Embodiment
Below with reference to the accompanying drawings the present invention is made an explanation, at first explain according to the light diffusion phenomena of prior art in optical diffusion film.
Figure 1A is the sectional view of optical diffusion film that has the high-index regions of cylindrical formation according to prior art.In polymer film 2 to approach the column high-index regions 3 of optical wavelength perpendicular to the aligned formation diameter on film surface.Column high-index regions 3 plays lens pillar, makes incident light perpendicular to film, promptly is parallel to the longitudinal axis of column structure, and with the Gaussian distribution scattering, maximum half-breadth for example is about 10-20 °.In the optical diffusion film of Figure 1A, when big with respect to the incident angle of film 1, when making that light enters with the inclination angle bigger with respect to the longitudinal axis of cylinder, the light scattering characteristic forfeiture also causes high-transmission rate.For example, there is not scattering ground transmission in fact with light with respect to film 45 ° of-60 ° of angle incidents in surface.
Figure 1B represents to pass the transmitted intensity of the light of film at θ emergence angle place for inciding the film surface with right angle (incident angle is 0 °).This transmitted intensity is with Gaussian distribution, and spread and selectivity can be represented by maximum half-breadth.In Figure 1B, maximum half-breadth is 10 °.
Fig. 1 C represents to have the sectional view of the conventional scattering film of the filling material formula that is dispersed in the polymer film, and Fig. 1 D represents the scattering strength of transmitted light in the mode identical with Figure 1B.Figure 1B and 1D comparison shows that, the optical diffusion film of Figure 1A shows a kind of selective scattering characteristic (a specific width inscattering).
Fig. 2 represents for the dependence of the diffusion barrier diffusion property shown in Figure 1A to incident light direction and incident angle.The center representative of coordinate axis is drawn in directivity and the intensity of pattern (annulus 4) representative at coordinate center perpendicular to the optical transmission scattered light of film surface incident perpendicular to the light of film surface incident.Annulus 4 is represented the isotropic scatterning of scattered light, and annulus size is represented scattering strength, shows that emergent light locates strong scattering in the angle less with respect to incident light axis (for example 10-20 °).Oval logo 5 on the coordinate axis and 6 representatives from perpendicular to the direction on film surface to the transmission of the x of film direction of principal axis (normal direction on plane shown in Figure 1 is defined as the x direction of principal axis) cant angle theta (x) angle incident and the directivity and the intensity of scattered light.A little less than the scattering strength of transmitted light and scattered light 5 and 6 total ratio vertical incidence, lack than the scattering of seeing at the y direction of principal axis at the x direction of principal axis.Similarly, circle on the y coordinate axis or pattern of oval shapes 7 and 8 representatives from perpendicular to the direction on film surface to perpendicular to the transmission of y direction of principal axis cant angle theta (y) the angle incident of the x axle of film and the directivity and the intensity of scattered light.A little less than the scattering strength of transmitted light and scattered light 7 and 8 total ratio vertical incidence, lack than the scattering of seeing at the x direction of principal axis at the y direction of principal axis.As shown in Figure 2, can be from observing the violent scattering of light in particular range perpendicular to the direction on film surface with 0 ° of incident angle 4 incident, but along with the increase of incident angle, the size of oval 5-8 diminishes, be that light scattering weakens, make all in fact light all by transmission.This also shows, for the light 5-8 of oblique incidence, laterally than more scattering taking place in the direction that is parallel to incident direction.
Fig. 3 A represents the sectional view of a diffusion barrier 21, and the cylindrical region (lens pillar) 23 that wherein is similar among Figure 1A is not orientated in the direction on the surface that is orthogonal to polymer film 22, and in the y axle tilt angle theta with respect to film
0Direction orientation (left-hand among Fig. 3 A is the direction of y before axially).Light scattering in this film demonstrates a specific character, in the incident of the y direction of cylindrical region 23 corresponding to the incident on the diffusion barrier normal direction in Figure 1A.As a result, shown in Fig. 3 B, show scattering properties based on the film surface to represent with Fig. 2 same way as.
In Fig. 3 B, the y direction of principal axis of transmitted light 24 films is with θ
0The incident of angle shows the round scattering corresponding to incident on the normal direction of film shown in Figure 1B.From the transmitted light 25 of the normal incidence of film corresponding to from y axle negative angle θ
0To the incident of film shown in Figure 2, it is a kind of oval scattering, and scattering strength is less than the intensity of transmitted light 24, but has very strong directivity at the x direction of principal axis.In the y of film axle negative direction with θ
0The transmitted light 26 of incident has bigger and incident angle with respect to the direction of principal axis of lens pillar, and thereby enter lens pillar in the other direction with an inclination angle, make scattering (intensity) reduce.Show the oval scattering properties of the inclination shown in Fig. 3 B from the transmitted light 27 and 28 of the x direction of principal axis incident of film, and transmitted light 27 and 28 is tending towards showing stronger directivity at the y direction of principal axis.
The result, when the diffusion barrier shown in Fig. 3 A and the 3B combines with a reflectance coating, observer's (direction of observation) is in y axial oppositely (direction of observation), light scattering consumingly in specific angular range of (forward of y axle) incident from the front, and therefore also in the scattering of observer's direction generation certain strength, reflected light also has some scatterings simultaneously.The light of (the axial forwards/reverse of x) incident is also producing the intensity scattering of convergent effect in observer's direction from a right side/left side, and the transmission reflection of light also a little less than.Therefore, when watching the liquid crystal indicator that disposes diffusion barrier shown in Fig. 3 A and the 3B such as cellular display screen, the front that is backwards to from the y axle, the light of (forward of y axle) or a right side/left side (forwards/reverse of x axle) incident with certain convergent effect scattering, makes the observer observe the display screen brighter than isotropic scatterning film shown in Figure 2 in observer's direction from the front.
For understanding of the present invention, all as shown in Figure 3A be better than comprising in the existing diffusion barrier with selective scattering characteristic and convergent effect of other diffusion barrier of diffusion barrier shown in Figure 1 also not report.But prior art is included in disclosing as the purposes of the cylindrical region of the polymer film medium dip formation of diffusion barrier.The all identical situation of this all vergence direction is the situation of the diffusion barrier shown in Fig. 3 A just.
On the contrary, the invention provides a kind of diffusion barrier, wherein in polymer film, form the high-index regions of the column structure of cross sectional shape with extension, extend at the thickness direction of film in this district, and the zone of extending is in a specific direction orientation of film, and the preferred column structure that extends is parallel to the film surface or with respect to the film surface tilt.Both there be not open do not advise this concrete structure and effect in the prior art yet.
Fig. 4 represents the film surface according to this diffusion barrier of the present invention.Diffusion barrier 31 has a large amount of high-index regions 33 that are dispersed in the polymer film 32, and this high-index regions 33 is extended and orientation at the specific direction of film.In Fig. 4, the direction of the major axis of high index of refraction extension area 33 orientation is the x axle of film, and short-axis direction is the y direction of principal axis of film.
When high index of refraction extension area 33 during in diffusion barrier 31 medium dips of the present invention, vergence direction is preferably in the y direction of principal axis.Fig. 5 B represents to have picture on surface shown in Figure 4 in the mode identical with Fig. 2 and has in y direction of principal axis cant angle theta
0The scattering properties of the diffusion barrier of the extension area (aspect ratio is about 2: 1) 33 of angle (about 20 °) is shown in Fig. 5 A.
In Fig. 5 B, when xsect column structure scattering that the light from the y axle forward entrance of film is extended, light in the transmissivity of high index of refraction extension area 33 long axis directions than height at short-axis direction, and therefore, the scattering of light characteristic of having passed this film is a kind of directional scattering characteristic, show higher directional scattering at the y direction of principal axis thus, as oval 34 show, and the ellipse of scattered light more is partial to the y axle when passing cylindrical-shaped structure than light with less inclination.Even also show axial directional scattering characteristic 35 at y for light from the normal incidence of film.This also is applied to from the light of the dextrad of film and left-hand (x direction of principal axis) incident, and can obtain scattering properties 36 and 37, and this characteristic is out of shape longlyer at the y direction of principal axis than the scattering properties among Fig. 3 B.In either case, light is stronger than in Fig. 3 B of the scattering strength of observer's direction (y oppositely axial).Fig. 5 B has also represented from the optical transmission of the first quartile of xy coordinate system and the second quadrantal heading incident and scattering properties 38.These transmissions and scattering properties 38 also have bigger scattered light intensity in view directions (y is axial oppositely).Therefore, if diffusion barrier is a display screen, then from be scattered and converge to view directions (y is axial oppositely) except the incident light (illumination light) in the wide of observer's all directions, especially forward behind, its degree is higher than the situation that high-index regions is a cylindrical-shaped structure.In addition, transmission and scattering properties 39 in view directions (y is axial oppositely) are tending towards shortening at the y direction of principal axis, this and be interpreted as high transmittance, and the light of selected scattering and convergence is reflected at the reflectance coating place on all directions of removing the observer behind, in angular field of view, be reflected to no excessive scattering as mentioned above, and again.Therefore, this is also useful to the brightness that improves reflected image.
As mentioned above, scattering film of the present invention preferably has the column structure with respect to the film surface tilt, but need not tilt, and they also can form in the normal direction of film.
Fig. 6 B represents scattering properties for the diffusion barrier 41 with picture on surface shown in Figure 4 in the mode identical with Fig. 2, wherein in polymer film 42, form high-index regions 43 and in as shown in Figure 6A embrane method to forming column structure.
In the case, light perpendicular to film incident has higher light transmission in the long axis of ellipse direction ratio at short-axis direction, and therefore at the short-axis direction of ellipse, be that more scattering (transmission and scattering properties 44) takes place for the y direction of principal axis (left and right directions of figure) of film.Y-axis directional scattering at the light of y direction of principal axis oblique incidence is lower than amount that tilts with respect to column structure of normal incident light, but in y direction of principal axis also scattering (transmission and scattering properties 45 and 46).On the other hand, incide the long axis direction of column structure with the light of a gradient incident from the x direction of principal axis (being orthogonal to the direction of figure) of film, and therefore seldom, and total scattering also reduces (transmission and scattering properties 47 and 48) in the scattering of short-axis direction (y direction of principal axis).
In situation shown in Figure 6, by high-index regions is changed into elongated shape from circle, make to obtain to have scattering properties, and especially have the scattering properties 44 and 45 of higher selective scattering from the light of forward entrance with respect to the observer than multiple scattering in view directions.
The method that forms the column structure of the cross sectional shape that extends in diffusion barrier of the present invention is had no particular limits, and can adopt any known method, but preferable methods is the polymer film formation high index of refraction column structure that has radiosusceptibility by the selectivity radiation.Polymer film can be a kind of prepolymer or monomer before radiation, and can be by a kind of method polymerization that can comprise heating after radiation if desired.Column structure in the radiation sensitive polymer film can be by at first forming mask layer, forming a kind of sectional hole patterns of extension and with the formation such as sectional hole patterns radiation radiation sensitive polymer film of predetermined angle through extending in mask layer on the surface of radiation sensitive polymer film.Photoetching is a kind of known mask forming method.Perhaps also the radiation sensitive polymer film can be exposed under the scanning radiation with direct formation radiation sensitive area.This method can also comprise high-index material is encapsulated into by laser beam or other method and is formed in the hole in the polymer film.
The radiation-sensitive polymer film has no particular limits, and wherein high-index regions forms by radiant exposure, and OMNIDEX (registered trademark), HRF150 and the HRF600 that for example can use commercially available DuPont to produce.
Refractive index according to the present invention to polymer film original material and high-index regions has no particular limits, and can be chosen to and other the optical element coupling of element as using, but usually preferably near 1.48 refractive index.Not preferred birefringence, painted because it will cause, but, can have birefringence for allowing birefringent purpose.Itself is preferably made polymer film parent material and high-index regions by the high light transmission material.The refringence of preferred polymers parent material and high-index regions is big as much as possible, but generally refringence is arranged on the scope of 0.005-0.2.Refringence less than 0.005 will hinder the acquisition of moderate scattering properties.Refringence is preferably in the scope of 0.005-0.1.
The refractive index of polymer film parent material and high-index regions can be two kinds of changing mutually at the interface sharp, but preferably little by little change so that obtain preferred scattering properties.
The diameter that is formed on the high-index regions of the extension in the diffusion barrier of the present invention be from tens nanometers to the hundreds of micron, for the relation of optical wavelength and minor axis and major axis, preferably at 50nm-100 μ m, especially preferred 100nm-50 μ m.If diameter is too big or too little, then can not obtain required scattering properties owing to transmittance.
The average-size that is formed on major axis in the high-index regions xsect of the extension in the diffusion barrier of the present invention and minor axis must be greater than 1: 1 than (average aspect ratio), but normally be selected in 1.2: 1-10: 1 scope, preferably 1.5: 1-5: 1 scope, especially near 2: 1.If average aspect ratio surpasses 10: 1, then scattering properties reduces.The shape of the high-index regions of extending is preferably ellipse, but also can be rectangle, bar shaped, avette etc.The high-index regions that is formed in the diffusion barrier of the present invention can also comprise zone of equiaxial crystals, circle typically.No matter be only to exist the high-index regions of extending or extension area and zone of equiaxial crystals to be blended between the high-index regions, on the specific direction of film in the xsect of high-index regions the average-size of major axis and minor axis all preferably be in the scope of afore mentioned rules than (average aspect ratio).
The size and the aspect ratio that are formed on the high-index regions of the extension in the diffusion barrier of the present invention can be different between the high-index regions of each extension, perhaps can be all identical.But, preferably select size and aspect ratio to prevent Moire effect and provide effect at random with satisfied scattering properties.
The characteristics that are formed on the high-index regions of the extension in the diffusion barrier of the present invention are to be orientated on the specific direction of film, but the high-index regions of all extensions needn't be in identical direction orientation, and reach required dispersion effect if their orientations are average just enough.
The film relative inclination of column structure that is formed on the high-index regions of the extension in the diffusion barrier of the present invention generally is in 0-50 ° scope, preferably is in 10-20 ° scope.As above-mentioned with reference to the accompanying drawings as described in, preferably the high-index regions of Yan Shening tilts with respect to the normal direction of film, so that provide better choice scattering and convergence characteristics.The inclination angle of the high-index regions of extending, be that the inclination angle of column structure is from the viewpoint of scattering properties and best identical with regard to making, but because even column structure also can show general scattering properties by mean obliquity with different angle tilts, simultaneously tilt profiles also has the desirable visual angle-selective scattering of in the visual angle of broad generation and the effect of convergence characteristics, so preferred this situation.In addition, have the high-index regions of extension of the column structure of two or more (as intersect) different angle can be on purpose in conjunction with to obtain specific scattering properties.
The thickness of diffusion barrier of the present invention has no particular limits, but usually will be in the scope of about 2 μ m~100 μ m.
Diffusion barrier of the present invention helps as the diffusion barrier that is applicable to liquid crystal indicator, especially reflective and transflective liquid crystal indicator.
The embodiment of Fig. 7 and 8 expression liquid crystal indicators.63 of liquid crystal layers are formed with between the glass plate 61 and 65 of electrode 62 and 64 thereon, and diffusion barrier 66 is placed on (Fig. 7) on the glass plate 65 of light incident side usually or is placed on the surface of the reflectance coating 67 under the glass plate 61 of light reflection side (Fig. 8).When using retardation plate 68 and polarizing coating 69, they are usually located at the outside (not shown among Fig. 8) of diffusion barrier 66.Diffusion barrier 66 can be placed on both sides, and the structure of liquid crystal indicator is not limited to structure shown here.
When light from the back side of liquid crystal layer during, between backlight and liquid crystal layer, promptly a common optical diffusion film layer is set in incident light one side from the backlight radiation.In the situation of the liquid crystal indicator that has back light system, blooming of the present invention and reflecting polarizer combination provide a good result.Fig. 9 represents the embodiment that blooming of the present invention and reflecting polarizer make up in having the liquid crystal indicator of back light system.
For the liquid crystal indicator of for example cell phone or PDA is used a reflecting polarizer, reliable brightness in the time of must cremasteric reflex.When using reflecting polarizer, excessively increase the brightness that the attempt of brightness will cause reflecting and reduce.For the liquid crystal indicator such as cell phone or PDA, this blooming is preferably by transmission with reflect one and can produce bright, the highly effect of the optical diffusion film of visual image.
In Fig. 9,71 is optical diffusion films, and 72 is reflecting polarizers, the 73rd, and a kind of based on acrylic acid cementing agent, 74 is light pipes, 75 is light sources.The glass plate 61 of liquid crystal indicator shown in Figure 8 is attached to optical diffusion film 71 usually.The optical convergence that sends from light pipe 74 is at BEF (optical convergence sheet, not shown), and enters reflecting polarizer 72.The S ripple was reflected when the P ripple of incident light passed reflecting polarizer 72.The P ripple of the light that is reflected at the BEF place also passes, and the S ripple is reflected simultaneously.The S ripple is transformed into the P ripple when this process repeats, and allows to utilize the S ripple that also was not used in the prior art thus.That is, though the S ripple is set at the polarizing coating cutting in the common liquid crystals display device, the use of reflecting polarizer makes the S wave energy that has been polarized the conventional cutting of film enough effectively utilize.According to the present invention, be not in backlight, to use BEF utterly, and light needn't be assembled.Even do not have radiation backlight ground that reflecting polarizer is used as reflectance coating, and therefore its performance always is lower than total reflectance coating, but it still can suitably be used as reflective LCD device.
As shown in figure 10, blooming of the present invention is used as optical diffusion film 76, and makes up with the conventional known optical diffusion film 77 with isotropic scatterning characteristic, thereby is manufactured on the liquid crystal indicator that forward has wide visual angle and brightness.This isotropic scatterning optical diffusion film needs not to be the form of film.For example, when blooming of the present invention links or be bonded to reflectance coating, glass plate etc., can be with bonding agent or comprise with matrix polymer different refractivity arranged the contact adhesive of ball packing as blooming to bonding agent or contact adhesive that reflectance coating or glass plate stick or link, form light diffusion layer or binder couse thus.By combination isotropic scatterning optical diffusion film or light diffusion layer and blooming of the present invention, surround lighting is spread widely by the isotropic scatterning optical diffusion film, and comprises that the light of extensive diffusive light assembled by blooming of the present invention at forward.Therefore, the effect of the effect of blooming of the present invention and conventional isotropic scatterning film works together, and the liquid crystal indicator that makes it possible to obtain also has a very wide visual angle simultaneously when demonstrate bright image when the place ahead is watched.
Be that example is further introduced liquid crystal indicator below with the cell phone.Use as Fig. 4 or diffusion barrier shown in Figure 5, and the long axis direction that makes the high-index regions 83 of extension is oriented in the left and right directions of cell phone 81 display screens 82, shown in Figure 11 B, and diffusion barrier is arranged to column structure 83 inclinations, make the film surface side of column structure point to the upper end of screen, the film bottom side end of column structure points to the lower end of screen, preferably provides best scattering properties.In this type of cell phone, when observer 86 sees cell phone 81, from the observer back and the top reflected by liquid crystal display cells to the light of the wide range incident of observer front and top, and optionally reflected again, main can the coalescence reflection on observer 86 direction.The mode of this scattering/reflection characteristic has improved the brightness of image of display screen under the most common service condition of cell phone etc.
Figure 12 represents another embodiment of liquid crystal indicator of the present invention.Liquid crystal indicator 91 generally includes a polarizing coating (seeing 69 among Fig. 7), but its polarization axis direction 93 is orientated with the vertical direction 94 from display screen 92 with tilting a given angle θ (for example approximately 35-45 °) to the left or to the right in having this situation of polarizing coating usually.Because polarizing coating utilizes the light of polarization axis direction,, make that the scattering on polarization axis direction is more so scattering film of the present invention also preferably has the short-axis direction of the extension area (xsect of column structure) that is arranged on the polarized film polarization axis direction.Still in the case, preferred extension area and polarization axle are coordinated well, if but coordinate just enough basically.
Above-mentioned characteristic is identical for the incident from the light to the liquid crystal indicator radiation backlight, and therefore can realize brightness and visual excellent images under transmission and reflective condition.In addition, as mentioned above, even when reflecting polarizer or isotropic scatterning optical diffusion film use together with optical diffusion film of the present invention, still can be when forward obtains Billy with conventional optical diffusion film brighter display image, also can obtain the demonstration at wide visual angle simultaneously.The present invention will be further explained by the following examples, but these embodiment do not do any restriction to the present invention.
Embodiment
Embodiment 1
Present embodiment will be referring to Figure 13.Utilization is coated with the poly terephthalic acid diethyl alcohol ester film 101 of OMNIDEX HRF 600 of DuPont company of 50 μ m thickness as photopolymer 102, and the mask 103 of elliptical aperture pattern is bonded on the surface of this photosensitive polymer layer 102 having as shown in Figure 4 by hard contact method.The slotted eye pattern of mask has 2: 1 the major axis and the ratio of minor axis, and major axis dimension is at 500nm~30 μ m, average out to 2 μ m.Slotted eye is a uniaxial orientation.
The ultraviolet ray that obtains from mercury lamp be converged to parallel beam and optionally from the mask 103 with normal direction θ=0-50 ° of angle eradiation with respect to mask.Radiated time from several seconds to a few minutes.Thermal treatment one hour under 120 ℃ of temperature then.
Produce a kind of diffusion barrier like this, with the predetermined column structure that is formed slopely, have the cross-sectional structure that conforms to the sectional hole patterns of mask with respect to embrane method line direction with high-index regions.The refractive index of the polymer substrate of diffusion barrier is 1.47, and the refractive index of high-index regions is 1.52.
Check the transmission and the scattering properties of the diffusion barrier that obtains in this way, as shown in figure 14, incident light 106 imports from a side of diffusion barrier 105, photo-detector 107 is placed on the opposition side of film, and the position that changes photo-detector 107 is to determine the relation of radiative direction and angle (with respect to the direction and the angle of the incident light direction of propagation) and transmitted light intensity.In addition, change incident direction of light and angle to determine the relation of radiative direction and angle (with respect to the direction and the angle of the incident light direction of propagation) and transmitted light intensity.The definition of incident light and radiative direction and angle is with reference to figure 1-6 and above-mentioned explanation.
Fig. 5 B represents that diffusion barrier is for respect to optical transmission and the scattering properties of photopolymer with 20 ° of angle radiation.That is,, the incident direction of column structure y direction is defined as the lip-deep y axle of film, does not almost have the pellucidity of scattering in the reverse existence of y axle if the long axis of ellipse direction is defined as the x axle.On the other hand, the first half through y direction of principal axis forward axial reverse light from the axial forward of x to x demonstrates the anisotropic scattering that concentrates on forward.As a result, incident light in positive convergence, is provided the forward brightness of enhancing by effectively.
Embodiment 2
With the photopolymer of embodiment 1 same type on to use oval-shaped major axis and minor axis ratio be 1.5: 1 mask, make diffusion barrier in the mode identical, except optical radiation angle θ is 20 ° with embodiment 1.
Estimate transmission and scattering properties according to the mode identical with embodiment 1.
As embodiment 1, effectively realize the convergence of incident light at forward.
Embodiment 3
With the photopolymer of embodiment 1 same type on to use oval-shaped major axis and minor axis ratio be 2: 1 mask, make diffusion barrier in the mode identical, except optical radiation angle θ is 10 ° with embodiment 1.
Estimate transmission and scattering properties according to the mode identical with embodiment 1.
As embodiment 1, effectively realize the convergence of incident light at forward.
Embodiment 4
With the photopolymer of embodiment 1 same type on to use oval-shaped major axis and minor axis ratio be 1.5: 1 mask, make diffusion barrier in the mode identical, except optical radiation angle θ is 10 ° with embodiment 1.
Estimate transmission and scattering properties according to the mode identical with embodiment 1.
As embodiment 1, effectively realize the convergence of incident light at forward.
Embodiment 5
With the photopolymer of embodiment 1 same type on to use oval-shaped major axis and minor axis ratio be 1.5: 1 mask, make diffusion barrier in the mode identical, except optical radiation angle θ is 0 ° with embodiment 1.
Estimate transmission and scattering properties according to the mode identical with embodiment 1.
The transmission and the scattering properties that obtain are shown in Fig. 6 B.Specifically, incide the mode scattering of light to extend on film surface (the y direction of principal axis of film) along film y direction of principal axis from the short-axis direction of ellipse.Assembled effectively at forward at the light that this side up.Light is very important for the LCD of small-sized data set (cell phone) in effective convergence of forward, and the diffusion barrier of embodiment 5 shows effective optical convergence in this direction.