JP2001194517A - Optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop an optical film forming a transmissive, or reflective and transmissive combined, liquid crystal display device which is thin, lightweight and has bright and easy-to-see display by efficiently converting the optical path of the incident light from the side face direction into the viewing direction. SOLUTION: The optical film is provided with an adhesive layer 12 on one surface of a transparent film 11 with <=0.1 difference in refractive index between itself and its surface layer and a repeatingly projecting and recessing structure 13 equipped with an optical path converting slope A1 directed to nearly defined directions with 35-48 deg. inclined angle with respect to the film surface on the other surface of the transparent film. Consequently the optical film is utilized for the transmissive mode liquid crystal display by adhering it to the liquid crystal display panel, arranging an illuminator to the side face and efficiently converting the optical path of the light incident from the side face into the viewing direction of the panel. Furthermore, the optical film is utilized for the reflective mode liquid crystal display by providing a flat surface part between the optical path converting slopes of the optical film, efficiently making external light incident and reflecting the incident light via a reflection layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film capable of efficiently changing the optical path of side-incident light in a viewing direction to form a thin, lightweight, bright and easy-to-view transmissive or reflective / transmissive liquid crystal display device. .

[0002]

BACKGROUND OF THE INVENTION In order to suppress the weight increase due to the enlargement of TV and personal computer screens and to reduce the size and weight of portable personal computers and mobile phones, further reduction in the thickness and weight of transmissive liquid crystal display devices is required. It is difficult to reduce the thickness and weight of a conventional backlight provided with a direct type or a sidelight type light guide plate. By the way, in the direct type backlight, the light diffusion plate and the reflection plate are arranged together with the illuminating device directly below the liquid crystal display panel, so that the thickness is usually 4 mm or more. Even for the sidelight type light guide plate, the plate thickness is 1 mm or more due to the need for light transmission. When a light diffusing plate, a reflecting plate, a prism sheet, or the like is disposed thereon, the thickness usually becomes 3 mm or more.

Also, a transflective liquid crystal display device in which a transflective reflector is disposed between the transmissive liquid crystal display panel and the backlight so that the transflective plate can be viewed even in a reflection mode by external light is known. Had been. The arrangement of the semi-transmissive reflector is intended to enable visibility in the reflection mode, without which the visibility in the reflection mode by external light is dark, and it is difficult to substantially function as a reflective liquid crystal display device. However, in addition to adding bulkiness and weight by adding a transflective reflector, the transflective reflector disperses the transmitted light and reflected light, so that the visibility in the transmission mode is darkened, and the visibility in the reflection mode is also reduced. There is a problem that it is difficult to make the brightness darker than that dedicated to reflection by a reflection layer having a high reflectance.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an optical film capable of efficiently converting the light incident on a side surface into a viewing direction to form a thin, lightweight, bright and easy-to-view transmissive or reflective / transmissive liquid crystal display device. The task is to develop

[0005]

According to the present invention, a transparent film has an adhesive layer having a refractive index difference of 0.1 or less with respect to a surface layer on one side of the transparent film, and has an inclination angle of 35 with respect to the film surface on the other side of the transparent film. It is an object of the present invention to provide an optical film having a repeating structure of irregularities having an optical path changing slope which is oriented substantially at a constant angle of up to 48 degrees.

[0006]

According to the optical film of the present invention, by arranging the optical film along the viewing surface of a liquid crystal display panel having an illuminating device on the side surface, the incident light from the side surface or the transmitted light thereof can be transmitted to the optical film. The light path is efficiently converted in the viewing direction of the liquid crystal display panel through the light path changing slope to be used for the liquid crystal display in the transmission mode, and a transmission type liquid crystal display device which is thin, lightweight, bright, and excellent in display quality is formed. be able to. In addition, by providing a flat surface portion between the optical path changing slopes of the optical film, external light can be efficiently incident, and the incident light can be reflected through a reflective layer to be used for a liquid crystal display in a reflection mode. In addition to the mode mechanism, a reflection mode mechanism can be formed, so that a reflection-transmission type liquid crystal display device which is excellent in thinness, lightness, brightness, and display quality can be formed.

The above-mentioned effect is mainly due to the use of an optical film of an optical path control type by oblique reflection. That is, by reflecting the incident light from the side surface or the transmitted light from the side surface through the optical path conversion slope, the optical path can be changed with good directivity, and good visibility in the transmission mode is achieved, and a flat surface can be easily formed between the optical path conversion slopes. It can be arranged and transmits external light through its flat surface to ensure sufficient external light incidence, and good visibility in the reflection mode is achieved. As shown in FIG. 10, it is difficult to achieve the above-mentioned effect by the scattering reflection method through the rough surface using the scattering sheet 6 or the like. Incidentally, in Japanese Patent Application Laid-Open No. H5-158033, a reflection type liquid crystal is used for display by illuminating light from a side surface of a liquid crystal display panel, totally reflecting the light on a viewing side cell substrate, and scattering the reflected light by a rough surface type reflection plate. Teach the display device.

However, in the above case, the light available for display is light that is emitted from the panel out of the condition of total reflection due to scattering. Generally, the scattered light has a normal distribution having a peak in the regular reflection direction. Proceedings of the 20th LCD Symposium 3
G510, Tohoku University; Uchida, etc.), the display light is light inclined at a greater angle than the front (vertical) direction and is difficult to use effectively for display, and becomes dark in the front direction. If the scattering by the rough reflector is increased, the amount of light in the front direction in the reflection mode is reduced, which is disadvantageous for display (SID 96).
DIGEST P149-152). Therefore, in the rough surface scattering / reflection method, since the scattering intensity required for both the transmission mode and the reflection mode is in a trade-off relationship, it is difficult to make the scattering intensity advantageous for both modes.

[0009] On the other hand, the optical film of the present invention, which is of an optical path control type by oblique reflection, mainly uses light in the specular reflection direction showing a peak and controls the optical path of the reflected light, which is advantageous for display. Directivity, in particular, directivity in the front direction can be easily provided, and a bright transmission mode can be achieved. Also, even in the reflection mode, it is possible to ensure efficient incidence and reflection / transmission of external light by utilizing a flat portion other than the slope of the optical film, and to easily balance the light into a state advantageous for both the reflection mode and the transmission mode. it can.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical film according to the present invention has an adhesive layer having a refractive index difference of 0.1 or less with respect to the surface layer on one side of the transparent film, and has an inclined surface with respect to the film surface on the other side of the transparent film. It has a repeating structure of irregularities having an optical path changing slope having an angle of 35 to 48 degrees and oriented in a substantially constant direction. Examples are shown in FIGS. 1 (a) to 1 (h). 1
Is an optical film, 11 is a transparent film, 12 is an adhesive layer, 13 is irregularities having an optical path changing slope A1, that is, a repeating structure layer of the optical path changing means A, and 14 is a release sheet. As shown in FIG. 1 (g), the repeating structure of the optical path changing means A may be formed integrally with the transparent film 11.

The optical film 1 is arranged in the direction along the viewing surface of the liquid crystal display panel P having the illuminating device 5 on the side surface as illustrated in FIG. 7, and the incident light or the transmitted light from the side direction by the illuminating device is transmitted. The light is reflected through the light path changing slope A1 as shown by the arrow, and the light path is changed to the side of the transparent film 11 not having the slope, that is, in the viewing direction of the liquid crystal display panel P, and the light is emitted from the transparent film. It is an object of the present invention to be able to use as illumination light (display light).

The transparent film 11 has, on one side of the film, an inclined surface A1 for reflecting the incident light from the lateral direction or the transmitted light in a predetermined direction and changing the optical path, as illustrated in FIG. It is assumed. In this case, in the present invention, as shown in FIG. 1, the inclination angle θ1 with respect to the film surface A4 is substantially constant at 35 to 48 degrees from the point of obtaining illumination light having excellent directivity in the front direction via optical path conversion. The optical path changing means A has a concavo-convex pattern having an optical path changing slope A1 facing the direction, that is, a repeating structure of the optical path changing means A.

FIGS. 1A to 1H show examples of the optical path changing means A having the above-described optical path changing slope A1. In (a) to (c), (g), and (h), the optical path conversion means A has a substantially triangular cross section, and in (d) and (e), a substantially rectangular cross section, and in (f), a substantially pentagonal cross section. Consist of things. Also, in (a), two optical path conversion slopes A by isosceles triangles
1, (b), (g) and (h) show the optical path changing slope A
1 and an optical path changing means A having a steep slope A2 whose inclination angle is larger than the slope A1.

On the other hand, in (c), an optical path changing means A having a light path converting slope A1 and a gentle slope A3 having a small inclination angle as a unit is formed on the entire surface on one side of the film as a repetitive structure of an adjacent continuous state. (A) to (c),
(E), (g), and (h) have optical path conversion means A having concave portions (grooves), and (d) and (f) have optical path conversion means A having convex portions (projections). Consists of

Therefore, as in the above-described example, the optical path changing means can be formed on a convex portion or a concave portion having an equilateral surface or a slope having the same inclination angle, and the optical path changing slope is different from a steep slope or a gentle slope or an inclination angle. It can also be formed in a convex portion or a concave portion formed of a slope, and the form of the slope can be appropriately determined by the number and position of the side direction in which light is incident. Rather than maintaining the slope function by improving the scratch resistance, it is advantageous that the slope is hardly damaged by being formed as an optical path changing means composed of concave portions rather than convex portions.

A more preferable optical film, for example, in achieving the above-described characteristics such as directivity in the front direction, is such that the substantially constant direction in which the optical path changing slope A1 faces is a direction facing the side direction in which light enters. . Therefore, for example, when light is incident from two or more side surfaces of the optical film 1 as shown in FIG.
An optical film having the following is preferably used.

When the two opposing sides of the optical film are directed to the side where light enters as shown in FIG.
As shown in FIG. 1 (d), two optical path conversion slopes A1 by the optical path conversion means A having a substantially isosceles triangle in cross section as shown in FIG.
(E) As shown in (f), there are two optical path changing slopes A1 formed by the optical path changing means A having a substantially trapezoidal or quadrangular or substantially pentagonal cross section in such a state that the ridge line is in the direction along the side direction. An optical film 1 having two or more surfaces in which the optical path changing slope facing in a substantially constant direction includes a surface facing in the opposite direction based on one surface is preferably used.

In the case where two sides adjacent to each other in the vertical and horizontal directions of the optical film are set to the side direction in which light is incident, the optical path changing slope A is set in such a manner that the ridge lines are in both vertical and horizontal directions corresponding to the side surfaces.
An optical film having 1 is preferably used. Further, in the case where three or more side surfaces including the opposing and vertical and horizontal sides are the side directions on which light is incident, an optical film having an optical path changing slope A1 composed of the above combination is preferably used.

As described above, the optical path changing slope A1 plays a role of reflecting the light incident on the surface A1 out of the incident light from the side direction or the transmitted light, and changing the optical path. In this case, as shown in FIG. 1 (a), by setting the inclination angle θ1 of the optical path changing slope A1 with respect to the film surface to 35 to 48 degrees, incident light from the side direction or transmitted light thereof can be made perpendicular to the film surface. By changing the optical path, illumination light having excellent directivity to the front can be efficiently obtained.

If the inclination angle θ1 is less than 35 degrees, the optical path of the reflected light is greatly shifted in the direction of 30 degrees or more from the front direction, making it difficult to use it effectively for display, resulting in poor brightness in the front direction.
When the angle exceeds 48 degrees, the condition for totally reflecting the incident light or the transmitted light from the side direction is deviated, and the leakage light from the optical path conversion slope increases, resulting in poor light utilization efficiency of the incident light from the side direction. A preferable inclination angle θ1 of the optical path conversion slope A1 from the viewpoint of optical path conversion having excellent directivity to the front and suppression of leak light.
Is 38 to 45 degrees, especially 40 to 44 degrees, considering the total reflection condition based on refraction of transmission light according to Snell's law.

The optical path changing means A having the above-described optical path changing slope A1 is formed as a repeating structure of irregularities for the purpose of reducing the thickness of the optical film. In this case, the angle of inclination with respect to the film surface as illustrated in FIG. 1 is more than the point of reflecting the incident light from the side direction backward and efficiently transmitting the light to the opposite side surface to emit light as uniformly as possible over the entire optical film. Is less than 5 degrees,
In particular, it is preferable to adopt a structure including a flat surface including a gentle slope A3 of 4 degrees or less, particularly 3 degrees or less, or a film surface A4 having the inclination angle of about 0 degrees. Therefore, FIGS. 1 (b), (e),
In the optical path changing means A including the steep slope A2 illustrated in (g) and (h), the angle of the steep slope is 35 degrees or more, particularly 50 degrees or more, and particularly 60 degrees or more, so that the width of the film surface A4 can be widened. Is preferred.

The flat surface consisting of the gentle slope A3 and the film surface A4 has a portion where external light is incident and a portion where the external light is incident when the reflective layer 4 is disposed on the back side of the optical film 1 as shown in FIGS. It is possible to function as a transmission part of the reflected light through the reflection layer 4 of the incident light, thereby enabling the display in the reflection mode by the external light with the lighting device turned off to form a reflective / transmission type liquid crystal display device. Is possible.

In the above case, in particular, the slope A as shown in FIG.
1. When the optical path conversion means A is formed of a repeating structure adjacent to A3, the angle difference between the gentle slope A3 and the film surface is within 5 degrees, preferably within 4 degrees, especially within 3 degrees, of the entire optical film. Further, it is preferable that the difference in the inclination angle between the nearest gentle slopes is within 1 degree, preferably within 0.3 degree, particularly within 0.1 degree. The purpose of this is to prevent the reflected light path through the gentle slope A3 from largely changing, particularly not to change greatly between the nearest gentle slopes. The case of the optical path changing means A using the slopes A1 and A3 as shown in FIG.

The light path conversion means A is formed by occupying an area or width of a gentle slope A3 having a tilt angle with respect to the film surface of 5 degrees or less or a flat surface composed of the film surface A4, rather than obtaining a bright display in the external light mode. Based on one side of the film, the inclination angle is preferably 10 times or more, more preferably 12 times or more, especially 15 times or more, that of the slopes A1 and A2 having the inclination angle of 35 degrees or more. This aims at improving the incident efficiency of external light and the transmission efficiency of reflected light through the reflective layer.

As shown in FIGS. 2 to 4, the optical path converting means A is provided so that its ridge line is parallel or inclined along the side of the light incidence side. May be formed continuously from one end to the other end of the optical film 1, or may be formed discontinuously and discontinuously as in the example of FIG.

In the case of discontinuous formation as described above, the length along the side surface direction of the concave / convex formed by the groove or the protrusion is five times the depth or the height in view of the incident efficiency of the transmission light and the optical path conversion efficiency. The length is preferably at least 500 μm, more preferably 10 to 480 μm, and particularly preferably 50 to 450 μm, from the viewpoint of achieving uniform light emission on the optical film.

The slope forming the optical path conversion means A may be formed in an appropriate surface form such as a straight surface, a refraction surface, a curved surface, etc., and the cross-sectional shape of the optical path conversion means A and the optical path conversion slope A1 through the same. Is not particularly limited. Since the light path conversion slope A1 is a factor in determining the luminance in the transmission (lighting) mode, the light emission uniformity on the optical film, and in the reflection / transmission type, the uniformity of the light emission in the external light mode as appropriate. And the distribution path density can be used to control the optical path conversion light quantity.

Therefore, the inclination angles of the slopes A1, 2, and 3 may be constant over the entire surface of the sheet, or may be reduced on the optical film in consideration of absorption loss and attenuation of transmission light due to the previous optical path conversion. For the purpose of achieving uniform light emission, as shown in the example of FIG.
May be increased.

The optical path changing means A may have a constant pitch as shown in the examples of FIGS. 2 and 3. Alternatively, the pitch may be gradually narrowed as the distance from the light incident side increases as shown in the examples of FIGS. Then, the distribution density of the optical path changing means A can 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 optical path conversion means A may be composed of a combination of irregularities having different shapes and the like in addition to the pitch. In addition, FIG.
In 6, the direction of the arrow is the light transmission direction.

In the case of a reflection / transmission type liquid crystal display device, if the optical path changing slope A1 overlaps the pixels of the liquid crystal display panel, the display light may be insufficiently transmitted, resulting in an unnatural display. It is preferable to make the overlap area as small as possible rather than a point to secure a sufficient light transmittance through the flat surfaces A3 and A4. From this point, the pixel pitch of the liquid crystal display panel is generally 100 to 30.
Considering that it is 0 μm, it is preferable that the optical path conversion slope A1 is formed so as to be 40 μm or less, preferably 3 to 20 μm, particularly 5 to 15 μm based on the projection width to the film surface. Such a projection width is more preferable than the point where the coherent length of the fluorescent tube is generally set to about 20 μm, and the like, from the viewpoint of preventing the deterioration of display quality due to diffraction.

On the other hand, it is preferable that the distance between the optical path changing slopes A1 is larger than the above-mentioned point. On the other hand, the optical path changing slope A1 substantially forms the illumination light by the light path changing of the incident light from the side as described above. Since it is a functional part, if the interval is too wide, the lighting at the time of lighting may be sparse and unnatural display may occur. In view of them, the repetition pitch of the optical path conversion slope A1 is 5 mm or less, especially It is preferably from 20 μm to 3 mm, particularly preferably from 50 μm to 2 mm.

In the case of an optical path changing means having a repeating structure of irregularities, moire may occur due to interference with pixels of a liquid crystal display panel. Moire can be prevented by adjusting the pitch of the repeating structure, but as described above, the pitch of the repeating structure has a preferable range. Therefore, a solution for a case where moire occurs in the pitch range becomes a problem. In the present invention, as shown in the example of FIG. 3, it is preferable to form a ridge line of the unevenness so as to be inclined with respect to the lateral direction so that the repeating structure of the unevenness can be arranged in an intersecting state with respect to the pixel to prevent moire.

In the above case, the inclination angle θ2 with respect to the side surface direction
Is too large, the reflection via the optical path conversion slope A1 is deflected, and a large deviation occurs in the direction of the optical path conversion, which tends to deteriorate the display quality. Therefore, the inclination angle θ2 of the ridge line with respect to the side surface direction is ± 30. It is preferable that the temperature be within ± 25 degrees, particularly within ± 25 degrees, and within ± 20 degrees. The sign of ± means the inclination direction of the ridgeline with respect to the side direction. In the case where the resolution of the liquid crystal display panel is low and moire is not generated or when moire is negligible, it is preferable that the ridge line is parallel to the side direction.

The transparent film having an optical path changing means can be prepared by, for example, pressing a thermoplastic resin into a mold capable of forming a predetermined shape under heating to transfer the shape, or heating and melting the thermoplastic resin or heat or solvent. A method of filling a resin that has been fluidized through a mold into a mold that can be formed into a predetermined shape, and filling a mold that can form a predetermined shape with a liquid resin that can be polymerized with heat, ultraviolet light, or radiation such as electronicity It can be formed by an appropriate method such as a method of casting and performing a polymerization treatment.

A preferred method of forming a transparent film having an optical path changing means is, for example, to apply a curable resin which can be polymerized by ultraviolet rays or radiation to one surface of the transparent film, and apply the coating layer to a predetermined uneven structure of a mold. After being cured by irradiation with ultraviolet light or radiation or the like in close contact with the formation surface of the transparent film, an optical path is formed on one side of the transparent film through a mold having a predetermined uneven structure as in a method of peeling and collecting the transparent film from the mold. This is a method of adding a repeating structure of irregularities having a conversion slope.

As described above, the transparent film having the light path changing means can be obtained by integrally molding with the light path changing means, or can be obtained by a method in which the light path changing means is added to one side of the transparent film. it can. In the latter case, the output efficiency may be greatly reduced due to interface reflection or the like if the refractive index difference between the optical path conversion means to be added and the transparent film is large, and the transparent film and the optical path conversion means to be added from the point of preventing the emission efficiency. It is preferable that the difference in the refractive index be as small as possible, particularly within 0.10, particularly within 0.05. In that case, it is preferable to increase the refractive index of the optical path changing means to be added, as compared with the transparent film, from the viewpoint of emission efficiency.

The transparent film and the optical path changing means can be formed of an appropriate material exhibiting transparency in accordance with the wavelength range of light incident via an illumination device or the like. Incidentally, in the visible light region, for example, acrylic resins, polycarbonate resins, transparent resins represented by cellulose resins, norbornene resins, and the like, curable resins that can be polymerized with heat, ultraviolet rays, radiation such as electron beams, and the like. Can be

In particular, it is preferable to use a material having no birefringence or a material having a small birefringence to form a transparent film having a small phase difference by a casting method or the like. In addition, internal stress may be generated in the transparent film by the bonding process,
It is preferable to use a material having a small photoelastic coefficient from the viewpoint of preventing the occurrence of a phase difference due to such internal stress. The thickness of the transparent film can be appropriately determined, but is generally 300 μm or less, especially 5 to 200 μm, particularly 10 to 100 μm from the viewpoint of thinning. The transparent film is shown in FIG.
As in the example of (h), it may be formed as two or more layers of superimposed bodies 11A and 11B made of the same or different kinds of resins, and need not be formed as an integrated single layer of one kind of material.

As shown in the example of FIG. 1, the optical film has an adhesive layer 12 provided on a surface of the transparent film 11 which does not have the repeating structure 13 of irregularities. The adhesive layer 12 is for bonding an optical film to a support member such as a liquid crystal display panel, and the bonding treatment via the adhesive layer is performed by the reflection efficiency through the optical path conversion slope A1 of the optical path conversion means A, and hence the reflection efficiency. The purpose is to improve the luminance by effectively utilizing the incident light from the side direction. The adhesive layer is formed by using an adhesive having a base polymer of a suitable polymer such as a rubber, an acrylic, a vinyl alkyl ether or a silicone, a polyester or a polyurethane, a polyether, a polyamide, or a styrene. Can be used. Among them, those excellent in transparency, weather resistance, heat resistance and the like, such as an acrylic pressure-sensitive adhesive having a polymer mainly composed of an alkyl ester of acrylic acid or methacrylic acid as a base polymer, are preferably used.

In the present invention, as shown by arrows in FIG. 9, the present invention prevents light from being confined in the optical film due to interfacial reflection due to a difference in refractive index and cannot be emitted, and the amount of light that cannot be emitted and is lost is suppressed. For this reason, an adhesive layer having a difference in refractive index from the transparent film within 0.1, particularly within 0.08, particularly within 0.05 is used. The adhesive layer is, for example, silica or alumina, titania or zirconia,
Appropriate transparent particles such as inorganic particles that may be conductive, such as tin oxide, indium oxide, cadmium oxide, and antimony oxide, and organic particles, such as a crosslinked or uncrosslinked polymer.
A light-diffusing type may be used by containing two or more species. It is preferable to temporarily cover the pressure-sensitive adhesive layer with a release sheet 14 as shown in the example of FIG. 1 for the purpose of preventing entry of foreign matter and the like until the pressure-sensitive adhesive layer is put to practical use.
Further, for the same reason as described above, the difference in the refractive index from the support member to which the adhesive layer is adhered is preferably within 0.15, more preferably within 0.10, particularly preferably within 0.05.

The optical film may be a transparent film in which a substrate such as a sheet for protecting the optical path changing slope is closely attached to the surface on which the optical path changing slope is formed.
The optical film may be one in which the reflective layer 4 is disposed in close contact with the surface of the transparent film 11 on which the optical path changing slope is formed, as illustrated in FIGS. Such a reflective layer is intended to improve the light use efficiency by reversing and re-injecting the light leaking from the surface of the transparent film on which the optical path conversion slope is formed, and to form a liquid crystal display device for both reflection and transmission. .

The reflection layer can be formed of an appropriate material such as a conventional white sheet. Above all, for example, a coating layer containing a powder of a high reflectivity metal such as aluminum, silver, gold, copper, chromium, or an alloy thereof in a binder resin, the above-mentioned metal, etc. and a dielectric multilayer film are formed by a vacuum deposition method. A layer formed by an appropriate thin film forming method such as a sputtering method or the like, a reflective sheet having the above-mentioned coating layer or the attached layer supported by a substrate made of a film or the like, a reflective layer having a high reflectivity made of a metal foil or the like. It is particularly preferable when a reflective / transmissive liquid crystal display device is formed.

The reflection layer to be formed may have a light diffusion function. By diffusing the reflected light on the diffuse reflection surface, directivity in the front direction can be improved,
In the case of roughening, the occurrence of Newton rings due to close contact can be prevented, and visibility can be improved.

The light-diffusing reflection layer is formed on a film substrate or the like having a fine uneven structure on the surface by an appropriate method such as a surface roughening method by sandblasting or matting, or a particle addition method. It can be performed by a method of providing a reflection layer reflecting the fine uneven structure. The formation of the reflective layer having a fine uneven structure reflecting the fine uneven structure on the surface is performed by, for example, applying a metal to a film base by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method, or a sputtering method, or a plating method. It can be carried out by a method of attaching to the surface of the like.

The optical film according to the present invention converts the incident light or the transmitted light from the side direction of the lighting device or the like through the optical path changing slope into an optical path which is advantageous for visual recognition and emits the light with high light utilization efficiency. In addition, it shows good transparency to external light, and as shown in FIGS. 7 and 8, the viewing back side (back) of the liquid crystal display panel P in which the lighting devices 5 and 51 are arranged on one or more side surfaces. Various devices such as a transmissive liquid crystal display device which is bright and easy to see by arranging it on the viewing side (fluorocarbon) and a reflective / transmissive liquid crystal display device excellent in low power consumption can be formed.

By the way, according to the above-mentioned liquid crystal display device,
Most of the incident light from the side direction through the lighting device is transmitted rearward via the upper and lower cell substrates 21 and 28 via reflection based on the law of refraction based on the thickness ratio of each layer in the liquid crystal display panel, The light incident on the optical path changing slope A1 of the optical film 1 is efficiently converted in the viewing direction, particularly in the front direction, while emission (leakage) from the surface is prevented,
Other light is transmitted backward by total reflection, enters the optical path conversion slope A1 at the rear, is efficiently optical path-converted in the viewing direction, and can achieve a display with excellent brightness over the entire panel display surface.

In the above description, as the liquid crystal display panel P,
An optical system having at least a suitable transmission type having at least a liquid crystal cell, that is, a liquid crystal cell in which a liquid crystal 25 is sealed between cell substrates 21 and 28 via a sealing material 24 as shown in FIGS. It is possible to use one that emits incident light from the side on which the film 1 is disposed as display light from the other side through control by a liquid crystal or the like, and the type is not particularly limited.

Incidentally, specific examples of the above-mentioned liquid crystal cell include twisted and non-twisted systems such as TN liquid crystal cell, STN liquid crystal cell, IPS liquid crystal cell, HAN liquid crystal cell, OCB liquid crystal cell and VA liquid crystal cell, guest host system, and the like. A liquid crystal cell of a ferroelectric liquid crystal system, a liquid crystal cell of a light diffusion type, or the like can be given, and a driving method of the liquid crystal may be an appropriate method such as an active matrix method or a passive matrix method. The driving of the liquid crystal is usually performed by a transparent electrode 2 provided inside a pair of cell substrates 21 and 28 as illustrated in FIGS.
Via steps 2 and 27.

As the cell substrate, an appropriate transparent substrate made of glass, resin, or the like can be used. In particular, a substrate made of an optically isotropic material is preferable from the viewpoint of display quality and the like. Further, a material having excellent colorless transparency such as a non-alkali glass plate with respect to a blue glass plate is preferable in terms of improvement of luminance and display quality, and a resin substrate is more preferable in terms of lightness and the like. The thickness of the cell substrate is not particularly limited, and can be appropriately determined according to the sealing strength of the liquid crystal and the like. Generally, it is 10μ from the point of balance between light transmission efficiency and thin and light weight.
m to 5 mm, preferably 50 μm to 2 mm, especially 100 μm to 1 mm.

In forming the liquid crystal cell, if necessary, one or two or more appropriate functional layers such as an alignment film such as a rubbing film for aligning liquid crystal and a color filter for color display are provided. be able to. As shown in the figure, the alignment films 23 and 26 usually have transparent electrodes 22 and 27.
And a color filter (not shown) is usually provided between one of the cell substrates 21 and 28 and the transparent electrode.

In the liquid crystal display panel, as shown in FIGS. 7 and 8, one or more suitable optical layers such as polarizing plates 31, 34, retardation plates 32, 33, and light diffusing layers are added to the liquid crystal cell. May be done. A polarizing plate aims at achieving display using linearly polarized light, and a retardation plate aims at improving display quality by compensating for a phase difference due to birefringence of liquid crystal and the like. In addition, the light diffusion layer expands the display range by diffusing display light, equalizes brightness by leveling bright line-like light emission through the slope of the optical film, and enters the optical film by diffusing transmission light in the liquid crystal display panel. The purpose is to increase the amount of light.

As the above-mentioned polarizing plate, an appropriate polarizing plate can be used, and there is no particular limitation. Rather than obtaining a display with a good contrast ratio due to the incidence of highly linearly polarized light,
For example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film is adsorbed with a dichroic substance such as iodine or a dichroic dye and stretched. A high-polarization film such as an absorption-type polarizing film made of such a film or a film provided with a transparent protective layer on one or both sides thereof can be preferably used.

For the formation of the transparent protective layer, those having excellent transparency, mechanical strength, heat stability and moisture shielding property are preferably used. Examples thereof include acetate resins, polyester resins, and polyether sulfone. Resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin or acrylic resin, polyether resin or polyvinyl chloride, polymer such as styrene resin or norbornene resin, or acrylic or urethane resin, Examples thereof include thermosetting or ultraviolet-curing resins such as acrylic urethane, epoxy, and silicone. The transparent protective layer can be provided by a bonding method of a film or a coating method of a polymer liquid or the like.

The polarizing plate to be used, in particular, the polarizing plate on the viewing side, may have been subjected to a non-glare treatment or an anti-reflection treatment for the purpose of preventing the visibility from being inhibited by surface reflection of external light. Non-glare treatment can be performed by forming a fine uneven structure on the surface by various methods such as a roughening method such as a sand blast method or an embossing method, a method of blending transparent particles such as silica, etc. It can be applied by a method of forming a coherent vapor deposition film. The non-glare treatment and the anti-reflection treatment can also be applied to the above-mentioned method of bonding a film provided with a fine surface unevenness structure or an interference film. The polarizing plate can be provided on both sides of the liquid crystal cell as shown in the drawing, or can be provided only on one side of the liquid crystal cell.

On the other hand, a birefringent film obtained by stretching a film made of a suitable polymer such as those exemplified in the above-mentioned transparent protective layer by a suitable method such as uniaxial or biaxial is also used as a retardation plate. An appropriate film such as an alignment film of a liquid crystal polymer such as a liquid crystal polymer or a discotic one or a film in which the alignment layer is supported by a transparent substrate can be used. The refractive index in the vertical direction may be controlled.

As shown in the figure, the compensating retardation plates 32 and 33 are usually arranged as necessary between the polarizing plates 31 and 34 on the viewing side and / or the back side and the liquid crystal cell. Can be appropriately selected depending on the wavelength range or the like. Further, the retardation plate may be used by superposing two or more layers for the purpose of controlling optical characteristics such as retardation.

The light diffusion layer can also be provided by an appropriate method using a coating layer or a diffusion sheet having a fine surface irregularity structure according to the non-glare layer. The light diffusion layer can be disposed as an adhesive layer 35 also serving as an adhesive between the polarizing plate 34 and the retardation plate 33 as shown in the figure according to the above-mentioned adhesive layer 12 containing transparent particles, thereby achieving a reduction in thickness. be able to. The light diffusion layer can be arranged on the outer side (viewing side) of the polarizing plate. However, by arranging the light diffusion layer on the liquid crystal cell side of the polarizing plate 34 as shown in the figure, light is absorbed after external light is absorbed by the polarizing plate. Since the light is incident on the diffusion layer, reflection loss due to back scattering through the light diffusion layer can be advantageously suppressed.

On the other hand, the illumination device arranged on the side surface of the liquid crystal display panel aims to make light used as illumination light for the liquid crystal display device enter from the side surface of the liquid crystal display panel.
This makes it possible to reduce the thickness and weight of the liquid crystal display device in combination with an optical film disposed on the back or front of the panel. Any suitable lighting device can be used. For example, a linear light source such as a (cold or hot) cathode tube, a point light source such as a light-emitting diode, or an array in which the light sources are arranged linearly or in a plane, or a point light source An illumination device or the like in which a light source and a linear light guide plate are combined to convert incident light from a point light source into a linear light source via the linear light guide plate can be preferably used.

As shown in the examples of FIGS.
It can be arranged on one or more side surfaces of the liquid crystal display panel P. When the lighting device is arranged on two or more side surfaces, the plurality of side surfaces may be a combination of opposing side surfaces as in the example of FIG. 8, or may be a combination of side surfaces that cross vertically and horizontally. A combination of three or more sides may be used.

The illuminating device enables visual recognition in the transmission mode by turning on the light. In the case of a reflective / transmission type liquid crystal display device, it is not necessary to turn on the light when viewing in the reflection mode by external light. Therefore, it can be switched between lighting and extinguishing. An arbitrary method can be adopted as the switching method, and any of the conventional methods can be adopted. Note that the illumination device may be of a different color emission type capable of switching the emission color, or may be of a different color emission type through different types of illumination devices.

As shown in the figure, for the lighting devices 5 and 51,
If necessary, a combination may be provided in which appropriate auxiliary means such as a reflector 52 surrounding the liquid crystal display panel P are arranged to guide the divergent light to the side surface. As the reflector, a suitable 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 be used as a fixing means that also surrounds the lighting device by, for example, bonding the end to an end of a liquid crystal display panel such as a cell substrate.

In the present invention, optical elements or components such as a liquid crystal cell, a polarizing plate, and a retardation plate forming the liquid crystal display device described above may be entirely or partially laminated and integrated and fixed. , May be arranged in an easily separable state. It is preferable to be in a fixed state rather than to prevent reduction in contrast by suppressing interface reflection. An appropriate transparent adhesive such as a pressure-sensitive adhesive can be used in the adhesion and adhesion treatment, and the transparent adhesive layer can be made to contain the above-mentioned transparent particles and the like to form an adhesive layer having a diffusion function.

The above-mentioned optical element or component, particularly on the visual side, is treated with an ultraviolet absorber such as a salicylate compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, a nickel complex salt compound, or the like. UV absorption ability can be imparted by such means.

[0064]

Example 1 Acrylic UV-curable resin (Aronix UV-3701 manufactured by Toagosei Co., Ltd.) was placed in a mold previously processed into a predetermined shape.
Is dropped and filled with a dropper, and an 80 μm-thick triacetylcellulose (TAC) film (surface-saponified product) is allowed to stand still thereon, and is adhered tightly with a rubber roller to remove excess resin and air bubbles, and then a metal halide lamp is used. After being cured by irradiating ultraviolet rays, it is peeled from the mold and cut into a predetermined size to obtain a transparent film having a TAC film having a refractive index of 1.49 and an optical path changing means layer having a refractive index of 1.533. An optical film was obtained by attaching an adhesive layer having a refractive index of 1.47 to the surface having no means.

The above-mentioned optical film has a width of 60 mm and a depth of 45 mm, and has prism-shaped concave portions whose ridges are parallel and continuous in the width direction at a pitch of 210 μm (FIG. 1c).
The inclination angle of the light path conversion slope A1 changes in the range of 42.5 to 43 degrees, the inclination angle of the gentle slope A3 changes in the range of 1.8 to 3.5 degrees, and the inclination change of the nearest gentle slope changes to 0. Within 1 degree, the projection width of the optical path conversion slope to the film surface is 10 to 10.
The projection surface ratio of the gentle slope / optical path changing slope to the film surface is 12 μm or more.

Next, a light diffusion film comprising a TAC film having an adhesive layer containing resin fine particles adhered to the viewing side of a commercially available TN type liquid crystal cell, and a polarizing plate is adhered to the front and back of the cell. After disposing a cold cathode tube on the side surface of a white transmissive TN liquid crystal display panel and surrounding it with a reflector made of a silver-evaporated reflective sheet, bonding both ends to the upper and lower surfaces of the panel and fixing the cold cathode tube The optical film is adhered to the polarizing plate on the viewing back side via the adhesive layer such that the optical path conversion slope faces in parallel with the cold cathode tube, and a reflecting plate made of a white polyester film is arranged on the back of the optical film. Thus, a transmission type liquid crystal display device was obtained.

Embodiment 2 The inclination angle of the light path changing slope A1 is about 42 degrees, the apex angle with the steep slope A2 is 70 degrees, and the area of the flat surface A4 is 10 times the total projected area of the light path changing slope and the steep slope on the film surface. A transmissive liquid crystal display device was obtained in accordance with Example 1 by using the optical film having the above-described optical path changing means (FIG. 1b).

Example 3 An inclination angle of about 42 degrees and a projection width on a film surface of 10 μm
m of the optical path conversion slope A1 and a steep slope A2 having an inclination angle of about 55 degrees.
An optical path converting means (FIG. 1b) having a length of 80 μm and having a length direction substantially parallel to the width direction, and the optical path converting means gradually increasing in density with distance from the light incident side in the depth direction A transmissive liquid crystal display device was obtained in the same manner as in Example 1 except that the optical film (FIG. 6) was used. The area of the flat surface A4 is 10 times or more the total projected area of the optical path changing slope and the steep slope on the film surface.

Example 4 An inclination angle of about 42 degrees and a projection width on a film surface of 10 μm
An optical path converting means (FIG. 1a) having a length of 80 μm and consisting of an isosceles triangle formed by an optical path converting slope A1 having a length of m is provided in a state where its length direction is parallel to the width direction, and the optical path converting means is provided with light incident in the depth direction. Example 1 was the same as Example 1 except that an optical film (FIG. 4) was randomly arranged so that the density gradually increased from the side toward the center, and the cold cathode tubes were arranged on two opposite sides using the optical film. A semi-transmissive liquid crystal display device was obtained. The area of the flat surface A4 is at least 10 times the total area of the two optical path changing slopes.

Example 5 An inclination angle of about 42 degrees and a projection width on a film surface of 10 μm
optical path changing means (FIG. 1e) having a groove having a length of 80 μm and having a substantially rectangular cross section having two optical path changing slopes A1 having a length of approximately m and having a length direction substantially parallel to the width direction. Is an optical film that is randomly arranged so that the density gradually increases from the light incident side in the depth direction toward the center from the light incident side in the depth direction. A display device was obtained. Note that the area of the flat surface A4 is at least 10 times the area of the optical path conversion unit.

Example 6 A reflective / transmissive liquid crystal according to Example 2, except that an optical film having a reflective layer made of a silver vapor-deposited film was provided on the surface on which the optical path changing means was formed, and the back reflector was omitted. A display device was obtained.

Comparative Example 1 A transmissive liquid crystal display device (FIG. 10) was obtained according to Example 1, except that a scattering sheet produced by sandblasting was used instead of the optical film. In addition, the scattering sheet was arrange | positioned with the rough surface as the visual back side.

Comparative Example 2 The inclination angle of the optical path changing slope was about 30 degrees, the apex angle with the steep slope was 70 degrees, and the area of the flat portion A4 was 10 times or more the total projected area of the optical path changing slope and the steep slope on the film surface. A transmissive liquid crystal display device was obtained in accordance with Example 1, except that an optical film having an optical path changing means (FIG. 1b) was used.

Comparative Example 3 A cold-cathode tube was placed on the side of a 1.2 mm thick light guide plate having a textured rough surface on the viewer's back side, and was surrounded by a reflector made of a silver-evaporated reflection sheet. The part is adhered to the upper and lower surfaces of the light guide plate, and it is arranged on a reflector made of a white polyester film, and a commercially available normally white transmissive TN liquid crystal panel is arranged thereon via a light diffusion plate. A transmissive liquid crystal display was obtained.

COMPARATIVE EXAMPLE 4 A reflective / transmissive liquid crystal display according to Example 6, except that the scattering film of Comparative Example 1 in which a reflective layer made of a silver vapor-deposited film was provided on the scattering surface was used and the back reflector was omitted. The device was obtained.

COMPARATIVE EXAMPLE 5 Reflection / transmission according to Example 6, except that the back reflector was omitted using the optical film of Comparative Example 2 in which a reflective layer made of a silver vapor-deposited film was provided on the surface on which the optical path changing means was formed. A dual-use liquid crystal display device was obtained.

Evaluation Test With regard to the transmissive or reflective / transmissive liquid crystal display devices obtained in the examples and comparative examples, the cold cathode tubes were turned on in the state where no voltage was applied to the liquid crystal display panel, and the central portion of the device was operated in the transmissive mode. Was examined with a luminance meter (BM7, manufactured by Topcon Corporation). Further, the front luminance in the white state in the reflection mode in which external light from the ring-shaped illumination with the cold-cathode tube turned off was incident at an angle of 15 degrees was also examined. The results are shown in the following table.

[0078]

From the table, it can be seen that in the example, in the transmissive mode, superior front luminance was achieved as compared with the comparative examples 1, 2, 4, and 5. This is because in Comparative Examples 1, 2, 4, and 5, light was emitted in the direction opposite to the light source in the transmission mode, and the emitted light had poor brightness in the front direction and hardly contributed to display. In particular, in Comparative Examples 1 and 4, the emitted light was poor in any direction.

Further, in Examples 4 and 5, the improvement in luminance by the two-lamp system is remarkable, and it can be seen that the brightness is higher than that of the sidelight type light guide plate of Comparative Example 3. In the method using the sidelight type light guide plate of Comparative Example 3, the thickness increase due to the light guide plate was remarkable, and it was difficult to reduce the thickness. Furthermore, in the transmission mode, there was no problem in visual recognition in a state where a voltage was applied to the liquid crystal display panel, and the display quality was good. Further, in the state where the light diffusion film was removed in Example 2, the visibility was inferior to the case where the light diffusion film was provided, but the front luminance was not inferior.

On the other hand, even in the reflection mode, when the voltage is applied to the liquid crystal display panel, Example 6 and Comparative Example 4,
In Example 5, the display was free from image distortion and the like.
Was darker than Example 6. As described above, in the embodiment, a bright display is achieved in the transmission mode, and also in the reflection mode of the sixth embodiment, a bright display is achieved. Thus, according to the present invention, bulkiness and weight increase by the light guide plate can be avoided. It can be seen that a transmissive or reflective / transmissive liquid crystal display device with good display quality can be formed while achieving a thin and light weight by the film method.

[Brief description of the drawings]

FIG. 1 is an explanatory side view of an example of an optical film (optical path conversion slope).

FIG. 2 is an explanatory plan view of an optical path changing slope;

FIG. 3 is an explanatory plan view of another optical path changing slope;

FIG. 4 is an explanatory plan view of still another optical path conversion slope;

FIG. 5 is a side view of another optical film example.

FIG. 6 is an explanatory side view of still another optical film example.

FIG. 7 is an explanatory sectional view of an example of a transmissive (reflective / transmissive) liquid crystal display device.

FIG. 8 is an explanatory sectional view of another example of a transmissive (reflective / transmissive) liquid crystal display device.

FIG. 9 is an explanatory diagram of a relationship between a refractive index and an optical path.

FIG. 10 is an explanatory sectional view of an example of a conventional transmission type liquid crystal display device.

[Explanation of symbols]

 1: Optical film 11: Transparent film 12: Adhesive layer 13: Optical path conversion means layer A: Optical path conversion means A1: Optical path conversion slope A3, 4: Flat surface 4: Reflective layer P: Liquid crystal display panel 5, 51: Illumination device 21 , 28: cell substrate 25: liquid crystal layer 31, 34: polarizing plate 32, 33: retardation plate

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiko Ariyoshi 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 2H038 AA55 BA01 2H042 CA12 CA17 2H091 FA14Z FA23Z FA32Z FB02 FC17 FD06 LA11 LA17 LA18

Claims (11)

[Claims] 1. A transparent film having an adhesive layer having a refractive index difference of 0.1 or less with respect to a surface layer on one surface of the transparent film, and having an inclination angle of 35 to 48 degrees with respect to the film surface on the other surface of the transparent film. An optical film having a repeating structure of irregularities having an optical path changing slope directed in a certain direction. 2. The optical system according to claim 1, wherein there are two or more optical path changing slopes oriented in a substantially constant direction including a surface oriented in the opposite direction with respect to one surface, and the adhesive layer is covered with a release sheet. the film. 3. The optical film according to claim 1, wherein the inclination angle of the optical path changing slope with respect to the film surface is 38 to 45 degrees. 4. The optical film according to claim 1, wherein the optical path changing slope is based on a groove structure having an approximately isosceles triangle in cross section or another triangle in cross section. 5. The optical film according to claim 1, wherein the optical path conversion slope is based on a groove or projection structure having a substantially rectangular cross section or a substantially pentagonal cross section. 6. A method according to claim 1, wherein the flat surface having an inclination angle of not more than 5 degrees with respect to the film surface is one of the inclined surfaces having an inclination angle of not less than 35 degrees based on the occupied area on one side of the film.
Optical film having 0 times or more. 7. The method according to claim 1, wherein the uneven structure having the optical path changing slope has an inclination angle of 3 with respect to the film surface.
It is based on an optical path changing slope of 8 to 45 degrees, a flat surface having an inclination angle of 5 degrees or less and a flat surface having a width of 10 times or more the optical path changing slope, and a substantially triangular continuous groove extending from one end to the other end of the film. Some optical films. 8. The uneven structure according to claim 1, wherein the concave-convex structure having the optical path changing slope is based on a discontinuous groove having a polygonal cross section of approximately three to five, and the length of the discontinuous groove is five times the depth. As described above, the optical film in which the optical path changing slope is formed in the groove length direction at an inclination angle of 38 to 45 degrees with respect to the film surface, and the area of the discontinuous groove portion occupying one surface of the film is 10% or less. 9. The optical film according to claim 1, wherein a reflection layer is closely attached to a surface having an uneven structure having an optical path changing slope. 10. The method according to claim 1, wherein the ridge line of the optical path changing slope is parallel to one side of the transparent film or ± 30.
An optical film that tilts within a degree. 11. The optical film according to claim 1, wherein the adhesive layer is a light diffusion type.