JPWO2015166941A1 - Liquid crystal display - Google Patents

Abstract

An object of the present invention is to provide a liquid crystal display device in which the warpage of a liquid crystal display panel is sufficiently reduced and display unevenness is thereby suppressed. The liquid crystal display device of the present invention is a liquid crystal display device including a display panel including a first polarizing plate, a liquid crystal cell, and a second polarizing plate, and a backlight, wherein the first polarizing plate is a liquid crystal cell. The first polarizer, the protective film F1, and the protective film F2 are disposed; the second polarizing plate is disposed on the backlight side surface of the liquid crystal cell, and the second polarizer. And a protective film F3 and a protective film F4; the absorption axis of the first polarizer is parallel to the long-side direction α of the display panel and orthogonal to the absorption axis of the second polarizer When the shrinkage force represented by the formula (1) of the protective film F1 is W1 and the shrinkage force represented by the formula (1) of the protective film F4 is W4, the ratio W1 / W4 of the shrinkage force exceeds 0.84. 1.2 or less.

Description

  The present invention relates to a liquid crystal display device.

  Liquid crystal display devices are often used for displays such as televisions because they consume less power and are thin. In recent years, displays have become larger and thinner.

  The liquid crystal display device includes a liquid crystal display panel including a liquid crystal cell and a pair of polarizing plates that sandwich the liquid crystal cell. However, when the display is enlarged, the liquid crystal display panel is likely to warp due to the dimensional change of the polarizing plate. Further, when the display is thinned, the distance between the liquid crystal display panel and the backlight is small, so that the warped liquid crystal display panel and the backlight are likely to contact each other, and display unevenness such as egg unevenness is likely to occur. Furthermore, when the warped liquid crystal display panel comes into contact with the housing (bezel), display unevenness such as corner unevenness is likely to occur.

  As a method for suppressing the dimensional change of the polarizing plate, a liquid crystal display device in which the protective films F1 and F4 are laminated with a base material layer and a control layer for controlling moisture permeability has been proposed (for example, Patent Document 1). ).

  Further, as a method of suppressing the warpage of the liquid crystal display panel, the dimensional change rate C1 due to the hygroscopic expansion of the viewing side polarizing plate is made larger than the dimensional change rate C2 due to the hygroscopic expansion of the backlight side polarizing plate; There has been proposed a liquid crystal display device in which the water content W1 of the polarizing plate is smaller than the water content W2 of the backlight side polarizing plate (for example, Patent Documents 2 and 3). Further, (the sum of the products of the elastic modulus in the long side direction and the cross-sectional area in the short side direction of the viewing side polarizing plate) / (the product of the elastic modulus in the long side direction and the cross-sectional area in the short side direction of the backlight side polarizing plate) There has also been proposed a liquid crystal display device or the like configured such that the total sum is equal to or less than a certain value (for example, Patent Document 4).

JP 2013-160863 A JP 2013-037104 A JP 2007-292966 A JP 2006-267503 A

  However, in patent document 1, although the moisture permeability of the water | moisture content of the protective films F1 and F4 can be reduced to some extent, it was not enough to suppress the dimensional change of a polarizing plate fully.

  In Patent Documents 2 and 3, it is possible to reduce the warpage of a liquid crystal display panel when a liquid crystal display device immediately after production is placed in a low humidity environment to a high humidity environment; It did not suppress the warpage of the liquid crystal display panel. That is, although the warpage of the liquid crystal display panel in the liquid crystal display device immediately after manufacture can be suppressed, the effect decreases with the elapsed time, and the warpage of the liquid crystal display panel in the use environment cannot be suppressed.

  In Patent Document 4, warping of the liquid crystal display panel can be suppressed to some extent by increasing the rigidity of the polarizing plate on the backlight side, but sufficient rigidity cannot be imparted. Therefore, the warp of the liquid crystal display panel cannot be sufficiently reduced.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device in which warpage of a liquid crystal display panel is sufficiently reduced and display unevenness is thereby suppressed.

（式（１）において、Ｗは、保護フィルムの前記長辺方向αの収縮力（Ｎ／ｍ）を表し、Ｔは、保護フィルムの前記長辺方向αの引張弾性率（Ｐａ）を表し、Ｓは、保護フィルムの下記式（２）で表される前記長辺方向αの湿度変化に伴う寸法変化率（％）を表し、ｔは、保護フィルムの厚み（ｍ）を表す）

（式（２）において、Ｓは、保護フィルムの前記長辺方向αの湿度変化に伴う寸法変化率（％）、Ｌ０は、保護フィルムの２３℃５５％ＲＨ下における前記長辺方向αの長さ、Ｌ１は、保護フィルムの２３℃２０％ＲＨ下における前記長辺方向αの長さ、Ｌ２は、保護フィルムの２３℃８０％ＲＨ下における前記長辺方向αの長さを表す）
［２］ 前記液晶セルの視認側の面から前記保護フィルムＦ１の視認側の面までの距離をＤ１、前記保護フィルムＦ１の下記式（３）で表される前記長辺方向αの収縮モーメントをＭ１とし、前記液晶セルのバックライト側の面から前記保護フィルムＦ４の前記バックライト側の面までの距離をＤ４、前記保護フィルムＦ４の下記式（３）で表される前記長辺方向αの収縮モーメントをＭ４としたとき、収縮モーメントの比Ｍ１／Ｍ４が０．７以上１．２以下である、［１］に記載の液晶表示装置。

（式（３）において、Ｍは、保護フィルムの前記長辺方向αの収縮モーメント（Ｎ）、Ｗは、保護フィルムの前記長辺方向αの収縮力（Ｎ／ｍ）、Ｄは、保護フィルムの液晶セルの表面からの距離（ｍ）を表す）
［３］ 前記液晶セルは、液晶層と、前記液晶層を挟持する一対のガラス基板とを含み、前記ガラス基板の厚みをｔ’（ｍｍ）、前記液晶表示パネルの長辺方向の長さをｌ（ｍｍ）としたとき、ｔ’／ｌが０．０００１〜０．０００７である、［１］または［２］に記載の液晶表示装置。
［４］ 前記保護フィルムＦ４は、厚み３０〜８０μｍのセルロースエステル系フィルムである、［１］〜［３］のいずれかに記載の液晶表示装置。
［５］ 前記保護フィルムＦ２およびＦ３は、厚み２０〜６０μｍのセルロースエステル系フィルム、または厚み２０〜６０μｍのシクロオレフィン系フィルムである、［１］〜［４］のいずれかに記載の液晶表示装置。[1] A liquid crystal display device including a first polarizing plate, a liquid crystal cell, a liquid crystal display panel including a second polarizing plate, and a backlight, wherein the first polarizing plate is the liquid crystal cell. The first polarizer, the protective film F1 disposed on the viewing side surface of the first polarizer, and the surface of the first polarizer on the liquid crystal cell side The second polarizing plate is disposed on a surface of the liquid crystal cell on the backlight side, the second polarizer, and the second polarizer on the liquid crystal cell side. A protective film F3 disposed on the surface, and a protective film F4 disposed on the surface of the second polarizer on the backlight side, and the absorption axis of the first polarizer is that of the liquid crystal display panel Parallel to the long side direction α and orthogonal to the absorption axis of the second polarizer, The shrinkage force in the long side direction α represented by the following formula (1) of the protective film F1 is W1, and the shrinkage force in the long side direction α represented by the following formula (1) of the protective film F4 is W4. When the liquid crystal display device has a contraction force ratio W1 / W4 of more than 0.84 and not more than 1.20.

(In Formula (1), W represents the contraction force (N / m) in the long-side direction α of the protective film, T represents the tensile elastic modulus (Pa) in the long-side direction α of the protective film, S represents the dimensional change rate (%) accompanying the humidity change in the long side direction α represented by the following formula (2) of the protective film, and t represents the thickness (m) of the protective film.

(In Formula (2), S is a dimensional change rate (%) accompanying the humidity change in the long side direction α of the protective film, and L0 is the length of the protective film in the long side direction α under 23 ° C. and 55% RH. L1 represents the length of the long side direction α under 23 ° C. and 20% RH of the protective film, and L2 represents the length of the long side direction α under 23 ° C. and 80% RH of the protective film)
[2] The distance from the viewing side surface of the liquid crystal cell to the viewing side surface of the protective film F1 is D1, and the contraction moment of the long side direction α represented by the following formula (3) of the protective film F1. M1, and the distance from the backlight side surface of the liquid crystal cell to the backlight side surface of the protective film F4 is D4, the long side direction α of the protective film F4 represented by the following formula (3) The liquid crystal display device according to [1], wherein the contraction moment ratio M1 / M4 is 0.7 or more and 1.2 or less when the contraction moment is M4.

(In Formula (3), M is the shrinking moment (N) of the long side direction α of the protective film, W is the shrinking force (N / m) of the long side direction α of the protective film, and D is the protective film. Represents the distance (m) from the surface of the liquid crystal cell)
[3] The liquid crystal cell includes a liquid crystal layer and a pair of glass substrates sandwiching the liquid crystal layer. The thickness of the glass substrate is t ′ (mm), and the length in the long side direction of the liquid crystal display panel is set. The liquid crystal display device according to [1] or [2], wherein t ′ / l is 0.0001 to 0.0007 when l (mm).
[4] The liquid crystal display device according to any one of [1] to [3], wherein the protective film F4 is a cellulose ester film having a thickness of 30 to 80 μm.
[5] The liquid crystal display device according to any one of [1] to [4], wherein the protective films F2 and F3 are a cellulose ester film having a thickness of 20 to 60 μm or a cycloolefin film having a thickness of 20 to 60 μm. .

  ADVANTAGE OF THE INVENTION According to this invention, the curvature of a liquid crystal display panel can fully be reduced, and the liquid crystal display device by which the display nonuniformity by it was suppressed can be provided.

It is a schematic diagram which shows an example of the fundamental structure of a liquid crystal display device. It is a schematic diagram which shows the positional relationship of the absorption axis of the polarizer and MD direction of a protective film in a liquid crystal display device. It is a figure which shows the state of the curvature of a liquid crystal display panel.

<Liquid crystal display device>
The liquid crystal display device of the present invention includes a liquid crystal display panel and a backlight. The liquid crystal display panel includes a liquid crystal cell, a first polarizing plate disposed on the surface on the viewing side, and a second polarizing plate disposed on the surface on the backlight side.

  FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a liquid crystal display device. As shown in FIG. 1, the liquid crystal display device 10 of the present invention includes a liquid crystal display panel 20 and a backlight 30.

  The planar shape of the liquid crystal display panel 20 is usually a rectangle, and includes a long side α and a short side β. The diagonal length of the liquid crystal display panel 20 is preferably 26 inches or more, more preferably 30 inches or more and 100 inches or less. The liquid crystal display panel 20 includes a liquid crystal cell 40, a first polarizing plate 50 disposed on the viewing side surface, and a second polarizing plate 60 disposed on the backlight side surface.

  The display mode of the liquid crystal cell 40 may be various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), and IPS. From the viewpoint of obtaining a high contrast, the VA (MVA, PVA) mode is preferable, and from the viewpoint of obtaining a wide viewing angle, the IPS mode is preferable.

  The liquid crystal cell 40 has a pair of transparent substrates 41 and 43 and a liquid crystal layer 45 sandwiched between them.

  The transparent substrates 41 and 43 are transparent resin substrates or glass substrates, preferably glass substrates. The thickness of the transparent substrates 41 and 43 is preferably 1 mm or less, more preferably 0.3 mm or more and less than 0.7 mm, for the purpose of reducing the thickness of the liquid crystal display device, and 0.3 to 0.6 mm. More preferably.

  When the thickness of the glass substrate is t ′ (mm) and the length in the long side direction α of the liquid crystal display panel 20 is l (mm), t ′ / l is preferably 0.0001 to 0.0007, It is more preferably 0.0002 to 0.0005, and further preferably 0.0002 to 0.0004. If t ′ / l is in the above range, the length l of the liquid crystal display panel 20 in the long side direction α is large and the thickness t ′ of the glass substrate is small. Therefore, the liquid crystal display panel 20 warps due to the contraction force of the polarizer. Cheap. In such a case, the warpage of the liquid crystal display panel 20 can be reduced by setting the ratio W1 / W4 of the contraction force between the protective films F1 and F4 to a predetermined range as will be described later.

  A pixel electrode for applying a voltage to the liquid crystal molecules can be disposed on one of the pair of transparent substrates 41 and 43 (for example, the transparent substrate 41). The counter electrode may be further disposed on the transparent substrate 41 on which the pixel electrode is disposed, or may be disposed on the other transparent substrate 43. The color filter can be usually disposed on the other transparent substrate 43.

  The liquid crystal layer 45 includes liquid crystal molecules having a negative or positive dielectric anisotropy, for example, when the liquid crystal cell 40 is a VA system. The liquid crystal molecules are liquid crystal when no voltage is applied (when no electric field is generated between the pixel electrode and the counter electrode) due to the alignment regulating force of the alignment film provided on the surface of the transparent substrate 41 on the liquid crystal layer side. The long axis of the molecule is oriented so as to be substantially perpendicular to the surface of the transparent substrate. Then, by applying an image signal (voltage) to the pixel electrode, the liquid crystal molecules are aligned so that the major axis thereof is in the horizontal direction with respect to the substrate surface, thereby changing the transmittance and reflectance of each sub-pixel. To display the image.

  The first polarizing plate 50 includes a first polarizer 51 and a protective film 53 (protective film F1, hereinafter sometimes referred to as “F1”) disposed on the surface of the first polarizer 51 on the viewing side. , And a protective film 55 (protective film F2, hereinafter sometimes referred to as “F2”) disposed on the surface of the first polarizer 51 on the liquid crystal cell side. The second polarizing plate 60 includes a second polarizer 61 and a protective film 63 disposed on the liquid crystal cell side surface of the second polarizer 61 (protective film F3, hereinafter may be referred to as “F3”). And a protective film 65 (protective film F4, hereinafter may be referred to as “F4”) disposed on the surface of the second polarizer 61 on the backlight side.

  The first polarizing plate 50 and the second polarizing plate 60 can be bonded to the liquid crystal cell 40 via the pressure-sensitive adhesive layer 71, respectively. Although the thickness in particular of the adhesive layer 71 is not restrict | limited, For example, it can be set as about 10-80 micrometers. The adhesive layer 71 may not be arranged.

  FIG. 2 is a schematic diagram illustrating the positional relationship between the absorption axis of the polarizer and the MD direction of the protective film in the liquid crystal display device. As shown in FIG. 2, the absorption axis of the first polarizer 51 is preferably parallel to the long side direction α of the liquid crystal display panel 20. The absorption axis of the first polarizer 51 is preferably parallel to the MD direction of the protective film 53 (F1) (preferably a direction orthogonal to the in-plane slow axis direction). The absorption axis of the second polarizer 61 is preferably parallel to the short side direction β (direction orthogonal to the long side direction α) of the liquid crystal display panel 20. The absorption axis of the second polarizer 61 is preferably parallel to the MD direction of the protective film 65 (F4) (preferably a direction orthogonal to the in-plane slow axis direction).

  As described above, when a liquid crystal display device used for a display such as a television is moved from a high-humidity environment to a low-humidity environment, the liquid crystal display panel tends to warp so as to protrude toward the backlight side. The reason why such a liquid crystal display panel warps is not necessarily clear, but is considered as follows.

  That is, in the liquid crystal display device used for a display such as a television, the absorption axis of the first polarizer 51 on the viewing side is parallel to the long side direction α of the liquid crystal display panel 20 as described above. Therefore, when the first polarizer 51 is exposed from a high-humidity environment to a low-humidity environment, the first polarizer 51 easily contracts in the long-side direction α of the liquid crystal display panel 20. On the other hand, the absorption axis of the second polarizer 61 on the backlight side is parallel to the short side direction β of the liquid crystal display panel 20. Therefore, when the second polarizer 61 is exposed from a high-humidity environment to a low-humidity environment, the second polarizer 61 easily contracts in the short side direction β of the liquid crystal display panel 20. The contraction force of the first polarizer 51 contracting in the long side direction α of the liquid crystal display panel 20 is larger than the contraction force of the second polarizer 61 contracting in the short side direction β of the liquid crystal display panel 20. The liquid crystal display panel 20 is considered to be easily warped so as to protrude toward the backlight side (see FIG. 3).

  When the warpage of the liquid crystal display panel 20 exceeds a certain level, it is considered that the non-uniformity of egg comes into contact with the backlight 30; the non-uniformity of corner occurs due to contact with the bezel of the housing.

  On the other hand, the present inventors increase the contraction force of the second polarizing plate 60 on the backlight side in the long-side direction α of the liquid crystal display panel, so that the first polarizing plate 60 on the viewing side is increased. It has been found that the contraction force of the polarizing plate 50 in the long side direction α of the liquid crystal display panel can be offset. The shrinkage force of the polarizing plate on the backlight side can be adjusted by, for example, the protective film 63 (F3) or the protective film 65 (F4). Among them, the protective film 63 (F3) disposed on the liquid crystal cell side is less likely to contract when moved from a high humidity environment to a low humidity environment, and hardly generates contraction force. On the other hand, the protective film 65 (F4) disposed on the backlight side easily contracts when moved from a high-humidity environment to a low-humidity environment, and easily generates contraction force. Therefore, it has been found that it is effective to adjust the ratio of the shrinkage force between the protective film 53 (F1) of the first polarizing plate 50 and the protective film 65 (F4) of the second polarizing plate 60.

That is, the contraction force represented by the following formula (1) in the long side direction α of the liquid crystal display panel of the protective film 53 (F1) of the first polarizing plate 50 on the viewing side is W1, and the second on the backlight side. When the contraction force represented by the following formula (1) of the protective film 65 (F4) of the polarizing plate 60 in the long side direction α of the liquid crystal display panel is W4, the ratio W1 / W4 of the contraction force is 0.84. It is preferably above 1.20 or less, more preferably from 0.87 to 1.15, and even more preferably from 0.90 to 1.10. By setting W1 / W4 to a certain value or less, the contraction force in the long side direction α of the liquid crystal display panel 20 of the first polarizing plate 50 on the viewing side is changed to the liquid crystal display panel 20 of the second polarizing plate 60 on the backlight side. Can be offset moderately by the contraction force in the long side direction α. By setting W1 / W4 to be equal to or larger than a certain value, it is possible to suppress the contraction force of the second polarizing plate 60 on the backlight side from becoming excessively large and warping the liquid crystal display panel to be convex toward the viewing side. Thus, by setting W1 / W4 within the above range, the contraction force in the long side direction α of the liquid crystal display panel of the second polarizing plate 60 on the backlight side is appropriately increased, and the liquid crystal of the polarizing plate on the viewing side is obtained. The contraction force in the long side direction α of the display panel can be canceled appropriately. As a result, the warp of the liquid crystal display panel 20 can be sufficiently reduced.

T in Formula (1) indicates the tensile elastic modulus (Pa) of the protective film in the long side direction α of the liquid crystal display panel. The tensile elastic modulus of the protective film can be measured by the following procedure.
1) A protective film is cut into a shape of No. 1 with a size of 150 mm (long side direction α) × 10 mm (short side direction β) to obtain a test piece.
2) After humidity-conditioning this test piece for 24 hours in an environment of 23 ° C. and 55% RH, the tensile modulus of elasticity in the long side direction α is measured according to the method described in JIS K 7127. The tensile tester uses Tensilon RTC-1225A manufactured by Orientec Co., Ltd., and the tensile speed is 100 mm / min. The tensile modulus is calculated by setting the elastic modulus analysis start point to 2 (MPa) and the elastic modulus analysis end point to 60 (MPa).

S in the formula (1) indicates a dimensional change rate (%) accompanying a humidity change in the long side direction α of the liquid crystal display panel of the protective film, which is represented by the following formula (2).

The dimensional change rate S (%) of the protective film can be measured by the following procedure.
1) Cut out into a size of 25 cm in length (measurement direction) × 5 cm in width so that the long side direction α of the liquid crystal display panel 20 of the protective film becomes the longitudinal direction, and use it as a test piece. Pin holes are formed at intervals of 20 cm in the longitudinal direction of the test piece, and after humidity conditioning at 23 ° C. and a relative humidity of 55% for 24 hours, the distance between the pin holes is measured with a pin gauge to obtain a measured value L0.
2) Next, the test piece is conditioned for 24 hours in a humid heat environment of 23 ° C. and a relative humidity of 20%, and then the distance between the pin holes is measured with a pin gauge to obtain a measured value L1.
3) Further, after adjusting the test piece for 24 hours at 23 ° C. and 80% relative humidity, the distance between the pin holes is measured with a pin gauge to obtain a measured value L2.
4) Apply these measurement values to the following equation to calculate the dimensional change rate (%).
Dimensional change rate (%) = {(L2-L1) / L0} × 100

  T of Formula (1) shows the thickness (m) of a protective film.

  In order to set W1 / W4 in the above range, the shrinkage force W1 of the protective film 53 (F1) in the long side direction α of the liquid crystal display panel may be reduced, or the liquid crystal display panel of the protective film 65 (F4). The contraction force W4 in the long side direction α may be increased; it is preferable to increase the contraction force W4 in the long side direction α of the liquid crystal display panel of the protective film 65 (F4).

  The shrinkage force W4 of the protective film 65 (F4) can be adjusted by the thickness of the protective film, stretching conditions, and the like. For example, in order to increase the contraction force of the protective film 65 (F4) in the long side direction α of the liquid crystal display panel, 1) the thickness of the protective film 65 (F4) is increased, or 2) a film-like material at the start of stretching. It is preferable to increase the residual solvent amount of 3), 3) lower the stretching temperature, 4) lower the stretching ratio; more preferably satisfy the above 2) to 4) simultaneously; 1) to 4 above It is more preferable to satisfy all of

The shrinkage force of the protective film 53 (F1) and the protective film 65 (F4) in the long side direction α of the liquid crystal display panel may be set so that the ratio of shrinkage force (W1 / W4) is in the above range. Not limited. The contraction force in the long side direction α of the liquid crystal display panel of the protective film 65 (F4) is, for example, 64 × 10 ^{3 to} 100 × 10 ³ N / m, more preferably 68 × 10 ^{3 to} 100 × 10 ³ N / m. sell. The shrinkage force in the long side direction α of the liquid crystal display panel of the protective film 53 (F1) is, for example, 50 × 10 ^{3 to} 100 × 10 ³ N / m, more preferably 70 × 10 ^{3 to} 100 × 10 ³ N / m. sell.

  Furthermore, from the principle of the lever, the first polarizing plate 50 on the viewing side is larger as the distance from the surface of the liquid crystal cell of the protective film 65 (F4) of the second polarizing plate 60 on the backlight side that generates contraction force is larger. A force that cancels the contraction force of the lens can act greatly.

Accordingly, the distance from the viewing side surface of the liquid crystal cell to the viewing side surface of the protective film 53 (F1) of the first polarizing plate 50 is represented by D1 and the following formula (3) of the protective film 53 (F1). The contraction moment in the long side direction α is M1, and the distance from the backlight side surface of the liquid crystal cell to the backlight side surface of the protective film 65 (F4) of the second polarizing plate 60 is D4, and the protective film 65 (F4 ) Where M4 is the contraction moment in the long side direction α represented by the following formula (3); the ratio M1 / M4 of the contraction moment is preferably more than 0.6 and less than 1.2, and more than 0.7 It is more preferably 1.2 or less, and further preferably 0.9 or more and less than 1.1.

  W of Formula (3) shows the contraction force (N / m) in the long side direction α of the liquid crystal display panel of the protective film represented by Formula (1). D shows the distance (m) from the surface of the liquid crystal cell of a protective film. For example, in FIG. 1, the distance D1 from the surface of the liquid crystal cell of the protective film 53 (F1) is the thickness of the pressure-sensitive adhesive layer 71, the thickness of the protective film 55 (F2), the thickness of the first polarizer 51, and the protective film. This is the total thickness of 53 (F1).

  In order to set M1 / M4 in the above range, the shrinkage force W4 of the protective film 65 (F4) is set to a certain value or more, for example, to increase the shrinkage force ratio W1 / W4; and the protective film 65 (F4) It is preferable to make the distance D4 from the surface of the liquid crystal cell larger than the distance D1 from the surface of the liquid crystal cell of the protective film 53 (F1). The distance D4 from the surface of the liquid crystal cell of the protective film 65 (F4) can be adjusted by the thickness of the adhesive layer 71, the protective film 63 (F3), the second polarizer 61, the protective film 65 (F4), and the like.

  When the distance D4 from the surface of the liquid crystal cell of the protective film 65 (F4) is larger than the distance D1 from the surface of the liquid crystal cell of the protective film 53 (F1), D4 / D1 is, for example, more than 1 and not more than 2.5; Preferably it may be 1.5 or more and 2 or less. The total thickness of the protective film 53 (F1), the first polarizer 51, and the protective film 53 (F2) is TT1; the protective film 63 (F3), the second polarizer 61, and the protective film 65 (F4) When the total thickness is TT4, TT4 / TT1 may be more than 1 and 2.5 or less; preferably 1.15 or more and 2 or less.

<About protective films 53 (F1) and 65 (F4)>
The protective films 53 (F1) and 65 (F4) are preferably films mainly composed of cellulose ester.

(Cellulose ester)
The cellulose ester is a compound obtained by esterifying cellulose and at least one of an aliphatic carboxylic acid having 2 to 22 carbon atoms and an aromatic carboxylic acid. Examples of the cellulose ester include cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose benzoate, cellulose acetate benzoate, and the like. Among them, those having low retardation are preferable, and cellulose triacetate is preferable.

  The total substitution degree of the acyl group of the cellulose ester is about 2.0 to 3.0, preferably 2.5 to 3.0, more preferably 2.7 to 3.0, and still more preferably 2.8 to 3.0. 2.95. In order to reduce the retardation development property, it is preferable to increase the total substitution degree of the acyl group.

  The number of carbon atoms of the acyl group contained in the cellulose ester is preferably 2-7, and more preferably 2-4. In order to obtain good heat resistance, the acyl group contained in the cellulose ester preferably contains an acetyl group. The substitution degree of the acyl group having 3 or more carbon atoms is preferably 0.9 or less, and more preferably 0.

  The substitution degree of the acyl group of cellulose ester can be measured by the method prescribed in ASTM-D817-96.

The weight average molecular weight of cellulose ester, in order to obtain the mechanical strength of certain level is 5.0 is preferably ^{× 10 4 ~5.0 × 10 5,} 1.0 × 10 5 ~3.0 × 10 ⁵ is more preferable, and 1.5 × 10 ^{5 to} 2.9 × 10 ⁵ is even more preferable. The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the cellulose ester is preferably 1.0 to 4.5.

The weight average molecular weight and molecular weight distribution of the cellulose ester can be measured by gel permeation chromatography (GPC). The measurement conditions are as follows.
Solvent: Methylene chloride Column: Three Shodex K806, K805, K803G (manufactured by Showa Denko KK) are connected and used.
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 1.0 × 10 ^{6 to} 5.0 × 10 ² 13 calibration curves are used. The 13 samples are preferably selected at approximately equal intervals.

  The cellulose ester content can be 50% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more based on the film.

  The protective films 53 (F1) and 65 (F4) may further contain various additives such as a plasticizer, an ultraviolet absorber, a peeling aid, and a matting agent (fine particles) as necessary.

(UV absorber)
The ultraviolet absorber may be a benzotriazole compound, a 2-hydroxybenzophenone compound, a salicylic acid phenyl ester compound, or the like. Specifically, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- Triazoles such as (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4 -Benzophenones such as methoxybenzophenone.

  The UV absorber may be a commercially available product. Examples thereof include Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, and Tinuvin 928 manufactured by BASF Japan, or 2, 2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; examples of commercially available products are manufactured by ADEKA Corporation LA31) and the like.

  The content of the ultraviolet light inhibitor can be about 1 ppm to about 5.0%, preferably about 0.5 to about 3.0% by mass ratio with respect to the cellulose ester.

(Matting agent)
The matting agent can be fine particles made of an inorganic compound or an organic compound. Examples of inorganic compounds constituting the matting agent include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated calcium silicate. , Aluminum silicate, magnesium silicate and calcium phosphate. Of these, silicon dioxide and zirconium oxide are preferable, and silicon dioxide is more preferable in order to reduce an increase in haze of the obtained film.

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (above, Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP -30, Seahoster KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), nip seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs) and the like.

  The particle shape of the matting agent is indefinite, needle-like, flat or spherical, and may be preferably spherical, for example, because the transparency of the resulting film is easily improved. One kind of matting agent may be used, or two or more kinds may be used in combination.

  When the size of the matting agent particles is close to the wavelength of visible light, the light is scattered and the transparency is lowered. Therefore, the size of the particles of the matting agent is preferably smaller than the wavelength of visible light. / 2 or less is preferable. However, if the size of the particles is too small, the effect of improving slipperiness may not be exhibited, so the size of the particles is preferably in the range of 80 to 180 nm. The particle size means the size of an aggregate when the particle is an aggregate of primary particles. When the particles are not spherical, the size of the particles means the diameter of a circle corresponding to the projected area.

  The content of the matting agent can be about 0.05 to 1.0% by mass, preferably 0.1 to 0.8% by mass with respect to the cellulose ester.

(Thickness)
The thicknesses of the protective films 53 (F1) and 65 (F4) may be set so that the ratio M1 / M4 of the contraction moment is in the above range, and may be in the range of 10 to 100 μm, for example. Especially, it is preferable that the thickness of the protective film 65 (F4) is 30-80 micrometers, and it is more preferable that it is 40-80 micrometers. From the viewpoint of making the contraction force ratio (W1 / W4) easy to be within the above range, it is preferable that the thickness t4 of the protective film 65 (F4) is appropriately larger than the thickness t1 of the protective film 53 (F1). The thickness ratio t1 / t4 of the protective film 53 (F1) and the protective film 65 (F4) can be more than 0.5 and less than 1, preferably 0.55 or more and less than 1, more preferably 0.6 or more and less than 1.

(Tensile modulus)
The tensile elastic moduli of the protective films 53 (F1) and 65 (F4) in the MD direction (preferably in the direction perpendicular to the in-plane slow axis direction) and TD direction (preferably in the in-plane slow axis direction) The force ratio (W1 / W4) and the contraction moment ratio (M1 / M4) may be set so as to be in the above range, and are not particularly limited, but may be in the range of 3500 to 5500 MPa, for example. Among them, the tensile elastic modulus in the TD direction (in-plane slow axis direction) of the protective film 65 (F4) is, for example, 3700 MPa or more, preferably 3900 MPa or more; MD direction (in-plane slow axis) of the protective film 53 (F1) The tensile modulus of elasticity in the direction perpendicular to the direction can be, for example, less than 3700 MPa. The tensile modulus can be adjusted mainly by the stretching temperature. The tensile modulus can be measured by the method described above.

(Dimensional change rate)
The dimensional change rates of the protective films 53 (F1) and 65 (F4) in the MD direction (direction perpendicular to the in-plane slow axis direction) and TD direction (in-plane slow axis direction) are the ratios of the above-mentioned contraction force. (W1 / W4) and the ratio of contraction moments (M1 / M4) may be set so as to be in the above range, and are not particularly limited, but may be in the range of 0.2% to 0.5%, for example. Among them, the dimensional change rate in the TD direction (in-plane slow axis direction) of the protective film 65 (F4) is, for example, 0.2% or more, preferably 0.22% or more; MD direction of the protective film 53 (F1) The dimensional change rate in the direction (perpendicular to the in-plane slow axis) can be, for example, 0.4% or less. The dimensional change rate can be adjusted mainly by the draw ratio, the draw temperature, and the residual solvent amount at the start of the draw. The dimensional change rate can be measured by the method described above.

(Retardation)
In the protective films 53 (F1) and 65 (F4), the in-plane retardation R ₀ measured under conditions of a measurement wavelength of 590 nm and 23 ° C. and 55% RH is preferably 0 to 20 nm. More preferably, it is 10 nm. The thickness direction retardation Rth of the protective film measured under the conditions of a measurement wavelength of 590 nm and 23 ° C. and 55% RH is preferably 0 to 80 nm, and more preferably 0 to 50 nm.

Retardations _R0 and Rth are defined by the following equations, respectively.
Formula (I): R ₀ = (nx−ny) × d (nm)
Formula (II): Rth = {(nx + ny) / 2−nz} × d (nm)
(In formulas (I) and (II),
nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the film; ny represents the refractive index in the direction y perpendicular to the slow axis direction x in the in-plane direction of the film. Nz represents the refractive index in the thickness direction z of the film; d (nm) represents the thickness of the film)

The retardations _R0 and Rth can be determined by the following method, for example.
1) Condition the protective film at 23 ° C. and 55% RH. The average refractive index of the protective film after humidity adjustment is measured with an Abbe refractometer or the like.
The protective film after 2) humidity, measuring the _{R 0} when the light is incident in parallel to the measurement wavelength 590nm to normal of the film surface, KOBRA21ADH, in Oji Scientific Corporation.
3) With KOBRA21ADH, the slow axis in the plane of the protective film is set as the tilt axis (rotation axis), and light having a measurement wavelength of 590 nm from the angle (incident angle (θ)) with respect to the normal of the surface of the retardation film Is measured for the retardation value R (θ). The retardation value R (θ) can be measured at 6 points every 10 °, with θ ranging from 0 ° to 50 °. The in-plane slow axis of the protective film can be confirmed by KOBRA21ADH.
4) nx, ny, and nz are calculated by KOBRA21ADH from the measured R ₀ and R (θ) and the above-described average refractive index and film thickness, and Rth at a measurement wavelength of 590 nm is calculated. The measurement of retardation can be performed under conditions of 23 ° C. and 55% RH.

  The protective film preferably has a total light transmittance of 80% or more, more preferably 90% or more, and still more preferably 93% or more.

  The haze value of the protective film is preferably 1.0% or less, and more preferably 0.5% or less. The haze can be measured with a haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) in accordance with JIS K-7136.

(Production method of protective films 53 (F1) and 65 (F4))
The protective films 53 (F1) and 65 (F4) are preferably manufactured by a solution casting method (cast) in order to reduce streak-like failure. That is, the protective films 53 (F1) and 65 (F4) are: 1) a step of obtaining a dope containing a cellulose ester, 2) a step of casting the dope on a support and drying it to obtain a film-like product, 3) A step of peeling the obtained film-like material from the support, and 4) a step of drying and stretching the film-like material.

1) Dissolution process The organic solvent used for the preparation of the dope solution can be used without limitation as long as it sufficiently dissolves each of the above components such as cellulose ester. Examples of the chlorinated organic solvent include methylene chloride. Examples of non-chlorine organic solvents include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone and the like. Of these, methylene chloride is preferred.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. By containing alcohol in the dope solution, the film-like material is gelled, and peeling from the metal support becomes easy. Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, methanol and ethanol are preferable because the stability of the dope, the boiling point is relatively low, and the drying property is good.

  Dissolution of cellulose ester and the like includes a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, and a method performed under pressure above the boiling point of the main solvent. Is preferred.

2) Casting step The dope solution is fed to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump). Then, the dope solution is cast from the slit of the pressure die to a casting position on an endless metal support (for example, a stainless belt or a rotating metal drum) that is transferred infinitely.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface.

3) Solvent evaporation / peeling step The dope solution cast on the metal support is heated on the metal support to evaporate the solvent in the dope solution to obtain a film-like material.

  In order to evaporate the solvent, there are a method of blowing wind from the dope liquid surface side, a method of transferring heat from the back surface of the support by a liquid, a method of transferring heat from the front and back by radiant heat, etc. The drying efficiency is good and preferable. The dope solution on the metal support is preferably dried on the support in an atmosphere within the range of 40 to 100 ° C. In order to maintain the atmosphere in the range of 40 to 100 ° C., it is preferable to apply hot air at this temperature to the dope liquid surface on the metal support or to heat by means such as infrared rays.

  The film-like material obtained by evaporating the solvent on the metal support is peeled off at the peeling position. The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

The amount of residual solvent of the film-like material on the metal support at the time of peeling can be set in the range of 50 to 120% by mass, for example. The amount of residual solvent in the film-like material is defined by the following formula.
Residual solvent amount (%) = (mass before heat treatment of film-like material−mass after heat treatment of film-like material) / (mass after heat treatment of film-like material) × 100
The heat treatment for measuring the residual solvent amount represents performing a heat treatment at 140 ° C. for 1 hour.

  The peeling tension when peeling the metal support and the film is usually in the range of 196 to 245 N / m. However, if wrinkles easily occur during peeling, peeling with a tension of 190 N / m or less is preferable. Further, it is more preferable to peel with a tension of 80 N / m or less.

4) Stretching step The stretching of the film-like material is preferably performed in the width direction (TD direction), transport direction (MD direction) or oblique direction of the film; more preferably in the width direction (TD direction). When stretching in both the width direction (TD direction) and the transport direction (MD direction) of the film, stretching in the width direction (TD direction) of the film and stretching in the transport direction (MD direction) may be performed sequentially. You may do it simultaneously.

  The shrinkage force of the protective film can be adjusted by stretching ratio, stretching temperature, stretching speed, residual solvent amount at the start of stretching, and the like. In order to increase the shrinkage force in the stretching direction of the protective film, it is preferable to lower the stretching ratio, lower the stretching temperature, increase the stretching speed, and increase the amount of residual solvent in the film-like material at the start of stretching.

  Therefore, the protective film 53 (F1) and the protective film 65 (F4) in which the ratio of shrinkage force (W1 / W4) satisfies the above range may be films manufactured under different stretching conditions. For example, the protective film 65 (F4) may be a film having a relatively high shrinkage force in the stretching direction; the protective film 53 (F1) may be a film having a relatively low shrinkage force in the stretching direction.

  In order to obtain the protective film 65 (F4) having a high shrinkage force in the stretching direction, the stretching ratio is lowered, the stretching temperature is lowered, the stretching speed is increased, and the amount of residual solvent in the film-like material at the start of stretching is large. It is preferable to do.

  By reducing the stretching ratio, the dimensional change rate in the stretching direction of the protective film can be increased. The draw ratio is preferably 1 to 22%, more preferably 5 to 15%. If the draw ratio is too low, the tensile elastic modulus may be too low. On the other hand, when the draw ratio is too high, the resulting protective film may be whitened. The draw ratio is defined as (stretching direction length of the film after stretching−stretching direction length of the film before stretching) / (length in the stretching direction of the film before stretching) × 100 (%).

  By lowering the stretching temperature, the tensile elastic modulus and dimensional change rate in the stretching direction of the protective film can be increased. The stretching temperature is in the range of (Tg-40) to (Tg + 20) ° C. when the glass transition temperature of the cellulose ester is Tg; specifically, it is preferably 135 to 165 ° C., and preferably 140 to 165 ° C. It is more preferable. If the stretching temperature is too low, the resulting protective film may be whitened.

  By increasing the residual solvent amount of the film-like material at the start of stretching, the dimensional change rate in the stretching direction of the protective film can be increased. The residual solvent amount of the film-like material at the start of stretching is preferably 7 to 18%, and more preferably 10 to 15%. If the residual solvent amount is too small, the resulting protective film may be whitened. The residual solvent amount of the film-like material at the start of stretching can be calculated by the same method as the residual solvent amount of the film-like material at the time of peeling.

  Thus, in order to sufficiently increase the shrinkage force in the stretching direction of the protective film 65 (F4), the stretching ratio is in the range of 1 to 22%, the stretching temperature is in the range of 135 to 160 ° C., and at the start of stretching. The residual solvent amount is preferably in the range of 7 to 18%.

  The protective film 53 (F1) can be manufactured under the same stretching conditions as those of a normal protective film. For example, the stretch ratio in producing the protective film 53 (F1) can be in the range of 15-40%; the stretch temperature can be in the range of 150-170 ° C .; and the residual solvent amount can be in the range of 5-15%.

<About protective films 55 (F2) and 63 (F3)>
The protective films 55 (F2) and 63 (F3) preferably contain a cellulose ester as a main component or a cycloolefin resin as a main component.

(Cellulose ester)
The cellulose ester may be the same as the cellulose ester described above. The cellulose ester may preferably be cellulose triacetate. The total substitution degree of the acyl group of the cellulose ester is about 2.0 to 3.0. When there is no need to increase the phase difference, the total substitution degree of the acyl group can be more than 2.5 and not more than 3.0, preferably 2.7 to 3.0. When the phase difference is set to a certain value or more, the total substitution degree of the acyl group can be 2.0 to 2.5. The number of carbon atoms of the acyl group contained in the cellulose ester is more preferably 2 to 4, and in order to obtain good heat resistance, all the acyl groups contained in the cellulose ester are preferably acetyl groups.

(Cycloolefin resin)
The cycloolefin resin is a polymer containing a structural unit having an alicyclic structure derived from a cycloolefin. The cycloolefin resin may be a cycloolefin addition (co) polymer or a bicycloolefin ring-opening addition (co) polymer. Examples of cycloolefins include cyclohexene and the like; examples of bicycloolefins include norbornene and tetracyclododecene, preferably norbornene.

  Examples of the copolymer component in the cycloolefin copolymer include an α-olefin and an aromatic compound having a vinyl group. Examples of α-olefins include ethylene and propylene. Examples of the aromatic compound having a vinyl group include styrene and α-methylstyrene. The proportion of the structural units derived from cycloolefin in the copolymer of cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). The copolymer component contained in the cycloolefin copolymer may be only one type or two or more types. For example, the copolymer of cycloolefin may be a ternary copolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group.

  Examples of the cycloolefin resin include cycloolefin resins described in JP 2010-78700 A. Examples of commercially available cycloolefin resins include ZEONOR (manufactured by ZEON Corporation), ZEONEX (manufactured by ZEON Corporation), APEL (manufactured by Mitsui Chemicals, Inc.) and the like. It is done. Examples of commercially available cycloolefin resin films include Essina (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), ZEONOR film (manufactured by Nippon Zeon Co., Ltd.), and the like. .

(Thickness)
Although the thickness of the protective films 55 (F2) and 63 (F3) depends on the required retardation value, it can be about 10 to 80 μm, preferably 20 to 60 μm. By making the thickness of the protective films 55 (F2) and 63 (F3) below a certain value, the polarizing plate can be thinned, and the dimensional change of the polarizing plate due to heat and humidity can be reduced. On the other hand, by setting the thickness of the protective films 55 (F2) and 63 (F3) to a certain value or more, it is easy to obtain a retardation value that is a certain value or more.

(Retardation)
The retardation of the protective films 55 (F2) and 63 (F3) can be set according to the type of liquid crystal cell to be combined. For example, the in-plane retardation R ₀ (590) measured at a wavelength of 590 nm under 23 ° C. RH 55% of the protective films 55 (F 2) and 63 (F 3) can be 20 to 130 nm, preferably 30 to 100 nm. The retardation Rth (590) in the thickness direction can be 100 to 300 nm, preferably 100 to 200 nm. A protective film having a retardation in the above range is suitable as a retardation film such as a VA mode liquid crystal cell.

Further, the in-plane retardation R ₀ (590) measured at a wavelength of 590 nm under 23 ° C. RH 55% of the protective films 55 (F2) and 63 (F3) can be −10 to 10 nm, preferably −5 to 5 nm. . The retardation Rth (590) in the thickness direction can be −10 to 10 nm, preferably −5 to 5 nm. A protective film having a retardation in the above range is suitable as a retardation film such as an IPS mode liquid crystal cell.

The retardations _R0 and Rth are defined as described above.

<Regarding First Polarizer 51 and Second Polarizer 61>
The first polarizer 51 and the second polarizer 61 are elements that allow only light having a plane of polarization in a certain direction to pass through, and a typical polarizer currently known is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  The polyvinyl alcohol-based polarizing film may be a film (preferably a film further subjected to a durability treatment with a boron compound) dyed with iodine or a dichroic dye after uniaxially stretching the polyvinyl alcohol-based film; A film obtained by dying an alcohol film with iodine or a dichroic dye and then uniaxially stretching (preferably a film further subjected to a durability treatment with a boron compound) may be used.

  The thicknesses of the first polarizer 51 and the second polarizer 61 are preferably 2 to 30 μm, more preferably 5 to 30 μm, and still more preferably 10 to 30 μm.

<About the manufacturing method of the 1st polarizing plate 50 and the 2nd polarizing plate 60>
The first polarizing plate 50 (or the second polarizing plate 60) has a protective film 53 (F1) (or a protective film 65 (F4) on one surface of the first polarizer 51 (or the second polarizer 61). )) Can be obtained through a step of attaching the protective film 55 (F2) (or the protective film 63 (F3)) to the other surface via an adhesive. The adhesive used for the bonding may be a completely saponified polyvinyl alcohol aqueous solution (water glue) or an active energy ray-curable adhesive.

  The active energy ray-curable adhesive composition is a photo radical polymerization composition using photo radical polymerization, a photo cation polymerization composition using photo cation polymerization, or a hybrid type using both photo radical polymerization and photo cation polymerization. It can be a composition or the like.

  A radical photopolymerizable composition is a composition containing a radically polymerizable compound containing a polar group such as a hydroxy group and a carboxy group described in JP-A-2008-009329 and a radically polymerizable compound containing no polar group at a specific ratio. It can be a thing. The radical polymerizable compound is preferably a compound having an ethylenically unsaturated bond capable of radical polymerization. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

  The cationic photopolymerization type composition comprises (α) a cationically polymerizable compound, (β) a cationic photopolymerization initiator, and (γ) light having a wavelength longer than 380 nm, as disclosed in JP 2011-028234 A. It may be a composition containing each component of a photosensitizer exhibiting maximum absorption and (δ) naphthalene photosensitizer.

  Such a polarizing plate is, for example, a step of subjecting the surface of the protective film to easy adhesion (corona treatment, plasma treatment, etc.); a step of applying an active energy ray-curable adhesive to at least one of the polarizer and the protective film; It can be manufactured through a step of bonding the polarizer and the protective film through the obtained adhesive layer; a step of curing the adhesive layer in a state where the polarizer and the protective film are bonded.

<About the backlight 30>
The backlight 30 is disposed so as to face the protective film 65 (F4). An arbitrary optical member can be disposed between the backlight 30 and the protective film 65 (F4).

  The backlight 30 may be a sidelight (edge light) type surface light source in which a known light source is disposed on the side of the light guide plate, or a direct type surface light source in which a known light source is arranged under the diffusion plate. Examples of known light sources include cold cathode fluorescent lamps (CCFL), hot cathode fluorescent lamps (HCFL), external electrode fluorescent lamps (EEFL), flat fluorescent lamps (FFL), light emitting diode elements (LEDs), organic electroluminescent elements (OLEDs). ) Is included.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

1. Production of protective film <Production of film 1>
(Preparation of fine particle additive solution 1)
11 parts by mass of fine particles A (Aerosil R976 manufactured by Nippon Aerosil Co., Ltd.) and 89 parts by mass of ethanol were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to obtain a fine particle dispersion 1.

  99 parts by mass of methylene chloride was added to the dissolution tank, and 5 parts by mass of the fine particle dispersion 1 was slowly added with sufficient stirring. Furthermore, the secondary particles were dispersed by an attritor so that the particle size of the secondary particles became a predetermined size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain a fine particle additive solution 1.

(Preparation of dope)
First, methylene chloride and ethanol were charged into a pressure dissolution tank, and then cellulose ester (cellulose triacetate having an acetyl group substitution degree of 2.9) was charged with stirring. This was completely dissolved with heating and stirring. The obtained solution was prepared as Azumi Filter Paper No. Filtration using 244 gave a main dope solution. The obtained main dope solution was put into a sealed container and further dissolved with stirring to obtain a dope solution.
(Dope solution composition)
Cellulose ester (A) (cellulose triacetate: acetyl group substitution degree 2.9, weight average molecular weight Mw: 282000): 100 parts by mass Additive A: 10 parts by mass Fine particle additive solution 1: 10 parts by mass Tinuvin 928 (Ciba Japan ( Co., Ltd.): 2.5 parts by mass Methylene chloride: 340 parts by mass Ethanol: 64 parts by mass

  The prepared dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1.7 m using an endless belt casting apparatus. The temperature of the stainless steel belt was adjusted to 30 ° C. After the solvent was evaporated on the stainless steel belt support until the amount of residual solvent in the cast dope solution reached 75%, the obtained film-like material was supported on the stainless steel belt with a peeling tension of 130 N / m. It peeled from the body.

The peeled film was stretched 22% in the width direction (TD direction) with a tenter while applying heat at 160 ° C. The residual solvent amount at the start of stretching was 10%. The residual solvent amount was determined from the following equation.
Residual amount of solvent in film (%) = (mass before heat treatment of film-like mass after heat treatment of film-like material) / (mass after heat treatment of film-like material) × 100
(The heat treatment means a heat treatment at 140 ° C. for 1 hour)

  The resulting film was dried while being transported through the drying zone by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m. The obtained film was cut into a predetermined width with a slitter, and then embossed to give an emboss height of 6 μm at the end in the width direction of the film by an embossing device. Thereby, a film 1 having a film width of 1.89 m and a film thickness of 58 μm was obtained.

<Production of films 2-3 and 20>
Films 2 to 3 and 20 were produced in the same manner as the film 1 except that the film thickness of the obtained film was changed as shown in Table 1. The film thickness was adjusted according to the casting amount.

<Preparation of films 4-7>
Films 4 to 7 were produced in the same manner as film 1 except that the draw ratio was changed as shown in Table 1.

<Production of films 8 to 11>
Films 8 to 11 were produced in the same manner as film 1 except that the stretching temperature was changed as shown in Table 1.

<Preparation of film 12>
A film 12 was produced in the same manner as the film 1 except that the stretching temperature and the stretching ratio were changed as shown in Table 1.

<Production of films 13 to 15>
Films 13 to 15 were produced in the same manner as film 1 except that the amount of residual solvent at the start of stretching was changed as shown in Table 1.

<Preparation of films 16-18>
Films 16 to 18 were produced in the same manner as the film 1 except that the residual solvent amount at the start of stretching, the stretching temperature, and the stretching ratio were changed as shown in Table 1.

（上記一般式（１）中、Ｒ^１は水素原子であり、Ｒ^２およびＲ^３はメチル基である）<Production of Film 19>
A (meth) acrylic resin having a lactone ring structure represented by the following general formula (1) was prepared. This (meth) acrylic resin has a copolymerization monomer mass ratio = methyl methacrylate / 2- (hydroxymethyl) methyl acrylate = 8/2, a lactone cyclization rate of about 100%, and a lactone ring structure content ratio of 19.4. %, Weight average molecular weight 133000, melt flow rate 6.5 g / 10 min (240 ° C., 10 kgf), Tg 131 ° C. Pellets of a mixture (Tg 127 ° C.) of 90 parts by mass of this (meth) acrylic resin and 10 parts by mass of acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) were prepared.

(In the general formula (1), R ¹ is a hydrogen atom, and R ² and R ³ are methyl groups)

  This pellet was supplied to a biaxial extruder and melt extruded into a sheet at about 280 ° C. to obtain a film having a lactone ring structure with a thickness of 80 μm. This film was stretched 1.5 times in length and 1.8 times in width under a temperature condition of 160 ° C., and had a thickness of 40 μm, an in-plane retardation Δnd: 0.8 nm, and a thickness direction retardation Rth: 1.5 nm. A (meth) acrylic resin film was obtained.

  The tensile elastic modulus and dimensional change rate of the obtained film were measured by the following methods.

<Tensile modulus>
(Tensile modulus in MD direction)
The obtained film was cut into a shape of No. 1 with a size of 150 mm (MD direction) × 10 mm (TD direction), and used as a test piece. The test piece was conditioned at 23 ° C. and 55% RH for 24 hours, and then pulled in the MD direction according to the method described in JIS K 7127, and the tensile modulus in the MD direction was measured. As the tensile tester, Tensilon RTC-1225A manufactured by Orientec Co., Ltd. was used, and the tensile speed was 100 mm / min. The tensile elastic modulus in the MD direction was calculated by setting the elastic modulus analysis start point to 2 (MPa) and the elastic modulus analysis end point to 60 (MPa).

(Tensile modulus in TD direction)
The obtained film was cut into a No. 1 shape with a size of 150 mm (TD direction) × 10 mm (MD direction) to obtain a test piece; the same as described above except that the test piece was pulled in the TD direction. The tensile elastic modulus in the TD direction was measured.

<Dimensional change rate>
(Dimension change rate in MD direction)
1) The obtained film was cut into a size of 25 cm in length (measurement direction) × 5 cm in width so that the MD direction was the longitudinal direction, and used as a test piece. Pin holes were formed at intervals of 20 cm in the MD direction of this test piece, and after adjusting the humidity for 24 hours at 23 ° C. and 55% relative humidity, the distance between the pin holes was measured with a pin gauge to obtain a measured value L0.
2) Subsequently, the test piece was conditioned for 24 hours in a humid heat environment of 23 ° C. and a relative humidity of 20%, and then the interval between the pin holes was measured with a pin gauge to obtain a measured value L1.
3) Further, the specimen was conditioned at 23 ° C. and 80% relative humidity for 24 hours, and the distance between the pin holes was measured with a pin gauge to obtain a measured value L2.
4) These measurement values were applied to the following formula to calculate the dimensional change rate (%) in the MD direction.
Dimensional change rate (%) = {(L2-L1) / L0} × 100

(Dimension change rate in TD direction)
The obtained film was cut into a size of 25 cm in length (measurement direction) × 5 cm in width so that the TD direction was the longitudinal direction, and used as a test piece. The dimensional change rate (%) in the TD direction was measured in the same manner as described above, except that pin holes were formed at intervals of 20 cm in the TD direction of the test piece and the distance between the pin holes was measured.

The production conditions and physical properties of the obtained film are shown in Table 1.

  As shown in Table 1, the thickness of the film is large (films 1 to 3), the amount of residual solvent in the film-like material at the start of stretching is large (films 1 and 13 to 15), and the stretching temperature is low (films 1 and 8-11) It turns out that the shrinkage force of the width direction (TD direction) of a film obtained is so large that a draw ratio is low (films 1 and 4-7). However, if the amount of residual solvent at the start of stretching is too small (film 15), the stretching temperature is too low (film 11), or the stretching ratio is too high (film 4), the resulting film will be whitened and a protective film It turns out that it is not suitable as.

2. Production of Liquid Crystal Display Device <Example 1>
(Production of polarizer)
A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. The uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 20 μm.

(Preparation of the first polarizing plate)
The surface of the produced film 1 was subjected to alkali saponification treatment as follows. Specifically, the film 1 produced above was immersed in a 1.5N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes, then washed in a water-washing bath at room temperature, and 0.1N sulfuric acid was used at 30 ° C. It was summed up. The obtained film 1 was again washed in a water bath at room temperature and then dried with hot air at 100 ° C. Similarly to this, Konica Minolta Tac KC4CR (manufactured by Konica Minolta Co., Ltd.) was prepared, and the surface was subjected to alkali saponification treatment.

  The film 1 having a surface subjected to alkali saponification treatment, the polarizer, and KC4CR having been subjected to alkali saponification treatment were bonded together via a 3% by weight aqueous solution of polyvinyl alcohol (PVA-117H manufactured by Kuraray Co., Ltd.) as an adhesive. A laminate of KC4CR was obtained. Bonding is performed such that the saponification surface of the film and the saponification surface of KC4CR are in contact with the polarizer; and the MD direction of the film and the slow axis of KC4CR are parallel to the absorption axis of the polarizer. I went like that. The obtained laminate was dried to obtain a first polarizing plate.

(Production of second polarizing plate)
A second polarizing plate was produced in the same manner except that the film 1 was changed to the film 3 in the production of the first polarizing plate.

(Production of liquid crystal display device)
A commercially available VA type liquid crystal television (Skyworth 55E61HR) having a diagonal line length of 55 inches and a t ′ / l of 0.0004 was prepared. The two polarizing plates are peeled off from the liquid crystal television, the prepared first polarizing plate is disposed on the viewing side surface of the liquid crystal cell, and the prepared second polarizing plate is disposed on the backlight side surface of the liquid crystal cell. Then, KC4CR (protective films F2 and F3) were attached to each other via an adhesive so that the liquid crystal cell side was obtained, thereby obtaining a liquid crystal display device. The thickness of the adhesive layer was 0.02 mm in all cases. The transmission axis of the first polarizing plate (viewing side polarizing plate) is the short side direction β of the liquid crystal display panel; the transmission axis of the second polarizing plate (backlight side polarizing plate) is the long side direction of the liquid crystal display panel They were placed in crossed Nicols so that α. The two glass plates used in the liquid crystal cell each had a thickness of 0.5 mm.

<Examples 2-9, Comparative Examples 1-3 and 11>
A liquid crystal display device was produced in the same manner as in Example 1 except that the type of the protective film F4 of the second polarizing plate was changed as shown in Table 2.

<Example 10>
As the first polarizing plate and the second polarizing plate, a liquid crystal display device was obtained in the same manner as in Example 1 except that polarizing plates prepared by the following methods were used.
(Preparation of photocurable adhesive)
After mixing the following components, defoaming was performed to prepare a photocurable adhesive liquid. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.
(Composition of photocurable adhesive liquid)
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate: 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries): 40 parts by mass 1,4-butanediol diglycidyl ether: 15 parts by mass Triarylsulfonium hexafluorophosphate: 2.3 parts by mass 9,10-dibutoxyanthracene: 0.1 parts by mass 1,4-diethoxynaphthalene: 2.0 parts by mass

(Preparation of the first polarizing plate)
The surface of the produced film 1 was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the adhesive solution prepared above was applied to the corona discharge treated surface of the film 1 with a bar coater so that the film thickness after curing was about 3 μm to form an adhesive layer. The produced polarizer was bonded to the obtained adhesive layer.

Similarly, KC4CR (manufactured by Konica Minolta Co., Ltd.) was prepared, and the surface thereof was subjected to corona discharge treatment. The conditions for the corona discharge treatment were the same as described above. Next, the adhesive solution prepared above was applied to the corona discharge treated surface of the film with a bar coater so that the film thickness after curing was about 3 μm to form an adhesive layer. A polarizer of a polarizer having a polarizing plate protective film bonded on one side was bonded to this adhesive layer to obtain a laminate of film 1 / polarizer / KC4CR. This laminate was irradiated with ultraviolet rays so that the accumulated light amount became 750 mJ / cm ² using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), and an adhesive layer was formed. Cured to obtain a first polarizing plate.

(Production of second polarizing plate)
A second polarizing plate was produced in the same manner except that the film 1 was changed to the film 3 in the production of the first polarizing plate.

<Example 11>
A commercially available IPS liquid crystal television (LG Electronics 55LS5600) having a diagonal length of 55 inches and a t ′ / l of 0.0004 was prepared. The two polarizing plates of this IPS type liquid crystal television were peeled off, and the first polarizing plate produced in Example 1 on the viewing side surface of the liquid crystal cell; the first polarizing plate produced in Example 1 on the backlight side surface of the liquid crystal cell. The 2nd polarizing plate was affixed through the adhesive and the liquid crystal display device was obtained. The thickness of the adhesive layer was 0.02 mm in all cases. The transmission axis of the first polarizing plate (viewing side polarizing plate) is the short side direction β of the liquid crystal display panel; the transmission axis of the second polarizing plate (backlight side polarizing plate) is the long side direction of the liquid crystal display panel They were placed in crossed Nicols so that α. The two glass plates used in the liquid crystal cell each had a thickness of 0.5 mm.

<Examples 12 to 15>
Except for changing at least one of the thickness of the pressure-sensitive adhesive layer for bonding the first polarizing plate and the liquid crystal cell and the thickness of the pressure-sensitive adhesive layer for bonding the second polarizing plate and the liquid crystal cell as shown in Table 2 Obtained a liquid crystal display device in the same manner as in Example 1.

<Example 16, Comparative Examples 4-6>
A liquid crystal display device was produced in the same manner as in Example 1 except that the thickness of at least one of the protective film F1 of the first polarizing plate and the protective film F4 of the second polarizing plate was changed as shown in Table 2. .

<Comparative Examples 7 to 10>
A liquid crystal display device was produced in the same manner as in Example 1 except that at least one of the protective film F1 for the first polarizing plate and the protective film F4 for the second polarizing plate was changed as shown in Table 2. .

<Example 17>
The type of the protective film F2 for the first polarizing plate and the protective film F3 for the second polarizing plate was changed to the cycloolefin resin film shown in Table 2 (Zeonor film (manufactured by Nippon Zeon Co., Ltd., thickness 50 μm)). Produced a liquid crystal display device in the same manner as in Example 1.

  Display unevenness of the obtained liquid crystal display device was evaluated by the following method.

<Display unevenness in the front direction>
The obtained liquid crystal display device was held in an environment of 40 ° C. and 95% RH for 24 hours, and then held in an environment of 40 ° C. and 20% RH for 2 hours. After that, it was moved to an environment of 23 ° C. and 55% RH, and the liquid crystal display device was kept on in a black display state. At this time, when observed from the front of the liquid crystal display device, luminance unevenness during black display was observed, and the degree of occurrence of luminance unevenness was evaluated according to the following criteria.
◎: Unevenness is hardly visually recognized ○: Light unevenness is visually recognized △: Clear unevenness is visually recognized at the edge (corner) of the screen ×: Clear unevenness is visually recognized in the middle of the screen according to the above unevenness

The manufacturing conditions of the liquid crystal display devices of Examples 1 to 17 and Comparative Examples 1 to 11 are shown in Table 2, and the evaluation results are shown in Table 3.

  In the liquid crystal display devices of Examples 1 to 17 in which the shrinkage force ratio W1 / W4 is in the range of more than 0.84 and less than 1.2, it can be seen that display unevenness due to warpage of the liquid crystal display panel is suppressed. In contrast, the liquid crystal display devices of Comparative Examples 5 and 8 in which the ratio W1 / W4 of contraction force is 0.84 or less, and Comparative Examples 1 to 4, and 6 to 7 and 9 in which W1 / W4 is greater than 1.20. In the liquid crystal display devices Nos. 11 to 11, display unevenness due to warpage of the liquid crystal display panel was observed.

  Specifically, in the liquid crystal display devices of Comparative Examples 5 and 8, the liquid crystal display panel warps so that the contraction force of the polarizing plate on the backlight side is relatively large and protrudes to the viewing side, resulting in display unevenness. It is thought that occurred. On the other hand, in the liquid crystal display devices of Comparative Examples 1 to 4, 6 to 7, and 9 to 11, the contraction force of the polarizing plate on the backlight side is insufficient, and the warp of the liquid crystal display panel that protrudes toward the backlight side is sufficient. It is thought that it could not be reduced.

  Moreover, even if the ratio W1 / W4 of contraction force is the same from Examples 12 to 16, the contraction moment M1 / M4 is preferably 0.7 or more and 1.2 or less, more preferably 0.9 or more. It can be seen that display unevenness is further suppressed when it is 1.0 or less. From this, it can be seen that the warpage of the liquid crystal display panel depends not only on the ratio W1 / W4 of the contraction force between the first polarizer and the second polarizer but also on the ratio M1 / M4 of the contraction moment.

  This application claims the priority based on Japanese Patent Application No. 2014-094848 of May 1, 2014 application. The contents described in the application specification and the drawings are all incorporated herein.

  ADVANTAGE OF THE INVENTION According to this invention, the curvature of a liquid crystal display panel can be reduced and the liquid crystal display device by which the display nonuniformity by it was reduced can be provided.

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 20 Liquid crystal display panel 30 Backlight 40 Liquid crystal cell 41, 43 Transparent substrate 45 Liquid crystal layer 50 1st polarizing plate 51 1st polarizer 53 Protective film (F1)
55 Protective film (F2)
60 Second polarizing plate 61 Second polarizer 63 Protective film (F3)
65 Protective film (F4)
71 Adhesive layer

Claims (5)

A liquid crystal display device including a first polarizing plate, a liquid crystal cell, a liquid crystal display panel including a second polarizing plate, and a backlight,
The first polarizing plate is disposed on the viewing side surface of the liquid crystal cell, the first polarizer, the protective film F1 disposed on the viewing side surface of the first polarizer, and the first A protective film F2 disposed on the surface of the polarizer of the liquid crystal cell side,
The second polarizing plate is disposed on the backlight side surface of the liquid crystal cell, the second polarizer, and a protective film F3 disposed on the liquid crystal cell side surface of the second polarizer, A protective film F4 disposed on the backlight side surface of the second polarizer,
The absorption axis of the first polarizer is parallel to the long side direction α of the liquid crystal display panel, and is orthogonal to the absorption axis of the second polarizer,
The contraction force in the long side direction α represented by the following formula (1) of the protective film F1 is defined as W1, and the contraction force in the long side direction α represented by the following formula (1) of the protective film F4 is defined as W4. A liquid crystal display device in which the ratio W1 / W4 of shrinkage force is more than 0.84 and not more than 1.20.

(In Formula (1),
W is the contraction force (N / m) in the long side direction α of the protective film,
T is the tensile elastic modulus (Pa) in the long side direction α of the protective film,
S is a dimensional change rate (%) accompanying the humidity change in the long side direction α represented by the following formula (2) of the protective film:
t represents the thickness (m) of the protective film)

(In Formula (2),
S is the dimensional change rate (%) accompanying the humidity change in the long side direction α of the protective film,
L0 is the length of the long side direction α under 23 ° C. and 55% RH of the protective film,
L1 is the length of the long side direction α under 23 ° C. and 20% RH of the protective film
L2 represents the length of the long side direction α under 23 ° C. and 80% RH of the protective film) The distance from the surface on the viewing side of the liquid crystal cell to the surface on the viewing side of the protective film F1 is D1, and the contraction moment of the long side direction α represented by the following formula (3) of the protective film F1 is M1, The distance from the backlight side surface of the liquid crystal cell to the backlight side surface of the protective film F4 is D4, and the contraction moment of the protective film F4 in the long side direction α represented by the following formula (3): When M4
The liquid crystal display device according to claim 1, wherein the ratio M1 / M4 of the contraction moment is 0.7 or more and 1.2 or less.

(In Formula (3),
M is the contraction moment (N) of the protective film in the long side direction α,
W is the contraction force (N / m) in the long side direction α of the protective film,
D represents the distance (m)) from the surface of the liquid crystal cell of the protective film) The liquid crystal cell includes a liquid crystal layer and a pair of glass substrates sandwiching the liquid crystal layer,
2. The t ′ / l is 0.0001 to 0.0007, where t ′ (mm) is the thickness of the glass substrate and 1 (mm) is the length in the long side direction of the liquid crystal display panel. A liquid crystal display device according to 1.   The liquid crystal display device according to claim 1, wherein the protective film F <b> 4 is a cellulose ester film having a thickness of 30 to 80 μm.   The liquid crystal display device according to claim 1, wherein the protective films F2 and F3 are cellulose ester films having a thickness of 20 to 60 µm or cycloolefin films having a thickness of 20 to 60 µm.

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