JPH0315005A - Optical phase difference plate and production thereof - Google Patents

Abstract

PURPOSE:To obtain the optical phase difference plate which has high transparency and can be used as a lambda plate without being worked to a special shape, etc., by forming the crystal structure of a vinylidene fluoride resin as a beta type structure and specifying the retardation value to 500 to 650nm. CONSTITUTION:The optical phase difference plate is constituted of the film which consists of the compsn. consisting of the vinylidene fluoride resin and methyl methacrylate resin at >=65/35 to <=85/15 mixing ratio by weight and is stretched and oriented. The crystal structure of the vinylidene fluoride resin consists mainly of the beta type structure and the film is so formed as to have dimensional stability and to have the retardation value ranging 500 to 650nm. The adequate use of the above-mentioned plate as the lambda plate for phase compensation for the purpose of preventing coloration of a liquid crystal display for black and white displaying is possible in this way. The phase compensation which is lighter in the weight of the device and lower in cost than the phase compensation consisting of the conventional liquid crystal layer is thus obtd.

Description

[Detailed description of the invention]

[Industrial Field of Application J] The present invention relates to a plastic optical retardation plate used in an optical control element, and in particular to an optical retardation plate suitable for use in phase correction to prevent coloring of the screen of a black-and-white liquid crystal display. Regarding the retardation plate. [Jubei Technology J] In a transmissive monochrome liquid crystal display, the incident light first passes through a polarizing plate on the back side and becomes linearly polarized light, then enters the liquid crystal layer and changes to elliptically polarized light. If this elliptically polarized light is emitted through a polarizing plate as is, the degree of circularly polarized light differs depending on the wavelength, so the intensity of the transmitted light will differ, causing coloration on the display. Therefore, in order to prevent coloring, phase interpolation is necessary to return the elliptically polarized light to linearly polarized light.
A black and white display has been obtained by layering a phase compensation liquid crystal layer on top of the display liquid crystal layer, but this has been problematic in terms of weight and cost. For this reason, it is desired to use a transparent plastic film with oriented molecules as an optical retardation plate instead of a liquid crystal layer for phase trapping. Here, an optical retardation plate is a film or sheet-like material that has birefringence, and when a light ray passes through it, the difference in refractive index in two mutually orthogonal directions (1) In order to prevent discoloration of the above-mentioned black and white liquid crystal display, it is necessary to use a so-called λ plate in which the phase difference between the output wavelength and the input wavelength λ is equal to the input wavelength.
Although the application of λ plates to various optical applications is being considered, there is currently no satisfactory product. For example, what has been proposed for the λ plate is two or more optically anisotropic films or sheets with birefringence stretched in the uniaxial direction so that their optical principal axes are perpendicular to each other. A method of overlapping (Japanese Unexamined Patent Publication No. 167304/1983),
Alternatively, there is one λ plate that is not superimposed on each other (Japanese Unexamined Patent Publication No. 189804/1989!). In addition, there is a retardation plate that is made by cutting a birefringent crystal on an inclined plane with respect to an optical pongee (Japanese Patent Application Laid-Open No. 62-218905), which deals with variations in the wavelength of the light source. It is a retardation plate processed into a mold. [Problem to be Solved by the Invention 1] The present invention is a single film or sheet having a uniform thickness without being processed into a special shape, has high transparency, can maintain its transparency, and has a letter size of 3. value R is 50
The present invention aims to provide an optical retardation plate that can be used as a λ plate and has a retardation that maintains an arbitrary constant value within the range of 0 to 650 n-. The mutually orthogonal phase difference δ is as follows: δ=(27r/A)(Tle − 7to)d=(
:)r/A)-ΔTl-d. Here, d is the thickness of the retardation plate, Tle and Tto are the refractive indexes for orthogonal angles, and λ is the wavelength of the incident light. Δn is the birefringence, and ΔTl = (71 e − no). Moreover, the retardation value R is R=Δn-d (unit n
*). When the wavelength of the incident light changes, the phase difference changes, so it is necessary to adjust the retardation plate according to the wavelength of the incident light. The average wavelength of natural light is 550 nm, but the average wavelength of the commonly used sodium D line is 589 nm. When trying to obtain a λ plate, it is necessary that the retardation value R be the same as the wavelength of the incident light beam, and the retardation plate used in liquid crystal displays must have a retardation value R within the range of 500 to 6500. It is required to become.
Since the thickness d of an optical retardation plate used in a liquid crystal display is about 50 to 200 μ pupil, the desired birefringence Δn is determined according to the retardation values R and d. When considering the use as a λ plate as described above, the birefringence Δn of the plastic that makes up the film or sheet is
It is necessary that the value is positive and large. Conventionally, polycarbonate and polyvinyl alcohol are known as transparent plastics with molecular orientation. Vinylidene fluoride-based FJ4 resin, represented by vinylidene poly77ide (PVDF), has molecular orientation, and the stretched film of P■Ko has a refractive index in the stretching direction of nI1 and a refractive index in the direction perpendicular to the stretching direction. If n soil is the birefringence ΔTI=
In addition to showing a large positive value, (71+1-T'l) has excellent properties such as weather resistance, chemical resistance, and dust resistance, but PVDF is crystalline and has insufficient transparency. Films containing only PVDF have not been used as optical retardation plates. On the other hand, methyl methacrylate resins, typified by polymethyl methacrylate (PHM^), have a mediocre birefringence Δn, but are amorphous and have excellent transparency. The present inventor focused on this point and developed a mixed system of vinylidene fluoride resin and methyl methacrylate resin that has transparency and a desired birefringence, and has characteristics suitable for an optical retardation plate. I did research to find out. For the mixed system of Jumai, P■ Kano and PMM^, the PVDF content is 35% by weight or less! Transparency is good in some cases, but
There is a report that transparency decreases rapidly when the amount of PVDF increases (USP 3459834, 1969).
. However, even if a film or sheet with a PVDF of 35% or less is transparent, the PVDF is
Since DF,l is small, it does not have enough birefringence to be used as a λ plate. In addition, in the mixed system of PVDF and PMM^, for those with a composition of Pv leaf of 14 to 60% by weight, PVDF/P
There is a report that the birefringence Δn changes with the blending ratio of MM^, stretching ratio, and stretching temperature (Bern
dR, IIal+n and Joachim II
, Wendorff, ``POLYMER''', Vo
l. 26, ρpl619-1622 (1985))
. However, in this document, PVDF is 60% by weight.
There are no reports of more m or no, usually PV
It was thought that the higher the composition ratio of DF, the lower the transparency, so it cannot be expected from this document that a material with a larger amount of PVDF would be used for applications that require transparency, and it is not suitable for use as a λ plate. There is no consideration given to the use of Also, the letter decisin value is lIi? rllll's! It is also unclear whether it will be maintained without changing over time. According to the research of the present inventor, PVDF and PM
Films or sheets produced by simply stretching the I4^ mixed composition in a certain shape do not have a gap in which the retardation value cannot maintain the original value, and depending on the composition, the transparency also decreases over time. This is because it has been found that Therefore, it is not possible to predict an optical retardation plate that can be used as a λ plate from this document. The present invention provides a PVDF/PHMA mixed film or sheet that maintains transparency over a period of time,
The present inventors have discovered a film or sheet whose retardation value R maintains a certain value in the range of 500 to 650 nm for a long period of time, and has made it to provide an optical retardation plate that can be used as a λ plate. [Sendan J for Solving the Problems The optical retardation plate according to the present invention has a mixing ratio of vinylidene fluoride resin and methyl methacrylate resin in a weight ratio of 65/35 or more and 85/15 or less. The crystal structure of the vinylidene fluoride resin is mainly a β-type structure, the film or sheet has dimensional stability, and has a retardation value R.
is in the range of 500 to 650 nm. Here, when the crystal structure of vinylidene fluoride resin is mainly β-type structure, it means that the crystal fraction of β-type VT structure is 50% or more in the infrared absorption spectrum, that is, the crystal fraction of A-type structure is 50% or more. means less;
The crystal fraction of β-type VT structure is preferably 60% or more, more preferably 70% or more. The measurement method is S. The method of Osaki et al.
al or Polymer Science Vol.
13, 1071-1083 (1975))
Based on the following exposure: That is, there is a peak for crystals with an α-type structure at a wave number of 530 cm-' in the infrared absorption spectrum, and a peak for crystals with a β-type structure is at a wave number of 510 cm-'. From the collection of the positions of each peak, the absorbance for the α configuration is Dsxo=lofl+ocIo/I)53. The absorbance for the β-type configuration is D s+o=lOf+o(ro/I)s+. Therefore, the crystal fraction of the β-type structure can be calculated using the following formula. The optical retardation plate according to the present invention is manufactured as follows.
In other words, in the method for manufacturing an optical retardation plate according to the present invention, the mixing ratio of the vinylidene heptatide resin and the methyl methaxolate resin is 65% by weight.
A mixture having a composition of 35 or more and 85/15 or less is uniformly kneaded, formed into a film or sheet by melt extrusion, and then steeply rolled to form a film or sheet in which the crystal structure of vinylidene fluoride a {Jffl is β type. After making the structure the main part, the film or sheet is coated with 25 to 150
The 'vf' characteristic refers to stretching at 50°C to 160°C, followed by heat treatment at 50 to 160°C. In the present invention, vinylidene fluoride l {As the fat, vinylidene fluoride homopolymer, copolymers containing 50 mol% or more of vinylidene fluoride at the Vt or Jjl position, and two or more of these polymers are used. It may also be a polymer blend. Suitable materials copolymerizable with vinylidene fluoride include tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trifluorochloroethylene, vinyl fluoride, and the like. In addition to the methyl methacrylate homopolymer, the methyl methacrylate-based resin contains 70 mol% or more of methyl methacrylate monomer as a constituent unit and 30 mol% of acrylic ester or methacrylic ester other than methyl methacrylate. Copolymers containing the following, and furthermore, polymer blends consisting of 249 or more of these polymers. In addition, examples of suitable acrylic esters in the above-mentioned copolymer include methyl acrylate, ethyl acrylate, and probyl acrylate, and examples of methacrylic esters other than methyl methacrylate include ethyl methacrylate and probyl methacrylate. Ru. In addition, a small amount of a third component can also be included. Vinylidene fluoride resin/
In a film or sheet of a mixed methyl methacrylate resin, the birefringence Δn changes depending on the mixing ratio of vinylidene fluoride resin/methyl methacrylate tirfrrI and the stretching ratio. Vinylidene fluoride M tree W1/
As for the mixing ratio of the methyl methacrylate resin, the larger the amount of the vinylidene fluoride resin having a large birefringence, the larger the birefringence Δn of the mixed system. I/tardation value R
In order to keep the wavelength in the range of 500 to 650 nm, it is desirable that the mixing ratio of vinylidene fluoride resin be as large as possible. Furthermore, in order to stably maintain the letter score R, which is set in the range of 500 to 650 questions, it is desirable that the mixing ratio of the vinylidene fluoride resin be as high as possible. On the other hand, regarding transparency, the above vinylidene fluoride F
It is made by uniformly kneading JIN and methyl methacrylate resin at various mixing ratios, melting and shaping into a film or sheet, quenching, stretching at 90°C, and then heat treatment.
The treated film or sheet must have a light transmittance as shown in FIG. 11 L Ta,
fjS1 Figure ii, iHI11 treatment l150μm<7)
J! This is a graph showing the light transmittance versus weight percent of methyl methacrylate resin when a 7-inch sheet was heat-treated at 100° C. for 10 minutes. In the fjS1 diagram, the light transmittance gradually changes from 100% by weight of the methyl methacrylate resin, that is, 0 weight% of the vinylidene fluoride resin, as the amount of the vinylidene fluoride resin increases. However, vinylidene fluoride'A6
{1] FF The light transmittance reaches a minimum value around 50% by weight, and when the vinylidene fluoride resin exceeds 50% by weight, the light transmittance increases again, and the 7-/vinylidene fluoride resin reaches a minimum value of 70% by weight.
It shows a huge value near ffi amount%. What is noteworthy in the fjS1 diagram is that although the sheet was heat-treated after stretching, the vinylidene fluoride resin content was in the range of 58 to 85 ffl, and the sheet had a very high light transmittance. It is to have. Further, according to the inventor's experiments, the sheet before being subjected to the heat treatment after the stretching treatment has a light transmittance as shown in the fP12 diagram. That is, vinylidene fluoride resin has 5
Without having a minimum value near 0% by weight, the sheet has a light transmittance as high as that of methyl methacrylate based resin Jffll00% by weight up to 80% by weight of vinylidene fluoride based resin. Therefore, considering only the requirement of transparency, heat treatment seems to be rather undesirable.
Generally, in vinylidene fluoride resin formulation systems,
This is because heat treatment is thought to promote the crystallinity of vinylidene fluoride resin and reduce its transparency. However, even sheets that are not subjected to heat treatment will undergo crystallization and change in light transmittance as shown in Figure 1 due to changes over time, for example, if they are left at room temperature for one to several months. This is further accelerated when used at temperatures higher than room temperature. In other words, vinylidene fluoride resin and methyl methacrylate are uniformly kneaded, molded, and sharply stretched so that the crystal structure of the vinylidene fluoride resin in the sheet before stretching is mainly β-type. , for sheets stretched at 25 to 150°C, 1M58 for vinylidene fluoride
It was revealed that there is a region where transparency is not inhibited in the range of ~85% speed. And the above specific!
As long as a material with a chemical composition of 1.1 to 1.1 is used, the presence or absence of heat treatment has no effect on transparency. However, the present inventor found that heat treatment after stretching improves the retardation value, as described later, and maintains a constant retardation value within the composition range of 65 to 85% by weight of the vinylidene heptatide resin. It was discovered that it also has the effect of holding For this reason, in the gI method according to the present invention, heat treatment after stretching treatment is adopted as an essential step, and by applying heat treatment to vinylidene fluoride resin containing 65 to 85% by weight, the letter pattern can be improved. We succeeded in obtaining a film or sheet that satisfies the twin conditions of citane value and transparency and is suitable for use as a λ plate. First, regarding the condition of transparency ν, from FIG.
The light transmittance power C is preferably around 70/30.
This is a condition for obtaining an excellent 7-inolem sheet with a transparency greater than 90%. The above IJ
The reason why transparency with a light transmittance of more than 90% can be obtained in the light range can be considered as follows. Methyl methacrylate resin is of poor quality and has excellent transparency, whereas vinylidene fluoride resin has fine crystals with a β-type structure and large spheres with a crystal diameter of several micrometers to several tens of micrometers. There are crystals with an α-type structure that elongate up to the crystal structure, and it is known that the growth of crystals with an α-type structure inhibits transparency, but in the case of the above range, vinylidene fluoride This is thought to be because the methyl methacrylate resin inhibits the formation of crystals of the α-type structure of the vinylidene fluoride resin 1m by sufficiently uniformly mixing the oil and the methyl methacrylate resin. In other words, this is considered to be because the above region is a special region in which the β-structured crystal is stabilized. In this area,
Although α-type hη crystals do not exist at all, as far as the crystal fraction in the infrared absorption spectrum shows, α-type hη crystals do not exist at all.
There are only a few crystals of η structure, less than 50%. In other words, a film or sheet with high light transmittance can be obtained in a composition range in which the crystal structure of the vinylidene fluoride resin is mainly a β-type structure, and in that composition range, the mixing ratio of the vinylidene fluoride resin can be reduced. Since it has a high birefringence, it is possible to obtain a desired birefringence. In the above, transparency has been described in terms of light transmittance that affects screen brightness 1rFj, but regarding the public price that affects image clarity, the optical retardation plate according to the present invention has a haze value of 2%. A smaller, clearer image can be obtained. As mentioned above, in a mixed system, the larger the amount of vinylidene fluoride resin, the larger the birefringence Δn,
If the shaped film or sheet is unstretched,
The birefringence Δn is insufficient to keep the retardation value within the range of 500 to 650 nm. It is necessary to increase the degree of crystal orientation and increase Δn by subjecting the formed film or sheet to a stretching process. However, no matter how high the stretching ratio is to obtain a birefringence that makes the bitterdesicon scale a desired value, it is practically meaningless if the value changes significantly over time. According to the findings of the present inventors, even if dimensional stability is achieved by heat treatment after stretching, for example, the composition ratio of vinylidene heptadide resin and methyl methacrylate resin is 5.
At 0750 or 60/40, a change in retardation value of 15% and 5%, respectively, was observed after 50 hours at 70°C. The inventor found that the more vinylidene fluoride resin there is, the more the stretching process J
! I! The retardation becomes more stable through the subsequent heat treatment, and the mixing ratio of vinylidene fluoride (O) fat and methyl methacrylate resin is 85/+H ratio.
It has been found that the letterform value is maintained almost constant when it is 35 or more, and with the configuration of the present invention, it is 90%
The present invention has been completed by discovering that the above-mentioned transparency can be satisfied. Vinylidene fluoride resin and methyl methacrylate resin +1
The desirable mixing ratio of ff is 70730 or more in terms of weight ratio8
It is less than 0/20. In the present invention, dimensional stability is defined as a shrinkage rate in the stretching direction of 2% or less after stretching and heating a film or sheet at 40°C for 24 hours. According to experiments, the shrinkage rate is 10% or more without heat treatment, whereas it is less than 2% with heat treatment. The temperature of the heat treatment to provide such dimensional stability is
50°C or more and 160°C or less, preferably 70 to 145
It is ℃. At temperatures lower than 50°C, the retardation value measured with a polarized microscope may change over time, and heating at temperatures higher than 160°C may cause operational problems as the film or sheet will soften. This is because the retardation value will not improve even if heated to a higher temperature. The heat treatment temperature is preferably higher than the search temperature of the optical retardation plate. Once heat-treated at a constant temperature, in the structure of the present invention, the retardation value does not change at lower temperatures and remains approximately constant. The reason why the retardation value is improved by this heat treatment is due to the increase in the crystallinity of the vinylidene fluoride resin and the increase in the birefringence based on the improvement in the molecular orientation of the amorphous part of the vinylidene fluoride resin. It is considered a thing. Even if the stretching ratio is small, the heat treatment increases the birefringence, so in the case of the present invention, a desired retardation value can be obtained even with a thin film or sheet with a thickness of 100 μm or less. In the method for manufacturing an optical retardation plate according to the present invention, first, a mixture consisting of the vinylidene fluoride resin and methyl methacrylate resin as raw materials in a weight ratio of 65/35 to 85715 is prepared. Knead evenly. Here, "uniformly" means that when a film or sheet is formed by melt extrusion and then rapidly cooled, the vinylidene fluoride a! The intention is to sufficiently knead the fat so that the crystal structure of the fat is mainly a β-type structure in the infrared absorption spectrum described above. When the degree of crosstalk is low, an α-type structure is exhibited, but as the degree of crosstalk is high, a β-type structure is exhibited. Specifically, after uniformly mixing both resins using a generally known method for uniformly mixing resins, such as a Henschel mixer sifro-pregnancy or a Bren r, a single- or twin-screw mixer is used. Melt-knead the mixture by appropriately setting the L/D, compression ratio, screws, etc. of the extrusion so that the resin and ll components are well kneaded using an extrusion rock etc., and manufacture pellets of the mixture. This can be carried out by a method using this pellet as a raw material, or by intra-particle polymerization of a methyl methacrylate monomer within the vinylidene fluoride resin particles.The material obtained by the above method is then rolled, usually T-die method (extrusion method using T-die), inflation method (
A film or sheet is obtained by melting or shaping into a film or sheet by extrusion method (using a linguine) or by using an extrusion mill of a type that allows good kneading. This film or sheet is formed by melt extrusion and then immediately released. The degree of sharpness is determined so that the crystal structure of the vinylidene fluoride tree Lm in the film or sheet of the stretched hole I is mainly a β-type structure. The crystal fraction of β-type structure is preferably 60% or more, particularly preferably 70% or more. Rapid cooling is a method of forcibly adding rapid cooling rather than leaving it at room temperature, and specifically, it is 80 degrees Celsius or less, preferably 40 degrees Celsius or less.
A method is employed in which at least one surface of the film or sheet is brought into contact with a liquid or solid refrigerant at a temperature of 0°C or lower, more preferably 25°C or lower. The thicker the film or sheet is, the more difficult it is for the center to be rapidly cooled, so the temperature of the refrigerant needs to be lower. Furthermore, the higher the mixing ratio of the vinylidene fluoride resin, the lower the temperature should be used for rapid cooling. Usually, quenching with water is sufficient, but quenching with a refrigerant of 10° C. or lower is preferable. The unstretched film or sheet thus obtained is stretched using a stretching mill such as a roll or tenter type. The temperature during stretching is 25°C or higher and 1.50°C or lower. If the temperature is less than 25°C, orientation unevenness tends to occur during stretching, and if the temperature exceeds 150°C, it approaches a molten state, making stretching difficult. The temperature is preferably 60 to 140°C, more preferably 80 to 130°C. 80℃, especially 60℃
If it is concave downward, the stability of the letter dacian will be slightly lacking, and 13
This is because when the temperature exceeds 0°C, especially 140°C, the degree of orientation is difficult to increase and processability is difficult. Stretching is performed on a film or sheet in which the vinylidene fluoride resin is in a molten or unmolten state, preferably in an unmolten state. The stretching is 1-tsumugi stretching or 2-tsumugi stretching. The stretching ratio is determined so that the retardation value is in the range of 500 to 650, since the retardation value is the product of the birefringence based on the degree of orientation of the film or sheet and the thickness of the film or sheet. In the case of 1 pongee stretching, the stretching ratio in the stretching direction is greater than 1 but not more than 3 times, preferably 1. 05 to 2.0 times, more preferably 1.1 to 1.5 times. In the case of 2III stretching, the product of the stretching ratio in the longitudinal direction and the stretching ratio in the lateral direction is set to be 1.3 to 9.5, preferably 1.5 to 6.0. The heat treatment after the stretching treatment is preferably carried out while applying stress (tension) so that the film or sheet is in a taut state at least at the final stage of the heat treatment. Moreover, the tension state is maintained even during the cooling process after the heat treatment. This is to prevent the film or sheet from deforming and to maintain a constant shape. The initial stage of heat treatment is performed with or without applying stress (tension) to the film or sheet. As mentioned above, the temperature of the heat treatment is 50°C or more and 160°C or less, preferably 70°C or more and 145°C or less, and the heat treatment time is 1 second or more, preferably 3 seconds or more, and more preferably 10 seconds or more. ．． Within the above temperature range, the lower the temperature, or the more stress is applied at the same temperature, the longer it takes. But,
It is common that heating for one hour or more does not change the effect even if heated for longer. Within 30 minutes at temperatures lower than 100℃, 100℃~1
Heating at 20°C for less than 10 minutes and at 120°C or higher for less than 5 minutes is enough to achieve the desired effect. Annealing may be performed after heat treatment if necessary. [Effect 1] In the method for manufacturing an optical retardation plate of the present invention, vinylidene fluoride resin and methyl methacrylate resin are mixed in a ratio of 65/3.
In order to uniformly knead the mixture with a specific blending ratio of 5 or more and 85/15 or less, it is melt-shaped, stretched, and then heat-treated.
Dimensional stability and retardation value of 5
It is possible to obtain a film or sheet that maintains a certain value within the range of 00 to 650 nm. At the above-mentioned specific composition ratio, the effect of uniform kneading and rapid cooling of the raw materials prevents the crystallization of the α-type structure of the vinylidene fluoride resin, and the β-type structure is mainly maintained stably. Therefore, the transparency of the film or sheet is not impaired even by the heat treatment after the stretching treatment, and a light transmittance of more than 90% is maintained. Examples and comparative examples are shown below. In each Example and Comparative Example, the retardation value R was measured using a Berek convensator manufactured by Olympus Optical Industries, Ltd.
i (average wavelength 589n+i) and the rI. Calculated from the product of . Moreover, the light transmittance and haze value were measured using Model TC-113 manufactured by Tokyo Denshoku Co., Ltd. according to JIS-K7105.

[Example 11] Polyvinylidene fluoride (manufactured by Kagaku Kogyo, trade name: KF Polymer #1100) and polymethyl methacrylate (manufactured by Kyowa Kagaku Kogyo, trade name: Parapetsu) IIR-1000
) Each was mixed at a weight fraction of 80/20, blended for 10 minutes using a dice blender, melted and kneaded using a single pongee extrusion to create mixed pellets, and then this pellet was shaped into a sheet using a T-shaped tool. The sample was extruded and passed through a cooling roll with water circulating inside to give an unstretched sheet with a thickness of 170 μm. The crystal fraction of β-type VT structure of PVDF in this unstretched sheet was 70%, and the retardation value was 220 nm. Subsequently, the film was uniaxially stretched 1.3 times at 90°C, resulting in a film with a thickness of 130μ and a retardation value of 41O.
It became n-1 seat. Further, the sheet was heated at 80°C under tension.
When heat treatment was performed for 45 minutes at a temperature ranging from The light transmittance of these sheets is 94% or more, and the haze value is 0.
．． It was 3% or less, and had extremely excellent transparency. The measurement results are shown in Table 1. Moreover, the crystal fraction of the β-type structure of PVDF in these sheets was within the range of 75 to 85%. All of these sheets had a shrinkage rate of 1.5% or less after being heated at 40°C for 24 hours, and had dimensional stability. Furthermore, the above sheet was placed in a constant temperature drying oven at 70℃50.
After a period of time, the retardation value, light transmittance, and 1/haze value were measured, and as a result, there was almost no change. [Example 2I An unstretched sheet with a thickness of 160 μm was prepared in the same manner as in Example 1, and uniaxially stretched at 90° C. for 1. When the setting was set to 15 times, the thickness of the sheet after stretching was 140
The crystal fraction of β-type structure of P■ leaf was 72%, and the retardation value was 345 nm. When this sheet was heat treated for 10 minutes in the range of 110°C to 130°C under the same tension as in Example 1, the retardation value was 500 at each heat treatment temperature.
The value was within the range of ~650 nm, and a sheet that could be used as a λ plate was obtained. The light transmittance of this sheet was 94% or more in all cases, and the weight value was 0.3% or less with an I/1 deviation. The measurement results are shown in Table 1. In addition, the crystal fraction of β-type structure of PVDF in these sheets was within the range of 75 to 85%. All of these sheets had a shrinkage rate of 1.5% or less after being heated at 40° C. for 24 hours, and had dimensional stability. Further, the above sheet was placed in a constant temperature drying oven at 70°C for 50 hours, and the retardation value, light transmittance, and haze value were measured, and as a result, there was almost no change. [Example 3] An unstretched sheet having a thickness of 174 μm was prepared in the same manner as in Example 1, with the weight fraction of polyvinylidene fluoride and polymethyl methacrylate being 70,730. The crystal fraction of the β-type structure of PVDF in this unstretched sheet was 78%, and the retardance a value was 190 nm. This unstretched sheet was uniaxially stretched 1.15 times at 80° C., resulting in a thickness of 150 μm and a retardation value of 417 nm. When this stretched sheet was heated under tension at a temperature in the range of 80°C to 100°C for 45 minutes, the retardation value was determined to be a specific value within the range of 500 to 650n for each heating temperature. A sheet that can be used as a λ plate was obtained. The light transmittance of this sheet is 94% or more, and the haze value is 0.3.
% or less. The measurement results are shown in Table 1. Further, the crystal fraction of the β-type structure of PVDF in these sheets was within the range of 80 to 95%. Both of these sheets after 24 hours at 40°C.
The shrinkage rate was 1.5% or less, and the product had dimensional stability. Furthermore, the retardation value, light transmittance, and haze value were measured after placing the above sheet in a constant temperature drying oven for 50 hours at 70°C. As a result, the change rate of the retardation a value was 1.5 to 2.
．． It remained at 5%, with almost no other changes. [Example 4] A 130 μm thick sheet was produced in the same manner as in Example 1, except that the weight fraction of polyfluorinated vinylite and polymethyl methacrylate was changed to 65/35. The β-type crystal fraction of PVDF in this unstretched sheet was 76%, and the retardation silane value was 160n. This unstretched sheet was uniaxially stretched 1.3 times at 75°C, resulting in a thickness of 100 μm and a retardation value of 345 nm. This stretched sheet was heated at 80°C to 1
When heat treatment was performed at a temperature of ylAlII1 of 20° C. for 10 minutes, a sheet usable as a λ plate having a specific retardation value within the range of 500 to 600 nm was obtained for each heating temperature. The light transmittance of these sheets is 94% or more, and the haze value is 0.4%.
It was below. The measurement results are shown in Table 1. Moreover, the crystal fraction of the β-type structure of PVDF in these sheets was within the range of 80 to 95%. All of these sheets had a shrinkage rate of 1.5% or less after being heated at 40° C. for 24 hours, and had dimensional stability. Furthermore, the above sheet was placed in a constant temperature drying oven at 70℃50.
As a result of measuring the retardation value, light transmittance, and haze value after opening, the change rate of the retardation value was 2.0 ~
It remained at 3.0%, with almost no other changes. Comparative Example 1] An unstretched sheet having a thickness of 150 μm was prepared in the same manner as in Example 1, except that the weight fraction of polyvinylidene fluoride and polymethyl methacrylate was 90,710. The crystal fraction of the β-type structure of PVDF in this unstretched sheet was 28%, and the retardation value was 290 nm. This unstretched sheet was stretched once at 110° C. by a factor of 1.10, and as a result, the thickness was 140 μm and the retardation value was 480 nm. This stretched sheet was put under tension for 14
After heat treatment at 5°C for 45 minutes, 590nm
A sheet with a letter decimal value of 3 was obtained. Furthermore, the retardation value, light transmittance, and haze value of this sheet after being heated at 70°C for 50 hours were measured, and as a result, there was almost no change. However, this sheet has a light transmittance of 85%.
Moreover, the haze value was extremely high at 3.5%, and it could not be used as an optical retardation plate for preventing coloring of the screen of a liquid crystal display. Table 1 shows the characteristic values of the sheet. Furthermore, the crystal fraction of the β-type structure of PVDF in these sheets was all below 60%.

Comparative Example 21 An unstretched sheet having a thickness of 130 μm was prepared in the same manner as in Example 1, except that the weight fraction of polyvinylidene fluoride and polymethyl methacrylate was 60,740. The crystal fraction of β-type VTA of PVDF in this unstretched sheet was 76%, and the retardation value was 140 nm. This unstretched sheet was stretched 1.3 times at 75°C, resulting in a thickness of 100μ and a retardation value of 300n.
It became s. This stretched sheet was heated at 120°C under tension.
When heat-treated for 10 minutes at
．． It was 7%. The sheet characteristics iff are shown in Table 1. In addition, the crystal fraction of the Pv leaf β-type structure in this sheet was 80%. Furthermore, the shrinkage rate of this sheet after 24 hours at 40°C was 1.5.
% or less and had dimensional stability. However, the retardation value, light transmittance, and haze value were measured after 50 hours at 70°C by placing the above-mentioned sheet in a constant-temperature drying oven. As a result, the rate of change in retardation value was 5%. Comparative Example 31 An unstretched sheet having a thickness of 200 μm was prepared in the same manner as in Example 1, except that the weight fraction of polyvinylidene heptadide and polymethyl methacrylate was 50,750. The crystal fraction of the β-type structure of PVDF in this unstretched sheet was 78%, and the retardation value was 70 nm. When this unstretched sheet was stretched twice at 50°C, it had a thickness of 100 μm and a retardation value of 240 nm. This stretched sheet was held under tension for 13 minutes.
When heat treatment was performed at 0℃ for 45 minutes, the result was 650 na.
A sheet with a retardation value of
Retardation value after 50 hours at 0℃ is 750n
m, an increase of about 15%. Besides, 40
After 24 hours at ℃, the shrinkage rate was 3.5%, and it could not be used as an optical retardation plate for preventing coloring of the screen of a liquid crystal display. The characteristic values of the sheet are shown in Table 1. Also, the PV in these sheets
The crystal fraction of the β-type structure of DF was 83% without heat treatment after stretching, and 45% with heat treatment.
The β-type structure was not stabilized. [Example 5J An unstretched sheet having a thickness of 170 μm was obtained in the same manner as in Example 1 except that the weight fraction of polyvinylidene fluoride and polymethyl methacrylate was 85,715. The crystal fraction of the β-type structure of PVDF in this unstretched sheet was 65%. When this unstretched sheet was stretched 1.2 times by 1ld+ at 100°C, the thickness was 140 μm, the retardation value was 360 nm, and the light transmittance was 90%.
The haze value was 1.0%. When this stretched sheet was heated under tension at 100°C for 10 minutes, the result was 1
The crystal fraction of β-type structure of 1 V D F is 76%,
The retardation value was 520 nm. Table 1 shows the characteristics of the sheet. The shrinkage rate of this sheet after 24 hours at 40° C. was 1%, and it had dimensional stability as defined in the present invention. Also, put the above sheet in a constant temperature dryer at 70℃5.
When the retardation value, light transmittance and V haze value were measured after 0 hours, they were almost the same as the initial values. [Example 6] As in Example 1, an unstretched sheet with a thickness of 200 μl was produced using IlIIR. The crystal fraction of the β-type structure of PVDF in this sheet is 80%, which is 0, and the retardation value is 80.
It was ns+. This sheet was heated at 80°C in the longitudinal direction to 1.3
After being uniaxially stretched to 100%, it was then stretched at 90°C to
This was stretched twice to obtain a stretched sheet with a thickness of 100 μm. After completion of stretching, this biaxially stretched sheet is heated to about 3
% relaxation heat treatment was applied. 1!1 of the sheet after heat treatment
The pupil size is 105μ and the retardation value R is 590rv+.
The light transmittance was 94%, the shrinkage rate after 24 hours at 40°C was within 1%, and the crystal fraction of the β-type structure was over 80%. Table 1 Example PVDF/PMM^ Rolling I1 Processing Thickness No.
μ Ugly 1 80/20
1.3 times 1302 3 4 5 85/15 1.3 times 1.2 times 140 ■ 90710 1.1 times 140 〃 2 60740 1.3 times 100 3 50750 2 times 1oo Heat treatment ℃ 80℃ 45 minutes before heat treatment 90℃ 45 minutes 100℃ 45 minutes Before heat treatment 110℃ 10 minutes 120℃ 10 minutes 130℃ 10 minutes Before heat treatment 80℃ 45 minutes ℃10 minutes 120'' CIO minutes Before heat treatment Before heat treatment 145℃ 45 minutes Before heat treatment 120℃ 10 minutes Before heat treatment 130℃ 45 minutes R Light transmission rate Haze value 94.4 94.4 94.4 94.3 94 .3 94,3 94.3 94.3 94.4 94.4 94.4 94.3 94.2 94.2 94.2 94.0 90.O 85.0 85.0 93.5 93.0 94.0 30.5 [Effects of the Invention] According to the present invention, a single film or sheet having a uniform thickness maintains a light transmittance of more than 90%,
Furthermore, it has dimensional stability and has a retardation value R of 500.
Since it is possible to obtain an optical retardation plate whose retardation value is within the range of ~650n-1 and whose retardation value is kept constant,
It can be suitably used as a phase compensation lambda plate to prevent coloring in black-and-white liquid crystal displays, and the device is lighter in weight than conventional phase compensation systems using liquid crystal layers.
Moreover, it can be provided at a low price.

[Brief explanation of drawings]

? The tS1 diagram shows the results of sheets obtained by uniformly kneading vinylidene fluoride resin and methyl methacrylate resin at various mixing ratios, melting and shaping the resin into a sheet, and heat-treating the sheet after stretching. It is a graph showing light transmittance versus resin weight percentage. FIG. 2 is a graph showing the light transmittance relative to the weight percent of the methyl methacrylate resin for the sheet shown in FIG. 1 before being subjected to the heat treatment. Yu Uzotsu Prison (o/o) Inukaba 41 boundary rate (%)

Claims (2)

[Claims] (1) A stretched or oriented film or sheet having a composition in which the mixing ratio of vinylidene fluoride resin and methyl methacrylate resin is 65/35 or more and 85/15 or less by weight, and the crystals of vinylidene fluoride resin An optical retardation plate characterized in that the structure is mainly a β-type structure, the film or sheet has dimensional stability, and a retardation value R is within a range of 500 to 650 nm. (2) A mixture of vinylidene fluoride resin and methyl methacrylate resin in a weight ratio of 65/35 to 85/15 is uniformly kneaded, formed into a film or sheet by melt extrusion, and then rapidly cooled. After the crystal structure of the vinylidene fluoride resin in the film or sheet is made to be mainly β-type structure, the film or sheet is stretched at 25 to 150°C, and after the stretching process, A method for manufacturing an optical retardation plate, characterized in that heat treatment is performed at ~160°C.