JP2000221507A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the use efficiency of the light emitted from a light source device and to provide a low-cost liquid crystal display device. SOLUTION: The device consists of a light source device 1 having at least a light source 5, reflection layer 6 and light transmission layer 7, a polarizing separator 2 and a polarized light rotator 3 and a liquid crystal panel 4 having a liquid crystal layer 8 and polarizing layers 9 applied on the outside of the liquid crystal layer 8 successively laminated on the light-emitting face of the light source device 1. The polarized light separator 2 consists of a polarizing film having a cholesteric liquid crystal layer, and the polarizing rotator 3 consists of a uniaxially anisotropic polyester film having the double refraction(Re) expressed by the following formula and <=10% max. strain in the orientation main axis. The formula is λ×(n-0.5)/4<=Re<=λ×(n+0.5)/4, wherein, λis the wavelength and (n) is an odd number in positive integers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device used for a liquid crystal television, a liquid crystal display for a personal computer, a projection type liquid crystal display device, and the like.

[0002]

2. Description of the Related Art In recent years, technical progress in liquid crystal display devices, particularly liquid crystal display devices using color display devices, has been remarkable, and liquid crystal display devices of high display quality not inferior to CRTs have been developed. Among the liquid crystal display elements, at present, a transmissive liquid crystal display device using a backlight as a light source device for monochrome display instead of a reflective liquid crystal display device without a backlight (light source device) has become mainstream. I have. In particular, in color display, a display is not formed without a backlight, and the use of a backlight is becoming an essential condition in a direct-view liquid crystal display device.

On the other hand, a color liquid crystal display device has a TN type liquid crystal and a TFT formed by active matrix driving using TFTs.
FT type liquid crystal display device and multiplex drive STN
There is a liquid crystal display device in which a polarizing layer (polarizing plate) is disposed on a light incident side and a light emitting side of a liquid crystal cell in which a liquid crystal layer is held by a glass substrate. The display is performed by modulating the polarization state. However, since the polarization directions of the light incident on the liquid crystal cell are irregular and random polarization, the TFT liquid crystal display device and the S
In any of the TN liquid crystal display devices, more than half of the incident light is absorbed by the polarizing layer disposed on the incident side of the liquid crystal cell, so that the utilization efficiency of the incident light is low, resulting in a dark display screen. Was. In this state, in order to make the display screen brighter, there is a problem that the power consumption in the backlight increases. Therefore, it has been required to increase the amount of light emitted from the backlight without increasing the power consumption, or to reduce the absorption of the light emitted from the backlight in the display device.

As a method of increasing the amount of light emitted from the backlight, in an edge-light type backlight, the material forming the light guide layer and the interface reflection characteristics of the light guide layer are improved, so that the light guide layer is connected to the end portion from the end. Increasing the function of transmitting incident light in the direction of the light guide layer surface, or changing the shape of the light guide layer surface that avoids total reflection conditions, by forming a white diffusion layer on the light guide layer surface, The lenticular or the method of forming the Fresnel shape of the prism has taken measures such as enhancing the function of emitting the transmitted light to the liquid crystal display element side.

[0005] Further, for each member (light guide layer, light diffusion layer, etc.) constituting the backlight, a material having a high light transmittance is adopted, for example, a device for suppressing light loss and improving light use efficiency. It has been done. In order to improve the front luminance of the backlight, one or two light-condensing layers may be formed outside the light-diffusing layer so that light transmitted through the light-diffusing layer and collected in the front direction is collected as much as possible. Is being done. The light-condensing layer is made of a transparent sheet with a number of small irregularities such as prisms, waves, and pyramids on the surface.It refracts outgoing light transmitted through the light diffusion layer and collects it at the front to increase the brightness of the irradiated surface. To improve it.

On the other hand, when the depth tolerance of the device is large, such as when a liquid crystal display device is used as a light modulator of a transmission type projector, absorption of light emitted from the backlight in the display device is reduced. In order to improve the utilization efficiency of the emitted light, a polarization separator that separates unpolarized light into polarized light orthogonal to each other is interposed between the backlight and the liquid crystal panel having the liquid crystal cell and the polarizing layer. It has been conventionally proposed that the light is directly emitted from the polarization separator, and the other light is focused on the light source device and used again as the light source light (for example, Japanese Patent Application Laid-Open No. 4-184429).
Attempts have also been made to use a polarization separator in addition to a conventional liquid crystal display device. In this case, as the polarization separator, a multilayer polarizing plate or a dielectric multilayer polarizing plate (for example, see
No. 105929) has been proposed.

However, in a method of using a conventional polarization splitter in addition to a conventional liquid crystal display device, the polarization splitter itself is as expensive as an expensive multilayer polarization conversion element or a dielectric multilayer polarization conversion element. Since a function is realized by combining a quarter-wave plate or a half-wave plate, there is a problem that a polarization separator as a system becomes expensive.

It has been attempted to reduce the cost by using a polymer film such as polycarbonate or polyester or a retardation film of a liquid crystal polymer film as the above-mentioned quarter-wave plate or half-wave plate. Polyester having a low resin cost has hardly been used because it has a large photoelastic coefficient and is not uniform as compared with polycarbonate.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device in which the efficiency of use of light emitted from a light source device is improved and the cost is lower.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have used a specific polarization conversion element as a polarization separator,
Furthermore, it was found that the above-mentioned problems were solved by using a polyester resin film controlled to specific physical properties as a polarization rotator in combination with the polarization separator,
The present invention has been completed.

That is, the present invention provides a light source device 1 having at least a light source 5, a reflection layer 6, and a light guide layer 7, and the light source device 1
Polarized light separator 2 sequentially arranged on the light exit surface side of
And a liquid crystal display device including a polarization rotator 3 and a liquid crystal panel 4 having a liquid crystal layer 8 and a polarizing layer 9 provided outside the liquid crystal layer 8, wherein the polarization separator 2 mainly includes a cholesteric liquid crystal layer. A polarizing film, wherein the polarization rotator 3 has a retardation value (Re) in the range represented by the formula (1), and has a maximum distortion of 1 or more in the main axis of alignment.
This is a liquid crystal display device mainly composed of a uniaxial anisotropic polyester film at 0 ° or less. λ × (n−0.5) / 4 ≦ Re ≦ λ × (n + 0.5) / 4 (1) (in the formula, λ represents a substantial wavelength, and n represents an odd number among positive integers.)

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings. FIG. 1 is a sectional view showing an example of the configuration of the liquid crystal display device of the present invention. As shown in FIG.
The liquid crystal display device A mainly includes a light source device 1 and a polarization separator 2 that is sequentially arranged on the light emitting surface side of the light source device 1.
, A polarization rotator 3, and a liquid crystal panel 4.

The light source device 1 is of an edge light type mainly composed of a light source 5, a reflection layer 6, and a light guide layer 7, and the light source 5 of a substantially linear illuminant is provided on an illuminating surface of a plate-like light guide layer 7. A light source 5 is provided with a lamp cover made of a reflector, which is disposed in close contact with one or two sides of an end portion of the light guide layer 7 to introduce light into the light guide layer 7. The light emitted from the light source 5 travels in the in-plane direction of the light guide layer 7 and exits the light source device 1 from the surface opposite to the surface on which the reflective layer 6 is formed. The light that has proceeded to the reflective layer 6 is also reflected by the reflective layer 6 and exits the light source device 1 from a surface opposite to the surface on which the reflective layer 6 is formed.

In the present invention, the materials and devices constituting the light source 5, the reflection layer 6, and the light guide layer 7 of the light source device 1 are not particularly limited, and those generally used can be used.

The polarized light separator 2 separates incident light passing through the light guide layer 7 of the light source device 1 into left and right circularly polarized lights, transmits one of them, and reflects the other. The reflected light is confined between the polarization separator 2 and the reflection layer 6 of the light source device 1, and is converted into a predetermined circularly polarized light while repeating reflection between the polarization separator 2 and the polarization separator 2 so that the light can pass through the polarization separator 2. The incident light that has passed through the light guide layer 7 is emitted together with circularly polarized light that has been in a predetermined state from the beginning. That is, by making the polarization state uniform, the unused portion of the emitted light from the light source that is reflected by the polarizing layer 9 or the like of the liquid crystal panel 4 is reduced.

In the present invention, the polarization separator 2 mainly has a cholesteric liquid crystal layer. The cholesteric liquid crystal constituting the cholesteric liquid crystal layer is not particularly limited, but it is preferable to use a liquid crystal polymer in terms of the superposition efficiency and the thickness of the cholesteric liquid crystal layer. Further, a cholesteric liquid crystal having a large birefringence is preferable because the wavelength range of the selective reflection becomes wider.

Examples of the liquid crystal polymer include a main chain type liquid crystal polymer such as polyester, a side chain type liquid crystal polymer having an acrylic main chain, a methacryl main chain, a siloxane main chain, and the like; a nematic liquid crystal polymer containing a low molecular weight chiral agent; A liquid crystal polymer having a chiral component, a mixed liquid crystal polymer of a nematic type and a cholesteric type, and the like can be given.
Among these liquid crystal polymers, a liquid crystal polymer having a glass transition temperature of 30 to 150 ° C. is preferably used in terms of handling and the like.

In the polarization separator 2, the thickness of the cholesteric liquid crystal layer is not particularly limited. However, the thickness of the cholesteric liquid crystal layer is not limited in order to prevent the disorder of the alignment and to prevent the transmission from being lowered, the selective reflectivity (the wavelength range showing circular dichroism), and the like. , Preferably from 0.5 to 100 μm, more preferably from 1 to 70 μm, particularly preferably from 1 to 50 μm.

In the polarization separator 2, the cholesteric liquid crystal layer may be a single layer or a multilayer structure having two or more layers. Multilayering is advantageous from the viewpoint of widening the wavelength range of the separation function and addressing the wavelength shift of oblique incident light. In this case, the layers are stacked so that the center wavelength of the light reflected as circular polarized light outside the specified range is different. Is preferred.

The cholesteric liquid crystal layer may contain various additives such as stabilizers, plasticizers, metals and the like, if necessary, as long as the effects of the present invention are not impaired.

In the present invention, the polarization separator 2 may be in the form of a polarizing film composed of a liquid crystal polymer exhibiting a cholesteric phase or a laminated body in which a liquid crystal layer composed of a cholesteric liquid crystal is laminated on a transparent substrate such as a resin film. Films and the like.

In the present invention, the method for producing the polarizing film constituting the polarization separator 2 is not particularly limited, and a commonly used production method may be used depending on the constitution and the material used. it can.

In the present invention, the cholesteric liquid crystal layer is preferably formed as a flat layer from the viewpoint of equalizing the separation performance including oblique incident light, and is formed as a multilayer structure of two or more layers. Even in this case, each layer is preferably flat.

The polarization rotator 3 is disposed on the side opposite to the light source device 1 side of the polarization separator 2. The polarization rotator 3
It has the same function as a quarter-wave plate, and
The phase of the emitted circularly polarized light is changed through the polarization rotator 3, and is converted into a state having a large amount of linearly polarized light components such as linearly polarized light and flat elliptically polarized light. This converted light transmits through the polarizing layer 9 without being absorbed when the linear polarization direction matches the transmission axis of the polarizing layer 9 constituting the liquid crystal panel 4.
The unused portion of the light from the light source device 1 due to the absorption of light is reduced.

In the present invention, the polarization rotator 3 has a retardation value (R) in a range represented by the following equation (1).
e) and mainly comprises a uniaxially anisotropic polyester-based film having a main axis of orientation having a maximum strain of 10 ° or less. λ × (n−0.5) / 4 ≦ Re ≦ λ × (n + 0.5) / 4 (1) (in the formula, λ represents a substantial wavelength, and n represents an odd number among positive integers.)

The retardation value (Re) is determined by the biaxial refractive index anisotropy (ΔN = | Nx−N) perpendicular to the film.
y |) and the film thickness d (= ΔN × d). In addition, since it is difficult to satisfy the above conditions in the entire visible light range, it is preferable that the above conditions be satisfied when light having a wavelength of about 550 nm is used.

The retardation value (Re) is preferably within (n ± 0.2) times λ / 4, more preferably
It is better to be within (n ± 0.1) times of λ / 4. When the retardation value (Re) exceeds the range of (n ± 0.5) times λ / 4, the phase of the circularly polarized light is changed and the state cannot be converted to a state having a large amount of linearly polarized light. The desired effect is reduced.

In the present invention, the uniaxial anisotropic polyester film used as the polarization rotator 3 needs to have a maximum value of distortion of the main orientation axis of 10 degrees or less, preferably 8 degrees or less, more preferably 5 degrees or less. It is better to be below the degree. If the maximum value of the main alignment axis is more than 10 degrees, the uniformity of the brightness, contrast, etc. of the entire liquid crystal display screen becomes poor.

In the present invention, the heat shrinkage at 100 ° C. of the uniaxially anisotropic polyester film constituting the polarization rotator 3 is preferably 0.5% or less, more preferably 0.3% or less, and particularly preferably 0% or less. .1% or less. If the heat shrinkage is larger than 0.5%, heat from the light source generates internal stress, which changes birefringence and easily causes display unevenness.

In the present invention, the haze of the uniaxially anisotropic polyester film constituting the polarization rotator 3 is preferably 1% or less, more preferably 0.8% or less, and particularly preferably 0.5% or less. Good. If the haze is larger than 1%, the visibility of the liquid crystal display screen tends to be poor.

The uniaxially anisotropic polyester film used as the polarization rotator 3 in the present invention is not particularly limited as long as it satisfies the above conditions. For example, 80 mol% or more of the repeating unit is ethylene terephthalate or Examples of the film include a film made of a polyester resin mainly composed of a polyester that is ethylene-2,6 naphthalate.

The polyester resin constituting the uniaxially anisotropic polyester film may be added to other components, such as ethylene terephthalate or ethylene-2,6 naphthalate, as far as the component does not impair the function of the present invention. It may be one obtained by copolymerizing a polymerization component. Other copolymerization components include isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4′-dicarboxydiphenyl,
4,4′-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid,
5-sodium sulfoisophthalic acid, dicarboxylic acid components such as 1,4-dicarboxycyclohexane, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol,
Examples thereof include diol components such as an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These dicarboxylic acid components and glycol components can be used in combination of two or more as necessary. Along with the carboxylic acid component and glycol component,
An oxycarboxylic acid such as p-oxybenzoic acid can be used in combination. Further, as the other copolymer component, a small amount of a compound containing an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be contained.

The polyester resin constituting the uniaxially anisotropic polyester film may be one of the polyester resins described above or a mixture of two or more polyester resins.

As the polyester resin constituting the uniaxially anisotropic polyester film used as the polarization rotator 3 in the present invention, it is most preferable that the polyester resin contains few impurities, has high transparency, and has excellent mechanical properties. It is preferable to use an inexpensive polyethylene terephthalate-based resin (PET) mainly composed of polyethylene terephthalate.

The polyester resin constituting the above-mentioned uniaxially anisotropic polyester film may be, if necessary, a lubricant, an antiblocking agent, a heat stabilizer and an antioxidant within a range not to impair the function of the present invention. And known additives such as an antistatic agent, a light resistance agent, and an impact resistance improver. However, since transparency is required for optical applications, it is preferable to minimize the amount of additives to be added.

The method for producing the uniaxially anisotropic polyester film is not particularly limited. For example, a non-oriented polyester obtained by melting the above polyester resin and extruding it into a sheet is heated with a tenter at a temperature equal to or higher than the glass transition temperature. After the transverse stretching, a method of performing a heat setting treatment may be used.

In the present invention, the uniaxially anisotropic polyester film used as the polarization rotator 3 is prepared by the above-mentioned production method, after the transverse stretching and before the heat setting treatment.
Relaxing the film in the longitudinal direction is important for reducing the distortion of the main orientation axis. The temperature for the relaxation treatment is preferably 90 to 200 ° C., more preferably 12 to 200 ° C.
The temperature is preferably from 0 to 180 ° C. The amount of relaxation is not particularly limited, and may be appropriately set depending on the transverse stretching conditions. However, in the film after the relaxation treatment, the heat shrinkage at 100 ° C. is 0.5%.
% Is preferably set to the amount of relaxation and the temperature.

In the above-mentioned manufacturing method, the temperature of the heat setting treatment is preferably from 180 to 250 ° C., more preferably from 200 to 245 ° C. In the heat setting treatment, the heat fixing treatment is first performed at a fixed length, and the relaxation treatment in the width direction is preferably 1 to 10%, more preferably 2 to 5%.
%, A uniaxial anisotropic polyester film having excellent heat resistance can be obtained by reducing the distortion of the main alignment axis.

The thickness of the uniaxially anisotropic polyester film is not particularly limited, but is preferably 20 to 400 μm in consideration of the use of the uniaxially stretched polyester film and the workability of incorporation into the liquid crystal display of the present invention. Preferably it is. If the thickness is less than 20 μm, the mechanical strength is not sufficient, and if the thickness exceeds 400 μm, the advantage of the plastic film being thin is reduced.

In the present invention, the polarization rotator 3 only needs to satisfy the conditions such as the relationship of the retardation value (Re) as a whole, and the uniaxially anisotropic polyester film constituting the polarization rotator 3 is a single layer. Or a multi-layer structure of two or more layers. In the case of a multilayer structure having two or more layers, two or more layers having different retardation values (Re) may be laminated.

In the present invention, the liquid crystal panel 4 has a liquid crystal layer 8 and a polarizing layer 9 provided outside the liquid crystal layer 8, and is disposed on the side opposite to the polarization separator 2 side of the polarization rotator 3. Is done. The material constituting the liquid crystal layer 8 and the polarizing layer 9 is not particularly limited, and a material generally used for a general liquid crystal panel can be used. The liquid crystal panel 4
There is also no particular limitation on the structure of the liquid crystal cell. For example, the liquid crystal is held on a glass substrate to form a liquid crystal cell (liquid crystal layer 8), and a polarizing plate formed in a film shape on the surface of the glass substrate is disposed as a polarizing layer 9. It may have another configuration required for a liquid crystal panel such as a transparent electrode.

In the present invention, when the liquid crystal panel 4 is disposed on the side opposite to the polarization separator 2 side of the polarization rotator 3, the liquid crystal panel 4 with respect to the fast axis or the slow axis of the polarization rotator 3. The angle at which the polarization axis of the polarizing layer 9 is disposed can be appropriately set according to the phase difference characteristic of the polarization rotator 3, the characteristic of the circularly polarized light incident on the polarization rotator 3, and the like.
For the linear polarization direction of the polarized light transmitted through the polarization rotator 3,
It is preferable to dispose the polarizing layer 9 so that the transmission axes thereof are parallel. When the direction of the linear polarization of the polarized light transmitted through the polarization rotator 3 is not parallel to the transmission axis of the polarizing layer 9, the transmitted polarized light is absorbed by the polarizing layer 9, and the effect of the present invention is not sufficiently exhibited.

The method of manufacturing the liquid crystal display device of the present invention is not particularly limited, and the above-mentioned constituent members may be sequentially laminated or separately formed within a range not impairing the operation of the present invention. It can be manufactured by using a generally used manufacturing method.

The liquid crystal display device of the present invention may have, in addition to the above-described configuration, another configuration generally provided in a liquid crystal display device, as long as the operation of the present invention is not impaired. For example, in the liquid crystal panel 4, a light diffusion layer, an anti-glare layer, an anti-reflection layer, a protection layer, provided outside the polarizing layer 9 on the display screen side,
Alternatively, a compensating retardation layer provided between the liquid crystal cell (liquid crystal layer 8) and the polarizing layer 9 on the display screen side and / or the light source device 1 side is sequentially laminated or formed in a sheet shape. A well-known optical element such as a lens sheet, a light diffusion plate, a reflector sheet or the like for obtaining a sufficient front luminance may be appropriately arranged.

Hereinafter, the effects of the present invention will be described in more detail with reference to Examples and Test Examples, but the present invention is not limited thereto.

Test Example 1. Test method (1) Retardation value (R
e) Measurement Two sheets of the uniaxially stretched polyethylene terephthalate film or uniaxially stretched polyethylene-2,6-naphthalate film used as the polarization rotator 3 in Examples 1 to 4, Comparative Examples 1 and 2, and Reference Examples 1 and 2. 4cm × 2cm so that the orientation axis is orthogonal to the orientation axis
A rectangular sample is cut out to form a sample, and the two orthogonal refractive indices of the orientation axis are determined by the Abbe refractive index (ATAGO 4T,
(Manufactured by Atago Co., Ltd.), and the value obtained by subtracting the smaller value of the refractive index from the larger value of the refractive index is multiplied by the thickness of the film to obtain a retardation value (Re). did.

(2) Measurement of Maximum Strain of Alignment Principal Axis in Polarization Rotator 3 Uniaxially stretched polyethylene terephthalate film used as polarization rotator 3 in Examples 1, 2, 4, Comparative Examples 1, 2, and Reference Examples 1 and 2, Or uniaxially stretched polyethylene-2,6
-For the naphthalate film, a measurement sample was prepared by the following method, and the orientation main axis of the sample was determined by microwave, and the orientation of the other three points was determined when the molecular orientation angle of the point measured first was 0 degree. The maximum value was determined from the one with the largest difference in the angles. To measure the orientation angle of the main axis by microwave, a molecular orientation meter (MOA manufactured by Kanzaki Paper Co., Ltd.)
-2001A) was used. [Sample preparation method] When the film shape at the time of manufacture is a roll shape, 1000 times in the longitudinal direction from the rolled film.
The sample was cut out so as to have a total width in the width direction of mm and a measurement sample. Further, when the film shape at the time of manufacture is a sheet shape, draw a rectangle having the largest area inscribed in the sheet-like film, and share a vertex of the rectangle with two sides of 100 m.
An m square was cut out from four vertices and cut out to obtain a measurement sample.

(3) Measurement of heat shrinkage in polarization rotator 3 Uniaxially stretched polyethylene terephthalate film or uniaxial film used as polarization rotator 3 in Examples 1, 2, 4, Comparative Examples 1 and 2, and Reference Examples 1 and 2. Stretched polyethylene-2,6
-The naphthalate film was cut out into a square having a side of 100 mm to obtain a measurement sample. For the measurement sample, draw a circle with a diameter of 50 mm around the intersection of the diagonal lines, leave it in a hot-air dryer heated to 100 ° C. for 30 minutes with no load, take it out, and take out the dimensional change of the circle with a digitizer. Read through the diagonal intersection,
From the length (B) of the portion where the heat shrinkage is maximum, the following formula (2)
Was used to determine the heat shrinkage. Heat shrinkage = (50−B) / 50 × 100 (%) (2)

(4) Haze Measurement in Polarization Rotator 3 Uniaxially stretched polyethylene terephthalate film or uniaxially stretched polyethylene used as polarization rotator 3 in Examples 1, 2, 4, Comparative Examples 1 and 2, and Reference Examples 1 and 2. -2, 6
-About a naphthalate film, the haze in five places was measured using the turbidimeter (Nippon Denshoku Industries Co., Ltd. product NDH-300), and the average value was set as the haze in the polarization rotator 3.

(5) Measurement of total light transmittance in polarization rotator 3 Uniaxially stretched polyethylene terephthalate film used as polarization rotator 3 in Examples 1, 2, 4, Comparative Examples 1 and 2, and Reference Examples 1 and 2, or Uniaxially stretched polyethylene 2-, 6
-The total light transmittance of the naphthalate film was measured in the same manner as in Test Example (4).

(6) Frontal luminance measurement of liquid crystal display device The liquid crystal display devices of Examples 1 to 4, Comparative Examples 1 and 2, and Reference Examples 1 and 2 were measured using a luminance meter (manufactured by Minolta Camera Co., Ltd.). The front luminance 3 hours after the start of lighting of the light source device 1 was measured. In the evaluation, the ratio was displayed assuming that the front luminance in a conventional liquid crystal display device (the liquid crystal display devices of Examples 1 to 4 excluding the polarization separator 2 and the polarization rotator 3) was 1.

(7) Measurement of Contrast of Liquid Crystal Display Device For the liquid crystal display devices of Examples 1 to 4, Comparative Examples 1 and 2, and Reference Examples 1 and 2, the contrast after 3 hours from the start of lighting of the light source device 1 was visually evaluated. did.

2. Test Results The results of the above tests (1) to (7) are shown in Table 1.

[0054]

[Table 1]

[0055]

EXAMPLES [Production of Liquid Crystal Display Device] A liquid crystal display device having the configuration shown in FIG. 1 was produced using the following constituent materials.
In addition, the liquid crystal panel 4 was arranged so that the contrast of light transmitted through the liquid crystal panel 4 and visually recognized was highest. [Constituent materials of liquid crystal display device] Light source device 1 Light source 5: fluorescent lamp Reflective layer 6: aluminum vapor deposition layer Light guide layer 7: polymethyl methacrylate plate (thickness: 5 mm) Polarization separator 2: cholesteric liquid crystal layer (methacrylic main chain) (A chiral agent is added to the side chain type nematic liquid crystal polymer of Example 1) formed film (selective reflectivity in a wavelength range of 400 to 700 nm) Polarization rotator 3: uniaxially stretched polyethylene terephthalate film Liquid crystal panel 4: (liquid crystal layer 8 and polarizing layer 9)

Example 1 Polyethylene terephthalate (manufactured by Toyobo Co., Ltd.) was extruded through a film forming die onto a water-cooled rotary quenching drum to form an unstretched film. This unstretched film is stretched 3.7 times in the width direction at 90 ° C., and then annealed at 120 ° C. for 10 seconds. After coming out of the tenter, both ends of the film are trimmed at a position 20 mm from the end and heated. A site with a small amount of contraction was excised. Subsequently, after a 5% relaxation treatment at 160 ° C. in the longitudinal direction, it was heat-set at 245 ° C., and further relaxed at 200 ° C. by 4% to obtain a uniaxially stretched polyethylene terephthalate film having a thickness of 55 μm. Using the uniaxially stretched polyethylene terephthalate film as the polarization rotator 3, a liquid crystal display device was prepared according to the method described above, and Example 1 was performed.

Example 2 In the same manner as in Example 1, a uniaxially stretched polyethylene terephthalate film having a thickness of 110 μm was obtained. Using the uniaxially stretched polyethylene terephthalate film as the polarization rotator 3, according to the method described above, a liquid crystal display device was prepared,
Example 2 was used.

Example 3 In the same manner as in Example 1 except that a lens sheet (BEF-II, manufactured by Sumitomo 3M) was arranged between the light source device 1 and the polarization separator 2 in the liquid crystal display device of Example 1. Thus, a liquid crystal display device was prepared, and Example 3 was performed.

Example 4 Polyethylene-2,6-naphthalate (Toyobo Co., Ltd.)
) To obtain a uniaxially stretched polyethylene-2,6-naphthalate film having a thickness of 56 µm in the same manner as in Example 1. Using a uniaxially stretched polyethylene-2,6-naphthalate film as the polarization rotator 3, according to the method described above,
A liquid crystal display device was prepared, and the liquid crystal display device was obtained as Example 4.

Comparative Example 1 A uniaxially stretched polyethylene terephthalate film having a thickness of 115 μm was obtained in the same manner as in Example 1. Using the uniaxially stretched polyethylene terephthalate film as the polarization rotator 3, according to the method described above, a liquid crystal display device was prepared,
Comparative Example 1 was used.

Comparative Example 2 Polyethylene terephthalate (manufactured by Toyobo Co., Ltd.) was extruded through a film forming die onto a water-cooled rotary quenching drum to form an unstretched film. After stretching this unstretched film 3.7 times in the width direction at 90 ° C.,
The film was heat-set at 45 ° C., and then relaxed at 200 ° C. for 4% to obtain a uniaxially stretched polyethylene terephthalate film having a thickness of 55 μm. Using the uniaxially stretched polyethylene terephthalate film as the polarization rotator 3, a liquid crystal display device was prepared according to the method described above, and Comparative Example 2 was obtained.

Reference Example 1 A uniaxially stretched polyethylene terephthalate film having a thickness of 55 μm was obtained in the same manner as in Example 1 except that the heat setting temperature in the tenter was 170 ° C. Using the uniaxially stretched polyethylene terephthalate film as the polarization rotator 3, a liquid crystal display device was prepared according to the method described above, and the result was referred to as Reference Example 1.

Reference Example 2 A 110 μm-thick uniaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the transverse stretching ratio in the tenter was changed to 2.0. Using the uniaxially stretched polyethylene terephthalate film as the polarization rotator 3, a liquid crystal display device was prepared according to the method described above, and the result was referred to as Reference Example 2.

[0064]

According to the liquid crystal display of the present invention, the polarization separator 2 is provided.
Is a polarizing film mainly composed of a cholesteric liquid crystal layer, and the polarization rotator 3 is composed of a uniaxial anisotropic polyester film having specific physical properties. The unused portion of the light from the light source is reduced, the front luminance is increased without increasing the power consumption by the light source device 1, and the same front luminance as a conventional liquid crystal display device using an expensive polarization separator is realized. become able to. In addition, since the polarization separator and the polarization rotator have simple structures, and use a low-cost polyester film as the polarization rotator, an inexpensive liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a configuration of a liquid crystal display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source device 2 Polarization separator 3 Polarization rotator 4 Liquid crystal panel 5 Fluorescent lamp 6 Reflection layer 7 Light guide layer 8 Liquid crystal layer 9 Polarization layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiichiro Yokoyama 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. Research Laboratory 2H091 FA08Y FB02 FD09 FD10 FD14 FD21 GA17 KA02 KA10 LA18

Claims (5)

[Claims] 1. A light source device 1 having at least a light source 5, a reflection layer 6, and a light guide layer 7, a polarization separator 2, which is sequentially arranged on the light emitting surface side of the light source device 1, and a polarization rotation device. Vessel 3
And a liquid crystal panel 4 having a liquid crystal layer 8 and a polarizing layer 9 provided outside the liquid crystal layer 8, wherein the polarization separator 2 is a polarizing film having a cholesteric liquid crystal layer. The rotator 3 is mainly made of a uniaxially anisotropic polyester film having a retardation value (Re) in the range represented by the following formula (1) and having a maximum distortion of the main orientation axis of 10 degrees or less. Characteristic liquid crystal display device. λ × (n−0.5) / 4 ≦ Re ≦ λ × (n + 0.5) / 4 (1) (in the formula, λ represents a substantial wavelength, and n represents an odd number among positive integers.) 2. The uniaxially anisotropic polyester film constituting the polarization rotator 3 has a heat shrinkage at 100 ° C. of 0.5% or less.
The liquid crystal display device according to the above. 3. The liquid crystal display device according to claim 1, wherein a haze of the uniaxial anisotropic polyester film constituting the polarization rotator 3 is 1% or less. 4. The method according to claim 1, wherein the uniaxially anisotropic polyester film constituting the polarization rotator 3 is mainly made of polyethylene terephthalate resin (PET). Liquid crystal display. 5. The polarizing layer 9 in the liquid crystal panel 4 with respect to the direction of linear polarization of polarized light transmitted through the polarization rotator 3.
5. The transmission axes of the light emitting elements are parallel to each other.
The liquid crystal display device according to claim 1.