JP2007286388A - Thin polarizing plate provided with optical compensation film and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin polarizing plate having an optical compensation operation and to provide a manufacturing method therefor. <P>SOLUTION: The polarizing plate comprises: a polarizing films 223, 233; transparent substrates 221, 231, 232; a first optical compensation film 241; and a second optical compensation film 242, wherein each polarizing film has a polarizing operation and is provided with the upper surface and the lower surface, the transparent substrate 221 is stuck to the upper surface of the polarizing film 223, the first optical compensation film 241 is stuck to the lower surface of the polarizing film 223, the second optical compensation film 242 is joined to the side opposite from the polarizing film 223, of the first optical compensation film and thereby one sheet of transparent substrate which is originally provided in the polarizing plate is replaced with the optical compensation film and, at the same time, the contrast and color hue produced at an angle in the oblique direction of the liquid crystal display device is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thin polarizing plate provided with an optical compensation film and a method for manufacturing the same, and more particularly to an optical compensation film on a polarizing plate applied to an inner flat-panel LCD liquid crystal display device. The present invention relates to an optical compensation film that can be provided and a method for manufacturing the same.

Liquid crystal displays (LCDs) are widely used on various electronic information devices, and are used in televisions, personal computers, mobile phones, PDAs, and the like. Among them, the TFT-LCD has characteristics of high-speed response and front high contrast, and has become a mainstream technology for liquid crystal displays in recent years.

As shown in FIG. 1, a known liquid crystal display 10 includes a liquid crystal member 11 and two polarizing plates 12 and 13 (Polarizer) installed on the upper and lower surfaces of the liquid crystal member 11. The liquid crystal member 11 is composed of a glass substrate and members such as a large number of liquid crystal molecules attached to the upper and lower surfaces of the glass substrate. The polarizing plate 12 (or 13) is formed by coating the polarizing film 123 (or 133) with two transparent substrates 121 and 122 (or 131 and 132), and can perform hue compensation.

The liquid crystal display device 10 (LCD) adopting the IPS technology does not necessarily require an optical compensation film (Optical Compensatory Sheet), and has a function of a wide viewing angle in an oblique angle direction, and is relative in directions of 45 degrees and 135 degrees. High contrast can be provided. However, when actually observed at an inclination angle, the liquid crystal display device 10 using the well-known IPS (In-Plane Switching) technology is in a state where the screen is all black and the yellow or red color is shifted in the direction of the inclination angle. Occurs, the color is not completely black, and the contrast cannot be achieved in an ideal state. For example, as shown in FIG. 2, the color distribution in the direction of the inclination angles of 45 degrees and 135 degrees has a noticeable discoloration phenomenon. As described above, the liquid crystal display device 10 using the known IPS (In-Plane Switching) technology is discolored in the direction of the tilt angle, and further, an ideal contrast cannot be obtained, thereby degrading the quality of the display device. Yes.

Later, research was announced to add an optical compensator 14 on the liquid crystal display device 10, and the visible effect at the tilt angle was improved and the hue was improved. As shown in FIG. 12 is provided with an optical compensation plate 14. The optical compensator 14 includes a transparent substrate 141 and single-layer or multi-layer light retardation films 142 and 143 (Phase Retarder). The light retardation films 142 and 143 can generate a phase difference between a predetermined angle and direction with respect to light of a specific wavelength, and improve the display quality on the tilt angle of the liquid crystal display device 10. The polarizing plates 12 and 13 on both the upper and lower sides of the liquid crystal member 11 are composed of polarizing films 123 and 133 sandwiched between transparent substrates 121, 122, 131 and 132. For example, all of the prior arts such as the Republic of China Patent Publication Nos. 451071, 562955, 528882, 558643, and US Pat. Has improved.

In the above-described known technique, as shown in FIG. 3, after the polarizing plates 12 and 13 and the optical compensator 14 are manufactured independently, they are bonded by an adhesive. Each of the polarizing plates 12 and 13 and the optical compensator 14 must be produced, and at least one transparent substrate 122, 132, and 141 is required to provide sufficient strength and hardness, respectively, 12 and 13 need to protect the polarizing films 123 and 133 by the transparent substrates 121, 122, 131, and 132 on both upper and lower sides. If the number of transparent substrates and PSA layers is increased, not only the thickness of the liquid crystal display device 10 is increased, but also the light transmittance and the optical characteristics are further reduced, so that further improvement is required.
JP 2005-301248 A JP 2005-301235 A

In the present invention, not only can a polarizing plate be replaced with a single transparent substrate by two optical compensation films built on the polarizing plate, but the polarizing plate can be made relatively thin, and the liquid crystal display device has an inclination angle. It is an object of the present invention to provide an optically compensated thin polarizing plate and a method for manufacturing the same, which can improve the contrast and discoloration problems occurring in the process.

  Another object of the present invention is to provide a liquid crystal display device having a thin polarizing plate having an optical compensation function.

In order to achieve the above object, the thin polarizing plate having an optical compensation function of the present invention is composed of a polarizing film, a transparent substrate, a first optical compensation film, and a second optical compensation film. The polarizing film can provide a polarizing effect, and the polarizing film comprises an upper surface and a lower surface. The transparent substrate is bonded to the upper surface of the polarizing thin film. The first optical compensation film is bonded to the lower surface of the polarizing film. The second optical compensation film is bonded to the polarizing film on the side away from the first optical compensation film. The first optical compensation film satisfies nx> ny = nz, the second optical compensation film satisfies nx = ny <nz, and the combination of the first optical compensation film and the second optical compensation film is further
0.1 nm <Ro (a) + Ro (b) <220 nm;
−270 nm <Rth (a) + Rth (b) <110 nm;
−300 nm <Rth (a) <− 10 nm;
The optical conditions are satisfied.

nx is the refractive index in the x-axis direction on the surface of the optical compensation film, ny is the refractive index in the y-axis direction on the surface of the optical compensation film, nz is the refractive index in the z-axis direction on the surface of the optical compensation film, and Ro (a ) And Rth (a) are the Ro and Rth values of the second optical compensation film, and Ro (b) and Rth (b) are the Ro and Rth values of the first optical compensation film, respectively.
Ro = (nx−ny) * d;
Rth = {(nx + ny) / 2−nz} * d;
d represents the thickness of the optical compensation film.

The thin polarizing plate provided by the present invention can not only replace the polarizing plate with a single transparent substrate by two optical compensation films built on the polarizing plate, but also make the polarizing plate relatively thin, The liquid crystal display device can improve the problem of contrast and discoloration generated at an inclination angle.

The main principle of the polarizing plate having an optical compensation function of the present invention is that two optical compensation films are built in on the upper polarizing plate of the liquid crystal display device, and the original polarizing plate is formed on one transparent substrate by the optical compensation film. Not only can it be replaced, but it is also possible to make the polarizing plate relatively thin and to improve the contrast and discoloration problems that occur at tilt angles with respect to the IPS-LCD.

As shown in FIGS. 4 and 5, the liquid crystal display device 20 includes a liquid crystal member 21, an upper polarizing plate 22, and a lower polarizing plate 23. The upper polarizing plate 22 includes a first optical compensation film 241 and a second optical security film 242 built therein.

In the first embodiment of the present invention, it is preferable that the liquid crystal member 21 is an IPS liquid crystal member 21 and, therefore, red discoloration occurs in the directions of the tilt angles (45 degrees and 135 degrees). However, the liquid crystal member 21 may be formed of a TN (Twisted Nematic) type or MVA (M-Virtical Alignment) type liquid crystal member. The liquid crystal member 21 is generally composed of a glass substrate and a large number of liquid crystal molecules distributed on the glass substrate, and the liquid crystal member 21 has a liquid crystal alignment direction 211 defined according to the directionality of the liquid crystal particle alignment. In the first embodiment, the liquid crystal alignment direction 211 is a horizontal direction as shown in FIG. Since the liquid crystal member 21 is a well-known technique and is not a feature of the present invention, its detailed configuration and function will not be described.

The lower polarizing plate 23 is installed on the lower surface of the liquid crystal member 21. In the first embodiment, the lower polarizing plate 23 includes two transparent substrates 231 and 232 and a polarizing thin film 233 sandwiched between the two transparent substrates 231 and 232. The material of the transparent substrates 231 and 232 can be made using a known thermoplastic resin, but other materials having excellent mechanical strength, permeability, high transparency, thermal stability, optical isotropy, etc. It is also possible to consist of Specific examples of the transparent substrates 231 and 232 can be formed of a transparent resin such as TAC (Tracetyl Cellulose), propionyl cellulose, polyamide, polycarbonate, polyester, polystyrene, polyacrylate, norbornene polymer. Of these, TAC (Tracetyl Cellulose) after the surface is subjected to a saponification reaction by alkali treatment is most preferable in consideration of optical properties of the polarizing plate and weather resistance such as heat resistance and moisture resistance. In general, TAC Ro values commonly found in the market are between 0-5 nm and Rth values are between 35-55 nm. The polarizing film 233 is made of a PVA film containing polyvinyl alcohol. Iodine or a dichroic substance (dichroic dye or the like) is absorbed by the PVA film and then stretched to become a polarizing film 233 having a specific polarizing effect. The lower polarizing plate 23 can define a stretching direction 234 according to the direction in which the polarizing film 233 is stretched in the manufacturing process. In the first embodiment, the extending direction 234 of the lower polarizing plate 23 is the direction of the left and right arrows as shown in FIG. As described above, the extending direction 234 of the lower polarizing plate 23 is equivalent to the liquid crystal alignment direction 211 of the liquid crystal member 21. The techniques such as the transparent substrates 231 and 232 and the polarizing film 233 are known techniques, and a detailed description of the configuration and efficacy is omitted.

The upper polarizing plate 22 is installed on the upper surface of the liquid crystal member 21. In the first embodiment, the upper polarizing plate 22 includes a transparent substrate 221, a first optical compensation film 241, a second optical compensation film 242, and a polarizing thin film 223. The transparent substrate 221 is bonded to the upper surface of the polarizing film 223, the first optical compensation film 241 is bonded to the lower surface of the polarizing film 223, and the second optical compensation film 242 is separated from the first optical compensation film 241. It is bonded to the polarizing film 223 on the side. Thus, the polarizing film 223 is sandwiched between the transparent substrate 221 and the first optical compensation film 241 to constitute the upper polarizing plate 22. Since both the transparent substrate 221 and the polarizing film 223 of the upper polarizing plate 22 are similar to the above-described lower polarizing plate 23, the detailed contents of the members are not described. The difference is that the stretching direction 224 of the polarizing film 223 of the upper polarizing plate 22 is a direction penetrating the drawing as shown in FIG. Thus, the extending direction 224 of the polarizing film 223 of the upper polarizing plate 22 is perpendicular to the liquid crystal alignment direction 211 of the liquid crystal member 21. Therefore, the stretching direction 234 of the polarizing film 233 of the lower polarizing plate 23 is also perpendicular to the stretching direction 224 of the polarizing film 223 of the upper polarizing plate 22.

As shown in FIG. 4, in the first embodiment, the first optical compensation film 241 and the second optical compensation film 242 are built in the upper polarizing plate 22, and are above the polarizing film 223 of the upper polarizing plate 22 and the liquid crystal member 21. It is sandwiched between the sides. The two optical compensation films 241 and 242 each generate a phase difference in a predetermined angle and direction with respect to light of a specific wavelength, for example, adjusting the hue or contrast in the inclination angle directions of 45 degrees and 135 degrees, Compensation is provided, and the IPS liquid crystal display device 20 improves the red discoloration and contrast problems that occur at tilt angles. In the first embodiment, the first optical compensation film 241 is formed by infiltrating a transparent polymer film with a dye and then stretched in a specific direction, and the first optical compensation film 241 satisfies the following optical conditional expression: nx> ny = nz. nx represents the refractive index in the x-axis direction on the surface of the optical compensation film, ny represents the refractive index in the y-axis direction on the surface of the optical compensation film, and nz represents the refractive index in the z-axis direction on the surface of the optical compensation film. The first optical compensation film 241 that satisfies the optical conditional expression nx> ny = nz is generally referred to as A-Plate. The first optical compensation film 241 can define the maximum refractive index direction 244 according to the direction stretched in the manufacturing process. As shown in FIG. 4, the maximum refractive index direction 244 of the first optical compensation film 241 is equivalent to the liquid crystal alignment direction 211 of the liquid crystal member 21.

  The second optical compensation film 242 is formed by applying an alignment layer and a liquid crystal material on a transparent polymer film and arranging the liquid crystal material along a specific direction, thereby forming the second optical compensation 242 with an optical conditional expression: nx = ny <nz can be satisfied. The second optical compensation film 242 that satisfies the optical conditional expression: nx = ny <nz is usually referred to as C + Plate. As shown in FIG. 4, the alignment direction of the liquid crystal material in the manufacturing process of the second optical compensation film 242 is the vertical direction in FIG. Therefore, the liquid crystal material alignment direction of the second optical compensation film 242 is perpendicular to both the liquid crystal alignment direction 211 of the liquid crystal member 21 and the stretching direction 224 of the polarizing film 223 of the upper polarizing plate 22.

  In the first embodiment, the combination of the first optical compensation film 241 and the second optical compensation film 242 satisfies the following optical conditional expression.

0.1 nm <Ro (a) + Ro (b) <220 nm;
−270 nm <Rth (a) + Rth (b) <110 nm;
−300 nm <Rth (a) <− 10 nm;
Ro (a) and Rth (a) are the Ro and Rth values of the second optical compensation film, respectively, Ro (b) and Rth (b) are the Ro and Rth values of the first optical compensation film, respectively.
Ro = (nx−ny) * d;
Rth = {(nx + ny) / 2−nz} * d;
d represents the thickness of the optical compensation film.

  By incorporating the first optical compensation film 241 and the second optical compensation film 242 in the upper polarizing plate 22, the problem of contrast and discoloration generated in the tilt angle of the IPS-LCD is improved. The first optical compensation film 241 and the second optical compensation film 242 are coated on the lower surface of the polarizing film 223 of the upper polarizing plate 22 and can be replaced with the originally required transparent substrate. As described above, the present invention can be configured to be thinner than a polarizing plate in which an optical compensation film is produced alone in a known technical structure and bonded onto the polarizing plate.

  As shown in FIG. 5, the manufacturing method of the thin polarizing plate which has an optical compensation effect | action of this invention is comprised from the following steps.

Step 31: A first optical compensation film 241 is prepared.

Step 32: An alignment layer 2421 and a liquid crystal material layer 2422 are applied on the first optical compensation film 241, and a second optical compensation film 242 is formed on the first optical compensation film 241 by a combination of the alignment layer 2421 and the liquid crystal material layer 2422. Form. In the first embodiment, since the second optical compensation film 242 is formed on the first optical compensation film 241, there is no other medium between them.

Step 33: The first optical compensation film 241 on which the second optical compensation film 242 is formed, the polarizing film 223, and the transparent substrate 221 are coupled to each other, and the polarizing film 223 is interposed between the transparent substrate 221 and the first optical compensation film 241. A polarizing plate having an optical compensation action is formed. This polarizing plate is like the upper polarizing plate 22 of the first embodiment shown in FIG.

As shown in FIGS. 6 and 7, the liquid crystal display device 40 includes a liquid crystal member 41, an upper polarizing plate 42, and a lower polarizing plate 43. A first optical compensation film 441 and a second optical compensation film 442 are built in the upper polarizing plate 42. In the second embodiment, the upper polarizing plate 42 is sandwiched between the transparent substrate 421, the first optical compensation film 441, the second optical compensation film 442, and the first optical compensation film 441 and the second optical compensation film 442. A polarizing film 423 is provided. Similarly, the lower polarizing plate 43 includes two transparent substrates and a polarizing film 433 sandwiched between the two transparent substrates 431 and 432. The liquid crystal member 41, the first optical compensation film 441, the second optical compensation film 442, the transparent substrates 421, 431, and 432, the polarizing films 423 and 433, and other materials and optical conditions are shown in FIG. Detailed description is omitted. As shown in FIG. 6, the second embodiment is different in that a pressure sensitive adhesive 443 (PSA; Pressure Sensitive Adhesive) is further provided between the first optical compensation film 441 and the second optical compensation film 442. It is. In the second embodiment, the manufacturing process is different in order to add one layer of pressure-sensitive adhesive 443, and the manufacturing process of the second embodiment of the thin polarizing plate is composed of the following steps as shown in FIG. .

Step 51: Provide a base material 445, a first optical compensation film 441, a polarizing film 423, and a transparent substrate 421.

Step 52: An alignment layer 4421 and a liquid crystal material 4422 are sequentially applied on the substrate 445. A second optical compensation film 442 is formed on the base material 445 by a combination of the alignment layer 4421 and the liquid crystal material 4422, and the polarizing film structure is sandwiched between the transparent substrate 421 and the first optical compensation film 441. Constitute. At this time, the base material 445 having the second optical compensation film 442, the transparent substrate 421, the polarizing film 423, and the polarizing plate having the first optical compensation film 441 are handled such as being transported, stored and sold alone. It becomes possible.

Step 53: The structure of the polarizing plate composed of the first optical compensation film 441, the polarizing film 423, and the transparent substrate 421 is bonded to the second optical compensation film 442 with a pressure sensitive adhesive (PSA) 443, The second optical compensation film 442 is adjacent to the first optical compensation film 441 through the pressure-sensitive adhesive 443, and the base 445 is exposed to the outermost layer.

Step 54: The substrate 445 is removed, and the second optical compensation film 442 is bonded onto the polarizing plate structure with the pressure-sensitive adhesive 443.

The above-described manufacturing method of the present invention makes it possible to directly incorporate the light retardation film layer in the optical compensation film into the polarizing plate. The polarizing plate achieves an optical compensation effect and has a good viewing angle range and display quality. Rather, the thickness is reduced with respect to known techniques, and the light transmittance and optical characteristics can be improved relative to each other.

In the present invention, preferred embodiments have been disclosed as described above. However, the present invention is not limited to the present invention, and any person who is familiar with the technology can use various methods within the spirit and scope of the present invention. Therefore, the protection scope of the present invention is based on the content specified in the claims.

It is sectional drawing of a well-known liquid crystal display. It is a curve figure of the color distribution state in the state where the screen of the liquid crystal display device of a well-known IPS technique is black. It is sectional drawing of the optical compensation board of a well-known liquid crystal display. 1 is a cross-sectional view of a first embodiment in which a thin polarizing plate having an optical compensation function of the present invention is installed on a liquid crystal display device. It is a manufacturing-process figure of the thin-shaped polarizing plate 1st Example of this invention of FIG. It is sectional drawing of the 2nd Example which installed the thin-shaped polarizing plate which has the optical compensation effect | action of this invention on the liquid crystal display device. It is a manufacturing-process figure of the thin-shaped polarizing plate 2nd Example of this invention of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Well-known liquid crystal display 111 Liquid crystal member 12, 13 Polarizing plate 121, 122, 131, 132, 141 Transparent substrate 123, 133 Polarizing film 14 Optical compensator 142, 143 Light retardation film 20, 40 Liquid crystal display device 21, 41 Liquid crystal members 211, 411 Liquid crystal alignment directions 22, 42 Upper polarizing plates 221, 231, 232, 441, 431, 432 Transparent substrates 223, 233, 423, 433 Polarizing films 224, 234 Stretching directions 23, 43 Lower polarizing plates 241, 441 First optical compensation films 242, 442 Second optical compensation film 244 Maximum refractive index direction 443 Pressure sensitive adhesives 31-33, 51-54 Steps

Claims (5)

It consists of a polarizing film, a transparent substrate, a first optical compensation film, a second optical compensation film,
The polarizing film has a polarizing action and has an upper surface and a lower surface,
The transparent substrate is bonded to the upper surface of the polarizing film,
The first optical compensation film is bonded to the lower surface of the polarizing film,
A thin polarizing plate having an optical compensation function, wherein the second optical compensation film is bonded to the opposite side of the polarizing film of the first optical compensation film. The first optical compensation film satisfies an optical conditional expression; nx> ny = nz, and the second optical compensation film satisfies an optical conditional expression; nx = ny <nz,
Here, nx represents the refractive index in the x-axis direction on the surface of the optical compensation film, ny represents the refractive index in the y-axis direction on the surface of the optical compensation film, nz represents the refractive index in the z-axis direction on the surface of the optical compensation film,
The first optical compensation film and the second optical compensation film further have the following optical conditional expression:
0.1 nm <Ro (a) + Ro (b) <220 nm;
−270 nm <Rth (a) + Rth (b) <110 nm;
−300 nm <Rth (a) <− 10 nm;
Where Ro (a) and Rth (a) are the Ro and Rth values of the second optical compensation film, respectively, and Ro (b) and Rth (b) are the Ro and Rth values of the first optical compensation film, respectively. And
Ro = (nx−ny) * d;
Rth = {(nx + ny) / 2−nz} * d;
The thin polarizing plate having an optical compensation function according to claim 1, wherein d represents a thickness of the optical compensation film. Prepare the first optical compensation film,
An alignment layer and a liquid crystal material layer are sequentially applied on the first optical compensation film, and a combination of the alignment layer and the liquid crystal material forms a second optical compensation film on the first optical compensation film,
The first optical compensation film on which the second optical compensation film is formed is bonded to the polarizing film and the transparent substrate, and the polarizing film is sandwiched between the transparent substrate and the first optical compensation film, thereby having an optical compensation function. A method for producing a thin polarizing plate having an optical compensation function, comprising a polarizing plate. The first optical compensation film satisfies the optical conditional expression; nx> ny = nz, the second optical compensation film satisfies the optical conditional expression; nx = ny <nz,
Here, nx represents the refractive index in the x-axis direction on the surface of the optical compensation film, ny represents the refractive index in the y-axis direction on the surface of the optical compensation film, nz represents the refractive index in the z-axis direction on the surface of the optical compensation film,
The first optical compensation film and the second optical compensation film further have the following optical conditional expression:
0.1 nm <Ro (a) + Ro (b) <220 nm;
−270 nm <Rth (a) + Rth (b) <110 nm;
−300 nm <Rth (a) <− 10 nm;
Where, where
Ro (a) and Rth (a) are the Ro and Rth values of the second optical compensation film, respectively, Ro (b) and Rth (b) are the Ro and Rth values of the first optical compensation film, respectively.
Ro = (nx−ny) * d;
Rth = {(nx + ny) / 2−nz} * d;
4. The method for producing a thin polarizing plate having an optical compensation function according to claim 3, wherein d represents a thickness of the optical compensation film. A base material is prepared, an alignment layer and a liquid crystal material layer are sequentially applied on the base material, a second optical compensation film is formed on the base material by a combination of the alignment layer and the liquid crystal material, and further, a first optical compensation film, A polarizing film and a transparent substrate are prepared, and a polarizing plate structure is configured by sandwiching the polarizing film between the transparent substrate and the first optical compensation film,
The polarizing plate structure composed of the first optical compensation film, the polarizing film and the transparent substrate is bonded to the second optical compensation film with an adhesive, and the second optical compensation film and the first optical compensation film are adjacent to each other. And expose the substrate to the outermost layer,
A method for producing a thin polarizing plate having an optical compensation function, wherein the substrate is removed and a second optical compensation film is bonded onto the polarizing plate structure.

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