JP2001228332A - Polarizing element, light source for polarized light and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device for polarized light which uses a dichroic polarizing element and a reflection type polarizing element, and to effectively use light in a liquid crystal display device which uses the light source device for polarized light. SOLUTION: A reflection type polarizing element 52 and a dichroic polarizing element 51 are arranged with the transmission axes for polarized light coincident with each other on an optical path to constitute a composite type polarizing device 80. The dichroic polarizing element 51 show >=44% transmittance T(P)(λ) and >=50% polarization degree P(P)(λ) at the wavelength λbetween 400 nm and 700 nm or shows >=44% luminosity-corrected transmittance Y(P) and >=50% luminosity-corrected polarization degree P(P, y). The light source device 40 for polarized light is composed of the polarizing device 80, a light source member 60 disposed in the reflection polarizing element 51b side of the device 80, and a reflection plate 63 disposed in the opposite side of the light source member 60 to the polarizing device 80. Further, the light source device 40 for polarized light is disposed on the back face of a liquid crystal cell 20 to constitute the liquid crystal display device 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing element, a polarized light source device and a liquid crystal display.

[0002]

2. Description of the Related Art Liquid crystal display devices are used in various fields because of their small size and light weight. A conventional liquid crystal display device will be described with reference to FIG.
The device controls the polarization state of light passing therethrough by electrically changing the alignment state of liquid crystal molecules in the liquid crystal cell 20. The liquid crystal cell 20 usually includes two opposing transparent electrodes, that is, a transparent electrode 21 on the rear side and a transparent electrode 22 on the front side, and a liquid crystal layer 23 sandwiched between the transparent electrodes 21 and 22. Has a liquid crystal cell 2
A front-side dichroic polarizing element 31 for detecting the polarization state of light transmitted through 0, a front-side optical element 30 such as a front-side retardation element 32 is disposed, and only a specific polarized light is extracted on the back. A polarized light source device 45 for emitting light toward the liquid crystal cell 20 is arranged. This polarized light source device 45
A dichroic polarizing element 51 disposed on the back of the liquid crystal cell 20,
A rear optical element 50 such as a phase difference element 52, a light source member 60 disposed on the rear side thereof, a reflecting plate 63 disposed further behind the optical element 50, the liquid crystal cell 20 and the light source member 60;
And the diffusion sheet 70 and / or the lens sheet 71 disposed between the two. The light source member 60 in FIG.
Is composed of a light guide plate 62 in which a light source 61 is arranged on the side. On the back side of the light guide plate 62, a reflective layer such as white dot printing 64 may be formed. In the polarized light source device 45, the dichroic polarizing element 51 functions as a filter that transmits only necessary polarized light by absorbing unnecessary polarized light, and thus is ideal for natural light in a non-polarized state. Even in the state, 50% of the light is absorbed, and the light is not used effectively.

Therefore, a reflective polarizing element is disposed closer to the light source member 60 than the dichroic polarizing element 51, and the polarized light in the vibration direction, which is absorbed by the dichroic polarizing element 51, is reflected beforehand. For example, Japanese Patent Publication No. 9-507308 proposes a method of effectively utilizing light by returning to the side and recycling the light to improve the screen brightness of the liquid crystal display device with the same power consumption. This publication discloses that a reflective polarizing element and a dichroic polarizing element are arranged in the same optical path and are preferably bonded to form a highly efficient optical polarizing device. Furthermore, for applications where a predetermined absorption ratio and high transmittance are required, the absorption ratio of the optical polarizing device is increased, the reflectance is reduced, and the absorption ratio of the dichroic polarizing element at this time is reduced. It is described that the absorption loss can be reduced in the polarizing element. According to this publication, the preferred absorption ratio of the dichroic polarizing element is 10 to 99.
99%, more preferably 50-99%, and the preferred absorption ratio of the reflective polarizing element is 20-99.99%,
Most preferably, it is 90 to 99.9%.
However, means for further improving the brightness of the polarized light source device and the liquid crystal display device has not been known conventionally, including this publication.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a polarized light source device using a dichroic polarizing element and a reflective polarizing element to improve the light use efficiency, and a screen using the polarized light source device. In a liquid crystal display device with improved brightness,
The purpose is to achieve more effective use of light.

[0005]

Means for Solving the Problems The present inventors have proposed a composite polarizing element comprising a reflective polarizing element and a dichroic polarizing element arranged on the same optical path so that the polarization transmission axes coincide with each other. By limiting the transmittance and the degree of polarization of the dichroic polarizing element to a predetermined range, when this polarizing element is used for a polarized light source device, the polarized light source device becomes brighter than a conventional polarized light source device. The inventors have found that the used liquid crystal display device has an image quality equal to or higher than that of a conventional liquid crystal display device, and can obtain a brighter screen, and thus has accomplished the present invention.

That is, according to the present invention, from a first point of view, a reflection type polarizing element and a dichroic polarizing element are arranged on the same optical path so that their polarization transmission axes coincide with each other. The polarizing element has a transmittance T (P) (λ) of at least 44% at least at a specific wavelength λ between 400 nm and 700 nm.
And a composite polarizing element having a polarization degree P (P) (λ) of 50% or more. Polarization degree P (P) (λ)
Is 100%.

According to another aspect of the present invention, a reflective polarizing element and a dichroic polarizing element are arranged on the same optical path so that their polarization transmission axes coincide with each other. 4
Having a visibility correction transmittance Y (P) of 4% or more,
A composite polarizing element having a visibility correction polarization degree P (P, y) of 50% or more is also provided. Visibility correction polarization degree P (P, y)
Also, the upper limit is 100%.

[0008] In these polarizing elements, a preferred reflective polarizing element is a multilayer laminate comprising at least two kinds of polymer films. Another preferred reflection type polarizing element is a polymer film in which at least two kinds of polymers form a sea-island structure. Still another preferred reflection-type polarizing element is obtained by laminating a quarter-wave plate on a film made of cholesteric liquid crystal.

In these polarizing elements, the dichroic polarizing element can be, for example, an iodine-based polarizing film. The dichroic polarizing element can be a dye-based polarizing film.

In these polarizing elements, the reflection type polarizing element and the dichroic polarizing element can be bonded via a pressure-sensitive adhesive. As described above, when the reflective polarizing element and the dichroic polarizing element are bonded by the pressure-sensitive adhesive, the visibility correction transmittance Y (P) of the combined polarizing element is preferably 4
It becomes 2% or more. Further, the visibility correction polarization degree P (P, y) of each of the composite polarizing elements described above is preferably 80% or more.

[0011] The polarized light source device according to the present invention is a composite polarized light element specified as described above, a light source member arranged on the reflective polarizing element side, and a polarizing element of the light source member. It is composed of a reflector disposed on the opposite side. In this polarized light source device, it is preferable to arrange at least one diffusion sheet between the reflective polarizing element and the light source member. Further, in this polarized light source device, the light source member can be constituted by a light guide plate having a light source disposed at an end. In a polarized light source device using such a light guide plate, it is preferable that at least one diffusion sheet is disposed between the reflection type polarization element and the light guide plate. One lens sheet can be arranged, and at least one lens sheet can be arranged between the diffusion sheet and the light guide plate. Of course, between the reflection type polarizing element and the diffusion sheet and between the diffusion sheet and the light guide plate can be arranged. At least one lens sheet can also be arranged both between the plates.

The liquid crystal display device according to the present invention is a polarized light source device specified as described above, a liquid crystal cell arranged on the dichroic polarizing element side, and a polarized light source device of the liquid crystal cell. It is composed of a front dichroic polarizing element arranged on the opposite side. In this liquid crystal display device, the polarized light source device and the liquid crystal cell can be bonded using a pressure-sensitive adhesive. In addition, the liquid crystal cell and the front dichroic polarizing element can also be bonded using a pressure-sensitive adhesive.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The reflection type polarizing element of the present invention transmits polarized light in a specific vibration direction and reflects polarized light orthogonal to the polarized light. As such a reflective polarizer, for example, a reflective polarizer using a difference in the reflectance of a polarization component depending on the Brewster angle (for example, Japanese Patent Application Laid-Open No.
JP-A-6-508449), a reflective polarizing element utilizing selective reflection characteristics of cholesteric liquid crystal, specifically, a laminate of a film made of cholesteric liquid crystal and a quarter-wave plate (for example, see Japanese Unexamined Patent Application Publication No. JP-A-3-45906), a reflective polarizing element provided with a fine metal linear pattern (for example, one described in JP-A-2-308106), and at least two kinds of polymer films laminated. A reflective polarizing element utilizing the anisotropy of the reflectance due to the refractive index anisotropy (for example, those described in Japanese Patent Application Laid-Open No. 9-506837),
A reflective polarizing element having a sea-island structure formed of at least two kinds of polymers in a polymer film and utilizing anisotropy of reflectance due to anisotropy of refractive index (for example, US Pat. No. 5,82
No. 5,543), a reflective polarizing element utilizing particles dispersed in a polymer film and utilizing the anisotropy of the reflectance due to the anisotropy of the refractive index (for example, JP-A-11-509014) ), A reflection-type polarizing element utilizing inorganic particles dispersed in a polymer film and utilizing the anisotropy of the reflectance based on the scattering power difference depending on the size (for example, Japanese Patent Application Laid-Open No. 9-297204). ) Can be used.

The thickness of these reflective polarizing elements is not particularly limited. However, when the polarizing element of the present invention is used in a liquid crystal display device or the like, it is preferably thinner, specifically 1 mm or less, more preferably 0.2 mm. It is preferred that: Therefore, a reflective polarizing element utilizing selective reflection characteristics of a cholesteric liquid crystal, a reflective polarizing element utilizing at least two kinds of polymer films laminated and utilizing the anisotropy of the reflectance due to the refractive index anisotropy, and a polymer film A reflective polarizing element having a sea-island structure composed of at least two kinds of polymers therein and utilizing the anisotropy of the reflectance due to the refractive index anisotropy is used to reduce the thickness of the polarizing element of the present invention. Is particularly preferred.

The dichroic polarizing element in the present invention transmits linearly polarized light in a specific vibration direction and absorbs polarized light orthogonal to the polarized light. As such a dichroic polarizing element, for example, a known iodine-based polarizing film or dye-based polarizing film can be used. The iodine-based polarizing film is a film in which iodine is adsorbed on a stretched polyvinyl alcohol film, and the dye-based polarizing film is a film in which a dichroic dye is adsorbed on a stretched polyvinyl alcohol film. These polarizing films are preferably ones in which one or both sides of the polarizing film are covered with a plastic film in order to improve durability. As the material of the plastic to be coated for this protection, cellulose diacetate, cellulose triacetate, polyethylene terephthalate, norbornene resin and the like can be used. The thickness of the dichroic polarizing element is not particularly limited. However, when the composite polarizing element of the present invention is used for a liquid crystal display element or the like, the thinner is preferable, specifically 1 mm or less, and more preferably 0.2 mm. It is preferred that:

The composite type polarizing element according to the present invention is such that the above-mentioned reflective polarizing element and dichroic polarizing element are arranged on the same optical path so that their polarization transmission axes coincide with each other. Here, the polarization transmission axis refers to the direction of the polarization element that maximizes the transmittance of the polarized light by rotating the polarization element when the polarized light in the specific vibration direction enters from the direction perpendicular to the polarization element. In this polarizing element, the reflection type polarizing element and the dichroic polarizing element can be used in a state where they are merely overlapped, or they can be used in a state where they are separated from each other. It is preferable that both are adhered to each other in order to suppress reflection at the interface and improve performance such as transmittance. Also, as a dichroic polarizing element, although high transmittance, but not necessarily sufficient wet heat durability,
For example, when using an iodine-based polarizing film, use a reflective polarizing element having a low moisture permeability, and if both are adhered to each other via a pressure-sensitive adhesive, the dichroic polarizing element is on the liquid crystal cell side,
Since it rarely comes into contact with air, it also leads to an improvement in wet heat durability of the polarizing element or the liquid crystal display device incorporating the polarizing element. The kind of the pressure-sensitive adhesive is not particularly limited, and various types of known pressure-sensitive adhesives can be used, but it is most preferable to use an acrylate-based pressure-sensitive adhesive.

The transmissivity T (P) (λ) at a certain wavelength λ of a reflective polarizing element, a dichroic polarizing element, or a polarizing element laminated so that the polarization axes of the two elements are coincident with each other, Maximum transmittance for light (polarized light transmission axis direction transmittance) T
Using (P, T) (λ) and the transmittance (polarized light transmission axis orthogonal direction transmittance) T (P, E) (λ) for the polarized light orthogonal to the polarized light, it is calculated by the following equation (I). Is done.

T (P) (λ) = {T (P, T) (λ) + T (P, E) (λ)} / 2 (I)

The degree of polarization P (P) (λ) at a certain wavelength λ of these polarizing elements is determined by the transmittance T in the direction of the polarized light transmission axis.
(P, T) (λ) and transmittance T (P, E) (λ)
Is calculated by the following equation (II).

P (P) (λ) = {T (P, T) (λ) -T (P, E) (λ)} / {T (P, T) (λ) + T (P, E) (λ)} (II)

Furthermore, the parallel transmittance T (P, //) (λ) and the orthogonal transmittance T (P, ⊥) of each of these polarizing elements at a certain wavelength λ.
(λ) is the polarization transmission axis direction transmittance T (P, T) (λ) and the polarization transmission axis orthogonal direction transmittance T (P, E) (λ), using the following formula (III) and Calculated by (IV).

T (P, //) (λ) = [{T (P, T) (λ)} ² + {T (P, E) (λ)} ² ] / 2 (III) T (P, ⊥) (λ) = T (P, T) (λ) × T (P, E) (λ) (IV)

The transmittance T (P) (λ) and the parallel transmittance T
(P, //) (λ) and orthogonal transmittance T (P, ⊥) (λ)
The stimulus value Y in the C light source 2 degree visual field is calculated according to 8701, and the luminosity correction transmittance Y (P), the luminosity correction parallel transmittance Y (P, //), and the luminosity correction orthogonal transmittance Y ( P, ⊥) are obtained. Then, by using the luminosity correction parallel transmittance Y (P, 及 び) and the luminosity correction orthogonal transmittance Y (P, ⊥),
The visibility correction polarization degree P (P, y) is calculated by the following equation (V).

P (P, y) = [{Y (P, //)-Y (P, ⊥)} / {Y (P, //) + Y (P, ⊥)}] ^1/2 (V )

The transmittance T (P, T) (λ) in the direction of the polarization transmission axis and the transmittance T (P, E) in the direction perpendicular to the polarization transmission axis, which are the basis of the calculations by the above equations (I) to (V). ) (λ), and various transmittances and degrees of polarization calculated based on these formulas are 0 to
It is a value that changes in the range of 1, but when displaying in%,
The value may be multiplied by 100.

In the present invention, the dichroic polarizing element constituting the composite polarizing element specified from the first viewpoint is 400 nm.
At least at a specific wavelength λ between 700 nm and 700 nm, the transmittance T (P) (λ) is 44% or more and the degree of polarization P (P) (λ) is 50% or more. Here, the transmittance T
(P) (λ) is preferably higher, specifically, more preferably 45% or more. Although the upper limit of the degree of polarization P (P) (λ) is 100%, it is preferable that the upper limit is also high. That is, the degree of polarization P (P) (λ) of the dichroic polarizing element is preferably 80% or more, more preferably 90% or more, especially 9%.
More preferably, it is at least 5%.

The transmittance T of the dichroic polarizing element in the present invention
(P) (λ) and the degree of polarization P (P) (λ) are from 400 nm to 700
It is sufficient that the above relationship is satisfied at a certain wavelength λ up to nm. Of course, it is preferable to satisfy the above relationship in the entire wavelength range from 400 nm to 700 nm,
Since the transmittance T (P) (λ) and the degree of polarization P (P) (λ) vary depending on the wavelength, if the above relationship cannot be satisfied in the entire wavelength range from 400 nm to 700 nm, the light emission of the light source It is important to satisfy the above relationship for at least one of the wavelengths corresponding to the spectrum. For example, when a cold-cathode tube is used as a light source, the emission spectrum is represented by a bright line, blue is about 430 nm, and green is about 54 nm.
0 nm and red correspond to a wavelength of about 610 nm. Therefore, it is important that the transmittance T (P) (λ) is at least 44% in at least one of these wavelength values.
In particular, the transmittance T (P) (λ) for green light corresponding to a wavelength near about 540 nm, which has the highest visibility in the visible wavelength region.
Is preferably at least 44%. Furthermore, about 610 nm
Even for the red wavelength corresponding to the nearby wavelength, the transmittance T
Those having (P) (λ) of 44% or more are more preferable. Of course, it is more preferable that the transmittance T (P) (λ) for blue light corresponding to a wavelength near about 430 nm is not less than 44% together with the transmittance for green and red light.

In the present invention, the dichroic polarizing element constituting the composite polarizing element which is preferably used for performing multicolor display in a liquid crystal display device or the like, which is specified from the second viewpoint, is as follows. The visibility correction transmittance Y (P) is 44% or more, and the visibility correction polarization degree P (P, y) is 50% or more. Here, the visibility correction transmittance Y (P) is preferably higher, and more specifically, more preferably 45% or more.
The upper limit of the visibility correction polarization degree P (P, y) is 100%, and it is preferable that the upper limit is also higher. That is, the visibility correction polarization degree P (P, y) is preferably 80%, more preferably 90% or more, and particularly preferably 95% or more.

In the present invention, a transmittance T (P) (λ) of 44% or more and a polarization degree P (P) of 50% or more at a certain wavelength λ between 400 nm and 700 nm, as specified from a first viewpoint. ) (λ), and have a luminosity corrected transmittance Y (P) of at least 44% and a luminosity corrected polarization degree P (P, y) of at least 50%, as specified from a second point of view. Of course, the present invention also includes a composite polarizing element in which a dichroic polarizing element that satisfies the points is used and the reflective polarizing element and the dichroic polarizing element are arranged on the same optical path so that the polarization transmission axes coincide.

In a preferred embodiment of the present invention, in a complex type polarizing element in which a reflective polarizing element and a dichroic polarizing element are closely adhered via a pressure-sensitive adhesive, visibility-corrected transmittance is used. More preferably, Y (P) is at least 42%. Further, in the composite polarizing element according to the present invention, the visibility correction polarization degree P (P, y) is preferably 80% or more, more preferably 90% or more, and particularly preferably 99% or more. preferable. This visibility correction polarization degree P (P, y) is, for example, 9
A value of 9.9% or more, or substantially close to 100%, is more advantageous for application as a polarized light source device or a liquid crystal display device.

In the polarized light source device of the present invention, a light source member and a reflector are arranged in this order on the reflective polarizing element side of the above-mentioned laminated polarizing element. The light source member used in the polarized light source device may be a light source that directly emits light, or the light from the light source may be indirectly transmitted through another part, such as a light source and a light guide plate shown in FIG. It may be one that emits light. The type of light source is not particularly limited, and various types of light sources used in known polarized light source devices and liquid crystal display devices can be used. Specifically, cold cathode tubes,
Light emitting diodes, inorganic or organic EL (electroluminescent) lamps and the like can be used.

The reflector constituting the polarized light source device is not particularly limited, and those used in known polarized light source devices and liquid crystal display devices can be used. Specifically, a white plastic sheet having a cavity formed therein, a plastic sheet having a surface coated with a white pigment such as titanium oxide or zinc white, and a multilayer laminated plastic formed by laminating at least two types of plastic films having different refractive indexes. A sheet, a sheet made of a metal such as aluminum or silver, and the like can be given. These sheets may be either mirror-finished or rough-surfaced. The material of the plastic sheet constituting the reflector is not particularly limited, and polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, norbornene resin, polyurethane, polyacrylate, polymethyl methacrylate, and the like can be used.

Further, the light source member of the polarized light source device can be constituted by a light guide plate having a light source disposed laterally or below. The light guide plate referred to herein is a plate that takes in light emitted from a light source and functions as a planar light emitting body, and various known light guide plates can be used. Examples of such a light guide plate include a plate made of a plastic sheet or a glass plate, which has been subjected to unevenness processing, white dot printing processing, hologram processing, and the like on the back side. The material of the plastic sheet is not particularly limited, but polycarbonate, norbornene resin, polymethyl methacrylate and the like are preferably used.

It is preferable to arrange a diffusion sheet between the reflective polarizing element and the light source member, for example, between the reflective polarizing element and the light guide plate. The diffusion sheet is a sheet that scatters and transmits incident light, and is generally an optical element having a total light transmittance of 60% or more and a haze rate of 10% or more. Here, the higher the total light transmittance of the diffusion sheet, the better. That is, the total light transmittance of the diffusion sheet is 80.
%, More preferably 85% or more.
Such a diffusion sheet is not particularly limited. For example, a plastic sheet or a glass plate obtained by subjecting a plastic sheet or a glass plate to a surface roughening treatment, a plastic sheet or a glass plate in which cavities are formed or particles are added, or the like. Can be used. The material of the plastic sheet here is not particularly limited, but examples thereof include polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, norbornene resin, polyurethane, polyacrylate, and polymethyl methacrylate. The surface roughening treatment is not particularly limited, but may be, for example, sand blasting, processing by embossing roll pressing, plastic particles, glass particles, or a method of applying a mixture of particles such as silicon particles to a resin on the surface. Can be mentioned. Two or more of these diffusion sheets can be used as needed.

When such a diffusion sheet is arranged, it is preferable to arrange a lens sheet between the reflection type polarizing element and the diffusion sheet and / or between the diffusion sheet and the light source member, for example, the light guide plate. More preferred. The lens sheet referred to here collects light emitted from a light source, and various types known in the art can be used.
As such a lens sheet, for example, a sheet in which many fine prisms are formed on a plastic sheet,
A micro-lens array in which convex lenses and concave lenses are laid out is exemplified. Two or more of these lens sheets can be used as necessary.

The liquid crystal display device of the present invention comprises a liquid crystal cell and a front dichroic polarizing element arranged in this order on the dichroic polarizing element side of the above-mentioned polarized light source device. In this case, a retardation film (retardation element) or the like can be disposed on the dichroic polarization element side of the polarization light source device, and a liquid crystal cell can be disposed thereon. It can be arranged in combination with a phase difference element.
A liquid crystal cell used in such a liquid crystal display device is a liquid crystal cell in which liquid crystal is injected into the cell, and the state of polarized light transmitted through the cell is changed by changing the alignment state of the liquid crystal by applying a voltage. It is. Examples of such a liquid crystal cell include a well-known TN (twisted nematic) liquid crystal cell, TF
T (thin film transistor) driven TN liquid crystal cells, In-Plane nematic liquid crystal cells, VA (vertical alignment) nematic liquid crystal cells, STN (super twisted nematic) liquid crystal cells, and the like can be used. As the dichroic polarizing element on the front side, an ordinary iodine-based polarizing film or a dye-based polarizing film can be used.

In this liquid crystal display device, it is possible to bond between the polarized light source device and the liquid crystal cell and / or between the liquid crystal cell and the front dichroic polarizing element using a pressure-sensitive adhesive.
This is preferable for reducing light loss due to unnecessary reflection at the interface. When a retardation element is arranged between the polarized light source device and the liquid crystal cell, or when a retardation element is arranged between the liquid crystal cell and the front dichroic polarizing element, each of these layers is made of a pressure-sensitive adhesive. Preferably they are glued. The type of the pressure-sensitive adhesive is not particularly limited, and various known ones can be used. Among them, it is most preferable to use an acrylate-based pressure-sensitive adhesive.

One embodiment of the liquid crystal display device according to the present invention is shown in FIG.
Shown in In this example, a dichroic polarizing element 51 and a reflective polarizing element 53 are laminated to form a composite polarizing element 80, and a light guide plate having a light source 61 disposed on the side of the reflective polarizing element 53. A light source member 60 composed of 62 is located, and a reflecting plate 63 is disposed behind the light source member 60 (on the side opposite to the combined polarizing element 80), thereby constituting the polarized light source device 40 according to the present invention. On the back side of the light guide plate 62, in order to efficiently scatter and reflect light from the light source 61, for example,
White dot printing 64 and the like are provided. In this example, a diffusion sheet 70 is disposed on the front side of the light guide plate 62,
Further, a lens sheet 71 is disposed on the front side, that is, between the reflective polarizing element 53 and the diffusion sheet 70. On the other hand, the dichroic polarizing element 5 of the combined polarizing element 80
On one side, a phase difference element 52 is laminated, and on the front side thereof, a liquid crystal cell 20 in which a rear transparent electrode 21 and a front transparent electrode 22 face each other and in which a liquid crystal 23 is sealed is arranged. On the front side, the front side dichroic polarizing element 31
Are laminated via the front-side retardation element 32 to constitute the liquid crystal display device 10 according to the present invention. The light source 61 for the light guide plate 62 may be arranged on the back surface of the light guide plate 62. Further, the light source member 60 including the light source 61 and the light guide plate 62 can be replaced with another component, for example, a light emitting diode or an EL lamp.

[0039]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Here, as the dichroic polarizing element, “SK1832A” and “SR1862A” which are iodine-based polarizing films sold by Sumitomo Chemical Co., Ltd., and according to their manufacturing methods, the transmittance and the degree of polarization are described. 3 obtained by adjusting
Kinds of iodine-based polarizing films (hereinafter referred to as dichroic polarizing elements A, B and C, respectively) were used. Also, as a reflective polarizing element, 2 is sold by Sumitomo 3M Limited.
"DBEF", which is a film composed of a laminate of various polymer films, was used. With respect to these dichroic polarizing elements and reflective polarizing elements, the haze ratio, transmittance, degree of polarization, luminous efficiency corrected transmittance, luminous efficiency corrected polarization degree, and hue were evaluated by the following methods.

(1) Haze ratio Each of the above polarizing elements was cut into 5 cm squares, and 1.1 mm
The haze value of a haze computer “HG” manufactured by Suga Test Instruments Co., Ltd.
M-2DP ". The results are shown in Table 1.

[0042]

[Table 1]

(2) Transmittance and Degree of Polarization The measurement of the haze rate revealed that the dichroic polarizing element and the reflective polarizing element used here all had low haze values. Was performed by linear transmission spectrum measurement using a spectrophotometer. A Nicol prism was installed in a sample chamber measurement light emission part of a self-recording spectrophotometer “UV-2200” manufactured by Shimadzu Corporation so as to emit polarized light in a specific vibration direction. On the optical path of the polarized light, the respective polarizing elements bonded to the glass plate via a pressure-sensitive adhesive are arranged so that the polarized light is vertically incident, and the transmittance of the polarized light is maximized. Orientation and incident wavelength 4
The measurement was performed from 00 nm to 700 nm in increments of 10 nm, and the transmittance T (P, T) (λ) in the direction of the polarized light transmission axis at each wavelength λ was determined. Next, the directions of these polarizing elements are rotated by 90 °, and measurement is performed again from the incident wavelength of 400 nm to 700 nm in steps of 10 nm, and the transmittance T (P, E) (λ) in the direction perpendicular to the polarization transmission axis at each wavelength λ is measured. ). From these measured values, the transmittance T (P) (λ) and the degree of polarization P (P) (λ) of each polarizing element were calculated by the formulas (I) and (II). 430 nm, 54
Table 2 shows the measurement results of the transmittance and the degree of polarization at each wavelength of 0 nm and 610 nm.

[0044]

[Table 2] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Name transparently rate (%) polarization degree (%) 430 nm 540 nm 610 nm 430 nm 540 nm 610 nm ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Dichroic polarizing element A 41.7 44.5 44.4 97.5 99.0 99.6 Dichroic polarizing element B 43.3 45.5 45.1 93.9 96.7 98.5 Dichroic polarizing element C 45.4 47.6 47.1 87.1 89.3 91.4 Dichroic polarizing element SK1832A 37.3 41.4 40.6 99.9 100.0 100.0 Polarizer SR1862A 39.6 43.5 43.5 99.8 99.9 100.0 ─────────────────────────────────── Reflective polarizer DBEF 43.5 45.9 46.2 96.5 90.0 89.4 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

(3) Visibility corrected transmittance, visibility corrected polarization degree and hue Transmittance T (P, T) (λ) and polarized light transmission axis in the direction of the polarized light transmission axis at each wavelength obtained in (2) above. Transmissivity T in orthogonal direction
From the measured value of (P, E) (λ), the parallel transmittance T at each wavelength
(P, //) (λ) and orthogonal transmittance T (P, ⊥) (λ) are represented by the above formula (III)
And (IV), and their transmittances T (P) (λ),
Based on the values of the parallel transmittance T (P, //) (λ) and the orthogonal transmittance T (P, ⊥) (λ), calculate the stimulus value Y in the C light source 2 degree visual field according to JIS Z 8701, Visibility corrected transmittance Y
(P), the luminosity corrected parallel transmittance Y (P, //) (λ) and the luminosity corrected orthogonal transmittance Y (P, () (λ). Further, using the luminosity correction parallel transmittance Y (P, //) (λ) and the luminosity correction orthogonal transmittance Y (P, ⊥) (λ), the luminosity correction polarization The degree P (P, y) was determined. Further, the object colors (L ^* , a ^* , b ^* ) were calculated from the transmittance at each wavelength obtained in the above (2) according to JIS Z 8729. Table 3 shows the measurement results of the luminosity correction transmittance, the luminosity correction polarization degree, and the hue.

[0046]

[Table 3] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Name visibility correction visibility correction color phase transmittance (% ) Degree of polarization (%) L ^* a ^* b ^* ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Dichroic polarizing element A 44.4 99.1 72.5 -1.2 2.1 Dichroic polarizing element B 45.4 97.2 73.1 -1.3 1.6 Dichroic polarizing element C 47.3 90.2 74.4 -1.1 1.8 Dichroic polarizing element SK1832A 41.0 100.0 70.2 -2.1 2.6 Dichroic polarizing element SR1862A 43.4 99.9 71.8 -1.6 3.0 ──────────────────────────────── Reflective polarizer DBEF 44.8 94.7 72.7 1.3 -1.8 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Examples 1 to 3, Comparative Examples 1 and 2 A dichroic polarizing element A having the optical performance shown in Tables 1 to 3,
B, C, any of SK1832A and SR1862A and a reflective polarizing element DBEF were laminated to produce a composite polarizing element.
As a sample, a glass plate was bonded to the dichroic polarizing element side of each polarizing element via a pressure-sensitive adhesive, the light receiving intensity was measured by the following method to evaluate the brightness enhancement effect, and the screen contrast was further evaluated. Was evaluated, and the results are shown in Table 4.

(4) Measurement of received light intensity and evaluation of brightness enhancement effect As shown in FIG. 3, a light source 61 composed of a cold cathode tube is disposed at an end of a light guide plate 62 on which a white dot print 64 is provided on the back surface. A light source device 47 is provided by disposing a reflection plate 63 made of foamed PET (polyethylene terephthalate) on the back side of the light guide plate 62 and a diffusion sheet 70 on the front side. on the other hand,
The polarizing element 80 obtained by laminating the dichroic polarizing element and the reflective polarizing element as described above is connected to the polarizing element 80 via the pressure-sensitive adhesive 83.
The dichroic polarizing element of the polarizing element 80 was bonded to the glass plate 84 having a thickness of 1 mm such that the dichroic polarizing element was on the glass plate 84 side, thereby producing a polarizing element / glass plate integrated product 85 for evaluation. Then, the polarizing element / glass plate integrated product 85 manufactured above is placed on the diffusion sheet 70 of the light source device 47 so that the reflective polarizing element of the polarizing element 80 is on the lower side, that is, the light source device 47 side. To obtain a polarized light source device 42. The photometric unit 86 connected to the light receiving unit of the spectrophotometer by an optical fiber 87 was arranged in the vertical direction of the polarized light source device 42 assembled as described above. The bright line spectra corresponding to blue, green and red of the cold cathode fluorescent lamp 61 used as the light source of the polarized light source device 42 are as follows:
Since they were 435 nm, 545 nm and 612 nm, respectively, the received light intensity at these wavelengths was measured. The brightness enhancement effect is obtained by using an iodine-based polarizing film “SK1832” sold by Sumitomo Chemical Co., Ltd. instead of the polarizing element 80.
A "was used to evaluate the light receiving intensity ratio when each of the above polarizing elements was used, based on the received light intensity measured at the same wavelength as above.

(5) Screen Contrast On one side of the polarized light source device 47 used in (4) above, an iodine-based polarizing film “SK1832A” sold by Sumitomo Chemical Co., Ltd. was used. Polarized light source device 4
7, the same polarizing film “SK1832A” is arranged on the other half surface so that its polarized light transmission axis is parallel to the polarized light transmission axis of the polarized light source device 47. The following three levels were visually evaluated. ：: Very high contrast, ：: High contrast, ×: Low contrast.

[0050]

[Table 4] Example No. Dichroic light receiving intensity Ratio contrast Polarizer 435 nm 545 nm 612 nm 実 施 Example 1 A 1.43 1.51 1.54 ◎ Example 2 B 1.47 1.54 1.59 ◎ Example 3 C 1.51 1.56 1.59 ○ 比較 Comparative Example 1 SK1832A 1.27 1.38 1.39 ◎ Comparative Example 2 SR1862A 1.37 1.49 1.53 ◎ ━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━

Examples 4 to 6, Comparative Examples 3 and 4 A dichroic polarizing element A having the optical performance shown in Tables 1 to 3,
B, C, any one of SK1832A and SR1862A and the reflective polarizing element DBEF were adhered to each other with an acrylate-based pressure-sensitive adhesive to prepare a composite polarizing element. For each polarizing element, the transmittance, the degree of polarization, the luminosity-corrected transmittance, the luminosity-corrected polarization degree, and the hue were measured in the same manner as in the above (1) to (3). The results are shown in Table 6. The light receiving intensity ratio and the contrast were evaluated in the same manner as in Example 1 using each polarizing element. The results are shown in Table 7.

[0052]

[Table 5] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example No. Dichroic transmittance (%) bias Light intensity (%) Polarizer 430 nm 540 nm 610 nm 430 nm 540 nm 610 nm ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━ Example 4 A 39.2 42.4 42.7 99.7 99.9 100.0 Example 5 B 39.7 42.5 42.9 99.3 99.9 99.9 Example 6 C 39.9 42.9 42.8 99.6 99.4 99.7 ────────────────── ─────────────── Comparative Example 3 SK1832A 34.6 38.6 38.5 100.0 100.0 100.0 Comparative Example 4 SR1862A 36.9 40.4 41.3 100.0 100.0 100.0 ━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━━━━━

[0053]

[Table 6] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example No. Dichroism Visibility correction Visibility correction hue polarizing element Transmittance (%) Degree of polarization (%) L ^* a ^* b ^* ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 4A 42.3 99.9 71.1 -1.2 2.6 Example 5 B 42.5 99.9 71.2 -1.0 4.2 Example 6 C 42.6 99.5 71.3 -0.9 2.1 ──────────────────────── ────── Comparative Example 3 SK1832A 38.5 100.0 68.4 -1.9 2.9 Comparative Example 4 SR1862A 41.0 100.0 70.2 -1.3 3.3 ━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━

[0054]

[Table 7] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example No. Dichroic light receiving intensity Ratio contrast Polarizer 435 nm 545 nm 612 nm ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 4 A 1.51 1.57 1.62 ◎ Example 5 B 1.53 1.57 1.62 ◎ Example 6 C 1.54 1.57 1.63 ○ ──────────────────────────── Comparative Example 3 SK1832A 1.33 1.43 1.44 ◎ Comparative Example 4 SR1862A 1.43 1.52 1.56 ◎ ━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━

As can be seen from Tables 4 to 7, when a polarizing element in which a dichroic polarizing element having a high transmittance is combined with a reflective polarizing element according to the present invention is used, light reception is higher than that of the comparative example. The intensity ratio increases, and the transmittance also increases.
In particular, by tightly laminating the dichroic polarizing element and the reflective polarizing element using a pressure-sensitive adhesive as in Examples 4 to 6, it is possible to further increase the light receiving intensity ratio. It can be brighter.

[0056]

By using the composite polarizing element according to the present invention, a brighter screen can be obtained even with the same power consumption as the conventional one. For this reason, for example, the power consumption for obtaining the same screen brightness as that of the related art can be reduced, and the liquid crystal display device can be used for a long time with one charge of the battery. In addition, the capacity of the battery can be reduced, and the size and weight of the liquid crystal display device can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view showing an example of a conventional liquid crystal display device.

FIG. 3 is a schematic cross-sectional view of an evaluation device used in Examples.

[Explanation of symbols]

 10, 15 ... liquid crystal display device, 20 ... liquid crystal cell, 21, 22 ... transparent electrode, 23 ... liquid crystal layer, 30 ... front side optical element, 31 ... front side dichroic polarizing element, 32 ... ... front-side retardation element, 40, 42, 45 ... polarized light source device, 47 ... light source device, 50 ... rear-side optical element, 51 ... dichroic polarizing element, 52 ... phase difference element, 53 ... ... Reflection type polarizing element, 60 ... Light source member, 61 ... Light source, 62 ... Light guide plate, 63 ... Reflection plate, 64 ... White dot printing, 70 ... Diffusion sheet, 71 ... Lens sheet, 80 ... ... composite polarizing element, 83 ... pressure-sensitive adhesive, 84 ... glass plate, 85 ... integrated polarizing element for evaluation and glass plate, 86 ... light receiving part, 87 ... optical fiber.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G02F 1/13363 G09F 9/00 313 G09F 9/00 313 324 324 324 336J 336 G02F 1/1335 530

Claims (13)

[Claims] 1. A reflection type polarizing element and a dichroic polarizing element are arranged on the same optical path so that their polarization transmission axes coincide with each other, and the dichroic polarizing element has a certain wavelength between 400 nm and 700 nm. At λ, the transmittance T (P) (λ) of 44% or more and 50
%. A polarizing element having a degree of polarization P (P) (λ) of at least%. 2. A reflection type polarizing element and a dichroic polarizing element are arranged on the same optical path so that their polarization transmission axes coincide with each other, and the dichroic polarizing element has a luminous efficiency corrected transmittance of 44% or more. Y (P)
And a visibility correction polarization degree P (P, y) of 50% or more. 3. A multi-layer laminate comprising at least two kinds of polymer films, a polymer film having at least two kinds of polymers forming a sea-island structure, and a film comprising a cholesteric liquid crystal. The polarizing element according to claim 1, wherein the polarizing element is selected from a laminate with a half-wave plate. 4. The polarizing element according to claim 1, wherein the dichroic polarizing element is selected from an iodine-based polarizing film and a dye-based polarizing film. 5. The polarizing element according to claim 1, wherein the reflective polarizing element and the dichroic polarizing element are adhered via a pressure-sensitive adhesive. 6. The polarizing element according to claim 5, which has a luminosity corrected transmittance Y (P) of 42% or more. 7. The polarizing element according to claim 1, which has a visibility correction polarization degree P (P, y) of 80% or more. 8. The polarizing element according to claim 1, a light source member disposed on the reflective polarizing element side thereof, and a reflector disposed on the opposite side of the light source member from the polarizing element. A polarized light source device comprising: 9. The polarized light source device according to claim 8, wherein at least one diffusion sheet is disposed between the reflective polarizing element and the light source member. 10. The polarized light source device according to claim 8, wherein the light source member comprises a light guide plate and a light source disposed at an end thereof. 11. At least one diffusion sheet is disposed between the reflection type polarizing element and the light guide plate, and at least one lens is provided between the reflection type polarization element and the diffusion sheet and / or between the diffusion sheet and the light guide plate. 2. The sheet according to claim 1, wherein the sheet is arranged.
The polarized light source device according to 0. 12. The polarized light source device according to claim 8, a liquid crystal cell disposed on the dichroic polarizing element side thereof, and a liquid crystal cell disposed on the opposite side of the liquid crystal cell from the polarized light source device. A liquid crystal display device comprising a front dichroic polarizing element. 13. The liquid crystal display device according to claim 12, wherein a portion between the polarized light source device and the liquid crystal cell and / or a portion between the liquid crystal cell and the front dichroic polarizing element are bonded with a pressure-sensitive adhesive.