JP2002337164A - Method for producing optical film and liquid crystal display device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a light emitting means in which grooves of a fine structure in which both ends are dug at an acute angle are arranged with high positional accuracy, and to efficiently emit light incident from the side surface of a liquid crystal display panel. Development of a manufacturing method capable of efficiently obtaining an optical film excellent in thinness capable of forming a thin, light, bright, and easily viewable liquid crystal display device by changing the optical path in the viewing direction well. A radiation-curable resin applied layer applied to a transparent film (11) has an inclination angle of 35 with respect to the film surface.
An electroforming mold (2) having a convex portion (21) capable of forming a light emitting means composed of a plurality of concave portions (A) having an optical path changing slope (a) of -48 degrees is brought into close contact with the coating layer. A method for producing an optical film, in which a molding layer (12) that reflects the surface shape of a casting mold is formed, radiation is irradiated from the side of the transparent film, and the molding layer is cured (13) and separated from the mold. A liquid crystal display device comprising an optical film disposed on at least one side of a liquid crystal cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical film capable of forming a thin, light, bright, and easy-to-view liquid crystal display device by efficiently converting the light incident from the side of a liquid crystal display panel into an optical path in a viewing direction. About.

[0002]

BACKGROUND OF THE INVENTION A reflection type liquid crystal display device of a front light type in which a side light type light guide plate is arranged on a viewing side surface of a liquid crystal display panel has been known (Japanese Patent Laid-Open No. 11-25 / 1999).
No. 0715). However, since the light guide plate is formed by machining, it is difficult to perform fine processing, and it is difficult to precisely arrange the light emitting means including the groove at a predetermined position in a small size and to cut both ends of the groove at an acute angle. However, there is a problem that it is difficult to reduce the thickness of the liquid crystal display device, and it is difficult to reduce the thickness and weight of the liquid crystal display device.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to a light emitting device having light emitting means in which both ends are formed with a fine structure groove dug at an acute angle with a high degree of positional accuracy. It is an object of the present invention to develop a manufacturing method capable of efficiently obtaining an optical film having an excellent thinness that can form a thin, light, bright, and easy-to-view liquid crystal display device by efficiently converting the optical path in the viewing direction.

[0004]

According to the present invention, there is provided a light emitting means comprising a plurality of concave portions having an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to a film surface by applying a coating layer of a radiation-curable resin applied to a transparent film. Is adhered to an electroforming mold having a convex portion capable of forming a, forming a molding layer on the coating layer which reflects the surface shape of the electroforming mold, irradiating radiation from the transparent film side, and curing the molding layer. The present invention provides a method for producing an optical film, characterized in that the optical film is separated from a metal mold, and a liquid crystal display device, wherein the optical film is arranged on at least one side of a liquid crystal cell.

[0005]

According to the present invention, a coating layer of a radiation-curable resin is formed into a predetermined shape via an electroforming mold and subjected to a curing treatment. It is possible to efficiently obtain an optical film having light emitting means arranged with high accuracy, and to efficiently convert the light incident from the side surface of the liquid crystal display panel in the viewing direction to thin and light, bright and easy to see. A liquid crystal display device for display can be formed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the production method according to the present invention, a coating layer of a radiation-curable resin applied to a transparent film is formed of a plurality of concave portions having an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to the film surface. The light emitting means is brought into close contact with an electroforming mold having a convex portion, and a molding layer that reflects the surface shape of the electroforming mold is formed on the coating layer, and radiation is irradiated from the transparent film side to form the molding layer. The optical film is obtained by curing the layer and separating it from the mold. The manufacturing process is illustrated in FIG. 1 is an optical film, 11 is a transparent film, and 13 is a molded cured layer of a radiation-curable resin. In addition, the example of a figure has shown from formation of an electroforming metal mold (I-C) to formation of an optical film (D, E).

As shown in the figure, an optical film 1 is formed by a plurality of concave portions A having an optical path changing slope a having an inclination angle θ1 of 35 to 48 degrees with respect to the film surface via an electroforming mold 2 having a predetermined convex portion 21. It is formed by molding light emitting means. The electroforming mold can be formed by, for example, a method of performing an electroforming method on the insulating film 3 having the predetermined concave portion A ′ formed by dry etching as shown in FIGS.

[0008] By forming the concave portion by dry etching, fine processing can be performed with much higher precision than mechanical processing, and a groove (recess) having both ends dug at an acute angle.
Can be distributed and arranged with high positional accuracy. Dry etching, which is preferable from the viewpoint of fine processing accuracy, is a method using laser light. As the laser, for example, one or more appropriate lasers such as an excimer laser, a YAG laser, a CO ₂ laser, and a femtosecond laser can be used. Particularly, a laser having an oscillation wavelength in the ultraviolet region of 400 nm or less is preferable.

On the other hand, as the insulating film to be etched, a film made of a suitable electrically insulating material can be used, and there is no particular limitation. By the way, examples are polyester resin, epoxy resin, urethane resin, polystyrene resin, polyethylene resin, polyamide resin, polyimide resin, AB
Examples include films made of S resin, polycarbonate resin, silicone resin, and the like. In particular, an insulating film made of a polyimide resin can be preferably used from the viewpoint of heat resistance, chemical resistance, and laser workability. The thickness of the film is optional, but is preferably 500 μm or less, and more preferably 10 μm or less, in view of the handleability during etching (FIG. 1A) and the formation of an electroforming mold, strength, and the ability to form a concave portion corresponding to the light emitting means.
〜200 μm is preferred.

Light emitting means comprising a plurality of predetermined concave portions, that is, concave portions having an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to the film surface for the purpose of being provided on the optical film as shown in the example of FIG. The insulating film 3 having the concave portion A ′ corresponding to the above is formed by, for example, a method of performing an ablation process with a laser beam on the insulating film through a mask of a predetermined shape and etching and removing a predetermined portion of the insulating film. Can be. In this case, an insulating film having the target concave portions is efficiently formed by using a mask in which a plurality of openings having a size corresponding to the light emitting means including the target plural concave portions are arranged in a predetermined distribution state. be able to.

As shown in FIG. 1B, the electroforming mold 2 is formed by applying an electroforming method to the insulating film 3 having a predetermined concave portion. Thereby, the mold 2 having the convex portions 21 corresponding to the concave portions A 'provided in the insulating film 3 with high precision can be formed as in the example of FIG. In the above-described electroforming method, a metal is filled on a side provided with the concave portion of the insulating film to form an electroformed mold including a metal layer having a replica of a surface shape of the side provided with the concave portion of the insulating film. A method according to the related art can be applied. Therefore, when forming the metal layer, a conductive film is provided on the side of the insulating film on which the concave portion is provided, and a method according to the related art can be applied to the formation of the conductive film.

There is no particular limitation on the type of metal forming the electroforming mold. Generally, for example, gold, silver, copper, iron, nickel, cobalt, or alloys thereof are used. It may be added. The kind of metal used may be one kind or two or more kinds, and an electroforming mold formed by laminating different kinds of metals can also be formed. The thickness of the metal layer formed as the electroformed mold may be determined as appropriate. In order to prevent breakage at the time of separation from the insulating film and handleability at the time of forming the optical film, the thickness of the portion having no convex portion is about 0.02 to 3 mm. A mold is preferred.

As shown in FIG. 1D and FIG. 1E, the optical film is formed by applying a radiation-curable resin to the transparent film 11 and applying the applied layer to the surface of the electroformed mold 2 on which the convex portions 21 are formed. The molding layer 1 in which the surface shape on the side of the convex portion of the electroforming mold is copied onto the coating layer by being brought into close contact with the coating layer, and thereby the surface shape is copied.
2 is formed and irradiated with radiation from the side of the transparent film 11 to cure the molded layer, thereby forming a cured layer 13
Is separated from the electroforming mold 2 together with the transparent film 11 as necessary. Thus, the electroforming mold has a concave portion and a surface shape corresponding to the surface shape on the convex portion forming side with high precision, and accordingly, the inclination angle with respect to the film surface is 35 to 48.
It is possible to obtain an optical film having a light emitting means composed of a plurality of concave portions having an optical path changing slope.

In the above, a preferred method of manufacturing an optical film is to wind a deformable electroforming mold around the outer periphery of a cylindrical or cylindrical circular rotating body, and rotate the electroforming mold while rotating the electroforming mold through the rotating body. On the lower electroforming mold, the coating layer of the radiation-curable resin provided on the long transparent film is successively pressed to form a molding layer that reflects the surface shape of the electroforming mold, while continuously forming the molding layer. This is a method of continuously producing an optical film by irradiating radiation.

As described above, according to the method of the present invention, as shown in the example of FIG. 2, the optical film 1 having the light emitting means comprising a plurality of concave portions A having an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to the film surface is provided. What you get. In addition, the optical film reflects incident light from the side surface of the liquid crystal cell having a light source on the side surface or transmitted light from the side direction of the liquid crystal through an optical path changing slope, and the back surface side (the side having no light emitting means).
Accordingly, it is an object of the present invention to change the optical path in the viewing direction of the liquid crystal display panel and emit the light, and to use the emitted light as illumination light (display light) for the liquid crystal display panel or the like. Therefore, the optical film is generally arranged so that the surface on which the light emitting means is formed is on the outside in the direction along the plane of the liquid crystal cell.

In the above, the transparent film which may form an optical film is formed by using one or more kinds of appropriate materials exhibiting transparency according to the wavelength range of light incident through a light source or the like. be able to. Incidentally, in the visible light region, for example, acrylic resins, polycarbonate resins, transparent resins represented by cellulose resins, norbornene resins, and the like, and curable resins that can be polymerized by heat, ultraviolet rays, radiation such as electron beams, and the like. .

The preferred refractive index of the transparent film is equal to or higher than that of the liquid crystal cell, especially the cell substrate, in order to increase the efficiency of incidence on the light path changing slope to obtain a liquid crystal display device which is bright and has excellent uniformity. 1.49 or more, especially 1.52
That is all. From the viewpoint of suppressing surface reflection in the case of a front light system, the refractive index is preferably 1.6 or less, more preferably 1.56 or less, and particularly preferably 1.54 or less.
Note that such a refractive index is generally based on the D-line in the visible light range, but is not limited to the above when the wavelength range of the incident light has specificity, and may be in accordance with the wavelength range. Yes (same below).

From the viewpoint of obtaining a liquid crystal display device with less display unevenness by suppressing unevenness in brightness and color, a transparent film which does not exhibit birefringence or has small birefringence, particularly, an in-plane average retardation of 30 nm. These are: When a transparent film having a small phase difference is used, when linearly polarized light enters through an optical film or the like, the polarization state can be favorably maintained, which is advantageous for preventing a deterioration in display quality.

From the viewpoint of preventing display unevenness, the average in-plane retardation of the transparent film is preferably 20 nm or less, more preferably 15 nm or less.
It is more preferably 10 nm or less, particularly 10 nm or less, and the variation of the phase difference at each location is as small as possible. Further, a transparent film made of a material having a small photoelastic coefficient is preferable from the viewpoint of suppressing the internal stress generated in the transparent film and preventing the occurrence of a phase difference due to the internal stress. In addition, the average retardation in the thickness direction of the transparent film is preferably 50 nm or less, more preferably 30 nm or less, and particularly preferably 20 nm or less from the viewpoint of preventing display unevenness and the like.

The formation of such a low retardation transparent film is as follows:
For example, it can be performed by an appropriate method such as a method of removing internal optical distortion by a method of annealing an existing film or the like. A preferred forming method is a method of forming a transparent film having a small retardation by a casting method. The above-mentioned retardation in the transparent film is preferably based on light in the visible region, particularly light having a wavelength of 550 nm. The above-mentioned average retardation in the plane is defined by (nx−ny) × d, and the average retardation in the thickness direction is ｛(nx + ny) / 2.
−nz｝ d. Where nx is the average refractive index in the direction showing the maximum refractive index in the film plane, ny
Is the average refractive index in the direction orthogonal to the nx direction in the film plane, nz is the average refractive index in the thickness direction of the film,
d means the average thickness of the film.

The transparent film is usually formed as a single layer, but may be formed as a laminate made of the same or different materials. The thickness of the transparent film can be appropriately determined and is not particularly limited, but is preferably 5 to 500 μm, more preferably 10 to 300 μm, particularly 20 to 10 from the viewpoint of thinning and weight reduction.
0 μm is preferred. With such a thickness, sizing by punching or the like can be easily performed.

The light emitting means provided on the optical film is shown in FIG.
As in the example of E, the inclination angle θ1 with respect to the film surface is 35 to 4
It is formed by a plurality of concave portions A having an optical path changing slope a of 8 degrees. By the way, in the illustrated example, it is formed of a concave portion having a substantially triangular cross section and having an optical path conversion slope a and an elevation b having a large slope angle θ2. The concave means that the optical film is concave (groove).

As described above, the incident light or the transmitted light from the side direction of the light source disposed on the side surface of the liquid crystal cell or the like is transmitted through the optical path changing slope a to the rear surface side of the optical film having no light emitting means, and the liquid crystal is converted. Light having excellent directivity in the normal direction to the cell or the like can be emitted from the side where the transparent film is provided with good use of light from the light source. If the inclination angle of the optical path conversion slope is less than 35 degrees, the angle of display light emitted from the liquid crystal display panel exceeds 30 degrees, which is disadvantageous for visual recognition. On the other hand, if the angle of inclination of the optical path changing slope exceeds 48 degrees, light is likely to leak from the slope without being totally reflected and the light use efficiency is reduced.

In the above case, when the reflection method using the light path changing slope is used instead of the reflection method using the light emitting means having a roughened surface, the light is hardly reflected in the vertical direction and is inclined more greatly than the front direction from the liquid crystal display panel. The light is emitted in the direction, and the liquid crystal display becomes dark and the contrast becomes poor. Efficient total reflection through the light path conversion slope and emits light with good directivity in the normal direction of the film surface from the back surface on the side where the transparent film is attached,
The preferable inclination angle θ of the optical path conversion slope from the viewpoint of efficiently illuminating the liquid crystal cell and achieving a bright and easy-to-view liquid crystal display.
1 is 38-45 degrees, especially 40-43 degrees.

The light emitting means may be formed as a stripe-shaped recess continuous from one side to the other side, but is preferably formed as a plurality of discontinuously interrupted recesses as shown in the example of FIG. is there. The concave portions may be distributed in parallel based on the optical path changing slope as shown in the figure, or may be irregularly distributed. Furthermore, the distribution state may be a pit-like (concentric) arrangement with respect to the virtual center. Further, the concave portion may have an appropriate form such as a substantially triangular shape to a substantially pentagonal shape based on a cross section with respect to the optical path conversion slope. In general, the recess is formed to have a substantially triangular cross section as shown in the figure from the viewpoint of reduction in visibility due to size reduction and production efficiency. Note that "substantially" such as the above-mentioned triangular shape means that a change such as a change in the angle of a side or a circularization of an angle formed by the intersection of the sides is permitted.

The arrangement state of the plurality of concave portions can be appropriately determined according to the form or the like. As described above, the light path conversion slope a is configured to reflect the incident light from the side direction by the light source in the illumination mode toward the back side of the optical film to change the light path, so that the concave portion having the light path conversion slope is provided. By distributing the light on one side of the transparent film so that the total light transmittance is 75 to 92% and the haze is 4 to 20%, it is possible to efficiently illuminate the liquid crystal cell by changing the light path from the side direction through the light source. This is more preferable in that a bright surface light source is obtained to achieve a bright and excellent contrast liquid crystal display. Such characteristics of the total light transmittance and the haze can be achieved by controlling the size and distribution density of the concave portion. For example, the occupied area based on the projected area of the light emitting means on the surface of the optical film on which the light emitting means is formed is reduced by one. / 100-1 / 8, especially 1
/ 50 to 1/10, especially 1/30 to 1/15.

More specifically, if the size of the optical path conversion slope is large, the existence of the slope is easily recognized by the observer, and the display quality is greatly reduced, and the uniformity of illumination with respect to the liquid crystal cell is also likely to be reduced. In consideration of the above, it is preferable that the length of the optical path conversion slope is 5 times or more, more preferably 8 or more, especially 10 or more, of the depth of the recess. In addition, the length of the optical path conversion slope is 500 μm or less, particularly 200 μm.
Hereinafter, particularly, 10 to 150 μm, the depth and width of the concave portion are 2 μm.
It is preferably from 100 to 100 μm, more preferably from 5 to 80 μm, particularly preferably from 10 to 50 μm. The length is based on the length in the long side direction of the optical path conversion slope, that is, the continuous direction of the grooves of the concave portions, and the depth is based on the light emitting means forming surface of the transparent film. The width is based on the length in a direction orthogonal to the long side direction and the depth direction of the optical path conversion slope.

The surface on which the concave portion is formed and which does not satisfy the light path changing slope a having a predetermined inclination angle, for example, the upright surface b facing the light path changing slope a in FIG. Does not contribute to the emission of light from the back surface, and preferably does not affect display quality, light transmission or light emission as much as possible. By the way, if the inclination angle θ2 of the vertical surface with respect to the film surface is small, the projected area with respect to the film surface becomes large, and in the external light mode by the front light method in which the optical film is arranged on the viewing side, the surface reflected light by the vertical surface returns to the observation direction. Display quality is easily impaired.

Therefore, it is more advantageous that the inclination angle θ2 of the upright surface or the like is larger, so that the projection area with respect to the film surface can be reduced and the decrease in the total light transmittance can be suppressed. The angle can be made smaller, the surface reflected light can be reduced, and the reflected light can be tilted in the film surface direction, so that the influence on the liquid crystal display can be suppressed. From such a point, a preferable inclination angle θ2 of the elevation surface or the like is 60 degrees or more,
Especially 70 degrees or more, especially 75 to 90 degrees.

The inclined surface forming the concave portion A may be formed in an appropriate surface form such as a linear surface, a refraction surface, and a curved surface. Further, the cross-sectional shape of the concave portion may be such that the inclination angle or the like is constant over the entire surface of the sheet, or the uniformity of light emission on the optical film may be taken into account by absorbing loss or attenuation of transmitted light due to optical path conversion. The concave portion may be made larger as the distance from the side surface on which light is incident is increased for the purpose of realizing the structure. Further, the concave portions may have a constant pitch, or the pitch may be gradually narrowed as the distance from the side surface on which light is incident increases, so that the distribution density of the concave portions may be increased. Furthermore, the light emission on the optical film can be made uniform at a random pitch, and the random pitch is more advantageous than the prevention of moiré due to interference with pixels. Therefore, the light emitting means may be composed of a combination of concave portions having different shapes and the like in addition to the pitch.

It is preferable that the light path changing slope in the concave portion faces the direction of light to be incident from the side of the liquid crystal cell, from the viewpoint of improving the emission efficiency. Therefore, when the linear light source is used, the optical path conversion slope is preferably oriented in a certain direction. In addition, when a point light source such as a light emitting diode is used, it is preferable that the optical path conversion slope faces the direction of the light emission center of the point light source.

The shape of the intermittent end of the concave portion is not particularly limited. However, it is preferable that the concave portion is dug at an acute angle from the viewpoint of suppressing the effect of reducing the incident light on the portion. Is preferably at an angle of 60 to 90 degrees in accordance with the vertical plane. Also, the optical film has flat and smooth surfaces on its front and back surfaces except for the concave portion forming the light emitting means, and particularly, an angle change of ± 2 degrees or less, particularly 0 °.
It is preferably a flat surface. It is preferable that the angle change is within 1 degree per 5 mm in length. By making such a flat surface, most of the film surface can be made a smooth surface with an angle change of 2 degrees or less, and the light transmitted inside the liquid crystal cell can be used efficiently and uniform light emission without disturbing the image. Can be achieved.

As described above, the pit-shaped arrangement of the concave portions A is as follows.
A point light source is arranged on the side of a liquid crystal display panel or the like, and the incident light or the transmission light from the side direction by the point light source is converted into an optical path through an optical path changing slope a to make the optical film as uniform as possible. It is an object of the present invention to cause light having excellent directivity in a normal direction to a liquid crystal cell or the like to be emitted from an optical film with efficient use of light from a light source. Therefore, the pit-like arrangement is preferably performed so that a virtual center is formed on the end face of the optical film or outside thereof so that the point light source can be easily arranged. The virtual center can be formed at one position or at two or more positions with respect to the same or different optical film end faces.

As described above, according to the production method of the present invention, an optical film comprising a molded cured layer of a radiation-curable resin forming a light emitting means separate from the transparent film can be obtained. In this case, the optical film can be obtained as a transparent film and the molded cured layer fixedly integrated by utilizing a radiation-induced curing treatment, or the molded cured layer separated from the transparent film can be obtained. It can also be obtained as a layer. Separation of the transparent film and the cured molding layer can be achieved by an appropriate method such as a method of treating the transparent film with a release agent.

The radiation-curable resin forming the molded cured layer may be, for example, an appropriate resin which can be cured by irradiation with radiation such as acrylic or urethane, especially ultraviolet or / and electron beam. One or more kinds can be used, and the kind is not particularly limited. Above all, a radiation-curable resin capable of forming a molded cured layer having excellent light transmittance is preferable. Further, in the case of the fixing and integration, if the refractive index difference between the molded cured layer and the transparent film is large, the light emission efficiency may be greatly reduced due to interface reflection or the like. A radiation-curable resin capable of forming a molded cured layer having a difference as small as possible, particularly within 0.10, particularly within 0.05, is preferred. Further, in that case, it is preferable to increase the refractive index of the formed cured layer to be added, as compared with the transparent film, from the viewpoint of emission efficiency. In addition, the thickness of the coating layer of the radiation-curable resin formed on the transparent film is 1 to 5 times the height of the convex portion in the electroforming mold, preferably 1.1 to 3 times.
The factor is preferably 1.2 times to 2 times, but is not limited thereto.

The optical film according to the present invention is capable of observing incident light from the side of the light source or transmitted light from the side direction of the light source through the light emitting means (optical path changing slope) in a direction (normal direction) excellent in verticality advantageous for visual recognition. The light path can be converted to emit light with high utilization efficiency, and it can exhibit good transparency to external light. For example, bright and easy-to-view thin and lightweight reflective or transmissive external light / illumination Various devices such as a dual-purpose liquid crystal display device can be formed.

The liquid crystal display device can be formed, for example, by a method in which an optical film is arranged on at least one side of a liquid crystal cell such that the side having the light emitting means is on the outside. In that case, the illumination mechanism is formed by arranging one or more light sources on one or more side surfaces of the liquid crystal cell, particularly on one or more side surfaces of the cell substrate on which the optical film is arranged. be able to. The optical film is preferably bonded to a liquid crystal cell or the like via an adhesive layer from the viewpoint of achieving a bright display.

In the case of an optical film having light emitting means arranged in pits when forming the above-mentioned illumination mechanism, the pits are arranged so that bright display is achieved by efficiently utilizing radial incident light from a point light source. It is preferable to arrange a point light source on the side of the liquid crystal cell on a vertical line including the virtual center of the light emitting means. In such an arrangement of the point light source corresponding to the virtual center, the side on which the point light source is arranged of the cell substrate is protruded depending on whether the virtual center of the light emitting means is at the end face of the optical film or outside thereof. Appropriate countermeasures such as the method can be adopted.

As the light source disposed on the side surface of the liquid crystal cell, any suitable light source can be used. For example, in addition to the above-mentioned point light sources such as light emitting diodes, linear light sources such as (cold and hot) cathode tubes, and point light sources An array in which light sources are arranged linearly or in a plane, or a combination of a point light source and a linear light guide plate to convert incident light from the point light source into a linear light source through the linear light guide plate And the like can be preferably used.

The light source is preferably arranged on the side of the cell where the optical path changing slope of the optical film faces, from the viewpoint of emission efficiency. By arranging the optical path conversion slope so as to face the light source as perpendicularly as possible, including the case of the above-mentioned pit-shaped arrangement, efficiently convert the incident light from the side surface through the light source into a surface light source. Light can be emitted with high efficiency. In the case of the pit-shaped arrangement, one or two positions corresponding to the virtual center of the light emitting means in the optical film.
A point light source can be arranged at more than one location.

The light source enables visual recognition in an illumination mode by turning on the light source. In the case of a liquid crystal display device for both external light and illumination, it is necessary to turn on the light source when viewing in the external light mode using external light. Since there is no such switch, it can be switched between ON and OFF. An arbitrary method can be adopted as the switching method, and any of the conventional methods can be adopted. Note that the light source may be of a different color emission type capable of switching emission colors, or may be of a type capable of emitting different colors through different types of light sources.

It is to be noted that the light source may be a combination in which appropriate auxiliary means such as a reflector surrounding the liquid crystal cell are arranged in order to guide the divergent light to the side surface of the liquid crystal cell, if necessary. As the reflector, an appropriate reflection sheet such as a resin sheet, a white sheet, or a metal foil provided with a high-reflectance metal thin film can be used. The reflector can also be used as a fixing means that also serves as a surrounding of the light source by, for example, bonding the end to an end of a cell substrate or the like.

In general, a liquid crystal display device appropriately assembles components such as a liquid crystal cell functioning as a liquid crystal shutter, a driving device associated therewith, a front light or a backlight, and a reflection layer and a compensating retardation plate as necessary. It is formed by things. In the present invention, there is no particular limitation except that an illumination mechanism is formed by using the above-described optical film and light source, and it can be formed according to a conventional front light type or backlight type. Therefore, the liquid crystal cell to be used is not particularly limited, and an appropriate reflection type or transmission type in which liquid crystal is sealed between cell substrates via a sealing material and display light is obtained through light control by the liquid crystal or the like. Can be used.

Incidentally, specific examples of the above-mentioned liquid crystal cell include twisted and non-twisted types such as TN type liquid crystal cell, STN type liquid crystal cell, IPS type liquid crystal cell, HAN type liquid crystal cell, OCB type liquid crystal cell and VA type liquid crystal cell. System, a guest host system or a ferroelectric liquid crystal system, or a light diffusion type liquid crystal cell such as an internal diffusion system. The liquid crystal driving method may be an appropriate one such as an active matrix method or a passive matrix method.

In a front-light type reflection type liquid crystal display device, the arrangement of a reflective layer is indispensable. The position of the reflective layer may be provided inside the liquid crystal cell so as to also serve as an electrode, or may be provided outside the liquid crystal cell. It can also be provided.
For the reflective layer, for example, a coating layer containing a powder of a high-reflectance metal such as aluminum, silver, gold, copper, or chromium in a binder resin, an attached layer of a metal thin film formed by a vapor deposition method, or the like; Sheet, a metal foil, a transparent conductive film, a dielectric multilayer film or the like, which is supported by a base material, and can be formed as an appropriate reflective layer according to the related art. When a transmissive liquid crystal display device is used for both external light and illumination, a reflective layer disposed outside the optical film can be appropriately formed according to the above.

On the other hand, a transmission type liquid crystal display device can be formed by arranging an optical film as a component of a backlight on the viewing back side of a liquid crystal cell. In that case,
By providing a reflective layer on the back side (outside) of the light emitting means, light leaking from an optical path changing slope or the like is reflected and returned to the direction of the liquid crystal cell, so that it can be used for cell illumination and luminance can be improved. At this time, by using the reflection layer as a diffuse reflection surface, the reflected light can be diffused and directed in the front direction, and can be directed in a more effective direction by visual recognition. Further, by providing the above-mentioned reflective layer, it can be used as a transmissive liquid crystal display device of both external light and illumination type.

[0047]

EXAMPLE 1 A 25 μm-thick polyimide film was irradiated with an excimer laser beam having a wavelength of 248 nm through a predetermined mask and dry-etched by ablation processing to form a plurality of grooves each having a triangular concave section. Was formed (FIG. 1A). The groove has a length of about 100 μm, a width of about 10 μm, and a depth of about 8 μm, and has a slope having an inclination angle of about 42 degrees with respect to the film surface and an upright surface having an inclination angle of about 70 degrees facing the slope. Next, nickel is filled into the grooved surface of the insulating film by an electroforming method to form a metal layer having a thickness of about 500 μm, and then the insulating film is separated therefrom to form a metal layer having a predetermined convex portion forming surface. A casting mold was obtained (FIG. 1, b).

Next, an acrylic UV curable resin was applied to one side of a transparent PC (polycarbonate) film having a thickness of 60 μm to a thickness of 75 μm, and the electroformed metal was applied to the outer periphery of the columnar rotating body with respect to the applied layer. The mold roll formed by winding the mold is pressed under rotation to continuously transfer the shape of the convex portion forming surface of the mold to form a molding layer and to extrude air bubbles.
The molded layer is cured by irradiating ultraviolet rays from the C film side,
The PC film was peeled off from the mold roll together with the cured molding layer fixed thereto to obtain an optical film having a light emitting means (Figs. 1D and 1E). The light emitting means has an optical path changing slope having an inclination angle of about 42 degrees with respect to the film surface, and an upright surface having an inclination angle of about 70 degrees with respect to the film surface.
It was composed of a plurality of recesses having a thickness of about 10 μm, a width of about 10 μm and a depth of about 8 μm. Both ends of the groove were dug at an acute angle.

Comparative Example A light guide plate having light emitting means formed of stripe-shaped grooves formed by machining was used.

Evaluation Test A liquid crystal display device incorporating the optical film according to the example or the light guide plate according to the comparative example was formed. As a result, occurrence of moire was confirmed in the comparative example. However, in the embodiment, moire did not occur because the light emitting means was formed by arranging minute-sized recesses densely and densely. Further, the optical film of the example is much thinner and lighter than the light guide plate of the comparative example, and the accuracy of the shape and arrangement position of the concave portion forming the light emitting means is also compared with the light guide plate of the comparative example. And the resolution in the liquid crystal display device was high.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a manufacturing process.

FIG. 2 is an explanatory perspective view of an optical film.

[Explanation of symbols]

 1: Optical film 11: Transparent film 12: Molded layer 13: Molded hardened layer A: Concave a: Optical path conversion slope 2: Electroforming mold 3: Insulating film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiji Umemoto 1-1-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Ryoji Kinoshita 1-2-1, Shimohozumi, Ibaraki-shi, Osaka No. Nitto Denko Corporation F-term (reference) 2H091 FA14Z FA23X FA42X FA45X FB04 FC19 FC23 FD06 LA11 4F204 AA44 AD05 AD08 AH73 EA03 EB01 EB12 EK01 EK18

Claims (9)

[Claims] 1. The method according to claim 1, wherein the coating layer of the radiation-curable resin applied to the transparent film has an inclination angle of 35 to 48 with respect to the film surface.
A light emitting means consisting of a plurality of concave portions having an optical path conversion slope with a convex portion capable of forming a convex portion capable of forming the light emitting means, and forming a molding layer on the coating layer which reflects the surface shape of the electroformed mold. A method for producing an optical film, comprising irradiating radiation from the side of the transparent film, curing the molded layer and separating the molded layer from a mold. 2. The method for manufacturing an optical film according to claim 1, wherein the electroforming mold is formed by performing an electroforming method on an insulating film having predetermined recesses formed by dry etching. 3. The method according to claim 2, wherein the dry etching is performed by laser light. 4. The method for producing an optical film according to claim 3, wherein the laser has an oscillation wavelength in an ultraviolet region. 5. An electroformed mold according to claim 1, wherein the electroformed mold is wound around an outer periphery of a circular rotating body, and a coating layer of a radiation-curable resin is sequentially pressure-bonded to the rotating electroformed mold through the rotating body. A method for continuously producing an optical film, in which a molding layer that reflects the surface shape of an electroformed mold is formed while irradiating the molding layer with radiation. 6. The method for producing an optical film according to claim 1, wherein the molding layer is cured using at least one of ultraviolet rays and electron beams. 7. The method according to claim 1, wherein the concave portion forming the light emitting means has a substantially triangular cross-section formed by an optical path changing slope and an upright face having an angle of inclination of 60 to 90 degrees with respect to the film surface. The length of the optical path changing slope in the long side direction is 500 μm or less, 5 times or more the depth of the concave portion, and the depth of the concave portion is 100 μm or less, in the long side direction and the depth direction of the optical path converting slope. A method for manufacturing an optical film having a width in a direction perpendicular to the optical film of 100 μm or less. 8. The method for producing an optical film according to claim 1, wherein the transparent film and the cured layer of the molding layer are fixedly integrated, or the cured film of the molding layer is separated from the transparent film. 9. A liquid crystal display device comprising an optical film produced by the method according to claim 1 and arranged on at least one side of a liquid crystal cell.