JP2003050314A - Polarizing plate and liquid crystal display - Google Patents

Abstract

[PROBLEMS] To develop a polarizing plate capable of forming a thin, lightweight, bright, and easy-to-view liquid crystal display device by efficiently changing the optical path of light incident from the side surface of a liquid crystal display panel in the viewing direction. A transparent protective layer (1A) having a plurality of light emitting means (A) having an optical path changing slope (a) having an inclination angle of 35 to 48 degrees with respect to a plane formed by a polarizer (1C) on one surface or both surfaces. A polarizing plate (1) having the polarizer (1B) on at least one side of a polarizer, and a liquid crystal display device comprising the polarizing plate disposed on at least one side of a liquid crystal cell. [Effect] By incorporating a polarizing plate into a liquid crystal display panel, light incident from a side surface of the liquid crystal display panel can be efficiently and directionally redirected in the viewing direction through the optical path conversion slope of the light emitting means. Based on this, it is possible to form a liquid crystal display device that is thin, light, bright, and easy to view.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention efficiently forms a liquid crystal display device which is thin, lightweight, bright, and has less image disturbance and is easy to view by efficiently converting the light incident from the side surface of a liquid crystal display panel to a viewing direction. Ulu polarizing plate.

[0002]

2. Description of the Related Art Conventionally, a front light type reflective liquid crystal display device in which a side light type light guide plate is disposed on the viewing side of a liquid crystal display panel causes an increase in thickness and weight.
For the purpose of reducing the thickness and weight of the liquid crystal display panel, there has been known a reflection type liquid crystal display device in which incident light from the side direction is reflected through a viewing side cell substrate of a liquid crystal display panel and can be used as illumination light. 5-158033).

However, since the reflected light from the rough surface is used as the illumination light, it is difficult to obtain a bright display. That is, since the reflected light is strongly reflected in the regular reflection direction with respect to the light transmission direction and the light intensity becomes small in a normal distribution with respect to the angle, it is strongly emitted in a direction largely inclined from the front direction of the liquid crystal panel, There was a problem that the display was dark in the normal viewing direction in the front direction.

[0004]

DISCLOSURE OF THE INVENTION The present invention is directed to the development of a polarizing plate 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 in the viewing direction. Is an issue.

[0005]

According to the present invention, at least a transparent protective layer having a plurality of light emitting means on one side or both sides, which has an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to a plane formed by the polarizer, is provided at least in the polarizer. It is intended to provide a polarizing plate having one side and a liquid crystal display device having the polarizing plate arranged on at least one side of a liquid crystal cell.

[0006]

According to the present invention, by incorporating a polarizing plate into a liquid crystal display panel, the light incident from the side surface of the liquid crystal display panel can be efficiently and easily directed through the optical path changing slope of the light emitting means. The optical path can be changed to the viewing direction, and based on this, it is possible to form a thin, lightweight, bright, and easily viewable liquid crystal display device.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate according to the present invention has a transparent protective layer having a plurality of light emitting means on one side or both sides, which has an optical path changing slope having an inclination angle of 35 to 48 degrees with respect to a plane formed by a polarizer. It has at least one side of the child. An example thereof is shown in FIG. Reference numeral 1 is a polarizing plate, 1A is a light emitting means forming layer, 1B and 1D are transparent protective layers, 1C is a polarizer, A is a light emitting means, and a is an optical path conversion slope.

An appropriate polarizer can be used as the polarizer and is not particularly limited. Generally, a polarizer is used. From the viewpoint of obtaining a good contrast ratio display due to the incidence of highly linearly polarized light, it is more hydrophilic than those such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film. A polarizer having a high degree of polarization, such as an absorption-type polarizer formed by adsorbing and stretching a dichroic substance such as iodine or a dichroic dye on a molecular film, can be preferably used.

The polarizing plate is formed by providing a transparent protective layer having a predetermined light emitting means on one side or both sides on at least one side of the polarizer. When a transparent protective layer having a predetermined light emitting means is provided only on one side of the polarizer, a transparent protective layer having no light emitting means may be provided on the other side of the polarizer, if necessary.

The transparent protective layer can be formed using one or two or more kinds of appropriate materials exhibiting transparency depending on the wavelength range of light incident via a light source or the like. By the way, in the visible light range, for example, acrylic resins, polycarbonate resins, cellulose resins, norbornene resins, transparent resins represented by polyolefin resins, etc., curable resins that can be polymerized by radiation such as heat, ultraviolet rays, and electron beams. And so on. Above all, a transparent protective layer which is excellent in transparency, mechanical strength, thermal stability and moisture shielding property is preferably used.

Further, the refractive index is equal to that of the liquid crystal cell, especially the cell substrate thereof, from the viewpoint of increasing the incidence efficiency of the light emitting means on the slope for changing the optical path and obtaining a liquid crystal display device which is bright and has excellent uniformity. Above all, above 1.49, especially 1.5
Two or more transparent protective layers are preferably used. When the front light system is used, the refractive index is preferably 1.6 or less, more preferably 1.56 or less, and especially 1.54 or less from the viewpoint of suppressing surface reflection. 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 incident light has peculiarities, etc. You can also (same below).

Further, a transparent protective layer which is preferable from the viewpoint of suppressing unevenness in brightness and unevenness in color to obtain a liquid crystal display device having small unevenness in display is preferably one which does not exhibit birefringence or has small birefringence. Is 30 nm or less. By using a transparent protective layer having a small retardation, when linearly polarized light enters through a polarizer, 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 in the transparent protective layer is preferably 20 nm or less, and particularly 15 nm.
It is particularly preferable that the thickness is 10 nm or less, and the variation in the phase difference between the places is as small as possible. Further, the transparent protective layer made of a material having a small photoelastic coefficient is preferable from the viewpoint of suppressing the internal stress that tends to occur in the transparent protective layer by the adhesion treatment and preventing the occurrence of the phase difference due to the internal stress. In addition, the average phase difference in the thickness direction of the transparent protective layer is 50 nm.
Hereafter, it is preferably 30 nm or less, particularly 20 nm or less from the viewpoint of preventing display unevenness.

The transparent protective layer having such a low retardation can be formed by an appropriate method such as a method of removing an internal optical strain by a method of annealing an existing film.
A preferable forming method is a method of forming a transparent protective layer having a small retardation by a casting method. The above-mentioned retardation in the transparent protective layer is due to light in the visible region, especially at a wavelength of 550 nm.
It is preferably based on the above light.

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. Where nx is the average refractive index in the in-plane maximum refractive index direction, ny is the average refractive index in the in-plane direction orthogonal to the nx direction, nz is the average refractive index in the thickness direction of the transparent protective layer, and d is transparent. It means the average thickness of the protective layer.

The transparent protective layer may be formed as a single layer or as a laminated body made of the same or different materials. By the way, in the example of FIG. 1, the transparent protective layer on the side having the light emitting means is composed of a laminate in which the light emitting means forming layer 1A is integrated with the transparent film 1B, and the transparent protective layer 1D on the other side is a single layer. I'm sorry. The transparent protective layer may be formed as a single layer of the light emitting means forming layer 1A only. The thickness of the transparent protective layer is 5 to 500 μm including the case where it is made of a laminated body from the viewpoint of thinning and lightening.
m, especially 10 to 300 μm, particularly preferably 20 to 100 μm.

A general form of the polarizing plate is one in which a transparent protective layer having a light emitting means on only one side is provided on one side of the polarizer so that the side having the light emitting means is on the outside.
In that case, the surface of the transparent protective layer on the side having no polarizer is
It is preferably smooth. The transparent protective layer can be adhered to the polarizer using an appropriate transparent adhesive such as polyvinyl alcohol. In the case where the transparent protective layer has a light emitting means, it is preferable to carry out an adhesion treatment with an appropriate transparent pressure-sensitive adhesive such as acrylic or rubber.

The light emitting means A in the polarizing plate 1 is arranged so that the surface on which the light emitting means is formed is the outer side in the direction along the cell plane of the liquid crystal cell having the light source 51 on the side surface as illustrated in FIG. The incident light or the transmitted light from the side surface by the light source is reflected through the optical path conversion slope a to the rear surface side (polarizer side), and accordingly, the optical path is converted in the viewing direction of the liquid crystal display panel and emitted from the polarizer 1C side. The emitted light can be used as illumination light (display light) for a liquid crystal display panel or the like.

In order to obtain the above emission characteristics, the light emitting means is provided with an optical path changing slope a having an inclination angle θ1 of 35 to 48 degrees with respect to the plane formed by the polarizer, as in the example of FIG. Thereby, the incident light from the side surface direction or the transmitted light by the light source arranged on the side surface of the liquid crystal cell or the like is converted to the rear surface side through the optical path conversion slope a, that is, the polarizer side,
Light having excellent directivity in the normal direction to the liquid crystal cell or the like can be efficiently emitted from the polarizing plate as the light source light.

When the inclination angle of the optical path changing slope is less than 35 degrees, when a reflecting plate is arranged on the back side of the visible side of the liquid crystal cell to reflect the optical path changing light, a liquid crystal display panel of display light based on the reflected light is provided. Further, the emission angle exceeds 30 degrees, which is disadvantageous for visual recognition. On the other hand, when the inclination angle of the optical path changing slope exceeds 48 degrees, total reflection is not performed and light leakage easily occurs from the slope, and the light use efficiency is reduced.

In the above case, when the scattering method of the light emitting means having a roughened surface is used instead of the reflection method of the optical path changing slope, it is difficult to reflect in the vertical direction, and the liquid crystal display panel is inclined more than the front direction. The liquid crystal display is dark because the light is emitted in the direction, and the contrast is poor.

Efficient total reflection through the optical path conversion slopes and directivity emission from the polarizing plate in the direction normal to the plane formed by the polarizer, and the liquid crystal cell is efficiently illuminated to achieve a bright and easy-to-see liquid crystal display. From this point, the inclination angle θ1 of the optical path conversion slope is preferably 38 to 45 degrees, and more preferably 40 to 43 degrees.

The light emitting means is formed of a suitable shape having one or more of the above-mentioned optical path changing slopes, for example, a concave portion or a convex portion having a shape such as a triangle to a pentagon based on the cross section with respect to the optical path changing slope. be able to. Incidentally, the example of FIG. 1 shows the light emitting means having a triangular cross section, which includes the optical path changing slope a and the elevation b having a large inclination angle θ2.
It may be a light emitting means having an isosceles triangular cross section having a two-sided optical path changing slope a. The polygon of the cross section is
This is not a strict meaning, and variations such as a change in the angle of the side and a rounding of the angle formed by the intersections of the sides are allowed.

As described above, the light emitting means may be formed as a convex portion, but it is preferable that the light emitting means is formed as a concave portion as shown in the figure from the viewpoints of light utilization efficiency and scratch resistance. . Above all, the light emitting means formed of a concave portion having a triangular cross section is preferable from the viewpoints of reduction in visibility due to size reduction and manufacturing efficiency. The concave portion means that it is recessed inside the polarizing plate (groove), and the convex portion means that it protrudes outside the polarizing plate (mountain).

Further, a plurality of light emitting means are formed for the purpose of downsizing and further thinning. In that case, as illustrated as a plan view in FIGS. 2 to 4, a continuous light emitting means is arranged in a stripe form from one side to the other side, or a plurality of light emitting means are distributed in a discontinuous intermittent manner. It can be formed as an item. The light emitting means may be distributed in parallel as in the example of FIG. 2 or irregularly as in the example of FIG. 3 based on the optical path conversion slope in the continuous or discontinuous state. May be. Further, as in the example of FIG. 4, it may be in a distribution state in which the pits are arranged with respect to the virtual center.

The arrangement state of the plurality of light emitting means can be appropriately determined according to its form and the like. As described above, the optical path conversion slope a is for reflecting the incident light from the side surface from the light source in the illumination mode in the direction of the polarizer and converting the optical path, and thus the light emitting means having such an optical path conversion slope is provided. Distributing in the transparent protective layer so that the total light transmittance is 75 to 92% and the haze is 4 to 20%, the light from the side direction via the light source is subjected to optical path conversion to efficiently illuminate the liquid crystal cell. This is preferable from the viewpoint of obtaining a surface light source and achieving a liquid crystal display that is bright and has excellent contrast.

The characteristics of total light transmittance and haze can be achieved by controlling the size and distribution density of the light emitting means, and for example, the projected area of the light emitting means occupying the surface of the transparent protective layer on which the light emitting means is formed. Occupied area based on 1/100 to 1
/ 8, especially 1/50 to 1/10, especially 1/30 to 1/1
It can be achieved by setting it to 5.

More specifically, when 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 deteriorated, and the uniformity of illumination on the liquid crystal cell is also likely to be deteriorated. In consideration of the above, when the continuous light emitting means is distributed in parallel as in the example of FIG.
The repetition pitch is 2 mm or less, preferably 20 μm to 1 mm, especially 50 to 500 μm, and the projection width of the optical path conversion slope with respect to the plane formed by the polarizer is 40 μm or less, especially 3 to 20.
It is preferable that the thickness is μm, particularly 5 to 15 μm.

The parallel distribution of the continuous light emitting means may be parallel to one side of the polarizing plate, or may be arranged in an intersecting state within 30 degrees. The latter is effective in preventing moire due to interference with the pixels of the liquid crystal cell. The moire can be prevented also by adjusting the pitch of the parallel array. Therefore, the pitch may change and may not be a constant pitch.

On the other hand, when the discontinuous light emitting means are distributed in parallel or irregularly as in the example of FIGS. 3 and 4, or when they are distributed in a pit shape with respect to the virtual center, the above-mentioned characteristics are achieved. In addition to the reflection efficiency due to the optical path conversion slope,
It is preferable that the length of the optical path conversion slope is 5 times or more the depth of the light emitting means, particularly 8 or more, and particularly 10 or more.

The length of the optical path changing slope is 500 μm or less, especially 200 μm or less, especially 10 to 150 μm, and the depth and width of the light emitting means are 2 μm to 100 μm, especially 5 to 80 μm.
It is preferably m, particularly 10 to 50 μm. The above-mentioned length is the length in the long side direction of the optical path conversion slope, and the depth is based on the light emitting means forming surface of the transparent protective layer. 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.

A surface which forms the light emitting means and which does not satisfy the optical path conversion slope a having a predetermined inclination angle, for example, FIG.
The vertical surface b or the like facing the optical path conversion slope a in does not contribute to the emission of the incident light from the side surface of the cell from the rear surface, and does not affect display quality or light transmission or light emission as much as possible. Is preferred.

By the way, when the inclination angle θ2 of the elevation surface with respect to the plane formed by the polarizer is small, the projected area of the elevation surface with respect to the plane formed by the polarizer becomes large, and the polarizing plate 1 is placed on the viewing side as illustrated in FIG. In the external light mode in which the front light system is arranged, the surface-reflected light from the vertical surface returns to the viewing direction and the display quality is likely to be impaired.

Therefore, the larger the inclination angle θ2 of the vertical surface is, the more advantageous it is. Therefore, the projected area on the plane formed by the polarizer can be reduced and the reduction of the total light transmittance can be suppressed. In addition, the apex angle due to the optical path changing slope and the elevation can be reduced, the surface reflected light can be reduced, and the reflected light can be tilted in the plane direction of the polarizing plate, and the influence on the liquid crystal display can be suppressed. From this point of view, the preferred inclination angle θ2 of the elevation or the like is 50 degrees or more, preferably 60 degrees or more, and particularly 75 to 90 degrees.

The inclined surface forming the light emitting means A may be formed in an appropriate surface shape such as a straight surface, a refraction surface, or a curved surface. Further, the cross-sectional shape of the light emitting means may be such that the inclination angle or the like is constant over the entire surface of the sheet, or the light emitted on the polarizing plate is dealt with by absorption loss or attenuation of transmitted light due to the previous optical path conversion. The light emitting means may be made larger as it is farther from the side surface on the side where the light is incident, for the purpose of making the light uniform.

It is also possible to use light emitting means having a constant pitch, and the side on which light is incident (arrows) as in the examples of FIGS.
It is possible to increase the distribution density of the light emitting means by gradually narrowing the pitch as the distance from the side surface increases. Further, the light emission on the polarizing plate 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 formed of a combination of different shapes and the like in addition to the pitch.

The optical path changing slope in the light emitting means is shown in FIG.
It is preferable to face the direction of the incident light (arrow) from the side surface direction of the liquid crystal cell as in the example of 1) from the viewpoint of improving the emission efficiency. Therefore, when a linear light source is used, it is preferable that the optical path conversion slope faces a direction with respect to one side of the polarizing plate or a fixed direction as illustrated in FIGS. When a point light source such as a light emitting diode is used, it is preferable that the optical path conversion slope faces the direction of the light emission center of the point light source as in the example of FIG.

The shape of the intermittent end of the light emitting means is not particularly limited, but it is 30 degrees or more, preferably 45 degrees or more, especially 60 degrees from the viewpoint of suppressing the influence of the reduction of incident light to that portion. The above slope is preferable. The surface of the transparent protective layer and the surface of the polarizing plate, except for the light emitting means, is a flat surface that is as smooth as possible, especially ± 2.
It is preferable that the angle change is equal to or less than 0 degree, and in particular, the flat surface is 0 degree. Further, it is preferable that the angle change is within 1 degree per 5 mm in length.

With such a flat surface, most of the transparent protective layer or the polarizing plate can be a smooth surface with an angle change of 2 degrees or less, and the light transmitted inside the liquid crystal cell can be efficiently used. Uniform light emission without disturbing the image can be achieved. It is also preferable from the viewpoint of ease of adhesion treatment of the transparent protective layer with the polarizer.

As described above, in the pit-like arrangement of the light emitting means A as illustrated in FIG. 4, the point light source is arranged on the side surface of the liquid crystal display panel or the like, and the radial incident light from the side surface is generated by the point light source. Or, the transmitted light is subjected to optical path conversion through the optical path conversion slope a to cause the polarizing plate to emit light as uniformly as possible, and the light excellent in directivity in the normal direction to the liquid crystal cell or the like is efficiently used as the light source of the polarizing plate. It is intended to be emitted from.

Therefore, it is preferable that the pit-shaped arrangement is performed so that a virtual center is formed on the end face of the polarizing plate or on the outer side thereof so that the point light source can be arranged easily. The virtual center can be formed at one place or two or more places on the same or different polarizing plate end faces.

The formation of the transparent protective layer having the light emitting means includes
It can be performed by an appropriate method. By the way, as an example, a method of transferring a shape by pressing a transparent protective layer made of a thermoplastic resin under heating to a mold capable of forming a predetermined light emitting means,
A method of filling a heat-melted thermoplastic resin or a resin fluidized through heat or a solvent into a mold capable of forming a predetermined light emitting means, or a polymerization treatment with heat, ultraviolet rays, or radiation such as electron beams. There is a method in which a liquid resin, a monomer, an oligomer or the like is filled or cast in a mold capable of forming a predetermined light emitting means and a polymerization treatment is carried out.

Further, a transparent resin is coated with a liquid resin, a monomer, an oligomer or the like which can be polymerized by radiation such as heat, ultraviolet rays or electron beams, and the coating layer is formed into a mold capable of forming a predetermined light emitting means. A method of pressing and molding followed by polymerization treatment, filling the liquid resin or the like into a mold capable of forming a predetermined light emitting means, and arranging a transparent film in close contact on the filling layer and irradiating with ultraviolet rays or radiation. A method of performing a polymerization treatment may also be used. These methods can also be applied to the formation of a polarizing plate using a polarizer for the transparent film.

The above-described method is particularly advantageous for forming a transparent protective layer having a light emitting means in the same body by integrally molding the transparent protective layer provided with the light emitting means. Particularly, in the latter method using a transparent film, a transparent protective layer 1B having a light emitting means forming layer 1A, which is separate from the transparent protective layer 1B, is formed as in the example of FIG. In that case, if the difference in refractive index between the light emitting means forming layer and the transparent protective layer to be added is large, the emission efficiency may be significantly reduced due to interface reflection or the like.

Therefore, from the viewpoint of suppressing the decrease in the emission efficiency, the difference in the refractive index between the transparent protective layer and the light emitting means forming layer should be made as small as possible, preferably 0.10 or less, particularly 0.0 or less.
It is preferably within 5. Further, in that case, it is preferable from the viewpoint of emission efficiency that the refractive index of the light emitting means forming layer to be added is higher than that of the transparent protective layer. For forming the light emitting means forming layer, an appropriate transparent material corresponding to the wavelength range of incident light can be used in accordance with the transparent protective layer.

In the method using the above film, the transparent protective layer (light emitting means forming layer) formed after the polymerization treatment using a film treated with a release agent or the like.
A method of separating the film from the film can also be adopted. In that case, the film used need not be transparent.

If necessary, the surface of the transparent protective layer on which the light emitting means is formed is subjected to non-glare treatment or anti-reflection treatment for the purpose of preventing visual interference due to surface reflection of external light, and hard coat treatment for the purpose of preventing scratches. And so on. A polarizing plate having a transparent protective layer subjected to such treatment,
Particularly, it can be preferably used for a front light system.

In the non-glare treatment described above, the surface is finely roughened by various methods such as a surface roughening method such as a sand blast method or an embossing method, or a resin coating method in which the transparent particles such as silica are mixed. It can be applied by The antireflection treatment can be performed by a method of forming an interfering vapor deposition film. Further, the hard coat treatment can be performed by a method of applying a hard resin such as a curable resin. The non-glare treatment, the antireflection treatment, and the hard coat treatment can also be performed by a method of adhering a film that has been subjected to one or more treatments.

An adhesive layer for optionally adhering the transparent protective layer and the polarizer to each other can be provided on one or both of the adhesion-treated surfaces. The adhesion treatment via the adhesive layer is intended to improve the reflection efficiency through the optical path conversion slope a of the light emitting means A, and further improve the brightness by effectively using the incident light from the side surface direction.

From the viewpoint of the above purpose, it is preferable to use an adhesive layer having a small difference in refractive index from the transparent protective layer and the polarizer.
The adhesive layer which is more preferable than the transparent protective layer in terms of suppressing the total reflection and increasing the incidence efficiency of the light transmitted by the liquid crystal cell to the transparent protective layer to obtain a liquid crystal display device which is bright and has excellent uniformity is more preferable than the transparent protective layer. It has a refractive index higher than or equal to a low refractive index and is higher than or close to that of the cell substrate of the liquid crystal cell.

Incidentally, when the refractive index is lower than that of the cell substrate of the liquid crystal cell, the incident light from the side surface is likely to undergo total reflection during its transmission. A resin plate or an optical glass plate is usually used for the cell substrate, and in the case of a non-alkali glass plate, the refractive index is 1.
Since it is generally about 51 to 1.52, most of the transmitted light having an angle that can enter the transparent protective layer from the cell is ideally subjected to the adhesive treatment through an adhesive layer having a refractive index higher than that. Can be incident on the transparent protective layer without being totally reflected at the adhesive interface.

From the viewpoint of improving display brightness and in-plane brightness uniformity by suppressing the amount of light loss that cannot be emitted due to the confinement action based on total reflection, light transmission of the adhesive layer, liquid crystal cell, transparent protective layer, etc. The preferred refractive index difference at each interface between the mold optical layers is 0.15 or less, especially 0.10 or less, and particularly 0.0
It is within 5. Therefore, the preferable refractive index of the adhesive layer is 1.
It is 49 or more, especially 1.50 or more, and particularly 1.51 or more. Therefore, it is preferable that the adhesive layer for adhering the polarizing plate to the liquid crystal cell or the like also satisfies the above refractive index condition.

For the formation of the adhesive layer, an appropriate adhesive such as an adhesive which is cured by irradiation with ultraviolet rays or radiation or by heating can be used without any particular limitation. The adhesive layer can be preferably used from the viewpoints of handling properties such as simple adhesiveness and stress relaxation properties that suppress the generation of internal stress.

To form the above-mentioned adhesive layer, for example, a suitable polymer such as rubber type, acrylic type, vinyl alkyl ether type, silicone type, polyester type, polyurethane type, polyether type, polyamide type, or styrene type base polymer is used. An adhesive or the like may be used. Above all, those having excellent transparency, weather resistance, heat resistance and the like, such as an acrylic pressure-sensitive adhesive containing a polymer mainly composed of an alkyl ester of acrylic acid or methacrylic acid as a base polymer, are preferably used.

The adhesive layer may be made of, for example, inorganic particles such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, nonmonium oxide, or the like, which may be electrically conductive, or an organic material such as a crosslinked or uncrosslinked polymer. One or two or more kinds of suitable transparent particles such as a system particle may be contained to obtain a light diffusion type.

If necessary, the polarizing plate may be provided with a transparent adhesive layer for adhering to other members such as a liquid crystal cell. The adhesive layer can be based on the above. It is preferable that the adhesive layer is temporarily attached and covered with a release sheet for the purpose of preventing the entry of foreign matter and the like until the adhesive layer is put into practical use.

The polarizing plate according to the present invention, through the light emitting means (optical path conversion slope), makes incident light from the side direction by the light source or transmitted light in a direction excellent in verticality (normal direction) advantageous for visual recognition. It is possible to change the optical path and emit light with high light utilization efficiency, and also show good transparency to external light. For example, it is thin and lightweight reflective and transmissive external light / illumination that is bright and easy to see. Various devices can be formed, such as dual-purpose liquid crystal display devices. An example of the liquid crystal display device is shown in FIG. The figure shows an example of a reflective liquid crystal display device for both external light and illumination. 20 and 30 are cell substrates in a liquid crystal cell, 40 is a liquid crystal layer, and 31 is a reflective layer.

As shown in the figure, the liquid crystal display device can be formed by disposing the polarizing plate 1 on at least one side of the liquid crystal cell. In that case, the polarizing plate is generally arranged such that the side having the light emitting means is on the outside. Further, it is preferable that the polarizing plate is adhered to a liquid crystal cell or the like via an adhesive layer from the viewpoint of achieving bright display.

The illumination mechanism is, as shown in the figure, one or more side surfaces of the liquid crystal cell, particularly the cell substrate 2 on the side where the polarizing plate 1 is arranged.
One or two or more light sources 5 on one or two or more sides of 0
It can be formed by arranging 1. In the case of forming a polarizing plate having light emitting means arranged in pits as in the example of FIG. 4 in order to achieve bright display by efficiently utilizing radial incident light from a point light source, a pit arrangement is adopted. It is preferable to dispose a point light source on the side surface of the liquid crystal cell on a vertical line including the virtual center of the light emitting means.

In such arrangement of the point light sources corresponding to the virtual center, the cell substrate 20 as shown in the example of FIG. 5 is selected depending on whether the virtual center of the light emitting means is on the end face of the polarizing plate or on the outside thereof. Appropriate countermeasures such as a method of protruding the side on which the point light source is arranged can be adopted. The same applies when another light source such as a linear light source is arranged.

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 changing slopes of the polarizing plate face each other. Including the above-mentioned pit-shaped arrangement,
By arranging the optical path conversion slope so as to face the light source as perpendicularly as possible, it is possible to efficiently convert incident light from the side surface via the light source into a surface light source and emit light with high efficiency.

Therefore, in the case of a polarizing plate having a light emitting means having a plurality of optical path changing slopes, such as one having a two-sided optical path converting slope like a cross section of an isosceles triangle, the cell substrates are opposed to each other. It is also possible to arrange a number of light sources corresponding to a plurality of optical path changing slopes, such as both side surfaces. Further, in the case of the pit-shaped arrangement, the point light source can be arranged at one place or two or more places corresponding to the virtual center of the light emitting means in the polarizing plate.

The light source enables visual recognition in the illumination mode by turning on the light source, and in the case of a liquid crystal display device for both external light and illumination type, 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 and 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.

As shown in the example of FIG. 5, the light source 51 is a combination of appropriate auxiliary means such as a reflector 52 surrounding the light source 51 for guiding the divergent light to the side surface of the liquid crystal cell, if necessary. You can also As the reflector, an appropriate reflection sheet such as a resin sheet provided with a high reflectance metal thin film, a white sheet or a metal foil may be used. The reflector is
It can also be used as a fixing means which doubles as surrounding the light source by a method of adhering the end to the end of the cell substrate or the like.

A liquid crystal display device generally comprises a liquid crystal cell functioning as a liquid crystal shutter, a driving device associated therewith, a front light or a back light (polarizing plate), and optional components such as a reflection layer and a retardation plate for compensation. Are formed by appropriately assembling. In the present invention, there is no particular limitation except that an illumination mechanism is formed using the above-mentioned polarizing plate and light source, and it can be formed according to a conventional front light type or backlight type.

Therefore, the liquid crystal cell used is not particularly limited, and the sealing material 4 is provided between the cell substrates 20 and 30 as shown in the figure.
It is possible to use an appropriate reflective type or transmissive type in which the liquid crystal 40 is sealed through the liquid crystal 1 and the display light is obtained through the light control by the liquid crystal or the like. By the way, specific examples thereof include twisted and non-twisted types such as TN type liquid crystal cells, STN type liquid crystal cells, IPS type liquid crystal cells, HAN type liquid crystal cells, OCB type liquid crystal cells and VA type liquid crystal cells, guest host type and ferroelectrics. Examples of the liquid crystal cell include an organic liquid crystal cell, a light diffusion type liquid crystal cell such as an internal diffusion type, and the like.

Further, the liquid crystal driving system may be an appropriate system such as an active matrix system or a passive matrix system. The liquid crystal is usually driven through the electrodes 21 and 31 provided inside the cell substrate as shown in FIG.

In the reflective liquid crystal display device, the disposition of the reflective layer is indispensable, but the disposition position may be provided inside the liquid crystal cell as illustrated in FIG. 5 or may be provided outside the liquid crystal cell. it can. Therefore, in the example of FIG.
Also serves as a reflective layer.

For the reflective layer, for example, a coating layer containing a powder of a high-reflectance metal such as aluminum, silver, gold, copper, or chromium in a binder resin, an attached layer of a metal thin film by a vapor deposition method, and the coating thereof. It can be formed as an appropriate reflective layer in accordance with the prior art, such as a reflective sheet in which a layer or an attached layer is supported by a base material, a metal foil, a transparent conductive film, or a dielectric multilayer film. When a transmissive liquid crystal display device is used for both external light and illumination, the reflective layer arranged outside the polarizing plate on the back side can be appropriately adapted according to the above description.

On the other hand, a transmissive liquid crystal display device can be formed by disposing a polarizing plate on the back side of a liquid crystal cell. 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 is reflected and returned to the direction of the liquid crystal cell, which can be used for cell illumination and the brightness can be improved. it can. At this time, by making the reflection layer a diffuse reflection surface, the reflected light can be diffused and directed to the front direction, and can be directed to an effective direction by visual recognition. 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.

When the reflective layer is arranged outside the liquid crystal cell in the above-mentioned transmissive type, the cell substrate or the electrode must be formed as a transparent substrate or a transparent electrode in order to enable liquid crystal display. On the other hand, when the electrode 31 also serving as a reflective layer is provided inside the liquid crystal cell as in the example of FIG. 5, the cell substrate 20 and the electrode 21 on the viewing side are transparent substrates and transparent electrodes to enable liquid crystal display. Although it needs to be formed, the cell substrate 30 on the back side does not need to be transparent like the reflective layer 31 and may be formed of an opaque body.

The thickness of the cell substrate is not particularly limited and can be appropriately determined depending on the strength of liquid crystal filling and the size of the light source to be arranged. Generally, 10 μm to 5 mm, especially 50 μm to 2 from the viewpoint of balance between optical transmission efficiency and thinness and lightness.
mm, in particular 100 μm to 1 mm. The thickness of the cell substrate may be different on the side where the light source is arranged and the side where the light source is not arranged, or may be the same. From the viewpoint of improving the brightness, it is advantageous to make the cell substrate on the side where the light source is arranged thick.

When forming the liquid crystal cell, FIG.
As in the above example, the alignment films 22 and 32 such as a rubbing film for aligning the liquid crystal, the color filter 23 for realizing color display, the low refractive index layer 24, the retardation plate 25, and the like can be provided. Generally, the alignment film is arranged adjacent to the liquid crystal layer, and the color filter is arranged between the cell substrate and the electrodes. For the purpose of controlling display light via linearly polarized light, another polarizer may be arranged as necessary on the liquid crystal cell side not having the polarizing plate according to the present invention. Therefore, the polarizing plate or the polarizer can be arranged at an appropriate position on one or both of the viewing side and the back side of the liquid crystal cell.

The low-refractive-index layer described above causes the incident light from the side surface direction through the light source to be interface-reflected and efficiently transmitted to the rear side in the direction away from the light source, and the light is also efficiently transmitted to the rear optical path conversion slope. It aims to improve the uniformity of brightness on the entire cell display surface by making the light incident well. The low-refractive-index layer can be formed as a transparent layer made of an appropriate low-refractive-index material such as an inorganic material such as a fluorine compound or an organic material.

The arrangement position of the low refractive index layer is such that the brightness of the cell display is improved on the inner side of the cell substrate 20 on which the light source 51 is arranged as in the example of FIG. 5, that is, on the surface of the substrate opposite to the polarizing plate-attached side. It is preferable from the point. Moreover, the refractive index is 0.0 than that of the cell substrate.
1 or more, especially 0.02 to 0.15, particularly 0.05 to 0.
A low refractive index layer having a low index of 10 is preferable from the viewpoint of improving the brightness of cell display.

When the liquid crystal display device is formed, a liquid crystal display panel is provided, if necessary, in addition to the above-mentioned non-glare layer and the like, one or more appropriate optical layers such as a light diffusion layer and a retardation plate. You can also The light diffusion layer is intended to expand the display range by diffusing the display light, uniformize the brightness by equalizing the light emission, and increase the amount of light incident on the polarizing plate by diffusing the transmission light in the liquid crystal cell. The above-mentioned additional optical layer may be laminated and integrated with a polarizing plate through an adhesive layer or the like, if necessary, and applied to a liquid crystal cell.

The light diffusing layer can be provided by an appropriate method such as a coating layer or a diffusing sheet having a surface fine uneven structure according to the above non-glare layer. The light diffusing layer may be arranged as a layer which also functions as an adhesive layer by blending transparent particles in the adhesive layer, which allows the liquid crystal display device to be thinned. As the light diffusion layer, one layer or two or more layers can be arranged at an appropriate position such as between the polarizing plate and the cell substrate on the viewing side.

Further, the above-mentioned retardation plate is usually disposed between the polarizing plate or the like on the viewing side and / or the back side and the cell substrate for the purpose of expanding the viewing angle by optical compensation and preventing coloration. It As the retardation plate for compensation, an appropriate one may be used depending on the wavelength range and the like, and the retardation plate may be formed as one layer or as a superposed layer of two or more retardation layers.

The retardation plate is a birefringent film obtained by stretching a film made of an appropriate transparent polymer by an appropriate method such as uniaxial or biaxial, and an orientation of an appropriate liquid crystal polymer such as nematic or discotic. It can be obtained as a film or its orientation layer supported by a transparent substrate,
It may be one in which the refractive index in the thickness direction is controlled under the action of the heat shrinkage force of the heat shrinkable film.

In the reflection type liquid crystal display device of FIG. 5 described above, the visual recognition by both external light and illumination is that the light emitted from the back surface of the polarizing plate 1 is the liquid crystal as shown by the arrow in the illumination mode by turning on the light source 51. The reflective layer 3 via the cell
After being reflected by 1, the display light which reaches the polarizing plate through the liquid crystal cell in the reverse direction and is transmitted from the portion other than the light emitting means A is visually recognized.

On the other hand, in the external light mode in which the light source is turned off, the light incident from a portion other than the light emitting means on the light emitting means forming surface of the polarizing plate 1 passes through the reflective layer 31 and reverses in the liquid crystal cell according to the above. The display light that has reached the polarizing plate via the light is transmitted through the portion other than the light emitting means.

On the other hand, in the transmissive liquid crystal display device,
In the visual recognition by dual use of illumination, in the illumination mode in which the light source is turned on, the display light which is emitted from the polarizer layer of the polarizing plate disposed on the back side enters the liquid crystal cell and is transmitted through the polarizer is visually recognized. In the external light mode when the light source is turned off, the external light entering from the viewing side surface passes through the liquid crystal cell and reaches the polarizing plate, and the light entering from the part other than the light emitting means of the light emitting means forming surface is reflected on the back surface. The display light which is inverted through the provided reflection layer and transmitted through the inside of the liquid crystal cell in the opposite direction is visually recognized.

In the present invention, the respective parts forming the above-mentioned liquid crystal display device may be wholly or partially laminated and integrated and fixed, or may be arranged in an easily separable state. From the viewpoint of preventing the deterioration of contrast by suppressing interface reflection, it is preferable that it is in a fixed state,
It is preferable that at least the polarizing plate and the liquid crystal cell are in a tightly adhered state. An appropriate transparent adhesive such as a pressure-sensitive adhesive may be used for the fixing treatment, and the transparent adhesive layer may contain transparent particles or the like to form an adhesive layer having a diffusion function.

The above-mentioned formed parts, especially those on the visible side, are treated with an ultraviolet absorber such as a salicylate compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex salt compound. It can also have ultraviolet absorption ability.

[0086]

EXAMPLES Reference Example A transparent conductive layer of indium tin oxide (ITO) is formed on an alkali-free glass plate having a refractive index of 1.52 by a sputtering method, and a polyvinyl alcohol solution is spin-coated on the transparent conductive layer and dried. The film was rubbed to obtain cell substrates on the viewing side and the back side. In the cell substrate on the viewing side, magnesium fluoride was vapor-deposited on a glass plate to form a low refractive index layer, plasma treatment was performed in an argon atmosphere, and then an ITO transparent conductive layer was formed thereon.

Next, after the rubbing surfaces of the cell substrates on the visible side and the back side are opposed to each other so that the rubbing directions are orthogonal to each other, a gap adjusting material made of spherical glass beads is arranged, and then the periphery is sealed with an epoxy resin. After that, the liquid crystal (B
A liquid crystal cell was formed by injecting a chiral agent (a mixture of 1 part by weight of MC-32 manufactured by Merck & Co., Inc.) into 200 parts by weight of E-7 by DH.

Example 1 A transparent film having a thickness of 60 μm and made of polycarbonate (PC) was coated with about 100 μm of an ultraviolet curable acrylic resin.
After coating with a thickness of m, the coating layer is adhered to a mold that has been processed into a predetermined shape in advance with a rubber roller, and excess resin and bubbles are pushed out, and then ultraviolet rays are irradiated with a metal halide lamp to cure it. It was peeled from the mold and cut into a predetermined size to obtain a transparent protective layer having a light emitting means. When the refractive index of the UV curable resin after curing was measured, it was 1.5.
It was 15.

The transparent protective layer has a width of 30 mm and a length of 40.
mm, the optical path conversion slopes that are continuous over the width direction are arranged in parallel in the length direction at a pitch of 210 μm, and have a plurality of light emitting means that form a triangular section between the slope surface and the surface facing it. is there. The projection width of the optical path conversion slope with respect to the plane formed by the film is 10 μm, the inclination angle is 42.5 degrees, and the inclination angle of the facing surface is about 75 degrees. Further, the area of the flat surface formed of the portion other than the light emitting means in the surface on which the light emitting means is formed is 12 times or more the sum of the optical path conversion slope and the facing surface. Further, the total light transmittance and the haze of this transparent protective layer were measured to be 8 each.
It was 9% and 7%.

Next, the side of the transparent protective layer having no light emitting means and the polyvinyl alcohol film type polarizer are pressure-bonded with a pressure-bonding roller via an acrylic pressure-sensitive adhesive layer having a refractive index of 1.515 to obtain a polarizing plate. It was Then, the polarizing plate is bonded to the visible side of the liquid crystal cell obtained in the reference example via the acrylic adhesive layer having a refractive index of 1.523 with the polarizing plate as the outer side of the light emitting means forming side, and the polarizing layer having the reflective layer is provided on the back side of the cell. The plates were similarly bonded to obtain a reflective liquid crystal display device.

Comparative Example A reflective liquid crystal display device was obtained in the same manner as in Example 1 except that a polarizing plate provided with a transparent protective layer having no light emitting means was used as the polarizing plate on the viewing side.

Evaluation Test A cold cathode tube was placed on the side surface of the viewing-side cell substrate of the reflection type liquid crystal display device obtained in Example 1 and Comparative Example, surrounded by a silver vapor-deposited polyester film, and the film end was surrounded by the back-side cell. About the one with double-sided adhesive tape adhered to the upper and lower surfaces of the substrate to hold and fix the cold cathode tube, the cold cathode tube was turned on in the dark room without applying voltage to the liquid crystal cell, 5 mm from the incident side surface, the central part, the opposite end The front luminance at a position of 5 mm was examined with a luminance meter (BM7 manufactured by Topcon). The results are shown in the table below.

[0093]

From the table, it can be seen that the embodiment is far superior in brightness as compared with the comparative example, and is also excellent in uniformity of brightness on the entire panel. In the embodiment, the display is bright even in the external light mode and is excellent in its uniformity.
As described above, according to the present invention, while avoiding the bulkiness and the weight increase due to the use of the conventional sidelight type light guide plate, it is a thin type capable of emitting surface light only by providing an illuminating device on the side surface of the liquid crystal display panel on which the polarizing plate is arranged. It can be seen that it is possible to form a lightweight liquid crystal display device for both external light and illumination.

[Brief description of drawings]

FIG. 1 is an explanatory side view of a polarizing plate.

FIG. 2 is an explanatory plan view of a light emitting means.

FIG. 3 is an explanatory plan view of another light emitting means.

FIG. 4 is an explanatory plan view of still another light emitting means.

FIG. 5 is an explanatory side view of a liquid crystal display device.

[Explanation of symbols]

1: Polarizing plate 1A: Light emitting means forming layer (A: Light emitting means a: Optical path changing slope) 1B, 1D: Transparent protective layer 1C: Polarizer 20, 30: Cell substrate 40: Liquid crystal layer 51: Light source

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Seiji Umemoto             Nittoden 1-2, Shimohozumi, Ibaraki City, Osaka Prefecture             Within Kou Co., Ltd. (72) Inventor Yuki Nakano             Nittoden 1-2, Shimohozumi, Ibaraki City, Osaka Prefecture             Within Kou Co., Ltd. F-term (reference) 2H042 BA04 BA12 BA14 BA20                 2H049 BA02 BA06 BA26 BB17 BB28                       BB43 BB52 BB63 BC22                 2H091 FA08 FA21Z FA23Z FD07                       FD12 LA03 LA11 LA12 LA13                       LA18

Claims (12)

[Claims] 1. A transparent protective layer having, on one side or both sides, a plurality of light emitting means having an optical path conversion slope having an inclination angle of 35 to 48 degrees with respect to a plane formed by the polarizer, is provided on at least one side of the polarizer. Characteristic polarizing plate. 2. The polarizing plate according to claim 1, wherein the transparent protective layer has a light emitting means only on one surface on the side not having a polarizer. 3. The polarizing plate according to claim 2, wherein the surface of the transparent protective layer on the side having no polarizer is smooth. 4. The polarizing plate according to claim 1, wherein the transparent protective layer is adhered to the polarizer via an adhesive layer. 5. The polarizing plate according to claim 4, wherein the adhesive layer is an adhesive layer. 6. The polarizing plate according to claim 1, wherein the light emitting means in the transparent protective layer is a recess. 7. The polarizing plate according to claim 6, wherein the concave portion forming the light emitting means is triangular based on the cross section with respect to the optical path conversion slope. 8. The length of the optical path conversion slope in the concave portion forming the light emitting means in the long side direction is 500 μm or less, which is 5 times or more the depth of the concave portion, and the depth of the concave portion according to claim 6 or 7. Is 100 μm or less, and the width of the optical path changing slope in the direction orthogonal to the long side direction and the depth direction is 100 μm or less. 9. The polarizing plate according to claim 6, wherein a surface of the concave portion which forms the light emitting means, the surface facing the optical path conversion slope is an upright surface having an inclination angle of 60 to 90 degrees with respect to a plane formed by the polarizer. 10. The polarizing plate according to claim 6, wherein the concave portions forming the light emitting means are arranged parallel or irregularly based on the optical path conversion slope, or in a pit shape with respect to the virtual center. 11. A liquid crystal display device comprising the polarizing plate according to claim 1 arranged on at least one side of a liquid crystal cell. 12. The liquid crystal display device according to claim 11, wherein the polarizing plate is adhered via an adhesive layer so that the side having the light emitting means is the outside.