KR20160079693A - Optical film and solution film-forming method - Google Patents

Abstract

Provided are an optical film having a protective film function and a brightness improving function of a polarizing plate, and a solution film forming method capable of manufacturing the long optical film. The present invention forms a flexible film by continuously stretching a first dope and a second dope on a driving belt and forms a wetting film generated by peeling the flexible film from the belt. A concave part and a convex part are formed on a second layer formed by the second dope of the wetting film by using a formation providing roller. The wetting film is guided to a heating room and a heating process is performed for 15 minutes. The optical film is obtained by the heating process. The obtained optical film includes a cellulose acylate layer (21) and a hardening layer (22). A refractive index of the hardening layer (22) is larger than a refractive index of the cellulose acylate layer (21). A prism sheet (16) is obtained from the optical film.

Description

OPTICAL FILM AND SOLUTION FILM-FORMING METHOD [0002]

The present invention relates to an optical film and a solution film-forming method for producing the optical film.

In recent years, a liquid crystal display (LCD) has become widespread. This liquid crystal display device has characteristics such as low power consumption and thinness and is used in various devices ranging from a large-sized device such as a home television to a monitor of a notebook computer, a small-sized device such as a digital camera, and a mobile phone. As such a liquid crystal display device, a backlight type which illuminates a liquid crystal panel with a backlight has been popular.

A general configuration of a backlight type liquid crystal display device includes a liquid crystal panel that changes the transmittance of light according to an electric signal and a light source unit (backlight) that irradiates light from behind the liquid crystal panel. A liquid crystal panel is composed of a pair of polarizers arranged in a crossed Nicols state and a liquid crystal cell interposed between the polarizers and changing a polarization state of light transmitted therethrough. The light source unit includes a light source such as a fluorescent tube and an LED (Light Emitting Diode), a diffusion sheet for scattering and diffusing light from the light source, and a so-called BEF A brightness enhancement film called a brightness enhancement film, or the like. As described above, the liquid crystal display device is constituted by a plurality of members, and in order to further reduce the thickness of the liquid crystal display device, the individual members are made thinner. For example, cellulose acylate films, which are widely used as protective films for polarizing plates, have become thinner in recent years.

As the brightness enhancement sheet, a prism sheet is widely used. This prism sheet deflects the light emitted in the oblique direction from the light source in the normal direction of the liquid crystal panel. As a prism sheet in which a plurality of prisms having a triangular cross section on one side are formed at a constant pitch, there is a prism sheet in which the direction of a prism (hereinafter referred to as a prism surface) is arranged to be directed toward the liquid crystal panel side Type prism sheet (so-called upward prism sheet) and a total reflection type prism sheet (so-called downward prism sheet) in which the prism surface faces the light source side. The upward prism sheet refracts the light beam toward the normal direction of the liquid crystal panel when the light ray incident from the surface opposite to the prism surface is emitted from the slope surface of the prism. On the other hand, the downward prism sheet totally reflects light rays from a light source which is incident from one slope of the prism and travels inside the prism toward the normal line direction of the liquid crystal panel on the other slope.

Further, as described in, for example, JP-A-2009-157029, an optical film in which a prism is formed is also known. As described in Japanese Patent Application Laid-Open No. 2005-173057, for example, in the case where a pattern is formed in the interior, two resins cured with ultraviolet rays are superimposed on glass, There is an optical element in which a lattice pattern is formed.

As a method for producing an optical film having a prism formed therein, for example, as described in Japanese Patent Application Laid-Open No. 2009-157029, after the ionizing radiation cured resin is pressed and transferred onto the surface on which the prism is formed, To thereby cure the ionizing radiation curable resin, thereby forming an optical element. There is provided a method of manufacturing an optical element in which a pattern is formed in the interior of the optical element, for example, as disclosed in Japanese Patent Application Laid-Open No. 2005-173057, There has been proposed a method in which a pattern is given to a resin through a curing resin and a second ultraviolet curable resin is placed on the pattern side of the first ultraviolet curable resin and pressed to form an optical element.

However, even if the individual members are thinned, the thickness of the liquid crystal display device is limited. Further, when the above-mentioned cellulose acylate film is made thinner, there is a problem that the handling property (handling property) at the time of making a polarizing plate is poor. Further, when the prism sheet is made thin, the warp of the prism sheet becomes large, which causes a problem in making the polarizer. Therefore, it is desired to reduce the number of members of the liquid crystal display device by contributing to the function of improving the brightness of the prism sheet in the cellulose acylate film, thereby contributing to reduction in thickness.

According to the manufacturing method described in Japanese Patent Application Laid-Open No. 2009-157029, ionized radiation curable resin does not enter the concave portion of the prism pattern and minute voids are formed. This method is a reliable manufacturing method Can not. Similarly, according to the production method described in Japanese Patent Application Laid-Open No. 2005-173057, the second ultraviolet curable resin may not be contained in the concave portion of the pattern of the first ultraviolet curable resin, and minute voids may be formed. The method is not a reliable manufacturing method. Further, the production method described in Japanese Patent Application Laid-Open No. 2005-173057 can not produce a long optical film made of, for example, a prism sheet because continuous production is difficult.

An object of the present invention is to provide an optical film having a function as a protective film and a brightness improving function of a polarizing plate, and a solution film-forming method capable of producing the optical film in a long time.

The optical film of the present invention comprises a cellulose acylate layer and a cured layer. The cellulose acylate layer has one surface serving as one film surface of the optical film, and contains cellulose acylate. The cured layer has one surface serving as the other film surface of the optical film and is formed of a transparent thermosetting resin on the other side of the cellulose acylate layer and has a refractive index higher than that of the cellulose acylate layer, And has a plurality of prisms.

The cellulose acylate is preferably cellulose triacetate. The thermosetting resin preferably has a refractive index in the range of 1.50 or more and 2.20 or less.

The thermosetting resin is preferably produced by thermosetting a thermosetting compound having a polymerizable group comprising an ethylenic unsaturated bond. The thermosetting compound preferably has at least two of the above-mentioned polymerizable groups in one molecule.

It is preferable that the optical film is disposed on the polarizing film on the light source side of the liquid crystal display device having the liquid crystal cell and the two polarizing films and is provided in close contact with the light source side of the polarizing film.

The solution film-forming method of the present invention has the first step, the second step, the third step and the fourth step described below and produces an optical film having a plurality of prisms. The first step is a step in which a first dope containing cellulose acylate and a first solvent and a second dope containing a cellulose acylate and a thermosetting compound which thermally cures a transparent thermosetting resin having a refractive index higher than that of cellulose acylate and a second solvent The second dope made of the first dope and the second dope made of the first dope are formed by continuous pliability on the traveling casting support body to form a flexible film in which the first layer made of the first dope and the second layer made of the second dope are superimposed. The second step forms a wet film by peeling the flexible film from the flexible support in a state where the first solvent and the second solvent remain. The third step is a configuration roller in which a plurality of concave portions and convex portions each having a triangular cross section extending in the width direction of the flexible film are alternately formed along the circumferential direction on the peripheral surface, Thereby forming a plurality of prisms continuously in the second layer. In the fourth step, the flexible film or the wet film having a residual solvent amount of not more than 300% with respect to the solid component through the third step is transported for at least 15 minutes while heating, thereby exfoliating the thermosetting compound onto the plurality of prisms, Is dried to cure the thermosetting compound.

In the fourth step, it is preferable that the flexible film or the wet film is heated and maintained at a temperature within the range of 140 ° C or higher and 200 ° C or lower.

In the fourth step, it is preferable to heat the flexible film or the wet film by carrying it in a temperature-controlled atmosphere.

The thermosetting resin preferably has a refractive index in the range of 1.50 or more and 2.20 or less. The molecular weight of the thermosetting compound is preferably in the range of 250 to 2,000. The thermosetting compound preferably has a polymerizable group composed of an ethylenically unsaturated bond and more preferably has at least two polymerizable groups in one molecule.

The optical film of the present invention has a function of improving the brightness in addition to the function of the protective film of the polarizing plate. Further, according to the solution film-forming method of the present invention, it is possible to produce an optical film having a function as a protective film and a function for improving brightness of a polarizing plate over a long period of time.

The above objects and advantages will be readily apparent to those skilled in the art by reading the detailed description of the preferred embodiments with reference to the accompanying drawings.
1 is an explanatory view showing an example of a configuration of a liquid crystal display device using a prism sheet according to the present invention.
2 is a perspective view showing an appearance of a prism sheet;
3 is a cross-sectional view of a prism sheet;
FIG. 4 is an explanatory view schematically showing a liquid film-forming equipment according to the present invention. FIG.
5 is an explanatory view showing a configuration of a shape imparting device;
6 is a cross-sectional view of the main surface of the shape-imparting roller;
7 is an explanatory diagram of a wet film and an optical film;
8 is an explanatory view schematically showing a solution film-forming equipment.

1, the liquid crystal display device 10 includes a liquid crystal panel 11 and a light source unit 12. The liquid crystal panel 11 is composed of a liquid crystal cell 13 and two polarizing plates 14 and 15. The liquid crystal cell 13 is formed by enclosing a liquid crystal between transparent glass substrates. By applying a voltage between transparent electrodes formed on the inner surface of each glass substrate, the polarization state of the transmitted light is changed. The polarizing plate 14 and the polarizing plate 15 are disposed in a crossed Nicols state and the liquid crystal cell 13 is disposed between the polarizing plate 14 and the polarizing plate 15. As a result, the polarization state of the linearly polarized illumination light transmitted through the polarizing plate 15 is changed to the liquid crystal cell 13 for each pixel, and the amount of light transmitted through the polarizing plate 14 is adjusted to display an image.

The polarizing plate 14 is composed of a polarizing film 14a and a pair of protective films 14b and 14c adhered to both surfaces thereof. The polarizing plate 15 is composed of a polarizing film 15a, a protective film 15b and a prism sheet 16. The protective film 15b is pasted on the surface of the polarizing film 15a on the liquid crystal cell 13 side. The prism sheet 16 is a sheet cut from an optical film 33 (see Fig. 4) prepared by using a solution casting method described later, and is composed of a cellulose acylate layer 21 and a cured layer 22 . This prism sheet 16 is attached to the surface of the polarizing film 15a on the side of the light source unit 12 and functions as a protective film of the polarizing film 15a and a total reflection type prism sheet (upward prism sheet) . The details of the prism sheet 16 will be described later with reference to other drawings.

The light source unit 12 illuminates the liquid crystal panel 11 from behind and is of the edge light type including the light source lamp 17, the light guide plate 18, and the reflective film 19. The light source lamp 17 uses a rod-shaped fluorescent tube or a plurality of LEDs (light emitting diodes) arranged in a line shape. The light source lamp 17 is provided with an end portion ). The illumination light emitted from the light source lamp 17 is directly reflected by the reflector 17a and is incident from the end of the light guide plate 18 to the inside. The light guide plate 18 reflects the incident illumination light inside the liquid crystal panel 11 to project the liquid crystal panel 11 in the oblique direction with a slope with respect to the normal to the liquid crystal panel 11 from the exit surface 18a, . The reflective film 19 reflects the illumination light emitted from the surface of the light guide plate 18 opposite to the liquid crystal panel 11 and returns the light to the light guide plate 18. [

As shown in Fig. 2, the prism sheet 16 is a one-piece structure in which the cellulose acylate layer 21 and the cured layer 22 are overlapped. The cellulose acylate layer 21 is formed of cellulose acylate and may contain an additive such as an anti-deterioration agent and ultraviolet absorber (UV agent) in addition to the cellulose acylate. In this embodiment, TAC (triacetyl cellulose, cellulose triacetate) is used as the cellulose acylate. However, other cellulose acylate may be used instead of TAC. That is, other acyl groups may be used instead of acetyl groups. Among the cellulose acylates, the present invention is particularly effective when the substitution degree of the acyl group in the hydroxyl group (hydroxyl group) of the cellulose satisfies the following formulas (I) to (III). In the formulas (I) to (III), A and B represent degrees of substitution of an acyl group for a hydrogen atom in the hydroxyl group of cellulose, A represents an acetyl group substitution degree, and B represents an acyl group having 3 to 22 carbon atoms ≪ / RTI > The total acyl substitution degree Z of the cellulose acylate is a value obtained by A + B.

(I) 2.7? A + B? 3.0

(II) 0? A? 3.0

(III) 0? B? 2.9

Further, in the case where DAC (diacetyl cellulose, cellulose diacetate) is used in place of, or in addition to, TAC, the substitution degree of the acyl group in the hydroxyl group of the cellulose satisfies the following formula (IV) Do.

(IV) 2.0? A + B < 2.7

From the viewpoint of the wavelength dispersion of retardation, the sum B of the degree of substitution A of the acetyl group of DAC and the degree of substitution of the acyl group having 3 to 22 carbon atoms, satisfying the formula (IV) And (VI).

(V) 1.0 < A < 2.7

(VI) 0? B < 1.5

The glucose unit having? -1,4 bonding constituting cellulose has a free hydroxyl group (hydroxyl group) at 2-position, 3-position and 6-position. The cellulose acylate is a polymer (polymer) obtained by esterifying a part or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio of the esterified hydroxyl groups of cellulose to the 2-position, 3-position and 6-position, respectively (100% esterification is referred to as substitution 1).

Details of the cellulose acylate are described in paragraphs [0140] to [0195] of Japanese Patent Application Laid-Open No. 2005-104148, and these descriptions are also applicable to the present invention. Also, additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers (UV agents), optically anisotropic control agents, retardation control agents, dyes, matting agents, stripping agents and release promoting agents are likewise disclosed in JP-A-2005-104148 Are described in detail in paragraphs [0196] to [0516] of the present invention, and these descriptions are also applicable to the present invention.

The cured layer 22 is formed of a transparent thermosetting resin (thermosetting polymer). The thermosetting resin is produced by curing the thermosetting compound by heating, and details of the thermosetting compound will be described later. When the refractive index of the cellulose acylate layer 21 is N21 and the refractive index of the cured layer 22 is N22, the refractive index N22 is higher than the refractive index N21. As a result, when the illumination light is emitted from the cured layer 22 to the cellulose acylate layer 21, refraction occurs. The refractive index difference obtained by N22-N21 is preferably 0.20 or more, more preferably 0.30 or more, and still more preferably 0.50 or more. The thermosetting resin preferably has a refractive index in the range of 1.50 or more and 2.20 or less, more preferably 1.50 or more and 1.80 or less, and more preferably 1.50 or more and 1.60 or less. Also, the main cellulose acylate has a TAC refractive index of 1.48 and a DAC refractive index of 1.48.

One surface of the cellulose acylate layer 21 is one sheet surface of the prism sheet 16 and one surface of the cured layer 22 is the other sheet surface of the prism sheet 16 and any sheet surface is a flat flat surface . These sheet surfaces are formed smoothly, and the degree of smoothing (hereinafter referred to as the smoothing degree) is within a range in which the arithmetic mean roughness Ra in accordance with Japanese Industrial Standard JIS B0601-2013 is 1 占 퐉 or more and 10 占 퐉 or less. The prism sheet 16 adheres to the polarizing film 15a in such a manner that the flat surface on the side of the cured layer 22 faces the light source unit 12 and the flat surface on the side of the cellulose acylate layer 21 adheres to the polarizing film 15a .

The boundary surface between the cellulose acylate layer 21 and the cured layer 22 is a surface shape in which triangular irregularities are repeated in one direction and the cured layer 22 is provided on the boundary with the cellulose acylate layer 21, 22a. Each prism 22a is in the form of a prism having a triangular cross section and arranged in a direction orthogonal to the extending direction of each prism 22a.

The prism sheet 16 is incident on the flat surface of the cured layer 22 side with the illumination light from the light guide plate 18 (see Fig. 1). The prism sheet 16 controls the distribution of illumination light so as to increase the amount of illumination light emitted in the normal direction of the liquid crystal panel 11. [ That is, the prism sheet 16 deflects the illumination light emitted in the oblique direction from the light guide plate 18 in the normal direction of the liquid crystal panel 11. Specifically, the illumination light emitted in the oblique direction from the light guide plate 18 travels through the interior of the cured layer 22 and exits from the slope of the prism 22a, so that the cured layer 22 and the cellulose acylate layer 21, And is deflected in the normal line direction. The prism sheet 16 has a size substantially equal to the back surface of the liquid crystal panel 11.

In FIG. 3, the thickness T16 of the prism sheet 16 is in the range of 100 占 퐉 to 200 占 퐉. The apex angle? 1 of the prism 22a (hereinafter, referred to as a prism apex angle) is in the range of 40 ° to 130 ° and the bottom opening angle θ 2 is in the range of 40 ° to 130 °. The height H22a from the bottom of the prism 22a to the top (hereinafter referred to as the prism height) is in the range of 10 占 퐉 to 60 占 퐉. The pitch (hereinafter referred to as a prism pitch) P22a, which is the distance between the top and the bottom of the prism 22a, is in the range of 30 占 퐉 to 100 占 퐉.

The solution film-forming equipment 30 shown in FIG. 4 manufactures the above-mentioned optical film 33 from the first dope 31 and the second dope 32. The first dope 31 is obtained by dissolving TAC in a first solvent and the second dope 32 is obtained by dissolving a thermosetting compound which is a TAC and a cured layer 22 in a second solvent. The first dope 31 and the second dope 32 may contain various additives described above in addition to TAC. The first dope 31 and the second dope 32 may use other cellulose acylate as described above instead of or in addition to TAC. The cellulose acylates of the first dope 31 and the second dope 32 are preferably the same material from the viewpoint of making the refractive index in the cellulose acylate layer 21 uniform.

As the first solvent and the second solvent, a mixture in which dichloromethane, methanol and n-butanol are mixed at a mass ratio of 800: 135: 65 is used in this embodiment. The first solvent and the second solvent are not limited thereto, and may be a single substance or a mixture as long as it dissolves the cellulose acylate to be used. Examples of the substance usable as a component of the solvent include ethanol, methyl acetate, N-methylpyrrolidone and the like. When the first solvent and the second solvent are single substances, it is preferable to use the same material from the viewpoint of more reliably suppressing the phase separation in the cellulose acylate layer. From the same viewpoint, when at least one of the first solvent and the second solvent is used as a mixture, it is preferable that the first solvent and the second solvent have a common component. When the first solvent and the second solvent are a mixture of a plurality of common components, it is more preferable that the mixing ratios of the components are the same from the same viewpoint.

The thermosetting compound may be a monomer or an oligomer such as a dimer, a trimer or the like. The molecular weight of the thermosetting compound is preferably from 250 to 2,000, more preferably from 500 to 2,000, and still more preferably from 1,000 to 2,000. The molecular weight of the thermosetting compound is a weight average molecular weight and is determined by gel permeation chromatography (GPC) in terms of polystyrene.

The thermosetting compound preferably has a polymerizable group composed of an ethylenic unsaturated bond. Examples of the polymerizable group include acryloyloxy group, methacryloyloxy group, acryloyl group, and methacryloyl group.

The thermosetting compound is more preferably a polyfunctional (meth) acrylate compound having at least two polymerizable groups comprising ethylenic unsaturated bonds in one molecule. Examples thereof include ethylene glycol di (meth) acrylate, bisphenol A tetraethoxydi (meth) acrylate, bisphenol A tetrapropoxydi (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl Glycol di (meth) acrylate, and the like. The polymerizable group in the present embodiment is an acryloyloxy group.

The solution film-forming equipment 30 is provided with a flexible device 34, a shape imparting device 35, a first ablation device 37, a heating chamber 40, a second ablation device 41 and a winding device 42 have.

The flexible device 34 forms the wet film 43 in a state of containing the solvent by the first dope 31 and the second dope 32. The flexible device 34 includes a belt 46, a pair of backup rollers 47, a flexible die 48, and the like. The belt 46 is an endless flexible support formed in an annular shape and extends between a pair of backup rollers 47 so that the space between the backup rollers 47 is substantially horizontal. Each of the backup rollers 47 is connected to a drive shaft of the motor 47a and rotates at the same speed in the circumferential direction indicated by the arrow A by the motors 47a. The rotation of the backup rollers 47 causes the belt 46 to circulate.

The flexible die 48 continuously discharges the first dope 31 and the second dope 32 to the surface of the running belt 46. Thereby, the flexible film 50 in a state in which the first dope 31 is superimposed on the second dope 32 is continuously formed on the surface of the second belt 46. The decompression chamber 49 is provided on the back side of the first dope 31 and the second dope 32 portion from the discharge port (not shown) of the flexible die 48 to the surface of the belt 46 The upstream side in the traveling direction of the belt 46) is reduced to prevent the vibration or breakage of the portion.

The temperature controller (51) supplies the temperature regulated heat transfer medium to each backup roller (47). As a result, the temperature of the flexible film 50 is controlled through the backup rollers 47 and the belts 46. In this embodiment, the dry flexible film, that is, the flexible film is gelled by drying only, and the temperature of the warmer 51 is controlled so as to promote the evaporation of the solvent of the flexible film 50. Drying is carried out by blowing only, but it may be heated in addition to blowing air. By heating, gelation proceeds more quickly.

The blower 52 and the backside heater 53 are disposed along the conveyance path of the flexible film 50 by the belt 46 and adjust the drying speed of the flexible film 50. [ The flexible device 34 includes both the blower 52 and the backside heater 53, but may be provided with either one. The blower 52 is arranged so as to face the flexible surface 46a (see Fig. 5) of the belt 46 in which the first dope 31 and the second dope 32 are flexible and the flexible film 50 is formed, A dry gas (for example, dry air) adjusted to a predetermined temperature is flowed out from each nozzle 52a to the vicinity of the flexible film 50. [ In the present embodiment, two blowers 52 are provided along the traveling direction of the belt 46, but the number of the blowers 52 is not particularly limited and may be one or three or more. The back side heater 53 is disposed opposite to the side opposite to the flexible side 46a of the belt 46 and heats the flexible film 50 with the belt 46 interposed therebetween. Although one back side heater 53 is provided in the present embodiment, the number of back side heaters 53 is not particularly limited and may be one or three or more.

The flexible device 34 further includes a take-up roller 56 (see FIG. 5) and a chamber 57. The belt 46, the flexible die 48, the decompression chamber 49, and the like are accommodated in the chamber 57. In the chamber 57, a condenser (condenser) for evaporating the solvent from the first dope 31, the second dope 32, the flexible film 50, and the wet film 43 to condense the gaseous solvent is disposed have. The solvent liquefied by the condenser is sent to the recovery device and recovered. The illustration of the condenser and the recovery device is omitted.

The flexible film 50 is dried during the conveyance by the belt 46 and is conveyed downstream from the belt 46 in the gel state in which the fluidity is lost while containing the solvent. The shape imparting device 35 is disposed in the vicinity of the position where the flexible film 50 is thinned from the belt 46. [

The shape imparting device 35 of the present embodiment has a function of thinning the flexible film 50 from the belt 46 and a function of removing the flexible film 50, that is, the wet film 43, (See Fig. 7 (B)) on the concave portion 44a and the convex portion 44b. The first layer 43a (see FIG. 7) of the wet film 43 is formed by the first dope 31 and the second layer 43b (see FIG. 7) is formed by the second dope 32 Layer. Although the shape imparting device 35 is provided inside the chamber 57 surrounding the belt 46, the flexible die 48 and the decompression chamber 49 in the present embodiment, That is, between the flexible device 34 and the first ablation device 37. Details of the shape imparting device 35 will be described later.

The wet film 43 from the shape imparting device 35 is sent to the first ablation device 37. The first ablation device 37 is for ablating the side portion from the wet film 43. The first ablation device 37 has an upper blade and a lower blade as cutting blades, and these cutting blades are disposed at the passing positions of the respective sides of the wet film 43. The wet film 43 coming into the first ablation device 37 may have a shape such that the side portion is, for example, waving, and this side portion is jointed by the first ablation device 37, (43) of the heating chamber (40) is stabilized by the roller (63) described later. The wet film 43 whose sides are cut off by the first ablation device 37 is sent to the heating chamber 40.

The inside of the heating chamber (40) is adjusted to a predetermined temperature range by a temperature controller (64). The temperature regulator 64 maintains the inside of the heating chamber 40 at a predetermined temperature, for example, by introducing the temperature-adjusted air into the heating chamber 40 while exhausting the inside of the heating chamber 40. In the heating chamber 40, a plurality of rollers 63 for spreading the wet film 43 are disposed therein, and the wet film 43 is conveyed in the heating chamber 40. The wet film 43 is heated while passing through the heating chamber 40 heated by the temperature controller 64 to become the optical film 33 in the atmosphere around the conveying path.

Evaporation of the solvent is promoted by heating in the heating chamber 40 to dry the wet film 43 and form the cured layer 22 (see Figs. 1 to 3). A thermosetting compound contained in the second layer 43b is formed on the surface of the second layer 43b (see Fig. 7) provided with the concave portion 44a and the convex portion 44b by the shape imparting device 35 as described later , And the cured layer 22 is formed by allowing it to exude by heating and further curing it by a heating furnace. In addition, leveling (smoothening) occurs during the progress of curing of the thermosetting compound on the surface of the liquid thermosetting compound permeated. The conveying time under heating may be adjusted by adjusting the length of the conveying path of the wet film 43 in the heating chamber 40 by appropriately increasing the number of the rollers 63 or by adjusting the conveying speed of the wet film 43 And the like.

Heating by the heating chamber 40 is performed on the wet film 43 having a residual solvent amount of 300% or less with respect to the solid component contained in the wet film 43. When the wet film 43 is heated by passing through the heating chamber 40 as described above, the wet film 43 can be guided into the heating chamber 40 after the residual solvent amount reaches 300% or less with respect to the solid component . This residual solvent amount is a value at the start of heating, that is, in the wet film 43 provided in the heating chamber 40. Leveling and curing of the above-mentioned thermosetting compound and drying of the wet film 43 are reliably performed by conveying the wet film 43 having a residual solvent amount of 300% or less while heating for at least 15 minutes. Further, the amount of the residual solvent in the wet film 43 provided for heating is more preferably 100% or less, and more preferably 50% or less.

The solid component in the present embodiment is TAC and a thermosetting compound used as cellulose acylate, but when the various additives described above are used, these additives are also included in the solid component. Further, since the mass of the thermosetting compound is changed by curing, the mass of the thermosetting compound is set to a value after curing, that is, as a thermosetting resin. When the mass of the wet film 43 to be measured, to which the amount of the residual solvent is to be determined, is X, and the mass after completely drying the wet film 43 is Y, the amount of the residual solvent is expressed by {(XY) / Y } × 100%, which is a so-called dry weight standard value (in%). The term &quot; completely dried &quot; does not necessarily mean that the residual amount of solvent is strictly &quot; 0 &quot;. In the present embodiment, the mass after the wet film 43 to be measured is subjected to a drying treatment in a thermostatic chamber at 120 ° C or higher and a relative humidity of 10% or lower for 3 hours or more is defined as Y.

In this example, the temperature of the wet film 43 is adjusted by adjusting the temperature of the atmosphere around the transport path by the exhaust and supply of air in the heating chamber 40, but the method of adjusting the temperature of the wet film 43 is not limited thereto Do not. Other examples of the method of adjusting the temperature of the wet film 43 include radiant heating by an IR (Infrared) heater, conduction heating by roller heating, and the like. Conductive heating by roller heating is to adjust the temperature by heating the wet film 43 by bringing the roller whose temperature of the main surface is adjusted into contact with the wet film 43. However, the method of adjusting the temperature of the wet film 43 by adjusting the ambient temperature around the transport path ensures that the permeation of the thermosetting compound, leveling and curing, and drying of the wet film 43 are carried out securely It is preferable from the viewpoint that it is possible. Since the wet film 43 is thin, it is not necessary to detect the temperature of the wet film 43 with a temperature detector or the like, and the temperature in the heating chamber 40 May be regarded as the temperature of the wet film (43).

In the heating chamber 40, it is preferable to heat the wet film 43 so that the temperature is maintained within a predetermined range. The range of the temperature may be set in accordance with the curing temperature of the thermosetting compound, but it is more preferably within the range of 140 占 폚 to 200 占 폚. Further, it is not necessary to maintain the constant value within this range, and it may be changed during conveyance within this range. By setting the temperature of the wet film 43 at 140 占 폚 or higher, the aforementioned penetration of the thermosetting compound is promoted as compared with the case where the temperature is lower than 140 占 폚. Further, by setting the temperature at 200 占 폚 or lower, the denaturation of the wet film 43 is more reliably suppressed as compared with the case where the temperature is higher than 200 占 폚. The transportability of the wet film 43 is more reliably maintained. Modification of the wet film 43 is, for example, softening or heat shrinkage of the wet film 43. The temperature maintained by the heating of the wet film 43 is more preferably in the range of 140 ° C or higher and 200 ° C or lower, and more preferably 180 ° C or higher and 200 ° C or lower.

The second ablation device 41 is for continuously cutting both sides of the optical film 33 to have a predetermined width. The second ablation device is configured in the same manner as the first ablation device 37. The winding device 42 is for winding the optical film 33 having a predetermined width into a roll shape and a winding core 65 for winding the optical film 33 is set.

Further, a well-known tenter (not shown) may be provided between the shape imparting device 35 and the first ablation device 37. The tenter advances the drying of the wet film 43 while conveying the wet film 43 in a state in which the width of the wet film 43 is regulated. The tenter is composed of, for example, a plurality of clips, an air supply portion, an air outlet portion, and the like. Each clip grips a side of the wet film 43, respectively. A plurality of clips are attached to the annular chain at predetermined intervals, and the chain is provided so as to be movable along a rail disposed on both sides of the transport path of the wet film 43, . As a result, each clip moves along the rail. One of the rails and the other of the rails are arranged in a straight line, and when the distance between the two rails is constant, the two rails may be combined. The air supply unit supplies the dry gas adjusted to various temperatures to the air outlet, and blows the dry gas from the air outlet to the wet film (43) in the tenter. Further, the holding member for holding the wet film 43 is not limited to a clip, and may be a pin plate that penetrates and holds a plurality of fins on the side of the wet film 43. Since the amount of the residual solvent in the wet film 43 is very large, a pin plate can be used when the wet film 43 is torn by holding by the clip. When the tenter is installed as described above, the first ablation device 37 cuts off the retaining trace by the holding member of the tenter from the wet film 43.

As shown in Fig. 5, the shape imparting apparatus 35 includes the above-described pick-up roller 56 and shape-imparting roller 68. [ The rotation shaft of the peeling roller 56 is disposed parallel to the rotation axis of the backup roller 47. In this example, the peeling roller 56 is disposed on the opposite side of the conveying path of the wet film 43 from the belt 46, and the wet film 43 is wound around the main surface. The peeling roller 56 is driven to rotate in accordance with the conveyance of the wet film 43. The flexible film 50 is pulled at a predetermined punching position PP by pulling the wet film 43 toward the downstream of the solution film forming equipment 30 while the wet film 43 is wrapped around the peeling roller 56. [ The belt 46 is peeled off from the belt 46. Further, the peeling roller 56 may be rotated by a motor in synchronization with the conveyance of the wet film 43.

The shaping roller 68 is provided opposite to the peeling roller 56 and cooperates with the peeling roller 56 to form a second layer 43b 7), the concave portion 44a and the convex portion 44b are alternately formed in the carrying direction Z1. That is, the peeling roller 56 functions as a peeling member for peeling the flexible film 50 to form the wet film 43, and also functions as a peeling member for imparting a shape for forming the prism 22a to the wet film 43 It also functions as a member.

The concave portion 68a and the convex portion 68b each having a triangular cross section are formed on the main surface of the shape imparting roller 68 to form a concave portion 44a and a convex portion 44b in the wet film 43, Respectively. The concave portions 68a and the convex portions 68b extend in the axial direction of the shape imparting roller 68 or in the width direction of the wet film 43 and alternately formed along the circumferential direction of the shape imparting roller 68 have. The shaping roller 68 is rotated by the motor 69 while sandwiching the wet film 43 between the shaping roller 68 and the peeling roller 56. The direction of rotation of the shape-imparting roller 68 is a direction in which the wet film 43 is conveyed (counterclockwise in the figure). The shaping roller 68 presses the wet film 43 being conveyed from the side of the second layer 43b (see FIG. 7) formed of the second dope 32 on the peeling roller 56, The concave portion 68a and the convex portion 68b are transferred to the second layer 43b to form the concave portion 44a and the convex portion 44b.

6, the shapes of the concave portions 68a and the convex portions 68b of the shape imparting roller 68 are determined by the concave portions 44a and the convex portions 44b to be formed. The shape of the concave portion 44a and the convex portion 44b to be formed is determined according to the prism 22a. The pitch P68a which is the distance between the vertexes of the convex portion 68b and the convex portion 68b adjacent to each other in the circumferential direction is equal to the pitch between the prism pitch P22a and the vertexes of the adjacent convex portions 44b And less than 100 탆.

The apex angle? 3 of the convex portion 68b becomes smaller than the apex apex angle? 1 and the opening angle? 4 of the concave portion 68a is made smaller than the above-described opening angle? 2 . The height H68a of the convex portion 68b (depth of the concave portion 68a) is preferably larger than the prism height H22a described above. This is because evaporation of the solvent from the wet film 43 decreases the depth of the concave portion 44a formed by the convex portion 68b and the height of the convex portion 44b formed by the concave portion 68a , The opening angle of the concave portion 44a which becomes the prism apex angle 1 and the apex angle of the convex portion 44b which becomes the opening angle 2 are respectively increased.

As shown in Fig. 5, it is preferable that the shape-regulating roller 68 is provided with a pressure regulator 70 as in this embodiment. The pressure regulator 70 adjusts the pressing force of the shape imparting roller 68 with respect to the wet film 43 when transferring the shapes of the concave portions 68a and the convex portions 68b. The pressure regulator 70 adjusts the pressing force to more reliably form the concave portion 44a and the convex portion 44b with respect to the wet film 43. [

It is preferable that the shape imparting roller 68 is provided with a tempering device 73 for adjusting the main surface temperature as in the present embodiment. The temperature controller 73 regulates the temperature of the main surface of the shape-imparting roller 68 within a temperature range for keeping the gelled wet film 43 in a gel state. The temperature for maintaining the gel state is as described above. It is also preferable that a warming-up unit 74 for adjusting the temperature of the main surface is provided on the peeling roller 56 as in this embodiment. The temperature controller 74 regulates the temperature of the main surface of the peeling roller 56 within the temperature range for keeping the wet film 43 in the gel state, like the temperature controller 73. The concave portion 44a and the convex portion 44b can be formed in the same manner as the convex portion 44b by adjusting the temperature of the main surface of each of the shaping roller 68 and the peeling roller 56 within the temperature range for maintaining the gel state of the wet film 43. [ Is easily and surely formed. The amount of the residual solvent in the wet film 43 in which the concave portions 44a and the convex portions 44b are formed by the shape imparting device 35 is usually set to be lower than the amount of the residual solvent when entering the heating chamber 40 Is high.

The operation of the above configuration will be described. The first dope 31 and the second dope 32 are supplied to the flexible die 48 and joined together inside the flexible die 48 and discharged toward the running belt 46. [ The first layer made of the first dope 31 is superimposed on the second layer made of the second dope 32 on the belt 46 whose temperature is controlled by the backup roller 47, . The first dope 31 and the second dope 32 are continuously discharged from the flexible die 48 and the belt 46 continues running so that the flexible film 50 is continuously formed ).

The formed flexible film 50 is transported in accordance with the running of the belt 46. During this transportation, the solvent in the flexible film 50 is evaporated by the heating by the back-up roller 47, the supply of the drying gas by the blower 52 and the heating by the back surface heater 53, And the flexible film 50 is gelled.

The coagulated film 50 which has been gelled by drying is removed from the belt 46 at the retracted position PP while being kept in the gel state by the peeling roller 56 (second step). 7 (A), the encapsulated flexible film 50, that is, the wet film 43 has a first layer 43a formed of the first dope 31 and a second layer 43b formed of the second dope 32, And the layer 43b are overlapped with each other. Since the first dope 31 and the second dope 32 are overlapped with each other in a state containing a large amount of solvent, the first dope 31 and the second dope 32 are disposed between the first layer and the second layer in the flexible film 50, No voids are formed between the first layer 43a and the second layer 43b. The wet film 43 is transported toward the shape imparting device 35. By controlling the surface temperature of the peeling roller 56, the gel state is maintained even when it comes into contact with the peeling roller 56.

When the wet film 43 is conveyed to the position of the shaping roller 68, the wet film 43 is sandwiched between the shaping roller 68 and the peeling roller 56 while being rotated, and the second layer 43b . Thus, the shape of the concave portion 68a or the convex portion 68b is transferred to the second layer 43b as shown in FIG. 7B on the portion of the wet film 43 held. The concave portion 44a serving as the prism 22a of the optical film 33 and the concave portion 44b serving as the convex portion of the optical film 33 are formed in the second layer 43b of the wet film 43, (44b) are alternately formed sequentially (third step).

Since the main surface temperature of the shape imparting roller 68 is within the temperature range where the gel state of the wet film 43 is maintained while the concave portions 44a and the convex portions 44b are formed as described above, 43 are kept in a gel state. Therefore, the concave portion 44a and the convex portion 44b are more reliably and easily formed on the second layer 43b of the wet film 43. [

The wet film 43 having the concave portions 44a and the convex portions 44b formed by the shape imparting roller 68 as described above is sent from the shape imparting device 35 to the first ablation device 37. [ The wet film 43 is cut on both sides by the first cutting device 37, and is guided to the heating chamber 40 after the residual solvent amount becomes 300% or less. The wet film 43 passes through the heating chamber 40 for at least 15 minutes, i.e., over 15 minutes. In this way, while being conveyed in the heating chamber 40, it is heated, and the drying proceeds by this heating. Prior to and during the drying, the thermosetting compound seeps out from the concave portion 44a in the second layer 43b and the cellulose acylate contained in the second layer 43b comes into contact with the first layer 43a, . The thermosetting compound exudes in a liquid phase, and the liquid level of the exothermic thermosetting compound is displaced so as to be higher, but the leveling action maintains a smooth state. The thermosetting compound penetrating is cured by the heat applied from the atmosphere to form a thermosetting resin, whereby the cured layer 22 is formed. Also, during formation of the cured layer 22, the cellulose acylate of the first layer 43a and the second layer 43b is integrated to form the cellulose acylate layer 21. 7 (C), the optical film 33 comprising the cellulose acylate layer 21 and the cured layer 22 is obtained by drying and the penetration, leveling and curing of the thermosetting compound (The fourth step).

Since the first solvent and the second solvent are evaporated by drying, the optical film 33 becomes thinner than the wet film 43 naturally. As described above, the depth of the concave portion 44a and the height of the convex portion 44b of the wet film 43 decrease with the evaporation of the first solvent and the second solvent, respectively, And the apex angle of the convex portion 44b increase. 7B and Fig. 7C, the optical film 33 is formed so that the prism height H22a is equal to the depth of the concave portion 44a in the wet film 43 and the convex portion The prism apex angle? 1 and the opening angle? 2 are formed to be larger than the opening angle of the concave portion 44a in the wet film 43 and the apex angle of the convex portion 44b.

Since the cellulose acylate layer 21 and the cured layer 22 are transparent, they have a function as a protective film of the polarizing plate. The optical film 33 has a cured layer 22 having a refractive index higher than that of the cellulose acylate layer 21 and the cured layer 22 is formed with the prism 22a at the boundary with the cellulose acylate layer, When the illumination light from the light source unit 12 is emitted from the cured layer 22 to the cellulose acylate layer 21, refraction occurs. As a result, the optical film 33 exhibits a brightness enhancement function. In addition, since the prism 22a is formed inside, when the optical film 33 is used as a sheet and used for the liquid crystal panel 11, the prism 22a does not contact other members, and therefore, There is no. Therefore, the brightness enhancement function is maintained. Since the film surface on the side of the cellulose acylate layer 21 is smoothly formed, it is closely attached to the polarizing film 14b.

Since the difference in refractive index obtained by N22-N21 is 0.2 or more, the optical film 33 exhibits a brightness enhancement function more reliably. Since the refractive index of the thermosetting resin is in the range of 1.50 or more and 2.20 or less, the refractive index difference with respect to the cellulose acylate layer 21 is sufficiently imparted, and the brightness improving function is reliably expressed.

The second dope 32 is preferably a thermosetting compound having a polymerizable group composed of an ethylenic unsaturated bond, so that the radical reaction is favorably promoted to form a crosslinked structure. Further, since the thermosetting compound has at least two of the above-mentioned polymerizable groups in one molecule, an optical film (33) having sufficient hardness after thermosetting can be obtained. Since the thermosetting compound has a molecular weight of 250 or more, the viscosity of the liquid material containing the exothermic thermosetting compound is higher than that of the thermosetting compound having a molecular weight of 250 or more. Therefore, even when disturbance is caused during conveyance of the wet film 43, Further, since the thermosetting compound has a molecular weight of 2000 or less, the cured layer 22 can be formed more reliably because it permeates more reliably onto the concave portion 44a and the convex portion 44b in the fourth step described above.

Since the wet film 43 in the heating chamber 40 is maintained at a temperature within the range of 140 ° C. to 200 ° C., drying, leveling and curing of the thermosetting compound proceeds more reliably, The prism 22a is more reliably formed, and each film surface is formed with a high smoothness. Further, since the wet film 43 is kept at the temperature within the above-mentioned range, the denaturation is more surely suppressed, so that the good transportability in the heating chamber 40 is more reliably maintained. In the heating chamber 40, since the temperature of the wet film 43 is adjusted by the atmosphere around the conveying path, drying, leveling and hardening of the thermosetting compound are simple and more reliably performed.

As described above, the solution film-forming equipment 30 can continuously carry out the respective processes of the first step, the second step, the third step and the fourth step as described above, so that the elongated optical film 33 is produced. The optical film 33 is wound in the form of a roll in the winding device 42. The optical film 33 wound in the form of a roll is cut to a predetermined size in a later process and used as a prism sheet 16.

Although the shapes of the concave portions 44a and the convex portions 44b are imparted to the wet film 43 on the peeling roller 56 by the shape imparting roller 68 in the above embodiment, The heating chamber 40 may be at a different position as long as it is upstream of the heating chamber 40. For example, the shape imparting roller 68 and the nip roller (not shown) are disposed on the conveying path between the first ablation device 37 and the heating chamber 40, whereby the shape of the wet film 43 . The shape imparting roller 68 may be pressed by pressing the flexible film 50 on the flexible support such as the belt 46 or the drum.

In the above-described embodiment, the drying is carried out, but the so-called cooling may be performed by drying and cooling the flexible film 50 instead of the drying, thereby making the gel. In this case, the warmer 51 supplies the cooled heat transfer medium to the backup roller 47, thereby cooling the belt 46 such that the fluidity of the flexible film 50 is lowered compared with the case where the fluidity is only dry. In the case of cooling and cooling, by the cooling by the backup roller 47, the supply of the drying gas by the blower 52 and the cooling by the back surface heater 53, the solvent in the flexible film 50 being conveyed is evaporated and dried And then it is cooled down to gel. The flexible support is not limited to the belt 46. For example, instead of the belt 46, a drum may be used, and the first dope 31 and the second dope may be discharged by being discharged on the main surface of the rotating drum. In the case of the so-called drying softness in which the flexible film is dried and solidified, the belt 46 is often used. In the case of cooling softness, a drum is often used, but a drum may be used for drying softness and a belt may be used for cooling softness .

8, the flexible device 90 is for applying a shape to the flexible film 50 by pressing the shape imparting roller 68. As shown in Fig. The flexible device 90 has a drum 92 as a flexible support in place of the belt 46 in Fig. 4 and also has a warmer 93 and a shape-imparting roller 68. Fig. 4 and 5 are given the same reference numerals as those in Fig. 4 and Fig. 5, and description thereof is omitted. The flexible die 48 discharges the first dope 31 and the second dope 32 so as to overlap the second dope 32 on the first dope 31 toward the drum 92. As a result, the flexible film 50 in which the first layer and the second layer are integrally superimposed is formed (first step). The motor 92a is connected to the drive shaft of the drum 92 and rotates in the circumferential direction indicated by an arrow (counterclockwise in the figure) by the motor 92a. The flexible film 50 is transported by the rotation of the drum 92.

The shape-imparting roller 68 is provided so as to face the drum 92, and the rotation axis is disposed in parallel with the rotation axis of the drum 92. Drum 92 is used in this example as a flexible support in cooling ducts. The temperature control of the flexible film 50 lowers the temperature of the main surface of the drum 92 by flowing the heat transfer medium cooled in the drum 92 by the warmer 93. The flexible film 50 is gelled by this temperature control. The gelled flexible film 50 is guided between the drum 92 and the shape imparting roller 68 by the conveying by the drum 92 and is guided by the shape imparting roller 68 to the second Layer (not shown) side. 5) and the convex portion 68b (see Fig. 5) of the shape-imparting roller 68 are transferred to the second layer of the flexible film 50. In this case, the shape of the concave portion 68a Since the shape imparting roller 68 rotates together with the conveyance of the flexible film 50, the concave portion 44a (Fig. 5 (b)) as the prism 22a is formed in the second layer of the flexible film 50 as in the case of the wet film 43 (See Fig. 5) and the convex portion 44b (see Fig. 5) are alternately formed sequentially (third step).

The flexible film 50 is peeled off by the peeling roller 56 in a state containing the first solvent and the second solvent, and the wet film 43 is formed (the second step). Thus, the third step may be performed after the second step. In this example, the peeling roller 56 is disposed on the side of the drum 92 with respect to the conveying path of the wet film 43. In order to maintain the shape of the concave portion 44a and the convex portion 44b formed in the flexible film 50. [ The wet film 43 is guided to the first ablation device 37 as in the case of using the solution film formation equipment 30 of Fig. Then, the film is made into an optical film 33 through a fourth step by the heating chamber 40, and is wound in a roll form in the winding device 42.

In each of the above embodiments, so-called co-casting is performed in which the first dope 31 and the second dope 32 are discharged from the flexible die 48 in the state of being superimposed on the flexible support. However, the first dope 31 and the second dope 32 may be so-called sequential or flexible that they are discharged from a flexible die arranged in the running direction of the flexible support. In the above example, the optical film 33 is used as a prism sheet of a total reflection type, but it can also be used as a refraction type prism sheet.

[Example]

[Example 1] - [Example 4]

Examples 1 to 4 in which the optical film 33 was produced by cooling flexing by a solution casting facility in which the flexible device 34 of the solution film-forming equipment 30 was replaced by a flexible device 90 were carried out. The thicknesses of the cellulose acylate layer 21 and the cured layer 22 were each 40 mu m. TAC was used as the cellulose acylate of the first dope 31 and the second dope 32. As the thermosetting compound of the second dope 32, UV-1700B (refractive index: 1.58) manufactured by Nippon Kogaku Kagaku Kogyo Co., Ltd. and KAYARAD (registered trademark) of Nihon Kayaku Co., M-309 (refractive index: 1.52) manufactured by Toagosei Co., Ltd. was used in Example 3, and light acrylate (manufactured by Kyoeisha Chemical Co., Ltd.) was used in Example 4, NP-A (refractive index: 1.50) were respectively used. The molecular weights of these thermosetting compounds are shown in the column of "molecular weight" in Table 1 and the number of polymerizable groups (number of functional groups) in the column of "number of polymerizable groups" in Table 1.

The concave portion and the convex portion were formed by the shape imparting roller 68 on the flexible film 50 having the residual solvent amount of 270%. A shape imparting roller 68 having a roller apex angle 3 of 90 占 and a pitch P68a of 50 占 퐉 which is a distance between the vertexes of the convex portion 68b and the convex portion 68b adjacent to each other in the circumferential direction is used. The atmosphere inside the heating chamber 40 was adjusted to 190 占 폚 and the wet film 43 was conveyed to pass the heating chamber 40 for 15 minutes.

The refractive index N21 of the cellulose acylate layer 21 and the refractive index N22 of the cured layer 22 were measured for each of the obtained optical films 33 to determine whether or not there was a brightness enhancement function and the degree of flatness of the film surface on the cured layer 22 side . Each evaluation method and criteria are as follows. The refractive index N21 and the refractive index N22 were measured by a digital subtracting refractometer DR-A1 (manufactured by Atago Co., Ltd.). The refractive index N21 of each optical film 33 was 1.48. The refractive index N22 is shown in the &quot; refractive index N22 &quot;

1. Presence or absence of brightness enhancement function

The presence or absence of the brightness enhancement function was evaluated by the following microscopic observation and the luminance improvement rate.

(1) Microscopic observation

Each of the obtained optical films (33) was sectioned in the thickness direction using a microtome and observed with an optical microscope. According to this observation, the case where the boundary between the cellulose acylate layer 21 and the cured layer 22 on which the plurality of prisms 22a are formed was confirmed to be acceptable, and the case where the observation was rejected. As a result of this microscopic observation, the optical film 33 of any embodiment was acceptable.

(2) Brightness Improvement Rate

First, as a reference sample, a flat film having a flat film surface with a single layer structure in which a prism 22a was not formed therein was manufactured. The polymer used in the dope is TAC. The luminance of the obtained flat film was measured by the following method, and the luminance of this flat film was taken as B1. The luminance of each optical film 33 was measured by the same method as the luminance of the flat film, and the luminance of the optical film 33 was B2. Then, the luminance improvement rate (unit:%) was obtained by the expression of {(B2-B1) / B1} × 100.

The method of measuring the luminance is as follows. The optical film 33 was placed so that the cured layer 22 was brought into contact with a light table (surface illuminator, light source: commercially available fluorescent lamp Panasonic Corporation 86W / HF tube, FHF86EX-D, 10) manufactured by DENKO KOGYO KABUSHIKI KAISHA) To the light table. The front luminance was measured by a luminance meter (BM-9A manufactured by DOC CONCOUNH HOUSE Co., Ltd.) at a distance of 350 mm from the optical film 33, and the luminance was measured.

It was decided that there was a brightness enhancement function when passing through a microscope observation and the luminance improvement rate was 5% or more. In the case where the microscope observation was rejected and the microscope observation was acceptable but the luminance improvement rate was less than 5%, no luminance improvement function was determined. The optical film 33 of any of the embodiments also had a luminance improvement ratio of 10% as determined by the above-described method and a luminance improvement function.

2. Smoothness of film surface

On the film surface on the side of the cured layer 22 side of each optical film 33, nine positions in total of six positions at intervals of 5 cm in the first direction and at intervals of 5 cm in the second direction orthogonal to the first direction As a measurement target area. Each of nine measurement target areas has a size of 600 mu m x 600 mu m. The arithmetic average roughness Ra in accordance with Japanese Industrial Standard JIS B0601-2013 was measured for each measurement target area, and the nine arithmetic mean roughnesses obtained were Ra1, Ra2, Ra3, ... , Ra8, and Ra9. The device used was the VertScan 2.0 system from RYOKA. (Unit: 占 퐉) obtained by the following formula (Ra1 + Ra2 + Ra3 + ... + Ra8 + Ra9) / 9 was obtained as the smoothness of the film surface.

When the smoothness of the obtained film surface is 1 占 퐉 or more and 5 占 퐉 or less, the thickness is A, the thickness is more than 5 占 퐉 and the thickness is 10 占 퐉 or less, and the thickness is C when it is more than 10 占 퐉. A and B are passed, and C is not. The results are shown in Table 1.

[Table 1]

[Comparative Example 1]

The TAC of the second dope 32 of the Example was replaced by 2-methoxyethyl methacrylate of Mitsubishi Rayon Co., Ltd., whose refractive index was 1.42, which is lower than that of cellulose acylate, to produce an optical film. Other conditions are the same as in the embodiment. A boundary was confirmed between the cured layer and the cellulose acylate layer 21, and a plurality of prisms were confirmed at the boundary with the cellulose acylate layer 21 of the cured layer. Therefore, in the evaluation of the above-mentioned microscopic observation, it was acceptable. However, the refractive index N21 of the cellulose acylate layer 21 was 1.48, and the refractive index of the cured layer was 1.42. As a result, the brightness enhancement rate was found to be zero. In Comparative Example 1, it was determined that there was no brightness enhancement function, and therefore evaluation of the smoothness of the film surface was not performed.

10: Liquid crystal display
13: liquid crystal cell
15a: Polarizing film
16: prism sheet
21: cellulose acylate layer
22: Cured layer
22a: prism
30: Solution forming equipment
31, 32: First and second docks
33: Optical film
35: shape giving device
40: heating chamber
43: wet film
50:

Claims (13)

A cellulose acylate layer having a film surface on one side and containing cellulose acylate,
Wherein the cellulose acylate layer has a surface that is the other film surface and is formed of a transparent thermosetting resin on the other surface of the cellulose acylate layer and has a refractive index higher than that of the cellulose acylate layer, A cured layer having a plurality of prisms
And an optical film. The method according to claim 1,
Wherein the cellulose acylate is cellulose triacetate. 3. The method according to claim 1 or 2,
Wherein the thermosetting resin has a refractive index ranging from 1.50 to 2.20. 3. The method according to claim 1 or 2,
Wherein the thermosetting resin is produced by thermosetting a thermosetting compound having a polymerizable group comprising an ethylenic unsaturated bond. 5. The method of claim 4,
Wherein the thermosetting compound has at least two polymerizable groups in one molecule. 3. The method according to claim 1 or 2,
An optical film provided on a polarizing film on a light source side of a liquid crystal display device having a liquid crystal cell and two polarizing films and provided in close contact with a light source side of the polarizing film. A solution casting method for producing an optical film having a plurality of prisms,
A first dope containing a cellulose acylate and a first solvent and a second dope containing a cellulose acylate and a thermosetting compound which generates a thermosetting resin having a refractive index higher than cellulose acylate by thermosetting and a second solvent , A continuous flexible film is cast on the running flexible support to form a flexible film in which the first layer of the first dope and the second layer of the second dope are overlapped A first step,
A second step of forming a wet film by peeling the flexible film from the flexible support in a state where the first solvent and the second solvent remain,
A plurality of concave portions and convex portions each having a triangular cross section extending in the width direction of the flexible film and alternately formed along the circumferential direction on the peripheral surface of the flexible film; A third step of successively forming the plurality of prisms in the second layer by pressing,
The flexible film or the wet film having a residual solvent amount of not more than 300% with respect to the solid component through the third step is transported for at least 15 minutes while being heated so that the thermosetting compound is exuded onto the plurality of prisms, A fourth step of drying the wet film to cure the thermosetting compound
And forming a solution on the surface of the substrate. 8. The method of claim 7,
Wherein the fourth step comprises heating the flexible film or the wet film to maintain the temperature within a range of 140 ° C or higher and 200 ° C or lower. 9. The method according to claim 7 or 8,
Wherein the fourth step is a step of heating the flexible film or the wet film by transporting in a temperature controlled atmosphere. 9. The method according to claim 7 or 8,
Wherein the thermosetting resin has a refractive index ranging from 1.50 to 2.20. 9. The method according to claim 7 or 8,
Wherein the molecular weight of the thermosetting compound is in the range of 250 to 2,000. 9. The method according to claim 7 or 8,
Wherein the thermosetting compound has a polymerizable group comprising an ethylenic unsaturated bond. 13. The method of claim 12,
Wherein the thermosetting compound has at least two polymerizable groups in one molecule.

Images