JP2003043214A - Optically functional sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optically functional sheet having a flat surface form which can be subjected to surface processing or can be laminated with other functional sheets, which generates a light converging function depending on the inner state, and which has an inner converging function to converge all of rays diverging in the vertical and lateral directions of the screen by one sheet. SOLUTION: The optically functional sheet has an arranged layer in which a transparent phase and a diffusion phase are alternately arranged in the plane direction. In the cross section of the arranged layer along the plane direction of the sheet, the diffusion phase is arranged as a continuous phase having segments connected to one another, and the transparent phase is arranged as a discontinuous phase segmented by the diffusion phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light condensing material attached to various displays, and more particularly to an optical functional sheet suitable for use as a backlight in a liquid crystal display.

[0002]

2. Description of the Related Art In recent years, various displays have been used for various purposes such as portable devices, personal computers, monitors and televisions. Among them, liquid crystal displays are widely used from small products for mobile devices to recently large-sized products such as monitors and televisions. Since the liquid crystal display is not a light-emitting body itself, it can be displayed by making light incident from the back side by a backlight.

Further, the backlight is required not only to illuminate light but also to light the entire screen uniformly and brightly. Therefore, in order to turn on the backlight uniformly, an optical functional sheet such as a diffusion film or a prism sheet is usually attached. That is, in a backlight, a diffusion film for equalizing the emission distribution of light rays is placed on the light guide plate, and further, in order to improve the brightness of the front, it is usually used by stacking prism sheets for collecting light in the front direction. Has been done.

The prism sheet is a sheet having a structure in which a large number of prisms each having a substantially triangular cross section are arranged. By using this sheet, the light from the backlight can be efficiently collected in the front direction. Brightness is improved. Furthermore, when particularly high brightness is required, two prism sheets are used so that the prism rows are orthogonal to each other. First, the light that spreads in the vertical direction of the screen is condensed in the front direction, and then in the horizontal direction of the screen. A method of converging the spreading light in the front direction is adopted.

[0005]

However, since the prism rows on the surface of the prism sheet are extremely fine and have a structure with a sharp apex angle, there is a problem that the surface is easily damaged during manufacturing or handling.

Further, the optical functional sheets used for these backlights are required to have further improved performance and efficiency, thinner and lighter weight, and in order to achieve these, for example, surface coating / pasting Means such as function integration by matching are effective. However, such a surface treatment is impossible in the case of a film such as a prism sheet which has irregularities on the surface or which exhibits performance by utilizing the irregularities on the surface.

Furthermore, in the prism sheet, since it is not possible to form a prism array which exerts a light-collecting effect simultaneously in the two-dimensional directions within the plane, the light in the vertical direction of the screen and the light in the horizontal direction of the screen are condensed by one sheet. Can not do it.

[0008] Therefore, an object of the present invention is to have a flat surface shape that can be surface-processed and laminated with another functional sheet, and can exert a light condensing function depending on the internal form. An object of the present invention is to provide an optical functional sheet having an internal light condensing function capable of simultaneously concentrating light that spreads in the vertical direction and light that spreads in the horizontal direction on a single sheet.

[0009]

The optical functional sheet of the present invention is an optical functional sheet having an array layer in which a transparent phase and a diffusion phase are alternately arrayed in a plane direction, and is a sheet within the array layer. In the cross section in the plane direction, the diffusion phase is arranged as a continuous phase interconnected with each other, and the transparent phase is arranged as a discontinuous phase divided by the diffusion phase.

Further, the optical functional sheet of the present invention preferably further has the following requirements. (A) In the cross section of the array layer in the sheet surface direction, the shape of the transparent phase is a shape selected from a substantially triangular shape, a substantially quadrangular shape, a substantially hexagonal shape, a circle, and an ellipse. (B) In the cross section of the array layer in the sheet surface direction, the area ratio of the transparent phase and the diffusion phase is 50/1 to 1/1. (C) The ratio (L / p) of the length L of the transparent phase in the sheet thickness direction to the minor axis length p of the transparent phase in the sheet surface direction cross section in the arrangement layer is 2 to 10. (D) The ratio (q / p) of the major axis length q and the minor axis length p of the transparent phase in the sheet surface direction cross section in the array layer is 1 to 10. (E) The diffusion phase is made of a material in which fine particles having a refractive index different from that of the matrix component are dispersed in a transparent matrix component. (F) It has a sheet structure in which an array layer is formed on a base film. (G) The substrate film is in a transparent matrix component,
The matrix component is a diffusion film in which fine particles having different refractive indexes are dispersed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The optical functional sheet of the present invention is an optical functional sheet having an array layer in which transparent phases and diffusion phases are alternately arrayed in the surface direction, and the sheet surface direction in the array layer is In the cross section, the diffusion phase is arranged as a continuous phase interconnected with each other, and the transparent phase is arranged as a discontinuous phase divided by the diffusion phase. An example of the array layer in which the transparent phase and the diffusion phase are arrayed in this way is shown in FIG. Figure 1
FIG. 4 is a perspective view schematically showing a part of the array layer, the upper surface of the drawing corresponds to the surface of the array layer, and the vertical direction of the drawing corresponds to the thickness direction of the array layer. In FIG. 1, the transparent phase 2 has a substantially square shape and is arranged as mutually discontinuous phases. In addition, the diffusion phase 1 existing in a grid pattern so as to fill the space between the transparent phases is arranged as a continuous phase interconnecting with each other. Furthermore, it can be seen from the cross-sectional view (FIG. 3 (a)) taken along the dotted line in FIG. 1 that the transparent phase and the diffusion phase are alternately arranged in the plane direction.

As described above, the arrangement layer in the optical functional sheet of the present invention is arranged as a continuous phase in which the diffusion phases 1 are connected to each other and the transparent phase 2 is diffused in the sheet surface cross section in the arrangement layer. It is characterized in that they are arranged as discontinuous phases separated by phases. As used herein, the term "continuous phases that are interconnected with each other" means that they are connected in the sheet surface direction cross section of the array layer, and the "discontinuous discontinuous phase" is the sheet surface direction cross section of the array layer. Shows that the layers showing the same performance are scattered without being connected. That is, when observed in a cross section of the array layer in the sheet surface direction, it was confirmed that the transparent phase 2 having a polygonal shape or a circular shape was scattered in the diffusion phase 1 connected in the plane, and When the inside is observed in a perspective view, it is confirmed that a large number of polygonal columns or cylinders of the transparent phase 2 are arranged inside the sheet of the diffusion phase 1 perpendicularly to the sheet surface.

The arrangement layer in the sheet of the present invention is
It is preferable that the transparent phase 2 has a shape selected from a substantially triangular shape, a substantially quadrangular shape, a substantially hexagonal shape, a circular shape, and an elliptical shape in a cross section of the arrangement layer in the sheet surface direction. 2 (a)-
(D) is a cross-sectional view in a cross section parallel to the sheet surface in the array layer, and schematically illustrates the shape of the transparent phase 2. 2A shows a case where the transparent phase 2 has a circular cross section, FIG. 2B shows a triangular shape, FIG. 2C shows a quadrangular shape, and FIG. 2D shows a hexagonal shape. The following are examples. The transparent phase 2 may be aligned as in the case shown, or may be randomly arranged.

3 (a) to 3 (g) are cross-sectional views for illustrating the shape of the diffusion phase 1 in the cross-section of the arrangement layer in the sheet of the present invention. In addition, the cross-sectional view of FIG.
It corresponds to a cross-sectional view taken along the dotted line in FIG. As the shape of the diffusion phase 1 observed in the cross section,
Rectangle (Figs. 3 (a), (f), (g)), trapezoid (Fig. 3)
(B)), triangles (FIG. 3 (c)), deformed versions thereof (FIGS. 3 (d) and (e)), and mixtures of these are preferable, but other shapes are also used. be able to. That is, in addition to FIG. 3A in which the diffusion phase 1 having a rectangular cross section is almost perpendicular to the sheet surface,
The forms (b) to (e) are also included. Also, FIG.
As shown in (f) and (g), when the diffusion phase 1 does not exist near the upper surface and / or the lower surface of the array layer, and the upper surface and / or the lower surface of the array layer are covered with the transparent phase 2. Is also preferably used.

In this arrangement layer, it is preferable that the area of the transparent phase 2 is equal to or larger than the area of the diffusion phase 1 in the cross section of the arrangement layer in the sheet surface direction, and the area ratio (transparent phase 2 / diffusion). Phase 1) is preferably 50/1 to 1/1, and more preferably 40/1 to 2/1. By setting the area ratio to 50/1 to 1/1,
It is preferable because the diffusion phase can exert a sufficient luminance improving effect without lowering the light utilization efficiency.

Further, the ratio of the major axis length q of the transparent phase 2 to the minor axis length p (q /
It is preferable that p) is 1 to 10. The major axis length q and the minor axis length p of the transparent phase 2 are cross-sectional views in a cross section parallel to the sheet surface in the arrangement layer, as in FIGS. 2 is an enlarged view of the two transparent phases 2 therein), the longest and the shortest of the lengths circumscribing the outer shape of the transparent phase 2 with parallel line segments, respectively, The major axis length is q and the minor axis length is p. This ratio (q
It is preferable to set / p) to 1 to 10 because the light rays spreading in all directions can be efficiently focused on the front surface. Furthermore, since the values of p and q can be freely selected, there is an advantage that the light collecting performance in the two-dimensional direction, that is, the vertical and horizontal directions can be freely designed.

Further, the ratio (L / p) of the length L of the transparent phase in the sheet thickness direction to the minor axis length p of the transparent phase in the sheet surface direction cross section in the arrangement layer is 2 to 10. preferable. The length L in the thickness direction refers to the thickness of the transparent phase 2 in the array layer, as shown in FIG. By setting this ratio to 2 to 10, the diffusion phase 1 can be obtained without lowering the light utilization efficiency.
This is preferable because it is possible to obtain a sufficient brightness improving effect.

The thickness of the array layer in the optical functional sheet of the present invention is preferably 10 μm to 10 mm, and 10 μm.
It is more preferably m to 5 mm.

Examples of the material of the transparent phase 2 constituting the alignment layer in the optical functional sheet of the present invention include polyester resins such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate and polybutylene terephthalate, and polycarbonate. Polyolefin resins such as polystyrene, polyethylene, polypropylene and polymethylpentene, acrylic resins such as polyamide, polyether, polyesteramide, polyetherester, polyvinyl chloride and poly (meth) acrylic acid ester, alicyclic polyolefin and these A transparent resin or the like, which is composed of a copolymer containing as a main component, a mixture of these resins, or the like can be preferably used, but is not particularly limited. The term "transparent" as used herein means that light is transmitted substantially straight within the phase.

The diffusion phase 1 is not particularly limited, but is preferably made of a material in which fine particles having a refractive index different from that of the matrix component are dispersed in a transparent matrix component. Examples of the transparent matrix component include polyester resins such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, and polybutylene terephthalate, polycarbonate resins, polyolefin resins such as polystyrene, polyethylene, polypropylene, polymethylpentene, and polyamide. , Acrylic resins such as polyethers, polyesteramides, polyetheresters, polyvinyl chloride, poly (meth) acrylic acid esters, alicyclic polyolefins, and copolymers containing these as the main components, or mixtures of these resins, etc. Examples of such transparent resins include, but are not particularly limited to. The fine particles are not particularly limited as long as they have a refractive index different from that of the matrix component, and examples thereof include bubbles, inorganic fine particles, and organic fine particles.

The optical functional sheet of the present invention may be a single-layer sheet consisting only of the above-mentioned alignment layer, but it is on the base film from the viewpoint of mechanical strength, heat resistance, handleability, etc. of the sheet itself. A sheet structure in which an array layer is formed is also a preferred embodiment.

In the case of a sheet structure in which an alignment layer is formed on a base film, a polyester film such as polyethylene terephthalate or polyethylene-2,6-naphthalate is preferably used as the base film. To be The base film may be transparent, but it is more preferable to use a diffusion film.
The diffusion film in this case has a structure in which fine particles having a refractive index different from that of the matrix component are dispersed in a transparent matrix component, and is a diffusion film having a diffusion function incorporated inside the film. By using the diffusion film as the base film, it becomes possible to achieve the functions of the diffusion film and the prism sheet, which have been conventionally used, with one sheet.

The thickness of the substrate film is 20 to 500 μm, more preferably 30 to 300 μm from the viewpoint of mechanical strength and the like.
m, and more preferably 50 to 200 μm.

An example of the method for producing the optical functional sheet of the present invention is shown below. The manufacturing method is not limited to the methods listed here. As an example, an optical functional sheet having a structure in which an array layer in which diffusion phases are arrayed in a lattice shape in the surface direction as shown in FIG. 1 is formed on a base film will be described.

As one method, a transparent photocurable resin is applied on a substrate film, and the applied layer is covered with a photomask having a pattern having a grid-like light-shielding portion, and the film is exposed to light through the photomask and developed. . As a result, a substantially rectangular transparent phase is formed. Next, there is a method in which a resin containing fine particles and the like is embedded between the transparent patterns to form a diffusion phase, thereby obtaining the desired optical functional sheet. Further, as another method, a resin containing fine particles and the like is applied to one surface of the base film, and a diffusion phase is formed by a method of ejecting an abrasive through a mask and scraping it into a desired shape (sandblast method), After that, there is a method of filling the gap with a transparent photocurable resin and then photocuring it.

The mechanism by which the brightness enhancement effect is exhibited when the optical functional sheet of the present invention is used as a film for a backlight of a liquid crystal display will be described with reference to FIG.

In FIG. 5, the diffusion sheet 4 is arranged on the upper surface side of the light guide plate 5, the optical functional sheet 3 of the present invention is further arranged thereon, and the reflection sheet 7 is arranged on the lower surface side of the light guide plate 5. Are arranged. Further, a fluorescent tube 6 is arranged on the side surface of the light guide plate 5. Note that FIG. 5 shows the relative positional relationship of these members, and when used as a backlight, these members are in contact with each other. The light emitted from the fluorescent tube 6 enters the light guide plate from the side surface of the light guide plate 5, and exits upward from the upper surface of the light guide plate 5 through the diffusion sheet 4 and the sheet 3 of the present invention.

The sheet 3 of the present invention has an arrangement layer in which the transparent phase 2 and the diffusion phase 1 are alternately arranged in the plane direction. In this arrangement layer, the transparent phase 2 and the diffusing phase 1 are alternately arranged in the plane direction, so that the diffusing phase 2 serves as a wall for diffusing light rays. That is, in the arrangement layer of the sheet of the present invention,
Rays incident from the surface direction (from below in FIG. 5) are
The diffuse phase 2 is diffusely transmitted or diffusely reflected. This diffusion is the point. By being diffused, the number of light rays emitted in the side direction (horizontal direction in FIG. 5) can be reduced, and more light rays can be scattered in the front direction (upward direction in FIG. 5), which results in brightness in the front direction. Is improved. If a specular reflection layer is used instead of the sheet of the present invention, the light rays incident from below in FIG. 5 are emitted while maintaining the incident angle, and thus are not condensed in the front direction. The brightness at the front is not improved.

Further, in the arrangement layer of the sheet 3 of the present invention,
This structure has a structure in which the transparent phase 2 is discontinuously distributed in the diffusion phase 1 that continuously spreads, and by adopting this structure, a single sheet can efficiently direct incident light rays in all directions to the front. The light can be focused in any direction. On the other hand, in the case of the conventionally used prism sheet, one sheet can collect light in one of the vertical and horizontal directions,
In order to exert a vertical and horizontal two-dimensional light-collecting effect, it is necessary to use two prism sheets and stack them so that the respective prism arrays are orthogonal to each other. However, in the case of the optical functional sheet of the present invention, it is possible to exhibit a vertical and horizontal two-dimensional light-condensing effect with a single sheet by adopting the above structure.

Further, the sheet of the present invention can be preferably used as a sheet for a backlight of a liquid crystal display, and in this case, by stacking it on a light guide plate or a diffuser plate, the brightness in the front direction can be efficiently obtained. Can be improved.

Further, the optical functional sheet of the present invention has the feature that the surface is smooth because its light collecting function is exerted by the structure of the array layer existing inside the sheet. Therefore, the surface can be processed.
In addition, it is possible to bond with a base material having other functions, and it is possible to manufacture a multifunctional high-performance sheet having multiple functions. For example, a sheet having both a high diffusion function and a high brightness function can be obtained even if it is thin, by adhering it to a diffusion plate having a smooth surface and integrating them.

[0032]

EXAMPLES The present invention will now be described with reference to examples, but the present invention is not necessarily limited to these.

Example 1 A polyethylene terephthalate (PET) film was coated with a composition for the diffusion phase having the following composition so that the dry film thickness was 200 μm. Calcium carbonate (average particle size 2 μm) 60 parts by weight Ethyl cellulose 16 parts by weight Terpineol 24 parts by weight

Next, after mounting a sandblasting mask having a grid pattern, unnecessary portions were shaved off. Alumina was used as the abrasive. Subsequently, an ultraviolet curable composition composed of tetrahydrofurfuryl methacrylate was embedded in the scraped portion, and the transparent phase was formed by curing the composition by irradiating it with ultraviolet rays to prepare the desired optical functional sheet. The in-plane pattern of the array layer in the obtained optical functional sheet is a sheet having a square transparent phase as shown in FIG. 1, and the in-plane pitch is a transparent phase / diffused phase = 20.
It was μm / 50 μm.

The obtained optical functional sheet was placed on a straight tube 4-lamp type backlight for a personal computer monitor in a relative positional relationship as shown in FIG. 5, and a color luminance meter BM-7 (manufactured by Topcon Corporation) ) Was used to measure the front luminance. The brightness was improved by 72% as compared with the case of measuring without the optical functional sheet. Compared to the case where two prism sheets are used orthogonally like a conventional prism sheet, the number of sheets can be reduced and the assembling work can be omitted.

(Examples 2 to 4) The in-plane transparent phase pattern of the array layer in the optically functional sheet has a perfect circle (Example 2,
2A), regular triangle (Example 3, FIG. 2B), regular hexagon (Example 4, FIG. 2D), except that the pattern of the sandblasting mask was changed. An optical functional sheet was produced in the same manner as in 1, and the luminance was measured in the same manner. In each pattern, the distance between the centers of adjacent transparent phases is 70 μm (transparent phase 25 μm / diffusion phase 20
μm / transparent phase 25 μm). As a result of the brightness measurement, the brightness improvement rates are 68% (Example 2) and 71%.
(Example 3), 72% (Example 4), a high brightness improving effect was obtained.

[0037]

EFFECTS OF THE INVENTION According to the present invention, it has a flat surface shape that can be surface-processed and laminated with other function sheets, and can exert a light-collecting function depending on the internal form. A single sheet can be used as an optical functional sheet that has an internal light-collecting function that can simultaneously collect light that spreads in the vertical direction of the screen and light that spreads in the horizontal direction. Useful for.

Further, since the optical functional sheet of the present invention can be integrated with another function sheet having a smooth surface (for example, a diffusion sheet), it has a high brightness and thin type having both the light condensing function and the other functions. It is also possible to make an integrated sheet and apply it to a liquid crystal display member such as a backlight.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a part of an array layer in an example of the optical functional sheet of the present invention. In the figure, the colored portion indicates the diffusion phase 1 and the colorless portion indicates the transparent phase 2.

2 (a) to 2 (d) are cross-sectional views in a cross section parallel to the sheet surface in the arrangement layer of the optical functional sheet of the present invention, schematically illustrating the shape of the transparent phase 2. FIG.

3 (a) to 3 (g) are each a cross-sectional view of an alignment layer in the optical functional sheet of the present invention, schematically illustrating the shape of the diffusion phase 1 in the cross-section.

4 (a) and 4 (b) are cross-sectional views in a cross section parallel to the sheet surface in the array layer in the optical functional sheet of the present invention, in which two transparent phases 2 are enlarged. Is shown.

FIG. 5 is a device structure diagram showing a relative positional relationship of each member in the backlight used in the luminance measurement of the example.

[Explanation of symbols]

1 diffusion phase 2 transparent phase 3 Optical functional sheet of the present invention 4 diffusion sheet 5 Light guide plate 6 fluorescent tubes 7 Reflective sheet

Claims (8)

[Claims] 1. An optical functional sheet having an array layer in which a transparent phase and a diffusive phase are alternately arrayed in a plane direction, wherein the diffusive phase is continuous with each other in a sheet plane direction cross section in the array layer. An optical functional sheet, wherein the optically functional sheet is arranged as a transparent phase and is arranged as a discontinuous phase separated by a diffusion phase. 2. In the sheet surface direction cross section in the array layer,
The shape of the transparent phase is a triangle, a rectangle, a hexagon, a circle,
A shape selected from an ellipse.
The optically functional sheet described. 3. A sheet surface direction cross section in the array layer,
The optical functional sheet according to claim 1 or 2, wherein the area ratio of the transparent phase and the diffusion phase is 50/1 to 1/1. 4. The length L of the transparent phase in the sheet thickness direction.
And the minor axis length p of the transparent phase in the sheet surface direction cross section in the array layer (L / p) is 2 to 10, The optical according to any one of claims 1 to 3, wherein Functional sheet. 5. The ratio (q / p) of the major axis length q and the minor axis length p of the transparent phase in the cross section of the arrangement layer in the sheet surface direction is 1.
10. The optical functional sheet according to claim 1, wherein the optical functional sheet is 10. 6. The optical function according to claim 1, wherein the diffusion phase is made of a material in which fine particles having a refractive index different from that of the matrix component are dispersed in a transparent matrix component. Sex sheet. 7. The optical functional sheet according to claim 1, which has a sheet structure in which an array layer is formed on a base film. 8. The optical functionality according to claim 7, wherein the base film is a diffusion film made of a material in which fine particles having a refractive index different from that of the matrix component are dispersed in a transparent matrix component. Sheet.