JPH04245202A - Phase difference plate - Google Patents

Abstract

PURPOSE:To eliminate chromatic unevenness and enlarge the degree of freedom in processing, by embodying ring-form olephin polymeride as a film or sheet ductilely stretched uniaxially, and giving it a specific retardation value and dispersion. CONSTITUTION:Ring-form olephin polymeride is embodied as a film or sheet ductilely stretched uniaxially, and its retardation value shall be 135-700nm and dispersion by within 15nm. Forming a phase difference plate from this olephin polymeride is made through such procedures as embodying into film or sheet by the solvent casting method, calender method, etc., and stretching uniaxially according to the purpose.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD This invention relates to a novel retardation plate using a cyclic olefin polymer.

0002

[Prior Art] A retardation plate is a film or sheet having birefringence, which causes a difference in the refractive index in two orthogonal directions to the light that passes through the retardation plate, so that the light rays that are perpendicular to each other after passing through the retardation plate differ. This gives a phase difference of .

[0003] This retardation plate is used in various anti-glare filters.
It is also used to make liquid crystal displays clearer. For the above applications, a retardation plate is used that produces a phase difference in the range of 1/4 to 1λ with respect to the wavelength λ of the incident light beam.

As materials constituting the above-mentioned retardation plate, cellulose resin, polyvinyl alcohol resin, and recently polycarbonate resin have been put into practical use. -189804 publication and JP-A-1-201
This is reported in Publication No. 608, etc.

[0005]

[Problems to be Solved by the Invention] However, although the above-mentioned retardation plate is being considered for various uses such as anti-glare purposes and sharpening of liquid crystal display, it is still difficult to obtain sufficient quality, that is, retardation. - At present, there is no retardation plate that has uniform dimensional stability, moisture resistance, solvent resistance, etc. Specifically, the retardation value unevenness is 1/4 to 1
For a λ plate, the thickness is required to be within 15 nm, preferably within 10 nm.

[0006] In addition, retardation plates are often used by laminating them with polarizing plates, etc., and are required to have solvent resistance during adhesive processing and dimensional stability under moist heat after lamination. The current situation is that even the polycarbonate resins currently available are not fully satisfactory.

[0007] Here, the retardation value (hereinafter referred to as R value)
is the thickness t of the film or sheet and the thickness t of the film or sheet.
The product of the birefringence Δn of the retardation film or sheet is expressed as R = t × Δn, and when the retardation film or sheet is placed under crossed Nicols so that its optical principal axis is 45 degrees, the smaller the value is, Indicates that the hue is uniform.

[0008]

[Means for Solving the Problems] The present invention provides a film or sheet formed by uniaxially stretching a cyclic olefin polymer, the film or sheet having a retardation value of 135 to 135.
This is a retardation plate characterized by a wavelength of 700 nm and a variation within 15 nm.

[0009] The cyclic olefin polymer mentioned here is

[
0010

[Chemical formula 1]

Polyolefin 3 is a polyolefin 3 obtained by hydrogenating a polymer 2 having an unsaturated bond obtained by ring-opening polymerization of a norbornene monomer 1 derived from cyclopentadiene shown in the following. This polyolefin 3 is colorless and transparent because it is amorphous, and exhibits mechanical toughness and a high glass transition temperature because it has a rigid five-membered ring in the polymer main chain.

In order to use a cyclic olefin polymer as a retardation plate, it is formed into a film or sheet by a known film forming method, that is, a solvent casting method, a calendering method, or an extrusion method, and then uniaxially shaped into a film or sheet. This is achieved by stretching accordingly. Methods for stretching in the uniaxial direction include known stretching methods such as a longitudinal uniaxial stretching method using a pair or more of rolls with different circumferential speeds, a transverse uniaxial stretching method using a tenter, and an inter-roll compression stretching method. You can choose from.

[0013] The R value covers 1/4 to 1λ (1λ = 589 nm) for anti-glare purposes and for sharpening liquid crystal displays.
A value of 135 to 700 nm is preferable. For liquid crystal display applications, the variation in R value is limited to 15 nm. If it is larger than that, the color will be uneven and cannot be used.

[0014] The stretching temperature is the glass transition temperature (Tg)
As mentioned above, it is preferable that the temperature is 10 to 25°C higher than Tg, but this is not particularly limited as it varies depending on the degree of polymerization of the polymer. If the temperature is low, stress concentration type stretching occurs and R
Value dispersion increases. On the other hand, if the temperature is too high, it becomes difficult to develop birefringence and a large stretching ratio is required, resulting in problems such as R-value variation and increased neck-in.

The stretching ratio depends proportionally on the thickness of the film or sheet, and also on the stretching temperature, but is between 10 and 3.
00% (1.1 to 3 times), preferably 15 to 110% (
1.15 to 2.1 times) is better. If it is lower than this, it will become thicker than necessary, and if it is higher than this, problems such as variation in R value and increase in neck-in may occur.

[0016]

[Function] As a characteristic of the cyclic olefin polymer used in the present invention, a photoelastic constant of 1 is compared to the conventionally used polycarbonate.
Since it is about 1/10 lower than carbonate, the R value can be kept low in the film forming stage, and a sheet or film with a uniform R value can be obtained. Further, in the stretching stage, fine control of the R value becomes possible. 2. Due to its low hygroscopicity, it has excellent dimensional stability and durability under moist heat. 3. High solvent resistance makes secondary processing such as adhesive processing easy. The retardation plate of the present invention is based on these characteristics.

[0017]

[Examples] The present invention will be further explained below based on Examples.

Example 1 As a cyclic olefin polymer, ZE manufactured by Nippon Zeon Co., Ltd.
Using ONEX280, press temperature 32 by hot press molding
At 0℃, thickness 300μ, width 250mm, length 250m
m sheets were obtained.

With this sheet heated to 150°C, hold the two opposing sides with clamps and stretch at a stretching rate of 15%.
It was stretched 45% in one direction in 1 minute.

The obtained sheet has an average R value of 591 nm and is a one-wavelength retardation plate, and the variation in R value is 6 nm.
It was uniform with m.

[0021] The R value was measured using a K
Using an OBRA-21D automatic birefringence meter, measurements were taken at 32 points at intervals of 25 mm in the vertical and horizontal directions in a central area with a width of 100 mm and a length of 200 mm, which is free from the effects of necking and clamping.

[0022] Next, this 100 x 200 mm sheet was kept in an atmosphere of 80°C and 90% relative humidity for 24 hours.
When the amount of deformation was measured, no deformation was observed.

Examples 2 to 4

[0024]

[Table 1]

The same procedure as in Example 1 was carried out except for the conditions shown below. The results are also shown. However, only in Example 3, the R value was measured at 36 points in a range of width 75 mm and length 300 mm, as in Example 1, because the stretching ratio was high and the influence of neck-in was large.

[0026]

[Effects of the Invention] As described above, the retardation plate of the present invention has no color unevenness under crossed nicols, has extremely good dimensional stability,
Furthermore, since a raw material polymer with a low photoelastic constant is used, the R value can be easily controlled during stretching.

Claims (1)

[Claims] Claim 1: A film or sheet formed by stretching a cyclic olefin polymer in the uniaxial direction, the retardation value of which is 135 to 700 nm, and the variation is within 15 nm. A retardation plate featuring