JP2003080524A - Method for manufacturing optical film and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a method for manufacturing an optical film with a remarkable thinness suited for forming a liquid crystal display device which is thin, lightweight and bright in image display for comfortable viewing by efficiently changing the light path of an incident light from the side of a liquid crystal display panel in a visually recognizable direction. SOLUTION: This method for manufacturing an optical film manufactures an optical film which has a plurality of recessed parts (51) of a triangle cross section obtained by emitting a laser beam (1) through a projection mask (2) with a formed laser beam permeable part (21) of a specified shape and partially removing a forming material of a polymer film (5) by etching. Further, the method for manufacturing an optical film manufactures an optical film by forming a mold by electrocasting, using the above-described optical film as a matrix and using the mold. Also a liquid crystal with an optical film arranged at least on one of the sides of a liquid crystal cell is provided. Consequently, an optical film having a light projection means comprising precisely positioned recessed parts of a microstructure having both end parts engraved at an acute angle, is obtained.

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, lightweight, bright and easy-to-read liquid crystal display device by efficiently changing the optical path of light incident from the side surface of a liquid crystal display panel to a viewing direction. Regarding

[0002]

2. Description of the Related Art Conventionally, there has been known a front light type reflection type liquid crystal display device in which a side light type light guide plate is arranged on the viewing side surface of a liquid crystal display panel (JP-A-11-25).
No. 0715). However, since the light guide plate is formed by mechanical processing, it is difficult to perform fine processing, resulting in recesses (grooves).
It is difficult to reduce the thickness of the liquid crystal display device because it is difficult to accurately dispose the light emitting means consisting of a small size at a predetermined position and to cut both ends of the groove at an acute angle, and it is difficult to reduce the thickness and weight of the liquid crystal display device. There was a problem.

[0003]

DISCLOSURE OF THE INVENTION The present invention has a light emitting means in which concave portions having a fine structure whose both end portions are dug in at an acute angle are arranged with high positional accuracy, and light incident from the side surface of a liquid crystal display panel is provided. It is an object of the present invention to develop a manufacturing method capable of obtaining an optical film excellent in thinness capable of forming a liquid crystal display device which is thin, lightweight, bright, and easy to see by efficiently changing the optical path to the viewing direction.

[0004]

According to the present invention, a laser beam is irradiated through a projection mask having a laser beam transmitting portion having a predetermined shape, and the laser beam transmitted from the projection mask is passed through an optical device for producing a projected image. At least one of the projection mask and the polymer film is moved while irradiating the polymer film while controlling the size and changing the irradiation amount of the laser light, thereby forming the polymer film forming material. By partially removing it by laser etching, an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to the polymer film plane and 5
It has an elevation of 0 to 90 degrees and its cross-sectional shape is triangular.
It is intended to provide a method for producing an optical film, which comprises forming a light emitting means in which a plurality of concave portions each having a rectangular opening on the polymer film surface are distributed on one surface of the polymer film.

According to the present invention, a metal layer is formed by electroforming on the surface of the optical film manufactured by the above method on which the light emitting means is formed, and then the metal layer and the optical film are separated to form a mold. A method for producing an optical film forming die, which is characterized in that the surface of the optical film forming die having a convex portion capable of forming a light emitting means is adhered with a radiation-curable resin, A method for producing an optical film, characterized by forming a molding layer that mirrors the shape of the emitting means, irradiating the molding layer with radiation to cure and then separating from the mold, and the optical film produced by the above method. It is intended to provide a liquid crystal display device characterized in that a film is arranged on at least one side of a liquid crystal cell.

[0006]

According to the present invention, it is possible to obtain an optical film having a light emitting means in which concave portions having a fine structure with both end portions dug in at an acute angle are arranged with high positional accuracy, based on the laser etching method. By using this, it is possible to efficiently change the optical path of the light incident from the side surface of the liquid crystal display panel in the viewing direction to form a thin, lightweight, bright, and easily viewable liquid crystal display device. In particular, in a method of molding a radiation curable resin into a predetermined shape through a mold formed by an electroforming method and curing the resin, an optical film having a predetermined light emitting means can be efficiently obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The manufacturing method according to the present invention is an optical device for irradiating a laser beam through a projection mask having a laser beam transmitting portion having a predetermined shape and producing a projected image of the laser beam transmitted from the projection mask. The size of the polymer film is controlled by moving at least one of the projection mask and the polymer film while irradiating the polymer film while controlling the size of the polymer film while changing the irradiation amount of laser light. By partially removing the forming material by laser etching, an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to the polymer film plane and an elevation surface of 50 to 90 degrees are provided, and the cross-sectional shape is An optical film is obtained by forming light emitting means having a plurality of triangular concave portions each having a rectangular opening on the surface of the polymer film distributed on one surface of the polymer film.

An example of the steps of the above-mentioned manufacturing method is illustrated in FIGS. Reference numeral 1 is a laser oscillator for irradiating laser light, 2 is a projection mask on which laser light transmitting portions 21 and 22 having a predetermined shape are formed, and 4 is projection images 41 and 42 of laser light.
A lens as an optical device for producing a laser beam, 5 is a polymer film irradiated with laser light, and 51 is an optical path conversion slope having an inclination angle of 35 to 48 degrees with respect to a plane formed by the polymer film 5,
It has a vertical surface of 50 to 90 degrees, the cross-sectional shape is triangular, and the opening on the polymer film surface is a rectangular concave portion.

Reference numeral 3 is a mask stage for fixing and holding the projection mask 2, and 6 is a work stage for holding and holding the polymer film 5. The mask stage 3 and the work stage 6 in the illustrated example can be independently moved via drive sources (not shown) in the X-axis, Y-axis, and Z-axis directions based on the three-dimensional orthogonal coordinates, and the X-axis and Y-axis can be moved. Axial rotation is possible in each axis of the axis and the Z axis.

Therefore, the position and the arrangement angle of the projection mask 2 can be controlled independently of the polymer film 5 through the movement or / and the rotation of the mask stage 3 in the respective axial directions. Further, the position and the arrangement angle of the polymer film 5 can be controlled independently of the projection mask 2 through the movement and / or the axial rotation of the work stage 6 in the respective axial directions.

The laser oscillator 1 and the optical device 4 are configured so as to move integrally and / or axially rotate in conjunction with the mask stage 3. However, the laser oscillator 1 and the optical device 4 can be independently moved and rotated in the respective axial directions, and the position and the arrangement angle with respect to the mask stage 3 (projection mask 2) can be controlled. .

As described above, the laser light from the laser oscillator 1 is converted into the laser light transmitting portion 2 in the projection mask 2.
1, 22 to form a laser beam image of a predetermined shape, the size of the beam image is controlled through the lens 4,
The polymer film 5 is irradiated and the forming material of the polymer film is etched by the laser beam to disappear and be removed.

In the above case, by moving the projection mask 2 and / or the polymer film 5 while irradiating the polymer film with laser light, the polymer film forming material is continuously formed according to the moving distance. It can be removed to form a recess (groove) having a desired shape, and the forming material at a predetermined position of the polymer film can be partially removed by intermittent laser irradiation.

Further, by changing the irradiation amount of the laser beam, the amount of removal by the laser etching can be controlled and the cross-sectional shape of the recess can be changed. As the irradiation amount of the laser light is increased, the removal amount is increased, and the deep recess can be formed. Therefore, by making the irradiation amount of the laser light have a triangular distribution such as 51 in FIG. 2B, it is possible to form a target concave portion having a triangular cross section.

In the above, the irradiation amount of laser light can be changed by an appropriate method. Incidentally, in the example of FIG. 1, the irradiation amount of the laser light can be changed based on the shape of the laser light transmitting portion 21 in the projection mask 2. That is, as shown in FIG. 2a, by making the shape of the laser light transmitting portion 21 triangular, the irradiation amount can be gradually increased from the apex to the bottom as shown in FIG. 2b.

Therefore, when a projection mask having a triangular laser beam transmitting portion is used, the size of the laser beam image transmitted therethrough is controlled through an optical device, and a laser beam image having a predetermined size is formed on the polymer film. While irradiating, the projection mask 2 and / or the polymer film 5 is moved by a predetermined distance in one direction as indicated by the arrow in the example of FIG. 1, so that the cross-sectional shape is triangular and the opening on the polymer film surface is rectangular. A shaped recess can be formed.

By repeating the above operation for a predetermined position of the polymer film, as shown in FIG.
It is possible to obtain an optical film having a light emitting means in which a plurality of 1 are distributed on one surface of the polymer film 5. By controlling the apex angle of the triangle forming the laser light transmitting portion, it is possible to adjust the angle of the optical path conversion slope in the formed concave portion. Further, the triangle may be an isosceles triangle as shown in the drawing, or may not be an isosceles triangle.

On the other hand, in the case of the projection mask 2 having the rectangular laser beam transmitting portion 22 as shown in FIG. 3, the laser beam transmittance is changed to that shown in FIG.
51, a method of providing a triangular distribution such as 51, a method of providing a laser beam image formed by the optical device 4 with a triangular distribution through a filter, etc. 3), a method of controlling the irradiation intensity of the laser beam while moving the laser beam in the direction of the arrow as illustrated in FIG. 3, and a method of providing the triangular distribution, and a method of using two or more of them together. The amount of laser light irradiation can be changed by the abrasion processing method. The above method can also be applied to the case of the method shown in FIG.

According to the method of the present invention, as shown in FIG. 5A, the inclination angle θ1 with respect to the plane formed by the polymer film 5 is 35 to 48 degrees, and the inclination angle θ is the same.
2 has a vertical surface b of 50 to 90 degrees, a cross-sectional shape is triangular, and a plurality of concave portions 51 having rectangular openings in the polymer film surface are distributed on one surface of the polymer film. The light emitting means is formed to obtain an optical film.

In the above, as the laser oscillator,
For example, one kind or two or more kinds of appropriate materials such as excimer laser, YAG laser, CO ₂ laser and femtosecond laser can be used. Above all, an oscillator that can obtain laser light in the ultraviolet region having a wavelength of 400 nm or less is preferable from the viewpoint of precision of fine processing. The shape and size of the recesses to be formed and their distribution arrangement depend on the resolving power and positioning accuracy of the laser processing machine with additional optical equipment, and the accuracy of the formed slope depends on the oscillation frequency of the laser processing machine and the stage etc. Since it depends on the moving speed and accuracy, it is preferable to use a high-precision processing machine.

As the projection mask, an appropriate one made of an ultraviolet shielding material such as metal can be used. It is also possible to use a glass mask formed by vapor-depositing an appropriate ultraviolet-shielding material such as metal or dielectric on a glass plate made of quartz or the like, and patterning the vapor-deposited layer to form a laser light transmitting portion. In this case, it is easy to form the above-mentioned filter type laser light transmitting portion.

The vapor deposition material for the above-mentioned glass mask is not limited, but chromium, aluminum, molybdenum, a dielectric multilayer film or the like is preferable in terms of durability against laser light and resolution. Note that two or more projection masks can be overlapped and used for laser light irradiation. It is also possible to partially change the laser light transmittance in the laser light transmitting portion by the superposition method to provide a filter effect.

At the time of forming each recess as described above and further forming the light emitting means in which a plurality of the recesses are distributed, at least one of the projection mask and the polymer film is moved. In that case, the projection is performed. It is also possible to adopt a method of moving both the mask and the polymer film in synchronization.

The polymer film may be made of any suitable material that exhibits electrical insulation and can be etched by laser light, and is not particularly limited. Generally, a polymer film is used. Especially, from the viewpoint of workability by laser light in the ultraviolet region, ultraviolet absorbing one is preferable. Further, those having excellent transmittance in the visible light region are preferable. The film thickness is
Although it is optional, it is less than 500 μm, especially 10-200 μm from the viewpoints of handling property during processing, sharpness of the edge part of the formed recess, flatness of the processed surface, etc.
Is preferred.

Incidentally, examples of the polymer film include polyester resins, epoxy resins, urethane resins, polystyrene resins, polyethylene resins, polyamide resins, polyimide resins, ABS resins, polycarbonate resins and silicone resins. Examples include coating films and films made of resin and the like. Above all, a thermosetting resin, particularly a polymer film made of a polyimide resin, is preferable in terms of heat resistance, chemical resistance, and laser processability. The polymer film may be held on a glass substrate or a metal plate as necessary and placed on the work stage.

The optical films can be manufactured one by one by the method described above. A preferred method for producing an optical film in terms of mass productivity is to use the optical film obtained by the above method as a mother die to produce a mold for forming an optical film,
It is a method of mass-producing optical films using the mold.

In the above-mentioned method, for example, a metal layer is formed by electroforming on the surface of the optical film serving as a matrix on which the light emitting means is formed, and then the metal layer and the optical film are separated to form an optical film. A mold is manufactured, and a radiation-curable resin is adhered to the surface of the mold having a convex portion that can form the light emitting means, and a molding layer that reflects the shape of the light emitting means is formed. After the layer is irradiated with radiation to be cured, the produced optical film can be separated from the mold.

An example of steps of the above method is shown in FIG. The illustrated example shows from the formation of the mold (A to C) to the formation of the optical film (D, E). As shown in the figure, the optical film 8 has a plurality of concave portions having a concave portion having an optical path changing slope a having an inclination angle θ1 of 35 to 48 degrees with respect to the film surface via a mold 7 having a predetermined convex portion 71. Is formed by molding.

The mold 7 is formed by applying the electrocasting method to the polymer film (optical film) 5 provided with the light emitting means composed of a plurality of predetermined recesses 51 as in the example of FIG. 1B. . Thereby, as in the example of FIG. 1C, it is possible to form the mold 7 having the convex portion 71 corresponding to the concave portion 51 provided in the polymer film 5 with high accuracy.

The electrocasting method comprises a metal layer having a replica of the surface shape of the polymer film on the side where the recess is provided, which is filled with metal. A conventional method of forming a mold can be applied. Therefore, when forming the metal layer, the conductive film is provided on the side of the polymer film on which the concave portion is provided, but a method similar to the conventional method can be applied to the formation of the conductive film.

The type of metal forming the mold is not particularly limited, and, for example, gold, silver, copper, iron, nickel or cobalt, or alloys thereof are generally used.
It may be a material to which nitride, phosphorus or the like is added. The type of metal used may be one type, or two or more types, and it is also possible to form a die formed by laminating different metals.

The thickness of the metal layer formed as a mold may be appropriately determined. Preventing damage when separating from the polymer membrane,
From the viewpoint of handling properties when forming the optical film, it is preferable to use a metal foil or metal plate made of a metal layer having a thickness of about 0.02 to 3 mm in a portion having no convex portion as a mold.

As shown in the example of FIG. 1D, the optical film 8 is formed in close contact with the surface of the mold 7 on which the convex portion 71 is formed, with a radiation-curable resin applied and supported on a transparent film or the like as needed. Then, the surface shape on the side where the convex portion of the mold is formed is copied to the radiation-curable resin layer, thereby forming a molding layer that reflects the surface shape, and irradiating it with radiation to cure the molding layer, and the molding This is performed by separating the hardened layer 8 from the mold 7.

As described above, as shown in FIG. 1E, the mold 81 has the concave portion 81 and the surface shape which correspond to the surface shape on the convex portion forming side with high accuracy. Therefore, the light emitting means in the polymer film 5 of the master mold has high accuracy. The angle of inclination θ with respect to the film surface
1 is an optical path conversion slope a of 35 to 48 degrees, and the inclination angle θ2
An optical film 8 having a vertical surface b of 50 to 90 degrees, a transverse cross-sectional shape being triangular, and a plurality of concave portions 81 each having a rectangular opening on the film surface distributed on one side.
Is obtained.

In the above-mentioned preferred method for producing the optical film, the deformable mold is wound around the outer circumference of the cylindrical or cylindrical circular rotary body, and the mold is rotated while rotating the mold through the rotary body. A coating layer of radiation-curable resin provided on a long transparent film is sequentially pressure-bonded to a mold to continuously form a molding layer that reflects the surface shape of the mold, and a transparent film is interposed in the molding layer. It is a method of continuously producing an optical film by irradiating with radiation.

As described above, according to the method of the present invention, an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to a plane formed by the polymer film 5 or the film (8) as in the example of FIG. 4 and 50 to 90.
A concave portion 51 (81) having a triangular cross-sectional shape and a rectangular opening on the polymer film surface or the film surface.
To obtain an optical film 5 (8) having a light emitting means in which a plurality of the above are distributed on one surface.

The above-mentioned optical film reflects the light incident from the side surface of the liquid crystal cell through the light source or the transmitted light thereof through the optical path changing slope to the back surface side (the side having no light emitting means), and accordingly the liquid crystal. It is possible to change the optical path in the viewing direction of the display panel and emit the light, and use the emitted light as illumination light (display light) for the liquid crystal display panel or the like. Therefore, the optical film is usually arranged so that the surface on which the light emitting means is formed is the outer side in the direction along the plane of the liquid crystal cell.

In the above description, the transparent film, which may be used for supporting the radiation-curable resin to form an optical film as necessary, exhibits transparency depending on the wavelength range of light incident through a light source or the like. It can be formed by using one kind or two or more kinds of such materials. By the way, in the visible light range, for example, acrylic resins and polycarbonate resins, transparent resins typified by cellulose resins and norbornene resins,
Examples thereof include curable resins that can be polymerized with heat, ultraviolet rays, or ultraviolet rays such as electron beams.

From the viewpoint of increasing the incidence efficiency on the optical path changing slope and obtaining a liquid crystal display device which is bright and has excellent uniformity, the transparent film has a preferable refractive index equal to or higher than that of the liquid crystal cell, particularly the cell substrate thereof. Especially 1.49 or more, especially 1.
52 or more. Also, it is 1.6 or less, especially 1.56, from the point of suppressing the surface reflection when using the front light system.
It is particularly preferable that the refractive index be 1.54 or less. It should be noted 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 peculiarities, etc., and depends on the wavelength range. You can also do the same below.

A transparent film which is preferable from the viewpoint of suppressing unevenness in brightness and unevenness in color and obtaining a liquid crystal display device with less unevenness in display is a film which does not exhibit birefringence or has small birefringence.
The average in-plane retardation is 30 nm or less. By using a transparent film having a small retardation, when linearly polarized light enters through an optical film or the like, the polarization state can be favorably maintained, which is advantageous in preventing deterioration of display quality.

From the viewpoint of preventing display unevenness, the average in-plane retardation of the transparent film is preferably 20 nm or less, especially 1
It is more preferably 5 nm or less, particularly 10 nm or less, and the variation in the phase difference between the locations 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, especially 20 nm or less from the viewpoint of preventing display unevenness.

The formation of such a low retardation transparent film is
For example, it may be performed by an appropriate method such as a method of annealing an existing film, a method of removing internal optical distortion, or the like. A preferable forming method is a method of forming a transparent film having a small retardation by a casting method. The retardation in the transparent film is preferably based on light in the visible range, particularly light having a wavelength of 550 nm.

The above-mentioned in-plane average phase difference is (nx
-Ny) × d, and the average phase difference in the thickness direction is
It is defined by {(nx + ny) / 2−nz} × d. Here, 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, and nz is the average refractive index in the film thickness direction. , D means the average thickness of the film.

The transparent film is usually formed as a single layer, but it 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 from the viewpoint of reduction in thickness and weight, it is 5 to 500 μm, especially 10 to 300 μm, and particularly 20 to 10 μm.
0 μm is preferred. With such a thickness, size processing such as punching can be easily performed.

The light emitting means provided on the optical film is, as in the example of FIGS. 4 and 5, an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to the plane formed by the polymer film 5 or the film 8 and 50 to 90 degrees. And a rectangular cross-sectional shape, and a plurality of concave portions 51, 81 having rectangular openings on the polymer film surface or film surface are formed on one surface.

The recess having a triangular cross section is advantageous from the viewpoints of reduction in visibility due to size reduction and manufacturing efficiency.
The recessed portion means that it is recessed (groove) in the polymer film or the optical film. Further, the cross section means a cross section of the concave portion with respect to the optical path conversion slope. It should be noted that the triangle based on the cross section is not in a strict sense, and changes in the angles of the surfaces and roundness at the corners of the intersections of the surfaces are allowed.

As described above, the incident light or the transmitted light from the side surface direction by the light source arranged on the side surface of the liquid crystal cell,
It is possible to output the light having excellent directivity in the normal direction to the liquid crystal cell or the like by utilizing the light source conversion efficiency through the optical path conversion to the rear surface side of the optical film having no light emitting means through the slope a. .

When the inclination angle of the optical path changing slope is less than 35 degrees, the angle of the display light emitted from the liquid crystal display panel exceeds 30 degrees, which is disadvantageous for visual recognition. On the other hand, when the inclination angle of the optical path conversion slope exceeds 48 degrees, light is apt to leak from the slope without being totally reflected, and the light utilization efficiency decreases.

In the case where the reflection method by the light path changing slope is replaced by the scattering reflection method by the light emitting means having a roughened surface, it is difficult to reflect in the vertical direction and tilts more largely than the front direction from the liquid crystal display panel. The liquid crystal display is dark because it is emitted in the vertical direction, and the contrast is poor.

Efficiently totally reflect the light through the optical path changing slope, and emit the light with good directivity in the direction normal to the polymer film surface or the film surface from the side having no light emitting means to efficiently illuminate the liquid crystal cell. From the viewpoint of achieving a bright and easy-to-read liquid crystal display, the preferable inclination angle θ1 of the optical path conversion slope is 38
It is 45 degrees, especially 40 to 43 degrees.

The light emitting means may be formed as a stripe-shaped concave portion which is continuous from one side to the other side, but is preferably formed as a plurality of concave and intermittent concave portions as in the example of FIG. Is. The concave portions may be distributed in parallel as in the example of FIG. 4 based on the optical path conversion slope, or may be irregularly distributed. Further, it may be in a distribution state in which the pits are arranged in a pit shape (concentric shape) with respect to the virtual center.

By the way, the distribution of the above-mentioned pit-like arrangement is
When irradiating with laser light, a virtual center is assumed on the end face of the polymer film or outside thereof, and the projection mask or / and the polymer film is moved in a direction orthogonal to a virtual radiation derived from the virtual center. Can be formed. Incidentally, assuming that there are two or more virtual centers, the light emitting means may be composed of a plurality of recesses distributed in a pit shape with respect to each virtual center.

The arrangement of the plurality of recesses can be appropriately determined according to the form thereof. As described above, the optical path changing slope a reflects the incident light from the side surface from the light source toward the back surface in the illumination mode to change the optical path. Therefore, all the light is transmitted through the concave portion having the optical path changing slope. The ratio of 75 to 92% and the haze of 4 to 20% can be distributed on one side of the optical film so that the light from the side direction via the light source is subjected to optical path conversion to efficiently illuminate the liquid crystal cell. It is preferable from the viewpoint of obtaining a light source and achieving a bright liquid crystal display with excellent contrast.

The characteristics of the total light transmittance and the haze can be achieved by controlling the size and distribution density of the recesses, and for example, the occupation based on the projected area of the light emitting means in the surface on which the light emitting means is formed in the optical film. Area is 1/100 to 1 /
8, especially 1/50 to 1/10, especially 1/30 to 1/15
Can be achieved.

More specifically, if the size of the optical path changing slope is large, it is easy for an observer to recognize the existence of the slope, the display quality is likely to be greatly deteriorated, and the uniformity of illumination to the liquid crystal cell is also likely to be deteriorated. In consideration of this, it is preferable that the length of the optical path changing slope is 5 times or more the depth of the recess, particularly 8 or more, especially 10 or more. The length of the optical path conversion slope is 500 μm or less, especially 200
less than μm, especially 10-150 μm, the depth and width of the recess is 2
μm to 100 μm, especially 5 to 80 μm, especially 10 to 50 μm
It is preferable that

The above length is based on the length of the optical path changing slope in the long side direction, that is, the direction in which the recesses are continuous, and the depth is based on the light emitting means forming surface of the optical film. The width is based on the length of the optical path conversion slope in the direction orthogonal to the long side direction and the depth direction.

The surface forming the concave portion, which does not satisfy the optical path conversion slope a having a predetermined inclination angle, that is, the upright surface b facing the optical path conversion slope a, emits incident light from the cell side surface from the rear surface. It is preferable that it does not contribute to the display quality and does not affect display quality, light transmission or light emission as much as possible. By the way, if the inclination angle θ2 of the elevation is small, the projected area on the film surface becomes large, and in the external light mode by the front light method in which the optical film is placed on the viewing side, the surface reflected light by the elevation returns to the viewing direction and is displayed. It becomes easy to impair the quality.

Therefore, the larger the inclination angle θ2 of the vertical surface is, the more advantageous it is. Therefore, the projected area with respect to the film surface can be reduced and the reduction of the total light transmittance can be suppressed, and the apex angle between the optical path changing slope and the vertical surface can be suppressed. It can be made small and the surface reflected light can be reduced, and the reflected light can be inclined in the film surface direction, and the influence on the liquid crystal display can be suppressed. From such a point, the preferable inclination angle θ2 of the elevation is 60 degrees or more, preferably 70 degrees or more, and particularly 75 to 90 degrees.

The inclined surface forming the concave portion 51 (81) may be formed in an appropriate surface shape such as a straight surface, a refraction surface, or a curved surface. In addition, the cross-sectional shape of the recess may be such that the inclination angle and the like are constant over the entire surface of the sheet, or the light emission on the optical film is made uniform by coping with absorption loss and attenuation of transmitted light due to previous optical path conversion. For the purpose of increasing the size, the recess may be made larger as the distance from the side surface on which light is incident increases.

Further, the concave portions may be arranged at a constant pitch, or the pitch may be gradually narrowed as the distance from the side surface on which the light is incident increases, and the distribution density of the concave portions may be increased. Further, the light emission on the optical film can be made uniform at a random pitch. The random pitch is more advantageous than prevention of moire 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.

From the viewpoint of improving the emission efficiency, it is preferable that the optical path changing slope in the concave portion faces the direction of incident light from the side surface direction of the liquid crystal cell. Therefore, when the linear light source is used, it is preferable that the optical path conversion slope faces a certain direction. Further, when the 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 and the like of the intermittent end of the concave portion is not particularly limited, but it is preferable that it is dug into an acute angle from the viewpoint of suppressing the influence of the reduction of incident light to that portion and the like. According to the above-mentioned elevation, it is preferable that the angle is 60 to 90 degrees.

Further, the optical film has flat surfaces which are as smooth as possible except for the concave portions forming the light emitting means, and the angle change is ± 2 degrees or less, especially 0 degrees flat. It is preferably a surface. Also, the change in angle is 5
It is preferably within 1 degree per mm. With such a flat surface, the angle change of most of the film surface is 2
It is possible to make the surface smooth or less, the light transmitted inside the liquid crystal cell can be efficiently used, and uniform light emission without disturbing the image can be achieved.

As described above, in the pit-like arrangement of the concave portions, the point light source is arranged on the side surface of the liquid crystal display panel or the like, and the radial incident light or the transmitted light from the side surface direction of the point light source is converted into the optical path changing slope a. The optical path is changed through the optical film so that the optical film emits light as uniformly as possible, and the light having excellent directivity in the normal direction to the liquid crystal cell or the like is emitted from the optical film with high utilization efficiency of the light source. .

Therefore, it is preferable that the pit-like arrangement of the concave portions is performed so that a virtual center is formed on the end surface of the optical film or on the outer side thereof so that the point light source can be arranged easily. The virtual center can be formed at one location or at two or more locations on the same or different optical film end faces.

In the above, when a transparent film for supporting is used in the formation of the molding and curing layer of the radiation curable resin, the optical film may be obtained by integrally bonding the transparent film and the molding and curing layer. Alternatively, it can be obtained as a product formed from the molding and curing layer separated from the transparent film. Separation of the transparent film and the molded and cured layer can be achieved by an appropriate method such as a method of surface-treating the transparent film with a release agent.

The radiation-curable resin for forming the above-mentioned molding / curing layer is, for example, an appropriate resin which can be cured by irradiation of ultraviolet rays such as acrylic resin and urethane resin, and in particular ultraviolet rays and / or electron beam irradiation. One kind or two or more kinds can be used, and the kind is not particularly limited. Above all, a radiation curable resin capable of forming a molding and curing layer having excellent light transmittance is preferable.

Further, in the case of fixing and integrating as described above, if the difference in refractive index between the molding and hardening layer and the transparent film is large, the light emission efficiency may be greatly reduced due to interface reflection or the like. From the viewpoint of preventing this, a radiation-curable resin that has a refractive index difference with the transparent film as small as possible and can form a mold-hardened layer of 0.10 or less, particularly 0.05 or less is preferable.

Further, in the above case, it is preferable from the viewpoint of emission efficiency that the refractive index of the additional molding and hardening layer is higher than that of the transparent film. The thickness of the radiation-curable resin coating layer formed on the transparent film is 1 to 5 times the height of the protrusions in the mold, preferably 1.1 to 3 times, and particularly 1.2 to 2 times. Preferred, but not limited to.

In the optical film according to the present invention, through the light emitting means (optical path conversion slope), the incident light from the side surface of the light source or the transmitted light is excellent in vertical direction which is advantageous for visual recognition (normal direction). It is possible to change the optical path of the light to emit light efficiently and to have good transparency to external light. For example, it is thin and light reflective or transmissive external light that is bright and easy to see. It is possible to form various devices such as an illumination type liquid crystal display device.

The liquid crystal display device can be formed by, for example, a method of arranging the optical film on at least one side of the liquid crystal cell so that the side having the light emitting means is the outside. In that case, the illumination mechanism is formed by disposing 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. can do. Further, the optical film is preferably adhered to a liquid crystal cell or the like via an adhesive layer from the viewpoint of achieving bright display.

In the case of forming the above-mentioned illumination mechanism, in the case of an optical film having a light emitting means arranged in a pit shape, a pit shape is achieved because the radial incident light from the point light source is efficiently used to achieve a bright display. It is preferable to arrange the point light source on the side surface of the liquid crystal cell on the vertical line including the virtual center of the arranged light emitting means. In such 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 projected depending on whether the virtual center of the light emitting means is on the end face of the optical film or on the outside thereof. Appropriate countermeasures such as methods can be adopted.

As the light source arranged on the side surface of the liquid crystal cell,
An appropriate one can be used. For example, in addition to the point light sources such as the light emitting diodes described above, a linear light source such as a (cold, heat) cathode tube, an array body in which the point light sources are arranged in a line or a plane, or a point light source and a line conductor. A combination of light plates to convert incident light from a point light source into a linear light source via a linear light guide plate can be preferably used.

From the standpoint of emission efficiency, it is preferable that the light source is arranged on the side surface of the cell where the optical path conversion slope of the optical film faces. Including the above-mentioned pit-shaped arrangement, by arranging the optical path conversion slope to face the light source as perpendicularly as possible, the incident light from the side surface via the light source can be efficiently converted into a surface light source. It is possible to emit light with high efficiency. In the case of the pit-shaped arrangement, the point light source may be arranged at one place or two or more places corresponding to the virtual center of the light emitting means in the optical film.

The light source enables visual recognition in the 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 visually recognizing in the external light mode by external light. Since there is no light, it is possible to switch the light on / off. As the switching method, any method can be adopted, and any conventional method can be adopted. Note that the light source may be of a different color emission type capable of switching the emission color, or may be of a type capable of emitting different color light through different light sources.

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

In a liquid crystal display device, generally, a liquid crystal cell functioning as a liquid crystal shutter, a driving device associated therewith, a front light or a back light, and if necessary, components such as a reflection layer and a compensating retardation plate are appropriately assembled. 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-mentioned 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 a liquid crystal is sealed between the cell substrates via a sealing material, and an appropriate reflection type or a liquid crystal cell is used to obtain display light through optical control by the liquid crystal or the like. A transparent type can be used.

By the way, specific examples of the above-mentioned liquid crystal cell include twist type and non-twist type 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. Examples thereof include a liquid crystal cell of a liquid crystal system, a guest-host system, a ferroelectric liquid crystal system, or a light diffusion type liquid crystal cell such as an internal diffusion system. Further, the liquid crystal driving method may be an appropriate method such as an active matrix method or a passive matrix method.

In a front-light type reflection type liquid crystal display device, it is essential to dispose a reflective layer, but the disposition position may be provided inside the liquid crystal cell as an electrode or outside the liquid crystal cell. Can also be provided.

The reflective layer is, 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 by a vapor deposition method, or the coating layer. It can be formed as an appropriate reflective layer according to the conventional method such as a reflective sheet in which a working layer or an attached layer is supported by a base material, a metal foil, a transparent conductive film, a dielectric multilayer film, or the like. When a transmissive liquid crystal display device is used for both external light and illumination, the reflective layer arranged on the outer side of the optical film can also be an appropriate one according to the above description.

On the other hand, a transmissive liquid crystal display device can be formed by arranging an optical film on the back side of the liquid crystal cell as viewed, which constitutes a backlight. In that case,
By providing a reflection layer on the back side (outer side) of the light emitting means, light leaking from the optical path conversion slope or the like can be reflected and returned to the direction of the liquid crystal cell, which can be used for cell illumination and can improve brightness. .

In the above case, by using the reflection layer as a diffusive reflection surface, the reflected light can be diffused and directed in the front direction, and can be visually recognized in an effective direction. Further, by providing the above-mentioned reflective layer, it can be used as a transmissive liquid crystal display device for both external light and illumination.

[0084]

EXAMPLES Example 1 A projection mask having a laser light transmitting portion formed by providing an opening formed of an isosceles triangle having an apex angle of 84 degrees in a metal foil,
Excimer laser light with a wavelength of 248 nm has a beam width of 1.5 mm.
And irradiate the mask transmitted light through the lens to 1/15 and irradiate the polyimide film with a thickness of 50 μm, while moving the projection mask in the beam width direction through the fixed mask stage, A laser light transmitting portion was completely passed through between the beams having a width of 1.5 mm to form a recess (FIG. 1).

The concave portion has a triangular cross section, and the deepest etched portion corresponds to the base of the isosceles triangle forming the laser light transmitting portion of the projection mask. 0) corresponded to the vertical angle of the mask. In addition, the concave portion has a length of about 100 μm and a width of about 10 μm.
μm, depth of about 8 μm, tilt angle to film surface is about 4
2 degree optical path conversion slope, and the inclination angle facing it is about 75
It had a degree of elevation (Fig. 2a).

Then, the above operation was repeated to form a polymer film (optical film as a matrix) having a plurality of concave portions in a predetermined distribution state on one surface of the polyimide film (FIG. 5A). Next, nickel is filled on the concave surface of the polymer film by an electroforming method to form a metal layer having a thickness of about 500 μm, and then the polymer film is peeled off from the metal layer to have a predetermined convex formation surface. A mold was obtained (Fig. 5B, C).

A radiation-curable resin is applied to the surface of the mold in which the convex portions are formed in a thickness of 75 μm to form a molding layer whose surface shape is shown, and then radiation is applied to the molding layer to form the molding layer. After curing, the formed and cured layer was peeled off from the mold to obtain an optical film having a light emitting means (FIG. 5D,
E).

The light emitting means in the above-mentioned optical film has an optical path changing slope having an inclination angle of about 42 degrees with respect to the film surface and a vertical surface facing the optical path changing slope having an inclination angle of about 75 degrees, and has a length of about 100 μm and a width of about 100 μm. It was composed of a plurality of recesses each having a depth of 10 μm and a depth of about 8 μm, which corresponded to the light emitting means composed of the recesses provided in the master mold polyimide film with high accuracy. Also, both ends of the recess were dug into the acute angle.

Comparative Example A light guide plate having a light emitting means composed of stripe-shaped recesses 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, generation of moire was confirmed in the comparative example. However, in the embodiment, since the light emitting means is composed of minute recesses arranged in a dense and dense manner, moire does not occur. In addition, the optical film of the example is far superior to the light guide plate of the comparative example in thinness and lightness, and the accuracy of the shape and arrangement position of the recess forming the light emitting means is also better than that of the light guide plate of the comparative example. The liquid crystal display device has a high resolution.

From the above-mentioned embodiment, it is understood that by scanning the inside of the laser beam from one end to the other, it is possible to form a concave portion in which both ends are dug into an acute angle. It can also be seen that the concave portion having a triangular cross section can be formed by using a projection mask having a triangular laser beam transmitting portion. In that case, the inclination angle of the optical path changing slope with respect to the film surface can be controlled by the apex angle of the triangle forming the laser light transmitting portion.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a manufacturing method.

FIG. 2 is an explanatory view of a projection mask and a recess formed by the projection mask.

FIG. 3 is an explanatory diagram of another manufacturing method.

FIG. 4 is a perspective explanatory view of an optical film.

FIG. 5 is an explanatory view of still another manufacturing method.

[Explanation of symbols]

1: Laser oscillator 2: Projection mask 21, 22: Laser light transmitting part 4: Optical equipment 41, 42: projected image 5: Polymer film (optical film) 51: recess a: Optical path conversion slope b: Elevation 7: Mold 8: Optical film 81: Recess a: Optical path conversion slope b: Elevation

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C25D 1/10 C25D 1/10 4F204 G02B 5/02 G02B 5/02 C 5F072 5/04 5/04 A E F 6 / 00 331 6/00 331 G02F 1/13357 G02F 1/13357 H01S 3/00 H01S 3/00 B // B29K 79:00 B29K 79:00 101: 10 101: 10 B29L 11:00 B29L 11:00 (72) Inventor Atsushi Hino 1-2-2 Shimohozumi, Ibaraki-shi, Osaka Prefecture Nitto Denko Corporation (72) Inventor Kiyoji Umemoto 1-21-2 Shimohozumi, Ibaraki-shi, Osaka Prefecture Nitto Denko Corporation (72) Inventor Yuki Nakano 1-2-2 Shimohozumi, Ibaraki-shi, Osaka Prefecture Nitto Denko Corporation (72) Inventor Ryoji Kinoshita 1-2-1 Shihohozumi, Ibaraki-shi, Osaka Nichito Denko Corporation F-term ( Reference) 2H038 AA55 BA06 2H042 CA12 CA15 CA17 2H091 FA21X FA23X FC17 FC23 FC26 LA11 LA12 4E068 AF01 CD10 DB10 4F202 AA36 AA40 AG01 AH73 AJ0 2 CA07 CB01 CD03 CD04 CD12 4F204 AA36 AA45 AG01 AH73 AJ02 EA03 EB01 EK18 5F072 AA06 JJ12 YY06

Claims (11)

[Claims] 1. A laser beam is radiated through a projection mask on which a laser beam transmitting portion having a predetermined shape is formed, and the size of the laser beam transmitted from the projection mask is controlled through an optical device that produces a projected image. And, while irradiating the polymer film while changing the irradiation amount of laser light, at least one of the projection mask and the polymer film is moved, and the forming material of the polymer film is partially etched by laser etching. Of the polymer film surface having a triangular cross-sectional shape and an optical path conversion slope having an inclination angle of 35 to 48 degrees with respect to the plane of the polymer film and an elevation surface of 50 to 90 degrees by being removed. 2. A method for producing an optical film, comprising forming a light emitting means in which a plurality of concave portions each having a rectangular opening are distributed on one surface of the polymer film. 2. The method for producing an optical film according to claim 1, wherein the laser light has a wavelength in the ultraviolet range. 3. The method for manufacturing an optical film according to claim 1, wherein a plurality of projection masks are overlapped and a laser beam is irradiated. 4. The method of manufacturing an optical film according to claim 1, wherein both the projection mask and the polymer film are moved in synchronization with each other. 5. The method for producing an optical film according to claim 1, wherein the polymer film is used while being held on a glass substrate or a metal plate. 6. The method for producing an optical film according to claim 1, wherein the polymer film is a polymer film. 7. The method for producing an optical film according to claim 6, wherein the polymer film is made of a thermosetting resin. 8. The method for manufacturing an optical film according to claim 7, wherein the thermosetting resin is a polyimide resin. 9. A mold is obtained by forming a metal layer on the surface of the optical film of claim 1 on which the light emitting means is formed by electroforming, and then separating the metal layer and the optical film. A method for producing a mold for forming an optical film, comprising: 10. A radiation curable resin is adhered to the surface of the optical film forming die according to claim 9 having a convex portion capable of forming a light emitting means, and the shape of the light emitting means is copied. A method for producing an optical film, which comprises forming a molding layer, irradiating the molding layer with radiation to cure the molding layer, and separating the molding layer from a mold. 11. A liquid crystal display device comprising an optical film produced by the method according to claim 1 or 8 arranged on at least one side of a liquid crystal cell.