in a decrease in dimensional accuracy.

In the invention according to claim 3, in the optical sheet according to claim 1 or 2, the transmittance of the reflective layer is 15% or less.
According to the present invention, since the transmittance is low, the light use efficiency of the light source can be further improved.

According to a fourth aspect of the present invention, in the backlight unit, the optical sheet according to any one of the first to third aspects and the reflective layer of the optical sheet are sandwiched between the base material of the optical sheet. And a light source unit having a light emitting surface disposed on the surface.
According to this invention, since the optical sheet according to any one of claims 1 to 3 is used, the same effect as the invention according to any one of claims 1 to 3 is provided.

According to a fifth aspect of the present invention, the display device includes the backlight unit according to the fourth aspect and a liquid crystal display unit that displays an image using light from the backlight unit as display light.
According to this invention, since the backlight unit according to claim 4 using the optical sheet according to any one of claims 1 to 3 is used, the same effect as the invention according to any one of claims 1 to 3 is used. Is provided.

According to a sixth aspect of the present invention, in the method for manufacturing an optical sheet, a reflection that constitutes a light-shielding pattern having an optical opening with a first radiation curable resin on one surface of a substrate made of a light transmissive film. A second radiation-curing property at a position facing the optical opening of the reflective layer formed in the first molding step on the other surface of the substrate; And a second molding step of molding a plurality of optical elements with a resin.
According to this invention, the reflective layer which comprises the light-shielding pattern which has an optical opening with the 1st radiation curable resin is shape | molded by the 1st shaping | molding process on the one side of the base material which consists of a transparent film. To do. Next, in the second molding step, a plurality of optical materials are formed by the second radiation curable resin on the other surface of the base material at a position facing the optical opening of the reflective layer formed in the first molding step. The element is molded. Thereby, the optical sheet of Claim 1 can be manufactured.
In the first molding step, the first radiation curable resin can be cured quickly and uniformly because the other surface of the base material is not formed with a shape that causes radiation unevenness such as an optical element. .
In the second molding step, a mold for introducing the second radiation curable resin for molding the optical element is disposed on the other surface of the substrate, and the side of the reflective layer molded in the first molding step Irradiate from. Radiation enters from the optical aperture of the reflective layer and cures the second radiation curable resin. At this time, the mold for molding the optical element is positioned in alignment with the mold for molding the reflective layer, so that the formation position of the optical element is well aligned with the optical opening of the reflective layer. be able to. Moreover, by aligning in this way, the radiation which injects from an optical opening can osmose | permeate well in 2nd radiation curable resin, and efficient hardening can be accelerated | stimulated.

  According to the optical sheet of the present invention, the backlight unit using the same, the display device, and the manufacturing method thereof, the light-shielding pattern is formed on the optical sheet by the reflective layer formed of the radiation curable resin. Can be taken out efficiently and can be easily manufactured.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The optical sheet which concerns on embodiment of this invention is demonstrated with the backlight unit and display apparatus using the same.
FIG. 1 is a schematic partial cross-sectional view showing a schematic configuration of a display device according to an embodiment of the present invention. FIG. 2 is a schematic explanatory view illustrating a state of the optical sheet according to the embodiment of the present invention viewed from A. In addition, since each figure is a schematic diagram, the dimension ratio etc. are exaggerated (and the following is also the same).

As shown in FIG. 1, the display device 100 according to the present embodiment includes a light source unit 20, an optical sheet 21, a diffusion plate 7, and a liquid crystal display unit 22 stacked in this order, and from the liquid crystal display unit 22 toward the upper side in the figure. By emitting display light whose display is controlled by an image signal, a rectangular image in plan view is displayed. FIG. 1 shows a configuration for about two pixels at the end.
The light source unit 20 and the optical sheet 21 constitute a backlight unit 23.
Hereinafter, based on such an arrangement, the upper direction in FIG. 1 may be simply referred to as a display screen side, and the lower direction may be simply referred to as a back side. That is, the arrow A in FIG. 1 indicates the direction in which the optical sheet 21 is viewed from the back side.

In the present embodiment, the light source unit 20 has an emission surface 2b (light emission surface) having an area covering the range of the display screen of the liquid crystal display unit 22 on the display screen side, and extends the light incident from the side surface 2a. A transparent light guide plate 2 that is guided to the light exit surface 2b, is disposed adjacent to the side surface 2a of the light guide plate 2, and is provided on the back side of the light guide plate 2 with a light source 1 that allows white light to enter from the side surface 2a. The reflective film 3 is disposed adjacent to the light guide plate 2 and reflects the light emitted from the light guide plate 2 to the opposite side of the light exit surface 2b to the light guide plate 2 side and re-enters the light.
However, the light source unit 20 is not limited to such a configuration as long as white light can be emitted to the back side of the optical sheet 21, and any known light source unit may be employed.

The optical sheet 21 collects a part of the light emitted from the light exit surface 2 b of the light guide plate 2 and transmits it to the display screen side, reflects the other light to the light guide plate 2 side, and reenters the light guide plate 2. It is something to be made.
In the present embodiment, the reflective layer 6 is formed on one surface of the light-transmitting base film 4, and the condenser lens 5 is formed on the other surface. The reflective layer 6 is disposed in the vicinity of the light exit surface 2 b of the light guide plate 2.

The base film 4 is a transparent material having light transmittance with respect to the wavelength of the light emitted from the light source unit 20, and a material used for the optical member can be used without any particular limitation. In consideration of production efficiency and the like, it is preferable to use a plastic film.
In this embodiment, polyethylene terephthalate (PET) that is easy to handle is used. As the thickness of the base film 4, for example, a thickness of 50 μm to 200 μm can be used. Below, it demonstrates as what uses a 75 micrometer PET film (A4300 by Toyobo Co., Ltd.) as an example.
However, other resins such as acrylic resins such as polymethyl methacrylate, polycarbonates, acrylic-styrene copolymers, styrene resins, and polyvinyl chloride can also be suitably used.

In this embodiment, the reflective layer 6 forms a light-shielding pattern having stripe-shaped openings 30 (optical openings) having a pitch P and a width W, as shown in FIGS. (PW), a substantially rectangular cross section having a height H is extended in the depth direction of FIG. Therefore, at the opening 30, an air layer having a thickness of at least H is formed between the base film 4 and the emission surface 2 b of the light guide plate 2.
In this embodiment, the pitch P coincides with the arrangement pitch of the pixel regions 9a (see FIG. 2) of the liquid crystal display unit 22.
The material of the reflective layer 6 can be molded from an appropriate material as long as a good reflectance is obtained. In this embodiment, a material obtained by mixing a white pigment with a radiation curable resin is used.

Examples of radiation curable resins include ultraviolet curable resins and electron beam curable resins.
For example, a composition in which a reaction diluent, a photopolymerization initiator, a photosensitizer, or the like is added to urethane (meth) acrylate and / or epoxy (meth) acrylate oligomer can be used.
The urethane (meth) acrylate oligomer is not particularly limited, and examples thereof include polyols such as ethylene glycol, 1,4 butanediol, neopentyl glycol, polycaprolactone polyol, polyester polyol, polycarbonate diol, and polytetramethylene glycol. , Hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylene isocyanate, and other polyisocyanates.
Although it does not specifically limit as an epoxy (meth) acrylate oligomer, For example, the terminal glycidyl ether of a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a phenol novolak type epoxy resin, a bisphenol A type propylene oxide adduct, fluorene epoxy It can be obtained by reacting an epoxy resin such as a resin with (meth) acrylic acid.

As the white pigment, an appropriate pigment can be employed, and for example, titanium dioxide (TiO ₂ ) or the like can be employed.

The condensing lens 5 is an optical element for condensing diffused light that passes through the opening 30 toward the display screen.
In this embodiment, it consists of a cylindrical lens array arranged so that the focal position extends along the center line 32 (see FIG. 2) of the opening 30 on the base film 4.
In the present embodiment, the lens shape of the condenser lens 5 is an aspherical shape in which an elliptical surface is used as a reference surface and correction is performed using a higher order term in order to improve the light collection efficiency. However, a known appropriate lens shape, for example, another aspherical surface, an elliptical surface, a spherical surface, or the like may be employed depending on the required light collecting performance.

  Such a fine shape of each condenser lens 5 is easily formed by molding a radiation curable resin with a lens mold. The radiation curable resin for molding the condenser lens 5 can be appropriately selected from the same resins exemplified above according to the necessary refractive index. However, the resin used for the reflective layer 6 is not necessarily the same.

  The diffusion plate 7 diffuses light emitted from the optical sheet 21 toward the display screen, suppresses luminance unevenness of the display light, and gives an appropriate viewing angle to the display light. For example, a plastic plate or a plastic film in which a high refractive index material that scatters light in a transparent material is dispersed, or a glass plate with a light diffusion layer formed on the surface, such as float glass, blue plate glass, BK7, or the like is adopted. be able to.

  The liquid crystal display unit 22 is configured, for example, by enclosing liquid crystal between two sealing substrates on which an alignment film and a transparent electrode are formed, and the liquid crystal panel 9 that forms a liquid crystal shutter for each pixel region 9a. It is sandwiched between two polarizing plates 8 and 10.

Here, a method for manufacturing the optical sheet 21 will be described.
FIG. 3 is a schematic explanatory view illustrating a schematic configuration of an optical sheet manufacturing apparatus for performing the optical sheet manufacturing method according to the embodiment of the present invention. FIG. 4A is a front view of a mold roller used in the method of manufacturing an optical sheet according to the embodiment of the present invention. 4B and 4C are enlarged partial cross-sectional views of FIG. FIG. 5 is a process explanatory view illustrating a process of forming a reflective layer of the optical sheet according to the embodiment of the present invention. FIG. 6 is a process explanatory diagram illustrating a molding process of the optical element of the optical sheet according to the embodiment of the present invention. FIG. 7 is a graph showing the relationship between the thickness of the reflective layer and the transmittance of the optical sheet according to the embodiment of the present invention. The horizontal axis indicates the layer thickness (μm), and the vertical axis indicates the transmittance (%).

  As shown in FIG. 3, the optical sheet manufacturing apparatus 200 that manufactures the optical sheet 21 includes a film unwinding unit 40, a reflective layer forming unit 41, an optical element forming unit 42, and an optical sheet winding unit 43, which are sequentially arranged. In the meantime, the substrate film 4 is continuously conveyed, and in the process, the first molding step for molding the reflective layer 6 and the second molding step for molding the condenser lens 5 can be performed sequentially. ing.

In the film unwinding part 40, the base film 4 is unwound from the film reel 44 on which the PET film original fabric used for the base film 4 is installed via a roller 46, and conveyed to the reflective layer forming part 41.
In addition, the unrolled base film 4 may be subjected to an appropriate easy-adhesion treatment such as a surface modification treatment in order to improve the adhesion of the radiation curable resin during the conveyance process in the film unwinding section 40. Good.

In the reflective layer molding unit 41, the first molding process is performed using the mold roller 48.
As shown in FIGS. 4A and 4B, the mold roller 48 has grooves 48a formed on the roller surface over the circumferential direction of the roller corresponding to the convex shape of the reflective layer 6, with a pitch p _{1 in the} roller axial direction. The necessary number of strips is formed, and constitutes a reflective layer molding plate.
As shown in FIG. 4B, the groove portion 48a has a trapezoidal shape with a groove depth h, a groove bottom portion having a width w, and a groove side surface being opened radially outward at an angle θ. In this way, by providing the groove side surface of the groove portion 48a with an inclination, it is possible to ensure the releasability at the time of molding.

The base film 4 transported to the reflection layer molding unit 41 is wound around the outer periphery of the mold roller 48 by the winding roller 45 and transported in synchronization with the rotation of the mold roller 48.
On the other hand, in the mold roller 48, on the upstream side in the rotation direction of the winding roller 45, a radiation curable resin 60 (first radiation curable resin) in which a white pigment is mixed in each groove 48a by the radiation curable resin supply unit 50. ) Is supplied (coated). Therefore, as shown in FIG. 5, the rotation proceeds in a state where the radiation curable resin 60 is filled between each groove portion 48 a and one surface of the base film 4. When the radiation curable resin 60 is applied, productivity can be improved by using a squeegee or the like as appropriate.
In this state, a radiation Q ₁ for curing the radiation curable resin 60 is irradiated from a radiation source 47 disposed opposite to the mold roller 48. Radiation Q ₁ is transmitted through the substrate film 4, the radiation curable resin 60 in the respective grooves 48a it is possible to fully irradiation, can be rapidly cured without causing such curing unevenness. As a result, the amount of irradiation can be minimized and distortion due to shrinkage during curing can be minimized.

The base film 4 is separated from the mold roller 48 by the separation roller 49 when the curing of the radiation curable resin 60 is completed, and the reflective layer 6 cured together with the base film 4 is released from the mold roller 48. The
After the mold release, the resin of the reflective layer 6 may be dried using a dryer or the like as appropriate.

In this way, the reflective layer 6 is formed on the base film 4 at the reflective layer forming portion 41.
For example, with respect to the thickness 75 μm of the base film 4 and the arrangement pitch P = 140 μm of the reflective layer 6, as an example of a value suitable for manufacturing on the optical characteristics of the optical sheet 21, if molding shrinkage is ignored, The shape of the groove 48a can be set to p ₁ = 140 μm, h = 12 μm, w = 80 μm, and θ = 5 °. As a result, the reflective layer 6 having a height H = 12 μm is formed at an equal pitch by opening the width W of the opening 30 = 58 μm.
Here, considering the molding shrinkage of the radiation curable resin 60 and the shrinkage of the base film 4, setting the shape of the groove 48 a is the same as in general molding.

  The angle θ of the groove 48a can also serve as a function of regulating the incident angle of light incident on the opening 30 in addition to the draft function. Therefore, for example, if there is no problem in releasability, the angle may be set up to about θ = 45 ° as necessary in the incident angle range. For example, even if the width W is reduced, a sufficient amount of light transmitted toward the condenser lens 5 can be secured by increasing the angle θ.

  The compounding ratio of the white pigment to the radiation curable resin 60 can be appropriately set in consideration of moldability, curability, and reflectance (transmittance). For example, when there are too many white pigments, it cannot fix to the base film 4, and penetration of radiation becomes difficult. Therefore, it is preferable to adjust the reflectance (transmittance) by appropriately setting the thickness of the reflective layer 6 in a state where the mixing ratio of the white pigment is appropriate.

For example, when 17% of a white pigment made of TiO ₂ was mixed with the radiation curable resin 60 having a refractive index of 1.5, the transmittance of the reflective layer 6 having the above shape was 11%.
As a result of further various experiments conducted by the inventor, the minimum value and maximum value of the transmittance showed changes as indicated by curves 300 and 301, respectively, as shown in the graph of FIG. That is, as the layer thickness increases, the transmittance decreases and gradually decreases with a certain layer thickness.
From this result, it is understood that if the preferable transmittance is 15%, the thickness H of the reflective layer 6 may be 10 μm or more.
In addition, the upper limit of the layer thickness can be set as appropriate, but even if the layer thickness is increased, the decrease in transmittance becomes moderate. In addition, since radiation hardly penetrates and the amount of resin increases, the curing time becomes longer and the production efficiency decreases. In addition, molding shrinkage increases and dimensional accuracy deteriorates. Therefore, the layer thickness is preferably 20 μm or less.

  In addition, although the reflectance should be taken into consideration for the light utilization efficiency, the reflectance is affected by the underlayer and the like, and therefore, the transmittance was examined for convenience of measurement. Since the light absorptance is determined by the material of the white pigment or the radiation curable resin 60, the transmittance is substantially the same as that defining the reflectance.

Next, the base film 4 having the reflective layer 6 formed on one surface is conveyed to the optical element molding unit 42. In the optical element molding unit 42, the second molding process is performed using the mold roller 51.
As shown in FIGS. 4A and 4C, the mold roller 51 has grooves 51a formed on the roller surface over the circumferential direction of the roller corresponding to the lens shape of the condenser lens 5, with a pitch p in the roller axial direction. _The number of strips required in ₂ is formed, and constitutes an optical element molding plate.
The groove 51a is formed in a shape represented by a groove depth d and an aspherical curvature radius R, as shown in FIG. Here, p ₂ , d, and R are set so as to obtain a necessary shape and pitch of the condenser lens 5 in consideration of molding shrinkage and the like.
The position of the mold roller 51 in the axial direction is such that, for example, the fixing position of the mold roller 51 is adjusted with a fine adjustment screw or the like so that the condenser lens 5 is formed at a predetermined position facing the opening 30. By adjusting with the means, the positional relationship with the mold roller 48 is aligned.

The other surface of the base film 4 on which the reflective layer 6 is formed is wound around the outer periphery of the mold roller 51 by the winding roller 45, and is conveyed in synchronization with the rotation of the mold roller 51. (See FIG. 3).
On the other hand, the radiation curable resin 61 (second radiation curable resin) is supplied to the mold roller 51 by the radiation curable resin supply unit 53 on the upstream side in the rotation direction of the winding roller 45 (the second radiation curable resin). ). Therefore, as shown in FIG. 7, the rotation proceeds in a state in which the radiation curable resin 61 is filled between each groove 51 a and the other surface of the base film 4.
In this state, from the radiation source 52 disposed opposite to the mold roller 51, the radiation Q ₂ to which curing the radiation curable resin 61 is irradiated. Radiation Q ₂ are mainly incident from the opening 30 to the substrate film 4 is irradiated with radiation curable resin 61 in the grooves 51a. At this time, since each groove 51 a faces the opening 30, the radiation curable resin 61 is cured by the light diffused from the opening 30. Since the radiation curable resin 61 is a transparent material, easy to radiation Q ₂ penetration even through the opening 30, but uncured portions so as not to remain, for irradiating sufficient amount of light.

In the present process, the radiation Q ₂ is irradiated also to the reflective layer 6. Therefore, the radiation Q ₂ is, if each of the radiation curable resin 60, 61 can be cured is kept to a minimum curing step the curing of the reflective layer 6 as needed for transfer at the first molding step In the second molding step, the curing required for the radiation curable resin 60 may be completed together with the curing of the radiation curable resin 61.
In this case, since the molding shrinkage due to the progress of curing in the first molding step can be further reduced, the dimensional change after the first molding step can be suppressed, and molding with higher accuracy becomes possible.

The base film 4 on which the reflective layer 6 is formed is separated from the mold roller 51 by the separation roller 49 at the stage where the curing of the radiation curable resin 61 is completed, and the condensing lens 5 cured together with the base film 4 is formed. The mold is released from the mold roller 51.
Thus, the second molding process is completed.

The optical sheet 21 thus formed is conveyed to the optical sheet take-up unit 43 and taken up on the take-up reel 54.
When the optical sheet 21 is bonded to the diffusion plate 7, the optical sheet 21 may not be wound around the take-up reel 54 but may be connected to a line for bonding / bonding with the diffusion plate 7 as it is to proceed to the next step. .

Thus, according to the manufacturing method of the optical sheet of this embodiment, the optical sheet 21 is sequentially performed by the optical sheet manufacturing apparatus 200 while the base film 4 is being transported. Can be produced continuously.
At that time, the reflective layer 6 and the condenser lens 5 are formed on the base film 4 using the aligned mold rollers 48 and 51 in this order, so that each is manufactured as a separate sheet. Thus, it is possible to manufacture with high accuracy of positioning without taking time and effort.
Even in this embodiment, the positional relationship between the mold rollers 48 and 51 needs to be adjusted. However, since the respective molding steps of the reflective layer 6 and the condenser lens 5 are continuously performed under constant conditions, the alignment is initially performed. All you need to do is

Next, the operation of the display device 100 will be described focusing on the operation of the optical sheet 21.
The light emitted from the light source 1 is incident on the side surface 2a of the light guide plate 2, a part of the light is totally reflected according to the light beam angle and propagates in the extending direction of the light guide plate 2, and the other is an optical sheet from the output surface 2b. 21 and the entire back surface of the optical sheet 21 is illuminated.
The light emitted from the emission surface 2 b is incident on the base film 4 in the range of the opening 30 and is transmitted to the display screen side, and is reflected on the back side by the reflective layer 6 in the range of the reflective layer 6. The transmittance of the reflective layer 6 is set to 15% or less, and since a white pigment is dispersed in the reflective layer 6, light of, for example, more than 80% is reflected except for some absorbing components.
The light reflected to the back side enters the light guide plate 2 from the exit surface 2b according to the incident angle, and is reused as illumination light. The light reflected on the surface of the emission surface 2b is divided into transmitted light and reused light as described above.

The light emitted from the emission surface 2b toward the opening 30 is emitted in various directions with divergence angles, and the width of the light flux is restricted to W by the opening 30 and between the reflection layers 6 Since the light is incident on the base film 4 having a higher refractive index from the air layer formed in the above, the divergence angle is narrowed by the refraction action.
Then, the light advances through the base film 4 and is emitted from the condenser lens 5 at the position facing the opening 30 to the display screen side. At this time, since the focal position of the condenser lens 5 is set in the vicinity of the center line 32 on the opening 30 of the base film 4, the light emitted from the condenser lens 5 is reflected by the condenser lens 5. Is condensed in the direction having the refracting power (the left-right direction in FIG. 1), and becomes light that travels substantially parallel to the optical axis 31.
This light is diffused by the diffusing plate 7 and enters the liquid crystal display unit 22 as light having a larger divergence angle, and changes to the polarization state of each pixel region 9a controlled by a driving unit (not shown) based on the image signal. Accordingly, light from the predetermined pixel region 9a is transmitted as display light, and image display is performed.

  Here, if the light from the opening 30 is emitted in a range larger than the NA of the condenser lens 5, it is not used as display light, and light amount loss occurs or incident on other pixel regions 9a to cause luminance unevenness. To wake you up. Therefore, in order to improve the light use efficiency and the display image quality, the width W of the opening 30 is preferably narrow. However, if the width W is too narrow, the parallelism of the light emitted from the condenser lens 5 becomes too strong, which may cause the moire due to luminance unevenness and the viewing angle to become too narrow. Accordingly, the width W is appropriately set in consideration of these.

Thus, the optical sheet 21 of the present embodiment can improve the utilization efficiency for the light of the light source by providing the reflective layer 6 using the white pigment, and the reflective layer 6 is formed by molding with a radiation curable resin. Therefore, the alignment with respect to the condensing lens 5 becomes easy and can be manufactured easily.
Further, by forming the reflective layer 6 by molding with a radiation curable resin, the reflective layer 6 can be accurately manufactured even if the arrangement pitch of the reflective layer 6 is a fine pitch of, for example, several tens of μm. This is suitable for increasing the pixel pitch.

  In the above description, the example in which the diffusion plate 7 is disposed between the liquid crystal display unit 22 and the optical sheet 21 has been described. However, a diffusion layer may be provided inside the optical sheet 21. For example, a diffusion layer may be provided by coating or bonding at a position between the base film 4 and the reflective layer 6, or a light diffusing material is dispersed in the base film 4 or the condenser lens 5. Thus, a diffusion layer may be formed.

  In the above description, the example in which the condensing lens 5 is used as the optical element has been described. However, for example, an optical element that can regulate the traveling direction of light by a refraction action may be used for such a lens element. It is not limited. For example, you may employ | adopt the shape which comprises a prism.

  In the above description, the example in which the condenser lens 5 and the reflective layer 6 are arranged along the column direction of the pixel region 9a has been described. According to this, the shape of the mold roller for molding each is simplified, but it corresponds to each pixel region 9a by using a mold roller in which concave and convex portions corresponding to the lens shape and the reflective layer shape are arranged in a lattice shape. In addition, an opening and a condensing lens may be formed. In this case, the reflective layer is formed by a single slit structure in which a plurality of rectangular openings corresponding to the pixel region 9a are arranged in a grid pattern.

  In the above description, the reflective layer is described as an example using a radiation curable resin mixed with a white pigment. However, as long as necessary reflectance characteristics are obtained, the reflective layer is not limited to a configuration mixed with a white pigment. . For example, pigments or particles other than white may be mixed.

  In the above description, the configuration of the color display is not particularly described as the display device. However, for example, if a known configuration such as providing a color filter between the liquid crystal display unit 22 and the optical sheet 21 is added. Needless to say, the present invention can also be applied to a display device that performs color display.

It is a typical fragmentary sectional view showing a schematic structure of a display device concerning an embodiment of the present invention. It is a schematic explanatory drawing which shows the mode of A view of the optical sheet which concerns on embodiment of this invention. It is a schematic explanatory drawing explaining the schematic structure of the optical sheet manufacturing apparatus for performing the manufacturing method of the optical sheet which concerns on embodiment of this invention. It is the front view of the metal mold | die roller used for the manufacturing method of the optical sheet which concerns on embodiment of this invention, and its expanded partial sectional drawing. It is process explanatory drawing explaining the formation process of the reflection layer of the optical sheet which concerns on embodiment of this invention. It is process explanatory drawing explaining the formation process of the optical element of the optical sheet which concerns on embodiment of this invention. It is a graph which shows the relationship between the layer thickness of the reflection layer of the optical sheet which concerns on embodiment of this invention, and the transmittance | permeability.

Explanation of symbols

2b Output surface (light output surface)
4 Base film (base material)
5 Condensing lens (optical element)
6 Reflective layer 9a Pixel area 20 Light source 21 Optical sheet 22 Liquid crystal display 23 Backlight unit 30 Opening (optical opening)
41 reflective layer molding part 42 optical element molding part 47, 52 radiation source 48, 51 mold roller 50, 53 radiation curable resin supply part 60 radiation curable resin (first radiation curable resin)
61 Radiation curable resin (second radiation curable resin)
100 Display device

Claims (6)

A substrate made of a light transmissive film;
A reflective layer formed of a radiation curable resin on one surface of the substrate;
A plurality of optical elements formed on the other surface of the substrate;
An optical sheet, wherein a light-shielding pattern having an optical opening is formed at a position opposed to the plurality of optical elements by the reflective layer.     The optical sheet according to claim 1, wherein a thickness of the reflective layer is 10 μm or more and 20 μm or less.   The optical sheet according to claim 1, wherein a transmittance of the reflective layer is 15% or less. The optical sheet according to any one of claims 1 to 3,
A backlight unit comprising: a light source portion having a light emitting surface arranged so as to sandwich the reflective layer of the optical sheet with the base material of the optical sheet. The backlight unit according to claim 4,
A display device comprising a liquid crystal display unit that displays an image using light from the backlight unit as display light. A first molding step of molding a reflective layer constituting a light-shielding pattern having an optical opening with a first radiation-curable resin on one surface of a substrate made of a light-transmitting film;
A second optical element is molded on the other surface of the base material by a second radiation curable resin at a position facing the optical opening of the reflective layer formed in the first molding step. A method for producing an optical sheet, comprising:

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