JP7837751B2 - Liquid crystal photomask laminate and exposure apparatus - Google Patents

Description

This invention relates to a liquid crystal photomask laminate and an exposure apparatus.

One of the main manufacturing processes for printed circuit boards and flat panel displays (FPDs) involves a process using photolithography technology. In this process, for example, a photoresist film formed on a substrate is selectively exposed by irradiating it with light, such as ultraviolet light, through a photomask with a predetermined pattern. The photoresist film is then developed to form a resist pattern.

Conventionally, photomasks are manufactured by forming a light-shielding film and a photoresist film on a transparent substrate such as quartz glass, selectively exposing the photoresist film to a predetermined pattern, developing it to form a resist pattern, and then etching the light-shielding film through the resist pattern. However, photomasks are designed each time for each circuit design to be manufactured, and several to dozens of masks are required to produce a single product, resulting in the problem of requiring a large amount of time and expense to produce them all.
To address this problem, liquid crystal photomasks have been considered (Patent Documents 1-4). By using a liquid crystal photomask in an exposure apparatus, the pattern can be electrically rewritten without having to replace the photomask.

Japanese Patent Application Publication No. 60-33530 Japanese Unexamined Patent Publication No. 4-137792 JP-A-4-157466 Japanese Patent Application Publication No. 6-301190

However, in liquid crystal photomasks, the transmission and shielding of exposure light are controlled by multiple pixels arranged vertically and horizontally on the main surface. Therefore, if the pattern to be formed includes line patterns or space patterns (hereinafter collectively referred to as "inclined patterns") extending in a direction inclined with respect to the pixel arrangement direction (vertical and horizontal directions) (for example, Figure 11), the inclined pattern in the liquid crystal photomask pattern (mask pattern) will not be a straight line but will be zigzag (for example, Figure 12). In this case, the inclined pattern will also be zigzag in the formed resist pattern, which can reduce the accuracy of the pattern. This problem becomes more pronounced as the pattern resolution increases.

The present invention aims to provide a liquid crystal photomask laminate and exposure apparatus capable of forming a resist pattern having a gradient pattern with good accuracy.

The present invention has the following aspects.
[1] A liquid crystal photomask and a light diffuser laminated on either the light incident side or the light output side of the liquid crystal photomask,
The light diffuser has a first main surface and a second main surface opposite to the first main surface, and when linear light is incident on the first main surface along the direction normal to the first main surface, and the distribution of diffused light emitted from the second main surface is measured with the angle of the normal direction of the second main surface being 0°, the angular width at 1/10 of the maximum intensity of the diffused light is 45° or less, and the haze value is 55% or more, characterized in that the light diffuser has a first main surface and a second main surface opposite to the first main surface, and when linear light is incident on the first main surface along the direction normal to the first main surface, the distribution of diffused light emitted from the second main surface is measured with the angle of the normal direction of the second main surface being 0°, the angular width at 1/10 of the maximum intensity of the diffused light is 45° or less, and the haze value is 55% or more.
[2] The light diffuser is the liquid crystal photomask laminate of [1], wherein the linear transmittance in the direction normal to the first main surface is 40% or less.
[3] The liquid crystal photomask laminate of [1] or [2], wherein the light diffuser is an anisotropic diffusion film whose light diffusivity changes depending on the angle of incident light.
[4] The liquid crystal photomask laminate of [3], wherein the anisotropic diffusion film comprises a matrix and a plurality of columnar structures having different refractive indices from the matrix, and the plurality of columnar structures extend in the thickness direction of the anisotropic diffusion film.
[5] The liquid crystal photomask laminate of [4], wherein the scattering center axis angle of the anisotropic diffusion film is 10° or less.
[6] A liquid crystal photomask laminate of [4] or [5], wherein each of the plurality of columnar structures has an aspect ratio of 1 to 10, expressed as the ratio of the major axis to the minor axis (major axis/minor axis) in a cross section perpendicular to the extending direction of the columnar structure.
[7] The light diffuser is a liquid crystal photomask laminate of any of [1] to [6], which is laminated on the light-emitting surface side of the liquid crystal photomask.
An exposure apparatus using one of the liquid crystal photomask laminates described in [8] [1] to [7].

According to the present invention, a liquid crystal photomask laminate and exposure apparatus capable of forming a resist pattern including a gradient pattern with good accuracy can be provided.

A schematic cross-sectional view showing an example of a liquid crystal photomask laminate. A schematic cross-sectional view showing an example of a light diffuser. A three-dimensional polar coordinate representation to explain the scattering center axis of an anisotropic diffusion film. A schematic diagram showing the structure of an anisotropic diffusion film having a rod-shaped columnar structure, and the behavior of transmitted light incident on this anisotropic diffusion film. A schematic diagram showing the structure of an anisotropic diffusion film having a plate-like columnar structure, and the behavior of transmitted light incident on this anisotropic diffusion film. An explanatory diagram showing a method for evaluating the light diffusion properties of anisotropic diffusion films. A graph showing the relationship between the angle of incident light and linear transmittance in an anisotropic diffusion film having a rod-shaped columnar structure as shown in Figure 4. A schematic cross-sectional view showing another example of a liquid crystal photomask laminate. A schematic cross-sectional view showing another example of a liquid crystal photomask laminate. A schematic diagram showing an example of a pattern including a slope pattern. A schematic diagram showing the pattern shown in Figure 11 displayed on a liquid crystal photomask. A schematic diagram showing an example of a method for manufacturing an anisotropic diffusion film, including an optional step (S3). A schematic diagram showing an example of a method for manufacturing an anisotropic diffusion film, including an optional step (S3).

The present invention will be described below with reference to the attached drawings and embodiments. However, the present invention is not limited to the following embodiments.
Note that the dimensional ratios in Figures 1-13 are for illustrative purposes only and may differ from actual dimensions. Furthermore, in the following drawings, identical components are indicated using the same terminology and reference numerals, and explanations of redundant components may be omitted.

Figure 1 is a schematic cross-sectional view of a liquid crystal photomask laminate 1 according to one embodiment of the present invention.
The liquid crystal photomask laminate 1 comprises a liquid crystal photomask 2 and a light diffuser 3. The light diffuser 3 is laminated to the light-emitting side (lower side in the figure) of the liquid crystal photomask 2 via a transparent adhesive layer 4.

(Liquid crystal photomask)
There are no particular restrictions on the liquid crystal photomask 2; any publicly available one can be used.
The liquid crystal photomask 2 is typically configured as a dot matrix type liquid crystal display device in which a predetermined number of pixels are arranged in the vertical and horizontal directions. By appropriately controlling the driving of each pixel, a predetermined pattern of transparent portions is formed as a whole, and an image is drawn by the transmitted light.

A control device (not shown) is connected to the liquid crystal photomask 2 for driving and controlling it. A memory device (not shown) is connected to the control device for storing various mask patterns as electronic pattern data. The control device reads pattern data corresponding to a desired mask pattern from the pattern data corresponding to various mask patterns pre-stored in the memory device. Based on this pattern data, the control device drives and controls the liquid crystal photomask 2, thereby driving and controlling each pixel of the liquid crystal photomask 2, and ultimately forming the desired mask pattern as a matrix image.

The pixel size of the liquid crystal photomask is preferably 10 μm to 500 μm, and more preferably 20 μm to 200 μm. If the pixel size is above the lower limit, the manufacturing cost of the liquid crystal panel tends to be high, but manufacturing is not difficult. If the pixel size is below the upper limit, the resolution is not too low, which is advantageous for pattern formation.

(Light diffuser)
The light diffuser 3 has a first main surface 3a and a second main surface 3b opposite to the first main surface 3a. In this embodiment, the light diffuser 3 is positioned with the first main surface 3a facing the liquid crystal photomask 2.

When linear light is incident on the light diffuser 3 from the first main surface 3a along the direction normal to the first main surface 3a, and the distribution of diffused light emitted from the second main surface 3b is measured with the angle of the normal direction of the second main surface 3b set to 0°, the angular width at 1/10 of the maximum intensity of the diffused light (Full Width at Tenth Maximum, hereafter sometimes referred to as FWTM) is 45° or less, preferably 40° or less, and more preferably 35° or less.
FWTM is an indicator of the light diffusion properties of the light diffuser 3. If FWTM is above the lower limit, the light from the liquid crystal photomask 2 is diffused, which can suppress the formation of zigzag patterns in the sloped portions of the resist pattern. If FWTM is below the upper limit, excessive light diffusion can be prevented, which can reduce the accuracy of the pattern.

The light diffuser 3 has a haze value of 55% or more, preferably 60% or more, and more preferably 70% or more. If the haze value is above the lower limit, the light from the liquid crystal photomask 2 is diffused, which can suppress the formation of a zigzag pattern in the sloped portion of the resist pattern. If the haze value is below the upper limit, excessive light diffusion can be prevented from reducing the pattern accuracy.
The haze value is measured in accordance with JIS K7136:2000.

The light diffuser 3 preferably has a linear transmittance of 40% or less in the direction normal to the first main surface 3a, and more preferably 2% to 25%. If the linear transmittance in the direction normal is above the lower limit, excessive light diffusion that reduces pattern accuracy can be suppressed, and if it is below the upper limit, the light diffusion performance is better.
"Linear transmittance" is the ratio of the amount of light transmitted in a straight line (linear transmitted light amount) to the amount of incident light (incident light amount) when light is incident on a light diffuser at a certain incident light angle, and is expressed by the following formula. The straight line direction refers to the direction of propagation of the incident light. Linear transmitted light amount can be measured by the method described in Japanese Patent Application Publication No. 2015-191178.
Linear transmittance (%) = (linear transmitted light amount / incident light amount) x 100

The light diffuser 3 preferably does not contain any components that absorb exposure light so as not to affect the exposure light during exposure. For example, if the exposure light is ultraviolet light, the light diffuser 3 preferably does not contain ultraviolet absorbers or the like.

The thickness of the light diffuser 3 is preferably 10 μm to 500 μm, more preferably 15 μm to 250 μm, and even more preferably 20 μm to 100 μm. If the thickness of the light diffuser 3 is above the lower limit, the light diffusion performance is superior; if it is below the upper limit, excessive light diffusion that reduces pattern accuracy can be suppressed.

The light diffuser 3 can be appropriately selected from known light diffusers, taking into consideration the characteristics such as the full width at half maximum (FWHM). Examples of light diffusers 3 include isotropic diffusion films and anisotropic diffusion films. Among these, anisotropic diffusion films are preferred from the viewpoint of controlling diffusion width and light focusing properties.

An "isotropic diffusion film" is a light diffusion film whose light diffusion properties do not change with the angle of incident light. Known isotropic diffusion films can be used; for example, a film in which multiple fine particles with different refractive indices from the matrix are dispersed in a matrix.
An "anisotropic diffusion film" is a light diffusion film whose light diffusion properties change depending on the angle of incident light. In other words, it is a light diffusion film that exhibits an incident light angle dependence on its light diffusion properties, where the linear transmittance changes depending on the angle of incident light. Known anisotropic diffusion films can be used.

Figure 2 is a schematic cross-sectional view showing an example of an anisotropic diffusion film. In this example, the anisotropic diffusion film 3A has a matrix 31 and a plurality of columnar structures 32 (also referred to as "columnar structures") with refractive indices different from those of the matrix 31. Each of the columnar structures 32 extends in the thickness direction of the anisotropic diffusion film 3A.

The angle between the extension direction of the multiple columnar structures 32 of the anisotropic diffusion film 3A (the direction in which the columnar structures 32 are oriented from one surface to the other on the main surface of the anisotropic diffusion film 3A) and the normal direction of the anisotropic diffusion film 3A (hereinafter sometimes referred to as the "columnar structure extension angle") is preferably 7° or less, more preferably 4° or less, particularly preferably 2° or less, and most preferably 0°. If the columnar structure extension angle is within the above range, differences in diffusion due to orientation are less likely to occur, and a uniform diffusion effect is easily obtained.
Furthermore, the columnar structure extension angle can be adjusted to a desired angle by changing the direction of the light rays irradiated onto the sheet-like composition containing the photopolymerizable compound when manufacturing the anisotropic diffusion film 3A.
Furthermore, the columnar structure extension angle is calculated by observing the thickness-direction cross-section of the anisotropic diffusion film 3A with an optical microscope, measuring the angle between the extension direction of the columnar structure and the normal direction of the main surface of the anisotropic diffusion film 3A for any 10 columnar structures, and using the average value of these measurements.

There are no particular restrictions on the cross-sectional shape perpendicular to the extension direction of the columnar structure 32. For example, it may be circular, elliptical, polygonal, irregular, or a combination of these.

The columnar structure 32 has an aspect ratio, expressed as the ratio of the major axis to the minor axis (major axis/minor axis) in a cross section perpendicular to the extension direction of the columnar structure 32, which is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 2. If the aspect ratio is below the upper limit, differences in diffusion depending on the orientation are less likely to occur, and a uniform diffusion effect can be obtained.
Here, the "major axis" is the maximum diameter in the cross-section described above, and the "minor axis" is the maximum diameter in the direction perpendicular to the major axis direction.

The average value of the major axis of each of the multiple columnar structures 32 is preferably 0.5 μm or more, and more preferably 1 μm or more. Furthermore, the average value of the major axis is preferably 100 μm or less, and more preferably 50 μm or less. If the average value of the major axis is above the lower limit, the diffusivity tends to improve. If the average value of the major axis is below the upper limit, the suppression of appearance defects tends to improve.
These lower and upper limits can be combined as appropriate.

The average value of the short axis of each of the multiple columnar structures 32 is preferably 0.5 μm or more, and more preferably 1 μm or more. Furthermore, the average value of the short axis is preferably 10 μm or less, and more preferably 5 μm or less. If the average value of the short axis is above the lower limit, the diffusivity tends to improve. If the average value of the short axis is below the upper limit, the suppression of appearance defects tends to improve.
These lower and upper limits can be combined as appropriate.

The shape of the cross-section perpendicular to the extension direction of the columnar structure 32 can be confirmed with an optical microscope.
The average values for the major axis and minor axis are the average values obtained by measuring the major axis and minor axis in cross-sections perpendicular to the extension direction of 10 arbitrarily selected columnar structures 32, respectively.
The aspect ratio is calculated by dividing the average value of the major axis, as determined above, by the average value of the minor axis.

The refractive indices of the matrix 31 and the columnar structure 32 do not need to be different from each other. The degree to which their refractive indices differ is not particularly limited and is relative. If the refractive index of the matrix 31 is lower than that of the columnar structure 32, the matrix 31 will be in the low refractive index region. Conversely, if the refractive index of the matrix 31 is higher than that of the columnar structure 32, the matrix 31 will be in the high refractive index region.
Here, it is preferable that the refractive index at the interface between the matrix 31 and the columnar structure 32 changes gradually. By changing it gradually, the change in diffusivity when the angle of incident light is changed becomes extremely abrupt, making it less likely for scintillation to occur. The refractive index at the interface between the matrix 31 and the columnar structure 32 can be changed gradually by forming the matrix 31 and the columnar structure 32 by phase separation associated with light irradiation.

The anisotropic diffusion film 3A typically consists of a cured product of a composition containing a photopolymerizable compound (a photocurable composition). When this composition is cured, regions with different refractive indices are formed. Photocurable compositions will be described in detail later.
In this invention, both "photopolymerization" and "photocuring" refer to a polymerization reaction in which a photopolymerizable compound is exposed to light.

The anisotropic diffusion film 3A has a scattering center axis. In the anisotropic diffusion film 3A, each of the columnar structures 32 is formed such that its extension direction is substantially parallel to the scattering center axis. Therefore, the multiple columnar structures 32 in the same anisotropic diffusion film 3A are substantially parallel to each other.
The extension direction of the columnar structure 32 and the scattering center axis are said to be approximately parallel only if they satisfy the law of refractive index (Snell's law), and they do not need to be strictly parallel. Snell's law states that when light is incident on the interface between a medium with refractive index n1 and a medium with refractive index n2, the relationship n1sinθ1 = n2sinθ2 holds between the incident light angle θ1 and the refraction angle θ2. For example, if n1 = 1 (air) and n2 = 1.51 (anisotropic diffusion film), and the inclination of the scattering center axis (incident light angle) is 30°, the extension direction of the columnar structure 32 (refraction angle) will be approximately 19°. Even if the incident light angle and refraction angle are different in this way, as long as Snell's law is satisfied, they are included in the concept of approximately parallelism in this embodiment. In particular, when the normal angle of the anisotropic diffusion film 3A is set to 0° and the extension angle of its columnar structure 32 is set to 0°, the scattering center axis angle also becomes 0°, and the scattering center axis angle and the extension direction become perfectly parallel, not just approximately parallel.
When light incident on the anisotropic diffusion film 3A at a predetermined incident angle, diffusion is prioritized when the incident angle is approximately parallel to the extending direction (orientation direction) of the columnar structure 32, and transmission is prioritized when the incident angle is not approximately parallel to the extending direction. Therefore, when the angle of light incident on the anisotropic diffusion film 3A changes, the linear transmittance also changes. Specifically, in the anisotropic diffusion film 3A, incident light is strongly diffused in the normal direction (i.e., the extending direction of the columnar structure 32) and within the range of incident angles close to the normal direction (diffusion region), but diffusion weakens and linear transmittance increases in the range of incident angles beyond that (non-diffusion region).

The "scattering center axis" refers to the direction in which, when the angle of incident light on an anisotropic diffusion film is changed, the light diffusion properties coincide with the angle of incident light that exhibits approximate symmetry with respect to that angle of incident light. The phrase "approximately symmetry" is used because if the scattering center axis is tilted with respect to the normal direction of the anisotropic diffusion film, the optical properties (optical profile, described later) will not be strictly symmetrical. The scattering center axis can be confirmed from the angle of incident light that exhibits approximate symmetry in the optical profile.
Figure 3 shows a three-dimensional polar coordinate representation to explain the scattering center axis (P). In the three-dimensional polar coordinate representation, if the surface of the anisotropic diffusion film is the xy-plane and the normal is the z-axis, the scattering center axis can be expressed by the polar angle θ and the azimuthal angle φ. In other words, Pxy in Figure 3 can be said to be the length direction of the scattering center axis projected onto the surface of the anisotropic diffusion film.
In this invention, the polar angle θ (0° ≤ θ < 90°) between the normal of the anisotropic diffusion film (z-axis shown in Figure 3) and the scattering center axis is defined as the scattering center axis angle. Furthermore, the sign of the scattering center axis angle is defined as + when the scattering center axis is tilted to one side and - when it is tilted to the other side with respect to a plane that passes through both a predetermined axis of symmetry in the plane direction of the anisotropic diffusion film (for example, the axis of MD (Machine Direction, details described later) passing through the centroid of the anisotropic diffusion film 3A and the normal direction of the anisotropic diffusion film).
An anisotropic diffusion film may have multiple groups of columnar structures with different inclinations (a collection of columnar structures with the same inclination) within a single layer. In this case, where there are multiple groups of columnar structures with different inclinations within a single layer, there will also be multiple scattering center axes corresponding to the inclination of each group of columnar structures.

The scattering center axis angle of the anisotropic diffusion film 3A is preferably 10° or less, more preferably 5° or less, particularly preferably 3° or less, and most preferably 0°. If the scattering center axis angle is within the above range, differences in diffusion depending on orientation are less likely to occur, and a uniform diffusion effect can be obtained.
The scattering center axis angle, or polar angle θ, is measured using a bending-angle photometer.
The scattering center axis angle can be adjusted to a desired angle by changing the direction of the light beam irradiated onto the sheet-like composition containing the photopolymerizable compound when manufacturing the anisotropic diffusion film 3A.

The maximum linear transmittance of the anisotropic diffusion film 3A is preferably 10% to 75%, more preferably 15% to 65%, and even more preferably 20% to 55%. If the maximum linear transmittance of the anisotropic diffusion film 3A is within the above range, a better balance between diffusion and light concentration is achieved.
The minimum linear transmittance of the anisotropic diffusion film 3A is preferably 25% or less, more preferably 15% or less, and even more preferably 10% or less. If the minimum linear transmittance of the anisotropic diffusion film 3A is below the above upper limit, the balance between diffusion and light concentration is better.
"Maximum linear transmittance" is the linear transmittance of light incident at the incident angle that maximizes linear transmittance. "Minimum linear transmittance" is the linear transmittance of light incident at the incident angle that minimizes linear transmittance. Maximum linear transmittance > Minimum linear transmittance. A lower minimum linear transmittance indicates a decrease in the amount of linearly transmitted light (an increase in haze value). Therefore, a lower minimum linear transmittance indicates an increase in the amount of diffused light.

Here, with reference to Figures 4-7, we will explain the light diffusion properties of the anisotropic diffusion film 3A in more detail.
Here, we will explain using an anisotropic diffusion film 3B having a rod-shaped columnar structure (also called a pillar structure) and an anisotropic diffusion film 3C having a plate-shaped columnar structure (also called a louver structure) as examples. Figures 4 and 5 are schematic diagrams showing the structures of anisotropic diffusion films 3B and 3C respectively, and the behavior of transmitted light incident on these anisotropic diffusion films. In Figures 4 and 5, reference numeral 32A indicates the pillar structure, and reference numeral 32B indicates the louver structure. Figure 6 is an explanatory diagram showing a method for evaluating the light diffusion properties of anisotropic diffusion film 3B. Figure 7 is a graph showing the relationship between the incident light angle and linear transmittance in anisotropic diffusion film 3B.

The method for evaluating light diffusion is as follows. First, as shown in Figure 6, the anisotropic diffusion film 3B is placed between the light source 201 and the detector 202. In this embodiment, the incident light angle is defined as 0° when the irradiated light I from the light source 201 is incident from the direction normal to the anisotropic diffusion film 3B. The anisotropic diffusion film 3B is positioned so that it can be rotated arbitrarily around a straight line L as its central axis, while the light source 201 and the detector 202 are fixed.
Here, the straight line L is a straight line that is in the same direction as the direction TD (hereinafter referred to as Traverse Direction), which is perpendicular to the flow direction MD (hereinafter referred to as Traverse Direction), when the coating flow direction during the manufacture of the anisotropic diffusion film is defined as MD (hereinafter referred to as Traverse Direction), and that passes through the centroid of the anisotropic diffusion film. However, if a pillar structure is present and the pillar structure is inclined, the straight line L is in the same direction as the direction perpendicular to the inclination direction of the columnar structure, and that passes through the centroid of the anisotropic diffusion film.
According to this method, a sample (anisotropic diffusion film 3B) is placed between the light source 201 and the detector 202, and the amount of linearly transmitted light that passes straight through the sample and enters the detector 202 is measured while changing the angle with respect to a straight line L on the surface of the sample as the central axis, thereby determining the linear transmittance.

Figure 7 shows the evaluation results of the light diffusion properties of the anisotropic diffusion film 3B when TD in Figure 4 is selected as the straight line L of the rotation center axis shown in Figure 6. In other words, it shows the dependence of the light diffusion properties (light scattering properties) of the anisotropic diffusion film 3B on the incident light angle, measured using the method shown in Figure 6. The vertical axis of Figure 7 shows the linear transmittance, which is an index of the degree of scattering (in this embodiment, the ratio of the amount of parallel light emitted in the same direction as the incident direction when a predetermined amount of parallel light is incident on it; more specifically, linear transmittance = amount of light detected by detector 202 when anisotropic diffusion film 3B is present / amount of light detected by detector 202 when anisotropic diffusion film 3B is absent), and the horizontal axis shows the angle of incident light on the anisotropic diffusion film 3B. The sign of the incident light angle indicates that the direction of rotation of the anisotropic diffusion film 3B is opposite.
In this invention, "scattering" and "diffusion" have the same meaning.

When the direction of light incident on the anisotropic diffusion film 3B at a predetermined incident angle is approximately parallel to the orientation direction of a region with a different refractive index from the matrix (the extension direction of the pillar structure 32A), diffusion is prioritized; when it is not parallel to this direction, transmission is prioritized. Therefore, as shown in Figure 7, the anisotropic diffusion films 3B and 3C have an incident angle dependence of light diffusion, where the linear transmittance changes depending on the incident angle of light on the anisotropic diffusion film. Here, the curve showing the incident angle dependence of light diffusion as shown in Figure 7 will be referred to as the "optical profile." Although the optical profile does not directly represent light diffusion, if we interpret that the decrease in linear transmittance is accompanied by an increase in diffuse transmittance, it can be said that it generally indicates light diffusion.
While a typical isotropic diffusion film exhibits a mountain-shaped optical profile with a peak around 0°, the anisotropic diffusion film 3B exhibits a valley-shaped optical profile. When the incident light angle in the direction of the scattering center axis of the pillar structure 32A is set to 0° (the extension direction of the columnar structure is also 0°), the linear transmittance initially reaches a minimum value at incident light angles of ±5 to ±20°, compared to the linear transmittance when incident at 0°. As the absolute value of the incident light angle increases, the linear transmittance increases, and the linear transmittance reaches a maximum value at incident light angles of ±40 to ±60°.
The anisotropic diffusion film 3C, having a louver structure 32B, exhibits the same properties as the anisotropic diffusion film 3B. When the direction of light incident at a predetermined incident angle is approximately parallel to the orientation direction of a region with a different refractive index from the matrix (the height direction of the louver structure 32B), diffusion is prioritized. When the direction is not parallel to this direction, transmission is prioritized. Therefore, similar to the anisotropic diffusion film 3B, it exhibits an incident light angle dependence of light diffusion and shows a valley-shaped optical profile.

Thus, the anisotropic diffusion films 3B and 3C exhibit the property that incident light is strongly diffused in the incident light angle range close to the scattering center axis, but diffusion weakens and linear transmittance increases in the incident light angle range beyond that.
Hereinafter, the angular range of two incident light angles with respect to the linear transmittance that is the midpoint between the maximum linear transmittance and the minimum linear transmittance will be referred to as the diffusion region (the width of this diffusion region will be called the "diffusion width"), and the other incident light angle range will be referred to as the non-diffusive region (transmission region).
Let's take the optical profile shown in Figure 7 as an example to explain the diffuse and non-diffusive regions in detail. In this optical profile, the maximum linear transmittance is approximately 52%, the minimum linear transmittance is approximately 9%, and the intermediate linear transmittance is approximately 30%. The incident light angle range between the two incident light angles for this intermediate linear transmittance (the range of incident light angles inside the two dashed lines on the optical profile shown in Figure 7 (including an incident light angle of 0°) is the diffuse region, and the range of incident light angles outside of that range is the non-diffusive region (transmitted region).
On the other hand, in the anisotropic diffusion film 3B having the pillar structure 32A, as shown in the appearance of transmitted light on the projection surface in Figure 4, the transmitted light is approximately circular, and exhibits approximately the same light diffusion properties in both MD and TD directions. In other words, in the anisotropic diffusion film 3B having the pillar structure 32A, diffusion is isotropic. Furthermore, as shown in Figure 7, even when the incident light angle is changed, the change in light diffusion properties (especially the optical profile near the boundary between the non-diffusing and diffusing regions) is relatively gradual.
In contrast, in the anisotropic diffusion film 3C having a louver structure 32B, as shown in the appearance of transmitted light on the projection surface in Figure 5, the transmitted light is roughly needle-shaped, and the light diffusion properties differ greatly between MD and TD. That is, in the anisotropic diffusion film 3C having a louver structure 32B, the diffusion is anisotropic. Specifically, in the example shown in Figure 5, the diffusion is wider in MD than in the case of the pillar structure, but narrower in TD than in the case of the pillar structure.

(transparent adhesive layer)
The transparent adhesive layer 4 is not particularly limited, and any transparent adhesive layer known as OCA (optical transparent adhesive) or the like can be used.
The transparent adhesive layer 4 generally contains a base resin and optionally further contains other components. Examples of the base resin for the transparent adhesive layer 4 include polyester resins, epoxy resins, polyurethane resins, silicone resins, and acrylic resins. Acrylic resins are preferred due to their high optical transparency and relatively low cost.
The thickness of the transparent adhesive layer 4 is, for example, about 5 μm to 50 μm.
The total light transmittance of the transparent adhesive layer 4 (JIS K7361-1:1997) is preferably 60% to 100%, more preferably 80% to 100%, and even more preferably 90% to 100%.

(Method for manufacturing a liquid crystal photomask laminate)
The liquid crystal photomask laminate 1 can be manufactured, for example, by bonding a light diffuser 3 to the light-emitting surface of a liquid crystal photomask 2 via a transparent adhesive layer 4.
There are no particular restrictions on the method of bonding; it can be done using any known method.

Liquid crystal photomask 2 can be a commercially available liquid crystal photomask. It may also be one manufactured by a known manufacturing method.
The transparent adhesive layer 4 can be a commercially available transparent adhesive sheet. It may also be one manufactured by a known manufacturing method.

The light diffuser 3 can be a commercially available product. It may also be manufactured using a known manufacturing method. For example, an anisotropic diffusion film 3A can be obtained by appropriately adjusting the heating temperature of the photocurable composition, the thickness of the photocurable composition layer, the adjustment of oxygen inhibition by a mask or nitrogen atmosphere, and the direction of light irradiation to the photocurable composition, referring to the methods disclosed in Japanese Patent Publication No. 2005-265915, Japanese Patent Publication No. 2006-119241, International Publication No. 2014/084361, Japanese Patent Publication No. 2015-191178, etc. An isotropic diffusion film can be obtained by appropriately adjusting the amount of resin fine particles added to the coating, referring to the method disclosed in International Publication No. 2018/051639.

An example of a method for manufacturing the anisotropic diffusion film 3A is described below.
The manufacturing method in this example mainly comprises the following steps.
(S1) A step of providing a layer of a composition containing a photopolymerizable compound (hereinafter also referred to as "photocurable composition") on a substrate.
(S2) A process to obtain parallel light rays from a light source.
(S3) If necessary, a step (optional step) to obtain a directional light ray by injecting a parallel light ray into a directional diffusion element.
(S4) A step of injecting a light ray (a parallel light ray obtained in step (S2) or a directional light ray obtained in step (S3)) into a layer of the photocurable composition and curing the layer of the photocurable composition.

<Photocurable composition>
Photocurable compositions are materials that polymerize and harden upon irradiation with light, and typically contain a photopolymerizable compound and a photoinitiator. Examples of light include ultraviolet (UV) light and visible light.
Examples of photocurable compositions that can be used include the following:
(1) A compound comprising a single photopolymerizable compound and a photoinitiator.
(2) A compound comprising multiple photopolymerizable compounds and a photoinitiator.
(3) A compound comprising one or more photopolymerizable compounds, a polymer compound that does not exhibit photopolymerization properties, and a photoinitiator.

In all of the above compositions, light irradiation forms micron-order fine structures with different refractive indices within the anisotropic diffusion film 3A.
Even if only one type of photopolymerizable compound forms the anisotropic diffusion film 3A, differences in density create differences in refractive index. This is because areas with strong light irradiation intensity cure faster, causing polymerization and curing material to migrate around these cured regions, resulting in the formation of regions with high refractive index and regions with low refractive index.
Therefore, in the composition of (1) above, it is preferable to use a photopolymerizable compound that exhibits a large change in refractive index before and after photopolymerization. In the compositions of (2) and (3) above, it is preferable to combine multiple materials with different refractive indices. Specifically, the change in refractive index or difference in refractive index referred to here is preferably a change or difference of 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more.

Examples of photopolymerizable compounds include compounds having radically polymerizable or cationically polymerizable functional groups (such as macromonomers, polymers, oligomers, and monomers).
Examples of radically polymerizable functional groups include functional groups having unsaturated double bonds, such as acryloyl groups, methacryloyl groups, and allyl groups. Examples of cationically polymerizable functional groups include epoxy groups, vinyl ether groups, and oxetane groups.

Compounds having radically polymerizable functional groups (radically polymerizable compounds) include compounds containing one or more unsaturated double bonds in their molecules. Specific examples include acrylic oligomers known by names such as epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate, as well as 2-ethylhexyl acrylate, isoamyl acrylate, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isonorbornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl acrylate. Examples of acrylate monomers include leloyoxyphthalic acid, dicyclopentenyl acrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, bisphenol A EO adduct diacrylate, trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexaacrylate. These compounds may be used individually or in combination. Methacrylates can also be used similarly, but generally, acrylates are preferred over methacrylates because they have a faster photopolymerization rate.

Examples of compounds having cationic polymerizable functional groups (cationically polymerizable compounds) include compounds having one or more epoxy groups, vinyl ether groups, or oxetane groups in their molecule.
Examples of compounds containing epoxy groups include the following, but are not limited to these.
Diglycidyl ethers of bisphenols such as 2-ethylhexyl diglycol ether, biphenyl glycidyl ether, bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetrachlorobisphenol A, and tetrabromobisphenol A; polyglycidyl ethers of novolac resins such as phenol novolac, cresol novolac, bromized phenol novolac, and orthocresol novolac; diglycidyl ethers of alkylene glycols such as ethylene glycol, polyethylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, 1,4-cyclohexanedimethanol, EO adducts of bisphenol A, and PO adducts of bisphenol A; and glycidyl esters such as glycidyl esters of hexahydrophthalic acid and diglycidyl esters of dimer acid;
3,4-Epoxycyclohexylmethyl-3',4'-Epoxycyclohexanecarboxylate, 2-(3,4-Epoxycyclohexyl-5,5-Spiro-3,4-Epoxy)cyclohexane-meth-dioxane, di(3,4-Epoxycyclohexylmethyl)adipate, di(3,4-Epoxy-6-methylcyclohexylmethyl)adipate, 3,4-Epoxy-6-methylcyclohexyl-3',4'-Epoxy-6'-methylcyclohexanecarboxylate, methylenebis(3,4-Epoxycyclo Alicyclic epoxy compounds such as xane, dicyclopentadiene diepoxide, ethylene glycol di(3,4-epoxycyclohexylmethyl) ether, ethylene bis(3,4-epoxycyclohexanecarboxylate), lactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, tetra(3,4-epoxycyclohexylmethyl)butanetetracarboxylate, and di(3,4-epoxycyclohexylmethyl)-4,5-epoxytetrahydrophthalate.

Examples of compounds containing a vinyl ether group include, but are not limited to, diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxybutyl vinyl ether, ethyl vinyl ether, dodecyl vinyl ether, trimethylolpropane trivinyl ether, and propenyl ether propylene carbonate. While vinyl ether compounds are generally cationic polymerizable, radical polymerization is also possible when combined with acrylates.
Examples of compounds having an oxetane group include 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene and 3-ethyl-3-(hydroxymethyl)-oxetane.

The cationic polymerizable compounds described above may be used individually or in combination.
The photopolymerizable compounds are not limited to those described above. Furthermore, fluorine atoms (F) may be introduced into the photopolymerizable compounds to lower their refractive index and create a sufficient refractive index difference. Sulfur atoms (S), bromine atoms (Br), and various metal atoms may be introduced into the photopolymerizable compounds to raise their refractive index and create a sufficient refractive index difference. In addition, as disclosed in Japanese Patent Publication No. 2005-514487, it is also effective to add functional ultrafine particles, in which photopolymerizable functional groups such as acrylic groups, methacrylic groups, and _epoxy groups are introduced into the surface of ultrafine particles made of high refractive index metal oxides such as titanium dioxide ( _TiO₂ ), zirconium oxide ( _ZrO₂ ), and tin oxide (SnO₂x), to the above-mentioned photopolymerizable compounds.

The photopolymerizable compound may include a photopolymerizable compound having a silicone skeleton. The photopolymerizable compound having a silicone skeleton polymerizes and hardens in an orientation according to its structure (mainly ether bonds), forming a low refractive index region, a high refractive index region, or both a low refractive index region and a high refractive index region. In this case, either the matrix 31 or the columnar structure 32 corresponds to the low refractive index region, and the other corresponds to the high refractive index region.
In the low refractive index region, it is preferable that the amount of silicone resin, which is a cured product of a photopolymerizable compound having a silicone skeleton, be relatively high. Since silicone resin contains more silicon (Si) than compounds without a silicone skeleton, the relative amount of silicone resin can be confirmed by using EDS (Energy Dispersive X-ray Spectrometer) with silicon as an indicator.

The photopolymerizable compound having a silicone skeleton may be a monomer, oligomer, prepolymer, or macromonomer. There are no particular restrictions on the type and number of radically polymerizable or cationic polymerizable functional groups, but it is preferable to have polyfunctional acryloyl or methacryloyl groups, as a greater number of functional groups increases the crosslinking density and makes it easier to create differences in refractive index. Furthermore, compounds having a silicone skeleton may have insufficient compatibility with other compounds due to their structure, but in such cases, compatibility can be improved by urethane formation. Examples of such compounds include silicones, urethanes, and (meth)acrylates having acryloyl or methacryloyl groups at their terminal ends.
In this invention, "(meth)acrylate" means that it may be either acrylate or methacrylate.

Examples of silicone skeletons include those represented by the following formula (1). In formula (1), _R1 , _R2 , _R3 , _R4 , _R5 , and _R6 each independently have a functional group such as a methyl group, alkyl group, fluoroalkyl group, phenyl group, epoxy group, amino group, carboxyl group, polyether group, acryloyl group, or methacryloyl group. In formula (1), n is preferably an integer from 1 to 500.

The weight-average molecular weight (Mw) of the photopolymerizable compound having a silicone skeleton is preferably 500 to 50,000, and more preferably 2,000 to 20,000. A weight-average molecular weight within this range facilitates a sufficient photocuring reaction.

A photopolymerizable compound having a silicone skeleton and a compound without a silicone skeleton may be used in combination. This makes it easier for low refractive index regions and high refractive index regions to be formed separately, and the degree of anisotropy is increased.
Compounds that do not have a silicone skeleton include photopolymerizable compounds, thermoplastic resins, and thermosetting resins, and these can also be used in combination.
As photopolymerizable compounds, polymers, oligomers, and monomers having radically polymerizable or cationic polymerizable functional groups can be used (provided they do not have a silicone backbone).
Examples of thermoplastic resins include polyester, polyether, polyurethane, polyamide, polystyrene, polycarbonate, polyacetal, polyvinyl acetate, acrylic resins and their copolymers and modified products. When using thermoplastic resins, they are dissolved using a solvent that dissolves them, and after coating and drying, a photopolymerizable compound having a silicone backbone is cured with ultraviolet light to form an anisotropic light-diffusing layer.
Examples of thermosetting resins include epoxy resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters and their copolymers and modified products. When using thermosetting resins, a photopolymerizable compound having a silicone backbone is cured with ultraviolet light, and then the thermosetting resin is cured by appropriate heating to form an anisotropic light-diffusing layer.
The most preferred compounds that do not have a silicone skeleton are photopolymerizable compounds, which offer excellent productivity due to their ease of separation between low and high refractive index regions, the elimination of the need for solvents and drying processes when using thermoplastic resins, and the elimination of the need for a thermal curing process like that of thermosetting resins.

When a photocurable composition contains a photopolymerizable compound having a silicone skeleton and a compound without a silicone skeleton, the ratio of these compounds by mass is preferably in the range of 15:85 to 85:15, and more preferably in the range of 30:70 to 70:30. This range facilitates phase separation between the low refractive index region and the high refractive index region.

Examples of photoinitiators for polymerizing radical polymerizable compounds include benzophenone, benzyl, Michlar's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzyldimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy-2-methyl-1-phenylpropane-1-one, and 1-hydroxycyclohexylphenyl ketal. Examples include ton, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, di-η(5)-cyclopentadienylbis[2,6-difluoro-3-(pyrrole-1-yl)phenyl]titanium(IV), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. These compounds may be used individually or in combination.

Photoinitiators for polymerizing cationic polymerizable compounds are compounds that generate an acid upon light irradiation, and this generated acid can polymerize the aforementioned cationic polymerizable compound. Generally, onium salts and metallocene complexes are preferred. As onium salts, diazonium salts, sulfonium salts, iodonium salts, phosphonium salts, selenium salts, etc. _{, are used, and anions such as BF₄⁻, PF₁⁻, AsF₁⁻, and SbF₁⁻ are} ^used _as ^{counterions to} _these ^salts . Specific examples include 4-chlorobenzenediazonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, (4-phenylthiophenyl)diphenylsulfonium hexafluoroantimonate, (4-phenylthiophenyl)diphenylsulfonium hexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide-bis-hexa Examples of such compounds include, but are not limited to, fluorophosphates, (4-methoxyphenyl)diphenylsulfonium hexafluoroantimonate, (4-methoxyphenyl)phenyliodonium hexafluoroantimonate, bis(4-t-butylphenyl)iodonium hexafluorophosphate, benzyltriphenylphosphonium hexafluoroantimonate, triphenylselenium hexafluorophosphate, and (η5-isopropylbenzene)(η5-cyclopentadienyl)iron(II) hexafluorophosphate. These compounds may be used individually or in combination.

In the photocurable composition, the photoinitiator content is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, and even more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the photopolymerizable compound. A content of 0.01 parts by mass or more results in good photocurability. A content of 10 parts by mass or less ensures good formation of a columnar structure. Furthermore, it can suppress the hardening of the surface while reducing internal curability or causing discoloration.

Examples of polymer compounds that do not possess photopolymerizability include acrylic resins, styrene resins, styrene-acrylic copolymers, polyurethane resins, polyester resins, epoxy resins, cellulose resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, and polyvinyl butyral resins. These polymer compounds and photopolymerizable compounds must have sufficient compatibility before photocuring; however, various organic solvents and plasticizers can be used to ensure this compatibility. When using acrylate as the photopolymerizable compound, acrylic resin is preferred as the non-photopolymerizable polymer compound due to its compatibility.

Photoinitiators are usually used by directly dissolving the powder in a photopolymerizable compound. However, if solubility is poor, the photoinitiator can be pre-dissolved in a very small amount of solvent at a high concentration beforehand.
Examples of solvents include ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, and xylene.
Various known dyes and sensitizers can be added to improve photopolymerization properties.
A thermosetting initiator capable of curing photopolymerizable compounds by heating can also be used in combination with the photoinitiator. In this case, heating after photocuring is expected to further accelerate and complete the polymerization curing of the photopolymerizable compound.

<Step (S1)>
In step (S1), a layer of the photocurable composition is provided on the substrate.
The substrate is not particularly limited and includes, for example, glass such as quartz glass and soda glass; and resin films such as polyethylene terephthalate (PET), triacetylcellulose (TAC), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polycarbonate (PC), polyimide (PI), polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), cycloolefin copolymer (COC), norbornene-containing resin, polyethersulfone (PES), cellophane, and aromatic polyamide.

Conventional coating and printing methods are applied to form a layer of light-curable composition on a substrate. Specifically, coatings such as air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calender coating, dam coating, dip coating, and die coating, as well as intaglio printing such as gravure printing and stencil printing such as screen printing, can be used. If the light-curable composition has low viscosity, a weir of a certain height can be created around the substrate, and the light-curable composition can be cast within this weir. The thickness of the light-curable composition layer can be adjusted by adjusting the height of this weir.

After forming a layer of the photocurable composition, a mask that locally changes the light irradiation intensity may be laminated on the light-irradiated side of the photocurable composition layer to prevent oxygen inhibition of the photocurable composition and efficiently form the columnar structure 32. The mask material is preferably one in which a light-absorbing filler such as carbon is dispersed in a matrix, so that some of the incident light is absorbed by the carbon, but the openings allow sufficient light transmission. Such a matrix may be transparent plastics such as PET, TAC, polyvinyl acetate (PVAc), PVA, acrylic resin, polyethylene, inorganic materials such as glass, quartz, or a sheet containing these matrices with patterning to control the amount of ultraviolet light transmitted or pigments that absorb ultraviolet light. If such a mask is not used, oxygen inhibition of the photocurable composition can also be prevented by performing light irradiation under a nitrogen atmosphere. Furthermore, simply laminating a normal transparent film on top of the photocurable composition layer is also effective in preventing oxygen inhibition and promoting the formation of the columnar structure 32.

<Step (S2)>
In step (S2), parallel light rays are obtained from the light source.
Typically, short-arc ultraviolet light sources are used as light sources, specifically high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, xenon lamps, etc.
When a layer of a photocurable composition is irradiated with light rays parallel to a desired scattering center axis, and the photocurable composition is cured, a plurality of columnar cured regions (columnar structures) extending along the direction of irradiation of the parallel light rays are formed within the layer of the photocurable composition.
Methods for obtaining such parallel light rays include arranging a point light source and placing an optical lens, such as a Fresnel lens, between the point light source and the layer of the photocurable composition to irradiate with parallel light rays, and arranging a linear light source and interposing a collection of cylindrical objects between the linear light source and the layer of the photocurable composition, and irradiating with light through these cylindrical objects (see Japanese Patent Publication No. 2005-292219). Using a linear light source is preferable because it allows for continuous production.
A chemical lamp (a fluorescent lamp that emits ultraviolet light) can be used as a linear light source. Chemical lamps with a diameter of 20 to 50 mm and an emission length of 100 to 1500 mm are commercially available and can be appropriately selected according to the size of the anisotropic diffusion film 3A to be created.

<Step (S3)>
Step (S3) is an optional step. In step (S3), the parallel light rays obtained in step (S2) are incident on a directional diffusion element to obtain directional light rays.
Referring to Figures 13 and 14, the method for manufacturing the anisotropic diffusion film, including step (S3), will be described. As shown in Figures 13 and 14, parallel light rays D from the light source 300 are incident on the directional diffusion elements 301 and 302 to become directional light E, and this directional light E is incident on the photocurable composition layer 303, curing the photocurable composition layer 303.

The directional diffusion elements 301 and 302 used in process (S3) only need to impart directionality to the parallel light rays D incident from the light source 300.

Figures 13 and 14 show how directional light E is incident on the photocurable composition layer 303, with a large amount of diffusion in the X direction and almost no diffusion in the Y direction.
To obtain such directional light E, for example, a method can be employed in which needle-shaped fillers with a high aspect ratio are contained within the directional diffusion elements 301 and 302, and the needle-shaped fillers are oriented so that their long axis extends in the Y direction. In addition to using needle-shaped fillers in the directional diffusion elements 301 and 302, various other methods can be used.

Here, the aspect ratio of the directional light E is preferably 2 to 20. A columnar structure having an aspect ratio approximately corresponding to this aspect ratio is formed. The upper limit of the aspect ratio is more preferably 10 or less, and more preferably 5 or less. By keeping the aspect ratio below the upper limit, interference rainbows and glare can be suppressed. The aspect ratio of light E is expressed as the ratio of the major axis to the minor axis (major axis/minor axis) of light E at the light incident surface of layer 303 of the photocurable composition.

In step (S3), the size of the formed columnar structure (aspect ratio, minor axis SA, major axis LA, etc.) can be appropriately determined by adjusting the spread of the directional light E. For example, an anisotropic diffusion film of this form can be obtained in either Figure 13 or Figure 14. The difference between Figure 13 and Figure 14 is that the spread of the directional light E is relatively larger in Figure 13 and smaller in Figure 14. The size of the columnar structure will differ depending on the size of the spread of the directional light E.

The spread of directional light E primarily depends on the type of directional diffusion elements 301 and 302 and the distance between them and the photocurable composition layer 303. As this distance decreases, the size of the columnar structure decreases, and as it increases, the size of the columnar structure increases. Therefore, the size of the columnar structure can be adjusted by adjusting this distance.

<Step (S4)>
The light irradiated onto the layer of the photocurable composition must contain wavelengths capable of curing the photopolymerizable compound, and typically, light with wavelengths centered around 365 nm from a mercury lamp is used. When producing an anisotropic diffusion film 3A using this wavelength range, the illuminance is preferably in the range of 0.01 to 100 mW/ ^cm² , and more preferably in the range of 0.1 to 20 mW/ ^cm² . The light irradiation time is not particularly limited, but is preferably 10 to 180 seconds, and more preferably 30 to 120 seconds.
As described above, a specific internal structure is formed in the photocurable composition layer by irradiating it with low-intensity light for a relatively long period of time. However, with such light irradiation alone, unreacted monomer components may remain, causing stickiness and problems with handling and durability. In such cases, additional irradiation with high-intensity light of 1000 mW/ ^cm² or more can polymerize the remaining monomers. This light irradiation may be performed from the opposite side of the layered mask.
Subsequently, the substrate can be peeled off to obtain an anisotropic diffusion film 3A.

(Application)
The liquid crystal photomask laminate 1 is used in an exposure apparatus. The exposure apparatus using the liquid crystal photomask laminate 1 is used, for example, to form a resist pattern on the substrate surface by photolithography.
The configuration of an exposure apparatus using the liquid crystal photomask laminate 1 may be the same as that of a known exposure apparatus, except that it includes the liquid crystal photomask laminate 1 instead of a conventional photomask. An example of an exposure apparatus is the one described in Japanese Patent Application Publication No. 2004-85955, which includes an illumination optical system that includes a light source and irradiates light, an exposure control system that includes a photomask placed in the optical path of the illumination light from the illumination optical system, and an exposure optical system that holds a substrate on which a photoresist film is formed so that the illumination light that has passed through the photomask is irradiated.
The main light sources include ultraviolet light.

As for the resist pattern formed by the exposure apparatus using the liquid crystal photomask laminate 1, a pattern including a gradient pattern, as shown in Figure 12, is preferred due to the usefulness of the present invention.
The inclined pattern is a line pattern or space pattern that extends in a direction inclined with respect to the pixel arrangement direction of the liquid crystal photomask 2 (vertical direction (up and down direction in the figure) and horizontal direction (left and right direction in the figure)) (when the vertical direction is defined as 0°, the direction is greater than 0° and less than 90°).

(Effects and Benefits)
In the liquid crystal photomask laminate 1 described above, since the light diffuser 3 is laminated on the liquid crystal photomask 2, the light emitted from the liquid crystal photomask 2 is appropriately diffused by the light diffuser 3. Therefore, even if the pattern displayed on the liquid crystal photomask 2 includes a sloped pattern, the sloped pattern of the formed resist pattern will not become zigzag, resulting in good accuracy of the resist pattern.
In particular, when the light diffuser 3 is an anisotropic diffusion film, it has the ability to concentrate light in a specific direction (for example, the front direction), which can suppress unintended exposure and further improve accuracy.

(Other embodiments)
Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. The configurations and combinations thereof in the above embodiments are examples, and additions, omissions, substitutions, and other modifications to the configurations are possible without departing from the spirit of the present invention.
For example, as shown in Figure 8, the liquid crystal photomask laminate 1A may have no transparent adhesive layer 4, and the liquid crystal photomask 2 and the light diffuser 3 may be directly laminated. Such a liquid crystal photomask laminate can be obtained, for example, by directly forming the light diffuser 3 on the main surface of the liquid crystal photomask 2.
As shown in Figure 9, the liquid crystal photomask laminate 1B may be configured such that the light diffuser 3 is laminated on the light incident surface side (upper side in the figure) of the liquid crystal photomask 2. In this case, the light incident on the liquid crystal photomask 2 is appropriately diffused by the light diffuser 3, suppressing the zigzag pattern. The light diffuser 3 may be laminated via a transparent adhesive layer 4, as in the liquid crystal photomask laminate 1B, or it may be laminated directly.
It is preferable that the light diffuser 3 be laminated on the light-emitting side of the liquid crystal photomask 2, because diffusing the light after the parallel light for exposure has passed through the liquid crystal photomask allows for proper control of light shielding and exposure of the liquid crystal photomask.

The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Angle width (FWTM) at 1/10th of the maximum intensity of diffused light from the light diffuser)
Using a goniotphotometer (Genesia, Goniot/Far Field Profiler), a straight beam of light was incident from the normal direction to one main surface of the light diffuser. The intensity distribution (transmittance at each angle) of the diffused light that exited (transmitted) the light diffuser from the opposite main surface was measured in the range of -75° to +75° on a straight line perpendicular to the normal direction, with the angle of the normal direction of the other surface set to 0°. The FWTM was calculated using the angular width between two points that represent 1/10 of the maximum value of the diffused light intensity.
However, if the FWTM differs depending on the orientation in which the light diffuser is measured, the average value of the FWTM at the orientation where the FWTM is maximum and the FWTM at the orientation where the FWTM is minimum was used.

(Linear transmittance in the direction normal to the main surface of the light diffuser, maximum linear transmittance, minimum linear transmittance, scattering center axis angle)
Using a goniotphotometer (Genesia, Goniot/Far Field Profiler), linear light was incident from the normal direction (surface normal direction) of one main surface of the light diffuser according to the method shown in Figure 6 above. The linear light emitted (transmitted) from the opposite main surface of the light diffuser was measured, the linear transmittance was calculated, and this linear transmittance was plotted for each angle to create an optical profile.
Linear transmittance was measured using a luminous efficiency filter at wavelengths in the visible light region.
Based on the optical profile obtained from the above measurements, the maximum value (maximum linear transmittance) and minimum value (minimum linear transmittance), as well as the scattering center axis angle, which is the incident light angle with approximately symmetry in the said profile, were determined.

(Haze value of light diffuser)
The haze value (Hz) was measured using a haze meter (NDH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136.

(Angle of columnar structure extension in anisotropic diffusion film)
In the case of an anisotropic diffusion film having multiple columnar structures, the columnar structure extension angle, which is the angle between the extension direction of the columnar structures and the normal direction of the film, was calculated by observing the thickness-direction cross-section of the anisotropic diffusion film with an optical microscope and measuring the angle between the extension direction of the columnar structures (the direction in which the columnar structures are oriented from one surface to the other on the main surface of the anisotropic diffusion film) and the normal direction of the main surface of the anisotropic diffusion film for any 10 arbitrary columnar structures, and then calculating the average value of these angles.

(Aspect ratio of the columnar structure of anisotropic diffusion film)
In the case of an anisotropic diffusion film having multiple columnar structures, the average values of the major axis and minor axis were calculated by observing a cross-section perpendicular to the direction of extension of the columnar structures using an optical microscope, measuring the major and minor axes of the cross-sectional shapes of 10 arbitrarily selected columnar structures 32, and averaging these values.
The aspect ratio was calculated by dividing the average of the major axes by the average of the minor axes.

(Preparation of isotropic diffusion film)
An isotropic diffusion film was prepared using the method described below, with reference to Japanese Patent Publication No. 2002-122714.
To 100 parts by weight of an acrylic adhesive with a refractive index of 1.47 (product name: SK Dyne™ 206, total solids content 18.8%, solvent: ethyl acetate, methyl ethyl ketone, manufactured by Soken Chemical Co., Ltd.), 0.5 parts of an isocyanate curing agent (product name: L-45, manufactured by Soken Chemical Co., Ltd.) and 0.2 parts of an epoxy curing agent (product name: E-5XM, manufactured by Soken Chemical Co., Ltd.) were added to the base coating. A predetermined amount of silicone resin fine particles (Tospearl 145, refractive index 1.43, particle size 4.5 μm) with a refractive index different from that of the adhesive was added, and the mixture was stirred with an agitator for 30 minutes to disperse the fine particles, thereby preparing coating a for isotropic diffusion film.
A coating b for isotropic diffusion film was prepared in the same manner as described above, except that the amount of silicone resin fine particles added was changed.
Similarly, coating c for isotropic diffusion films was prepared in the same manner as described above, except that the amount of silicone resin fine particles added was changed.
For comparison, a coating d for transparent adhesive film was prepared in the same manner as above, except that silicone resin fine particles were not added.

The prepared isotropic diffusion film coatings a to c or transparent adhesive film coating d were applied to a 38 μm thick release PET film (Lintec Corporation, product name: 38C) using a comma coater to a film thickness of 25 μm after solvent drying, and dried to form isotropic diffusion films a to c or transparent adhesive film d. A 38 μm thick release PET film (Lintec Corporation, product name: 3801) was then laminated on top of the film.
Table 1 shows the FWTM, linear transmittance in the plane normal direction, maximum linear transmittance, minimum linear transmittance, and haze value (Hz) for isotropic diffusion films a to c.

(Lens diffuser)
As lens diffusers, LSD1°, LSD5°, LSD30°, and LSD60° (all manufactured by Optical Solutions Co., Ltd.) were prepared.
Table 1 shows the FWTM, linear transmittance in the surface normal direction, maximum linear transmittance, minimum linear transmittance, and haze value (Hz) for each lens diffuser plate.

(Fabrication of anisotropic diffusion films)
An anisotropic diffusion film was prepared using the method described below, with reference to Japanese Patent Publication No. 2006-119241 and International Publication No. 2014/084361.
A UV-curable resin composition was prepared by mixing the following components.
20 parts by mass of silicone urethane acrylate (manufactured by RAHN, product name: 00-225/TM18, refractive index: 1.460, weight-average molecular weight: 5,890).
30 parts by mass of neopentyl glycol diacrylate (manufactured by Daicel Cytec, trade name Ebecryl 145, refractive index: 1.450).
15 parts by mass of bisphenol A EO adduct diacrylate (manufactured by Daicel Cytec, trade name: Ebecyl 150, refractive index: 1.536).
40 parts by mass of phenoxyethyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., product name: Light Acrylate PO-A, refractive index: 1.518).
4 parts by mass of 2,2-dimethoxy-1,2-diphenylethane-1-one (BASF, trade name: Irgacure 651).

A 50 μm high partition wall was formed around the entire edge of a 100 μm thick PET film (manufactured by Toyobo Co., Ltd., product name: A4300) using a dispenser with a curable resin. The above UV-curable resin composition was dropped into this partition wall and covered with another PET film.
A liquid film of a 50 μm thick ultraviolet-curable resin composition, sandwiched between PET films on both sides, was irradiated for 1 minute with ultraviolet light, a parallel beam with an irradiation intensity of 30 mW/ ^cm² , from the reflected irradiation unit of a UV spot light source (Hamamatsu Photonics, product name: L2859-01), to obtain seven types of PET-coated single-layer anisotropic diffusion films e to k, each with a thickness of 50 μm and numerous columnar structures. Table 1 shows the FWTM, linear transmittance in the plane normal direction, maximum linear transmittance, minimum linear transmittance, haze value (Hz), extension direction of the columnar structures, and aspect ratio for each anisotropic diffusion film e to k.

Furthermore, the optical properties of each anisotropic diffusion film, namely the maximum linear transmittance and the scattering center axis angle (relative to the normal direction of the anisotropic diffusion film), as well as the aspect ratio of each columnar structure, were obtained by adjusting the heating temperature of the liquid film made from the UV-curing resin composition and the direction of the irradiated UV light, as well as by whether or not to place a directional diffusion element that can change the aspect ratio of parallel light rays between the anisotropic diffusion film and the reflected light irradiation unit, and, if a directional diffusion element is used, by adjusting the position of the directional diffusion element (bringing it closer to or further away from the anisotropic diffusion film). In this way, seven types of anisotropic diffusion films were obtained.
The directional diffusion element imparts directionality to the incident parallel light rays. In this embodiment, a directional diffusion element containing needle-shaped microparticles with a high aspect ratio was used. The aspect ratio of the columnar structure was formed to approximately correspond to the aspect ratio of the parallel light rays modified by the directional diffusion element.

(Examples 1-6, Comparative Examples 1-9)
The light diffusers shown in Table 2 were laminated onto the light-emitting side of a 187 ppi (pixels per inch) liquid crystal display to create liquid crystal photomask laminates for Examples 1 to 6 and Comparative Examples 1 to 9.

(Zigzag blurring effect in a liquid crystal photomask laminate; image blurring)
For each of the liquid crystal photomask laminates in the examples and comparative examples, a display was created on the liquid crystal display screen inside the liquid crystal photomask laminate, with a 45° diagonal line running from the upper left to the lower right as the boundary, such that one side was displayed in black and the other side in white.
This boundary was visually observed using a 30x magnification loupe to determine whether the zigzag pattern caused by pixels at the boundary had disappeared (smoothed out) and whether there was any image blurring at the boundary.
The evaluation results are shown in Table 2.

<Evaluation Criteria>
The evaluation criteria in Table 2 are as follows:
"Zigzag erasing effect"
◎ No zigzag pattern can be observed.
〇 A very slight zigzag pattern can be observed, but it is at a level that does not pose any practical problems.
△ A slight zigzag pattern is visible, but it is at a level that does not pose any practical problems.
× There is a zigzag pattern.
"Image blur"
◎ No image blur.
There is a slight blur in the image, but it is at a level that does not pose any practical problems.
× The image is blurry.

The isotropic diffusion film a and anisotropic diffusion films e-i used in Examples 1-6 had high haze values, which resulted in a high effect in smoothing out pixel-induced zigzags when used in a liquid crystal photomask laminate. At the same time, because the FWTM was relatively narrow, image blur was also suppressed.
On the other hand, in Comparative Example 1, which did not use a light diffuser, and in Comparative Examples 2-6 and 9, which used isotropic diffusion films b and c, anisotropic diffusion films j and k, and lens diffusers (LSD 1°, 5°) with low haze values, the diffusion was insufficient, and the zigzag caused by pixels could not be sufficiently smoothed. Furthermore, in Comparative Examples 7 and 8, which used lens diffusers (LSD 30°, 60°) with high haze values but wide FWTM, the zigzag caused by pixels could be smoothed without practical problems, but image blur was observed because the FWTM was too wide.

1. Liquid crystal photomask laminate, 2. Liquid crystal photomask, 3. Light diffuser, 3A, 3B, 3C. Anisotropic diffusion film, 3a. First main surface, 3b. Second main surface, 4. Transparent adhesive layer, 31. Matrix, 32. Columnar structure, 32A. Rod-shaped columnar structure (pillar structure), 32B. Plate-shaped columnar structure (louver structure)

Claims (7)

The system comprises a liquid crystal photomask and a light diffuser laminated on the light-emitting surface side of the liquid crystal photomask,
The light diffuser has a first main surface and a second main surface opposite to the first main surface, and when linear light is incident on the first main surface along the direction normal to the first main surface, and the distribution of diffused light emitted from the second main surface is measured with the angle of the normal direction of the second main surface being 0°, the angular width at 1/10 of the maximum intensity of the diffused light is 45° or less, and the haze value is 55% or more, characterized in that the light diffuser has a first main surface and a second main surface opposite to the first main surface, and when linear light is incident on the first main surface along the direction normal to the first main surface, the distribution of diffused light emitted from the second main surface is measured with the angle of the normal direction of the second main surface being 0°, the angular width at 1/10 of the maximum intensity of the diffused light is 45° or less, and the haze value is 55% or more. The liquid crystal photomask laminate according to claim 1, wherein the light diffuser has a linear transmittance of 40% or less in the direction normal to the first main surface. The liquid crystal photomask laminate according to claim 1 or 2, wherein the light diffuser is an anisotropic diffusion film whose light diffusivity changes depending on the angle of incident light. The liquid crystal photomask laminate according to claim 3, wherein the anisotropic diffusion film comprises a matrix and a plurality of columnar structures having refractive indices different from those of the matrix, and the plurality of columnar structures extend in the thickness direction of the anisotropic diffusion film. The liquid crystal photomask laminate according to claim 4, wherein the scattering center axis angle of the anisotropic diffusion film is 10° or less. The liquid crystal photomask laminate according to claim 4 or 5, wherein each of the plurality of columnar structures has an aspect ratio of 1 to 10, expressed as the ratio of the major axis to the minor axis (major axis/minor axis) in a cross-section perpendicular to the extending direction of the columnar structure. An exposure apparatus using a liquid crystal photomask laminate according to any one of claims 1 to 6 .