JP2008268297A - Thin polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin polarizing plate which exhibits excellent optical characteristics and has thickness less than 100 μm. <P>SOLUTION: The thin polarizing plate is characterized in that its thickness is 80 μm or less, its degree of polarization is 99.9% or more, its transmittance is 35% or more, and its reflectance is 30% or more. The thin polarizing plate comprises: a substrate 1 having grid-shaped protruding parts 1a on its surface; dielectric layers 2 mounted on regions including the grid-shaped protruding parts 1a; and metal wires 3 mounted on the dielectric layers 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin polarizing plate that exhibits excellent optical properties in a very thin state.

  In recent years, mobile terminal devices such as mobile phones have been required to be thinner and lighter, and it has been required to reduce the thickness of each member as much as possible. The same applies to a polarizing plate which is a component of a portable terminal device, and it is desired to make it as thin as possible while maintaining necessary optical characteristics.

  A typical polarizing plate is an absorptive polarizing plate formed by adding iodine to PVA (polyvinyl alcohol) resin. This absorptive polarizing plate is formed by laminating protective films of TAC (triacetyl cellulose) resin on both sides of a polarizing film obtained by adding iodine to PVA. In order to exhibit the light absorption performance, the polarizing film needs to have a thickness that allows three to five iodine atoms to be disposed, and has a thickness of at least 20 μm. Further, the TAC film is usually 40 μm in thickness. Therefore, the thickness of the absorption polarizing plate is about 100 μm as a whole.

In addition, Patent Document 1 discloses a reflective polarization type polarizing plate using a refractive index difference caused by selective reflection of cholesteric liquid crystal or lamination of films, and the entire thickness of this polarizing plate is about 100 μm. .
JP 04-268505 A

  As described above, any of the conventional absorption-type or reflection-type polarizing plates has a thickness of 100 μm or more, exhibits excellent optical characteristics, and has no thickness of less than 100 μm. is the current situation.

  This invention is made | formed in view of this point, and it aims at providing the thin polarizing plate which exhibits the outstanding optical characteristic and is less than 100 micrometers in thickness.

  The thin polarizing plate of the present invention has a thickness of 80 μm or less, a degree of polarization of 99.9% or more, a transmittance of 35% or more, and a reflectance of 30% or more.

  In the thin polarizing plate of the present invention, a substrate having a grid-like convex portion on the surface, a dielectric layer provided on a region including the grid-like convex portion, and a metal wire provided on the dielectric layer It is preferable that it is comprised by these.

  The liquid crystal display device of the present invention comprises a liquid crystal panel, illumination means for irradiating the liquid crystal panel with light, and the thin polarizing plate disposed between the liquid crystal panel and the illumination means. And

  According to the thin polarizing plate of the present invention, the thickness is 80 μm or less, the degree of polarization is 99.9% or more, the transmittance is 35% or more, and the reflectance is 30% or more. A thin polarizing plate that exhibits optical characteristics and has a thickness of less than 100 μm can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a part of a thin polarizing plate according to an embodiment of the present invention. This thin polarizing plate is mainly composed of a base material 1 having a lattice-like convex portion 1a on the surface, a dielectric layer 2 provided on the base material 1, and a metal wire 3 standing on the dielectric layer 2. It is configured. The dielectric layer 2 is not necessarily provided.

  The material used for the substrate 1 may be a material that is substantially transparent in the visible light region, but is preferably a resin excellent in workability. For example, polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin resin (COP), cross-linked polyethylene resin, polyvinyl chloride resin, polyarylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyetherimide resin, polyether Amorphous thermoplastic resins such as sulfone resin, polysulfone resin, polyether ketone resin, polyethylene terephthalate resin (PET), polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic polyester resin, polyacetal Examples thereof include crystalline thermoplastic resins such as resins and polyamide resins, and ultraviolet curable resins and thermosetting resins such as acrylics, epoxies, and urethanes. Moreover, you may use the composite base material which combined the ultraviolet curable resin and the thermosetting resin, inorganic substrates, such as glass, the said thermoplastic resin, and a triacetate resin as the base material 1. FIG.

  The pitch p of the lattice-like convex portions 1a of the substrate 1 is 150 nm or less, preferably 80 nm to 120 nm in consideration of polarization characteristics over a wide band in the visible light region. The smaller the pitch p, the better the polarization characteristics. However, for visible light, sufficient polarization characteristics can be obtained at a pitch p of 80 to 120 nm. If the polarization characteristics of the short wavelength light in the vicinity of 400 nm are not important, the pitch p may be increased to about 150 nm.

  In the present invention, the pitch p of the grid-like convex portions 1a of the substrate 1, the pitch of the dielectric layer 2, and the pitch of the metal wires 3 are substantially equal to the pitch of the wire grid of the present invention, and take the same pitch. Can do.

  There is no restriction | limiting in the cross-sectional shape of the grid-like convex part 1a of the base material 1. FIG. Examples of the cross-sectional shape include a trapezoidal shape, a rectangular shape, a square shape, a prism shape, and a sine wave shape such as a semicircular shape. Here, the sinusoidal shape means that it has a curved portion formed by repetition of a concave portion and a convex portion. In addition, the curved part should just be a curved curve, for example, the shape which has a constriction in a convex part is also included in a sine wave form. Further, from the viewpoint of facilitating covering of the lattice-like convex portion 1a of the substrate 1 and at least a part of its side surface with the dielectric, it is preferable that the end portion, vertex, or valley of the shape is curved with a gentle curvature. Further, from the viewpoint of increasing the adhesion strength between the substrate 1 and the dielectric layer 2, it is more preferable that these cross-sectional shapes are sinusoidal.

  As a method of providing the grid-like convex portions on the substrate 1, there is a method in which a mold having a grid-like convex portion having a pitch of 150 nm or less on the surface is used to transfer and mold the grid-like convex portions on the surface of the substrate. It is done. Here, the mold having a grid-like convex part with a pitch of 150 nm or less on the surface is made conductive in order by a resist pattern having a grid-like convex part with a pitch of 150 nm or less, obtained by electron beam lithography or interference exposure. It can be produced by performing a treatment, a plating treatment, and a substrate removal treatment.

  The dielectric constituting the dielectric layer 2 may be a dielectric that is substantially transparent in the visible light region. A dielectric material having strong adhesion between the material constituting the substrate 1 and the metal constituting the metal wire 3 can be suitably used. For example, silicon (Si) oxide, nitride, halide, carbide alone or a composite thereof, aluminum (Al), chromium (Cr), yttrium (Y), zirconia (Zr), tantalum (Ta), Metal oxides such as titanium (Ti), barium (Ba), indium (In), tin (Sn), zinc (Zn), magnesium (Mg), calcium (Ca), cerium (Ce), copper (Cu) , Nitrides, halides, carbides or composites thereof (dielectrics in which other elements, simple substances, or compounds are mixed in a dielectric substance) can be used.

  The method for forming the dielectric layer 2 on the region including the lattice-shaped protrusions of the substrate 1 having the lattice-shaped protrusions 1 a is appropriately selected depending on the material constituting the dielectric layer 2. For example, a physical vapor deposition method such as a sputtering method or a vacuum vapor deposition method can be suitably used. The sputtering method is preferable from the viewpoint of adhesion strength.

  The metal constituting the metal wire 3 is preferably a metal having high light reflectance in the visible light region and good adhesion to the material constituting the dielectric layer 2. For example, it is preferably made of aluminum (Al), silver (Ag), or an alloy thereof. From the viewpoint of cost, it is more preferable that it is made of Al or an Al alloy.

  As a method of depositing metal on the substrate 1 or the dielectric layer 2 to form the metal wire 3, the material constituting the substrate 1 or the dielectric layer 2 and the metal constituting the metal wire 3 are used. The method is not particularly limited as long as sufficient adhesion can be obtained. For example, a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method can be suitably used. Among them, a method is preferable in which the metal can be selectively stacked on the convex portion of the dielectric layer 2 selectively or biased to one side surface of the convex portion of the dielectric layer 2. An example of such a method is a vacuum deposition method.

  The thin polarizing plate having the above configuration includes a base region and a polarizing region provided on the base region. Since the thickness H of the base region is basically the thickness of the substrate 1, it is about 5 μm to about 80 μm. Further, the thickness h of the polarizing region is 1 μm or less including the lattice-like convex portion 1a, the dielectric layer 2, and the metal wire 3. Therefore, the total thickness of the thin polarizing plate is 80 μm or less.

  The thin polarizing plate having the above configuration has a polarization region of a wire grid polarizing plate, so that the degree of polarization is 99.9% or more, the transmittance is 35% or more, and the reflectance is 30% or more.

  Next, the case where the thin polarizing plate according to the present invention is used in a liquid crystal display device will be described. FIG. 2 is a diagram showing a liquid crystal display device using a thin polarizing plate according to an embodiment of the present invention.

  The liquid crystal display device shown in FIG. 2 includes a lighting device 11 such as a backlight that emits light, a thin polarizing plate 12 disposed on the lighting device 11, and a liquid crystal panel 132 disposed on the thin polarizing plate 12. And the polarizing plate 133. That is, the thin polarizing plate 12 according to the present invention is disposed between the liquid crystal panel 132 and the lighting device 11.

  The liquid crystal panel 132 is a transmissive liquid crystal panel, and is configured by sandwiching a liquid crystal material or the like between glass and a transparent resin substrate. In the liquid crystal display device of FIG. 2, description of various optical elements such as a polarizing plate protective film, a retardation film, a diffusion plate, an alignment film, a transparent electrode, and a color filter that are usually used is omitted.

  In the liquid crystal display device having such a configuration, the light emitted from the illumination device 11 is incident from the base side of the substrate 1 of the thin polarizing plate 12 and is emitted from the wire side through the liquid crystal panel 132 to the outside. (Arrow direction in the figure). In this case, since the thin polarizing plate 12 exhibits an excellent degree of polarization in the visible light region, a display with high contrast can be obtained. Further, when higher contrast is required, light (external) incident from the outside of the polarizing plate 133, that is, from the direction opposite to the lighting device 11, is transmitted through the liquid crystal panel 132 and reflected by the thin polarizing plate 12. In order to prevent returning to the outside of the liquid crystal panel 132 again, an absorption type polarizing plate 131 using a dichroic polarizing material such as iodine or liquid crystal is interposed between the thin polarizing plate 12 and the liquid crystal panel 132. It is preferable to insert the thin polarizing plate 12 with the polarization axis aligned. In this case, the absorption type polarizing plate preferably has a high transmittance and may have a low degree of polarization.

Next, examples performed for clarifying the effects of the present invention will be described.
(Preparation of a substrate having a grid-like convex part)
-Creation of fine concavo-convex lattice shape A fine concavo-convex lattice was formed on a substrate coated with a photoresist on glass by using an electron beam drawing method. When the surface and cross section of this resist pattern were observed with a field emission scanning electron microscope (FE-SEM), the pitch and height of the fine concavo-convex grating were 115 nm / 130 nm (pitch / height), respectively. It was found that the cross-sectional shape was a substantially trapezoidal shape, the shape from the upper surface was a striped lattice shape, the width of the convex portion was 45 nm, and the width of the valley portion was 70 nm.

Nickel stamper fabrication The obtained resist pattern surface with a 115 nm pitch was coated with 30 nm of gold as a conductive treatment by sputtering, and then electroplated with nickel, and a nickel stamper having a fine concavo-convex grating with a thickness of 0.3 mm on the surface. Was made.

・ Preparation of lattice-shaped convex transfer film using UV curable resin Apply about 1 μm of UV curable resin (PAK01 manufactured by Toyo Gosei Co., Ltd.) to a 40 μm thick polyethylene terephthalate resin film (hereinafter referred to as PET film). On the nickel stamper having the 115 nm pitch fine concavo-convex grating on the surface with the surface facing down, air is placed between the nickel stamper and the PET film from each end, and the central wavelength of 365 nm is from the PET film side. Ultraviolet rays were irradiated at 1000 mJ / cm ² using an ultraviolet lamp to transfer the fine uneven lattice of the nickel stamper. The obtained lattice-like convex transfer film was observed by FE-SEM, and it was confirmed that the cross-sectional shape was substantially trapezoidal and the shape from the upper surface was a striped lattice.

(Preparation of polarizing plate with high degree of polarization: Examples)
Formation of Dielectric Layer Using Sputtering Method A lattice-shaped convex transfer film produced using an ultraviolet curable resin as described above was coated with a dielectric using a sputtering method. In this embodiment, a case where silicon nitride is used as a dielectric will be described. The dielectric was coated at an Ar gas pressure of 0.67 Pa, a sputtering power of 4 W / cm ² , and a coating speed of 0.22 nm / s. As a layer thickness comparison sample, a glass substrate having a smooth surface was inserted into the apparatus simultaneously with the lattice-shaped convex transfer film, and film formation was performed so that the dielectric laminate thickness on the smooth glass substrate was 5 nm.

-Metal deposition using vacuum deposition method After forming a dielectric layer on the lattice-shaped convex transfer film, a metal wire was formed using an electron beam vacuum deposition method (EB deposition method). In this example, aluminum (Al) was used as the metal. Deposition was performed with a degree of vacuum of 2.5 × 10 ⁻³ Pa, a deposition rate of 20 nm / s, and a substrate temperature of room temperature. As a layer thickness comparison sample, a glass substrate having a smooth surface was inserted into the apparatus at the same time as the dielectric laminated lattice-shaped convex transfer film, and vapor deposition was performed so that the Al deposition thickness on the smooth substrate was 170 nm. Note that the angle θ formed by the normal of the substrate surface and the evaporation source in a plane perpendicular to the longitudinal direction of the lattice was 20 °.

・ Elimination of unnecessary metal by etching After laminating dielectric and Al on the lattice-shaped convex transfer film, the film is treated in a 0.1 wt% sodium hydroxide aqueous solution at room temperature for a treatment time of 30 seconds to 120 seconds. In FIG. 1, the substrate was washed (etched) while changing at intervals of 10 seconds, and immediately washed with water to stop the etching. The film was dried to obtain a thin polarizing plate. The film thickness was 41 μm.

(Evaluation of polarization performance by spectrophotometer)
About the thin polarizing plate of the obtained Example, the degree of polarization and the light transmittance were measured using the spectrophotometer. Here, the transmitted light intensity in a parallel Nicols state and a crossed Nicols state with respect to linearly polarized light was measured, and the degree of polarization and the light transmittance were calculated from the following equations. The measurement wavelength range was 400 nm to 700 nm as visible light.
Polarization degree = [(Imax−Imin) / (Imax + Imin)] × 100%
Light transmittance = [(Imax + Imin) / 2] × 100%
Here, Imax is the transmitted light intensity at the time of parallel Nicols, and Imin is the transmitted light intensity at the time of crossed Nicols.
As a result, the degree of polarization of the thin polarizing plate etched for 90 seconds was 99.91%, and the light transmittance was 41.9%.

(Reflectance evaluation)
About the thin polarizing plate of the obtained Example, when the light incident on the wire grid surface at an incident angle of 8 degrees was measured using a spectrophotometer, it was 41.3%.

(Preparation of thin polarizing plate: Comparative Example 1)
The iodine-containing PVA film was thinned to a thickness of 10 μm, and an TAC film having a thickness of 20 μm was laminated on both sides to prepare an absorption type polarizing plate. About this absorption type polarizing plate, the polarization degree and the light transmittance were investigated as described above. As a result, the degree of polarization was 96.5% and the light transmittance was 46.8%. For this reason, this absorption-type polarizing plate did not exhibit sufficient optical performance. In particular, the degree of polarization is considered to be a low value because there is not enough iodine to exhibit polarization performance.

(Preparation of thin polarizing plate: Comparative Example 2)
The brightness enhancement film (laminated reflective polarizing film: DBEF) was thinned by peeling off the laminate at a half thickness portion to a thickness of 50 μm. About this reflection type polarizing plate, polarization degree, light transmittance, and reflectance were investigated as mentioned above. As a result, the degree of polarization was 90.2%, the light transmittance was 53.1%, and the reflectance was 45.2%. For this reason, sufficient optical performance was not exhibited.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, the dimensions, materials, and the like in the above-described embodiment are illustrative, and can be changed as appropriate. Moreover, the polarizing plate in the said embodiment does not need to be a plate-shaped member, and may be a sheet form and a film form as needed. In addition, various modifications can be made without departing from the scope of the present invention.

It is sectional drawing which shows a part of thin-type polarizing plate which concerns on embodiment of this invention. It is a figure which shows the liquid crystal display device using the thin-shaped polarizing plate which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 1a Lattice-like convex part 2 Dielectric layer 3 Metal wire 11 Illuminating device 12 Thin polarizing plate 131,133 Polarizing plate 132 Liquid crystal panel

Claims (3)

  A thin polarizing plate having a thickness of 80 μm or less, a degree of polarization of 99.9% or more, a transmittance of 35% or more, and a reflectance of 30% or more.   It is comprised by the base material which has a grid | lattice-like convex part on the surface, the dielectric material layer provided on the area | region containing the said grid-like convex part, and the metal wire provided on the said dielectric material layer. The thin polarizing plate according to claim 1.   A liquid crystal panel, an illuminating means for irradiating the liquid crystal panel with light, and the thin polarizing plate according to claim 1 or 2 disposed between the liquid crystal panel and the illuminating means. A liquid crystal display device.

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