JP2019060904A - Optical sheet, surface light source device, image source unit, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet capable of enhancing the adhesion between a base material layer and an optical functional layer. A base material layer 31 made of polycarbonate and an optical functional layer 32 laminated on one surface of the base material layer are provided, and the optical functional layer has a light transmitting portion 33 and a light absorbing portion 34. The light transmitting unit includes unit light transmitting elements 33b having a predetermined cross section, extending in one direction, and being arranged in a plurality of directions at predetermined intervals in a direction different from the one direction, and the light absorbing unit includes a light absorbing unit. It is formed between adjacent unit light transmitting elements, and the light transmitting portion is formed of an ultraviolet curable resin containing phenoxyethyl acrylate. [Selection diagram] FIG. 4

Description

  The present invention relates to an optical sheet for controlling the emission direction of incident light, and a surface light source device, an image source unit, and a display device including the same.

  Display devices such as car navigations, televisions, monitors of personal computers, etc. are equipped with an image source for emitting an image to be displayed, and an optical sheet for improving the quality of the image light and providing it to the observer side.

  As such an optical sheet, for example, a technology as disclosed in Patent Document 1 is disclosed. Here, a base film layer (base layer) and an optical functional layer in which light transmitting portions and light absorbing portions are alternately arranged on one surface of the base film layer are described. Moreover, it is shown by patent document 1 that polycarbonate may be applied to a base film layer from a viewpoint of restraining retardation low.

JP, 2010-217871, A

  However, in the case where a polycarbonate is used for the base material layer, the adhesion between the layers may be insufficient if an ultraviolet ray curable resin is used for the light transmitting portion of the optical functional layer laminated on the base material layer. Therefore, although it is described in Patent Document 1 that the base material layer may be subjected to primer treatment, it takes time and effort, and sufficient adhesion is not always obtained.

  Then, this invention makes it a subject to provide the optical sheet which can improve the adhesiveness of a base material layer and an optical function layer in view of the said problem. Moreover, a surface light source device, an image source unit, and a display device provided with the optical sheet are provided.

  Hereinafter, the present invention will be described. In addition, in order to make an understanding of this invention easy, the referential mark of an accompanying drawing is added in parentheses, but thereby, this invention is not limited to the form of illustration.

  One aspect of the present invention comprises a substrate layer (31) made of polycarbonate and an optical functional layer (32) laminated on one surface of the substrate layer, the optical functional layer comprising a light transmitting portion ( 33) and a light absorbing portion (34), and the light transmitting portion has a predetermined cross section and extends in one direction, and a plurality of unit light beams arranged at predetermined intervals in a direction different from the one direction An optical sheet (30, comprising a transmitting element (33b), wherein the light absorbing portion is formed between adjacent unit light transmitting elements, and the light transmitting portion is formed of an ultraviolet curable resin containing phenoxyethyl acrylate. 130).

  The optical sheet (130) is a protective layer (135) made of a resin containing no phenoxyethyl acrylate on the surface of the optical functional layer (32) opposite to the side on which the base material layer (31) is laminated. May be stacked.

  In addition, a rough surface may be formed on the surface of the protective layer (135) opposite to the side on which the optical function layer (32) is laminated.

  Furthermore, the surface light source device (20) provided with the light source (25) and the said optical sheet (30, 130) arrange | positioned rather than this light source by the observer side can be provided.

  Also, it is possible to provide an image source unit (10) including the surface light source device (30) and a liquid crystal panel (15) disposed on the light exit side of the surface light source device.

  In addition, it is possible to provide a display device in which the video source unit (10) is housed in a housing.

  According to the present invention, the adhesion between the base material layer and the optical functional layer can be enhanced, and peeling can be suppressed.

It is a disassembled perspective view explaining the imaging | video source unit 10 concerning one form. FIG. 3 is an exploded view showing a cross section of the image source unit 10; 5 is an exploded view showing another cross section of the image source unit 10. FIG. FIG. 5 is an enlarged view focusing on the optical sheet 30. FIG. It is the figure which expanded the optical sheet 30 further. It is a figure explaining the optical path which permeate | transmits the optical sheet 30. FIG. It is a figure explaining the optical sheet 130. FIG.

  Hereinafter, the present invention will be described based on the embodiments shown in the drawings. However, the present invention is not limited to these embodiments. In the drawings, for the sake of easy understanding, the shapes may be enlarged, deformed, or exaggerated, and some repetitive symbols may be omitted.

FIG. 1 is a view for explaining one mode, and is an exploded perspective view of an image source unit 10 including an optical sheet 30. As shown in FIG. 2 is a part of an exploded sectional view of the image source unit 10 cut along a line (line along the vertical direction) indicated by II-II in FIG. 1, and FIG. 3 is indicated by III-III. A part of the exploded cross-sectional view of the image source unit 10 cut along a dashed line (line along the horizontal direction) is shown.
Although such a video source unit 10 is not described in detail, a video source unit 10, such as a power source for operating the video source unit 10 and an electronic circuit for controlling the video source unit 10, is provided in a housing (not shown). The display is housed with the usual equipment needed to operate as. The present embodiment describes a liquid crystal display source unit as one aspect of the image source unit and a liquid crystal display device as one aspect of the display device. The video source unit 10 will be described below.

  The image source unit 10 includes a liquid crystal panel 15, a surface light source device 20, and a functional film 40. In the present embodiment, the optical sheet 30 is included in the surface light source device 20. 1 to 3 also show the orientation in the posture in which the display device is installed.

  The liquid crystal panel 15 includes an upper polarizing plate 13 disposed on the viewer side, a lower polarizing plate 14 disposed on the surface light source device 20 side, and a liquid crystal disposed between the upper polarizing plate 13 and the lower polarizing plate 14. And a layer 12. The upper polarizing plate 13 and the lower polarizing plate 14 separate the incident light into two orthogonal polarization components (P wave and S wave), and convert the polarization components in one direction (parallel to the transmission axis) (for example, P Wave) and has a function of absorbing a polarization component (for example, S wave) in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

  In the liquid crystal layer 12, a plurality of pixels are arranged in the vertical and horizontal directions in the direction along the layer surface, and an electric field can be applied to each area forming one pixel. Then, the orientation of the pixel to which the electric field is applied changes. As a result, a polarization component (for example, P wave) parallel to the transmission axis transmitted through the lower polarization plate 14 disposed on the surface light source device 20 side (ie, the light entrance side) passes through the pixel to which the electric field is applied. The polarization direction is rotated by 90 °, while maintaining the polarization direction as it passes through the pixel to which no electric field is applied. Therefore, depending on whether or not an electric field is applied to the pixel, the polarization component (for example, P wave) transmitted through the lower polarizing plate 14 is further transmitted through the upper polarizing plate 13 disposed on the light output side or the upper polarizing plate 13 Can be absorbed and shut off.

  In this manner, the liquid crystal panel 15 has a structure that controls transmission or blocking of light from the surface light source device 20 for each pixel to express an image.

  There are several types of liquid crystal panels, but the type is not particularly limited in this embodiment, and a liquid crystal panel of a known type can be used. Specific examples thereof include TN, STN, VA, MVA, IPS, OCB and the like.

Next, the surface light source device 20 will be described.
The surface light source device 20 is an illumination device which is disposed on the opposite side of the liquid crystal panel 15 to the viewer side and emits planar light to the liquid crystal panel 15. As can be seen from FIGS. 1 to 3, the surface light source device 20 of this embodiment is configured as an edge light type surface light source device, and includes the light guide plate 21, the light source 25, the light diffusion plate 26, the prism layer 27, and the reflective polarizing plate The optical sheet 30 and the reflective sheet 39 are provided.

  The light guide plate 21 has a base 22 and a back surface optical element 23, as can be seen from FIGS. The light guide plate 21 is a plate-like member as a whole formed of a translucent material. In this embodiment, one plate surface side on the viewer side of the light guide plate 21 is a smooth surface, the other plate surface side on the opposite side is a back surface, and a plurality of back surface optical elements 23 are on the back surface. It is arranged.

  Various materials can be used as materials for the base 22 and the back surface optical element 23. However, materials widely used as materials for optical sheets to be incorporated into display devices, and having excellent mechanical properties, optical properties, stability, processability, etc., can be used inexpensively. For example, thermoplastic resins such as polymer resins having an alicyclic structure, methacrylic resins, polycarbonate resins, polystyrene resins, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers, ABS resins, polyether sulfones and the like And epoxy acrylate and urethane acrylate reactive resins (ionizing radiation curable resins etc.) and the like.

  The base 22 has a plate-like shape having a predetermined thickness in a portion where light is guided inside and the base of the back surface optical element 23.

The back surface optical element 23 is a protruding element formed on the back surface side of the base 22, and in the present embodiment, is a triangular prism. The back surface optical elements 23 are in the form of columns extending in the horizontal direction at the ridges of the projecting tops, and the plurality of back surface optical elements 23 are arranged at a predetermined pitch in a direction (vertical direction) orthogonal to the extending direction. The cross section of the back surface optical element 23 according to the present embodiment is a triangle, but is not limited to this, and may be a polygon, a hemisphere, a part of a sphere, a lens shape, or the like.
The arrangement direction of the plurality of back surface optical elements 23 is preferably a light guiding direction. That is, the ridges of the back surface optical elements 23 extend in the direction away from the light sources 25 and in the direction in which the light sources 25 are arranged, or in the case of one long light source, parallel to the extending direction of the light sources.

  The “triangular shape” in the present specification includes not only a triangular shape in a strict sense but also a substantially triangular shape including a limit in manufacturing technology and an error at the time of molding. Similarly, terms used to specify other shapes and geometric conditions, such as "parallel," "orthogonal," "ellipse," "circle," etc. used in this specification are also strictly bound. It is assumed that the same optical function can be interpreted including errors that can be expected.

  The light guide plate 21 having such a configuration can be manufactured by extrusion molding or by forming the back surface optical element 23 on the base 22. In the light guide plate 21 manufactured by extrusion molding, the base 22 and the back surface optical element 23 can be integrally formed. Moreover, when manufacturing the light-guide plate 21 by shaping, the back surface optical element 23 may be the same resin material as the base 22, or may be a different material.

Referring back to FIGS. 1 to 3, the light source 25 will be described. The light source 25 is disposed on one side surface (end surface) of the side surface (end surface) of the base 22 of the light guide plate 21 in the direction in which the back surface optical element 23 is arranged. The type of the light source is not particularly limited, but can be configured in various modes such as a fluorescent lamp such as a linear cold cathode tube, a point LED (light emitting diode), or an incandescent lamp. In the present embodiment, the light source 25 is composed of a plurality of LEDs, and can be individually and independently adjusted to turn on and off each LED and / or the brightness when each LED is turned on by a control device (not shown) There is.
In this embodiment, as described above, the light source 25 is disposed on the side surface (end surface) on one side, but the light source is also disposed on the side surface (end surface) opposite to the side surface (end surface) It may be in the form of In this case, the shape of the back surface optical element is also formed according to a known example.

Next, the light diffusion plate 26 will be described. The light diffusion plate 26 is a layer which is disposed on the light output side of the light guide plate 21 and has a function of diffusing and emitting the light incident thereon. As a result, the uniformity of the light emitted from the light guide plate 21 can be further enhanced, and the flaws present in the light guide plate 21 can be made inconspicuous.
As a specific embodiment of the light diffusion plate, a known light diffusion plate can be used, and for example, a form in which a light diffusion agent is dispersed in a base material can be mentioned.
The light diffusion plate 26 can be used as a support plate of the prism layer 27 as in this embodiment. When the light exit surface of the light guide plate 21 is smooth, the light diffusion plate 26 may be bonded to the light guide plate 21 to be integrated.

The prism layer 27 is a layer provided on the liquid crystal panel 15 side with respect to the light diffusion plate 26 and having a unit prism 27 a that is convex toward the liquid crystal panel 15 side, as can be seen from FIGS. 1 to 3. In the present embodiment, the unit prism 27a has a predetermined cross section and extends in the light guiding direction of the light guide plate 21 (in the present embodiment, the vertical direction). The plurality of unit prisms 27a are arranged in a direction different from the light guide direction (in the present embodiment, in a plan view, a direction orthogonal to the light guide direction, a horizontal direction).
The cross-sectional shape of the unit prism of such a prism layer can apply a well-known shape according to the function to require. The shape can further diffuse or condense light.
Further, the extending direction and the arranging direction of the unit prisms are not limited to the above-described embodiment, but may be other embodiments. For example, the unit prisms may have a predetermined cross section and extend in a direction orthogonal to the light guide direction of the light guide plate 21, and a plurality of unit prisms may be arranged in the light guide direction.

  Next, the reflective polarizing plate 28 will be described. The reflective polarizing plate 28 decomposes the incident light into two orthogonal polarization components (P wave and S wave), and transmits the polarization component (for example, P wave) in one direction (direction parallel to the transmission axis) And has a function of reflecting a polarization component (for example, an S wave) in the other direction (a direction parallel to the reflection axis) orthogonal to the one direction. The structure of such a reflection type polarizing plate can apply a well-known thing.

  Next, the optical sheet 30 will be described. FIG. 4 is an enlarged view of a part of the optical sheet 30 from the viewpoint of FIG. As can be seen from FIGS. 1 to 4, the optical sheet 30 is provided on the base layer 31 formed in a sheet shape and one surface of the base layer 31 (in the present embodiment, the surface on the light guide plate 21 side) And an optical function layer 32.

The base layer 31 is a flat sheet-like member that supports the optical function layer 32.
The base layer 31 is formed of polycarbonate. Polycarbonates have excellent mechanical properties, optical properties, stability, processability and the like, and can be obtained at low cost. Furthermore, the birefringence (retardation) can be suppressed to be small in consideration of the combination of the surface light source device 20 and the lower polarizing plate 14, and high heat resistance can also be obtained. According to this, it can be used also in the application for which high heat resistance is required, such as in-vehicle application. Specifically, the glass transition point of polycarbonate resin is 143 ° C., and in general, it is suitable for in-vehicle use where durability at about 105 ° C. is required.

  The optical function layer 32 is a layer laminated on one surface of the base material layer 31 (in the present embodiment, the surface on the light guide plate 21 side), and has a light transmitting portion 33 (including a base portion 33a and a unit light transmitting element 33b) And a light absorbing portion 34. The optical function layer 32 has a cross section shown in FIG. 4 and has a shape extending in the back / front side (horizontal direction when the image source unit 10 is viewed from the front) in the plane of the drawing. In the direction, the unit light transmitting elements 33b of the light transmitting section 33 and the light absorbing sections 34 are alternately arranged.

The light transmitting portion 33 is a portion whose main function is to transmit light, and in the present embodiment, the sheet-like base portion 33a and the unit light transmitting element 33b are provided in the cross section shown in FIG. 2 and FIG. It is configured.
The base portion 33a is a sheet-like member in which one surface is laminated on the base material layer 31, the unit optical element 33b is disposed on the other surface, and adjacent unit light transmitting elements 33b are connected. In the present embodiment, the base portion 33 a of the light transmitting portion 33 is in contact with one surface of the base layer 31, and the optical function layer 32 is disposed on the base layer 31.

  The unit light transmission element 33b is an element having a substantially trapezoidal cross-sectional shape having a long lower bottom on the base layer 31 side (base portion 33a side) and a short upper bottom on the opposite side (light guide plate 21 side). The unit light transmitting element 33b maintains the cross section along the layer surface of the base material layer 31 and extends in one direction (horizontal direction in the present embodiment), and predetermined in a direction different from this extending direction (vertical direction in the present embodiment) Arranged at intervals of And between the unit light transmissive elements 33b adjacent to each other, an interval (groove) having a substantially trapezoidal cross section is formed. Therefore, the space (groove) has a long lower base on the upper bottom side (light guide plate 21 side) of the unit light transmission element 33b, and the lower base side of the unit light transmission element 33b (base portion 33a side, base layer) 31) has a trapezoidal cross section having a short upper bottom, and the light absorbing portion 34 is formed by being filled with a necessary material described later.

  The unit light transmitting element 33b has a refractive index of Nt. Such unit light transmission elements 33 b and the base portion 33 a can be formed by curing the light transmission portion constituting composition. Details will be described later. Although the value of the refractive index Nt is not particularly limited, the refractive index is from the viewpoint of appropriately reflecting light (including total reflection) at the interface with the light absorbing portion 34 in the slope of the trapezoidal cross section as described later. It is preferable that it is 1.47 or more. However, since the material having an excessively high refractive index is often easily broken, the refractive index is preferably 1.61 or less. More preferably, it is 1.49 or more and 1.56 or less, further preferably 1.56.

  Such a light transmission part 33 is comprised by hardening the ultraviolet curing resin composition containing phenoxyethyl acrylate. That the light transmission part 33 is comprised by the said composition can be known from the non-reacted phenoxyethyl acrylate (monomer) remaining in the light transmission part 33, for example.

By forming the light transmitting portion with such a composition, in this embodiment, in the base portion 33a, phenoxyethyl acrylate dissolves the surface of the polycarbonate which is the base material layer 31, and the surface is roughened and the mixed layer is formed. Occur. That is, a thin roughened mixed layer (not shown) is formed at the interface between the light transmitting portion 33 (in this embodiment, the base portion 33a) and the base layer 31.
As a result, the adhesion between the substrate layer 31 and the light transmitting portion 33 can be enhanced, so that the substrate layer and the optical function layer can be firmly adhered without requiring an additional step such as primer treatment. Become.

In this embodiment, adjacent unit light transmitting elements 33b are connected by the base portion 33a, and this is in contact with the base layer 31, so that the base portion 33a is made of an ultraviolet curable resin composition containing phenoxyethyl acrylate. However, normally, the unit light transmission element 33 b and the base portion 33 a are integrally formed of the same material at the same time in the manufacturing process.
Further, the base portion 33 a is not necessarily provided, and the unit light transmitting element 33 b may be in direct contact with the base layer 31. At that time, the light transmitting portion is composed only of the unit light transmitting element 33b.

The light absorbing portion 34 functions as an interval formed in the above-described interval (groove) formed between adjacent unit light transmitting elements 33b, and has a cross-sectional shape similar to that of the interval. Accordingly, the short upper bottom faces the liquid crystal panel 15 side (the base layer 31 side), and the long lower bottom is the light guide plate 21 side. The light absorbing portion 34 has a refractive index of Nr and is configured to be able to absorb light. Specifically, the light absorbing particles are dispersed in a transparent resin having a refractive index of Nr. The refractive index Nr is lower than the refractive index Nt of the unit light transmitting element 33b. As described above, by making the refractive index of the light absorbing portion 34 smaller than the refractive index of the unit light transmitting element 33, light incident on the unit light transmitting element 33b under the predetermined conditions is properly made at the interface with the light absorbing portion 34. It can be totally reflected. Further, even when the total reflection condition is not satisfied, part of the light is reflected at the interface.
The value of the refractive index Nr is not particularly limited, and is preferably 1.47 or more on the premise that the total internal reflection can be appropriately performed. However, since the material having an excessively high refractive index is often easily broken, the refractive index is preferably 1.61 or less. More preferably, it is 1.49 or more and 1.56 or less, further preferably 1.49.

  The difference in refractive index between the refractive index Nt of the unit light transmitting element 33b and the refractive index Nr of the light absorbing portion 34 is not particularly limited, but is preferably greater than 0 and 0.14 or less, preferably 0.05 or more. It is preferable that it is 14 or less. By increasing the refractive index difference, more light can be totally reflected.

  The optical function layer 32 is not particularly limited, but can have, for example, the following shape. The figure which further expanded a part of FIG. 4 to FIG. 5 was represented.

In the interface between the unit light transmitting element 33 b and the light absorbing portion 34, θ ₁₁ shown in FIG. 5 is the interface 34 a which is the upper side of the light absorbing portion 34 when the optical sheet 30 is in the posture as shown in FIG. And the normal to the layer surface of the optical function layer 32. θ ₁₂ is an angle between the normal to the layer surface of the optical function layer 32 and the interface 34 b on the lower side of the light absorbing portion 34 among the interfaces of the unit light transmitting element 33 b and the light absorbing portion 34 in the same posture .
In the present embodiment, θ ₁₁ is preferably 0 ° or more and 10 ° or less. theta ₁₁ which means that the inclination from the light guide plate 21 side (light incident side) as down toward the liquid crystal panel 15 side (light outgoing side, the base layer 31 side) and larger than 0 °.
Similarly, θ ₁₂ is preferably 0 ° or more and 10 ° or less. The theta ₁₂ is greater than 0 ° means that the inclination from the light guide plate 21 side (light incident side) as raised toward the liquid crystal panel 15 side (light outgoing side, the base layer 31 side).

The relationship between the angle magnitudes of θ ₁₁ and θ ₁₂ can be configured as needed. For example, if θ ₁₁ <θ ₁₂ , the upper viewing angle can be made wider than the lower viewing angle with respect to the viewing angle of the image light provided from the image source unit 10.

It is preferable that the pitch of the unit light transmissive element 33b and the light-absorbing portion 34, represented by _{P a} is 20μm or more 100μm or less in FIG. 4, it is more preferably 30μm or more 100μm or less. The thickness of the light absorbing portion 34 indicated by _Da in FIG. 4 is preferably 50 μm or more and 150 μm or less, and more preferably 60 μm or more and 150 μm or less. Within these ranges, the balance between light transmission and light absorption can be made more appropriate.

  In this embodiment, an example is shown in which the interface between the unit light transmission element 33b and the light absorbing portion 34 is straight in cross section, but the present invention is not limited to this. May be Further, the cross-sectional shapes of the plurality of unit light transmission elements 33 b and the light absorbing portions 34 may be the same, or may be different cross-sectional shapes with predetermined regularity.

The optical sheet 30 can be produced, for example, as follows.
First, the light transmitting portion 33 is formed on one surface of the base layer 31. This is a substrate sheet to be a substrate layer 31 made of polycarbonate between a mold roll having on the surface a shape capable of transferring the shape of the unit light transmission element 33b and a nip roll arranged to face this. Insert At this time, the base portion 33a can be formed by providing a predetermined distance between the mold roll and the nip roll. And a mold roll and a nip roll are rotated, supplying the composition which comprises a light transmissive part between a base material sheet and a mold roll. Thus, the composition constituting the light transmission part is filled in the groove (shape obtained by inverting the shape of the unit light transmission element) corresponding to the unit light transmission element formed on the surface of the mold roll, and the composition is used as the mold roller Along the surface shape of the

  Here, the composition which comprises a light transmissive part is an ultraviolet curable resin composition containing phenoxyethyl acrylate as mentioned above.

Light for curing by a light irradiation device is applied from the substrate sheet side to the composition which is sandwiched between the mold roll and the substrate sheet and which constitutes the light transmitting portion filled therein. Thereby, the composition can be cured and its shape can be fixed. Then, the base layer 31 and the formed light transmitting portion 33 are released from the mold roll by the mold release roll.
In the process of forming such a light transmission part, the composition which comprises a light transmission part melt | dissolves the surface of a base material layer, and roughening and formation of a mixed layer are performed.

  Next, the light absorbing portion 34 is formed. In order to form the light absorbing portion 34, first, the space (groove) between the unit light transmitting elements 33b formed above is filled with the composition constituting the light absorbing portion. After that, the excess composition is scraped off with a doctor blade or the like. Then, the remaining composition can be cured by irradiating ultraviolet light from the unit light transmitting element 33 side to form the light absorbing portion 34.

The material used as the light absorbing portion is not particularly limited, and for example, it is colored in a photocurable resin such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate. There may be mentioned compositions in which the light absorbing particles are dispersed.
The composition constituting the light absorbing portion may also contain phenoxyethyl acrylate.

Further, instead of dispersing the light absorbing particles, the entire light absorbing portion can be colored with a pigment or a dye.
When light absorbing particles are used, light absorbing colored particles such as carbon black are preferably used, but the present invention is not limited to these and selectively absorbs a specific wavelength according to the characteristics of image light. Colored particles may be used. Specific examples thereof include organic fine particles colored with carbon black, graphite, metal salts such as black iron oxide, dyes, pigments and the like, colored glass beads, and the like. In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality and availability. The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less, more preferably 1.0 μm or more and 10 μm or less, and still more preferably 1.0 μm or more and 4.0 μm or less.
Here, the “average particle size” means a diameter obtained by observing 100 light absorbing particles with an electron microscope, measuring the diameter, and arithmetically averaging.

  The optical sheet 30 can be obtained as described above.

  Referring back to FIGS. 1 to 3, the reflection sheet 39 of the surface light source device 20 will be described. The reflective sheet 39 is a member for reflecting the light emitted from the back surface of the light guide plate 21 and causing the light to enter the light guide plate 21 again. The reflective sheet 39 is a sheet made of a material having high reflectance such as metal, and a sheet capable of so-called specular reflection such as a sheet including a thin film (for example, a metal thin film) made of a material having high reflectance as a surface layer. It can be preferably applied.

  The functional film 40 is a layer which is disposed on the light output side of the liquid crystal panel 15 and has a function of improving the quality of image light and protecting the image source unit 10. Examples thereof include an antireflective film, an antiglare film, a hard coat film, a color tone correction film, a light diffusion film, and the like, and these are configured singly or in combination.

  Next, the operation of the image source unit 10 having the above-described configuration will be described while showing an example of an optical path. However, the example of the optical path is conceptual for the purpose of explanation, and does not strictly represent the degree of reflection or refraction.

  First, as shown in FIG. 2, light emitted from the light source 25 enters the light guide plate 21 from the light entrance surface which is the side surface (end surface) of the light guide plate 21. As an example, FIG. 2 shows an example of an optical path of the lights L21 and L22 incident on the light guide plate 21 from the light source 25.

  As shown in FIG. 2, the light L21 and L22 incident on the light guide plate 21 repeats total reflection due to the difference in refractive index with air on the light exit side of the light guide plate 21 and the reverse surface on the opposite side, Go down to the bottom of 2).

  However, the back surface optical element 23 is disposed on the back surface of the light guide plate 21. Therefore, as shown in FIG. 2, the light L21 and L22 traveling in the light guide plate 21 changes its traveling direction by the back surface optical element 23, and enters the light exit surface and the back surface at an incident angle less than the total reflection critical angle. There is also. In this case, the light may be emitted from the light exit surface of the light guide plate 21 and the reverse surface on the opposite side.

  The lights L21 and L22 emitted from the light exit surface are directed to the light diffusion plate 26 disposed on the light exit side of the light guide plate 21. On the other hand, the light emitted from the back surface is reflected by the reflection sheet 39 disposed on the back surface of the light guide plate 21, and enters the light guide plate 21 again to travel in the light guide plate 21.

  The light traveling in the light guide plate 21 and the light which is changed in direction by the back surface optical element 23 and reaches the light exit surface at an incident angle less than the total reflection critical angle are in each section along the light guide direction in the light guide plate 21. It occurs. For this reason, the light traveling in the light guide plate 21 is emitted little by little from the light exit surface. Thereby, the light quantity distribution along the light guide direction of the light radiate | emitted from the light emission surface of the light-guide plate 21 can be equalized.

The light emitted from the light guide plate 21 then reaches the light diffusion plate 26 and the uniformity is enhanced. The light diffused or collected by the prism layer 27 as needed and emitted from the prism layer 27 reaches the reflective polarizing plate 28. Here, light in the polarization direction along the transmission axis of the reflective polarizing plate 28 is transmitted through the reflective polarizing plate 28 and directed to the optical sheet 30.
On the other hand, the light in the polarization direction along the reflection axis of the reflective polarizing plate 28 is reflected as shown by the dotted arrow in FIG. 2 and returned to the light guide plate 21 side. The returned light is reflected by the light guide plate 21, the back surface optical element 23 or the reflective sheet 39 and travels to the side of the reflective polarizing plate 28 again. At the time of this reflection, the polarization direction of part of the light is changed, and part of it is transmitted through the reflective polarizing plate 28. Other light is returned to the light guide plate again. Thus, the light reflected by the reflective polarizing plate 28 can also be transmitted through the reflective polarizing plate 28 by repeating reflection. Thereby, the utilization factor of the light from the light source 25 is enhanced.
Here, the light emitted from the reflective polarizing plate 28 has a polarization direction along the transmission axis of the lower polarizing plate 14 and is polarized light that transmits the lower polarizing plate 14.

The light emitted from the reflective polarizing plate 28 reaches the optical sheet 30. The light incident on the optical sheet 30 travels with the following optical path. An example of the optical path in the optical sheet 30 is shown in FIG.
The light L21 and the light L22 shown in FIG. 2 and the light L61 and the light L62 shown in FIG. 6 are the interface 34a on the upper side of the light absorbing portion 34 among the interfaces of the unit light transmitting element 33b and the light absorbing portion 34. Head for Then, the light is totally reflected at the interface 34 a to be light obliquely upward on the viewer side, and light is controlled in a desired direction.
At this time, if the interface 34b below the light absorbing portion 34 in the interface between the unit light transmitting element 33b and the light absorbing portion 34 is inclined to be directed obliquely upward to the viewer side, light L21, light It becomes difficult for the light absorbing portion 34 to inhibit the progress of light such as L22, light L61, and light L62, and more light can be guided in a desired direction.

Further, the light L23 shown in FIG. 2 and L63 shown in FIG. 6 are obliquely upward on the viewer side, and the interface 34b is not totally reflected by the interface 34b between the unit light transmitting element 33b and the light absorbing portion 34. Since the light travels at a transmitting angle, it is transmitted through the interface 34 b and absorbed by the light absorbing portion 34.
Thus, light emitted at a viewing angle equal to or more than a predetermined angle can be efficiently absorbed and blocked, and further, the traveling direction control of light can be efficiently performed.
In addition, such light is likely to be incident on the liquid crystal panel and cause problems such as a decrease in contrast and color inversion, so that such light can be absorbed.

  The light emitted from the optical sheet 30 is incident on the lower polarizing plate 14 of the liquid crystal panel 15. The lower polarizer 14 transmits one polarization component of the incident light and absorbs the other polarization component. The light transmitted through the lower polarizing plate 14 is selectively transmitted through the upper polarizing plate 13 in accordance with the state of the electric field application to each pixel. In this manner, by selectively transmitting the light from the surface light source device 20 for each pixel by the liquid crystal panel 15, an observer of the liquid crystal display device can observe an image. At that time, the image light is provided to the observer through the functional film 40, and the quality of the image is enhanced.

  FIG. 7 shows a diagram for explaining an optical sheet 130 of another form. FIG. 7 is a view corresponding to FIG. Since the other matters can be considered the same as the optical sheet 30, the optical sheet 130 will be described here.

  The optical sheet 130 is configured to have a base layer 31, an optical functional layer 32, and a protective layer 135. The base layer 31 and the optical function layer 32 are the same as the optical sheet 30, and therefore, the same reference numerals are given and the description is omitted.

The protective layer 135 is a layer disposed on the surface of the optical functional layer 32 on the side on which the base layer 31 is not disposed, and is formed of a UV curable resin composition not containing phenoxyethyl acrylate. .
As a result, the remaining unreacted phenoxyethyl acrylate contained in the unit light transmitting element 33b of the optical function layer 32 can be barrier-protected by the protective layer 135 to prevent the influence on the other layers. Examples of the influence on other layers include the occurrence of optical unevenness (blocking) due to partial sticking to other layers laminated on the optical sheet 130, deterioration of the other sheet, and the like. .

  In addition, a rough surface may be provided on the surface of the protective layer 135 opposite to the side laminated on the optical function layer 32. By this, it is possible to add functions of preventing optical adhesion and improving the uniformity of light.

[Configuration of optical sheet]
Example 1
An optical sheet was produced following the example of the optical sheet 30 shown in FIGS. 1 to 6 as Example 1. The specific shape of the optical sheet according to Example 1 is as follows.

(Base material layer)
・ Material: Polycarbonate resin ・ Thickness: 130μm

(Optical function layer)
The pitch of the unit light transmitting element and the light absorbing portion: 39 μm (P _{a in} FIG. 4)
· Light absorbing portion upper bottom width: 4 μm (W _{a in} FIG. 4)
· Bottom width of light absorbing portion: 10 μm (W _{b in} FIG. 4)
· Light absorbing portion upper side inclination angle: 3 ° (θ _{11 in} FIG. 5)
· Light absorbing portion lower side inclination angle: 0 ° (θ _{12 in} FIG. 5)
· Thickness of light absorbing portion: 102 μm (D _{a in} FIG. 4)
・ Thickness of optical function layer: 127 μm
・ Thickness of base: 25 μm
· Material and refractive index of light transmitting portion (unit light transmitting element and base portion): UV curable urethane acrylate resin containing phenoxyethyl acrylate having a refractive index of 1.56 · Material of light absorbing portion and refractive index: refractive index 1 20 mass% of acrylic beads containing carbon black and having an average particle diameter of 4 μm dispersed in an ultraviolet-curable urethane acrylate resin of .49

Example 2
A protective layer was laminated on the optical functional layer of the optical sheet of Example 1 according to the example of the optical sheet 130 (see FIG. 7). The protective layer was made of an ultraviolet-curable urethane acrylate resin not containing phenoxyethyl acrylate having a refractive index of 1.56, and the thickness was 25 μm.
In addition, a rough surface having a surface roughness Ra of 0.38 μm (JIS B 0601: 2001) was formed on the side of the protective layer opposite to the side in contact with the optical function layer. The surface roughness was measured by a shape measuring laser microscope (VK-8700) manufactured by Keyence Corporation.

Comparative Example 1
Among the optical sheets described in Example 1, the material of the light transmitting portion (unit light transmitting element and base portion) was formed of an ultraviolet curable urethane acrylate resin not containing phenoxyethyl acrylate. Other than this is the same as the first embodiment.

Reference Example 1
Among the optical sheets described in Example 2, the protective layer was formed of a phenoxyethyl acrylate-containing ultraviolet-curable urethane acrylate resin having a refractive index of 1.56. Other than this is the same as the second embodiment.

[Evaluation method]
<Contact test>
The optical sheets of Example 1, Example 2, and Comparative Example 1 were subjected to the adhesion test by the cross cut method in accordance with JIS K5600-5-6. In the test, an ISO cross cut guide CCI-2 manufactured by Kotec Co., Ltd. was used as a jig, a cutter was SB50K manufactured by Olfa Co., and a tape was CT405AP-24 manufactured by Nichiban Co., Ltd.

<Blocking test>
A blocking test was performed on the optical sheets of Example 2 and Reference Example 1. This is done without adhering a reflective polarizing plate (3M Japan Co., Ltd., DBEF-D2-280) having a polycarbonate base on the protective layer of the optical sheet, fixing the four sides with a frame, and keeping the temperature at 105 ° C. I kept it for 72 hours.

[result]
<Result of adhesion test>
The optical sheets of Example 1 and Example 2 were classified 0 (no peeling). On the other hand, the optical sheet of Comparative Example 1 was Class 4 (partly or completely caused large peeling).

<Result of blocking test>
In the optical sheet of Example 2, no blocking occurred between the protective layer and the reflective polarizing plate. On the other hand, in the optical sheet of Reference Example 1, blocking occurred between the protective layer and the reflective polarizing plate, and optical unevenness occurred.

10 image source unit 15 liquid crystal panel 20 surface light source device 21 light guide plate 25 light source 26 light diffusion plate 27 prism layer 28 reflection type polarizing plate 30 optical sheet 31 base layer 32 optical function layer 33 light transmitting portion 33a base portion 33b unit light transmission Element 34 Light Absorber

Claims (6)

A substrate layer made of polycarbonate,
An optical functional layer laminated on one surface of the base material layer,
The optical function layer has a light transmitting portion and a light absorbing portion,
The light transmitting portion includes unit light transmitting elements extending in one direction with a predetermined cross section and arranged in a direction different from the one direction at predetermined intervals.
The light absorbing portion is formed between adjacent unit light transmitting elements,
The light transmitting portion is formed of an ultraviolet curable resin containing phenoxyethyl acrylate,
Optical sheet.   The optical sheet according to claim 1, wherein a protective layer of a resin not containing phenoxyethyl acrylate is laminated on the surface of the optical functional layer opposite to the side on which the base material layer is laminated.   The optical sheet according to claim 1, wherein a rough surface is formed on the surface of the protective layer opposite to the side on which the optical functional layer is laminated.   The surface light source device provided with a light source and the optical sheet in any one of the Claims 1 thru | or 3 arrange | positioned rather than this light source at the observer side.   An image source unit comprising: the surface light source device according to claim 4; and a liquid crystal panel disposed on the light exit side of the surface light source device.   The display apparatus with which the imaging | video source unit of Claim 5 was accommodated in the housing | casing.

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